vvEPA
United                                 August 2007
Environmental Protection	EPA/600/R-07/093
            Annexes for the
            Integrated Science Assessment
            for Oxides of Nitrogen -
            Health Criteria
            (First External Review Draft)

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                                                EPA/600/R-07/093
                                                   August 2007
              Annexes for the
     Integrated Science Assessment
for Oxides of Nitrogen - Health Criteria
     National Center for Environmental Assessment-RTF Division
            Office of Research and Development
            U.S. Environmental Protection Agency
               Research Triangle Park, NC

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                                  DISCLAIMER
      This document is a first external review draft being released for review purposes only and
does not constitute U.S. Environmental Protection Agency policy. Mention of trade names or
commercial products does not constitute endorsement or recommendation for use.
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          Annexes for the Integrated Science Assessment
              for Oxides of Nitrogen - Health Criteria
                       ANNEX CHAPTERS
AXl.  CHAPTER 1 ANNEX - INTRODUCTION	AX1-1
AX2.  CHAPTER 2 ANNEX - ATMOSPHERIC CHEMISTRY OF NITROGEN
     AND SULFUR OXIDES	AX2-1
AX3.  CHAPTER 3 ANNEX - AMBIENT CONCENTRATIONS AND
     EXPOSURES	AX3-1
AX4.  CHAPTER 4 ANNEX - TOXICOLOGICAL EFFECTS OF NITROGEN
     DIOXIDE AND RELATED OXIDES OF NITROGEN	AX4-1
AX5.  CHAPTER 5 ANNEX - CONTROLLED HUMAN EXPOSURE STUDIES
     OF NITROGEN OXIDES	AX5-1
AX6.  CHAPTER 6 ANNEX - EPIDEMIOLOGICAL STUDIES OF HUMAN
     HEALTH EFFECTS ASSOCIATED WITH AMBIENT OXIDES OF
     NITROGEN EXPO SURE	AX6-1
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                           Annex Table of Contents
AX1.  CHAPTER 1 ANNEX - INTRODUCTION	AX1-1
      AX1.1   LEGISLATIVE REQUIREMENTS	AX1-2
      AX1.2   HISTORY OF REVIEWS OF THE PRIMARY NAAQS FORNO2	AX1-3
      AX1.3   REFERENCES	AX1-5

AX2.  CHAPTER 2 ANNEX - ATMOSPHERIC CHEMISTRY OF NITROGEN AND
      SULFUR OXIDES	AX2-1
      AX2.1   INTRODUCTION	AX2-1
      AX2.2   CHEMISTRY OF NITROGEN OXIDES IN THE TROPOSPHERE	AX2-2
             AX2.2.1   Basic Chemistry	AX2-2
             AX2.2.2   Nonlinear Relations between Nitrogen Oxide
                      Concentrations and Ozone Formation	AX2-9
             AX2.2.3   Multiphase Chemistry Involving NOX	AX2-12
      AX2.3   CHEMISTRY OF SULFUR OXIDES IN THE TROPOSPHERE	AX2-24
      AX2.4   MECHANISMS FOR THE AQUEOUS PHASE  FORMATION
             OF SULFATE AND NITRATE	AX2-28
      AX2.5   TRANSPORT OF NITROGEN AND SULFUR OXIDES IN
             THE ATMOSPHERE	AX2-31
      AX2.6   SOURCES AND EMISSIONS OF NITROGEN OXIDES,
             AMMONIA, AND SULFUR DIOXIDE	AX2-35
             AX2.6.1   Interactions of Nitrogen Oxides with the Biosphere	AX2-35
             AX2.6.2   Emissions of NOX, NH3, and SO2	AX2-48
             AX2.6.3   Field Studies Evaluating Emissions Inventories	AX2-56
      AX2.7   METHODS USED TO CALCULATE CONCENTRATIONS OF
             NITROGEN OXIDES AND THEIR CHEMICAL
             INTERACTIONS IN THE ATMOSPHERE	AX2-58
             AX2.7.1   Chemistry-Transport Models	AX2-59
             AX2.7.2   CTM Evaluation	AX2-73
      AX2.8   SAMPLING AND ANALYSIS OF NITROGEN AND SULFUR
             OXIDES	AX2-86
             AX2.8.1   Availability and Accuracy of Ambient Measurements
                      forNOy	AX2-86
             AX2.8.3   Techniques for Measuring Other NOy Species	AX2-95
             AX2.8.4   Remote Sensing of Tropospheric NO2 Columns for
                      Surface NOX Emissions and Surface NO2 Concentrations .... AX2-96
             AX2.8.5   SAMPLING AND ANALYSIS FOR  SO2	AX2-98
             AX2.8.6   Sampling and Analysis for Sulfate, Nitrate, and
                      Ammonium	AX2-101
      AX2.9   POLICY RELEVANT BACKGROUND CONCENTRATIONS
             OF NITROGEN AND SULFUR OXIDES	AX2-110
      AX2.10 REFERENCES	AX2-129
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                            Annex Table of Contents
                                    (cont'd)
AX3.  CHAPTER 3 ANNEX - AMBIENT CONCENTRATIONS AND
      EXPOSURES	AX3-1
      AX3.1   INTRODUCTION	AX3-1
      AX3.2   AMBIENT CONCENTRATIONS OF NITROGEN OXIDES
              AND RELATED SPECIES	AX3-2
              AX3.2.1  Spatial and Temporal Variability in Ambient
                       Concentrations of NO2 and Related Species in
                       Urban Areas	AX3-4
              AX3.2.2  Temporal Variability in Nitrogen Oxides	AX3-8
              AX3.2.4  Relationships Between NO2 and Other Pollutants	AX3-19
              AX3.2.5  Abundance of NOy Species	AX3-24
      AX3.3   METHODS FOR MEASURING PERSONAL AND INDOOR
              NO2 CONCENTRATIONS	AX3-30
              AX3.3.1  Issues in Measuring Personal/Indoor NO2	AX3-30
      AX3.4   NITROGEN OXIDES IN INDOOR AIR	AX3-40
              AX3.4.1  Indoor Sources and Concentrations of Nitrogen Oxides	AX3-40
              AX3.4.2  Reactions of NO2 in Indoor Air	AX3-47
              AX3.4.3  Contributions from Outdoor NO2	AX3-53
      AX3.5   PERSONAL EXPOSURE	AX3-55
              AX3.5.1  Personal Exposures and Ambient (Outdoor)
                       Concentrations	AX3-57
              AX3.5.2  Personal Exposure in Microenvironments	AX3-67
              AX3.5.3  Exposure Indicators	AX3-84
      AX3.6   CONFOUNDING AND SURROGATE IS SUES	AX3-86
      AX3.7   A FRAMEWORK FOR MODELING HUMAN EXPOSURES TO
              NO2 AND RELATED PHOTOCHEMICAL AIR POLLUTANTS	AX3-94
              AX3.7.1  Introduction: Concepts, Terminology, and
                       Overall Summary	AX3-94
              AX3.7.2  Population Exposure Models: Their Evolution and
                       Current Status	AX3-100
              AX3.7.3  Characterization of Ambient Concentrations of NO2
                       and Related Air Pollutants	AX3-103
              AX3.7.4  Characterization of Microenvironmental Concentrations.... AX3-105
              AX3.7.5  Concluding Comments	AX3-113
      AX3.8   EXPO SURE ERROR	AX3-114
      AX3.9   REFERENCES	AX3-169
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                         Annex Table of Contents
                                (cont'd)
AX4. CHAPTER 4 ANNEX - TOXICOLOGICAL EFFECTS OF NITROGEN
      DIOXIDE AND RELATED OXIDES OF NITROGEN	AX4-1
     AX4.2  DOSIMETRY OF INHALED NITROGEN OXIDES	AX4-7
            AX4.2.1   Mechanisms of NO2 Absorption	AX4-8
            AX4.2.3   Regional and Total Respiratory Absorption of NO2	AX4-11
     AX4.3  REFERENCES	AX4-50

AX5. CHAPTER 5 ANNEX - CONTROLLED HUMAN EXPOSURE STUDIES
     OF NITROGEN OXIDES	AX5-1
     AX5.1  INTRODUCTION	AX5-1
            AX5.1.1   Considerations in Controlled Human Exposure Studies	AX5-2
     AX5.2  EFFECTS OF NITROGEN DIOXIDE IN HEALTHY SUBJECTS	AX5-4
     AX5.3  THE EFFECTS OF NITROGEN OXIDE EXPOSURE IN
            SENSITIVE SUBJECTS	AX5-4
     AX5.4  EFFECTS OF MIXTURES CONTAINING NITROGEN OXIDES	AX5-6
     AX5.5  REFERENCES	AX5-16

AX6. CHAPTER 6 ANNEX - EPIDEMIOLOGICAL STUDIES OF HUMAN
     HEALTH EFFECTS ASSOCIATED WITH AMBIENT OXIDES OF
     NITROGEN EXPO SURE	AX6-1
     AX6.1  REFERENCES	AX6-143
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                                 Annex List of Figures

Number

AX2-1.      Schematic diagram of the cycle of reactive nitrogen species in
            the atmosphere [[[ AX2-3
AX2-2.      Measured values of O3 and NOZ (NOy-NOx) during the
            afternoon at rural sites in the eastern United States (gray circles) and
            in urban areas and urban plumes associated with Nashville, TN
            (gray dashes), Paris, FR (black diamonds) and Los Angeles, CA (X's) ....... AX2-12
AX2-3 .      Structures of nitro-poly cyclic aromatic hydrocarbons ................................... AX2- 1 6
AX2-4.      Formation of 2-nitropyrene (2NP) from the reaction of OH with
            gaseous pyrene (PY) [[[ AX2-17
AX2-5 .      Transformations of sulfur compounds in the atmosphere .............................. AX2-26
AX2-6.      Comparison of aqueous-phase oxidation paths .............................................. AX2-29
AX2-7.      Diel cycles of median concentrations (upper panels) and fluxes
            (lower panels) for the Northwest clean sector, left panels) and
            Southwest (polluted sector, right panels) wind sectors at Harvard Forest,
            April-November, 2000, for NO, NO2, and O3/10 .......................................... AX2-43
AX2-8.      Simple NOX photochemical canopy model outputs ....................................... AX2-44
AX2-9.      Hourly (dots) and median nightly (pluses) NO2 flux vs.  concentration,
            with results of least-squares fit on the hourly data (curve) ............................ AX2-45
AX2-1 1 .     Averaged profiles at Harvard Forest give some evidence of
            some NO2 input near the canopy top from light-mediated ambient
            reactions,or emission from open stomates [[[ AX2-46
AX2-12.     Summer (June-August) 2000  median concentrations
            (upper panels), fractions of NOy (middle panels), and fluxes (lower
            panels) of NOy and component species separated by wind direction
            (Northwest on the left and Southwest on the right) ....................................... AX2-47
AX2-13.     Scatter plot of total nitrate (HNO3 plus aerosol nitrate) wet
            deposition (mg(N)m 2yr^) of the mean model versus measurements
            for the North American Deposition Program (NADP) network .................... AX2-70
AX2-14.     Same as Figure AX2-13 but for sulfate wet deposition
                    '1 [[[ AX2-71
AX2-15a,b.  Impact of model uncertainty on control strategy predictions
            for O3 for two days (August lOa and lib, 1992) in Atlanta, GA .................. AX2-76

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                                Annex List of Figures
                                       (cont'd)

Number                                                                         Page

AX2-17a.    Time series for measured gas-phase species in comparison with results
            from a photochemical model	AX2-78
AX2-17b.    Time series for measured gas-phase species in comparison
            with results from a photochemical model	AX2-79
AX2-18.     Correlations for O3 versus NOZ (NOy-NOx) in ppb from
            chemical transport models for the northeast corridor, Lake Michigan,
            Nashville, the San Joaquin Valley, and Los Angeles	AX2-81
AX2-19a,b.  Evaluation of model versus measured O3 versus NOy for
            two model scenarios for Atlanta	AX2-83
AX2-20a,b.  Evaluation of model versus: (a) measured O3 versus NOZ
            and (b) O3 versus the sum 2H2O2 + NOZ for Nashville, TN	AX2-84
AX2-21.     Time series of concentrations of RO2, HO2, and OH radicals,
            local O3 photochemical production rate and concentrations of NOX
            from measurements made during BERLIOZ	AX2-85
AX2-22.     Tropospheric NO2 columns (molecules NO2/ cm2) retrieved
            from the SCIAMACHY satellite instrument for 2004-2005	AX2-97
AX2-23.     Annual mean concentrations of NO2 (ppbv) in surface air
            over the United States in the present-day (upper panel) and policy
            relevant background (middle panel) MOZART-2 simulations	AX2-112
AX2-24.     Same as Figure AX2-23 but for SO2 concentrations	AX2-113
AX2-25.     Same as for Figure AX2-23 but for wet and dry deposition of
            HNO3, NH4NO3, NOX, HO2NO2, and organic nitrates (mg N m~VJ)	AX2-114
AX2-26.     Same as Figure AX2-23 but for SOX deposition
            (SO2 +  SO4)(mgSm"V1)	AX2-115
AX2-27.     July mean soil NO emissions (upper panels; 1 x 10 9 molecules cm"2 s1)
            and surface PRB NOX concentrations (lower panels; pptv) over the
            United  States  from MOZART-2 (left) and GEOS-Chem (right) model
            simulations in which  anthropogenic O3 precursor emissions were set to
            zero in North America	AX2-116
AX3.1.      Location of ambient NO2 monitors in the United States	AX3-3
AX3.2.      NO2 concentrations measured at 4 m (Van) and at 15 m at NY
            Department of Environmental Conservation sites (DEC709406 and
            DEC709407)	AX3-7
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                                 Annex List of Figures
                                        (cont'd)
Number                                                                           Page

AX3.3.      Composite, diurnal variability in 1-h average NO2 in urban areas	AX3-9
AX3.4a-e.   Time series of 24-h average NO2 concentrations at individual sites
            in New York City from 2003  through 2006	AX3-10
AX3.5a-e.   Time series of 24-h average NO2 concentrations at individual sites in
            Atlanta, GA from 2003 through 2005	AX3-11
AX3.6a-g.   Time series of 24-h average NO2 concentrations at individual sites
            in Chicago, IL from 2003 through 2005	AX3-12
AX3.7a-b.   Time series of 24-h average NC>2 concentrations at individual sites
            in Baton Rouge, LA from 2003 through 2005	AX3-13
AX3.8a-g.   Time series of 24-h average NC>2 concentrations at individual sites
            in Houston, TX from 2003 through 2005	AX3-14
AX3.9a-h.   Time series of 24-h average NC>2 concentrations at individual sites
            in Los Angeles, CA from 2003 through 2005	AX3-15
AX3.9i-n.   Time series of 24-h average NC>2 concentrations at individual sites
            in Los Angeles, CA from 2003 through 2006	AX3-16
AX3. lOa-d.  Time series of 24-h average NC>2 concentrations at individual sites
            in Riverside, CA from 2003 through 2006	AX3-17
AX3. lOe-i.  Time series of 24-h average NC>2 concentrations at individual sites
            in Riverside, CA from 2003 through 2006	AX3-18
AX3.11.     Nationwide trends in annual meanNO2 concentrations	AX3-20
AX3.12.     Trends in annual meanNO2 concentrations by site type	AX3-20
AX3.13a-d.  Correlations of NC>2 to O3 vs. correlations of NC>2 to CO for Los
            Angeles, CA (2001-2005)	AX3-22
AX3.14.     Relationship between O3, NO, and NO2 as a function of NOX
            concentration	AX3-23
AX3.15.     Variation of odd  oxygen  (= O3 + NO2) with NOX	AX3-23
AX3.16a-d.  Measured O3 (ppbv) versus PAN (pptv) in Tennessee, including
            (a) aircraft measurements, and (b, c, and d) suburban sites near
            Nashville	AX3-26
AX3.17.     Relationship between benzene and NOy at a measurement site in
            Boulder, CO	AX3-27
AX3.18.     Ratios of PAN to NO2 observed at Silwood Park, Ascot, Berkshire,
            U.K. from July 24 to August  12 1999	AX3-27
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                                 Annex List of Figures
                                        (cont'd)

Number                                                                           Page

AX3.19.     Ratios of HONO to NC>2 observed in a street canyon (Marylebone Road)
            in London, U.K. from 11 a.m. to midnight during October 1999	AX3-28
AX3.20.     Concentrations of particulate nitrate measures as part of the
            Environmental Protection Agency PA's speciation network	AX3-29
AX3.21.     Percentage of time people spend in different environments	AX3-41
AX3.22.     Average residential outdoor concentration versus concentration during
            commuting forNC>2	AX3-77
AX3.23.     Schematic description of a general framework identifying the processes
            (steps or components) involved in assessing inhalation exposures and
            doses for individuals and populations	AX3-98
AX3.24.     Errors associated with components of the continuum from ambient
            air pollution to adverse health outcome	AX3-115
AX3.25.     A systematic approach to evaluate whether NC>2 itself is causing the
            observed adverse health outcome or NO2 is acting as a surrogate for
            other pollutants	AX3-120


AX5.1.      Airway  inflammation in response to NC>2 inhalation in healthy subjects	AX5-5
AX5.2.      Effects of NC>2 inhalation on allergen challenge in subjects with asthma	AX5-6
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                                 Annex List of Tables

Number

AX2-1.      Atmospheric Lifetimes of Sulfur Dioxide and Reduced Sulfur
            Species With Respect to Reaction With OH, NO3, and Cl Radicals	AX2-119
AX2-2a.     Relative Contributions of Various Reactions to the Total S(IV)
            Oxidation Rate within a Sunlit Cloud, 10 Minutes after Cloud
            Formation	AX2-120
AX2-2b.     Relative Contributions of Various Gas and Aqueous Phase Reactions
            to Aqueous Nitrate Formation within a Sunlit Cloud, 10 Minutes
            after Cloud Formation	AX2-121
AX2-3.      Emissions of Nitrogen Oxides, Ammonia, and Sulfur Dioxide in the
            United States in 2002	AX2-122
AX2-3.      Satellite Instruments Used to Retrieve Tropospheric NO2 Columns	AX2-128

AX3.1.      Summary of Percentiles of NO2 Data Pooled  Across Monitoring
            Sites (2003-2005) Concentrations are in ppm	AX3-121
AX3.2.      Spatial Variability of NO2 in Selected United states Urban Areas	AX3-122
AX3.3.      NOX and NOy Concentrations at Regional Background Sites in the
            Eastern United States. Concentrations are GIVEN in ppb	AX3-122
AX3.4.      Range of Pearson Correlation Coefficients Between NO2 and O3, CO
            andPM2.5AX3-123
AX3.5.      Passive Samplers Used inNO2 Measurements	AX3-124
AX3.6.      The Performance of Sampler/Sampling Method for NO2
            Measurements in the Air	AX3-125
AX3.7.      NO2 Concentrations (ppb) in Homes in Latrobe Valley, Victoria,
            Australia 	AX3-126
AX3.8.      NO2 Concentrations (ppb) in Homes in Connecticut	AX3-126
AX3.9.      NO2 Concentrations Near Indoor Sources - Short-Term Averages	AX3-127
AX3.10.     NO2 Concentrations Near Indoor Sources - Long-Term Averages	AX3-128
AX3.11.     Summary of Regression Models of Personal Exposure to
            Ambient/Outdoor NO2	AX3-129
AX3.12.     Average Ambient and Nonambient Contributions to Population
            Exposure 	AX3-130
AX3.13.     The Association Between Personal Exposures and Ambient
            Concentrations	AX3-131
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                                 Annex List of Tables
                                       (cont'd)
Number                                                                          Page

AX3.14.     Indoor/Outdoor Ratio and the Indoor vs. Outdoor Regression Slope	AX3-134
AX3.15.     NO2 Concentrations (ppb) in Different Rooms	AX3-141
AX3.16.     Indoor and Outdoor Contributions to Indoor Concentrations	AX3-143
AX3.17.     The Association Between Indoor, Outdoor, and Personal NO2	AX3-145
AX3.19.     Personal NO2 Levels Stratified by Demographic and Socioeconomic
            Factors (Concentrations are in ppb and Slopes are Dimensionless)	AX3-164
AX3.20.     Correlations (Pearson Correlation Coefficient) Between Ambient
            NO2 and Ambient Copollutants	AX3-165
AX3.21.     Correlations (Pearson Correlation Coefficient) Between Personal
            NO2 and Personal Copollutants	AX3-166
AX3.22.     Correlations (Pearson Correlation Coefficient) Between Personal
            NO2 and Ambient Copollutants	AX3-166
AX3.23.     Correlations (Pearson Correlation Coefficient) Between Ambient
            NO2 and Personal Copollutants	AX3-167
AX3.24.     The Essential Attributes of the pNEM, HAPEM, APEX, SHEDS,
            andMENTOR-lA	AX3-168

AX4.1.      Effects of Nitrogen  Dioxide (NO2) on Oxidant and
            Antioxidant Homeostasis	AX4-22
AX4.2.      Effect of Nitrogen dioxide (NO2) on Lung Amino Acids,
            Proteins, and Enzymes	AX4-25
AX4.3.      Effects of Nitrogen  oxide (NO2) on the Immune System
            of Animals	AX4-29
AX4.4.      Effects of Nitrogen  Dioxide on Alveolar Macrophages	AX4-30
AX4.5.      Effect of Nitrogen Dioxide (NO2) on Susceptibility to
            Infectious Agents	AX4-36
AX4.6.      Effect of Nitrogen Dioxide (NO2) on Hematological Parameters21	AX4-44
AX4.7.      Effects of Nitric Oxide with Iron and on Enzymes and Nucleic Acids	AX4-46
AX4.8A.    Genotoxicity of NO2 In Vitro and In Plants	AX4-47
AX4.8B.    Genoticity of NO2 In Vivo	AX4-48
AX4.8C.    Genotoxicity of NO In Vitro and In Vivo	AX4-49
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                                 Annex List of Tables
                                       (cont'd)
Number                                                                         Page

AX5.1.      Clinical Studies of NO2 Exposure in Healthy Subjects	AX5-7
AX5.2.      Effects of NO2 Exposure in Subjects with Respiratory Disease
            (see Table AX5-3 for Studies with Allergen Challenge)	AX5-11
AX5.3.      Effects of NO2 Exposure on Response to Inhaled Allergen	AX5-12
AX5.4.      Effects of Exposure to NO2 with Other Pollutants	AX5-14

AX6.1.      Studies Examining Exposure to Indoor NO2 and Respiratory Symptoms	AX6-1
AX6.2.      Studies Examining Exposure to Ambient NO2 and Acute Respiratory
            Symptoms Using Generalized Estimating Equations (GEE) in the
            Analysis Method	AX6-4
AX6.3-1.    Respiratory Health Effects of Oxides of Nitrogen:  Hospital Admissions	AX6-7
AX6.3-2.    Respiratory Health Effects of Oxides of Nitrogen:  Emergency
            Department Visits	AX6-42
AX6.3-3.    Respiratory Health Effects of Oxides of Nitrogen: General
            Practitioner/Clinic Visits	AX6-66
AX6.4-1.    Human Health Effects of Oxides of Nitrogen: CVD Hospital
            Admissions and Visits: United States and Canada	AX6-70
AX6.4-2.    Human Health Effects of Oxides of Nitrogen: CVD Hospital
            Admissions and Visits: Australia and New Zealand	AX6-85
AX6.4-3.    Human Health Effects of Oxides of Nitrogen: CVD Hospital
            Admissions and Visits: Europe	AX6-90
AX6.4-4.    Human Health Effects of Oxides of Nitrogen: CVD Hospital
            Admissions and Visits: Asia	AX6-99
AX6.5-1.    Studies Examining Exposure to Ambient NO2 and Heart Rate
            Variability as Measured by Standard Deviation of Normal-to-Normal
            Intervals (SDNN)	AX6-105
AX6.6-1.    Birth Weight and Long-Term NO2 Exposure Studies	AX6-107
AX6.6-2.    Preterm Delivery and Long-Term NO2 Exposure Studies	AX6-109
AX6.6-3.    Fetal Growth and Long-Term NO2 Exposure Studies	AX6-111
AX6.7-1.    Lung Function and Long-Term NO2 Exposure	AX6-112
AX6.7-2.    Asthma and Long-Term NO2 Exposure	AX6-114
AX6.7-3.    Respiratory Symptoms and Long-Term NO2 Exposure	AX6-118
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                                Annex List of Tables
                                      (cont'd)
Number                                                                       Page

AX6.8.      Lung Cancer	AX6-121
AX6.9.      Effects of Acute NOX Exposure on Mortality. Risk Estimates are
            Standardized for per 20 ppb 24-h Avg NO2 Increment	AX6-122
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                     Authors, Contributors, and Reviewers
Authors

Dr. Dennis J. Kotchmar (NOX Team Leader)—National Center for Environmental Assessment
(B243-01), U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Mary Ross (Branch Chief)—National Center for Environmental Assessment (B243-01),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Kathleen Belanger, Yale University, Epidemiology and Public Health, 60 College Street,
New Haven, CT 06510-3210

Dr. James S. Brown—National Center for Environmental Assessment (B243-01),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Douglas Bryant—Cantox Environmental Inc., 1900 Minnesota Court, Mississauga, Ontario
L8S IPS

Dr. Ila Cote—National Center for Environmental Assessment (B243-01), U.S. Environmental
Protection Agency, Research Triangle Park, NC 27711

Dr. Mark Frampton—Strong Memorial Hospital, 601 Elmwood Ave., Box 692, Rochester, NY
14642-8692

Dr. Janneane Gent—Yale University, CPPEE, One Church Street, 6th Floor, New Haven, CT
06510

Dr. Vic Hasselblad—Duke University, 29 Autumn Woods Drive, Durham, NC 27713

Dr. Kazuhiko Ito—New York University School of Medicine, 57 Old Forge Road, Tuxedo, NY
10987

Dr. Jee Young Kim—National Center for Environmental Assessment (B243-01),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Ellen Kirrane—National Center for Environmental Assessment (B243-01),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Thomas Luben—National Center for Environmental Assessment (B243-01),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Andrew Maier—Toxicology Excellence for Risk Assessment, 2300 Montana Avenue,
Suite 409, Cincinnati, OH 45211
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                     Authors, Contributors, and Reviewers
                                       (cont'd)
Authors
(cont'd)

Dr. Qingyu Meng—National Center for Environmental Assessment (B243-01),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Joseph Pinto—National Center for Environmental Assessment (B243-01),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Paul Reinhart—National Center for Environmental Assessment (B243-01),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. David Svendsgaard—National Center for Environmental Assessment (B243-01),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Lori White—National Center for Environmental Assessment (B243-01),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711
Contributors

Dr. Dale Allen, University of Maryland, College Park, MD

Dr. Jeffrey Arnold—National Center for Environmental Assessment (B243-01),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Ms. Louise Camalier, U.S. EPA, OAQPS, Research Triangle Park, NC

Dr. Russell Dickerson, University of Maryland, College Park, MD

Dr. Tina Fan, EOHSI/UMDNJ, Piscataway, NJ

Dr. Arlene Fiore, NOAA/GFDL, Princeton, NJ

Dr. Panos Georgopoulos, EOHSI/UMDNJ, Piscataway, NJ

Dr. Larry Horowitz, NOAA/GFDL, Princeton, NJ

Dr. William Keene, University of Virginia, Charlottesville, VA

Dr. Randall Martin, Dalhousie University, Halifax, Nova Scotia



August 2007                              xvi         DRAFT-DO NOT QUOTE OR CITE

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                     Authors, Contributors, and Reviewers
                                       (cont'd)
Contributors
(cont'd)

Dr. Maria Morandi, University of Texas, Houston, TX

Dr. William Munger, Harvard University, Cambridge, MA

Mr. Charles Piety, University of Maryland, College Park, MD

Dr. Sandy Sillman, University of Michigan, Ann Arbor, MI

Dr. Helen Suh, Harvard University, Boston, MA

Ms. Debra Walsh—National Center for Environmental Assessment (B243-01),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Charles Wechsler, EOHSI/UMDNJ, Piscataway, NJ

Dr. Clifford Weisel, EOHSI/UMDNJ, Piscataway, NJ

Dr. Jim Zhang, EOHSI/UMDNJ, Piscataway, NJ


Reviewers

Dr. Tina Bahadori—American Chemistry Council, 1300 Wilson Boulevard, Arlington, VA
22209

Dr. Tim Benner—Office of Science Policy, Office of Research and Development, Washington,
DC 20004

Dr. Daniel Costa—National Program Director for Air, Office of Research and Development,
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Robert Devlin—National Health and Environmental Effects Research Laboratory, Office of
Research and Development, U.S. Environmental Protection Agency, Chapel Hill, NC

Dr. Judy Graham—American Chemistry Council, LRI, 1300 Wilson Boulevard, Arlington, VA
22209

Dr. Stephen Graham—Office of Air and Radiation, U.S. Environmental Protection Agency,
Research Triangle Park, NC 27711


August 2007                             xvii         DRAFT-DO NOT QUOTE OR CITE

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                      Authors, Contributors, and Reviewers
                                       (cont'd)
Reviewers
(cont'd)

Ms. Beth Hassett-Sipple—U.S. Environmental Protection Agency (C504-06), Research Triangle
Park, NC 27711

Dr. Gary Hatch—National Health and Environmental Effects Research Laboratory, Office of
Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC
27711

Dr. Scott Jenkins—Office of Air Quality Planning and Standards, U.S. Environmental Protection
Agency (C504-02), Research Triangle Park, NC 27711

Dr. David Kryak—National Exposure Research Laboratory, Office of Research and
Development, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Mr. John Langstaff—U.S. Environmental Protection Agency (C504-06), Research Triangle Park,
NC27711

Dr. Morton Lippmann—NYU School of Medicine, 57 Old Forge Road, Tuxedo, NY 10987

Dr. Thomas Long—National Center for Environmental Assessment (B243-01),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Karen Martin—Office of Air and Radiation, U.S. Environmental Protection Agency
(C504-06), Research Triangle Park, NC 27711

Dr. William McDonnell—William F. McDonnell Consulting, 1207 Hillview Road, Chapel Hill,
NC27514

Dr. Dave McKee—Office of Air and Radiation/Office of Air Quality Planning and Standards,
U.S. Environmental Protection Agency (C504-06), Research Triangle Park, NC 27711

Dr. Lucas Neas—National Health and Environmental Effects Research Laboratory, Office of
Research and Development, U.S. Environmental Protection Agency, Chapel Hill, NC 27711

Dr. Russell Owen—National Health and Environmental Effects Research Laboratory, Office of
Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC
27711

Dr. Haluk Ozkaynak—National Exposure Research Laboratory, Office of Research and
Development, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711
August 2007                             xviii        DRAFT-DO NOT QUOTE OR CITE

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                     Authors, Contributors, and Reviewers
                                       (cont'd)
Reviewers
(cont'd)

Dr. Jennifer Peel—Colorado State University, 1681 Campus Delivery, Fort Collins, CO 80523-
1681

Mr. Harvey Richmond—Office of Air Quality Planning and Standards/Health and
Environmental Impacts Division, U.S. Environmental Protection Agency (C504-06), Research
Triangle Park, NC 27711

Mr. Joseph Somers—Office of Transportation and Air Quality, U.S. Environmental Protection
Agency, 2000 Traverwood Boulevard, Ann Arbor, MI 48105

Ms. Susan Stone—U.S. Environmental Protection Agency (C504-06), Research Triangle Park,
NC27711

Dr. John Vandenberg—National Center for Environmental Assessment (B243-01), Office of
Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC
27711

Dr. Alan Vette—National Exposure Research Laboratory, Office of Research and Development,
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Mr. Ron Williams—National Exposure Research Laboratory, Office of Research and
Development, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. William Wilson—Office of Research and Development, National  Center for Environmental
Assessment (B243-01), U.S. Environmental Protection Agency, Research Triangle Park, NC
27711
August 2007                              xix        DRAFT-DO NOT QUOTE OR CITE

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             U.S. Environmental Protection Agency Project Team
              for Development of Integrated Scientific Assessment
                              for Oxides of Nitrogen
Executive Direction

Dr. Ila Cote (Acting Director)—National Center for Environmental Assessment-RTF Division,
(B243-01), U.S. Environmental Protection Agency, Research Triangle Park, NC 27711
Scientific Staff

Dr. Dennis Kotchmar (NOX Team Leader)—National Center for Environmental Assessment
(B243-01), U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Jeff Arnold—National Center for Environmental Assessment (B243-01),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. James S. Brown—National Center for Environmental Assessment (B243-01),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Jee Young Kim—National Center for Environmental Assessment (B243-01),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Ellen Kirrane—National Center for Environmental Assessment (B243-01),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Tom Long—National Center for Environmental Assessment (B243-01),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Thomas Luben—National Center for Environmental Assessment (B243-01),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Quingyu Meng—National Center for Environmental Assessment (B243-01),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Joseph Pinto—National Center for Environmental Assessment (B243-01),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Paul Reinhart—National Center for Environmental Assessment (B243-01),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Mary Ross—National Center for Environmental Assessment (B243-01),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711
August 2007                             xx        DRAFT-DO NOT QUOTE OR CITE

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              U.S. Environmental Protection Agency Project Team
              for Development of Integrated Scientific Assessment
                              for Oxides of Nitrogen
                                      (cont'd)
Scientific Staff
(cont'd)

Dr. David Svendsgaard—National Center for Environmental Assessment (B243-01),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. Lori White—National Center for Environmental Assessment (B243-01),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Dr. William Wilson—National Center for Environmental Assessment (B243-01),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711
Technical Support Staff

Ms. Emily R. Lee—Management Analyst, National Center for Environmental Assessment
(B243-01), U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Ms. Christine Searles—Management Analyst, National Center for Environmental Assessment
(B243-01), U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Ms. Debra Walsh—Program Analyst, National Center for Environmental Assessment (B243-01),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

Mr. Richard Wilson—Clerk, National Center for Environmental Assessment (B243-01),
U.S. Environmental Protection Agency, Research Triangle Park, NC 27711
Document Production Staff

Ms. Barbra H. Schwartz—Task Order Manager, Computer Sciences Corporation,
2803 Slater Road, Suite 220, Morrisville, NC 27560

Mr. John A. Bennett—Technical Information Specialist, Library Associates of Maryland,
11820 Parklawn Drive, Suite 400, Rockville, MD 20852

Mrs. Melissa Cesar—Publication/Graphics Specialist, Computer Sciences Corporation,
2803 Slater Road, Suite 220, Morrisville, NC 27560
August 2007                             xxi        DRAFT-DO NOT QUOTE OR CITE

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             U.S. Environmental Protection Agency Project Team
              for Development of Integrated Scientific Assessment
                              for Oxides of Nitrogen
                                      (cont'd)
Document Production Staff
(cont'd)

Mrs. Rebecca Early—Publication/Graphics Specialist, TekSystems, 1201 Edwards Mill Road,
Suite 201, Raleigh, NC 27607

Mr. Eric Ellis—Records Management Technician, InfoPro, Inc., 8200 Greensboro Drive, Suite
1450, McLean, VA 22102

Ms. Stephanie Harper—Publication/Graphics Specialist, TekSystems, 1201 Edwards Mill Road,
Suite 201, Raleigh, NC 27607

Ms. Sandra L. Hughey—Technical Information Specialist, Library Associates of Maryland,
11820 Parklawn Drive, Suite 400, Rockville, MD 20852

Dr. Barbara Liljequist—Technical Editor, Computer Sciences Corporation, 2803 Slater Road,
Suite 220, Morrisville, NC 27560

Ms. Molly Windsor—Graphic Artist, Computer Sciences Corporation, 2803 Slater Road,
Suite 220, Morrisville, NC 27560
August 2007                             xxii        DRAFT-DO NOT QUOTE OR CITE

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                     U.S. Environmental Protection Agency
                         Science Advisory Board (SAB)
        Staff Office Clean Air Scientific Advisory Committee (CASAC)
             CASAC NOX and SOX Primary NAAQS Review Panel
Chair
Dr. Rogene Henderson*, Scientist Emeritus, Lovelace Respiratory Research Institute,
Albuquerque, NM

Members

Mr. Ed Avol, Professor, Preventive Medicine, Keck School of Medicine, University of Southern
California, Los Angeles, CA

Dr. John R. Balmes, Professor, Department of Medicine, Division of Occupational and
Environmental Medicine, University of California, San Francisco, CA

Dr. Ellis Cowling*, University Distinguished Professor At-Large, North Carolina State
University, Colleges of Natural Resources and Agriculture and Life Sciences, North Carolina
State University, Raleigh, NC

Dr. James D. Crapo [M.D.]*, Professor, Department of Medicine, National Jewish Medical and
Research Center, Denver, CO

Dr. Douglas Crawford-Brown*, Director, Carolina Environmental Program; Professor,
Environmental Sciences and Engineering;  and Professor, Public Policy, Department of
Environmental Sciences and Engineering,  University of North Carolina at Chapel Hill, Chapel
Hill, NC

Dr. Terry Gordon, Professor, Environmental Medicine, NYU School of Medicine, Tuxedo, NY

Dr. Dale Hattis, Research Professor, Center for Technology, Environment, and Development,
George Perkins Marsh Institute, Clark University, Worcester, MA

Dr. Patrick Kinney, Associate Professor,  Department of Environmental Health Sciences,
Mailman School of Public Health, Columbia University, New York, NY

Dr. Steven Kleeberger, Professor, Laboratory Chief, Laboratory of Respiratory Biology,
NIH/NIEHS, Research Triangle Park, NC

Dr Timothy Larson, Professor, Department of Civil and Environmental Engineering, University
of Washington, Seattle, WA
August 2007                             xxiii        DRAFT-DO NOT QUOTE OR CITE

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                     U.S. Environmental Protection Agency
                         Science Advisory Board (SAB)
        Staff Office Clean Air Scientific Advisory Committee (CASAC)
             CASAC NOX and SOX Primary NAAQS Review Panel
                                      (cont'd)

Members
(cont'd)

Dr. Kent Pinkerton, Professor, Regents of the University of California, Center for Health and
the Environment, University of California, Davis, CA

Mr. Richard L. Poirot*, Environmental Analyst, Air Pollution Control Division, Department of
Environmental Conservation, Vermont Agency of Natural Resources, Waterbury, VT

Dr. Edward Postlethwait, Professor and Chair, Department of Environmental Health Sciences,
School of Public Health, University of Alabama at Birmingham, Birmingham, AL

Dr. Armistead (Ted) Russell*, Georgia Power Distinguished Professor of Environmental
Engineering, Environmental Engineering Group, School of Civil and Environmental
Engineering, Georgia Institute  of Technology, Atlanta, GA

Dr. Richard Schlesinger, Associate Dean, Department of Biology, Dyson College, Pace
University, New York, NY

Dr. Christian Seigneur, Vice  President, Atmospheric and Environmental Research, Inc., San
Ramon, CA

Dr. Elizabeth A. (Lianne) Sheppard, Research Professor, Biostatistics and Environmental &
Occupational Health Sciences, Public Health and Community Medicine, University of
Washington, Seattle, WA

Dr. Frank Speizer [M.D.]*, Edward Kass Professor of Medicine, Channing Laboratory,
Harvard Medical School, Boston, MA

Dr. George Thurston, Associate Professor, Environmental Medicine, NYU School of Medicine,
New York University, Tuxedo, NY

Dr. James Ultman, Professor, Chemical Engineering, Bioengineering Program, Pennsylvania
State University, University Park, PA

Dr. Ronald Wyzga, Technical Executive, Air Quality Health and Risk, Electric Power Research
Institute, P.O. Box 10412, Palo Alto, CA
August 2007                            xxiv        DRAFT-DO NOT QUOTE OR CITE

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                    U.S. Environmental Protection Agency
                        Science Advisory Board (SAB)
        Staff Office Clean Air Scientific Advisory Committee (CASAC)
             CASAC NOX and SOX Primary NAAQS Review Panel
                                    (cont'd)


SCIENCE ADVISORY BOARD STAFF

Mr. Fred Butterfield, CASAC Designated Federal Officer, 1200 Pennsylvania Avenue, N.W.,
Washington, DC, 20460, Phone: 202-343-9994, Fax: 202-233-0643 fbutterfield.fred@epa.gov)
(Physical/Courier/FedEx Address: Fred A. Butterfield, III, EPA Science Advisory Board Staff
Office (Mail Code 1400F), Woodies Building,  1025 F Street, N.W., Room 3604, Washington,
DC 20004, Telephone: 202-343-9994)

* Members of the statutory Clean Air Scientific Advisory Committee (CASAC) appointed by the EPA
 Administrator
August 2007                            xxv       DRAFT-DO NOT QUOTE OR CITE

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                      Annex Abbreviations and Acronyms
 a
 AA
 ACCENT

 AgNOR
 AIRPEX
 AIRQUIS
 AIRS
 AM
 AMF
 AMI
 APEX
 APIMS
 AQCD
 AQEG
 ATS
 ATTILA
 BAL
 BALF
 BERLIOZ
 BHPN
 BLF
 BME
 Br
 Br
 Br2
 BrCl
 BrdU
 BrO
 C
 Cx T
 CAA
 CAPs
 CARB
 CASAC
 CB4
alpha; probability value
arachidonic acid
European Union project Atmospheric Composition Change: the
European Network of Excellence
argyrophilic nucleolar organizer region
Air Pollution Exposure (model)
Air Quality Information System (model)
Aerometric Information Retrieval System
alveolar macrophage
air mass factor
average medial thickness
Air Pollution Exposure (model)
atmospheric pressure ionization mass spectrometer
Air Quality Criteria Document
Air Quality Expert Group
American Thoracic Society
type of Lagrangian model
bronchoalveolar lavage
bronchoalveolar lavage fluid
Berlin Ozone Experiment
7V-bis(2-hydroxyl-propyl)nitrosamine
bronchial lavage fluid
Bayesian Maxim Eutropy
bromine
bromine ion
molecular bromine
bromine chloride
bromodeoxyuridine
bromine oxide
concentration
concentration  x time; concentration times duration of exposure
Clean Air Act
concentrated ambient particles
California Air Resources Board
Clean Air Scientific Advisory Committee
Carbon Bond 4 (chemical mechanism)
August 2007
                 XXVI
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 CC10
 CCN
 CD
 CD4+
 CD8+
 CDC
 CEPEX
 CFD
 CG
 cGMP
 CH4
 C5H8
 CHAD
 CH3-CHO
 CH3CH(O)OONO2
 CH3CN
 CH3-C(O)
 CH3-C(O)H
 CH3C(O)O
 CH3-C(0)02,
 CH3-C(O)OO
 CH3OOH
 (CH3)2S
 CH3-S-H
 CH3S03H
 CH3-S-S-CH3
 Cl
 cr
 CLaMS
 C1NO2
 C1NO3
 CMAQ
 CMAQ
 CMSA
 CO
 COD
Clara cell 10-kDa protein
cyanomethylidyne radical
criteria document
helper T lymphocyte
suppressor T lymphocyte
Centers for Disease Control and Prevention
Central Equatorial Pacific Experiment
Computational Fluid Dynamics
cloud-to-ground (flash)
cyclic guanosine-3',5'-monophosphate
methane
ethene
ethane
isoprene
Consolidated Human Activities Database
acetaldehyde
peroxyacetyl nitrate
acetonitrile
acetyl radical
acetaldehyde
peroxyacetyl radical
acetyl peroxy, peroxyacetyl

methyl hydroperoxide
dimethylsulfide
methyl mercaptan
methanesulfonic acid
dimethyl disulfide
chorine
chorine ion
type of Lagrangian model
nitryl chloride
chlorine nitrate
Community Model for Air Quality;
Community Multiscale Air Quality (model)
consolidated metropolitan statistical area
carbon monoxide
coefficient of divergence
August 2007
                 XXVll
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 COPD
 CPBM
 CS2
 CTM
 DEP
 DEPcCBP
 DL
 DMN
 DMSO
 DNA
 DNS
 DOAS
 DU
 EC
 ECRHS
 EDMAS
 EDXRF
 EE
 eGPx
 ELF
 EMD
 EPA
 ER
 ESR
 ETS
 EXPOLIS

 FEVi
 FL
 FLEXPART
 FPD
 FT
 FTIR
 FVC
 FW2
 yGCS
 yGT
 yN205
chronic obstructive pulmonary disease
Canyon Plume-Box Model
carbon disulfide
chemistry transport model
diesel exhaust particulates
diesel exhaust particulates extract-coated carbon black particles
detection limit
dimethylnitrosamine
dimethylsulfoxide
deoxyribonucleic acid
Direct Numerical Simulation
differential optical absorption spectroscopy
Dob son units
molecular carbon
European Community Respiratory Health Survey
Exposure and Dose Modeling and Analysis System
energy dispersive X-ray fluorescence
energy expenditure
extracellular glutathione peroxidase
epithelial lining fluid
Ecole des Mines de Douai (laboratory)
U.S. Environmental Protection Agency
emergency room
electron spin resonance (spectroscopy)
environmental tobacco smoke
Air Pollution Exposure Distributions of Adult Urban Populations in
Europe
forced expiratory volume in 1 second
fluoranthene
type of Lagrangian model
flame photometric detection
free troposphere
Fourier Transform Infrared Spectroscopy
forced vital capacity
black carbon soot model
gamma-glutamylcysteine  synthetase
glutamyltranspeptidase
uptake coefficient for N2O5
August 2007
                 XXVlll
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 GC/ECD
 GEE
 GEOS-CHEM

 GEOS-1 DAS
 GIS
 GMP
 GOME
 GS
 GSH
 GSSG
 GST
 H+
 H2
 HAPEM
 HCHO
 HC1
 HCN
 HCs
 HEADS
 5-HETE
 HNO3
 HNO4
 H02
 H202
 HOBr
 HOC1
 HONO, HNO2
 HO2NO2
 HOX
 H2S
 HSO3
 HSO3
 HSO4
 H2SO4
 hv
 I
 I2
gas chromatography-electron capture detection
Generalized Estimating Equations
three-dimensional model of atmospheric composition driven by
assimilated Goddard Earth Orbiting System observations
NASA Goddard Earth Orbiting System Data Assimilation System
Geographic Information System
guanosine-3',5'-monophosphate
Global Ozone Monitoring Instrument
glutathione synthetase
glutathione; reduced glutathione
oxidized glutathione; glutathione disulfide
glutathione S-transferase (e.g., GST Ml, GST PI, GST Tl)
hydrogen ion
molecular hydrogen; hydrogen gas
Hazardous Air Pollutant Exposure Model
formaldehyde
hydrochloric acid
hydrogen cyanide
hydrocarbons
Harvard-EPA Annular Denuder System
5-hydroxyeicosatetraenoic acid
nitric acid
pernitric acid
hydroperoxyl; hydroperoxy radical
hydrogen peroxide
hypobromous acid
hypochlorous  acid
nitrous acid
peroxynitric acid
hypohalous acid
hydrogen sulfide
hydrogen sulfite ion
hydrogen sulfite
bisulfate ion
sulfuric acid
solar ultraviolet photon
iodine
molecular iodine
August 2007
                  XXIX
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 IBEM
 1C
 ICAM-1
 ICARTT

 Ig
 IIASA
 IL
 IMPROVE
 INDAIR
 IN03
 INTEX-NA

 IQR
 JPL
 Ka
 KH
 KH
 Kw
 LDH
 LES
 LIF
 LP
 LPG
 LT
 LWC
 M
 MAQSIP
 MAX
 MBL
 MCM
 MEM
 MENTOR-1A
 MET
 MgO
 MIESR
 MM5

 MOBILE6
Individual Based Exposure Models
intracloud (flash); ion chromatography
intercellular adhesion molecule-1
International Consortium for Atmospheric Research on Transport and
Transformation
immunoglobulin (e.g., IgA, IgE, IgG)
International Institute for Applied Systems Analysis
interleukin (e.g., IL-1, IL-6, IL-8)
Interagency Monitoring of Protected Visual Environments
(model)
iodine nitrate
NASA Intercontinental Chemical Transport Experiment - North
America
interquartile range
Jet Propulsion Laboratory
acid dissociation constant in M
Henry's Law constant in M atm"1
potassium hydride
ion product of water
lactic acid dehydrogenase
Large Eddy Simulation
laser-induced fluorescence
long-path
liquified propane gas
leukotriene (e.g., LTB4, LTC4, LTD4, LTE4)
liquid water content
air molecule
Multiscale Air  Quality Simulation Platform
multi axis
marine boundary layer
master chemical mechanism
model ensemble mean
Modeling Environment for Total Risk for One-Atmosphere studies
metabolic equivalent of work
magnesium oxide
matrix isolation electron spin resonance (spectroscopy)
National Center for Atmospheric Research/Penn State Mesoscale
Model
Highway Vehicle Emission Factor Model
August 2007
                  XXX
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 MoOx
 MOZART-2
 MPAN
 mRNA
 MSA
 15N
 N
 N, n
 NA, N/A, N.A.
 NAAQS
 Na2CO3
 NADP
 NADPH
 NaHCO3
 NARSTO
 NASA
 NCAR
 NDMA
 NEM
 NERL
 2NF
 NH2
 NH3
 NH4+
 NH4C1
 NHLBI
 NH4NO3
 (NH4)2SO4
 NIST
 NK
 NMHCs
 NMOCs
 NMOR
 NO
 NO2
 NO2
 NO3
 NO3
molybdenum oxide
(model)
peroxymethacryloyl nitrate; peroxy-methacrylic nitric anhydride
messenger ribonucleic acid
metropolitan statistical area
nitrogen-15 radionuclide
nitrogen
number of observations
not available
National Ambient Air Quality Standards
sodium carbonate
National Atmospheric Deposition Program
reduced nicotinamide adenine dinucleotide phosphate
sodium bicarbonate
North American Regional Strategy for Atmospheric Ozone
National Aeronautics and Space Administration
National Center for Atmospheric Research
7V-nitrosodimethylamine
National Ambient Air Quality Standards Exposure Model
National Exposure Research Laboratory
2-nitrofluoranthene
amino
ammonia
ammonium ion
ammonium chloride
U.S. National Heart,  Lung and Blood Institute
ammonium nitrate?
ammonium sulfate
National Institute of Standards and Technology
natural killer (lymphocytes)
nonmethane hydrocarbons
nonmethane organic compounds
7V-nitrosomorpholine
nitric oxide
nitrogen dioxide
nitrite
nitrate (radical)
nitrate
August 2007
                  XXXI
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 N205
 NOX
 NOy
 NOZ
 NP
 1NP
 NPAHs
 NR
 NR, N.R., N/R
 NRC
 NSA
 nss
 NTRMs
 16Q
 03
 OAQPS
 OC
 OCS
 OC'D)
 OH
 OMI
 0(3P)
 OPE
 OSPM
 Ox
 P(HN03)
 P,P
 P9o
 PAHs
 PAMS, PAMs
 PAN
 Pa02
 PAQSMs
 PAR
 PBEM
 PIXE
 PM
dinitrogen pentoxide
nitrogen oxides; oxides of nitrogen
sum of NOX and NOZ; odd nitrogen species
oxides of nitrogen and nitrates; difference between NOy and NOX
national park
1-nitropyrene
nitro polycyclic aromatic hydrocarbons
data not relevant
not reported
National Research Council
nitrosating agent
non-sea-salt
NIST Traceable Reference Materials
oxygen-16 radionuclide
ozone
Office of Air Quality Planning and Standards
organic carbon
carbonyl sulfide
electronically excited oxygen atom
hydroxyl radical
Ozone Monitoring Instrument
ground-state oxygen atom
ozone production efficiency
Danish Operational Street Pollution Model
odd oxygen species; total oxidants
particulate nitrate
probability value
values of the 90th percentile absolute difference in concentrations
polycyclic aromatic hydrocarbons
Photochemical Aerometric Monitoring System
peroxyacetyl nitrate; peroxyacyl nitrate
partial pressure of arterial oxygen
photochemical air quality simulation models
proximal alveolar region
Population Based Exposure Models
particle induced X-ray emission
particulate matter
combination of coarse and fine particulate matter
August 2007
                  xxxn
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 PMiQ-2.5
 PM2.5
 PMA
 PM-CAMx

 PMN
 PMT
 pNEM
 POM
 ppb
 ppbv
 ppm x h
 ppm
 PPN
 ppt
 pptv
 PRB
 psi
 PTEAM
 PTEP
 PTFE
 PY
 r
 R2
 RACM
 RADM
 RAMs
 RANS
 RAPS
 RBC
 RCS
 RDBMS
 REHEX
 RH
 RIOPA
 RMR
 RNO2
 RO2
coarse particulate matter
fine particulate matter
phorbol myri state acetate
Particulate Matter Comprehensive Air Quality Model with
Extensions
polymorphonuclear leukocytes
photomultiplier tube
Probabilistic National Ambient Air Quality Standard Exposure Model
particulate organic matter
parts per billion
parts per billion by volume
parts per million x hours
parts per million
peroxypropionyl nitrate; peroxypropionic nitric anhydride
parts per trillion
parts per trillion by volume
policy relevant background
pounds per square inch
Particle Total Exposure Assessment Methodology (study)
PMio Technical Enhancement Program
polytetrafluoroethylene (Teflon)
pyrene
correlation coefficient
coefficient of determination
Regional Air Chemistry Mechanism
Regional Acid Deposition Model
Regional Atmospheric Modeling System
Reynolds Averaged Numerical Simulation
Regional Air Pollution Study
red blood cell
Random Component Superposition (model)
Relational Database Management Systems
Regional Human Exposure Model
relative humidity
Relationship of Indoor, Outdoor, and Personal Air (study)
resting metabolic rate
nitro compounds
organic peroxyl; organic peroxy
August 2007
                 XXXlll
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 RONO2
 ROONO2, RO2NO2
 ROS
 rP
 rs
 RSD
 G
 34§
 S2*
 S20
 SAPALDIA
 SCE
 SCIAMACHY

 SCOS97
 SGV
 SHEDS
 SMOKE
 SO
 SO2
 S03
 SOA
 SONEX
 SOS
 SP
 SRM
 STE
 STEP
 STN
 STPD
 STREET
 STRF
 T
 T
 TAR
 TEA
 TOLAS
 TEA
organic nitrate
peroxy nitrate
reactive oxygen species
Pearson correlation coefficient
Spearman rank correlation coefficient
relative standard deviation
sigma; standard deviation
sulfur-34 radionuclide
electronically excited sulfur molecules
disulfur monoxide
Study of Air Pollution and Lung Diseases in Adults
sister chromatid exchange
Scanning Imaging Absorption Spectrometer for Atmospheric
Chartography
1997 Southern California Ozone Study
subgrid variability
Simulation of Human Exposure and Dose System
Spare-Matrix Operator Kernel Emissions (system)
sulfur monoxide
sulfur dioxide
sulfur trioxide
secondary organic aerosol
Subsonic Assessment Ozone and Nitrogen Oxides Experiment
Southern Oxidant Study
surfactant protein (e.g., SP-A, SP-D)
standard reference material
stratospheric-tropospheric  exchange
Stratospheric-Tropospheric-Exchange Proj ect
Speciation Trends Network
standard temperature and pressure, dry
type of street canyon model
Spatio-Temporal Random Field (theory)
tau; atmospheric lifetime
time; duration of exposure
Third Assessment Report
thiobarbituric acid
tunable-diode laser absorption spectroscopy
triethanolamine
August 2007
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 TexAQS
 Tg
 THEES
 TNF
 TOR
 Torr
 TRACE-P
 TTFMS
 TVOCs
 TX
 UAM
 UMD-CTM
 UV
 VE
 VESTA
 VOC
 VT
 WHO
 XRF
Texas Air Quality Study
teragram
Total Human Environmental Exposure Study
tumor necrosis factor (e.g., TNF-a)
thermal-optical reflectance
unit of pressure
Transport and Chemical Evolution over the Pacific
two-tone frequency-modulated spectroscopy
total volatile organic compounds
thromboxane (e.g., TXA2, TXB2)
Urban Airshed Model
University of Maryland Chemical Transport Model
ultraviolet
total ventilation rate
Five (V) Epidemiological Studies on Transport and Asthma
volatile organic compound
tidal volume
World Health  Organization
X-ray fluorescence
August 2007
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 i            AX1.  CHAPTER 1 ANNEX - INTRODUCTION
 2
 O
 4          The draft Annexes are prepared in support of the draft Integrated Science Assessment for
 5    Oxides of Nitrogen - Health Criteria (EPA/600/R-07/093).  The Integrated Science Assessment
 6    (ISA) presents a concise synthesis of the most policy-relevant science to form the scientific
 7    foundation for the review of the primary (health-based) national ambient air quality standards
 8    (NAAQS) for nitrogen dioxide (NO2).  This series of Annexes provide more extensive and
 9    detailed summaries of the most pertinent scientific literature.  The Annexes identify, evaluate,
10    and summarize scientific research in the areas of atmospheric sciences, air quality analyses,
11    exposure assessment, dosimetry, controlled human exposure studies, toxicology, and
12    epidemiology, focusing on studies relevant to the review of the primary NAAQS.
13          These draft Annexes are organized by scientific study areas and include research that is
14    relevant to  the key policy questions discussed previously to provide an evidence base supporting
15    the development of the ISA, risk, and exposure assessments. In Annex 1, we provide legislative
16    background and history of previous reviews of the NAAQS for oxides of nitrogen.  In Annex 2,
17    we present evidence related to the physical and chemical processes controlling the production,
18    destruction, and levels of reactive nitrogen compounds in the atmosphere, including both
19    oxidized and reduced species. Annex 3 presents information on environmental concentrations,
20    patterns, and human exposure to ambient oxides of nitrogen; however, most information relates
21    to NC>2. Annex 4 presents results from toxicological studies as well as information on dosimetry
22    of oxides of nitrogen.  Annex 5 discusses results from controlled human exposure studies, and
23    Annex 6 discusses evidence from epidemiological studies. These Annexes include more detailed
24    information on health or exposure studies that is summarized in tabular form, as well as more
25    extensive discussion of atmospheric chemistry, source, exposure, and dosimetry information.
26    Annex tables for health studies are generally organized to include information  about
27    (1) concentrations of oxides of nitrogen levels or doses and exposure times, (2) description of
28    study methods employed, (3) results and comments, and (4) quantitative outcomes for oxides of
29    nitrogen measures.
30
31
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 1    AX1.1     LEGISLATIVE REQUIREMENTS
 2           Two sections of the Clean Air Act (CAA) govern the establishment and revision of the
 3    national ambient air quality standards (NAAQS). Section 108 (U.S. Code, 2003a) directs the
 4    Administrator to identify and list "air pollutants" that "in his judgment, may reasonably be
 5    anticipated to endanger public health and welfare" and whose "presence in the ambient air results
 6    from numerous or diverse mobile or stationary sources" and to issue air quality criteria for those
 7    that are listed. Air quality criteria are intended to "accurately reflect the latest scientific
 8    knowledge useful in indicating the kind and extent of identifiable effects on public health or
 9    welfare which may  be expected from the presence of [a] pollutant in ambient air."
10           Section  109 (U.S. Code, 2003b) directs the Administrator to propose and promulgate
11    "primary" and "secondary" NAAQS for pollutants listed under Section 108. Section 109(b) (1)
12    defines a primary standard as one "the attainment and maintenance of which in the judgment of
13    the Administrator, based on such criteria and allowing an adequate margin of safety, are requisite
14    to protect the public health."1  A secondary standard, as defined in Section 109(b)(2), must
15    "specify a level of air quality the attainment and maintenance of which, in the judgment of the
16    Administrator, based on such criteria, is required to protect the public welfare from any known
17    or anticipated adverse effects associated with the presence of [the] pollutant in the ambient air."2
18           The requirement that primary standards include an adequate margin of safety was
19    intended to address uncertainties associated with inconclusive scientific and technical
20    information available at the time of standard setting.  It was also intended to provide a reasonable
21    degree of protection against hazards that research has not yet identified. See Lead Industries
22    Association v. EPA, 647 F.2d 1130, 1154 (D.C.  Cir 1980), cert, denied, 449 U.S. 1042 (1980);
23    American Petroleum Institute v. Costle, 665 F.2d 1176,  1186 (D.C. Cir. 1981), cert, denied,
24    455 U.S. 1034(1982).  Both kinds of uncertainties are components of the risk associated with
25    pollution at levels below those at which human health effects can be said to occur with
      1 The legislative history of Section 109 indicates that a primary standard is to be set at "the maximum permissible
       ambient air level ... which will protect the health of any [sensitive] group of the population" and that, for this
       purpose, "reference should be made to a representative sample of persons comprising the sensitive group rather
       than to a single person in such a group" [U.S. Senate (1970)].
      2 Welfare effects as defined in Section 302(h) [U.S. Code, 2005)] include, but are not limited to, "effects on soils,
       water, crops, vegetation, man-made materials, animals, wildlife, weather, visibility and climate, damage to and
       deterioration of property, and hazards to transportation, as well as effects on economic values and on personal
       comfort and well-being."
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 1    reasonable scientific certainty. Thus, in selecting primary standards that include an adequate
 2    margin of safety, the Administrator is seeking not only to prevent pollution levels that have been
 3    demonstrated to be harmful but also to prevent lower pollutant levels that may pose an
 4    unacceptable risk of harm, even if the risk is not precisely identified as to nature or degree.
 5           In selecting a margin of safety, the U.S.  Environmental Protection Agency (EPA)
 6    considers such factors as the nature and severity of the health effects involved, the size of
 7    sensitive population(s) at risk, and the kind and degree of the uncertainties that must be
 8    addressed. The selection of any particular approach to providing an adequate margin of safety is
 9    a policy choice left specifically to the Administrator's judgment.  See Lead Industries
10    Association v. EPA,  supra, 647 F.2d at 1161-62.
11           In setting standards that are "requisite" to protect public health and welfare, as provided
12    in Section 109(b), EPA's task is to establish standards that are neither more nor less stringent
13    than necessary for these purposes. In so doing,  EPA may not consider the costs of implementing
14    the standards. See generally Whitman v. American Trucking Associations, 531 U.S. 457,
15    465-472, and 475-76 (U.S. Supreme Court, 2001).
16           Section 109(d)(l) requires that "not later than December 31, 1980, and at 5-year intervals
17    thereafter, the Administrator shall complete a thorough review of the criteria published under
18    Section 108 and the national ambient air quality standards and shall make such revisions in such
19    criteria and standards and promulgate such new standards as may be appropriate ...."  Section
20    109(d)(2) requires that an independent scientific review committee "shall complete a review of
21    the criteria ... and the national primary and secondary ambient air quality standards ... and shall
22    recommend to the Administrator any new standards and revisions of existing criteria and
23    standards as may be appropriate ...."  Since the early 1980s, this independent review function
24    has been performed by the Clean Air Scientific  Advisory Committee (CAS AC) of EPA's
25    Science Advisory Board.
26
27
28    AX1.2     HISTORY OF REVIEWS OF THE PRIMARY NAAQS FOR NO2
29           On April 30,  1971, EPA promulgated identical primary and secondary NAAQS for
30    nitrogen dioxide (NC^), under Section 109 of the Act, set at 0.053 parts per million (ppm),
31    annual  average (Federal Register, 1971). In 1982, EPA published Air Quality Criteria for
32    Oxides of Nitrogen (1982 NOX AQCD) (U.S. Environmental Protection Agency, 1982), which

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 1   updated the scientific criteria upon which the initial NC>2 standards were based.  On February 23,
 2   1984, EPA proposed to retain these standards (Federal Register, 1984). After taking into account
 3   public comments, EPA published the final decision to retain these standards on June 19, 1985
 4   (Federal Register, 1985).
 5          On July 22, 1987, EPA announced that it was undertaking plans to revise the 1982 NOX
 6   air quality criteria (Federal Register, 1987). In November 1991, EPA released an updated draft
 7   air quality criteria document (AQCD) for CASAC and public review and comment (Federal
 8   Register,  1991). The draft document provided a comprehensive assessment of the available
 9   scientific  and technical information on heath and welfare effects associated with NO2 and other
10   oxides of nitrogen. The CASAC reviewed the document at a meeting held on July 1, 1993, and
11   concluded in a closure letter to the Administrator that the document "provides a scientifically
12   balanced and defensible summary of current knowledge of the effects of this pollutant and
13   provides an adequate basis for EPA to make a decision as to the appropriate NAAQS for NCV
14   (Wolff, 1993).
15          The EPA also prepared a draft Staff Paper that summarized and integrated the key studies
16   and scientific evidence contained in the revised AQCD and identified the critical elements to be
17   considered in the review of the NO2 NAAQS.  The Staff Paper received external review at a
18   December 12, 1994 CASAC meeting. CASAC comments and recommendations were reviewed
19   by EPA staff and incorporated into the final draft of the Staff Paper as appropriate.  CASAC
20   reviewed  the final draft of the Staff Paper in June 1995 and responded by written closure letter
21   (Wolff, 1995).  In September of 1995, EPA finalized the document entitled, "Review of the
22   National Ambient Air Quality Standards for Nitrogen Dioxide Assessment of Scientific and
23   Technical Information" (U.S. Environmental Protection Agency, 1995).
24          Based on that review, the Administrator announced her proposed decision not to revise
25   either the primary or the secondary NAAQS for NO2 (Federal Register, 1995). The decision not
26   to revise the NO2 NAAQS was finalized after careful evaluation of the comments received on the
27   proposal.  The level for both the existing primary and secondary NAAQS for NO2 is 0.053 ppm
28   annual arithmetic average, calculated as the arithmetic mean of the 1-h NO2 concentrations.
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 1   AX1.3   REFERENCES
 2
 3   Federal Register. (1971) National primary and secondary ambient air quality standards. F. R.
 4          (April 30) 36: 8186-8201.
 5   Federal Register. (1984) Proposed reaffirmation of the National Ambient Air Quality Standards
 6          for Nitrogen Dioxide. F. R. 49 (February 23): 6866-6879.
 7   Federal Register. (1985) Retention of the national ambient air quality standards for nitrogen
 8          dioxide: final rule. F. R. (June 19) 50:  25,532-25,545.
 9   Federal Register. (1987) Air quality criteria for carbon monoxide; air quality criteria for oxides
10          of nitrogen. F. R. 52 (July 22): 27580.
11   Federal Register. (1991) Draft criteria document for oxides of nitrogen. F. R. 56 (November 25):
12          59285.
13   Federal Register. (1995) National ambient air  quality standards for nitrogen dioxide: proposed
14          decision. F. R. 60 (October 11): 52874-52889.
15   U.S. Code. (2003a) Clean Air Act, §108, air quality criteria and control techniques. U. S. C. 42:
16          §7408.
17   U.S. Code. (2003b) Clean Air Act, §109, national ambient air quality standards. U. S. C. 42:
18          §7409.
19   U.S. Code. (2005) Clean Air Act, §302, definitions. U. S. C.  42: §7602(h).
20   U.S. Court of Appeals for the District of Columbia. (1980) Lead Industries v. U.S.
21          Environmental Protection Agency. 647 F2d 1130, 1154 (DC Cir. 1980).
22   U.S. Court of Appeals for the District of Columbia. (1981) American Petroleum Institute v.
23          Costle. 665 F2d 1176,  1186 (DC Cir. 1981).
24   U.S. Environmental Protection Agency. (1982) Air quality criteria for oxides of nitrogen.
25          Research Triangle Park, NC: Office of Health and Environmental Assessment,
26          Environmental Criteria and Assessment Office; EPA report no. EPA-600/8-82-026.
27          Available from: NTIS, Springfield, VA; PB83-131011.
28   U.S. Environmental Protection Agency. (1995) Review of the national ambient air quality
29          standards for nitrogen dioxide: assessment of scientific and technical information.
30          Research Triangle Park, NC: Office of Air Quality Planning and Standards; report no.
31          EPA/452/R-95-005.
32   U.S. Senate. (1970) National Air Quality Standards Act of 1970: report of the Committee on
33          Public Works, United States Senate together with individual views to accompany S.
34          4358. Washington, DC: Committee on Public Works; report no. CONG/91-1196.
35   U.S. Supreme Court. (2001) Whitman v. American Trucking Association. 531  U.S. 457 (nos. 99-
36          1257 and 99-1426).
37   Wolff, G. T. (1993)  On a NOx-focused control strategy to reduce O3. J. Air Waste Manage.
38          Assoc. 43: 1593-1596.
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1   Wolff, G. T. (1996) Closure by the Clean Air Scientific Advisory Committee (CASAC) on the
2          staff paper for parti culate matter [letter to Carol M. Browner, Administrator, U.S. EPA].
3          Washington, DC: U.S. Environmental Protection Agency, Clean Air Scientific Advisory
4          Committee; EPA-SAB-CASAC-LTR-96-008; June 13.
5
6
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 i            AX2.  CHAPTER 2 ANNEX-ATMOSPHERIC
 2       CHEMISTRY OF NITROGEN AND SULFUR OXIDES
 o
 4
 5   AX2.1   INTRODUCTION
 6          Nitrogen oxides (NOX) along with volatile organic compounds (VOCs) including
 7   anthropogenic and biogenic hydrocarbons, aldehydes, etc. and carbon monoxide (CO) serve as
 8   precursors in the formation of ozone (O3) and other elements of photochemical smog. Nitrogen
 9   oxides are defined here as nitric oxide (NO) and nitrogen dioxide (NO2), the latter of which is a
10   U.S. EPA Criteria Air Pollutant; similarly, oxides of sulfur (SOX) are defined here to be sulfur
11   monoxide (SO), sulfur dioxide (802), the largest component of SOX and also a U.S. EPA Criteria
12   Air Pollutant, and sulfur trioxide (SO3).  SO3 rapidly reacts with water vapor to form H2SO4, and
13   only SO2 is present in the atmosphere at detectable levels.
14          Nitrogen dioxide is an oxidant and can further react to form other photochemical
15   oxidants, in particular the organic nitrates, including peroxy acetyl nitrates (PAN) and higher
16   PAN analogues. It can also react with toxic compounds such as poly cyclic aromatic
17   hydrocarbons (PAHs) to form nitro-PAHs, which may be even more toxic than the precursors.
18   Nitrogen dioxide together with sulfur dioxide (802), another U.S. EPA criteria air pollutant, can
19   be oxidized to the strong mineral acids, nitric acid (HNO3) and sulfuric acid (H2SO4), which
20   contribute to the acidity of cloud, fog, and rainwater, and can form ambient particles.
21          The role of NOX in O3 formation was reviewed in Chapter 2 (Section 2.2) of the latest
22   AQCD for Ozone and Other Photochemical Oxidants (U.S. Environmental Protection Agency,
23   2006 CD06), and in numerous texts (e.g., Seinfeld and Pandis, 1998; Jacob, 2000; Jacobson,
24   2002). Mechanisms for transporting O3 precursors, the factors controlling the efficiency of O3
25   production from NOX, methods for calculating O3 from its precursors, and methods for
26   measuring NOX were all reviewed in Section 2.6 of CD06.  The  main points from those
27   discussions in CD06 and updates, based on new materials will be presented here. Ammonia
28   (NH3) is included here because its oxidation can be a source of NOX, and it is a precursor for
29   ammonium ions (NH4+), which play a key role in  neutralizing acidity in ambient particles and in
30   cloud, fog, and rain water. Ammonia is also involved in the ternary nucleation of new particles,
31   and it reacts with gaseous HNO3 to form ammonium nitrate (NH4NO3), which is a major
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 1    constituent of ambient Parti culate Matter (PM) in many areas.  Ammonia is also involved in over
 2    nitrification of aqueous and terrestrial ecosystems and participates in the N cascade (Galloway
 3    et al., 2003)
 4          The atmospheric chemistry of NOX is discussed in Section AX2.2, and of SC>2 in Section
 5    AX2.3. Mechanisms for the formation of aqueous-phase sulfate (SC>42 ) and nitrate (NOs ) are
 6    reviewed in Section AX2.4. Sources and emissions of NOX, NHa, and SC>2 are discussed in
 7    Section AX2.5. Modeling methods used to calculate the atmospheric chemistry, transport, and
 8    fate of NOX and 862 and their oxidation products are presented in Section AX2.6. Measurement
 9    techniques for the nitrogen-containing compounds and for 862, nitrates, sulfates, and ammonium
10    ion are discussed in Section AX2.8. Estimates of policy-relevant background concentrations of
1 1    NOX and SOX are given in Section AX2.9.  An overall review of key points in this chapter is
12    given in Section AX2. 1 1 .
13          The overall chemistry of reactive nitrogen compounds in the atmosphere is summarized
14    in Figure AX2-1 and is described in greater detail in the following sections. Nitrogen oxides are
15    emitted primarily as NO with smaller quantities of NC>2. Emissions of NOX are spatially
16    distributed vertically with some occurring at or near ground level and others aloft as indicated in
17    Figure AX2-1 .  Because of atmospheric chemical reactions, the relative abundance of different
18    compounds contributed by different sources varies with location. Both anthropogenic and
19    natural (biogenic) processes emit NOX. In addition to gas phase reactions, multiphase processes
20    are important for forming aerosol-phase pollutants, including aerosol
21
22
23   AX2.2    CHEMISTRY OF NITROGEN OXIDES IN THE TROPOSPHERE
24
25   AX2.2.1   Basic Chemistry
26          There is a rapid photochemical cycle in the troposphere that involves photolysis of NC>2
27   by solar UV-A radiation to yield NO and a ground-state oxygen atom, O(3P):

2g                                N02 + hv -> NO + 0(-lP)5                       (AX2_1}
29   This ground-state oxygen atom can then combine with molecular oxygen (©2) to form Os; and,
30   colliding with any molecule from the surrounding air (M = N2, C>2, etc), the newly formed Os
3 1   molecule, transfers excess energy and is stabilized:

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     Hit
                                                      Long range transport to remote
                                                      regions at low  temperatures
                                                                 nitro-PAHs
                                                                 R-G=C-lt
                                                                   nitrosamines,
                                                                   nitro-phenols,
                                                                   quinones, etc.
                                                               RO.
                                                              •	2_^,RONO
                                                                       deposition
                                                 emissions
    Figure AX2-1.
                   Schematic diagram of the cycle of reactive nitrogen species in the
                   atmosphere. MPP refers to multi-phase process; hv to a photon of
                   solar energy.
2
3
4

5
6
7
                            O(3P) + O2 + M-*O3 + M,

where M = N2, O2. Reaction AX2-2 is the only significant reaction forming Os in the
troposphere.
      NO and Os react to reform NO2:
                                                                                 (AX2-2)
                               NO+O3   , .,^  . V£.                        (AX2-3)
Reaction AX2-3 is responsible for O3 decreases and NO2 increases found near sources of NO
(e.g., highways), especially at night when the actinic flux is 0.  Oxidation of reactive VOCs leads
to the formation of reactive radical species that allow the conversion of NO to NO2 without the
participation of Os (as in Reaction AX2-3):
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                                                                                   (AX2-4)
 2          Ozone, therefore, can accumulate as NO2 photolyzes as in Reaction AX2-1, followed by
 3   Reaction AX2-2.  Specific mechanisms for the oxidation of a number of VOCs were discussed in
 4   the O3 AQCD (U.S. Environmental Protection Agency, 2006).
 5          It is often convenient to speak about families of chemical species defined in terms of
 6   members that interconvert rapidly among themselves on time scales that are shorter than those
 7   for formation or destruction of the family as a whole. For example, an "odd oxygen" (Ox) family
 8   can be defined as

 9                             Ox =         + 0('D) + Q3 + N02)
10   In much the same way, NOX is sometimes referred to as "odd nitrogen". Hence, we see that
1 1   production of Ox occurs by the schematic Reaction AX2-4, and that the sequence of reactions
12   given by reactions AX2-1 through AX2-3 represents no net production of Ox. Definitions of
13   species families and methods for constructing families are discussed in Jacobson (1999) and
14   references therein. Other families that include nitrogen-containing species (and which will be
1 5   referred to later in this chapter) include:
24
25
17   One can then see that production of Ox occurs by the schematic Reaction AX2-4, and that the
18   sequence of reactions given by reactions AX2-1 through AX2-3 represents no net production of
19   Ox. Definitions of species families and methods for constructing families are discussed in
20   Jacobson (1999) and references therein. Other families that include nitrogen-containing species,
21   and which will be referred to later in this chapter, are:  (which is the sum of the products of the
22   oxidation of NOX)

        NOZ = I (HNO3 + HNO4 + NO 3 + 2NO2OS + PAN(CH3CHO - OO - NO2) + other
23      organic mitmties + halogen nitrates + partieulate nitrate);
                                  NOy = NOX + NOZ +
                                             =
                                           x
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            The reaction of NO2 with O3 leads to the formation of N(V radical,
 2                                                          .                        (AX2.5)

 3   However, because the NOs radical photolyzes rapidly (lifetime of ~5 s during the
 4   photochemically most active period of the day around local solar noon (Atkinson et al., 1992a),
                                                                                   (AX2.6a)

 6                                                                                 (AX2-6b)
 7    its concentration remains low during daylight hours, but can increase after sunset to nighttime
 8    concentrations of <5 x 107 to 1  x 1010 molecules cm"3 (<2 to 430 parts per trillion (ppt)) over
 9    continental areas influenced by anthropogenic emissions of NOX (Atkinson et al., 1986). At
10    night, NO3, rather than the hydroxyl radical (OH), is the primary oxidant in the system.
1 1          Nitrate radicals can combine with NO2 to form dinitrogen pentoxide (N2Os):

12                                 NO 3  + N02 *-^*N205                      (AX2_?)

13    and N2Os both photolyzes and thermally decomposes back to NO2 and NOs during the day;
14    however, N2O5 concentrations ([N2O5]) can accumulate during the night to parts per billion (ppb)
15    levels in polluted urban atmospheres.
16          The tropospheric chemical removal processes for NOX include reaction of NO2 with the
17    OH radical and hydrolysis of N2Os in aqueous aerosol solutions if there is no organic  coating.
18    Both of these reactions produce
19                                                                                  (AX2.g)
20                                    '^"^         ,-,-j                         (AX2-9)
21          The gas-phase reaction of the OH radical with NO2 (Reaction AX2-8) initiates one of the
22    major and ultimate removal processes for NOX in the troposphere.  This reaction removes OH
23    and NO2 radicals and competes with hydrocarbons for OH radicals in areas characterized by high
24    NOX concentrations, such as urban centers  (see Section AX2.2.2).  The timescale (T) for


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 1    conversion of NOX to HNOs in the planetary boundary layer at 40 N latitude ranges from about
 2    4 hours in July to about 16 hours in January.  The corresponding range in T at 25 N latitude is
 3    between 4 and 5 hours, while at 50 N latitude, HNO3 T ranges from about 4 to 20 hours (Martin
 4    et al., 2003).  In addition to gas-phase HNOs, Golden and Smith (2000) have shown on the basis
 5    of theoretical studies that pernitrous acid (HOONO) is also produced by the reaction of NC>2 and
 6    OH radicals.  However, this channel of production most likely represents a minor yield
 7    (approximately 15% at the surface) (Jet Propulsion Laboratory, 2003). Pernitrous acid will also
 8    thermally decompose and can photolyze.  Gas-phase HNOs formed from Reaction AX2-8
 9    undergoes wet and dry deposition to the surface, and uptake by ambient aerosol particles.
10    Reaction AX2-8 limits NOX T to a range of hours to days.
11          In addition to the uptake of HNO3 on particles and in cloud drops, it photolyzes and
12    reacts with OH radicals via
13                                  *"'~j   «•    ~"  "~/                      (AX2-10)
14    and

15                                 UNO 3 + OH-* NO3 + H2O,                     (AX2 11

16    The lifetime of HNOs with respect to these two reactions is long enough for HNOs to act as a
17    reservoir species for NOX during long-range transport, contributing in this way to NO2 levels and
18    to Os formation in areas remote from the source region of the NOX that formed this HNOs.
19          Geyer and Platt (2002) concluded that Reaction AX2-9 constituted about 10% of the
20    removal of NOX at a site near Berlin, Germany during spring and summer.  However, other
21    studies found a larger contribution to HNOs production from Reaction AX2-9.  Dentener and
22    Crutzen (1993) estimated 20% in summer and 80% of HNOs production in winter is from
23    Reaction AX2-9. Tonnesen and Dennis (2000) found between 16 to 31% of summer HNOs
24    production was from Reaction AX2-9.  The contribution of Reaction AX2-9 to  HNOs formation
25    is highly uncertain during both winter and summer. The importance of Reaction AX2-9 could be
26    much higher during winter than during summer because of the much lower concentration of OH
27    radicals and the enhanced stability of ^Os due to lower temperatures and less sunlight.  Note
28    that Reaction AX2-9 proceeds as a heterogeneous reaction.  Recent work in the northeastern U.S.
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 1    indicates that this reaction is proceeds at a faster rate in power plant plumes than in urban plumes
 2    (Brown et al., 2006a,b; Frost et al., 2006).
 3          OH radicals also can react with NO to produce nitrous acid (HONO or HNO2):
 4                                                                                  (AX2_12)

 5    In the daytime, HNO2 is rapidly photolyzed back to the original reactants:
 f.                                   HNO-t + hv.                        ,AYO irv
 6                                        *-                                         (AX2-13)
 7    Reaction AX2-12 is, however, a negligible  source of HONO, which is formed mainly by
 8    multiphase processes (see Section AX2.2.3). At night, heterogeneous reactions of NO2 in
 9    aerosols or at the earth's surface result in accumulation of HONO (Lammel and Cape, 1996;
10    Jacob, 2000; Sakamaki et al.,  1983; Pitts et al., 1984; Svensson et al., 1987; Jenkin et al.,  1988;
1 1    Lammel and Perner, 1988; Notholt et al., 1992a,b). Harris et al. (1982) and Zhang et al. (2006)
12    (e.g.) suggested that photolysis of this HNO2 at sunrise could provide an important early-
13    morning source of OH radicals to drive Os formation
14          Hydroperoxy (HO2) radicals can react with NO2 to produce pernitric acid (HNO4):
                                                                                    (AX2-14)
16    which then can thermally decompose and photolyze back to its original reactants. The acids
17    formed in these gas-phase reactions are all water soluble.  Hence, they can be incorporated into
18    cloud drops and in the aqueous phase of particles.
19          Although the lifetimes of HNO4 and N2Os are short (minutes to hours) during typical
20    summer conditions, they can be much longer at the lower temperatures and darkness found
21    during the polar night.  Under these conditions, species such as PAN, HNOs, HNO4, and N2Os
22    serve as NOX reservoirs that can liberate NO2 upon the return of sunlight during the polar spring.
23    A broad range of organic nitrogen compounds  can be directly emitted by combustion sources or
24    formed in the atmosphere from NOX emissions. Organic nitrogen compounds include the PANs,
25    nitrosamines, nitro-PAHs, and the more recently identified nitrated organics in the quinone
26    family. Oxidation of VOCs produces organic peroxy radicals (RO2), as discussed in the latest
27    AQCD for Ozone and Other Photochemical Oxidants (U.S. Environmental Protection Agency,


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 1   2006).  Reaction of RC>2 radicals with NO and NC>2 produces organic nitrates (RONO2) and
 2   peroxynitrates (RC^
 3                                RO^NO-H-^RONO,                    (AX2.15)

 4                              R02 + N02^i-+R02N02                   (AX2_16)

 5         Reaction (AX2-15) is a minor branch for the reaction of RO2 with NO.  The major branch
 6   produces RO and NO2, as discussed in the next section; however, the organic nitrate yield
 7   increases with carbon number (Atkinson, 2000).
 8         The most important of these organic nitrates is PAN, the dominant member of the
 9   broader family of peroxyacylnitrates which includes peroxypropionyl nitrate (PPN) of
10   anthropogenic origin and peroxymethacrylic nitrate (MPAN) produced from isoprene oxidation.
11   The PANs are formed by the combination reaction of acetyl peroxy radicals with NO2:

12                        CH3C(0)-00 + N02 -> CH3C(0)OON02            (AX2-17)

13   where the acetyl peroxy radicals are formed mainly during the oxidation of ethane (C2H6).
14   Acetaldehyde (CH3CHO) is formed as an intermediate species during the oxidation of ethane.
15   Acetaldehyde can be photolyzed or react with OH radicals to yield acetyl radicals:

16                          CH3-C(0)H + hv -> CHs-C(0) + H               (AX2-18)
                                                CH^C(O) + H2O

18   Acetyl radicals then react with O2 to yield acetyl peroxy radicals

19                       CH3-C(0) + 02 + M ^ CH3C(0)-00 + M

20   However, acetyl peroxy radicals will react with NO in areas of high NO concentrations

21                       CH3(CO)-00 + NO ^ CH3(CO)-Q + NO2           (AX2-21)
22   and the acetyl-oxy radicals will then decompose

23                               CH3(CO)-0 -» CH, + C02
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 1    Thus, the formation of PAN is favored at conditions of high ratios of NC>2 to NO, which are most
 2    typically found under low NOX conditions. The PANs both thermally decompose and photolyze
 3    back to their reactants on timescales of a few hours during warm sunlit conditions, with lifetimes
 4    with respect to thermal decomposition ranging from ~1 hour at 298 K to -2.5 days at 273 K, up
 5    to several weeks at 250 K.  Thus, they can provide an effective sink of NOX at cold temperatures
 6    and high solar zenith angles, allowing release of NO2 as air masses warm, in particular by
 7    subsidence. The PANs are also removed by uptake to vegetation (Sparks et al., 2003;
 8    Teklemariam and Sparks, 2004).
 9          The organic nitrates may react further, depending on the functionality of the R group, but
10    they will typically not return NOX and can therefore be viewed mainly as a permanent sink for
11    NOX, as alkyl nitrates are sparingly soluble and will photolyze. This sink is usually small
12    compared to HNOs formation, but the formation of isoprene nitrates may be a significant sink for
13    NOX in the United States in summer (Liang et al.,  1998).
14          The peroxynitrates produced by (1-16) are thermally unstable and most have very short
15    lifetimes (less than a few minutes) owing to thermal decomposition back to the original
16    reactants. They are thus not effective sinks of NOX.
17
18    AX2.2.2    Nonlinear Relations between Nitrogen Oxide Concentrations and
19                Ozone Formation
20          Ozone is unlike some other species whose rates of formation vary directly with the
21    emissions of their precursors in that Os production (P(Os)) changes nonlinearly with the
22    concentrations of its precursors.  At the low NOX concentrations found in most environments,
23    ranging from remote continental areas to rural and suburban areas downwind of urban centers,
24    the net production of O?,  increases with increasing NOX. At the high NOX concentrations found in
25    downtown metropolitan areas, especially near busy streets and roadways, and in power plant
26    plumes, there is net destruction of Os by (titration) reaction with NO. Between these two
27    regimes is a transition stage in which Os shows only a weak dependence on NOX concentrations.
28    In the high NOX regime, NO2 scavenges OH radicals which would otherwise oxidize VOCs to
29    produce peroxy radicals, which in turn would oxidize NO to NO2. In the low NOX regime, VOV
30    (VOC) oxidation generates, or at least does not consume, free radicals, and Os production varies
31    directly with NOX. Sometimes the terms ' VOC-limited' and 'NOx-limited' are used to describe
32    these two regimes. However, there are difficulties with this usage because: (l)VOC

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 1    measurements are not as abundant as they are for NOX, (2) rate coefficients for reaction of
 2    individual VOCs with free radicals vary over an extremely wide range, and (3) consideration is
 3    not given to CO nor to reactions that can produce free radicals without invoking VOCs.  The
 4    terms NOx-limited and NOx-saturated (used by, e.g., Jaegle et al., 2001) will be used wherever
 5    possible to describe these two regimes more adequately. However, the terminology used in
 6    original articles will also be kept.  The chemistry of OH radicals, which are responsible for
 7    initiating the oxidation of hydrocarbons,  shows behavior similar to that for O?, with respect to
 8    NOX concentrations (Hameed et al., 1979; Pinto et al., 1993; Poppe et al., 1993; Zimmerman and
 9    Poppe, 1993).  These considerations introduce a high degree of uncertainty into attempts to relate
10    changes in Os concentrations to emissions of precursors. It should also be noted at the outset that
11    in a NOx-limited (or NOx-sensitive) regime, O3 formation is not insensitive to radical production
12    or the  flux of solar UV photons, just that Os formation is more sensitive to NOX. For example,
13    global tropospheric Os is sensitive to the concentration of CH4 even though the troposphere is
14    predominantly NOx-limited.
15          Various analytical techniques have been proposed that use ambient NOX and VOC
16    measurements to derive information about Os production and  O3-NOX-VOC sensitivity.
17    Previously (e.g., National Research Council,  1991), it was suggested that Os formation in
18    individual urban areas could be understood in terms of measurements of ambient NOX and VOC
19    concentrations during the early morning. In this approach, the ratio of summed (unweighted by
20    chemical reactivity) VOC to NOX concentrations is used to determine whether conditions are
21    NOx-sensitive or VOC sensitive. This technique is inadequate to characterize Os formation
22    because it omits many factors recognized as important for P(Os), including:  the effect of
23    biogenic VOCs (which are not present in urban centers during early morning); important
24    individual differences in the  ability of VOCs  to generate free radicals, rather than just from total
25    VOC concentration and other differences in Os-forming potential for individual VOCs (Carter,
26    1995); the effect of multiday transport; and general changes in photochemistry as air moves
27    downwind from urban areas  (Milford et al., 1994).
28          Jacob et al. (1995) used a combination of field measurements and a chemical transport
29    model (CTM) to show that the formation of Os changed from  NOx-limited to NOx-saturated as
30    the season changed from summer to fall at a monitoring site in Shenandoah National Park, VA.
31    Photochemical production of Os generally occurs together with production of various other

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 1    species including HNOs, organic nitrates, and hydrogen peroxide (H2O2).  The relative rates of
 2    P(Os) and the production of other species varies depending on photochemical conditions, and can
 3    be used to provide information about O3-precursor sensitivity.
 4          There are no hard and fast rules governing the levels of NOX at which the transition from
 5    NOx-limited to NOx-saturated conditions occurs. The transition between these two regimes is
 6    highly spatially and temporally dependent. In the upper troposphere, responses to NOX additions
 7    from commercial aircraft have been found which are very similar to these in the lower
 8    troposphere (Bruhl  et al., 2000).  Bruhl et al. (2000) found that the NOX levels for O3 production
 9    versus loss are highly sensitive to the radical sources included in model calculations.  They found
10    that inclusion of only CH4 and CO oxidation leads to a decrease in net 63 production in the
11    North Atlantic flight corridor due to NO emissions from aircraft. However, the additional
12    inclusion of acetone photolysis was found to shift the maximum in Os production to higher NOX
13    mixing ratios, thereby reducing or eliminating areas in which Os production rates decreased due
14    to aircraft emissions.
15          Trainer et al. (1993) suggested that the slope of the regression line between Os and
16    summed NOX oxidation products (NOZ, equal to the difference between measured total reactive
17    nitrogen, NOy, and NOX) can be used to estimate the rate of P(Os) per NOX (also known as the 63
18    production efficiency, or OPE). Ryerson et al. (1998, 2001) used measured correlations between
19    Os and NOZ to identify different rates of Os production in  plumes from large point sources.
20          Sillman (1995) and Sillman and He (2002) identified several secondary reaction products
21    that show different  correlation patterns for NOx-limited conditions and NOx-saturated conditions.
22    The most important correlations are for Os versus NOy,  Os versus NOZ, Os versus HNOs, and
23    H2O2 versus HNOs. The correlations between Os and NOy, and Os and NOZ are especially
24    important because measurements of NOy and NOX are widely available. Measured Os versus
25    NOZ (Figure AX2-2) shows distinctly different patterns  in different locations. In rural areas and
26    in urban areas such as Nashville, TN, Os shows a strong correlation with NOZ and a relatively
27    steep slope to the regression line.  By contrast, in Los Angeles Os also increases with NOZ, but
28    the rate of increase  of O3 with NOZ is lower and the O3 concentrations for a given NOZ value are
29    generally lower.
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 1          The difference between NOx-limited and NOx-saturated regimes is also reflected in
 2   measurements of H2O2. Formation of H2O2 takes place by self-reaction of photochemically-
 3   generated HO2 radicals, so that there is large seasonal variation of H2O2 concentrations, and
                    250-1	
               .0
                Q.
                Q.
     Figure AX2-2.
                                                  x
                                 X
                                           X
                                         X
                                         x-
                                                        X
                                       X
                                       X
                                                            -x-
                                                       X  X
                                                      X
                                                                    X
                                                                          X
                                                                           X
                                                                         X
                                      10
                          20
                      NOZ (ppb)
       30
40
Measured values of O3 and NOZ (NOy-NOx) during the afternoon at
rural sites in the eastern United States (gray circles) and in urban
areas and urban plumes associated with Nashville, TN (gray dashes),
Paris, FR (black diamonds) and Los Angeles, CA (X's)
 4   values in excess of 1 ppb are mainly limited to the summer months when photochemistry is more
 5   active (Kleinman, 1991). Hydrogen peroxide is produced in abundance only when Os is
 6   produced under NOx-limited conditions.  When the photochemistry is NOX-saturated, much less
 7   H2O2 is produced. In addition, increasing NOX tends to slow the formation of H2O2 under NOX-
 8   limited conditions. Differences between these two regimes are also related to the preferential
 9   formation of sulfate during summer and to the inhibition of sulfate and hydrogen peroxide during
10   winter (Stein and Lamb, 2003). Measurements in the rural eastern United States (Jacob et al.,
11   1995), at Nashville (Sillman et al., 1998), and at Los Angeles (Sakugawa and Kaplan, 1989)
12   show large differences in H2O2 concentrations likely due to differences in NOX availability at
13   these locations.
14
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 1    AX2.2.3    Multiphase Chemistry Involving NOX
 2          Recent laboratory studies on sulfate and organic aerosols indicate that the reaction
 3    probability yN2os is in the range of 0.01 to 0.05 (Kane et al., 2001; Hallquist et al., 2003;
 4    Thornton et al., 2003).  Tie et al.  (2003) found that a value of 0.04 in their global model gave the
 5    best simulation of observed NOX  concentrations over the Arctic in winter.
 6          Using aircraft measurements over the northeastern U.S., Brown et al. (2006b) found that
 7    the uptake coefficient for N2Os, yN2Os, on the surfaces of particles depends strongly on their
 8    sulfate content. They found that  yN2Os was highest (0.017) in regions where the aerosol  sulfate
 9    concentration was highest and lower elsewhere (<0.0016). This result contrasts with that of
10    Dentener and Crutzen (1993) who concluded that yN2Os would be independent of aerosol
11    composition, based on a value for yN2Os of 0.1, implying that the heterogeneous hydrolysis of
12    N2O5 would be saturated for typical ambient aerosol surface areas. The importance of this
13    reaction to tropospheric chemistry depends on the value of yN2Os. If it is 0.01 or lower, there
14    may be difficulty in explaining the loss of NOy and the formation of aerosol nitrate, especially
15    during winter. A decrease in N2Os slows down the removal of NOX by leaving more NO2
16    available for reaction and thus increases Os production. Based on the consistency between
17    measurements of NOy partitioning and gas-phase models, Jacob (2000) considers it unlikely that
18    HNOs is recycled to NOX in the lower troposphere in significant concentrations. However, only
19    one of the reviewed studies (Schultz et al., 2000) was conducted in the marine troposphere and
20    none was conducted in the MBL. An investigation over the equatorial Pacific reported
21    discrepancies between observations and theory (Singh et al., 1996) which might be explained by
22    HNOs recycling.  It is important to recognize that both Schultz et al. (2000) and Singh et al.
23    (1996) involved aircraft sampling at altitude which, in the MBL, can significantly under-
24    represent sea salt aerosols and thus most total NOs (defined to be HNOs + NOs ) and large
25    fractions of NOy in marine air (e.g., Huebert et al.,  1996). Consequently, some caution is
26    warranted when interpreting constituent ratios and NOy budgets based on such data.
27          Recent work in the Arctic has quantified significant photochemical recycling of NOs  to
28    NOX and attendant perturbations of OH chemistry in snow (Honrath et al., 2000; Dibb et  al.,
29    2002; Domine and Shepson, 2002) which suggest the possibility that similar multiphase
30    pathways could occur in aerosols. As mentioned above, NOs is photolytically reduced to NO2
31    (Zafiriou and True, 1979) in acidic sea salt solutions (Anastasio et al., 1999). Further photolytic

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 1    reduction of NC>2 to NO (Zafariou and True, 1979) could provide a possible mechanism for
 2    HNOs recycling.  Early experiments reported production of NOX during the irradiation of
 3    artificial seawater concentrates containing NO3 (Petriconi and Papee, 1972).  Based on the
 4    above, HNOs recycling in sea salt aerosols is potentially important and warrants further
 5    investigation. Other possible recycling pathways involving highly acidic aerosol solutions and
 6    soot are reviewed by Jacob (2000).
 7           Stemmler et al. (2006) studied the photosensitized reduction of NO2 to HONO on humic
 8    acid films using radiation in the UV-A through the visible spectral regions. They also found
 9    evidence for reduction occurring in the dark, reactions which may occur involving surfaces
10    containing partly  oxidized aromatic structures. For example, Simpson et al. (2006) found that
11    aromatic compounds constituted -20% of organic films coating windows in downtown Toronto.
12    They calculated production rates of HONO that are compatible with observations of high HONO
13    levels in a variety of environments. The photolysis of HONO formed this way could  account for
14    up to 60% of the integrated source of OH radicals in the inner planetary boundary layer.  A
15    combination of high NO2 levels and surfaces of soil and buildings and other man-made structures
16    exposed to diesel exhaust would then be conducive to HONO formation and, hence, to high
17    [OH] (Xu et al., 2006).
18           Ammann  et al. (1998) reported the efficient conversion of NO2 to HONO on fresh soot
19    particles in the presence of water.  They suggest that interaction between NO2 and soot particles
20    may account for high mixing ratios of HONO observed in urban environments.  Conversion of
21    NO2 to HONO and subsequent photolysis and HONO to NO + OH would constitute a NOX-
22    catalyzed Os sink involving snow.  High concentrations of HONO can lead to the rapid growth in
23    OH concentrations shortly after sunrise, giving a "jump start" to photochemical smog formation.
24    Prolonged exposure to ambient oxidizing agents appears to deactivate this process.  Broske et al.
25    (2003)  studied the interaction of NO2 on secondary organic aerosols and concluded that the
26    uptake  coefficients were too low for this reaction to be an important source of HONO in the
27    troposphere.
28           Choi and Leu (1998) evaluated the interactions of HNO3 on model black carbon soot
29    (FW2), graphite, hexane, and kerosene soot.  They found that HNOs decomposed to NO2 and
30    H2O at higher HNOs surface coverages, i.e., P(HNO3) > = 10~4 Torr. None of the soot models
31    used were reactive at low HNOs coverages, at P(HNO3) = 5 x 10~7 Torr or at temperatures below

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 1    220 K.  They conclude that it is unlikely that aircraft soot in the upper troposphere/lower
 2    stratosphere reduces HNO3.
 3          Heterogeneous production on soot at night is believed to be the mechanism by which
 4    HONO accumulates to provide an early morning source of HOX in high NOX environments
 5    (Harrison et al., 1996; Jacob, 2000).  HONO has been frequently observed to accumulate to
 6    levels of several ppb overnight, and this has been attributed to soot chemistry (Harris et al.,  1982;
 7    Calvert et al., 1994; Jacob, 2000).
 8          Longfellow et al. (1999) observed the formation of HONO when methane, propane,
 9    hexane, and kerosene  soots were exposed to NO2. They suggested that this reaction may account
10    for some part of the unexplained high levels of HONO observed in urban areas.  They comment
11    that without details about the surface area, porosity, and amount of soot available for this
12    reaction, reactive uptake values cannot be estimated reliably.  They comment that soot and NO2
13    are produced in close proximity during combustion, and that large quantities of HONO have
14    been  observed in aircraft plumes.
15          Saathoff et al.  (2001) studied the heterogeneous loss of NO2, HNO3, NO3/N2O5,
16    HO2/HO2NO2 on soot aerosol using a large aerosol chamber.  Reaction periods of up to several
17    days were monitored and results used to fit a detailed model.  Saathoff et al. derived reaction
18    probabilities at 294 K and 50% RH for NO2, NO3, HO2, and HO2NO2 deposition to soot; HNO3
19    reduction to NO2; and ^Os hydrolysis. When these probabilities were included in
20    photochemical box model calculations of a 4-day smog event, the only noteworthy influence of
21    soot was a 10% reduction in the second day O3 maximum, for a soot loading of 20 jig nT3, i.e.,
22    roughly a factor of 10 times observed black carbon loadings seen in U.S. urban areas, even
23    during air pollution episodes.
24          Mufioz and Rossi (2002) conducted Knudsen cell studies of HNO3 uptake on black and
25    grey decane soot produced in lean and rich flames, respectively. They observed HONO  as the
26    main species released following HNO3 uptake on grey soot, and NO and traces of NO2 from
27    black soot. They conclude that these reactions would only have relevance in special situations in
28    urban settings where soot and HNO3 are present in high concentrations simultaneously.
29
30    Formation ofNitro PAHs
31          Nitro-polycyclic aromatic hydrocarbons (nitro-PAHs) (see Figure AX2-3 for some
32    example nitro-PAHs)  are generated from incomplete combustion processes through electrophilic

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      2-nitronaphthalene    9-nitroanthracene    2-nitrofluoranthene  6-nitrobenzo(a)pyrene
      Figure AX2-3.       Structures of nitro-polycyclic aromatic hydrocarbons.
 1    reactions of polycyclic aromatic hydrocarbons (PAHs) in the presence of NC>2 (International
 2    Agency for Research on Cancer [IARC], 1989; World Health Organization [WHO], 2003).
 3    Among combustion sources, diesel emissions have been identified as the major source of nitro-
 4    PAHs in ambient air (Bezabeh et al., 2003; Gibson, 1983; Schuetzle, 1983; Tokiwa and Ohnishi,
 5    1986). Direct emissions of NPAHs in PM vary with type of fuel, vehicle maintenance, and
 6    ambient conditions (Zielinska et al., 2004).
 7          In addition to being directly emitted, nitro-PAHs can also be formed from both gaseous
 8    and heterogeneous reactions of PAHs with gaseous nitrogenous pollutants in the  atmosphere
 9    (Arey et al., 1986; Arey et al., 1989, Arey, 1998; Perrini, 2005; Pitts, 1987; Sasaki et al., 1997;
10    Zielinska  et al., 1989). Different isomers of nitro-PAHs are formed through different formation
11    processes. For example, the most abundant nitro-PAH in diesel particles is 1-nitropyene (1NP),
12    followed by 3-nitrofluoranthene (3NF) and 8-nitrofluoranthene (8NF) (Bezabeh et al., 2003;
13    Gibson, 1983; Schuetzle, 1983; Tokiwa and Ohnishi, 1986).  However, in ambient particulate
14    organic matter (POM), 2-nitrofluoranthene (2NF) is the dominant compound, followed by 1NP
15    and 2-nitropyrene (2NP) (Arey et al., 1989; Bamford et al., 2003; Reisen and  Arey, 2005;
16    Zielinska  et al., 1989), although 2NF and 2NP are not directly emitted from primary combustion
17    emissions. The reaction mechanisms for the different nitro-PAH formation processes have been
18    well documented and are presented in Figure AX2-3.
19          The dominant process  for the formation of nitro-PAHs in the atmosphere  is gas-phase
20    reaction of PAHs with OH radicals in the presence of NOX (Arey et al., 1986,  Arey,  1998;
21    Atkinson  and Arey,  1994; Ramdahl et al., 1986; Sasaki et al., 1997). Hydroxyl radicals can be
22    generated photochemically or at night through ozone-alkene reactions, (Finlayson-Pitts and Pitts,
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 1   2000). The postulated reaction mechanism of OH with PAHs involves the addition of OH at the
 2   site of highest electron density of the aromatic ring, for example, the 1-position for pyrene (PY)
 3   and the 3-position for fluoranthene (FL). This reaction is followed by the addition of NO2 to the
 4   OH-PAH adduct and elimination of water to form the nitroarenes (Figure AX2-4, Arey et al.,
 5   1986; Aktinson et al., 1990; Pitts, 1987). After formation, nitro-PAHs with low vapor pressures
 6   (such as 2NF and 2NP) immediately migrate to particles under ambient conditions (Fan et al.,
 7   1995; Feilberg et al., 1999). The second order rate-constants for the reactions of OH with most
 8   PAHs range from 10~10 to 10~12 cm3molecule~ V1 at 298 K with the yields ranging from -0.06 to
 9   -5% (Atkinson and Arey, 1994). 2NF and 2NP have been found as the most abundant nitro-
10   PAHs formed via reactions of OH with gaseous PY and FL, respectively in ambient  air.
     Figure AX2-4.
                                             OH
                                                         |NO£
                              2NP
Formation of 2-nitropyrene (2NP) from the reaction of OH with
gaseous pyrene (PY).
11          The second important process for the formation of nitro-PAHs in the atmosphere is the
12   nitration of PAHs by NOs in the presence of NOX at night (Atkinson et al., 1990; Atkinson and
13   Arey, 1994; Sasaki et al., 1997). Nitrate radicals can be generated by reaction of ozone (Os) with
14   NO2 in the atmosphere by Reaction AX2-5:
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                                                                                     (AX2-5)
 2          Similar to the mechanism of OH reactions with PAHs, NOs initially adds to the PAH ring
 3   to form an NOs-PAH adduct, followed by loss of HNOs to form nitro-PAHs (Atkinson et al.,
 4    1990; Atkinson and Arey, 1994; Sasaki et al., 1997). For example, in the mixture of naphthalene
 5   and N2Os-NO3-NO2, the major products formed through the NOs reaction are 1- and 2-nitro-
 6   naphthalene (INN and 2NN) (Atkinson et al., 1990; Feilberg et al., 1999; Sasaki et al., 1997).
 7   2NF and 4NP were reported as the primary products of the gas-phase reactions of FL and PY
 8   with NOs radical, respectively (Atkinson et al., 1990; Atkinson and Arey, 1994).
 9          The reaction with NOs is of minor importance in the daytime because NOs radical is not
10   stable in sunlight. In addition, given the rapid reactions of NO with NOs and with Os in the
11   atmosphere (Finlay son-Pitts and Pitts 2000), concentrations of NOs at ground level are low
12   during daytime.  However, at night, concentrations of NO3 radicals formed in polluted ambient
13   air are expected to increase. According to Atkinson et al. (1991), the average NOs concentration
14   is about 20 ppt in the lower troposphere  at night and can be as high as 430 ppt.  It is also worth
15   noting that significant NOs radical concentrations are found at  elevated altitudes where O3  is
16   high but NO is low (Reissell and Arey, 2001; Stutz et al., 2004).  When NO3 reaches high
17   concentrations, the formation of nitro-PAHs  by the reaction of gaseous PAHs with NO3 may be
18   of environmental significance. At 10~17 - 10~18 cm3 molecule  V1, the rate constants of NO3
19   with most PAHs are several orders of magnitude lower than those of OH with the same PAHs;
20   however, the yields of nitro-PAHs from NO3 reactions are generally much higher than those of
21   OH reactions. For example, the  yields of 1-NN and 2NF are 0.3% and 3%, respectively from
22   OH reactions, but the yields are  17% and 24% for these two compounds generated from the NO3
23   radical reactions (Atkinson and Arey 1994).  Therefore, formation of nitro-PAHs via reactions of
24   NO3 at nighttime under certain circumstances can be significant.
25          The third process of nitro-PAH formation in the atmosphere is nitration of PAHs by
26   NO2/N2Os in the presence of trace amounts of HNO3 (HNO3) in both gas and particle phases.
27   This mechanism could be operative throughout the day and night (Pitts et al., 1983,  1985a, b;
28   Grosjean et al., 1983; Ramdahl et al., 1984; Kamens et al., 1990).  The formation  of nitro-
29   fluoranthenes was observed when adsorbed FL was exposed to gaseous ^Os, and the
30   distribution of product NF isomers was 3- >  8- > 7- > 1- NF (Pitts et al., 1985a, b).  The


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 1   proposed mechanism for this reaction was an ionic electrophilic nitration by nitronium ion
 2   (NC>2+). It was speculated that ^Os became ionized prior to the reaction with FL (Zielinska
 3   et al., 1986).  Only 1NP was observed for the reaction of PY with ^Os on filters (Pitts et al.,
 4   1985b). Compared to the reactions of OH and NOs, nitration of PAHs by NO2/N2Os is less
 5   important.
 6          Measurements of nitro-PAHs in ambient air provide evidence for the proposed reaction
 7   mechanism, i.e. the reactions of OH and NOs radicals with PAHs are the major sources of
 8   nitro-PAHs (Bamford and Baker, 2003; Reisen and Arey, 2005; and references therein).  2NF is
 9   a ubiquitous component of ambient POM, much higher than 1NP, itself a marker of combustion
10   sources. Nitro-PAH isomer ratios show strong seasonality.  For instance, the mean ratios of
11   2NF/1NP were higher in summer than in winter (Bamford et al., 2003; Reisen and Arey, 2005),
12   indicating that reactions of OH and NOs with FL are the major sources of nitro-PAHs in ambient
13   air in summer. The ratio of 2NF/1NP was lower in winter than in summer because of lower OH
14   concentrations and, therefore, less production of 2NF via atmospheric reactions.  A ratio of
15   1NP/2NF greater than 1 was observed in locations with major contributions from vehicle
16   emissions (Dimashki et al., 2000; Feilberg et al., 2001). In addition, the ratio of 2NF/2NP was
17   also used to evaluate the contribution of OH and NOs initiated reactions to the ambient nitro-
18   PAHs (Bamford et al., 2003; Reisen and Arey, 2005).
19          The concentrations for most nitro-PAHs found in ambient air are much lower than
20   1 pg/m3, except NNs, 1NP, and 2NF, which can be present at several pg/m3. These levels are
21   much lower (~2 to -1000 times lower) than their parent PAHs.  However, nitro-PAHs are much
22   more toxic than PAHs (Durant et al., 1996; Grosovsky et al., 1999; Salmeen et al., 1982; Tokiwa
23   et al., 1998; Tokiwa and Ohnishi, 1986). Moreover, most nitro-PAHs are present in particles
24   with a mass median diameter <0.1 |im.
25          Esteve et al. (2006) examined the reaction of gas-phase NO2 and OH radicals with
26   various PAHs adsorbed onto model diesel paniculate matter (SRM 1650a, NIST). Using pseudo
27   second order rate coefficients,  they derived lifetimes for conversion of the particle-bound PAHs
28   to nitro-PAHs of a few days (for typical urban NO2 levels of 20 ppb). They also found that the
29   rates of reaction of OH with the PAHs were about four orders of magnitude larger than for the
30   reactions involving NO2. However, since the concentrations of NO2 used above are more than
31   four orders of magnitude larger than those for OH (106-107/cm3), they concluded that the

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 1    pathway involving NC>2 is expected to be favored over that involving OH radicals. Consistent
 2    with the importance of the gas-phase formation of NPAHS, both the mutagenic potency of PM
 3    and the content of NPAHs in PM vary by particle size, and are higher in the submicron size
 4    range (Xu and Lee, 2000; Kawanaka et al., 2004).
 5          The major loss process of nitro-PAHs is photodecomposition (Fan et al., 1996; Feilberg
 6    et al., 1999; Feilberg and Nielsen, 2001), with lifetimes on the order of hours.  However, lacking
 7    direct UV light sources indoors, nitro-PAHs are expected have a longer lifetimes (days) indoors
 8    than outdoors; and may therefore pose increased health risks. Many nitro-PAHs are semi- or
 9    nonvolatile organic compounds. As stated above, indoor environments have much greater
10    surface areas than outdoors. Thus, it is expected that gas/particle distribution of nitro-PAHs
11    indoors will be different from those in ambient air.  A significant portion of nitro-PAHs will
12    probably be adsorbed by indoor surfaces, such as carpets, leading to different potential  exposure
13    pathways to nitro-PAHs in indoor environments. The special characteristics of indoor
14    environments, which can affect the indoor chemistry and potential exposure pathways
15    significantly, should be taken  into consideration when conducting exposure studies of nitro-
16    PAHs.
17          Reaction with OH and NOs radicals is a major mechanism for removing gas-phase PAHs,
18    with OH radical initiated reactions predominating depending on season (Vione et al., 2004;
19    Bamford et al., 2003). Particle-bound PAH reactions occur but tend to be slower.
20    Nitronaphthalenes tend to remain in the vapor phase, but because phase partitioning depends on
21    ambient temperature, in very cold regions these species can condense (Castells et al., 2003)
22    while the higher molecular weight PAHs such as the nitroanthracenes, nitrophenantrenes and
23    nitrofluoranthenes condense in and on PM (Ciganek et al., 2004; Cecinato, 2003).
24
25    Multiphase Chemical Processes Involving Nitrogen Oxides and Halogens
26          Four decades of observational data on Os in the troposphere have revealed numerous
27    anomalies not easily explained by gas-phase HOX-NOX photochemistry. The best-known
28    example is the dramatic depletion of ground-level Os during polar sunrise due to multiphase
29    catalytic cycles involving inorganic Br and Cl radicals (Barrie et al., 1988; Martinez et  al., 1999;
30    Foster et al., 2001). Other examples of anomalies in tropospheric O3 at lower  latitudes  include
31    low levels of Os (<10 ppbv) in the marine boundary layer (MBL) and overlying free troposphere
32    (FT) at times over large portions of the tropical Pacific (Kley et al., 1996),  as well as post-sunrise

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 1    Os depletions over the western subtropical Pacific Ocean (Nagao et al., 1999), the temperate
 2    Southern Ocean (Galbally et al., 2000), and the tropical Indian Ocean (Dickerson et al., 1999).
 3    The observed O3 depletions in near-surface marine air are generally consistent with the model-
 4    predicted volatilization of Br2, BrCl, and C12 from sea salt aerosols through autocatalytic halogen
 5    "activation" mechanisms (e.g., Vogt et al., 1996; von Glasow et al., 2002a) involving these
 6    aqueous phase reactions.
                                                                                   (AX2-23)

 g                            HOCL + Br- + H+^ BrCl + H2O                  (AX2-24)
 9                              HOC1 + Cl~ + /f+ H» C/2 + H2O                  (AX2-25)
10    In polluted marine regions at night, the heterogeneous reaction
12    may also be important (Finlayson-Pitts et al., 1989; Behnke et al., 1997; Erickson et al., 1999).
13    Diatomic bromine, BrCl, C12, and C1NO2 volatilize and photolyze in sunlight to produce atomic
14    Br and Cl.  The acidification of sea salt aerosol via incorporation of HNOs (and other acids)
15    leads to the volatilization of HC1 (Erickson et al., 1999), e.g.
16                               HN03+C1--*HCI+N03-                   (AX2_2?)

17    and the corresponding shift in phase partitioning can accelerate the deposition flux to the surface
18    of total NO3  (Russell et al., 2003; Fischer et al., 2006).  However, Pryor and Sorensen (2000)
19    have shown that the dominant form of nitrate deposition is a complex function of wind speed. In
20    polluted coastal regions where HC1 from Reaction 35 often exceeds 1 ppbv, significant
21    additional atomic Cl~ is produced via:

22                                  HC1  + OH -> Cl + H2O                     (AX2-28)
23    (Singh and Kasting, 1988; Keene et al., 2007).  Following production, Br and Cl atoms
24    catalytically destroy O3 via:
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                                                  XO + 02                        (AX2-29)
                                     XD+H02-*HOX+02                      (AX2_30)
                                                                                   (AXM1)
 4   where (X = Br and Cl).
 5   Formation  of Br and Cl nitrates via
 6                                                                                 (AX2.32)
 7    and the subsequent reaction of XNO3 with sea salt and sulfate aerosols via
 a                             XNO3 + H2O -> MM" + ,ff+ + NO3
 o                                       "k
 9    and:
10                                  XN03+Y  ~~»IY + .,^                      (AX2-34)
11    (where Y = Cl, Br, or I) accelerates the conversion of NOX to paniculate NO3  and thereby
12    contributes indirectly to net O3 destruction (Sander et al., 1999; Vogt et al., 1999, Pszenny et al.,
13    2004). Most XNO3 reacts via reaction 34 on sea salt whereas reaction 33 is more important on
14    sulfate aerosols.  Partitioning of HC1 on sulfate aerosols following Henry's Law provides Cl  for
15    reaction 34 to form BrCl. Product NO3  from both reactions AX2-33 and AX2-34 partitions
16    with the gas-phase HNO3 following Henry's Law. Because most aerosol size fractions in the
17    MBL are near equilibrium with respect to HNO3 (Erickson et al., 1999;  Keene et al., 2004), both
18    sulfate and sea salt aerosol can sustain the catalytic removal of NOX and re-activation of Cl and
19    Br with no detectable change in composition.  The photolytic reduction  of NO3" in sea salt
20    aerosol solutions recycles NOX to the gas phase (Pszenny et al., 2004). Halogen chemistry also
21    impacts O3 indirectly by altering OH/HO2 ratios (XO + HO2 -> HOX + O2 ->  OH + X) (e.g.,
22    Stutz et al., 1999; Bloss et al., 2005).
23          In addition to O3 destruction via reaction AX2-37, atomic Cl oxidizes hydrocarbons
24    (HCs) primarily via hydrogen abstraction to form HC1 vapor and organz products (Jobson et al.,
25    1994; Pszenny et al., 2006). The  enhanced  supply of odd-H radicals from HC  oxidation leads to
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 1    net 63 production in the presence of sufficient NOX (Pszenny et al., 1993).  Available evidence
 2    suggests that Cl~ radical chemistry may be a significant net source for 63 in polluted
 3    coastal/urban air (e.g., Tanaka et al., 2003; Finley and Saltzman, 2006).
 4          An analogous autocatalyic Os destruction cycle involving multiphase iodine chemistry
 5    also operates in the marine atmosphere (Alicke et al., 1999, Vogt et al., 1999; McFiggans et al.,
 6    2000; Ashworth et al., 2002). In this case, the primary source of I is believed to be either
 7    photolysis of CH2I2, other I-containing gases (Carpenter et al.,  1999; Carpenter, 2003), and/or
 8    perhaps I2 (McFiggans et al., 2004; Saiz-Lopez and Plane, 2004; McFiggans, 2005) emitted by
 9    micro-and macro flora.  Sea salt and sulfate aerosols provide substrates for multiphase reactions
10    that sustain the catalytic I-IO cycle.  The IO radical has been measured by long-path (LP) and/or
11    multi axis (MAX) differential optical absorption spectroscopy (DOAS) at Mace Head, Ireland;
12    Tenerife, Canary Islands; Cape Grim, Tasmania; and coastal New England, USA; having
13    average daytime levels of about 1 ppt with maxima up to 7 ppt (e.g., Allan  et al., 2000; Pikelnaya
14    et al., 2006). Modeling suggests that up to 13% per day of Os in marine air may be destroyed via
15    multiphase iodine chemistry (McFiggans et al., 2000).  The reaction of IO with NO2 followed by
16    uptake of INOs into aerosols (analogous to Reactions AX2-9 through AX2-11) accelerates the
17    conversion of NOX to particulate NOs and thereby contributes to net 63 destruction. The
18    reaction IO + NO —> I + NO2 also influences NOX cycling.
19          Most of the  above studies have focused on halogen-radical chemistry and related
20    influences on NOX cycling in coastal and urban air.  However, available evidence suggests that
21    similar chemical transformations proceed in other halogen-rich tropospheric regimes.  For
22    example, Cl, Br, and/or I oxides have been measured at significant concentrations in near-surface
23    air over the Dead Sea, Israel, the Great Salt Lake, Utah (e.g., Hebestreit et al., 1999; Stutz et al.,
24    1999, 2002; Zingler and Platt, 2005), and the Salar de Uyuni salt pan in the Andes mountains
25    (U. Platt, unpublished data, 2006); high column densities of halogenated compounds have also
26    been observed from satellites over the northern Caspian Sea (Wagner et al., 2001; Hollwedel
27    et al., 2004). The primary source of reactive halogens in these regions is thought to be from
28    activation along the lives of that in reactions in AX2-23 through AX2-25 involving concentrated
29    salt deposits on surface evaporite pans. High concentrations of BrO have also been measured in
30    volcanic plumes (Bobrowski et al., 2003, Gerlach, 2004). Although virtually unexplored, the
31    substantial emissions of inorganic halogens during biomass burning (Lobert et al., 1999; Keene

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 1    et al., 2006) and in association with crustal dust (Keene et al., 1999; Sander et al., 2003) may
 2    also support active halogen-radical chemistry and related transformations involving NOX
 3    downwind of sources. Finally, observations from satellites, balloons, and aircraft indicate that
 4    BrO is present in the free troposphere at levels sufficient to significantly influence
 5    photochemistry (e.g., von Glasow et al., 2004).
 6
 7
 8    AX2.3     CHEMISTRY OF SULFUR OXIDES IN THE TROPOSPHERE
 9          The four known monomeric sulfur oxides are sulfur monoxide (SO), sulfur dioxide
10    (SO2), sulfur tri oxide (SO3), and disulfur monoxide (S2O).  SO can be formed by photolysis of
1 1    SO2 at wavelengths less than 220 nm, and so could only be found in the middle and upper
12    stratosphere (Pinto et al., 1989). SOs can be emitted from the stacks of power plants and
13    factories however, it reacts extremely rapidly with H2O in the stacks or immediately after release
14    into the atmosphere to form H2SO4. Of the four species, only SO2 is present at concentrations
15    significant for atmospheric chemistry and human exposures.
16          Sulfur dioxide can be oxidized either in the gas phase, or, because it is soluble, in the
17    aqueous phase in cloud drops.  The gas-phase oxidation of SO2 proceeds through the reaction
                                                                                  (AX2-35)
19   followed by

                                                                                  (AX2.36)

                                                                                  (AX2-37)
22   Since H2SO4 is extremely soluble, it will be removed rapidly by transfer to the aqueous phase of
23   aerosol particles and cloud drops. Rate coefficients for reaction of SO2 with HO2 or NOs are too
24   low to be significant (JPL, 2003).
25          SO2 is chiefly but not exclusively primary in origin; it is also produced by the
26   photochemical oxidation of reduced sulfur compounds such as dimethyl sulfide (CHa-S-CHa),
27   hydrogen sulfide (H2S), carbon disulfide (CS2), carbonyl sulfide (OCS), methyl mercaptan
28   (CHa-S-H), and dimethyl disulfide (CHa-S-S-CHa) which are all mainly biogenic in origin.
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 1    Their sources are discussed in Section AX2.5. Table AX2-1 lists the atmospheric lifetimes of
 2    reduced sulfur species with respect to reaction with various oxidants. Except for OCS, which is
 3    lost mainly by photolysis (x~6 months), all of these species are lost mainly by reaction with OH
 4    and NOs radicals. Because OCS is relatively long-lived in the troposphere, it can be transported
 5    upwards into the stratosphere. Crutzen (1976) proposed that its oxidation serves as the major
 6    source of sulfate in the stratospheric aerosol layer sometimes referred to the "Junge layer,"
 7    (Junge et al., 1961) during periods when volcanic plumes do not reach the stratosphere.
 8    However, the flux of OCS into the stratosphere is probably not sufficient to maintain this
 9    stratospheric aerosol layer.  Myhre et al. (2004) propose instead that SO2 transported upwards
10    from the troposphere is the most likely source, have become the upward flux of OCS is too small
11    to sustain observed sulfate loadings in the Junge layer.  In addition, insitu measurements of the
12    isotopic composition of sulfur do not match those of OCS (Leung et al., 2002). Reaction with
13    NOs radicals at night most likely represents the major loss process for dimethyl sulfide and
14    methyl mercaptan. The mechanisms for the oxidation of DMS are still not completely
15    understood. Initial attack by NOs and OH radicals involves H atom abstraction, with a smaller
16    branch leading to OH addition to the S atom. The OH addition branch increases in importance as
17    temperatures decrease and becoming the major pathway below temperatures of 285 K
18    (Ravishankara, 1997).  The adduct may either decompose to form methane  sulfonic acid (MSA),
19    or undergo further reactions in the main pathway, to yield dimethyl sulfoxide (Barnes et al.,
20    1991). Following H atom abstraction from DMS, the main reaction products include MSA and
21    SO2.  The ratio of MSA to SO2 is strongly temperature dependent, varying from about 0.1 in
22    tropical waters to about 0.4 in Antarctic waters (Seinfeld and Pandis, 1998). Excess sulfate (over
23    that expected from the sulfate in seawater) in marine aerosol is related mainly to the production
24    of SO2 from the oxidation of DMS.  Transformations among atmospheric sulfur compounds are
25    summarized in Figure AX2-5.
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                      hvt O
           OH
                      Tropopause
    Figure AX2-5.       Transformations of sulfur compounds in the atmosphere.
    Source: Adapted from Berresheim et al. (1995).
1   Multiphase Chemical Processes Involving Sulfur Oxides and Halogens
2          Chemical transformations involving inorganic halogenated compounds effect changes in
3   the multiphase cycling of sulfur oxides in ways analogous to their effects on NOX. Oxidation of
4   dimethylsulfide (CH3)2S by BrO produces dimethyl sulfoxide (CH3)2SO (Barnes et al., 1991;
5   Toumi, 1994), and oxidation by atomic chloride leads to formation of SO2 (Keene et al., 1996).
6   (CHs^SO and SO2 are precursors for methanesulfonic acid (CHaSOsH) and H2SO/t. In the MBL,
7   virtually all H2SO4 and CHaSOsH vapor condenses onto existing aerosols or cloud droplet, which
8   subsequently evaporate, thereby contributing to aerosol growth and acidification. Unlike
9   CHsSOsH, H2SO4 also has the potential to produce new particles (Korhonen et al., 1999; Kumala
    August 2007
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 1    et al., 2000), which in marine regions is thought to occur primarily in the free troposphere.  Saiz-
 2    Lopez et al. (2004) estimated that observed levels of BrO at Mace Head would oxidize (CH3)2S
 3    about six times faster than OH and thereby substantially increase production rates of H2SO4 and
 4    other condensible S species in the MBL. Sulfur dioxide is also scavenged by deliquesced
 5    aerosols and oxidized to H2SO4 in the aqueous phase by several strongly pH-dependent pathways
 6    (Chameides and Stelson, 1992; Vogt et al., 1996; Keene et al., 1998). Model calculations
 7    indicate that oxidation of S(IV) by O3 dominates in fresh, alkaline sea salt aerosols, whereas
 8    oxidation by hypohalous acids (primarily HOC1) dominates in moderately acidic solutions.
 9    Additional paniculate non-sea salt (nss) SC>42  is generated by SO2 oxidation in cloud droplets
10    (Clegg and Toumi, 1998). Ion-balance calculations indicate that most nss SC>42  in short-lived
11    (two to 48  hours) sea salt size fractions accumulates in acidic aerosol solutions and/or in acidic
12    aerosols processed through clouds (e.g., Keene et al., 2004). The production, cycling, and
13    associated  radiative effects of S-containing aerosols in marine and coastal air are regulated in
14    part by chemical transformations involving inorganic halogens (von Glasow et al., 2002b).
15    These transformations include:  dry-deposition fluxes of nss SC>42 in marine air dominated,
16    naturally, by the sea salt size fractions (Huebert et al., 1996; Turekian et al., 2001); HC1 phase
17    partitioning that regulates sea salt pH and associated pH-dependent pathways for S(IV) oxidation
18    (Keene et al., 2002; Pszenny et al., 2004); and potentially important oxidative reactions with
19    reactive halogens for (CH3)2S and S(IV). However, both the absolute magnitudes and relative
20    importance of these processes in MBL S cycling are poorly understood.
21           Iodine chemistry has been linked to ultrafme particle bursts at Mace Head (O'Dowd
22    et al., 1999, 2002).  Observed bursts coincide with the elevated concentrations of IO and are
23    characterized by particle concentrations increasing from background levels to up to
24    300,000 cm"3 on a time scale of seconds to minutes.  This newly identified source of marine
25    aerosol would provide additional aerosol surface area for condensation of sulfur oxides and
26    thereby presumably diminish the potential  for nucleation pathways involving H2SO4. However,
27    a subsequent investigation in  polluted air along the New England, USA coast found no
28    correlation between periods of nanoparticle growth and corresponding concentrations of I oxides
29    (Russell et al., 2006). The potential importance of I chemistry in aerosol nucleation and its
30    associated  influence on sulfur cycling remain highly uncertain.
31

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 1   AX2.4    MECHANISMS FOR THE AQUEOUS PHASE FORMATION OF
 2              SULFATE AND NITRATE
 3          The major species containing sulfur in clouds are HSOs and SOs2 , which are derived
 4   from the dissolution of SC>2 in water and are referred to as S(IV); and HSO/f and SC>42 , which
 5   are referred to as S(VI).  The major species capable of oxidizing S(IV) to S(VI) in cloud water
 6   are 63, peroxides (either H2O2 or organic peroxides), OH radicals, and ions of transition metals
 7   such as Fe and Cu that can catalyze the oxidation of S(IV) to S(VI) by 62.
 8          The basic mechanism of the aqueous phase oxidation of 862 has long been studied and
 9   can be found in numerous texts on atmospheric chemistry, e.g., Seinfeld and Pandis (1998),
10   Jacob (2000), and Jacobson (2002). The steps involved in the aqueous phase oxidation of SC>2
1 1   can be summarized as follows (Jacobson, 2002):
12          Dissolution of SO2

13                                   SO2(g) <=> SO2(aq)                       (AX2-38)
14          The formation and dissociation of H2SO3

                SO2(aq) + H2O(aq) o H2SO3 <£> H + + HSOf o 2H+ + SO32~
1 J                          *""•*"'*                             ™    if\.J\^~J 7 }
16   In the pH range commonly found in rainwater (2 to 6), the most important reaction converting
17   S(IV) to S(VI) is
1 g                      HS03- + H202 + H+^> S042~ + H20                  (AX2-40)
19   as SOi2 is much less abundant than HSOs".
20          Major pathways for the aqueous phase oxidation of S(IV) to S(VI) as a function of pH are
21   shown in Figure AX2-6. For pH up to about 5.3, H2O2 is seen to be the dominant oxidant; above
22   5.3, Os, followed by Fe(III) becomes dominant.  Higher pHs are expected to be found mainly in
23   marine aerosols. However, in marine aerosols, the chloride-catalyzed oxidation of S(IV) may be
24   more important (Zhang and Millero, 1991; Hoppel and Caffrey, 2005).  Because NH4+ is so
25   effective in controlling acidity, it affects the rate of oxidation of S(IV) to S(VI) and the rate of
26   dissolution of SC>2 in particles and cloud drops.
27
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    Figure AX2-6.
                             10-'
                         T   10'10
                         5
                         •"****
                         ~Q
                         \
                         55  10'12

                         I
                             10-14
                             10
                              -16
                             10'
                              ,-18
                                                           T      T
                                                   H2°2
                                       I      i       !      I       I
        0123456
                          PH
Comparison of aqueous-phase oxidation paths.  The rate of
conversion of S(IV) to S(VI) is shown as a function of pH.  Conditions
assumed are:  [SO2(g)] = 5 ppb; [NO2(g)] = 1 ppb; [H2O2(g)] = 1 ppb;
[O3(g>] = 50 ppb; [Fe(III)(aq)] = 0.3 uM; [Mn(II)(aq)] = 0.3 uM.
     Source: Seinfeld and Pandis (1998).
1          Nitrogen dioxide is also taken up in cloud drops and can be oxidized to NOs , although it
2   is much less soluble than SC>2 and this pathway is of minor importance. Instead, the uptake of
3   more highly soluble nitrogen-containing acids initiates aqueous-phase chemistry of NOs
4   formation.
5          Warneck (1999) constructed a box model describing the chemistry of the oxidation of
6   SC>2 and NC>2 including the interactions of N and S species and minor processes in sunlit cumulus
7   clouds. The relative contributions of different reactions to the oxidation of S(IV) species to
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 1    S(VI) and NO2 to NO3 10 minutes after cloud formation are given in Tables AX2-2a and
 2    AX2-2b. The two columns show the relative contributions with and without transition metal
 3    ions. As can be seen from Table AX2-2a, SO2 within a cloud (gas + cloud drops) is oxidized
 4    mainly by H2O2 in the aqueous phase, while and the gas-phase oxidation by OH radicals is small
 5    by comparison. A much smaller contribution in the aqueous phase is made by methyl
 6    hydroperoxide (CH3OOH) because it is formed mainly in the gas phase and its Henry's Law
 7    constant is several orders of magnitude smaller that of H2O2. After H2O2, HNO4 is the major
 8    contributor to S(IV) oxidation. The contribution from the gas phase oxidation of SO2 to be small
 9    by comparison to the aqueous -phase reactions given above.
10          In contrast to the oxidation of SO2, Table AX2-2b  shows that the oxidation of NO2 occurs
11    mainly in the gas phase within clouds,  implying that the gas phase oxidation of NO2 by OH
12    radicals predominates.  Clouds occupy about 15%, on average, of the volume of the troposphere.
13          The values shown in Tables AX2-2a and AX2-2b indicate that only about 20% of SO2 is
14    oxidized in the gas phase, but about 90% of NO2 is oxidized in the gas phase.  Thus,  SO2 is
15    oxidized mainly by aqueous-phase reactions, but NO2 is oxidized  mainly by gas phase reactions.

16    Multiphase Chemical Processes Involving Sulfur Oxides and Ammonia
17          The phase partitioning of NH3 with deliquesced aerosol  solutions is controlled primarily
18    by the thermodynamic properties of the system expressed  as follows:
                                         KH         K~h
                              AIH   j	-v r \ftf   i  j- ^  r ww ~M  • v /r w+i
19                           A**3g «-> yvn3aqi  *+  \riti 4 j -r Aw/[/Tf  j               (AX2-41)
20
21    where KH and Kb are the temperature-dependent Henry's Law and dissociation constants
22    (62 M atnT1) (1.8 x 1CT5 M), respectively, for NH3, and Kw is the  ion product of water (1.0 x
23    10~14 M) (Chameides, 1984).  It is evident that for a given amount of NHX (NH3 + particulate
24    NH4+) in the system, increasing aqueous concentrations of particulate H+ will shift the
25    partitioning of NH3 towards the condensed phase.  Consequently,  under the more polluted
26    conditions  characterized by higher concentrations  of acidic sulfate aerosol, ratios of gaseous NH3
27    to particulate NH4+ decrease (Smith et  al., 2007).  It also follows that in marine air, where
28    aerosol acidity varies substantially as a function of particle size, NH3 partitions preferentially to
29    the more acidic sub-|im size fractions (e.g., Keene et al., 2004; Smith et al., 2007).

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 1          Because the dry-deposition velocity of gaseous NH3 to the surface is substantially greater
 2    than that for the sub-|im, sulfate aerosol size factions with which most particulate NH4+ is
 3    associated, dry-deposition fluxes of total NH3 are dominated by the gas phase fraction (Russell
 4    et al., 2003; Smith et al., 2007). Consequently, partitioning with highly acidic sulfate aerosols
 5    effectively increases the atmospheric lifetime of total NH3 against dry deposition. This shift has
 6    important consequences forNH3 cycling and potential ecological effects. In coastal New
 7    England during summer, air transported from rural eastern Canada contains relatively low
 8    concentrations of particulate non-sea salt (nss) SC>42  and total NH3 (Smith et al., 2007).  Under
 9    these conditions, the roughly equal partitioning of total NH3 between the gas and particulate
10    phases sustains substantial dry-deposition fluxes of total NH3 to the coastal ocean (median of
11    10.7 jimol nT2 day"1).  In contrast, heavily polluted air transported from the industrialized
12    midwestern United States contains concentrations of nss SC>42  and total NH3 that are, about a
13    factory of 3 greater, based on median values. Under these conditions, most total NH3 (>85%)
14    partitions to the highly acidic sulfate aerosol size fractions and, consequently, the median dry-
15    deposition flux of total NH3 is 30% lower than that under the cleaner northerly flow regime. The
16    relatively longer atmospheric lifetime of total NH3 against dry deposition under more polluted
17    conditions implies that, on average, total NH3 would accumulate to higher atmospheric
18    concentrations under these conditions and also be subject to atmospheric transport over longer
19    distances. Consequently, the importance NHX of removal via wet deposition would also increase.
20    Because of the inherently sporadic character of precipitation, we might expect by greater
21    heterogeneity in NH3 deposition fields and any  potential responses by sensitive ecosystems
22    downwind of major S-emission regions.
23
24
25    AX2.5   TRANSPORT OF NITROGEN AND SULFUR OXIDES IN
26             THE ATMOSPHERE
27          Major episodes of high O3 concentrations in the eastern United Sates and in Europe are
28    associated with slow moving high-pressure systems.  High-pressure systems during the warmer
29    seasons are associated with subsidence, resulting in warm, generally cloudless conditions with
30    light winds. The subsidence results in stable conditions near the surface, which inhibit or reduce
31    the vertical mixing of O3 precursors (NOX, VOCs, and CO). Photochemical activity is enhanced
32    because of higher temperatures and the availability of sunlight. However, it is becoming

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 1    increasingly apparent that transport of 63 and NOX and VOC from distant sources can provide
 2    significant contributions to local [63] even in areas where there is substantial photochemical
 3    production. There are a number of transport phenomena occurring either in the upper boundary
 4    layer or in the free troposphere which can contribute to high Os values at the surface. These
 5    phenomena include stratospheric-tropospheric exchange (STE), deep and shallow convection,
 6    low-level jets, and the so-called "conveyor belts" that serve to characterize flows around frontal
 7    systems.
 8
 9    Convective Transport
10          Crutzen and Gidel (1983), Gidel (1983), and Chatfield and Crutzen (1984) hypothesized
11    that convective clouds played an important role in rapid atmospheric vertical transport of trace
12    species and first tested simple parameterizations of convective transport in  atmospheric chemical
13    models.  At nearly the same time,  evidence was shown of venting the boundary layer by shallow,
14    fair weather cumulus clouds (e.g., Greenhut et al., 1984; Greenhut, 1986).  Field experiments
15    were conducted in 1985 which resulted in verification of the hypothesis that deep convective
16    clouds are instrumental in atmospheric transport of trace constituents (Dickerson et al.,  1987).
17    Once pollutants are lofted to the middle and upper troposphere, they typically have a much
18    longer chemical lifetime and with the generally stronger winds at these altitudes, they can be
19    transported large distances from their source regions.  Transport of NOX from the boundary layer
20    to the upper troposphere by convection tends to dilute the higher in the boundary layer
21    concentrations and extend the NOX lifetime from less than 24 hours to several days.
22    Photochemical reactions occur during this long-range transport. Pickering  et al. (1990)
23    demonstrated that venting of boundary layer NOX by convective clouds (both shallow and deep)
24    causes enhanced Os production in the free troposphere. The dilution of NOX at the surface can
25    often increase Os production efficiency.  Therefore, convection aids in the transformation of
26    local pollution into a contribution to global atmospheric pollution. Downdrafts within
27    thunderstorms tend to bring air with less NOX from the middle troposphere  into the boundary
28    layer. Lightning produces NO which is directly injected chiefly into the middle and upper
29    troposphere.  The total global production of NO by lightning remains uncertain, but is on the
3 0    order of 10% of the total.
31
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 1    Observations of the Effects ofConvective Transport
 2          The first unequivocal observations of deep convective transport of boundary layer
 3    pollutants to the upper troposphere were documented by Dickerson et al. (1987).
 4    Instrumentation aboard three research aircraft measured CO, Os, NO, NOX, NOy, and
 5    hydrocarbons in the vicinity of an active mesoscale convective system near the
 6    Oklahoma/Arkansas border during the 1985 PRE-STORM experiment. Anvil penetrations about
 7    two hours after maturity found greatly enhanced mixing ratios inside the cloud of all of the
 8    aforementioned species compared with outside it.  Nitric oxide mixing ratios in the anvil
 9    averaged 3 to 4 ppbv, with individual 3-min observations reaching 6 ppbv; boundary layer NOX
10    was typically 1.5 ppbv or less outside the cloud. Therefore, the anvil observations represent a
11    mixture of boundary layer NOX and NOX contributed by lightning. Luke et al.  (1992)
12    summarized the air chemistry data from all 18 flights during PRE-STORM by categorizing each
13    case according to synoptic flow patterns.  Storms in the maritime tropical flow regime
14    transported large amounts of CO, Os, and NOy into the upper troposphere with the
15    midtroposphere remaining relatively clean. During frontal passages a combination of stratiform
16    and convective clouds mixed pollutants more uniformly into the middle and upper levels.
17          Prather and Jacob (1997) and Jaegle et al. (1997) noted that precursors of HOX are also
18    transported to the upper troposphere by deep convection, in addition to primary pollutants (e.g.,
19    NOX, CO, VOCs).  The HOX precursors of most importance are water vapor, HCHO, H2O2,
20    CHaOOH,  and acetone.  The hydroperoxyl radical is critical for oxidizing NO  to NO2 in the Os
21    production process as described above.
22          Over remote marine areas, the effects of deep convection on trace gas distributions differ
23    from those over moderately polluted continental regions.  Chemical measurements taken by the
24    NASA ER-2 aircraft during the Stratosphere-Troposphere Exchange Project (STEP) off the
25    northern coast of Australia show the influence of very deep convective events.  Between 14.5
26    and 16.5 km on the February 2-3, 1987 flight, chemical profiles that included pronounced
27    maxima in CO, water vapor,  and CCN, and minima of NOy, and O3 (Pickering et al., 1993).
28    Trajectory analysis showed that these air parcels likely were transported  from convective cells
29    800-900 km upstream.  Very low marine boundary layer mixing ratios of NOy and Os in this
30    remote region were apparently transported upward in the convection. A  similar result was noted
31    in CEPEX (Central Equatorial Pacific Experiment; Kley et al., 1996) and in INDOEX (Indian

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 1    Ocean Experiment) (deLaat et al., 1999) where a series of ozonesonde ascents showed very low
 2    upper tropospheric 63 following deep convection.  It is likely that similar transport of low-ozone
 3    tropical marine boundary layer air to the upper troposphere occurs in thunderstorms along the
 4    east coast of Florida. Deep convection occurs frequently over the tropical Pacific.  Low-ozone
 5    and low-NOx convective outflow likely will descend in the subsidence region of the subtropical
 6    eastern Pacific, leading to some of the cleanest air that arrives at the west coast of the United
 7    States.
 8          The discussion above relates to the effects of specific convective events. Observations
 9    have also been conducted by NASA aircraft in survey mode, in which the  regional  effects of
10    many convective events can be measured. The SONEX (Subsonic Assessment Ozone and
11    Nitrogen Oxides Experiment) field program in 1997 conducted primarily upper tropospheric
12    measurements over the North Atlantic.  The regional effects of convection over North America
13    and the Western Atlantic on upper tropospheric NOX were pronounced (Crawford et al., 2000;
14    Allen et  al., 2000).  A discussion of the results of model calculations of convection and its effects
15    can be found in Section AX2.7.
16
17    Effects on Photolysis Rates and Wet Scavenging
18          Thunderstorm clouds are optically very thick, and, therefore, have  major effects on
19    radiative fluxes and photolysis rates. Madronich (1987) provided modeling estimates of the
20    effects of clouds of various optical  depths on photolysis rates. In the upper portion of a
21    thunderstorm anvil, photolysis is likely to be enhanced by a factor of 2 or more due to multiple
22    reflections off the ice crystals. In the lower portion and beneath the cloud, photolysis is
23    substantially decreased. With enhanced photolysis rates, the NO/NO2 ratio in the upper
24    troposphere is driven to larger values than under clear-sky conditions. Existing experimental
25    evidence seems to confirm, at least qualitatively these model results (Kelley et al., 1994).
26          Thunderstorm updraft regions, which contain copious amounts of water, are regions
27    where efficient scavenging of soluble species can occur (Balkanski et al., 1993). Nitrogen
28    dioxide itself is not very soluble and therefore wet scavenging is not a major removal process for
29    it.  However, a major NOX reservoir species, HNOs is extremely soluble.  Very few direct field
30    measurements of the amounts of specific trace gases that are scavenged in storms are available.
31    Pickering et al. (2001) used a combination of model estimates of soluble species that did not
32    include wet scavenging and observations of these species from the upper tropospheric outflow

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 1   region of a major line of convection observed near Fiji. Over 90% of the and in the outflow air
 2   appeared to have been removed by the storm. About 50% of CH3OOH and about 80% of HCHO
 3   had been lost.
 4          Convective processes and small-scale turbulence transport pollutants both upward and
 5   downward throughout the planetary boundary layer and the free troposphere. Ozone and its
 6   precursors (NOX, CO, and VOCs) can be transported vertically by convection into upper part of
 7   the mixed layer on one day, then transported overnight as a layer  of elevated mixing ratios,
 8   perhaps by a nocturnal low-level jet, and then entrained into a growing convective boundary
 9   layer downwind and brought back to the surface.
10          Because NO  and NO2 are only slightly soluble, they can be transported over longer
11   distances in the gas phase than can more soluble species which can be depleted by deposition to
12   moist surfaces, or  taken up more readily on aqueous surfaces of particles. During transport, they
13   can be transformed into reservoir species such as HNOs, PANs, and ^Os. These species can
14   then contribute to  local NOX concentrations in remote areas. For example, it is now well
15   established that PAN decomposition provides a major source of NOX in the remote troposphere
16   (Staudt et al., 2003). PAN decomposition in subsiding air masses from Asia over the eastern
17   Pacific could make an important contribution to Os and NOX enhancement in the U.S.
18   (Kotchenruther et  al., 2001; Hudman et al.,  2004).  Further details about mechanisms for
19   transporting ozone and its precursors were described at length in CD06.
20
21
22   AX2.6    SOURCES AND EMISSIONS OF NITROGEN OXIDES,
23              AMMONIA, AND SULFUR DIOXIDE
24          All three of the species listed in the title to this section have both natural and
25   anthropogenic sources.  In Section AX2.6.1, interactions of NOX with the terrestrial biosphere are
26   discussed. Because of the tight coupling between processes linking emissions and deposition,
27   they are discussed together.  In Section AX2.6.2, emissions of NOX, NH3, and SO2 are discussed.
28   Field studies evaluating emissions inventories are discussed in Section AX2.6.3.
29
30   AX2.6.1   Interactions of Nitrogen Oxides with the Biosphere
31          Nitrogen oxides affect vegetated ecosystems, and in turn the atmospheric chemistry of
32   NOX is influenced  by vegetation. Extensive research on nitrogen  inputs from the atmosphere to

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 1    forests was conducted in the 1980s as part of the Integrated Forest Study, and is summarized by
 2    Johnson and Lindberg (1992). The following sections discuss sources of NOX from soil,
 3    deposition of NOX to foliage, reactions with biogenic hydrocarbons, and ecological effects of
 4    nitrogen deposition.
 5
 6    NOX Sources
 1
 8    Soil NO
 9          Nitric oxide NO from soil metabolism is the dominant, but not exclusive, source of
10    nitrogen oxides from the biosphere to the atmosphere. As noted below, our understanding of
11    NC>2 exchange with vegetation suggests that there should be emission of NC>2 from foliage when
12    ambient concentrations are less than about 1 ppb. However, Lerdau et al. (2000) have pointed
13    out that present understanding of the  global distribution of NOX is not consistent with a large
14    source that would be expected in remote forests if NO2 emission was important when
15    atmospheric concentrations were below the compensation point.
16          The pathways for nitrification and denitrification include two gas-phase intermediates,
17    NO and N2O,  some of which can escape.  While N2O is of interest for its greenhouse gas
18    potential and role in stratospheric chemistry it is not considered among the reactive nitrogen
19    oxides important for urban and regional air  quality and will not be discussed further.
20    Temperature and soil  moisture are critical factors that control the rates of reaction  and
21    importantly the partitioning between  NO and N2O which depend on oxygen levels: in flooded
22    soils where oxygen levels are low, N2O is the dominant soil nitrogen gas; as soil dries, allowing
23    more O2 to diffuse, NO emissions increase.  In very dry soils microbial activity is inhibited and
24    emissions of both N2O and NO decrease.  Nitrogen metabolism in soil is strongly dependent on
25    the substrate concentrations.  Where nitrogen is limiting, nitrogen is efficiently retained and little
26    gaseous nitrogen is released.  Where  nitrogen is in excess of demand, gaseous nitrogen emissions
27    increase; consequently, soil NO emissions are highest in fertilized agriculture and tropical soils
28    (Davidson and Kingerlee, 1997; Williams et al., 1992).
29
30    Sinks
31          Several reactive nitrogen are species are deposited to vegetation, among them, HNOs,
32    NO2, PAN, and organic nitrates.

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 1   HNO3
 2          Deposition of HNO3 appears to be relatively simple.  Field observations based on
 3   concentration gradients and recently using eddy covariance demonstrate rapid deposition that
 4   approaches the aerodynamic limit (as constrained by atmospheric turbulence) in the Wesely
 5   (1989) formulation based on analogy to resistance.  Surface resistance for HNOs uptake by
 6   vegetation is negligible. Deposition rates are independent of leaf area or stomatal conductance,
 7   implying that deposition occurs to branches, soil, and leaf cuticle as well as internal leaf surfaces.
 8          Deposition velocities (Vd) typically exceed 1 cm s^and exhibit a daily pattern controlled
 9   by turbulence characteristics: midday maximum and lower values at night when there is stable
10   boundary layer.
11
12   Deposition of NO 2
13          Nitrogen dioxide interaction with vegetation is more complex.  Application of 15N-
14   labeled Nitrogen Dioxide demonstrates that Nitrogen Dioxide is absorbed and metabolized by
15   foliage (Siegwolf et al., 2001; Mocker et al., 1998; Segschneider et al., 1995; Weber, et al.,
16    1995). Exposure to NC>2 induces nitrate reductase (Weber et al., 1995, 1998), a necessary
17   enzyme for assimilating oxidized nitrogen. Understanding of NC>2 interactions with foliage is
18   largely based on leaf cuvette and growth chamber studies, which expose foliage or whole plants
19   to controlled levels of NO2 and measure the fraction of NO2 removed from the chamber air. A
20   key finding is that the fit of NC>2 flux to NC>2 concentration, has a non-zero intercept, implying a
21   compensation point or internal concentration.  In studies at very low NO2 concentrations
22   emission from foliage is observed (Teklemariam and Sparks, 2006). Evidence for a
23   compensation point is not solely based on the fitted intercept. Nitrogen dioxide uptake rate to
24   foliage is clearly related to stomatal conductance. Internal resistance is variable, and may be
25   associated with concentrations of reactive species such as ascorbate in the plant tissue that react
26   with NC>2 (Teklemariam and Sparks, 2006). Foliar NC>2 emissions show some dependence on
27   nitrogen content (Teklemariam and Sparks, 2006). Internal NC>2 appears to derive from plant
28   nitrogen metabolism.
29          Two approaches to modeling NO2 uptake by vegetation are the resistance-in-series
30   analogy which  considers flux (F) as the product of concentration (C) and Vd, where is related to
31   the sum of aerodynamic, boundary layer, and internal resistances (Ra, Rb, and RC ; positive fluxes
32   are from atmosphere to foliage)

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 1                                           F - CVd                               (AX2-42)

 2                                     Vd~ (Ra + Rb + RcT]                        (AX2-43)
 3          Ra and Rb and controlled by turbulence in the mixed layer; RC is dependent on
 4    characteristics of the foliage and other elements of the soil, and may be viewed as 2 combination
 5    of resistance internal to the foliage and external on the cuticle, soils, and bark. This approach is
 6    amenable to predicting deposition in regional air quality models (Wesely, 1989).  Typically, the
 7    NC>2, Vd is less than that for Os, due to the surface's generally higher resistance to NO2 uptake,
 8    consistent with N(Vs lower reactivity.
 9          Alternatively, NC>2 exchange with foliage can be modeled from a physiological viewpoint
10    where the flux from the leaf is related to the stomatal conductance and a concentration gradient
11    between the ambient air and interstitial air in the leaf.  This approach best describes results for
12    exchange with individual foliage elements, and is expressed  per unit leaf (needle) area. While
13    this approach provides linkage to leaf physiology, it is not straightforward to scale up from the
14    leaf to ecosystem scale:
15
Ss(Ca  Q)                            (AX2-44)
16          This model implicitly associates the compensation point with a finite internal
17    concentration.  Typically observed compensation points are around 1 ppb.  Finite values of
18    internal NC>2 concentration are consistent with metabolic pathways that include oxides of
19    nitrogen.  In this formulation, the uptake will be linear with NC>2 concentration, which is
20    typically observed with foliar chamber studies.
21          Several studies have shown the UV dependence of NC>2 emission, which implies some
22    photo-induced surface reactions that release NC>2. Rather than model this as a UV-dependent
23    internal concentration, it would be more realistic to add an additional term to account for
24    emission that is dependent on light levels and other surface characteristics:
25                                       sa           s                            (AX2-45)
26          The mechanisms for surface emission are discussed below.  Measurement of NC>2 flux is
27    confounded by the rapid interconversion of NO, NC>2, and Os (Gao et al., 1991).
28

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 1   PAN Deposition
 2          Peroxyacetyl nitrate is phytotoxic, so clearly it is absorbed at the leaf. Observations
 3   based on inference from concentration gradients and rates of decline at night (Shepson et al.,
 4    1992; Schrmipf et al., 1996) and leaf chamber studies (Teklemariam and Sparks, 2004) have
 5   indicated that PAN uptake is slower than that of Os; however, recent work in coniferous canopy
 6   with direct eddy covariance PAN flux measurements indicated a Vd more similar to that of O^.
 1   Uptake of PAN is under stomatal control, has a non-zero deposition at night, and is influenced by
 8   leaf wetness (Turnipseed et al., 2006). On the other hand, flux measurements determined by
 9   gradient methods over a grass surface showed a Vd closer to 0.1 cm s'1, with large uncertainty
10   (Doskey et al.,  2004). A factor of 10 uncertainty remains in Vd 0.1-1  cm s'1 giving a range.
11   Whether the discrepancies are methodological or indicate intrinsic differences between different
12   vegetation is unknown.  Uptake of PAN is smaller than its thermal decomposition in all cases.
13
14   Organic Nitrates
15          The biosphere also interacts with NOX through hydrocarbon emissions and their
16   subsequent reactions to form multi-functional organic nitrates. Isoprene nitrates are an important
17   class of these.  Isoprene reacts with OH to form a radical that adds NO2 to form a hydroxyalkyl
18   nitrate.  The combination of hydroxyl and nitrate functional group makes these compounds
19   especially soluble with low vapor pressures; they likely deposit rapidly (Shepson et al., 1996;
20   Treves et al., 2000).  Many other unsaturated hydrocarbons react by analogous routes.
21   Observations at Harvard Forest show a substantial fraction of total NOy not accounted for by
22   NO, NO2 and PAN, which is attributed to the organic nitrates (Horii et al., 2006, Munger et al.,
23    1998). Furthermore, the total NOy flux exceeds the sum of HNOs, NOX, and PAN, which implies
24   that the organic nitrates are a substantial fraction of nitrogen deposition.  Other observations that
25   show evidence of hydoxyalkyl nitrates include those of Grossenbacher et al. (2001) and Day
26   et al. (2003).
27          Formation of the hydroxyalkyl nitrates occurs after VOC + OH reaction.  In some sense,
28   this mechanism is just an alternate pathway for OH to react with NOX to form a rapidly
29   depositing species.  If VOC were not present, OH would be available to react with NO2 when it
30   is present instead to form
31
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 1   HONO
 2          Nitrous acid formation on vegetative surfaces at night has long been observed based on
 3   measurements of positive gradients (Harrison and Kitto, 1994). Surface reactions of NO2
 4   enhanced by moisture were proposed to explain these results. Production was evident at sites
 5   with high ambient NO2; at low concentration, uptake of HONO exceeded the source.
 6   Daytime observations of HONO when rapid photolysis is expected to deplete ambient
 7   concentrations to very low levels implies a substantial source of photo-induced HONO formation
 8   at a variety of forested sites where measurements have been made. Estimated source strengths
 9   are 200-1800 pptv hr1 in the surface layer (Zhou et al., 2002a, 2003), which is about 20 times
10   faster than all nighttime sources. Nitrous acid sources could be important to OH/HO2 budgets as
1 1   HONO is rapidly photolyzed by sunlight to OH and NO. Additional evidence of light-dependent
12   reactions to produce HONO comes from discovery of a HONO artifact in pyrex sample inlet
13   lines exposed to ambient light. Either covering the inlet or washing it eliminated the HONO
14   formation (Zhou et al., 2002b). Similar reactions might serve to explain observations of UV-
15   dependent production of NOX in empty foliar cuvettes that had been exposed to ambient air (Hari
16   et al., 2003; Raivonen et al., 2003).
17          Production of HONO in the dark is currently believed to occur via a heterogeneous
18   reaction involving NO2 on wet surfaces (Jenkin et al., 1988; Pitts et al., 1984; He et al., 2006;
19   Sakamaki et al., 1983), and it is proposed that the mechanism has first-order dependence in both
20   NO2 and H2O (Kleffmann et al., 1998; Svensson et al., 1987) despite the stoichiometry.
21   However, the molecular pathway of the mechanism is still under debate. Jenkin et al. (1988)
22   postulated a H2O-NO2 water complex reacting with gas phase NO2 to produce HONO, which is
23   inconsistent with the formation of an N2O4 intermediate leading to HONO as proposed by
24   Finlayson-Pitts et al. (2003). Another uncertainty is whether the reaction forming HONO is
25   dependent on water vapor (Svensson et al., 1987; Stutz et al., 2004) or water adsorbed on
26   surfaces  (Kleffmann et al., 1998).  Furthermore, the composition of the surface and the available
27   amount of surface or surface-to-volume ratio can significantly influence the HONO production
28   rates (Kaiser and Wu, 1977; Kleffmann et al., 1998; Svensson et al., 1987), which may explain
29   the difference in the rates observed between laboratory and atmospheric measurements.
30          There is no consensus on a chemical mechanism for photo-induced HONO production.
3 1   Photolysis of HNOs or NOs  absorbed on ice or in surface water films has been proposed
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 1    (Honrath et al., 2002; Ramazan et al., 2004; Zhou et al., 2001, 2003). Alternative pathways
 2    include NO2 interaction with organic surfaces such as humic substances (George et al., 2005;
 3    Stemmler et al., 2006). Note that either NO3  photolysis or heterogeneous reaction of NO2 are
 4    routes for recycling deposited nitrogen oxides back to the atmosphere in an active form.  Nitrate
 5    photolysis would return nitrogen that heretofore was considered irreversibly deposited, surface
 6    reactions between NO2 and water films or organic molecules would decrease the effectiveness of
 7    observed NO2 deposition if the HONO were re-emitted.
 8
 9    Fast Homogeneous Reactions
10          Inferences from observations at Blodgett Forest (Cohen et al. in prep) suggest that
11    radicals from Os + VOC react with NOX in the canopy to produce HNOs and organic nitrates
12    among other species. This mechanism would contribute to canopy retention of soil NO emission
13    in forests with high VOC possibly more effectively than the NO to NO2 conversion and foliar
14    uptake of NO2 that has been proposed to reduce the amount of soil NO that escapes to the supra-
15    canopy atmosphere (Jacob and Bakwin, 1991).
16
17    Some NO 2 and HNOs Flux Data from Harvard Forest
18
19    Observations from TDL Measurements of NO 2
20          Harvard Forest is a rural site in central Massachusetts, where ambient NOX, NOy, and
21    other pollutant concentrations and fluxes of total NOy have been measured since 1990 (Munger
22    et al., 1996).  An intensive study in 2000 utilized a Tunable Diode Laser Absorption
23    Spectrometer (TDLAS) to measure NO2 and HNOs. TDLAS has an inherently fast response, and
24    for species such as NO2 and HNOs with well-characterized spectra it provides  an absolute and
25    specific measurement.  Absolute concentrations of HNOs were measured, and  the flux inferred
26    based on the dry deposition inferential method that uses momentum flux measurements to
27    compute a deposition velocity and derives an inferred flux (Wesely and Hicks, 1977; Hicks et al.,
28    1987). Direct eddy covariance calculations for HNOs were not possible because the atmospheric
29    variations were attenuated by interaction with the inlet walls despite very short residence time
30    and use of fluorinated silane coatings to make the inlet walls more hydrophobic.  Nitrogen Oxide
31    response was adequate to allow both concentration and eddy covariance flux determination.
32    Simultaneously, NO and NOy eddy covariance fluxes were determined with two separate Os

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 1    chemiluminescence detectors, one equipped with a H2-gold catalyst at the inlet to convert all
 2    reactive nitrogen compounds to NO. Additionally, the measurements include concentration
 3    gradients for NO, NO2, and O3 over several annual cycles to examine their vertical profiles in the
 4    forest canopy.
 5           Overall, the results show typical NO2 concentrations of 1 ppb under clean-air conditions
 6    and mean concentrations up to 3 ppb at night and 1 ppb during daytime for polluted  conditions.
 7    Net positive fluxes (emission) of NO2 were evident in the daytime and negative fluxes
 8    (deposition) were observed at night (Figure AX2-7).  Nitric oxide fluxes were negative during
 9    the daytime and near zero at night.
10           In part the opposite NO and NO2 fluxes are simply consequences of variable NO/NO2
11    distributions responding to vertical gradients in light intensity and  O3 concentration, which
12    resulted in no net flux of NOX (Gao et al.,  1993). In the Harvard Forest situation, the NO and
13    NO2 measurements were not at the same height above the canopy,  and the resulting  differences
14    derive at least in part from the gradient in  flux magnitude between the two inlets (Figure AX2-8).
15           At night, when NO concentrations are near 0 due to titration by ambient O3 there is not a
16    flux of NO to offset NO2 fluxes. Nighttime data consistently show NO2 deposition (Figure
17    AX2-9), which increases with increasing NO2 concentrations. Concentrations above 10 ppb
18    were rare at this site, but the few high NO2 observations suggest a  nonlinear dependence on
19    concentration. The data fit a model with Vd of -0.08 plus an enhancement term that was second
20    order in NO2 concentration.  The second order term implies that NO2 deposition rates to
21    vegetation in polluted urban sites would be considerably larger than what was observed at this
22    rural site.
23           After accounting for the NO-NO2 null cycle the net NOX flux could be derived. Overall,
24    there was a net deposition of NOX during the  night and essentially zero flux in the day, with large
25    variability in the magnitude and sign of individual flux observations  (Figure AX2-10). For the
26    periods with [NO2] > 2 ppb, deposition was always observed.  These canopy-scale field
27    observations are consistent with a finite compensation point for NO2 in the canopy that offsets
28    foliar uptake or even reverses it when concentrations are especially low. At concentrations
29    above the compensation point, NOX is absorbed by the canopy. Examination of concentration
30    profiles corroborates the flux measurements (Figure AX2-11).  During daytime for low-NOx
31    conditions, there is a local maximum in the concentration profile near the top of the  canopy

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                      NW
                                                  SW
 o
 _
 E
 c
 O
 O
 E
 3b
 x
 3
      0--
         [NO]
         [NO]

FNO
FNO.,   - A
FO /10	
                                _f.
                                     11
                6       12       18

                     Hours
                                            6       12       18

                                                Hours
Figure AX2-7.
          Diel cycles of median concentrations (upper panels) and fluxes (lower
          panels) for the Northwest clean sector, left panels) and Southwest
          (polluted sector, right panels) wind sectors at Harvard Forest, April-
          November, 2000, for NO, NO2, and O3/10.  NO and O3 were sampled
          at a height of 29 m, and NO2 at 22 m.  Vertical bars indicate 25th and
          27th quartiles for NO and NO2 measurements. NO2 concentration
          and nighttime deposition are enhanced under southwesterly
          conditions, as are O3 and the morning NO maximum.
Source: Horn et al. (2004).
August 2007
                             AX2-43
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                                     Simple Model
              100
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0,0   0,2   0.4   0.6  0,8   1.0-2-1     0     1     2
   Concentration (nmol mol"1)       Flux {nnnoi mol"1 cm s"1)

  Simple NOX photochemical canopy model outputs. Left panel,
  concentrations of NO (dashed) and NO2 (solid); right, fluxes of NO
  (dashed) and NO2 (solid). Symbols indicate measurement heights for
  NO (29m) and NO2 (22m) at Harvard Forest. The model solves the
  continuity equation for NO concentration at 200 levels, d/dz(-
  Kc(dNO/dz)) = PNO - LNO, where PNO = [NO]/tl, LNO = [NO]/t2,
  and zero net deposition or emission of NOX is allowed.  NOX (NO +
  NO2) is normalized to Ippb. tl = 70s in this example. Due to the
  measurement height difference, observed upward NO2 flux due to
  photochemical cycling alone should be substantially larger than
  observed downward NO flux attributable to the same process.
Source: Horn (2002).
August 2007
                     AX2-44
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                                   FNO2 (night) = F0 + V0 [NO2] + a [NO2J2
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    Figure AX2-9.
Hourly (dots) and median nightly (pluses) NOi flux vs. concentration,
with results of least-squares fit on the hourly data (curve). The flux is
expressed in units of concentration times velocity (nmol mol'1 cm s'1)
in order to simplify the interpretation of the coefficients in the least-
squares fit.  Pressure and temperature corrections have been taken
into account in the conversion from density to mixing ratio.
     Source: Horn et al. (2004).
1   where Os has a local minimum, which is consistent with foliar emission or light-dependent
2   production of NOX in the upper canopy. Depletion is evident for both NOX and Os near the forest
3   floor.  Air reaching the ground has passed through the canopy where uptake is efficient and the
4   vertical exchange rates near the ground are slow.  At night, the profiles generally decrease with
5   decreasing height above the ground, showing only uptake.  At higher concentrations, the daytime
6   NOX concentrations are nearly constant through the canopy; no emission is evident from the
7   sunlit leaves.
8          Figure AX2-12 compares observed fluxes of all the observed species. The measured NOX
9   and estimated PAN fluxes are small relative to the observed total NOy flux. In  clean air,
    August 2007
                    AX2-45
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Figure AX2-11.     Averaged profiles at Harvard Forest give some evidence of some
                   input near the canopy top from light-mediated ambient reactions, or
                   emission from open stomates.
Source: Horn et al. (2004).
August 2007
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                                  Summer 2000
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               Summer (June-August) 2000 median concentrations (upper panels),
               fractions of NOy (middle panels), and fluxes (lower panels) of NOy and
               component species separated by wind direction (Northwest on the left
               and Southwest on the right). Vertical lines in the flux panels show
               25th and 75th quartiles of F(NOy) and F(HNO3); negative fluxes
               represent deposition; F(NOX) is derived from eddy covariance F(NO)
               and F(NO2) measurements (corrected for photochemical cycling),
               F(HNC>3) is inferred, and F(NOy) was measured by eddy covariance.
               The sum of NOX, HNOs, and PAN accounts for all of the NOy
               concentration and flux for Northwesterly (unpolluted background)
               flows, whereas up to 50% of NOy and F(NOy) under Southwesterly
               flows are in the form of reactive nitrogen species whose fluxes are not
               measured or estimated here.
Source: Horn et al. (2006).
August 2007
                                 AX2-47
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 1    accounts for nearly all the NOy flux and the sum of all measured species is about equal to the
 2    NOy concentration. However, in polluted conditions, unmeasured species are up to 25% of the
 3    NOy, and HNO3 fluxes cannot account for all the total NOy flux observed. Likely these
 4    unmeasured NOy species are hydroxyalkyl nitrates and similar compounds and are rapidly
 5    deposited.  Although NO2 uptake may be important to the plant, because it is an input directly to
 6    the interior of foliage that can be used immediately in plant metabolism, it is evidently not a
 7    significant part of overall nitrogen deposition to rural sites.  The deposition of HNOs and
 8    multifunctional organic nitrates are the largest elements of the nitrogen dry deposition budget.
 9    Two key areas of remaining uncertainty are the production of HONO over vegetation and the
10    role of very reactive biogenic VOCs.  HONO is important because its photolysis is a source of
11    OH radicals, and its formation may represent an unrecognized mechanism to regenerate
12    photochemically active NOX from nitrate that had been considered terminally removed from the
13    atmosphere.

14    Ecosystem Effects
15    In addition to the contribution to precipitation acidity, atmospheric nitrogen oxides have
16    ecological  effects. Total loading by both and wet and dry deposition is the relevant metric for
17    considering ecosystem impacts. At low inputs, nitrogen deposition adds essential nutrients to
18    terrestrial ecosystems. Most temperate  forests are nitrogen limited; thus the inputs stimulate
19    growth.  Anthropogenic nitrogen may influence some plant species different and alter the
20    distribution of plant species (cf. Wedin  and Tilman, 1996). At high nitrogen loading, where
21    nitrogen inputs exceed nutrient requirements, deleterious effects including forest decline
22    associated  with 'nitrogen saturation' are seen (Aber at al., 1998; Driscoll et al., 2003). In aquatic
23    ecosystems, however, nitrogen is may or may not be  limiting, but in brackish waters  atmospheric
24    deposition  of anthropogenic nitrogen is suspected of contributing to  eutrophication of some
25    coastal waters and lakes (see Bergstrom and Jansson, 2006; Castro and Driscoll, 2002).
26
27    AX2.6.2 Emissions of NOX, NH3, and SO2
28
29    Emissions  ofNOx
30          Estimated annual emissions of NOX, NH3, and SO2 for 2002 (U.S. Environmental
31    Protection  Agency, 2006) are shown in  Table AX2-3. Methods for estimating emissions of

      August 2007                             AX2-48      DRAFT-DO NOT QUOTE OR CITE

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 1    criteria pollutants, quality assurance procedures, and examples of emissions calculated by using
 2    data are given in U.S. Environmental Protection Agency (1999).  Discussions of uncertainties in
 3    current emissions inventories and strategies for improving them can be found in NARSTO
 4    (2005).
 5          As can be seen from the table, combustion by stationary sources, such as electrical
 6    utilities and various industries,  accounts for roughly half of total anthropogenic emissions of
 7    NOX. Mobile sources account for the other half, with highway vehicles representing the major
 8    mobile source component. Approximately half the mobile source emissions are contributed by
 9    diesel engines, the remainder are emitted by gasoline-fueled vehicles and other sources.
10          Emissions of NOX associated with combustion arise from contributions from both fuel
1 1    nitrogen and atmospheric nitrogen.  Combustion zone temperatures greater than about 1300 K
12    are required to fix atmospheric N2:
13                                                                                 (AX2.4fi)

14    Otherwise, NO can be formed from fuel N according to this reaction:

15                        CaHbOcNd + 02  -> xC02 + yH20 + zNO           (AX2-47)
      In addition to NO formation by the schematic reactions given above, some NO2 and CO
16    are also formed depending on temperatures, concentrations of OH and HO2 radicals and O2
17    levels. Fuel nitrogen is highly variable in fossil fuels, ranging from 0.5 to 2.0 percent by weight
1 8    (wt %) in coal to 0.05% in light distillates (e.g., diesel fuel), to 1 .5 wt % in heavy fuel oils (UK
19    AQEG, 2004).  The ratio of NO2 to NOX in primary emissions ranges from 3 to 5 % from
20    gasoline engines, 5 to 12% from heavy-duty diesel trucks, 5 to 10% from vehicles fueled by
21    compressed natural gas and from 5 to 10% from stationary sources. In addition to NOX, motor
22    vehicles also emit HONO, with ratios of HONO to NOX ranging from 0.3% in the Caldecott
23    Tunnel, San Francisco Bay (Kirchstetter and Harley, 1996) to 0.5 to 1.0% in studies in the
24    United Kingdom (UK AQEG, 2004).  The NO2 to NOX ratios in emissions from turbine jet
25    engines are as high as 32 to 35 % during taxi and takeoff (CD93).  Sawyer et al. (2000) have
26    reviewed the factors associated with NOX emissions by mobile sources.  Marine transport
      August 2007                            AX2-49       DRAFT-DO NOT QUOTE OR CITE

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 1    represents a minor source of NOX, but it constitutes a larger source in the EU where it is expected
 2    to represent about two-thirds of land-based sources (UK AQEG, 2004).
 3
 4    NOX Emissions from Natural Sources (Soil, Wild Fires, and Lightning)
 5
 6    Soil
 1          Emission rates of NO from cultivated soil depend mainly on fertilization levels and soil
 8    temperature. About 60% of the total NOX emitted by soils occurs in the central corn belt of the
 9    United States. The oxidation of NHa, emitted mainly by livestock and soils, leads to the
10    formation of NO, also NH4+ and NOs  fertilizers lead to NO emissions from soils. Estimates of
11    emissions from natural sources are less certain than those from anthropogenic sources.  On a
12    global scale, the contribution of soil emissions to the oxidized nitrogen budget is on the order of
13    10% (van Aardenne et al., 2001; Finlayson-Pitts and Pitts, 2000; Seinfeld and Pandis, 1998), but
14    NOX emissions from fertilized fields are highly variable. Soil NO emissions can be estimated
15    from the fraction of the applied fertilizer nitrogen emitted as NOX, but the flux varies strongly
16    with land use and temperature. Estimated globally averaged fractional applied nitrogen loss  as
17    NO varies from 0.3% (Skiba et al., 1997) to 2.5% (Yienger and Levy, 1995).  Variability within
18    biomes to which fertilizer is applied, such as shortgrass versus tallgrass prairie, accounts for  a
19    factor of three in uncertainty (Williams et al.,  1992; Yienger and Levy,  1995; Davidson and
20    Kingerlee, 1997).
21          The local contribution  can be much greater than the global average, particularly in
22    summer and especially where  corn is grown extensively.  Williams et al. (1992) estimated that
23    contributions to NO budgets from soils in Illinois are about 26% of the emissions from industrial
24    and commercial processes in that State. In Iowa, Kansas, Minnesota, Nebraska, and South
25    Dakota, all states with smaller human populations, soil emissions may dominate the NO budget.
26    Conversion of NHa to NOs (nitrification) in aerobic soils appears to be the dominant pathway to
27    NO. The mass and chemical form of nitrogen (reduced or oxidized) applied to soils, the
28    vegetative cover, temperature, soil moisture, and agricultural practices such as tillage all
29    influence the amount of fertilizer nitrogen released as NO.
30          Emissions of NO from soils peak in summer when Os formation is also at a maximum.
31    An NRC  panel report (NRC, 2002) outlined the role of agriculture in emissions of air pollutants
32    including NO and NH3.  That report recommends immediate implementation of best

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 1    management practices to control these emissions, and further research to quantify the magnitude
 2    of emissions and the impact of agriculture on air quality. Civerolo and Dickerson (1998) report
 3    that use of the no-till cultivation technique on a fertilized cornfield in Maryland reduced NO
 4    emissions by a factor of seven.
 5
 6    NOxfrom Biomass Burning
 1          During biomass burning, nitrogen is derived mainly from fuel nitrogen and not from
 8    atmospheric N2, since temperatures required to fix atmospheric N2 are likely to be found only in
 9    the flaming crowns of the most intense boreal forest fires.  Nitrogen is present mainly in plants as
10    amino (NH2) groups in amino acids. During combustion, nitrogen is released mainly in
11    unidentified forms, presumably as N2, with very little remaining in fuel ash. Apart from N2, the
12    most abundant species in biomass burning plumes is NO.  Emissions of NO account for only
13    about 10 to  20% relative to fuel N (Lobert et al., 1991). Other species such as NO2, nitriles,
14    ammonia, and other nitrogen compounds account for a similar amount. Emissions of NOX are
15    about 0.2 to 0.3% relative to total biomass burned (e.g., Andreae,  1991; Radke et al., 1991).
16    Westerling et al. (2006) have noted that the frequency and  intensity of wildfires in the western
17    U.S. have increased substantially since 1970.
18
19    Lightning Production of NO
20          Annual global production of NO by lightning is the most uncertain source of reactive
21    nitrogen. In the last decade, literature values of the global  average production rate range from
22    2 to 20 Tg N per year. However, the most likely range is from 3 to 8 Tg N per year, because the
23    majority of the recent estimates fall in this range. The large uncertainty stems from several
24    factors: (1) a large range of NO production rates per meter of flash length (as much as two orders
25    of magnitude); (2) the open question of whether cloud-to-ground (CG)  flashes and intracloud
26    flashes (1C) produce substantially different amounts of NO; (3) the global flash rate; and (4) the
27    ratio of the number of 1C flashes to the number of CG flashes. Estimates of the amount of NO
28    produced per flash have been made based on theoretical considerations (e.g., Price et al., 1997),
29    laboratory experiments (e.g., Wang et al., 1998); field experiments (e.g., Stith et al.,  1999;
30    Huntrieser et al., 2002,  2007) and through a combination of cloud-resolving model simulations,
31    observed lightning flash rates, and anvil measurements of NO (e.g., DeCaria et al., 2000, 2005;
32    Ott et al., 2007). The latter method was also used by Pickering et al. (1998), who showed that

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 1    only ~5 to 20% of the total NO produced by lightning in a given storms exists in the boundary
 2    layer at the end of a thunderstorm. Therefore, the direct contribution to boundary layer 63
 3    production by lightning NO is thought to be small. However, lightning NO production can
 4    contribute substantially to Os production in the middle and upper troposphere. DeCaria et al.
 5    (2005) estimated that up to 10 ppbv of ozone was produced in the upper troposphere in the first
 6    24 hours following a Colorado thunderstorm due to the injection of lightning NO.  A series of
 7    midlatitude and subtropical thunderstorm events have been simulated with the model of DeCaria
 8    et al.  (2005), and the derived NO production per CG flash averaged 500 moles/flash while
 9    average production per 1C flash was 425 moles/flash (Ott et al., 2006).
10          A major uncertainty in mesoscale and global chemical transport models is the
11    parameterization of lightning flash rates. Model variables such as cloud top height, convective
12    precipitation rate, and upward cloud mass flux have been used to estimate flash rates.  Allen and
13    Pickering (2002) have evaluated these methods  against observed flash rates from satellite, and
14    examined the effects on ozone production using each method.
15
16    Uses of Satellite Data to Derive Emissions
17          Satellite data have been shown to be useful for optimizing estimates of emissions of NO2.
18    (Leue et al., 2001; Martin et al., 2003; Jaegle et al., 2005).  Satellite-borne  instruments such as
19    GOME (Global Ozone Monitoring Experiment; Martin et al., 2003; and references therein) and
20    SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric Chartography;
21    Bovensmann et al.,  1999) retrieve tropospheric  columns of NO2, which can then be combined
22    with model-derived chemical lifetimes of NOX to yield emissions of NOX.
23          Top-down inference of NOX emission inventory from the satellite observations of NO2
24    columns by mass balance requires at minimum three pieces of information: the retrieved
25    tropospheric NO2 column, the ratio of tropospheric NOX to NO2 columns, and the NOX lifetime
26    against loss to stable reservoirs. A photochemical model has been used to  provide information
27    on the latter two pieces of information.  The method is generally applied exclusively to land
28    surface emissions, excluding lightning.  Tropospheric NO2 columns are insensitive to  lightning
29    NOX emissions since most of the lightning NOX  in the upper troposphere is present as NO at the
30    local  time of the satellite  measurements  (Ridley et al., 1996), owing to the  slower reactions of
31    NO with O3 there.
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 1          Jaegle et al. (2005) applied additional information on the spatial distribution of emissions
 2    and on fire activity to partition NOX emissions into sources from fossil fuel combustion, soils,
 3    and biomass burning. Global a posteriori estimates of soil NOX emissions are 68% larger than
 4    the a priori estimates. Large increases are found for the agricultural region of the western United
 5    States during summer, increasing total U.S. soil NOX emissions by a factor of 2 to 0.9 Tg N yr"1.
 6    Bertram et al. (2005) found clear signals in the SCIAMACHY observations of short intense NOX
 7    pulses following springtime fertilizer application and subsequent precipitation over agricultural
 8    regions of the western United States.  For the agricultural region in North-Central Montana, they
 9    calculate a yearly SCIAMACHY top-down estimate that is 60% higher than a commonly used
10    model of soil NOX emissions by Yienger and Levy (1995).
11          Martin et al. (2006) retrieved tropospheric nitrogen dioxide (NC^) columns for
12    May 2004 to April 2005 from the SCIAMACHY satellite instrument to derive top-down NOX
13    emissions estimates via inverse modeling with a global chemical transport model (GEOS-Chem).
14    The top-down emissions were combined with a  priori information from a bottom-up emission
15    inventory with error weighting to achieve an improved a posteriori estimate of the global
16    distribution of surface NOX emissions. Their a posteriori inventory improves the GEOS-Chem
17    simulation of NOX, PAN, and HNO3 with respect to airborne in situ measurements over and
18    downwind of New York City. Their a posteriori inventory shows lower NOX emissions from the
19    Ohio River valley during summer than during winter, reflecting recent controls on NOX
20    emissions from electric utilities. Their a posteriori inventory is highly consistent (R2 = 0.82,
21    bias = 3%) with the NEI99 inventory for the United States.  In contrast, their a posteriori
22    inventory is 68% larger than a recent inventory by Streets et al. (2003) for East Asia for the year
23    2000.
24
25    Emissions ofNHs
26          Emissions of NH3 show a strikingly different pattern from those of NOX. Three-way
27    catalysts used in motor vehicles emit small amounts of NH3 as a byproduct during the reduction
28    of NOX.  Stationary combustion  sources make only a small contribution to emissions of NH3
29    because efficient combustion favors formation of NOX and, NH3 from combustion is produced
30    mainly by inefficient, low temperature fuel combustion.  For these reasons,  most emissions of
31    NH3 arise from fertilized soils and from livestock.
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 1          The initial step in the oxidation of atmospheric NH? to NO is by reaction with OH
 2    radicals. However, the lifetime of NH? from this pathway is sufficiently long (-1-2 months
 3    using typical OH values 1-2 x 106/cm3) that it is a small sink compared to uptake of NH3 by
 4    cloud drops, dry deposition, and aerosol particles. Thus, the gas-phase oxidation of NH? makes a
 5    very small contribution as a source of NO.  Holland et al. (2005) estimated wet and dry
 6    deposition of NHX, based on measurements over the continental U.S., and found that emissions
 7    of NH3 in the National Emissions Inventory are perhaps underestimated by about a factor of two
 8    to three.  Reasons for this imbalance include under-representation of deposition monitoring sites
 9    in populated areas and the neglect of off-shore transport in their estimate. The use  of fixed
10    deposition velocities that do not reflect local conditions at the time of measurement introduces
11    additional uncertainty into their estimates of dry deposition.
12
13    Emissions of SO2
14          As can be seen from Table AX2-3, emissions of SO2 are due mainly to the combustion of
15    fossil fuels by electrical utilities and industry.  Transportation related sources make only a minor
16    contribution. As a result, most SO2 emissions originate from point sources.  Since  sulfur is a
17    volatile component of fuels, it is almost quantitatively released during combustion and emissions
18    can be calculated on the basis of the sulfur content of fuels to greater accuracy than for other
19    pollutants such as NOX or primary PM.
20          The major natural sources of SO2 are volcanoes and biomass burning and DMS oxidation
21    over the  oceans. SO2 constitutes a relatively minor fraction (0.005% by volume) of volcanic
22    emissions (Holland, 1978). The ratio of H2S to SO2 is highly variable in volcanic gases. It is
23    typically much less than one, as in the Mt. Saint Helen's eruption (Turco et al., 1983). However,
24    in addition to being degassed from magma, H2S can be produced if ground waters,  especially
25    those containing organic matter, come into contact with volcanic gases. In this case, the ratio of
26    H2S to SO2 can be greater than one. H2S produced this way would more likely be emitted
27    through  side vents than through eruption columns (Pinto et al.,  1989). Primary particulate sulfate
28    is a component of marine aerosol and is also produced by wind erosion of surface soils.
29          Volcanic sources of SO2 are limited to the Pacific Northwest, Alaska, and Hawaii.  Since
30    1980, the Mount St. Helens volcano in the Washington Cascade Range (46.20  N, 122.18 W,
31    summit 2549 m asl) has been a variable source of SO2. Its major effects came in the explosive
32    eruptions of 1980, which primarily affected the northern part of the mountainous western half of

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 1    the US. The Augustine volcano near the mouth of the Cook Inlet in southwestern Alaska
 2    (59.363 N, 153.43 W, summit 1252 m asl) has had variable SC>2 emission since its last major
 3    eruptions in 1986. Volcanoes in the Kamchatka peninsula of eastern region of Siberian Russia
 4    do not significantly effect surface SO2 concentrations in northwestern North America.  The most
 5    serious effects in the U.S. from volcanic SC>2 occurs on the island of Hawaii. Nearly continuous
 6    venting of SC>2 from Mauna Loa and Kilauea produces SC>2 in such large amounts that >100 km
 7    downwind of the island SC>2 concentrations can exceed 30 ppbv (Thornton and Bandy, 1993).
 8    Depending on wind direction, the west coast of Hawaii (Kona region) has had significant
 9    deleterious effects from 862 and acidic  sulfate aerosols for the past decade.
10          Emissions of SC>2 from burning vegetation are  generally in the range of 1  to 2% of the
11    biomass burned (see e.g., Levine et al.,  1999).  Sulfur is bound in amino acids in vegetation.
12    This organically bound sulfur is released during combustion. However, unlike nitrogen, about
13    half of the sulfur initially present in vegetation is found in the  ash (Delmas, 1982).  Gaseous
14    emissions are mainly in the form of SC>2 with much smaller amounts of H2S and OCS.  The ratio
15    of gaseous nitrogen to sulfur emissions  is about 14, very close to their ratio in plant tissue
16    (Andreae, 1991). The ratio of reduced nitrogen and sulfur species such as NH3 and H2S to their
17    more oxidized forms, such as NO and 862, increases from flaming to smoldering phases of
18    combustion, as emissions of reduced species are favored by lower temperatures and 62 reduced
19    availability.
20          Emissions of reduced sulfur species are associated typically with marine organisms living
21    either in pelagic or coastal zones and with anaerobic bacteria in marshes and estuaries.
22    Mechanisms for their oxidation were discussed in Section AX2.2.  Emissions of dimethyl sulfide
23    (DMS) from marine plankton represent  the largest single  source of reduced sulfur species to the
24    atmosphere (e.g., Berresheim et al., 1995). Other sources such as wetlands and terrestrial plants
25    and soils probably account for less than 5% of the DMS global flux, with most of this coming
26    from  wetlands.
27          The coastal and wetland sources of DMS have a dormant period in the fall/winter from
28    senescence of plant growth. Marshes die back in fall and winter, so dimethyl sulfide emissions
29    from  them are lower, reduced light levels in winter at mid to high latitudes reduce cut
30    phytoplankton growth which also tends  to reduce DMS emissions. Western coasts at mid to high
31    latitudes have reduced levels of the light that drive photochemical  production and oxidation of

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 1   DMS. Freezing at mid and high latitudes affects the release of biogenic sulfur gases, particularly
 2   in the nutrient-rich regions around Alaska. Transport of 862 from regions of biomass burning
 3   seems to be limited by heterogeneous losses that accompany convective processes that ventilate
 4   the surface layer and the lower boundary layer (Thornton et al., 1996, TRACE-P data archive).
 5          However, it should be noted that reduced sulfur species are also produced by industry.
 6   For example, DMS is used in petroleum refining and in petrochemical production processes to
 7   control the formation of coke and carbon monoxide. In addition, it is used to control dusting in
 8   steel mills. It is also used in a range of organic syntheses. It also has a use as a food flavoring
 9   component. It can also be oxidized by natural or artificial means to dimethyl sulfoxide (DMSO),
10   which has several important solvent properties.
11
12   AX2.6.3    Field Studies Evaluating Emissions Inventories
13          Comparisons of emissions model predictions with observations have been performed in a
14   number of environments. A number of studies of ratios of concentrations of CO to NOX and
15   NMOC to NOX during the early 1990s in tunnels and ambient air (summarized in Air Quality
16   Criteria for Carbon Monoxide (U.S. Environmental Protection Agency, 2000)) indicated that
17   emissions of CO and NMOC were systematically underestimated in emissions inventories.
18   However, the results of more recent studies have been mixed in this regard, with many studies
19   showing agreement to within ±50% (U.S. Environmental Protection Agency, 2000).
20   Improvements in many areas have resulted from the process of emissions model development,
21   evaluation, and further refinement.  It should be remembered that the conclusions from these
22   reconciliation studies depend on the assumption that NOX emissions are predicted correctly by
23   emissions factor models. Roadside remote sensing data indicate that over 50% of NMHC and
24   CO emissions are produced by less than about 10% of the vehicles (Stedman et al., 1991). These
25   "super-emitters" are typically poorly maintained vehicles. Vehicles of any age engaged in off-
26   cycle operations (e.g., rapid accelerations) emit much more than if operated in normal driving
27   modes.  Bishop and Stedman (1996) found that the most important variables governing CO
28   emissions are fleet age and owner maintenance.
29          Emissions inventories for North America can be evaluated by comparison to measured
30   long-term trends and or ratios of pollutants in ambient air. A decadal field study of ambient CO
31   at a rural site in the Eastern U.S. (Hallock-Waters et al.,  1999) indicates a downward trend
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 1    consistent with the downward trend in estimated emissions over the period 1988 to 1999 (U.S.
 2    Environmental Protection Agency, 1997), even when a global downward trend is accounted for.
 3    Measurements at two urban areas in the United States confirmed the decrease in CO emissions
 4    (Parrish et al., 2002). That study also indicated that the ratio of CO to NOX emissions decreased
 5    by almost a factor of three over 12 years (such a downward trend was noted in AQCD 96).
 6    Emissions estimates (U.S. Environmental Protection Agency, 1997) indicate a much smaller
 7    decrease in this ratio, suggesting that NOX emissions from mobile sources may be underestimated
 8    and/or increasing.  Parrish et al. (2002) conclude that Os photochemistry in U.S. urban areas may
 9    have become more NOx-limited over the past decade.
10          Pokharel et al. (2002) employed remotely sensed emissions from on-road vehicles and
11    fuel use data to estimate emissions in Denver.  Their calculations indicate a continual  decrease in
12    CO, HC, and NO emissions from mobile sources over the 6-year study period. Inventories based
13    on the ambient data were 30 to 70% lower for CO, 40% higher for HC, and 40 to 80% lower for
14    NO than those predicted by the MOBILE6 model.
15          Stehr et al.  (2000) reported simultaneous measurements of CO, SO2, and NOy  at an East
16    Coast site. By taking advantage of the nature of mobile sources (they emit NOX and CO but little
17    802) and power plants (they emit NOX and SO2 but little CO), the authors evaluated emissions
18    estimates for the eastern United States.  Results indicated that coal combustion contributes 25 to
19    35% of the total NOX emissions in rough agreement with emissions  inventories (U.S.
20    Environmental Protection Agency, 1997).
21          Parrish et al. (1998) and Parrish and Fehsenfeld (2000) proposed methods to derive
22    emission rates by examining measured ambient ratios among individual VOC, NOX and NOy.
23    There is typically a strong correlation among measured values for these species because emission
24    sources are geographically collocated, even when individual sources are different. Correlations
25    can be used to derive emissions ratios between species, including adjustments for the impact of
26    photochemical aging. Investigations of this type include correlations between CO and NOy (e.g.,
27    Parrish et al., 1991), between individual VOC species and NOy (Goldan et al., 1995, 1997, 2000)
28    and between various individual VOC (Goldan et al., 1995, 1997; McKeen and Liu, 1993;
29    McKeen et al., 1996).  Buhr et al. (1992) derived emission estimates from principal component
30    analysis (PCA) and other statistical methods. Many of these studies are summarized in Trainer
31    et al. (2000), Parrish et al. (1998), and Parrish and Fehsenfeld (2000).  Goldstein and Schade

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 1    (2000) also used species correlations to identify the relative impacts of anthropogenic and
 2    biogenic emissions. Chang et al. (1996, 1997) and Mendoza-Dominguez and Russell (2000,
 3    2001) used the more quantative technique of inverse modeling to derive emission rates, in
 4    conjunction with results from chemistry-transport models.
 5
 6
 7    AX2.7     METHODS USED TO CALCULATE CONCENTRATIONS OF
 8               NITROGEN OXIDES AND THEIR CHEMICAL
 9               INTERACTIONS IN THE ATMOSPHERE
10          Atmospheric chemistry and transport models are the major tools used to calculate the
11    relations among O3, other oxidants, and their precursors, the transport and transformation of air
12    toxics, the production of secondary organic aerosol, the evolution of the particle size distribution,
13    and the production and deposition of pollutants affecting ecosystems.  Chemical transport
14    models are driven by emissions inventories for primary species such as the precursors for Os and
15    PM and by meterological fields produced by other numerical models.  Emissions of precursor
16    compounds can be divided into anthropogenic and natural source categories. Natural sources can
17    be further divided into biotic (vegetation, microbes, animals) and abiotic (biomass burning,
18    lightning) categories.  However, the distinction between natural sources and anthropogenic
19    sources is often difficult to make as human activities affect directly, or indirectly, emissions from
20    what would have been considered natural sources during the preindustrial era.  Emissions from
21    plants and animals used in agriculture have been referred to as anthropogenic or natural in
22    different applications. Wildfire emissions may be considered to be natural, except that forest
23    management practices may have led to the buildup of fuels on the forest floor, thereby altering
24    the frequency and severity of forest fires. Needed meteorological quantities such as winds and
25    temperatures are taken from operational analyses, reanalyses, or circulation models. In most
26    cases, these are off-line analyses, i.e., they are not modified by  radiatively active species such as
27    63 and particles generated by the model.
28          A brief overview of atmospheric chemistry-transport models is given in Section AX2.7.1.
29    A discussion of emissions inventories of precursors used by these models is given in Section
30    AX2.7.2. Uncertainties in emissions estimates have also been discussed in Air Quality Criteria
31    for Particulate Matter (U.S. Environmental Protection Agency,  2004). Chemistry-transport
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 1    model evaluation and an evaluation of the reliability of emissions inventories are presented in
 2    Section AX2.7.4.
 3
 4    AX2.7.1    Chemistry-Transport Models
 5          Atmospheric CTMs have been developed for application over a wide range of spatial
 6    scales ranging from neighborhood to global.  Regional scale CTMs are used:  1) to obtain better
 7    understanding of the processes controlling the formation, transport, and destruction of gas-and
 8    particle-phase criteria and hazardous air pollutants; 2) to understand the relations between Os
 9    concentrations and concentrations of its precursors such as NOX and VOCs, the factors leading to
10    acid deposition, and hence to possible damage to ecosystems; and 3) to understand relations
11    among the concentration patterns of various pollutants that may exert adverse health effects.
12    Chemistry Transport Models are also used for determining control strategies for 63 precursors.
13    However, this application has met with varying degrees of success because of the highly
14    nonlinear relations between 63 and emissions of its precursors, and uncertainties in emissions,
15    parameterizations of transport, and chemical production and loss terms. Uncertainties in
16    meteorological variables and emissions can be large enough to lead to significant errors in
17    developing control strategies (e.g., Russell and Dennis, 2000; Sillman et al., 1995).
18          Global scale CTMs are used to address issues associated with climate change,
19    stratospheric ozone depletion, and to provide boundary conditions for regional scale models.
20    CTMs include mathematical (and often simplified) descriptions of atmospheric transport, the
21    transfer of solar radiation through the atmosphere, chemical reactions, and removal to the surface
22    by turbulent motions and precipitation for pollutants emitted into the model domain.  Their upper
23    boundaries extend anywhere from the top of the mixing layer to the mesopause (about 80 km in
24    height), to obtain more realistic boundary conditions for problems involving stratospheric
25    dynamics.  There is a trade-off between the size of the modeling domain and the grid resolution
26    used in the CTM that is imposed by  computational resources.
27          There are two major formulations of CTMs in  current use.  In the first approach, grid-
28    based, or Eulerian, air quality models, the region to be modeled (the modeling domain) is
29    subdivided into a three-dimensional array of grid cells. Spatial derivatives in the species
30    continuity equations are cast in finite-difference there  are also some finite-element models, but
31    not many applications form over this grid, and a system of equations for the concentrations of all
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 1    the chemical species in the model are solved numerically at each grid point.  Time dependent
 2    continuity (mass conservation) equations are solved for each species including terms for
 3    transport, chemical production and destruction, and emissions and deposition (if relevant), in
 4    each cell. Chemical  processes are simulated with ordinary differential equations, and transport
 5    processes are simulated with partial differential equations.  Because of a number of factors such
 6    as the different time  scales inherent in different processes, the coupled, nonlinear nature of the
 7    chemical process terms, and computer storage limitations, all of the terms in the equations are
 8    not solved simultaneously in three dimensions. Instead, operator splitting, in which terms in the
 9    continuity equation involving individual processes are solved sequentially, is used. In the second
10    CTM formulation, trajectory or Lagrangian models, a large number of hypothetical air parcels
11    are specified as following wind trajectories.  In these models, the original system of partial
12    differential equations is transformed into a system of ordinary differential equations.
13          A less common approach is to use a hybrid Lagrangian/Eulerian model, in which certain
14    aspects of atmospheric chemistry and transport are treated with a Lagrangian approach and
15    others are treaded in  an Eulerian manner (e.g., Stein et al., 2000).  Each approach has its their
16    advantages and disadvantages. The Eulerian approach is more general in that it includes
17    processes that mix air parcels and allows integrations to be carried out for long periods during
18    which individual air  parcels lose their identity.  There are, however, techniques for including the
19    effects of mixing in Lagrangian models such as FLEXPART (e.g., Zanis et al., 2003), ATTILA
20    (Reithmeier and Sausen, 2002), and CLaMS (McKenna et al., 2002).
21
22    Regional Scale Chemistry Transport Models
23          Major modeling efforts within the U.S. Environmental Protection Agency center on the
24    Community Multiscale Air Quality modeling system (CMAQ, Byun and Ching, 1999; Byun and
25    Schere, 2006).  A number of other modeling platforms using Lagrangian and Eulerian
26    frameworks have been reviewed in the 96 AQCD for Os (U.S. EPA, 1997), and in Russell and
27    Dennis (2000).  The  capabilities of a number of CTMs designed to study local- and regional-
28    scale air pollution problems are summarized by Russell and Dennis (2000).  Evaluations of the
29    performance of CMAQ are given in Arnold et al.  (2003), Eder and Y (2005), Appel  et al. (2005),
30    and Fuentes and Raftery (2005).  The domain of CMAQ can extend from several hundred km to
31    the hemispherical scale. In addition, both of these classes of models allow the resolution of the
32    calculations over specified areas to vary.  CMAQ is most often driven by the MM5 mesoscale

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 1    meteorological model (Seaman, 2000), though it may be driven by other meteorological models
 2    (e.g., RAMS).  Simulations of 63 episodes over regional domains have been performed with a
 3    horizontal resolution as low as 1 km, and smaller calculations over limited domains have been
 4    accomplished at even finer scales. However, simulations at such high resolutions require better
 5    parameterizations of meteorological processes such as boundary layer fluxes, deep convection
 6    and clouds (Seaman, 2000), and finer-scale emissions.  Finer spatial resolution is necessary to
 7    resolve features such as urban heat island circulations; sea, bay, and land breezes; mountain and
 8    valley breezes, and the nocturnal low-level jet.
 9           The most common approach to setting up the horizontal domain is to nest a finer grid
10    within a larger domain of coarser resolution.  However, there are other strategies such as the
11    stretched grid (e.g., Fox-Rabinovitz  et al., 2002) and the adaptive grid. In a stretched grid, the
12    grid's resolution continuously varies throughout the domain, thereby eliminating any potential
13    problems with the sudden change from one resolution to another at the boundary. Caution
14    should be exercised in using such a formulation, because certain parameterizations that are valid
15    on a relatively coarse grid scale (such  as convection) may not be valid on finer scales. Adaptive
16    grids are not fixed at the start of the  simulation, but instead adapt to the needs  of the simulation
17    as it evolves (e.g., Hansen et al., 1994). They have the advantage that they can resolve processes
18    at relevant spatial scales. However,  they can be very slow if the situation to be modeled is
19    complex. Additionally, if adaptive grids are used for separate meteorological, emissions, and
20    photochemical models, there is no reason a priori why the resolution of each grid should match,
21    and the gains realized from increased resolution in one model will be wasted in the transition to
22    another model. The use of finer horizontal resolution in CTMs will necessitate finer-scale
23    inventories of land use and better knowledge of the exact paths of roads, locations of factories,
24    and, in general, better methods for locating sources and estimating their emissions.
25           The vertical resolution of these CTMs is variable, and usually configured to have higher
26    resolution near the surface and decreasing aloft. Because the height of the boundary layer is of
27    critical importance in simulations of air quality, improved resolution of the boundary layer height
28    would likely improve air quality simulations.  Additionally, current CTMs do not adequately
29    resolve fine scale features such as the nocturnal low-level jet in part because little is known about
30    the nighttime boundary layer.
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 1          CTMs require time-dependent, three-dimensional wind fields for the period of
 2    simulation. The winds may be either generated by a model using initial fields alone or with four-
 3    dimensional data assimilation to improve the model's performance, fields (i.e., model equations
 4    can be updated periodically or "nudged", to bring results into agreement with observations.
 5    Modeling efforts typically focus on simulations of several days'  duration, the typical time scale
 6    for individual Os episodes, but there have been several attempts  at modeling longer periods.  For
 7    example, Kasibhatla and Chameides (2000) simulated a  four-month period from May to
 8    September of 1995 using MAQSIP. The current trend in modeling applications is towards
 9    annual simulations.  This trend is driven in part by the need to better understand observations of
10    periods of high wintertime PM (e.g., Blanchard et al., 2002) and the need to simulate 63 episodes
11    occurring outside of summer.
12          Chemical kinetics mechanisms (a set of chemical reactions) representing the important
13    reactions occurring in the atmosphere are used in CTMs to estimate the rates of chemical
14    formation and destruction of each pollutant simulated as a function of time. Unfortunately,
15    chemical mechanisms that explicitly treat the reactions of each individual reactive species are too
16    computationally demanding to be incorporated into CTMs. For  example, a master chemical
17    mechanism includes approximately 10,500 reactions involving 3603 chemical species (Derwent
18    et al., 2001).  Instead, "lumped"  mechanisms, that group compounds of similar chemistry
19    together, are used.  The chemical mechanisms used in existing photochemical 63 models contain
20    significant uncertainties that may limit the accuracy of their predictions; the accuracy of each of
21    these mechanisms is also limited by missing chemistry.  Because of different approaches to the
22    lumping of organic compounds into surrogate groups, chemical mechanisms  can produce
23    somewhat different results under similar conditions. The CB-IV chemical mechanism (Gery
24    et al., 1989), the RADMII mechanism (Stockwell et al., 1990), the SAPRC (e.g., Wang et al.,
25    2000a,b; Carter, 1990) and the RACM mechanisms can be used  in CMAQ. Jimenez et al. (2003)
26    provide brief descriptions of the  features of the main mechanisms in use and they compared
27    concentrations of several key species predicted by seven chemical mechanisms in a box model
28    simulation over 24 h. The average deviation from the average of all mechanism predictions for
29    63 and NO over the daylight period was less than 20%, and was  10% for NC>2 for all
30    mechanisms. However, much larger  deviations were found for HNOs, PAN, HO2, H^C^, C^4,
31    and CsHg (isoprene).  An analysis for OH radicals was not presented. The large deviations

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 1    shown for most species imply differences between the calculated lifetimes of atmospheric
 2    species and the assignment of model simulations to either NOx-limited or radical quantity limited
 3    regimes between mechanisms. Gross and Stockwell (2003) found small differences between
 4    mechanisms for clean conditions, with differences becoming more significant for polluted
 5    conditions, especially for NC>2 and organic peroxy radicals. They caution modelers to consider
 6    carefully the mechanisms they are using. Faraji et al. (2006) found differences of 40% in peak
 7    Ih Os in the Houston-Galveston-Brazoria area between simulations using SAPRAC and CB4.
 8    They attributed differences in predicted 63 concentrations to differences in the mechanisms of
 9    oxidation of aromatic hydrocarbons.
10           CMAQ and other CTMs (e.g., PM-CAMx) incorporate processes and interactions of
11    aerosol-phase chemistry (Mebust et al., 2003). There have also been several attempts to study
12    the feedbacks of chemistry on atmospheric dynamics using meteorological models, like MM5
13    (e.g., Grell et al., 2000; Liu et al., 2001a; Lu et al., 1997; Park et al., 2001). This coupling is
14    necessary to simulate accurately feedbacks such as may be caused by the heavy aerosol loading
15    found in forest fire plumes (Lu et al., 1997; Park et al., 2001), or in heavily polluted areas.
16    Photolysis rates in CMAQ can now be calculated interactively with model produced  63, NC>2,
17    and aerosol fields (Binkowski et al., 2007).
18           Spatial and temporal characterizations of anthropogenic and biogenic precursor emissions
19    must be specified as inputs to a CTM.  Emissions inventories have been compiled on grids of
20    varying resolution for many hydrocarbons, aldehydes, ketones, CO, NH3, and NOX. Emissions
21    inventories for many species require the application of some algorithm for calculating the
22    dependence of emissions on physical variables such as temperature and to convert the
23    inventories into formatted emission files required by a CTM.  For example, preprocessing of
24    emissions data for CMAQ is done by the SMOKE (Spare-Matrix Operator Kernel Emissions)
25    system. For many species, information concerning the temporal variability of emissions is
26    lacking, so long-term (e.g., annual or Os-season) averages are used in short-term,  episodic
27    simulations.  Annual emissions estimates are often modified by the emissions model to produce
28    emissions more characteristic of the time of day and season. Significant errors in emissions can
29    occur if an inappropriate time dependence or a default profile is used.  Additional complexity
30    arises in model calculations because different chemical mechanisms are based on different
31    species, and inventories constructed for use with another mechanism must be adjusted to reflect

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 1    these differences.  This problem also complicates comparisons of the outputs of these models
 2    because one chemical mechanism may produce some species not present in another mechanism
 3    yet neither may agree with the measurements.
 4           In addition to wet deposition, dry deposition (the removal of chemical species from the
 5    atmosphere by interaction with ground-level surfaces) is an important removal process for
 6    pollutants on both urban and regional scales and must be included in CTMs.  The general
 7    approach used in most models is the resistance in series method, in which where dry deposition
 8    is parameterized with a Vd, which is represented as Vd = (ra + rb + re)"1 where ra, ib, and rc
 9    represent the resistance due to atmospheric turbulence, transport in the fluid sublayer very near
10    the elements of surface such as leaves or soil, and the resistance to uptake of the surface itself.
11    This approach works for a range of substances, although it is inappropriate for species with
12    substantial emissions from the surface or for species whose deposition to the surface depends on
13    its concentration at the surface itself. The approach is also modified somewhat for aerosols:  the
14    terms rb and rc are replaced with a surface Vd to account for gravitational settling. In their
15    review, Wesley and Hicks (2000)  point out several shortcomings of current knowledge of dry
16    deposition.  Among those shortcomings are difficulties in representing dry deposition over
17    varying terrain where horizontal advection plays a significant role in determining the magnitude
18    of ra and difficulties in adequately determining a Vd for extremely stable conditions such as those
19    occurring at night (e.g., Mahrt, 1998).  Under the best of conditions, when a model is exercised
20    over a relatively small area where dry deposition measurements have been made, models still
21    commonly show uncertainties at least as large as ±30% (e.g., Massman et al., 1994; Brook et al.,
22    1996; Padro, 1996). Wesely and Hicks (2000) state that an important result of these comparisons
23    is that the current level of sophistication of most dry deposition models is relatively low, and that
24    deposition estimates therefore must rely heavily on empirical data. Still larger uncertainties  exist
25    when the surface features in the built environment are not  well known or when the surface
26    comprises a patchwork of different surface types, as is  common in the eastern United States.
27           The initial  conditions, i.e., the concentration fields  of all species computed by a model,
28    and the boundary conditions,  i.e., the concentrations of species along the horizontal and upper
29    boundaries of the model domain throughout the simulation must be specified at the beginning of
30    the simulation. It would be best to specify initial and boundary conditions according to
31    observations.  However, data for vertical profiles of most species of interest are sparse.  The

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 1    results of model simulations over larger, preferably global, domains can also be used. As may be
 2    expected, the influence of boundary conditions depends on the lifetime of the species under
 3    consideration and the time scales for transport from the boundaries to the interior of the model
 4    domain (Liu et al., 2001 b).
 5          Each of the model components described above has an associated uncertainty, and the
 6    relative importance of these uncertainties varies with the modeling application. The largest
 7    errors in photochemical modeling are still thought to arise from the meteorological and
 8    emissions inputs to the model (Russell and Dennis, 2000). Within the model itself,  horizontal
 9    advection algorithms are still thought to be significant source of uncertainty (e.g., Chock and
10    Winkler, 1994), though more recently, those errors are thought to have been reduced (e.g.,
11    Odman et al., 1996). There are also indications that problems with mass conservation continue
12    to be present in photochemical and meteorological models (e.g., Odman and Russell, 1999);
13    these can result in significant simulation errors.  The effects of errors in initial conditions can be
14    minimized by including several days "spin-up" time in a simulation to allow the model to be
15    driven by emitted species before the simulation of the period of interest begins.
16          While the effects  of poorly specified boundary conditions propagate through the model's
17    domain, the effects of these errors remain undetermined. Because many meteorological
18    processes occur on spatial scales which are smaller than the model grid spacing (either
19    horizontally or vertically) and thus are not calculated explicitly, parameterizations of these
20    processes must be used and these introduce additional uncertainty.
21          Uncertainty also arises in modeling the chemistry of Os formation because it is highly
22    nonlinear with  respect to NOX concentrations.  Thus, the volume of the grid cell into which
23    emissions are injected is important because the nature of Os chemistry (i.e., Os production or
24    titration) depends in a complicated way on the concentrations of the precursors and  the OH
25    radical as noted earlier.  The use of ever-finer grid spacing allows regions of Os titration to be
26    more clearly separated from regions of Os production.  The use of grid spacing fine enough to
27    resolve the chemistry in individual power-plant plumes is too demanding of computer resources
28    for this to be attempted in most simulations. Instead, parameterizations of the effects of sub-
29    grid-scale processes such as these must be developed; otherwise serious errors can result if
30    emissions are allowed to mix through an excessively large grid volume before the chemistry step
31    in a model calculation is performed. In light of the significant differences between atmospheric

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 1    chemistry taking place inside and outside of a power plant plume (e.g., Ryerson et al., 1998 and
 2    Sillman, 2000), inclusion of a separate, meteorological module for treating large, tight plumes is
 3    necessary. Because the photochemistry of O3 and many other atmospheric species is nonlinear,
 4    emissions correctly modeled in a tight plume may be incorrectly modeled in a more dilute plume.
 5    Fortunately, it appears that the chemical mechanism used to follow a plume's development need
 6    not be as detailed as that used to simulate the rest of the domain, as the inorganic reactions are
 7    the most important in the plume see (e.g., Kumar and Russell, 1996). The need to include
 8    explicitly plume-in-grid chemistry only down to the level of the smallest grid disappears if one
 9    uses the adaptive grid approach mentioned previously, though such grids are more
10    computationally intensive.  The differences in simulations are significant because they can lead
11    to significant differences in the calculated sensitivity of O3 to its precursors (e.g.,  Sillman et al.,
12    1995).
13          Because the chemical production and loss terms in the continuity equations for individual
14    species are coupled, the chemical calculations must be performed iteratively until calculated
15    concentrations converge to within some preset criterion. The number of iterations and the
16    convergence criteria chosen also can introduce error.
17
18    Global Scale CTMs
19          The importance of global transport of 63 and 63 precursors and their contribution to
20    regional 63 levels  in the United States is slowly becoming apparent. There are presently on the
21    order of 20 three-dimensional global models that have been developed by various groups to
22    address problems in tropospheric chemistry.  These models resolve synoptic meteorology,
23    O3-NOx-CO-hydrocarbon photochemistry, have parameterizations for wet and dry deposition,
24    and parameterize sub-grid scale vertical mixing processes  such as  convection.  Global models
25    have proven useful for testing and advancing scientific understanding beyond what is possible
26    with observations  alone.  For example, they can calculate quantities of interest that cannot be
27    measured directly, such as the export of pollution from one continent to the global atmosphere  or
28    the response of the atmosphere to future perturbations to anthropogenic emissions.
29          Global simulations are typically conducted at a horizontal resolution of about 200 km2.
30    Simulations of the effects of transport from long-range transport link multiple horizontal
31    resolutions from the global to the local scale. Finer resolution will only improve scientific
32    understanding to the extent that the governing processes are more  accurately described at that

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 1    scale.  Consequently, there is a critical need for observations at the appropriate scales to evaluate
 2    the scientific understanding represented by the models.
 3          During the recent IPCC-AR4 tropospheric chemistry study coordinated by the European
 4    Union project Atmospheric Composition Change: the European Network of excellence
 5    (ACCENT), 26 atmospheric CTMs were used to estimate the impacts of three emissions
 6    scenarios on global atmospheric composition, climate, and air quality in 2030  (Dentener et al.,
 7    2006a).  All models were required to use anthropogenic emissions developed at IIASA (Dentener
 8    et al., 2005) and GFED version 1 biomass burning emissions (van der Werf et al., 2003) as
 9    described in Stevenson et al. (2006). The base simulations from these models were evaluated
10    against a suite of present-day observations. Most relevant to this assessment report are the
11    evaluations with ozone and NO2, and for nitrogen and sulfur deposition (Stevenson et al., 2006;
12    van Noije et al., 2006; Dentener et al., 2006a), which are summarized briefly below.
13          An analysis of the standard deviation of zonal mean and tropospheric column Os reveals
14    large inter-model variability in the tropopause region and throughout the polar troposphere,
15    likely reflecting differences in model tropopause levels and the associated stratospheric injection
16    of 63 to the troposphere (Stevenson et al., 2006).  Ozone distributions in the tropics also exhibit
17    large standard deviations (-30%), particularly as compared to the mid-latitudes (-20%),
18    indicating larger uncertainties in the processes that influence ozone in the tropics:  deep tropical
19    convection, lightning NOX, isoprene emissions and chemistry, and biomass burning emissions
20    (Stevenson et al., 2006).
21          Stevenson et al., (2006) found that the model ensemble mean (MEM) typically captures
22    the observed seasonal cycles to within one standard deviation. The largest discrepancies
23    between the MEM and observations include: (1) an underestimate of the amplitude of the
24    seasonal cycle at 30°-90°N with a 10 ppbv overestimate of winter ozone, possibly due to the lack
25    of a seasonal cycle in anthropogenic emissions or to shortcomings in the stratospheric influx of
26    63, and (2) an overestimate of 63 throughout the northern tropics. However, the MEM was
27    found to capture the observed seasonal cycles in the Southern Hemisphere, suggesting that the
28    models adequately represent biomass burning and natural emissions.
29          The mean present-day global ozone budget across the current generation of CTMs differs
30    substantially from that reported in the IPCC TAR, with a 50% increase in the mean chemical
31    production (to 5100 Tg Oj yr"1), a 30% increase in the chemical and deposition loss terms (to

      August 2007                            AX2-67      DRAFT-DO NOT QUOTE OR CITE

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 1    4650 and 1000 Tg 63 yr *, respectively) and a 30% decrease in the mean stratospheric input flux
 2    (to 550 Tg 63 yr"1) (Stevenson et al., 2006). The larger chemical terms as compared to the IPCC
 3    TAR are attributed mainly to higher NOX (as well as an equatorward shift in distribution) and
 4    isoprene emissions, although more detailed NMHC schemes and/or improved representations of
 5    photolysis, convection, and stratospheric-tropospheric exchange may also contribute (Stevenson
 6    et al., 2006).
 7           A subset of 17 of the 26 models used in the Stevenson et al. (2006) study was used to
 8    compare with three retrievals of NO2 columns from the GOME instrument (van Noije et al.,
 9    2006) for the year 2000. The higher resolution models reproduce the observed patterns better,
10    and the correlation among simulated and retrieved columns improved for all models when
11    simulated values are smoothed to a 5° x 5° grid,  implying that the models do not accurately
12    reproduce the small-scale features of NO2 (van Noije et al., 2006). Van Noije et al. (2006)
13    suggest that variability in simulated NC>2 columns may reflect a model differences in OH
14    distributions and the resulting NOX lifetimes, as well as differences in vertical mixing which
15    strongly affect partitioning between NO and NO2.  Overall, the models tend to underestimate
16    concentrations in the retrievals in industrial regions (including the eastern United States) and
17    overestimate them in biomass burning regions (van Noije et al., 2006).
18           Over the eastern United States, and industrial regions more generally, the spread in
19    absolute column abundances is generally larger among the retrievals than among the models,
20    with the discrepancy among the retrievals particularly pronounced in winter (van Noije et al.,
21    2006), suggesting that the models  are biased low, or that the European retrievals may be biased
22    high as the Dalhousie/SAO retrieval is closer to the model estimates.  The lack of seasonal
23    variability in fossil fuel combustion  emissions may contribute to a wintertime model
24    underestimate (van Noije et al., 2006) that is manifested most strongly over Asia.  In biomass
25    burning regions, the models generally reproduce the timing of the seasonal cycle of the
26    retrievals, but tend to overestimate the seasonal cycle amplitude, partly due to lower values in the
27    wet season, which may reflect an underestimate in wet season soil NO emissions (van Noije
28    et al., 2006, Jaegle et al., 2004, 2005).
29
      August 2007                             AX2-68      DRAFT-DO NOT QUOTE OR CITE

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 1   Deposition in Global CTMs
 2          Both wet and dry deposition are highly parameterized in global CTMs. While all current
 3   models implement resistance schemes for dry deposition, the generated Vd generated from
 4   different models can vary highly across terrains (Stevenson et al., 2006).  The accuracy of wet
 5   deposition in global CTMs is tied to spatial and temporal distribution of model precipitation and
 6   the treatment of chemical scavenging. Dentener et al. (2006b) compared wet deposition across
 7   23 models with available measurements around the globe. Figures AX2-13 and AX2-14 below
 8   extract the results of a comparison of the 23-model mean versus observations from Dentener
 9   et al. (2006b) over the eastern United States for nitrate and sulfate deposition, respectively.  The
10   mean model results are strongly correlated with the observations (r > 0.8), and usually capture
11   the magnitude of wet deposition to within a factor of 2 over the eastern United States (Dentener
12   et al., 2006b). Dentener et al. (2006b) conclude that 60-70% of the participating models capture
13   the measurements to within 50% in regions with quality controlled observations. This study then
14   identified world regions receiving >1000 mg (N) nT2 yr"1 (the "critical load") and found that
15   20% of the natural vegetation (non-agricultural) in the United States is exposed to nitrogen
16   deposition in excess of the critical load threshold (Dentener et al., 2006b).
17
18   Modeling the Effects of Convection
19          The  effects of deep convection can be simulated using cloud-resolving models, or in
20   regional or global models in which the convection is parameterized.  The Goddard Cumulus
21   Ensemble (GCE) model (Tao and Simpson, 1993) has been used by Pickering et al. (1991;
22   1992a,b; 1993; 1996), Scala et al. (1990) and Stenchikov et al. (1996) in the analysis of
23   convective transport of trace gases. The cloud model is nonhydrostatic and contains a detailed
24   representation of cloud microphysical processes. Two- and three-dimensional versions of the
25   model have been applied in transport  analyses.  The initial conditions for the model are usually
26   from a sounding of temperature, water vapor and winds representative  of the region of storm
27   development.  Model-generated wind fields can be used to perform air parcel trajectory analyses
28   and tracer advection calculations.
29
      August 2007                             AX2-69      DRAFT-DO NOT QUOTE OR CITE

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                    600
                    400
                 0)
                •o
                 o
                    200
                                            Ave. model; 227 Ave. Mea. 195 r: 0.82 n = 228

                                            2 param, fit: y - 51,1 + 0.90x

                                            1 param. fit; y ~ 1.08x

                                            Percentage within ± 50%; 74,8
                       0
200            400

 Measurement
                                              600
Figure AX2-13.
Scatter plot of total nitrate (HNOs plus aerosol nitrate) wet deposition

(mg(N)m 2yr-1) of the mean model versus measurements for the

North American Deposition Program (NADP) network. Dashed lines

indicate factor of 2. The gray line is the result of a linear regression

fitting through 0.
Source: Dentener et al. (2006b).
August 2007
                   AX2-70
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                     1000
                      800-
                       600-
                      400-
                      200
                                                    _
                                      '• "• • . • ... l\   «
                                          Jl "J * •
                                      •   fmm.-j      •   •
      Ave. modsi; 383 Ave. B^eas; 322 n 0,8? n - 226
      2 param fit; y = 114.0 + 0 J?x
      1 param fit; y = 1,00x
                          0        200      400       600      800      1000
                                            Measurement
                                                                                    2
     Figure AX2-14.     Same as Figure AX2-13 but for sulfate wet deposition (mg(S)m  yr
     Source: Dentener et al. (2006b).

 1          Such methods were used by Pickering et al. (1992b) to examine transport of urban
 2   plumes by deep convection.  Transport of an Oklahoma City plume by the 10-11 June 1985
 3   PRE-STORM squall line was simulated with the 2-D GCE model. This major squall line passed
 4   over the Oklahoma City metropolitan area, as well as more rural areas to the north.  Chemical
 5   observations ahead of the squall line were conducted by the PRE-STORM aircraft.  In this event,
 6   forward trajectories from the boundary layer at the leading edge of the storm showed that almost
 7   75% of the low-level inflow was transported to altitudes exceeding 8 km.  Over 35% of the air
 8   parcels reached altitudes over 12 km. Tracer transport calculations were performed for CO,
 9   NOX, O3, and hydrocarbons.  Rural boundary layer NOX was only 0.9 ppbv, whereas the urban
10   plume contained about 3 ppbv. In the rural case, mixing ratios of 0.6 ppbv were transported up
11   to 11 km.  Cleaner air descended at the rear of the storm lowering NOX at the surface from 0.9 to
     August 2007
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 1    0.5 ppbv.  In the urban plume, mixing ratios in the updraft core reached 1 ppbv between 14 and
 2    15 km.  At the surface, the main downdraft lowered the NOX mixing ratios from 3 to 0.7 ppbv.
 3          Regional chemical transport models have been used for applications such as simulations
 4    of photochemical Os production, acid deposition, and fine PM. Walcek et al. (1990) included a
 5    parameterization of cloud-scale aqueous chemistry, scavenging, and vertical mixing in the
 6    chemistry model of Chang et al. (1987). The vertical distribution of cloud microphysical
 7    properties and the amount of sub-cloud-layer air lifted to each cloud layer are determined using a
 8    simple entrainment hypothesis (Walcek and Taylor, 1986). Vertically integrated 63 formation
 9    rates over the northeast U. S. were enhanced by -50% when the in-cloud vertical motions were
10    included in the model.
11          Wang et al. (1996) simulated the 10-11 June 1985 PRE-STORM squall line with the
12    NCAR/Penn State Mesoscale Model (MM5; Grell et al.,  1994; Dudhia,  1993). Convection was
13    parameterized as a sub-grid-scale process in MM5 using the Kain Fritsch (1993) scheme. Mass
14    fluxes and detrainment profiles from the convective parameterization were used along with the
15    3-D wind  fields in CO tracer transport calculations for this convective event.
16          Convective transport in global chemistry and transport models is treated as a sub-grid-
17    scale process that is parameterized typically using cloud mass flux information from a general
18    circulation model or global data assimilation system.  While GCMs can provide data only for a
19    "typical" year, data assimilation systems can provide "real" day-by-day meteorological
20    conditions, such that CTM output can be compared directly with observations of trace gases.
21    The NASA Goddard Earth Observing System Data Assimilation System (GEOS-1 DAS and
22    successor systems; Schubert et al., 1993; Bloom et al., 1996; Bloom et al., 2005) provides
23    archived global data sets for the period 1980 to present, at 2° x 2.5° or better resolution with
24    20 layers or more in the vertical. Deep convection is parameterized with the Relaxed
25    Arakawa-Schubert scheme (Moorthi and Suarez, 1992) in GEOS-1 and  GEOS-3 and with the
26    Zhang and McFarlane (1995) scheme in GEOS-4. Pickering et al. (1995) showed that the cloud
27    mass fluxes from GEOS-1 DAS are reasonable for the 10-11 June 1985 PRE-STORM squall line
28    based on comparisons with the GCE model (cloud-resolving model) simulations of the same
29    storm. In addition, the GEOS-1 DAS cloud mass fluxes compared favorably with the regional
30    estimates of convective transport for the central U.  S. presented by Thompson et al. (1994).
31    However, Allen et al. (1997) have shown that the GEOS-1 DAS overestimates the amount and

      August 2007                            AX2-72       DRAFT-DO NOT QUOTE OR CITE

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 1   frequency of convection in the tropics and underestimates the convective activity over
 2   midlatitude marine storm tracks.
 3          Global models with parameterized convection and lightning have been run to examine
 4   the roles of these processes over North America. Lightning contributed 23% of upper
 5   tropospheric NOy over the  SONEX region according to the UMD-CTM modeling analysis of
 6   Allen et al. (2000). During the summer of 2004 the NASA Intercontinental Chemical Transport
 7   Experiment - North America (INTEX-NA) was conducted primarily over the eastern two-thirds
 8   of the United States, as a part of the International Consortium for Atmospheric Research on
 9   Transport and Transformation (ICARTT). Deep convection was prevalent over this region
10   during the experimental period. Cooper et al. (2006) used a particle dispersion model simulation
11   for NOX to show that 69-84% of the upper tropospheric Oj enhancement over the region in
12   Summer 2004 was due to lightning NOX.  The remainder of the enhancement was due to
13   convective transport of Os  from the boundary layer or other sources of NOX. Hudman et al.
14   (2007) used a GEOS-Chem model simulation to show that lightning was the dominant source of
15   upper tropospheric NOX over this region during this period.  Approximately 15% of North
16   American boundary layer NOX emissions were shown to have been vented to the free troposphere
17   over this region based on both the observations and the model.
18
19   AX2.7.2    CTM Evaluation
20          The comparison of model predictions with ambient measurements represents a critical
21   task for establishing the accuracy of photochemical models and evaluating their ability to serve
22   as the basis for making effective control strategy decisions.  The evaluation of a model's
23   performance, or its adequacy to perform the tasks for which it was designed can only be
24   conducted within the context of measurement errors and artifacts. Not only are there analytical
25   problems, but there are also problems in assessing the representativeness of monitors at ground
26   level for comparison with model values which represent typically an average over the volume of
27   a grid box.
28          Evaluations of CMAQ are given in Arnold et al. (2003) and Fuentes and Raftery (2005).
29   Discrepancies between model predictions and observations can be used to point out gaps in
30   current understanding of atmospheric chemistry and to  spur improvements in parameterizations
31   of atmospheric chemical and physical processes. Model evaluation does not merely involve a


     August 2007                             AX2-73      DRAFT-DO NOT QUOTE OR CITE

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 1    straightforward comparison between model predictions and the concentration field of the
 2    pollutant of interest.  Such comparisons may not be meaningful because it is difficult to
 3    determine if agreement between model predictions and observations truly represents an accurate
 4    treatment of physical and chemical processes in the CTM or the effects of compensating errors in
 5    complex model routines.  Ideally, each of the model components (emissions inventories,
 6    chemical mechanism, meteorological driver) should be evaluated individually.  However, this is
 7    rarely done in practice.
 8          Chemical transport models for 63 formation at the urban/regional scale have traditionally
 9    been evaluated based on their ability to simulate correctly 63. A series of performance statistics
10    that measure the success of individual model simulations to represent the observed distribution
11    of ambient O3, as represented by a network of surface measurements at the urban scale were
12    recommended by the U.S. Environmental Protection Agency (U.S. EPA, 1991; see also Russell
13    and Dennis, 2000). These statistics  consist of the following:
14          •     Unpaired peak Os concentration within a metropolitan region (typically for a
15                single day).
16          •     Normalized bias equal to the summed difference between model and measured
17                hourly concentrations divided by the sum of measured hourly concentrations.
18          •     Normalized gross error, equal to the summed unsigned (absolute value) difference
19                between model and measured hourly concentrations divided by the sum of
20                measured hourly concentrations.
21
22    Unpaired peak prediction accuracy, Au;
                                                          -*100%,
23                                       ^o(x't)max                              (AX2-48)
24   Normalized bias, D;
                           D=L| {cp(Xi,t)-c0(Xi,t)}   t = ]24
25                              N i=l        C0(Xj,t)                               (AX2-49)
26   Gross error, Ed (for hourly observed values of Os >60 ppb)
     August 2007                            AX2-74      DRAFT-DO NOT QUOTE OR CITE

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 1                                N u        CX-Y/./)                              (AX2-50)
 2          The following performance criteria for regulatory models were recommended in U.S.
 3    Environmental Protection Agency (1991): unpaired peak Os to within ±15% or ±20%;
 4    normalized bias within ± 5% to ± 15%; and normalized gross error less than 30% to 35%, but
 5    only when 63 the concentration >60 ppb.  This can lead to difficulties in evaluating model
 6    performance since nighttime and diurnal cycles are ignored. A major problem with this method
 7    of model evaluation is that it does not provide any information about the accuracy of O3-
 8    precursor relations predicted by the model. The process of Os formation is sufficiently complex
 9    that models can predict Os correctly without necessarily representing the Os formation process
10    properly.  If the Os formation process is incorrect, then the modeled source-receptor relations
11    will also be incorrect.
12          Studies by Sillman et al. (1995, 2003), Reynolds et al. (1996) and Pierce et al. (1998)
13    have identified instances in which different model scenarios can be created with very different
14    (Vprecursor sensitivity, but without significant differences in the predicted 63 fields.
15    Figures AX2-15a,b provides an example.  Referring to the O3-NOX-VOC isopleth plot (Figure
16    AX2-16), it can be seen that similar Os concentrations can be found for photochemical
17    conditions that have very different sensitivity to NOX and VOCs.
18          Global-scale CTMs have generally been evaluated by comparison with measurements for
19    a wide array of species, rather than just for Os (e.g., Wang et al., 1998; Emmons et al., 2000; Bey
20    et al., 2001; Hess, 2001; Fiore et al., 2002). These have included evaluation of major primary
21    species (NOX, CO, and selected VOCs) and an array of secondary species (HNOs, PAN, H2O2)
22    that are often formed concurrently with Os. Models for urban and regional Os have also been
23    evaluated against a broader ensemble of measurements in a few cases, often associated with
24    measurement intensives (e.g., Jacobson et al., 1996; Lu et al., 1997; Sillman et al., 1998). The
25    results of a comparison between observed and computed concentrations from Jacobson et al.
26    (1996) for the Los Angeles Basin are shown in Figures AX2-17a,b.
27          The highest concentrations of primary species usually occur in close proximity to
28    emission sources  (typically in urban centers) and at times when dispersion rates are low.  The
29    diurnal cycle includes high concentrations at night, with maxima during the morning rush hour,
30    and low concentrations during the afternoon (Figure AX2-17a).  The afternoon minima are

      August 2007                            AX2-75      DRAFT-DO NOT QUOTE OR CITE

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                25
            >  20
            JQ
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 x
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                              0.316
                                0.1
                                               JO
                                               ex
                                               Q.
                                   1.0     3,16     10.0      31.6     100,0
                                VOC Emission Rate (1012 molec. cm-2 s-1)
     Figure AX2-16.     Ozone isopleths (ppb) as a function of the average emission rate for
                         NOX and VOC (1012 molec. cm"2 s"1) in zero dimensional box model
                         calculations. The isopleths (solid lines) represent conditions during
                         the afternoon following 3-day calculations with a constant emission
                         rate, at the hour corresponding to maximum Os. The ridge line
                         (shown by solid circles) lies in the transition from NOx-saturated to
                         NOx-limited conditions.
 1   driven by the much greater rate of vertical mixing at that time.  Primary species also show a
 2   seasonal maximum during winter, and are often high during fog episodes in winter when vertical
 3   mixing, is suppressed. By contrast, secondary species such as Os are typically highest during the
 4   afternoon (the time of greatest photochemical activity), on sunny  days and during summer.
 5          During these conditions, concentrations of primary species may be relatively low.  Strong
 6   correlations between primary and secondary species are generally observed only in downwind
 7   rural areas where all anthropogenic species are simultaneously elevated. The difference in the
 8   diurnal cycles of primary species (CO, NOX and ethane) and secondary species (Os, PAN,  and
 9   HCHO) is evident in Figure AX2-17b.
10          Models for urban and regional chemistry have been evaluated less extensively than
11   global-scale models in part because the urban/regional context presents a number of difficult
     August 2007
                   AX2-77
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               I
               0.
               a
               OJ
               ._

               I
               i
               a.
               a.
               Ui
0,30

0,25

0-20

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               a.
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Figure AX2-17a.
Reseda
03<9)
      Predicted
      Observed
                      0    8    16    24   32   40   48    56    64    72
                                 Hoyr After First Midnight
Reseda
NOX (g)
	• Predicted
•	• Observed
                      0    8    16    24   32   40   48    56    64    72
                                 Hour After First Midnight
                          Riverside
                          C0(g)
                                  	 Predicted
                                  - - - - Observed
    0    8    16    24    32   40   48   56    64    72
               Hoyr After First Midnight

 Time series for measured gas-phase species in comparison with results
 from a photochemical model. The dashed lines represent
 measurements, and solid lines represent model predictions (in parts
 per million, ppmv) for August 26-28,1988 at sites in southern
 California. The  horizontal axis represents hours past midnight,
 August 25. Results represent Os and NOX at Reseda, and CO at
 Riverside.
Source: Jacobsonetal. (1996).
August 2007
                    AX2-78
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                  0,060

               |  0.050
               a
              3  0,040
               o
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              DC
               Ui  0.020

              s  °'010
                  0,000
    0.030

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o
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    0.000
               IB
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                  0,020
              ">*
              E  0,016
              a.
              3;
                  °'012
                  0,008
                  0 004
                  0.000
           Claremont
           Ethane (g)
                                        	•  Predicted
                                        O   Observed
                            8    16   24    32    40   48   56   64    72
                                 Hour After First Midnight
                           Claremont
                           Formaldehyde (g)
                                  	  Predicted
                                   O    Observed
                                              o
                           j_
                      0     8    16   24    32    40   48   56   64    72
                                 Hour After First Midnight
       Los Angeles
       PAN (g)
                                      	  Predicted
                                      	Observed
                                16   24    32    40   48   56   64    72
                                 Hour After First Midnight
Figure AX2-17b.
Time series for measured gas-phase species in comparison with results
from a photochemical model. The circles represent measurements,
and solid lines represent model predictions (in parts per million,
ppmv) for August 26-28,1988 at sites in southern California. The
horizontal axis represents hours past midnight, August 25. Results
represent ethane and formaldehyde at Claremont, and PAN at Los
Angeles.
Source: Jacobsonetal. (1996).
August 2007
                   AX2-79
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 1    challenges.  Global-scale models typically represent continental-scale events and can be
 2    evaluated effectively against a sparse network of measurements. By contrast, urban/regional
 3    models are critically dependent on the accuracy of local emission inventories and event-specific
 4    meteorology, and must be evaluated separately for each urban area that is represented.
 5           The evaluation of urban/regional models is also limited by the availability of data.
 6    Measured NOX and speciated VOC concentrations are widely available through the EPA PAMs
 7    network, but questions have been raised about the accuracy of those measurements and the data
 8    have not yet been analyzed thoroughly.  Evaluation of urban/regional models versus
 9    measurements has generally relied on results from a limited number of field studies in the United
10    States.  Short-term, research-grade measurements for species relevant to 63 formation, including
11    VOCs,  NOX, PAN, HNO3, and H2O2 are also available at selected rural and remote sites (e.g.,
12    Daum et al., 1990, 1996; Martin et al., 1997; Young et al.,  1997; Thompson et al., 2000; Hoell
13    et al., 1997, 1999; Fehsenfeld et al., 1996a; Emmons et al., 2000; Hess, 2001; Carroll et al.,
14    2001).  The equivalent measurements are available for some polluted rural sites in the eastern
15    United  States, but only at a few urban locations (Meagher et al.,  1998; Hiibler et al., 1998;
16    Kleinman et al., 2000, 2001; Fast et al.,  2002; new SCAQS-need reference). Extensive
17    measurements have also been made in Vancouver (Steyn et al., 1997) and in several European
18    cities (Staffelbach et al., 1997; Prevot et al., 1997, Dommen et al., 1999; Geyer et al., 2001;
19    Thielman et al., 2001; Martilli et al., 2002;  Vautard et al., 2002).
20           The results of straightforward comparisons between observed and predicted
21    concentrations of Os can be misleading  because of compensating errors, although this possibility
22    is diminished when a number of species are compared. Ideally, each of the main modules of a
23    CTM system (for example, the meteorological model and the chemistry and radiative transfer
24    routines) should be evaluated separately. However, this is  rarely done in practice.  To better
25    indicate how well  physical  and chemical processes are being represented in the model,
26    comparisons of relations between concentrations measured in the field and concentrations
27    predicted by the model can be made.  These comparisons could involve ratios and correlations
28    between species.  For  example, correlation  coefficients could be calculated between primary
29    species as a means of evaluating the accuracy of emission inventories or between secondary
30    species as a means of evaluating the treatment of photochemistry in the model. In addition,
31    spatial relations involving individual species (correlations,  gradients) can also be used as a means

      August 2007                             AX2-80      DRAFT-DO NOT QUOTE OR CITE

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1   of evaluating the accuracy of transport parameterizations. Sillman and He (2002) examined
2   differences in correlation patterns between 63 and NOZ in Los Angeles, CA, Nashville, TN, and
3   various sites in the rural United States. Model calculations (Figure AX2-18) show differences in
4   correlation patterns associated with differences in the sensitivity of Os to NOX and VOCs.
5   Primarily NOx-sensitive (NOx-limited) areas in models show a strong correlation between Os and
6   NOZ with a relatively steep slope, while primarily VOC-sensitive (NOX-saturated) areas in
7   models show lower Os for a given NOZ and a lower O3-NOZ slope.  They found that differences
8   found in measured data ensembles were matched by predictions from chemical  transport models.
             250
               0
    Figure AX2-18.
                                                    20
                                               NOZ (ppb)
Correlations for Os versus NOZ (NOy-NOx) in ppb from chemical
transport models for the northeast corridor,  Lake Michigan,
Nashville, the San Joaquin Valley, and Los Angeles.  Each location is
classified as NOx-limited or NOx-sensitive (circles), NOx-saturated or
VOC-sensitive (crosses), mixed or with near-zero sensitivity (squares),
and dominated by NOX titration (asterisks) based on the model
response to reduced NOX and VOC.
    Source: Sillman and He (2002).
    August 2007
                   AX2-81
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 1          Measurements in rural areas in the eastern U.S. show differences in the pattern of
 2    correlations for 63 versus NOZ between summer and autumn (Jacob et al., 1995; Hirsch et al.,
 3    1996), corresponding to the transition from NOx-limited to NOx-saturated patterns, a feature
 4    which is also matched by CTMs.
 5          The difference in correlations between secondary species in NOx-limited to NOX-
 6    saturated environments can also be used to evaluate the accuracy of model predictions in
 7    individual applications. Figures AX2-19a and AX2-19b show results for two different model
 8    scenarios for Atlanta.  As shown in the figures, the first model scenario predicts an urban plume
 9    with high NOy and 63 formation apparently suppressed by high NOy. Measurements show much
10    lower NOy in the Atlanta plume. This error was especially significant because the model
11    locations sensitive to NOX. The second model scenario (with primarily NOx-sensitive
12    conditions) shows much better agreement with measured values. Figure AX2-20a,b shows
13    model-measurement comparisons for secondary species in Nashville, showing better agreement
14    with measured with conditions. Greater confidence in the predictions made by CTMs will be
15    gained by the application of techniques such as these on a more routine basis.
16          The ability of chemical mechanisms to calculate the concentrations of free radicals under
17    atmospheric conditions was tested in the Berlin Ozone Experiment, BERLIOZ (Volz-Thomas
18    et al., 2003) during July and early August at a site located about 50 km NW of Berlin.  (This
19    location was chosen because  Os episodes in central Europe are often associated with SE winds.)
20          Concentrations of major compounds such as O3, hydrocarbons, etc., were fixed at
21    observed values.  In this regard, the protocol used in this evaluation is an example of an
22    observationally high NOy were not sensitive to NOX, while locations with lower NOy were
23    primarily based method. Figure AX2-21 compares the concentrations of RO2, HO2, and OH
24    radicals predicted by RACM and MCM with observations made by the laser-induced
25    fluorescence (LIF) technique and by matrix isolation ESR spectroscopy (MIESR). Also shown
26    are the production rates of Os calculated using radical concentrations predicted by the
27    mechanisms and those obtained by measurements, and measurements of NOX concentrations. As
28    can be seen, there is good agreement between measurements of RO2, HO2, OH, radicals with
29    values predicted by both mechanisms at high concentrations of NOX  (>10 ppb). However, at
30    lower NOX concentrations, both mechanisms substantially overestimate OH concentrations and
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                               10           20
                                       NOy (ppb)
Figure AX2-19a,b.  Evaluation of model versus measured Os versus NOy for two model
                   scenarios for Atlanta. The model values are classified as NOX- limited
                   (circles), NOx-saturated (crosses), or mixed or with low sensitivity to
                   NOX (squares).  Diamonds represent aircraft measurements.
Source: Sillmanetal. (1997).
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         Q.
        •S
         n
        O
            160
            140
              0
            160
                             10
                       20
                   NOZ (ppb)
      30
40
              0
                             10           20           30
                                 2H2O2 + NOZ (ppb)
                                                 40
Figure AX2-20a,b.
Evaluation of model versus:  (a) measured Os versus NOZ and (b) Os
versus the sum 2H2O2 + NOZ for Nashville, TN. The model values are
classified as NOx-limited (gray circles), NOx-saturated (X's), mixed or
near-zero sensitivity (squares), or dominated by NOX titration (filled
circles). Diamonds represent aircraft measurements.
Source: Sillmanetal. (1998).
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I"O
 I

 o
CO
O
           «M
           O
 2

 0
 6

 4

 2

 0

10
           (0
           o
           O    o
           s*   10
           3
           a.
           ~    5
           6
           «««»<
           °-    o
           & 20
           Q.
           5 10
           z
                0
                     O   L!F
                     •   MIESR
                       8
                                            W I
                                   y.yv
                                                  J(O1Df 106 (s-
                      10        12        14

                           UT 20.7.98
                                                16
Figure AX2-21.
        Time series of concentrations of ROi, HOi, and OH radicals, local Os
        photochemical production rate and concentrations of NOX from
        measurements made during BERLIOZ. Also shown are comparisons
        with results of photochemical box model calculations using the RACM
        and MCM chemical mechanisms.
Source: Volz-Thomas et al. (2003).
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 1   moderately overestimate HO2 concentrations.  Agreement between models and measurements is
 2   generally better for organic peroxy radicals, although the MCM appears to overestimate their
 3   concentrations somewhat.  In general, the mechanisms reproduced the HO2 to OH and RO2 to
 4   OH ratios better than the individual measurements. The production of Os was found to increase
 5   linearly with NO (for NO <0.3 ppb) and to decrease with NO (for NO >0.5 ppb).
 6          OH and HO2 concentrations measured during  the PM2 5 Technology Assessment and
 7   Characterization Study conducted at Queens College  in New York City in the summer of 2001
 8   were also compared with those predicted by RACM (Ren et al., 2003). The ratio of observed to
 9   predicted HO2 concentrations over a diurnal cycle was 1.24 and the ratio of observed to predicted
10   OH concentrations was about 1.10 during the day, but the mechanism significantly
11   underestimated OH concentrations during the night.
12
13
14   AX2.8    SAMPLING AND ANALYSIS OF NITROGEN AND
15              SULFUR OXIDES
16
17   AX2.8.1   Availability  and Accuracy of Ambient Measurements for NOy
18          Section AX2.8.1-AX2.8.4 focus on current methods and on promising new technologies,
19   but no attempt is made here to cover the extensive development of these methods or of methods
20   such as wet chemical techniques, no longer in widespread use.  More detailed discussions of
21   these methods may be found elsewhere (U.S. Environmental Protection Agency, 1993,  1996).
22   McClenny (2000), Parrish and Fehsenfeld (2000), and Clemitshaw (2004) reviewed methods for
23   measuring NOX and NOy compounds. Discussions in Sections 2.8.1-2.8.4 center on
24   chemiluminescence and optical Federal Reference and Equivalent Methods (FRM and FEM,
25   respectively).
26          The use of methods such as observationally based methods or source apportionment
27   models, either as stand-alone methods or as a basis for evaluating chemical transport models, is
28   often limited by the availability and accuracy of measurements. Measured NOX and speciated
29   VOC concentrations are widely available in the United States through the PAMS network.
30   However, challenges have been raised about both the accuracy of the measurements and their
31   applicability.
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 1          The PAMs network currently includes measured NO and NOX. However, Cardelino and
 2    Chameides (2000) reported that measured NO during the afternoon was frequently at or below
 3    the detection limit of the instruments (1 ppb), even in large metropolitan regions (Washington,
 4    DC; Houston, TX; New York, NY).  Nitric dioxide measurements are made with commercial
 5    chemilluminescent detectors with hot molybdenum converters. However, these measurements
 6    typically include a wide variety of other reactive N species, such as organic nitrates in addition to
 7    NOX, and cannot be interpreted as a "pure" NOX measurement (see summary in Parrish and
 8    Fehsenfeld, 2000).  Detection of these species can be considered an interference or a cross
 9    sensitivity  useful for understanding the chemistry of the air.
10          Total reactive nitrogen (NOy) is included in the PAMS network only at a few sites. The
11    possible expansion of PAMS to include more widespread NOy measurements has been suggested
12    (McClenny, 2000). NOy measurements are also planned for inclusion in the NCore network
13    (U.S. EPA, 2005). A major issue to be considered when measuring NOX and NOy is the
14    possibility  that HNOs, a major component of NOy, is sometimes lost in inlet tubes and not
15    measured (Luke et al., 1998; Parrish and Fehsenfeld, 2000). This problem is especially critical if
16    measured NOy is used to identify NOx-limited versus NOx-saturated conditions. The problem is
17    substantially alleviated although not necessarily completely solved by using much shorter inlets
18    on NOy monitors than on NOX monitors and by the use of surfaces less likely to take up HNOs.
19    The correlation between Os and NOy differs for NOx-limited versus NOx-saturated locations, but
20    this difference is driven primarily by differences in the ratio of Oj to HNOs. If HNOs were
21    omitted from the NOy measurements, then the measurements would represent  a biased estimate
22    and their use would be problematic.
23
24    AX2.8.1.1  Calibration Standards
25          Calibration gas standards of NO, in N2 (certified at concentrations of approximately 5 to
26    40 ppm) are obtainable from the Standard Reference Material (SRM) Program of the National
27    Institute of Standards and Technology (NIST), formerly the National Bureau of Standards
28    (NBS), in Gaithersburg, MD. These SRMs are supplied as compressed gas mixtures at about
29    135 bar (1900 psi) in high-pressure aluminum cylinders containing 800 L of gas at standard
30    temperature and pressure, dry (STPD) National Bureau of Standards, 1975; Guenther et al.,
31    1996). Each cylinder is supplied with a certificate stating concentration and uncertainty.  The
32    concentrations are certified to be accurate to ±1 percent relative to the stated values.  Because of

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 1    the resources required for their certification, SRMs are not intended for use as daily working
 2    standards, but rather as primary standards against which transfer standards can be calibrated.
 3          Transfer stand-alone calibration gas standards of NO in N2 (at the concentrations
 4    indicated above) are obtainable from specialty gas companies. Information as to whether a
 5    company supplies such mixtures is obtainable from the company, or from the SRM Program of
 6    NIST. These NIST Traceable Reference Materials (NTRMs) are purchased directly from
 7    industry and are supplied as compressed gas mixtures at approximately 135 bar (1900 psi) in
 8    high-pressure  aluminum cylinders containing 4,000 L of gas at STPD. Each cylinder is supplied
 9    with a certificate stating concentration and uncertainty. The concentrations are certified to be
10    accurate to within ±1 percent of the stated values (Guenther et al., 1996). Additional details can
11    be found in the previous AQCD for Oj (U.S. Environmental Protection Agency, 1996).
12
13    AX2.8.1.2 Measurement of Nitric Oxide
14
15    Gas-phase Chemiluminescence (CL) Methods
16          Nitric oxide can be measured reliably using the principle of gas-phase
17    chemiluminescence induced by the reaction of NO with Os at low pressure. Modern commercial
18    NOX analyzers have sufficient sensitivity and specificity for adequate measurement in urban and
19    many rural locations (U.S. Environmental Protection Agency, 1993, 1996,2006). Research
20    grade CL instruments have been compared under realistic field conditions to spectroscopic
21    instruments, and the results indicate that both methods are reliable (at concentrations relevant to
22    smog studies) to better than 15 percent with 95 percent confidence. Response times are on the
23    order of 1 minute. For measurements meaningful for understanding Os formation, emissions
24    modeling, and N deposition, special care must be taken to zero and calibrate the instrument
25    frequently. A chemical zero, obtained by reacting the NO up-stream and out of view of the
26    photomultiplier tube, is preferred because it accounts for interferences such as light emitting
27    reactions with unsaturated hydrocarbons. Calibration should be performed with NTRM-of
28    compressed NO in N2.  Standard additions of NO at the inlet will account for NO loss or
29    conversion to NO2 in the lines. In summary, CL methods, when operated carefully in an
30    appropriate manner, can be suitable for measuring or monitoring NO (e.g., Crosley, 1996).
31
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 1   Spectroscopic Methods for Nitric Oxide
 2          Nitric oxide has also been successfully measured in ambient air with direct spectroscopic
 3   methods; these include two-photon laser-induced fluorescence (TPLIF), tunable diode laser
 4   absorption spectroscopy (TDLAS), and two-tone frequency-modulated spectroscopy (TTFMS).
 5   These were reviewed thoroughly in the previous AQCD and will be only briefly summarized
 6   here. The spectroscopic methods demonstrate excellent sensitivity and selectivity for NO with
 7   detection limits on the order of 10 ppt for integration times of 1 min. Spectroscopic methods
 8   compare well with the CL method for NO in controlled laboratory air, ambient air, and heavily
 9   polluted air (e.g., Walega et al.,  1984; Gregory et al., 1990; Kireev et al., 1999). These
10   spectroscopic methods remain in the research arena due to their complexity, size, and cost, but
11   are essential for demonstrating that CL methods are reliable for monitoring NO concentrations
12   involved in Os formation—from around 20 ppt to several hundred of ppb.
13          Atmospheric pressure laser ionization followed by mass spectroscopy has also been
14   deployed for detection of NO and NO2. Garnica et al. (2000) describe a technique involving
15   selective excitation at one wavelength followed by ionization at a second wavelength. They
16   report good selectivity and detection limits well below 1  ppb. The practicality of the instrument
17   for ambient monitoring, however, has yet to be demonstrated.
18
19   AX2.8.1.3 Measurements of Nitrogen Dioxide
20
21   Gas-Phase Chemiluminescence Methods
22          Reduction of NO2 to NO, on the surface of a heated (to 300 to 400 °C) molybdenum
23   oxide substrate followed by detection of the chemiluminescence produced during the reaction of
24   NO with Os at low pressure as described earlier for measurement  of NO serves as the basis of the
25   FRM for measurement of ambient NO2. However, the substrate used in the reduction of NO2 to
26   NO is not specific to NO2; hence the chemiluminescence analyzers are subject to interference
27   nitrogen oxides other than NO2 produced by oxidized NOy compounds, or NOZ. Thus, this
28   technique will overestimate NO2 concentrations particularly in areas downwind of sources of NO
29   and NO2 as NOX is oxidized to NOZ in the form  of PANs and other organic nitrates, and HNOs
30   and HNO4. Many of these compounds are reduced at the catalyst with nearly the same efficiency
31   as NO2. Interferences have also been found from a wide range of other compounds as described
32   in the latest AQCD for NO2.

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 1    Other Methods
 2          Nitrogen dioxide can be selectively converted to NO by photolysis.  For example,
 3    (Ryerson et al., 2000) developed a gas-phase chemiluminescence method using a photolytic
 4    converter based on a Hg lamp with increased radiant intensity in the region of peak NC>2
 5    photolysis (350 to 400 nm) and producing conversion efficiencies of 70% or more in less than
 6    Is.  Metal halide lamps with conversion efficiency of about 50% and accuracy on the order of
 7    20% (Nakamura, et al., 2003) have been used.  Because the converter produces little radiation at
 8    wavelengths less than 350 nm, interferences from HNOs and PAN are minimal. Alternative
 9    methods to photolytic reduction followed by CL are desirable to test the reliability of this widely
10    used technique.  Any method based on a conversion to measured species presents potential for
11    interference a problem. Several atmospheric species, PAN and HO2NO2 for example, dissociate
12    to NC>2 at higher temperatures.
13          Laser induced fluorescence for NC>2 detection involves excitation  of atmospheric NC>2
14    with laser light emitted at wavelengths too long to induce photolysis. The resulting excited
15    molecules relax in a photoemissive mode and the fluorescing photons are counted. Because
16    collisions would rapidly quench the electronically excited NC>2, the reactions are conducted at
17    low pressure. Matsumi et al. (2001) describe a comparison of LIF with a photofragmentation
18    chemiluminescence instrument. The LIF system involves excitation at 440 nm with a multiple
19    laser system. They  report sensitivity of 30 ppt in 10 s and good agreement between the two
20    methods under laboratory conditions at mixing ratios up to 1.0 ppb.  This high-sensitivity LIF
21    system has yet to undergo long-term field tests.  Cleary et al. (2002) describe field tests of a
22    system that uses continuous, supersonic expansion followed by excitation at 640 nm with a
23    commercial cw external-cavity tunable diode laser. More recently, LIF has been successfully
24    used to detect NC>2 with accuracy of about 15% and detections limits well below 1 ppb. When
25    coupled with thermal dissociation, the technique also measures peroxy nitrates such as PAN,
26    alkyl nitrates, HNO4 and HNO3 (Cohen, 1999; Day et al., 2002; Farmer et al., 2006; Perez et al.,
27    2007; Thornton et al., 2003).  This instrument can have very fast sampling rates be fast (>1 Hz)
28    and shows good correlation with chemiluminescent techniques, but remains a research-grade
29    device.
30          Nitrogen Dioxide can be detected by differential optical absorption spectroscopy (DOAS)
31    in an open, long-path system by measuring narrow band absorption features over a background

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 1    of broad band extinction (e.g., Stutz et al., 2000; Kim and Kim, 2001). A DOAS system
 2    manufactured by OPSIS is designated as a Federal Equivalent Method for measuring NO2.
 3    DOAS systems can also be configured to measure NO, HONO, and NO3 radicals. Typical
 4    detection limits are 0.2 to 0.3 ppbv for NO,  0.05 to 0.1 ppbv for NO2, 0.05 to 0.1 ppbv for
 5    HONO, and 0.001  to 0.002 ppbv for NO3, at path lengths of 0.2, 5, 5, and 10 km, respectively.
 6    The obvious advantage compared to fixed point measurements is that concentrations relevant to
 7    a much larger area are obtained, especially if multiple targets are used. At the same time, any
 8    microenvironmental artifacts are minimized over the long path integration. A major limitation in
 9    this technique had  involved inadequate knowledge of absorption cross sections. Harder et al.
10    (1997) conducted an experiment in rural Colorado involving simultaneous measurements of NO2
11    by DOAS and by photolysis followed by chemiluminescence.  They found differences of as
12    much as 110% in clean air from the west, but for NO2 mixing ratios in excess of 300 ppt, the two
13    methods agreed to  better than 10%.  Stutz (2000) cites two intercomparisons of note. Nitric
14    oxide was measured by DOAS, by photolysis of NO2 followed by chemiluminescence,  and by
15    LIF during July 1999 as part of the SOS in Nashville, TN. On average, the three methods agreed
16    to within 2%, with some larger differences likely caused by  spatial variability over the DOAS
17    path. In another study in Europe, and a multi-reflection set-up over a 15  km path, negated the
18    problem of spatial  averaging here agreement with the chemiluminescence detector following
19    photolytic conversion was excellent (slope = 1.006 ± 0.005;  intercept = 0.036 ± 0.019; r = 0.99)
20    over a concentration range from about 0.2 to 20 ppbv.
21          Nitric oxide can also be detected from space with DOAS-like UV spectroscopy
22    techniques (Kim et al., 2006; Ma et al., 2006).  These measurements appear to track well with
23    emissions estimates and can be a useful indicator of column  content as well as for identifying hot
24    spots in sources. See also Richter, et al., 2005. Leigh (2006) report on a DO AS method that
25    uses the  sun as a light source and compares well with an in situ chemiluminescence  detector in
26    an urban environment.
27          Chemiluminescence on the surface of liquid Luminol has also been used for  measurement
28    of NO2 (Gaffney et al., 1998; Kelly et al., 1990; Marley et al., 2004; Nikitas et al., 1997; Wendel
29    et al., 1983).  This  technique is sensitive and linear, and more specific than hot MoOx.  Luminol
30    does not emit light when exposed to NHOs  or alkyl nitrates,  but does react with PAN.  This
31    interference can be removed by chromatographic separation  prior to detection and the resulting

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 1    measurement compares well with more specific techniques for moderate to high (> 1 ppb) mixing
 2    ratios of NO2.
 3          Several tunable diode laser spectroscopy techniques have been used successfully for NO2
 4    detection (Eisele et al., 2003; Osthoff et al., 2006).  These devices remain research grade
 5    instruments, not yet practical for urban monitoring.
 6
 7    Measurements of Total Oxidized Nitrogen Species, NOy
 8          Gold catalyzed CO, or H2 reduction or as conversion on hot molybdenum oxide catalyst
 9    have been used to reduce NOy to NO before then detection by chemiluminescence (Fehsenfeld
10    et al., 1987; Crosley, 1996). Both techniques offer generally reliable measurements, with
11    response times on the order of 60 s and a linear dynamic range demonstrated in field
12    intercomparisons from about 10 ppt to 10's of ppb. Under certain conditions, HCN, NH3, RNO2,
13    and CH3CN can be converted to NO, but at normal concentrations and humidity these are minor
14    interferences.  Thermal decomposition followed by LIF has also been used for NOy detection, as
15    described above. In field comparisons, instruments based on these two principles generally
16    showed good agreement (Day et al., 2002).  The experimental uncertainty is estimated to be of
17    15-30%.
18
19    AX2.8.1.4  Monitoring for NOi Compliance Versus Monitoring for Ozone Formation
20          Regulatory measurements of NO2 have been focused on demonstrating compliance with
21    the NAAQS for NO2. Today, few locations violate that standard, but NO2 and related NOy
22    compounds remain among the most important atmospheric trace gases to measure and
23    understand. Commercial instruments for NO/NOX detection are generally constructed with an
24    internal converter for reduction of NO2 to NO,  and generate a signal referred to as NOX.  These
25    converters, generally constructed of molybdenum oxides (MoOx), reduce not only NO2 but also
26    most other NOy species.  Unfortunately, with an internal converter, the instruments may not give
27    a faithful indication of NOy either—reactive species such as HNOs will adhere to the walls of the
28    inlet system.  Most recently, commercial vendors such as Thermo Environmental (Franklin, MA)
29    have offered NO/NOy detectors with external Mo converters. If such instruments are calibrated
30    through the inlet with a reactive nitrogen  species such as propyl nitrate,  they give accurate
31    measurements of total NOy, suitable for evaluation of photochemical models.  (Crosley, 1996;
32    Fehsenfeld et al., 1987; Nunnermacker et al., 1998; Rodgers and Davis, 1989).  Under conditions

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 1    of fresh emissions, such as in urban areas during the rush hour, NOy ~ NOX and these monitors
 2    can be used for testing emissions inventories (Dickerson, et al., 1995; Parrish, 2006). The State
 3    of Maryland for example is making these true NOy measurements at the Piney Run site in the
 4    western part of the state. These data produced at this site can be more reliably compared to the
 5    output of CMAQ and other chemical transport models.
 6
 7    Summary of Methods for Measuring NO 2
 8          A variety of techniques exist for reliable monitoring of atmospheric NC>2 and related
 9    reactive nitrogen species.  For demonstration of compliance with the NAAQS for NC>2,
10    commercial chemiluminescence instruments are adequate. For certain conditions, luminol
11    chemiluminescence is adequate. Precise measurements of NC>2 can be made with research grade
12    instruments such as LIF and TDLS. For path-integrated concentration determinations UV
13    spectroscopic methods provide useful information. Commercial NOX instruments are sensitive to
14    other NOy species, but do not measure NOy quantitatatively.  NOy instruments with external
15    converters offer measurements more useful for comparison to chemical transport model
16    calculations.
17
18    AX2.8.2    Measurements of HNO3
19          Accurate measurement of HNOs, has presented a long-standing analytical challenge to
20    the atmospheric chemistry community. In this context, it is useful to consider the major factors
21    that control HNOs  partitioning between the gas and deliquesced-particulate phases in ambient
22    air. In equation form,

23                       HN03g 4~A> [HN03aq] <-2-Kff+] + \N03-]           (AX2-51)
24    where KH is the Henry's Law constant in M ataf * and Ka is the acid dissociation constant in M.
25          Thus, the primary controls on HNOs phase partitioning are its thermodynamic properties
26    (KH, Ka, and associated temperature corrections), aerosol liquid water content (LWC), solution
27    pH, and kinetics. Aerosol LWC and pH are controlled by the relative mix of different acids and
28    bases in the system, hygroscopic properties of condensed compounds, and meteorological
29    conditions (RH, temperature, and pressure). It is evident from relationship AX2-51 that, in the
30    presence of chemically distinct aerosols of varying acidities (e.g., super-Jim predominantly sea

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 1    salt and sub-|im predominantly S aerosol), HNOs will partition preferentially with the less-acidic
 2    particles; and this is consistent with observations (e.g., Huebert et al., 1996; Keene and Savoie,
 3    1998; Keene et al., 2002). Kinetics are controlled by atmospheric concentrations of HNO3 vapor
 4    and participate NOs and the size distribution and corresponding atmospheric lifetimes of
 5    particles against deposition. Sub-jim diameter aerosols typically equilibrate with the gas phase
 6    in seconds to minutes while super-um aerosols require hours to a day or more (e.g., Meng and
 7    Seinfeld, 1996; Erickson et al.,  1999). Consequently, smaller aerosol size fractions are typically
 8    close to thermodynamic equilibrium with respect to HNOs whereas larger size fractions (for
 9    which atmospheric lifetimes against deposition range from hours to a few days) are often
10    undersaturated (e.g., Erickson et al., 1999; Keene and Savioe, 1998).
11           Many sampling techniques for HNO3 (e.g., annular denuder, standard filterpack and mist-
12    chamber samplers)  employ upstream prefilters to remove particulate species from sample air.
13    However, when chemically distinct aerosols with different pHs (e.g., sea  salt and S aerosols) mix
14    together on a bulk filter, the acidity of the bulk mixture will be greater than that of the less acidic
15    aerosols with which most NO3  is associated.  This change in pH may cause the bulk mix to be
16    supersaturated with respect to HNOs leading to volatilization and, thus, positive measurement
17    bias in HNOs sampled downstream. Alternatively, when undersaturated super-Jim size fractions
18    (e.g., sea salt) accumulate on a bulk filter and chemically interact over time with HNOs in the
19    sample air stream, scavenging may lead to negative bias in HNOs sampled downstream.
20    Because the magnitude of both  effects will vary as functions of the overall composition and
21    thermodynamic  state of the multiphase system, the combined influence can cause net positive or
22    net negative measurement bias in resulting data. Pressure drops across particle filters can also
23    lead to  artifact volatilization and associated positive bias in HNOs measured downstream.
24           Widely used methods for measuring HNOs include standard filterpacks configured with
25    nylon or alkaline-impregnated filters (e.g., Goldan et al., 1983; Bardwell et al., 1990), annular
26    denuders (EPA Method IP-9), and standard mist chambers (Talbot et al.,  1990). Samples from
27    these instruments are typically analyzed by ion chromatography. Intercomparisons of these
28    measurement techniques (e.g., Hering et al., 1988; Tanner et al., 1989; Talbot et al., 1990) report
29    differences on the order of a factor of two or more.
30           More recently, sensitive HNOs measurements based on the principle of Chemical
31    lonization Mass Spectroscopy (CIMS) have been reported (e.g., Huey et al., 1998; Mauldin

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 1    et al., 1998; Furutani and Akimoto, 2002; Neuman et al., 2002).  CIMS relies on selective
 2    formation of ions such as SiFs -FINOs or HSC>4 -FINOs followed by detection via mass
 3    spectroscopy.  Two CIMS techniques and a filter pack technique were intercompared in Boulder,
 4    CO (Fehsenfeld et al., 1998). Results indicated agreement to within 15% between the two CIMS
 5    instruments and between the CIMS and filterpack methods under relatively clean conditions with
 6    HNOs mixing ratios between 50 and 400 pptv. In more polluted air, the filterpack technique
 7    generally yielded higher values than the CIMS suggesting that interactions between chemically
 8    distinct particles on bulk filters is a more important source of bias in polluted continental  air.
 9    Differences were also greater at lower temperature when particulate NOs  corresponded to
10    relatively greater fractions of total NOs .
11
12    AX2.8.3    Techniques for Measuring Other NOy Species
13          Methods for sampling and analysis of alkyl nitrates in the atmosphere have been
14    reviewed by Parrish and Fehsenfeld (2000).  Peroxyacetylnitrate, PPN, and MPAN are typically
15    measured using a chromatograph followed by electron capture detectors or GC/ECD (e.g.,
16    Gaffney et al., 1998), although other techniques such as FTIR could also be used. Field
17    measurements are made using GC/ECD with a total uncertainty of ± 5 pptv + 15% (Roberts
18    etal., 1998).
19          In the IMPROVE network and in the EPA's speciation network, particulate nitrate in the
20    PM2.5 size range is typically collected on nylon filters downstream of annular denuders coated
21    with a basic solution capable of removing acidic gases such as HNOs, HNO2, and SO2. Filter
22    extracts are then analyzed by ion chromatography (1C) for nitrate, sulfate, and chloride. Nitrite
23    ions are also measured by this technique but their concentrations are almost always beneath
24    detection limits. However, both of these networks measure nitrate only in the PM2.5 fraction.
25    Because of interactions with more highly acidic components on filter surfaces, there could be
26    volatilization of nitrate in PMio samples. These effects are minimized if separate aerosol  size
27    fractions are collected, i.e., the more acidic PM2 5  and the more alkaline PMi0-2.5 as in a
28    dichotomous sampler or multistage impactor.
29
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 1   AX2.8.4    Remote Sensing of Tropospheric NO2 Columns for Surface NOX
 2                Emissions and Surface NO2 Concentrations
 3          Table AX2-3 contains an overview of the three satellite instruments that are used retrieve
 4   tropospheric NC>2 columns from measurements of solar backscatter. All three instruments are in
 5   polar sun-synchronous orbits with global measurements in the late morning and early afternoon.
 6   The spatial resolution of the measurement from SCIAMACHY is 7 times better than that from
 7   GOME (Ozone Monitoring Instrument), and that from OMI (Ozone Monitoring Instrument) is
 8   40 times better than that from GOME.
 9          Figure AX2-22 shows tropospheric NO2 columns retrieved from SCIAMACHY.
10   Pronounced enhancements are evident over major urban and industrial emissions. The high
11   degree of spatial heterogeneity over the southwestern United States provides empirical evidence
12   that most of the tropospheric NO2 column is concentrated in the lower troposphere.
13   Tropospheric NO2 columns are more sensitive to NOX in the lower troposphere than in the upper
14   troposphere (Martin et al., 2002).  This sensitivity to NOX in the lower troposphere is due to the
15   factor of 25 decrease in the NO2/NO ratio from the surface to the upper troposphere (Bradshaw
16   et al., 1999) that is driven by the temperature dependence of the NO + Os reaction. Martin et al.
17   (2004a) integrated in situ airborne measurements of NO2 and found that during summer the
18   lower mixed layer contains 75% of the tropospheric NO2 column over Houston and Nashville.
19   However, it should be noted that these measurements are also sensitive  to surface albedo and
20   aerosol loading.
21          The retrieval involves three steps:  (1) determining total NO2 line-of-sight (slant) columns
22   by spectral fitting of solar backscatter measurements, (2) removing the stratospheric columns by
23   using data from remote regions where the tropospheric contribution to the column is small, and
24   (3) applying an air mass factor (AMF) for the scattering atmosphere to convert tropospheric slant
25   columns into vertical columns.  The retrieval uncertainty is determined  by (1) and (2) over
26   remote regions where there is little tropospheric NO2, and by (3) over regions in regions  of
27   elevated tropospheric NO2 (Martin et al., 2002; Boersma et al., 2004).
28          The paucity of in situ NO2 measurements motivates the inference of surface NO2
29   concentrations from satellite measurements of tropospheric NO2 columns. This prospect would
30   take advantage of the greater sensitivity of tropospheric NO2 columns to NOX in the lower
     August 2007                            AX2-96      DRAFT-DO NOT QUOTE OR CITE

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     Figure AX2-22.
                                                           8
                        10
                  Tropospheric NOi columns (molecules NOi/ cm ) retrieved from the
                  SCIAMACHY satellite instrument for 2004-2005.
     Source: Martin et al. (2006).
 1
 2
 3
 4
 5
 6
 1
 8
 9
10
11
12
troposphere than in the upper troposphere as discussed earlier. Tropospheric NC>2 columns show
a strong correlation with in situ NC>2 measurements in northern Italy (Ordonez et al., 2006).
      Quantitative calculation of surface NO2 concentrations from a tropospheric NO2 column
would require information on the relative vertical profile. Comparison of vertical profiles of
NO2 in a chemical transport model (GEOS-Chem) versus in situ measurements over and
downwind of North America shows a high degree of consistency (Martin et al., 2004b; Martin
et al., 2006), suggesting that chemical transport models could be used to infer the relationship
between surface NO2 concentrations and satellite observations of the tropospheric NO2 column.
      However, the satellites carrying the spectrometer (GOME/SCIAMACHY/OMI) are in
near polar, sun-synchronous orbits. As a result, these measurements are made only once per day,
typically between about 10:00 to 1 1 :00 a.m. or 1 p.m. local time, during a brief overflight.  Thus
the utility of these measurements is limited as they would likely miss short-term features.
     August 2007
                                    AX2-97
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 1   AX2.8.5    SAMPLING AND ANALYSIS FOR SO2
 2          Currently, ambient 862 is measured using instruments based on pulsed fluorescence. The
 3   UV fluorescence monitoring method for atmospheric 862 was developed to improve upon the
 4   flame photometric detection (FPD) method for SO2, which in turn had displaced the
 5   pararosaniline wet chemical method for SC>2 measurement. The pararosaniline method is still the
 6   FRM for atmospheric SC>2, but is rarely used because of its complexity and slow response, even
 7   in its automated forms.  Both the UV fluorescence and FPD methods are designated as FEMs by
 8   the EPA, but UV fluorescence has largely supplanted the FPD approach because of the UV
 9   method's inherent linearity, sensitivity, and the absence of consumables, such as the hydrogen
10   gas needed for the FPD method.
11          Basically,  862 molecules absorb ultraviolet (UV) light at one wavelength and emit UV
12   light at longer wavelengths.  This process is known as fluorescence, and involves the  excitation
13   of the SC>2 molecule to a higher energy (singlet) electronic state. Once excited, the molecule
14   decays non-radiatively to a lower energy electronic state from which it then decays to the
15   original, or ground, electronic state by emitting a photon of light at a longer wavelength (i.e.,
16   lower energy) than the original, incident photon.  The process can be summarized by the
17   following equations:

18                                   S02+hv,^S02*                        (AX2_52)

19                                    S02*^S02+hv2                        (AX2_53)

20   where SO2* represents the excited state of SC>2, h vj, and h V2 represent the energy of the
21   excitation and fluorescence photons, respectively, and hv22 molecules in the sample gas.
23          In commercial analyzers, light from a high intensity UV lamp passes through a
24   bandwidth filter, allowing only photons with wavelengths around the 862 absorption  peak (near
25   214 nm) to enter the optical chamber.  The light passing through the source bandwidth filter is
26   collimated using a UV lens and passes through the optical chamber, where it is detected on the
27   opposite side of the chamber by the reference detector.  A photomultiplier tube (PMT) is offset
28   from and placed perpendicular to the light path to detect the SC>2 fluorescence. Since the SC>2
29   fluorescence (330 nm) is at a wavelength that is different from the excitation wavelength, an

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 1    optical bandwidth filter is placed in front of the PMT to filter out any stray light from the UV
 2    lamp. A lens is located between the filter and the PMT to focus the fluorescence onto the active
 3    area of the detector and optimize the fluorescence signal.  The Detection Limit (DL) for a non-
 4    trace level SO2 analyzer is 10 parts per billion (ppb) (Code of Federal Regulations, Volume 40,
 5    Part 53.23c). The SC>2 measurement method is subject to both positive and negative interference.
 6
 7    Sources of Positive Interference
 8          The most common source of interference is from other gases that fluoresce in a similar
 9    fashion to SC>2 when exposed to far UV radiation. The most significant of these are poly cyclic
10    aromatic hydrocarbons (PAHs); of which naphthalene is a prominent example. Xylene is
11    another hydrocarbon that can cause interference.
12          Such compounds absorb UV photons and fluoresce in the region of the 862 fluorescence.
13    Consequently, any such aromatic hydrocarbons that are in the optical chamber can act as a
14    positive interference.  To remove this source of interference, the high sensitivity SC>2 analyzers,
15    such as those to be used in the NCore network (U.S. Environmental Protection Agency, 2005),
16    have hydrocarbon scrubbers to remove these compounds from the sample stream before the
17    sample air enters the optical chamber.
18          Another potential source of positive interference is nitric oxide (NO).  NO fluoresces in  a
19    spectral region that is close to the SO2 fluorescence. However, in high sensitivity SO2 analyzers,
20    the bandpass filter in front of the PMT is designed to prevent NO fluorescence from  reaching the
21    PMT and being detected. Care must be exercised when using multicomponent calibration gases
22    containing both NO and SO2 that the NO rejection ratio of the SO2 analyzer is sufficient to
23    prevent NO interference. The most common  source of positive bias (as constrasted with positive
24    spectral interference) in high-sensitivity SO2 monitoring is stray light reaching the optical
25    chamber.  Since SO2 can be electronically excited by a broad range of UV wavelengths, any
26    stray light with an appropriate wavelength that enters the optical chamber can excite SO2 in the
27    sample and increase the fluorescence signal.
28          Furthermore, stray light at the wavelength of the SO2 fluorescence that enters the optical
29    chamber may impinge on the PMT and increase the fluorescence signal. Several design features
30    are incorporated to minimize the stray light that enters the chamber. These features include the
31    use of light filters, dark surfaces, and opaque tubing to prevent light from entering the chamber.
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 1          Luke (1997) reported the positive artifacts of a modified pulsed fluorescence detector
 2    generated by the co-existence of NO, CS2, and a number of highly fluorescent aromatic
 3    hydrocarbons such as benzene, toluene, o-xylene, m-xylene, p-xylene, m-ethyltoluene,
 4    ethylbenzene, and 1,2,4-trimethylbenzene.  The positive artifacts could be reduced by using a
 5    hydrocarbon "kicker" membrane.  At a flow rate of 300 standard cc min"1 and a pressure drop of
 6    645 torr across the kicker, the interference from ppm levels of many aromatic hydrocarbons was
 7    eliminated entirely.
 8          Nicks and Benner (2001) described a sensitive SO2 chemiluminescence detector, which
 9    was based on a differential measurement where response from ambient SCh is determined by the
10    difference between air containing 862  and air scrubbed of 862 where both air samples contain
11    other detectable sulfur species, and the positive artifact could also be reduced through this way.
12
13    Sources of Negative Interference
14          Nonradiative deactivation (quenching) of excited SC>2 molecules can occur from
15    collisions with common molecules in air, including nitrogen, oxygen, and water. During
16    collisional quenching, the excited SC>2  molecule transfers energy, kinetically allowing the SC>2
17    molecule to return to the original lower energy state without emitting a photon.  Collisional
18    quenching results in a decrease in the 862 fluorescence and results in the underestimation of 862
19    concentration in the air sample.  The concentrations of nitrogen and oxygen are constant in the
20    ambient air, so quenching from those species at a  surface site is also constant, but the water
21    vapor content of air can vary. Luke (1997) reported that the response of the detector could be
22    reduced by about 7% and 15% at water vapor mixing ratios of 1 and 1.5 mole percent
23    (RH = 35 to 50% at 20-25 °C and  1 atm for a modified pulsed fluorescence detector (Thermo
24    Environmental Instruments, Model 43s). Condensation of water vapor in sampling lines must be
25    avoided, as it can absorb SO2 from the sample air.  The simplest approach to avoid condensation
26    is to heat sampling lines to a temperature above the expected dew point, and within a few
27    degrees of the controlled optical bench temperature. At very high 862 concentrations, reactions
28    between electronically excited 862 and ground state 862 to form 863 and SO might occur
29    (Calvert et al., 1978).  However, this possibility has not been examined.
30
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 1    Other Techniques for Measuring SO 2
 2          A more sensitive SC>2 measurement method than the UV-fluorescence method was
 3    reported by Thornton et al (2002).  Thornton et al (2002) reported an atmospheric pressure
 4    ionization mass spectrometer. The high measurement precision and instrument sensitivity were
 5    achieved by adding isotopically labeled SO2 (34S16C>2) continuously to the manifold as an internal
 6    standard. Field studies showed that the method precision was better than 10% and the limit of
 7    detection was less than 1 pptv for a sampling interval of Is.
 8          Sulfur Dioxide can be measured by LIF at around 220 nm (Matsumi et al. (2005).
 9    Because the laser wavelength is alternately tuned to an 862 absorption peak at 220.6 and bottom
10    at 220.2  nm, and the difference signal at the two wavelengths is used to extract the SO2
11    concentration, the technique eliminates interference from either absorption or fluorescence by
12    other species and has high sensitivity (5 pptv in 60 sec). Sulfur Dioxide can also be measured by
13    the same DO AS instrument that can measure NC>2.
14          Photoacoutsic techniques have been employed for SC>2 detection, but they generally have
15    detection limits suitable only for source monitoring (Gondal, 1997; Gondal and Mastromarino,
16    2001).
17          Chemical Ionization Mass Spectroscopy (CIMS) utilizes ionization via chemical
18    reactions in the gas phase to determine an unknown sample's mass spectrum and identity. High
19    sensitivity (10 ppt or better) has been achieved with uncertainty of-15% when a charcoal
20    scrubber is used for zeroing and the sensitivity is measured with isotopically labeled 34SC>2
21    (Hanke et al., 2003; Huey et al., 2004; Hennigan et al., 2006).
22
23    AX2.8.6    Sampling and Analysis for Sulfate, Nitrate, and  Ammonium
24
25    Sampling Artifacts
26          Sulfate, nitrate, and ammonium are commonly present in PM2.5. Most PM2.5 samplers
27    have a size-separation device to separate particles so that only those particles  approximately
28    2.5 |im or less are collected on the sample filter. Air is drawn through the sample filter at a
29    controlled flow rate by a pump located downstream of the sample filter. The  systems have two
30    critical flow rate components for the capture of fine paniculate: (1) the flow of air through the
31    sampler  must be at a flow rate that ensures that the size cut at 2.5 jim occurs;  and (2) the flow
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 1    rate must be optimized to capture the desired amount of paniculate loading with respect to the
 2    analytical method detection limits.
 3          When using the system described above to collect sulfate, nitrate and particulate
 4    ammonium, sampling artifacts can occur because of: (1) positive sampling artifact for sulfate,
 5    nitrate, and particulate ammonium due to chemical reaction; and (2) negative sampling artifact
 6    for nitrate and ammonium due to the decomposition and evaporation.
 7
 8    Sampling and Analysis Techniques
 9
10    Denuder-Filter Based Sampling and Analysis Techniques for Sulfate, Nitrate, and Ammonium
11          There are two major PM speciation ambient air-monitoring networks in the U.S.: the
12    Speciation Trend Network (STN),  and the Interagency Monitoring of Protected Visual
13    Environments (IMPROVE) network.  The current STN samplers include three filters: (1) Teflon
14    for equilibrated mass and elemental analysis including elemental sulfur; (2) a HNOs denuded
15    nylon filter for ion analysis including NO3 and SO4, (3) a quartz-fiber filter for elemental and
16    organic carbon. The IMPROVE sampler, which collects two 24-h samples per week,
17    simultaneously collects one sample of PMio on a Teflon filter, and three samples of PM2.5 on
18    Teflon, nylon, and quartz filters. PM2.5 mass concentrations are determined gravimetrically from
19    the PM2 5 Teflon filter sample. The PM2 5 Teflon filter sample is also used to determine
20    concentrations of selected elements. The PM2 5 nylon filter sample, which is preceded by a
21    denuder to remove acidic gases, is analyzed to determine nitrate and sulfate aerosol
22    concentrations. Finally, the PM2.5  quartz filter sample is analyzed for OC and EC using the
23    thermal-optical reflectance (TOR)  method.  The STN and the IMPROVE networks represent a
24    major advance in the measurement of nitrate, because the combination of a denuder (coated with
25    either Na2COs or MgO) to remove HNOs vapor and a Nylon filter to adsorb HNOs vapor
26    volatilizing from the collected ammonium nitrate particles overcomes the loss of nitrate from
27    Teflon filters.
28          The extent to which sampling artifacts for particulate NH3+ have been adequately
29    addressed in the current networks is not clear. Recently, new denuder-filter sampling systems
30    have been developed to measure sulfate, nitrate, and ammonium with an adequate correction of
31    ammonium sampling artifacts. The denuder-filter system,  Chembcomb Model 3500  speciation
32    sampling cartridge developed by Rupprecht & Patashnick Co, Inc. could be used to collect

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 1    nitrate, sulfate, and ammonium simultaneously. The sampling system contains a single-nozzle
 2    size-selective inlet, two honeycomb denuders, the aerosol filter and two backup filters (Keck and
 3    Wittmaack, 2005). The first denuder in the system is coated with 0.5% sodium carbonate and
 4    1% glycerol and collects acid gases such as HCL, SC>2, HONO, and HNOs. The second denuder
 5    is coated with 0.5% phosphoric acid in methanol for collecting NHa.  Backup filters collect the
 6    gases behind denuded filters. The backup filters are coated with the same solutions as the
 7    denuders. A similar system based on the same principle was applied by Possanzini et al. (1999).
 8    The system contains two NaCl-coated annular denuders followed by other two denuders coated
 9    with NaCCVglycerol and citric acid, respectively. This configuration was adopted to remove
10    HNOs quantitatively on the first NaCl denuder.  The third and forth denuder remove 862 and
11    NH3, respectively. A polyethylene cyclone and a two-stage filter holder containing three filters
12    is placed downstream  of the denuders.  Aerosol fine particles are collected on a Teflon
13    membrane.  A backup nylon filter and a subsequent citric acid impregnated filter paper collect
14    dissociation products (HNOs and NHa) of ammonium nitrate evaporated from the filtered
15    particulate matter.
16          Several traditional and new methods could be used to quantify elemental S collected on
17    filters: energy dispersive X-ray fluorescence, synchrotron induced X-ray fluorescence, proton
18    induced X-ray emission (PIXE), total reflection X-ray fluorescence, and scanning electron
19    microscopy. Energy dispersive X-ray fluorescence (EDXRF) (Method IO-3.3, U.S. EPA, 1997;
20    see 2004 PM CD for details) and PIXE are the most commonly used methods. Since sample
21    filters often contain very small amounts of particle deposits, preference is given to methods that
22    can accommodate small sample sizes and require little or no sample preparation or operator time
23    after the samples are placed into the analyzer. X-ray fluorescence (XRF) meets these needs and
24    leaves the sample intact after analysis so it can be submitted for additional examinations by other
25    methods as needed.  To obtain the greatest efficiency and sensitivity, XRF typically places the
26    filters in a vacuum which may cause volatile compounds (nitrates and organics) to evaporate.
27    As a result, species that can volatilize such as ammonium nitrate  and certain organic compounds
28    can be lost during the analysis.  The effects of this volatilization are important if the PTFE filter
29    is to be subjected to subsequent analyses of volatile species.
30          Polyatomic ions such as sulfate, nitrate, and ammonium are quantified by methods such
31    as ion chromatography (1C) (an alternative method commonly used for ammonium analysis is

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 1    automated colorimetry).  All ion analysis methods require a fraction of the filter to be extracted
 2    in deionized distilled water for sulfate and NaCOs/NaHCOs solution for nitrate and then filtered
 3    to remove insoluble residues prior to analysis.  The extraction volume should be as small as
 4    possible to avoid over-diluting the solution and inhibiting the detection of the desired
 5    constituents at levels typical of those found in ambient PM2.5  samples. During analysis, the
 6    sample extract passes through an ion-exchange column which separates the ions in time for
 7    individual quantification, usually by an electroconductivity detector. The ions are identified by
 8    their elution/retention times and  are quantified by the conductivity peak area or peak height.
 9           In a side-by-side  comparison of two of the major aerosol monitoring techniques (Hains
10    et al., 2007), PM2.5 mass and major contributing species were well correlated among the different
11    methods with r-values in excess  of 0.8. Agreement for mass, sulfate, OC, TC, and ammonium
12    was good while that for nitrate and BC was weaker.  Based on reported uncertainties, however,
13    even daily concentrations of PM2.5 mass and major contributing species were often  significantly
14    different at the 95% confidence level. Greater values of PM2.5 mass and individual species were
15    generally reported from Speciation Trends Network methods than from the Desert Research
16    Institute Sequential Filter Samplers.  These differences can only be partially accounted for by
17    known random errors.  The authors concluded that the current uncertainty estimates used in the
18    STN network may underestimate the actual uncertainty.
19
20    Positive Sampling Artifacts
21           The reaction of 862 (and other acid gases) with basic  sites on glass fiber filters or with
22    basic coarse particles on  the filter leads to the formation of sulfate (or other nonvolatile salts,
23    e.g., nitrate, chloride).  These positive artifacts lead to the overestimation of total mass, and
24    sulfate, and probably also nitrate concentrations.  These problems were largely overcome by
25    changing to quartz fiber or Teflon filters and by the separate collection of PM2.5.  However, the
26    possible reaction of acidic gases with basic coarse particles remains a possibility, especially with
27    PMio and PMio-2.5 measurements. These positive artifacts could be effectively eliminated by
28    removing acidic gases in the sampling line with denuders coated with NaCl or Na2CC>3.
29           Positive sampling artifacts also occur during measurement of particulate NH4.  The
30    reaction of NHa with acidic particles (e.g. 2NH3 + H2SO4 -> (NH/t^SO/t), either during sampling
31    or during transportation,  storage, and equilibration could lead to an overestimation of parti culate
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 1    NH4 concentrations. Techniques have been developed to overcome this problem: using a
 2    denuder to remove NH3 during sampling and to protect the collected PM from NH3 (Suh et al.,
 3    1992, 1994; Brauer et al., 1991; Koutrakis et al., 1988a,b; Keck and Wittmaack, 2006;
 4    Possanzini et al., 1999; Winberry et al., 1999). Hydrogen fluoride, citric acid, and phosphorous
 5    acids have been used as coating materials for the NH3 denuder.  Positive artifacts for particulate
 6    NH4 can also be observed during sample handling due to contamination. No chemical analysis
 7    method, no matter how accurate or precise, can adequately represent atmospheric concentrations
 8    if the filters to which these methods are applied are improperly handled.  Ammonia is emitted
 9    directly from human sweat, breath and smoking.  It can then react with acidic aerosols on the
10    filter to form ammonium sulfate, ammonium bisulfate and ammonium nitrate if the filter was not
11    properly handled (Sutton el al., 2000). Therefore, it is important to keep filters away from
12    ammonia sources, such as human breath, to minimize neutralization of the acidic compounds.
13    Also, when filters are handled, preferably in a glove box, the analyst should wear gloves that are
14    antistatic  and powder-free to act as an effective contamination barrier.
15
16    Negative Sampling Artifact
17           Although sulfate is relatively stable on a Teflon filter,  it is now well known that
18    volatilization losses of particulate nitrates occur during sampling.
19           For nitrate, the effect on the accuracy of atmospheric particulate measurements from
20    these volatilization losses is more significant for PM2.5 than for PMio. The FRM for PM2.5 will
21    likely suffer a loss of nitrates similar to that experienced with other simple filter collection
22    systems.  Sampling artifacts resulting from the loss of particulate nitrates represents a significant
23    problem in areas such as southern California that  experience high loadings of nitrates.  Hering
24    and Cass  (1999) discussed errors in PM2.5 mass measurements due to the volatilization of
25    particulate nitrate. They examined data from two field measurement campaigns that were
26    conducted in southern California:  (1) the Southern California Air Quality Study (SCAQS)
27    (Lawson, 1990) and (2) the 1986 CalTech study (Solomon et  al., 1992).  In both these studies,
28    side-by-side sampling of PM2.5 was conducted. One sampler  collected particles directly onto a
29    Teflon  filter. The second sampler consisted of a denuder to remove gaseous HNO3 followed by
30    a nylon filter that absorbed the HNO3 as it evaporated from NITXNO3.  In both studies, the
31    denuder consisted of MgO-coated glass tubes (Appel et al., 1981).  Fine particulate nitrate
32    collected  on the Teflon filter was compared to fine particulate nitrate collected on the denuded

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 1    nylon filter. In both studies, the PM2.5 mass lost because of ammonium nitrate volatilization
 2    represented a significant fraction of the total PM2.5 mass.  The fraction of mass lost was higher
 3    during summer than during fall (17% versus 9% during the SCAQS study, and 21% versus 13%
 4    during the CalTech study).  In regard to percentage loss of nitrate, as opposed to percentage loss
 5    of mass discussed above, Hering and Cass (1999) found that the amount of nitrate remaining on
 6    the Teflon filter samples was on average 28% lower than that on the denuded nylon filters.
 7          Hering and Cass (1999) also  analyzed these data by extending the evaporative model
 8    developed by Zhang and McMurry (1987). The extended model used by Hering and Cass (1999)
 9    takes into account the dissociation of collected particulate ammonium nitrate on Teflon filters
10    into HNOs and NHs via three mechanisms: (1) the scrubbing of HNOs and NH? in the sampler
11    inlet (John et al. (1988) showed that clean PMi0 inlet surfaces  serve as an effective denuder for
12    HNOs); (2) the heating of the filter substrate above ambient temperature by sampling; and (3) the
13    pressure drop across the Teflon filter. For the sampling systems modeled, the flow-induced
14    pressure drop was measured to be less than 0.02 atm, and the corresponding change in vapor
15    pressure was 2%, so losses driven by pressure drop were not considered  to be significant in this
16    work. Losses from Teflon filters were found to be higher during the summer than during the
17    winter, higher during the day compared to night, and reasonably consistent with modeled
18    predictions.
19          Finally, during the SCAQS (Lawson, 1990) study, particulate samples also were collected
20    using a Berner impactor and greased Tedlar substrates in size ranges from 0.05 to 10 jim in
21    aerodynamic diameter. The Berner impactor PM2.5 nitrate values were much closer to those
22    from the denuded nylon filter than those from the  Teflon filter, the impactor nitrate values being
23    -2% lower than the nylon filter nitrate for the fall measurements and -7% lower for the summer
24    measurements. When the impactor collection was compared to the Teflon filter collection for a
25    nonvolatile species (sulfate), the results were in agreement. Chang et al. (2000) discuss reasons
26    for reduced loss of nitrate from impactors.
27          Brook and Dann (1999) observed much higher nitrate losses during a study in which they
28    measured particulate nitrate in Windsor and Hamilton, Ontario, Canada,  by three techniques:
29    (1) a single Teflon filter in a dichotomous sampler, (2) the Teflon filter in an annular denuder
30    system (ADS), and (3) total nitrate including both the Teflon filter  and the nylon back-up filter
31    from the ADS.  The Teflon filter from the dichotomous sampler averaged only 13% of the total

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 1    nitrate, whereas the Teflon filter from the ADS averaged 46% of the total nitrate. The authors
 2    concluded that considerable nitrate was lost from the dichotomous sampler filters during
 3    handling, which included weighing and X-ray fluorescence (XRF) measurement in a vacuum.
 4          Kim et al. (1999) also examined nitrate-sampling artifacts by comparing denuded and
 5    non-denuded quartz and nylon filters during the PMio Technical Enhancement Program (PTEP)
 6    in the South Coast Air Basin of California. They observed negative nitrate artifacts (losses) for
 7    most measurements; however, for a significant number of measurements, they observed positive
 8    nitrate artifacts. Kim et al. (1999) pointed out that random measurement errors make it difficult
 9    to measure true amounts of nitrate loss.
10          Diffusion  denuder samplers, developed primarily to measure particle strong acidity
11    (Koutrakis et al.,  1988b, 1992), also can be used to study nitrate volatilization.  Such techniques
12    were used to measure loss of particulate nitrate from Teflon filters in seven U.S. cities (Babich
13    et al., 2000). Measurements were made with two versions of the Harvard-EPA Annular Denuder
14    System (HEADS). HNOs vapor was removed by a Na2CC>3-coated denuder. Particulate nitrate
15    was the sum of nonvolatile nitrate collected on a Teflon filter and volatized nitrate collected on a
16    Na2CC>3-coated filter downstream of the Teflon filter (full HEADS) or on a Nylon filter
17    downstream of the Teflon filter (Nylon HEADS).  It was found that the full HEADS (using a
18    Na2CO3 filter) consistently underestimated the total parti culate nitrate by approximately 20%
19    compared to the nylon HEADS. Babich et al. (2000) found significant nitrate losses in
20    Riverside, CA; Philadelphia, PA; and Boston, MA, but not in Bakersfield, CA; Chicago, IL;
21    Dallas, TX; or Phoenix, AZ, where measurements were made only during the winter. Tsai and
22    Huang (1995) used a diffusion denuder to study the positive and negative artifacts on glass and
23    quartz filters.  They found positive artifacts attributed to SC>2 and HNOs reaction with basic sites
24    on glass fibers and basic particles and negative artifacts attributed to loss of HNOs and HC1 due
25    to volatilization of NH4NO3 and NH4C1 and reaction of these species with acid sulfates.
26          Volatile compounds can also leave the filter after sampling and prior to filter weighing or
27    chemical  analysis. Losses of NOs, NH4, and Cl from glass and quartz-fiber filters that were
28    stored in unsealed containers at ambient air temperatures for 2 to 4 weeks prior to analysis
29    exceeded 50 percent (Witz et al.,  1990). Storing filters in sealed containers and under
30    refrigeration will  minimize these losses.
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 1          Negative sampling artifacts due to decomposition and volatilization are also significant
 2    for particulate ammonium.  Ammonium particulates, especially NH4 N? nitrate NH4 Cl are very
 3    sensitive to some environmental factors, such as temperature, relative humidity, acidity of
 4    aerosols, as well as to filter type (Spurny,  1999; Keck and Wittmaack, 2005). Any change in
 5    these parameters during the sampling period influences the position of the equilibrium between
 6    the particle phase and the gas phase. Keck and Wittmaack (2005) observed that at temperatures
 7    below OC, acetate-nitrate, quartz fiber, and Teflon filters could properly collect particulate NH/t
 8    NH3 and Cl.  At temperature above 0°C, the salts were lost from quartz fiber and Teflon filters,
 9    more so the higher the temperature and with no significant difference between quartz fiber and
10    Teflon filters. The salts were lost completely from denuded quartz fiber filters above about 20C,
11    and from  non-undenuded quartz fiber and Teflon filters above about 25C. It is anticipated that
12    current sampling techniques underestimate NH4 concentrations due to the volatilization of NH4,
13    but fine particle mass contains many acidic compounds and consequently, a fraction of
14    volatilized NH4 (in the form of NHa) can be retained on a PTFE filter by reaction with the acid
15    compounds.  Therefore, it is reasonable to assume that NH4 loss will be less than the nitrate loss.
16    Techniques have been applied to particulate ammonium sampling to correct particulate
17    ammonium concentrations due to  evaporation: a backup filter coated with hydrofluoric acids,
18    citric acid, or phosphorous acids, is usually introduced to absorb the evaporated ammonium (as
19    ammonia); the total ammonium concentration is the sum of the particle phase ammonium
20    collected on the Teflon filter and the ammonia concentration collected on the backup filter.
21
22    Other Measurement Techniques
23
24    Nitrate
25          An integrated collection and vaporization cell was developed by Stolzenburg and Hering
26    (2000) that provides automated, 10-min resolution monitoring of fine-particulate nitrate.  In this
27    system, particles are collected by a humidified impaction process and analyzed in place by flash
28    vaporization  and chemiluminescent detection of the evolved NOX. In field tests in which the
29    system was collocated with two FRM samplers, the automated nitrate sampler results followed
30    the results from the FRM, but were offset lower. The system also was collocated with a HEADS
31    and a SASS speciation sampler (MetOne Instruments).  In all these tests, the automated sampler
32    was well correlated to other samplers with slopes near 1 (ranging from 0.95 for the FRM to 1.06

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 1    for the HEADS) and correlation coefficients ranging from 0.94 to 0.996. During the Northern
 2    Front Range Air Quality Study in Colorado (Watson et al., 1998), the automated nitrate monitor
 3    captured the 12-min variability in fine-particle nitrate concentrations with a precision of
 4    approximately ± 0.5 |ig/m3 (Chow et al., 1998).  A comparison with denuded filter
 5    measurements followed by ion chromatographic (1C) analysis (Chow and Watson, 1999) showed
 6    agreement within ± 0.6 |ig/m3 for most of the measurements, but exhibited a discrepancy of a
 7    factor of two for the elevated nitrate periods.  More recent intercomparisons took place during
 8    the 1997 Southern California Ozone Study (SCOS97) in Riverside, CA. Comparisons with
 9    14 days of 24-h denuder-filter sampling gave a correlation coefficient of R2 = 0.87 and showed
10    no significant bias (i.e., the regression slope is not significantly different from 1).  As currently
11    configured,  the system has a detection limit of 0.7 |ig/m3 and a precision of 0.2 |ig/m3.
12
13    Sulfate
14          Continuous methods  for the quantification of aerosol sulfur compounds first remove
15    gaseous sulfur (e.g., SC>2, H^S) from the sample stream by a diffusion tube denuder followed by
16    the analysis of particulate  sulfur (Cobourn et al., 1978;  Durham et al., 1978; Huntzicker et al.,
17    1978; Mueller and Collins, 1980; Tanner et al., 1980).  Another approach is to measure total
18    sulfur and gaseous sulfur separately by alternately removing particles from the sample stream.
19    Particulate sulfur is obtained as the difference between  the total and gaseous sulfur (Kittelson
20    et al., 1978). The total sulfur content is measured by a  flame photometric detector (FPD) by
21    introducing  the sampling stream into a fuel-rich, hydrogen-air flame (e.g., Stevens et al., 1969;
22    Farwell and Rasmussen, 1976) that reduces sulfur compounds and measures the intensity of the
23    chemiluminescence from electronically excited sulfur molecules (S2*).  Because the formation
24    of S2* requires two sulfur atoms, the intensity of the chemiluminescence is theoretically
25    proportional to the square of the concentration of molecules that contain a single sulfur atom.
26    In practice, the exponent is between 1 and 2 and depends on the sulfur compound  being analyzed
27    (Dagnall et al.,  1967; Stevens et al., 1971). Calibrations are performed using both particles and
28    gases as standards.  The FPD can also be replaced by a chemiluminescent reaction with ozone
29    that minimizes  the potential  for interference and provides a faster response time (Benner and
30    Stedman, 1989, 1990). Capabilities added to the basic  system include in situ thermal analysis
31    and sulfuric acid speciation (Cobourn et al., 1978; Huntzicker et al., 1978; Tanner et al., 1980;
32    Cobourn and Husar, 1982).  Sensitivities for particulate sulfur as low as 0.1 |ig/m3, with time

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 1   resolution ranging from 1 to 30 min, have been reported. Continuous measurements of
 2   particulate sulfur content have also been obtained by on-line XRF analysis with resolution of
 3   30 min or less (Jaklevic et al.,  1981). During a field-intercomparison study of five different
 4   sulfur instruments, Camp et al. (1982) reported four out of five FPD systems agreed to within
 5   ± 5% during a 1-week sampling period.
 6
 7
 8   AX2.9    POLICY RELEVANT BACKGROUND CONCENTRATIONS OF
 9              NITROGEN AND SULFUR OXIDES
10          Background concentrations of nitrogen and sulfur oxides used for purposes of informing
11   decisions about NAAQS are referred to as Policy Relevant Background (PRB) concentrations.
12   Policy Relevant Background concentrations are those concentrations that would occur in the
13   United States in the absence of anthropogenic emissions in continental North America (defined
14   here as the United States, Canada, and Mexico).  Policy Relevant Background concentrations
15   include contributions from natural sources everywhere in the world and from anthropogenic
16   sources outside these three countries. Background levels so defined facilitate separation of
17   pollution levels that can be controlled by U.S. regulations (or through international agreements
18   with neighboring countries) from levels that are generally uncontrollable by the United States.
19   EPA assesses risks to human health and environmental effects from NC>2 and SC>2 levels in
20   excess of PRB concentrations.
21          Contributions to PRB concentrations include natural emissions of NC>2, 862, and
22   photochemical reactions involving natural emissions of reduced nitrogen and sulfur compounds,
23   as well as their long-range transport from outside North America.  Natural sources of NO2 and its
24   precursors include biogenic emissions, wildfires, lightning, and the stratosphere. Natural sources
25   of reduced nitrogen compounds, mainly NHa, include biogenic emissions and wildfires. Natural
26   sources of reduced sulfur species include anaerobic microbial activity in wetlands and volcanic
27   activity.  Volcanos and biomass burning are the major natural source of SC>2. Biogenic
28   emissions from agricultural activities are not considered in the formation of PRB concentrations.
29   Discussions of the sources and estimates of emissions are given in Section AX2.6.2.
30
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 1   Analysis ofPRB Contribution to Nitrogen and Sulfur oxide Concentrations and Deposition
 2                 over the United States
 3          The MOZART-2 global model of tropospheric chemistry (Horowitz et al., 2003) is used
 4   to diagnose the PRB contribution to nitrogen and sulfur oxide concentrations, as well as to total
 5   (wet plus dry) deposition.  The model setup for the present-day simulation has been published in
 6   a series of papers from a recent model intercomparison (Dentener et al., 2006a,b; Shindell et al.,
 7   2006; Stevenson et al., 2006; van Noije et al., 2006). MOZART-2 is driven by National Center
 8   for Environmental  Prediction meteorological fields and IIASA 2000 emissions at a resolution of
 9   1.9° x 1.9° with 28 sigma levels in the vertical, and it includes gas- and aerosol phase chemistry.
10   Results shown in Figures AX2-23 to AX2-27 are for the meteorological year 2001. Note that
11   color images are available  on the web.  An additional "policy relevant background" simulation
12   was conducted in which continental North American anthropogenic emissions were set to zero.
13          We first examine the role of PRB in contributing to NC>2 and SC>2 concentrations in
14   surface air. Figure AX2-23 shows the annual mean NC>2 concentrations in surface air in the base
15   case simulation (top panel) and the PRB simulation (middle panel), along with the percentage
16   contribution of the background to the total base case NO2 (bottom panel). Maximum
17   concentrations in the base case simulation occur along the Ohio River Valley and in the
18   Los Angeles basin. While present-day concentrations are often above 5 ppbv, PRB is less than
19   300 pptv over most of the continental United States,  and less than 100 pptv in the eastern United
20   States.  The distribution of PRB (middle panel of Figure AX2-23) largely reflects the distribution
21   of soil NO emissions,  with some local enhancements due to biomass burning such as is seen in
22   western Montana.  In the northeastern United States, where present-day NO2 concentrations are
23   highest, PRB contributes < 1 % to the total.
24          The spatial  pattern  of present-day SO2 concentrations over the United States is similar to
25   that of NO2, with highest concentrations (>5 ppbv) along the Ohio River valley (upper panel
26   Figure AX2-24). Background SO2 concentrations are orders of magnitude smaller, below
27   10 pptv over much of the United States (middle panel of Figure AX2-24). Maximum PRB
28   concentrations of SO2 are 30 ppt. In the Northwest where there are geothermal sources of SO2,
29   the contribution of PRB to total SO2 is 70 to 80%. However, with the exception of the West
30   Coast where volcanic  SO2  emissions enhance PRB concentrations, the PRB contributes <1% to
31   present-day SO2 concentrations in surface air (bottom panel Figure AX2-24).
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                                         Total
                                       ioo°W
                                 sfw
                                      Background
                              Percent BacKg round Contribution
                                       100°'»V
                                 eo°w
Figure AX2-23.
Annual mean concentrations of NOi (ppbv) in surface air over the
United States in the present-day (upper panel) and policy relevant
background (middle panel) MOZART-2 simulations.  The bottom
panel shows the percentage contribution of the background to the
present-day concentrations. Please see text for details.
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                                     Total
               soDN ?
               4Q°N
               30°N
                                   10Q°W
              30°W
                                   Background
                                   ::::;  Ciffe^
                           Percent Background Contribution
Figure AX2-24.     Same as Figure AX2-23 but for SOi concentrations.
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                                        Total
                                     Background
                            Percent Background Contribution
                        13Q°W
               ao°w
Figure AX2-25.     Same as for Figure AX2-23 but for wet and dry deposition of HNO
                                                                    -2  -K
                                         '3?
                   NH4NO3, NOX, HO2NO2, and organic nitrates (mg N m y  ).
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                                       Total
                                    Background
                            Percent Background Contribution
Figure AX2-26.      Same as Figure AX2-23 but for SOX deposition (SO2 + SO4)
                   (mg S m V1).
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        50°N
        45°N
        30°N
        25°N
              12Q°>A
                     MOZART-2 SOIL NO
                                                            GEOS-Chem SOIL NO,
                         100°»
        SfN
        45DN
        40°N
        35°N
        3tfN
        Z5°N
                  MOZART-2 Surf ace NO JUL
                                                           GEOS-Chem Surface NO
              I3AV
 IOO°'.V
scrtv
                                                                 100°VV
                                                                            aa°vv
    Figure AX2-27.
July mean soil NO emissions (upper panels; 1 x 10 9 molecules cm 2 s1)
and surface PRB NOX concentrations (lower panels; pptv) over the
United States from MOZART-2 (left) and GEOS-Chem (right) model
simulations in which anthropogenic Os precursor emissions were set
to zero in North America.
1          The spatial pattern of NOy (defined here as HNO3, NH4NO3, NOX, HO2NO2, and organic
2   nitrates) wet and dry deposition is shown in Figure AX2-25. Figure AX2-25 (upper panel)
3   shows that highest values are found in the eastern U.S. in and downwind of the Ohio River
4   Valley.  The pattern of nitrogen deposition in the PRB simulation (Figure AX2-25, middle
5   panel), however, shows maximum deposition centered over Texas and in the Gulf Coast region,
6   reflecting a combination of nitrogen emissions from lightning in the Gulf region, biomass
7   burning in the Southeast, and from microbial activity in soils (maximum in central Texas and
8   Oklahoma).  The bottom panel of Figure AX2-25 shows that the PRB contribution to nitrogen
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 1    deposition is less than 20% over the eastern United States, and typically less than 50% in the
 2    western United States where NOy deposition is low (25-50 mg N nT2 yr"1).
 3          Present-day SOX (SO2 + SO4 ~) deposition is largest in the Ohio River Valley, likely due
 4    to coal-burning power plants in that region, while background deposition is typically at least an
 5    order of magnitude smaller (Figure AX2-26). Over the eastern United States, the background
 6    contribution to SOX deposition is <10%, and it is even smaller (<1%) where present-day SOX
 7    deposition is highest.  The contribution of PRB to sulfate deposition is highest in the western
 8    United States (>20%) because of geothermal sources of SO2 and oxidation of dimethyl sulfide in
 9    the surface of the eastern Pacific.
10          Thus far, the discussion has focused on results from the MOZART-2 tropospheric
11    chemistry model. In Figure AX2-27, results from MOZART-2 are compared with those from
12    another tropospheric chemistry model, GEOS-Chem (Bey et al., 2001), which was previously
13    used to diagnose PRB O3  (Fiore et al., 2003; U.S. EPA, 2006). In both models, the surface PRB
14    NOX concentrations tend to mirror the distribution of soil NO emissions, which are highest in the
15    Midwest. The higher soil NO emissions in GEOS-Chem (by nearly a factor of 2) as compared to
16    MOZART-2 reflect different assumptions regarding the contribution to soil NO emissions
17    largely through fertilizer,  since GEOS-Chem total soil NO emissions are actually higher than
18    MOZART-2 (0.07 versus 0.11 Tg N) over the United States in July.  Even with the larger PRB
19    soil NO emissions, surface NOX concentrations in GEOS-Chem are typically below 500 pptv.
20          It is instructive to also consider measurements of SO2 at relatively remote monitoring
21    sites, i.e., site located in sparsely populate areas not subject to obvious local sources of pollution.
22    Berresheim et al. (1993) used a type of atmospheric pressure ionization mass spectrometer
23    (APIMS) at Cheeka Peak, WA (48.30N 124.62W, 480 m asl), in April 1991  during a field study
24    for DMS oxidation products. Sulfur Dioxide concentrations ranged between 20 and 40 pptv.
25    Thornton et al. (2002) have also used an APIMS with  an isotopically labeled internal standard to
26    determine background SO2 levels.  SO2 concentrations of 25 to 40 pptv were observed in
27    northwestern Nebraska in October 1999 at 150m above ground using the NCAR C-130
28    (Thornton, unpublished data).  These data are comparable to remote central south Pacific
29    convective boundary layer SO2 (Thornton et al., 1999).
30          Volcanic sources of SO2 in the US are limited to the Pacific Northwest, Alaska, and
31    Hawaii.  Since 1980 the Mt. St. Helens volcano in Washington Cascade Range (46.20 N,

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 1   122.18 W, summit 2549 m asl) has been a variable source of 862. Its major impact came in the
 2   explosive eruptions of 1980, which primarily affected the northern part of the mountain west of
 3   the US. The Augustine volcano near the mouth of the Cook Inlet in southwestern Alaska
 4   (59.363 N, 153.43 W, summit 1252 m asl) has had SC>2 emissions of varying extents since its last
 5   major eruptions in 1986.  Volcanoes in the Kamchatka peninsula of eastern region of Siberian
 6   Russia do not particularly impact the surface concentrations in the northwestern NA.  The most
 7   serious impact in the US from volcanic SC>2 occurs on the island of Hawaii.  Nearly continuous
 8   venting of 862 from Mauna Loa and Kilauea produce 862 in such large amounts so that
 9   >100 km downwind of the island SC>2 concentrations can exceed 30 ppbv (Thornton and Bandy,
10   1993). Depending on the wind direction the west coast of Hawaii (Kona region) has had
11   significant impacts from SO2 and acidic sulfate aerosols for the past decade. Indeed,  SO2 levels
12   in Volcanoes National Park, HI exceeded the 3-h and the 24-h NAAQS in 2004 -2005.  The
13   area's design value is 0.6 ppm for the 3-h, and 0.19 ppm for the 24-h NAAQS (U.S. EPA, 2006).
14          Overall, the background contribution to nitrogen and sulfur oxides over the United States
15   is relatively small, except for SC>2 in areas where there is volcanic activity.
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       TABLE AX2-1. ATMOSPHERIC LIFETIMES OF SULFUR DIOXIDE AND
   REDUCED SULFUR SPECIES WITH RESPECT TO REACTION WITH OH, NO3,
                                   AND CL RADICALS
OH
Compound
SO2
CH3-S-CH3
H2S
CS2
ocs
CH3-S-H
CH3-S-S-CH3
k x 1012
1.6
5.0
4.7
1.2
0.0019
33
230
T
7.2d
2.3d
2.2 d
9.6 d
17y
8.4 h
1.2 h
N03
k x 1012
NA
1.0
NA
<0.0004
<0.0001
0.89
0.53
T

l.lh

>116d
>1.3y
1.2 h
2.1 h
Cl
k x 1012
NA
400
74
<0.004
<0.0001
200
NA

T

29 d
157 d
NR
NR
58 d

 Notes:
 NA = Reaction rate coefficient not available. NR = Rate coefficient too low to be relevant as an atmospheric loss mechanism.
 Rate coefficients were calculated at 298 K and 1 atmosphere.
 y = year, d = day. h = hour. OH = 1 x 106/cm3; NO3 = 2.5 x 108/cm3; Cl = 1 x 103/cm3.

 1 Rate coefficients were taken from JPL Chemical Kinetics Evaluation No. 14 (JPL, 2003).
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   TABLE AX2-2A. RELATIVE CONTRIBUTIONS OF VARIOUS REACTIONS TO
  THE TOTAL S(IV) OXIDATION RATE WITHIN A SUNLIT CLOUD, 10 MINUTES
	AFTER CLOUD FORMATION	
	Reaction	% of Totala	% of Totalb	
 Gas Phase
 OH+SO2                                3.5                       3.1
 Aqueous Phase
 O3 + HSO3                               0.6                       0.7
 O3 + SO32                                7.0                       8.2
 H2O2 + SO3                              78.4                     82.1
 CH3OOH + HSO3                         0.1                       0.1
 HNO4 + HSO3                            9.0                       4.4
 HOONO + HSO3                         <0.1                     <0.1
 HSO5  +HSO3                            1.2                      <0.1
 SO5 +SO32                             <0.1                     <0.1
 HSO5  + Fe2+	0.6	
 a In the absence of transition metals.
 b In the presence of iron and copper ions.

Source: Adapted from Warneck (1999).
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      TABLE AX2-2B. RELATIVE CONTRIBUTIONS OF VARIOUS GAS AND
  AQUEOUS PHASE REACTIONS TO AQUEOUS NITRATE FORMATION WITHIN
 	A SUNLIT CLOUD, 10 MINUTES AFTER CLOUD FORMATION	
          Reaction                   % of Totala                  % of Total b
Gas Phase
OH + NO2 + M
Aqueous Phase
N2O5g + H2O
NO3 + cr
NO3 + HSO3
NO3 + HCOO
HNO4 + HSO3
HOONO + NO3
O3+NO2

57.7

8.1
<0.1
0.7
0.6
31.9
0.8
<0.1

67.4

11.2
0.1
1.0
0.8
20.5
<0.1
<0.1
 a In the absence of transition metals.
 b In the presence of iron and copper ions.
Source: Adapted from Warneck (1999).
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  TABLE AX2-3. EMISSIONS OF NITROGEN OXIDES, AMMONIA, AND SULFUR
                 DIOXIDE IN THE UNITED STATES IN 2002
2002 Emissions (Tg/year)
Source Category
TOTAL ALL SOURCES
FUEL COMBUSTION TOTAL
FUEL COMB. ELEC. UTIL.
Coal
Bituminous
Subbituminous
anthracite & lignite
Other
Oil
Residual
Distillate
Gas
Natural
Process
Other
Internal Combustion
FUEL COMBUSTION INDUSTRIAL
Coal
Bituminous
Subbituminous
anthracite & lignite
Other
Oil
Residual
Distillate
Other
Gas
Natural
Process
Other
Other
wood^ark waste
liquid waste
Other
Internal Combustion
NO,1

23.19
9.11
5.16
4.50
2.90
1.42
0.18
<0.01
0.14
0.13
0.01
0.30
0.29
0.01
0.05
0.17
3.15
0.49
0.25
0.07
0.04
0.13
0.19
0.09
0.09
0.01
1.16
0.92
0.24
0.01
0.16
0.11
0.01
0.04
1.15
NH3

4.08
0.02
0.01
0.01




O.01


0.01


O.01
O.01
O.01
O.01




O.01



0.01



O.01



0.01
S02

16.87
14.47
11.31
10.70
8.04
2.14
0.51

0.38
0.36
0.01
0.01


0.21
0.01
2.53
1.26
0.70
0.10
0.13
0.33
0.59
0.40
0.16
0.02
0.52



0.15



0.01
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   TABLE AX2-3 (cont'd). EMISSIONS OF NITROGEN OXIDES, AMMONIA, AND
             SULFUR DIOXIDE IN THE UNITED STATES IN 2002
2002 Emissions (Tg/year)
FUEL COMB. OTHER
Commercial/Institutional Coal
Commercial/Institutional Oil
Commercial/Institutional Gas
Misc. Fuel Comb. (Except Residential)
Residential Wood
Residential Other
distillate oil
bituminous/subbituminous coal
Other
INDUSTRIAL PROCESSES TOTAL
CHEMICAL & ALLIED PRODUCT MFC
Organic Chemical Mfg
Inorganic Chemical Mfg
sulfur compounds
Other
Polymer & Resin Mfg
Agricultural Chemical Mfg
ammonium nitrate/urea mfg.
Other
Paint, Varnish, Lacquer, Enamel Mfg
Pharmaceutical Mfg
Other Chemical Mfg
METALS PROCESSING
Non-Ferrous Metals Processing
Copper
Lead
Zinc
Other
Ferrous Metals Processing
Metals Processing NEC
NO,1
0.80
0.04
0.08
0.25
0.03
0.03
0.36
0.06
0.26
0.04
1.10
0.12
0.02
0.01


<0.01
0.05


0.00
0.00
0.03
0.09
0.01




0.07
0.01
NH3
<0.01
<0.01
0.01
0.01
0.01





0.21
0.02
0.01
0.01


O.01
0.02
O.01
0.02


0.01
O.01
O.01




0.01
0.01
S02
0.63
0.16
0.28
0.02
0.01
0.01
0.16
0.15
O.01
O.01
1.54
0.36
0.01
0.18
0.17
0.02
O.01
0.05


0.00
0.00
0.12
0.30
0.17
0.04
0.07
0.01
0.01
0.11
0.02
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   TABLE AX2-3 (cont'd). EMISSIONS OF NITROGEN OXIDES, AMMONIA, AND
             SULFUR DIOXIDE IN THE UNITED STATES IN 2002
2002 Emissions (Tg/year)
PETROLEUM & RELATED INDUSTRIES
Oil & Gas Production
natural gas
Other
Petroleum Refineries & Related Industries
fluid catalytic cracking units
Other
Asphalt Manufacturing
OTHER INDUSTRIAL PROCESSES
Agriculture, Food, & Kindred Products
Textiles, Leather, & Apparel Products
Wood, Pulp & Paper, & Publishing Products
Rubber & Miscellaneous Plastic Products
Mineral Products
cement mfg
glass mfg
Other
Machinery Products
Electronic Equipment
Transportation Equipment
Miscellaneous Industrial Processes
SOLVENT UTILIZATION
Degreasing
Graphic Arts
Dry Cleaning
Surface Coating
Other Industrial
Nonindustrial
Solvent Utilization NEC
NO,1
0.16
0.07


0.05


0.04
0.54
0.01
<0.01
0.09
0.01
0.42
0.24
0.01
0.10
<0.01
<0.01
0.01
0.01
0.01
0.01
O.01
O.01
O.01
O.01
0.01
0.01
NH3
O.01
O.01


0.01
0.01
O.01

0.05
O.01
O.01
0.01
0.01
0.01



O.01
O.01

0.05
0.01
0.01
O.01
O.01
O.01
O.01


S02
0.38
0.11
0.11
0.01
0.26
0.16
0.07
0.01
0.46
0.01
O.01
0.10
0.01
0.33
0.19

0.09
O.01
O.01
0.01
0.02
0.01
0.01
O.01
O.01
O.01
O.01


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   TABLE AX2-3 (cont'd). EMISSIONS OF NITROGEN OXIDES, AMMONIA, AND
             SULFUR DIOXIDE IN THE UNITED STATES IN 2002
2002 Emissions (Tg/year)
STORAGE & TRANSPORT
Bulk Terminals & Plants
Petroleum & Petroleum Product Storage
Petroleum & Petroleum Product Transport
Service Stations: Stage II
Organic Chemical Storage
Organic Chemical Transport
Inorganic Chemical Storage
Inorganic Chemical Transport
Bulk Materials Storage
WASTE DISPOSAL & RECYCLING
Incineration
Industrial
Other
Open Burning
Industrial
land clearing debris
Other
POTW
Industrial Waste Water
TSDF
Landfills
Industrial
Other
Other
NO,1
<0.01
<0.01
0.01
0.01
0.01
0.01
0.01
O.01
O.01
0.01
0.17
0.06


0.10



O.01
0.01
0.01
0.01


O.01
NH3
O.01
O.01
0.01
0.01

0.01

O.01

O.01
0.14
0.01


0.01



0.14
0.01
0.01
0.01


O.01
S02
0.01
O.01
0.01
0.01
0.01
0.01
O.01
O.01
O.01
O.01
0.03
0.02

0.01
0.01
O.01

O.01
O.01
0.01
0.01
0.01
0.01
O.01
O.01
August 2007
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   TABLE AX2-3 (cont'd). EMISSIONS OF NITROGEN OXIDES, AMMONIA, AND
             SULFUR DIOXIDE IN THE UNITED STATES IN 2002
2002 Emissions (Tg/year)
TRANSPORTATION TOTAL
HIGHWAY VEHICLES
Light-Duty Gas Vehicles & Motorcycles
light-duty gas vehicles
Motorcycles
Light-Duty Gas Trucks
light-duty gas trucks 1
light-duty gas trucks 2
Heavy-Duty Gas Vehicles
Diesels
heavy-duty diesel vehicles
light-duty diesel trucks
light-duty diesel vehicles
OFF-HIGHWAY
Non-Road Gasoline
Recreational
Construction
Industrial
lawn & garden
Farm
light commercial
Logging
airport service
railway maintenance
recreational marine vessels
Non-Road Diesel
Recreational
Construction
Industrial
lawn & garden
Farm
light commercial
Logging
airport service
railway maintenance
recreational marine vessels
NOX 1 NH3
12.58 0.32
8.09 0.32
2.38 0.20
2.36
0.02
1.54 0.10
1.07
0.47
0.44 <0.01
3.73 <0.01
3.71
0.01
0.01
4.49 0.01
0.23 0.01
0.01
0.01
0.01
0.10
0.01
0.04
0.01
0.01
O.01
0.05
1.76 O.01
0.00
0.84
0.15
0.05
0.57
0.08
0.02
0.01
O.01
0.03
S02
0.76
0.30
0.10
0.10
0.00
0.07
0.05
0.02
0.01
0.12



0.46
0.01










0.22










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    TABLE AX2-3 (cont'd).  EMISSIONS OF NITROGEN OXIDES, AMMONIA, AND
                  SULFUR DIOXIDE IN THE UNITED STATES IN 2002
             2002 Emissions (Tg/year)
       NOX
         NH,
 SO,
 Aircraft
 Marine Vessels
   Diesel
   residual oil
   Other
 Railroads
 Other
   liquefied petroleum gas
   compressed natural gas
 MISCELLANEOUS
 Agriculture & Forestry
   agricultural crops
   agricultural livestock
 Other Combustion
 Health Services
 Cooling Towers
 Fugitive Dust
 Other
 Natural Sources
        0.09
        1.11
        1.11
        0.98
        0.32
        0.29
        0.04
        0.39
       <0.01
        3.10
         O.01
          3.53
          3.45
         0.01
          2.66
          0.08
                           0.01
                           0.18
 0.05
 0.00
 0.10
<0.01
                                           0.10
          0.03
 1 Emissions are expressed in terms of NO2.
 2 Estimate based on Guenther et al. (2000).

Source: U.S. Environmental Protection Agency (2006).
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           TABLE AX2-3.  SATELLITE INSTRUMENTS USED TO RETRIEVE
                             TROPOSPHERIC NO2 COLUMNS.
Instrument
GOME

SCIAMACHY

OMI

Coverage
1995-2002

2002-

2004-

Typical U.S.
Measurement Time
10:30-11:30 AM

10:00-11:00 AM

12:45-1:45 PM

Typical
Resolution
(km)
320 x 40

30x60

13x24

Return Time
(days)1
3

6

1

Instrument
Overview
Burrows et al.
(1999)
Bovensmann
etal. (1999)
Levelt et al.
(2006)
  Return time is reported here for cloud free conditions. Note that due to precession of the satellite's orbit, return measurements are close to
 but not made over the same location. In practice, clouds decrease observation frequency by a factor of 2.
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38
X
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 i                AX3.  CHAPTER 3 ANNEX-AMBIENT
 2                CONCENTRATIONS AND EXPOSURES
 o
 4
 5   AX3.1    INTRODUCTION
 6          Topics discussed in this chapter include the characterization of ambient air quality for
 7   nitrogen dioxide (NO2), the uses of these data in assessing human exposures to NO2;
 8   concentrations and sources of NC>2 in different microenvironments, and personal exposures to
 9   NC>2.  The NC>2 data contained in this chapter are taken mainly from the U.S. Environmental
10   Protection Agency's Air Quality System (AQS) database (formerly the AIRS database) (U.S.
11   Environmental Protection Agency, 2007).
12
13   Characterizing Ambient NO2 Concentrations
14          The "concentration" of a specific air pollutant is typically defined as the amount (mass)
15   of that material per unit volume of air. However, most of the data presented in this chapter are
16   expressed as "mixing ratios" in terms of a volume-to-volume ratio (e.g., parts per million [ppm]
17   or parts per billion [ppb]. Data expressed this way are often referred to as concentrations, both in
18   the literature and in the text, following common usage. Human exposures are expressed in units
19   of mixing ratio times time.
20
21   Relationship to the 1993 Air Quality Criteria Document for Nitrogen Oxides
22          The 1993 AQCD for Oxides of Nitrogen emphasized NC>2 indoor sources (gas stoves)
23   and the relationship between personal total  exposure and indoor or outdoor NC>2 concentrations.
24   At that time, only few personal exposure studies had been conducted with an emphasis on
25   residential indoor NC>2 sources and concentrations. Although the concept of microenvironment
26   had been introduced in the document, NO2  concentrations were seldom reported for
27   microenvironments other than residences. Exposure measurements at that time relied on Palmes
28   tubes  and Yanagisawa badges; and exposure-modeling techniques were limited mainly to simple
29   linear regression. In the 1993 AQCD, NC>2 was treated as an independent risk factor, and
30   confounding issues were not mentioned in the human environmental exposure chapters.
31          The current chapter summarizes and discusses the state-of-the-science and technology
32   regarding NC>2 human exposures since 1993. Since then, numerous human exposure studies
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 1   have been conducted with new measurement and modeling techniques. Microenvironmental
 2   measurements were not limited to residential indoor environments; NC>2 concentrations were also
 3   measured in vehicles, schools and offices, and microenvironments close to traffic.  More indoor
 4   sources have been identified and more NO2 formation and transformation mechanisms in the
 5   indoor environment have been reported. Both indoor and outdoor NC>2 have been treated as
 6   components of a pollutant mixture, and therefore the concepts of confounding and surrogacy
 7   have been discussed in the current chapter.
 8
 9
10   AX3.2    AMBIENT CONCENTRATIONS OF NITROGEN OXIDES AND
11              RELATED SPECIES
12          As discussed in Chapter 2, most measurements of NOX are made by instruments that
13   convert NC>2 to NO, which is then measured by chemiluminescence.  However, the surface
14   converters that reduce NC>2 to NO also reduce other reactive NOy species.  As indicated in
15   Chapter 2, NOy compounds consist of NOX, gas phase inorganic nitrates, such as C1NO3; organic
16   nitrates, such as PANs; inorganic acids, given by the formulas HNOy (y = 2 to 4); and particulate
17   nitrate. In urban areas or in rural areas where there are large local sources, NO and NO2 are
18   expected to be the major forms of NOy.  Thus, interference from PANs and other NOy species
19   near sources are expected to minor; in most rural and remote areas, interference may be
20   substantial as concentrations of other NOy species may be  much larger than those for NO and
21   NO2 (National Research Council, 1991).  Examples will be presented in Section AX3.3.5.
22          Data for NOX in addition to NO2 is reported into the U. S. Environmental Protection
23   Agency's Air Quality System (AQS), but data for NO is not reported, even though measurements
24   of NO are not affected by artifacts caused by products of NO2 oxidation and therefore should be
25   the most reliable.  By definition, NOX is equal to the sum of NO and NO2, so the concentration of
26   NO can be found by subtraction. However, measurements are obtained for NO and NOX every 2
27   to 3 min, but hourly averages for NO2 and NOX are reported into AQS. The locations of NO2
28   monitoring sites are shown in Figure AX3.1. As can be seen from Figure AX3.1, there are large
29   areas of the United States for which data for ambient NO2  are not collected. The percentile
30   distribution of NO2 concentrations in urban and nonurban  areas in the U.S. for different
31   averaging periods is shown in Table AX3.1.
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                      Monitor Locator Map - Criteria Air Pollutants
                                         United States
                                                                           ,• •>
                                                        *,,:-.*
               Monitor Location: A NO2 frt=3?5)              '   «-;'
                                  Shaded states have monitors
     Figure AX3.1.    Location of ambient NOi monitors in the United States.
 1          Because of their short lifetime with respect to oxidation to PANs and HNOs, NOX
 2   concentrations are highly spatially and temporally variable. Average concentrations range from
 3   tens of ppt in remote areas of the globe to tens of ppb in urban cores, i.e., by three orders of
 4   magnitude. Median NO, NOX, and NOy concentrations at the surface are typically below 0.01,
 5   0.05, and 0.3 ppb, respectively, in  remote areas such as Alaska, northern Canada, and the eastern
 6   Pacific; median NOy concentrations range from about 0.7 to about 4.3 ppb at regional
 7   background sites in the eastern United States (Emmons et al., 1997). Note that the last two
 8   values, especially, contain a substantial contribution from pollution. Maximum short-term
 9   average (1-h) NOX concentrations near heavy traffic (e.g., in Los Angeles, CA) approach 1 ppm,
10   but these levels decrease rapidly away from sources. Even at sites where such high hourly
11   values are found, 24-h average concentrations are much lower. For example, the maximum 24-h
12   average NOX concentration at any  site in Los Angeles in 2004 was 82 ppb.
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 1          NO2 concentrations are likewise highly spatially and temporally variable.  The overall
 2    annual mean concentration of NO2 at U.S. monitoring sites is about 15 ppb. Most sites
 3    monitoring NO2 are located in populated areas and values outside of urban and suburban areas
 4    can be much lower. Perhaps the most comprehensive characterization of ambient NO2 levels has
 5    been performed by the California Air Resources Board (CARB) as part of the review of the air
 6    quality standards for California (CARB, 2007). On a statewide basis, the average NO2
 7    concentration was about 15 ppb from 2002 to 2004.  Highest average values of about 27 ppb
 8    were found in the South Coast Air Basin.  The maximum 1-h average NO2 concentration during
 9    the same period was 262 ppb, again in the South Coast Air Basin. However, maximum 1-h
10    concentrations of NO2 were about 150 ppb in Los Angeles, CA in 2004, implying that the high
11    NOX level (~lppm) cited above for Los Angeles consisted mainly of NO.  It is highly unlikely
12    that NOX oxidation products constituted a significant fraction of the NOX reported.
13
14    AX3.2.1    Spatial and Temporal Variability in Ambient Concentrations of
15                NO2 and Related Species in Urban Areas
16          As noted earlier, the number  of monitoring sites reporting data for NO2 is considerably
17    smaller than for other criteria pollutants.  As a result, there are few urban areas where there exist
18    sufficient data to evaluate the spatial variability in NO2 even though most of the NO2 monitors
19    are found in urban or suburban areas. Analyses of spatial variability in NO and NO2 are thus
20    limited to Los Angeles, CA and Chicago, IL.  Also, as noted in Chapter 2, current methods for
21    measuring NO2 are subject to interference from its oxidation products. Hence the reported
22    values represent upper limits for the  true NO2 concentration.  Near highways or other NOX
23    sources, the measurements should give more accurate values, but because of variability in the
24    time needed for conversion of NOX to NOZ, no firm rules can be applied to account for the
25    presence of NOZ species such as HNOs and PANs. These considerations introduce additional
26    uncertainty into the interpretation of any metrics (e.g., correlation coefficients, concentration
27    differences) that are used to characterize spatial variability in NO2 concentrations.
28          The spatial variability in 1 h average NO2 concentrations in New York, NY; Atlanta, GA;
29    Chicago, IL; Houston, TX; Los Angeles, CA; and Riverside, CA is characterized in this section.
30    These areas were chosen to provide analyses to help guide risk assessment and to provide a
31    general overview of the spatial variability of NO2 in cities where health outcome studies have
32    been conducted. Statistical analyses of the human health effects  of airborne pollutants based on

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 1    aggregate population time-series data have often relied on ambient concentrations of pollutants
 2    measured at one or more central sites in a given metropolitan area. In particular, cities with low
 3    traffic densities that are located downwind of major sources of precursors are heavily influenced
 4    by long range transport and tend to show smaller spatial variability (e.g., New Haven, CT) than
 5    those source areas with high traffic densities located upwind (e.g., New York, NY).
 6          Metrics for characterizing spatial variability include the use of Pearson correlation
 7    coefficients, values of the 90th percentile (P90) of the absolute difference in concentrations, and
 8    coefficients of divergence (COD) The COD is defined as follows:
                                    COD-I - V- V ( XJj" xft V?
                                    ^uujk-  VpL\x;i + xJ
 9                                               *=/    IJ    Ik                          (AX3-1)
10    where xy- and x;k represent observed concentrations averaged over some measurement averaging
11    period (hourly, daily, etc.), for measurement period /' at sitey and site k andp is the number of
12    observations.  These methods of analysis follow those used for characterizing PM2.5 and PMi0-2.5
13    concentrations in Pinto et al. (2004) and in the latest edition of the PM AQCD (U.S.
14    Environmental Protection Agency, 2004a).
15           Summary statistics for the spatial variability in several urban areas across the United
16    States are shown in Table AX3.2. These areas were chosen because they are the major urban
17    areas with at least five monitors operating from 2003 to 2005. Values in parentheses below the
18    city name refer to the number of sites colleting data. The second column shows the mean 1 h
19    average concentration across all sites and the range in means at individual sites.  The third
20    column gives the range of Pearson correlation coefficients between individual site pairs in the
21    urban area.  The fourth column shows the 90th percentile absolute difference in concentrations
22    between site pairs.  The fifth column gives the coefficient of divergence (COD).
23           As can be seen from the table, mean concentrations at individual  sites vary by factors of
24    1.5 to 6 in the MS As examined. Correlations between individual site pairs range from slightly
25    negative to highly positive in a given urban area. The sites in New York City tend to be the most
26    highly correlated and show the highest mean levels, reflecting their proximity to traffic, as
27    evidenced by the highest mean concentration of all the entries.  However, correlation coefficients
28    are not sufficient for describing spatial variability as concentrations at two sites may be highly
29    correlated but show differences in levels. Thus, the range in mean concentrations is given.  Even

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 1    in New York City, the spread in mean concentrations is about 40% of the city-wide mean
 2    (12/29). The relative spread in mean concentrations is larger in the other urban areas shown in
 3    Table AX3.2. As might be expected, the 90th percentile concentration spreads are even larger
 4    than the spreads in the means.
 5           The same statistics shown in Table AX3.2 have been used to describe the spatial
 6    variability of PM2.5 (U.S. Environmental Protection Agency, 2004; Pinto et al., 2005) and 63
 7    (U.S. Environmental Protection Agency, 2006).  However, because of relative sparseness in data
 8    coverage for NO2, spatial variability in all cities that were considered for PM2.5 and 63 could not
 9    be considered here. Thus, the number of cities included below is much smaller than for either Os
10    (24 urban areas) or PM2.5 (27 urban areas). Even in those cities where there are monitors for all
11    three pollutants, data may not have been collected at the same locations and even if they were,
12    there would be variable influence from local sources.  For example, concentrations of NO2
13    collected near traffic will be highest in an urban area, but concentrations  of Os will tend to be
14    lowest because of titration by NO forming NO2.  However, some general observations can still
15    be made.  Mean concentrations of NO2 at individual monitoring sites are not as highly variable
16    as for 63 but are more highly variable than PM2.5. Lower bounds on inter-site  correlation
17    coefficients for PM2 5 and for Os tend to be much higher than NO2 in the same areas shown  in
18    Table AX3.2. CODs for PM2.5 are  much lower than for O3, whereas CODs for NO2 tend to be
19    the largest among the three pollutants. Therefore, it is apparent that there is the potential for
20    errors from the use of ambient monitors to characterize exposures either at the community or
21    personal level, and that this potential may be higher than for either Os or PM2 5.
22
23    Small Scale Vertical Variability
24           Inlets to instruments for monitoring gas phase criteria pollutants can be located from 3 to
25    15m above ground level (CFR 58,  Appendix E, 2002). Depending on the pollutant, either there
26    can be positive, negative or no vertical gradient from the ground to the monitor inlet. Pollutants
27    that are formed over large areas by  atmospheric photochemical reactions and are destroyed by
28    deposition to the surface or by reaction with pollutants emitted near the surface show positive
29    vertical gradients.  Pollutants that are emitted by sources at or just above ground level show
30    negative vertical gradients.  Pollutants with area sources and have minimal deposition velocities
      August 2007                             AX3-6      DRAFT-DO NOT CITE OR QUOTE

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 1   show little or no vertical gradient. Restrepo et al. (2004) compared data for criteria pollutants
 2   collected at fixed monitoring sites at 15 m above the surface on a school rooftop to those
 3   measured by a van whose inlet was 4 m above the surface at monitoring sites in the South Bronx
 4   during two sampling periods in November and December 2001.  They found that CO, SO2, and
 5   NC>2 showed positive vertical gradients, whereas Os showed a negative vertical gradient and
 6   PM2.5 showed no significant vertical gradient. As shown in Figure AX3.2, NC>2 mixing ratios
 7   obtained at 4 m (mean -74 ppb) were about a factor of 2.5 higher than at 15 m (mean -30 ppb).
 8   Because tail pipe emissions occur at lower heights, NC>2 values could have been much higher
 9   nearer to the surface, and the underestimation of NC>2 values by monitoring at 15  m even larger.
10   Restrepo et al. (2004) note that the use of the NC>2 data obtained by the stationary monitors
11   would result in an underestimate of human exposures to NC>2 in the South Bronx.  However, this
12   issue is most likely not unique to the South Bronx and could arise in  other large urban areas in
13   the U.S. with populations of similar demographic and socioeconomic characteristics.
              0.12
               0,1
              0,08
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              0.02
                           *   *
                    *     *
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                                                                 AK      f"f^
                                                                i A^  a   / / \    f
                                                                V          V<
                                  .4... -Van — *--DEC709408---A--DEC709407
     Figure AX3.2.    NOi concentrations measured at 4 m (Van) and at 15 m at NY
                      Department of Environmental Conservation sites (DEC709406 and
                      DEC709407).
     Source: Restrepo et al. (2004).
     August 2007
                                  AX3-7
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 1    AX3.2.2    Temporal Variability in Nitrogen Oxides
 2
 3    AX3.2.2.1   Diurnal Variability in NOi Concentrations
 4          As might be expected from a pollutant having a major traffic source, the diurnal cycle of
 5    NO2 in typical urban areas is characterized by traffic emissions, with peaks in emissions
 6    occurring during morning and evening rush hour traffic.  Motor vehicle emissions consist mainly
 7    of NO, with only about 10% of primary emissions in the form of NC>2. The diurnal pattern of
 8    NO and NO2 concentrations is  also strongly influenced by the diurnal variation in the mixing
 9    layer height.  Thus, during the morning rush hour when mixing layer heights are still low, traffic
10    produces a peak in NO and NO2 concentrations.  As the mixing layer height increases during the
11    day, dilution of emissions occurs.  During the afternoon rush hour, mixing layer heights are at or
12    are near their daily maximum values resulting in dilution of traffic emissions through a larger
13    volume than  in the morning. Starting near sunset, the mixing layer height drops and conversion
14    of NO to NO2 occurs without photolysis of NO2 recycling NO.
15    The composite diurnal variability of NO2 in selected urban areas with multiple sites (New York,
16    NY; Atlanta, GA; Baton Rouge, LA; Chicago. IL; Houston, TX; Riverside, CA;  and
17    Los Angeles, CA) is shown in Figure AX3.3.  Figure AX3.3 shows that lowest hourly median
18    concentrations are typically found at around midday and that highest hourly median
19    concentrations are found either in the early morning or in mid-evening. Median values range by
20    about a factor of two from about 13 ppb to about 25 ppb. However, individual hourly
21    concentrations can be considerably higher than these typical median values, and hourly NO2
22    concentrations > 0.10 ppm can be found at any time of day.
23
24    AX3.2.2.2   Seasonal Variability in NO2 Concentrations
25
26    Urban Sites
27          As might be expected from an atmospheric species that behaves essentially like a primary
28    pollutant emitted from surface  sources, there is strong  seasonal variability in NOX and NO2
29    concentrations. Highest concentrations are found during winter, consistent with lowest mixing
30    layer heights found during the year.  Mean and peak concentrations in winter can be up to a
31    factor of two larger than in the  summer at several sites in Los Angeles County.
32
      August 2007                             AX3-8       DRAFT-DO NOT CITE OR QUOTE

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             a
             3
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             o
             1
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0.19-
0.18-
0.17-
0.16-
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0.10-
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             I
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                    0
       1 '  I ' I'1 I ' f  ' I '  I
       1234567
i  r i ' i  ' i f  i • i •  i ' i  ' i '  i > i '  i ' i  ' i ' i  ' i '
8  9  10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
                                                  Hour
     Figure AX3.3.
      Composite, diurnal variability in 1-h average NOi in urban areas. Values
      shown are averages from 2003 through 2005. Boxes define the
      interquartile range, and the whiskers the 5th and 95th percentile values.
      Asterisks denote individual values above the 95th percentile.
 1          The month-to-month variability in NC>2 at individual sites in selected urban areas is

 2   illustrated in Figures AX3.4 to AX3.10.  Seasonal patterns can be found at some sites but not in

 3   others. There appears to be a somewhat regular pattern for the southern cities with winter

 4   maxima and summer minima.  Monthly maxima tend to be found from late winter to early spring

 5   in Chicago and New York with minima occurring from summer through the fall. However, in

 6   Los Angeles and Riverside, monthly maxima tend to occur from autumn through early winter

 7   with minima occurring from spring through early summer.

 8
 9   Regional Background Sites

10          Surface NOX and NOy data obtained in Shenandoah National Park, VA from 1988 to

11   1989 show wintertime maxima and summertime minima (Doddridge et al., 1991, 1992; Poulida

12   et al., 1991). NOX and NOy data collected in Harvard Forest, MA from  1990 to 1993 show a

13   similar seasonal pattern (Munger et al., 1996). In addition the within-season variability was

14   found to be smaller in the summer than in the winter as shown in Table AX3.3.
     August 2007
                             AX3-9
                 DRAFT-DO NOT CITE OR QUOTE

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a. New York, NY,
                  SUBURBAN
b. Hew York, NY.   URBAN and CENTER CITY
   -

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                                                            Sample Date (mm/dd/yyyy)
c. New York, NY    URBAN and CENTER CITY
                                             d. New York, NY.   URBAN and CENTER CITY
   JR.
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               SampI* Date (mm/ddYyyyy)
                                                             Sample Date (mm/dd/yyyy)
Figure AX3.4a-e.
                     a. Mew York, NY,   URBAN and CENTER CITY
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     a. Atlanta, GA.
                                   SUBURBAN
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        01/01/2003   07/01/2003   01/01/2004  07/01/2004  01/01/2005   07/01/2005   01/01/2006
                             Sample Date (mm/dd/yyyy)
     b. Atlanta, GA.
                           URBAN and CENTER CITY
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         01/01/2003  07/01/2003   01/01/2004  07/01/2004  01/01/2005   07/01/2005   01/01/2006
                             Sample Date fmm/dd/yyyy)
Figure AX3.5a-e.
                    Time series of 24-h average NOi concentrations at individual sites in
                    Atlanta, GA from 2003 through 2005. A natural spline function (with
                    9 degrees of freedom) was fit and overlaid to the data (dark solid line).
August 2007
                                       AX3-11
                                  DRAFT-DO NOT CITE OR QUOTE

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            >, IL.
                        RURAL
                                          SUBURBAN
                                 	
                    Sample Date (mm/dd/yyyy)
                                                             Sample Dale {mmftldfyyyy)
      c Chicago, IL.
                      SUBURBAN
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                                                             Sampie Date C
      e Chicago. IL
      I *„
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                          f. ChKwgo. it    URBAN and CENTER CITY
                    Sample Date (mntfdd/yyyy)
                                                             Sampie Date ^
Figure AX3.6a-g.
                           a chi«go,iL   URBAN and CENTER CITY
                          o "•
                          O
                                        Sample Date {
Time series of 24-h average NOi concentrations at individual sites in

Chicago, IL from 2003 through 2005. A natural spline function (with

9 degrees of freedom) was fit and overlaid to the data (dark solid line).
August 2007
                     AX3-12       DRAFT-DO NOT CITE OR QUOTE

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    a. Baton Rouge, LA,
                          SUBURBAN


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                            01/01/2004                                 01/01/2006
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                             Sample Date fmm/dd/yyyy)
                             and            CITY
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                                      07/01/2004
                             Sample Date (mm/dd/yyyy)
Figure AX3.7a-b.
           Time series of 24-h average NOi concentrations at individual sites in
           Baton Rouge, LA from 2003 through 2005. A natural spline function
           (with 9 degrees of freedom) was fit and overlaid to the data (dark
           solid line).
August 2007
                              AX3-13
DRAFT-DO NOT CITE OR QUOTE

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     a. H0ystona TX
                      SUBURBAN
                                                13. Houston, TX,
                                           SUBURBAN
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                                        Simple Date |
     c Houston, TX,
                      SUBURBAN
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                                                d. Houston, TX
                                           SUBURBAN

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                                                              Sample Date (mmldd/yyyyj
     • Houston, TX    URBAN and CENTER CITY
     Q, s '
                   Sample Date (mm/dd/yyyy)
                                                i Houston. TX,    URBAN and CENTER CITY
                                                              Sample Date jmm/dd/yyyy)
Figure AX3.8a-g.
                          fl, Houston, TX.    URBAN and CENTER CITY
                          E i,,.
                          5 l*
                                        Sample Date (mm/dd/yyyy)
Time series of 24-h average NOi concentrations at individual sites in

Houston, TX from 2003 through 2005.  A natural  spline function (with


9 degrees of freedom) was fit and overlaid to the data (dark solid line).
August 2007
                     AX3-14       DRAFT-DO NOT CITE OR QUOTE

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        - Los Anfpt^g, CA,
                        SUBURBAN
                     Sample Date {mmfdd/yyyy)
                                                                 SUBURBAN
                                                               „ I1* ^tfr&vffirr "«t   , *Tmt»Sf*ii***lf " ^ i ' i
                                                              Sample Dst© fmm/eld/yyyy)
       c Los Angeles, CA
                        SUBURBAN
                     Samplo Date |m
                          t) Los Anides, CA      SUBURBAN
                                                              Sample Date (mmMd
-------
i, LOS Angeles, CA,  URBAN and CENTER CITY
                         j. LOS Angeles, CA, URBAN and CENTER CITY
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                         i. Los Angetes, CA, URBAN and CENTER CITY
                                      .    -
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                                                   Sample Date (mm/dd/yyyy)
m. LOS Angeles, CA. URBAN and CENTER CITY
                         n. LOS Angeles, CA, URBAN and CENTER CITY
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                                      Sampit Date (mm/dd/yyyy)
Figure AX3.9i-n.
     Time series of 24-h average NOi concentrations at individual sites in

     Los Angeles, CA from 2003 through 2006. A natural spline function

     (with 9 degrees of freedom) was fit and overlaid to the data (dark

     solid line).
August 2007
                      AX3-16      DRAFT-DO NOT CITE OR QUOTE

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     a Ri¥erside, CA,
                     RURAL
                                                  t>. Riverside, CA,
                   SUBURBAN
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                                                             Sampis Date (mm/ddlyyyy)
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                   SUBURBAN
d. Riverside, CA.
                   SUBURBAN
          i
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                    Sample Date (mm/dd/yyyy)
                                                             >-w if*  11 .j! :,'>s  jv.itr.'-xi  o
                                                             Sample Date (mm/2 concentrations from
3    1983 to 2002. As can be seen from the figure, NC>2 concentrations have decreased by about 10%
4    per decade. As can be seen from Figure AX3.12, most monitoring sites are located in either
5    urban (49) or suburban (58) areas and comparatively few monitoring sites are located in rural
6    areas (14). Figure AX3.12 also shows that decreases have been at least twice as large in urban
1    and suburban areas than in rural areas and that NO2 concentrations in urban and suburban areas
8    are roughly twice those in rural areas.  Note that a land use characterization of rural does not
     August 2007
                                         AX3-17
          DRAFT-DO NOT CITE OR QUOTE

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e. Riverside, CA.
                   SUBURBAN
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                                             SUBURBAN
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                                          Sample Oate (mm/dd/yyyy)
g. Riverside, CA.
                   SUBURBAN
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                                          Sample Date (mm/ddfyyyy)
                      i. Riverside, CA.    URBAN and CENTER CITY
                                       3!i 1CC«
                                       Sample
                                              j-cu*   o"iH'»s
Figure AX3.10e-i.
Time series of 24-h average NOi concentrations at individual sites in
Riverside, CA from 2003 through 2006. A natural spline function
(with 9 degrees of freedom) was fit and overlaid to the data (dark
solid line).
August 2007
AX3-18
                                    DRAFT-DO NOT CITE OR QUOTE

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 1    imply that a site is free of local pollution influences, as evidenced by the still relatively high
 2    values at rural sites compared to those found in remote areas of the globe.  Rural sites can be
 3    affected by nearby highways, power plants, and other sources.
 4          In addition to the downward trend in annual mean concentrations of NC>2 shown in
 5    Figures AX3.11 and AX3.12, hourly maximum concentrations have also declined, as evidenced
 6    by a number of peak values above 250 ppb across the United States in 1988.  In contrast only one
 7    hourly maximum concentration above 250 ppb was found in 2004 (however, this may have been
 8    a measurement artifact as it represented a one h spike that was many times the next highest
 9    concentration at this site), and all other values were less than about 150 ppb.
10
11    AX3.2.4   Relationships Between NO2 and Other Pollutants
12          Determining the relationships between NC>2 and other pollutants is important for better
13    understanding the findings of time-series epidemological studies relating NO2 to mortality
14    (e.g., Burnett et al., 2004). Correlations between NO2 and CO, 63, and PM2.5 were calculated for
15    monitoring sites in Los Angeles and Riverside, CA; Chicago, IL; Washington, D.C.; and New
16    York City. Correlations were calculated using both hourly and 24-h average data with similar
17    results. The ranges of Pearson correlation coefficients between 24-h average NC>2 and Os, CO
18    and PM2.5 for 2000 through 2004 at monitoring sites in a few urban areas are shown in Table
19    AX3.4. As can be seen from the table, correlations of NO2 with O3 range from negative to
20    slightly positive; with CO they range from slightly negative to highly positive, and with PM2.5
21    they range from slightly to moderately positive. However, it should be noted that these
22    correlations are based on annual data from sites influenced by local sources.  In general, there is
23    a strong seasonal  variation in the correlations, r, with lowest values of r between NO2 and O3
24    found in winter.
25          In order to understand the relations between atmospheric species as shown in Table
26    AX3.4, an important distinction must be made between primary (directly  emitted) species and
27    secondary (photochemically produced) species. In general, it is more likely that primary species
28    will be more highly correlated with each other, and that secondary species will be more highly
29    correlated with each other. By contrast, primary and secondary species are less likely to be
30    correlated with each other.  Secondary reaction products tend to correlate with each other, but
      August 2007                             AX3-19      DRAFT-DO NOT CITE OR QUOTE

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       83                     90  SI  §2 §3  94 §5  96  97 98  99 00 01 02








Figure AX3.11.      Nationwide trends in annual mean NOi concentrations.




Source:  U.S. Environmental Protection Agency (2003).
       .030
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       .COS
       .MO
                                                       Rurstlsites
                                   14
                Suburban Sites      58
            62  S3 64  85 B& S?  88  »„-• $0  91  92 8»3  94 95  y6 97 9© y§ 00 01

                                            Year



Figure AX3.12.      Trends in annual mean NOi concentrations by site type.




Source:  U.S. Environmental Protection Agency (2003)
August 2007
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 1    there is considerable variation. Some species (e.g., 63 and organic nitrates) are closely related
 2    photochemically and correlate with each other strongly.
 3          Although NC>2 is produced mainly by the reaction of directly emitted NO with Oj with
 4    a small contribution from direct emissions, in practice, it behaves like a primary species. The
 5    timescale for conversion of NO to NO2 is relatively rapid (~1 or 2 min for Os = 40 ppb and
 6    ambient temperatures from 273 to 298 K), so NO and NO2 ambient concentrations rapidly
 7    approach values determined by the photochemical steady state. The sum of NO and NO2 (NOX)
 8    behaves like a typical primary species, while NO and NO2 reflect some additional complexity
 9    based on photochemical interconversion. Chemical interactions among Os, NO and NO2 have
10    the effect of converting Os to NO2 and vice versa, which can result in a significant negative
1 1    correlation between O3 and NO2.
12    Most CO in urban air is emitted from motor vehicles and so is primary in origin. Os is a
13    secondary pollutant.  Figures AX3.13a-d show seasonal plots of correlations between NO2 and
14    Os versus correlations between NO2 and CO. As can be  seen from the figures, NO2 is positively
15    correlated with CO during all  seasons at all sites. However, the sign  of the correlation of NO2
16    with Os varies with season, ranging from negative during winter to slightly positive during
17    summer.  There are at least two main factors contributing to the observed seasonal behavior.
18    Os and radicals correlated with it tend to be higher during the summer, thereby tending to
19    increase the NO2 to NO ratio according  to the expression below (Equation AX3-2).

                              NO?  _ kj(O3) + k?(HO7) + k,(RO2)
20                                                                                   (AX3-2)
21          NOZ compounds formed from the oxidation of NOX are also expected to be correlated
22    with Os and increased photochemical activity.  Because of interference of NOZ compounds with
23    the measurement of NO2 by conventional chemiluminescent monitors, they may also tend to
24    increase the correlation of NO2 with Os during the warmer months. However, there is not
25    enough information on the seasonal behavior in their concentrations to quantify the contribution
26    of NOZ compounds.
27          Relationships between Os, NO, and NO2 are shown in Figures AX3. 14 and AX3. 15.
28    Figure AX3. 14 shows daylight average concentrations based on data collected from November
29    1998 and 1999 at several sites in the United Kingdom representing a wide range of pollution

      August 2007                            AX3-21      DRAFT-DO NOT CITE OR QUOTE

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-0,2-
-0.4 -
-0,6-
-0,8 -



0.2 0,4 0.6 0.8

* /%*$
* **
NO2; CO
Spring
0.8-
0,6-
0.4-
0.2-
1 -0.8 -0.6 -0.4 -0.2 (
-0.2-
-0.4 •
•0.6-
-0,8-



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'^ * A.***
i o^ 0.4 0.6 ie





cT
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«
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«
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z



Summer
0.8-
0.6-
0.4-
0.2-
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-0.8-


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	 x 	 i 	 i 	 » 	 ^ 	 • 	
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Fall
0.8-
0,8-
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0.2-
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-0.2-
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-0.6 -
-0.8-



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                       NO2: CO
                                                              NO2; CO
    Figure AX3.13a-d.  Correlations of NOi to Os vs. correlations of NOi to CO for Los
                        Angeles, CA (2001-2005).
4
5
6
conditions (open symbols). The solid lines represent calculations of photostat!onary state values
subject to the constraint that Ox = 31.1 + 0.104(NOX), where Ox = O3 + NO2. Note that Ox is
defined in the UK AQG report as oxidant, as used in this document, and in the latest AQCD for
Ozone and other Photochemical Oxidants (U.S. Environmental Protection Agency, 2006) it is
taken to refer to "odd oxygen" as defined in Section 2.2. The reason is that oxidants also include
PANs, peroxides, and reactive oxygen species in particles etc., in addition to Os and NO2.  The
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             a)
100
                             100
                                      200
                                               300
                                      400
                                                                 500
                                                                          60C
Figure AX3.14.
  Relationship between Os, NO, and NOi as a function of NOX
  concentration. Open circles represent data collected at a number of
  sites in the United Kingdom. Lines represent calculated relationships
  based on photostationary state.
Source: Clapp and Jenkin (2001).
               b)  100
                    80
                                                 local contribution to oxidant
                                                     (NO,-dependent)
                                     regional contribution to oxidant
                                          (NO < -independent)
                              100     200      300      400
                                           [N0,xl(ppb)
                                             500      600
Figure AX3.15.     Variation of odd oxygen (= Os + NOi) with NOX.  The figure shows the
                    "regional" and the "local" contributions.  Note that Ox refers to odd
                    oxygen in the document and the latest Os AQCD.
Source: Clapp and Jenkin (2001).
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 1    intercept of 63 with the y-axis at about 30 ppb is representative of background values of 63 in
 2    the UK.  The figure shows how Os decreases with increasing NO and NOX.  NO constitutes more
 3    than about 90% of NOX at high values of NOX as available O3 is titrated away.
 4          Figure AX3.15 shows how the concentration of Ox (=03 + NO2) varies with that of NOX.
 5    As in Figure AX3.14, Os intercepts the y-axis at about 30 ppb, corresponding to background Ox
 6    which is composed almost exclusively of Os. Ox increases in a linear fashion, as given by the
 7    regression relation above, as NOX increases. This relationship results from the emissions of NO2
 8    (an oxidant and a component of odd oxygen) varying linearly with emissions of NOX, especially
 9    after NO has reacted with Os to form NO2 as shown in Figure AX3.14. Thus the concentration
10    of Ox (and not Os, as is often stated) can be taken to be the sum of regional and local
11    contributions.
12          Figure AX3.15 shows that primary emissions  from motor vehicles are major sources of
13    oxidant in the form of NO2, as evidenced by the high  values of Ox at elevated NOX.
14
15    AX3.2.5   Abundance of NOy Species
16          Data for individual NOy species are much less abundant than for either oxides of nitrogen
17    or for total NOy. Data for NOy species are collected typically as part of research field studies,
18    e.g., the Southern Oxidant Study (SOS), Texas Air Quality Study  (TexAQS I and TexAQS II) in
19    the United States. So this information is simply not available for a large number of areas in the
20    United States.
21
22    PANs
23          Organic nitrates consist of PAN, a number of  higher-order species with photochemistry
24    similar to PAN (e.g., PPN), and species such as alkyl  nitrates with somewhat different
25    photochemistry.  These species are produced by a photochemical process very similar to that of
26    Os. Photochemical production is initiated by the reaction of primary and secondary VOCs with
27    OH radicals, the resulting organic radicals subsequently react with NO2 (producing PAN and
28    analogous species) or with NO (producing alkyl nitrates). The same sequence (with organic
29    radicals reacting with NO) leads to the formation of 03.
30          In addition, at warm temperatures, the concentration of PAN forms a photochemical
31    steady state with its radical precursors on a timescale  of roughly 30 min. This steady state value
32    increases with the ambient concentration of Os (Sillman et al., 1990).  Ozone and PAN may

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 1    show different seasonal cycles, because they are affected differently by temperature.  Ambient
 2    63 increases with temperature, driven in part by the photochemistry of PAN (see description in
 3    Chapter 2). The atmospheric lifetime of PAN decreases rapidly with increasing temperature due
 4    to thermal decomposition. Based on the above, the ratio of Os to PAN is expected to show
 5    seasonal changes, with highest ratios in summer, although there is no evidence from
 6    measurements.  Measured ambient concentrations (Figures AX3.16a-d) show a strong nonlinear
 7    association between Os and PAN, and between Os and other organic nitrates (Pippin et al., 2001;
 8    Roberts et al., 1998). Moreover, the uncertainty in the relationship between 63 and PAN grows
 9    as the level of PAN increases.  Individual primary VOCs are generally highly correlated with
10    each other and with NOX (Figure AX3.17).
11          Measurements and models show that PAN in the United States includes major
12    contributions from both anthropogenic and biogenic VOC precursors (Horowitz et al., 1998;
13    Roberts et al., 1998). Measurements in Nashville during the 1999 summertime Southern
14    Oxidants Study (SOS) showed PPN and MPAN amounting to 14% and 25% of PANs,
15    respectively (Roberts et al., 2002). Measurements during the TexAQS 2000 study in Houston
16    indicated PAN concentrations of up to 6.5 ppbv (Roberts et al., 2003).  PAN measurements  in
17    southern California during the SCOS97-NARSTO study indicated peak concentrations of
18    5-10 ppbv, which can be contrasted to values of 60-70 ppbv measured back in 1960 (Grosjean,
19    2003).  Vertical profiles measured from aircraft over the United States and off the Pacific  coasts
20    typically show PAN concentrations above the boundary layer of only a few hundred pptv,
21    although there are significant enhancements associated with long-range transport of pollution
22    plumes from Asia (Kotchenruther et al., 2001a; Roberts et al., 2004).
23          Observed ratios of PAN to NO2 as a function of NOX at a site at Silwood Park, Ascot,
24    Berkshire, UK are shown in Figure AX3.18 United Kingdom Air Quality Expert Group (U.K.
25    AQEG, 2004).  As can be seen there is a very strong inverse relation between the ratio and the
26    NOX concentration, indicating photochemical oxidation of NOX has occurred in aged air masses
27    and  that PAN can make a significant contribution to measurements of NO2 especially at low
28    levels of NO2 (cf Section 2-8). It should be noted that these ratios will likely differ from those
29    found in the U.S. because of differences in the composition of precursor emissions, the higher
30    solar zenith angles found in the UK compared to the U.S., and different climactic conditions.
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ti
12(7 » "-
v • > " f
100[ '- 4»r * -t> i ': t, •-
Jf?fr 1
| 20
c >C
S 120^ ,J I
o , .i*|!Y
100 , +, fe.^'1
so: jjfr
40 *
20;
JL! ' j i!
} J v *
' f
#r
F
IT4^' ^~*4--^
, , 1 \


                                              PAM (pptv)
     Figure AX3.16a-d.   Measured O3 (ppbv) versus PAN (pptv) in Tennessee, including (a)
                         aircraft measurements, and (b, c, and d) suburban sites near
                         Nashville.
1
2
3
 5
 6
 9
10
11
12
13
14
15
     Source: Roberts etal. (1998).

            Nevertheless, these results indicate the potential importance of interference from NOy
     compounds in measurements
    HONO
           The ratio of HONO to NO2 as a function of NOX measured at a curbside site in a street
    canyon in London, UK is shown in Figure AX3.19 (U.K. AQEG, 2004).  The ratio is highly
    variable, ranging from about 0.01 to 0.1, with a mean -0.05. As NO2 constitutes several percent
    of motor vehicle emissions of NOX, the above implies that emissions of HONO represent a few
    tenths of a percent of mobile NOX emissions.  A similar range of ratios have been observed at
    other urban sites in the United Kingdom (Lammel and Cape, 1996).  The ratios of HONO to
    NO2 shown in Figure AX3.19 indicate that HONO can make a measurable contribution to
    measurements of NO2 (cf.  Section 2-8). However, similar arguments about extrapolating the
    use of UK data to  the U.S. can be made for HONO as for PAN.
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Figure AX3.17.
                            1.5-
                 i < 10 ppbv
             o SO2> 10 ppbv
                            0.0
                                       40   60   80   100   120
                                        NOy {ppbv)
Relationship between benzene and NOy at a measurement site in
Boulder, CO. Instances with SOi >10 ppb are identified separately
(open circles), because these may reflect different emission sources.
Source: Goldanetal. (1995).
                0,20
                                       40        60
                                        [NOX] (ppb}
                                      80
                                                                  100
Figure AX3.18.     Ratios of PAN to NOi observed at Silwood Park, Ascot, Berkshire,
                   U.K. from July 24 to August 12 1999. Each data point represents a
                   measurement averaged over 30 minutes.
Source: UK AQEG (2004).
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                      0,3 i		-	—	—-
                      0,2
                   o
                   o
                   X  0.1 ^
                                  200
                                            400
                                                      600
                                                  {ppb)
                                                                800
                                                                          1000
     Figure AX3.19.
Ratios of HONO to NOi observed in a street canyon (Marylebone
Road) in London, U.K. from 11 a.m. to midnight during October
1999. Data points reflect 15-min average concentrations of HONO
and NO2.
     Source: UK AQEG (2004).

 1   HNO3 and NO 3
 2          Elevated Os is generally accompanied by elevated HNOs, although the correlation is not
 3   as strong as between Os and organic nitrates. Ozone is often associated with HNOs, because
 4   they have the same precursor (NOX).  However, HNOs can be produced in significant quantities
 5   in winter, even when Os is low. The ratio between Os and HNOs also shows great variation in
 6   air pollution events, with NOx-saturated environments having much lower ratios of Os to HNOs
 7   (Ryerson et al.,  2001). Aerosol nitrate is formed primarily by the combination of nitrate
 8   (supplied by HNOs) with ammonia, and may be limited by the availability of either nitrate or
 9   ammonia. Nitrate is expected to correlate loosely with O3 (see above), whereas ammonia is not
10   expected to correlate with Os.
11          Concentrations of particulate nitrate measured as part of the Environmental Protection
12   Agency's speciation network at several locations are shown in Figure AX3.20.  Concentrations
13   shown are annual averages for 2003. Also shown are the estimated contributions from regional
14   and local sources. A concentration of 1 |ig/m3 corresponds to -0.40 ppb equivalent gas phase
15   concentration for MV. Thus, annual average parti culate nitrate can account for several ppb of
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                                                     Nitrates
      Figure AX3.20.
                                   Fresno
                                 Missoula
                              Salt Lake City
                                    Tulsa
                                 St. Louis
                               Birmingham
                               Indianapolis
                                   Atlanta
                                 Cleveland
                                 Charlotte
                                 Richmond
                                 Baltimore
                              New York City
                                   [3 Regional
                                    Contribution
                                    local
                                    Contribution
                                                               10
                                          12
                                            Annual Average Concentration
                                                 of Nitrates, pg/m3
Concentrations of particulate nitrate measures as part of the
Environmental Protection Agency PA's speciation network. 1 ug/m3
-0.45 ppb equivalent gas phase concentration for NOs". (Note:
Regional concentrations are derived from the rural IMPROVE
monitoring network, http://vista.cira.colostate.edu/improve.
      Source: U.S. Environmental Protection Agency (2004).

 1          NOy, with the higher values in the West. There is a strong seasonal variation, which is
 2    especially pronounced in western areas where there is extensive wood burning in the winter
 3    resulting in a larger fractional contribution of local sources.  Areas in the East where there are
 4    topographic barriers might be expected to show higher fractional  contributions from local
 5    sources than other eastern areas that are influenced by regionally  dispersed sources.
 6          However, depending on the acidity of the particles, which in turn depends strongly on
 7    their sulfate and ammonium contents, higher nitrate concentrations  could be found in coarse
 8    mode particles PMio-2.5 than in PM2.5 samples.  The average nitrate  content of PM2.5 and PMio is
 9    typically about a percent in the eastern United States; and 15.7%  and 4.5% in the western United
10    States (U.S. Environmental Protection Agency, 1996).  These values suggest that most of the
11    nitrate was in the PM2.5 size fraction in the studies conducted in the western United States, but
12    nitrate in the studies in the eastern United States was mainly in the PMio-2.5 size fraction.
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 1   Nitro-PAHs
 2          Nitro-PAHs (NPAHs) are widespread and found even in high altitude, relatively
 3   unpolluted environments (Schauer et al., 2004) but there are differences in composition and
 4   concentration profiles both within and between sites (rural vs. urban) as well as between and
 5   within urban areas (Albinet et al., 2006; Soderstrom et al., 2005; Naumova et al., 2002, 2003),
 6   with some differences in relative abundances of nitro- and oxo-PAHs also reported. Source
 7   attribution has remained largely qualitative with respect to concentrations or mutagenicity (Eide
 8   et al., 2002). The spatial and temporal  concentration pattern for the NPAHs may differ from that
 9   of the parent compounds (PAHs) because concentrations of the latter are dominated by direct
10   emission from local combustion sources.  These emissions results in higher concentrations
11   during atmospheric conditions more typical of wintertime when mixing heights tend to be low.
12   The concentrations of secondary NPAHs are elevated under conditions that favor hydroxyl and
13   nitrate radical formation, i.e., during conditions more typical of summertime, and are enhanced
14   downwind of areas of high emission density of parent PAHs and show diurnal variation (Fraser
15   et al., 1998; Reisen and Arey, 2005; Kameda et al., 2004). Nitro-napthalene concentrations in
16   Los Angeles, CA varied between about 0.15 to almost 0.30 ng/m3 compared to 760 to
17   1500 ng/m3 for napthalene. Corresponding values for Riverside, CA were 0.012 to more than
18   0.30 ng/m3 for nitro-napthalene and 100 to 500 ng/m3 for napthalene. Nitro-pyrene
19   concentrations in LA varied between approximately 0.020 to 0.060 ng/m3 compared to 3.3 to
20   6.9 ng/m3 pyrene, whereas corresponding values for Riverside were 0.012 to 0.025 ng/m3 and 0.9
21   to 2.7 ng/m3.
22
23
24   AX3.3    METHODS FOR MEASURING PERSONAL AND INDOOR NO2
25              CONCENTRATIONS
26
27   AX3.3.1   Issues in Measuring  Personal/Indoor NO2
28
29   Background
30          Nitrogen dioxide, a criteria air pollutant, has been sampled in ambient and indoor air
31   using active pumped systems both for continuous monitoring and collection onto adsorbents,  and
32   by diffusive samplers of various designs, including badges and tubes. Nitrogen dioxide
33   concentrations in personal air have been typically measured using diffusive samplers because

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 1    they are: (1) small in size and light-weight, (2) unobtrusive and thus more readily used by study
 2    participants, (3) comparatively easier to use and handle in field studies because they do not
 3    require power (e.g., battery or extra electrical sources), (4) cost-effective, and (5) usable not only
 4    for residential indoor and outdoor air sampling but also personal monitoring. However, diffusive
 5    samplers usually have lower equivalent sampling rates than active methods and so require
 6    relatively long sampling times (24 h or longer).  Consequently, diffusive samplers including
 7    those used for NC>2 monitoring provide integrated but not short-term concentration
 8    measurements.
 9          Both active and passive sampling methods can collect other gas-phase nitrogen oxide
10    species.  However, semivolatile nitrogen  oxide compounds require separation of the gas- and
11    particle-bound phases.  This selective separation of gases from gas-particle matrices is
12    commonly done by means of diffusion denuders (Vogel,  2005), an approach also useful for
13    measuring other gas phase airborne contaminants such as SC>2 (Rosman et al., 2001).
14    Application of denuder sampling to personal exposure or indoor air monitoring has been
15    relatively limited.
16          Active air sampling with a pump can collect larger volumes of air and thus detect the
17    lower concentrations found in community environments within relatively short time periods.
18    Automated active sampling methods have been the preferred method used to monitor NO2
19    continuously at ambient sites for environmental  regulation compliance purposes. However,
20    practical considerations impede the use of these continuous monitors in residential air and
21    exposure monitoring studies. Small, low flow active samplers using battery-operated pumps
22    have been used instead, however, there are only a few such studies.
23          The first passive sampling devices for NO2 were intended for occupational exposure
24    monitoring, but were later adapted for environmental  monitoring purposes.  Since this sampler,
25    the Palmes tubes (Palmes et al., 1976), was first developed, other tube, badge-type (Yanagisawa
26    and Nishimura, 1982) and radial (Cocheo et al.,  1996) diffusive samplers have been employed as
27    monitors in exposure studies worldwide.  The theories behind and applications of Palmes Tubes
28    and Yanagisawa badges have been described in the last AQCD for Oxides of Nitrogen (U.S.
29    Environmental Protection Agency, 1993). There are currently several commercially available
30    samplers (e.g., Ogawa, Radiello®, Analyst™) which are modifications of the original Palmes
31    tube design. Most modifications are directed at  reducing effects related to meteorological

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 1    conditions (e.g., insufficient or too high a wind speed, humidity, temperature), increasing the
 2    sampling uptake rate, and improving analytical sensitivity.
 3
 4    Active (Pumped) Sampling
 5          Nitrogen dioxide measurement by active pumping systems as part of continuous monitors
 6    has been widely employed for ambient air monitoring as these instruments require relatively
 7    little maintenance; however they have been used less frequently for indoor sampling. Devices
 8    needing a pump to draw air can measure average concentrations of pollutants over short time
 9    periods, but are not generally  suitable for measuring personal exposures because they are heavy
10    and  large.  Some exposure studies employed this approach for active sampling with stationary
11    chemiluminescent analyzers or portable monitors to measure nitrogen dioxide levels in
12    residential indoor air (Mourgeon et al., 1997; Levesque et al., 2000; Chau et al., 2002).
13    Recently, Staimer and his colleagues (2005) evaluated a miniaturized active sampler, suitable for
14    personal exposure monitoring, to estimate the daily exposure of pediatric asthmatics to nitrogen
15    dioxide, and reported that this small active sampling system is useful for this purpose in
16    environmental exposure epidemiology studies where daily measurements are desired.
17
18    Passive (Diffusive) Sampling
19          Passive samplers are based on the well known diffusion principle described by Pick's law
20    (Krupa and Legge, 2000). A  convenient formulation of this law that can be easily related to
21    sampler design considerations is:
22
23    where:
24    J = flux (mg/s)
25    D = diffusion coefficient in air (cm2/s)
26    A = diffusion cross-sectional area of the sampler (cm2)
27    L = diffusion path length from the inlet to sorbent (cm),
28    Cair = concentration of analyte in air (mg/cm3)
29    Csor = concentration of analyte at the sorbent (mg/cm3)
30
J — U (A /L)( L, ajr- C ,5Or}                         (AX3 -3 )
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 1          The term D(A/L) can be related to the uptake or sampling rate (cmVs) which is
 2    conceptually analogous to the sampling rate in an active monitor.  Once the amount of analyte in
 3    the passive sampler sorbent is determined, the concentration in air (Ca;r) can be calculated as:

 4                   Concentration(mg/cm3) = M'(mg)/D(A/L)(cm3/$)/t(sec)        (AX3-4)
 5    where:
 6          M = mass of analyte collected in the sorbent
 7          t = sampling time
 8
 9          Pick's law strictly applies only under ideal, steady state conditions assuming that the
10    sorbent is a perfect sink. However, there can be deviations between the theoretical sampling rate
11    for a given analyte and the actual rate depending on sampling conditions.  It is also clear that
12    sampling rate can be optimized by modifying the geometry of the diffusive sampler, either by
13    reducing L, increasing A or a suitable combination. However, the impact of deviations from
14    ideality on actual sampling rate due to geometry also poses a limit to the extent of possible
15    modifications. Thus, passive samplers, either diffusive or permeation, are prepared as tubes or
16    badges.  These two main designs are the basis for all further modifications which, as indicated
17    above, have been made in order to improve efficiency, reduce sensitivity to wind turbulence of
18    the samplers, and to simplify analyte desorption. Tube-type samplers are characterized by a
19    long, axial diffusion length, and a low cross-sectional area; this results in relatively low sampling
20    rates (Namiesnik et al., 2005).  Badge-type samplers have a shorter diffusion path length and a
21    greater cross-sectional area which results in uptake rates that are typically higher than diffusion
22    tubes (Namiesnik et al., 2005) but the sampling rate may be more variable because it is more
23    affected by turbulence. Physical characteristics of these two fundamental  passive sampler types,
24    tube-type and badge-type, are summarized and provided in Table AX3.5.  Performance
25    characteristics are presented in Table AX3.6.
26          The sorbent can be either physically sorptive or chemisorptive; passive samplers for NC>2
27    are chemisorptive, that is,  a reagent coated on a support (e.g.,  metal mesh, filter) reacts with the
28    NC>2. The sorbent is extracted  and analyzed for one or more reactive derivatives; the mass of
29    NC>2 collected is derived from the concentration of the derivative(s) based on the stoichiometry
30    of the reaction. Thus, an additional approach to reducing detection limits associated with passive

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 1    samplers is to modify the chemisorptive reaction and the extraction and analysis methods to
 2    increase analytical sensitivity.  However, although chemisorption is less prone to the back
 3    diffusion phenomenon of sorptive-only methods, analyte losses could occur due to interferences
 4    from other pollutants that also react with the sorbent or the derivatives. The most commonly
 5    used NC>2 passive samplers rely on the classical reaction with triethanolamine (TEA). TEA
 6    requires hydration for quantitative NC>2 sampling (i.e., 1:1 conversion to nitrite) and the reaction
 7    products have been subject to a number of investigations and several have been reported,
 8    including TEA-nitrate and nitrite, triethanolammonium nitrate, nitrosodiethanolamine, and
 9    triethanolamine N-oxide (Glasius et al., 1999).  Known interferences include HONO, PAN, and
10    nitric acid (Gair et al., 1991.).
11          The tube-type passive samplers (Palmes tubes) require week-long sampling periods and
12    have been extensively used for residential indoor/outdoor measurements, mostly for exploring
13    the relationship between indoor and outdoor levels (Cyrys et al., 2000; Raw et al., 2004; Simoni
14    et al., 2004; Janssen et al., 2001). Passive diffusion tubes have also been widely used for
15    measurements of NC>2 in ambient air (Gonzales et al., 2005; Gauderman et al., 2005; Da Silva
16    et al., 2006; Lewne et al., 2004; Stevenson et al., 2001; Glasius et al.,  1999).  Personal exposure
17    studies have also been conducted using the Palmes tubes (Mukala et al., 1996; Kousa et al.,
18    2001).  Some of these studies evaluated passive sampler performance by collocating them with
19    chemiluminescence analyzers during at least some portion of the field studies (Gair et al.,  1991;
20    Gair and Penkett, 1995; Plaisance et al., 2004; Kirby et al., 2001).  The majority of these studies
21    indicate that these samplers have very good precision (generally within 5%) but tend to
22    overestimate NO2 by 10 to 30%. However, there has not been a methodical evaluation of
23    variables contributing to variance for the range of samplers available when used in field
24    conditions.  Thus, it is not clear if the bias is due to deviations from ideal sampling conditions
25    that can affect actual sampling rates, contributions from co-reacting contaminants or, most
26    probably, a combination of these variables.
27          A badge-type sampler was introduced by Yanagisawa and Nishimura (1982) to overcome
28    the long sampling time required by Palmes tubes.  Since then, these sensitive NO2 short path
29    length samplers (Toyo Roshi Ltd) have been optimized and evaluated for indoor air and for
30    personal monitoring (Lee et al., 1993a,b).  They have been used  extensively for personal
31    exposure studies (Ramirez-Aguilar et al., 2002; Yanagisawa et al., 1986; Berglund et al., 1994,

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 1   Lee et al., 2004) and indoor air measurements (Kodoma et al., 2002; Bae et al., 2004; Algar
 2   et al., 2004; Shima and Adachi, 2000; Smedje, et al., 1997) and to a more limited amount for
 3   ambient monitoring (Tashiro and Taniyama, 2002; Levy et al., 2006; Norris and Larson, 1999).
 4   Due to the greater uptake rate resulting from the larger cross sectional area of the badges and
 5   shorter diffusion length compared to the tube-type samplers, sampling times can be decreased
 6   from one-week to one-day for typical environmental air concentrations. This makes diffusive
 7   filter-badges more suitable for shorter-term sampling while long-term ambient monitoring can
 8   still be conducted using the Palmes-tubes.
 9
10   Tube Type Samplers
11          Gradko Sampler (http://www.gradko.co.uk)
12          The Gradko sampler is based on the Palmes tube design (Gerboles et al., 2006b).
13   It collects O3 or NO2 by molecular diffusion along an inert tube by chemisorption. A stable
14   complex is formed with triethanolamine coated on a stainless steel screen in the tube. The
15   complex is spectroscopically analyzed by adding an azo die (Chao and Law, 2000).  The sampler
16   has a detection limit of 0.5 ppb for NO/NO2 and the precision of ± 6% above 5 ppb levels when
17   used for two weeks (Table AX3.6). This sampler has been used to measure personal exposures,
18   concentrations of residential air indoors such as in the kitchen and bedroom, and concentrations
19   of outdoor air (Chao and Law, 2000; Gallelli et al., 2002; Lai et al., 2004).  It has been used to
20   measure ambient NO2 levels in Southern California as a marker of traffic-related pollution in San
21   Diego County (Ross et al., 2006).
22
23          Passam Sampler (http://www.passam.ch)
24          This sampler is also based on the design of the Palmes tube (Palmes et al.,  1976).
25   It collects NO2 by molecular diffusion along an inert polypropylene tube to an absorbent,
26   triethanolamine. The collected NO2 is determined spectrophotometrically by the well-
27   established Saltzmann method. When used outdoors the samplers are placed in a special shelter
28   to protect them from rain and minimize wind turbulence effects.  The Passam sampler is sold in
29   two different models, one for long-term and one for short-term sampling.
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 1          Analyst™Sampler (http://www.monitoreurope.com)
 2          The Analyst™ sampler is also a modification of the open-Palmes-tube design and was
 3    developed by the Italian National Research Council (CNR - Institute Inquinamento
 4    Atmosferico) in 2000 (Bertoni et al., 2001).  The Analyst™ consists of a glass vessel, which
 5    contains a reactant supported on a stainless steel grid.  It is suitable for long-term monitoring
 6    (typically one month) of oxides of nitrogen, sulfur dioxide, and volatile organic compounds in
 7    ambient air. The target compound is analyzed by gas chromatography with minimum detection
 8    limit of 0.1 mg/m3 (-52  ppb) for a twelve-week sample duration, and has relatively high
 9    precision.  The Analyst™ method development (De Santis et al., 1997, 2002) and actual field
10    application (De Santis et al., 2004) have been described. The primary use for Analyst™ is as a
11    reliable tool for long-term determination of concentration in indoor as well as outdoor
12    environments (Bertoni et al., 2001) and as a screening tool for ambient monitoring to identify
13    pollution "hot spots" (De Santis et al., 2004).
14
15    Badge-Types Samplers
16          Ogawa Passive Sampler (http://www.ogawausa.com)
17          This sampler is a double face badge that can monitor NO, NOX, and NC>2.  The design can
18    be used also for the determination of 862, 63, and NH3 levels in air. The manufacturer-reported
19    detection limits for nitrogen oxides are 2.3 ppb and 0.32 ppb for 24-h and 168-h sampling,
20    respectively. Reported actual sampling rates for NO2 are two to three times higher than the
21    manufacturer's values. The normal operation ranges are 0 to 25 ppm for 24-h exposure and 0 to
22    3.6 ppm for 168-h exposure. The manufacturer recommends a sampling height of 2.5 meters and
23    storage time of up to 1 year when kept frozen.  Ogawa passive samplers have been extensively
24    used for human exposure studies to measure personal air concentrations and (or) indoor/outdoor
25    levels for residents in a number of locations, including adults of Richmond, Virginia (Zipprich
26    et al., 2002), children of Santiago, Chile (Rojas-Bracho et al., 2002), office workers of Paris,
27    France (Mosqueron et al., 2002), and cardiac compromised individuals of Toronto, Canada (Kim
28    et al., 2006). The samplers have been used also in air monitoring networks to assess traffic-
29    related pollutant exposure (Singer et al., 2004), as well as to evaluate spatial variability of
30    nitrogen dioxide ambient concentrations in Montreal, Canada (Gilbert et al., 2005).
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 1          IVL Sampler (http//www.ivl.se/en/business/monitoring/diffusive_samplers.asp)
 2          The IVL method development has been described in detail by Perm and Svanberg (1998).
 3    It was developed by Swedish Environmental Research Institute in the mid of 1980s (Sjodin et al.,
 4    1996), is designed to minimize turbulent wind effects outdoors as well as "starvation effects"
 5    indoors (i.e., very low face velocities), interferences from within sampling tube chemistry,
 6    temperature and humidity effects, and artifacts and losses during post-sampling storage.
 7    Manufacturer-reported detection limits for this sampler with sampling times of ~1 month are
 8    0.1 |ig/m3 (0.05 ppb) for NO2, and 0.5 |ig/m3 (0.42 ppb) for NO,  respectively. Due to its long
 9    sampling time, this sampler has been extensively used for NO2 background monitoring in
10    ambient air of rural or urban (Fagundez et al., 2001; Sjodin et al., 1996; Pleijel et al., 2004).
11
12          Willems Badge Sampler
13          The Willems badge, a short-term diffusion sampler, was developed at the University of
14    Wageningen, Netherlands, originally for airborne ammonia measurements and later for
15    measuring NO2 (Hagenbjork-Gustafsson et al., 1996). It consists of a cylinder of polystyrene
16    with a Whatman GF-A glass fiber filter impregnated with triethanolamine at its based held in
17    place by a 6 mm distance ring.  A Teflon filter is placed on the 6 mm polystyrene ring, which is
18    secured with a polystyrene ring of 3 mm (Hagenbjork-Gustafsson et al., 1996).  The badge is
19    closed by a polyethylene cap to limit influences by air turbulence. The diffusion length in the
20    badge is 6 mm. This sampler was evaluated for ambient air measurements in laboratory and
21    field tests (Hagenbjork-Gustafsson et al., 1999). It has a manufacturer's reported detection limit
22    of 2 |ig/m3 (~1 ppb) for 48 h sampling duration. When used for personal sampling in an
23    occupational setting with a minimum wind velocity of 0.3  m/s, detection limits of 18 (-9.4 ppb)
24    and 2 |ig/m3  (~1 ppb) for 1-h and 8-h sampling, respectively, have been reported (Hagenbjork-
25    Gustafsson et al., 2002, Glas et  al., 2004).
26
27    Radial Sampler Types
28          Radiello®  -the radial diffusive sampler (http://www.radiello.com)
29          Radiello®  samplers use radial diffusion over a microporous cylinder into an absorbing
30    inner cylinder, instead of axial diffusion, which increases the uptake rate by a factor of about
31    100 (Hertel et al., 2001).  Nitrogen dioxide is chemiadsorbed onto triethanolamine  as nitrite,
32    which is quantified by visible spectrometry. Sample collection of up to 15 days  is feasible but

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 1    relative humidity higher than 70% can cause interferences when used for extended periods of
 2    more than 7 days. The manufacturer-reported typical sampling rate for nitrogen dioxide
 3    sampling is 75 ± 3.72 ml/min at temperatures between -10 and 40 °C. The rate can vary with
 4    humidity in the range of 15 to 90% and wind speed between 0.1 and 10 m/s (Radiello® Manual,
 5    2006). A Danish study (S0rensen et al., 2005) recruited 30  subjects during each of four seasons
 6    in Copenhagen, and measured the subjects' personal exposures, home indoor/front door air
 7    concentrations during 2-day periods with this sampler.
 8
 9    EMD (Ecole des Mines de Douai) Sampler
10          A new high-uptake rate diffusive sampler has been recently developed by the Ecole
11    des Mines de Douai (EMD) laboratory (Piechocki-Minguy et al., 2003) and evaluated in the
12    laboratory and field for measurement of NC>2 levels in ambient air. It is composed of a porous
13    cartridge impregnated with triethanolamine and fitted in a cylindrical protective box equipped
14    with caps at its extremities (Piechocki-Minguy et al., 2006). The large sampling area (cartridge
15    surface)  and the two circular openings provide a high uptake rate (exceeding 50 cmVmin). The
16    sampling rate was reported to be on average 0.89 cm3/s for indoor sampling and 1.00 cm3/s for
17    outdoor sampling.  Detection limits were determined to be 11  |ig/m3 (-5.8 ppb) for 1-h
18    measurement. The sampling rate was not significantly influenced by wind at speeds higher than
19    0.3 m/s (Piechocki-Minguy et al., 2003). This sampler has been used in France to assess
20    personal exposures in a series of microenvironments (home, other indoor places, transport and
21    outdoor) for two 24-h time periods (weekday and weekend) (Piechocki-Minguy et al., 2006).
22
23    NO2 Measurements in Epidemological Studies
24          Since passive samplers are the most frequently used monitoring method in epidemiology
25    studies of NO2 effects, their performance compared to the long established chemiluminescence
26    monitoring method is critical for determining the contribution of measurement error to exposure
27    estimates. First, most passive samplers developed and used for personal and indoor exposure
28    studies need to be employed for at least 24 h to collect sufficient NO2 to be detected. Therefore,
29    the majority of measurements of personal exposure concentrations done to date represents daily
30    or longer integrated or average  exposure and cannot be used to assess acute, peak exposure
31    concentrations. Some newer passive samplers for nitrogen  dioxide have higher uptake rates and
32    active pump samplers with traditional battery operated sampling pumps and appropriate

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 1    adsorbents can collect sufficient NO2 in approximately one h and have been used in a few studies
 2    providing information on exposure in microenvironments and shorter term exposure
 3    concentration.  Hourly fluctuations in nitrogen dioxide concentrations may be important to the
 4    evaluation of exposure-health effects relationship, so continuous monitors, such as those used at
 5    central site monitoring stations are still the only approach for estimating short-term exposures.
 6          Second, interferences for other nitrogen oxide species can contribute to NC>2 exposure
 7    monitoring errors. Both the chemiluminescence analyzer and passive samplers experience these
 8    interferences but the kinetics and stoichiometry of interferent compound reactions have not been
 9    well established, especially for the passive samplers. As indicated earlier, TEA-based diffusive
10    sampling methods tend to overestimate NO2 concentrations in field comparisons with
11    chemiluminescence analyzers. This could be in part the result of chemical reactions between
12    ozone and nitric oxide (NO) within the diffusion tube, leading to as much as an overestimate up
13    to 30%, or differential sensitivity to other nitrogen oxides between the passive and active
14    samplers. Due to spatially and temporally variability of NO and NO2 concentrations, especially
15    at roadsides where nitric oxide concentrations are relatively high and when sufficient ozone is
16    present for interconversion between the species, lack of agreement between the passive sampler
17    and central continuous monitor can represent differences in sampler response (Heal et al., 1999,
18    Cox, 2003).  In the U.K., an alternative nitrogen dioxide monitoring plan using cost-effective and
19    simpler tube-type passive sampler has been proposed and implemented countrywide. However,
20    careful investigation of nitrogen dioxide levels revealed an overestimation, around 30% by the
21    passive sampler (Campbell et al., 1994). Another evaluation study (Bush et al., 2001) showed
22    that the overall average NO2 concentrations calculated from diffusion tube measurements were
23    likely to be within 10%  of chemiluminescent measurement data.
24          Third, the effect of environmental conditions (e.g., temperature, wind speed, and
25    humidity) on the performance of passive samplers is still a concern when using it for residential
26    indoor, outdoor, and personal exposure studies, because of sampling rates that deviate from ideal
27    and can vary through the sampling period. Overall, field test results of passive  sampler
28    performance are not consistent and they have not been extensively studied over a wide range of
29    concentrations, wind velocities, temperatures and relative humidities (Varshney and Singh,
30    2003). Therefore, studies directed at investigating the contributions from environmental
31    conditions to the performance of diffusive samplers in multiple locations need to be undertaken.

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 1   AX3.4    NITROGEN OXIDES IN INDOOR AIR
 2
 3   AX3.4.1   Indoor Sources and Concentrations of Nitrogen Oxides
 4          Penetration of outdoor NO2 and combustion in various forms are the major sources of
 5   NO2 to indoor environments. These environments include homes, schools, restaurants, theaters
 6   etc.  As might be expected, indoor concentrations of NO2 in the absence of combustion sources
 7   are determined by the infiltration of outdoor NO2 (Spengler et al., 1994; Weschler et al., 1994;
 8   Levy et al., 1998a), with a much smaller contribution from chemical reactions in indoor air.
 9   Indoor sources of nitrogen oxides have been characterized in several reviews, namely the last
10   AQCD for Oxides of Nitrogen (U.S. Environmental Protection Agency, 1993); the Review of the
11   Health Risks Associated with Nitrogen Dioxide and Sulfur Dioxide in Indoor Air for Health
12   Canada (Brauer et al., 2002); and the Staff Recommendations for revision of the NO2 Standard in
13   California (CARB, 2006). Mechanisms by which nitrogen oxides are produced in the
14   combustion zones of indoor sources were reviewed in the last AQCD for Oxides of Nitrogen
15   (U.S. Environmental Protection Agency, 1993) and will not be repeated here. Sources of
16   ambient NO2 are reviewed in Chapter 2 of this document.  It should also be noted that indoor
17   sources can affect ambient NO2 levels, particularly in areas in which atmospheric mixing is
18   limited.
19          Because most people spend most of their time indoors, personal exposure is primarily
20   determined by indoor air quality as shown in Figure AX3.21. Ideally, exposure to NO2 should
21   be cumulated over all indoor environments in which an individual spends time. These indoor
22   environments may include homes, schools, offices, restaurants, theaters, ice skating rinks, stores,
23   etc.  However, in a study by Leaderer et al. that used two-week integrated measures,
24   concentrations of NO2 inside the home accounted for 80% of the variance in total personal
25   exposure, indicating that home concentrations are a reasonable proxy for personal exposure
26   (Leaderer etal., 1986).
27
28   Homes
29          Combustion  of fossil and biomass fuels produce nitrogen oxides and the importance of
30   such sources for determining human exposures depends on how emissions are allowed to mix
31   into living areas and whether emissions are vented to the outdoors or not. Combustion of fossil
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                 NHAPS - Nation, Percentage Time Spent
                                 Total n = 9,W6
           IN A RESIDENCE 16S.7%}
                                                      TOTAL TIME SPENT
                                                       INDOORS 2 emissions. Depending on geographical
location, season, other sources, length of monitoring period, and household characteristics,
homes with gas cooking appliances have approximately 50% to over 400% higher NC>2
concentrations than homes with electric cooking appliances (Gilbert et al., 2006; Lee et al., 2002;
Lee et al., 2000; Garcia-Algar et al., 2004; Raw et al., 2004; Leaderer et al., 1986; Garcia-Algar,
2003). Gas cooking appliances remain significantly associated with indoor NC>2 concentrations
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 1    after adjusting for several potential confounders including season, type of community,
 2    socioeconomic status, use of extractor fans, household smoking, and type of heating
 3    (Garcia-Algar et al., 2004; Garrett, 1999).
 4          Gas appliances with pilot lights emit more NC>2 than gas appliances with electronic
 5    ignition. Spengler et al. (1994) found that NC>2 concentrations in bedrooms of homes with a gas
 6    range without a pilot light averaged 4 ppb higher than in homes with an electric range, but were
 7    15 ppb higher in homes with gas ranges with pilot lights. Lee et al. (1998) found somewhat
 8    larger differences in NC>2 concentrations in homes in the Boston area, with minor seasonal
 9    variation. Homes with gas stoves without pilot lights averaged between 11 ppb (summer) and
10    18 ppb (fall) higher than homes with electric stoves, while those with pilot lights averaged
11    between 19 ppb (summer) and 27 ppb (fall) higher than electric stove homes.
12          Use of extractor fans reduces NO2 concentrations in homes with gas cooking appliances
13    (Gallelli et al., 2002; Garcia-Algar et al., 2003), although absolute NO2 levels tend to remain
14    higher than in homes with electric stoves. In a multivariate analysis, Garcia-Algar et al. (2004)
15    found that having a gas cooker remained significantly increased NC>2 concentrations even after
16    adjusting for extractor fan use.  Raw et al. (2004) found only a small effect of extraction fan use
17    on NC>2 levels in the bedroom in gas cooker homes. Among homes with gas cooking, geometric
18    mean bedroom NC>2 levels were 1.7 ppb lower in homes with an extractor fan than in homes
19    without one.  As expected, among homes with no fossil fuel cooking, there were no differences
20    in mean bedroom levels of NC>2 in homes with and without extractor fans.
21
22    Other Combustion Sources
23          Secondary heating appliances are  additional sources of NC>2 in indoor environments,
24    particularly if they are unvented or inadequately vented. As heating costs increase, the use of
25    these secondary heating appliances tends  to increase.  From 1988 to 1994, an estimated
26    13.7 million homes used unvented heating appliances, with disproportionately higher usage rates
27    among southern, rural, low-income, and African-American homes (Slack and Heumann, 1997).
28    Of the 83.1 million households using gas stoves or ovens for cooking, 7.7 million (9.3%) also
29    used the stove for heating (Slack and Heumann, 1997).
30          Gas heaters, particularly when unvented or inadequately vented, produce high levels of
31    NC>2. Kodoma et al. (2002) examined the associations between secondary heating sources and
32    NC>2 concentrations measured over a 48-h exposure period  in the living rooms of homes in

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 1    Tokyo, Japan. They found much higher NC>2 concentrations during February 1998 and January
 2    1999 in homes with kerosene heaters in both southern (152.6 ppb and 139.7 ppb for 1998 and
 3    1999, respectively) and northern (102.4 and 93.1 ppb for 1998 and 1999, respectively) areas of
 4    Tokyo compared to homes with electric heaters (30.8 and 31.1 for the southern and 37.2 and
 5    31.6 for northern areas, 1998 and 1999, respectively).
 6          In a study by Garrett et al. (1999) of 78 homes in Latrobe Valley, Australia, the two
 7    highest indoor NC>2 levels recorded in the study were 129 ppb for the only home with an
 8    unvented gas heater and 69 ppb for a home with a vented gas heater. Levels of NO2 in the
 9    kitchens and living rooms of homes with a vented gas heater (mean = 6.9 ppb in living room,
10    7.3 ppb in kitchen, n = 15) were comparable to homes with gas stoves (mean = 6.7 ppb in living
11    room, 8.0 ppb in kitchen, n = 15) (Table AX3.7).  These concentrations include results from all
12    seasons combined, so the levels are somewhat lower than those found by Triche et al. (2005) for
13    winter monitoring periods only.
14          Triche et al. (2005) also found high levels of NO2 in homes with gas space heaters,
15    although information on whether the  appliance was vented or unvented was not available.  Data
16    from this study were analyzed in more detail and are shown in Table AX3.8. The median NC>2
17    concentration in the 6 homes with gas space heater use during monitoring periods with no gas
18    stove use was 15.3 ppb; a similar incremental increase in total NC>2 levels was noted for homes
19    with gas space heater use during periods when gas stoves were also used (Median = 36.6 ppb)
20    compared to homes where gas stoves were used but no secondary heating sources were present
21    (Median = 22.7 ppb) (Table AX3.8).
22          Shima and Adachi (1998) examined associations between household characteristics,
23    outdoor NC>2, and indoor NC>2 in 950 homes during the heating season (640 with unvented and
24    310 vented heaters) and 905 homes during the non-heating season in urban, suburban, and rural
25    areas of Japan.  While no information is provided on gas stove use, the authors note that nearly
26    all homes in Japan have gas stoves, though relatively few have pilot lights. During the heating
27    season, geometric mean NC>2 levels in homes with unvented heaters (66.4 ppb) are about three
28    times higher than in homes with vented heaters (20.6 ppb). In the non-heating season, the mean
29    levels were lower at only 13.8 ppb, suggesting a contribution from vented heaters as well.
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 1          In multivariate analyses, Gilbert et al. (2006) found that gas and mixed/other heating
 2    systems were significantly associated with NO2 levels, adjusting for presence of gas stoves and
 3    air exchange rates in 96 homes in Quebec City, Canada during the winter/early spring period.
 4    Many homes with gas space heaters also have gas stoves, and the contribution from multiple
 5    sources is much higher than from any single source alone (Garrett et al., 1999). In the Garrett
 6    et al. (1999) study, homes were classified into five categories: no indoor source (n = 15), gas
 7    stove only (n = 15), gas heater only (n = 14), smoker in the household only (n = 7), and multiple
 8    sources (n = 29). Homes with multiple sources had much higher NC>2 concentrations homes with
 9    either a gas stove only or gas heater only  (Table AX3.9).
10          Kerosene heaters are also important contributors to indoor NC>2 levels.  Leaderer et al.
11    (1986) enrolled a cohort of kerosene heater users identified from local kerosene dealers and a
12    cohort of controls systematically chosen from the same neighborhoods with each matched pair
13    treated as a sampling unit (i.e., sampled at the same randomly assigned time period).  A total of
14    302  homes were monitored for at least one two-week period.  While outdoor concentrations
15    never exceeded 100 |ig/m3 (53 ppb),  approximately 5% of homes with either no gas but
16    1 kerosene heater or gas but no kerosene heater had levels exceeding  53 ppb.  Between
17    17%-33% of homes with both gas and kerosene heater(s) exceeded this  limit, while nearly one
18    quarter of homes with no gas, but two or more kerosene heaters had these levels.
19          Data from Triche et al. (2005) (Table AX3.8) also indicated increased levels of NO2 for
20    kerosene heater homes during monitoring periods with no gas stove use (Median = 18.9 ppb)
21    compared to homes with no sources (Median = 6.3 ppb), which is similar to levels found in
22    homes using gas space heaters (Median =15.3 ppb). However, these NC>2 concentrations are of
23    the same magnitude as those in homes with gas stove use (Median = 17.2 ppb).
24          Data are available for unvented gas hot water heaters from a number of studies conducted
25    in the Netherlands.  Results summarized by Brauer et al. (2002) indicate that concentrations of
26    NC>2 in homes with unvented gas hot water heaters were 10 to 21 ppb higher than in homes with
27    vented heaters, which in turn,  had NC>2 concentrations 7.5 to 38 ppb higher than homes without
28    gas hot water heaters.
29          The contribution from combustion of biomass fuels has not been studied as extensively as
30    that  from gas.  A main conclusion from the previous AQCD was that properly  vented wood
31    stoves and fireplaces would make only minor contributions to indoor NC>2 levels.  Several studies

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 1    conclude that use of wood burning appliances does not increase indoor NO2 concentrations.
 2    Levesque et al. (2001) examined the effects of wood-burning appliances on indoor NO2
 3    concentrations in 49 homes in Quebec City, Canada. The homes, which had no other
 4    combustion source, were sampled for 24 h while the wood-burning appliance was being used.
 5    No significant differences in mean NC>2 levels were found in homes with (6.6 + 3.6 ppb) and
 6    without (8.8 + 1.9 ppb) a wood-burning appliance. Data from Triche et al. (2005) confirm these
 7    findings (Table AX3.8). Homes with wood burning sources had comparable NC>2 concentrations
 8    to homes without other secondary heating sources, with (Median = 5.9 ppb) and without (Median
 9    =16.7 ppb) gas stove use.
10          Table AX3.9 shows short-term average (minutes to a few hours) concentrations of NC>2 in
11    homes with combustion sources. The concentrations represent those found in different rooms in
12    houses sampled. However, concentrations are much higher in those persons directly exposed to
13    emissions. For example, Dennekamp et al. (2001) found NC>2 concentrations of about 1 ppm at
14    face level in front of a 4-burner gas range. Table AX3.10 shows long-term average (24-h to
15    2 week) concentrations of NC>2 in homes with combustion sources (mainly gas fired).
16          Data are available for unvented gas hot water heaters from a number of studies conducted
17    in the Netherlands. Results summarized by Brauer et al. (2002) indicate that concentrations of
18    NC>2 in homes with unvented gas hot water heaters were 10 to 21 ppb higher than in homes with
19    vented heaters, which in turn, had NC>2 concentrations 7.5 to 38 ppb higher than homes without
20    gas hot water heaters.
21          As can be seen from the tables,  shorter-term average concentrations tend to be much
22    higher than longer term averages. However, as Triche et al. (2005) point out, the 90th percentile
23    concentrations can be substantially greater than the medians, even for two week long samples.
24          This finding illustrates the high variability found among homes. This variability reflects
25    differences in ventilation of emissions from sources, air exchange  rates, the size of rooms etc.
26    The concentrations for short averaging periods that are listed in Table AX3.9 correspond to
27    about 10 to 30 ppb on  a 24-h average basis. As can be  seen from inspection of Table AX3.10,
28    these sources would contribute significantly to the longer term averages reported there if
29    operated on a similar schedule on a daily basis.  This implies that measurements made with long
30    averaging periods may not capture the nature of the diurnal pattern of indoor concentrations in
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 1    homes with strong indoor sources. This problem becomes more evident as ambient NC>2 levels
 2    decrease due to more efficient controls on outdoor sources.
 3          In 10% of homes with fireplaces studied by Triche et al. (2005), NC>2 concentrations were
 4    greater than or equal to 80 ppb, or about twice the level found in homes with no indoor
 5    combustion source (see Figure AX3.30).  In a study of students living in Copenhagen, S0rensen
 6    et al. (2005) found that personal exposures to NO2 were significantly associated with time
 7    exposed to burning candles in addition to other sources. However, they did not provide data for
 8    concentrations in spaces in which candles were burned. Results of studies relating NO2
 9    concentrations and exposures to environmental tobacco smoke (ETS) have been mixed.  Several
10    studies found positive associations between NC>2 levels and ETS (e.g., Linaker et al.,  1996);
11    Farrow et al., 1997; Aim et al.,  1998; Levy et al., 1998a; Monn et al., 1998; Cyrys et  al., 2000;
12    Lee et al., 2000; Garcia-Algar, 2004) whereas others have not (e.g., Hackney et al., 1992;
13    Kawamoto et al., 1993). In a study of 57 homes in  Brisbane, Australia (Lee et al., 2000), levels
14    of NC>2 were higher in homes with smokers present (14.9 + 7.7 ppb) than without smokers (9.9 +
15    5.0 ppb).  However, these concentrations did not account for presence of a gas range  (n = 18 of
16    57 homes had a gas range). Garrett et al. (1999) found that smoking in the home increased levels
17    of NC>2 in the winter, but not in the summer when windows tended to be opened. In a study of
18    students living in Copenhagen, S0rensen et al. (2005) did not find a significant association
19    between ETS and personal exposures to NC>2. However, they found that burning candles was a
20    significant prediction of bedroom levels of NC>2.
21
22    Other Indoor Environments
23          Indoor ice skating rinks have been cited as environments containing high levels of NC>2
24    when fuel powered ice resurfacing machines are used especially without ventilation.  As part of a
25    three year study, Levy et al. (1998b) measured NC>2 concentrations at 2  locations at the outside of
26    the ice surface in 19 skating rinks in the Boston area over 3 winters.  Although different passive
27    samplers were used in the first year (Palmes tubes, 7 day sampling time) and in years 2 and
28    3 (Yanagisawa badges, 1 day working hours) of the study, consistently high mean NC>2
29    concentrations were associated with the use of propane fueled resurfacers (248 ppb in the first
30    year and 206 ppb in the following years) and gasoline fueled resurfacers (54 ppb in the first year
31    and 132 ppb in the following years) than with electric resurfacers (30 ppb in the first  year and
32    37 ppb in the following years).  During all three years of the study peak NC>2 concentrations were

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 1    several times higher in the rinks with propane and gasoline fueled resurfacers than the values
 2    given above. A number of earlier studies have also indicated NO2 concentrations of this order
 3    and even higher (Paulozzi et al., 1993; Berglund et al., 1994; Lee et al., 1994; Brauer et al.,
 4    1997). In these studies peak averages were in the range of a few ppm.
 5
 6    AX3.4.2    Reactions of NOi in Indoor Air
 7          Chemistry in indoor settings can be both a source and a sink for NO2 (Weschler and
 8    Shields, 1997). NO2 is produced by reactions of NO with ozone or peroxy radicals, while NO2 is
 9    removed by gas phase reactions with ozone and assorted free radicals and by surface promoted
10    hydrolysis and reduction reactions.  The concentration of indoor NO2 also affects the
1 1    decomposition of peroxyacyl nitrates. Each of these processes is discussed in the following
12    paragraphs.  They are important not only because they influence the indoor NO2 concentrations
13    to which humans are exposed, but also because  certain products of indoor chemistry may
14    confound attempts to examine associations between NO2 and health.
15          Indoor NO can be oxidized to NO2 by reaction with ozone or peroxy radicals; the latter
16    are generated by indoor air chemistry involving Os and unsaturated hydrocarbons such as
17    terpenes found in air fresheners and other household products (Sawar et al., 2002a,b; Nazaroff
18    and Weschler, 2004; Carslaw, 2007).  The rate coefficient for the reaction
19                                                                                   (AX3.5)

20    at room temperature (298 K) is 1.9 x io~14 cmVmolec-sec or 4.67 x 10~4 ppb"1 s"1 (Jet
21    Propulsion Laboratory, 2006).  At an indoor Os concentration of 10 ppb and an indoor NO
22    concentration that is significantly less than that of Os, the half-life of NO is 2.5 min.  This
23    reaction is sufficiently fast to compete with even relatively fast air exchange rates.  Hence, the
24    amount of NO2 produced from NO tends to be limited by the amount of O3 available.  The
25    indoor concentrations of NO and Os are negatively correlated; significant concentrations of NO
26    can only accumulate when small amounts of Os are present and vice versa (Weschler et al.,
27    1994).
28          The rapid reaction between NO and Os also means that humans, themselves, can be
29    indirect sources of NO2 in the rooms they occupy. Exhaled human breath contains NO that is
30    generated endogenously (Gustafsson et al.,  1991). For a typical adult male, the average nasal

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 1    NO output is 325 nL min l or 23.9 jig h  l (Imada et al., 1996). If ozone is present in the indoor
 2    air, some or all of these exhaled NO molecules will be oxidized to NO2. To put this source in
 3    perspective, consider the example of an adult male in a 30 m3 room ventilated at 1 air change per
 4    hour (h-1) with outdoor air.  The steady-state concentration of NO in the room as a consequence
 5    of NO in exhaled breath is 0.80 jig m3 or 0.65 ppb if none of the NO were to be oxidized.
 6    However, assuming a meaningful concentration of ozone in the ventilation air (>5 ppb), most of
 7    this NO is oxidized to NO2 before it is exhausted from the room.  In this scenario, the single
 8    human occupant is indirectly a source for 0.65 ppb of NO2 in the surrounding air. At higher
 9    occupant densities, lower air exchange rates and elevated concentrations of O3 in the ventilation
10    air, human exhaled breath could contribute as much as 5 ppb to the total concentration of indoor
1 1    NO2.
12           The reaction of NO2 with ozone produces nitrate radicals  (NO3):
                                                                                      (AX3.6)

14    The second order rate-constant for this reaction at room temperature (298 K) is
15    3.2 x 1Q~17 cmVmolec-sec or 7.9 x 10~7 ppb"1 s"1 (Jet Propulsion Labatory, 2006).  For indoor
16    concentrations of 20 ppb and 30 ppb for O3 and NO2, respectively, the production rate of
17    NO3 radicals is 1.7 ppb h"1.  This reaction is strongly temperature dependent, an important
1 8    consideration given the variability of indoor temperatures with time of day and season. The
19    nitrate radical is photolytically unstable (Finlayson-Pitts and Pitts, 2000). As a consequence,
20    it rapidly decomposes outdoors during daylight hours.  Indoors, absent direct sunlight, nitrate
21    radical concentrations may approach those measured during nighttime hours outdoors. To date
22    there have been no indoor measurements of the concentration of nitrate radicals in indoor
23    settings. Modeling studies by Nazaroff and Cass (1986), Weschler et al. (1992), Sarwar et al.
24    (2002b), and Carslaw et al. (2007) estimate indoor nitrate radical concentrations in the range of
25    0.01 to 5 ppt,  depending on the indoor levels of O3 and NO2.
26          The nitrate radical and NO2 are in equilibrium with dinitrogen pentoxide (N2Os):
27                                                                                    (AX3.?)

28    Dinitrogen pentoxide reacts with water to form nitric acid. The gas phase reaction with water is
29    too slow (Sverdrup et al., 1987) to compete with air exchange rates in most indoor environments.

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 1    Due to mass transport limits on the rate at which N2Os is transported to indoor surfaces, reactions
 2    of N2Os with water sorbed to indoor surfaces are much slower than gas phase reactions between
 3    nitrate radicals and commonly occurring indoor alkenes.
 4          Once formed, NOs radicals can oxidize organic compounds by either adding to an
 5    unsaturated carbon bond or abstracting a hydrogen atom (Wayne et al., 1991). In certain indoor
 6    settings, the nitrate radical may be a more important indoor oxidant than either ozone or the
 7    hydroxyl radical. Table 8 in Nazaroff and Weschler (2004) illustrates this point. Assuming
 8    indoor concentrations of 20 ppb, 5 x 10~6 ppb, and 0.001 ppb for 63, OH, and NOs, respectively,
 9    the pseudo first-order rate constants for reactions of most terpenoids  are larger for reactions with
10    NOs than for reactions with either 63 or OH. For example, for the stated conditions, the half-
11    lives of d-limonene and a-pinene are roughly three times shorter as a consequence of reaction
12    with NOs versus reaction with Os.  The products of reactions between NOs and various organic
13    compounds include nitric acid, aldehydes, ketones, organic acids and organic nitrates; these have
14    been summarized by Wayne et al. (1991). Nitrate radicals and the products of nitrate radical
15    chemistry may be meaningful confounders in NO2 exposure studies.
16          Reactions between NO2 and various  free radicals can be an indoor  source of organo-
17    nitrates, analogous to the chain-terminating reactions observed in photochemical smog
18    (Weschler and Shields, 1997). Additionally, based on laboratory measurements and
19    measurements in outdoor air (Finlayson-Pitts and Pitts, 2000), one would anticipate that NO2,
20    in the presence of trace amounts of HNOs, can react with PAHs sorbed on indoor surfaces to
21    produce mono- and dinitro-PAHs.
22          As noted earlier in Chapter 2, HONO occurs in the atmosphere mainly via multiphase
23    processes involving NO2. HONO is observed to form on surfaces containing partially oxidized
24    aromatic structures (Stemmler et al., 2006) and on soot (Ammann et  al., 1998).  Indoors, surface-
25    to-volume ratios are much larger than outdoors, and the surface mediated hydrolysis of NO2 is a
26    major indoor source of HONO (Brauer et al., 1990; Febo and Perrino, 1991; Spicer et al., 1993;
27    Brauer et al., 1993; Spengler et al., 1993; Wainman et al., 2001; Lee  et al., 2002). Spicer et al.
28    (1993) made measurements in a test house that demonstrated HONO formation as a consequence
29    of NO2 surface reactions and postulated the following mechanism to  explain their observations:
30
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                        2 NO? + H2O/surface -> HONO(aq) +
 1                           "                           '
 2                                  HONO(aq) ^ HONO(g)                        (AX3.9)
 3    In a series of chamber studies, Brauer et al. (1993) reported HONO formation as a consequence
 4    of NC>2 surface reactions and further reported that HONO production increased with increasing
 5    relative humidity. Wainman et al. (2001) confirmed Brauer's findings regarding the influence of
 6    relative humidity. They also found that NO2 removal and concomitant HONO production was
 7    greater on synthetic carpet surfaces compared to Teflon surfaces, and that the affinity of a
 8    surface for water influences HONO's desorption from that surface. Lee et al. (2002) measured
 9    HONO and NO2 concentrations in 119 Southern California homes. Average indoor HONO
10    levels were about 6 times larger than outdoors (4.6 ppb versus 0.8 ppb).  Indoor HONO
11    concentrations averaged 17% of indoor NO2 concentrations, and the two were strongly
12    correlated.  Indoor HONO levels were higher in homes with humidifiers compared to homes
13    without humidifiers (5.9 ppb versus 2.6 ppb).  This last observation is consistent with the studies
14    of Brauer et al. (1993) and Wainman et al. (2001) indicating that the production rate of HONO
15    from NO2/surface reactions is larger at higher relative humidities. Based on detailed laboratory
16    studies, the hydrolysis mechanism, Equations AX3-8 and AX3-9, have been refined. Finlayson-
17    Pitts et al. (2003) hypothesize that the symmetric form of the NO2 dimer is sorbed on surfaces,
18    isomerizes to the asymmetric dimer which auto ionizes to NO^STOs ; the latter then reacts with
19    water to form HONO and surface adsorbed HNOs. FTIR-based analyses indicate that the surface
20    adsorbed HNOs exists as both undissociated nitric acid-water complexes, (HNO3)x(H2O)y, and
21    nitrate ion-water complexes, (MV)x(H2O)y (Dubowski et  al., 2004, Ramazan et al., 2006).
22    Such adsorbed species may serve as oxidizing agents for organic compounds sorbed to these
23    same surfaces (Ramazan et al.,  2006).
24          HONO and much smaller amounts of HNO3 are also emitted directly by combustion by
25    gas appliances and can infiltrate from outdoors.  Spicer et al.  (1993) compared the measured
26    increase in HONO in a test house resulting from direct emissions of HONO from a gas range and
27    from production by surface reactions of NO2.  They found  that emissions from the gas range
28    could account for about 84% of the measured increase in HONO and surface reactions for 11%
29    in an experiment that lasted several hours. An equilibrium between adsorption of HONO from
30    the gas range (or other indoor combustion sources) and HONO produced by surface reactions

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 1    (see Equation AX3-9) also determines the relative importance of these processes in producing
 2    HONO in indoor air. In a study of Southern CA homes (Lee et al., 2002), indoor levels of NO2
 3    and HONO were positively associated with the presence of gas ranges.
 4          It is known that the photolysis of HONO (g) in the atmosphere (outdoors) is a major
 5    source of the hydroxyl radical (OH). Given high indoor HONO concentrations and the presence
 6    of lighting (sun light penetrating windows, incandescent lights, fluorescent lights), the photolysis
 7    of indoor HONO may be a meaningful source of indoor hydroxyl radical, under favorable
 8    reaction conditions. Given the large suite of man-made chemicals present indoors at elevated
 9    concentrations, indoor free radicals  (e.g.,  OH and NOs) can initiate and drive a complex series of
10    indoor chemical reactions.
1 1          NO2 can also be reduced on  certain surfaces, forming NO.  Spicer et al. (1989) found that
12    as much as 15% of the NO2 removed on the surfaces of masonite, ceiling tile, plywood,
13    plasterboard, bricks, polyester carpet, wool  carpet, acrylic carpet and oak paneling was re-
14    emitted as NO. Weschler and Shields (1996) found that the amount of NO2 removed by charcoal
15    building filters were almost equally matched by the amount of NO subsequently  emitted by these
16    same filters.
17          Spicer et al. (1993) determined the 1st order rate constants for removal of several NOy
1 8    components by reaction with indoor surfaces.  They found lifetimes (e-folding times) of about
19    half an hour for HNOs, an hour for NO2, and hours for NO and HONO. Thus the latter two
20    components, if generated indoors are more likely to be lost to the indoor environment through
21    exchange with outside air than by removal on  indoor surfaces.  However, HONO is in
22    equilibrium with the nitrite ion (NO2 ) in aqueous surface films:
23                                  HONO(aq) <-> H+ + NOf                        (3_1Q)

24    Ozone oxidation of nitrite ions in such films is a potential sink for indoor HONO (Lee et al.,
25    2002).
26          Jakobi and Fabian (1997) measured indoor and outdoor concentrations of ozone and
27    peroxyacetyl nitrate (PAN) in several offices, private residences, a classroom, a gymnasium and
28    a car. They found that indoor levels of PAN were 70% to 90% outdoor levels, and that PAN's
29    indoor half-life ranged from 0.5 to 1 h. The primary indoor removal process is thermal
30    decomposition:

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 1                          CH3C(0)OON02 O CH3C(0)00 + NO2

 2    As is indicated by Equation AX3-11, PAN is in equilibrium with the peroxylacetyl radical and
 3    NO2. Hence, the indoor concentration of NO2 affects the thermal decomposition of PAN and,
 4    analogously, other peroxyacyl nitrates.  Peroxylalkyl radicals rapidly oxidize NO to NO2, so the
 5    indoor concentration of NO also influences the thermal decomposition of PAN type species
 6    (Finlayson-Pitts and Pitts, 2000).
 7          Reactions between hydroxyl radicals and aldehydes in the presence of NO2 can lead to
 8    the formation of peroxyacyl nitrates. Weschler and Shields (1997) have speculated that such
 9    chemistry may sometimes occur indoors. For example, the requisite conditions for the formation
10    of the highly irritating compound peroxybenzoyl nitrate may occur when ozone, certain terpenes,
11    styrene and NO2 are present simultaneously at low air exchange rates. This relatively common
12    indoor mixture of pollutants produces hydroxyl radicals and benzaldehyde, which  can
13    subsequently react as noted above. In her detailed model of indoor chemistry, Carslaw (2007)
14    explores the indoor formation of PAN-type species (see Figure 2 in the cited reference).
15          Recent work indicates that indoor NO2 also can affect the formation of secondary organic
16    aerosols  (SOA) resulting from the reaction of Os with terpenes such as d-limonene and oc-pinene
17    (N0jgaard et al., 2006).  At concentrations of 50 ppb for Os and the terpenes, NO2  decreased the
18    formation of SOA compared  to the levels formed in the absence of NO2.  The effect was more
19    pronounced for SOA derived from oc-pinene than d-limonene, and at lower NO2 concentrations,
20    appears to be explained by the Os loss resulting from its reaction with NO2. The resultant nitrate
21    radicals apparently are not as efficient at producing SOA as the lost Os.
22          Nitro-PAHs have been found in indoor environments (Mumford et al., 1991; Wilson
23    et al., 1991). The major indoor sources of nitro-PAHs include cooking, wood burning, and the
24    use of kerosene heater (World Health Organization (WHO), 2003).  It is also likely that nitro-
25    PAHs outdoors can infiltrate  indoors. One of the potential sources of nitro-PAHs indoors, which
26    has not been characterized, is reactions via indoor chemistry. The reactions of PAHs with OH
27    and NOs may occur in indoor environments.  Although no direct measurements of OH or NOs in
28    indoor environments, OH and NOs can be formed via indoor chemistry and may present at
29    significant levels indoors (Nazaroff and  Cass 1986, Sarwar et al., 2002a; Carslaw,  2007).
30    Concentrations of ~10~6 ppb for OH and 0.01-5 ppt of NOs have been predicted through indoor
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 1    chemical reactions (Nazaroff and Cass 1986, Sarwar et al., 2002a, Carslaw, 2007), depending on
 2    the indoor levels of 63, alkenes, and NC>2.  Observation of secondary organic aerosols (SOA)
 3    formation in a simulated indoor environment also suggested that ~10~5 ppb steady-state OH
 4    radicals were generated from the reactions of Os with terpenes (Fan et al., 2003).  PAHs are
 5    common indoor air pollutants (Chuang et al., 1991; Naumova et al., 2002), and the
 6    concentrations of some PAHs indoors are often higher than outdoors (Naumova et al., 2002).
 7    Therefore, the reactions of OH  and NOs with PAHs may occur at rates comparable to air
 8    exchange rates to form nitro-PAHs indoors. In addition, the reactions of NOs with PAHs may be
 9    more significant indoors than outdoors because indoor NOs is more stable due to the low uv in
10    indoor environments.  Given the high surface areas available indoors, the formation of nitro-
11    PAHs via surface reactions of PAHs with nitrating species may be more important compared to
12    heterogeneous reactions outdoors.
13          In summary, indoor chemistry can meaningfully alter the indoor concentration of NO2.
14    Indoor exposure to NO2 may be accompanied by indoor exposures to nitrate radicals, organic
15    nitrates, and nitro-PAHs.
16
17    AX3.4.3    Contributions from Outdoor NOi
18          As might be expected, indoor concentrations of NO2 in the absence of combustion
19    sources are primarily determined by outdoor NO2 concentrations (Spengler et al., 1994;
20    Weschler et al., 1994; Levy et al., 1998a), with a much smaller contribution from chemical
21    reactions in indoor air.
22          The exchange between NO2 in ambient air and in the indoor environment is influenced by
23    infiltration (air leakage), natural ventilation (air flow through intentional openings such as
24    windows), and mechanical ventilation (rarely used in residences) (Yang et al., 2004).
25    In temperate climates, winter is associated with lower indoor/outdoor ratios of NO2 since
26    windows and doors are usually  tightly closed and the only source of exchange is infiltration.
27    Newer homes tend to be built more tightly than older homes, so have even lower rates of
28    infiltration. During warmer weather, air conditioner use and opening of windows increase air
29    exchange between  outdoors and indoors.
30          Yang et al.  (2004) used  multiple integrated (7-day) NO2 measurements indoors and
31    outdoors to calculate penetration and source strength factors in Seoul, Korea and Brisbane,
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 1    Australia using a mass balance model considering a residence as a single chamber (Yang et al.,
 2    2004). They showed that, while penetration factors did not differ significantly between gas and
 3    electric range homes, source strength factors were much higher in homes with gas ranges in both
 4    Brisbane and Seoul (5.77 ± 3.55 and 9.12 ± 4.50, respectively) than in electric range homes in
 5    Brisbane (1.49 ± 1.25). Similarly, calculated NO2 source strengths (|ig/m3/h) were
 6    21.9 ± 21.8 and 44.7 ± 38.1 in gas homes in Brisbane and Seoul, respectively, and 6.6 ± 6.3 in
 7    electric homes in Brisbane.
 8
 9    Household Characteristics
10          Yang et al. (2004) found that levels of indoor NO2 (in |ig/m3) were associated with house
11    characteristics in 28 homes in Brisbane (where there were both electric and gas range homes).
12    Homes with a gas water heater had higher levels than those without (34.5 ± 16.4 versus 22.8 ±
13    12.1, p = 0.048), but these were unadjusted associations, and it is likely that many of the homes
14    with gas water heaters also had gas ranges. Homes with an attached garage had higher levels of
15    NO2 (33.1 ± 18.3) compared to homes without one (21.8 ± 8.8) (p =  0.039).  Attached garages
16    were not, however, associated with NO2 levels in a study in Quebec  City, Canada (Gilbert et al.,
17    2006). The authors suggested that the lack of association might be attributed to small numbers
18    (n = 18 homes with attached garages) or to the airtightness of homes in Canada compared to
19    those in Australia.
20          Location in a city  center was associated with higher NO2 levels in homes in Menorca
21    (one of the Balearic Islands off the coast of Spain with rural and small town residences), after
22    adjusting for gas cooker, extractor fan use, smoking in the home, type of central heating, season,
23    and social class (Garcia-Algar., 2004). In the same study, levels of indoor NO2 in Barcelona  (a
24    large coastal city in Spain) and Ashford (a medium-sized town in the southeast UK) were
25    significantly higher than those in Menorca
26          In a study of a random sample of 845 homes in England (Raw et al., 2004), levels of NO2
27    were significantly associated with dwelling type and age of home, but the authors attributed
28    these effects to the geographical location of the home (e.g., inner city). Garrett et al. (1999) also
29    found that age of house was significantly associated with NO2 levels in winter and summer. In
30    the study by Shima and Adachi,  (1998), differences in concentrations of NO2 between homes
31    with and without unvented heaters in the heating season were slightly lower among homes with
32    wood compared to aluminum window frames.  Type of window frames, but not structure type,

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 1   was associated with NO2 concentrations in the heating period for homes with unvented heaters
 2   (76.2 ±1.4 ppb versus 55.9 ±3.9 ppb in homes with aluminum and wood windows,
 3   respectively), but not in homes with vented heaters.  In the non-heating season, mean NO2 levels
 4   in the home varied by type of structure (steel/concrete or wood) and type of window frames
 5   (aluminum or wood), with wood structures and frames indicating a less airtight dwelling.
 6
 7
 8   AX3.5     PERSONAL EXPOSURE
 9
10   Components of Personal Exposure
11          Human exposure to NO2 consists of contact at the air boundary layer between the human
12   and the environment at a specific concentration for a specified period of time. People spend
13   various amount of time in different microenvironments with various NO2 concentrations. The
14   integrated NO2 exposure is the sum of the individual NO2 exposures over all possible time
15   intervals for all environments.  Therefore, the assessment of human exposures to NO2 can be
16   represented by the following equation:
                                          ET= I
17                                             '='                                 (AX3-12)
18   where ET is the time-weighted personal exposure concentration over a certain period of time, n is
19   the total number of environments that a person encounters,/ is the fraction of time spent in the
20   /'th environment, and Q is the average NO2 concentration in the rth environment during the time
21   fraction/. Depending upon the time fraction and environmental concentration we consider
22   during exposure assessment, the exposure a person experiences can be classified into
23   instantaneous exposure, peak exposure, averaged exposure, or integrated exposure.  These
24   distinctions are important because health effects caused by long-term low-level exposures may
25   be different from those resulting from short-term peak exposures.
26          The equation above represents the average personal exposure concentration is a linear
27   combination of the average concentration in the ambient environment and each
28   microenvironment, weighted by an individual's fraction of time spent in that environment.
29   Hence, personal exposure to NO2 is influenced by the microenvironmental concentration and the
30   amount of time spent in each microenvironment. In theory, a microenvironment could be any

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 1   three-dimensional space having a volume in which people spend a certain amount of time.
 2   In practice, microenvironments typically used to determine NC>2 exposures include residential
 3   indoor environment, other indoor locations, near-traffic outdoor environment, other outdoor
 4   locations, and in-vehicles. In other words, total personal exposure to NC>2 can be decomposed
 5   into exposure to NC>2 in different environments.  An individual's total exposure (Ex) can also be
 6   represented by the following equation:
      ET = Ea + Enona = {y0 + lM/W(«i + */)]}C0 + Enona =  0>o + I >'/i,,/:}Q + Enona
 1                             '                                     '                   (AX3-13)
 8    subject to the constraint

                                          y0 + I#i = 1
 9                                              '                                   (AX3-14)
10    where E& is the person's exposure to pollutants of ambient origin; Enona is the person's exposure
11    to pollutants that are not of ambient origin; y0  is the fraction of time people spend outdoors and y\
12    is the fraction of time they spend in microenvironment /'; F^R, P{, ah and k; are the infiltration
13    factor, penetration coefficient, air exchange rate, and decay rate for microenvironment /'.
14          In the case where microenvironmental exposures are dominated by one
15    microenvironment, Equation AX3-13 may be  approximated by
16             ET = Ea + Enona + {>' + ( ' -y)[Pa/(a + k)] } Ca + ERma = aCa + Eaona (AX3_15)

17   where E\ is the total personal exposure, Ea is the exposure to ambient generated pollutants, Enonag
18   is the nonambient generated pollutants, and_y is the time fraction people spent outdoors. Other
19   symbols have the same definitions in Equation AX3-13. If microenvironmental concentrations
20   are considered, then Equation AX3-15 can be recast as

21                       Cme = Ca + Cnona = [Pa/(a + k)]Ca + S/[V(a + k)]             (AX3-16)
22   where Cme is the concentration in a microenvironment; Ca and Cnona the contributions to Cme from
23   ambient and nonambient sources; S is the microenvironmental source strength; Fis the volume
24   of the microenvironment, and the symbols in brackets have the same meaning as in Equation
25   AX3-15.  In this equation, it is assumed that microenvironments do not exchange air with each
26   other, but only with ambient air.

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 1          The NO2 concentration in each microenvironment can show substantial spatial and
 2   temporal variability, which is determined by many factors, such as season, day of the week,
 3   personal age, occupation, house characteristics, personal activities, source emission rate, air
 4   exchange rate, and transport and removal mechanisms of NC>2. Failure to disaggregate total
 5   human exposure and assess human exposure in various microenvironments may result in
 6   exposure misclassification, which may obscure the true relations between ambient air pollution
 7   and health  outcomes.
 8          Studies reviewed in this section were generally conducted in North America (Canada, the
 9   United States, and Mexico) and European countries. Studies conducted in other parts of the
10   world were not the primary focus of this science review because exposure patterns may not be
11   similar to those in the United States. However, studies which might support general conclusions
12   (not country or cultural specific conclusions) about NC>2 exposures will be included.
13          Either Palmes tubes or Yanagisawa badges or Ogawa samplers were used to measure
14   personal exposures in most of the reviewed studies, and sometimes residential indoor and
15   outdoor concentrations.  Sampling time for each cartridge varied from 8 h to two weeks, and the
16   study design covered (1) longitudinal, in which each subject is measured for many days;
17   (2) pooled, in which each subject is measured for only one or two days, different days for
18   different subjects; and (3) daily-average, in which many subjects are measured on the same day.
19   Most studies focused primarily on children, and in some studies adults or people with respiratory
20   diseases were taken as study population.
21
22   AX3.5.1    Personal Exposures and Ambient (Outdoor) Concentrations
23          Numerous epidemiological studies have shown a positive association between ambient
24   (outdoor) NC>2 concentrations and adverse health effects. Since a causal  association requires
25   exposure, it is very important to evaluate personal exposure to ambient (outdoor) generated NC>2.
26   In this section, topics related to the total personal exposure and ambient (outdoor) generated NC>2
27   will be evaluated, such as the levels of personal exposure and ambient (outdoor) NC>2, the
28   attenuation factor of personal exposure to NC>2, the correlation between personal and  ambient
29   (outdoor) NC>2, and the factors determining the associations between personal exposure and
30   ambient (outdoor) level. Based on the science review, the following key questions will be
31   addressed:  1) When, where, how and how much are people exposed  to ambient (outdoor)


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 1    generated NO2? and 2) Is ambient (outdoor) NO2 a good surrogate for personal total exposure or
 2    personal exposure to ambient (outdoor) NCh?
 3          Personal exposures in most of the studies considered here were less than the
 4    corresponding outdoor or ambient concentrations. In the presence of local sources (indoor or
 5    local traffic sources), personal exposure levels could be higher than outdoor or ambient levels
 6    (Spengler et al., 1994; Nakai et al., 1995; Linn et al., 1996; Spengler et al., 1996; Raaschou-
 7    Nielsen et al., 1997; Aim et al., 1998; Levy et al., 1998a; Monn et al., 1998; Liard et al., 1999;
 8    Kramer et al., 2000; Linaker et al., 2000; Mukala et al., 2000; Gauvin et al., 2001; Monn, 2001;
 9    Rotko et al., 2001; Sarnat et al., 2001; Kodama et al., 2002; Mosqueron et al., 2002; Ramirez-
10    Aguilar et al., 2002; Rojas-Bracho et al., 2002; Lai et al., 2004; Nerriere et al., 2005; Sarnat
11    et al., 2005; S0rensen et al., 2005; Kim et al., 2006; Sarnat et al., 2006).
12          In a probability based population exposure study in Los Angeles Basin, 48 h indoor,
13    outdoor and personal exposures (pooled exposures) were reported for 682 participants (Spengler
14    et al., 1994). Spengler et al. (1994) found that the median personal exposure was 35 ppb and the
15    median outdoor level was 36 ppb. Linn et al. (1996) reported the results of a personal exposure
16    study for 269 school children from three Southern California communities.  During this
17    longitudinal study, 24 h  averaged personal exposures, as well as inside school, outside school
18    and ambient central site  NO2 levels, were measured by Yanagisawa badges for one week for
19    each season from 1992 to 1994. Results showed that mean personal exposure was 22 ppb and
20    the mean central site concentration was 37 ppb.  Kim et al. (2006) conducted a longitudinal,
21    multi-pollutant exposure study in Toronto, Canada. During the study, personal exposures (24-h
22    integrated by Ogawa sampler) to PM2.5, NC>2 and CO were measured for 28  subjects with
23    coronary artery disease one day a week for a maximum of 10 weeks, and were compared with
24    ambient  fixed site measurements. The mean NC>2 personal exposure was 14.4  ppb, which was
25    lower than the ambient site  concentrations (20-26 ppb). Sarnat et al. (2001) and Sarnat et al.
26    (2005) reported multi-pollutant exposure studies in Baltimore and Boston.  In the Baltimore
27    study, 24 h averaged personal exposure and ambient PM2.5, 63, NC>2, 862, and CO were
28    measured for 56 subjects (20 older adults, 21 children and 15 individuals with  COPD) in the
29    summer  of 1998 and the winter of 1999.  All subjects were monitored for  12 or 8 consecutive
30    days in each of the one or two seasons. Median ambient NC>2 levels were  higher than the median
31    personal levels in both seasons (about 10 ppb in difference). During the winter, both ambient

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 1    and personal exposure to NO2 were higher than the summer, the difference between ambient and
 2    personal exposure in winter was 1 to 2 ppb  smaller than the difference in the summer. In the
 3    Boston study, 24-h averaged personal and ambient PM2 5, O3, NO2, and SO2 were measured for
 4    20 healthy seniors and 23 schoolchildren. All subjects were measured for 12 consecutive 24-h
 5    periods in each of the 1 or 2 seasons.  Ambient NO2 levels were on average 6 to 20 ppb higher
 6    than the personal exposure levels for seniors during all sampling sessions.  For children's
 7    exposure, ambient NO2 levels were 7 to 13  ppb higher than the personal exposures in 4 out of
 8    6 sampling sessions, and in the other two sampling sessions (one in summer and one in winter)
 9    ambient levels were 1.8 to 2.6 ppb lower than personal exposures. Sarnat et al. (2006) measured
10    24-h averaged ambient and personal PM2.5, sulfate, elemental carbon, 63, and SO2 for 10 non-
11    smoking seniors in Steubenville, Ohio during the summer and fall of 2000. For each subject,
12    two consecutive 24 h personal exposure measurements were collected during each week for
13    23 weeks.  Data were stratified by the presence of gas stoves in homes. Personal exposure was
14    lower than the ambient level for homes without gas stoves (9.0 ppb for personal exposure versus
15    9.5 ppb for ambient level during the summer and 9.9 ppb versus 11.3 ppb during the fall), and
16    higher than ambient levels for homes with gas stoves (12.3 ppb for personal exposure versus 9.5
17    ppb for ambient level during the summer and 15.7 ppb versus  11.3 ppb during the fall).
18          Nerriere et al. (2005) investigated factors determining the discrepancies between personal
19    exposure and ambient levels in the Genotox ER study. During the study, forty-eight h averaged
20    PM2.5, PMio, and NO2 were collected in both summer and winter for each person in a cohort,
21    with 60 to  90 nonsmoking volunteers composed of two groups of equal size for adults and
22    children at four metropolitan areas in France (Grenoble, Paris, Rouen, and  Strasbourg). In each
23    city, subjects were selected so as to live in three different urban sectors contrasted in terms of air
24    pollution:  one highly exposed to traffic emissions, one influenced by local industrial sources,
25    and a background urban environment.  In each urban sector, a fixed ambient air monitoring
26    station was used to simultaneously collect the same air pollutants as personal exposure samplers.
27    Factors affecting the concentration discrepancies between personal exposure and corresponding
28    ambient monitoring site were investigated by a multiple linear regression model. Results showed
29    that the discrepancies were season, city and land use dependent. During the winter, city and land
30    use can interpret 31% of the variation of the discrepancy, and during the summer 54% of the
31    variation in the discrepancy can be interpreted by those factors. In most cases, ambient

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 1    concentrations were higher than the corresponding personal exposures. When using the ambient
 2    site to represent ambient levels, the largest difference between ambient and personal exposure
 3    was found at the "proximity to traffic" site, while the smallest difference was found at the
 4    "background" site.  When using urban background site as ambient level, the largest difference
 5    was observed at the "industry" site, and the smallest difference was observed at the background
 6    site, which reflected the heterogeneous distribution of NC>2 in an urban area.  During winter,
 7    differences between ambient site and personal exposure were larger than those in the summer.
 8    Age was not found to be a significant factor interpreting the discrepancies between ambient level
 9    and personal exposure.
10           S0rensen et al. (2005) reported that during the cold  season, median personal exposure
11    was higher than residential indoor and urban background concentrations, but lower than the
12    residential outdoor and street station concentrations (designed to capture the close to traffic
13    exposure). During the warm season, personal exposure was again lower than the street station
14    concentration but higher than the residential indoor, outdoor, and urban background
15    concentrations.  The implication of these findings is that ambient concentrations are the primary
16    factor in determining  exposures when there is no or little contribution from indoor sources and
17    that traffic is the most significant NC>2 source in this study.
18           The relative levels of ambient and personal exposure can also be expressed as ratios of
19    personal/ambient (Levy et al., 1998a; Rojas-Bracho et al., 2002; Sarnat et al., 2006). As shown
20    in Equation AX3-15,  personal exposure is related to ambient concentration through the
21    infiltration factor, the fraction of time people spend outdoors, indoor  sources and outdoor
22    concentration.  In the  absence of indoor sources, the ratio of personal exposure to ambient
23    concentration is sometimes also called the attenuation factor (a), which is always less than or
24    equal to one, and it is  a function of infiltration factor (F[nf) and the fraction of time people spend
25    outdoors (y).  The attenuation factor can be derived directly from measured personal and outdoor
26    concentrations or calculated from measured or estimated values of the parameters a, k, and P
27    (see Equation AX3-13 and Equation AX3-15) and the time spent in various microenvironments
28    from activity pattern diaries (Wilson et al., 2000).  Because a depends on building and lifestyle
29    factors, air exchange rate, and NC>2 decay rate, it will vary to a certain extent from region-to-
30    region, season-to-season, and by the type  of indoor microenvironment. Consequently, predicted
31    exposures based on these physical modeling concepts provide exposure distributions derived

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 1    conceptually as resulting from building, lifestyles, and meteorological considerations.  For any
 2    given population, the distribution of the coefficient a may represent substantial intra- and inter-
 3    personal variability based on personal activity patterns, building and other microenvironmental
 4    characteristics, and proximity to ambient and indoor sources. Distributions of a should be
 5    determined using population studies in order to evaluate the uncertainty and variability
 6    associated with model exposures. Unfortunately, only a few studies have reported the  value and
 7    distribution of the ratio of personal to ambient, and even fewer studies reported the value and
 8    distribution of attenuation factors based on sophisticated study designs. Rojas-Bracho et al.
 9    (2002) reported the median personal/outdoor ratio was 0.64 (with an interquartile range (IQR) of
10    0.45). Although it was less than one, the authors also reported the indoor/outdoor ratio (0.95
11    with an IQR of 0.48) of NO2 and based on the indoor/outdoor ratio, the authors pointed out that
12    the high median indoor/outdoor ratio was greater than the estimated effective penetration
13    efficiency, which supports the argument of the importance of indoor sources to indoor  NO2
14    levels.  Therefore, the attenuation factor in this study should be smaller than the ratio of
15    personal/ambient, which was 0.64.  Sarnat et al. (2006) reported that the ratio of
16    personal/ambient for NO2 was 2.05  and 1.27 for subjects with and without gas stoves in their
17    homes. The large personal/ambient ratio for the latter might be attributed to the influence of
18    indoor or local sources that were not identified and/or partly to measurement error.
19          The attenuation factor is one of the keys to evaluate personal exposure to ambient
20    generated NO2, or ambient contribution to personal exposure. However, the ratio of personal
21    exposure/ambient concentration will not accurately reflect the attenuation factor in the presence
22    of indoor sources. As shown above, in many cases, the ratio of personal exposure and  ambient
23    concentration was above one, which is physically impossible for the attenuation factor. The
24    random component superposition (RCS) model is an alternative way to calculate attenuation
25    factor using observed ambient and personal exposure concentrations (Ott et al., 2000).  The
26    Random Component Superposition  (RCS) statistical model (shown in Equation  AX3-15) uses
27    the slope of the regression line of personal concentration on the ambient or outdoor NO2
28    concentration to estimate the population average attenuation factor and means and distributions
29    of ambient/outdoor and nonambient contributions to personal NO2 concentrations (the  intercept
30    of the regression is the averaged nonambient contribution to personal exposure). This  model
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 1    assumes a linear superposition of the ambient and nonambient components of exposure and lack
 2    of correlation between these two components.
 3          The RCS model derives a mean a across all homes (assuming the infiltration behavior
 4    and time budget for all people are the same) from the linear regression of measured values of Et
 5    on Ca.. The product of the constant a and Ca from each home provides an estimate of the mean
 6    and distribution of Ea for the population of study homes. In practice, the mean and distribution
 7    of nonambient contributions (Enona) are given by the difference, Et - Ea, on a home-by-home
 8    basis.  The RCS-predicted distribution of Ea across the population of study homes is given by the
 9    product of the constant a and Ca from each home, and the mean of the ambient contribution is
10    the difference between the mean total personal exposure and the intercept of the regression line.
11    The RCS model has been widely applied to PM exposure studies PTEAM,  THEES, Toronto, and
12    RIOPA studies (Ott et al., 2000; Meng et al., 2005), but researchers have not intentionally used
13    this model for NC>2 exposure assessments. Although many studies explored the relationship
14    between personal exposure and ambient NC>2 concentrations using regression models, most of
15    those studies are not useful for evaluating the attenuation factor or helping  answer the question
16    of how much personal NCh  exposure comes from ambient air,  either because only R2 was
17    reported, or because log-transformed concentrations were used in the regression model, or
18    because physically meaningless multiple linear regression models (exploratory variables were
19    not independent of each other, e.g., both indoor, outdoor, indoor sources from questionnaire
20    responses and air exchange rate were used as exploratory variables) were used to interpret
21    personal exposure variations.  Only those simple linear regression models (personal versus
22    ambient or personal versus outdoor) and physically meaningful multiple linear regression models
23    (personal versus ambient + indoor source measured or identified by questionnaire) are useful for
24    evaluating the attenuation factor, and those models are summarized in Table AX3.11.  The
25    intercept of the regressions (i.e., the nonambient contribution to personal exposure) varies widely
26    from study to study (5 ppb to 18 ppb) and thus depends strongly on time and location. The slope
27    of these regression models (i.e., the population average attenuation factor) varies between 0.3 to
28    0.6 in most of the studies. The attenuation factor is determined by air exchange rate, penetration
29    and decay rate of NC>2 and also the fraction of time people spend outdoors.  S0rensen et al.
30    (2005) found that the attenuation factor was larger in the summer than in the winter. However,
31    Sarnat et al. (2006) found opposing results and said the reason was unknown. Based on the

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 1    regression model and reported mean personal exposure values, the ambient and nonambient
 2    contribution to personal exposure could be calculated using the method described above.  Since
 3    most researchers did not report the mean personal exposure and the regression model at the same
 4    time, ambient and nonambient contributions can only be calculated in four studies as shown in
 5    Table AX3.12. The ambient contribution to population exposures varies from 20% to 50% in
 6    these four studies.
 7          The RCS model calculates ambient contributions to indoor concentrations and personal
 8    exposures based on the statistical inferences of regression analysis. However, personal-outdoor
 9    regressions could be affected by extreme values (outliers either on the x or the y axis), such as a
10    high nonambient exposure on a day with low ambient concentration or vice versa. For this
11    reason outliers must be identified and their influence on the infiltration factor or attenuation
12    factor in the RCS model must be evaluated in order to obtain a robust result.  Another limitation
13    of the RCS model is that this model is not designed to estimate ambient and nonambient
14    contributions for individuals, in part because the use of a single attenuation factor does not
15    account from the large home-to home variations in actual air exchange rates, and penetration and
16    decay rates of NO2. As suggested by Meng et al. (2005) the use of a fixed attenuation factor
17    might underestimate ambient contributions to indoor concentrations and personal exposures and
18    could also overlook some of the exposure errors and cause large uncertainties in risk estimates.
19          The estimation of the ambient and nonambient contribution to personal exposure could be
20    improved by allowing for variations in air exchange rate, penetration and decay rate of NO2, and
21    the variations in the fraction of time people spend outdoors.  The mass balance model described
22    in Equation AX3-15  gives more flexibility than the RCS model if the distributions of P, k, a, and
23    y are known. A comprehensive assessment of the impact of ambient sources on personal
24    exposure would require detailed consideration of the mechanisms of NO2 formation,
25    transformation, transport and decay. In the research field of NO2 exposure assessment, no
26    published reports were  found that use the mass balance model to explore the relationship of
27    personal exposures to ambient NO2 concentrations. As mentioned in Section 3.4.2, the only
28    reported k values were  0.99 h-1 by Yamanaka (1984), and people always assumes the
29    penetration coefficient (P) is one for NO2, which might overestimate the ambient contribution
30    due to the chemical reactivity of NO2 during penetration.
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 1          The association between personal exposure and ambient NO2 was quantified by Pearson
 2    correlation coefficient (rp), Spearman correlation coefficient (rs), or coefficient of determination
 3    (R2) in regression models (Spengler et al., 1994; Linn et al.,  1996; Spengler et al., 1996;
 4    Raaschou-Nielsen et al.,  1997; Aim et al., 1998; Levy et al.,  1998a; Monn et al., 1998; Liard
 5    et al.,  1999; Kramer et al., 2000; Linaker et al., 2000; Mukala et al., 2000; Gauvin et al., 2001;
 6    Monn, 2001; Rotko et al., 2001; Sarnat et al., 2001; Kodama et al., 2002; Rojas-Bracho et al.,
 7    2002;  Lai et al., 2004; Sarnat et al., 2005; Kim et al., 2006; Sarnat et al., 2006). In Table
 8    AX3.13, the associations between personal exposure and ambient concentration found in these
 9    studies are summarized.
10          The association between personal NO2 exposure and ambient/outdoor NO2 concentration
11    varied from poor to good as shown in Table AX3.13. The strength of the correlation between
12    personal exposure and ambient/outdoor concentration for a population is determined by the
13    variations in indoor or other local sources, air exchange rate, penetration and decay rate of NO2
14    in different microenvironment, and time people spend in different microenvironments with
15    different NC>2 concentrations. The relationship is also a function of season and location
16    (rural/urban).  Aim et al.  (1998) indicated that the association between personal exposure and
17    outdoor concentration was stronger than the correlation between personal exposure and central
18    site concentration. However, Kim et al. (2006) pointed out that the association was not improved
19    using the ambient sampler closest to a home. Home ventilation is another important factor
20    modifying the personal-ambient relationships; we expect to observe the strongest associations for
21    subjects  spending time indoors with open windows.  Aim et  al. (1998) and Kodama et al. (2002)
22    observed the association between personal exposure and ambient concentration became stronger
23    during the summer than the winter.  However, Sarnat et al. (2006) reported that R2 decreased
24    from 0.34 for low ventilation population to 0.16 for high ventilation population in the summer,
25    and from 0.47 to  0.34 in the fall. This might be a caution that the association between personal
26    exposure and ambient concentration is complicated and is determined by many factors.
27    Exposure misclassification might happen if a single factor, such as season or ventilation status, is
28    used as an exposure indicator. Another factor affecting the personal to ambient association is the
29    subject's location, with higher correlation for subjects living in the rural areas and lower
30    correlation with subjects  living  in the urban areas (Rojas-Bracho et al., 2002; Aim et al., 1998).
31    Spengler et al. (1994) also observed that the relationship between personal exposure and outdoor

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 1    concentration was highest in areas with lower ambient NC>2 levels (R2 = 0.47) and lowest in areas
 2    with higher ambient NC>2 levels (R2 = 0.33). This might reflect the highly heterogeneous
 3    distribution, or the effect of local sources of NO2 in an urban area, and personal activities are
 4    more diverse in an urban area. However, this factor (location: urban vs. rural) might also interact
 5    with indoor sources because indoor sources could explain more personal exposure when ambient
 6    concentrations become lower and more homogeneously distributed.
 7           The association is also affected by indoor or local sources, and the association becomes
 8    stronger after those sources are controlled in the model.  Raaschou-Nielsen et al. (1997) observed
 9    that R2 increased from 0.15 for general population to 0.49 for a population who spent less than
10    2% of their time close to gas appliances and passive smoking in Copenhagen urban area, and R2
11    increased from 0.35 to 0.45 in the rural area for the population with the same characteristics.
12    When those who reported exposure to either gas appliances or passive smoking were excluded,
13    R2 increased to 0.59 in urban and 0.46 in the rural districts. Spengler et al. (1994) observed that
14    less of the variation in personal exposure was explained by outdoor concentrations for those who
15    had gas ranges with pilot lights (R2 = 0.44) than it is for the other two groups (R2 = 0.52). When
16    there is little or no contribution from indoor sources, ambient concentrations are the primary
17    factor in determining exposure, but if there are continuous indoor sources, the influence of
18    outdoor levels decrease. In the VESTA study, Gauvin et al. (2001)  reported low R2s in all three
19    cities. R2s increased for all three cities after controlling indoor air sources (e.g., gas cooking)
20    and ambient traffic densities: R2 increased from 0.01 to  0.43 for Grenoble, from 0.04 to 0.50 for
21    Toulouse, and from 0.02 to 0.37 for Paris. Other factors, such as  cross-sectional vs. longitudinal
22    study design,  and sampling duration might also affect the strength of the association. However,
23    the current science review cannot give a clear picture of the effects by those factors due the  lack
24    of key studies and data.
25           The correlation coefficient between personal exposure and ambient/outdoor concentration
26    has different meanings for different study designs.  There are three types of correlations
27    generated from different study designs: longitudinal, "pooled," and daily-average correlations.
28    Longitudinal correlations are calculated when data from  a study includes measurements over
29    multiple days for each subject (longitudinal study design).  Longitudinal correlations describe the
30    temporal relationship between daily personal NCh exposure or microenvironment concentration
31    and daily ambient NO2 concentration for each individual subject.  The longitudinal correlation

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 1    coefficient may differ for each subject. The distribution of correlations across a population could
 2    be obtained with this type of data.  Pooled correlations are calculated when a study involves one
 3    or only a few measurements per subject and when different subjects are studied on subsequent
 4    days. Pooled correlations combine individual subject/individual day data for the calculation of
 5    correlations. Pooled correlations describe the relationship between daily personal  NO2 exposure
 6    and daily ambient NO2 concentration across all subjects in the study. Daily-average correlations
 7    are calculated by averaging exposure across subjects for each day.  Daily-average  correlations
 8    then describe the relationship between the daily average exposure and daily ambient NO2
 9    concentration.
10           The type of correlation analysis can have a substantial effect on the value of the resultant
11    correlation coefficient. Mage et al. (1999) mathematically demonstrated that very low
12    correlations between personal exposure and ambient concentrations could be obtained when
13    people with very  different nonambient exposures are pooled, even though their individual
14    longitudinal correlations are high.  Data shown in Table AX3.13 demonstrate that  the
15    longitudinal correlations between personal exposure and ambient NC>2 concentrations were
16    higher than the correlations obtained from a pooled data set.
17           In conclusion, personal exposure to ambient/outdoor NC>2 is determined by many factors.
18    Physically, the determinant factors are ambient concentration, air exchange rate, NC>2 penetration
19    and decay rate, and also the fraction of time people spend outdoors. These factors are in turn
20    determined by factors, such as season, location of home, outdoor temperature and  so on.  These
21    factors  all help determine the contribution of ambient/outdoor generated NC>2 to personal
22    exposures. Personal activities determine when, where and how people are exposed to NC>2.  The
23    variations of these physical factors and indoor sources determine the strength of the association
24    between personal exposure and ambient concentrations both longitudinally and cross-sectionally.
25    In the absence of indoor and local sources, the personal exposure level is in between the ambient
26    level and the indoor level, but in the presence of indoor and local sources, personal exposures
27    could be much higher than both indoor and outdoor concentrations.  Again, the discrepancies
28    between personal exposures and ambient levels are determined by the considerations given
29    above.  Most researchers found that personal NC>2 was significantly associated with ambient NC>2
30    but the  strength of the association ranged from poor to good. Based on that finding,  some
31    researchers concluded that ambient NC>2 is a good surrogate for personal exposure, while others

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 1   reminded us that caution must be exercised if ambient NO2 is used as a surrogate for personal
 2   exposure. The crude association between personal exposure and ambient monitors could be
 3   improved when indoor or other local sources are well controlled during exposure assessment.
 4   The ambient contribution to personal exposure could be evaluated by the attenuation factor,
 5   which is the ratio of personal exposure to ambient level in the absence of indoor sources, or the
 6   slope of the RCS regression model.  The attenuation factor in the studies shown in Table AX3. 1 1
 7   ranged from 0.3 to 0.6.  The ambient and nonambients contributions could also be calculated
 8   from the RCS model, although only a few studies provide enough information for us to calculate
 9   them. The accuracy and precision of the estimation of ambient and nonambient contributions to
10   personal exposures could be improved if the variations for the physical factors given above were
1 1   known.  The mass balance model could give a more accurate and precise estimation if we knew
12   the distributions of these key physical factors.
13          Because people are exposed to ambient NO2 in microenvironments, and the fact that NO2
14   is heterogeneously distributed in urban areas (as shown in Section AX3.3.2), the association of
15   personal exposure to ambient NC>2 could be modified by microenvironmental characteristics.
16   Personal total exposure will be decomposed and further evaluated in each microenvironment in
17   the following section.
18
19   AX3.5.2   Personal Exposure in Microenvironments
20
2 1   Personal Exposure in the Residential Indoor Environment
22          People spend most of their daily time in a residential indoor environment (Klepeis et al.,
23   2001). NC>2 found in an indoor environment originates both indoor and outdoors; and therefore,
24   people in an indoor environment are exposed to both indoor and outdoor generated NC>2. The
25   physical parameters, which determine personal exposure to ambient and nonambient generated
26   NC>2,  have been shown in Equations AX3-13 to AX3-16.  In a residential indoor environment,
27   personal exposure to NC>2 can be summarized below (notations are the same as those in
28   Equations AX3-13 to AX3-16):
               Et = Ea + Enona = aCo + Enona = !>' + (/ ~ y}[PaAfl + k)]}Ca
29              tf ~*~ '  ~infa   nona                                          (AX3-17)
30   if people spend 100% of their time indoors, the equation above can be recast as

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                Enona = aCa + Enona = FinfCa + Enona = [Pa/(a + k)]Ca + S/[V(a + k)] =
                                                                                    (AX3-18)
 2    In other words, in a residential indoor environment, personal exposure concentration equals the
 3    residential indoor concentration (if there is no personal cloud) which can be broken down into
 4    two parts: indoor generation and ambient contribution.
 5           In a residential indoor environment, the relationship between personal NC>2 exposure and
 6    ambient NC>2 can be modified by the indoor environment in the following ways:  (1) during the
 7    infiltration processes, ambient NC>2 can be lost through penetration and decay (chemical and
 8    physical processes) in the indoor environment, and therefore, the concentration of indoor NC>2 of
 9    ambient origin is not the ambient NC>2 concentration but the product of the ambient NC>2
10    concentration and the infiltration factor (FM, or a if people spend 100% of their time indoors);
11    (2) in an indoor environment, people are exposed to not only ambient generated NC>2 but also
12    indoor generated NC>2, and therefore, the relative contribution of ambient and nonambient NC>2 to
13    personal exposure depends not only on the ambient NC>2 concentration but also on the infiltration
14    factor (attenuation factor) and the indoor source contribution; (3) the strength of the association
15    between personal exposure to NO2 of ambient origin and ambient NO2 concentration is
16    determined by the temporal and spatial variation in the infiltration factor; and (4) the strength of
17    the association between personal total  exposure and ambient NC>2 is determined by the variation
18    in the indoor source contribution and the variation in the infiltration factor.  Below, factors
19    affecting infiltration factor and the indoor source contribution will be evaluated, and the key
20    issues,  such as those mentioned above, related to ambient contribution to personal NC>2 exposure
21    will be  addressed.
22           Infiltration factor (F;nf) of NC>2, the physical meaning of which is the fraction of ambient
23    NO2 found in the indoor environment, is determined by the NO2 penetration coefficient (P), air
24    exchange rate (a), and the NC>2 decay rate (&), through the equation F[nf= Pa/(a + k). Information
25    on P and k for NC>2 is sparse. In most mass balance modeling work, researchers assume P
26    equals 1 because NC>2 is a gas, and assume k equals 0.99 IT1, which is cited from Yamanaka
27    (1984). Yamanaka (1984) systematically  studied the decay rates of NC>2 in a typical Japanese
28    living room.  The author used a chemical luminescence method to monitor the decay process of
29    indoor-originated NC>2. The author observed that the decay process of NC>2 followed
30    approximately first-order kinetics. The author also pointed out that the NC>2 decay processes was

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 1    both surface type and relative humidity (RH) dependent:  Under low RH (43.5-50%), the sink
 2    rate of NO2 was 0.99 ± 0.19 IT1, independent of interior surface properties; however, the NO2
 3    decay rate increased in proportion to RH above 50%, and in that RH range, the decay rate
 4    depended on the interior surface properties. Yang et al. (2004) estimated a decay rate of 0.94 h"1
 5    for Seoul and  1.05 h"1 for Brisbane. As it is well  known, the decay rate is dependent on lots of
 6    indoor parameters, such as indoor temperature, relative humidity, surface properties, surface-to-
 7    volume ratio, the turbulence of air flow, and co-existing pollutants, et al. However, in the indoor
 8    air modeling studies, a decay rate of 0.99 h"1 is a widely accepted parameter (Dimitroulopoulou
 9    et al., 2001; Kulkarni et al., 2002).  As a result, it  will over- or underestimate the real NC>2 decay
10    rate. A penetration coefficient (P) of 1  is also widely accepted for NO2 (Kulkarni et al., 2002;
11    Yang et al., 2004).  No systematic investigations have been found on NO2 penetration behaviors.
12    As a general principle, the upper limit of the penetration coefficient is 1, and it would be less
13    than 1 if NC>2 lost during penetration due to diffusion and chemical reactions.  Therefore, using a
14    penetration coefficient of 1 gives an upper bound  to the estimated infiltration coefficient.
15    Among P, k, and a, air exchange rate (a) is the most solidly based parameter and can be obtained
16    from a nationwide database (Pandian et al., 1998).
17          Although specific P, &, and a were not reported by most studies, a number of studies
18    investigated factors affecting P, &, and a (or indicators of P, k, and a), and their effects on indoor
19    and  personal exposures (Lee et al., 1996; Cotterill et al., 1997; Monn et al., 1998; Garcia-Algar
20    et al., 2003; S0rensen et al., 2005; Zota et al., 2005). Garcia-Algar et al. (2003) observed that
21    double-glazed windows had significant effect on indoor NC>2 concentrations.  Homes with
22    double-glazed windows had lower indoor concentrations (6 ppb lower) than homes with single
23    glazed windows. Cotterill et al. (1997) reported that single or double glazed window was a
24    significant factor affecting NC>2 concentrations in kitchen in the gas-cooker homes (31.4 ppb and
25    39.8 ppb for homes with single and double glazed windows, respectively).  The reduction of
26    ventilation can block outdoor NC>2 from coming into the indoor environment, and at the same
27    time it can also increase the accumulation of indoor generated NC>2. The same effect was found
28    for homes using air conditioners. Lee et al. (2002) observed that NO2 was 9 ppb higher in homes
29    with an air conditioner than homes without. The authors also observed that the use of humidifier
30    would reduce indoor NC>2 by 6 ppb. House type was another factor reported affecting ventilation
31    (Lee et al., 1996; Garcia-Algar et al., 2003). Lee  et al. (1996) reported that the building type was

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 1    significantly associated with air exchange rate: the air exchange rate ranged from 1.04 h l for
 2    single dwelling unit to 2.26 h"1 for large multiple dwelling unit.  Zota et al. (2005) reported that
 3    the air exchange rates were significantly lower in the heating season than the non-heating season
 4    (0.49 h"1 for the heating season and 0.85 h"1 for the non-heating season respectively).  It should
 5    be pointed out that both P and k are functions of complicated mass transfer mechanisms on the
 6    indoor surfaces, and therefore they are associated with air exchange rate, which has an impact on
 7    the turbulence of air flows indoors.  However, the relationship between P, k, and a has not been
 8    thoroughly investigated.  Factors mentioned above can significantly affect P, k, and a, and thus
 9    affect the relationship between indoor and outdoor NO2 concentration, and personal exposure
10    and outdoor NO2 concentration.
11    Due to the lack of specific P, k, and a for study homes or a study population, instead of using P,
12    k, and a, alternative approaches to obtain the infiltration factor are the ratio of indoor/outdoor
13    NC>2 and the regression based RCS model.  The basic rationale of the RCS model has been
14    introduced in the previous section. Without indoor sources, the ratio between indoor NC>2 and
15    outdoor NC>2 should be always less than or equal to 1.  If the indoor to outdoor ratio is larger than
16    1  (after adjusting for measurement error), we can surely say that indoor sources exist.  However,
17    if an indoor/outdoor ratio is less than one, we cannot exclude the effect of indoor sources;
18    otherwise, the infiltration factor would be overestimated.  In order to use an indoor/outdoor ratio
19    as the infiltration factor, study designs and questionnaires must be carefully read, and only the
20    ratio for homes without identified indoor sources can be used as an indicator of infiltration
21    factor. The population averaged infiltration factor is the slope of the regression line of indoor
22    concentration vs. outdoor concentration.  The reliability of the regression slope is dependent
23    upon the sample size and how to deal with the outlier effects. Indoor/outdoor ratios and the
24    regression slopes are summarized in Table AX3.14.  Those numbers, which can be considered as
25    an infiltration factor, are underlined and marked with bold font.  Most of the infiltration factors
26    ranges from 0.4 to 0.7. Theoretically, infiltration factor is a function of air exchange rate, which
27    has been indicated by season in some studies. However, most studies do not report the
28    infiltration factor by season, and therefore, a seasonal trend of infiltration factor could not be
29    observed in Table AX3.14.
30
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 1    As mentioned before, personal NCh exposure is not only affected by air infiltrating from
 2    outdoors but also by indoor sources.  The NO2 residential indoor sources reported are gas
 3    cooking, gas heating, kerosene heating, smoking and burning candles (Schwab et al., 1994;
 4    Spengler et al., 1994; Nakai et al., 1995; Lee et al., 1996; Linaker et al., 1996; Cotterill et al.,
 5    1997; Farrow et al., 1997; Kawamoto et al., 1997; Lee, 1997; Raaschou-Nielsen et al., 1997;
 6    Aim et al., 1998; Levy et al., 1998a; Monn et al., 1998; Garrett et al., 1999; Chao, 2001;
 7    Dennekamp et al., 2001; Dutton et al., 2001; Emenius et al., 2003; Kodama et al., 2002; Lee
 8    et al., 2002; Mosqueron et al., 2002; Garcia-Algar et al., 2003; Garcia-Algar et al., 2004; Lai
 9    et al., 2004; Lee et al., 2004; Yang et al., 2004; Zota et al., 2005; S0rensen et al., 2005; Lai et al.,
10    2006). Spengler et al. (1994) reported that personal exposures in homes with gas range with
11    pilot light were 15 ppb higher than those in homes with electric range, and it was 5 ppb higher in
12    homes with gas range without pilot light than homes with electric ranges. Schwab et al. (1994)
13    reported that homes with gas stove with pilot light had higher indoor NC>2 concentrations (peak
14    concentrations ranging from 30 to 35 ppb), followed by homes with gas stove without a pilot
15    light (peak concentrations ranging from 15 to 20 ppb) and then homes with electric stoves (peak
16    concentrations ranging from 5 to 10 ppb).  In an international study, Levy et al., (1998a) reported
17    that the use of a gas stove in the home was the dominant activity influencing NC>2 concentrations
18    with a 67% increase in mean personal NC>2 exposure and an increase in indoor-outdoor ratios
19    from 0.7 to 1.2. Smoking was found to be another significant factor elevating personal and
20    indoor NO2 exposure. Monn et al. (1998) reported that during 1-week integrated measurement,
21    smoking contributed 1 ppb more NC>2 exposure.  Aim et al. (1998) reported that one-week
22    integrated personal NC>2 exposure for smokers and nonsmokers were 12.9 ppb and 10.7 ppb,
23    respectively. Zota et al. (2005) observed that smoking was not a significant indoor source.
24    However, the authors pointed out that the  effect of smoking might have been overwhelmed by
25    the presence of the gas stove.  S0rensen et al. (2005) found that burning candles were
26    significantly associated with the elevation of indoor NC>2 (p = 0.02). NC>2 concentration in an
27    indoor environment affected by the indoor sources is not homogeneously distributed: NC>2
28    concentration is usually the highest in the  kitchen, lowest in the bedroom and the concentration
29    in a livingroom is in between as shown in  Table AX3.15.  The concentration differences between
30    a bedroom and a kitchen ranged from 1 ppb to 28 ppb, and largest difference occurred in homes
31    with gas stoves.

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 1          The concentration differences in indoor microenvironments reflect the differences in
 2    personal exposure in those microenvironments, which is related to personal activities and
 3    behaviors. People who spend more time in a kitchen are expected to have higher NO2 exposures.
 4    Also, in most exposure studies, integrated indoor and personal exposures were measured from
 5    2 days to 2 weeks with passive samplers.  Therefore, the peak exposure concentration could be
 6    even higher.
 7          Indoor source contributions to indoor and personal exposure are determined by indoor
 8    source strength (S),  house volume (F), air exchange rate (a) and the NO2  decay rate (K) in an
 9    indoor environment, through the equation Cnona = SI[V(ci + &)].  Indoor source strength has been
10    summarized in a previous section (Indoor sources and concentrations of nitrogen oxides). With a
11    mass balance approach, Yang et al. (2004) reported that the source strength for electric range
12    was 3.5 ppb/h, 11.5 ppb/h for gas range in Brisbane, and 23.4 ppb/h for gas range in Seoul. The
13    age of house and  the house type are associated with ventilation, indoor sources, and house
14    volume.  As mentioned before, Lee et al. (1996) reported that the building type was significantly
15    associated with volume of dwelling unit, and air exchange rate. Garrett et al. (1999) reported
16    that older houses  were associated with higher nitrogen dioxide levels, possibly as a result of
17    older and less efficient appliances in older homes or due to smaller rooms.
18          The relative contribution of indoor and outdoor NO2 to personal and indoor exposures
19    can be easily and precisely calculated if we know the physical determinants, such as P, k, a, and
20    indoor source strength. Probability based exposure models, such as SHEDS and APEX,  could be
21    used to evaluate the personal exposure to indoor and outdoor generated NO2.  Basically, those
22    exposure models  incorporate the physical and chemical processes determining indoor pollutant
23    concentrations as a function of outdoor concentration, indoor emission rates and building
24    characteristics; the combination of a microenvironment model and personal activity model will
25    allow researchers to evaluate the personal exposure to indoor and outdoor generated NO2. Due
26    to the lack of those parameters in publications, we are going to use a regression based RCS
27    model to evaluate the contribution of indoor and outdoor generated NO2 to personal  exposure.
28    The rationale to use the RCS model to estimate indoor and outdoor contribution to indoor and
29    personal NO2 have been introduced in the previous section. In summary, the regression intercept
30    of indoor NO2 concentration vs. outdoor NO2 concentration is the population mean indoor
31    contribution to indoor NO2; and the difference between the population mean NO2 and the

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 1    intercept in the population mean of outdoor contribution to indoor NC>2. The RCS model results
 2    are summarized in Table AX3.16.  As shown in Table AX3.16, the overall ambient contribution
 3    to indoor NC>2 is around 70% with a wide range from 40 to 90%. Indoor generated NC>2
 4    contribution is 10-20% less for homes with electric stoves if electric stove then indoor
 5    contribution is usually zero. With the lack of indoor sources, the role of indoor environment is a
 6    sink for outdoor generated NC>2 due to physical and chemical losses of NC>2 in the indoor
 7    environment (Yamanaka et al., 1984; Ekberg 1996; Kraenzmer 1999; Chao et al., 2001). Chao
 8    (2001) reported that the average sink strength of NC>2 in an indoor environment in Hong Kong
 9    was 0.42 mg/h.
10          In theory, personal exposure of ambient origin should be at least as much as the indoor
11    NC>2 of ambient origin in that people spend time in either an indoor or an outdoor environment.
12    However, it was shown in the previous part (Table AX3.12) that the ambient contribution to
13    population exposure ranged from 20% to 50% based on four studies (Rojas-Bracho et al., 2002;
14    Monn et al., 1998; Levy et al., 1998a; Spengler et al., 1994); and results here show that the
15    ambient contribution to indoor NC>2 is around 70% with a wide range from 40 to 90% based on
16    another four studies (Mosqueron et al., 2002; Yang et al., 2004; Kulkarni et al., 2002; Monn
17    et al., 1998).  It is not clear at present why the indoor NC>2 of ambient origin is larger than the
18    personal NC>2 exposure of ambient origin.
19          The strength of the indoor, outdoor and personal NC>2 associations (rp:  Pearson
20    correlation coefficient;  rs: Spearman correlation coefficient; and R2:  coefficient of
21    determination) are summarized in Table AX3.17.  The  strength of the associations are
22    determined by the variation in F;nf (P, k,  and a) and indoor source contributions from home to
23    home and from day to day. In general, the correlation between indoor and outdoor NC>2 ranges
24    from poor to good (rp: 0.06 to 0.86).  When we break down the correlation coefficient by season
25    and indoor sources, it is obvious that the association between indoor and outdoor NC>2 is stronger
26    during spring and summer but weaker during wintertime, and the association is stronger for
27    homes without indoor sources but weaker for homes with strong indoor sources.  Mukala et al.
28    (2000) reported an rp of 0.86 for the indoor and outdoor NO2 association during the spring and it
29    reduced to  0.54 during the winter.  Spengler et al. (1994) reported that the associations were
30    0.66 and 0.75 (rp) for homes with and without air conditioning  system, respectively.  Emenius
31    et al. (2003) reported that the association between indoor and outdoor NC>2 was 0.69 (rp) for

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 1    homes without smoker and without gas stove using, but the association was not significant for
 2    homes with gas stove or smokers. Yang et al. (2004) reported that the indoor and outdoor NC>2
 3    association was 0.70 (R2) for homes with electric ranges, and was 0.57 (R2) for homes with gas
 4    ranges. In other words, personal exposure to ambient NC>2 in a residential indoor environment
 5    will be modified the least when the air exchange rate is high and the indoor source contribution
 6    is not significant. Considering the large spatial variation in ambient NC>2 concentrations and the
 7    relative sparseness of ambient NC>2 monitors, the associations between indoor and outdoor
 8    concentrations are usually stronger than the associations between indoor and ambient
 9    concentrations. As  shown in Table AX3.17, a stronger personal vs. residential indoor
10    relationship than the personal vs. outdoor relationship has been reported by most studies (Lai
11    et al., 2004; Monn et al., 1998, Levy et al.,  1998a; Spengler et al., 1994; Kousa et al., 2001;
12    Linaker et al., 1996), which is a reminder that personal exposure to ambient NC>2 mostly happens
13    in the residential indoor environment.  It should be pointed out that the association between
14    indoor, outdoor and personal NC>2 and the relative contributions of indoor and outdoor NC>2 to
15    indoor and personal exposures were calculated based on time integrated indoor, outdoor and
16    personal NC>2 measurement with passive samplers and an average measurement time of a couple
17    of days to two weeks. In most studies, an equilibrium condition was assumed and the effects of
18    dynamics on the indoor, outdoor, and personal association were not evaluated, which could result
19    in missing the peak exposure and obscuring the real short-term outdoor contribution to indoor
20    and personal exposure. For example, the NO2 concentrations at locations close to busy  streets in
21    urban environments may vary drastically with time. If the measurement is carried out during a
22    non-steady-state period, the indoor/outdoor concentration ratio may indicate either a too low
23    relative importance of indoor sources (if the outdoor concentration is in an increasing phase) or a
24    too high relative importance of indoor resources  (if the outdoor concentration is in a decreasing
25    phase). The lower the air exchange rate, the greater the error due to the effects of transients
26    (Ekberg  et al., 1996).
27
28    School and Office
29    Workplaces (schools and offices) are the places where people spend most of their time after
30    homes in an urban area. The location, indoor sources as well as the ventilation pattern of schools
31    and offices could be different from people's homes. Therefore, personal exposure patterns in
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 1    schools and offices could be different from exposure patterns at home. However, NO2
 2    concentrations in schools and offices have only been measured in only a few exposure studies.
 3          Most studies reported the personal exposure levels were lower than or equal to office
 4    NC>2 levels. Lai et al. (2004) reported that a cohort in Oxford spent 17.5% of their daily time in
 5    offices, and mean personal total NO2 exposure was 15 ppb and 16.8 ppb for mean office
 6    concentrations.  Mosqueron et al. (2002) reported Paris office worker exposure levels and no
 7    significant difference was found between personal total exposure (22.8 ppb) and NC>2
 8    concentrations in office (23.5 ppb).  Personal exposures in schools were  studied in Helsinki,
 9    Southampton and Southern California.  Aim et al. (1998) and Mukala et al. (2000) reported the
10    personal exposure levels in Helsinki for pre-school children. They reported that median personal
11    exposures were lower than the median NO2 concentrations measured inside the day care center
12    (13.1 ppb for personal exposure versus 18.8 ppb for inside day-care center for downtown winter;
13    14.7 ppb versus 24.1 ppb for downtown spring; 8.9 ppb versus 15.2 ppb  for suburban winter; and
14    8.9 ppb versus 13.1 ppb for suburban spring).  Linaker et al. (1996) found that the geometric
15    mean of school children exposures (18.8 ppb) was higher than geometric means of the NC>2
16    concentrations in classrooms (8.4 to 14.1  ppb) in a study of children's exposures to NC>2 in
17    Southampton, UK.  A similar exposure pattern was found by Linn et al. (1996) during the
18    Southern  California school children exposure study.  During the study, personal exposure
19    (22 ppb) was higher than the NC>2 concentration inside school (16 ppb).  NC>2 concentration in
20    school/office is determined by ambient NO2 level, local traffic sources, floor height and building
21    ventilation pattern.  Partti-Pellinen et al. (2000) studied the effect of ventilation and air filtration
22    systems on indoor air quality in a children's day-car center in Finland. Without filtration, NOX
23    and PM generated by nearby motor traffic penetrated  readily indoors. With chemical filtration,
24    50 to 70% of nitrogen oxides could be removed. The authors suggested that the possible adverse
25    health effects of nitrogen oxides and particles indoors could be countered by efficient filtration.
26    Mosqueron et al. (2002) reported 24% of variations in in-office NC>2 concentrations could be
27    explained by outdoor NC>2 levels (18%), and floor height (6%) and an inverse relation was
28    observed  between in-office concentration and floor height. Aim et al. (1998) attributed the high
29    NC>2 concentration in the day-care center  to its close to major roads. Obviously, the relative
30    scale of personal exposure and school concentration also depends on personal activities outside
31    schools and workplaces.

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 1           Significant associations between personal exposure and workplace concentrations were
 2    reported by most studies. Mosqueron et al. (2002) reported office NO2 was a significant
 3    predictor of personal exposure and 15% of the personal exposure was explained by time
 4    weighted office NO2 concentrations.  Aim et al. (1998) reported population NO2 exposures were
 5    highly correlated with the NC>2 levels inside the day-care centers (R2 = 0.88). However, Lai et al.
 6    (2004) reported a nonsignificant Pearson correlation coefficient (0.15) between personal
 7    exposure and workplace indoor concentration and the authors suggested that the strong
 8    residential indoor sources and long time indoors obscured the personal versus office relationship.
 9    Personal total exposure is a function of NC>2 concentrations in different indoor and outdoor
10    microenvironments and how long a person stays in that microenvironment. The large variation
11    of NC>2 exposure in some microenvironments could obscure the association between personal
12    exposure and NC>2 concentrations in other microenvironments.
13
14    In Traffic
15           On-road NC>2 concentrations could be substantially higher than ambient or residential
16    outdoor NC>2 concentrations, especially in a  street canyon,  which are narrow with enclosing
17    architecture and slow-moving traffic. As  shown in Figure  AX3.22, NC>2 in heavy traffic
18    (-60 ppb) can be over twice the concentration in a residential outdoor level (-26 ppb) in North
19    America (Lee et al., 2000).  The UK and Scandinavian data in the plot may have been obtained
20    outside homes close to traffic. Westerdahl et al. (2005) reported on-road NC>2 concentrations in
21    Los Angeles ranging from 40 to 70 ppb on freeways, and 20 to 40 ppb on residential or arterial
22    roads. People in traffic can potentially  experience such high concentrations and NO2 exposures
23    due to the high air exchange rates for vehicles.  Park et al. (1998) measured the air exchange
24    rates in three stationary automobiles under four conditions: windows closed and no mechanical
25    ventilation, windows closed with fan set on recirculation, windows  open with no mechanical
26    ventilation, and windows closed with the fan set on fresh air.  The reported air exchange rates
27    varied from 1.0 to 3.0 IT1 with windows closed and no mechanical ventilation to 36.2 to 47.5 IT1
28    with windows closed and the  fan set on fresh air.  It implies that the NC>2 concentration inside a
29    vehicle is at least the same as the surrounding NC>2 concentration, or in other words, "on-road"
30    NO2 can quickly and almost completely infiltrate into the "in-vehicle" environment contribute to
31    in-vehicle personal exposures. Although people only spend a small fraction of their time in
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     Figure AX3.22.      Average residential outdoor concentration versus concentration
                         during commuting for
     Source: Lee et al. (2000).

 1   traffic (5% to 7%), exposure while commuting could be a significant contributor to personal
 2   exposure to NC>2 due to the high concentration of NC>2 in traffic. Liard et al. (1999) reported that
 3   both NO and NC>2 exposure levels increased with the number of hours spent in a car.  During the
 4   study, NO and NO2 concentrations were separated into three levels according to the distribution
 5   tertiles. Personal exposure levels increased from low to high when accordingly people spent
 6   from 2.5 h in a car to 6.7 h in a car. The same relationship only held for one of the two sampling
 7   periods, in which personal NO2 exposures increased from low to high when the time people
 8   spent in a car increased from 3.5 h to 5.7 h.
 9          Bell and Ashenden (1997) and Kirby et al. (1998) reported the NO2 concentration along
10   major roads and street canyons in UK, and they found that monthly mean NO2 concentrations on
1 1   major roads were consistently higher (up to 20 ppb) than those found 250 m away from the
12   major roads. It is important to distinguish between short-term peak exposure and chronic
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 1    exposures because health effects associated with short-term peak exposures might be different
 2    from chronic exposures to ambient NC>2.
 3          Other than infiltration of ambient air, the intrusion of the vehicle's own exhaust into the
 4    passenger cabin is another NO2 source contributing to personal exposure while commuting. The
 5    intrusion of a school bus's own exhaust into the bus cabin was found by Sabin et al. (2005), but
 6    the fraction of air inside the bus cabin from the bus's own exhaust was small, ranging from
 7    0.02% to 0.28%.  Marshall and Behrentz (2005) also reported the intrusion of exhaust into the
 8    bus cabin and indicated that average per capita inhalation of emissions from any single bus is
 9    105-106 times greater for a passenger on that school bus than for a typical resident in the same
10    area. CARB (2007) reported that self-pollution increased with increasing age of the bus. Fuel
11    type could be another factor affecting personal exposure while commuting.  Sonetal. (2004)
12    found that the two-day  averaged NO2 exposures for taxi drivers using LPG fueled vehicles
13    (26.3 ppb)  were significantly lower than those using diesel-fueled vehicle (38.1 ppb).  However,
14    in another taxi driver exposure study, Lewne et al. (2006) did not find an effect on taxi driver
15    exposures to NC>2 due to fuel differences (diesel versus petrol). Sabin et al. (2005) reported that
16    NC>2 concentrations were significantly higher inside diesel buses than inside the compressed
17    natural gas buses. CARB (2006) showed that the NC>2 concentrations on a conventional diesel
18    bus was 2.8 times higher than the ambient concentration (76 ppb in cabin versus 27 ppb  in
19    ambient) while windows were closed, and 3.85 times higher than the ambient concentration
20    (77 ppb in  cabin versus 20 ppb in ambient) while windows were open.  However, the ratio of
21    cabin NC>2 to ambient NC>2 was much lower for a compressed natural gas bus: 1.2 for windows
22    closed and 2.2 for windows opened.
23          While commuting, concentrations for personal exposure or in a vehicle  cabin could be
24    substantially higher than corresponding residential indoor, outdoor, and ambient concentrations.
25    Sabin et al. (2005) measured concentrations of a number of pollutants (black carbon, particulate
26    PAHs  and NC>2 in school buses on routes in Los Angeles. Mean cabin concentrations for
27    individual runs ranged  from 24 to  120 ppb. Concentrations of NC>2 tended to be slightly higher
28    for open compared to closed windows on urban routes.  These concentrations were typically
29    factors of 2.3 to 3.4 higher than  at ambient monitors in the area. However, the highest ratios
30    found ranged from 3.9  to 5.3. They concluded that children commuting in areas such as Los
31    Angeles may be exposed to much higher levels of pollutants than are obtained at ambient, central

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 1    site monitors. Lewne et al. (2006) reported work hour exposures to NO2 for taxi drivers
 2    (25.1 ppb), bus drivers (31.4 ppb) and lorry drivers (35.6 ppb). The ratios of in-vehicle
 3    exposures to urban background were 1.8, 2.7, and 2.8 for taxi drivers, bus drivers and lorry
 4    drivers, respectively.  Due to the high peak exposures during commuting, total personal exposure
 5    could be underestimated if exposure in traffic are not considered; and sometimes exposure in
 6    traffic can dominate personal exposure to NO2. In a personal exposure study in Brisbane and
 7    Queensland, Australia, two-day averaged indoor, outdoor, and personal NO2 were measured by
 8    Yanagisawa badges (Lee et al., 2000). Lee et al. (2000) found that estimated personal exposures
 9    (22.5 ppb) significantly underestimated the measured personal exposures (28.8 ppb) if personal
10    exposures in traffic were not considered. Son et al. (2004) reported two-day averaged indoor,
11    outdoor, in vehicle and personal NO2 concentrations measured by passive filter badges for
12    31 taxi drivers in Korea.  Measured personal  concentrations (30.3 ppb) were higher than both
13    residential indoor (24.7 ppb) and residential outdoor concentrations (23.8 ppb). A stronger
14    correlation was observed between personal NO2 exposures and interior vehicle NO2 levels, than
15    for residential indoor and residential outdoor levels (rp = 0.89 for Personal versus Vehicle, rp =
16    0.74 for Personal versus  Indoor; and rp = 0.71 for Personal versus Outdoor).
17          Variations in traffic exposure could be attributed to time spent in traffic, type of vehicle,
18    traffic congestion levels,  encounters with other diesel vehicles, type of fuel and driving location
19    (urban/rural) (Sabin et al., 2005;  Son et al., 2004; Chan et al., 1999).
20
21    Microenvironments Close to NO2 Sources
22          As suggested previously in this chapter, both large and small-scale variations exist in
23    ambient NO2 concentrations. In this section, those microenvironments and associated personal
24    exposures, which are close to traffic sources and might make significant  contributions to total
25    personal NO2 exposures are analyzed. These microenvironments could be residential outdoor
26    environments and some other outdoor environments, such as parking lots and playgrounds; they
27    could also be indoor environments as well, such as homes and classrooms. Concentrations in
28    these microenvironments and personal exposure characteristics in these microenvironments will
29    be summarized below.
30          Many studies show that outdoor NO2  levels are strongly associated with distance from
31    major roads (the closer to a major road, the higher the NO2 concentration) (Gilbert et al., 2005;
32    Roorda-Knape et al., 1998; Lai et al., 2001; Kodama et al., 2002; Gonzales et al., 2005; Cotterill

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 1    et al., 1997; Nakai et al., 1995).  Meteorological factors (wind direction and wind speed), and
 2    traffic density are also important for interpreting measured NO2 concentrations (Gilbert et al.,
 3    2005; Roorda-Knape et al., 1998; Rotko et al., 2001; Aim et al., 1998; Singer et al., 2004; Nakai
 4    et al., 1995).  Gonzales et al. (2005) found an inverse correlation between NO2 concentration and
 5    distance from a highway (rp = -0.81, p < 0.001) in the El Paso region. Nakai et al. (1995)
 6    reported the results of a study  designed to explore the differences of indoor, outdoor and personal
 7    exposure levels among residence zones located varying distances from major roads with heavy
 8    traffic in Tokyo. The authors  found that outdoor NO2 concentrations in Zone A (0-20 m from
 9    the road) was always the highest among the three zones (Zone B was 20-150 m from the road,
10    and Zone C was a reference zone in a suburban area). The differences of the mean levels
11    between Zone A and Zone C ranged from 11 ppb to 39 ppb. Kodama et al. (2002) reported NO2
12    levels for indoor, outdoor and personal exposure among 150 junior high school student homes in
13    two major traffic areas in Tokyo. Forty-eight h average NO2 concentrations were measured by
14    Yanagisawa badge.  NO2 tended to decrease according to distance from the roadside; the
15    difference was about 10 ppb between the roadside (0-50 m) and the site far away from the road
16    (200 m). Singer et al. (2004) reported results of the East Bay Children's Respiratory Health
17    Study.  The authors reported weekly integrated NO2 and NOX concentrations measured by
18    Ogawa  passive  samplers placed outside ten elementary schools and selected student residences
19    during 14 weeks in spring and 8  weeks in fall 2001.  The authors found that NO2 concentrations
20    increased with decreasing downwind distance for school and neighborhood sites within 350 m
21    downwind  of a  freeway, and schools located upwind or far downwind of freeways were
22    generally indistinguishable from one another and regional pollution levels. An exponential
23    equation was used to fit the measured concentrations to distance from the freeway: C(x) = KixK2
24    where C is  the measured concentration and x is the distance (m) from a freeway. A high R2 was
25    observed (R2  =  0.80, KI = 128, and K2 = -0.356 for NO2; R2 = 0.76, KI = 376, and K2 = -0.468).
26    According  to this equation, NO2 concentrations 100 m  away from the freeway are about 20% of
27    those at roadside.
28          Elevated NO2 concentrations were also observed and reported in parking lots and school
29    playgrounds.  Lee et al. (1999) reported the concentration of NO2 at a parking lot in Hong Kong
30    was 60  ppb, and the level was about the same for NO.  Colbeck (1998) reported that
31    concentrations in two parking lots in Colchester, UK were similar to those measured at the curb

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 1    side.  Exposure of car parking lot users to NC>2 is comparable to that arising in the vicinity of
 2    roads with moderate traffic density (-9000 vehicles per day). NO2 concentrations in one parking
 3    lot ranged from 30.4 to 47.1 ppb, while those in the payment booth ranged from 22.5 to 31.4 ppb.
 4    Rundell et al. (2006) reported PMi, NO2, SO2, CO, and Os concentrations at four elementary
 5    school playgrounds and one university soccer field in Pennsylvania. NC>2 concentrations were
 6    below 100 ppb.  The number concentration in the PMi size fraction decreased with distance
 7    away from the highway (from 140,000 number/cm3 within 10 m of the road to 40,000
 8    number/cm3 at 80 m).
 9          Indoor environments, which are close to traffic, include buildings and houses along
10    major, busy roads. Most studies show that indoor NC>2 is correlated with outdoor NC>2, and is
11    also a function of distance to traffic, traffic density and meteorological parameters.  The level of
12    indoor NC>2 in those microenvironments is also affected by indoor sources.  Bae et al. (2004)
13    reported indoor and outdoor concentrations of NC>2 in 32 shoe stalls in Seoul, which were located
14    on busy streets.  Working-hour (10 ± 2.1  h) NC>2 was measured by Yanagisawa passive filter
15    badges. Mean indoor and outdoor NC>2 concentrations were 57.4 and 58.1  ppb with a mean
16    indoor vs. outdoor ratio of 0.93. Maximum indoor and outdoor NC>2 concentrations were 94.1
17    and 96.3 ppb.  In this study, outdoor traffic generated NC>2 is likely the main source of indoor
18    exposures due to the lack of indoor NC>2 sources.  Outdoor and in-classroom NO2 were measured
19    using Palmes tubes during three 2-week periods in six city districts near motor ways in the West
20    of the Netherlands (Roorda-Knape et al.,  1998). NO2 concentrations in classrooms were
21    significantly correlated with car and total traffic density (rp = 0.68), percentage of time
22    downwind (rp = 0.88)  and distance of the school from the motorway (rp = -0.83). Cotterill et al.
23    (1997) measured indoor and outdoor NO2 in 40 homes in Huddersfield, UK, over three
24    consecutive two-week periods in late 1994 using Palmes tubes. The authors found that
25    proximity to a main road had little effect  on indoor levels of nitrogen dioxide (a mean of 1 ppb
26    indoor concentration difference was found for homes close to main roads and homes close to
27    side roads).  A t-test suggested that there  was no difference in indoor levels of nitrogen dioxide
28    due to proximity to the main road after indoor sources were controlled by the type of cookers.
29    In this study, meteorological parameters were measured, but meteorological parameters were not
30    controlled during data analysis.
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 1          Personal exposure is determined by both indoor and outdoor levels of NC>2.  Most studies
 2    show significant associations between personal exposure and the traffic density. The influence
 3    of indoor sources on personal exposure was also observed in those studies. Aim et al. (1998)
 4    reported the weekly personal NC>2 exposures of 246 children aged 3-6 years in Helsinki. Weekly
 5    personal exposures were measured for 13 weeks in winter and spring in 1991 using Palmes
 6    tubes. The 13 week geometric mean of the NO2 exposures was higher for the children living in
 7    the downtown (13.9 ppb) than in the suburban area (9.2 ppb, p = 0.0001). Rotko et al. (2001)
 8    reported the EXPOLIS-Helsinki study results and observed that the NO2 exposure was
 9    significantly associated with traffic volume near homes. The average exposure level of
10    138 subjects having low or moderate traffic near their homes was 12.3 ppb, while the level was
11    15.8 ppb for the 38 subjects having high traffic volume near home. Gauvin et al. (2001) reported
12    the VESTA study results.  An index of traffic density and proximity was constructed as the ratio
13    of traffic density to distance from a roadway.  The index was one of the significant interpreters of
14    personal exposure in all three cities (p < 0.05 for Grenoble and Toulouse, and 0.05 < p < 0.15 for
15    Paris). Kodama et al.  (2002) showed that personal exposure was similar to residential home NC>2
16    concentration for residences along busy roads. The authors also observed that personal exposure
17    levels were higher than outdoor levels during the winter, while during the summer, personal
18    exposure levels were lower than ambient levels, due to the influence of indoor sources and low
19    ventilations in the winter.  Although the personal to outdoor relationship was dominated by
20    indoor sources, the effects of outdoor NO2 on personal exposure could still be observed after
21    controlling the indoor source effects.  Nakai et al.  (1995) observed that personal exposure levels
22    basically followed the ambient concentrations patterns given above; i.e., exposures in Zone A
23    (0-20 m from the road) were the highest and exposures in Zone C (the suburban background
24    area) were the lowest for residents not using an unvented heater (as defined before, Zone A was
25    0-20 m from the road; Zone B was 20-150 m from the road. The maximum difference of
26    personal exposure between Zone A and Zone C was approximately 20 ppb. The NC>2 exposure
27    for a special population, athletes, was addressed by Carlisle et al. (2001).  The authors pointed
28    out that athletes could be a potential population at risk, if the ambient NO2 concentration is high
29    because (1) inhalation rate increases during exercise, (2) a large fraction of air is inhaled through
30    the mouth during exercise, effectively bypassing the normal nasal mechanisms for the filtration
31    of large particles and soluble vapors, and (3) the increased  air flow velocity carries pollutants

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 1    deeper into the respiratory tract and pulmonary diffusion capacity increases during exercise.
 2    This might also be true for outdoor workers but few data are available to perform the exposure
 3    assessment.
 4          Although traffic is a maj or source of ambient NC>2, industrial point sources are also
 5    contributors to ambient NC>2.  However, no published reports were found to address the effect of
 6    those sources on population exposure within the United States.  Nerriere et al. (2005) measured
 7    personal exposures to PM2 5, PMi0, and NC>2 in traffic dominated, urban background and
 8    industrial settings in Paris, Grenoble, Rouen, and Strasbourg, France.  They always found highest
 9    ambient concentrations and personal exposures close to traffic.  In some cases, urban and
10    background, concentrations of NC>2 were higher than in the industrial zone. However, PM levels
11    and personal exposures tended to be higher in the industrial area than in the traffic dominated
12    area.  It should be remembered that there can be high traffic emissions in industrial zones, such
13    as in the Ship Channel  in Houston, TX. In rural areas where traffic is sparse, other sources could
14    dominate. For example, Martin et al.  (2003) found pulses of NC>2 release from agricultural  areas
15    following rainfall and there are contributions from wildfires and residential wood burning.
16
17    Exposure Reconstruction
18          Personal exposure has been evaluated in each major microenvironment, where either the
19    NC>2 concentration is high or people spend most of their daily time. As shown in Equation AX3-
20    13, personal exposure could be reasonably reconstructed if we know the NC>2 concentration in
21    each microenvironment and the duration of personal exposure in each microenvironment. Levy
22    et al., (1998a) reconstructed personal exposures measured in an international study with a time-
23    weighted average exposure model (Equation AX3-12).  The personal exposure was reconstructed
24    based on the measured  NC>2 concentrations in residential indoor, residential outdoor, and
25    workplace microenvironments, and the time people spent in those environments.  The mean
26    measured personal NC>2 exposure was 28.8 ppb and a mean of estimated NC>2 exposure was 27.2
27    ppb. The Spearman correlation coefficient between personal  measured exposure and
28    reconstructed exposure was 0.81.  The same approach was applied by Kousa et al. (2001) to
29    reconstruct the personal exposures in the EXPOLIS study. A correlation coefficient of 0.86 was
30    observed for the association between measured NO2 exposure and reconstructed NO2 exposure
31    (data were log-transformed), and the slope and the intercept were 0.90 and 0.22 respectively for
32    the reconstructed exposure vs. measured exposure.  In the two studies mentioned above, NC>2

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 1    exposure during commuting was not measured. Probably that is part of the reason why
 2    reconstructed NC>2 exposure was lower than the measured NO2 exposure.
 3
 4    AX3.5.3    Exposure Indicators
 5          Physically, personal exposure levels are determined by those physical parameters in
 6    Equations AX3-12 to AX3-16, i.e., the time people spend in each microenvironment and the NC>2
 7    concentrations in each microenvironment, which is determined by source emission strength, air
 8    exchange rate, penetration coefficient, the NO2 decay rate and the volume of the
 9    microenvironment.  Any factors that can influence the above physical parameters can modify the
10    level of personal exposure.  These factors are defined as exposure indicators in this section.  The
11    indoor, outdoor and personal NC>2 levels on each stratum of those factors will be summarized.
12          Those factors can be classified in to the following categories: (1) factors associated with
13    environmental conditions,  such as weather and season; (2) factors associated with dwelling
14    conditions, such as the location of the house and ventilation system; (3) factors associated with
15    indoor sources, such as the type of range and the fuel type; (4) factors associated with personal
16    activities, such as the time spent on cooking or commuting; (5) socioeconomic status, such as the
17    level of education and the income level; and (6) demographic factors, such as age and gender.
18          Most studies addressed the influences of dwelling condition and indoor sources on indoor
19    and personal exposures. A few studies explored the impacts of environmental factors and
20    personal activities on personal exposures. Indoor and personal exposures have rarely been
21    stratified by socioeconomic and demographic factors.  Indoor, outdoor, and personal exposure
22    levels are presented in Table AX3.18, stratified by environmental factors, dwelling conditions,
23    indoor sources, and personal activities factors. The effects of socioeconomic and demographic
24    factors on the indoor, outdoor, and personal levels are summarized in Table AX3.19.
25          Season is an environmental factor affecting both indoor and outdoor levels, and thus
26    personal NC>2 levels. During the wintertime, the mixing height is usually lower than during the
27    summer, and therefore concentrations of many primary pollutants are higher than in the summer.
28    Wintertime is also a heating season, which usually leads to higher indoor source emissions and
29    lower air exchange rates.  Therefore, a higher indoor NC>2 concentration can be expected during
30    the winter. For most cases, the differences of indoor or personal NC>2 exposure between the
31    heating and non-heating season are within several ppb, but sometimes the difference could be
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 1    close to 20 ppb (Zota et al., 2005). Other environmental factors include day of the week
 2    (weekday versus weekend), and the wind direction, as shown in Table AX3.18.
 3          The dwelling conditions are also associated with indoor, outdoor, and personal NO2
 4    levels. Location of the dwelling unit is an indicator of ambient NO2 source strength. A house
 5    located in an urban center or close to a major road is expected to have higher outdoor and indoor
 6    NO2 levels, and the differences in NO2 exposures are often within 20 ppb based on passive
 7    sampler monitoring. The age of the house, house type, and window type can affect the
 8    ventilation of dwelling units, and sometimes the type of heating and cooking applicances in a
 9    house. Range and fuel type are the indoor source factors discussed the most in the literature. It
10    is common to see differences larger than 10 ppb in indoor and personal NO2 exposures between a
11    gas range home (especially gas range with pilot light) and an electric range home.  Sometimes
12    the differences could be as high as 40 ppb. For peak short-term exposures, the difference could
13    reach 100 ppb.
14          The level of personal exposure is dependent upon the time a person spends in each
15    microenvironment. Kawamoto et al. (1997), Levy et al. (1998a), and Chao and Law (2000)
16    clearly showed that personal NO2 exposure increases with time spent cooking or commuting.
17          The common findings are summarized above. However, there are inconsistencies in the
18    literature. For example, smoking is claimed to be a significant factor in some studies but not in
19    others, and the  same can be said for proximity to a major road. For another example, a higher
20    indoor NO2 level could be found in a rural home  rather than in an urban home (Table AX3.18),
21    although most studies  found the opposite.  Part of the reason is that exposure indicators function
22    together, as a multidimensional parameter space, on indoor and personal exposures.  They are
23    not independent of each other.  Unfortunately, studies have rarely been conducted to understand
24    the associations between these exposure indicators and to use the study findings to explain
25    indoor and personal NO2  exposures.
26          More effort put on exposure indicator studies should help in finding better surrogate
27    measurements for personal exposures.  Although misclassifying exposures in epidemiological
28    studies is almost inevitable, and it is unlikely that the personal exposures of all subjects will be
29    measured, a better knowledge of the effects of exposure indicators on personal exposure will
30    help reduce exposure errors in exposure and epidemiological studies and help interpret those
31    study results.

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 1   AX3.6     CONFOUNDING AND SURROGATE ISSUES
 2          Confounding is the technical term for finding an association for the wrong reason. It is
 3   associated with both the exposure and the disease being studied, but is not a consequence of the
 4   exposure. The confounder does not need to be an exposure for the disease under study. The
 5   confounding variable can either inflate or deflate the true relative risk.
 6          Since epidemological studies of NO2 often use ambient concentrations to reflect
 7   exposures, whether confounding of NC>2 findings is possible can be determined by examining
 8   associations among ambient concentrations and personal exposures to NC>2 and its relevant
 9   copollutants. Importantly, by examining these associations, it is also possible to evaluate
10   whether a copollutant may act as a confounder or as a proxy of ambient NC>2 concentrations.
11          The potential for confounding  of ambient NC>2 health effects is discussed in terms of four
12   relationships: (1) ambient NO2 and ambient copollutant concentrations, (2) personal NO2 and
13   personal copollutant exposures, (3) personal NC>2 exposures and ambient copollutant
14   concentrations, and (4) ambient NC>2 concentrations and personal copollutant exposures.
15
16   1) Associations between Ambient NO 2 and Ambient Copollutant Concentrations
17          Confounding of NC>2 health effects is often examined at the ambient level, since ambient
18   concentrations are generally used to reflect exposures in epidemiological studies.  The majority
19   of studies examining pollutant associations in the ambient environment have focused on ambient
20   NC>2, PM2.s (and its components), and CO, with fewer studies reporting the relationship between
21   ambient NC>2 and ambient 63 or 862.
22          Correlations between concentrations of ambient NO2 and other ambient pollutants, PM2.5
23   (and its components where available), CO, Os and SC>2 are summarized in Table AX3.20. Data
24   were compiled from Environmental Protection Agency's Air Quality  System and a number of
25   exposure studies.  Mean values of site-wise correlations are shown. As can be seen from the
26   table, NO2 is moderately correlated with PM2.5 (range: 0.37 to 0.78) and with CO (0.41 to 0.76)
27   in suburban and urban areas.  At rural  locations, such as Riverside, CA, associations between
28   ambient NO2 and ambient CO concentrations  (both largely traffic-related pollutants) are much
29   lower, likely as the result  of other sources of both CO and NO2 increasing in importance  in rural
30   areas. These sources include oxidation of CH4 and  other biogenic compounds, wood burning
31   and wildfires (for CO); and soil emissions, lightning, and wood burning and wildfires for NO2.
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 1    In urban areas, the ambient NO2-CO correlations vary widely. The strongest correlations are
 2    seen between NO2 and elemental carbon. Note that the results of Hochadel et al. (2006) for
 3    PM2.s optical absorbance have been interpreted in terms of elemental carbon (EC).  Correlations
 4    between ambient NO2 and ambient Os are mainly negative, with again considerable variability in
 5    the observed correlations. Only one study (Sarnat et al., 2001) examined associations between
 6    ambient NO2 and ambient SO2 concentrations, showing a negative correlation during winter.
 7    The robustness of this result needs to be examined in other cities.
 8          Kim et al. (2006) reported the associations between 24 h averaged NO2 and other
 9    pollutions for personal exposures and ambient concentrations in a study in Toronto, Canada from
10    August 1999 to November 2001. The median, mean, and standard deviation of the correlations
11    between ambient NO2 and ambient PM2 5 were 0.52, 0.44, and 0.35 respectively; and 0.81, 0.72,
12    and 0.22 respectively for the correlation between NO2 and CO.
13          In an exposure study in Steubenville, Ohio, Sarnat et al. (2006) reported the associations
14    between ambient concentrations and personal exposures for different pollutants.  Ambient NO2
15    was significantly associated with ambient PM2 5, sulfate and EC during the fall (slope = 0.38,
16    0.96, and 7.01; and R2 = 0.61, 0.49, and 0.68 respectively) but not during the summer (slope =
17    -0.01, -0.17, and 3.76; andR2 = 0.0, 0.01, and 0.06 respectively).
18          In a related study, Connell et al. (2005) reported the correlation between ambient NOX
19    and PM2 5 during a comprehensive air monitoring program in Steubenville, Ohio. Across the two
20    year study (August 2000-April 2002), the Spearman correlation coefficient (rs) between hourly
21    ambient PM2 5 and NO concentrations was 0.33, and between hourly ambient PM2 5 and NO2
22    concentrations was 0.50. The authors suggested the importance of a common factor influencing
23    ambient concentrations of these species.
24          Kim et al. (2005) analyzed particle composition and gas phase data collected during the
25    RAPS/RAMS study on St. Louis, MO from 1975  to 1977 in terms of source contributions to
26    PM2.5. This study examined the spatial variability of source contributions to PM2.5  at the ten
27    monitoring sites in that study.
28          Sarnat et al. (2001) and reported associations between personal exposures and ambient
29    concentration across pollutants in a study conducted in the Baltimore area. At the ambient level,
30    NO2 was significantly correlated with PM2 5 (rs =  0.37) and CO (rs = 0.75) during the summer
31    and with CO (rs = 0.76), SO2 (rs = -0.17), PM2.5 (rs = 0.75) and O3 (rs = -0.71) during the winter.

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 1          Linn et al. (1996) reported short-term air pollution exposures in Los Angeles area school
 2    children.  Correlations between different pollutants were weaker: rp = 0.11 for ambient NO2 and
 3    O3; rp = 0.25 for ambient NO2 and outdoor PM2 5.
 4          Lee et al. (2002) found that ambient NO2 was significantly correlated with Os
 5    (rp = -0.34).
 6
 7    Foreign Studies
 8          Hochadel et al. (2006) reported the results of research which is part of a cohort study on
 9    the impact of traffic-related air pollution on respiratory health, conducted at the western end of
10    the Ruhr-area in North-Rhine Westphalia, Germany. Strong correlations across the measurement
11    sites were observed between annual average PM2.5 absorbance and NO2 concentrations
12    (rp = 0.93), whereas PM2.5 mass concentration was less strongly correlated with NO2 (rp = 0.41).
13    The only  major absorbing agent in PM2.5 is elemental carbon (EC) as other components (sulfate,
14    nitrate, organic carbon) either do not absorb or at best are only weakly absorbing. Therefore,
15    correlations between PM2 5 absorbance and NO2 may be inferred as correlations between EC and
16    NO2.
17          Hazenkamp-von Ark et al. (2004) reported the PM2 5 and NO2 associations across 21
18    European study centers during ECRHS II.  The correlation between annual NO2 and PM2.5
19    concentrations is fair (Spearman correlation coefficient rs = 0.75), but when considered as
20    monthly means, the correlation is far less consistent and varies substantially between centers.
21    The authors pointed out that NO2 is attributed to traffic emissions, a relatively constant source of
22    pollution  throughout the year. PM2 5 on the other hand, can be driven by other sources such as
23    wind-blown dust, although usually it consists predominantly of primary and secondary particles
24    from combustion processes.  Sources,  such as Saharan dust in Spain, probably cause some of the
25    observed  patterns. The wide range of correlations between PM2 5 and NO2 evokes the hypothesis
26    that monthly PM2 5 mass concentrations in some centers may be driven by traffic emissions,
27    whereas in other centers, particles from other sources may be of further relevance.
28          Cyrys  et al. (2003) reported the results of a source apportionment study in Erfurt,
29    Germany. Hourly NO2 was correlated with NO, CO, PM0.oi-2.5 number concentration, and
30    PM0.oi-2.5  mass concentration  (rp = 0.73, 0.74, 0.55, and 0.50 respectively). Stronger correlations
31    were found daily correlation between NO2 and NO, CO, PMo.oi-2.5 number concentration, and
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 1    PMo.oi-2.5 mass concentration (rp = 0.87, 0.76, 0.71, and 0.66 respectively). The observed high
 2    correlations between CO, NO, and NO2 indicate that direct emissions from mobile sources might
 3    be the major contributors to the concentrations of these gaseous pollutants.
 4          Rojas-Bracho et al.  (2002) conducted a study of children's exposures in Santiago, Chile.
 5    During the study, indoor, outdoor, and personal PM2.5, PMio, PMio-2.s, and NO2 were measured
 6    24 h averaged for five consecutive days).  Outdoor NO2 was significantly associated with all PM
 7    fractions (slope = 1.82 and  R2 = 0.59 for PM2.5; slope = 3.12 and R2 = 0.57 for PMi0; and slope =
 8    1.11 and R2 = 0.32 for PM2.5-io).
 9          Modig et al. (2004)  investigated whether NO2 can be used to indicate ambient and
10    personal levels of benzene  and 1, 3-butadiene in air.  The stationary measurements showed
11    strong relations between 1,3-butadiene, benzene and NO2 (rp = 0.70 for NO2 and benzene; and
12    r = 0.77  for NO2 and 1,3-butadiene).  This study supports NO2 as a potential indicator for
13    1,3 butadiene and benzene  levels in streets or urban background air.
14          In summary, ambient NO2 was moderately correlated with corresponding ambient
15    concentrations of its co- pollutants. Based on associations in the ambient environment, results
16    suggest a possibility of confounding of ambient NO2 health effects by ambient PM2.5 (and its
17    components) and by ambient CO.
18
19    2) Associations between Personal (NO 2) and Personal Copollutant Exposures
20          For this section,  measured personal NO2  exposures are regarded as the "true" personal
21    exposure. The correlation between personal NO2 exposure and personal exposure to other
22    pollutants are summarized below in Table AX3.21.
23          In Kim et al. (2006), the median, mean and standard deviation of the correlation between
24    NO2 and PM2 5 personal exposures for eleven subjects were 0.43, 0.41, and 0.28 respectively;
25    and  0.16, 0.12, and 0.42 respectively for the correlation between NO2 and CO (Kim et al., 2006).
26          Although Sarnat et al. (2001) found that personal exposures to PM2 5 were generally not
27    significantly associated  with personal exposures to gases in Baltimore, personal NO2 was
28    significantly associated  with personal PM2.5 (slope = 0.18, intercept = 18.65, p < 0.01, and
29    n =  213) and personal PM2.5 of ambient origin (slope = 0.17, intercept = 12.77, p < 0.05, and
30    n =  150) during the summer.  There was some evidence to indicate that the strength of the
31    association was driven largely by the cohort of older adult subjects, and not by the children's or
32    COPD patients cohorts.  They noted that gas stove usage did not significantly affect personal

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 1   NO2 to PM2.5 relations, but did affect relations between personal NO2 and personal PM2.5 of
 2   ambient origin. They further pointed out that associations observed among pollutants in ambient
 3   air may not be reflected in personal exposures and that they may not persist across seasons.
 4   However, Lai et al. (2004) found that personal exposure to NO2 was slightly negatively
 5   correlated with personal exposure to PM2 5 and total VOCs in a study conducted from 1998 to
 6   2000 in Oxford, UK (- 0.1 for PM2.5, 0.3 for CO, and -0.11 for TVOCs).
 7          Modig et al. (2004) investigated whether NO2 can be used to indicate ambient and
 8   personal levels of benzene and 1, 3-butadiene in air. The results from the personal
 9   measurements showed a negligible association of NO2 with 1,3-butadiene (rp = 0.06) as well as
10   with benzene (rp = 0.10), while the correlation coefficient between benzene and 1,3-butadiene
11   was high and significant (rp = 0.67).  The weak relations found for the personal measurements do
12   not support the use of NO2 as an indicator for personal 1,3-butadiene and benzene exposure.
13   Although gas stove and kerosene heaters were almost absent in the study area, this study
14   included both smokers and non-smokers, but the data were not stratified. Smoking is a major
15   source of both benzene and 1,3-butadiene, in addition to motor vehicles.  If smoking were the
16   major cause of the poor association between NO2 and the gases in the personal measurements,
17   then this would indicate that smoking was not a major source of personal NO2. Thus, this study
18   cannot determine whether personal NO2 is an indicator of traffic generated VOCs and so the
19   interpretation of results in this paper is problematic.
20          In the Paris office worker study, no relation was observed between personal NO2 and
21   PM2.5 exposures (rp = 0.12, n = 53, p = 0.38) (Mosqueron et al., 2002).  In addition, NO2 and
22   PM2.s concentrations were correlated neither in-home (rp = 0.06, n = 54, p = 0.69) nor in-office
23   (rp = 0.05, n = 55, p = 0.74).
24
25   Associations with HONO
26          Spicer et al. (1993) and Wainman et al. (2000) suggested the presence of a strong indoor
27   source of HONO  from heterogeneous reactions involving NO2 and water films on indoor
28   surfaces. Hence,  combustion appliances are sources for exposures to both NO2 exposure and
29   HNO2.  Epidemiological studies of NO2 health effects should consequently consider the potential
30   confounding effects of NO2 and vice versa.
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 1          Jarvis et al. (2005) reported the indoor nitrous acid and lung function in adults as part of
 2    European Community Respiratory Health Survey (ECRHS).  Indoor HONO and indoor and
 3    outdoor NO2 were measured.  Indoor NO2 were correlated with HONO (rp = 0.77) but no
 4    significant association of indoor NO2 with symptoms or lung function was observed.
 5          Lee et al. (2002) studied the nitrous acid, nitrogen dioxide, and ozone concentrations in
 6    residential environments.  The authors found that indoor NO2 was significantly correlated with
 7    HONO (rp = 0.511).
 8          As shown above, very few studies showed the relationship between personal NO2
 9    exposure and other pollutant exposures. In general, personal NO2 was moderately correlated
10    with PM2.5 and CO. Due to the lack of personal HONO exposure data, indoor HONO was used
11    as an indicator for personal exposure, and current studies showed that indoor HONO was
12    correlated with indoor NO2 with high correlation coefficients, which suggested that the collect
13    ion of HONO exposure data would help interpret adverse health outcome in the NO2 health risk
14    assessment.
15
16    3) Personal (NO2) -Ambient Copollutants
17          The relationship between personal NO2 exposure and other ambient pollutants are
18    summarized in Table AX3.22.
19          In Steubenville, Ohio, Sarnat et al. (2006) found that personal NO2 was significantly
20    associated with ambient PM2.5 and ambient sulfate during the fall (slope = 0.17 and R2 = 0.21 for
21    PM2.5; and slope = 0.34  and R2 = 0.12 for sulfate);  and was significantly associated with ambient
22    EC in both summer and fall (slope =1.81 and R2 = 0.03 for the summer; and slope = 3.71 and
23    R2 = 0.32 for the fall).
24          Kim et al. (2006) also reported correlations between personal exposure and ambient
25    measurements across pollutants. The median, mean, and standard deviation of the correlation
26    between personal NO2 and ambient PM2 5 were 0.36, 0.30, and 0.30 respectively; and 0.17, 0.20,
27    and 0.41 respectively for the correlation between personal NO2 and ambient CO.  The authors
28    suggested that the existing correlation between PM2.5 and NO2 for both ambient measurements
29    and personal exposures suggests that there is potential for NO2 to be a confounder of PM2.5, and
30    vice versa. Therefore, it may be appropriate for time-series epidemiological studies to control
31    for confounding by NO2 in PM2 5 risk models, and  vice versa.
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 1          In a study conducted in Santiago, Chile (Rojas-Bracho et al., 2002) personal NO2 was
 2    moderately associated with PM2.5 (slope = 1.99 and r2 = 0.42) and PMio (slope = 2.13 and
 3    r2 = 0.15) but not coarse particles. At the indoor level, the same observation held (slope = 0.86
 4    and r2 = 0.22 for PM2 5; slope =1.0 and R2 = 0.2 for PMio). "However, in comparing the indoor
 5    and outdoor associations, we find that the latter is more highly significant and that the intercept
 6    is smaller. It is likely that in outdoor environments, there are more high-temperature combustion
 7    processes, which are associated with nitrogen oxide emissions.  Since nitrogen oxides are
 8    precursors of secondary particles, which partly form PM2.5, our results showed a stronger
 9    association between these two pollutions outdoors."
10          Lee et al. (2002) studied nitrous acid, nitrogen dioxide, and ozone concentrations in
11    residential environments.  The authors found that indoor NO2 was significantly correlated with
12    outdoor O3 (rp = -0.220).
13          These studies above show moderate correlations between personal NO2 exposure and
14    ambient PM2 5, PMio, EC, sulfate, and CO. Based on our knowledge that, moderate to strong
15    personal-ambient correlations exist for all the other pollutants mentioned above all of those
16    species might serve as confounders for NO2 exposure (detailed evaluation of the personal vs.
17    ambient relationship for these pollutants are beyond the scope of this document).
18
19    4) Ambient NO2-Personal Copollutant
20          Correlation between ambient NO2 and personal exposure to copollutants are summarized
21    in Table AX3.23.
22          Sarnat et al. (2006) found that ambient NO2 was significantly associated with personal
23    PM2.5 and personal sulfate during the fall  (slope = 0.93 and R2 = 0.25 for PM2.5; and
24    slope = 0.28 and R2 = 0.27 for sulfate); and was significantly associated with personal EC during
25    both summer and fall  (slope = 0.02 and R2 = 0.07 during the summer; and slope = 0.08 and
26    R2 = 0.49 during the fall) in Steubenville, OH.  Sarnat et al. (2006) suggested that for most cases,
27    ambient gas concentrations, although not  suitable proxies of gas exposures are equally not
28    suitable for particle exposures in time-series health studies. Despite this, numerous
29    epidemological studies have linked 24-h ambient gas concentrations to adverse health impacts,
30    suggesting that the gases may indeed elicit biological responses alone or in combination with
31    other pollutants, or are acting as proxies for shorter-term exposures. The authors pointed out that
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 1    for Steubenville in the fall, a season with strong associations between ambient particle and NO2
 2    concentrations, the separation of particle and NO2 health effects in daily time-series studies may
 3    be difficult, and more precise exposure metrics may be needed. The authors suggested that
 4    personal-ambient relationships are greatly dependent on ambient conditions (e.g., season and
 5    meteorology) and behavior (e.g., use of windows). However, further factors such as building
 6    design will also be extremely important, further exposure assessment work, particularly in
 7    different geographic and climatic zones, is needed.
 8          During both summer and winter in Baltimore (Sarnat et al., 2001), ambient NO2 was
 9    significantly associated with personal PM2.5 (slope = 0.42, intercept = 12.38, and n = 225 during
10    the summer; and slope = 0.24, intercept = 13.16, and n = 487 during the winter). Also significant
11    relationships held for ambient NO2 and personal exposures to PM2 5 of ambient origin. Ambient
12    NO2 was also significantly associated with personal EC (slope = 0.05 and p = 0.0001), as an
13    indicator of mobile source pollution. In conclusion, the authors suggested that ambient gases
14    were acting as surrogates for personal PM2.s exposure instead of confounding effects of personal
15    PM25 exposure.
16          Vinzents et al. (2005) found that ambient temperature and NO2 concentrations at one of
17    the street stations were the only significant predictors of ultra fine particle exposure during
18    bicycling in traffic (R2 = 0.74).  Kim et al. (2006) also reported correlations between personal
19    exposure and ambient measurements across pollutants.  The median, mean, and standard
20    deviation of the correlation between ambient NO2 and personal PM2 5 were 0.24, 0.29, and 0.33
21    respectively; and 0.26, 0.22, and 0.32 respectively for the correlation between ambient NO2 and
22    personal CO.
23          Studies above shows that ambient NO2 is moderately correlated with personal  EC and
24    ultrafme particle exposures, but only weakly to moderately correlated with personal PM2 5 mass
25    and sulfate exposures. Since ambient NO2 concentrations has been shown to be significant
26    proxy for corresponding personal NO2 exposures, these findings suggest that ambient NO2 may
27    be acting as a proxy not only for its own exposures but also to exposures to EC and ultrafme
28    particles.  As a result, it may not be possible to separate the health effects  of from those  of other
29    pollutants, especially from the same source.
30          In the analysis of the confounding effect of exposure, we are limited by the lack of key
31    data:  (1) multipollutant exposure  studies were rarely conducted and even fewer studies reported

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 1   the cross-level (ambient and personal exposure) and cross-pollutant correlations; (2) most studies
 2   focus on a several copollutants (PM and its components, CO, 63, and some VOCs) with little
 3   data available for other possibly important copollutants; (3) the impact of indoor and personal
 4   sources on the possibility of confounding has not yet been examined; and (4) the impact of
 5   measurement uncertainties, which can be large as mentioned in Section AX3.4.1, on
 6   confounding needs to be examined. Finally, the analysis shown above in the exposure
 7   assessment should be integrated with other analysis in other parts of the risk assessment.
 8
 9
10   AX3.7     A FRAMEWORK FOR MODELING HUMAN EXPOSURES TO
11               NO2 AND RELATED PHOTOCHEMICAL AIR POLLUTANTS
12
13   AX3.7.1    Introduction: Concepts, Terminology, and Overall Summary
14          Predictive (or prognostic) exposure modeling studies1,  specifically focusing on NO2,
15   could not be identified in the literature, though, often, statistical (diagnostic) analyses have been
16   reported using data obtained in various field exposure studies (see Section AX3.5.1). However,
17   existing prognostic modeling systems for the assessment of inhalation exposures can in principle
18   be directly applied to, or adapted for, NO2 studies; specifically, such systems include APEX,
19   SHEDS, and MENTOR-1 A, to be discussed in the following sections. Nevertheless, it should be
20   mentioned that such applications will be constrained by data limitations,  such as the degree of
21   ambient concentration characterization (e.g., concentrations at  the local level) and quantitative
22   information on indoor sources and sinks.
23          Predictive models of human exposure to ambient air pollutants such as NO2 can be
24   classified and differentiated based upon a variety of attributes.  For example, exposure models
25   can be classified as:
26          •      models of potential (typically maximum) outdoor exposure versus models of
27                 actual exposures (the latter including locally modified microenvironmental
28                 exposures, both outdoor and indoor),
29          •      Population Based Exposure Models (PBEM) versus Individual Based Exposure
30                 Models (IBEM),
      1 i.e. assessments that start from emissions and demographic information and explicitly consider the physical and
       chemical processes of environmental and microenvironmental transport and fate, in conjunction with human
       activities, to estimate inhalation intake and uptake.

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 1           •      deterministic versus probabilistic (or statistical) exposure models,
 2           •      observation-driven versus mechanistic air quality models (see Section AX3.7.3
 3                 for discussions about the construction, uses and limitations of this class of
 4                 mathematical models.
 5           Some points should be made regarding terminology and essential concepts in exposure
 6    modeling, before proceeding to the overview of specific developments reported in the current
 7    research literature:
 8           First, it must be understood that there is significant variation in the definitions of many of
 9    the terms used in the exposure modeling literature; indeed, the science of exposure modeling is a
10    rapidly evolving field and the development of a standard and commonly accepted terminology is
11    an ongoing process (see, e.g., WHO, 2004).
12           Second,  it should also be mentioned that, very often, procedures that are called exposure
13    modeling, exposure estimation, etc. in the scientific literature, may in fact refer to only a sub-set
14    of the complete  set of steps or components required for a comprehensive exposure  assessment.
15    For example, certain self-identified exposure modeling studies focus solely on refining the sub-
16    regional or local spatio-temporal dynamics of pollutant concentrations (starting from raw data
17    representing monitor observations or regional grid-based model estimates).  Though not
18    exposure studies per se, such efforts have value and are included in the discussion of the next
19    sub-section, as they provide potentially useful tools that can be used in a complete exposure
20    assessment.  On the other hand, formulations that are self-identified as exposure models but
21    actually focus only on  ambient air quality predictions, such as chemistry-transport models, are
22    not included in the discussion that follows.
23           Third, the process of modeling human exposures to photochemical pollutants
24    (traditionally focused on ozone) is very often identified explicitly with population-based
25    modeling, while models describing the specific mechanisms affecting the exposure of an actual
26    individual (at specific locations) to an air contaminant (or to a group of co-occurring gas and/or
27    aerosol phase pollutants) are usually associated with studies focusing specifically on indoor air
28    chemistry modeling.
29           Finally,  fourth, the concept of microenvironments, introduced in earlier sections of this
30    document, should be clarified further, as it is critical in developing procedures for exposure
31    modeling. In the past,  microenvironments have typically been defined as individual or aggregate

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 1    locations (and sometimes even as activities taking place within a location) where a homogeneous
 2    concentration of the pollutant is encountered. Thus a microenvironment has often been
 3    identified with an ideal (i.e. perfectly mixed) compartment of classical compartmental modeling.
 4    More recent and general definitions view the microenvironment as a control volume, either
 5    indoors or outdoors, that can be fully characterized by a set of either mechanistic or
 6    phenomenological governing equations, when appropriate parameters are available, given
 7    necessary initial and boundary conditions.  The boundary conditions typically would reflect
 8    interactions with ambient air and with other microenvironments. The parameterizations of the
 9    governing equations generally include the information on attributes of sources and sinks within
10    each microenvironment. This type of general definition allows for the concentration within a
11    microenvironment to be non-homogeneous (non-uniform), provided its spatial profile and
12    mixing properties can be fully predicted or characterized. By adopting this definition, the
13    number of microenvironments used in a study is kept manageable, but variability in
14    concentrations in each of the microenvironments can still be taken into account.
15    Microenvironments typically used to determine exposure include indoor residential
16    microenvironments, other indoor locations (typically occupational microenvironments), outdoors
17    near roadways, other outdoor locations, and in-vehicles. Outdoor locations near roadways are
18    segregated from other outdoor locations (and can be further classified into street canyons,
19    vicinities of intersections, etc.) because emissions from automobiles alter local concentrations
20    significantly  compared to background outdoor levels.  Indoor residential microenvironments
21    (kitchen, bedroom, living room, etc. or aggregate home microenvironment) are typically
22    separated from other indoor locations because of the time spent there and potential differences
23    between the residential environment and the work/public environment.
24          Once the actual individual and relevant activities and locations (for Individual Based
25    Modeling), or the sample population and associated spatial (geographical) domain (for
26    Population Based Modeling) have been defined along with the temporal framework of the
27    analysis (time period and resolution), the comprehensive modeling of individual/population
28    exposure to NO2 (and related pollutants) will in general require seven steps (or components, as
29    some of them do not have to be performed in sequence) that are listed below. This list represents
30    a composite based on  approaches and frameworks described in the literature over the last twenty -
31    five years (Ott, 1982;  Ott, 1985; Lioy, 1990; U.S. Environmental Protection Agency, 1992;

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 1    Georgopoulos and Lioy, 1994; U.S. Environmental Protection Agency, 1997; Buck et al., 2003;

 2    Price et al., 2003; Georgopoulos et al., 2005; WHO, 2005; U.S. Environmental Protection

 3    Agency, 2006a; Georgopoulos and Lioy, 2006) as well on the structure of various inhalation

 4    exposure models (NEM/pNEM, HAPEM, SHEDS, REHEX, EDMAS, MENTOR, ORAMUS,

 5    APEX, AIRPEX, AIRQUIS, etc., to be discussed in the following section) that have been used in

 6    the past or in current studies to specifically assess inhalation exposures.  Figure AX3.23, adapted

 7    from Georgopoulos et al. (2005), schematically depicts the sequence of steps involved that are

 8    summarized here (and further discussed in the following sub-sections).
 9
10          1.     Estimation of the background or ambient levels of both NO2 and related
11                 photochemical pollutants. This is done through either (or a combination of):
12
13                        a.      multivariate spatio-temporal analysis of fixed monitor data, or
14                        b.      emissions-based, photochemical, air quality modeling (typically
15                        with a regional, grid-based model such as Models-3/CMAQ or CAMx)
16                        applied in a coarse resolution mode.
17
18          2.     Estimation of local outdoor pollutant levels of both NO2 and related
19                 photochemical pollutants. These levels could typically characterize the ambient
20                 air of either an administrative unit (such as a census tract, a municipality, a
21                 county, etc.) or a conveniently defined grid cell of an urban scale air quality
22                 model. Again, this may involve either (or a combination of):
23
24                        a.      spatio-temporal statistical analysis of monitor data, or
25                        b.      application of an urban multi-scale, grid based  model (such as
26                        CMAQ or CAMx) at its highest resolution (typically around 2-4 km), or
27                        c.      correction of the estimates of the regional model using some
28                        scheme that adjusts for observations and/or for subgrid chemistry and
29                        mixing processes.
30
31          3.     Characterization of relevant attributes of the individuals or populations under
32                 study (residence and work locations,  occupation, housing data, income, education,
33                 age, gender, race, weight, and other physiological characteristics). For Population
34                 Based Exposure Modeling (PBEM) one can either:
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                 i,a. imissions: NEI (NET, NTI), State; Processing with SMOKE,
                   EMS-HAP, MOBILE/MOVES, NONROAO, FAAED, BEIS, etc.
                 i.b, Meteorole»: NWS, NCOC; Modeling MMS, RAMS, CAtMET
                 I.e. Land Use/land Cover, Topography: NLDC (USGS), etc.
                              il.a. Emissions: EMS-HAP
                              tLb, Local Meteorology - Local
                                 Effects: RAMS, FLUENT
;, Estimate background
. 9 levels of air pollutants
through
a. multivartate spatio-
temporal analysis of
monitor data
1b emisstons-tasad air »
quality mothflng
(with regional,
grid-based models: '
Models-3/ CMAQ, CAMx ]
and R1MSAD)

'•v Develop datalsase of
t,r individual subjects
\ attributes {residence 8t
j work location, housing
i characteristics, age,
j gender, race, income, etc.) >_
""l a. osllect study-specific
information
E>. supplement with
available relevant local,
I regional, and national
demographic
] information
f:
/' Study-specific survey
} (also OS Census,
I US Housing Survey)
- , Estimate local outdoor
-~ pollutant levels that
characterize tfte amiitent air of
! an administrative unit {such as
i census tract) or a conveniently
1 defined grid through
ti a. sp.stiotempoi ,ii statistical
analysis of monitor data
b. application of urban scale
model at tuft* resolution
c. swb§rid (e.§. pl«me-in-§rfd)
m0«l@fir)g
d. data/m@del assimilation
; ;,'; estimate icveJs and
J temporal profiles of
!»QiMit3nts i^ various
microenvironnientss (streets,
residences, offices, restaurants,
vehicles, etc.) through
—*• ». regression of ottservational
data
b. simple linear mass balance
c lymped (nonlin^sr) p€
§as/aer&soi chemistry models
d. combit^od chemistry St CF0
(DNS, IES, RAMS) motfels
^r • $
1 -f Be¥elop acthrily event
1 '" " |or exposure ©vent)
sequences for eaclt individual
! of the study for the exposure
j period
.] a. collect stud^'Sp^'fc
I information
l b. supplement with other
" available dat«i
I c. organize time-actwity
( database in format
i compatible with CHAD
i
,;• Calculate appropriate
' o inhalation rales for th«
members of the sample
population, combining the
phy$k»t®giol attriliut^s of the
W study subjects and the
activities pursued dyHng the
individual exposure events
j
1
'. i^'iJi:'^., 	 JLL: "i::
f ' Study-specific suwey S ICRI3 apd Other
(or default front f l>hystologiGil & METS
1 CHAD, NHAPS) i | Oatabases


^
' 1

Calculate ' ^ Hiolggieaily
exposures/ <" tased ,
intakes target tissue :
j dose modeling i
i
t »
_J


      Figure AX3.23.
Schematic description of a general framework identifying the
processes (steps or components) involved in assessing inhalation
exposures and doses for individuals and populations. In general
terms, existing comprehensive exposure modeling systems such as
SHEDS, APEX, and MENTOR-1A follow this framework.
      Source: Figure adapted with modifications from Georgopoulos et al. (2005).
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
a.      select a fixed-size sample population of virtual individuals in a
way that statistically reproduces essential demographics (age, gender,
race, occupation, income, education) of the administrative population unit
used in the assessment (e.g., a sample of 500 people is typically used to
represent the demographics of a given census tract, whereas a sample of
about 10,000 may be needed to represent the demographics of a county),
or
b.      divide the population-of interest into a set of cohorts representing
selected subpopulations where the cohort is defined by characteristics
known to influence exposure.
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 1          4.     Development of activity event (or exposure event) sequences for each member of
 2                 the sample population (actual or virtual) or for each cohort for the exposure
 3                 period. This could utilize:
 4
 5                        a.     study-specific information, if available
 6                        b.     existing databases based on composites of questionnaire
 7                        information from past studies
 8                        c.     time-activity databases, typically in a format compatible with U.S.
 9                        Environmental Protection Agency's Consolidated Human Activity
10                        Database (CHAD - McCurdy et al., 2000)
11
12          5.     Estimation of levels and temporal profiles of both NO2 and related photochemical
13                 pollutants in various outdoor and indoor microenvironments such as street
14                 canyons, roadway intersections, parks, residences, offices, restaurants, vehicles,
15                 etc.  This is done through either:
16
17                        a.     linear regression of available observational data sets,
18                        b.     simple mass balance models (with linear transformation and sinks)
19                        over the volume (or a portion of the volume) of the microenvironment,
20                        c.     lumped (nonlinear) gas or gas/aerosol chemistry models, or
21                        d.     detailed combined chemistry  and Computational Fluid Dynamics
22                        modeling.
23
24          6.     Calculation of appropriate inhalation rates for the members of the sample
25                 population, combining the physiological attributes of the (actual or virtual) study
26                 subjects and the activities pursued during the individual exposure events.
27
28          7.     Calculation of target tissue dose through biologically based modeling estimation
29                 (specifically, respiratory dosimetry modeling in the case of NO2 and related
30                 reactive photochemical pollutants) if sufficient information is available.
31
32          Implementation of the above framework for comprehensive exposure modeling has

33   benefited significantly from recent advances and expanded  availability of computational

34   technologies such as Relational Database Management Systems (RDBMS) and Geographic

35   Information Systems (GIS) (Purushothaman and Georgopoulos, 1997, 1999a,b; Georgopoulos
36   et al., 2005).
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 1          In fact, only relatively recently comprehensive, predictive, inhalation exposure modeling
 2    studies for ozone, PM, and various air toxics, have attempted to address/incorporate all the
 3    components of the general framework described here. In practice, the majority of past exposure
 4    modeling studies have either incorporated only subsets of these components or treated some of
 5    them in a simplified manner, often focusing on the importance of specific factors affecting
 6    exposure. Of course, depending on the objective of a particular modeling study, implementation
 7    of only a limited number of steps may be necessary.  For example, in a regulatory setting, when
 8    comparing the relative effectiveness of emission control strategies, the focus can be on expected
 9    changes in ambient levels (corresponding to those observed at NAAQS monitors) in relation to
10    the density of nearby populations.  The outdoor levels of pollutants, in conjunction  with basic
11    demographic information, can thus be used to calculate upper bounds of population exposures
12    associated with ambient air (as opposed to total exposures that would include contributions from
13    indoor sources) useful in comparing alternative control strategies.  Though the metrics derived
14    would not be quantitative indicators of actual human exposures, they can serve as surrogates of
15    population exposures associated with outdoor air, and thus aid  in regulatory decision making
16    concerning pollutant standards and in studying the efficacy of emission control strategies. This
17    approach  has been used in studies performing comparative evaluations of regional and local
18    emissions reduction strategies in the Eastern U.S (e.g., Purushothaman and Georgopoulos, 1997;
19    Georgopoulos et al., 1997a; Foley et al., 2003).
20
21    AX3.7.2   Population Exposure Models:  Their Evolution and Current Status
22          Existing comprehensive inhalation exposure models consider the trajectories of
23    individual human subjects (actual or virtual), or of appropriately defined cohorts, in space and
24    time as sequences of exposure events. In these sequences each event is defined by time, a
25    geographic location, a microenvironment, and the activity of the subject.  US Environmental
26    Protection Agency offices (OAQPS and NERL) have supported the most comprehensive efforts
27    in developing models implementing this general concept (see, e.g., Johnson, 2002), and these
28    efforts have resulted in the NEM/pNEM (National Exposure Model and Probabilistic National
29    Exposure Model - Whitfield et al., 1997), HAPEM (Hazardous Air Pollutant Exposure Model -
30    Rosenbaum, 2005), SHEDS (Simulation of Human Exposure and Dose System - Burke et al.,
31    2001), APEX (Air Pollutants Exposure model - US Environmental Protection Agency, 2006b,c),
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 1    and MENTOR (Modeling Environment for Total Risk studies - Georgopoulos et al., 2005;
 2    Georgopoulos and Lioy, 2006) families of models. European efforts have produced some
 3    formulations with similar general attributes as the above U.S. models but, generally, involving
 4    simplifications in some of their components.  Examples of European models addressing
 5    exposures to photochemical oxidants (specifically ozone) include the AirPEx (Air Pollution
 6    Exposure) model (Freijer et al., 1998), which basically replicates the pNEM approach and has
 7    been applied to the Netherlands,  and the AirQUIS (Air Quality Information System) model
 8    (Clench-Aas et al., 1999).
 9          The NEM/pNEM, SHEDS, APEX, and MENTOR-1A (MENTOR for One-Atmosphere
10    studies) families of models provide exposure estimates defined by concentration and breathing
11    rate for each individual exposure event, and then average these estimates over periods typically
12    ranging from one h to one year.  These models allow simulation of certain aspects of the
13    variability and uncertainty in the principal factors affecting exposure.  An alternative approach is
14    taken by the HAPEM family of models that typically provide annual average exposure estimates
15    based on the quantity of time spent per year in each combination of geographic locations and
16    microenvironments. The NEM,  SHEDS, APEX, and MENTOR-type models are therefore
17    expected to be more appropriate  for pollutants with complex chemistry such as NO2, and could
18    provide useful information for enhancing related health assessments.
19
20    More specifically, regarding the  consideration of population demographics and activity patterns:
21          1.     pNEM divides the population of interest into representative cohorts based on the
22                combinations of demographic characteristics (age, gender, and employment),
23                home/work district,  residential cooking fuel and replicate number, and then
24                assigns activity diary record from CHAD (Consolidated Human Activities
25                Database) to each cohort according to demographic characteristic, season, day-
26                type (weekday/weekend) and temperature.
27          2.     HAPEM6 divides the population of interest into demographic groups based on
28                age, gender and race, and then for each demographic group/day-type
29                (weekday/weekend) combination, select multiple activity patterns randomly (with
30                replacement) from CHAD and combine them to find the averaged annual time
31                allocations for group members in each census tract for different day types.
32          3.     SHEDS, APEX, and MENTOR-1 A generate population demographic files, which
33                contain a user-defined number of person records for each census tract of the
34                population based on proportions of characteristic variables (age, gender,
35                employment, and housing) obtained from the population of interest, and then
36                assign a matching activity diary record from CHAD to each individual record of

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 1                 the population based on the characteristic variables. It should be mentioned that,
 2                 in the formulations of these models, workers may commute from one census tract
 3                 to another census tract for work. So, with the specification of commuting
 4                 patterns, the variation of exposure concentrations due to commuting between
 5                 different census tracts can be captured.
 6
 7          The essential attributes of the pNEM, HAPEM, APEX, SHEDS, and MENTOR-1A
 8   models are summarized in Table AX3.24.
 9          The conceptual approach originated by the SHEDS models was modified and expanded
10   for use in the development of MENTOR-1 A (Modeling Environment for Total Risk - One
11   Atmosphere).  Flexibility was incorporated into this modeling system, such as the option of
12   including detailed indoor chemistry of the O3-NOX system and other relevant
13   microenvironmental processes, and providing interactive linking with CHAD for consistent
14   definition of population characteristics and activity events (Georgopoulos et al., 2005).
15          NEM/pNEM implementations  have been extensively applied to ozone studies in the
16   1980s and 1990s.  The historical evolution of the pNEM family of models of OAQPS started
17   with the introduction of the first NEM model in the  1980's (Biller et al., 1981). The first such
18   implementations of pNEM/Os in the 1980's used a regression-based relationship to estimate
19   indoor ozone concentrations from outdoor concentrations.  The second generation of pNEM/Os
20   was developed in 1992 and included a simple mass balance model  to estimate indoor ozone
21   concentrations. A report by Johnson et al. (2000) describes this version of pNEM/Os and
22   summarizes the results of an initial application of the model to 10 cities. Subsequent
23   enhancements to pNEM/Os and its input databases included revisions to the methods used to
24   estimate equivalent ventilation rates, to determine commuting patterns, and to adjust ambient
25   ozone levels to simulate attainment of proposed NAAQS. During the mid-1990's,
26   Environmental Protection Agency applied updated versions of pNEM/O3 to three different
27   population groups in selected cities: (1) the general population of urban residents,  (2) outdoor
28   workers, and (3) children who tend to  spend more time outdoors than the average child.  This
29   version of pNEM/Os used a revised probabilistic mass balance model to determine ozone
30   concentrations over one-h periods in indoor and in-vehicle microenvironments (Johnson, 2001).
31          In recent years, pNEM has been replaced by (or "evolved to") the Air Pollution Exposure
32   Model (APEX). APEX differs from earlier pNEM models in that the probabilistic features of the
33   model are incorporated into a Monte Carlo framework (Langstaff, 2007; US Environmental

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 1    Protection Agency, 2006b,c). Like SHEDS and MENTOR-1A, instead of dividing the
 2    population-of-interest into a set of cohorts, APEX generates individuals as if they were being
 3    randomly sampled from the population. APEX provides each generated individual with a
 4    demographic profile that specifies values for all parameters required by the model. The values
 5    are selected from distributions and databases that are specific to the age, gender, and other
 6    specifications stated in the demographic profile. Environmental Protection Agency has applied
 7    APEX to the study of exposures to ozone and other criteria pollutants; APEX can be modified
 8    and used for the estimation of NC>2 exposures, if required.
 9          Reconfiguration of APEX for use with NC>2 or other pollutants would require significant
10    literature review, data analysis, and modeling efforts. Necessary steps include determining
11    spatial scope and resolution of the model;  generating input files for activity data, air quality and
12    temperature data; and developing definitions for microenvironments and pollutant-
13    microenvironment modeling parameters (penetration and proximity factors, indoor source
14    emissions rates, decay rates, etc.) (ICF Consulting 2005, Decision Points for Configuring APEX
15    for Air Toxics Exposure Assessments). To take full advantage of the probablistic capabilities of
16    APEX, distributions of model input parameters should be used wherever possible.
17
18    AX3.7.3    Characterization of Ambient Concentrations of NO2 and  Related
19                Air Pollutants
20          As mentioned earlier, background  and regional outdoor concentrations of pollutants, over
21    a study domain, may be estimated either through emissions-based mechanistic modeling, through
22    ambient-data-based modeling, or through a combination of both. Emissions-based models
23    calculate the spatio-temporal fields of the pollutant concentrations using precursor emissions and
24    meteorological conditions as inputs.  The ambient-data-based models typically calculate spatial
25    or spatio-temporal distributions of the pollutant through the use of interpolation schemes, based
26    on either deterministic or stochastic models for allocating monitor station observations to the
27    nodes of a virtual regular grid covering the region of interest. The geostatistical technique of
28    kriging provides various standard procedures for generating an interpolated spatial distribution
29    for a given time, from data at a set of discrete points. Kriging approaches were evaluated by
30    Georgopoulos et al. (Georgopoulos et al.,  1997b) in relation to the calculation of local ambient
31    ozone concentrations for exposure assessment purposes, using either monitor observations or
32    regional/urban photochemical model outputs.  It was found that kriging is severely limited by the

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 1    nonstationary character of the concentration patterns of reactive pollutants; so the advantages this
 2    method has in other fields of geophysics do not apply here. The above study showed that the
 3    appropriate semivariograms had to be hour-specific, complicating the automated reapplication of
 4    any purely spatial interpolation over an extended time period.
 5          Spatio-temporal distributions of pollutant concentrations, such as ozone, PM, and various
 6    air toxics have alternatively been obtained using methods of the Spatio-Temporal Random Field
 7    (STRF) theory (Christakos and Vyas,  1998a,b). The STRF approach interpolates monitor data in
 8    both space and time simultaneously. This method can thus analyze information on temporal
 9    trends, which cannot be incorporated directly in purely spatial interpolation methods such as
10    standard kriging.  Furthermore, the  STRF method can optimize the use of data that are not
11    uniformly sampled in either space or time.  STRF was further extended within the Bayesian
12    Maximum Entropy (BME) framework and applied to ozone interpolation studies (Christakos and
13    Hristopulos,  1998; Christakos and Kolovos, 1999; Christakos, 2000). It should be noted that
14    these studies formulate an over-arching scheme for linking air quality with population dose and
15    health effects; however they are limited by the fact that they do not include any
16    microenvironmental effects.  MENTOR has incorporated STRF/BME methods as one of the
17    steps for performing a comprehensive analysis of exposure to ozone and PM (Georgopoulos
18    etal.,2005).
19          Subgrid spatial variability is a major issue with respect to characterizing local
20    concentrations of NC>2. Indeed, the fast rates of the reactions involving the O3-NOX system result
21    in significant concentration gradients in the vicinity of sources of NOX.  These gradients are not
22    resolved directly by currently operational grid photochemical air quality  simulation models
23    (PAQSMs) such as CMAQ and CAMx. However, both these models include a plume-in-grid.
24    (PinG) option (AER, 2004; Emery and Yarwood, 2005; Gillani and Godowitch, 1999; US
25    Environmental Protection Agency, 2006d) that can be used for large point NOX sources (such as
26    smokestacks). Nevertheless, PinG formulations typically will resolve gradients in upper
27    atmospheric layers and thus are not necessarily relevant to human exposure calculations, which
28    are affected by gradients caused by a multiplicity of smaller ground level or near ground level
29    combustion sources such as motor vehicles.
30          Currently PAQSMs are typically applied with horizontal resolutions of 36 km, 12 km,
31    and 4 km and a surface layer thickness that is typically of the order of 30 m.  Though

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 1    computationally it is possible to increase the resolution of these simulations, there are critical
 2    limits that reflect assumptions inherent in the governing equations for both (a) the fluid
 3    mechanical processes embodied in the meteorological models (e.g., typically MM5 and RAMS)
 4    that provide the inputs for the PAQSMs, and (b) the dispersion processes which become more
 5    complex at fine scales (see, e.g., Georgopoulos and Seinfeld, 1989) and thus cannot be described
 6    by simple formulations (such as constant dispersion coefficients) when the horizontal resolutions
 7    is 2 km or finer.
 8          Application of PAQSMs to urban domains is further complicated by urban topography,
 9    the urban heat island, etc. It  is beyond the scope, however, of the present discussion, to overview
10    the various issues relevant to urban fluid dynamics and related transport/fate processes of
11    contaminants. However, the issue of modeling subgrid atmospheric dispersion phenomena
12    within complex urban areas in a consistent manner is a very active research area. Reviews of
13    relevant issues and of available approaches for modeling urban fluid mechanics and dispersion
14    can be found in,  e.g., Fernando et al.  (2001) and Britter and Hanna (2003).
15          The issue of subgrid variability  (SGV) from the perspective of interpreting and evaluating
16    the outcomes of grid-based, multiscale, PAQSMs is discussed in Ching et al. (2006), who
17    suggest a framework that can provide for qualitative judgments  on model performance based on
18    comparing observations to the grid predictions and its SGV distribution. From the perspective of
19    Population Exposure Modeling, the most feasible/practical approach for treating subgrid
20    variability of local concentrations is probably through 1) the identification and proper
21    characterization  of an adequate number of outdoor microenvironments (potentially related to
22    different types of land use within the urban area as well  as to proximity to different types of
23    roadways) and 2) then, concentrations  in these microenvironments will have to be adjusted from
24    the corresponding local background ambient concentrations through either regression of
25    empirical data or various types of local atmospheric dispersion/transformation models.  This is
26    discussed further in the next  subsection.
27
28    AX3.7.4    Characterization of Microenvironmental Concentrations
29          Once the background and local ambient spatio-temporal concentration patterns have been
30    derived, microenvironments that can represent either outdoor or indoor  settings when individuals
31    come in contact with the contaminant of concern (e.g., NO2) must be characterized.  This process


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 1    can involve modeling of various local sources and sinks, and interrelationships between ambient
 2    and microenvironmental concentration levels. Three general approaches have been used in the
 3    past to model microenvironmental concentrations:
 4       •   Empirical (typically linear regression) fitting of data from studies relating ambient/local
 5          and microenvironmental concentration levels to develop analytical relationships.
 6       •   Parameterized mass balance modeling over, or within, the volume of the
 7          microenvironment.  This type of modeling has  ranged from very simple formulations, i.e.
 8          from models assuming ideal (homogeneous) mixing within the microenvironment (or
 9          specified portions of it) and only linear physicochemical transformations (including
10          sources and sinks), to models incorporating analytical solutions of idealized dispersion
11          formulations (such as Gaussian plumes), to models that take into account aspects of
12          complex multiphase chemical and physical interactions and nonidealities in mixing.
13       •   Detailed Computational Fluid Dynamics (CFD) modeling of the outdoor or indoor
14          microenvironment, employing either a Direct Numerical Simulation (DNS) approach, a
15          Reynolds Averaged Numerical  Simulation (RANS) approach, or a Large Eddy
16          Simulation (LES) approach, the latter typically for outdoor situations (see, e.g., Milner
17          et al., 2005; Chang and Meroney, 2003; Chang, 2006).

18          Parameterized mass balance modeling is the approach currently preferred for exposure
19    modeling for populations. As discussed earlier, the simplest microenvironmental setting
20    corresponds to a homogeneously mixed compartment,  in contact with possibly both
21    outdoor/local environments as well as other microenvironments. The air quality of this idealized
22    microenvironment is affected mainly by the following processes:
23          a.     Transport processes: These can include advection/convection and dispersion that
24                 are affected by local processes and obstacles such as vehicle induced turbulence,
25                 street canyons, building structures, etc.
26          b.     Sources and sinks: These can include local outdoor emissions, indoor emissions,
27                 surface deposition, etc.
28          c.     Transformation processes:  These can include local outdoor as well as indoor gas
29                 and aerosol phase chemistry, such as formation of secondary organic and
30                 inorganic aerosols.
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 1          Examples of the above are discussed next, specifically for outdoor and for indoor
 2    microenvironments.
 3
 4    AX3.7.4.1   Characterization of Outdoor Microenvironments
 5          Empirical regression analyses have been used in some studies to relate specific outdoor
 6    locations - that can be interpreted as generalized types of exposure microenvironments - to
 7    spatial variability of NO2 concentrations.  For example, Gilbert et al. (2005) in May 2003
 8    measured NO2 for 14 consecutive days at 67 sites across Montreal, Canada. Concentrations
 9    ranged from 4.9 to 21.2 ppb (median 11.8 ppb), and they used linear regression analysis to assess
10    the association between logarithmic values of NO2 concentrations and land-use variables via a
11    geographic information system. In univariate analyses, NC>2 was negatively associated with the
12    area of open space and positively associated with traffic count on nearest highway, the length of
13    highways within any radius from 100 to 750 m, the length of major roads within 750 m, and
14    population density within 2000 m.  Industrial land-use and the length of minor roads showed no
15    association with NC>2.  In multiple regression analyses, distance from the nearest highway, traffic
16    count on the nearest highway, length of highways and major roads within 100 m, and population
17    density showed significant associations with NC>2.  The authors of that study point out the value
18    of using land-use regression modeling to assign exposures in large-scale epidemological studies.
19    Similar analyses have been performed in a predictive setting by Sahsuvaroglu et al.  (2006) for
20    Hamilton, Ontario, Canada.
21          The category of parameterized mass balance models for outdoor microenvironments
22    includes various local roadway, intersection, and street canyon models. For example, Fraigneau
23    et al. (1995) developed a simple model to account for fast nitrogen oxide - ozone
24    reaction/dispersion in the vicinity of a motorway. Venegas and Mazzeo (2004) applied a
25    combination of simple point and area source analytical plume models to characterize NO2
26    concentration patterns in Buenos Aires, Argentina, which they used for a simplified (potential)
27    population exposure study.  ROADWAY-2 (Rao, 2002), is another near-highway pollutant
28    dispersion model that incorporates vehicle wake parameterizations derived from canopy flow
29    theory and wind tunnel measurements. The atmospheric velocity and turbulence fields are
30    adjusted to account for velocity-deficit and turbulence production in vehicle wakes and a
31    turbulent kinetic energy closure model of the atmospheric boundary layer is used to derive the
32    mean velocity, temperature, and turbulence profiles from input meteorological data.

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 1          In parameterized street canyon models, typically, concentrations of exhaust gases are
 2    calculated using a combination of a plume model for the direct contribution and a box model for
 3    the recirculating part of the pollutants in the street. Parameterization of flow and dispersion
 4    conditions in these models is usually deduced from analysis of experimental data and model tests
 5    that considered different street configurations and various meteorological conditions.
 6    An example of a current model that belongs in the parameterized mass balance category is the
 7    Danish Operational Street Pollution Model (OSPM) (Berkowicz, 2002), which updates earlier
 8    formulations of street canyon models such as STREET of Johnson et al. (1973) and CPBM
 9    (Canyon Plume-Box Model) of Yamartino and Weigand (1986).  A variation of this simple
10    approach is the model of Proyou et al. (1998), which uses a three-layer photochemical box model
11    to represent a street canyon.
12          A variety of CFD based street canyon models have been developed in recent years (see,
13    e.g., the series of International Conferences on Harmonization - http://www.harmo.org),
14    employing various alternatives  for closure of the turbulent transport equations. A review and
15    intercomparison of five of these models (CHENSI, CHENSI-2, MIMO, MISKAM, TASCflow)
16    vis-a-vis field data from a street canyon in Hannover, Germany can be found in the articles by
17    Sahm et al. (2002) and by Ketzel  et al. (2002).
18          These complex localized models could be useful for improving population exposure
19    model estimates by calculating  pollutant concentrations at the microenvironmental  level. Lack
20    of input parameter data and parameter variation  across the modeling domain (spatial and
21    temporal) contributes to uncertainty in microenvironmental concentrations calculated by exposre
22    models.  In such cases,  parameterized mass balance models could provide outdoor concentration
23    values for estimating exposure. If infiltration factors are known, these concentrations could also
24    be used to estimate indoor exposures.
25
26    AX3.7.4.2   Characterization of Indoor Microenvironments
27          Numerous indoor air quality modeling studies have been reported in the literature;
28    however, depending on the modeling scenario, only few of them address (and typically only a
29    limited subset of) physical and  chemical processes that affect photochemical oxidants indoors
30    (Nazaroff and Cass, 1986; Hayes, 1989, 1991; Freijer and Bloemen, 2000).
31          It is beyond the  scope of the present discussion to review in detail the current status of
32    indoor air modeling. Existing indoor air concentration models indeed are available as a wide

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 1    range of (a) empirical regression relationships, (b) parameterized mass balance models (that can
 2    be either single-zone—that is, single well-mixed room—or multi-zone models), and (c) CFD
 3    formulations. Recent overviews of this area can be found in Milner et al. (2005), who focus, in
 4    particular, on the issue of entrainment from outdoor sources, and in Teshome and Haghighat,
 5    (2004), who focus on different formulations of zonal models and on how they compare with
 6    more complex CFD models.
 7          Few indoor air models have considered detailed nonlinear chemistry, which, however,
 8    can have a significant effect on the indoor air quality, especially in the presence of strong indoor
 9    sources (e.g., gas stores and kerosene heaters,  in the case of NCh). Indeed, the need for more
10    comprehensive models that can take into account the complex, multiphase processes that affect
11    indoor concentrations of interacting gas phase pollutants and particulate matter has been
12    recognized and a number of formulations have appeared in recent years.  For example, the
13    Exposure and Dose Modeling and Analysis System (EDMAS) (Georgopoulos et al., 1997c)
14    included an indoor model with detailed gas-phase atmospheric chemistry to estimate indoor
15    concentrations resulting from penetration and  reaction of ambient pollutants.  This indoor model
16    was dynamically coupled with (a) the outdoor photochemical air quality models UAM-IV and
17    UAM-V, which provided the gas-phase composition of influent air; and (b) with a
18    physiologically based uptake and dosimetry model. Subsequent work (Isukapalli et al.,  1999)
19    expanded the approach of the EDMAS model  to incorporate alternative representations  of gas-
20    phase chemistry  as well as multiphase photochemistry and gas/aerosol interactions.  The
21    microenvironmental model corresponding to this more general formulation is mathematically
22    represented by the following equation, when an assumption of uniform mixing is used for each
23    component (e.g., individual room) of the indoor environment.  Sarwar et al. (2001) presented a
24    more comprehensive modeling study of the gas phase aspects of ozone indoor chemistry
25    focusing on the impact of different factors (such as outdoor ozone, indoor emissions, ventilation
26    rates, etc.) on the levels of indoor hydroxyl  radicals (OH), which in turn are expected to control
27    the rate of formation of secondary toxicants indoors.
             vt
28               "'     /-/          j=l               .1=1                             (AX3-19)
29   where,

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 1    Pi = volume of compartment (m3)
 2
 3    Q = concentration of species in compartment (mol/m3)
 4
 5    Xij = mass transfer coefficient from compartment (m/h)
 6
 7    ay = interfacial air exchange area between compartments (m2)
 8
 9    QJ = concentration in compartment i in equilibrium with concentration in j (mol/m3)
10
11    <2ij = volumetric flow rate from compartment i to j (m3/h)
12
13    R[ = rate of formation of species in compartment i (gmol/h)
14
15    and,
                       c     _ c      _ c
                  e  ( °i,emis   °i,depos   ^i.candens                          for gases
                   i  1C       C      4-*?      4-S*        4- ^     4- ?
jg                    ^i,emis ~ "i.depos   ^i.resusp "r °i,condens  ^i.nucl ~r **i,coagfor PM
17          More recent work (S0rensen and Weschler, 2002) has coupled CFD calculations with
1 8    gas-phase atmospheric chemistry mechanisms to account for the impact of nonideal flow mixing
19    (and associated concentration gradients) within a room on the indoor spatial distribution of ozone
20    and other secondary pollutants.  This work has identified potential limitations associated with the
21    assumption of uniform mixing in indoor microenvironments when calculating personal
22    exposures.
23          A recent indoor air model that specifically  focuses on NC>2 (along with CO, PMio, and
24    PM2.5 is INDAIR (Dimitroulopoulou et al., 2006).  The INDAIR model considers three
25    interconnected residential microenvironments: kitchen, lounge, and bedroom.  Removal
26    processes are lumped together and quantified via an apparent deposition velocity. Specifically, a
27    loss rate of 0.99 ± 0.19 IT1 (Yamanaka, 1984), is used in this model  corresponding to a mean
28    deposition velocity of 1.2 x 10~4 m s ~l. The sources of NO2 considered in INDAIR are from gas
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 1    stove cooking and from cigarette smoking, but only the former contributes significantly to indoor
 2    NO2 levels, based on available model parameterizations.
 3          Estimation of NC>2 emission rates from gas cooking utilized the following empirical
 4    information: (a) NOX emission rate equal to 0.125 g kWlT1 (Wooders, 1994); (b) an assumption
 5    that NC>2 represents 25% of the total NOX emissions and (c) gas consumption per household in
 6    cooking equal to 5-7 kWh day"1, assuming 1 h cooking per day.  By multiplying the estimates in
 7    (a), (b), and (c) together, NC>2 gas cooking  emission rates were calculated to be in the range 0.16
 8    to 0.22 g h'1, with a uniform distribution.
 9          In a range of simulations performed with INDAIR for houses in the UK, it was found that
10    the predicted maximum 1-h mean concentrations in the kitchen were increased, compared to no-
11    source simulations, by a factor of 10 for NO2 (30 for PMi0 and 15 for PM2.5) and were higher in
12    winter than in summer. Cooking activity in the kitchen resulted in significantly elevated 24 h
13    mean concentrations of NC>2, PMio, and PM2.5 in the lounge, as well as the kitchen, while there
14    was a  relatively small effect in the bedroom, which was not connected directly to the kitchen in
15    the model structure (i.e., the direct internal air exchange rate was zero).
16          A very wide range of predictions was derived from the  INDAIR simulations. The 95th
17    percentile concentrations were typically 50% higher than mean concentrations during periods of
18    average concentration, and up to 100% higher than mean concentrations during concentration
19    peaks, which were associated with cooking emissions.  There was approximately a factor of
20    2 variation in concentrations, and all modeled concentrations were below those outdoors.  The
21    effect  of cooking was to shift the distribution to the right, but the degree of variation was not
22    greatly increased.  This may reflect the fact that for the fixed emission scenarios that were used,
23    the additional variation in emission rates was small compared to that of other factors such as
24    deposition rate and air exchange rate.  In this scenario, modeled concentrations in the lounge all
25    remained below those outdoors, but a proportion of kitchens (16%) had modeled values above
26    the outdoor concentration.  For the gas-cooking scenario, indoor/outdoor ratios for NC>2 ranged
27    from 0.5 to 0.8 for the bedroom, 0.7 to 1.6  for the lounge and 0.9 to 3.6 for the kitchen.
28    According to Dimitrolopoulou et al. (2006), these results were  broadly consistent with
29    indoor/outdoor ratios reported for the UK.  Modeled peak concentrations associated with gas
30    cooking, of about 300 ppb in the kitchen and 100 ppb in the lounge, were  also consistent with
31    results from UK studies.

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 1    AX3.7.4.3   Characterization of Activity Events
 2          An important development in inhalation exposure modeling has been the consolidation of
 3    existing information on activity event sequences in the Consolidated Human Activity Database
 4    (CHAD) (McCurdy, 2000; McCurdy et al., 2000). Indeed, most recent exposure models are
 5    designed (or have been re-designed) to obtain such information from CHAD which incorporates
 6    24-h time/activity data developed from numerous surveys. The surveys include probability-
 7    based recall studies conducted by Environmental Protection Agency and the California Air
 8    Resources Board, as well as real-time diary  studies conducted in individual U.S. metropolitan
 9    areas using both probability-based and volunteer subject panels. All ages of both genders are
10    represented in CHAD. The data for each subject consist of one or more days of sequential
11    activities, in which each activity is defined by start time, duration, activity type (140 categories),
12    and microenvironment classification (110 categories).  Activities vary from one min to one h in
13    duration, with longer activities being subdivided into clock-hour durations to facilitate exposure
14    modeling.  A distribution of values for the ratio of oxygen uptake rate to body mass (referred to
15    as metabolic equivalents or METs) is provided for each activity type listed in CHAD.  The forms
16    and parameters of these distributions were determined through an extensive review of the
17    exercise and nutrition literature.  The primary source of distributional data was Ainsworth et al.
18    (1993), a compendium developed specifically to facilitate the coding of physical activities and to
19    promote comparability across studies.
20
21    AX3.7.4.4   Characterization of Inhalation Intake and Uptake
22          Use of the information in CHAD provides a rational way for incorporating realistic
23    intakes into exposure models by linking inhalation rates to activity information. As mentioned
24    earlier, each cohort of the  pNEM-type models, or each (virtual or actual) individual of the
25    SHEDS, MENTOR, APEX, and HAPEM4 models, is assigned an exposure  event sequence
26    derived from activity diary data. Each exposure event is typically defined by a start time, a
27    duration, assignments to a geographic location and microenvironment, and an indication of
28    activity level.  The most recent versions of the above models have defined activity levels using
29    the activity classification coding scheme incorporated into CHAD. A probabilistic module
30    within these models converts the activity classification code of each exposure event to an energy
31    expenditure rate, which in turn is converted  into an estimate of oxygen uptake rate. The oxygen
32    uptake rate is then converted into an estimate of total ventilation rate (VE), expressed in liters

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 1    min"1. Johnson (2001) reviewed briefly the physiological principles incorporated into the
 2    algorithms used in pNEM to convert each activity classification code to an oxygen uptake rate
 3    and describes the additional steps required to convert oxygen uptake to VE.
 4          McCurdy (1997a,b, 2000) has recommended that the ventilation rate should be estimated
 5    as a function of energy expenditure rate. The energy expended by an individual during a
 6    particular activity can be expressed as EE = (MET)(RMR) in which EE is the average energy
 7    expenditure rate (kcal min"1) during the activity and RMR is the resting metabolic rate of the
 8    individual expressed in terms of number of energy units expended per unit of time (kcal min"1).
 9    MET (the metabolic equivalent of tasks) is a ratio specific to the activity and is dimensionless. If
10    RMR is specified for an individual, then the above equation requires only an activity-specific
11    estimate of MET to produce an estimate of the energy expenditure rate for a given activity.
12    McCurdy et al. (2000) developed distributions of MET for the activity classifications appearing
13    in the CHAD database.
14          Finally, in order to relate intake to dose delivered to the lungs, it is important to take into
15    account the processes affecting uptake following inhalation intake of NC>2, in a biologically
16    based dosimetry modeling framework. As a reactive gas, NO2 participates in transformation
17    reactions in the lung epithelial lining fluid, and products of these reactions are thought to be
18    responsible for toxic effects (Postlethwait et., 1991), although kinetic modeling of these reactions
19    has not been performed.  Dosimetry models indicate that deposition varies spatially within the
20    lung and that this spatial variation is dependent on ventilation rate (Miller et al., 1982; Overton
21    and Graham, 1995).  Controlled exposure studies found that fractional uptake of NO2 increases
22    with exercises and ventilation rate (e.g., Bauer et al., 1986), making activities with high MET
23    values important for quantifying total NC>2 exposure. Further discussion of NC>2 dosimetry
24    modeling is provided in Section 4.2.
25
26    AX3.7.5   Concluding Comments
27          An issue that should be mentioned in closing is that of evaluating comprehensive
28    prognostic exposure modeling studies, for either individuals or populations, with field data.
29    Although databases that would be adequate for performing a comprehensive  evaluation are not
30    expected to be available any time soon, there have been a number of studies,  reviewed in earlier
31    sections of this Chapter, that can be used to start building the necessary information base.  Some
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 1    of these studies report field observations of personal, indoor, and outdoor ozone levels and have
 2    also developed simple semi-empirical personal exposure models that were parameterized using
 3    the observational data and regression techniques.
 4          In conclusion, though existing inhalation exposure modeling systems have evolved
 5    considerably in recent years, limitations of available modeling methods and data, in relation to
 6    potential NO2 studies that include the following, should be taken into account and be addressed
 7    by future research efforts:
 8       •  Ambient photochemical modeling systems are not optimized for estimating NO2 at a
 9          local scale.
10       •  Subgrid scale modeling (LES, RANS, DNS) is needed to properly characterize effects of
11          nonhomogeneous mixing (i.e., of spatial subgrid variability) on fast nonlinear chemical
12          transformations; the outcomes of this characterization then should be incorporated in
13          simpler models, appropriate for use in conjunction with exposure modeling systems.
14       •  Microenvironmental modeling efforts need to balance mechanistic detail and usability by
15          developing:
16          —     A simplified but adequate indoor chemistry mechanism for NO2 and related
17                 oxidants,
18          —     Databases of realistic distributions of indoor NO2 source magnitudes and
19                 activities,
20          —     Flexible, multi-zonal models of indoor residential and occupational
21                 microenvironments.
22          Existing prognostic modeling systems for inhalation exposure can in principle be directly
23    applied to, or adapted for, NO2 studies; APEX, SHEDS, and MENTOR-1A are candidates.
24    However, such applications would be constrained by data limitations such as ambient
25    characterization at the local scale and by lack of quantitative information for indoor sources and
26    sinks.
27
28
29    AX3.8     EXPOSURE ERROR
30          Discussions in this section focus on the errors associated with exposure assessments and,
31    in particular, with those that may be associated with using ambient NO2 as a surrogate of
32    personal NO2 exposure in epidemological time series studies. As shown in Figure AX3.24,
33    exposure error is one of the errors associated with epidemological studies linking pollutant

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     EPI
                                    Health
                          _^      Outcome

     Figure AX3.24.
Errors associated with components of the continuum from ambient
air pollution to adverse health outcome.
 1   concentrations in ambient air and human health responses. How exposure errors influence the
 2   epidemological findings depend upon the design of the epidemological study. In this section, the
 3   exposure errors will be discussed in the context of two common environmental epidemological
 4   study designs, time-series studies and chronic studies, in which central site NO2 concentrations
 5   are used as surrogates of personal exposure.
 6          In a broader sense, NO2 is an indicator of a chemical mixture, which might be the real
 7   agent(s) leading to epidemological findings.  Ambient, indoor or personal NO2 might indicate
 8   different chemical mixtures because of differences in the infiltration efficiency or chemical
 9   reactivity of other NOy species or in the composition of nearby sources. When using ambient
10   NO2 as a surrogate of personal exposure, issues of confounding and surrogate are raised.
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 1    Confounding issues have been discussed in Section AX3.6.  A brief summary of the confounding
 2    issues and a brief discussion of the surrogate issues will be provided in this section.
 3          Usually when discussing errors in the context of exposure assessments, errors resulting
 4    from limitations of analytical capabilities of monitoring instruments are lumped together with
 5    those caused by environmental factors such as spatial heterogeneity in ambient concentrations,
 6    the lack of identification of indoor and neighborhood sources etc. In certain instances these
 7    different errors may be linked.
 8          Measurements of NC>2 are subject to artifacts both at the ambient level and at the personal
 9    level. A discussion of the errors associated with ambient monitors is given in Section 2.8, and
10    one for errors associated with personal monitors is given in Section AX3.4. As noted earlier,
11    measurements of ambient NO2 are subject to variable interference caused by other NOy
12    compounds, in particular PANs,  organic nitrates, particulate nitrate and HNC>2 and HNOs. The
13    latter is taken up on inlet walls to varying degrees and likely causes variable (positive) artifacts
14    in NC>2 measurements.
15          Personal monitors are subject to interference by SC>2 and HONO and it is not clear to
16    what extent they are affected by  interference by the NOy species interfering with the ambient
17    monitors.  In addition, personal monitors generally require longer sampling times (typically  from
18    about a day to two weeks) and so will not be able to identify peak exposures occurring on time
19    scales of a few hours or less.  As noted by Pilotto et al. (1997) these exposures would have been
20    averaged out and associated health outcomes would not be properly attributed by monitors
21    requiring longer sampling times.  Often personal concentrations may either be below or not very
22    much above detection limits for the most commonly used personal samplers (see Table AX3.6).
23    Thus, associations between ambient and personal concentrations could be weakened between
24    ambient and personal concentrations of a given pollutant. In studies of multiple pollutants,
25    personal concentrations of one pollutant may be more strongly associated with ambient
26    concentrations of another pollutant if the measurements of the latter at the personal level are
27    subject to larger analytical  errors than are measurements of the former at the personal level.
28           Spatial heterogeneity in ambient concentrations helps determine how well concentrations
29    measured at ambient monitoring sites reflect exposures at the community and personal levels.
30    Correlations between different pairs of monitoring sites are not sufficient for characterizing
31    spatial variability, as there  may be significant differences in concentrations among monitoring

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 1    sites. This point has been demonstrated in Chapter 3 the latest AQCD for PM (U.S.
 2    Environmental Protection Agency, 2004) and Chapter 3 the latest AQCD for ozone and other
 3    photochemical oxidants (U.S. Environmental Protection Agency, 2006a).  As described earlier in
 4    Section AX3.2, concentrations of NC>2 are highly variable across the urban areas examined and
 5    will result in exposure characterization errors at least as significant as, if not larger, than those
 6    for Os and PM2.5. The problem is exacerbated for NO2 because of the sparseness of NOX
 7    monitors, compared to monitors for PM and O^. Thus, the use of central site monitors may be
 8    more problematic for NC>2 than for PM2.5 (e.g.).  As a result, little relation might be found
 9    between ambient central site monitors and personal exposures and/or indoor concentrations and
10    stronger associations might be found between cross pollutants at the ambient and personal levels.
11    In this case, it may be necessary to supplement existing ambient measurements to derive ambient
12    concentrations that are consistent with those of other pollutants, e.g., by the use of supplemental
13    'outdoor' monitors. Additional complexity arises if horizontal spatial gradients are large enough,
14    as might happen in going from urban to rural environments, as the lowest values measured might
15    be beneath quantification limits or even beneath detection.  Small scale horizontal variability
16    especially as found  near roads could be large.
17          As noted earlier  in Section AX3.2, variability in the vertical must be considered in
18    addition to horizontal variability.  NC>2 emitted at or near ground level exhibits strong vertical
19    gradients. Restrepo et al. (2004) found that NC>2 measured at 15 m above the surface was a
20    factor of higher than measurements of NO2 at 4 m.  Monitors placed at heights such as these will
21    be found in many inner urban areas.
22          In the framework developed by Zeger (2000) for analyzing errors in time-series
23    epidemological studies associated with exposure measurement errors, exposure errors could be
24    classified into three components:  (1) the difference between true ambient concentration and the
25    measured ambient concentration, (2) the difference between the measured ambient concentration
26    and the community  ambient exposure, and (3) the difference between the community ambient
27    exposure and the personal ambient exposure. These differences mentioned above are determined
28    by (1) the reliability of measurement techniques, (2) the spatial and temporal variation of
29    ambient NC>2 concentrations, and (3) personal activity and microenvironment characteristics.
30          In the context of chronic epidemological studies, the issue of misclassification also arises.
31    Personal exposure is composed of exposures to both ambient sources and nonambient sources.  If

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 1    total personal NO2 exposure is assumed to be responsible for the observed health outcomes, the
 2    use of ambient concentration as a surrogate for personal exposure could lead to misclassification
 3    and bias the epidemological findings.  The degree of the misclassification also depends on the
 4    spatial and temporal variation of ambient NO2, personal activities and microenvironment
 5    characteristics.
 6          In the Danish children exposure study, front door NC>2 as well as personal NC>2
 7    concentrations were measured (Raaschou-Nielsen et al., 1997).  To evaluate the extent of
 8    misclassification using outdoor NC>2 as an indicator of personal  exposure, Raaschou-Nielsen et
 9    al. (1997) reported that both the sensitivity (the proportion of correctly classified highly
10    exposure) and the specificity (the proportion of correctly classified low exposure) were 81% in
11    Copenhagen and 74% in the rural areas.  Similar results were reported by Lee, et al., (2004).
12          Exposure measurement errors could  also be evaluated by comparing the within subject
13    and between subject variations of individual exposures.  The higher the ratio of within variance
14    and between variance, the more the true exposure-effect relationship is biased (Armstrong et al.,
15    1992). During the Los Angeles NC>2 exposure study, Spengler et al. (1994) reported that the
16    within personal variation was 61.2  |ig/m3 and the variation between personal exposure was 608.2
17    |ig/m3.  Aim et al. (1998) reported that within personal variation explained 59% of the total
18    personal exposure variation and 41% of the total variation was accounted by between-subject
19    variation.
20          Simply speaking, two parameters could be used to evaluate the feasibility of using
21    ambient NC>2 concentrations as a surrogate for personal exposure: the correlation coefficient
22    between personal exposure and ambient concentrations (especially in the context of longitudinal
23    design and daily-averaged design), and the difference between personal exposure and ambient
24    concentration.  Extensive discussions of this issue have been provided in Section AX3.5, such
25    discussions are not repeated here and only general conclusions will be provided. The correlation
26    between personal exposure and ambient concentrations range from moderate to good. Personal
27    exposure concentrations are generally lower than ambient concentrations for homes with no
28    indoor or local sources but higher than ambient concentration for homes with indoor or local
29    sources.
30          In a broader context, NC>2 serves as an indicator of a pollutant mixture whose components
31    have different physical and chemical properties that may be the  real agent(s) causing the adverse

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 1    health effects. The components of the mixture are either primary or secondary, i.e., they either
 2    come from direct emissions or form through atmospheric chemical reactions. When the ambient
 3    mixture infiltrates into microenvironments, some components are lost due to absorption and
 4    chemical reaction, while some new components are formed through chemical reactions in indoor
 5    air.  At the same time, indoor primary sources could add more NC>2 along with other pollutants in
 6    the indoor environments. When evaluating the question of whether ambient NC>2 is the agent
 7    causing the observed adverse health effects, the two issues of confounding and surrogacy are
 8    raised.
 9          The definition and discussion  of the confounding issue from the perspective of exposure
10    analysis could be found in Section AX3.6.  In Section AX3.6, the following five questions were
11    evaluated (the five arrows in Figure AX3.24): (1) Are ambient copollutant concentrations
12    significantly associated with ambient NC>2? (2) Are personal exposures to copollutants
13    significantly associated with personal exposures to NO2?  (3) Are ambient pollutant
14    concentrations associated with their respective personal exposures? (4) Are ambient copollutants
15    surrogates for personal exposure to NC>2? (5) Is ambient NC>2 a surrogate for personal exposure
16    to copollutants? Based on the fact that NC>2 is correlated with other copollutants at both ambient
17    level and personal exposure levels and that cross-level correlations were also observed, we
18    concluded that caution should be exercised when dealing with the observed NC>2 health effect
19    and a more comprehensive analysis should be performed in conjunction with other components
20    of the risk assessment.
21          Another issue raised is the surrogate issue.  There are different meanings associated with,
22    to use the word "surrogate".  In summary, there are three scenarios involving the concept of a
23    surrogate and each one is associated with a question: (1) At ambient level, is ambient NC>2 a
24    good surrogate (tracer) for some ambient chemical or chemical mixture?  (2) At personal
25    exposure levels, is personal NC>2 exposure a good surrogate (tracer) for some chemical or
26    chemical mixture of personal exposure?  and  (3) At health effect levels, is NC>2 a good surrogate
27    for some chemical or chemical mixture causing an adverse health outcome? The first two
28    questions could be sufficiently answered by various source apportionment approaches to
29    evaluate the co-variation of NC>2 with other pollutants.  The third question is evaluated in Figure
30    AX3.25 with a systematic approach considering biological plausibility and exposure assessment.
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                                                                    ersonal NO2 Exposure
                                                                    rrelated with ambie
                                                                      o-pollutant
                    Personal NO2 Exposure
                     orrelated with ambie
                          NO2?
Causal Effects for NO2?
                      rsonal NO2 Exposure
                      rrelated with ambie
                       co-pollutants?
                                                                  NO2 is a surrogate for
                      rsonal NO2 Exposure
                     orrelated with ambie
                         -pollutants
Figure AX3.25.
A systematic approach to evaluate whether NO2 itself is causing the
observed adverse health outcome or NOi is acting as a surrogate for
other pollutants.
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TABLE AX3.1. SUMMARY OF PERCENTILES OF NO2 DATA POOLED ACROSS MONITORING SITES (2003-2005)
CJQ
r-K
to
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X
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to


o
H
6
o
0
H
O
HH
H
W
O
O
O
CONCENTRATIONS ARE IN PPM
Percentiles
Pooled Group/ Number of
Avg Time Values Mean 1 5 10 25 30 50 70 75
1-h Max Concentrations
Monitors in
CMSAs 288008 0.029 0.003 0.007 0.010 0.017 0.019 0.027 0.036 0.038
^™"torsnotm 460913 0.008 0.001 0.001 0.001 0.002 0.003 0.005 0.009 0.010
CMSAs
1-h Avg. Concentrations
Monitors in
CMSAs 6163408 0.015 0.001 0.003 0.003 0.006 0.007 0.012 0.019 0.022
ct/rs A*8 ^ m 460913 0.008 0.001 0.001 0.001 0.002 0.003 0.005 0.009 0.010
Daily 24-h Avg. Concentrations
Monitors in
CMSAs 282810 0.015 0.002 0.003 0.005 0.008 0.009 0.012 0.019 0.021
Monitors not in 2Q635
CMSAs
2-week Avg. Concentrations
Monitors in
CMSAs 21779 0.015 0.003 0.005 0.006 0.009 0.010 0.014 0.019 0.020
M°°1*°rsnotm 1588 0.008 0.001 0.001 0.001 0.003 0.003 0.007 0.009 0.012
Yearly Avg. Concentrations
Monitors in
CMSAs 758 0.015 0.004 0.006 0.007 0.011 0.012 0.015 0.018 0.019
Monitors not in M Q Qog OOQ1 OOQ1 Q OQ2 Q OQ3 Q OQ5 Q OQ9 OQ12 Qfin
CMSAs
3-yr Avg. Concentrations
Monitors in
CMSAs 247 0.015 0.004 0.006 0.007 0.011 0.012 0.015 0.018 0.019
Monitors not in
CMSAs 15 0.008 0.001 0.001 0.002 0.003 0.006 0.008 0.012 0.012


90 95 99 Max


0.048 0.055 0.072 0.201
0.019 0.026 0.040 0.189


0.033 0.040 0.053 0.201
0.019 0.026 0.040 0.189

0.028 0.034 0.045 0.129
0.017 0.021 0.030 0.081


0.026 0.031 0.038 0.076
0.016 0.020 0.030 0.039
0.025 0.028 0.033 0.037
0.015 0.016 0.017 0.017
0.025 0.028 0.032 0.033

0.014 0.016 0.016 0.016

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  TABLE AX3.2. SPATIAL VARIABILITY OF NO2 IN SELECTED UNITED STATES
                             URBAN AREAS
Mean 1-h
Concentration(ppb) r P90 (ppb)
New York, NY
(5)
Atlanta, GA
(5)
Chicago, IL
(7)
Houston, TX
(7)
Los Angeles, CA
(14)
Riverside, CA
(9)
29
(25-37) 0.77-0.90 7-19
** 0.22-0.89 7-24
(5-16)
(6-230) -°05-°-83 10-39
(T-'lS) °31-°-8° 6-2°
25
(14-33) 0.01-0.90 8-32
(, 2* 0.03-0.84 10-40
COD
0.08-0.23
0.15-0.59
0.13-0.66
0.13-0.47
0.08-0.51
0.14-0.70
       TABLE AX3.3. NOX AND NOY CONCENTRATIONS AT REGIONAL
 BACKGROUND SITES IN THE EASTERN UNITED STATES. CONCENTRATIONS
                           ARE GIVEN IN PPB
NO
Winter
Summer
NOX
Winter
Summer
NOy
Winter
Summer
Shenandoah NP, VA

0.39-2.2 l
0.12-0.28
—
—
—
2.7-8.6
2.3-5.7
Harvard Forest, MA

—
—
—
1-15
0.4-1.2
4.4 2
2.7 2
1 Ranges represent lo limits.
2 Values represent medians.
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      TABLE AX3.4. RANGE OF PEARSON CORRELATION COEFFICIENTS
 	BETWEEN NO2 AND O3, CO AND PM2.5	
  Monitoring Sites in                          Copollutant
Selected Areas
Los Angeles, CA
Riverside, CA
03
-0.59 to 0.19
-0.26 to 0.28
CO
0.11 to 0.83
0.15 to 0.65
PM25
0.45 to 0.56
 Chicago, IL              -0.20 to-0.13          -0.10 to 0.53         0.21 to 0.49
 Washington, DC              —                  —                 —
 New York City, NY           —                  —                 —
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                           TABLE AX3.5. PASSIVE SAMPLERS USED IN NO2 MEASUREMENTS
JW
r-K
to
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X
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6
o
0
H
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HH
H
W
Passive Sampler
Palmes tube

Gradko sampler
Passam Short
sampler Long
Analyst™
Yanagisawa badge
Ogawa sampler
IVL sampler
Willems badge
Radiello®
EMD sampler
Dimension
(diffusion length x
cross-sectional area) Absorbent
7.1cm x 0.71cm2 Triethanolamine

7.1cm x 0.93cm2 Triethanolamine
0.74cm x 0.75cm2 Triethanolamine
2.54cm x 3.27cm2 Active charcoal
1.0cm x 20cm2 Triethanolamine
0.6cm x 0.79cm2 Triethanolamine
Potassium iodide
1.0cm x 3.14cm2 & sodium arsenite
Triethanolamine-
0 . 6cm x 5 . 3 1 cm2 acetone
1 . 8cm x 2 . Ocm2 Triethanolamine
N.A. Triethanolamine
Analytical
Method
Spectrophotometry

Spectrophotometry
Spectrophotometry
Gas
chromatography
Spectrophotometry
Spectrophotometry
Spectrophotometry
Spectrophotometry
Spectrophotometry
Ion
chromatography
Sampling Rate
Manufacturer Experiment Reference
N.A. 0.92 cnrYmin Palmes et al. (1976)
Plaisance et al.
(2004)
1.2 cnrYmin 1.212 cnrYmin Gradko (2007)
15.5 cnrYmin N.A.
0.854 cnrYmin 0.833 cnrYmin Passam (2007)
De Santis et al.
N.A. 12.3 cnrYmin (2002)
Yanagisawa et al.
N.A. N.R. (1982
Ogawa & Company
(1998a) Gerboles
N.A. 16.2 cnrYmin et al. (2006a)
N.A. 29 cnrYmin Perm etal. (1998)
Hagenbjork-
Gustafsson et al.
N.A. 46 cnrYmin (2002)
75 cnrYmin N.R. Radiello® (2006)
Piechocki-Minguy
N.A. 53.4 cnrYmin etal. (2006)
        *N.A.: not available; N.R.: notreported.
O

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CJQ
         TABLE AX3.6. THE PERFORMANCE OF SAMPLER/SAMPLING METHOD FOR NO2 MEASUREMENTS
                                             IN THE AIR
r-K
to
o
o



X
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to

o
H
6
o
0
H
O
HH
H
W
Type Sampler
Active Impinger method
sampling
Chemiluminescence
Personal monitor
Passive Palmes tube
sampling
Gradko sampler
Passam Short
sampler
Long
Analyst™
Yanagisawa badge
Ogawa sampler
IVL sampler
Willems badge
Radiello®
EMD sampler
N.R.: not reported.


Optimal Duration of
Sampling
2-24 h
Continuous
Real-time
1-4 wks
2-4 wks
8-48 h
1-4 wks
1-3 mos
1-14 days
24-168 h
1 mo +
2-8 h& 1-7 days
1-24 h& 1-7 days
1-24 h



Concentration
Range
10 - 400 ppb
0.5 - 1000 ppb
0.1 -50ppm
10 - 100 ppb
1.0 -10,000 ppb
5 - 240 ug/m3
1 - 200 ug/m3
24 - 1,237 ug/m3
N.R.
0 - 3,600 ppb
0.1-400 ug/m3
2.0 - 150 ug/m3
1.0 -496 ppb
N.R.



Detection Limit
0.2 ppb
0.05 ppb
0.1 ppm
10 ppb
0.5 ppb
2-5 ug/m3
0.64 ug/m3
100 ug/m3
3.0 ppb
2.3 ppb
0.1 ug/m3
2 ug/m3
1.0 ppb
11 ug/m3




RSD < 5%
Accuracy ±
Precision ±
Uncertainty
Uncertainty
Accuracy ±
3%


RSD - 4%
Uncertainty
Uncertainty
Uncertainty



Comment

5%
5% above 5 ppb
-27% at 80 ug/m3
- 25% at 20-40 ug/m3
5%; Precision within


- 24%; RSD 22%
- 12%
-28%



O

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 TABLE AX3.7. NO2 CONCENTRATIONS (PPB) IN HOMES IN LATROBE VALLEY,
                           VICTORIA, AUSTRALIA
Living Room

No source
Gas stove only
Gas heater only
Smoking only
Multiple sources
Mean ppb
3.77
6.70
6.86
6.02
14.50
Min ppb
<0.37
1.57
2.20
0.94
2.25
Max ppb
9.27
18.32
18.06
14.61
114.66
Mean ppb
3.82
8.01
7.33
6.60
10.73
Kitchen
Min ppb
<0.37
2.62
2.88
1.83
2.62

Max ppb
8.17
24.14
26.23
16.44
128.80
Source: Garrettetal. (1999).
TABLE
AX3.8.
. NO2 CONCENTRATIONS (PPB) IN HOMES IN
No Gas Stove Used in Monitoring Period
Secondary
Heating
Source
None
Gas space
heater
Wood
burning
source
Kerosene
heater
GSH +
Wood
GSH + KH
Wood + KH
GSH +
Wood + KH
N
1018
6
200
159
3
0
73
0
10th
1.7
0.1
1.8
3.3
12.6
-
1.9
—
25th
3.5
9.2
3.6
7.1
12.6
-
8.2
—
Median
6.3
15.3
5.9
18.9
80.6
—
16.4
—
75th
12.3
68
12.2
42.7
81.9
—
35.2
—
90th
28.2
69.6
28.2
88.3
81.9
—
66.8
—
CONNECTICUT
Yes Gas Stove Used in Monitoring Period
N
564
6
78
14
5
1
5
1
10th
8.4
19.5
6
0
36.2
n/a
8.9
n/a
25th
14.5
34.6
9.5
9.6
44.8
n/a
12.7
n/a
Median
22.7
36.6
16.7
17.2
57.1
147.7
17.3
107.8
75th
33.8
54.8
31.4
33.6
114.
2
n/a
23.5
n/a
90th
48.1
147.2
58.6
46.1
156.6
n/a
72.9
n/a
Source: Triche et al. (2005).
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        TABLE AX3.9. NO2 CONCENTRATIONS NEAR INDOOR SOURCES -
                             SHORT-TERM AVERAGES
        Average
     Concentration
         (PPb)
 Peak Concentration
        (PPb)
      Comment
    Reference
  191 kitchen
  195 living room
  184 bedroom
 400 kitchen,
 living room,
 bedroom

 90 (low setting)
 350 (med setting)
 360 (high setting)
 N/R
 N/R
  180 to 650
375 kitchen
401 living room
421 bedroom
673 bedroom
N/R1
1000
1500
N/R
Cooked full meal with
use of gas stove and
range for 2 h, 20 min;
avg cone, is time-
weighted over 7 h.
Automatic oven
cleaning of gas stove.
Avgs are over the entire
cycle.
Natural gas unvented
fireplace,2 2-h-time-
weighted avg in main
living area of house
(177 m3).
Room concentration
with kerosene heater
operating for 46 min.
Room concentration
with gas heater
operating for 10 min.
Calculated steady-state
concentration from
specific unvented gas
space heaters operating
in a 1400 ft2  house,
1.0 ach.
Fortmann et al.
(2001)
Fortmann et al.
(2001)
Button et al.
(2001)
Girman et al.
(1982)

Girman et al.
(1982)

Girman et al.
(1982)
 1 N/R = Not Reported.
 2 Unvented fireplaces are not permitted in many areas such as California.

Source:  Adapted from CARB (2007).
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       TABLE AX3.10. NO2 CONCENTRATIONS NEAR INDOOR SOURCES -
 	LONG-TERM AVERAGES	
  Average Concentration
          (ppb)                           Comment                    Reference
 30 to 33
 22
 6 to 11
 55 (Median)
 41 (90th %-ile)
 80 (90th %-ile)
 84 (90th %-ile)
 147 (90th %-ile)
 52 (90th %-ile)
 18 bedrooms
 19 living rooms
 15 outdoors
Gas stoves with pilot lights.
Gas stoves without pilot lights.
Electric ranges.  Study conducted in 517
homes in Boston, values represent 2-wk
avgs.
Gas space heaters.
No indoor combustion source.
Fireplaces.
Kerosene heater.
Gas space heaters.
Wood stove.
All values represent 2-wk avgs in living
rooms.
Almost all homes had gas stoves. Values
represent 2-wk avgs.
                Lee etal. (1998)
                Triche et al.
                (2005)
                Zipprich et al.
                (2002)
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TABLE AX3.11. SUMMARY OF REGRESSION MODELS OF PERSONAL EXPOSURE TO AMBIENT/OUTDOOR NO2
Study Location
Rojas-Bracho et al. Santiago, urban
(2002)
Aim et al. (1998) Helsinki, downtown +





Monn et al.


suburban
(1998) Four urban + two rural
+ two alpine

Levy et al. (1998a) 15 cities in 18
^
X
OJ
1
to
VO

o
l>
H
6
o
0
H
o
i — i
H
W
O
O

Spengler et
(1994)
S0rensen et
(2005)


Sarnat et al.



Sarnat et al.

Sarnat et al.

countries
al. Los Angeles Basin

al. Copenhagen, urban



(2001) Baltimore



(2005) Boston

(2006) Steubenville

Season
Winter
Winter +
Spring
All


Winter

All

All
(>8 °C)
(<8 °C)
All
Summer


Winter
Summer
Winter
Summer
Fall
Model type
Personal vs. outdoor
Personal vs. central
Personal vs. outdoor
Personal (all subjects) vs. outdoor
Personal (no smokers and gas
cooking) vs. outdoor
Personal vs. outdoor

Personal vs. outdoor

Personal vs. outdoor
Personal vs. outdoor
Personal vs. outdoor
Personal vs. central
Personal vs. central


Personal vs. central
Personal vs. central
Personal vs. central
Personal vs. central
Personal vs. central
Slope (SE) Intercept / ppb R2
0.33 (0.05)
0.3
0.4
0.45
0.38

0.49

0.56

0.60 (0.07)
0.68 (0.09)
0.32(0.13)
0.56 (0.09)
0.04*


-0.05*
0.19
-0.03*
0.25 (0.06)
0.49 (0.05)
7.2 0.27
5.0 0.37
4.7 0.86
7.2 0.33
7.2 0.27

14.5 —

15.8 0.51

— —
— —
— —
— —
9.5 —


18.2 —
— —
— —
— 0.14
— 0.43
                   mificant at 1

-------
TABLE AX3.12. AVERAGE AMBIENT AND NONAMBIENT CONTRIBUTIONS TO POPULATION EXPOSURE
CJQ
r-K
to
o
o




OJ
i
o
O
H
6
o
0
H
O
HH
H
W
O
O
O
Study
Rojas-B radio
et al. (2002)
Aim et al.
(1998)
Monn et al.
(1998)

Levy et al.
(1998a)
Spengler et al.
(1994)
** Not reported.








Slope
Model Type (SE)
Personal vs. outdoor 0.33
(0.05)
Personal vs. central 0.3
Personal vs. outdoor 0.4
Personal (all subjects) 0.45
vs. outdoor
Personal (no smokers 0.38
and gas cooking) vs.
outdoor
Personal vs. outdoor 0.49
Personal vs. outdoor 0.56









Mean of Percent Percent
Personal Total Mean Ambient Ambient Nonambient
Intercept / Exposure / Contribution / Contribution Contribution
ppb ppb Ppb °/° 0//0
7.2 36.4 7.2 19.8 80.2
5.0 — 5.0 — —
4.7 — 4.7 — —
7.2 14.1 7.2 51.1 48.9
7.2 — 7.2 — —
14.5 28.8 14.5 50.3 49.7
15.8 37.6 15.8 42.0 58.0










-------
CJQ
TABLE AX3.13. THE ASSOCIATION BETWEEN PERSONAL EXPOSURES AND
                  AMBIENT CONCENTRATIONS
tyj
to
o
o








X
OJ
^

O
H
6
o
2;
o
H
O
HH
H
W
O
O
O
Study
Linn et al.
(1996)

Kramer et al.
(2000)
Rojas-B radio
et al. (2002)
Raaschou-
Nielsen et al.
(1997)
Aim et al.
(1998)








Monn et al.
(1998)




Study Design
Children, Southern California, 24 h averaged, one wk
consecutive measurement for each season (fall, winter, and
spring 1992-1994) for each child.
Children, West Germany, two one-wk averaged
measurements for each child each in March and Sept 1996
Children, Santiago, 24 h averaged sample for five
consecutive days for each child, winters of 1998 and 1999
Children, Copenhagen and rural areas, one-wk averaged, 2
measurements for each child in each month (Oct 1994,
April, May, and June 1995)
Children, Helsinki, one-week averaged, 13 wks for each
child in each season (winter and spring 1991)








Adults, Switzerland, eight regions in Swiss (four
urban/suburban, two rural and two alpine regions), one-wk
averaged, one measurement each mo (the first wk of the
mo) for each subject, between Dec 1993 to Dec 1994


Association Variable
Personal vs. central


Personal vs. outdoor
Personal vs. outdoor
Personal vs. outdoor

Personal vs. outdoor
Personal vs. outdoor
Personal vs. outdoor
Personal vs. outdoor
Personal vs. outdoor
Personal vs. outdoor
Personal vs. central
Personal vs. central
Personal vs. outdoor

Personal vs. central

Personal vs. outdoor





Location
pooled


pooled
urban
urban

urban
rural
downtown
suburban
downtown
suburban
downtown
suburban
pooled

pooled

pooled





Season
pooled


pooled
pooled
winter

pooled
pooled
winter
winter
spring
spring
spring
spring
pooled

pooled

pooled





rp, rs, or R2
0.63 (rp)


0.37 (rp)
0.06 (rp)
0.27 (R2)

0.15 (R2)
0.35 (R2)
0.46 (rp)
0.49 (rp)
0.80 (rp)
0.82 (rp)
0.64 (rp)
0.78 (rp)
0.86 (R2)

0.37 (R2)

0.33 (R2)






-------
CJQ
                   TABLE AX3.13 (cont'd). THE ASSOCIATION BETWEEN PERSONAL EXPOSURES AND
                                         AMBIENT CONCENTRATIONS
tyj
to
o
o
^








X
OJ
i
to
o
fj*
i-rj
H
6
o
o
^^
H
o
i — i
H
W
O
Study
Levy et al.
(1998a)


Kodama et al.
(2002)

Liard et al.
(1999)

Gauvin et al.
(2001)




Spengler et al.
(1994)



Kousa
etal. (2001)

Study Design
Adults, 18 cities across 15 countries, two-day averaged,
one measurement for each person, all people were
measured on the same winter day in February or March
1996
Junior high school students and their family members,
Tokyo, three-day averaged, samples were simultaneously
collected on Feb 24-26, Jun 2-4, July 13-15, and Oct 14-16
in 1998 and Jan 26-28 in 1999
Adults and Children, Paris, 4-day averaged, three
measurements for each person, during each measurement
session, all subjects were measured at the same time
during May/June 1996
Children, three French metropolitan areas, 48-h averaged,
one measurement for each child, all children in the same
city were measured on the same day. The study occurred
between April-June 1998 in Grenoble, May-June 1998 in
Toulouse, and June-Oct 1998 in Paris.



Probability based population, Los Angeles Basin, 48-h
averaged, one measurement per person in one of the eight
sampling cycles (microenvironmental component of the
study), from May 1987 to May 1988

Probability based population, Helsinki, Basel, and Prague,
48-h averaged, one measurement per person, during 1996
and 1997
Association Variable Location Season
Personal vs.



Personal vs.
Personal vs.

outdoor



outdoor
outdoor

Adults vs. central
Children vs.

Personal vs.
(Grenoble)
Personal vs.
(Toulouse)
Personal vs.
(Paris)

Personal vs.




Personal vs.


central

central

central
central


outdoor




outdoor


urban



urban
urban

urban
urban

urban

urban
urban


pooled




urban


winter



summer
winter

summer
summer

pooled

pooled
pooled


pooled




pooled


rp, rs, or R2
0.57 (rs)



0.24 (rp)
0.08 (rp)

0.41 (R2)
0.17(R2)

0.01 (R2)

0.04 (R2)
0.02 (R2)


0.48 (R2)




0.40 (R2)


O

-------
CJQ
TABLE AX3.13 (cont'd). THE ASSOCIATION BETWEEN PERSONAL EXPOSURES AND
                      AMBIENT CONCENTRATIONS
j~^
r-K
to
o
o











>
OJ
i

OJ



>
H
6
o
0
H
O
HH
H
W
Study
Linaker et al.
(2000)





Lai et al.
(2004)
Kim et al.
(2006)

Sarnat et al.
(2005)






Sarnat et al.
(2006)
Study Design
Asthmatic children, Southampton, one-wk averaged,
13 mos for each child, until Dec 1995





Adults, Oxford, 48-h averaged, once per person, between
Dec 1998 and Feb 2000
Coronary artery adults, Toronto, 24-h averaged, one day
a wk for 10 wks for each person, from Aug 1999 to Nov
2001
Seniors and schoolchildren, Boston, 24-h averaged, 12
consecutive days in each of the 1 or 2 seasons, summer of
1999 and winter of 2000





Seniors, Steubenville, 24-h averaged, the same two
consecutive days each wk for 23 wks, summer and fall of
2000
Association Variable
Personal vs. outdoor
(Overall
measurements across
children and time)
Personal vs. outdoor
(subject-wise)

Personal vs. outdoor

Personal vs. central
(ambient)

Personal vs. central
(subject wise)






Personal vs. central

Location Season
pooled, pooled
urban, no
major indoor
sources
By person pooled


urban pooled

urban pooled


urban summer



winter



urban summer
fall
rp, rs, or R2
Not
significant


-0.77 to 0.68
and median
-0.02(rp)
0.41 (rp)

0.57 (rs)


-0.25 to 0.5
(rs) with a
median of
0.3*
-0.5 to 0.9
(rs) with a
median of
0.4*
0.14(R2)
0.43 (R2)
* Values were estimated from figures in the original paper.















O

-------
                  TABLE AX3.14.  INDOOR/OUTDOOR RATIO AND THE INDOOR VS. OUTDOOR REGRESSION SLOPE
OQ
 to
 o
 o
               Study
                        Description
                             Season
             Regression Format or
                     Ratio
     Indoor
  Characteristics
Slope/Ratio/
    Fjnf
     Comments
 >
 X
Mosqueron et al.
(2002)
         Lee etal. (1999)
48 h residential indoor,
workplace, outdoor and
personal exposure were
measured for 62 Paris office
workers using Ogawa badges
from Dec 1999 to Sept 2000
                 The indoor and outdoor air
                 quality of 14 public places
                 with mechanical ventilation
                 systems in Hong Kong; from
                 Oct 1996 to March 1997;
                 Teflon bags were used to
                 collect indoor and outdoor
                 NO and NO2 during peak h
Overall study Residential indoor vs.
            ambient and using gas
            cooking
Cooking
                                                    seasons
                                                                 Office indoor vs. ambient None
                                                                 and floor height
    0.26
                                                                                                    0.56
                          Overall study Indoor vs. outdoor
                          seasons
                                      Indoor/outdoor ratio
                                                         0.59
                                                      0.53-1.03
                                                      (mean: 0.75)
The overall R is 0.14,
and ambient NO2 and
indoor cooking
account for 0.07 each.
The overall R2 is 0.24,
partial R2 for ambient
and floor height were
0.18 and 0.06,
respectively.
R2 was 0.59. The
slopes for NO and
NOX were 1.11 and
1.04 respectively.
0.83-2.68 for NO
(mean: 0.99)
0.78-1.68 for NOX
(mean: 0.94)
 H
 6
 o
 2
 o
 H
 O
 HH
 H
 W
O

-------
OQ
to
o
o
             TABLE AX3.14 (cont'd). INDOOR/OUTDOOR RATIO AND THE INDOOR VS. OUTDOOR REGRESSION SLOPE
Study
      Description
                                                        Season
Regression Format or         Indoor
        Ratio            Characteristics
                                           Slope/Ratio/
                                              Finf      Comments
>
X
H
6
o
2
o
H
O
HH
H
W
           Monn et al.
           (1997)
           Monn et al.
           (1997)
           Garcia-Algar
           et al. (2003)
During the SAPALDIA
(Spain) study, 48-72 h
indoor, outdoor, and
personal NO2 were
measured by Palmes tubes
between the winter of
1994 to the summer of
1995, and between May
and July of 1996
During the SAPALDIA
(Spain) study, 48-72 h
indoor, outdoor, and
personal NO2 were
measured by Palmes tubes
between the winter of
1994 to the summer of
1995, and between May
and July of 1996
Yanagisawa passive filter
badges were used to
measure indoor NO2
concentrations for 7~15
days for 340 homes in
Barcelona, Spain during
1996-1999. Outdoor
NO2 concentrations were
obtained from the fixed
monitoring stations by the
method of CL.
                                     Overall study
                                     seasons
                                     Overall study
                                     seasons
                                     Overall study
                                     seasons
Indoor/outdoor ratio      With gas-cooking
                                                                                          Without gas
                                                                                          cooking
Indoor/outdoor ratio      With gas-cooking
                                                                            Without gas
                                                                            cooking
Indoor/outdoor ratio
                                              > 1.2
                                                                                                  0.4-0.7
                                              > 1.2
                                             0.4-0.7
                                             0.8-1.0     Including
                                                        both homes
                                                        with and
                                                        without
                                                        indoor
                                                        sources.
O

-------
OQ
to
o
o
            TABLE AX3.14 (cont'd). INDOOR/OUTDOOR RATIO AND THE INDOOR VS. OUTDOOR REGRESSION SLOPE
>
X
H

6
o

2
o
H

O
HH
H
W
Study
Lee et al.
(1995)





Lee et al.
(2002)





Lee (1997)








Description Season
Two-wk averaged indoor Summer
(kitchen, living room, and
bedroom) and outdoor NO2
were measured by Palmes
tube for 517 homes from
November 1984 to Oct 1986
in Boston area.
Six-day integrated indoor and Overall
outdoor concentrations of study
NO2 in two communities in seasons
Southern California were
measured using Yanagisawa
badges for 119 homes in
April and May 1996.
Indoor and outdoor air Overall
quality at two staff quarters study
in Hong Kong were measured seasons
from January to Feb of 1996
by Chemical Luminescent
method in two staff quarters
in Hong Kong (TSTE, in a
downtown area; and ST in a
suburban area).
Regression Format Indoor
or Ratio Characteristics
Indoor/outdoor Electric stove
ratio homes





Indoor/outdoor With gas range
ratio ± SD
Without gas range
With air
conditioner
Without air
conditioner
Indoor/outdoor Downtown area
ratio (Range)







Slope/Ratio/Finf
0.81 (kitchen)

0.81 (living room)

0.77 (bedroom)


2.27 ±1.88

1.22 ±0.52
1.07 ±0.26

3.03 ±2.01

0.78 (0.70-0.87)
forNO2

0.92(0.77-1.10)
for NO

0.86(0.78-0.95)
forNOx

Comments
Homes with gas
stove and gas
stove with pilot
light have an I/O
ratio >1, but the
values were not
reported.
—

—
—

—

—








Suburban area
0.97(0.89-1.03)

   forNO2



0.92(0.77-3.14)

   for NO
O
                  0.86(0.89-1.03)

                     forMX

-------
CJQ
          TABLE AX3.14 (cont'd). INDOOR/OUTDOOR RATIO AND THE INDOOR VS. OUTDOOR REGRESSION SLOPE
r-K
to
o












X
UJ
1
OJ


o

rrt
H
6
o

0
o
1 — I
H
W
O
O
^^
Study Description
Garrett et al. Four-day averaged indoor
(1999) (bedroom, living room, and
kitchen) and outdoor NO2
was monitored using
Yanagisawa passive samplers
for 80 homes in the Latrobe
Valley, Victoria, Australia, in
March-April 1994, and Jan-
Feb, 1995.
Zotaetal. Two-wk integrated NO2 was
(2005) measured in 77 homes within
three Boston public housing
developments (low-income,
urban neighborhoods, where
asthma prevalence is high),
using Palmes tubes. Homes
were sampled between June
2002 and May 2003 for 2-wk
periods with up to three
sampling sessions in each
home.
Yang et al. Daily indoor and outdoor
(2004) NO2 concentrations were
measured for 30 consecutive
days in 28 house in Brisbane
(between April and May in
1999), and for 21 consecutive
days in 37 houses in Seoul
(between June and Aug in
2000) using Yanagisawa
badges.
Season
Overall
study
seasons






Overall
study
seasons









Overall
study
seasons






Regression Format or Indoor
Ratio Characteristics
Indoor/outdoor ratio No major indoor
sources (major
sources were gas
stove, vented gas
heater, and smoking)




Residential indoor vs. —
residential outdoor










Residential indoor vs. Brisbane with
residential outdoor electric range
Brisbane with gas
range
Seoul with gas range
Indoor/outdoor ratio Brisbane
Seoul


Slope/Ratio/
Finf Comments
0.8 The ratio
increased to
1.3, to 1.8 and
to 2.2 for
homes with
one, two, and
three major
indoor sources.

1.21 —











0.65 ±0.18 R2 was 0.70.

0.56 ±0.12 R2 was 0.57.

0.58 ±0.12 R2 was 0.52.
0.82 ±0.41 —
0.88 ±0.32 —



-------
OQ
to
o
o
           TABLE AX3.14 (cont'd). INDOOR/OUTDOOR RATIO AND THE INDOOR VS. OUTDOOR REGRESSION SLOPE
>
X
oo
H

6
O

2
o
H

O
HH
H
W
                                                     Regression Format or
Indoor
Study
Chao (2001)







Kulkarni etal.
(2002)






Monn et al.
(1998)






Description
48-h averaged indoor
and outdoor NO, and
NO2 were measured in
ten non-smoking
residential buildings
using Ogawa passive
samplers in the summer
of 1997 in Hong Kong.
48-h averaged indoor
and outdoor NO2 were
measured using passive
filter badge sampler in
the winter (Feb 1996)
and summer of 1996
(April) for 43 residence
in Mumbai.
One-wk averaged
indoor, outdoor, and
personal NO2 were
measured for more than
500 subjects between
Dec 1993 to Dec 1994
for a SAPALDIA study
subpopulation, once per
home.

Season
Overall
study
seasons





Overall
study
seasons





Overall
study
seasons





Ratio
Indoor/outdoor ratio







Residential indoor vs.
residential outdoor






Residential indoor vs.
residential outdoor


Residential indoor vs.
residential outdoor + gas
cooking + smoking +
ventilation

Indoor/outdoor ratio
Characteristics
—







Homes using LPG
Homes using
Kerosene





All homes
Homes without
smokers and gas-
cooking
All homes


All homes
Slope/Ratio/Finf
0.79 ±0.30
(range: 0.75 -
1.36)forNO2

0.98 ±0.19
(range: 0.29 -
1.25) for NO

0.92
0.73






0.47
0.40


0.55


0.7-0.8
Comments
—







R2 was 0.80.
R2 was 0.40.






R2 was 0.37.
R2 was 0.33.


Overall R2 was
0.58, but partial
R2 cannot be
derived.

—
O

-------
OQ
 to
 o
 o
TABLE AX3.14 (cont'd). INDOOR/OUTDOOR RATIO AND THE INDOOR VS. OUTDOOR REGRESSION SLOPE

   Study            Description         Season
                                                               Regression Format or
                                                                       Ratio
                                                            Slope/Ratio
                                     Indoor Characteristics     / Finf     Comments
 >
 X
 VO
 H
 6
 o
 2
 o
 H
 O
 HH
 H
 W
O
           Levy et al.
           (1998a);
           Spengler et al.
           (1996)
               48-h averaged indoor,
               outdoor, and personal
               exposures to NO2 were
               measured in 18 cities in
               15 countries around the
               world during a 2-day
               period in Feb or March
               1996.
Overall
study
seasons
Indoor/outdoor ratio
Boston, US               0.6 ± 0.4
Ottawa, Canada           0.5 ± 0.2
Mexico City, Mexico       1.9 ± 1.0
London, UK              0.6 ± 0.4
Watford, UK              0.8 ± 0.4
Geneva, Switzerland       0.8 ± 0.6
Kjeller, Norway           0.7 ± 0.4
Kuopio, Finland           0.5 ± 0.5
Berlin, Germany           0.3 ± 0.2
Erfurt, Germany           0.8 ± 0.7
Homes without gas stove      0.7
Homes with gas stove         1.2
Homes without kerosene      0.85
heater
Homes with kerosene         2.27
heater
Homes without gas space     0.96
heater
Homes with gas space        1.93
heater
Homes without gas water     0.94
heater
Homes with gas water        1.07
heater
Homes without smokers      0.92
present
Homes with smokers         1.16
present

-------
OQ
 to
 o
 o
TABLE AX3.14 (cont'd).  INDOOR/OUTDOOR RATIO AND THE INDOOR VS. OUTDOOR REGRESSION SLOPE
                                                    Regression Format or         Indoor         Slope/Ratio/
   Study            Description          Season             Ratio             Characteristics         Finf
                                                                          Comments
 >
 X
          Spengler et al.
          (1994)
          Lai et al. (2004)
              A Yanagisawa type of
              passive sample was used
              to measure the 48-h
              integrated indoor, outdoor
              and personal NO2 levels
              from the May of 1987 to
              the May of 1988.

              48-h averaged personal,
              indoor, outdoor and
              workplace NO2 levels
              were measured by passive
              filter badges for 50 adults
              in Oxford between 1998
              and 2000, once per person.
Overall study Residential indoor vs.
seasons       residential outdoor
Overall study Indoor/outdoor ratio
seasons
Gas range with pilot
light
Gas range without
pilot light
Electric stove
All homes
0.49       R2 was 0.44.

 0.4        R2 was 0.39.

 0.4        R2 was 0.41.


 0.9             —
                                                                                       Smoking homes
                                                                                       Non-smoking homes
                                                                                                      1.5
                                                                                                      1
 H
 6
 o
 2
 o
 H
 O
 HH
 H
 W
          Note: *Only data that are marked by underline and bold font can be considered as an infiltration factor.
O

-------
                          TABLE AX3.15. NO2 CONCENTRATIONS (PPB) IN DIFFERENT ROOMS
CJQ
to
O
o
X
OJ
H

6
o


o
H
O
HH
H
W
Study
Topp et al.
(2004)




Garrett et al.
(1999)






Cotterill et al.
(1997)








Zota et al.
(2005)




Conditions
First visit



Second visit

No identified
indoor sources
Gas stove homes
Gas heater
homes
Smoking homes
Homes with
multiple sources
Gas Stove homes
Electric cooker
homes
Gas cooker home
with single
glazing window

Gas cooker home
with double
glazing window
Overall
Heating season
Non-heating
season



Outdoor
12.4



12.5

4.7

4.7
4.7

4.7
4.7

20.9
20.9

20.9



20.9


19
21
17



Kitchen
—



—

3.8

8.0
7.3

6.6
10.7

35.6
9.9

31.4



39.8


43
50
33



Living Room
7.8



8.0

3.8

6.7
6.9

6.0
14.5

17.3
8.9

16.8



18.3


36
43
26



Bedroom Comments
7.2 Indoor and outdoor NO2 concentrations for 777 residential
homes in five study areas were measured: Erfurt,
Hamburg, Zerbst, Bitterfeld and Hettstedt during two
visits (from June 1995 to May 1997, and from April 1996
7.6 to Sept 1998). In the study, one-week averaged NO2 were
measured by Palmes tube.
3.0 Garrett (1999) investigated the levels and sources of NO2
in Australian homes. During the study, four-day averaged
6.3 NO2 was monitored using Yanagisawa passive samplers in
5 Q 80 homes in the Latrobe Valley, Victoria in March-April
1994, and Jan-Feb 1995.
5.7
11.2

11.5 Three consecutive two-week averaged outdoor, kitchen,
7.3 living room, and bedroom NO2 were measured using
Palmes tubes in 40 houses in Huddersfield, UK in late
H 0 1994. Half the houses were located close to a busy main
road and half on residential roads set back and parallel to
the main road. The sample was split so that half had gas
cookers and half had electric cookers. These subsets were
12-0 Spiit again so that half had double glazing and half had
single glazed windows.

— The indoor and outdoor NO2 concentrations for low-
	 income, urban neighborhoods were measured, where
asthma prevalence is high. NO2 was measured in 77
homes within three Boston public housing developments,
using Palmes tubes (two-wk integrated sample) placed in
the kitchen, living room, and outdoors. Air exchange rate
for each home was also measured.
O

-------
                             TABLE AX3.15 (cont'd). NO2 CONCENTRATIONS (PPB) IN DIFFERENT ROOMS
CJQ
r- 1-
to
o
o












>
!x!
rS
OJ
I
to
Study
Gallelli et al.
(2002)




Linaker
etal. (1996)


Kodama
et al. (2002)






Conditions
Overall study

With vent

Without vent

Overall study



Feb 1998
June 1998
July 1998
Oct 1998
Jan 1999



Outdoor Kitchen
— 24.6

— 18.1

— 30.9

— 27.2



40,31.3 81.8
38,28 33.2
29, 26.7 24.8
40,35 23.5
49, 50 70.9



Living Room
—



—

20.9



73.5
28.8
21.9
24.7
65.8



Bedroom
13.0



—

—



55.2
24
17.4
18.2
50.7



Comments
During the study, one-wk integrated indoor (kitchen and
bedroom) and personal NO2 were measured in Genoa,
Italy, for 89 subjects with Palmes samplers. Study
volunteers included students, workers, and housewives
living in three areas of Genoa differing by street traffic and
industrial plant location.
During the study, one-wk integrated personal, indoor
(kitchen, living room), classroom, and playground NO2
were measured using Palmes tubes for school children in
Southampton.
The first number in outdoor column was the ambient
concentration in the South Area; and the second number is
the ambient concentration in the North Area. During the
study, personal, indoor (kitchen, living room, bedroom and
study room), and outdoor NO2 were measured for 150
junior high school students with Yanagisawa badges in
Tokyo. The investigation was conducted five times
seasonally, 3 days each, from February 1998 to January
1999.
H
6
o
2
o
H
O
HH
H
W
          Chao and
          Law (2000)
Overall study
37.6
51.9
28.2
26.4       Personal and indoor exposures were monitored with
          passive sampler in Hong Kong for 60 subjects. Twelve of
          the subjects were selected to conduct more detailed study
          to examine the behavioral and microenvironmental effects
          on personal exposure to NO2.
O

-------
TABLE AX3.16. INDOOR AND OUTDOOR CONTRIBUTIONS TO INDOOR CONCENTRATIONS
CJQ
r-K
to
o
o







X
OJ
1^
OJ
o
H
6
o
0
H
O
HH
H
W
O
O
O
Study
Mosquero
net al.
(2002)
Yang
etal.
(2004)


Monn
etal.
(1998)










Percent
Mean Indoor Mean Outdoor Outdoor
Condition Slope Intercept Concentration Concentration Contribution
Overall 0.258 — 18.4 31.5 44.2
study

Brisbane, 0.65 0.8 10.3 — 92.4
electric
range
Brisbane, 0.56 3.0 18.3 — 83.5
gas range
Seoul, gas 0.58 4.8 33.4 40.4 85.7
range
Overall 0.47 3.2 11.0 16.2 70.5
study
Homes 0.40 3.2 6.8 16.2 53.1
without
smokers
and gas
cooking








Percent Indoor
Indoor Source
Contribution Strength Comments
55.8 — —

7.6 3.5ppb/h —

16.5 11.5ppb/ —
h
14.3 23.4 ppb/ —
h
29.5 — —

46.9 — Mean indoor
was
estimated
based on the
text
description.









-------
            TABLE AX3.16 (cont'd). INDOOR AND OUTDOOR CONTRIBUTIONS TO INDOOR CONCENTRATIONS
JQ
r-K
to
o
o




>
X
OJ
1
£
"^

o
H
6
o
0
H
O
HH
H
W
Percent Percent
Mean Indoor Mean Outdoor Outdoor Indoor
Study Condition Slope Intercept Concentration Concentration Contribution Contribution
Spengler Gas range 0.49 — 30 37 60.4 39.6
etal. (1994) with pilot
light


Gas range 0.4 — 22 33 60.0 40.0
without
pilot light
Electric 0.4 — 17 33 77.6 22.4
stove



Overall 0.49 8.64 27.2 38.3 68.2 31.8




Indoor
Source
Strength Comments
— Mean indoor
and mean
outdoor are
estimated from
Figure 2 in
Spengler et al.
(1994).
— Mean indoor
and mean
outdoor are
estimated from
Figure 2 in
Spengler et al.
(1994).
— Mean indoor
and mean
outdoor are
estimated from
Figure 2 in
Spengler et al.
(1994).
— —




O

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OQ
to
o
o
                     TABLE AX3.17. THE ASSOCIATION BETWEEN INDOOR, OUTDOOR, AND PERSONAL NO2
            Study
                  Summary
                           Condition
                       Indoor vs.
                       Outdoor
              Personal vs.
                 Indoor
Personal vs.
  Outdoor
Comments
Mosqueron
et al. (2002)
Simultaneous personal,
indoor, and in-office
48-h averaged NO2
concentrations were
measured with Ogawa
badges for 62 people,
and ambient
concentrations were
provided by local air
monitoring network.
Overall study
   0.07
(partial R2)
                Gas cooking
                interpreted another
                7% of indoor NO2
                variation
>
X
H
6
o
2
o
H
O
HH
H
W
         Emenius
         et al. (2003)
             Palmes tubes were
             used to measure indoor
             (in the main living
             room) and outdoor
             (outside the window of
             this room) NO2
             concentrations during
             a four-wk period
             (mean 28 days, range
             26-31) in the first
             winter season
             following recruitment
             in the case-control
             study.
                      Without smoker and       0.69 (rp)
                      gas stove was not
                      used
                                            With gas stove and        0.13 (rp)
                                            with smoker
                      With gas stove but        0.06 (rp)
                      without smoker
                                                                                             p = 0.43
                                                                                                                   p = 0.75
O

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OQ
to
o
o
                 TABLE AX3.17 (cont'd). THE ASSOCIATION BETWEEN INDOOR, OUTDOOR, AND PERSONAL NO2
             Study
                      Summary
                              Condition
                       Indoor vs.
                       Outdoor
             Personal vs.
                Indoor
Personal vs.
  Outdoor
Comments
Lee et al.       Indoor and outdoor air
(1999)         quality of 14 public places
               with mechanical
               ventilation systems in
               Hong Kong were measured
               fromOct 1996 to March
               1997.  Traffic peak h NO,
               NO2 was sampled using
               Teflon bags and then
               shipped back to the
               laboratory for further
               analysis.
                          Overall study
                       0.59 (R2)
                                          0.92 for NO and
                                          0.92 for NOX.
>
X
H
6
o
2
o
H
O
HH
H
W
Garcia-Algar
et al. (2003)
Yanagisawa passive filter
badges were used to
measure indoor NO2
concentrations for 7~15
days for 340 homes in
Barcelona, Spain during
1996-1999. Outdoor NO2
concentrations were
obtained from the fixed
monitoring stations by the
method of CL.
Overall study
0.15(rp)
              p = 0.007
O

-------
OQ
 to
 o
 o
                  TABLE AX3.17 (cont'd). THE ASSOCIATION BETWEEN INDOOR, OUTDOOR, AND PERSONAL NO2
Study
Summary
                                                      Condition
                                                              Indoor vs.
                                                               Outdoor
Personal vs.
  Indoor
Personal vs.
  Outdoor
Comments
 >
 X
 H
 6
 o
 2
 o
 H
 O
 HH
 H
 W
Lai et al.    The study was conducted
(2006)     between 1996 and 2000 in six
           EU cities: Athens, Basel,
           Helsinki, Milan, Oxford, and
           Prague. 48 h averaged indoor
           and outdoor NO2 were
           collected each home using
           diffusion tubes for 302 homes.

Lee et al.   Six-day integrated indoor and
(2002)     outdoor concentrations of NO2
           were measured in two
           communities in Southern
           California using Yanagisawa
           badges for 119 homes in April
           and May 1996.

Mukala    The one-week averaged
et al.       indoor (day-care center),
(2000)     outdoor (outside day care
           center) and personal NO2 for
           162 children aged 3-6 years
           old nitrogen dioxide exposure
           were measured by Palmes
           tube in Helsinki, in  1991.
                                                  Overall study
                                                          0.13 (partial R")
                                                                                      The overall R for the
                                                                                      multiple linear
                                                                                      regression was 0.67
                                                  Overall study
                                                              0.60 (rp)
                                      Spring
                                      Winter

                                      Spring (ambient vs.
                                      indoor)


                                      Winter (ambient vs.
                                      indoor)
                                                                         0.86 (rp)
                                                                         0.54 (rp)

                                                                         0.45 (rp)
                                            0.36 (rp)
O

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OQ
 to
 o
 o
        TABLE AX3.17 (cont'd). THE ASSOCIATION BETWEEN INDOOR, OUTDOOR, AND PERSONAL NO2
                                                                     Indoor vs.    Personal vs.  Personal vs.
   Study                  Summary                  Condition        Outdoor       Indoor      Outdoor      Comments
         Garrett et al.   Four-day averaged NO2 was
         (1999)        monitored using Yanagisawa passive
                       samplers in 80 homes in the Latrobe
                       Valley, Victoria, Australia in March-
                       April 1994, and Jan-Feb 1995.
                                                  Overall study
0.28 (R2)
Log 10
transformed data
 >
 X
 oo
 H
 6
 o
 2
 o
 H
 O
 HH
 H
 W
Cotterill et al.  Three consecutive two-week averaged
(1997)        outdoor, kitchen, living room, and
              bedroom NO2 were measured using
              Palme's tubes in 40 houses in
              Huddersfield, UK in late 1994.  Half
              the houses were located close to a
              busy main road and half on residential
              roads set back and parallel to the main
              road.  The sample was split so that
              half had gas cookers and half had
              electric cookers. These subsets were
              split again so that half had double
              glazing and half had single glazed
              windows.
                                                           Overall study
0.59 (rp)
O

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OQ
 to
 o
 o
 VO
        TABLE AX3.17 (cont'd).  THE ASSOCIATION BETWEEN INDOOR, OUTDOOR, AND PERSONAL NO2
                                                               Indoor vs.    Personal vs.    Personal vs.
   Study             Summary               Condition         Outdoor       Indoor        Outdoor           Comments
Yangetal.    Daily indoor and outdoor
(2004)       NO2 concentrations were
             measured for 30 consecutive
             days in 28 house in Brisbane
             (between April and May in
             1999), and for 21
             consecutive days in 37
             houses  in Seoul (between
             June and Aug in 2000) using
             Yanagisawa badges.
Lai et al.      During the study, 48-
(2004)       averaged personal,
             residential indoor,
             residential outdoor, and
             workplace indoor pollutants
             were measured for 50 adults
             between 1998 and 2000 in
             Oxford, once per person.
             NO2 were measured using
             passive sampling badges.
                                                 Brisbane, electric
                                                 range house
                                                 Brisbane, gas range
                                                 house
                                                 Seoul, gas range
                                                 house
                                                 Overall study
                        0.70 (R2)



                        0.57 (R2)

                        0.52 (R2)
                        0.29 (rp)       0.47 (rp)
                          (not        (p<0.0i)
                       significant)
                             -0.41 (rp)
                             (p < 0.05)
                            Data were log
                            transformed
 H
 6
 o
 2
 o
 H
 O
 HH
 H
 W
O
Monn et al.   During the study, one-wk
(1998)       integrated indoor, outdoor
             and personal samples were
             collected for a
             subpopulation (n = 140) of
             SAPALDIA study using
             Pamles tube between Dec
             1993 and Dec 1994 at eight
             study centers in Switzerland.
Overall study
Homes without
smoker and without
gas-cooking
0.37 (R2)
0.34 (R2)
0.51(R2)
0.47 (R2)
0.33 (R2)
0.27 (R2)

-------
 >
 X
 H

 6
 o

 2
 o
 H

 O
 HH
 H
 W
Study
Levy et
al.,
(1998a)





Spengler
etal.
(1994)












Summary
48-h averaged indoor,
outdoor and personal
NO2 were measured in
18 cities in 15
countries around the
world with passive
filter badges in Feb or
March, 1996.
Probability based
population, Los
Angeles Basin, 48-h
averaged indoor,
outdoor and personal
NO2 were measured
(microenvironmental
component of the
study), from May 1987
to May 1988






Condition
Overall study







Overall study
Electric range
Gas range without
pilot light

Gas range with pilot
light
With air conditioning
Without air
conditioning
High ambient
concentration
Low ambient
concentration
Indoor vs. Personal vs.
Outdoor Indoor
— 0.75 (rs)







0.4 (R2) 0.6 (R2)
0.41 (R2) —
0.39 (R2) —


0.44 (R2) —

0.66 (rp) —
0.75 (rp) -

— —

— —

Personal vs.
Outdoor Comments
0.57 (rs) —







0.51 (R2) —
0.52 (R2) —
—


0.44 (R2) —

— —
— —

0.47 (R2) —

0.33 (R2) —

O

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CJQ
to
o
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             TABLE AX3.17 (cont'd). THE ASSOCIATION BETWEEN INDOOR, OUTDOOR, AND PERSONAL NO2
X
Study
Kousa
etal.
(2001)






Linaker
etal.
(1996)





Summary Condition
The indoor, outdoor, and Overall study
personal NO2 relationship in
three EXPOLIS centers
(Basel, Helsinki, and Prague)
were reported. During the
study, 48-averaged indoor, Helsinki
outdoor, and personal NO2
were measured with Palmes
tubes during 1996-1997.
During the study, one-wk Overall study
integrated personal, indoor
(kitchen, living room),
classroom and playground
NO2 were measured using
Palmes tubes for 46 school
children aged 9-11 in
Southampton, UK.
Indoor vs. Personal vs. Personal vs.
Outdoor Indoor Outdoor Comments
0.44 (R2) 0.53 (R2) 0.37 (R2) Data were log-
transformed


— 0.45 (R2) 0.40 (R2) Data were log-
transformed



— 0.53-0.76 (rp) 0.61-0.65 (rp) Data were log-
transformed






H

6
o

2
o
H

O
HH
H
W
O

-------
OQ
to
o
o
              TABLE AX3.17 (cont'd). THE ASSOCIATION BETWEEN INDOOR, OUTDOOR, AND PERSONAL NO2
>
X
to
H

6
o

2
o
H

O
HH
H
W
O
Study
Aim et al.
(1998)

























Summary
During the study,
weekly personal,
indoor (day care
center), outdoor (day
care center), and
ambient site NO2
exposures of 246
children aged 3-6 yrs
O J
were measured with
Palmes tubes during
13 wks in winter and
spring in 1991 in
Helsinki.















Indoor vs.
Condition Outdoor
Overall study —

Winter —

Spring —

Winter downtown 0.44 (rp)



Spring downtown 0.84 (rp)
Winter suburban 0.22 (rp)


Spring suburban 0.46 (rp)
Downtown electric —
stove
Downtown gas stove —
Downtown non- —
smoking
Downtown smoking —
Suburban electric —
stove
Suburban gas stove —
Suburban non- —
smoking
Suburban smoking —
Personal vs.
Indoor
0.88 (R2)

—

—

0.32 (rp)



0.75 (rp)
0.04 (rp)


0.75 (rp)
0.67 (rp)

0.50 (rp)
0.67 (rp)

0.47 (rp)
0.55 (rp)


0.50 (rp)

0.48 (rp)
Personal vs.
Outdoor
0.86 (R2)

0.04 (partial R2)

0.50 (partial R2)

0.46 (rp)



0.80 (rp)
0.49 (rp)


0.82 (rp)
0.55 (rp)

0.59 (rp)
0.73 (rp)

0.51(rp)
0.63 (rp)


0.59 (rp)

0.46 (rp)
Comments
0.37 (R2) for personal
vs. ambient
p = 0.01; log
transformed data
p = 0.0001; log
transformed data

Personal vs. indoor
was not significant
(day-care center, not
residential indoor).

Personal vs. indoor,
and indoor vs. outdoor
were not significant
—
—

—
—

—
—

—
—

—

-------
OQ
to
o
o
      TABLE AX3.17 (cont'd). THE ASSOCIATION BETWEEN INDOOR, OUTDOOR, AND PERSONAL NO2
                                                    Indoor vs.     Personal vs.       Personal vs.
Study         Summary            Condition         Outdoor        Indoor          Outdoor           Comments
         Kodama    During the study,
         et al.       personal, indoor
         (2002)      (kitchen, living room,
                    bedroom, and study
                    room), and outdoor
                    NO2 were measured
                    for 150 junior high
                    school students with
                    Yanagisawa badges in
                    Tokyo.  The
                    investigation was
                    conducted five times
                    seasonally, 3 days
                    each, from Feb 1998 to
                    Jan 1999.
                              Summer
                              Winter
0.31(rp)
0.57 (rp)
0.24 (rp)
0.08 (rp)
H
6
o
2
o
H
O
HH
H
W
O

-------
CJQ
TABLE AX3.18. INDOOR, OUTDOOR, AND PERSONAL NO2 LEVELS STRATIFIED BY
                        EXPOSURE INDICATORS
      (CONCENTRATIONS ARE IN PPB AND SLOPES ARE DIMENSIONLESS)
to
o
o












>
X
OJ
L/l
[\


O
>
H
1
O
o
1— J
z;
0
H
O
H
W
O
o
o

Ambient
NO2
References Factor Name Factor levels Level
Environmental conditions
Singer etal. Wind Direction Upwind of freeway 20.5
(2004) Downwind and close 26.5
to freeway
Downward and far 21
from freeway
Zotaetal. Season Heating 21
(2005) Non-Heating 17
Serensen et al. Season < 8C 14.6
(2005) > 8C 7.8
Aim et al. Season Winter downtown —
(1998) smoker
Spring downtown —
smoker
Winter downtown —
nonsmoker
Spring downtown —
nonsmoker
Winter suburban —

smoker
Spring suburban —
smoker
Winter suburban —
nonsmoker
Spring suburban —
nonsmoker



Indoor Personal
Ambient NO2 Indoor NO2 Personal
Slope Level Slope Level Slope Comments

— — — — — —
— — — — — —

— — — — — —

— 43 — — — —
— 26 — — — —
— 8.9 — 11.4 — —
— 6.6 — 9.2 — —
— — — 13.5 — —

— — — 15.4 — —

— — — 13.0 — —

— — — 14.1 — —

— — — 11.2 — —


— — — 10.7 — —

— — — 9.2 — —

— — — 8.7 — —




-------
CJQ
to
O
o
>
X
H

6
O


O
H

O
HH
H
W
O
TABLE AX3.18 (cont'd). INDOOR, OUTDOOR, AND PERSONAL NO2 LEVELS STRATIFIED

                            EXPOSURE INDICATORS

         (CONCENTRATIONS ARE IN PPB AND SLOPES ARE DIMENSIONLESS)
                                                                                         BY
References Factor Name
Zota et al. Heating season
(2005)
Vukovich et al. Day
(2000)
Lee (1997) Day






Dwelling conditions
Levy et al. Window open
(1998a)
Cotterill et al. Window
(1997)




Partti-Pellinen Type of Filtration
et al. (2000)





Ambient
NO2
Factor Levels Level
— —

Weekday

Weekday —





Weekend —

With —
Without —
Single Glazing —
Double Glazing —
Single Glazing —

Double Glazing —

Mechanical filter 12.3

Mechanical intake 11.5
and mechanical filter
Mechanical intake 12.4
and mechanical and
chemical filter
Indoor Personal
Ambient NO2 Indoor NO2 Personal
Slope Level Slope Level Slope Comments
3.87 — 17.3 — — —

— — — — — 39% more than
weekend
— — — — — The effect of
weekday/week-
end is clear but
the paper didn't
give a value to
cite
— — — — — —

— — — 30 — —
— — — 26.7 — —
— 9.4 — — — —
— 9.4 — — — —
— 11.0 — — — Gas cooker
homes
— 12.0 — — — Gas cooker
homes
— 9.6 — — — —

— 12.5 — — — —

— 6.5 — — — —



-------
CJQ
TABLE AX3.18 (cont'd). INDOOR, OUTDOOR, AND PERSONAL NO2 LEVELS STRATIFIED BY
                            EXPOSURE INDICATORS
to
o
o









.
X
OJ
^
ON

O
^
i-rj
H
6
o
0
H
O
HH
H
W
O
O
O
(CONCENTRATIONS ARE IN PPB AND SLOPES ARE DIMENSIONLESS)


References Factor Name
Yanmanaka Surface type
etal. (1984)
Zota et al. Occupancy
(2005)
Levy et al. Occupancy
(1998a)
Emenius et al. Location
(2003)


Cotterill et al. Location
(1997)


Zota et al. Location
(2005)
Lee et al. (2004) Location
Liard et al. Location
(1999)






Factor Levels
—

—

1
2
Urban

Semi-urban
Suburban
On Main Road

50-85m from Main
Road
—

Industrial
Residential
Main Road
Side Road




Ambient Indoor Personal
NO2 Ambient NO2 Indoor NO2 Personal
Level Slope Level Slope Level Slope Comments
— — — — — Affect decay
rate
— — — 3.2 — — —

— — — — 25.9 — —
— — — — 30.8 — —
16.5 — 9.6 — — — —

11.3 — 6.4 — — — —
7.2 — 4.2 — — — —
— — 7.9 — — — Electric cooker
homes
— — 6.8 — — — Electric cooker
homes
— -0.0093 — — — — —

— — — — 34.9 — —
— — — — 27.8 — —
— — — — 28.1 — —
— — — — 24.3 — —





-------
CJQ
TABLE AX3.18 (cont'd). INDOOR, OUTDOOR, AND PERSONAL NO2 LEVELS STRATIFIED BY
                           EXPOSURE INDICATORS
         (CONCENTRATIONS ARE IN PPB AND SLOPES ARE DIMENSIONLESS)
to
o
o









X
OJ
01
^

References Factor Name Factor Levels
Nakai et al. Location < 20 m
(1995)

20-150 m


>150m


Aim et al. Location Downtown smoker
(1998) Suburban smoker
Downtown
nonsmoker
Suburban
nonsmoker
Ambient Indoor Personal
NO2 Ambient NO2 Indoor NO2
Level Slope Level Slope Level
42.4 — 43.8 — 43.1


34.9 — 38.4 — 35.9


20.3 — 36.4 — 30.1


— — — — 14.6
— — — — 10.9
— — — — 13.6

— — — — 9.0

Personal
Slope Comments
— Recalculated
based published
data
— Recalculated
based published
data
— Recalculated
based published
data
— —
— —

— —

fe
-LJ
H
1
O
o

0
H
O
H H
H
W
O
&
Lee etal. (1996) House structure Single DU
Small multi-DU

Large multi-DU
Single DU
Small multi-DU

Large multi-DU
Single DU

Small multi-DU
Large multi-DU
17
23

23.6
18.4
25.1

25.1
15.9

23.7
24.5
— 17 — —
— 28.9 — —

— 26.8 — —
— 17.8 — —
— 30.2 — —

— 25.4 — —
— 17.3 — —

— 27.8 — —
— 29.1 — —
— Winter
— Winter

— Winter
— Fall
— Fall

— Fall
— Summer

— Summer
— Summer
O

-------
CJQ
TABLE AX3.18 (cont'd). INDOOR, OUTDOOR, AND PERSONAL NO2 LEVELS STRATIFIED
                           EXPOSURE INDICATORS
         (CONCENTRATIONS ARE IN PPB AND SLOPES ARE DIMENSIONLESS)
                                                                                         BY
to
o
o












;>
X
OJ
01
oo


o
[>
H
1
O
o
2;
0
H
o
1 — I
H
W
O
O
O



References
Gallelli et al.
(2002)


Zota et al.
(2005)
Mosqueron
et al. (2002)
Liard et al.
(1999)
Gallelli et al.
(2002)
Yang et al.
(2004)
Garrett et al.
(1999)
Indoor sources
Zota et al.
(2005)

Lai et al. (2004)

Levy et al.
(1998a)

Belanger et al.
(2006)






Factor Name
Heating system

Frames

Floor level

Floor level

Extractor fan over
cooker
Chimney

Attached garage

Age of house


Supplemental
Heating with stove

Smoking

Smokers present


Ranges







Factor Levels
Individual
Central
Metal
Wood
—

—

Without
With
With vent
Without vent
With
Without
—


—


Smoking
Nonsmoking
With
Without

Electric
Gas




Ambient Indoor Personal
NO2 Ambient NO2 Indoor NO2
Level Slope Level Slope Level
— — 13.7 — —
— — 12.5 — —
— — 12.6 — —
— — 15.0 — —
— 2 — — —

— — — -1.78 —

— — — — 27.5
— — — — 24.8
— — 18.1 — —
— — 30.9 — —
— — 17.3 — —
— — 11.4 — —
— — — 0.5 —


— — — 7.84 —


— — 10.9 — 10.8
— — 11.5 — 14.1
— — — — 34.8
— — — — 26.8

— — 8.6 — —
— — 25.9 — —





Personal
Slope Comments
— Bedroom data
— Bedroom data
— Bedroom data
— Bedroom data
— —

— —

— —
— —
— Kitchen data
— Kitchen data
— —
— —
— —


— —


— —
— —
— —
	 	

— —
— —




-------
CJQ
TABLE AX3.18 (cont'd). INDOOR, OUTDOOR, AND PERSONAL NO2 LEVELS STRATIFIED BY
                           EXPOSURE INDICATORS
         (CONCENTRATIONS ARE IN PPB AND SLOPES ARE DIMENSIONLESS)
to
o
o










X
r N
OJ
L/l
VO

o
^
Prj
H
6
o
o
H
O
H
W
O
References
Cotterill et al.
(1997)


Yang et al.
(2004)
Schwab et al.
(1994)


Monn et al.
(1998)




Spengler et al.
(1994)



Aim et al.
(1998)
Raaschou-
Nielsen et al.
(1997)
Factor Name
Ranges



Ranges

Ranges



Ranges





Ranges




Ranges

Near fire


Factor Levels
Gas
Electric
Gas
Electric
Gas
Not Gas
Gas with pilot light
Gas without pilot
light
Electric
Gas Geneva
Electric Geneva
Gas Basle
Electric Basle
Gas Lugano
Electric Lugano





Electric smoker




Ambient Indoor
NO2 Ambient NO2 Indoor
Level Slope Level Slope
— — 35.6 —
— — 9.9 —
— — 11.5 —
— — 7.3 —
— — 18.3 —
— — 10.3 —
— — 20.3 —
— — 11.7 —

— — 8 —
— — 20.9 —
— — 16.8 —
— — 15.2 —
— — 12.6 —
— — 18.8 —
— — 15.7 —
— — — —




— — — —

	 	 	 	


Personal
NO2
Level
—
—
—
—
—
—
—
—

—
23.6
19.9
18.3
16.2
20.9
18.3
—




13.0

	


Personal
Slope Comments
— Kitchen
— Kitchen
— Bedroom
— Bedroom
— —
— —
— Summer 1998 data
— Summer 1998 data

— Summer 1998 data
— —
— —
— —
— —
— —
— —
— Gas with pilot was
15 ppb higher than
electric; gas without
pilot was 4 ppb
higher than electric
— —

0.052 —


O

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CJQ
to
o
o
X
OJ
H

6
o


o
H

O
HH
H
W
O
                TABLE AX3.18 (cont'd). INDOOR, OUTDOOR, AND PERSONAL NO2 LEVELS STRATIFIED

                                           EXPOSURE INDICATORS

                        (CONCENTRATIONS ARE IN PPB AND SLOPES ARE DIMENSIONLESS)
                                                                                         BY
References
Kawamoto et al.
(1997)

Lee et al. (2004)

Liardetal. (1999)

Kodama et al.
(2002)


Yang et al. (2004)

Levy et al.
(1998a)




Monn et al.
(1997)
Mosqueron et al.
(2002)
Raaschou-Nielsen
etal. (1997)
Factor Name
Heating time

Heating fuel

Heating appliance

Heater



Gas water heater

Gas water heater



Gas range

Gas cooking
Gas cooking
Gas appliances at
home
Factor Levels
Oil fan heater
Kerosene heater
Clean heater
Coal briquette
Petroleum
Gas
Other
Kerosene heater

Gas stove
Electric heater
With
Without
With
Without
With
Without
With
Without
With
Without


Ambient Indoor Personal
NO2 Ambient NO2 Indoor NO2 Personal
Level Slope Level Slope Level Slope Comments
— — — — — 2.59 —
— — — — — 1.17 —
— — — — — — —
— — — — 22.2 — —
— — — — 33.1 — —
— — — — 27.9 — —
— — — — 25.2 — —
— — 152.6 — — — Sourth area, Feb
1998
— — 77.5 — — — Sourth area, Feb
1998
— — 30.8 — — — Sourth area, Feb
1998
— — 18.1 — — — —
— — 11.9 — — — —
— — — — 30.5 — —
— — — — 28.2 — —
— — — — 36.4 — —
— — — — 28.5 — —
— — — — 34.8 — —
— — — — 20.5 — —
— — — — — — I/O > 1.2
— — — — — — I/O -0.4 -0.7
— — — 0.068 — — —
— — — — — 0.202 —

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OQ
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o
o
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6
o

2
o
H

O
HH
H
W
TABLE AX3.18 (cont'd). INDOOR, OUTDOOR, AND PERSONAL NO2 LEVELS STRATIFIED BY

                           EXPOSURE INDICATORS

         (CONCENTRATIONS ARE IN PPB AND SLOPES ARE DIMENSIONLESS)
References
Garrett et al.
(1999)








Button et al.
(2001)

Serensen et al.
(2005)
Liard et al.
(1999)
Raaschou-
Nielsen et al.
(1997)
Lee et al. (2004)


Liard et al.
(1999)
Factor Name
Gas and smoking









Fireplace setting


Exposure to burning
candle
Exposure to ETS

Exposure to ETS


Cooking fuel


Cooking appliance

Factor Levels
None





Gas stove
Gas heater
Smoking
Multiple
Low
Middle
High
—

With
Without



Petroleum
Gas
Coal briquette
Gas
Electric
Ambient Indoor
NO2 Ambient NO2 Indoor
Level Slope Level Slope
— — 3.0 —





— — 6.3 —
— — 5.0 —
— — 5.7 —
— — 11.2 —
— — 90 —
— — 350 —
— — 360 —
— — — —

— — — —
— — — —
— — — —


— — — —
— — — —
— — — —
— — — —
— — — —
Personal
NO2 Personal
Level Slope Comments
— — I/O ratio increase
from 0.8 to 1.3 to
1.8 to 2.2 in houses
with no, one, two,
or three major
indoors sources
— — —
— — —
— — —
— — —
— — —
— — —
— — —
— 0.031 —

25.1 — —
26.3 — —
— 0.056 —


26.1 — —
33.1 — —
20.6 — —
25.8 — —
25.5 — —
O

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CJQ
TABLE AX3.18 (cont'd). INDOOR, OUTDOOR, AND PERSONAL NO2 LEVELS STRATIFIED BY
                           EXPOSURE INDICATORS
         (CONCENTRATIONS ARE IN PPB AND SLOPES ARE DIMENSIONLESS)
to
o
o









J>
X
OJ
Oi
to


o
s>
H
6
o
0
H
O
HH
H
W

References Factor Name Factor Levels
Dennekamp Cooking 1 ring
etal. (2001)
2 rings

3 rings

4 rings

Boil water

Stir fry
Fry bacon

Bake cake

Roast meat
Bake potatoes



Ambient Indoor Personal
NO2 Ambient NO2 Indoor NO2
Level Slope Level Slope Level
— — 437 — —

— — 310 — —

— — 584 — —

— — 996 — —

— — 184 — —

— — 92 — —
— — 104 — —

— — 230 — —

— — 296 — —
— — 373 — —



Personal
Slope Comments
— The max 5 min
concentrations
— The max 5 min
concentrations
— The max 5 min
concentrations
— The max 5 min
concentrations
— The max 5 min
concentrations
— The max 5 min
concentrations
— The max 5 min
concentrations
— The max 5 min
concentrations
— The max 5 min
concentrations
— The max 5 min
concentrations



O

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OQ
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6
o

2
o
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O
HH
H
W
TABLE AX3.18 (cont'd). INDOOR, OUTDOOR, AND PERSONAL NO2 LEVELS STRATIFIED BY

                               EXPOSURE INDICATORS

          (CONCENTRATIONS ARE IN PPB AND SLOPES ARE DIMENSIONLESS)


References

Factor
Name


Factor Levels
Ambient
NO2
Level

Ambient
Slope
Indoor
NO2
Level

Indoor
Slope
Personal
NO2
Level

Personal
Slope


Comments
        Personal activities

        Levy et al.

        (1998a)
    Commute
Commuting less than

Ih
29.9

Chao and Law
(2000)





Kawamoto et al.
(1997)

Commute




Cooking to
stay home h
ratio
Cooking time
Without commuting — — —
< 1 h — — —
1-2 h — — —
2-3 h — — —
3-4 h — — —
4-6 h — — —
— — — —

— — — —
— 27.9 — —
— 21.7 — —
— 24.7 — —
— 24.6 — —
— 20.1 — —
— 27.9 — —
— — 55.4 —

— — 1.61 —
O

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CJQ
        TABLE AX3.19. PERSONAL NO2 LEVELS STRATIFIED BY DEMOGRAPHIC AND SOCIOECONOMIC FACTORS
                       (CONCENTRATIONS ARE IN PPB AND SLOPES ARE DIMENSIONLESS)
j~^
r-K
to
o
o
^










^
X
OJ
ON


DRAFT-DO I
^
0
H
O
HH
H
W
References
Rotkoetal. (2001)
Rotkoetal. (2001)
Raaschou-Nielsen (1997)
Lee etal., (2004)
Lee etal., (2004)
Rotkoetal. (2001)
Rotkoetal. (2001)
Raaschou-Nielsen (1997)
Rotkoetal. (2001)
Rotkoetal. (2001)
Rotkoetal. (2001)
Rotkoetal. (2001)
Rotkoetal. (2001)
Rotkoetal. (2001)
Algar et al. (2004)

Algar et al. (2004)
Algar et al. (2004)




Factor Type
Demography
Demography
Demography
Demography
Demography
Demography
Demography
Demography
Socioeconomic
Socioeconomic
Socioeconomic
Socioeconomic
Socioeconomic
Socioeconomic
Socioeconomic

Socioeconomic
Socioeconomic




Factor Name
Age
Age
Age
Gender
Gender
Gender
Gender
Gender
Education years
Education years
Employment
Employment
Occupational status
Occupational status
Employment

Employment
Employment




Factor levels Personal NO2 Level Personal Slope
25-34
35-55

Female
Male
Female
Male

<14 years
> 14 years
Employed
Not employed
Non white collar
White collar
Managerial, technical and
professional (Barcelona)
Skilled (manual and non-
manual) (Barcelona)
Unskilled and partly skilled
(Barcelona)




13.1
13.1
0.056
33
29
12.9
13.4
0.267
13.8
12.8
13.3
11.5
13.4
13.0
12.2

12.3
12.1




O

-------
   TABLE AX3.20. CORRELATIONS (PEARSON CORRELATION COEFFICIENT)
            BETWEEN AMBIENT NO2 AND AMBIENT COPOLLUTANTS
Study (ambient)
This CD
This CD
This CD
This CD
Kim et al. (2006)
Sarnat et al.
(2006)
Sarnat et al.
(2006)
Connell et al.
(2005)
Kim et al. (2005)
Sarnat et al.
(200 1)4
Sarnat et al.
(2001)
Hochadel et al.
(2006)
Hazenkamp-von
Arx et al. (2004)
Cyrys et al.
(2003)
Mosqueron et al.
(2002)
Rojas-Bracho
et al. (2002)
Location
Los Angeles
Riverside, CA
Chicago
New York City
Toronto
Steubenville, OH
(autumn)
Steubenville, OH
(summer)
Steubenville, OH

St. Louis (RAPS)
Baltimore, MD
(summer)
Baltimore, MD
(winter)
Ruhr area,
Germany
2 1 European cities
Erfurt, Germany
Paris
Santiago, Chile
PM25
0.49 (u3), 0.56 (s)

0.49 (s)
0.58 (u)
0.44
0.78 (0.70 for sulfate,
0.82 for EC)
0.00
(0.1 for sulfate, 0.24
for EC)
0.50


0.37
0.75
0.41, (0.93 for EC2)
0.75
0.50
0.69
0.77
CO O3 SO2
0.59 (u), -0.29 (u),
0.64 (s) -O.ll(s)
0.43 (u), 0.045 (u),
0.41 (s), 0.10(s),
0.15(r) -0.31(r)
0.53 (u), -0.20(u)
0.46 (s)
0.46 (u) -0.06 (u)
0.72




0.641
0.75 0.02
not significant
0.76 -0.71 -0.17


0.74


'Value with respect to NOX.
2Inferred based on EC as dominant contributor to PM2 5 absorbance.
 u: urban; s:  suburban; and r: rural
4Spearman correlation coefficient was reported
August 2007
AX3-165
DRAFT-DO NOT QUOTE OR CITE

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  TABLE AX3.21. CORRELATIONS (PEARSON CORRELATION COEFFICIENT)
        BETWEEN PERSONAL NO2 AND PERSONAL COPOLLUTANTS
Study
Kim et al. (2006)
Modig et al.
(2004)
Mosqueron et al.
(2002)
Jarvis et al.
(2005)
Location
Toronto
Umea
Paris
21
European
cities
PM25
0.41

0.12 but not
significant

CO VOCs HONO
0.12
0.06 for 1,3-butadiene;
and 0.10 for benzene

0.77 for indoor
NO2 and indoor
HONO
Lee et al. (2002)
Lai et al. (2004)   Oxford
       -0.1
      0.3   - 0.11 for TVOCs
                                             0.51 for indoor
                                             NO2 and indoor
                                             HONO
   TABLE AX3.22. CORRELATIONS (PEARSON CORRELATION COEFFICIENT)
          BETWEEN PERSONAL NO2 AND AMBIENT COPOLLUTANTS
      Study
  Location
PM25
Sulfate
EC    PMio    CO
Sarnat et al.
(2006)
Sarnat et al.
Steubenville /
Fall
Steubenville /
0.46

0.00
0.35

0.1
0.57

0.17
 (2006)
 Kim et al. (2006)
 Rojas-Bracho
 et al. (2002)
Summer
Toronto
Santiago
         not significant
 0.30
 0.65
                            0.20
                    0.39
August 2007
                 AX3-166
               DRAFT-DO NOT QUOTE OR CITE

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   TABLE AX3.23. CORRELATIONS (PEARSON CORRELATION COEFFICIENT)
          BETWEEN AMBIENT NO2 AND PERSONAL COPOLLUTANTS

    Study        Location     PM2.5      Sulfate      EC     Ultrafine-particle

 Sarnatetal.    Steubenville /    0.71        0.52       0.70
 (2006)        Fall

 Sarnatetal.    Steubenville/    0.00         0.1        0.26
 (2006)        Summer                not significant

 Vinzents      Copenhagen                                 0.49 (R2) explained by
 et al. (2005)                                              ambient NO2 and ambient
                                                         temperature
August 2007                          AX3-167     DRAFT-DO NOT QUOTE OR CITE

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  TABLE AX3.24. THE ESSENTIAL ATTRIBUTES OF THE PNEM, HAPEM, APEX,
                        SHEDS, AND MENTOR-1A

Exposure Estimate

Characterization of
the High-End
Exposures
Typical Spatial
Scale/Resolution

Temporal
Scale/Resolution

Population
Activity Patterns
Assembly

Microenvironment
Concentration
Estimation








Microenviron-
mental (ME)
Factors
Specification of
Indoor Source
Emissions
Commuting
Patterns
Exposure Routes

Potential Dose
Calculation
Physiologically
Based Dose
Variability/
Uncertainty
pNEM
Hourly averaged

Yes


Urban
areas/Census
tract level
A yr/one h


Top-down
approach


Non-steady-state
and steady-state
mass balance
equations (hard-
coded)






Random samples
from probability
distributions
Yes (gas-stove,
tobacco
smoking)
Yes

Inhalation

Yes

No

Yes

HAPEM
Annual averaged

No


Ranging from
urban to national/
Census tract level
A yr/one h


Top-down
approach


Linear
relationship
method (hard-
coded)







Random samples
from probability
distributions
Available; set to
zero in HAPEM6

Yes

Inhalation

No

No

No

APEX
Hourly averaged

Yes


Urban
area/Census tract
level
A yr/one h


Bottom-up
"person-
oriented"
approach
Non-steady-state
mass balance and
linear regression
(flexibility of
selecting
algorithms)





Random samples
from probability
distributions
Yes (multiple
sources defined
by the user)
Yes

Inhalation

Yes

No

Yes

SHEDS
Activity event
based
Yes


Urban
areas/Census
tract level
A yr/event based


Bottom-up
"person-oriented"
approach

Steady-state mass
balance equation
(residential) and
linear regression
(non-residential)
(hard-coded)





Random samples
from probability
distributions
Yes (gas-stove,
tobacco smoking,
other sources)
Yes

Inhalation

Yes

Yes

Yes

MENTOR-1A
Activity event
based
Yes


Multiscale/
Census tract level

A yr/activity
event based time
step
Bottom-up
"person-oriented"
approach

Non-steady-state
mass balance
equation with
indoor air
chemistry
module or
regression
methods
(flexibility of
selecting
algorithms)
Random samples
from probability
distributions
Yes (multiple
sources defined
by the user)
Yes

Multiple
(optional)
Yes

Yes

Yes (Various
"Tools")
August 2007
AX3-168
DRAFT-DO NOT QUOTE OR CITE

-------
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25
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 i          AX4.  CHAPTER 4 ANNEX - TOXICOLOGICAL
 2       EFFECTS OF NITROGEN DIOXIDE AND RELATED
 3                            OXIDES OF NITROGEN
 4
 5
 6   Effects of Nitrogen Dioxide on Antioxidant and Antioxidant Metabolism
 7          Nitrogen dioxide is an oxidant and lipid peroxidation is believed to be a major molecular
 8   event responsible for its toxicity. As a result, there has been considerable attention paid to the
 9   effect of NO2 on the antioxidant defense system in the epithelial lining fluid and in pulmonary
10   cells. Repeated exposures to NO2 at concentrations ranging from 75 to 62,040 |ig/m3 (0.04 to
11   33 ppm) have revealed effects on low molecular weight antioxidants such as glutathione, vitamin
12   E, and vitamin C, as well as some enzymes involved in cell oxidant homeostasis.
13          A number of studies have investigated the hypothesis, originally proposed by Menzel
14   (1970), that antioxidants might protect the lung from NC>2 damage by inhibiting lipid
15   peroxidation (see Table AX4.1).  Changes in the activity of enzymes in the lungs of NO2-
16   exposed animals that regulate levels of glutathione (GSH) have been reported at relatively low
17   exposure concentrations. Sagai et al. (1984) studied the effects of prolonged (9 and 18 months)
18   exposure to 75, 752, and 7520 |ig/m3 (0.04, 0.4, and 4.0 ppm) NC>2 on rats. After either exposure
19   duration, non-protein sulfhydryl levels were increased at 752 |ig/m3 or greater, and exposure to
20   7520 |ig/m3 (4.0 ppm) decreased the activity of GSH peroxidase but increased
21   glucose-6-phosphate dehydrogenase activity. Glutathione peroxidase activity was also decreased
22   in rats exposed to 752 |ig/m3 NC>2 for 18 months. Three GSH S-transferases were also studied,
23   two of which (aryl ^-transferase and aralkyl ^-transferase) exhibited decreased activities after
24   18 months of exposure to 752 |ig/m3 or greater NC>2. No effects were observed on the activities
25   of 6-phosphogluconate dehydrogenase, superoxide  dismutase, or disulfide reductase. Effects
26   followed a concentration- and exposure-duration response function.  The decreases in
27   glutathione-related enzyme activities were inversely related to the apparent formation of lipid
28   peroxides (see lipid peroxidation subsection). Shorter exposures (4 months) to NC>2 between
29   752 and 7520 |ig/m3 (0.4 and 4.0 ppm) also caused concentration- and duration-dependent
30   effects on antioxidant enzyme activities (Ichinose and Sagai, 1982).  For example,
31   glucose-6-phosphate dehydrogenase increased, reaching a peak at 1 month, and then decreased
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 1    towards the control value.  Briefer (2-week) exposures to 752 |ig/m3 (0.4 ppm) NC>2 caused no
 2    such effects in rats or guinea pigs (Ichinose and Sagai, 1989).
 3           The activities of GSH reductase and glucose-6-phosphate dehydrogenase were
 4    significantly increased during exposure tol 1,700 |ig/m3 (6.2 ppm) NC>2 for 4 days; GSH
 5    peroxidase activity was not affected (Chow et. al., 1974).  The possible role of edema and
 6    cellular inflammation in these findings was not examined.  Since NC>2 had no significant effect
 7    on lung GSH peroxidase activity in this study, but did significantly increase the activities of GSH
 8    reductase and glucose-6-phosphate dehydrogenase, the authors concluded that NO2 attacks
 9    mainly GSH and NADPH.
10           Newer studies also identified effects on glutathione. Changes in glutathione status in the
11    blood and lung (bronchoalveolar lavage (BAL) fluid) occurred in rats exposed to 9400 |ig/m3
12    (5 ppm) and 18,800 |ig/m3 (10 ppm) NC>2 continuously for 24 h, but not for 7 days (Pagani et al.,
13    1994).  Total glutathione - total of reduced (GSH) and oxidized (GSSG) form - was significantly
14    increased in blood but not in BAL fluid; however, GSSG was elevated in BAL fluid only.  A
15    decreased GSH/GSSG ratio was observed in the blood and BAL fluid, but not in lung type II
16    cells, in rats continuously exposed to 18,800 |ig/m3 (10 ppm) NC>2 for 3 or 20 days (Hochscheid
17    et al., 2005). Interestingly, lipid peroxidation was decreased in type II cells at 3 days, but was
18    similar to controls at 20 days. Gene expression, as measured by mRNA levels of the enzymes
19    involved in the biosynthesis of glutathione - gamma-glutamylcysteine synthetase (yGCS) and
20    glutathione synthetase (GS), was decreased at both time points, but gamma-
21    glutamyltranspeptidase (yGT) mRNA expression was increased.  No GSH peroxidase activity
22    (important for hydroperoxide reduction of complex lipids) was detected at 3 days, and was
23    barely detected at 20 days.
24           Malnutrition of animals can drastically affect their response to toxicants, including NC>2.
25    Experimental interest in this area has mainly focused on dietary lipids, vitamin E and other lipid-
26    soluble antioxidants, and vitamin C and other water-soluble antioxidants.  Ayaz and Csallany
27    (1978)  exposed vitamin E-deficient and vitamin E-supplemented (30 or 300 mg/kg opf diet)
28    weanling mice continuously for 17 months to 940 or 1880 |ig/m3 (0.5 or 1.0 ppm) NC>2 and
29    assayed blood, lung,  and liver tissues for GSH peroxidase activity.  Exposure to 1880 |ig/m3
30    (1.0 ppm) NC>2 alone or combined with vitamin E deficiency decreased the enzyme activity in
31    the blood and lungs.  Neither vitamin E deficiency nor NC>2 exposure affected liver GSH

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 1    peroxidase activity. However, in vitamin E-supplemented mice, GSH peroxidase activity
 2    increased at 940 |ig/m3 (0.5 ppm) and 1880 |ig/m3 (1.0 ppm) NO2.
 3
 4    Lipid Metabolism and Content of the Lung
 5          Lipid peroxidation is an important mechanism of cell damage arising from changes in
 6    cell membrane structure and function.  The ability of NO2 exposure to induce lipid peroxidation
 7    in the respiratory tract has been well demonstrated in available studies as measured by increased
 8    ethane exhalation in the breath, as thiobarbituric acid (TEA) reactive substances in tissues, and
 9    as the content of conjugated dienes in tissue homogenates.
10          A number of studies have investigated the effects of NO2 exposure on lipid metabolism
11    and content of the lung. Lipid peroxidation induced by NO2 exposure has been detected at
12    exposure concentrations as low as 75 |ig/m3 (0.04 ppm). Increased ethane exhalation was
13    observed in rats  exposed to 75 or 225 |ig/m3 (0.04 or 0.12 ppm) after 9 and 18 months of
14    exposure (Sagai  et al., 1984). Exposure to 752 |ig/m3  (0.4 ppm) NO2 for 9 months or longer and
15    to 7520 |ig/m3 (4.0 ppm) for 6 months resulted in increased TEA reactants (Ichinose et al.,
16    1983). NO2 exposures for shorter durations also increased lipid peroxidation in rats.  For
17    example, NO2 concentrations of 2256 |ig/m3 (1.2 ppm) or greater for 1 week (Ichinose and
18    Sagai, 1982; Ichinose et al., 1983) increased ethane exhalation in rats, while exposure of
19    pregnant rats to  1000 |ig/m3 or 10,000 |ig/m3  (0.53 or  5.3 ppm) NO2 for 5 h/day for 21 days rats
20    resulted  in increases in lung lipid peroxidation products (Balabaeva and Tabakova, 1985).  These
21    results indicate at least some degree of duration-dependence in the formation of lipid
22    peroxidation, with lower effect thresholds identified with longer durations of exposure.
23          Lipid peroxidation results in altered phospholipid composition, which in turn may affect
24    membrane fluidity and thus, membrane function.  Significant depression of lipid content and
25    total content of saturated fatty acids such as phosphatidyl-ethanolamine, lecithin
26    (phosphatidylcholine), phosphatidylinositol, and phosphatidylserine were found in rats exposed
27    to 5450 |ig/m3 (2.9 ppm) NO2 for 24 h/day, 5 days/week for 9 months (Arner and Rhoades,
28    1973). Exposure of rabbits to 1880 |ig/m3 (1.0 ppm) NO2 for 2 weeks also caused depression of
29    lecithin synthesis after one week of exposure (Seto et al., 1975), while exposure of rats to
30    10,300 |ig/m3 (5.5  ppm) NO2 for 3  h/day for 7 or 14 days elicited only few changes in lipid
31    metabolism (Yokoyama et al., 1980). In beagle dogs,  the amount of unsaturated fatty acids in
32    the phospholipids from the lungs was increased after exposure to concentrations ranging from

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 1    9400 to 30,080 |ig/m3 (5 to 16 ppm), but not to 5640 |ig/m3 (3 ppm) (Dowell et al., 1971).
 2    Exposure of either mice or guinea pigs to an NC>2 level of 750 |ig/m3 (0.4 ppm) for a week
 3    resulted in a decreased concentration of phosphatidylethanolamine and a relative increase in the
 4    phosphatidylcholine concentration (Sagai et al., 1987). Concentration-and exposure duration-
 5    dependent increases were reported in phospholipid components in BAL fluid, when rats were
 6    exposed to 10 ppm NO2 continuously for 1 day or 3 days (Miiller et. al.,  1994).
 7          Functional studies conducted on surfactant phospholipid extracts indicated that NC>2
 8    exposures of 5 ppm or greater, but not to 0.8 ppm, directly impaired surface tension, although the
 9    structure of the surfactant protein A (SP-A) was not altered by NC>2 exposure. Changes in the
10    phospholipid composition of membranes may result in disruption of the cell membrane barrier.
11    Miiller et al. (2003) found that uptake of liposomes by type II lung cells occurred more easily
12    from animals exposed to 10 ppm NC>2 for 3 to 28 days, possibly as a result of increased demand
13    of phosphatidylcholine during lung injury.
14          Lipid peroxidation can also activate phospholipases. Activation of phospholipase Al in
15    cultured endothelial cells occurred atNC>2 concentration of 9400 |ig/m3 (5 ppm) after 40 h of
16    exposure  and was speculated to depend on a specific MVinduced increase in phosphatidyl
17    serine in the plasma membranes (Sekharam et al., 1991).
18          One function of phospholipases is the release of arachidonic acid (AA), which serves as a
19    mediator of inflammatory response. NC>2 exposure affects the release  and metabolism of
20    arachidonic acid both in vivo and in vitro.  The products of arachidonic acid metabolism, such as
21    prostaglandins, prostacyclin, thromboxanes, and leukotrienes play an important role (such as
22    recruitment of neutrophils to sights of local irritation) in modulating inflammatory response.
23    Schlesinger et al. (1990) reported elevated concentrations of thromboxane B2 (1x82) following
24    NC>2 exposures of 1880 |ig/m3 (1.0 ppm) for 2 h, depressed concentrations  at 5640 |ig/m3
25    (3.0 ppm), and significant depression 24 h postexposure at 18,880 |ig/m3 (10 ppm) NC>2.  The
26    same investigators also reported depressed level of 6-keto-prostaglandin Fla at 1880 |ig/m3
27    (1.0 ppm) NC>2, but exposure to NC>2 did not affect prostaglandins E2 and F2 and leukotriene B4
28    (LTB4) levels.
29          Changes in activation of arachidonate metabolism were also reported in rat alveolar
30    macrophages (AMs) when these animals were exposed to 940 |ig/m3 (0.5 ppm) NC>2 for 0.5, 1, 5,
31    and 10 days (Robison et al., 1993).  Unstimulated AM synthesis of LTB4 was depressed after

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 1    0.5 days and again after 5 days of exposure to NO2. Alveolar macrophage production of TxB2,
 2    LTB4, and 5-hydroxyeicosatetraenoic acid (5-HETE) in response to stimulation with the calcium
 3    ionophore, A23187, was depressed after 0.5 days of exposure and recovered to air-control values
 4    with longer exposure periods. 5-HETE levels were increased after 10 days of exposure.
 5    However, AM production of LTB4 in response to zymosan-activated rat serum was depressed
 6    only after 5 days of exposure.
 7          The effects of NO2 on structural proteins of the lungs have been of concern because
 8    elastic recoil is lost after exposure. Collagen synthesis rates are increased in rats exposed to NO2
 9    concentrations as low as 9400 |ig/m3 (5.0 ppm) NO2.  It has been assumed that increased
10    collagen synthesis reflect increases in total lung collagen which, if sufficient, could result in
11    pulmonary fibrosis after longer periods of exposure. Such correlation has yet to be confirmed by
12    in vivo studies involving NO2 exposure.
13          Alterations in xenobiotic metabolism pathways following NO2 exposure are also
14    summarized in Table AX4.2, in addition to changes in phase I enzymes (such as cytochrome
15    P450s) and phase II enzymes (GST as described earlier).  While these changes are not
16    necessarily toxic manifestations of NO2 per se,  such changes may impact the metabolism and
17    toxicity of other chemicals.  Glycolytic pathways are also apparently affected.  For example,
18    glycolytic metabolism was increased by NO2 exposure, apparently due to a concurrent increase
19    in type II cells (Mochitate et al.,  1985).
20
21    Emphysema Follow ing Nitrogen Dioxide Exposure
22          Emphysema as a result of chronic exposure to NO2 has been reported in animal studies.
23    The definition of emphysema has changed since the time that some of the studies have been
24    published; thus, it is important to compare the findings of the studies with the current definition
25    of emphysema. U.S. Environmental  Protection Agency (1993) evaluated the animal studies
26    reporting emphysema from chronic exposure to NO2 based upon the most recent definition of
27    emphysema from the report of the National Heart, Lung and Blood Institute (NHLBI), Division
28    of Lung Diseases Workshop (Snider  et al., 1985); see  U.S. Environmental Protection Agency
29    (1993) for the definitions of emphysema. Because the focus of this document is extrapolation of
30    NO2 exposures to potential hazards for humans, only those studies showing emphysema of the
31    type seen in human lungs will be discussed.
32

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 1          Emphysema was reported by Hay don et al. (1967) in rabbits exposed continuously
 2    (presumably 24 h/day) for 3 to 4 months to 15,000 or 22,600 |ig/m3 (8.0 or 12.0 ppm) NO2.  The
 3    investigators reported enlarged lungs that failed to collapse when the thorax was opened. When
 4    the lungs were fixed in an expanded state via the trachea using formaldehyde, there was evidence
 5    of enlarged airspaces with destructive changes in alveolar walls.  Although no stereology was
 6    performed, the changes observed appear to be emphysema of the type seen in human lungs.
 7          WHO (1997) has also reported a study by Freeman et al. (1972) in which rats were
 8    exposed to 37,600 |ig/m3 (20.0 ppm) NO2, which was reduced during the exposure to
 9    28,200 |ig/m3 (15.0 ppm) or to 18,800 |ig/m3 (10.0 ppm), for varying periods up to 33 months.
10    The lungs were fixed via the trachea, and morphometric analysis of the lung and alveolar size
11    indicated an enlargement of alveolar, reduction in alveolar surface, and alveolar destruction.
12    Although the investigators concluded that their study demonstrated emphysema in their NO2-
13    exposed rats, WHO (1997) noted that it was not entirely clear whether the experimental groups
14    or only the group exposed to 28,200 |ig/m3 (15.0 ppm) had emphysema.
15          Although many of the papers reviewed (U.S. Environmental Protection Agency, 1993)
16    reported finding emphysema, some of these studies were reported according to previous,
17    different criteria; some reports did not fully describe the methods used; and/or the results
18    obtained were not in sufficient detail to allow independent confirmation of the presence of
19    emphysema. For example, Hyde et al. (1978) reported no emphysema in beagle dogs exposed
20    16 h daily for 68 months to 1200 |ig/m3 (0.64 ppm) NO2 with 310 |ig/m3 (0.25 ppm) NO or to
21    263 |ig/m3 (0.14 ppm) NO2 with 2050 |ig/m3 (1.67 ppm) NO.  The dogs then breathed clean air
22    during a 32- to 36-month post-exposure period. The right lungs were fixed via the trachea at
23    30-cm fixative pressure in a distended state. Semiautomated image analysis was used for
24    morphometry of air spaces.  The dogs exposed to 1200 |ig/m3 NO2 with 310 |ig/m3 NO had
25    significantly larger lungs with enlarged air  spaces and evidence of destruction of alveolar walls.
26    These effects were not observed in dogs exposed to 270 |ig/m3 NO2 with 2050 |ig/m3 NO,
27    implying a significant role of the NO2 in the production of the  lesions.  The lesions in the dogs
28    exposed to the higher NO2 concentration meet the criteria of the 1985 NHLBI workshop for
29    emphysema of the type seen in human lungs.
30
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 1    Nitrates (NO3 )
 2          Busch et al. (1986) exposed rats and guinea pigs with either normal lungs or elastase-
 3    induced emphysema to ammonium nitrate aerosols at 1 mg/m3 for 6 h/day, 5 days/week for
 4    4 weeks.  Using light and electron microscopy, the investigators concluded that there were no
 5    significant effects of exposure on lung structure.
 6
 7
 8    AX4.2     DOSIMETRY OF INHALED NITROGEN OXIDES
 9          This section provides an overview of NC>2 dosimetry and updates information provided in
10    the 1993 AQCD for Oxides of Nitrogen. Dosimetry of NC>2 refers to the measurement or
11    estimation of the amount of NC>2 or its reaction products reaching and persisting at specific sites
12    in the respiratory tract following an exposure.  Nitrogen dioxide, classified as a reactive gas,
13    interacts with surfactants, antioxidants, and other compounds in the epithelial lining fluid (ELF).
14    The compounds thought responsible for adverse pulmonary effects of inhaled NC>2 are the
15    reaction products themselves or the metabolites of these products in the ELF. At the time of the
16    1993 AQCD for Oxides of Nitrogen, it was thought that inhaled NO2 probably reacted with the
17    water molecules in the ELF to form nitrous acid (HNO2) and nitric acid (HNOs).  However,
18    some limited data suggested that the absorption of NO2 was linked to reactive substrates in the
19    ELF and subsequent nitrite production. Since then, the reactive absorption of NO2 has been
20    examined in a number of studies (see Section 4.2.2).  These studies have characterized the
21    absorption kinetics and reactive substrates for NO2 delivered to various sites in the respiratory
22    tract. Researchers have attempted to obtain a greater understanding of how these complex
23    interactions affect NO2 absorption and NO2-induced injury.
24          With respect to quantifying absolute NO2 absorption, the following were reported in the
25    1993 AQCD for Oxides of Nitrogen. The principles of Os uptake were generally assumed
26    applicable for NO2 modeling studies. The results indicated that NO2 is absorbed throughout the
27    lower respiratory tract, but the major delivery site is the centriacinar region, i.e., the junction
28    between the conducting and respiratory airways in humans and animals. Experimental studies
29    have found that the total respiratory tract uptake in humans ranges from 72 to 92% depending on
30    the study and the breathing conditions.  The percent total uptake increases with increasing
31    exercise level.  In laboratory animals, upper respiratory tract uptakes ranged from as low as 25%
32    to as high as 94% depending on the study, species, air flow rate, and mode of breathing (nasal or

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 1    oral).  Upper respiratory tract uptake of NO2 was found to decrease with increasing ventilation.
 2    Uptake during nasal breathing was determined to be significantly greater than during oral
 3    breathing.
 4
 5    AX4.2.1    Mechanisms of NOi Absorption
 6           The ELF is the initial barrier against NO2 delivery to the underlying epithelial cells.
 7    Postlethwait and Bidani (1990) suggested that acute NO2 uptake  in the lower respiratory tract
 8    was rate limited by chemical reactions of NO2 with ELF constituents rather than by gas solubility
 9    in the ELF. Subsequently, Postlethwait et al. (1991) reported that inhaled NO2 (10 ppm) does
10    not penetrate the ELF to reach underlying sites and suggested that cytotoxicity may be  due to
11    NO2 reactants formed in the ELF.  Since then, the reactive absorption of NO2 has been  examined
12    in a number studies that have sought to identify reactive substrates for NO2 and quantify the
13    absorption kinetics of NO2 in the respiratory tract.
14    Postlethwait and Bidani (1994) concluded that the reaction between NO2 and water does not
15    significantly contribute to the absorption of inhaled NO2.  Uptake is a first-order process for NO2
16    concentrations less than 10 ppm, is aqueous substrate-dependent, and is saturable. The
17    absorption of inhaled NO2 is thought to be coupled with free radical-mediated hydrogen
18    abstraction to form FDSTO2 and an organic radical (Postlethwait and Bidani, 1989, 1994). At
19    physiologic pH, the HNO2 subsequently dissociates to H+ and nitrite (NO2 ). The concentration
20    of the resulting nitrite is thought insufficient to be toxic, so effects are thought to be due to the
21    organic radical and/or the proton load. Nitrite may enter the underlying epithelial cells and
22    blood.  In the presence of red blood cells, nitrite is oxidized to nitrate (NOs ) (Postlethwait and
23    Mustafa, 1981). Beyond cell susceptibility and the concentration of NO2 in the lumen, site-
24    specific injury was proposed to depend on rate of 'toxic'  reaction product formation and the
25    quenching of these products within the ELF. Related to the balance between reaction product
26    formation and removal, it was further suggested that cellular responses may be nonlinear with
27    greater responses being possible at low levels of NO2 uptake versus  higher levels of uptake.
28    Since the ELF may vary throughout the respiratory tract, the uptake of inhaled NO2 and reaction
29    with constituents of the pulmonary ELF may be related to the heterogeneous distribution of
30    epithelial injury observed from NO2 exposure.
31
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 1          Postlethwait et al. (1995) sought to determine the absorption substrates for NO2 in the
 2    ELF lavaged from male Sprague-Dawley rats. Since the bronchoalveolar lavage fluid (BALF)
 3    collected from the rats may be diluted up to 100-fold relative to the native ELF, the effect of
 4    concentrating the BAL fluid on NC>2 absorption was investigated.  A linear association was
 5    found between the first-order rate constant for NO2 absorption and the concentration of the
 6    BALF. This suggests that concentration of the reactive substrates in the ELF determines the rate
 7    of NC>2 absorption. The absorption due to specific ELF constituents was also examined in
 8    chemically pure solutions. Albumin, cysteine, reduced glutathione (GSH), ascorbic acid, and
 9    uric acid were hydrophilic moieties found to be active substrates for NC>2 absorption.
10    Unsaturated fatty acids (such as oleic, linoleic, and linolenic) were also identified as active
11    absorption substrates and thought to account for up to 20% of NO2 absorption. Vitamins A and
12    E exhibited the greatest reactivity of the substrates that were examined. However, the low
13    concentrations of uric acid and vitamins A and E were thought to preclude them from being
14    appreciable substrates in vivo. The authors concluded that ascorbate and GSH were the primary
15    NC>2 absorption substrates in rat ELF. Postlethwait et al. (1995) also found that the pulmonary
16    surfactant, dipalmitoyl phosphatidylcholine, was not an effective substrate for NC>2 absorption.
17    Later, Connor et al. (2001) suggested that dipalmitoyl phosphatidylcholine may actually inhibit
18    NO2 absorption.
19          In a subsequent study, Velsor and Postlethwait (1997) investigated the mechanisms of
20    acute epithelial injury from NO2  exposure.  The impetus for this work was to evaluate the
21    supposition that NC>2 reaction products rather than NC>2 itself cause epithelial injury. Red blood
22    cell membranes were immobilized to the bottom of Petri dishes, covered with a variety of well
23    characterized aqueous layers, and exposed to gaseous NC>2 (10 ppm  for 20 min).  The study
24    focused on the potential roles of  GSH and ascorbic acid reaction products in mediating cellular
25    injury. Based on negligible membrane oxidation when covered with only an aqueous phosphate
26    buffer, the diffusive/reactive resistance of a thin aqueous layer clearly prevented direct
27    interaction between NC>2 and the underlying membrane. The presence of unsaturated fatty acids
28    was not observed to affect NO2 absorption, but a sufficiently thin liquid layer was required for
29    membrane oxidation to occur. Interestingly, membrane oxidation was not a simple monotonic
30    function of GSH and ascorbic acid levels.  The maximal levels of membrane oxidation were
31    observed at low antioxidant levels versus null or high antioxidant levels. Glutathione and

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 1    ascorbic acid related membrane oxidation were superoxide and hydrogen peroxide dependent,
 2    respectively. The authors suggested that at the higher antioxidant concentrations, there was
 3    increased absorption of NO2, but little secondary oxidation of the membrane because the reactive
 4    species (e.g., superoxide and hydrogen peroxide) generated during absorption were quenched.
 5    At the low antioxidant concentrations, there was a lower rate of NO2 absorption, but oxidants
 6    were not quenched and so were available to interact with the cell membrane.
 7          Kelly et al. (1996a) examined the effect of a 4-h NO2 (2 ppm) exposure on antioxidant
 8    levels in bronchial lavage fluid (BLF) and BALF of 44 healthy nonsmoking adults (19-45 year,
 9    median 24 years). Subjects were randomly assigned to three groups and lavaged at either 1.5 h
10    (n = 15), 6 h (n = 15), or 24 h (n = 14) after the NO2 exposure.  The baseline concentrations of
11    uric acid and ascorbic acid were strongly correlated between the BLF and BALF within
12    individuals (r = 0.88, p < 0.001; r = 0.78, p = 0.001; respectively), whereas the concentrations of
13    GSH in the BLF and BALF were not correlated. Uric acid levels in both lavage fractions were
14    significantly reduced at 1.5 h (p < 0.04), significantly increased at 6 h (p < 0.05), and back to
15    baseline at 24 h postexposure.  A statistically significant loss of ascorbic acid was also found in
16    both lavage fractions at 1.5 h (p < 0.05). At 6 and 24 h postexposure, the ascorbic acid levels
17    had returned to baseline.  In contrast, GSH levels were significantly increased at both 1.5 h
18    (p < 0.01) and 6 h (p < 0.03) in BLF. At 24 h postexposure, the GSH levels in BLF returned to
19    baseline. Although GSH in BLF increased at 1.5 and 6 h postexposure, oxidized GSH levels
20    remained similar to baseline in both BLF and BALF. No changes in BALF levels of GSH were
21    observed at any time point.
22          The depletion of uric acid and ascorbic acid, but not GSH has also been observed with
23    ex vivo exposure of human BALF to NO2.  Kelly et al. (1996b) collected BALF from male lung
24    cancer patients (n = 16) and exposed the BALF ex vivo at 37°C to NO2 (0.05 to 2.0 ppm; 4 h) or
25    O3 (0.05 to 1.0 ppm; 4 h). Kelly and Tetley (1997) also collected BALF from lung cancer
26    patients (n = 12, 54 + 16 years) and exposed the BALF ex vivo to NO2  (0.05 to 1.0 ppm; 4 h).
27    Both studies found that NO2 depletes uric acid and ascorbic acid, but not GSH from BALF.
28    Kelly et al. (1996b) noted a differential  consumption of the antioxidants with uric acid loss being
29    greater than that of ascorbic acid which was lost at a much greater rate  than GSH. Kelly and
30    Tetley (1997) found that the rates of uric acid and ascorbic acid consumption were correlated
31    with their initial concentrations in the BAL fluid, such that higher initial antioxidant

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 1    concentrations were associated with a greater rate of antioxidant depletion.  Illustrating the
 2    complex interaction of antioxidants, these studies also suggest that GSH oxidized by NO2 may
 3    be again reduced by uric acid and/or ascorbic acid.
 4
 5    AX4.2.3    Regional and Total Respiratory Absorption of NOi
 6          There has been very limited work related to the quantification of NC>2 uptake since the
 7    1993 AQCD for Oxides of Nitrogen.  As a result, there is an abbreviated discussion here of some
 8    papers that were reviewed in the 1993 AQCD for Oxides of Nitrogen.
 9
10    AX4.2.3.1    Dosimetry Models
11          There is a paucity of theoretical studies investigating NO2 dosimetry. Like Os, NO2 is
12    highly reactive in ELF and is not very soluble. An Os model has been utilized to predict the
13    uptake of NO2 in the lower respiratory tract of humans, rats, guinea pigs, and rabbits (Miller
14    et al., 1982; Overton, 1984). In this model, there was a strong distinction between uptake and
15    dose. Uptake referred to the amount of NO2 being removed from gas phase per lung surface area
16    (jig/cm2), whereas, dose referred to the amount of NO2 per lung  surface area (jig/cm2) that
17    diffused through the ELF and reached the underlying tissues.
18          Miller et al. (1982) and subsequently Overton (1984) did not attempt to predict the
19    amount of reactants in the ELF or the transport of reactants to the tissues. Rather, they focused
20    mainly on the sensitivity of NO2 tissue dose on NO2 reaction rates in the ELF and the Henry's
21    law constant. Reaction rates of NO2 in the ELF were varied from zero, 50%, and 100% of the
22    reaction rate for Os in ELF. The Henry's law constant was varied from half to double the
23    Henry's law constant for NO2 in water at 37 °C.  Effects of species, lung morphology, and tidal
24    volume (Vx) were also examined.  In general, the model  predicted that NO2 is taken up
25    throughout the lower respiratory tract.  In humans, NO2 uptake was fairly constant from the
26    trachea to the first generation of respiratory bronchioles,  beyond which uptake decreased with
27    distal progression.  The NO2 tissue dose was highly dependent on the Henry's law constant and
28    reaction rate in the ELF. In the conducting airways, the NO2 tissue dose decreased as the
29    Henry's law constant increased (i.e., decreased gas solubility), whereas the NO2 tissue dose in
30    the alveolar region increased. The site of maximal NO2 tissue dose was fairly similar between
31    species, ranging from the first generation of respiratory bronchioles in humans to the alveolar
32    ducts in rats. In guinea pigs and rabbits, the maximal NO2 tissue dose was predicted to occur in

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 1    the last generation of respiratory bronchioles. The simulations showed that exercise increases
 2    the NO2 tissue dose in the pulmonary region relative to rest. Miller et al. (1982) also reported
 3    that increasing the NO2 reaction rate decreased NO2 tissue dose in the conducting airways, but
 4    had no effect on the dose delivered to the pulmonary region.
 5           Simultaneously occurring diffusion and chemical reactions in the ELF have been
 6    suggested as the limiting factors in Os (Santiago et al., 2001) and NO2 uptake (Postlethwait and
 7    Bidani, 1990). Hence, Miller et al. (1982) should have found an increase in the uptake of NO2 in
 8    the conducting airways with increasing the rate of chemical reactions in the ELF. This increase
 9    in NO2 uptake in the conducting airways would then lead to a reduction in the amount of NO2
10    reaching and taken up in the pulmonary region.  The Miller et al. (1982) model considered
11    reactions of NO2 with constituents in the ELF as protective in that these reactions reduced the
12    flux of NO2 to the tissues. Others have postulated that NO2-reactants formed in the ELF, rather
13    than NO2 itself, could actually cause adverse responses (Overton, 1984; Postlethwait and Bidani,
14    1994; Velsor and Postlethwait, 1997).
15          More recently, Overton and Graham (1995) examined NO2 uptake  in an asymmetric
16    anatomic model of the rat lung.  The multiple path model of Overton and Graham (1995)
17    allowed for variable path lengths from the trachea to the terminal bronchioles, whereas Miller
18    et al. (1982) used a single or typical path model of the conducting airways. The terms dose and
19    uptake were used synonymously to describe the amount of NO2 gas lost from the gas phase in a
20    particular lung region or generation by Overton and Graham (1995). Reactions of NO2 in the
21    ELF were not explicitly considered.  Their simulations were conducted for rats breathing at
22    2 mL VT at a frequency  of 150 breaths per minute. The mass transfer coefficients of 0.173,
23    0.026, and 0.137 cm/sec were assumed for the upper respiratory tract, the tracheobronchial
24    airways, and the pulmonary region, respectively.  Uptake was predicted to decrease with distal
25    progression into the lung. In general, the modeled NO2 dose varied among anatomically
26    equivalent ventilatory units as a function of path length from the trachea with shorter paths
27    showing greater dose. A sudden increase in NO2 uptake was predicted in the proximal alveolar
28    region (PAR) which was due to the increase in the assumed mass transfer coefficient relative to
29    the adjacent terminal bronchiole. Overton et al. (1996) showed that increasing the mass transfer
30    coefficient of the tracheobronchial airways would decrease the dose to the  PAR and vice versa.
31    Additionally, the PAR dose would also be reduced by the more realistic modeling of

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 1   tracheobronchial airways expansion during inspiration versus the static condition employed by
 2   Overton and Graham (1995).
 3          In summary, these modeling studies predict that the net NO2 dose (NO2 flux to air-liquid
 4   interface) gradually decreases distally from the trachea to the terminal bronchioles and then
 5   rapidly decreases in the pulmonary region. However, the tissue dose of NO2 (NO2 flux to liquid-
 6   tissue interface) is low in the trachea, increases to a maximum in the terminal bronchioles and
 7   the first generation of the pulmonary region, and then decreases rapidly with distal progression.
 8   The production of toxic NO2-reactants in the ELF and the movement of the reactants to the
 9   tissues as not been modeled.
10
11   Experimental Studies of NOi Uptake
12
13   Upper Respiratory Tract A bsorption
14          The nasal uptake of NO2 has been experimentally measured in dogs, rabbits, and rats
15   under conditions of unidirectional flow.  Yokoyama (1968) reported 42.1 + 14.9%
16   (Mean + StDev) uptake of NO2 (4 to 41 ppm) in the isolated nasal passages of two dogs
17   (3.5 L/min) and three rabbits (0.75 L/min) exposed to 7520 to 77,100 |ig/m3 (4 and 41 ppm)
18   NO2.  Uptake did not appear to depend on the exposure concentration and was relatively constant
19   over a 10 to 15 min period.  Cavanagh and Morris  (1987) measured uptakes of 28% and 25%
20   uptake of NO2 (76,000 |ig/m3; 40.4 ppm) in the noses of four naive and four previously exposed
21   rats (0.10 L/min), respectively. Uptake was not affected by a 4-h prior exposure (naive versus
22   previously exposed rats) to 76,000 |ig/m3 (40.4) ppm NO2 and was constant over the 24-min
23   period during which uptake was determined.
24          Kleinman and Mautz (1991) measured the penetration of NO2 through the upper airways
25   during inhalation in six tracheotomized dogs exposed to 1880 or 9400 |ig/m3 (1.0 or 5.0 ppm)
26   NO2.  Uptake in the nasal passages was significantly greater at 1880 |ig/m3 (1.0 ppm) than at
27   9400 |ig/m3 (5.0 ppm), although the magnitude of this difference was not reported.  The mean
28   uptake of NO2 (1880 |ig/m3;  1.0 ppm) in the nasal  passages decreased from 55% to 40% as the
29   ventilation rate increased from about 2 to 8 L/min. During oral breathing, uptake was not
30   dependent on concentration.  The mean oral uptake of NO2 (1880 and 9400 |ig/m3; 1.0 and
31   5.0 ppm) decreased from 65% to 30% as the ventilation rate  increased from 2 to 8 L/min.
32

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 1   Lower Respiratory Tract Absorption
 2          Postlethwait and Mustafa (1989) investigated the effect of exposure concentration and
 3   breathing frequency on the uptake of NC>2 in isolated perfused rat lungs. To evaluate the effect
 4   of exposure concentration, the lungs were exposed to NO2 (7520 to 37,600 |ig/m3; 4 to 20 ppm)
 5   while ventilated at 50 breaths/min with a VT of 2.0 mL. To examine the effect of breathing
 6   frequency, the lungs were exposed to NC>2 (94,000 |ig/m3; 5 ppm) while ventilated at 30-90
 7   breaths/min with a VT of 1.5 mL.  All exposures were for 90 min.  The uptake of NC>2 ranged
 8   from 59 to 72% with an average of 65% and was not affected by exposure concentration or
 9   breathing frequency. A combined regression showed a linear relationship between NC>2 uptake
10   and total inspired dose (25 to 330 jig NO2). Illustrating variability in NO2 uptake measurements,
11   Postlethwait and Mustafa (1989) observed 59% NC>2 uptake in lungs ventilated at 30 breaths/min
12   with a VT of 1.5 mL, whereas, Postlethwait and Mustafa (1981) measured 35% NC>2 uptake for
13   the same breathing condition. In another study, 73% uptake of NC>2 was reported for rat lungs
14   ventilated 50 breaths/min with a VT of 2.3 mL (Postlethwait et al., 1992).  It should be noted that
15   typical breathing frequencies are around 80, 100, and 160 breaths/min for rats during sleep, rest,
16   and light exercise, respectively (Winter-Sorkina and Cassee, 2002). Hence, the breathing
17   frequencies at which NC>2 uptake has been measured are lower than for rats breathing normally.
18          In addition to measuring upper respiratory tract uptakes, Kleinman and Mautz (1991)  also
19   measured NO2 uptake in the dog lung.  In general, there was about 90% NO2 uptake in the lungs
20   which was independent of ventilation rates from 3 to 16 L/min.
21
22   Total Respiratory Tract Absorption
23          Bauer et al. (1986) measured the uptake of NO2 (560 |ig/m3; 0.3 ppm) in 15 adult
24   asthmatics exposed for 30 min (20 min at rest, then 10 min exercising on a bicycle ergometer)
25   via a mouthpiece during rest and exercise. There was a statistically significant increase in uptake
26   from 72% during rest to 87% during exercise. The minute ventilation also increased from
27   8.1 L/min during rest to 30.4 L/min during exercise.  Hence, exercise increased the dose rate of
28   NC>2 by 5-fold in these subjects.  In an  earlier study of seven healthy  adults in which subjects
29   were exposed to a nitric oxide (NO)/NO2 mixture containing 550 to 13500 |ig/m3 (0.29 to
30   7.2 ppm) NC>2 for brief (but unspecified) periods, Wagner (1970) reported that NC>2 uptake
31   increased from  80% during normal respiration (VT, 0.4 L) to 90% during maximal respiration
32   (VT, 2 to 4 L).

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 1          Kleinman and Mautz (1991) also measured the total respiratory tract uptake of NO2
 2    (9400 |ig/m3; 5 ppm) in female beagle dogs while standing at rest or exercising on a treadmill.
 3    The dogs breathed through a small face mask. Total respiratory tract uptake of NO2 was 78%
 4    during rest and increased to 94% during exercise. In large part, this increase in uptake may be
 5    due to the increase in VT from 0.18 L during rest to 0.27 L during exercise.  Coupled with an
 6    increase in minute ventilation from 3.8 L/min during rest to 10.5  L/min during exercise, the dose
 7    rate of NO2 was 3-fold greater for the dogs during exercise than rest.
 8
 9    Distribution and Elimination of NO 2 Products
10          As stated earlier, NO2 absorption is coupled with nitrous acid (HNO2) formation, which
11    subsequently dissociates to H+ and nitrite (NO2 ). Nitrite enters the underlying epithelial cells
12    and subsequently the blood. In the presence of red blood cells and possibly involving
13    oxyhemoglobin, nitrite is oxidized to nitrate (NOs) (Postlethwait and Mustafa, 1981). Nitrate
14    may subsequently be excreted in the urine.  There has been concern that inhaled NO2 may lead to
15    N-nitrosamine production, many of which are carcinogenic, since NO2 can produce nitrite and
16    nitrate (in blood). Nitrate can be converted to nitrite by bacterial reduction in saliva, the
17    gastrointestinal tract, and the urinary bladder. Nitrite has been found to react with secondary
18    amines to form N-nitrosamines. This remains speculative since nitrosamines are not detected in
19    tissues of animals exposed by inhalation to NO2 unless precursors to nitrosamines and/or
20    inhibitors of nitrosamine metabolism are co-administered. Rubenchik et al. (1995) could not
21    detect N-nitrosodimethylamine (NDMA) in tissues of mice exposed to 7.5 to 8.5 mg/m3 NO2  for
22    1 h. NDMA was found in tissues, however, if mice were simultaneously given oral doses of
23    amidopyrine and 4-methylpyrazole, an inhibitor of NDMA metabolism. Nevertheless, the main
24    source of NO2 in the body is formed endogenously, and food is also a contributing source of
25    nitrite from the conversion  of nitrates.  Thus, the relative importance of inhaled NO2  to N-
26    nitrosamine formation has yet to be demonstrated.
27          Metabolism of inhaled NO2 may also transform other chemicals that may be present in
28    the body, in some cases into mutagens and carcinogens. Van Stee et al. (1995) exposed mice to
29    approximately 37,600 |ig/m3 (20 ppm) 15NO2 and to 1 g/kg morpholine simultaneously.
30    N-nitrosomorpholine (NMOR), a nitrosamine that is a potent animal carcinogen, was found in
31    the body of the exposed mice.  Ninety-eight point four percent was labeled with 15N that was
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 1    derived from the inhaled 15NC>2 and 1.6% was derived presumably from endogenous sources.
 2    Miyanishi et al. (1996) co-exposed rats, mice, guinea pigs and hamsters to NC>2 and various
 3    polycyclic aromatic hydrocarbons (PAHs) such as pyrene, fluorene, or anthracene. Nitro
 4    derivatives of these PAHs were excreted in the urine of co-exposed animals, which were found
 5    to be highly mutagenic in the Ames/S. typhimurium assay. Specifically, the nitrated metabolite
 6    of pyrene (l-nitro-6/8-hydroxypyrene and l-nitro-3hydroxypyrene) was detected in the urine.
 7    Further studies indicated that these metabolites are nitrated by an ionic reaction in vivo after the
 8    hydroxylation of pyrene in the liver.
 9
10    Extra-Pulmonary Effects of NO2 and NO
11          Exposure to NC>2 produces a wide array of health effects beyond the confines of the lung.
12    Thus, NO2 and/or some of its reactive products penetrate the lung or nasal epithelial and
13    endothelial layers to enter the blood and produce alteration in blood and various other organs.
14    Effects on the systemic immune system were discussed above and the summary of other
15    systemic effects is quite brief because the database suggests that effects on the respiratory tract
16    and immune response are of greatest concern. A more detailed discussion of extrapulmonary
17    responses can be found in U.S. Environmental Protection Agency (1993).
18
19    Body Weight, Hepatic, and Renal Effects
20          Conflicting results have been reported on whether NC>2 affects body weight gain in
21    experimental animals as a general indicator of toxicity (U.S. Environmental Protection Agency,
22    1993). Newer subchronic studies show no significant effects  on body weight in rats, guinea
23    pigs, and rabbits exposed up to 7526 |ig/m3 (4 ppm) NC>2 (Tepper et al., 1993; Douglas et al.,
24    1994; Fujimaki andNohara, 1994).
25          Effects on the liver,  such as changes in serum chemistry and xenobiotic metabolism, have
26    been reported by various investigators to result from exposure to NC>2 (U.S. Environmental
27    Protection Agency 1993). Drozdz et al. (1976) found decreased total liver protein and sialic
28    acid, but increased protein-bound hexoses in guinea pigs exposed to 2000  |ig/m3 (1.05  ppm)
29    NC>2, 8 h/day for 180 days.  Liver alanine and aspartate aminotransferase activity was increased
30    in the mitochondrial fraction but decreased in the cytoplasmic fraction of the liver. Electron
31    micrographs of the liver showed intracellular edema and inflammatory and parenchymal
32    degenerative changes.

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 1          No new studies on liver effects were located in the literature since the 1993 AQCD for
 2    Oxides of Nitrogen.  Several older studies have shown changes in kidney function and
 3    xenobiotic metabolism in animals following NO2, although no histopathological changes were
 4    reported.
 5          Increases in urinary protein and specific gravity of the urine were reported by Sherwin
 6    and Layfield (1974) in guinea pigs exposed continuously to 940 |ig/m3 (0.5 ppm) NO2 for
 7    14 days.  Proteinuria (albumin and alpha-, beta-, and gamma-globulins) was found in another
 8    group of animals when the exposure was reduced to 752 |ig/m3 (0.4 ppm) NO2 for 4 h/day.
 9    However, differences in water consumption or in the histology of the kidney were not found.
10    No new studies were located in the literature since the 1993 AQCD for Oxides of Nitrogen.
11
12    Brain Effects
13          There are several studies suggesting that NO2 affects the brain. Decreased activity of
14    protein metabolizing enzymes, increased glycolytic enzymes, changes in neurotransmitter levels
15    (5-HT and noradrenaline), and increased lipid peroxidation, accompanied by lipid profile and
16    antioxidant changes, have been reported (Farahani and Hasan, 1990, 1991, 1992; Sherwin et al.,
17    1986; Drozdz et al., 1975). The U.S. Environmental Protection Agency  (1993) concluded that
18    "none of these effects have been replicated and all reports lack sufficient methodological rigor;
19    thus,  the implications of these findings, albeit important, are not clear and require further
20    investigation".
21          A developmental neurotoxicity study by Tabacova et al.(1985) suggest that in utero
22    exposure to NO2 may result in postnatal neurobehavioral development changes as described in
23    the section on reproductive and developmental toxicology.
24          Van Stee et al. (1983) reported NMOR production in mice gavaged with 1 g of
25    morpholine/kg body weight per day and then exposed (5-6 h daily for 5 days) to 31,000 to
26    38,500 |ig/m3 (16.5 to 20.5 ppm) NO2. The single site containing the greatest amount of NMOR
27    was the gastrointestinal tract.  In a later experiment, 98.4% of the NMOR found in the body of
28    mice  exposed to -20 ppm (i.e., -37 600 mg/m3) 15NO2 and to 1 g/kg morpholine was labeled
29    with  15N that was derived from the 15NO2 to which the animals had been exposed by inhalation,
30    and 1.6% was derived from 14NO2 from presumably endogenous sources (Van Stee et. al., 1995).
31          Inhaled NO2 may also be involved in the production of mutagenic (and carcinogenic)
32    nitro  derivatives of other co-exposed compounds,  such as polycyclic aromatic hydrocarbons

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 1    (PAHs), via nitration reactions. Miyanishi et al. (1996) co-exposed rats, mice, guinea pigs and
 2    hamsters to 37,600 |ig/m3 (20 ppm) NO2 and various PAHs (pyrene, fluoranthene, fluorene,
 3    anthracene, or chrysene).  Nitro derivatives of these PAHs were excreted in the urine of these
 4    animals, which were found to be highly mutagenic in the AmesA?. typhimurium assay.
 5    Specifically, the nitrated metabolite of pyrene (l-nitro-6/8-hydroxypyrene and 1-nitro-
 6    3hydroxypyrene) was detected in the urine. Further studies indicated that these metabolites are
 7    nitrated by an ionic reaction in vivo after the hydroxylation of pyrene in the liver.
 8
 9    NO
10           The genotoxicity of NO has been studied both in vitro and in vivo (Arroyo et al., 1992;
11    Nguyen et al., 1992) (see Table AX4.8). Overall, the synthesis of these older studies suggests
12    that NO has some genotoxic potential; however, the effect is slight and to a lesser extent when
13    compared to NO2.
14
15    Effects of Mixtures Containing NO 2
16           Humans are generally exposed to NO2 in a mixture with other air pollutants.  A limitation
17    of animal toxicity studies is the extrapolation of dose-response data from controlled  exposures to
18    NO2 alone to air pollutant mixtures that are typically found in the environment. It is difficult to
19    predict the effects of NO2 in a mixture based on the effects of NO2 alone. In order to understand
20    how NO2 is affected by mixtures of other air pollutants, studies are typically conducted with
21    mixtures containing NO2 and one or two other air pollutants, such as Os and/or H2SO/t. The
22    result of exposure to two or more pollutants may be simply the sum of the responses to
23    individual pollutants (additivity), may be greater than the sum of the individual responses,
24    suggesting some type of interaction or augmentation of the response (synergism) or may be less
25    than additive (antagonism).
26           Animal toxicity studies have shown an array of interactions, including no interaction,
27    additivity or synergism. Because no clear understanding of NO2 interactions has yet emerged
28    from this database, only a brief overview is provided here.  A more substantive review can be
29    found in U.S. Environmental Protection Agency (1993).  There are animal studies, which have
30    studied the effects of ambient air mixtures containing NO2 or gasoline or diesel combustion
31    exhausts containing NOX.  Generally these studies provide useful information on the mixtures,
32    but lack NO2-only groups, making it impossible to discern the influence of NO2. Therefore, this

      August 2007                             AX4-18       DRAFT-DO NOT QUOTE OR CITE

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 1    class of research is not described here, but is reviewed elsewhere (U.S. Environmental Protection
 2    Agency, 1993).
 3
 4    Simple Mixtures Containing NO2
 5          Most of the interaction studies have involved NO2 and O3. After subchronic exposure,
 6    lung morphology studies did not show any interaction of NO2 with Os (Freeman et al., 1974) or
 7    with SO2 (Azouley et al., 1980). Some biochemical responses to NO2 plus Os display no
 8    positive interaction or synergism.  For example, Mustafa et al. (1984) found synergism for some
 9    endpoints (e.g., increased activities of O2 consumption and antioxidant enzymes), but no
10    interaction for others (e.g., DNA or protein content) in rats exposed for 7 days.  Ichinose and
11    Sagai (1989) observed a species dependence in regard to the interaction of 63 (752 |ig/m3,
12    0.4 ppm) and NO2 (752 |ig/m3, 0.4 ppm) after 2 weeks of exposure.  Guinea pigs, but not rats,
13    had a synergistic increase in lung lipid peroxides. Rats,  but not guinea pigs, had synergistic
14    increases in antioxidant factors (e.g., non-protein thiols,  vitamin C, glucose-6-phosphate
15    dehydrogenase, GSH peroxidase). Duration of exposure can have an impact. Schlesinger et al.
16    (1990) observed a synergistic increase in prostaglandin E2 and F2a in the lung lavage of rabbits
17    exposed acutely for 2 h to 5640 |ig/m3 (3.0 ppm) NO2 plus 588 |ig/m3 (0.3 ppm) Os; the response
18    appeared to have been driven by 63. However, with 7 or 14 days of repeated 2-h exposures, only
19    prostaglandin E2 was  decreased and appeared to have been driven by NO2; there was no
20    synergism (Schlesinger et al., 1991).
21          Using the infectivity model (see Section AX4.3.2.5 for protocol details), Ehrlich et al.
22    (1977) found additivity after acute exposure to mixtures of NO2 and O3 and synergism after
23    subchronic exposures. Exposure scenarios involving NO2 and Os have also been performed
24    using a continuous baseline exposure to one concentration or mixture, with superimposed short-
25    term peaks to a higher level (Ehrlich et al., 1979; Gardner, 1980, 1982; Graham et al., 1987).
26    Differences in the pattern and concentrations of the exposure are responsible for the increased
27    susceptibility to pulmonary infection, without indicating clearly the mechanism controlling the
28    interaction.
29           Some aerosols may potentiate response to NO2 by producing local changes in the lungs
30    that enhance the toxic action of co-inhaled NO2. The impacts of NO2 and H2SO4 on lung host
31    defenses have been examined by Schlesinger and Gearhart (1987) and Schlesinger (1987a). In
32    the former study,  rabbits were exposed for 2 h/day for 14 days to either 564 |ig/m3 (0.3 ppm) or

      August 2007                             AX4-19      DRAFT-DO NOT QUOTE OR CITE

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 1    1880 |ig/m3 (1.0 ppm) NO2, or 500 |ig/m3 H2SO4 alone, or to mixtures of the low and high NO2
 2    concentrations with H2SO4. Exposure to either concentration of NO2 accelerated alveolar
 3    clearance, whereas H2SO4 alone retarded clearance.  Exposure to either concentration of NO2
 4    with H2SC>4 resulted in retardation of clearance in a similar manner to that seen with H2SC>4
 5    alone. Using a similar exposure design but different endpoints, exposure of rabbits to
 6    1800 |ig/m3 (1.0 ppm) NO2 increased the numbers of PMNs in lavage fluid at all time points (not
 7    seen with either pollutant alone), and increased phagocytic capacity of AMs after two or six
 8    exposures (Schlesinger et al., 1987).  Exposure to 564 |ig/m3 (0.3 ppm) NO2 with acid, however,
 9    resulted in  depressed phagocytic capacity and mobility. The NO2/H2SO4 mixture was generally
10    either additive or synergistic, depending on the specific cellular endpoint being examined.
11          Exposure to high levels of NO2 (<9400 |ig/m3, 5.0 ppm) with very high concentrations of
12    H2SC>4 (1 mg/m3) caused a synergistic increase in collagen synthesis rate and protein content of
13    the lavage fluid of rats (Last and Warren, 1987; Last, 1989).
14
15    Complex Mixtures Containing NO2
16          Although many studies have examined the response to NO2 with only one additional
17    pollutant, the atmosphere in most environments is a complex mixture of more than two materials.
18    A number of studies have attempted to examine the effects of multi-component atmospheres
19    containing  NO2, but as mentioned before, in many cases the exact role of NO2 in the observed
20    responses is not always clear.  One study by Stara et al.  (1980) deserves mention because
21    pulmonary function changes appeared to progress after exposure ceased.
22          In the study  by Stara et al. (1980), dogs were exposed for 68 months (16 h/day) to raw or
23    photochemically reactive vehicle exhaust which included mixtures of NOX:  one with a high NO2
24    level and a low NO level (1200 |ig/m3, 0.64 ppm, NO2;  310  |ig/m3, 0.25 ppm, NO), and one with
25    a low NO2  level and a high NO level (270 |ig/m3, 0.14 ppm, NO2; 2050 |ig/m3, 1.67 ppm, NO).
26    At the end  of exposure, the animals were maintained for about 3 years in normal indoor air.
27    Numerous  pulmonary functions, hematological and histological endpoints were examined at
28    various times during and after exposure.  The lack of an NO2-only or NO-only group precludes
29    determination of the nature of the interaction. Nevertheless, the main findings are of interest.
30    Pulmonary function changes appeared to progress after exposure ceased. Dogs in the high NO2
31    group had morphological changes considered to be analogous to human centrilobular
      August 2007                            AX4-20       DRAFT-DO NOT QUOTE OR CITE

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1   emphysema. Because these morphological measurements were made after a 2.5- to 3-year
2   holding period in clean air, it cannot be determined with certainty whether these disease
3   processes abated or progressed during this time.  This study suggests progression of damage after
4   exposure ends.
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         TABLE AX4.1. EFFECTS OF NITROGEN DIOXIDE (NO2) ON OXIDANT AND ANTIOXIDANT HOMEOSTASIS"
OQ
to
o
o
to
to
H

6
o


o
H

O


O
H
W

O


O
HH
H
W
NO2 Concentration
jig/m3
75
752
7,520






752

752
2,260
7,520

752-940

940
1,880

1,880

1,880
4,330
11,600


2,260
3,380


3,760
18,800
ppm
0.04
0.4
4.0






0.4

0.4
1.2
4.0

0.4-0.5

0.5
1.0

1.0

1.0
2.3
6.2


1.2
1.8


2.0
10.0
Exposure
Continuous,
9 and
18 mos






2 wks

Continuous,
4 mos


Continuous,
1.5yrs
Continuous,
17 mos

4 h/day,
6 days
Continuous,
4 days



Continuous,
3 days


3 days

Gender Age
M 8 wks








NS NS

M 13
wks


F NS

F 4 wks


NS NS

M 8 wks




M 12
wks


M/F 5->60
days
Species (Strain)
Rat (Wistar)








Rat
Guinea Pig
Rat (Wistar)



Mouse
(NS)
Mouse (C57B 1/6 J)


Rat (Sprague-Dawley)

Rat
(Sprague-Dawley)



Rat (Sprague-Dawley)



Rat (Wistar) Guinea pig
(Dunkin Hartley)
Effects
NPSHs increased at >0.4 ppm after 9 or
18 mos; GSH peroxidase activity increased
after a 9-mo exposure to 4.0 ppm; G-6-P
dehydrogenase was increased after a 9- and
18-mo exposure to 4.0 ppm; no effects on
6-P-G dehydrogenase , SOD disulfide
reductase; some GSH S-transferase had
decreased activities after 18-mo exposure to
> 0.4 ppm.
No effect on TEA reactants, antioxidants, or
antioxidant enzyme activities.
Duration dependent pattern for increase in
activities of antioxidant enzymes; increase,
peaking at wk 4 and then decreasing.
Concentration-dependent effects.
Growth reduced; Vitamin E (30 or 300
mg/kg diet) improved growth.
At 1 ppm, GSH-peroxidase activity
decreased in vitamin E-deficient mice and
increased in Vitamin E- supplemented mice.
Vitamin E-supplement reduced lipid
peroxidation.
Activities of GSH reductase and G-6-P
dehydrogenase increased at 6.2 ppm
proportional to duration of exposure; plasma
lysozyme and GSH peroxidase not affected
at 6.2 ppm; no effects at 1.0 or 2.3 ppm.
Increases in G-6-P dehydrogenase, isocitrate
dehydrogenase, disulfide reductase, and
NADPH cytochrome c reductase activities at
1.8 ppm only.
Decreased SOD activity in 21 -day -old
animals.
References
Sagai et al.
(1984)
Ichinose et al.
(1983)





Ichinose and
Sagai (1989)
Ichinose and
Sagai
(1982)

Csallany (1975)

Ayaz and
Csallany (1978)

Thomas et al.
(1967)
Chow et al.
(1974)



Lee etal. (1989,
1990)


Azoulay-Dupuis
etal. (1983)

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OQ
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 o
         TABLE AX4.1 (cont'd). EFFECTS OF NITROGEN DIOXIDE (NO2) ON OXIDANT AND ANTIOXIDANT
	HOMEOSTASIS"	
 NO2 Concentration
Hg/m3
            17,900
            5,600
            13,200
             ppm
Exposure
                                                  Gender
Age
Species (Strain)
Effects
                                                                                                                                References
3,760 2.0 14 days
7,500 4.0 10 days
18,800 10.0 7 days
5,600 3.0 7 days
M 12-24 wks

M/F 1 day to
Rat (Wistar)

Rat (Sprague-Dawley)
G-6-P dehydrogenase increased at >2 ppm;
at 2 ppm, 14 days of exposure needed

Increased lipid peroxidation (TBA-reactive
Mochitate
etal. (1985)

Sevanian
              9.5
              7.0
                   7 h/day,
                   5 days/wks,
                   6 mos
                   4 days
                   4 days
               M
                                        M
                                                            >8wks
                                                            In utero and
                                                            6 mos

                                                            NS
          Rat (Fischer 344)
                                       Rat (Sprague-Dawley)
                    substances) with vitamin E deficiency.
                    Increase in GSH reductase activity in
                    younger rats and SDH peroxidase activity
                    in older rats.
                    No effects on parameters tested.

                    Increase in lung weight, G-6-P
                    dehydrogenase, GSH reductase, and GSH
                    peroxidase activities.
                        etal. (1982)
                        Mauderly
                        etal. (1987)

                        Mustafa
                        etal. (1979)
 to
                                                                                       Increased lung weight, G-6-P
                                                                                       dehydrogenase; and GSH reductase
                                                                                       activities.
H
6
o

o
H
O
O
H
W
O

O
HH
H
W
            18,800       10     4 days
           28,200       15     1-7 days
            7,520      4.0     3 h
                                        M/F       21-33yrs      Human
            9,400      5.0     Continuous, 24 h   M         NS
            18,800      10.0    7 days
                                                                Rats (CD Cobs)
                                                                                     Increase in lung weight, DNA content,
                                                                                     G-6-P dehydrogenase, 6-P-G
                                                                                     dehydrogenase, GSH reductase, disulfide
                                                                                     reductase, GSH peroxidase, disulfide
                                                                                     reductase, succinate oxidase, and
                                                                                     cytochrome oxidase activities; no effect on
                                                                                     lung protein
                                                                                     Decreased elastase inhibitory capacity and
                                                                                     increased lipid peroxidation products in
                                                                                     BAL of subjects not administered
                                                                                     supplement of vitamin C and E prior to
                                                                                     NO2 exposure.
                                                                                     Changes in the GSH levels in blood and
                                                                                     lung occurred in rats exposed for 24 h, but
                                                                                     returned to normal after 7 days.
                                                                                                       Mohsenin
                                                                                                       (1991)
                                                                                                       Pagani et al.
                                                                                                       (1994)

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OQ
 to
 o
 o
                    TABLE AX4.1 (cont'd). EFFECTS OF NITROGEN DIOXIDE (NO2) ON OXIDANT AND ANTIOXIDANT
                                                                           HOMEOSTASIS"
 to
H
6
o
o
H
O
O
H
W
O
O
HH
H
W
NO2 Concentration
fig/m3
11,000

28,000
53,000
17,900


18,800







26,320

ppm
6.0

15
28
9.5


10.0







14.0

Exposure
4 h/day,
30 days
7 days

7 h/day, 5 days/wk,
24 mos

Continuous
3 days,
20 days





NS

Gender Age Species (Strain) Effects
F NS Mouse Increase in GSH reductase and G-6-P
(NS) dehydrogenase activities.
Increase in GSH levels, G-6-P dehydrogenase,
and GSH peroxidase activities.
M 18 wks Rat (Fischer 344) Increase in GSH reductase activity in BAL.


NS NS Rat (Fisher 344) Decreased GSH/GSSG ratio in blood and
BALF, but not in lung type II cells. Lipid
peroxidation was decreased in type II cells at
3 days, but was similar to controls at 20 days.
mRNA expression of the enzymes involved in
the biosynthesis (yGCS and GS) was
decreased at both time points. jGT (redox of
GSH) mRNA expression was increased.
NS NS Human Rapid depletion of vitamin C, glutathione and
vitamin E
References
Csallany
(1975)


Mauderly
etal.,
(1990)
Hochscheid
et al. (2005)






Halliwell
etal. (1992)
           "Modified from US Environmental Protection Agency (1993).
           M= Male
           NPSHs= Nonprotein sulfhydryls.
           GSH= Glutathione.
           G-6-P dehydrogenase= Glucose-6-phosphate dehydrogenase.
           6-P-G dehydrogenase= 6-phosphosgluconate dehydrogenase.
           SOD= Superoxide dismutase.
           F-Female.
           NS= Not Stated.
           NADP= Nicotinamide-adenine dinucleotide phosphate (reduced form).
           TBA= Thiobarbituric acid

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OQ
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 o
  TABLE AX4.2. EFFECT OF NITROGEN DIOXIDE (NO2) ON LUNG AMINO ACIDS, PROTEINS, AND ENZYMES3
NO2 Concentration
                         ppm
                        Exposure     Gender
                                   Age
                                                                         Species
                                                                                                           Effects
                                                                                                                            References
 X
 I
 to
H
6
o

o
H
/O
o
H
W
O
n
HH
H
w
   752
   1,880
   5,640
   9,400
 752
2,260
7,520
              940
             1,880
             1,880
             14,100
             28,200
             47,000
             56,400
0.4
1.0
3.0
5.0
0.4
1.2
4.0
               0.5
               1.0
               1.0
               7.5
               15
               25
               30
                                 72 h
9,400
752

752

5.0
0.4

0.4

3h
Continuous,
1 wk
Continuous,
Iwk
                                 1-14 wks
                                               M
                                    M
                                NS          Guinea Pig


                                22-24 wks   Rat (Wistar)
                                                                                                                                        Sherwin and
                                                                                                                                        Carlson
                                                                                                                                        (1973)
                                                                                                                                        Takahashi
                                                                                                                                        etal. (1986)
        6 h/day,
        5 days/wk,
        4 wks
        6 h/day,
        2 days
                                  M        NS         Guinea Pig        No effect at 0.4 ppm; increase in BAL protein in        Selgrade
                                                        (Hartley)         vitamin C-depleted, but not normal, animals at 1.0 ppm  etal. (1981)
                                                                         and above.
Increased BAL protein in vitamin C-depleted guinea
pigs 15 h postexposure.

No effect on BAL protein.
Increased protein content of BAL from
vitamin-C-deficient guinea-pigs.

Complex concentration and duration dependence of
effects. Example: at 0.4 ppm, cytochrome P-450
levels decreased at 2 wks, returned to control level by
5 wks. At 1.2 ppm, cytochrome P-450 levels decreased
initially, increased at 5 wks, and decreased at 10 wks.
Effects on succinate-cytochrome c reductase also.
0.5 ppm; increase in urinary hydroxylysine output
starting during wk 1; BAL  hydroxylysine level,
angiotensin-converting enzyme level, and BAL protein
content unchanged.
1.0 ppm: gradual increase in urinary hydoxylysine
output, becoming significant the week after exposure
ended; BAL hydroxylysine level lower following
exposure and 4 wks postexposure; andiotensin-
converting enzyme level increased.

Concentration dependent increase in urinary
hydroxylysine output and BAL hydroxyxlysine content,
but only significant at >7.5 ppm and 15 ppm,
respectively; angiotensin-converting enzyme levels and
BAL protein increased in highest-exposed groups.	
                                               M
                                            NS         Rat
                                                        (Fischer 344)
                                                                                                               Evans et al.
                                                                                                               (1989)

-------
OQ
TABLE AX4.2 (cont'd).  EFFECT OF NITROGEN DIOXIDE (NO2) ON LUNG AMINO ACIDS, PROTEINS, AND
                                         ENZYMES3
" NOi Concentration
K")
l^
O
o
^











.
X
^
to


o

i-rj
H
6
o

0
H
/O
r*^S
O
H
W
O
O
HH
H
W

Hg/m3
1,880
9,400

752
2,260
7,520
3,760


1,504
9,400
18,800


3,760
7,520
18,800
5,640


6,770
13,500
20,300
27,100
7,520
18,800

7,520
18,800
47,000





ppm
1.05.0


1.2
1.2
4.0
2.0


0.8
5
10


2.0
4.0
10
3.0


3.6
7.2
10.8
14.4
4.0
10

4.0
10
25





Exposure
7h/day,
5 days/wk,
up to 15 wks
7 days


1,2, or 3 wks


1 or 3 days




14 days
10 days
7 days
7 days


24 h
12 h
8h
6h
10 days
7 days

6h/day
5 days/wk,
7, 14, and
21 days




Gender Age Species
M/F 14-16 wks Rat (Fischer 344)


M 10 wks Rat (Wistar)


M NS Guinea pig


? [check] ? [check] Rat ([check])




M 12-24 wks Rats (Wistar)


M/F 8 wks Rat
(Sprague-Dawley)

M 10-12 wks Rat
(Sprague-Dawley)


M 2 1-24 wks Rat (Wistar)


M NS Rat (Wistar)







Effects
Change in BAL and tissue levels of enzymes early
in exposure, resolved by 15 wks.

Decrease in levels of cytochrome P-450 at
1.2 ppm.

Increased lactate dehydrogenase (LDH) content of
the lower lobes of the lung

BAL protein content significantly increased in a
concentration- and exposure duration-dependent
manner, with the change becoming significant at
5 ppm for 3 days and at 10 ppm for > 1 day of
exposure.
Increase activity of lung glycolytic enzymes.


Various changes in lung homogenate protein and
DNA content and enzyme activities, changes more
severe in vitamin E-deficient rats.
Increased BAL protein >7.2 ppm.



Initial decrease in lung protein content followed by
an increase; changes on microsomal enzyme
activities.
Increased gamma-glutamyl transferase on days
14 and 21; no consistent effect on alkaline
phosphatase, LDH, or total protein.





References
Gregory
etal. (1983)

Mochitate
etal. (1984)

Sherwin and
Carlson
(1973)
Muller et al.
(1994)



Mochitate
etal. (1985)

Elsayed and
Mustafa
(1982)
Gelzleichter
etal. (1992)


Mochitate
etal. (1984)

Hooftman
etal. (1988)






-------
OQ
to
o
o
TABLE AX4.2 (cont'd). EFFECT OF NITROGEN DIOXIDE (NO2) ON LUNG AMINO ACIDS, PROTEINS, AND

                                        ENZYMES"
to
H

6
o


o
H

O


O
H
W

O


O
HH
H
W
NO2 Concentration
Hg/m3
8,100
9,020
9,020
9,400
9,400
9,400
9,400-
47,000
9,400
37,600
94,000
9,400
15,000
17,900
17,900
ppm
4.5
4.8
4.8
5.0
5.0
5.0
5.0-25.0
5.0
20.0
50.0
5.0
8.0
9.5
9.5
Exposure
16hrs
3hrs
8 h/day,
7 days
14-72 h
2wks
6 h/day,
6 days
Continuous,
7 days
3h

Continuous,
1, 3, or 7 days
Continuous, 14
days
7 h/day, 5
days/wk, 6 mos
7 h/day, 5
days/wk, 24 mos
Gender
M/F
M
M
F
M
NS
M
NS

M
F
M
M
Age
NS

8wks
NS
5 wks
NS
10-11 wks
NS

NS
NS
In utero
and 6 mos
18 wks
Species
Guinea pig
(Hartley)

Mouse (Swiss
Webster)
Mouse (NS)
Rat
(Fischer 344)
Mice
Rat (Sprague-
Dawley)
Rabbit
(New Zealand)

Rat
(Sprague-
Dawley)
Mouse (NS)
Rat
(Fischer 344)
Rat
(Fischer 344)
Effects
Increased lung wet weight, alterations in lung
antioxidant levels in Vitamin C- deficient animals.
Increased lung lavage fluid protein content in
vitamin C-deficient animals.
No significant changes in lung homogenate
parameters.
Increase in lung protein (14 to 58 h) by radioactive
label incorporation.
Increased amounts of the tryptophan metabolites
and xanthurenic and kynurenic acids excreted in
urine during wk 2 of exposure, but had returned to
normal levels by wk 4.
Modest increase in albumin in BAL; no effect on
LDH or lysosomal enzyme peroxidase.
Concentration-related increase in collagen synthesis
rate; 125% increase in rats exposed to 5.0 ppm.
Benzo [a] pyrene hydroxylase activity of trachea!
mucosa not affected.

Increased BAL protein at 3 days (day 7 not
measured); increased (120% collagen synthesis at
7 days (not measured other days).
Increase in lung protein.
Increase in BAL alkaline phosphatase, acid
phosphatase, and LDH in older rats only.
Increase in BAL levels of LDH and alkaline
phosphatase activities and in collagenous peptides.
References
Hatch et al.
(1986)

Mustafa et al.
(1984)
Csallany
(1975)
Suzuki et al.
(1988)
Rose et al.
(1989)
Last et al.
(1983)
Palmer et al.
(1972)

Last&
Warren
(1987)
Csallany
(1975)
Mauderly
etal. (1987)
Mauderly
etal. (1990)

-------
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 to
 oo
    TABLE AX4.2 (cont'd). EFFECT OF NITROGEN DIOXIDE (NO2) ON LUNG AMINO ACIDS, PROTEINS, AND
                                                          ENZYMES"
NO2 Concentration
Hg/m3
18,800
18,800
18,800
37,600
56,400
75,200
ppm Exposure Gender Age
10 24 h or 7 days M NS
10 Continuous, 14 M 8 wks
days
10 4 h M NS
20
30
40
Species
Rat (CD cobs)
Rat (Wistar)
Rat
(Long Evans)

Effects
Protein content of B ALF increased significantly in
rats after only 24 h. BALF elastase activity was not
affected, concentration-dependent increase in a-
1 proteinase inhibitor content after 24 h of exposure,
but not with longer exposures.
Changes in several enzymes in whole lung
homogenates.
Increased activities of various enzymes, sialic acid,
and B AL protein; attenuation by high dietary levels of
vitamin E.

References
Pagani et al.
(1994)
Sagai et al.
(1982)
Guthand
Mavis (1985,
1986)

"Modified from US Environmental Protection Agency (1993).
NS = Not Stated
LTB4 = Leukotriene B4
LDH = Lactate Dehydrogenase
M=Male
F= Female
BAL= Bronchoalveolar lavage
 H
 6
 o
 o
 H
O
 O
 H
 W
 O
 O
 HH
 H
 W

-------
              TABLE AX4.3. EFFECTS OF NITROGEN OXIDE (NO2) ON THE IMMUNE SYSTEM OF ANIMALS"
OQ
to
o
o
to
VO
H

6
o


o
H

O


O
H
W

O


O
HH
H
W
NO2 Concentration
fig/m3
940


188 base +
470, 940, or
1,880 peak
470



470


658


752
3,010

940 base +
2,820 peak



940 base +
3,760 peak
3,760





ppm
0.5

0.1 base +
0.25,0.5,
or 1.0
peak
0.25



0.25


0.35


0.4
1.6

0.5 base +
1.5 peak



0.5 base +
2.0 peak






Exposure
Continuous

Continuous base +
3 h/day, 5 days/wk
peak for 1, 3, 6, 9,
12 mos
7 h/day,
5 days/wk, 7wks


7 h/day,
5 days/ wk, 36 wks

7 h/day,
5 days/ wk, 12 wks

24 h/day
4 wks

22 h/day, 7 days/wk
base + 6 h/day,
5 days/wk peak for
1,3, 13, 52, 78 wks

24 h/day, 5 days/wk
base + 1 h/day,
5 days/wk peak for
3 mos




Gender Age Species
(Strain)
NS NS Mouse





F 6 wks Mouse
(AKR/cum)


F 5 wks Mouse
(AKR/cum)

M 6 wks Mouse
(C57BL/6J)

M 7 wks Mouse
(BALB/c)

M 10 wks Rat
(Fischer
344)


M 6 wks Mouse
(CD-I)






Effects
Suppression of splenic T and B cell
responsiveness to mitogens variable and not
related to concentration or duration, except for
the 940 ug/m3 continuous group, which had a
linear decrease in PHA-induced mitogenesis
with NO2 duration.
Reduced percentage of total T-cell population
and trend towards reduced percentage of
certain T-cell subpopulations; no reduction of
mature T cells or natural killer cells.
Reduced percentage of total T-cell population
and percentages of T helper/inducer cells on
days 37 and 181.
Trend towards suppression in total percentage
of T-cells. No effects on percentages of other
T-cell subpopulations.
Decrease in primary PFC response at
>752 ug/m3. Increase in secondary PFC
response at 3010 ug/m3.
No effect on splenic or circulatory B or T cell
response to mitogens. After 3 weeks of
exposure only, decrease in splenic natural
killer cell activity. No histological changes in
lymphoid tissues.
Vaccination with influenza A2/Taiwan virus
after exposure. Decrease in serum
neutralizing antibody; hemagglutination
inhibition antibody liters unchanged. Before
virus challenge, NO2 exposure decreased
serum IgA and increased IgGl, IgM, and
IgG2; after virus, serum IgA unchanged and
IgM increased.
References
Maigetter et al.
(1978)




Richters and Damji
(1988)


Richters and Damji
(1990)

Richters and Damji
(1988)

Fujimaki et al.
(1982)

Selgrade et al.
(1991)



Ehrlich et al.
(1975)







-------
                   TABLE AX4.4. EFFECTS OF NITROGEN DIOXIDE ON ALVEOLAR MACROPHAGES
OQ
to
o
o
H

6
o


o
H

O


O
H
W

O


O
HH
H
W
NO2 Concentration
Hg/m3
94 base + 3,760


1,130
188
1,880
9,400
37,600

376
940
3760





940


188 base +
1,880 peak

3,760

940 base+ 3,760
peak



ppm
0.05 base +
2.0 peaks

0.6
0.1
1.0
5.0
20

0.2
0.5
2.0





0.5


0.1 base +
1.0 peak

2.0

0.5 base +
2.0 peak



Exposure Gender Age
3 h base + three NS NS
15-minpeaks

3h
1 h NS NS




Gestation
12wks






Continuous, NS NS
24wks

Continuous
base + 3 -h peak,
5 days/wk, 24 wks

Continuous,
33 wks

Continuous base +
1-hpeak,
5 days/wk, 33 wks
Species (Strain) Effects
Human No effects at 0.05 ppm NO2 with
peaks; trend (p < 0.07) towards
AMs losing ability to inactivate
influenza virus at 0.6 ppm.
Rat At 5.0 ppm: increase in LTB4;
(Sprague-Dawley) concentration-related decrease in
(in vitro) SOD production in AMs at
> 1.0 ppm; increase in LDH in
AMS at 5.0 and 20 ppm
Rat (Brown- Reactive oxygen species
Norway) generation from alveolar
macrophages was significantly
suppressed in NO2 exposed
weanling animals; no changes in
reactive oxygen generating
capability in the embryonic
exposed animals.
Mouse No effects on AM morphology
at 0.5 ppm continuous or
0. 1 ppm base + peak.
After 21 weeks of exposure to
2.0 ppm continuous or 0.5 ppm
base + peak, morphological
changes were identified, such a
loss of surface processes,
appearance of fenestrae, bleb
formation, and denuded surface

areas.


Reference
Frampton
etal. (1989)


Robison
etal. (1990)



Kumae and
Arakawa
(2006)





Aranyi
etal. (1976)












-------
                TABLE AX4.4 (cont'd). EFFECTS OF NITROGEN DIOXIDE ON ALVEOLAR MACROPHAGES
OQ
to
o
o
>
H

6
o


o
H

O


O
H
W

O


O
HH
H
W
NO2 Concentration
fig/m3
560
1,880






560
1,880


560
1,880
5,640
18,800

560
1,880

940






940 base +
2,820 peak

3, 760 base +
11,300

ppm
0.3
1.0






0.3
1.0


0.3
1.0
3.0
10

1.0
10

0.5






0.5 base +
1.5 peak
2.0 base
+6.0 peak


Exposure Gender Age
2 h/day M NS
2, 6, 13 days






2 h/day up to M NS
14 days


2h M NS




2 h/day, 14 days

0.5, 1, 5 and NS NS
10 days exposure





Base 22 h/day, 7 M 1 day and
days/wk + two 1-h 6 wks
peaks, 5 days/wk,
6 wks


Species (Strain) Effects
Rabbit (New Zealand) Decreased phagocytic ability of
AMs at 0.3 ppm after 2 days of
exposure; increased at 1.0 ppm
after 2 days of exposure; no
effect on cell number or
viability; random mobility
reduced at 0.3 ppm only; no
effects after 6 days of exposure.
Rabbit (New Zealand) Increase in alveolar clearance.



Rabbit (New Zealand) Concentration-related
acceleration in clearance of
particles from lung with the
greatest increase at two lowest
concentrations, effects from
repeated exposures similar to
those seen after acute exposures
to same concentrations.
Rat Superoxide production in
(NS) alveolar macrophages from
B ALF, stimulated by phorbol
myrisate acetate (PMA), was
decreased after 0.5 days of
exposure, and continued to be
depressed after 1, 5, and 10 days.
Rat (Fischer 344) Trend towards increase in
number of AMs and cell volume
in younger animals; increase in
number of AMs and cell volume
in older rats.

Reference
Schlesing
er(1987)






Schlesing
erand
Gearhart
(1987)
Vollmuth
etal.
(1986)




Robinson
etal.
(1993)




Crapo
etal.
(1984)
Chang
etal.
(1986)

-------
                TABLE AX4.4 (cont'd). EFFECTS OF NITROGEN DIOXIDE ON ALVEOLAR MACROPHAGES
OQ
to
o
o
to
H

6
o


o
H

O


O
H
W

O


O
HH
H
W
NO2 Concentration
Hg/m3
1,000
2,500
5,000
1,880
3,760
7,520


1,880
9,400
28,200

1,880
3,760
7,520


1,880
28,200
45,120

1,880
9,400

1,880 base +
9,400 peaks


2,440-32,000


ppm
0.5
1.3
2.7
1.0
2.0
4.0


1.0
5.0
15

1.0
2.0
4.0


1.0 +
0.9 ppm No
15
24
1.0
5.0

base +
5.0 peaks


1.3-17


Exposure Gender
Continuous, M
28 days

24 h/day, 12 wks




6 h/day, 2 days NS



24 h/day, 12 wks




7 h/day, NS
5 days/wks for
1 1 or 22 exposures

7 h/day, M/F
5 days/wks

Base 7 h/day,
5 days/wks; two
1. 5 -h peaks/day;
15 wks
NS ("acute") F


Age Species (Strain)
6 wks Rat (Wistar)


Guinea pig
(NS)
Rat
(NS)

4-6 wks Mouse (CD 1)



Guinea pig
(NS)
Rat
(NS)

NS Rat (Long Evans)



14-16 wks Rat (Fischer 344)






NS Rat
(Sprague-Dawley)

Effects
Increase in AMs in highest exposed
group; no effects noted in 2 lowest
exposure groups.
IgE-mediated histamine release
from lung mast cells was enhanced
in guinea pigs, but not rats exposed
to 4.0 ppm. No effect observed at
lower concentrations.
Exposure-related decrease in AM
phagocytosis from 1.0-5.0 ppm,
decrease was not further affected by
15 ppm.
IgE-mediated histamine release
from lung mast cells was enhanced
in guinea pigs, but not rats exposed
to 4.0 ppm. No effect observed at
lower concentrations.
Stimulated clearance of particles
from lung at lowest concentration,
but decreased clearance rate at two
highest concentrations.
Accumulation of AMs.
Superimposed peak exposures
produced changes that may persist
with continued exposures.



Decreased production of superoxide
anion radical.

Reference
Rombout
etal.
(1986)
Fujimaki
and
Nohara,
1994

Rose et al.
(1989)


Fujimaki
and
Nohara,
(1994)

Ferin and
Leach
(1977)

Gregory
etal.
(1983)




Amoruso
etal.
(1981)

-------
TABLE AX4.4 (cont'd). EFFECTS OF NITROGEN DIOXIDE ON ALVEOLAR MACROPHAGES
CJQ
r-K
to
o
o
^












X
-^
w



O
£
H
6
o
2;
0
_J
^^
/o
r*^S
O
H
W
O
O
HH
H
W
NO2 Concentration
jig/m3 PPm
3,760 2.0
19,000 10


3,760 2.0


3,760 2.0

5,000 2.7

5,640-30,100 3-6

6,770 3.6
22,700 12.1


7,520 4
19,000 10
47,000 25



7,520 4.0













Exposure Gender Age Species (Strain)
3 days M/F 5,10,21, Guinea pig (Dunkin
45, 55, 60, Hartley)
and >60 Rat (Wistar)
days
8 h/day, 5 days/wk, M/F 3-4 yrs Baboon
6 mo

4h NS NS Human

24 h M 6 wks Rat (Wistar)

3h NS NS Dog (Beagle)

Ih F NS Rat (Sprague-Dawley)
2h (in vitro)


6 h/day, 7, 14, or M NS Rat (Wistar)
21 days




10 days 19-23 wks













Effects
Newborns were less affected
than adults when AMs were
tested for SOD levels.

Impaired AM responsiveness
to migration inhibitory factor.

Decreased phagocytosis and
superoxide anion release.
Increase in number of AMs.

Enhanced swelling of AMs.

Enhanced macrophage
agglutination with
concanavalin A at both
concentrations tested.
Changes in morphology at all
concentrations; increase in
number of AMs at > 10 ppm;
phagocytic capacity reduced
after 14 and 21 days of
exposure to 25 ppm.
Increase in number of AMs; no
increase in PMNs; increased
metabolic activity, protein, and
DNA synthesis; all responses
peaked on day 4 and returned
to normal on day 10.








Reference
Azoulay-
Dupuis et al.
(1983)

Green and
Schneider
(1978)
Devlin et al.
(1992)
Rombout
etal. (1986)
Dowell et al.
(1971)
Goldstein
etal. (1977)


Hooftman
etal. (1988)




Mochitate
etal. (1986)












-------
OQ
 to
 o
 o
	TABLE AX4.4 (cont'd).  EFFECTS OF NITROGEN DIOXIDE ON ALVEOLAR MACROPHAGES
 NO2 Concentration
                              ppm
                                  Exposure
                                                           Gender
                                       Age
                                         Species (Strain)
                                                      Effects
                                                                  Reference
 H
 6
 o

 o
 H
O
 O
 H
 W
 O

 O
 HH
 H
 W
     7,520
     15,000
4.0
8.0
Up to 10 days
NS
NS
Rat (Fischer 344)
Increase in number of AMs at both
concentrations, reaching a peak on
day 3 and 5; no increase in number
of PMNs; decrease in AM viability
throughout exposure period.
Suppression of phagocytic activity
after 7 days of exposure to 4 ppm
and after 5 days of exposure to
8 ppm; returned to normal value at
10 days. Decrease in superoxide
radical production, but at 4 ppm,
the effect became significant on
days 3, 5, and 10; at 8 ppm, the
effect was significant at all time
periods tested.
Suzuki et al.
(1986)
9,400
9,400
28,200
9,400
18,800
28,200
9,400-113,000



13,200

17,900
5.0
5
15
5
10
15
5-60



7.0

9.5
7 days
3 h after infection
with parainfluenza
3 virus
3h
3h



24 h

7 h/day; 5 days/wk;
18-22 mo
F
NS
M
Fb
NS



NS

M
NS
NS
NS
NS



NS

18wks
Mouse (CD-I)
Rabbit (New Zealand)
Humans (in vitro
exposure)
Rabbit (New Zealand)



Rabbit

Rat (Fischer 344)
No effect on phagocytic activity.
AMs lost resistance to challenge
with rabbit pox virus after exposure
to 15 ppm.
No change in cell viability, release
of neutrophil chemotactic factor, or
interleukin-1.
Inhibition of phagocytic activity.



Increased rosette formation in AMs
treated with lipase.
No effect on long-term clearance of
radiolabeled tracer particles.
Lefkowitz
etal. (1986)
Acton and
Myrvik
(1972)
Pinkston
etal. (1988)
Gardner et al.
(1969)
Acton and
Myrvik
(1972)
Hadley et al.
(1977)
Mauderly
etal. (1990)

-------
                        TABLE AX4.4 (cont'd).  EFFECTS OF NITROGEN DIOXIDE ON ALVEOLAR MACROPHAGES
CJQ
r-K
to
o
o
NO2 Concentration
fig/m3
18,800
19,000
19,000
19,000
47,000

ppm
10
10
10
10
25

Exposure Gender Age
Continuous 7 days NS NS
35 days NS NS
4h F NS
24 h M 12-13
wks

Species (Strain)
Rat
(NS)
Guinea pig
Mouse (Swiss)
Rat (Sprague-Dawley)

Effects
High influx of PMNs in the lung
(BALF) after 24 h of exposure,
reversed for macrophages; no
change in the lymphocyte
population.
63% increase in epithelial cells
positive for macrophage
congregation.
Increase in total pulmonary cells in
animals infected with some species
of bacteria.
Decreased phagocytosis at 25 ppm
only.

Reference
Pagani et al.
(1994)
Sherwin
etal. (1968)
Jakab (1988)
Katz and
Laskin
(1976)
H
6
o
o
H
O
O
H
W
O
O
HH
H
W
           aNS = Not stated.
           AMs = Alveolar macrophages.
           LTB4 = Leukotriene B4.
           LDH = Lactate dehydrogenase.
           M = Male
           F = Female
           SOD = Superoxide dismutase.
           PMNs = Polymorphonuclear leukocytes.
           bOnly one female used in study.

-------
OQ
to
o
o
                      TABLE AX4.5. EFFECT OF NITROGEN DIOXIDE (NO2) ON SUSCEPTIBILITY TO

                                                INFECTIOUS AGENTS"
H

6
o


o
H

O


O
H
W

O


O
HH
H
W
NO2 Concentration
fig/m3 ppm
100 base + 0.05 base +
188 peak 0.1 peak


940 base + 0.5
1,880 peak +
peak
2,256 base
+ 4,700
peak 1.2 base +
2.5 peak
376 base 0.2 base +
+ 1,504 0.8 peak
peak

564-940 0.3-0.5






Species
Exposure Gender Age (Strain) Infective Agent Effects
Continuous, base + F NS Mouse Streptococcus sp. No effect.
twice/day 1 h peaks, (CD-I)
5 days/wk for 15 days


Increased mortality.




Increased mortality.
23 h/day, 7 days/wk F 6-8 Mouse Streptococcus sp. Peak plus baseline
base+ twice daily 1 h wks (CD-I) caused significantly
peaks, 5 days/wk for greater mortality than
1 yr baseline.
Continuous, 3 mos F 4 wks Mouse A/PR/8 virus High incidence of
(ICR:JCL) adenomatous
proliferation peripheral
and bronchial epithelial
cells; NO2 alone and
virus alone caused less
„ ^. , severe alterations.
References
Gardner (1980,
1982)
Graham et al.
(1987)







Miller et al.
(1987)


Motomiya
etal. (1973)





                                                                                  No enhancement of

                                                                                  effect of NO2 and virus.

-------
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o
TABLE AX4.5 (cont'd). EFFECT OF NITROGEN DIOXIDE (NO2) ON SUSCEPTIBILITY TO

                           INFECTIOUS AGENTS"
H

6
o


o
H

O


O
H
W

O


O
HH
H
W
NO2 Concentration
jig/m3 ppm Exposure
940 0.5 Intermittent, 6 or
18 h/day, up to
12 mos
Continuous, 90
days


940-1,880 0.5-1.0 Continuous, 39
days
18,800
10 2 h/day, 1, 3, and
5 days
940-52,700 0.5-28 Varied


940 0.5 3 h/day, 3 mos
940 0.5 24 h/day,
1,880 1.0 7days/wk,
2,820 1.5 3 mos

9,400 5.0 3 days
Species
Gender Age (Strain) Infective Agent Effects
F NS Mouse (Swiss) K. pneumoniae Increased mortality
after 6 mos
intermittent exposure
or after 3, 6, 9, or 12
mos continuous
exposure, increased
mortality was
significant only in
continuously exposed
mice.
F NS Mouse (ICR, A/PR/8 Increased
dd) virus susceptibility to
infection.


F NS Mouse (CD-I) Streptococcus sp. Increase mortality
with increased time
and concentration;
concentrations is
more important than
time.
F 6-8 Mouse (CD2 Streptococcus sp. Increase in mortality
wks F!, CD-I) with reduction in
mean survival time.
F NS Mouse (CF-1) K. pneumoniae Significant increase in
mortality after 3 -day
exposure to 5.0 ppm;
no effect at other
concentrations, but
control mortality very
high.
References
Ehrlich and
Henry (1968)



Ito (1971)


Gardner et al.
(1977 a,b)
Coffin etal.
(1977)

Ehrlich et al.
(1979)
McGrath and
Oyervides
(1985)



-------
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 o
               TABLE AX4.5 (cont'd). EFFECT OF NITROGEN DIOXIDE (NO2) ON SUSCEPTIBILITY TO
	INFECTIOUS AGENTS"	
 NO2 Concentration
    jig/m3         ppm
              Exposure
 Gender    Age    Species (Strain)   Infective Agent
                                                 Effects
                                                       References
 oo
 H
 6
 o
 o
 H
O
 O
 H
 W
 O
 O
 HH
 H
 W
              940
             1,880
             3,760
             9,400
             1,880
             4,324
             12,408
    1,880
    4,700
    9,400
    18,800
                   1.0
                   2.0
                   5.0
                   1.0
                   2.3
                   6.6
                            4h
          17 h
                            M/F
M
          8-10 wks
NS
          Mouse
          (C57BL/6N)
Mouse (Swiss)
                Mycoplasma
                pulmonis
S. aureus after
exposure
 1.0
 2.5
 5.0
10.0
                                     4h
          NS        Mouse (Swiss)    S. aureus
Decrease in
intrapulmonary killing
only at 5.0 ppm.

No difference in
number of bacteria
deposited, but at the
two highest
concentrations, there
was a decrease in
pulmonary
bactericidal activity of
6 and 35%,
respectively; no effect
at 1.0 ppm
Injection with
corticosteroids
increased NO2-
induced impairment of
bactericidal activity at
>2.5 ppm.
                                     Davis et al.
                                     (1991, 1992)
Goldstein et al.
(1974)
                                                                Jakab (1988)
1,880 1.0 48 h M NS Mouse (Swiss
Webster)



1,800 1.0 3 h F 5-6 wks Mouse (CD-I)
5,640 3.0



Streptococcus
sp. S. aureus



Streptococcus
sp.



Increased proliferation
of Streptococcus in
lung of exposed mice
but no effect with
Streptococcus
Exercise on
continuously moving
wheels during
exposure increased
mortality at 3.0 ppm.
Sherwood et al.
(1981)



Illing et al.
(1980)




-------
OQ
 to
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 o
 OJ
 VO
 H
 6
 o

 o
 H
O
 O
 H
 W
 O

 O
 HH
 H
 W
 TABLE AX4.5 (cont'd).  EFFECT OF NITROGEN DIOXIDE (NO2) ON SUSCEPTIBILITY TO
                                      INFECTIOUS AGENTS"
NO2 Concentration
jig/m3
1,880
4,700
9,400
2,820-
94,000




2,820



ppm
1.0
2.5
5.0
1.5-
50




1.5



Exposure Gender Age Species (Strain)
6 h/day, 6 days NS


2h NS





Continuous or F
intermittent, 7 h/day,
7 days/wk, up to
15 days
4-6 wks Mouse (CD-I)


NS Mouse
(NS)
Hamster
(NS)
Monkey
(Squirrel)
NS Mouse (CD-I)



Infective Agent Effects
Cytomegalovirus Increase in virus
susceptibility at 5.0 ppm
only.
K. pneumoniae Increased mortality in
mice, hamsters, and
monkeys at >3.5, >35,
and 50 ppm NO2,
respectively

Streptococcus sp. After 1 wk, mortality with
continuous exposure was
greater than that for
intermittent after 2 wks,
References
Rose et al.
(1988, 1989)

Ehrlich
(1980)




Gardner et al.
(1979)
Coffin et al.
(1977)
            6,580
3.5
no significant difference
between continuous and
intermittent exposure.

Increased mortality with
increased duration of
exposure; no significant
difference between
continuous and
intermittent exposure;
with data adjusted for total
difference in C x T,
mortality essentially the
same.

-------
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o
o
-k
o
H

6
o


o
H

O


O
H
W

O


O
HH
H
W
TABLE AX4.5 (cont'd). EFFECT OF NITROGEN DIOXIDE (NO2) ON SUSCEPTIBILITY TO

                             INFECTIOUS AGENTS"
NO2 Concentration
jig/m3 PPm
2,820 base + 1.5 base +
8, 100 peak 4.5 peak
Exposure
Continuous 64 h,
then peak for 1,
3.5, or 7 h, then
continuous 18 h
base
Species
Gender Age (Strain) Infective Agent
F NS Mouse (CD-I) Streptococcus sp.
Effects
Mortality increased with 3.5-
and 7 h single peak when
bacterial challenge was after
an 18 h baseline exposure.
References
Gardner
(1980)
Gardner
(1982)
Graham et al.
(1987)
        8,100
                  4.5
                           1, 3.5, or 7 h


2,820


3,570
7,140
13,200
17,200
27,800

2,820-
9,400



1.5


1.9
3.8
7.0
9.2
14.8

1.5-
5.0

Mortality proportional to
duration when bacterial
challenge was immediate,
but not 18 h postexposure.
7 h/day, 4, 5, and NS NS Mouse Streptococcus sp. Elevated temperature (32°C)
7 days increased mortality after
7 days.
4 h M NS Mouse (NS) S. aureus Physical removal of bacteria
unchanged by exposure.
Bactericidal activity
decreased by 7, 14, and 50%,
respectively, in three highest
NO2-exposed groups.
3h F 6-10 Mouse (CF-1, Streptococcus sp. Increased mortality in mice
wks CD2FO exposed to > 2.0 ppm



Gardner
(1982)

Goldstein et al.
(1973)




Ehrlich et al.
(1977)
Ehrlich (1980)

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o
TABLE AX4.5 (cont'd). EFFECT OF NITROGEN DIOXIDE (NO2) ON SUSCEPTIBILITY TO

                           INFECTIOUS AGENTS"
>


^
H

6
o


o
H

O


O
H
W

O


O
HH
H
W
NO2 Concentration
jig/m3 ppm Exposure Gender Age Species (Strain) Infective Agent Effects
2,820
4,700
6,580
9,400
18,800
28,200



3,760


4,700
7,500
9,400
18,800
28,200





1.5 2h NS
2.5
3.5
5.0
10
15



2.0 1.5 h/day, 5 NS
days/wkfor 1,
2, and 3 wks
2.5 4 h F
4.0
5.0
10
15





6-8 wks Mouse (Swiss K. pneumoniae No effect at 1.5 or 2. 5 ppm;
Webster) increased mortality at 3.5 ppm
and above. Increase in
mortality when K. pneumoniae
challenge 1 and 6 h after 5 or
10 pm NO2 exposure; when K.
pneumoniae challenge 27 h
following NO2 exposure, effect
only at 15 ppm.
2 wks Hamster A/PR/8/34 Peak virus production in
(Golden Syrian) influenza virus tracheal explants occurred
(in vitro) earlier.
NS Mouse (Swiss) S. aureus, Concentration-related decrease
Proteus mirabilis, in bactericidal activity at > 4.0
Pasteurella ppm with S. aureus when NO2
pneumotropica exposure after bacterial
challenge; when NO2 exposure
was before challenge, effect at
10 ppm; NO2 concentrations
>5.0 ppm required to affect
bactericidal activity for other
tested microorganisms.
References
Purvis and
Ehrlich(1963)
Ehrlich(1979)






Schiff(1977)


Jakab (1987,
1988)









-------
OQ
 to
 o
 o
 to
 H
 6
 o

 o
 H
O
 O
 H
 W
 O

 O
 HH
 H
 W
   TABLE AX4.5 (cont'd). EFFECT OF NITROGEN DIOXIDE (NO2) ON SUSCEPTIBILITY TO
                                         INFECTIOUS AGENTS"
NO2 Concentration
jig/m3 ppm Exposure Gender Age
9,400 5.0 Continuous, M NS
2 mos
18,800 10 Continuous,
1 mo
Species (Strain)
Monkey
(Squirrel)
Infective Agent
K. pneumoniae
orA/PR/8
influenza virus
Effects
Increased viral-induced mortality
(1/3). Increase mKlebsiella-
induced mortality (2/7); no control
deaths.
Increased virus-induced mortality
(6/6) within 2-3 days after
References
Henry et al.
(1970)
           9,400
           18,880
5.0
10
4h
M/F       6-10 wks    Mouse
                     (C57B16N,
                     C3H/HeN)
                 infection; no control deaths.
                 Increase in Klebsiella-mduced
                 mortality (1/4), no control deaths.
 Mycoplasma      NO2 increased incidence and
 pulmonis         severity of pneumonia lesions and
                 decreased the number of organisms
                 needed to induce pneumonia; no
                 effect on physical clearance;
                 decreased mycoplasmal killing and
                 increased growth; no effect on
                 specific IgM in serum; C57B1/6N
                 mice generally more sensitive than
                 C3H/HeN mice.  At 10 ppm, one
                 strain (C57B1/6N) of mice had
	increased mortality.	
Parker et al.
(1989)

-------
>                      TABLE AX4.5 (cont'd). EFFECT OF NITROGEN DIOXIDE (NO2) ON SUSCEPTIBILITY TO

                                                             INFECTIOUS AGENTS3
to
o
o
H

6
o


o
H

O


O
H
W

O


O
HH
H
W
NO2 Concentration
jig/m3 ppm Exposure Gender Age Species (Strain) Infective Agent
18,800
28,200
65,800
94,000



9,400
10 2h
15
35
50

5 ?


M/F NS Monkey K. pneumoniae
(Squirrel)



? ? Mice Parainfluenza
(murine sendei
virus)
Effects
Clearance of bacteria from
lungs of 10-, 15-, and 35-ppm
groups delayed or prevented.
All three animals in highest
exposed group died.
Altered the severity but not
the course of the infection

References
Henry et al.
(1969)



Jakab (1988)


          "Modified from US Environmental Protection Agency (1993)

          F = Female.

          M = Male.

          NS = Not stated

          K. pneumoniae = Klebsiella pneumoniae

          S. aureus = Staphylococcus aureus.


          C x T = The product of concentration and time

-------
TABLE AX4.6. EFFECT OF NITROGEN DIOXIDE (NO2) ON HEMATOLOGICAL PARAMETERS"
CJQ
to
O
o
^












X
^
£


O
^
^
H
O1
O

0
H
O
H
W
O
O
HH
H
W
NO2 Concentration
Hg/m3
94

677

940-1,500 +


1500


1,880

1,800
9,400
1,880-56,400

2,400-5,640

3,760



3,760


7,520








ppm Exposure
0.05 Continuous 90
days
0.36 1 wk

0.5-0.8 + Continuous
1 to 1.5 mos

0.8 Continuous,
5 days

1.0 Continuous,
16 mos
1.0 Continuous,
5.0 18 mos
1-30 18 h

1.3-3.0 2h/day,
15 and 17 wks
2.0 Continuous,
14 mos


2.0 Continuous, up
to 6 wks

4.0 1-10 days








Gender
NS

NS

M/F


M


M

M

NS

NS

M/F


M
M


NS








Age
NS

NS

4 wks


7 wks


NS

NS

NS

NS

NS



8 wks


NS








Species (Strain)
Rat

Guinea Pig

Mouse (ICR:JCL)


Mouse (ICR)


Monkey (Squirrel)

Dog (Mongrel)

Mouse (NS)

Rabbit
(NS)
Monkey (Macaca
speciosa)
Rat
(Sprague-Dawley)
Rat
(Wistar)

Rat
(NS)







Effects
No effect on blood hemoglobin or RBCs.

Increase of red blood cell D-2,3-
diphosphogly cerate
Addition of 50 ppm CO to NO2 failed to affect
carboxy hemoglobin.

No effect on methemoglobin.


No effect on hematocrit or hemoglobin with
NO2 and influenza exposure.
No changes in hemoglobin or hematocrit. .

Concentration-related increase in
methemoglobin and nitrosylhemoglobin
Decreased RBCs.

With or without NaCl (330 ug/m3):
polycythemia with reduced mean corpuscular
volume and normal mean corpuscular
hemoglobin.
No effect on hemoglobin, hematocrit or RBC
count; no methemoglobin was observed.
Azoulayetal. (1978)
Increase in RBC sialic acid.








References
Shalamberidze
(1960)
Mersch et al.
(1973)
Nakajima and
Kusumoto
(1970)
Nakajima and
Kusumoto
(1968)
Fenters et al.
(1973)
Wagner et al.
(1965)
Case et al.
(1979)
Mitina (1962)

Furiosi et al.
(1973)


Azoulay et al.
(1978)

Kunimoto et al.
(1984)








-------
                TABLE AX4.6 (cont'd). EFFECT OF NITROGEN DIOXIDE (NO2) ON HEMATOLOGICAL PARAMETERS"
CJQ
«j
to
O
o
^





NO2 Concentration
fig/m3
7,520

9,400-
75,200
18,800


ppm
4.0

5-40

10


Exposure
NS

Ih

2 h/day,
5 days/wk, up to
30wks
Gender
NS

F

F


Age
NS

4 mos

6-8 wks


Species (Strain)
NS

Mouse (JCL:ICR)

Mouse (BALB/c)


Effects
Decrease in RBCs.

No increase in methemoglobin. Increased
nitrite and especially nitrate.
Small decrease in hemoglobin and mean
corpuscular hemoglobin concentration.

References
Mochitate and
Miura (1984)
Oda et al.
(1981)
Holt et al.
(1979)

          "Modified from US Environmental Protection Agency (1993).
          NS = Not stated.
          RBCs = Red blood cells.
          M = Male.
          F = Female.
          CO = Carbon monoxide.
          NaCl = Sodium chloride.
H
6
o
o
H
O
O
H
W
O
O
HH
H
W

-------
   TABLE AX4.7. EFFECTS OF NITRIC OXIDE WITH IRON AND ON ENZYMES
                                AND NUCLEIC ACIDS
                     Effect
                       Reference
 Sodium nitroprusside (NO donor) mobilizes iron
 from ferritin
          Reif and Simmons (1990)
 Modulation of arachidonic acid metabolism via
 interference with iron
          Kanneretal. (1991, 1992)
 Inhibition of aconitase (an enzyme in the Krebs
 cycle, and also complex 1 and 2 of the respiratory
 chain)
          Hibbsetal. (1988)
          Perssonetal. (1990)
          Stadleretal. (1991)
 Permanent modification of hemoglobin, possibly via   Moriguchi et al. (1992)
 deamination
 Deamination of DNA
          Wink etal. (1991)
 DNA strand breaks
          Nguyen etal. (1992)
 Inhibition of DNA polymerase and ribonucleotide     Lepoivre et al. (1991)
 reductase                                         Kwon et al. (1991)

 Antimitogenic; inhibition of T cell proliferation in     Fu & Blankenhorn (1992)
 rat spleen cells

 Inhibition of DNA synthesis, cell proliferation, and    Nakaki et al. (1990)
 mitogenesis in vascular tissue
 Inhibition of mitogenesis and cell proliferation
 (vascular smooth muscle cells)
          Garg and Hassid (1989)
 Adenosine diphosphate ribosylation is stimulated by   Nakaki et al. (1990)
 NO-generating agents
August 2007
AX4-46
DRAFT-DO NOT QUOTE OR CITE

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                                  TABLE AX4.8A.  GENOTOXICITY OF NO2 IN VITRO AND IN PLANTS
OQ
to
o
o
           Test Organism
                           End Point
                                Exposure
                               Comments
                            Results
           Reference
Salmonella TA100
Salmonella TA100

Salmonella TA 100
and TA 102
Mutations
Mutations

Mutations
         SalmonellaTAlOO    SOS repair
         E. co//, WP2
         E. coll
         Bacillus sub tills
         spores
         V79 hamster cells
                    Mutations
                    SOS repair
                    Mutations

                    Chromatid-type
                    aberrations, SCE
6-10 ppm, 40 mins
10-15 ppm, 6h

Bubbling of 10-90 ppm
through bact. susp.,
30 mins as above
Bubbling of 10-90 ppm
through bact. susp.,
30 mins

Bubbling of 10-90 ppm
through bact. susp.,
30 mins
Bubbling of 10-90 ppm
through bact. susp.,
30 mins
500 ppm, 2-3 h

10-100 ppm, 10 mins
Concentrations >10 ppm were
bacteriotoxic
                                                                    Effect not considered solely
                                                                    attributed to nitrite in
                                                                    suspension. No effect seen
                                                                    with NO gas.
                                                 Effect shown not to be solely
                                                 due to nitric acid or nitrite.
                                                 No effect if cells not washed
                                                 with Hank's salt solution
+     Isomuraetal. (1984)
+     Victorin and
      Stahlberg (1988)
      Kosakaetal. (1985)
                                                                                     Kosakaetal. (1985)
                                     Kosakaetal. (1986,
                                     1987)

                                     Kosakaetal. (1986,
                                     1987)

                                     Sasaki etal. (1980)

                                     Tsudaetal. (1981)
H
6
o
0
H
O
O
H
W
O
O
HH
H
W
V79 hamster cells
Don hamster cells
V79 hamster cells
Tradescantia
Tradescantia

Source: Victorin et al.
SCE
Mutations (8-G resistance)
DNA single -strand breaks
Micronuclei in pollen
Mutations in stamen hair

(1994).
2-3 ppm, 10 mins
2-3 ppm, 10 mins
10 ppm, 20 mins
5 ppm, 24 h
50 ppm, 6 h


VVAU-A A .1X4J.AAV J kJCt-Al. kJV/±L*l.±V/±±
prior to exposure
Slight response
Effect not due to formation of
nitrite



+ Shiraishi and
Bandow (1985)
Isomuraetal. (1984)
+ Gorsdorf et al.
(1990)
+ Ma etal. (1982)
+ Schairer etal. (1979)



-------
                                          TABLE AX4.8B. GENOTICITY OF NO2 IN VIVO
CJQ
to
o
o
oo
H

6
o


o
H

O


O
H
W

O


O
HH
H
W
Test Organism
Drosophila
Drosophila
Rats
Rats
Mice

Mice
End Point
Recessive lethals
Somatic mutations (wing spot test)
Mutations in lung cells (oubain res.)
Chromosome aberrations in lung cells
Chromosome aberrations in lymphocytes and
spermatocytes
Micronuclei in bone marrow
Exposure
500-7000 ppm, 1 h
50-280 ppm, 2 days
50-560 ppm, >12 days
27 ppm, 3 h
0. 1-10 ppm, 6 h

20 ppm, 23 h
Result Reference
Inoueetal. (1981)
Victorinetal. (1990)
+ Isomuraetal. (1984)
+ Isomuraetal. (1984)
Goochetal. (1977)

Victorinetal. (1990)
        Source: Victorin (1994).

-------
                                   TABLE AX4.8C. GENOTOXICITY OF NO IN VITRO AND IN VIVO
^            Test Organism                 End Point                        Exposure               Result         Reference
^       Salmonella TA100        Mutations                        25-30 ppm, 40 min                      +     Isomuraetal. (1984)
o       Salmonella              SOS repair                       Bubbling of 10-90 ppm                   -     Kosakaetal. (1985)
VO
H
6
o
o
H
O
o
H
W
O
O
HH
H
W
         Don hamster cells         Mutations (8-AG resistance)         2-3 ppm, 10 min                        +     Isomuraetal. (1984)
         V79 hamster cells         DNA single-strand breaks           500 ppm, 30 min                        -     Gorsdorf etal. (1990)
         TK 6 human cells         Mutations, DNA single-strand       Injection of 0.12-0.38 ml NO gas/ml        +     Nguyen etal. (1992)
                                 breaks                           of culture medium, 1 h
         Salmonella TA1535       Mutations                        30 min to 5-90 ppm                      +     Arroyo etal. (1992)
         Rats                    Mutations in lung cells (oubain      27 ppm, 3 h                            -     Isomuraetal. (1984)
                                 res.)

        Source: Victorin (1994); Arroyo et al. (1992) added.

-------
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39          presence of measurement error: an application of a measurement-error-resistant
40          technique. Environ. Health Perspect. 112: 1686-1690.


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 1   Zhang, H.; Lindwall, R.; Zhu, L.; Frostell, C.; Sun, B. (2003) Lung physiology and
 2          histopathology during cumulated exposure to nitric oxide in combination with assisted
 3          ventilation in healthy piglets. Pulm. Pharmacol. Ther. 16: 163-169.
 4   Zidek, J. V. (1997) Interpolating air pollution for health impact assessment. In: Barnett, E. V.;
 5          Turkman, K. F., eds. Pollution Assessment and Control. New York, NY: John Wiley &
 6          Sons.  (Statistics for the Environment, no. 3).
 7   Zipprich, J. L.; Harris, S. A.; Fox, J. C.; Borzelleca, J. F. (2002) An analysis of factors that
 8          influence personal exposure to nitrogen oxides in residents of Richmond, Virginia. J.
 9          Exposure Anal. Environ. Epidemiol. 12: 273-285.
10   Zmirou, D.; Schwartz, J.; Saez, M.; Zanobetti, A.; Wojtyniak, B.; Touloumi, G.; Spix, C.; Ponce
11          de Leon, A.; Le Moullec, Y.; Bacharova, L.; Schouten, J.; Ponka, A.; Katsouyanni, K.
12          (1998) Time-series analysis of air pollution and cause-specific mortality. Epidemiology
13          9:495-503.
14   Zota, A.; Adamkiewicz, G.; Levy, J.  L; Spengler, J. D. (2005) Ventilation in public housing:
15          implications for indoor nitrogen dioxide concentrations. Indoor Air 15: 393-401.
16
17
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 i      AX5.  CHAPTER 5 ANNEX - CONTROLLED HUMAN

 2           EXPOSURE STUDIES OF NITROGEN OXIDES
 o
 4
 5   AX5.1   INTRODUCTION
 6          This annex summarizes the effects of nitrogen oxides (NOX) on human volunteers

 7   exposed under controlled conditions. The goal is to review the scientific literature on human

 8   clinical studies of NOX exposure published since the 1993 Air Quality Criteria Document

 9   (AQCD) for Oxides of Nitrogen (U.S. Environmental Protection Agency, 1993).  Summary

10   findings from the 1993 AQCD are provided below. The primary focus will be on nitrogen

11   dioxide because it is the most abundant NOX species in the atmosphere and there are few human

12   studies of exposure to other NOX species.

13          The following are the conclusions drawn from the review of clinical studies of nitrogen

14   oxide exposure in the 1993 criteria document.

15          1.     Nitrogen dioxide causes decrements in lung function, particularly increased
16                airway resistance in healthy subjects at concentrations exceeding 2.0 ppm for 2 h.
17          2.     Nitrogen dioxide exposure results in increased airway responsiveness  in healthy,
18                nonsmoking subjects exposed to concentrations exceeding 1.0 ppm for exposure
19                durations of 1 hour or longer.
20          3.     Nitrogen dioxide exposure at levels above 1.5 ppm may alter numbers and types
21                of inflammatory cells in the distal airways or alveoli, but these responses depend
22                upon exposure concentration, duration, and frequency. Nitrogen dioxide may
23                alter function of cells within the lung and production of mediators that may be
24                important in lung host defenses.
25          4.     Nitrogen dioxide exposure of asthmatics causes, in some subjects, increased
26                airway responsiveness to a variety of provocative mediators, including cholinergic
27                and histaminergic chemicals, 862 and cold air.  However, the presence of these
28                responses appears to be influenced by the exposure protocol, particularly whether
29                or not the exposure includes exercise.
30          5.     Modest decrements in spirometric measures of lung function (3 to 8%) may occur
31                in some asthmatics and COPD patients under certain NC>2 exposure conditions.
32          6.     Nitric acid levels in the range of 50 to 200 ppb may cause some pulmonary
33                function responses in adolescent asthmatics, but not in healthy adults.  Other
34                commonly occurring NOX species do not appear to  cause any pulmonary function
35                responses at concentrations  expected in the ambient environment, even at higher
36                levels than in worst-case scenarios. However, not all  nitrogen oxides  acid species
37                have been studied sufficiently.
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 1          7.     No association between lung function responses and respiratory symptom
 2                 responses were observed.  Furthermore, there is little evidence of a concentration-
 3                 response relationship for changes in lung function, airway responsiveness, or
 4                 symptoms at the NO2 levels that are reviewed here.
 5
 6          In the summary and integration chapter of the 1993 NOX criteria document, one of the
 7    key health effects of most concern at near ambient concentrations of NO2 was increases in
 8    airway responsiveness of asthmatic individuals after short-term exposures. The 1993 AQCD
 9    notes the absence of a concentration-response relationship for NO2 exposure and airways
10    responsiveness in asthmatics. For example, most responses to NO2 that had been observed in
11    asthmatics occurred at concentrations between 0.2 and 0.5 ppm.  However, other studies showed
12    an absence of effects on airways responsiveness at much higher concentrations, up to 4 ppm.
13    Since 1993, additional studies suggest that exposure to low concentrations of NO2, either alone
14    or in combination with other pollutants such as SO2, may enhance allergen responsiveness in
15    asthmatic subjects.
16          In the years since the preparation  of the 1993 AQCD, many studies from a variety of
17    disciplines have convincingly demonstrated that exposure to particulate air pollution increases
18    the risk for cardiovascular events.  In addition, a number of epidemiological studies have shown
19    associations between ambient NO2 levels and adverse cardiovascular outcomes, at concentrations
20    well below those shown to cause respiratory effects. However, to date there remain very few
21    clinical studies of NO2 that include endpoints relevant to cardiovascular disease.
22
23    AX5.1.1    Considerations in Controlled Human Exposure Studies
24
25    Strengths and Limitations of Controlled Human Studies
26          The database for air pollution risk assessment arises from four investigative approaches:
27    epidemiology, animal toxicology, in vitro studies, and human inhalation  studies. Each possesses
28    advantages but also carries significant limitations. For example, the epidemiological
29    investigation examines exposures in the "real world" but struggles with the realities of
30    conducting research in the community, where cigarette smoking, socioeconomic status,
31    occupational exposures, meteorological variability, and exposure characterization are important
32    confounders. Outcomes are often evaluated from available health or mortality records or from
33    administered questionnaires, all of which have inherent limitations. Sophisticated measures of

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 1    physiological responses are often not practical in studies involving large populations, although
 2    they may be used in panel studies. In contrast, inhalation studies in animals allow precision in
 3    quantifying exposure duration and concentration, measurement of a wide variety of physiologic,
 4    biochemical, and histological endpoints, and examination of extremes of the exposure-response
 5    relationship. Often, however, interpretation of these studies is constrained by difficulty in
 6    extrapolating findings from animals to humans, especially when exposure concentrations are
 7    unrealistically high.
 8           Controlled, quantitative studies of exposed humans offer a third approach (Frampton
 9    et al., 2006). Human clinical studies attempt to engineer laboratory atmospheric conditions
10    relevant to ambient pollutant atmospheres, with careful control of concentrations, duration,
11    timing, and other conditions which may impact responses. These studies provide the opportunity
12    to measure symptoms and physiological markers of health effects that result from breathing the
13    atmospheres.  The carefully controlled environment allows investigators to identify responses to
14    individual pollutants, to characterize exposure-response relationships, to examine interactions
15    among pollutants, and to study the effects of other variables such as exercise, humidity, or
16    temperature.  Susceptible populations can participate, including individuals with acute and
17    chronic respiratory and cardiovascular diseases, with appropriate limitations based on subject
18    comfort and protection from risk. Endpoint assessment traditionally has included symptoms and
19    pulmonary function, but more recently a variety of markers of pulmonary, systemic, and
20    cardiovascular function have been used to assess pollutant effects.
21           Human clinical studies have limitations. For practical and ethical reasons, studies must
22    be limited to relatively small  groups, to short durations of exposure, and to pollutant
23    concentrations that are expected to produce only mild and transient responses. Findings from the
24    short-term exposures in clinical studies may provide limited insight into the health  effects of
25    chronic or repeated exposures.
26           Specific issues of protocol design in human clinical studies have been reviewed
27    (Frampton et al., 2006), and will not be considered further here, except in the context of specific
28    studies of NC>2 exposure described in the following pages.
29
30    Assessing the Findings from Controlled Human Studies
31           In clinical studies, humans are the species of interest, so findings have particular
32    relevance in risk assessment.  However, the utility of clinical studies in risk assessment is

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 1   tempered by the obvious need to avoid adverse health effects of the study itself. This usually
 2   means selecting subjects that are not the most susceptible to the pollutant being studied.
 3   Furthermore, clinical studies depend on outcome markers with variable relevance or validation
 4   as markers of true health effects.  The statement from the American Thoracic Society, "What
 5   constitutes an adverse health effect?" (American Thoracic Society, 2000) addresses issues
 6   relevant to selection and interpretation of outcome markers in clinical studies.
 7          The 1993 NC>2 AQCD included a description of key outcome measures that had been in
 8   use to that date. These included primarily respiratory outcomes, including pulmonary function
 9   tests such as spirometry, lung volumes, and airways resistance, and tests of pulmonary clearance
10   of inhaled aerosols. A brief description of bronchoalveolar lavage was also included, which had
11   come into use prior to 1993 to assess airway inflammation and changes in the epithelial lining
12   fluid in response to NC>2 exposure.
13
14
15   AX5.2    EFFECTS OF NITROGEN DIOXIDE IN HEALTHY SUBJECTS
16          Table AX5.1 summarizes  the key clinical studies of NC>2 exposure in healthy subjects
17   since 1993, with a few key studies included prior to that date.  Figure AX5.1 summarizes the
18   findings of these studies of airway inflammatory responses in relation to the total exposure to
19   NC>2, expressed as ppm-minutes.  Studies that did not include  a proper control air exposure were
20   not included, and studies using multiple  daily exposures were not included. All of the studies
21   portrayed in Figure AX5.1 involved intermittent exercise, and no attempt was made to adjust the
22   exposure metric for varying intensity and duration of exercise.
23
24
25   AX5.3    THE EFFECTS OF NITROGEN OXIDE EXPOSURE IN
26              SENSITIVE SUBJECTS
27          Table AX5.2 summarizes  studies of potentially sensitive subjects. The potential for NC>2
28   exposure to enhance responsiveness to allergen challenge in asthmatics deserves special mention.
29   Several recent studies, summarized in Table AX5.3, have reported that low-level exposures to
30   NO2, both at rest and with exercise,  enhance the response to specific allergen challenge in mild
31   asthmatics.
32          These recent studies involving allergen challenge suggest that NC>2 may enhance the
33   sensitivity to allergen-induced decrements in lung function, and increase the allergen-induced

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1   airway inflammatory response. Figure AX5.2 categorizes the allergen challenge studies as
2   "positive", i.e. showing evidence for increased responses to allergen in association with NC>2
3   exposure, or "negative", with the exposure metric expressed as ppm-min. In comparing Figure
4   AX5.2 with Figure AX5.1, it can be seen that enhancement of allergic responses in asthmatics
5   occurs at exposure levels more than an order of magnitude lower than those associated with
6   airway inflammation in healthy subjects. The dosimetry difference is even greater when
7   considering that the allergen challenge studies were generally performed at rest, while the airway
8   inflammation studies in healthy subjects were performed with intermittent exercise.
     Cellylar
     Response
    Mediator
    Response
         No
     Response
                        (2,3)
                   ( 1 ')
                          Study         ppm-min
                       1. Azadnivetal. 1998   720
                       2. Blomberg et al, 199?   430
                       3. Devlin et al. 1999     480
                       4. Frampton et at. 2002   270
                       5. Frampton et al. 2002   108
                       6. J6rresetal. 1995      180
                       7. Vagaggirmietal. 1996  18
                 0
200            400            600
     IMCL  ppm-minutes
                          800
    Figure AX5.1.   Airway inflammation in response to NOi inhalation in healthy subjects.
    August 2007
          AX5-5
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                      2,8
                                          5)(3h)
               9)3
                      4)(6h)
         Study         ppm-min
    1. Barck et a!. 2002      7.8
    2. Barck et a!. 2005a      23.4
    3. Barck et a!. 2005b      7.8
    4. Jenkins et al. 1999    72 (6h)
    5. Jenkins et a!. 1999    72 (3h)
    6. Strand etal. 1997      7.8
    7. Strand etal. 1998     31.2
    S.Tunnicliffeetal.  1994   24
    9. Tunnicliffe et al.  1994    6
    10. Wang etal. 1995a,b  144
             0
            50                 100

           IMCL ppm-minutes
                  150
    Figure AX5.2.
Effects of NOi inhalation on allergen challenge in subjects with asthma.
+: Significant effect of NOi. -:  No significant effect
*: Exposures included intermittent exercise.
1   AX5.4   EFFECTS OF MIXTURES CONTAINING NITROGEN OXIDES

2          Table AX5.4 summarizes human clinical studies of NO2-containing mixtures or

3   sequential exposures that are most relevant to ambient exposure scenarios.
    August 2007
                      AX5-6
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CJQ
TABLE AX5.1. CLINICAL STUDIES OF NO2 EXPOSURE IN HEALTHY SUBJECTS
t-*
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Reference
Avissar et al.
(2001)





Azadniv et al.
(1998)



Blomberg et al.
(1997)


Blomberg et al.
(1999)





Devlin et al.
(1999)





Drechsler-Parks
(1995)





Location
Rochester,
NY, USA





Rochester,
NY, USA



Sweden



Sweden






Chapel Hill,
North
Carolina,
USA



Santa
Barbara, CA,
USA




Participants
21 healthy
nonsmokers





2 studies,
12 healthy
nonsmokers in
each

30 healthy
nonsmokers


12 healthy
nonsmokers





8 healthy
nonsmokers





8 older healthy
nonsmokers





Approach & Methods
Measurements of extracellular
glutathione peroxidase (eGPx)
activity and protein levels in
epithelial lining fluid from NO2
exposure study described in
Frampton et al. (2002) (see
below).
Air vs. 2 ppm NO2 for 6 h with
intermittent exercise. Phase 1 :
BAL 18 h after exposure;
Phase 2: BAL immediately
after exposure.
Air vs. 2 ppm NO2 for 4 h,
with intermittent exercise


Air vs. 2 ppm NO2 for 4 h on
4 days, with intermittent
exercise.




Air and 2.0 ppm NO2 for 4 h
with intermittent exercise.





4 2-h exposures with
intermittent exercise: air, 0.60
ppm NO2, 0.45 ppm O3, and
0.60 ppm NO2 + 0.45 ppm O3.



Findings
No effects of NO2 exposure on eGPx
activity and protein concentrations.
(Ozone exposure decreased eGPx
activity and protein concentrations.)



Increased BAL neutrophils, decreased
blood CD8+ and null T lymphocytes 18
h after exposure. No effects on
symptoms or lung function.

Increased neutrophils and interleukin-8
in bronchial wash. Increases in specific
lymphocyte subsets in BAL fluid.
Symptoms/lung function not reported.
After 4 days of NO2, increased
neutrophils in bronchial wash but
decreased neutrophils in bronchial
biopsy. 2% decrease in FEVi after first
exposure to NO2, attenuated with
repeated exposure. Symptoms not
reported.
Increased bronchial lavage neutrophils,
IL-6, IL-8, alphai-antitrypsin, and tissue
plasminogen activator. Decreased
alveolar macrophage phagocytosis and
superoxide production. No effects on
pulmonary function. Symptoms not
reported.
Significant reduction in cardiac output
during exercise, estimated using
noninvasive impedance cardiography,
with NO2 + O3. Symptoms and
pulmonary function not reported.


Comments
NO2 up to 1.5 ppm for
3 hours did not deplete
this mode of
antioxidant defense in
the epithelial lining
fluid.

2 ppm NO2 for 6 h
caused mild
inflammation.


2 ppm NO2 for 4 h
caused airway
inflammation.

Decreased lung
function, not confirmed
in other studies at t his
concentration.
Conflicting information
on airway
inflammation.
2 ppm NO2 for 4 h
caused airway
inflammation.




Suggests cardiac effects
ofNO2 + O3. Small
number of subjects
limits statistical power,
has not been replicated.



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CJQ
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                         TABLE AX5.1 (cont'd).  CLINICAL STUDIES OF NO2 EXPOSURE IN HEALTHY SUBJECTS
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                         TABLE AX5.1 (cont'd). CLINICAL STUDIES OF NO2 EXPOSURE IN HEALTHY SUBJECTS
            Reference
                 Location
                Participants
                        Approach & Methods
                                           Findings
                                          Comments
 X
H
6
o

o
H
O
o
H
W
O
O
HH
H
W
Torres et al.
(1995)
Germany
          Kim et al.
          (1991)

          Morrow et al.
          (1992)
          Pathmanathan
          et al. (2003)
          Posin et al.
          (1978)
          Rasmussen
          etal. (1992)
          Rigas et al.
          (1997)
                Seattle,
                Washington,
                USA
                Rochester,
                NY, USA
                United
                Kingdom,
                Sweden

                Downey,
                CA, USA
               Denmark
8 healthy
nonsmokers &
12 mild asthmatics
             9 healthy athletes
             20 COPD subjects
             (14 current
             smokers) and
             20 elderly healthy
             (13 never-smokers,
             4 former smokers,
             3 current smokers)
             12 healthy
             nonsmokers
             10 healthy
             nonsmokers
             14 healthy
             nonsmokers
                             12 healthy
                             nonsmokers
Air or 1 ppm NO2 exposure for
3 h with intermittent exercise.
                   Air, 0.18, and 0.30 ppm NO2 for
                   30 min with exercise

                   Air vs. 0.3 ppm NO2 for 4 h with
                   intermittent exercise.
                   Air vs. 2 ppm NO2 for 4 h on
                   4 days, with intermittent
                   exercise. Bronchoscopy and
                   biopsy 1 h after exposure.
                   3 daily exposures for 2.5  h.
                   1st day: air; 2nd and 3rd days:
                   1 or 2 ppm NO2.  Intermittent
                   exercise. Subsequent control
                   series of 3 daily air exposures.
                   Air vs. 2.3 ppm NO2 for 5 h
                                2 h of 0.36 ppm NO2, 0.75 ppm
                                NO2, 0.36 ppm SO2, or 0.36 ppm
                                O3. Boluses of O3 every 30 min
                                to measure O3 absorption.
In asthmatics, 2.5% decrease FEVi
after NO2 vs. 1.3% decrease after air,
p = 0.01. FEVj decreased 20% in
1 subject after NO2. No significant
lung function effect in healthy
subjects. Changes in eicosanoids
(more pronounced in asthmatics), but
not inflammatory cells, in B AL fluid.
No effects on pulmonary function.
Symptoms not reported.

COPD: small declines in FVC and
FEVjwithNOz. Healthy: No
symptoms or pulmonary function
effects for group as a whole.  Healthy
smokers showed a 2.3% decline in
FEVj with NO2, and differed from
nonsmokers.
Epithelial expression of IL-5, IL-10,
IL-13, and ICAM-1 increased
following NO2 exposure. No data on
inflammatory cells in BAL fluid.
Reduced hemoglobin and hematocrit,
and red blood cell acetyl
cholinesterase.
                               Small increases in FVC and
                               Reduced lung permeability and blood
                               glutathione peroxidase after
                               exposure.
                               NO2 and SO2 increased O3 absorption
                               by increasing biochemical substrates.
Lung function effects
consistent with other
studies, suggesting some
asthmatics susceptible.
Evidence for mild airway
inflammation.
Small number of subjects
limits conclusions.

Mild lung function effects
of 0.3 ppm for 4 h in
exercising patients with
COPD.  Small number of
healthy smoking subjects
limits conclusions
regarding this group.
Supportive evidence for
pro-allergic airway
inflammation favoring
following NO2 exposure.
Suggests red blood cell
effects of NO2(see
Frampton et al., 2002).
Exposures not randomized.

Only 1 week between
exposures may have
confounded results.

Suggests breathing
mixtures of NO2 and O3
would increase O3 dose to
airways.

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OQ
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 o
 o
                         TABLE AX5.1 (cont'd). CLINICAL STUDIES OF NO2 EXPOSURE IN HEALTHY SUBJECTS
           Reference    Location
                            Participants
                                    Approach & Methods
                                                                Findings
                                                                            Comments
 X
 (Si
 I
 o
 H
 6
 o

 o
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O
 O
 H
 W
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 HH
 H
 W
Sandstrom
etal. (1990)
          Sandstrom
          etal. (1991)
Sandstrom
etal.
(1992a)

Sandstrom
etal.
(1992b)

Solomon
et al. (2000)
          Vagaggini
          etal. (1996)
                       Sweden
             Sweden
                       Sweden
                       Sweden
San
Francisco,
California,
USA
Italy
             32 healthy
             nonsmokers,
             4 groups of
             8 subjects
             18 healthy
             nonsmokers
             10 healthy
             nonsmoking men
             8 healthy
             nonsmokers
15 healthy
nonsmokers
                          7 healthy
                          nonsmokers
4 ppm NO2 for 20 min with 15 min
exercise.  BAL 4, 8, 24, 72 h after
exposure, compared with non-
exposure control BAL
2.25, 4.0,  5.5 ppm NO2 for 20 min
with light exercise. BAL 24 h after
exposure, compared with non-
exposure control BAL
4 daily exposures to 4 ppm NO2 for
20 min with 15 min exercise.  BAL
24 h after exposure, compared with
non-exposure control BAL.
1.5 ppm NO2 for 20 min with
15 min exercise, every 2nd day x 6.
BAL 24 h after exposure compared
with non-exposure control BAL.
Air or 2.0 ppm NO2 with
intermittent exercise, for 4 h
daily x 4.  BAL 18 hours after
exposure.
Air vs. 0.3 ppm NO2 for 1 h with
intermittent exercise.
                                                   Increase in BAL mast cells and
                                                   lymphocytes 4-24 h after exposure.
                                                   Increase in BAL mast cells (all
                                                   concentrations) and lymphocytes
                                                   (4.0 and 5.5 ppm).

                                                   Reduction in alveolar macrophages,
                                                   NK cells, and CDS lymphocytes in
                                                   BAL; reduction in total lymphocytes
                                                   in blood.
                                                   Reduced CD8+ T lymphocytes and
                                                   NK cells in BAL fluid.
Increased neutrophils in bronchial
lavage decreased CD4+ T
lymphocytes in BAL. No changes in
blood.
Mild increase in symptoms.  No
effects on lung function, nasal lavage,
or induced sputum.
                                    Study weakened by lack of
                                    control air exposure.
                                    Study weakened by lack of
                                    control air exposure.
                                    Study weakened by lack of
                                    control air exposure.
                                    Study weakened by lack of
                                    control air exposure.
Airway inflammation with
2 ppm NO2 for 4 daily 4 h
exposures.

Small number of subjects
limits statistical power.

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OQ
 to
 o
 o
  TABLE AX5.2.  EFFECTS OF NO2 EXPOSURE IN SUBJECTS WITH RESPIRATORY DISEASE (SEE TABLE AX5-3
 	FOR STUDIES WITH ALLERGEN CHALLENGE)	
           Reference   Location
                           Participants
                                 Approach & Methods
                                       Findings
                                             Comments
 >
 X
H
6
o

o
H
O
O
H
W
O

O
HH
H
W
Gong et al.
(2005)
Hackney
etal.
(1992)

Torres and
Magnussen
(1991)
Torres et al.
(1995)
          Morrow
          etal.
          (1992)
          Strand et al.
          (1996)
          Vagaggini
          etal.
          (1996)
Downey,   6 healthy
CA, USA   nonsmokers and
           18 ex-smokers with
           COPD
                       Downey,    26 smokers with
                       CA, USA   symptoms and
                                  reduced FEVi

                       Germany    11 mild asthmatics
Germany   8 healthy
           nonsmokers &
           12 mild asthmatics
            Rochester,   20 COPD,
            NY, USA   20 healthy elderly
             Sweden
            19 mild asthmatics
             Italy
           8 mild asthmatics,
           7 COPD
2 h exposures with
intermittent exercise to:
1) air, 2)0.4 ppmNO2>
3) 200 ug/m3 concentrated
ambient paniculate matter
(CAPs), 4) NO2 + CAPs
Personal monitoring and
chamber exposure to air and
0.3 ppm NO2 for 4 h with
intermittent exercise
Air vs. 0.25 ppm NO2 for
30 min with 10 min exercise

Air or 1 ppm NO2 exposure
for 3 h with intermittent
exercise.
Air vs. 0.3 ppm NO2 for 4 h
with intermittent exercise

Air vs. 0.26 ppm NO2 for
30 min with intermittent
exercise
Air vs. 0.3 ppm NO2 for 1 h
with intermittent exercise.
Reduced maximum mid-expiratory
flow rate and oxygen saturation with
CAPs exposures; no effects of NO2
alone or additive effect with CAPs.
                                                          No significant effects on lung
                                                          function.
No effects on lung function or
airways responsiveness to
methacholine.
In asthmatics, 2.5% decrease FEVi
after NO2 vs. 1.3% decrease after air,
p = 0.01.  FEVj decreased 20% in
1 subject after NO2. No significant
lung function effect in healthy
subjects.  Changes in eicosanoids
(more pronounced in asthmatics), but
not inflammatory cells, in B AL fluid.
Equivocal reduction in FVC with
COPD patients, but not healthy
subjects.
Increased airway responsiveness to
histamine 5 h after exposure. No
effects on lung function.
Mild decrease in FEY: in COPD
subjects in comparison with air
exposure, but not with baseline. No
effects on nasal lavage or induced
sputum.	
Exposures not fully randomized.
Small number of subjects limits
interpretation for healthy group.
Lung function effects consistent
with other studies, suggesting some
asthmatics susceptible. Evidence
for mild airway inflammation.
Small number of healthy subjects
limits statistical power.
Suggests increased nonspecific
airways responsiveness at much
lower concentration than healthy
subjects. Differs from findings in
Torres and Magnussen 1991
No convincing effect of NO2 in this
study.  Small number of subjects
limits statistical power.

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                           TABLE AX5.3. EFFECTS OF NO2 EXPOSURE ON RESPONSE TO INHALED ALLERGEN
OQ
 to
 o
 o
            Reference     Location   Participants
                                                          Approach & Methods
                                                                                                    Findings
                                          Comments
                                                                                                                          Key study suggesting that NO2
                                                                                                                          enhances inflammatory
                                                                                                                          response to allergen in mild
                                                                                                                          asthmatics.
                                                                                                                          Provides supporting evidence
                                                                                                                          that NO2 enhances the airway
                                                                                                                          inflammatory response to
                                                                                                                          allergen.
                                                                                                                          0.26 ppm NO2 did not enhance
                                                                                                                          nasal inflammatory response to
                                                                                                                          allergen challenge.
                                                                                                                          Small number of subjects
                                                                                                                          limits statistical power.
                                                                                                                          Suggests 0.4 ppm for 3 h with
                                                                                                                          intermittent exercise increases
                                                                                                                          allergen responsiveness.
X
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H
6
o

o
H
O
O
H
W
O

O
HH
H
W
          Barcketal.     Sweden     13 mild        30 min exposures to air and 0.26 ppm
          (2002)                     asthmatics,     NO2 (at rest?), allergen challenge 4 h
                                     4 ex-smokers   and BAL 19 h after exposure.
                                                   Randomized, crossover, double blind.
          Barcketal.     Sweden     18 mild        Day 1: 15 min exposures, Day 2:
          (2005a)                    asthmatics,     2 15-min exposures to air and 0.26 ppm
                                     4 ex-smokers   NO2 separated by 1 h, at rest. Allergen
                                                   challenge 4 h after exposure on day
                                                   1 and 3 h after exposure on day 2.
                                                   Sputum induction before exposure on
                                                   days 1 & 2, and morning of day 3.
                                                   Randomized, crossover, single blind.
          Barck et al.     Sweden     16 mild        30 min exposures to air and 0.26 ppm
          (2005b)                    asthmatics     NO2 at rest, nasal allergen challenge 4 h
                                     with rhinitis    after exposure. Nasal lavage before and
                                                   at intervals after exposure  and
                                                   challenge.
          Devalia et al.   United      8 mild         6 h exposures to combination of
          (1994)         Kingdom    asthmatics     0.4 ppm NO2 and 0.2  ppm SO2.
          Jenkins etal.   United       11 mild        1) 6-h exposures to air, 0.1 ppm ozone,
          (1999)        Kingdom    asthmatics      0.2 ppm NO2, and combination followed
                                                   by allergen challenge;
                                                   2) 3-h exposures to air, 0.2 ppm ozone,
                                                   0.4 ppm NO2, and combination;
                                                   All exposures with intermittent exercise.
Increased PMN in bronchial wash
and BAL fluid, increased
eosinophil cationic protein in
bronchial wash, and reduced cell
viability and BAL volume with
NO2 + allergen. No effects on
lung function response to allergen.
Increased eosinophilic cationic
protein in sputum and blood, and
increased myeloperoxidase  in
blood with NO2 + allergen.  No
differences in lung function or
sputum cells.
No significant differences
between air and NO2 exposure.
Increased allergen responsiveness
10 min after exposure to
combination of NO2 and SO2, but
not to individual gases.
All of the second exposure
scenarios (ozone, NO2, and
combination), but none of the first
exposure scenarios, resulted in
reduced concentration of allergen
causing a 20% decline in FEVi.
Authors conclude that
concentration more important than
total inhaled pollutant.

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                      TABLE AX5.3 (cont'd). EFFECTS OF NO2 EXPOSURE ON RESPONSE TO INHALED ALLERGEN
            Reference     Location    Participants
                                                 Approach & Methods
                                                                            Findings
                                                                                              Comments
 X
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O

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Rusznak
etal. (1996)
           Strand et al.
           (1997)
           Strand et al.
           (1998)
           Tunnicliffe
           etal. (1994)
           Wang et al.
           (1995a);
           Wang et al.
           (1995b)
           Wang et al.
           (1999)
United
Kingdom
               Sweden
               Sweden
              United
              Kingdom
              United
              Kingdom
              United
              Kingdom
13 mild
asthmatics
            18 patients
            with mild
            asthma, age
            18-50yrs
            16 patients
            with mild to
            moderate
            asthma, age
            21-52yrs
            10
            nonsmoking
            mild
            asthmatics age
            16-60 yrs.
            8 subjects
            completed.
            2 groups of
            8 subjects with
            allergic rhinitis

            16 subjects
            with allergic
            rhinitis
6 h exposures to combination of
0.4 ppm NO2 and 0.2 ppm SO2
                Exposure to 0.26 ppm NO2 for 30 min
                at rest, allergen challenge 4 h after
                exposure

                4 daily repeated exposures to 0.26 ppm
                NO2 for 30 min at rest
                Exposure to air, 0.1 ppm, and 0.4 ppm
                NO2 for 1 h at rest, separated by at
                least 1 week, followed by allergen
                challenge
                Exposure to 0.4 ppm NO2 (at rest?) for
                6 h followed by nasal allergen
                challenge and nasal lavage

                Treatment with nasal fluticasone or
                placebo for 4 weeks followed by
                exposure to 0.4 ppm NO2 for 6 h,
                allergen challenge, and nasal lavage
Increased allergen responsiveness
to combination of NO2 and SO2,
10 min, 24, and 48 h after
exposure.
Late phase, but not early phase,
response to allergen enhanced by
N02.

Significant increases in both early
and late phase response to allergen
after 4th day of exposure.
                                     Post-challenge reduction in FEVi
                                     after 0.4 ppm NO2 was greater
                                     than after air, for both the early
                                     (p < 0.009) and late (p < 0.02)
                                     responses. No difference in
                                     nonspecific airway
                                     responsiveness.
                                     Increase in myeloperoxidase and
                                     eosinophil cationic protein in
                                     nasal lavage fluid following
                                     allergen challenge.
                                     Fluticasone suppressed the NO2
                                     and allergen-induced increase in
                                     eosinophil cationic protein in
                                     nasal lavage fluid.	
                                                                                                                          Confirms findings of Devalia
                                                                                                                          etal. (1994), thatNO2 + SO2
                                                                                                                          for 6 h increases allergen
                                                                                                                          responsiveness.
                                                                                                                          Suggests 0.26 ppm NO2 for 30
                                                                                                                          min at rest increases late
                                                                                                                          response.

                                                                                                                          Suggests repeated 0.26 ppm
                                                                                                                          NO2 at rest increases allergen
                                                                                                                          response.
                                 Suggests threshold for allergen
                                 responsiveness effect is
                                 between 0.1 and 0.4 ppm for 1
                                 h resting exposure.
                                 Suggests enhanced nasal
                                 inflammatory response to
                                 allergen with 0.4 ppm.

                                 Confirms earlier findings of
                                 this group that 0.4 ppm NO2
                                 enhances nasal allergen
                                 response.	

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TABLE AX5.4. EFFECTS OF EXPOSURE TO NO2 WITH OTHER POLLUTANTS
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Reference
Devalia et al.
(1994)



Drechsler-
Parks (1995)





Gong et al.
(2005)




Hazucha et al.
(1994)


Torres and
Magnussen
(1990)

Koenig et al.
(1994)




Rubenstein
etal. (1990)



Location
United
Kingdom



Santa Barbara,
CA, USA





Downey, CA,
USA




Chapel Hill,
North
Carolina, USA

Germany



Seattle,
Washington,
USA



San Francisco,
California,
USA


Participants
8 mild asthmatics




8 older healthy
nonsmokers





6 healthy nonsmokers
and 18 ex-smokers
with COPD



21 healthy female
nonsmokers


14 nonsmoking mild
asthmatics


28 asthmatic
adolescents; 6 subjects
did not complete.



9 stable asthmatics




Approach & Methods
6 h exposures to combination of
0.4 ppm NO2 and 0.2 ppm SO2.



4 2-h exposures with intermittent
exercise: air, 0.60 ppm NO2,
0.45 ppm O3, and 0.60 ppm NO2 +
0.45 ppm O3.



2 h exposures with intermittent
exercise to: 1) air, 2) 0.4 ppm NO2,
3) 200 ug/m3 concentrated ambient
particulate matter (CAPs), 4) NO2 +
CAPs

2 h exposure to air or 0.6 ppm NO2
followed 3 h later by exposure to
0.3 ppm O3, with intermittent
exercise.
30 min exposures to air, 0.25 ppm
NO2, or 0.5 ppm SO2 at rest followed
15 min later by 0.75 ppm SO2
hyperventilation challenge.
Exposure for 90 min with
intermittent exercise to: 1) 0.12 ppm
ozone + 0.3 ppmNO2, 2) 0.12 ppm
ozone + 0.3 ppm NO2 + 68 ug/m3
H2SO4, or 3) 0.12 ppm ozone +
0.3 ppm NO2 + 0.05 ppm nitric acid.
30 min exposures to air or 0.3 ppm
NO2 with 20 min exercise, followed
1 h later by SO2 inhalation challenge.


Findings
Increased allergen
responsiveness 10 min after
exposure to combination of
NO2 and SO2, but not to
individual gases.
Significant reduction in cardiac
output during exercise,
estimated using noninvasive
impedance cardiography, with
NO2 + O3. Symptoms and
pulmonary function not
reported.
Reduced maximum mid-
expiratory flow rate and
oxygen saturation with CAPs
exposures; no effects of NO2
alone or additive effect with
CAPs.
NO2 enhanced spirometric
responses and airways
responsiveness following
subsequent O3 exposure.
NO2 but not SO2 increased
airways responsiveness to SO2
challenge.

No effects on pulmonary
function




No effects on pulmonary
function or SO2
responsiveness.


Comments
Small number of
subjects limits
statistical power.


Suggests cardiac
effects of NO2 + O3.
Small number of
subjects limits
statistical power, has
not been replicated.

Exposures not fully
randomized. Small
number of healthy
subjects limits
interpretation for
healthy group.
0.6ppmNO2
enhanced ozone
responses.

Findings contrast with
Rubenstein, et al.
(1990).

Absence of lung
function effects of 0.3
ppm NO2 consistent
with other studies; no
effects of mixtures.

Findings contrast with
Torres & Magnussen
etal. (1990).



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CJQ
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                         TABLE AX5.4 (cont'd). EFFECTS OF EXPOSURE TO NO2 WITH OTHER POLLUTANTS
            Reference
  Location
    Participants
      Approach & Methods
         Findings
     Comments
Rudell et al. Sweden
(1999)




10 healthy
nonsmokers




Air and diesel exhaust for 1 h, with
and without particle trap. NO2
concentration 1.2-1.3 ppm. BAL
24 h after exposures.


Increased neutrophils in BAL
fluid, no significant reduction
in effect with particle trap.



Filter only partially
trapped particles.
Unable to draw
conclusions about role
of NO2 in causing
effects.
          Rusznak et al.
          (1996)
United
Kingdom
13 mild asthmatics
6 h exposures to combination of
0.4 ppm NO2 and 0.2 ppm SO2.
Increased allergen
responsiveness to combination
of NO2 and SO2, 10 min, 24,
and 48 h after exposure.
Confirms findings of
Devaliaetal. (1994),
that NO2 + SO2 for 6 h
increases allergen
responsiveness.
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34
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   AX6. CHAPTER 6 ANNEX - EPIDEMIOLOGICAL
STUDIES OF HUMAN HEALTH EFFECTS ASSOCIATED
 WITH AMBIENT OXIDES OF NITROGEN EXPOSURE
August 2007               AX6-1    DRAFT-DO NOT QUOTE OR CITE

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                 TABLE AX6.1. STUDIES EXAMINING EXPOSURE TO INDOOR NO2 AND RESPIRATORY SYMPTOMS
                                                                                                                       NO2 Measurement
OQ
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                Author,
             Year/Outcome
                       OR or RR (95% CI)
                                                    Exposure                     Range
Subjects/Location       Analysis/Monitoring Device      Time     Mid-Range (ppb)   (ppb)
         Pilotto et al. (2004)

         daytime symptoms
         difficulty breathing
         chest tightness
         asthma attacks
         difficulty breathing,
         night
                              RR 2.44 (1.02, 14.29)=*
                              RR 2.22 (1.23, 4.00)*
                              RR 2.56 (1.08, 5.88)*

                              RR 3.12 (1.45, 7.14)*
                                                      118 asthmatic
                                                      children/Australia
                                                                     negative binomial/passive
                                                                     diffusion badges
                                                              mean (sd)
                                                   6 h        intervention 16 (7)    7, 38
                                                              mean (sd) control 47
                                                              (27)                12, 116
 X
         Pilotto et al. (1997)    OR 1.41 (0.63, 3.15)
         wheeze (>40 ppb)
                                                      388 children/Australia
                    generalized linear mixed
                    models/passive diffusion badges
                                                                                                   6 h
4, 132
H
6
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o
H
O
o
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W
O
O
HH
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Nitschke et al. (2006)

night symptoms
difficulty breathing
school max
home  max
chest tightness
school max
                              RR 1.23 (1.10, 1.39)
                              RR 1.06 (1.02, 1.10)

                              RR 1.25 (1.14, 1.37)
                                                      174 asthmatic
                                                      children/Australia
                                                                              negative binomial/passive
                                                                              diffusion badges
                                                   6 h        mean home 20 (22)
                                                                                                                        mean school 34 (28)

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    TABLE AX6.1 (cont'd).  STUDIES EXAMINING EXPOSURE TO INDOOR NO2 AND RESPIRATORY SYMPTOMS
                                                                                                              NO2 Measurement
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    Author, Year     OR or RR (95% CI)      Subjects/Location
                                                                                                              Exposure                   Range
                                                                                Analysis/Monitoring Device       Time   Mid-range (ppb)    (ppb)
         Garrett et al. (1998)                       148 children/Australia
         chest tightness        OR 1.53 (0.45, 5.32)
                                                                  multiple logistic regression/passive
                                                                  monitors
                                                                                                              4 days     med 6
                                                             plO-p90,
                                                             3,15
         Smith et al. (2000)

         children (n= 49, 0-14)
         chest tightness        OR 1.12 (1.07, 1.18)
                                        125 asthmatic
                                        adults/children/Australia
                                                                           GEE/passive diffusion badges
                                  4.5 h
                 4, 147
 X
 ON
 K>
Belanger et al. (2006)


multifamily housing
wheeze              RR 1.33 (1.05, 1.68)
chest tightness	RR1.51 (1.18, 1.91)
                                                 728 asthmatic
                                                 children/Northeast US
logistic, Poisson regression/Palmes
tubes
                                                                                                              2 wks
mean (sd) gas
home 26 (18)
mean (sd) elect
home 9 (9)
H
6
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o
H
O
o
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W
O
O
HH
H
W
Chauhan et al. (2003)
Increased symptom
score, comparing first
and second tertiles of
NO2 exposure
Increased symptom
score, comparing first
and third tertiles of
NO2 exposure
                              0.6 (0.01, 1.18)
                              2.1(0.52,3.81)
                                                 114 asthmatic children/
                                                 Southampton U.K.
                                                                           Palmes diffusion tubes
                                  7d
Exposure tertiles:  Chauhan et
<^4-7^>7      al. (2003)

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                                 TABLE AX6.1 (cont'd).  STUDIES EXAMINING EXPOSURE TO INDOOR NO2 AND
                                                                   RESPIRATORY SYMPTOMS
Author, Year
OR or RR (95% CI)
Subjects/Location

Analysis/Monitoring Device

Exposure
Time
NO2 Measurement
Mid-range (ppb)

Range
(ppb)
           van Strien et al.
           (2004)
           persistent cough
           <5.1ppb           RR1.0
           5.1, 9.9 ppb        RR 0.96 (0.69, 1.36)
           9.9, 17.4 ppb      RR 1.33 (0.94, 1.88)
           >17.4ppb         RR 1.52 (1.00, 2.31)
           shortness of breath
           <5.1ppb           RR1.0
           5.1, 9.9 ppb        RR 1.59 (0.96, 2.62)
           9.9, 17.4 ppb      RR 1.95 (1.17, 3.27)
           >17.4ppb         RR 2.38 (1.31, 4.34)
762 infants/Northeast US      Poisson regression
                                                                                                                                 med 10
H
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           Notes:
           Unless otherwise noted, results given for 20 ppb increase in NO2.
           *For purpose of comparison, RRs from Pilotto et al. (2004) are shown here as risk of symptoms given greater exposure to NO2,
           i.e., control (unflued gas heater) vs. intervention (flued or electric replacement heater).
           RRs reported by Pilotto el al. (2004) as protective effects for intervention vs. control.

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 >         TABLE AX6.2. STUDIES EXAMINING EXPOSURE TO AMBIENT NO2 AND ACUTE RESPIRATORY SYMPTOMS
|       	USING GENERALIZED ESTIMATING EQUATIONS (GEE) IN THE ANALYSIS METHOD	
 "                                                                   NO2 Measurement                 Correlation with Other Pollutants
 to	
 §                                                            Avg   Mid-range
 ^           Author, Year      OR(95%CI)  Location  Subjects   Time     (ppb)      Range (ppb)    PM2.S   PM10     O3      SO2     CO
         Children:  Multicity
         Studies
                                           US,      1844
         Schwartz etal. (1994)                6-Cities  children   24 h   med 13      plO-p90,5,24   0.35   0.36     -0.28     0.51
         cough, incidence:
         lag 1-4 mean         1.61(1.08,2.43)
                                                   864
                                           US,      asthmatic
         Mortimer et al. (2002)                NCICAS children   4 h    med 25      7,90                           0.27
         asthma symptoms:
         lag 1-6 mean         1.48(1.02,2.16)
                                           North    990
 t**J                                         America, asthmatic                     minplOtomax
 &       Schildcrout etal. (2006)               CAMP   children   24 h   med23      p90, 10,37             0.26,0.640.04,0.47  0.23,0.680.63,0.92
 •**•       asthma symptoms:
         lagO                1.06(1.00,1.13)
         lagl                1.04(0.97,1.10)
 O       lag 2                1.09(1.03,1.15)
 P>       3-day moving sum     1.04(1.01,1.07)
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O
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      TABLE AX6.2 (cont'd). STUDIES EXAMINING EXPOSURE TO AMBIENT NO2 AND ACUTE RESPIRATORY
         SYMPTOMS USING GENERALIZED ESTIMATING EQUATIONS (GEE) IN THE ANALYSIS METHOD
                                                                      NO-. Measurement
                                                                                              Correlation with Other Pollutants
             Author, Year
                                                       Avg    Mid-range
                     OR(95%CI)  Location  Subjects    time      (ppb)     Range (ppb)    PM2.5    PM10
                                                                 03
                                                       SO,
                   CO
 X
         Children: Single City
         Studies

         Pino et al. (2004)
         wheezy bronchitis:
         6-day lag
                                  Chile
504 infants  24 h
mean(sd) 41
(19)          p5-p95, 20, 81
                    1.14(1.04, 1.30)
Ostroetal. (2001)
cough, incidence: lag 3  1.07 (1.00, 1.14)
wheeze, incidence:
                                                   138
                                                   asthmatic
                                                   children,
                                           Southern African
                                           CA      American   1 h
         Iag3

         Delfino et al. (2002)
         asthma symptoms:
         lagO
                    1.05 (1.01, 1.09)
                                  Southern 22 asthmatic
                                  CA     children    8 h
                    1.91 (1.07,3.39)
                                                   84 asthmatic
                  mean (sd) 80
                  (4)           20,220
                  mean(sd) 15
                  (7)           6,34
                                                            mean (sd) 30
                           0.34     0.63
0.48
                                    0.55
0.26
Tl
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0
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Segalaetal. (1998)
asthma symptoms,
incidence: lag 0
lagl
lag 4
nocturnal cough,
incidence: lag 3

lag 4




Paris children 24 h (8) 13,65 (0.61)* 0.55 0.54

1.89(1.13,3.17)
1.36(0.70,2.64)
1.80(1.07,3.01)

1.44 (0.99, 2.08)

1.74 (1.20, 2.52)





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TABLE AX6.2 (cont'd). STUDIES EXAMINING EXPOSURE TO AMBIENT NO2 AND ACUTE RESPIRATORY
  SYMPTOMS USING GENERALIZED ESTIMATING EQUATIONS (GEE) IN THE ANALYSIS METHOD
j~^
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X
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i
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0
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O
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Author, Year
Just et al. (2002)
nocturnal cough,
incidence: lagO
lag 0-2
lag 0-4

Jalaludin et al. (2004)
wet cough:
lagO
Pino et al. (2004)
Adults

Segala et al. (2004)
sore throat, cough:
lag 0-4
von Klotetal. (2002)
wheeze, prev: 5-day
mean
phlegm, prev: 5 -day
mean
cough, prev: 5 -day
mean
breathing prob in a.m.:
5 -day mean
NO2 Measurement Correlation with Other Pollutants
Avg Mid-range
OR(95%CI) Location Subjects time (ppb) Range (ppb) PM2.S PM10 O3 SO2 CO
82 asthmatic mean (sd) 29
Paris children 24 h (9) 12,59 0.92* 0.54 0.09 0.69
2.11 (1.20,3.74)
1.80 (0.89, 3.84)
1.58 (0.73, 3.54)
148 children
with wheeze mean (sd) 15
Australia history 15 h (6) 3,79 0.26 -0.31

1.13 (1.00, 1.26)

46
nonsmoking mean (sd) 30
Paris adults 24 h (9) 12,71 0.82* 0.83
4.05 (1.20,
13.60)
53 asthmatic
Germany adults 24 h med 24 4, 63 0.74 0.36 0.82
1.15(1.02, 1.31)
1.22(1.10, 1.39)
1.15(1.00, 1.31)
1.25(1.10, 1.39)
Odds ratios (OR) given for 20 ppb increase in NO2 with 24-h averaging time, or 30 ppb for 1-h averaging time. (20 ppb increases also used for times between 1 and 24 h.) *BS



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TABLE AX6.3-1.  RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                  HOSPITAL ADMISSIONS
 X
H
6
o
o
H
O
o
H
W
O
O
HH
H
W
Reference, Study
Location, & Period
Outcomes, Design, & Methods
Mean Levels &
Monitoring Stations
Copollutants &
Correlations
Effects: Relative Risk or Percent Change
& Confidence Intervals (95%)
UNITED STATES
Moolgavkar (2000a,b,c)
Moolgavkar (2003)

Multi-city, United
States: Chicago, Los
Angeles, Maricopa
County, (Phoenix).

Period of Study:
1987-1995








Outcomes (ICD 9 codes): COPD including
asthma (490-496)
Age groups analyzed: 0-19, 20-64, 65+ (LA
only)
Study Design: Time series
Statistical Analyses: Poisson regression,
GAM
Covariates: day of wk, temporal trends,
temperature, relative humidity
Lag: 0-5 days








Chicago
Median: 25 ppb
IQR: 10 ppb

Los Angeles
Median: 38 ppb
IQR: 18 ppb

Maricopa
Median: 1 9 ppb
IQR: 12 ppb







Chicago:
PM10; r = 0.49
CO; r= 0.63
SO2; r = 0.44
O3;r = 0.02

LA:
PM2.5; r = 0.73
PM10; r = 0.70
CO; r= 0.80
S02; r = 0.74
03;r=-0.10

Maricopa:
PM10; r = 0.22
CO; r= 0.66
SO2; r = 0.02
O3;r=-0.23
Increment: 10 ppb

COPD, >65 yrs
Chicago 1.7% [CI 0.36, 3.05] lag 0 - GAM default
Chicago 2.04% [t = 2.99] lag 0 - GAM-100
Los Angeles 2. 5% [CI 1.85, 3.15] lag 0 - GAM
default
Los Angeles 2.84% [t = 13.32] lag 0 - GAM - 30
Los Angeles 1 .80% [t = 9.60] lag 0 - GAM - 100
Los Angeles 1 .78% [t = 7.72] lag 0 - NS-100
Phoenix 4.4% [CI 1.07, 7.84] lag 5

Chronic Respiratory Disease
Los Angeles
0-19 yrs 4.9% [CI 4.1, 5.7] lag 2
20-64 yrs 1.7% [CI 0.9, 2.1] lag 2

Multi-pollutant model
           Moolgavkar* et al.
           (1997)
           United States:
           Minneapolis-St. Paul

           Period of Study:
           1986-1991
  Outcomes (ICD 9 codes): COPD including
  asthma (490-496), Pneumonia (480-487)
  Age groups analyzed: 65+
  Study Design: Time series
  Statistical Analyses:  Semi-parametric
  Poisson regression, GAM
  Covariates: day of wk, season, temporal
  trends, temperature
  Statistical Package:  S Plus
  Lag: 0-3 days
NO2 24-h avg (ppb)

16.3 ppb
IQR: 9.5 ppb
PM10;r=0.31
S02;r=0.09
CO; r= 0.58
                                                                                                               NO2 andPM10: 1.72% [t = 3.18] lag 0 - GAM-100
                                                                                                               NO2 and PM2 5: 1.51% [t = 2.07] lag 0 - GAM-100
                                                                                                               Increment:  10 ppb
                  Sum of Pneumonia and COPD
                  2.2% [0.2, 4.2] lag 1

                  Pneumonia Only
                  3.1% [0.6, 5.6] lag 1,20 df
                  1.7% [-0.8, 4.2] lag 1, 130 df

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                TABLE AX6.3-1 (cont'd).  RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                                         HOSPITAL ADMISSIONS
 Reference, Study
Location, & Period
Outcomes, Design, & Methods
  Mean Levels &      Copollutants &    Effects: Relative Risk or Percent Change &
Monitoring Stations    Correlations             Confidence Intervals (95%)
           UNITED STATES (cont'd)
 X
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O
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           Neidell (2004)
           California

           Period of Study:
           1992-1998
                      Outcomes (ICD 9 codes): Asthma
                      Age groups analyzed: 
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                 TABLE AX6.3-1 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                                        HOSPITAL ADMISSIONS
 Reference, Study
Location, & Period
Outcomes, Design, & Methods
  Mean Levels &     Copollutants &    Effects: Relative Risk or Percent Change &
Monitoring Stations     Correlations              Confidence Intervals (95%)
           UNITED STATES (cont'd)
           Karr et al. (2006)
           Southern LA County,
           CA, United States

           Period of Study:
           1995-2000
                     Outcomes (ICD 9 codes): Acute
                     bronchiolitis (466.1)
                     Age groups analyzed:  0-1 yr
                     Study Design:  Case-crossover
                     N: 19,109
                     Statistical Analyses: Conditional logistic
                     regression
                     Covariates: day of wk, temperature,
                     humidity
                     Seasons: Nov-Maronly
                     Lag:  0-4 days
                                   1-h max NO2 (ppb)
                                   Mean: 59 ppb
                                   IQR: 26 ppb

                                   Number of Stations: 34
                      CO
                      PM2.5
 X
Increment: 26 ppb (IQR)

Acute bronchiolitis
OR 0.96 [0.94, 0.99] lag 4
OR 0.97 [0.95, 0.99] lag 1
Stratified by Gestational Age at Birth:
37-44 wks
0.98 [0.95, 1.00] lag 1; 0.97 [0.94, 0.99] lag 4
34-36 wks
0.90 [0.84, 0.97] lag 1; 0.94 [0.88, 1.02] lag 4
29-33 wks
1.01 [0.91, 1.13] lag 1; 0.90 [0.80, 1.01] lag 4
25-28 wks
0.94 [0.78, 1.13] lag 1; 0.90 [0.73, 1.11] lag 4
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O
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TABLE AX6.3-1 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:

                           HOSPITAL ADMISSIONS
X

 I

o
H

6
o


o
H

O


o
H
W

O


O
HH
H
W
Reference, Study
Location, & Period Outcomes, Design, & Methods
UNITED STATES
Linn et al. (2000)
Los Angeles, United
States

Period of Study:
1992-1995













(cont'd)
Outcomes (ICD 9 codes): Asthma (493),
COPD (APR-DRG 88), Pulmonary
diagnoses
(APR-DRG 75-101)
Age groups analyzed: >30
Study Design: Time series
N: 302,600
Statistical Analyses: Poisson regression,
GAM, OLS regression
Covariates: day of wk, holiday, max
temperature, min temperature, rain days,
mean temperature, barometric pressure,
season
Seasons: Winter (Jan-Mar), Spring (Apr-
Jun), Summer (Jul-Sep), Fall
(Oct-Dec)
Statistical Package: SPSS and SAS
Lag: 0, 1 days



Mean Levels &
Monitoring Stations

All concentrations are in
ppb.
Winter: 3. 4 ±1.3
Spring: 2.8 ±0.9
Summer: 3.4 ± 1.0
Autumn: 4.1 ± 1.4

Overall: 3.4 ±1.3











Copollutants &
Correlations

Winter:
CO; r= 0.89
PM10;r=0.88
O3;r=-0.23

Spring:
CO; r= 0.92
PM10; r = 0.67
03;r = 0.35

Summer
CO; r= 0.94
PM10;r=0.80
03;r = 0.11

Winter
CO; r= 0.84
PM10;r=0.80
03;r=-0.00

Effects: Relative Risk or Percent Change
& Confidence Intervals (95%)

Increment: 10 ppb

All pulmonary
All seasons: 0.7% ± 0.3%
Winter: 1.1% ±0.5%
Spring: 0.7% ±0.1%
Summer: 0.4% ±0.8%
Autumn: 1.2% ±0.4%
Asthma
All season: 1.4% ±0.5%
Winter: 2.8% ±0.1%
Spring: NR
Summer: NR
Autumn: 1.9% ±0.8%
COPD
All season: 0.8% ±0.4%
Winter: NR
Spring: NR
Summer: NR
Autumn: 1.6% ±0.6%





















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                TABLE AX6.3-1 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                                       HOSPITAL ADMISSIONS
 Reference, Study
Location, & Period
    Outcomes, Design, & Methods
    Mean Levels &
 Monitoring Stations
 Copollutants &
  Correlations
    Effects: Relative Risk or Percent
 Change & Confidence Intervals (95%)
           UNITED STATES (cont'd)
           Gwynn* et al. (2000)
           Buffalo, NY
           United States

           Period of Study:
           1988-1990

           Days:  1,090
                     Outcomes (ICD 9 codes): Respiratory
                     admissions: Acute bronchitis/bronchiolitis
                     (466); Pneumonia (480-4860); COPD and
                     Asthma (490-493, 496)
                     Age groups analyzed: 6
                     Study Design: Time series
                     N:  24,
                     Statistical Analyses:  Poisson regression
                     with GLM and GAM
                     Covariates: season, day of wk, holiday,
                     temperature, relative humidity
                     Lag: 0-3 days
                                       24-h avg NO2 (ppb):
                                       Min: 4.0
                                       25th:  15.5
                                       Mean:  20.5
                                       75th: 24.5
                                       Max:  47.5
                        IT" r = 0.22
                        SO42T = 0.36
                        PM10 r = 0.44
                        O3r=0.06
                        SO2r=0.36
                        CO r = 0.65
                        COH r = 0.72
                   Increment: 27 9 ppb (Max-Mean; IQR)

                   NO2 alone:
                   Max-Mean RR 1.033 (t = 1.32) lag 1
                   IQRRR1.01(t= 1.32) lag 1
 X
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O
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Zanobetti and
Schwartz (2006)
Boston, MA, United
States

Period of Study:
1995-1999
Outcomes (ICD 9 codes):  Pneumonia (480-
7)
Age groups analyzed:  65+
Special Population:  Medicare patients only
Study Design: Case-crossover
N: 24,857
Statistical Analyses: Conditional logisitic
regression
Covariates: apparent temperature, day of
wk
Seasons: Warm (Apr-Sep), Cool (Oct-Mar)
Statistical Package:  SAS
Lag:  0, 1 days, 0-1 avg
NO2 median 23.20 ppb;
90-10%: 20.41 ppb; For
lag 0-1 2 day avg 90-10%
= 16.8 ppb; IQR = 10.83

Number of Stations: 5
PM2.5;r=0.55
BC;r=0.70
CO; r= 0.67
O3;r=-0.14
Increment:  20.41 ppb (90-10%)
Pneumonia
-0.16% [-4.73, 4.42] lag 0

Increment:  16.78 ppb (90-10%)
Pneumonia
2.26% [-2.55, 7.01] lag 0-1

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TABLE AX6.3-1 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:

                           HOSPITAL ADMISSIONS
X
ON


to
H

6
o


o
H

O


O
H
W

O


O
HH
H
W
Reference, Study
Location, & Period
Outcomes, Design, & Methods
Mean Levels &
Monitoring Stations
Copollutants & Effects: Relative Risk or Percent Change
Correlations & Confidence Intervals (95%)
CANADA
Burnett etal. (1997a)
16 cities
Canada

Period of Study:
4/1981-12/1991

Days: 3,927




Yang et al. (2003)
Vancouver, Canada

Period of Study: 1986-
1998

Days: 4748






Outcomes (ICD 9 codes): All respiratory
admissions
(466, 480-6, 490-4, 496)
Study Design: Time series
N: 720,519
# of hospitals: 134
Statistical Analyses: random effects relative
risk regression model
Covariates: long-term trend, season, day of
wk, hospital,
Statistical Package: NR
Lag: 0, 1,2 day
Outcomes (ICD 9 codes): All respiratory
admissions (460-519)
Study Design: Case-crossover
Age groups analyzed: <3, >65
Statistical Analyses: conditional logistic
regression
Statistical Package: NR
Lag: 0-5 days





l-hmaxNO2(ppb)
Mean: 35.5
SD: 16.5
25th: 25
50th: 33
75th: 43
95th: 62
99th: 87




24-h avg NO2 (ppb):
Mean: 18.74
SD: 5.66
5th: 11.35
25th: 14.88
50th: 17.80
75th: 21.45
100th: 49.00
IQR: 5.57

Number of stations: 30


O3r=0.20 Increment: 10 ppb
CO
SO2 Single pollutant
COH NO2 and respiratory admissions, p = 0.772

Multipollutant model (adjusted for CO, O3, SO2,
COH, dew point):
RR 0.999 [0.9922, 1.0059] lag 0




CO Increment: 5. 57 ppb (IQR)
S02
O3 r = -0.32 All Respiratory Admissions <3 yrs:
COH NO2 alone: OR 1.05 [1.02, 1.09] lag 1
N02 + 03: OR 1.05 [1.02, 1.09] lag 1
NO2 + O3 + CO + COH + SO2: OR 1 .05
[0.99, 1.11] lag 1

All Respiratory Admissions >65 yrs:
NO2 alone: OR 1.05 [1.03, 1.07] lag 1
N02 + 03: OR 1.04 [1.02, 1.07] lag 1
N02 + 03 + CO + COH + S02: OR 1 .05
[1.01, 1.08] lag 1

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                        TABLE AX6.3-1 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:

                                                            HOSPITAL ADMISSIONS
Reference, Study
Location, & Period
Outcomes, Design, & Methods
Mean Levels & Copollutants & Effects: Relative Risk or Percent
Monitoring Stations Correlations Change & Confidence Intervals (95%)
CANADA (cont'd)
Fung et al. (2006)
Vancouver, BC, Canada

Period of Study:
6/1/95-3/31/99












Outcomes (ICD 9 codes): All respiratory
hospitalizations (460-519)
Age groups analyzed: 65+
Study Design: (1) Time series, (2) Case-
crossover, (3) DM-models (Dewanji and
Moolgavkar 2000, 2002)
N: 40,974
Statistical Analyses: (1 ) Poisson, (2)
conditional logistic regression, (3) DM
method - analyze recurrent data in which
the occurrence of events at the individual
level over time is available
Covariates: day of wk
Statistical Package: S-Plus and R
Lag: Current day, 3 and 5 day lag



NO2 24-h avg: Mean: CO; r = 0.74
16.83 ppb,SD = 4.34; COH;r=0.72
IQR: 5.43 ppb; range: SO2;r=0.57
7.22,33.89 PM10;r=0.54
PM2.5;r=0.35
PM10.2.5;
r=0.52
O3;r=-0.32









Increment: 5.43 ppb. (IQR)

NO2 Time series
RR 1.018 [1.003, 1.034] lag 0
RR 1.024 [1.004, 1.044] lag 0-3
RR 1.025 [1.000, 1.050] lag 0-5
RR 1.027 [0.998, 1.058] lag 0-7
NO2 Case-crossover
RR 1.028 [1.010, 1.047] lag 0
RR 1.035 [1.012, 1.059] lag 0-3
RR 1.032 [1.006, 1.060] lag 0-5
RR 1.028 [0.997, 1.060] lag 0-7
NO2 DM model
RR 1.012 [0.997, 1.027] lag 0
RR 1.018 [1.000, 1.037] lag 0-3
RR 1.007 [0.988, 1.026] lag 0-5
RR 1.002 [0.981, 1.023] lag 0-7
                                                                                                        DM method produced slightly higher RR

                                                                                                        estimates on O3, SO2, and PM2 5 compared to

                                                                                                        time series and case-crossover, and slightly

                                                                                                        lower RR estimates on COH, NO2, and PM10,

                                                                                                        though the results were not significantly

                                                                                                        different from one another.

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                         TABLE AX6.3-1 (cont'd).  RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                                              HOSPITAL ADMISSIONS
X
 I
-1^
H
6
o
o
H
O
O
H
W
O
O
HH
H
W
Reference, Study
Location, & Period
Outcomes, Design, & Methods
Mean Levels & Copollutants & Effects: Relative Risk or Percent Change
Monitoring Stations Correlations & Confidence Intervals (95%)
CANADA (cont'd)

Yang (2005)
Vancouver, BC, Canada

Period of Study:
1994-1998
Days: 1826




Outcomes (ICD 9 codes): COPD excluding
asthma (490-2, 494, 496)
Age groups analyzed: 65+
Study Design: Time series
N: 6,027
Statistical Analyses: Poisson regression
with GAM (with more stringent criteria)
Covariates: temperature, relative humidity,
day of wk, temporal trends, season
Statistical Package: S-Plus
Lag: 0-6 days, moving avgs
24-havg: 17.03 ppb, SD PM10;r=0.61
= 4.48;IQR: 5.47 ppb; SO2;r=0.61
Range: 4.28,33.89 CO; r= 0.73
03;r=-0.10
Winter: 19.20(4.86)
Spring: 15.36(3.72)
Summer: 16.33(4.57)
Fall: 17.27(3.77)

Number of Stations: 3 1

Increment: 5. 5 ppb (I QR)

COPD
>65 yrs, year round
RR 1.05 [1.01, 1.09] lag 0
RR 1.04 [1.00, 1.10] lag 0-1
RR 1.07 [1.01, 1.13] lag 0-2
RR 1.08 [1.02, 1.15] lag 0-3
RR 1.10 [1.03, 1.17] lag 0-4
RR1.11 [1.04, 1.19] lag 0-5
RR1.11 [1.04, 1.20] lag 0-6
                                                                                                          Two-pollutant model
                                                                                                          PM10:  RR 1.03 [0.90, 1.17] lag 0
                                                                                                          CO: RR 1.07 [0.96, 1.20] lag 0-6
                                                                                                          03:  RR 1.12 [1.04, 1.20] lag 0-6

                                                                                                          Multipollutant models
                                                                                                          N02, CO, S02, 03, PM10: RR 1.01 [0.88, 1.16]
                                                                                                          N02, CO, S02, 03: RR 1.06 [0.95,1.19]

                                                                                                          NO2 was strongest predictor of hospital admission
                                                                                                          for COPD among all gaseous pollutants in single-
                                                                                                          pollutant models

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                         TABLE AX6.3-1 (cont'd).  RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:

                                                               HOSPITAL ADMISSIONS
 X
H

6
o


o
H

O


O
H
W

O


O
HH
H
W
Reference, Study
Location, & Period
Outcomes, Design, & Methods
Mean Levels &
Monitoring Stations
Copollutants &
Correlations
Effects: Relative Risk or Percent Change
& Confidence Intervals (95%)
CANADA (cont'd)
Lin* et al. (2004)
Vancouver, BC
Canada

Period of Study:
1987-1991













Outcomes (ICD 9 codes): Asthma (493)
Age groups analyzed: 6-12
Study Design: Time series
N: 3,754 (2,331 male, 1,423 female)
Statistical Analyses: Semi-parametric
Poisson regression with GAM (with default
and more stringent criteria)
Covariates: Trend, day of wk,
Statistical package: S-Plus
Lag: Cumulative 1-7 day









24-h avg NO2 (ppb)
Mean: 18.65
SD: 5.59
Min: 4.28
25th: 14.82
50th: 17.75
75th: 21.36
Max: 45.36


Number of stations: 30








CO r = 0.73
S02r=0.67
03r=-0.03
PM2.5r=0.37
PM10r = 0.55














Increment: 6.54 ppb (IQR)

Boys 6-12 yrs by SES status: Low; High
Lag 1 RR 1.13 [1.04, 1.23]; 1.04 [0.95, 1.14]
Lag 2 RR 1.13 [1.02, 1.24]; 1.06 [0.95, 1.18]
Lag 3 RR 1.14 [1.02, 1.27]; 1.06 [0.94, 1.19]
Lag 4 RR 1.14 [1.02, 1.28]; 1.05 [0.92, 1.19]
Lag 5 RR 1.12 [0.99, 1.27]; 1.10 [0.96, 1.26]
Lag 6 RR 1.12 [0.98, 1.28]; 1.07 [0.93, 1.23]
Lag 7 RR 1.11 [0.97, 1.28]; 1.09 [0.94, 1.27]

Girls 6-12 yrs by SES status: Low; High
Lag 1 RR 1.07 [0.96, 1.19]; 1.01 [0.90, 1.13]
Lag 2 RR 1.03 [0.91, 1.17]; 0.98 [0.85, 1.12]
Lag 3 RR 1.04 [0.91, 1.20]; 0.98 [0.84, 1.13]
Lag 4 RR 1.11 [0.95, 1.29]; 1.01 [0.86,1.19]
Lag 5 RR 1.11 [0.94, 1.30]; 0.99 [0.83, 1.17]
Lag 6 RR 1.08 [0.91, 1.28]; 1.03 [0.86, 1.24]
Lag 7 RR 1.07 [0.90, 1.28]; 1.09 [0.90, 1.32]
                                                                                                          Multipollutant model (adjusted for SO2)

                                                                                                          Boys, Low SES:

                                                                                                          1.16 [1.06, 1.28] lag 1

                                                                                                          1.18 [1.03, 1.34] lag 4



                                                                                                          Results presented are default GAM, but authors

                                                                                                          state that use of natural cubic splines with a more

                                                                                                          stringent convergence rate produced similar results

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                  TABLE AX6.3-1 (cont'd).  RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                                           HOSPITAL ADMISSIONS
 Reference, Study
Location, & Period
    Outcomes, Design, & Methods
   Mean Levels &
 Monitoring Stations
Copollutants &
  Correlations
 Effects: Relative Risk or Percent Change &
         Confidence Intervals (95%)
           CANADA (cont'd)
 X
 Oi
 Oi
 H
 6
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 o
 H
O
 O
 H
 W
 O
 O
 HH
 H
 W
           Lin etal. (2003)
           Toronto, ON

           Period of Study:
           1981-1993
           Burnett etal. (1997b)
           Toronto, Canada
Period of Study:
1992-1994
                      Outcomes (ICD 9 codes): Asthma (493)
                      Age groups analyzed: 6-12
                      Study Design: Bi-directional case-crossover
                      N: 7,319
                      Statistical Analyses: Conditional logistic
                      regression
                      Covariates: Daily maximum and minimum
                      temperatures  and avg relative humidity
                      Lag:  Cumulative lag of 1-7 days.
Outcomes (ICD 9 codes): Respiratory
tracheobronchitis (480-6), COPD
(491-4,496)
Study Design: Time series
Statistical Analyses: Poisson regression,
GEE, GAM
Covariates: Temperature, dew point
temperature, long-term trend, season,
influenza, day of wk
Seasons: summers only
Lag: 0,1,2,3,4 days
                                         NO224-havg: 25.24
                                         ppb, SD = 9.04; IQR: 11
                                         ppb; Range: 3.00, 82.00
                                                                          Number of Stations: 4
MeanNO2:  38.5 ppb

IQRNO2: 5.75 ppb
Range: 12,81

Number of Stations:
6-11
                        CO; r= 0.55
                        S02;r=0.54
                        PM10;r=0.52
                        O3;r = 0.03
                        PM25;r=0.50
                        PM10-2.5;
                        r=0.38
PM10;r=0.61
CO; r= 0.25
Lf;r=0.25
S04;r=0.34
TP;r = 0.61
FP;r = 0.45
CP;r=0.57
COH;r=0.61
03;r = 0.07
SO2; r = 0.46
Increment: 11 ppb. (IQR)

Boys 6-12 yrs; Girls 6-12 yrs

Lag 0: OR 1.04 [0.99, 1.10]; 0.99 [0.92, 1.06]
Lag 0-1: OR 1.07 [1.00, 1.14]; 1.03 [0.94, 1.12]
Lag 0-2: OR 1.09 [1.01, 1.17]; 1.07 [0.96, 1.18]
Lag 0-3: OR 1.10 [1.01, 1.20]; 1.09 [0.97, 1.21]
Lag 0-4: OR 1.10 [1.00, 1.20]; 1.14 [1.02, 1.28]
Lag 0-5: OR 1.12 [1.01, 1.23]; 1.16 [1.02, 1.31]
Lag 0-6: OR 1.11 [1.00, 1.24]; 1.16 [1.02, 1.32]
Increment: 5.75 ppb (IQR)

Respiratory  - Percent increase
4.4% [CI 2.4, 6.4], lag 0

Copollutant and multipollutant models RR
(t-statistic):
NO2, COH:  1.018(1.36)
N02,Lf: 1.037(3.61)
NO2, SO4: 1.033(3.05)
NO2,PM10:  1.039(2.85)
N02,PM2.5: 1.037(3.13)
NO2, PM10.2.5: 1.037(2.96)
NO2, O3, SO2: 1.028(2.45)
N02, 03, S02, COH:  1.010(0.71)
NO2, O3, SO2, Lf: 1.027 (2.39)
N02, 03, S02, S04: 1.027(2.36)
N02, 03, S02, PM10:  1.028 (1.77)
NO2, O3, SO2, PM2.5:  1.028 (2.26)
N02, 03, S02, PM10.2.5:  1.022(1.71)

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                 TABLE AX6.3-1 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                                          HOSPITAL ADMISSIONS
 Reference, Study
Location, & Period
    Outcomes, Design, & Methods
   Mean Levels &
 Monitoring Stations
Copollutants &
 Correlations
                                                                                                                      Effects: Relative Risk or Percent Change
                                                                                                                            & Confidence Intervals (95%)
           CANADA (cont'd)
                                                                                                  COH;r = NR        Increment: 25.2 ppb (Mean)
 X
H
6
o
o
H
O
O
H
W
O
O
HH
H
W
Burnett etal. (1999)
Metro Toronto, Canada

Period of Study:
1980-1994
           Burnett* etal. (2001)
           Toronto, Canada

           Period of Study:
           1980-1994
Outcomes (ICD 9 codes): Asthma (493);
Obstructive lung disease (490-2,496);
Respiratory Infection (464, 466, 480-7, 494)
Study Design: Time series
Statistical Analyses: Poisson regression
model with stepwise analysis
Covariates: long-term trends, season, day of
wk, daily maximum temperature, daily
minimum temperature, daily avg dew point
temperature, daily avg relative humidity
Statistical Package: S-Plus, SAS
Lag: 0,1,2 day s, cumulative
                      Outcomes (ICD 9 codes): Croup (464.4),
                      pneumonia (480-486), asthma (493), acute
                      bronchitis/bronchiolitis (466)
                      Age groups analyzed:  <2 yrs
                      Study Design:  Time series
                      Statistical Analyses: Poisson regression
                      with GAM
                      Covariates:  temporal trend, day of wk,
                      temperature, relative humidity
                      Statistical Package:  S-Plus
                      Lag: 0-5 days
24 h mean: 25.2 ppb,
SD9.1,CV=36;
IQR = 23

Number of stations:  4
                                        l-hmaxNO2 (ppb)
                                        Mean:  44.1
                                        CV:  33
                                        5th:  25
                                        25th: 35
                                        50th: 42
                                        75th: 52
                                        95th: 70
                                        99th: 86
                                        100th:  146

                                        Number of stations:  4
                                                                                                 PM2.5; r = 0.50
                                                                                                 PM10.2.5;
                                                                                                 r=0.38
                                                                                                 PM10;r=0.52
                                                                                                 CO; r= 0.55
                                                                                                 SO2;r=0.54
                                                                                                 O3;r=-0.03
                        O3r=0.52
                        S02
                        CO
                        PM2.5
                        PM10.2.5
                   7.72 excess daily admissions due to pollution of all
                   sorts. 40.4% increase; or 3 excess daily admissions
                   traced to NO2.

                   Single-pollutant model percent increase (t statistic)
                   Asthma: 3.33% (2.37) lag 0
                   OLD 2.21% (1.07) lag 1
                   Respiratory infection: 6.89% (5.53), lag 2

                   Multipollutant model percent increase (SE)
                   Respiratory infection:
                   NO2 alone: 4.64 (SE>3)
                   NO2 + SO2+O3+PM2.5: 4.04 (SE>2)
                   NO2 + SO2+O3+PM10.2.5: 4.56 (SE>3)
                   NO2 + SO2+O3+PM10:  4.16(SE>3)
                   NO2 + O3 + PM2.5: 4.44 (SE  >2)
                   Increment: NR

                   All respiratory admissions:
                   Single-pollutant:
                   Percent increase: 20.2 (t = 3.43) lag 0-1

                   Multipollutant (adjusted for O3):
                   Percent increase: 7.1 (t = 1.09) lag 0-1

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                TABLE AX6.3-1 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                                          HOSPITAL ADMISSIONS
 Reference, Study
Location, & Period
Outcomes, Design, & Methods
                                           Mean Levels &      Copollutants &   Effects: Relative Risk or Percent Change &
                                         Monitoring Stations     Correlations              Confidence Intervals (95%)
           CANADA (cont'd)
 X
 oo
           Luginaah et al. (2005)
           Windsor, ON, Canada

           Period of Study:
           4/1/95-12/31/00
Outcomes (ICD 9 codes): Respiratory
admissions (460-519)
Age groups analyzed: 0-14,15-64, 65+, all
ages
Study Design: (1) Time series and (2) case-
crossover
N: 4,214
# of Hospitals: 4
Statistical Analyses: (1) Poisson regression,
GAM with natural splines (stricter criteria),
(2) conditional logistic regression with Cox
proportional hazards model
Covariates:  Temperature, humidity, change
in barometric pressure, day of wk
Statistical Package: S-Plus
Lag:  1,2,3 days
                                                              NO2 mean 1-h max:
                                                              38.9 ppb, SD= 12.3;
                                                              IQR: 16

                                                              Number of stations: 4
                                                            SO2; r = 0.22
                                                            CO; r= 0.38
                                                            PM10;r=0.33
                                                            COH; r=0.49
                                                            O3;r = 0.26
                                                            TRS; r = 0.06
Increment: 16 ppb (IQR)

Time series, females; males
All ages, lag 1 1.035 [0.971, 1.104]; 0.944
[0.886,1.006]
0-14 yrs, lag 2 1.114 [0.994, 1.248]; 0.955
[0.866,1.004]
15-65 yr, lag 3 1.121 [0.978,1.285], 1.012
[0.841,1.216]
65+yr,lagl 1.020 [0.930,1.119]; 0.9196
[0.832,1.016]

Case-crossover, females; males
All ages, lag 1 1.078 [0.995, 1.168]; 0.957
[0.883,1.036]
0-14 yrs, lag 2 1.189 [1.002, 1.411]; 0.933
[0.810,1.074]
15-65 yr, lag 3 1.114 [0.915,1.356]; 0.972
[0.744,1.268]
65+yr, lag 1 1.081 [0.964,1.212]; 0.915
[0.810,1.034]	
 H
 6
 o
 o
 H
O
 O
 H
 W
 O
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 HH
 H
 W

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                TABLE AX6.3-1 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                                          HOSPITAL ADMISSIONS
 Reference, Study
Location, & Period
                                     Outcomes, Design, & Methods
   Mean Levels &
 Monitoring Stations
 Copollutants &
  Correlations
 Effects: Relative Risk or Percent Change
       & Confidence Intervals (95%)
           AUSTRALIA/NEW ZEALAND
 X
 H
 6
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 H
O
 O
 H
 W
 O
 O
 HH
 H
 W
           Simpson et al. (2005a)
           Multi-city study,
           Australia (Sydney,
           Melbourne, Brisbane,
           Perth)

           Period of Study:
           1996-1999
                      Outcomes (ICD 9/ICD 10):  All respiratory
                      (460-519/JOO-J99 excluding J95.4-J95.9,
                      RO9.1, RO9.8), asthma (493/J45, J46,
                      J44.8), COPD (490-492, 494-496/J40-J44,
                      J47, J67), pneumonia with bronchitis (466,
                      480-486/J12-17, J18.0 J18.1 J18.8 J18.9 J20
                      J21)
                      Age groups analyzed: 15-64 (asthma), 65+
                      (all respiratory, COPD, asthma, pneumonia
                      with bronchitis)
                      Study Design: Time series
                      Statistical Analyses: Followed APHEA2
                      protocol: (1) Single city: (a) GAM with
                      default and more stringent criteria, (b) GLM
                      with default and more stringent criteria, (c)
                      penalized spline models.  (2) Multicity meta
                      analysis: random effects meta-analysis
                      Covariates: Temperature, relative humidity,
                      day of wk, holiday, influenza epidemic,
                      brushfire/controlled bum
                      Statistical Package: S-Plus, R
                      Lag: 0,1,2 days
Maxi 1 hNO2ppb
(range)

Brisbane: 24.1
(2.1,63.3)
Sydney:  23.7
(6.5, 59.4)
Melbourne:  23.7
(4.4, 66.7)
Perth: 16.3(1.9,41.0)
Brisbane:
03;r = 0.15
BSP;r = 0.50

Melbourne:
O3;r = 0.30
BSP;r = 0.29

Sidney:
03; r = 0.24
BSP;r = 0.54

Perth:
O3;r = 0.28
BSP; r = 0.62
Increment: Maxi 1 hNO2 IQR

Meta-analysis:

Respiratory
>65 yrs 1.0027 [1.0015, 1.0039] lag 0-1
COPD and Asthma
>65 yrs 1.0020 [1.0003, 1.0037] lag 0-1
Pneumonia and Acute Bronchitis
>65 yrs 1.0030 [1.0011, 1.0048] lag 0-1

Multipollutant Model
Respiratory >65 yrs
N02 Alone: 1.0027 [1.0015,1.0039] lagO-1
NO2+BSP: 1.0023 [1.0009, 1.0038] lag 0-1
N02+03:  1.0028 [1.0016, 1.0040] lag 0-1

GAM results from S-Plus and R similar to one
another, but different than results from GLM.
GAM results from S-Plus presented.

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                TABLE AX6.3-1 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                                         HOSPITAL ADMISSIONS
 Reference, Study
Location, & Period
Outcomes, Design, & Methods
  Mean Levels &
Monitoring Stations
Copollutants &
 Correlations
Effects:  Relative Risk or Percent Change
      & Confidence Intervals (95%)
           AUSTRALIA/NEW ZEALAND (cont'd)
 X
 to
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 6
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O
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           Barnett et al. (2005)
           Multicity,
           Australia/New
           Zealand; (Auckland,
           Brisbane, Canberra,
           Christchurch,
           Melbourne, Perth,
           Sydney)

           Period of Study:
           1998-2001
                      Outcomes (ICD 9/ICD 10): All respiratory
                      (460-519/JOO-J99 excluding J95.4-J95.9,
                      RO9.1, RO9.8), asthma (493/J45, J46,
                      J44.8), COPD (490-492, 494-496/J40-J44,
                      J47, J67), pneumonia with bronchitis (466,
                      480-486/J12-17, J18.0 J18.1 J18.8 J18.9 J20
                      J21)
                      Age groups analyzed: 0, 1-4, 5-14
                      Study Design: Case-crossover
                      Statistical Analyses: Conditional logistic
                      regression, random effects meta-analysis
                      Covariates: Temperature, current-previous
                      day temperature, relative humidity, pressure,
                      extremes of hot and cold, day of wk,
                      holiday, day after holiday
                      Season: Cool, May-Oct; Warm, Nov-Apr
                      Statistical Package: SAS
                      Lag:  0-1 days
                                    24-h avg (ppb) (range):
                                    Auckland 10.2
                                    (1.7,28.9)
                                    Brisbane 7.6 (1.4, 19.1)
                                    Canberra 7.0 (0,22.5)
                                    Christchurch 7.1
                                    (0.2,24.5)
                                    Melbourne 11.7 (2,29.5)
                                    Perth 9.0 (2, 23.3)
                                    Sydney 11.5(2.5,24.5)

                                    IQR: 5.1 ppb

                                    Daily Ih max (range):
                                    Auckland 19.1
                                    (4.2, 86.3)
                                    Brisbane 17.3 (4, 44.1)
                                    Canberra 17.9 (0, 53.7)
                                    Christchurch 15.7
                                    (1.2,54.6)
                                    Melbourne 23.2
                                    (4.4, 62.5)
                                    Perth 21.3 (4.4, 48)
                                    Sydney 22.6 (5.2, 51.4)

                                    IQR: 9.0 ppb
                       BS;r= 0.39, 0.63
                       PM2.5;r= 0.34, 0.68
                       PM10;r= 0.21, 0.57
                       CO; r= 0.53, 0.73
                       SO2;r= 0.15, 0.58
                       O3;r =-0.15, 0.28
                   Increment: 5.1 ppb (24 h) or per 9 ppb (1-h max).
                   (IQR)

                   24-h avg NO2 (5.1 ppb change)
                   Pneumonia and acute bronchitis
                   Oyrs 3.2% [-1.8, 8.4] lag 0-1
                   1-4 yrs 4.8% [-1.0, 11.0] lag 0-1
                   5-14 yrs (sample size too small)
                   Respiratory
                   Oyrs 3.1% [-1.0, 7.3] lag 0-1
                   1-4 yrs 2.4% [-0.8, 5.7] lag 0-1
                   5-14 yrs 5.8% [1.7, 10.1] lag 0-1
                   Asthma
                   0 yrs No analysis (poor diagnosis)
                   1-4 yrs 2.6% [-1.3, 6.6] lag 0-1
                   5-14 yrs 6.0% [0.2, 12.1] lag 0-1

                   1 h NO2 maximum (9.0 ppb change)
                   Pneumonia and acute bronchitis
                   Oyrs2..8% [-1.8, 7.7] lag 0-1
                   1-4 yrs 4.1% [-2.4, 11.0] lag 0-1
                   5-14 yrs (sample size too small)
                   Respiratory
                   Oyrs2.2% [-1.6, 6.1] lag 0-1
                   1-4 yrs 2.8% [0.7, 4.9] lag 0-1
                   5-14 yrs 4.7% [1.6, 7.9]  lag 0-1
                   Asthma
                   0 yrs No analysis (poor diagnosis)
                   1-4 yrs 2.5% [-0.2, 5.2] lag 0-1
                   5-14 yrs 2.6% [-2.2, 7.6] lag 0-1

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                TABLE AX6.3-1  (cont'd).  RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                                         HOSPITAL ADMISSIONS
 Reference, Study
Location, & Period
    Outcomes, Design, & Methods
   Mean Levels &
 Monitoring Stations
Copollutants &
  Correlations
 Effects: Relative Risk or Percent Change
       & Confidence Intervals (95%)
           AUSTRALIA/NEW ZEALAND (cont'd)
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           Erbas et al. (2005)
           Melbourne, Australia

           Period of Study :
           2000-2001
Hinwood et al. (2006)
Perth, Australia

Period of Study:
1992-1998
                      Outcomes (ICD 10): Asthma (J45, J46)
                      Age groups analyzed: 1-15
                      Study Design: Time series
                      N: 8,955
                      # of Hospitals: 6
                      Statistical Analyses: Poisson regression,
                      GAM and GEE
                      Covariates: Day of wk
                      Dose-response investigated?: Yes
                      Statistical Package: NR
                      Lag:  0,1,2 days
Outcomes (ICD 9): COPD (490-496,
excluding 493); Pneumonia (480-489.99);
Asthma (493)
Age groups analyzed: <\5, 65+, all ages
Study Design:  Case-crossover, time-
stratified
Statistical Analyses: Conditional logistic
regression
Covariates: Temperature, change in
temperature, maximum humidity, holiday,
day of wk
Statistical Package: NR
Lag:  0,1,2,3 days or cumulative 0-2 and 0-3
days
                                        1 hour mean NO2: 16.80
                                        ppb, SD = 8.61; range:
                                        2.43,63.00
24 h Mean [Std. Dev]
(10th and 90th centile)
All year 10.3 [5.0]
(4.4, 17.1)
Summer 9.6 [4.8]
(4.3, 15.7)
Winter 11.1 [5.1]
(4.8, 18.0)

Daily 1-hmax
Mean [Std. Dev]
All year 24.8 [10.1]
(13.3,37.5)
Summer 24.9 [8.9]
(12.4, 39.2)
Winter 24.7 [11.1]
(14.4,35.7)

Number of stations:  3
                        PM10
                        03
O3,r=-0.06
CO, r= 0.57
BS,r=0.39
PM10
PM2.5
Increment: 90th-1 Oth percentile

Inner Melbourne; increment = 25.54 ppb
RR 0.83 [0.68, 0.98] lag 0

Western Melbourne; increment = 28.86 ppb
RR 1.15 [1.03, 1.27] lag 2

Eastern Melbourne; increment = 17.67 ppb
RR 1.07 [0.93, 1.22] lag 0

South/Southeastern; increment = 17.74 ppb
RR 0.98 [0.79, 1.18] lag 1
Increment: 1 ppb  (all values were estimated from
the graphs)

All respiratory NO2 (24 hr)
>65 yrs OR 1.005  [1.001, 1.011] lag 1
All ages OR:  1.002 [0.998, 1.004] lag 1

Pneumonia NO2 (24 hr)
>65 yrs OR 1.006  [0.999, 1.014] lag 1
All ages OR:  1.002 [0.998, 1.010] lag 1

COPD NO2 (24 hr)
>65 yrs OR 1.004  [0.990, 1.012] lag 2
All ages OR:  1.001 [0.995, 1.010] lag 2

Asthma NO2 (24 hr)
0-14 yrs OR:  1.002 [0.998, 1.004] lag 0
>65 yrs OR 0.996  [0.988, 1.002] lag 0
All ages OR:  1.001 [0.999, 1.003] lag 0

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                TABLE AX6.3-1. (cont'd).  RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                                         HOSPITAL ADMISSIONS
 Reference, Study
Location, & Period
Outcomes, Design, & Methods
                                                                               Mean Levels &
                                                                             Monitoring Stations
Copollutants &
 Correlations
   Effects: Relative Risk or Percent
Change & Confidence Intervals (95%)
           AUSTRALIA/NEW ZEALAND (cont'd)
 X
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           Morgan etal. (1998a)
           Sydney, Australia

           Period of Study:
           1990-1994
           Petroeschevsky et al.
           (2001)
           Brisbane, Australia

           Period of Study:
           1987-1994
           Days: 2922
                      Outcomes (ICD 9): COPD (490-492, 494,
                      496); Asthma (493)
                      Age groups analyzed:  1-14,15-64, 65+, all
                      ages
                      Study Design: Timeseries
                      # of hospitals: 27
                      Statistical Analyses: APHEA protocol,
                      Poisson regression, GEE
                      Covariates:  long-term trend, temperature,
                      dew point, day of wk, holiday
                      Statistical Package: SAS
                      Lag: 0,1,2 days and cumulative
                      Outcomes (ICD 9): All respiratory (460-
                      519); Asthma (493)
                      Age groups analyzed:  0-4, 5-14, 15-64,
                      65+, all ages
                      Study Design: Timeseries
                      N:  33,710 (13,246 = asthma)
                      Statistical Analyses: APHEA protocol,
                      Poisson regression, GEE
                      Covariates:  Temperature, humidity, season,
                      infectious disease, day of wk, holiday
                      Season: Summer, Autumn, Winter, Spring,
                      All year
                      Dose-response investigated?:  Yes
                      Statistical Package: SAS
                      Lag: Single: 1,2,3 day
                      Cumulative: 0-2,0-4
                                    24 h daily mean: 15 ppb,
                                    SD = 6,range: 0, 52, IQR:
                                    11,90-lOthpercentile:  17

                                    Mean daily 1-h max: 29 ppb,
                                    SD = 3,range: 0,139, IQR:
                                    15, 90-1 Oth percentile:  29

                                    # of stations:  3-14, r = 0.52
                                    Mean (range) 24-h avg:
                                    Overall: 139(12,497)
                                    Summer:  97(20,331)
                                    Autumn:  129(33,319)
                                    Winter: 179(12,454)
                                    Spring: 153(35,497)

                                    Mean (range) 1-h max
                                    Overall: 282 (35, 1558)
                                    Summer:  206(35,580)
                                    Autumn:  256 (70, 585)
                                    Winter: 354(35,805)
                                    Spring: 321 (35, 1558)

                                    # of stations: 3,
                                    r= 0.43, 0.53
                                                                                                      PM(24 h), r = 0.53
                                                                                                      PM(lh),r=0.51
                                                                                                      O3,r=-0.9

                                                                                                      l-hmaxNO2:

                                                                                                      PM(24 h),r = 0.45
                                                                                                      PM (1 h),r = 0.44
                                                                                                      03,r=0.13
                                                                                                      Bsp
                                                                                                      03
                                                                                                      SO,
                   Increment:  90-1 Oth percentile

                   24-h avg (17 ppb)
                   Asthma:  1-14 yrs 3.28% [-1.72, 8.54] lag 0
                           15-64 yrs 2.29% [-2.97, 7.83] lag 0
                   COPD:  >65 yrs 4.30% [-0.75, 9.61] lag 1

                   Daily 1-h maximum (29 ppb)
                   Asthma:  1-14 yrs 5.29% [1.07, 9.68] lag 0
                           15-64 yrs. 3.18% [-1.53, 8.11] lag 0
                   COPD:  65+ yrs. 4.60% [-0.17, 9.61] lag 1

                   Multipollutant model (29 ppb)
                   Asthma:  1-14 yrs. 5.95% [1.11, 11.02] lag 0
                   COPD:  65+ yrs. 3.70% [-1.03, 8.66] lag 1

                   Increment:  10 ppb

                   Respiratory (1-h max):
                   0-4 yrs 1.015 [0.996, 1.035] lag 3
                   5-14 yrs 0.985 [0.950,1.021]  lag 0
                   All ages 0.989 [0.977, 1.002]  lag 1

                   Respiratory (24-h avg):
                   15-64 yrs 1.027 [0.984, 1.071] lag 0
                   >65 yrs 0.903 [0.851, 0.959] lag 5

                   Asthma (1-h max):
                   0-4 yrs 0.975 [0.947, 1.004] lagO
                   5-64 yrs 0.983 [0.949,1.018]  lag 1
                   All ages 0.962 [0.936, 0.989]  lag 0-2

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TABLE AX6.3-1 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:

                           HOSPITAL ADMISSIONS
X
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Reference, Study
Location, & Period
Outcomes, Design, & Methods
Mean Levels &
Monitoring Stations
Copollutants &
Correlations
Effects: Relative Risk or Percent Change
& Confidence Intervals (95%)
EUROPE
Anderson etal. (1997)
Multicity, Europe
(Amsterdam,
Barcelona, London,
Paris, Rotterdam)

Period of study:
1977-1989 for
Amsterdam and
Rotterdam
1986-1992 for
Barcelona
1987- 1991 for London
1980-1989 for Milan
1987- 1992 for Paris


Atkinson et al. (2001)
Multicity, Europe
(Barcelona,
Birmingham, London,
Milan, Netherlands,
Paris, Rome,
Stockholm)

Period of study:
1998-1997





Outcomes (ICD 9): COPD - unspecified
bronchitis (490), chronic bronchitis (491),
emphysema (492), chronic airways
obstruction (496)
Study Design: Time series
Statistical Analyses: APHEA protocol,
Poisson regression, meta-analysis
Covariates: trend, season, day of wk,
holiday, influenza, temperature, humidity
Season: Cool, Oct-Mar; Warm, Apr-Sep
Statistical Package: NR
Lag: 0,1,2 days and 0-3 cumulative





Outcomes (ICD 9): Asthma (493), COPD
(490-496), All respiratory (460-519)
Study Design: Timeseries
Statistical Analyses: APHEA protocol,
Poisson regression, meta-analysis
Covariates: season, temperature, humidity,
holiday, influenza
Statistical Package: NR
Lag: NR






24 h all year avg:
(ug/m3)
Amsterdam: 50
Barcelona: 53
London: 67
Paris: 42
Rotterdam: 52

1 -h max
Amsterdam: 75
Barcelona: 93
London' 67
Paris: 64

Rotterdam: 78


1-h max of NO2 (ug/m )

Barcelona: 94.4
Birmingham: 75.8
London: 95.9
Milan: 147.0
Netherlands: 50.1
Paris: 87.2
Rome: 139.7
Stockholm: 35.6





SO2
BS
TSP
03













SO2, O3, CO, BS
PM10; r =
Barcelona: 0.48
B'gham: 0.68
London: 0.70
Milan: 0.72
Netherlands: 0.64
Paris: 0.44
Rome: 0.32
Stockholm: 0.30





Increment: 50 ug/m3
Meta-analytic results - Weighted mean values from
6 cities

COPD- Warm season
24 hi. 03 [1.00, 1.06] lag 1
Ih 1.02 [1.00, 1.05] lag 1

COPD-Cool season
24 hi. 01 [0.99,1.03]
Ih 1.02 [0.99, 1.05]

COPD-A11 Year

24 hr 1.019 [1.002, 1.047] lag 1
24 hr 1.026 [1.004, 1.036] lag 0-3, cumulative
1 hr 1.013 [1.003, 1.022] lag 1
1 hr 1.014 [0.976, 1.054] lag 0-3, cumulative
Increment: 10 ug/m3 for PM10; change in NO2 not
described.

Asthma, 0 to 14 yrs:
ForPM10: 1.2% [0.2, 2.3]
ForPM10 + NO2: 0.1 [-0.8, 1.0]
Asthma, 1 5 to 64 yrs:
ForPM10: 1.1% [0.3, 1.8]
ForPM10 + N02: 0.4 [-0.5, 1.3]
COPD + Asthma, > 65 yrs
ForPM10: 1.0% [0.4, 1.5]
ForPM10 + N02: 0.8 [-0.6, 2.1]
All Respiratory, >65 yrs of age
ForPM10: 0.9% [0.6, 1.3]
ForPM10 + N02: 0.7 [-0.3, 1.7]

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                TABLE AX6.3-1 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                                        HOSPITAL ADMISSIONS
 Reference, Study
Location, & Period
Outcomes, Design, & Methods
  Mean Levels &
Monitoring Stations
Copollutants &
 Correlations
Effects:  Relative Risk or Percent Change &
        Confidence Intervals (95%)
           EUROPE (cont'd)
                  Increment:  50 ug/m  of 24-h avg for all cities
                  combined.

                  Asthma
                  15-64 yrs
                  1.029 [1.003, 1.055] lag 0-1
                  1.038 [1.008-1.068] lag 0-3, cumulative
                  <15 yrs
                  1.026 [1.006, 1.049] lag 2
                  1.037 [1.004, 1.067] lag 0-3, cumulative
                  1.080 [1.025, 1.140] -Winteronly

                  Two-pollutant models:
                  NO2/Black smoke
                  15-64 yrs
                  1.055 [1.005, 1.109] lag 0-1
                  15-64 yrs 1.088 [1.025, 1.155] cumulative 0-3
                  <15 yrs
                  1.036 [0.956, 1.122]

                  NO2/SO2
                  <15 yrs
                  1.034 [0.988, 1.082]
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           Sunyeretal. (1997)
           Multicity, Europe
           (Barcelona, Helsinki,
           Paris, London)

           Period of Study: 1986-
           1992
                      Outcomes (ICD 9):  Asthma (493)
                      Age groups analyzed:  <15, 15-64
                      Study Design:  Timeseries
                      Statistical Analyses: APHEA protocol,
                      Poisson regression, GEE; meta-analysis
                      Covariates: Humidity, temperature,
                      influenza, soybean, long-term trend, season,
                      day of wk
                      Season: Cool, Oct-Mar; Warm:
                      Apr-Sep
                      Statistical Package:  NR
                      Lag:  0,1,2,3 and cumulative 1-3
                                   24 h median (range)
                                   (ug/m3)
                                   Barcelona: 53 (5, 142)
                                   Helsinki: 35(9,78)
                                   London: 69(27,347)
                                   Paris: 42 (12, 157)

                                   # of stations:
                                   Barcelona: 3
                                   London: 2
                                   Paris: 4
                                   Helsinki: 8
                       SO2
                       black smoke
                       03

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                TABLE AX6.3-1 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                                        HOSPITAL ADMISSIONS
 Reference, Study
Location, & Period
                                    Outcomes, Design, & Methods
    Mean Levels &
  Monitoring Stations
Copollutants &
  Correlations
 Effects:  Relative Risk or Percent Change
       & Confidence Intervals (95%)
           EUROPE (cont'd)
 X
 ON
 to
           Schouten et al. (1996)
           Multicity, The
           Netherlands
           (Amsterdam,
           Rotterdam)

           Period of Study:
           04/01/77-09/30/89
                     Outcomes (ICD 9): All respiratory (460-
                     519), COPD (490-2, 494,496), Asthma
                     (493)
                     Age groups analyzed: 15-64, 65+, all ages
                     Study Design: Time series
                     Statistical Analyses: APHEA protocol,
                     Poisson regression
                     Covariates: Long-term trend, season,
                     influenza, day of wk, holiday, temperature,
                     humidity
                     Season: Cool, Nov-Apr; Warm:   May-Oct
                     Statistical Package: NR
                     Lag: 0,1,2 days; and cumulative 0-1 and 0-
                     3 day lags
24-h avg NO2

Amsterdam
Mean/Med: 50/50 ug/m3
Rotterdam
Mean: 54/52 ug/m3

Daily max 1 h
Amsterdam
Mean/Med: 75/75 ug/m3
Rotterdam
Mean/Med: 82/78 ug/m3

# of stations: 1 per city
S02
BS
03
Increment: 100 ug/m3 increment.

All respiratory, Amsterdam 24 h mean; 1-h max
15-64 yrsRR 0.890 [0.783,1.012]; 0.894 [0.821,
0.973] lag 1
>65 yrsRR 1.023 [0.907, 1.154]; 0.996 [0.918,
1.080] lag 2
All respiratory, Rotterdam 24 h mean; 1-h max
(1985-89)
15-64 yrs RR 0.965 [0.833,1.118]; 1.036 [0.951,
1.129] lagl
>65 yrs RR 1.172 [0.990, 1.387]; 1.073 [0.970,
1.186] lag 0
COPD, Amsterdam, 24 h mean,
All ages RR 0.937 [0.818, 1.079] lag 1
Asthma Amsterdam, 24 h mean ,
All ages RR 1.062 [0.887, 1.271] lag 2
COPD, Rotterdam 24 h mean
All ages RR 1.051 [0.903, 1.223] lag 2
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TABLE AX6.3-1 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:

                           HOSPITAL ADMISSIONS
Reference, Study
Location, & Period
Outcomes, Design, & Methods
Mean Levels &
Monitoring Stations
Copollutants & Effects: Relative Risk or Percent Change
Correlations & Confidence Intervals (95%)
EUROPE (cont'd)
Ponce de Leon et al.
(1996)
London, England

Period of Study:
04/1987-1988;
1991-02/1992









Outcomes (ICD 9): All respiratory (460-
519)
Age groups analyzed: 0-14, 15-64, 65+, all
ages
Study Design: Timeseries
N: 19,901
Statistical Analyses: APHEA protocol,
Poisson regression GAM
Covariates: Long-term trend, season,
influenza, day of wk, holiday, temperature,
humidity
Season: Cool, Oct-Mar; Warm:
Apr-Sep
Dose-Response Investigated?: Yes
Statistical Package: SAS
Lag: 0,1,2 days, 0-3 cumulative avg.


NO224-havg: 37.3 ppb,
Med: 35
SD=13.8
IQR: 14 ppb

1-hmax: 57.4 ppb,
Med: 51
SD = 26.4
IQR: 21 ppb

# of stations: 2





SO2 r = 0.45 Increment: 90th-10th percentile (24-h avg:
BS r = 0.44 27 ppb)
03
All year
All ages 1.0114 [1.006, 1.0222] lag 2
0-14 yrs 1.0104 [0.9943, 1.0267] Iag2
15-64 yr 1.0113 [0.9920, 1.0309] lag 1
>65 yr 1.0216 [1.0049, 1.0386] lag 2
Warm season
All ages 1.0276 [1.0042, 1.0515] lag 2
0-14 yrs 1.038 [1.0009, 1.0765] lag 2
15-64 yr 1.0040 [0.9651, 1.0445] lag 1
>65 yr 1.0326 [0.9965, 1.0699] lag 2
Cool season
All ages 1.0060 [0.9943, 10177] Iag2
0-14 yrs 1.0027 [0.9855, 1.0202] Iag2
15-64 yr 1.0136 [0.9920, 1.0357] lag 1
>65 yr 1.0174 [0.9994, 1.0358] lag 2
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                 TABLE AX6.3-1 (cont'd).  RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                                         HOSPITAL ADMISSIONS
 Reference, Study
Location, & Period
                                    Outcomes, Design, & Methods
Mean Levels & Monitoring
         Stations
Copollutants &
  Correlations
    Effects: Relative Risk or Percent
 Change & Confidence Intervals (95%)
           EUROPE (cont'd)
 X
 ON
 to
           Atkinson etal. (1999a)
           London, England

           Period of Study:
           1992 to 1994
           Days:  1096
                     Outcomes (ICD 9): All respiratory (460-
                     519), Asthma (493), Asthma + COPD (490-
                     6), Lower respiratory disease (466, 480-6)
                     Age groups analyzed: 0-14,15-64, 65+, all
                     ages
                     Study Design:  Time series
                     N:  165,032
                     Statistical Analyses: APHEA protocol,
                     Poisson regression
                     Covariates: Long-term trend, season,
                     influenza, day of wk, holiday, temperature,
                     humidity
                     Season: Cool, Oct-Mar; Warm:
                     Apr-Sep
                     Dose-Response Investigated?:  Yes
                     Statistical Package: SAS
                     Lag: 0,1,2 days, 0-1,0-2, 0-3 cum. avg.
NO2 1 h mean: 50.3 ppb, SD
17.0, Range: 22.0, 224.3 ppb,
10th centile: 34.3, 90th centile:
70.3

# of stations: 3,
r= 0.7, 0.96
03,
CO,
PMio
BS,
S02
Increment: 36 ppb (90th-10th centile)

All ages
Respiratory 1.64% [0.14, 3.15] lag 1
Asthma  1.80% [-0.77, 4.44 lag 0
0-14yrs
Respiratory 1.94% [-0.39, 4.32] lag 2
Asthma .  1% [-1.42, 5.77] lag 3
15-64yrs
Respiratory 1.61% [-0.82, 4.09] lag 1
Asthma  5.08% [0.81, 9.53] lag 1
65+ yrs
Respiratory 2.53% [0.58, 4.52] lag 3
Asthma 4.53% [-2.36, 11.91] lag 3
COPD3.53% [0.64, 6.50] lag 3
Lower Resp. 3.47% [0.08, 6.97] lag 3
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               TABLE AX6.3-1 (cont'd).  RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                                     HOSPITAL ADMISSIONS
 Reference, Study
Location, & Period
Outcomes, Design, & Methods
  Mean Levels &
Monitoring Stations
Copollutants &
 Correlations
Effects: Relative Risk or Percent Change
     & Confidence Intervals (95%)
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          EUROPE (cont'd)
Wong* et al. (2002)
London England and
Hong Kong

Period of Study:
London: 1992-1994
Hong Kong:
1995-1997

Days: 1,096



Outcomes (ICD 9): All respiratory
admissions (460-519); asthma (493)
Age groups analyzed: 15-64, 65+, all ages
Study Design: Timeseries
Statistical Analyses: APHEA protocol,
Poisson regression with GAM
Covariates: Long-term trend, season,
influenza, day of wk, holiday, temperature,
humidity, thunderstorms
Season: Cool, Oct-Mar; Warm: Apr-Sep
Dose-Response Investigated?: Yes
Statistical Package: S-Plus
Lag: 0,1,2,3,4 days, 0-1 cum. avg.
24 h NO2 ug/m3
Hong Kong
Mean: 55.9
Warm: 48.1
Cool 63. 8
SD 19.4
Range: 15.3,151.5
10th: 31.8
50th: 53.5
90th: 81.8

London
Mean: 64.3
Hong Kong
PM10r=0.82
S02r=0.37
O3r=0.43

London
PM10 r = 0.68
S02r=0.71
03r=-0.29




Increment: 10 ug/m

Asthma, 15-64 years
Hong Kong
ER -0.6 [-2. 1,1.0] lag 0-1
ER -1.3 [-2.6, 0.1] lag 1
Warm: ER -0.5 [-2.7, 1.6] lag 0-1
Cool: ER -0.6 [-2.8, 1.6] lag 0-1
London
ER 1.0 [0.0,2.1] lag 0-1
ER 1.1 [0.2,2.0] lag 2
Warm: ER 0.6 [-0.8, 2.0] lag 0-1
Cool- ER 1 3 F-0 1 7.81 lap 0-1
                                                          Warm:  62.6
                                                          Cool 66.1
                                                          SD 20.4
                                                          Range:  23.7,255.8
                                                          10th: 42.3
                                                          50th: 61.2
                                                          90th: 88.8

                                                          # of stations:
                                                          Hong Kong: 7,
                                                          r = 0.65, 0.90
                                                          London: 3,
                                                          r = 0.80
                                                                          Respiratory 65+ years
                                                                          Hong Kong
                                                                          ER 1.8 [1.2, 2.4] lag 0-1
                                                                          ER 1.3 [0.8,1.8] lag 0
                                                                          Warm: ER 0.8 [0.1, 1.6] lag 0-1
                                                                          Cool: ER 3.0 [2.1,3.9] lag 0-1
                                                                          +03:  ER 1.6 [1.0, 2.3] lag 0-1
                                                                          +PM10: ER 1.7 [0.8, 2.7] lag 0-1
                                                                          +SO2: ER 1.6 [0.8, 2.4] lag 0-1
                                                                          London
                                                                          ER-0.1 [-0.6, 0.5] lag 0-1
                                                                          ER 0.9 [0.5, 1.3] lag 3
                                                                          Warm: ER0.6 [-0.2, 1.4] lag 0-1
                                                                          Cool: ER -0.7 [-1.4, 0.0] lag 0-1
                                                                          +O3:  ER -0.1 [-0.5, 0.6] lag 0-1
                                                                          +PM10: ER-0.4 [-1.2, 0.4] lag 0-1
                                                                          +S02: ER -0.2 [-0.9, 0.5] lag 0-1

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               TABLE AX6.3-1 (cont'd).  RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                                        HOSPITAL ADMISSIONS
 Reference, Study
Location, & Period
Outcomes, Design, & Methods
  Mean Levels &
Monitoring Stations
Copollutants &
 Correlations
Effects:  Relative Risk or Percent Change &
        Confidence Intervals (95%)
           EUROPE (cont'd)
 X
 to
 VO
 H
 6
 o
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 H
O
 O
 H
 W
 O
 O
 HH
 H
 W
           Anderson etal. (1998)
           London, England

           Period of Study: April
           1987-February 1992

           Days: 1,782
                      Outcomes (ICD 9): Asthma (493)
                      Age groups analyzed: <15, 15-64, 65+
                      Study Design: Ti
                      N: 16
                      Statistical Analyses: APHEA protocol,
                      Poisson regression
                      Covariates: Time trends, seasonal
                      cycles,  day of wk, public holidays,
                      influenza epidemics, temperature,
                      humidity
                      Season: Cool (Oct-Mar); Warm
                      (Apr-Sep)
                      Dose-Response Investigated?: Yes
                      Statistical Package: S
                      Lag:  0,1,2 days
                                  24-h avg NO2 (ppb)
                                  Mean: 37.2
                                  SD: 12.3
                                  Range:  14, 182
                                  5th: 22
                                  10th:  25
                                  25th:  30
                                  50th:  36
                                  75th:  42
                                  90th:  50
                                  95th:  58

                                  1-h max NO2 (ppb)
                                  Mean: 57.2
                                  SD: 23.0
                                  Range:  21,370
                                  5th: 35
                                  10th:  38
                                  25th:  44
                                  50th:  52
                                  75th:  64
                                  90th:  81
                                  95th:  98

                                  Number of stations: 2
                       03
                       SO2
                       BS
                  Increment:  10 ppb in 24 h NO2

                  0-14yrs
                  Whole year RR 1.25 [0.3,2.2] lag 2; RR 1.77 [0.39,
                  3.18] lag 0-3
                  + 03   RR 1.13 [-0.10, 2.36] lag 2
                  + SO2  RR 0.97 [-0.05, 1.99] lag 2
                  + BS   RR 2.26 [0.83, 3.71] lag 2
                  Warm season RR 1.42 [-0.3, 3.17] lag 2; RR 3.01
                  [3.8, 5.72] lag 0-3
                  Cool season RR 1.18 [0.02, 2.35] lag 2; RR 1.22
                  [-0.48, 2.96] lag 0-3
                  15-64yrs
                  Whole year RR 0.95 [-0.26, 2.17] lag 0; RR 0.99
                  [-0.36, 3.36] lag 0-1
                  Warm RR 0.46 [-1.70, 2.67] lag 0; RR 0.05
                  [-2.45, 2.61] lag 0-1
                  Cool season RR 1.21  [-0.22,2.5] lag 0; RR 1.43
                  [-0.18, 3.06] lag 0-1
                  65+ yrs
                  Whole year RR 2.96 [0.67, 5.31] lag 2; RR 3.14
                  [-0.04, 6.42] lag 0-3
                  + 03    RR 4.51 [1.43, 7.69] lag 2
                  + S02   RR 2.49 [-0.25,  5.31] lag 2
                  + BS    RR 1.88 [-1.49, 5.36] lag 2
                  Warm     RR 1.89 [-2.41, 6.38] lag 2;
                  RR-1.76 [-7.27, 4.07] lag 0-3
                  Cool season RR 3.52 [0.81, 6.30] lag 2; RR 5.57
                  [1.85, 9.43] lag 0-3

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               TABLE AX6.3-1 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                                      HOSPITAL ADMISSIONS
 Reference, Study
Location, & Period
Outcomes, Design, &
      Methods
                                                                     Mean Levels &
                                                                  Monitoring Stations
Copollutants &
 Correlations
Effects: Relative Risk or Percent Change &
        Confidence Intervals (95%)
           EUROPE (cont'd)
 X
 ON
 OJ
 O
           Anderson etal. (1998)
           (cont'd)
                                                                                               + O3    RR 5.14 [0.69, 9.79] lag 2
                                                                                               + SO2   RR2.10 [-1.08, 5.39] lag 2
                                                                                               + BS    RR 4.47 [-0.04, 9.19] lag 2
                                                                                               All ages
                                                                                               Whole year RR 1.25 [0.49, 2.02] lag 2; RR2.05 [0.96,
                                                                                               3.15] lag 0-3
                                                                                               + O3    RR 1.08 [0.12, 2.05] lag 2
                                                                                               + S02   RR 0.99 [0.18, 1.81] lag 2
                                                                                               + BS    RR 1.23 [0.47, 2.00] lag 2
                                                                                               Warm      RR 1.15 [-0.25, 2.57] lag 2; RR 1.54
                                                                                               [-0.54, 3.67] lag 0-3
                                                                                               Cool season RR 1.30 [0.38, 2.23] lag 2; RR 2.26 [0.94,
                                                                                               3.59] lag 0-3
                                                                                               + 03    RR 0.50 [-0.79, 1.81] lag 2
                                                                                               + S02   RR 1.10 [0.12, 2.08] lag 2
                                                                                               + BS    RR 1.29 [0.37, 2.22] lag 2
H
6
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O
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W
O
O
HH
H
W
           Prescottetal. (1998)
           Edinburgh, United
           Kingdom

           Period of Study: 10/92-
           6/95
                      Outcomes (ICD 9): Pneumonia
                      (480-7), COPD + Asthma (490-
                      496)
                      Age groups analyzed: <65, 65+
                      Study Design: Time series
                      Statistical Analyses: Poisson log
                      linear regression
                      Covariates: Trend, seasonal and
                      wkly variation, temperature, wind
                      speed, day of wk
                      Lag: 0,1 or 3 day rolling avg
                           N02:  26.4 ± 7.0 ppb
                           Min:  9 ppb
                           Max:  58 ppb
                           IQR:  10 ppb

                           # of Stations:  1
                                                                                         CO
                                                                                         PM10
                                                                                         SO2
                                                                                         03
                                                                                         BS
                  Increment: 10 ppb

                  Respiratory admissions
                  >65 yrs
                  3.1 [-4.6, 11.5] rolling 3 day avg
                  <65 yrs
                  -0.2% [-7.5, 7.7] rolling 3 day avg

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               TABLE AX6.3-1 (cont'd).  RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                                       HOSPITAL ADMISSIONS
 Reference, Study
Location, & Period
Outcomes, Design, & Methods
  Mean Levels &
Monitoring Stations
Copollutants &
 Correlations
  Effects: Relative Risk or Percent
Change & Confidence Intervals (95%)
           EUROPE (cont'd)
 X
           Thompson etal. (2001)
           Belfast, Northern Ireland

           Period of Study:
           1993-1995
                      Outcomes: Asthma
                      ICD9:  NR
                      Age groups analyzed: 0-14
                      Study Design: Time series
                      N:  1,095
                      Number of hospitals:  1
                      Statistical Analyses: Poisson regression
                      Covariates:  Season, long-term trend,
                      temperature, day of wk, holidays
                      Season: Warm (May-Oct), Cold
                      (Nov-Apr)
                      Statistical Package: Stata
                      Lag: 0,1,2,3 days
                                   24 h mean:
                                   Warm:  19.2 (7.9) ppb;
                                   range: 13-23
                                   Cold: 23.3 (9.0) ppb;
                                   range: 18-28
                      SO2r=0.82
                      PM10 r = 0.77
                      CO r = 0.69
                      03r=-0.62
                      N0xr=0.93
                      log (NO) r = 0.84
                      log (CO) r = 0.69
                  Increment: 10 ppb

                  All seasons
                  RR 1.08 [1.03, 1.13] lag 0
                  RR1.11 [1.05, 1.17] lag 0-1
                  RR 1.10 [1.04, 1.17] lag 0-2
                  RR 1.12 [1.03, 1.02] lag 0-3
                  Warm season
                  RR 1.14 [1.04, 1.26] lag 0-1
                  Cold season
                  RR 1.10 [1.03, 1.17] lag 0-1
                  NO2 + Benzene
                  RR 0.99 [0.87, 1.13] lag 0-1
                  *Model made no allowance for possible
                  autocorrelation in the data or for extra-Poisson
                  variation
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                TABLE AX6.3-1 (cont'd).  RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                                        HOSPITAL ADMISSIONS
 Reference, Study
Location, & Period
Outcomes, Design, & Methods
  Mean Levels &
Monitoring Stations
Copollutants &
 Correlations
Effects: Relative Risk or Percent Change
     & Confidence Intervals (95%)
           EUROPE (cont'd)
 X
 ON
 OJ
 to
           Hagen et al. (2000)
           Drammen, Norway

           Period of Study:
           1994-1997
                      Outcomes (ICD 9): All respiratory
                      admissions (460-519)
                      Age groups analyzed: All ages
                      Study Design: Time series
                      Number of hospitals:  1
                      Statistical Analyses: Poisson regression
                      with GAM (adhered to HEI phase 1 .B
                      report)
                      Covariates:  Time trends, day of wk,
                      holiday, influenza, temperature, humidity
                      Lag: 0,1,2,3 days
                                   NO2 24-h avg (ug/m3):
                                   36.15, SD= 16

                                   IQR: 16.92 ug/m3

                                   # of Stations:  2
                      PM10r = 0.61         Increment: NO2: 16.92 ug/m3 (IQR); NO:
                      S02r=0.58          29ug/m3(IQR)
                      benzene r= 0.31
                      NO r = 0.70          Single-pollutant model
                      O3 r = -0.47          Respiratory disease only
                      Formaldehyde        NO2: RR 1.058 [0.994, 1.127]
                      r=0.68              NO:  1.048 [1.013, 1.084]
                      Toluene r = 0.65       All disease
                                          NO2: RR 1.011 [0.988,1.035]

                                          Two-pollutant model with PM10
                                          NO2 1.044 [0.966, 1.127]
                                          NO:  1.045 [1.007,1.084]

                                          Three-pollutant model with PM10 + Benzene
                                          N02 1.015 [0.939, 1.097]
                     	NO:  1.031 [0.986,1.077]	
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                TABLE AX6.3-1 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                                        HOSPITAL ADMISSIONS
  Reference, Study
 Location, & Period
                                      Outcomes, Design, & Methods
                                          Mean Levels &      Copollutants &   Effects: Relative Risk or Percent Change
                                        Monitoring Stations     Correlations          & Confidence Intervals (95%)
           EUROPE (cont'd)
 X
 H
 6
 o
 o
 H
O
 O
 H
 W
 O
 O
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 H
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           Oftedal et al. (2003)
           Drammen, Norway

           Period of Study:
           1994-2000
Ponka and Virtanen
(1994)
Helsinki, Finland

Period of Study:
1987-1989

Days: 1096
Outcomes (ICD 10): All respiratory
admissions (JOO-J99)
Age groups analyzed: All ages
Study Design:  Time series
Statistical Analyses: Semi-parametric
Poisson regression, GAM with more
stringent criteria
Covariates: Temperature, humidity,
influenza
Lag:  2,3 days

Outcomes (ICD 9): Chronic bronchitis and
emphysema (493)
Age groups analyzed: <65, >65
Study Design:  Time series
Statistical Analyses: Poisson regression
Covariates: Season, day of wk, year,
influenza, humidity, temperature
Season:  Summer (Jun-Aug), Autumn (Sep-
Nov), Winter (Dec-Feb), Spring (Mar-May)
Lag:  0-7 days
                                                              Mean:  33.8 ug/m ,
                                                              SD = 16.2

                                                              IQR: 20.8 ug/m3
24 h mean: 39 ug/m3,
SD = 16.2;
range: 4, 170

# of stations:  2
                       PM10
                       S02
                       03
                       Benzene
                       Formaldehyde
                       Toluene
SO2
03
TSP
Increment: 20.8 ug/m3 (IQR)

All respiratory disease

Single-pollutant model
RR 1.060 [1.017,1.105] lag 3

Two-pollutant model
Adjusted for PM10   RR 1.063 [1.008, 1.120]
Adjusted for benzene RR 1.046 [1.002, 1.091]

Increment: NR

Chronic bronchitis and emphysema
>65 yrs
RR 0.87 [0.71, 1.07] lag 0
RR 1.07 [0.86, 1.33] lag 1
RR 1.16 [0.93, 1.46] lag 2
RR 1.08 [0.86, 1.35] lag 3
RR 0.94 [0.76, 1.18] lag 4
RR 0.90 [0.72, 1.12] lag 5
RR1.31 [1.03, 1.66] lag 6
RR 0.82 [0.67, 1.01] lag 7
<65 yrs
NR

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                  TABLE AX6.3-1 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                                           HOSPITAL ADMISSIONS
 Reference, Study
Location, & Period
Outcomes, Design, & Methods
  Mean Levels &
Monitoring Stations
Copollutants &
 Correlations
Effects:  Relative Risk or Percent Change &
        Confidence Intervals (95%)
           EUROPE (cont'd)
 X
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 6
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O
 O
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           Dab+etal. (1996)
           Paris, France

           Period of Study :
           1/1/87-9/30/92
           Llorca et al. (2005)
           Torrelavega, Spain

           Period of Study:
           1992-1995

           Days: 1,461
                      Outcomes (ICD 9):  All respiratory (460-
                      519), Asthma (493), COPD (490-496)
                      Age groups analyzed:  All ages
                      Study Design:  Time series
                      Number of hospitals: 27
                      Statistical Analyses: Poisson regression,
                      followed APHEA protocol
                      Covariates: Temperature, relative
                      humidity, influenza, long-term trend,
                      season, holiday, medical worker strike
                      Lag: 0,1,2 days, 0-3 cumulative
                      Outcomes (ICD 9):  All respiratory
                      admissions (460-519)
                      Age groups analyzed: All ages
                      Study Design:  Time series
                      Number of hospitals: 1
                      Statistical Analyses:  Poisson regression
                      Covariates: Short and long-term trends
                      Statistical Package:  Stata
                      Lag: NR
                                   NO2 24-h avg: 45 ug/m3
                                   5th: 22,99th: 108.3

                                   Daily maximum 1 h
                                   concentration: 73.8 ug/m3
                                   5th: 37.5,99th:  202.7
                        SO2
                        03
                        PM13
                        BS
                                   24-h avg NO2:             SO2r= 0.588
                                   21.3 ug/m3, SD= 16.5      NO r= 0.855
                                                            TSPr=-0.12
                                   24-h avg NO:  12.2 ug/m3,   SH2r= 0.545
                                   SD= 15.2

                                   # of Stations: 3
                  Increment:  100 ug/m

                  All respiratory (1987-1990)
                  24-h avg NO2  RR 1.043 [0.997,1.090] lag 0
                  l-hmaxNO2 RR 1.015 [0.993, 1.037] lag 0

                  Asthma (1987-1992)
                  24-h avg RR 1.175 [1.059, 1.304] lag 0-1
                  1-hmax RR 1.081 [1.019, 1.148] lag 0-1

                  COPD
                  24-h avg RR 0.974 [0.898, 1.058] lag 2
                  1-hmax RR0.961 [0.919,1.014] lag 2

                  Increment:  100 ug/m3

                  Single-pollutant model
                  All cardio-respiratory admissions
                  NO2:  RR 1.37 [1.26, 1.49]
                  NO: RR 1.33 [1.22, 1.46]
                  Respiratory admissions
                  NO2:  RR 1.54 [1.34, 1.76]
                  NO: RR 1.35 [1.17, 1.56]

                  5-pollutant model
                  All cardio-respiratory admissions
                  NO2:  RR 1.20 [1.05, 1.39]
                  NO: RR0.93 [0.79,1.09]
                  Respiratory admissions
                  NO2:  RR 1.69 [1.34, 2.13]
                  NO: RR 0.87 [0.67, 1.13]

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                TABLE AX6.3-1 (cont'd).  RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                                         HOSPITAL ADMISSIONS
 Reference, Study
Location, & Period
Outcomes, Design, & Methods
  Mean Levels &
Monitoring Stations
Copollutants &
 Correlations
Effects:  Relative Risk or Percent Change
      & Confidence Intervals (95%)
           EUROPE (cont'd)
 X
 H
 6
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O
 O
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 O
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           Migliaretti and Cavallo
           (2004)
           Turin, Italy

           Period of Study:
           1997-1999
           Fusco*etal. (2001)
           Rome, Italy

           Period of Study :
           1/1/95-10/31/97
                       Outcome(s) (ICD 9): Asthma (493)
                       Age groups analyzed:  <4,4-\5
                       Study Design:  Case-Control
                       Controls: age matched with other
                       respiratory disease (ICD9:  460-7, 490-2,
                       494-6,500-19)
                       N:  cases = 734, controls = 25,523
                       Statistical Analyses: logistic regression
                       Covariates:  seasonality, temperature,
                       humidity, solar radiation
                       Seasons: Cold:  Oct-Mar; Warm:  Apr-Sep
                       Statistical Package: SPSS
                       Lag: 0-3 days and cumulative

                       Outcomes (ICD 9): All respiratory (460-
                       519 excluding 470-478), Asthma (493),
                       COPD (490-492, 494-496), Respiratory
                       infections (460-466, 480-486)
                       Age groups analyzed:  0-14, all ages
                       Study Design:  Time series
                       Statistical Analyses: Semi-parametric
                       Poisson regression with GAM
                       Covariates:  Influenza, day, temperature,
                       humidity, day of wk, holiday
                       Season: Warm (Apr-Sep), Cold (Oct - Mar)
                       Statistical Package: S-Plus 4
                       Lag: 0-4 days
                                                            TSP
                                    Controls:
                                    Mean:  113.3 ug/m3,
                                    SD = 30.5

                                    Cases:
                                    Mean:  117.4 ug/m3,
                                    SD = 29.7
                                    NO2 24-h avg (ug/m3):
                                    86.7,
                                    SD = 16.2

                                    IQR: 22.3 ug/m3

                                    # of stations: 5;
                                    r= 0.66-0.79
                       PM10:
                       All year r= 0.35
                       Cold r = 0.50
                       Warm r= 0.25
                       S02:
                       All year r= 0.33
                       Cold r = 0.40
                       Warm r= 0.68
                       CO:
                       All year r= 0.31
                       Cold r = 0.41
                       Warm r= 0.59
                       03:
                       All year r= 0.19
                       Cold r = 0.19
                       Warmr = 0.13
                                         Increment:  10 ug/m

                                         <4 yrs 2.8% [0.03, 5.03] lag 1-3 cumulative
                                         4-15 yrs 2.7% [-0.01, 6.06] lag 1-3 cumulative
                                         All ages 2.8% [0.07, 4.09] lag 1-3 cumulative

                                         Two-pollutant model adjusted for TSP
                                         N02 2.1% [-0.1, 5.6]
                  Increment: 22.3 ug/m (IQR)

                  All respiratory
                  All ages 2.5% [0.9, 4.2] lag 0
                  0-14 yrs 4.0% [0.6, 7.5] lag 0
                  Respiratory infections
                  All ages 4.0% [1.6, 6.5] lag 0
                  0-14 yrs 4.0% [0.2, 8.0] lag 0
                  Asthma
                  All ages 4.6% [-0.5, 10.0] lag 0
                  0-14 yrs 10.7% [3.0, 19.0] lag 1
                  COPD
                  >65 yrs 2.2% [-0.7, 5.2] lag 0

                  Multipollutant models
                  All respiratory (NO2 + CO)

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                TABLE AX6.3-1 (cont'd).  RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                                        HOSPITAL ADMISSIONS
 Reference, Study
Location, & Period
Outcomes, Design, & Methods
  Mean Levels &      Copollutants &    Effects: Relative Risk or Percent Change &
Monitoring Stations     Correlations             Confidence Intervals (95%)
           EUROPE (cont'd)
 X
 Oi
 OJ
 Oi
 H
 6
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O
 O
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 O
 O
 HH
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 W
           Fusco*etal. (2001)
           (cont'd)
           Pantazopoulou et al.
           (1995)
           Athens, Greece
                      Outcomes: All respiratory admissions
                      ICD9: NR
                      Age groups analyzed: All ages
                      Study Design: Time series
Period of Study :  1988   N:  15,236
                      Number of hospitals:  14
                      Statistical Analyses: Multiple linear
                      regression
                      Covariates: Season, day of wk, holiday,
                      temperature, relative humidity
                      Season: Warm (3/22-9/21), Cold (1/1-3/21
                      and 9/22-12/31)
                      Lag: NR
                                                            NO2 24-h avg

                                                            Winter: 94 |ig/m3,
                                                            SD = 25
                                                            5th: 59,50th: 93,95th:
                                                            135

                                                            Summer: 111 |ig/m3,
                                                            SD = 32
                                                            5th: 65,50th: 108,
                                                            95th: 173

                                                            # of stations: 2
                                                          CO
                                                          BS
                                        All ages:  0.9% [-0.8,2.8] lag 0
                                        0-14 yrs:  3.3% [-0.2, 6.9] lag 0
                                        Acute infections (NO2 + CO)
                                        All ages:  3.9% [1.3, 6.7] lag 0
                                        0-14 yrs:  2.9% [-1.0, 7.0] lag 0
                                        Asthma (NO2 + CO)
                                        All ages:  1.4% [-3.9, 7.1] lag 0
                                        0-14 yrs:  8.3% [-0.1, 17.4] lag 1
                                        COPD (N02 + CO)
                                        >65yrs:  -1.0%[-4.1,2.2]  lag 0

                                        Increment: 76 ng/m3 in winter and 108 ng/m3 in
                                        summer (95th-5th)

                                        Respiratory disease admissions

                                        Winter: Percent increase: 24% [6.4, 43.5]

                                        Summer:  Percent increase: 9.3% [-14.1, 24.4]

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                 TABLE AX6.3.1 (cont'd).  RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                                          HOSPITAL ADMISSIONS
 Reference, Study
Location, & Period
Outcomes, Design, & Methods
                                                                              Mean Levels &
                                                                           Monitoring Stations
Copollutants &
 Correlations
Effects:  Relative Risk or Percent Change &
        Confidence Intervals (95%)
           LATIN AMERICA
 X
H
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O
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W
O
O
HH
H
W
           Gouveia and Fletcher,
           (2000a)

           Sao Paulo, Brazil

           Period of Study:
           11/92-9/94
           Braga*etal. (2001)
           Sao Paulo, Brazil

           Period of Study:
           1/93-11/97
                      Outcomes (ICD 9):  All respiratory;
                      Pneumonia (480-486); asthma or bronchitis
                      (466,490,491,493)
                      Age groups analyzed:  
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                TABLE AX6.3-1 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                                        HOSPITAL ADMISSIONS
 Reference, Study
Location, & Period
Outcomes, Design, & Methods
  Mean Levels &      Copollutants &    Effects: Relative Risk or Percent Change &
Monitoring Stations     Correlations             Confidence Intervals (95%)
           LATIN AMERICA (cont'd)
 X
 oo
           Farhat* et al. (2005)
           Sao Paulo, Brazil

           Period of Study: 8/96-
           8/97

           Days:  396
                     Outcomes (ICD 9):
                     Pneumonia/bronchiopheumonia (480-6),
                     asthma (493), bronchiolitis (466),
                     Obstructive disease 493, 466)
                     Age groups analyzed: <\3
                     Study Design:  Time series
                     N: 1,021
                     Number of hospitals:  1
                     Statistical Analyses: Poisson regression
                     with GAM
                     Covariates: Time, temperature, humidity,
                     day of wk,  season
                     Statistical package: S-Plus
                     Lag: 0-7 days, 2,3,4 day moving avg
                                   Mean:  125.3 ug/m
                                   SD = 51.7

                                   IQR: 65.04 ug/m3

                                   Range:  42.5,369.5
                      PM10r = 0.83
                      SO2r=0.66
                      CO r = 0.59
                      O3 r = 0.47
Increment: 65.04 ug/mj (IQR)

Single pollutant models (estimated from graphs)

Asthma: = 32% [8,56] lag 0-2
Pneumonia: = 17.5% [2.5, 32.5] lag 0-3
Asthma or Bronchiolitis
N02 + PM10 47.7% [1.15, 94.2] lag 0-2
NO2 + SO2 33.1% [5.7, 60.5] lag 0-2
N02 + CO 28.8% [-0.2, 57.9] lag 0-2
N02 + 03 28.0% [-1.0, 57.0] lag 0-2
Multipollutant model (PM10, SO2, CO, O3)
39.3% [-14.9, 93.5] 2 day avg.
Pneumonia or bronchopneumonia
N02 + PM10 8.11% [-11.4, 27.6] lag 0-2
N02 + S02 13.1% [-3.4, 29.7] lag 0-2
NO2 + CO 12.4% [-5.6, 30.4] lag 0-2
NO2 + O3 14.6% [-4.9, 34.1] lag 0-2
Multipollutant model (PM10, SO2, CO, O3)
1.8% [-23.9,27.6] lag 0-2
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                           TABLE AX6.3-1 (cont'd).  RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                                                    HOSPITAL ADMISSIONS
Reference, Study
Location, & Period
Outcomes, Design, & Methods
Mean Levels & Copollutants & Effects: Relative Risk or Percent Change
Monitoring Stations Correlations & Confidence Intervals (95%)
ASIA
Lee et al. (2006)
Hong Kong, China

Period of Study: 1997-
2002

Days: 2,191





Outcomes (ICD 9): Asthma (493)
Age groups analyzed: 
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                TABLE AX6.3-1 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                                        HOSPITAL ADMISSIONS
 Reference, Study
Location, & Period
                                     Outcomes, Design, & Methods
  Mean Levels &
Monitoring Stations
Copollutants &
 Correlations
Effects:  Relative Risk or Percent Change
      & Confidence Intervals (95%)
           ASIA (cont'd)
 X
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O
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O
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           Tsai et al. (2006)
           Kaohsiung, Taiwan

           Period of Study:
           1996-2003

           Days: 2922
                      Outcomes (ICD 9): Asthma (493)
                      Study Design:  Case-crossover
                      N:  17,682
                      Statistical Analyses: Conditional logistic
                      regression
                      Covariates:  Temperature, humidity
                      Season: Warm (>25°C); Cool (<25°C)
                      Statistical package: SAS
                      Lag: 0-2 days cumulative
                                                                        NO224hmean:  27.20     PM10
                                                                        ppb                     SO2
                                                                        IQR:  17 ppb             03
                                                                        Range: 4.83,63.40        CO
                                                                        # of stations: 6
           Lee* et al. (2002)       Outcomes (ICD 10): Asthma (J45 - J46)     24hNO2(ppb)
           Seoul, Korea           Age groups analyzed: <15                 Mean:  31.5
                                 Study Design:  Time series                 SD:  10.3
           Period of Study:         N: 6,436                               5th:  16.0
           12/1/97-12/31/99        Statistical Analyses: Poisson regression, log  25th: 23.7
                                 link with GAM                          50th: 30.7
           Days: 822             Covariates: Time, day of wk, temperature,    75th: 38.3
                                 humidity                               95th: 48.6
                                 Season:  Spring (Mar-May), Summer (Jun-
                                 Aug), Fall (Sep-Nov), Winter (Dec-Feb)     # of stations: 27
                                 Statistical package: NR
                                 Lag:  0-2 days cumulative
                                                                                    SO2 r = 0.72
                                                                                    O3r=-0.07
                                                                                    CO r = 0.79
                                                                                    PM10 r = 0.74
                                         Increment:  17 ppb (IQR)

                                         Seasonality
                                         Single-pollutant model
                                         >25°C 1.259 [1.111,1.427] lag 0-2
                                         <25°C 2.119 [1.875,2.394] lag 0-2
                                         Dual-pollutant model
                                         Adjusted for PM10
                                         >25°C 1.082 [0.913,1.283] lag 0-2
                                         <25°C 2.105 [1.791,2.474] lag 0-2
                                         Adjusted for CO
                                         >25°C 0.949 [0.792,1.137] lag 0-2
                                         <25°C 2.30 [1.915, 2.762] lag 0-2
                                         Adjusted for SO2
                                         >25°C 1.294 [1.128,1.485] lag 0-2
                                         <25°C 2.627 [2.256, 3.058] lag 0-2
                                         Adjusted for O3
                                         >25°C 1.081 [0.945,1.238] lag 0-2
                                         <25°C 2.096 [1.851,2.373] lag 0-2

                                         Increment:  14.6 ppb (IQR)

                                         Asthma
                                         NO2RR 1.15  [1.10, 1.20] lag 0-2
                                         NO2 + PM10RR1.13 [1.07, 1.19] lag 0-2
                                         N02 + S02 RR 1.20 [1.11,1.29] lag 0-2
                                         NO2 + O3 RR 1.14 [1.09, 1.20] lag 0-2
                                         N02 + CO RR 1.12 [1.03, 1.22] lag 0-2
                                         NO2 + O3 + CO + PM10 + SO2 RR 1.098 [1.002,
                                         1.202]

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                 TABLE AX6.3-1 (cont'd).  RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                                           HOSPITAL ADMISSIONS
 X
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Reference, Study
Location, & Period
Outcomes, Design, & Methods
Mean Levels &
Monitoring Stations
Copollutants &
Correlations
Effects: Relative Risk or Percent Change &
Confidence Intervals (95%)
ASIA (cont'd)
Wong etal. (1999)
Hong Kong, China
Outcomes (ICD 9): All respiratory
admissions (460-6, 471-8, 480-7, 490-6);
Asthma (493), COPD (490-496), Pneumonia
Median 24 hNO2:
5 1.39 ug/m3
03
SO2
PM10 r = 0.79
Increment =10 ug/m
Overall increase in admissions:
Period of Study:         (480-7)
1994-1995              Age groups analyzed: 0-4, 5-64, >65, all
                       ages
                       # of hospitals:  12
                       Study Design:  Time series
                       Statistical Analyses:  Poisson regression
                       (followed APHEA protocol)
                       Covariates: Trend, season, day of wk,
                       holiday, temperature, humidity
                       Statistical package: SAS 8.02
                       Lag: days 0-3 cumulative
                                                                          Range:  16.41, 122.44
                                                                          25th: 39.93,75th: 66.50

                                                                          # of stations:  7,
                                                                          r= 0.68, 0.89
           Wong etal. (200la)
           Hong Kong, China

           Period of Study: 1993-
           1994
                       Outcomes (ICD 9): Asthma (493)
                       Age groups analyzed: <\5
                       N:  1,217
                       # of hospitals:  1
                       Study Design:  Time series
                       Statistical Analyses: Poisson regression
                       (followed APHEA protocol)
                       Covariates: Season, temperature, humidity
                       Season: Summer (Jun-Aug), Autumn (Sep-
                       Nov), Winter (Dec-Feb), Spring (Mar-May)
                       Lag: 0,1,2,3,4,5 days; and cumulative 0-2
                       and 0-3 days.
24-h avg
NO2 mean:  43.3 ug/m3,
SD=16.6
Range: 9, 106 ug/m3

Autumn:  51.7(17.6)
Winter: 46.6(15.5)
Spring: 40.7(11.8)
Summer:  32.6(13.7)

# of stations: 9
                                                                                                  PM10
                                                                                                  SO,
1.020 [1.013, 1.028] lag 0-3

Respiratory Relative Risks (RR)
0-4 yrs:  1.020 [1.010, 1.030] lag 0-3
5-64yrs: 1.023 [1.011, 1.034] lag 0-3
>65 yrs: 1.024 [1.014, 1.035] lag 0-3
Cold Season:  1.004 [0.988, 1.020]
N02 + highPM10:  1.009 [0.993,  1.025]
NO2 + highO3: 1.013 [0.999, 1.026]

Asthma: 1.026 [1.01,  1.042] lag 0-3
COPD:  1.029 [1.019,1.040] lag  0-3
Pneumonia: 1.028 [1.015, 1.041] lag 0-3

Increment: 10 ug/m3

Asthma
All year:  1.08 p= 0.001
Autumn:  1.08 p = 0.017
Winter:  NR
Spring: NR
Summer: NR
            Default GAM
           +Did not report correction for over-dispersion
           NR: Not Reported
           APHEA: Air Pollution and Health: A European Approach

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                    TABLE AX6.3-2. RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                              EMERGENCY DEPARTMENT VISITS
 Reference, Study
Location, & Period
Outcomes, Design, & Methods
Mean Levels of NO2 &
 Monitoring Stations
Copollutant             Effects and Interpretation:
Correlations     Relative Risk & Confidence Intervals (95%)
          UNITED STATES
 X
 to
          Jaffe et al. (2003)
          3 cities, Ohio,
          United States
          (Cleveland,
          Columbus,
          Cincinnati)

          Period of Study:
          7/91-6/96
                    Outcome (ICD-9): Asthma (493)
                    Age Groups Analyzed: 5-34
                    Study Design: Time series
                    N:  4,416
                    Statistical Analyses:  Poisson
                    regression using a standard GAM
                    approach
                    Covariates:  city, day of wk, wk,
                    yr, minimum temperature, overall
                    trend, dispersion parameter
                    Season: June to August only
                    Dose-response investigated: Yes
                    Statistical Package: NR
                    Lag: 0-3 days
                               Cincinnati
                               24-havg: 50ppb,
                               SD=15
                               Cleveland
                               24-havg: 48ppb,
                               SD=16

                               NO2 was not monitored in
                               Columbus due to
                               relatively low levels
                        Cincinnati:
                        PM10;r=0.36
                        SO2;r=0.07
                        O3;r = 0.60

                        Cleveland:
                        PM10; 0.34
                        SO2;r=0.28
                        O3; r = 0.42

                        No
                        multipollutant
                        models were
                        utilized.
               Increment: 10 ppb

               Cincinnati: 6% [-1.0, 13] lag 1
               Cleveland: 4% [-1,8] lag 1
               All cities: 3% [-1.0, 7]

               Attributable risk from NO2 increment:
               Cincinnati 0.72 (RR 1.06)
               Cleveland 0.44 (RR 1.04)

               Regression diagnostics for Cincinnati showed
               significant linear trend during entire study period
               and for each wk (6/1-8/31). No trends observed
               for Cleveland.

               Regression Models assessing exposure thresholds
               showed a possible dose-response for NO2 (percent
               increase after 40 ppb). No increased risk until
               minimum concentration of 40 ppb was reached.
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          Norris*etal. (1999)
          Seattle, WA,
          United States

          Period of Study:
          1995-1996
                    Outcome (ICD-9): Asthma (493)
                    Age groups analyzed: <18 yrs
                    Study Design: Time series
                    N:  900 ER visits
                    Statistical Analyses:
                    Semi-parametric Poisson
                    regression using GAM.
                    Covariates: day of wk, time
                    trends, temperature, dew point
                    temperature
                    Dose-response investigated: Yes
                    Statistical Package: NR
                    Lag: 0,2 days	
                               24 h:  20.2 ppb, SD = 7.1
                               IQR:  9 ppb

                               1-hmax: 34.0 ppb,
                               SD=  11.3
                               IQR:  12 ppb
                        CO; r = 0.66
                        PM; r = 0.66
                        SO2;r=0.25
               Increment: IQR

               24-h avg (9 ppb increment)
               RR 0.99 [0.90, 1.08] lag 2

               1-h max (12 ppb increment)
               RR1.05 [0.99, 1.12] lag 0

               Age and hospital utilization (high and low)
               segregation (<5, 5-11, and 12-17 yrs) did not
               figure significantly in the association between
               emergency room visits and asthma.

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              TABLE AX6.3-2 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                             EMERGENCY DEPARTMENT VISITS
 Reference, Study
Location, & Period   Outcomes, Design, & Methods
 Mean Levels of NO2 &
  Monitoring Stations
   Copollutant             Effects and Interpretation:
   Correlations     Relative Risk & Confidence Intervals (95%)
          UNITED STATES (cont'd)
 X
          Lipsettetal. (1997)   Outcome(s):  Asthma
          Santa Clara County,   ICD-9 Code(s): NR
          California,
          United States

          Period of Study:
          1988-1992
                    Age groups analyzed: All
                    Study Design: Time series
                    Statistical Analyses: Poisson
                    Regression; GEE repeated with
                    GAM
                    Covariates: minimum
                    temperature, day of study,
                    precipitation, hospital, day of
                    wk, yr, overdispersion parameter
                    Season: Winters only
                    Statistical Package: SAS,
                    S-Plus, Stata
                    Lag:  0-5 days
NO21-h mean: 69 ppb,
SD = 28
Range: 29, 150 ppb
PM10;r=0.82
COH; r = 0.8

No multipollutant
model due to high
correlation between
pollutants
Same day NO2 was associated with ER visits
for asthma (P = 0.013, p = 0.024)

Absence of association between lagged or
multiday specifications of NO2 and asthma ER
visits (data not shown) suggest that same day
association may be artifact of covariation with
PM10
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              TABLE AX6.3-2 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                            EMERGENCY DEPARTMENT VISITS
 Reference, Study
Location, & Period
Outcomes, Design, & Methods
Mean Levels of NO2 &
 Monitoring Stations
Copollutant            Effects and Interpretation:
Correlations     Relative Risk & Confidence Intervals (95%)
          UNITED STATES (cont'd)
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          Peel et al. (2005)
          Atlanta, GA, United
          States

          Period of Study:
          1/93-8/2000
                    Outcome(s) (ICD-9): All
                    respiratory (460-6, 477, 480-6,
                    480-6, 490-3, 496); Asthma (493);
                    COPD (491-2, 496); Pneumonia
                    (480-486); Upper Respiratory
                    Infection (460-6, 477)
                    Age groups analyzed: All, 2-18
                    Study Design: Time series
                    N: 484,830
                    # of Hospitals: 31
                    Statistical Analyses: Poisson
                    Regression, GEE, GLM, and
                    GAM (data not shown for GAM)
                    Covariates: day of wk, hospital
                    entry/exit, holidays, time trend;
                    season, temperature, dew point
                    temperature
                    Statistical Package: SAS, S-Plus
                    Lag: 0 to 7 days. 3 day moving
                    avgs.
                               1-hmax: 45.9ppb,
                               SD = 17.3
                        O3;r=0.42
                        SO2;r=0.34
                        CO; r = 0.68
                        PM10;
                        r = 0.46

                        Evaluated
                        multipollutant
                        models (data
                        not shown)
              Increment: 20 ppb

              All respiratory
              RR 1.016 [1.006, 1.027] lag 0-2, 3 day moving av
              Upper Respiratory Infection (URI)
              RR 1.019 [1.006, 1.031] lag 0-2, 3 day moving av
              Asthma
              All: 1.014 [0.997, 1.030] lag 0-2, 3 day moving
              avg
              2-18: 1.027 [1.005, 1.050] lag 0-2, 3 day moving
              avg
              Pneumonia
              RR 1.000 [0.983, 1.019] lag 0-2, 3 day moving av
              COPD
              RR 1.035 [1.006, 1.065] lag 0-2, 3 day moving av

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              TABLE AX6.3-2 (cont'd).  RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                            EMERGENCY DEPARTMENT VISITS
 Reference, Study
Location, & Period
Outcomes, Design, & Methods
Mean Levels of NO2 &
 Monitoring Stations
Copollutant            Effects and Interpretation:
Correlations     Relative Risk & Confidence Intervals (95%)
          UNITED STATES (cont'd)
 X
          Tolbert et al. (2000)
          Atlanta, GA, United
          States

          Period of Study:
          1993-1995
                   Outcome(s) (ICD-9): Asthma
                   (493), wheezing (786.09), Reactive
                   airways disease (RADS) (519.1)
                   Age groups analyzed: 0-16; 2-5,
                   6-10, 11-16
                   Study Design: Case-Control
                   N:  5,934
                   Statistical Analyses: Ecological
                   GEE analysis (Poisson model with
                   logit link) and logistic regression
                   Covariates: day of wk, day of
                   summer, yr, interaction of day of
                   summer and yr
                   Season: Summers only
                   Statistical Package:  SAS
                   Lag: 1 day (a priori)
                              NOX 1-h max
                              continuous
                              Mean: 81.7ppb,
                              SD = 53.8
                              Range = 5.35, 306

                              Number of stations: 2
                      PM10;r=0.44
                      O3;r = 0.51
               Increment: 50 ppb

               Age 0-16:
               RR 1.012 [0.987, 1.039] lag 1
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             TABLE AX6.3-2 (cont'd).  RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                           EMERGENCY DEPARTMENT VISITS
 Reference, Study
Location, & Period
Outcomes, Design, & Methods
Mean Levels of NO2 &
 Monitoring Stations
Copollutant           Effects and Interpretation:
Correlations    Relative Risk & Confidence Intervals (95%)
          UNITED STATES (cont'd)
 X
 Oi
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          Cassino* et al. (1999)
          New York City, NY
          United States

          Period of Study:
          1/1989-12/1993
                    Outcome(s) (ICD-9): Asthma
                    (493); COPD (496), bronchitis
                    (490), emphysema (492),
                    bronchiectasis (494)
                    Study Design: Time series
                    N: 1,115
                    # of Hospitals: 11
                    Statistical Analyses: Time series
                    regression, Poisson regression with
                    GLM and GAM; Linear
                    regression, Logistic regression
                    with GEE
                    Covariates: Season, trend, day of
                    wk, temperature, humidity
                    Statistical Package: S Plus and
                    SAS
                    Lag:  0-3 days
                              24-h avg NO2:
                              Mean: 45.0 ppb
                              Median: 43 ppb
                              10% 31 ppb
                              25% 37 ppb
                              75% 53 ppb
                              90% 63 ppb
                       03
                       CO
                       SO2
              Increment:  15 ppb (IQR)

              RR 0.97 [0.85, 1.09] lag 0
              RR 1.04 [0.92, 1.18] lag 1
              RR 1.06 [0.94, 1.2] lag 2
              RR 0.97 [0.86, 1.09] lag 3
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              TABLE AX6.3-2 (cont'd).  RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                            EMERGENCY DEPARTMENT VISITS
 Reference, Study
Location, & Period
                                 Outcomes, Design, & Methods
Mean Levels of NO2 &
 Monitoring Stations
Copollutant            Effects and Interpretation:
Correlations    Relative Risk & Confidence Intervals (95%)
          CANADA
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          Stiebetal. (1996)
          St. John, New
          Brunswick, Canada

          Period of Study:
          1984-1992
          (May-Sept only)
          Stieb* et al. (2000)
          Saint John, New
          Brunswick,  Canada

          Period of Study:
          Retrospective:
          7/92-6/94
          Prospective:
          7/94-3/96
                    Outcome(s): Asthma
                    ICD-9 Codes: NR
                    Age groups analyzed: 0-15, >15
                    Study Design: Time series
                    N:  1,163
                    # of Hospitals: 2
                    Statistical Analyses:  SAS NLIN
                    (Equivalent to Poisson GEE)
                    Covariates: day of wk, long-term
                    trends,
                    Season: Summers only (May-Sep)
                    Dose-response investigated?: Yes
                    Statistical Package:  SAS
                    Lag: 0-3 days
                    Outcome(s): Asthma; COPD;
                    Respiratory infection (bronchitis,
                    bronchiolitis, croup, pneumonia);
                    All respiratory
                    ICD-9 Codes: NR
                    Age groups analyzed: All
                    Study Design: Time series
                    N:  19,821
                    Statistical Analyses:  Poisson
                    regression, GAM
                    Covariates: day of wk, selected
                    weather variables in each model
                    Seasons:  All yr, summer only
                    Dose-Response investigated: Yes
                    Statistical Package:  S-Plus
                    Lag: all yr = 0; summer
                    only = 8
                                                                l-hmaxNO2 (ppb)
                                                                Mean: 25.2
                                                                Range:  0, 120
                                                                95th 60
                                                                Annual mean:  8.9 ppb
                                                                spring/fall mean:
                                                                10.0 ppb Max: 82
                        O3r=0.16      Increment:  NR
                        SO2r=-0.03
                        SO42~-r=0.16   NO2 + O3:  P = -0.0037 (0.0023) lag 2
                        TSPr=0.15
                        O3;r=-0.02
                        SO2;r=0.41
                        TRS;r=0.16
                        PM10;r=0.35
                        PM25;r = 0.35
                        H+;r=0.25
                        SO42~;
                        r = 0.33
                        COH; r = 0.49

                        Assessed
                        multipollutant
                        models
              Increment: 8.9 ppb (IQR)

              Respiratory visits:  -3.8%, p = 0.070 lag 0
              May to Sept: 11.5%, p = 0.17 lag 8

              Multipollutant model (NO2, O3, SO2)
              -3.6% [-7.5, 0.5] lag0

              Multipollutant model (ln(NO2), O3, SO2 COH)
              May to Sept: 4.7% [0.8 to 8.6]  lag 8

              Non-linear effect of NO2 on summertime
              respiratory visits observed and log
              transformation strengthened the association.

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              TABLE AX6.3-2 (cont'd).  RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                            EMERGENCY DEPARTMENT VISITS
 Reference, Study
Location, & Period
                                 Outcomes, Design, & Methods
 Mean Levels of NO2 &
  Monitoring Stations
 Copollutant            Effects and Interpretation:
 Correlations    Relative Risk & Confidence Intervals (95%)
          EUROPE and MIDDLE EAST
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          Sunyeretal. (1997)
          Multi-city, Europe
          (Barcelona, Helsinki,
          Paris, London)

          Period of Study:
          1986-1992
                    Outcomes (ICD-9): Asthma (493)
                    Age groups analyzed:  <15, 15-64
                    Study Design: Time series
                    Statistical Analyses: APHEA
                    protocol, Poisson regression,  GEE;
                    meta-analysis
                    Covariates:  Humidity,
                    temperature, influenza, soybean,
                    long-term trend, season, day of wk
                    Season: Cool, Oct-Mar; Warm:
                    Apr-Sep
                    Statistical Package: NR
                    Lag: 0,1,2,3 and cumulative  1-3
24-h median (range)
(ug/m3)
Barcelona: 53 (5, 142)
Helsinki: 35(9,78)
London: 69(27,347)
Paris:  42 (12, 157)

# of stations:
Barcelona: 3
London: 2
Paris:  4
Helsinki: 8
S02
black smoke
03
Increment: 50 ug/m3 of 24-h avg for all cities
combined

Asthma
15-64 yrs
  1.029 [1.003, 1.055] lag 0-1
  1.038 [1.008, 1.068] lag 0-3, cumulative

<15 yrs
  1.026 [1.006, 1.049] lag 2
  1.037 [1.004, 1.067] lag 0-3, cumulative
  1.080 [1.025, 1.140] -Winteronly

Two-pollutant models:
NO2/Black smoke
15-64 yrs 1.055 [1.005, 1.109] lag 0-1
15-64 yrs 1.088 [1.025, 1.155] cumulative 0-3
<15yrs  1.036 [0.956, 1.122]

NO2/SO2
<15yrs  1.034 [0.988, 1.082]

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               TABLE AX6.3-2 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                             EMERGENCY DEPARTMENT VISITS
            Reference, Study
           Location, & Period
                      Outcomes, Design, & Methods
Mean Levels of NO2 &
 Monitoring Stations
                     Effects and Interpretation:
Copollutant     Relative Risk & Confidence Intervals
Correlations                   (95%)
          EUROPE and MIDDLE EAST (cont'd)
 X
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O
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Atkinson et al.        Outcome(s) (ICD-9): Respiratory
(1999b)             ailments (490-496), including
London, United       asthma, wheezing, inhaler request,
Kingdom            chest infection, COPD, difficulty
                    in breathing, cough, croup,
Period of Study:       pleurisy, noisy breathing
1/92-1294            Age groups analyzed: 0-14;
                    15-64; >65; All ages
                    Study Design: Time series
                    N:  98,685
                    # of Hospitals: 12
                    Statistical Analyses:  Poisson
                    regression, APHEA protocol
                    Covariates: long-term trend,
                    season, day of wk, influenza,
                    temperature, humidity
                    Statistical Package: SAS
                    Lag: 0,1,0-2, and 0-3 days
                                                               1-hmax:  50.3 ppb, SD = 17.0
                                                               # of Stations: 3; r= 0.70, 0.96
                          NO2, O3
                          (8 h), SO2
                          (24 h), CO
                          (24 h), PM10
                          (24 h), BS
              Increment: 36ppb in 1-hmax

              Single-pollutant model
              Asthma Only
              0-14 yrs 8.97% [4.39, 13.74] lag 1
              15-64 yrs 4.44% [0.14, 8.92] lag 1
              All ages 4.37% [1.32, 7.52] lag 0
              All Respiratory
              0-14 yrs 2.17% [-0.49, 4.91] lag 1
              15-64 yrs 1.87% [-0.69, 4.49] lag 2
              >65 yrs 3.97% [0.51, 7.55] lag 0
              All Ages 1.20% [-0.57, 3.00]
              Two-pollutant model Asthma Only 0-14 yrs:
              SO2: 5.75% [0.39, 11.40] lag 1
              CO:  8.34% [3.61, 13.29] lag 0
              PM10: 6.95% [1.96, 12.19] lag 2
              BS: 8.32% [3.56, 13.30] lag 2
              O3:  9.68% [5.02, 14.54] lag 0

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              TABLE AX6.3-2 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                            EMERGENCY DEPARTMENT VISITS
  Reference, Study
 Location, & Period
 Outcomes, Design, & Methods
  Mean Levels of NO2 &
   Monitoring Stations
Copollutant           Effects and Interpretation:
Correlations   Relative Risk & Confidence Intervals (95%)
          EUROPE and MIDDLE EAST (cont'd)
 X
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Buchdahletal. (1996)
London, United
Kingdom

Period of Study:
3/1/92-2/28/93
Outcomes: Daily acute wheezy
episodes
ICD-9: NR
Age groups analyzed: < 16
Study Design: Case-control
N: 1,025 cases, 4,285 controls
Number of hospitals:  1
Statistical Analyses: Poisson
regression
Covariates:  Season, temperature,
wind speed
Season:  Spring (Apr-Jun),
Summer (Jul-Sep), Autumn
(Oct-Dec), Winter (Jan-Mar)
Statistical Package: Stata
Lag:  0-7 days
NO2 24-h yr round mean:
60 ug/m3, SD = 17

IQR: 17 ug/m3

Spring: 59(19)
Summer:  55 (18)
Fall: 66(13)
Winter: 61 (17)
                                                                                        SO2r=0.62
                                                                                        O3r=-0.18
              Increment: 17 ug/m3 (IQR)
                                                                                                      No adjustments to model
                                                                                                      RR 1.07 [1.01, 1.14] lag not specified

                                                                                                      Adjusted for temperature and season.
                                                                                                      RR 1.02 [0.96, 1.09] lag not specified
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                          TABLE AX6.3-2 (cont'd).  RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                                           EMERGENCY DEPARTMENT VISITS
             Reference, Study
            Location, & Period
Outcomes, Design, &
      Methods
Mean Levels of NO2 &
 Monitoring Stations
Copollutant            Effects and Interpretation:
Correlations    Relative Risk & Confidence Intervals (95%)
           EUROPE and MIDDLE EAST (cont'd)
 X
H
6
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H
O
O
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W
O
O
HH
H
W
           Thompson etal. (2001)
           Belfast, Northern Ireland

           Period of Study:
           1993-1995
                                  Outcome(s):  Asthma
                                  ICD-9 Code(s): NR
                                  Age groups analyzed: Children
                                  Study Design: Time series
                                  N:  1,044
                                  Statistical Analyses: Followed
                                  APHEA protocol, Poisson
                                  regression analysis
                                  Covariates:  Season, long-term
                                  trend, temperature, day of wk,
                                  holiday
                                  Season:  Warm (May-Oct); Cold
                                  (Nov-Apr)
                                  Statistical Package: Stata
                                  Lag: 0-3
                          Warm Season
                          NO2(ppb): Mean:  19.20;
                          SD: 7.90; IQR: 13.0,23.0
                          NOx(ppb): Mean:  35.50;
                          SD: 25.50; IQR: 21.0,40.0
                          NO(ppb): Mean:  16.4;
                          SD: 19.70; IQR: 7.0,17.0

                          Cold Season
                          NO2(ppb): Mean:  23.30;
                          SD: 9.00; IQR:  18.0,28.0
                          NOx(ppb): Mean:  50.50;
                          SD: 50.50; IQR: 26.0, 56.0
                          NO(ppb): Mean:  27.30;
                          SD: 43.10; IQR: 9.0,28.0
                           NO2:
                           PM10 r = 0.77
                           S02r=0.82
                           NOxr = 0.93
                           NO r= 0.84
                           O3r=-0.62
                           CO r= 0.69
                           Benzene
                            r =0.83

                           NOX:
                           PM10 r = 0.73
                           S02r=0.83
                           NO2 r = 0.92
                           NO r= 0.97
                           O3r=-0.73
                           CO r = 0.74
                           Benzene
                           r=0.86

                           NO:
                           PM10r=0.65
                           S02 r = 0.76
                           NOxr = 0.97
                           NO2 r = 0.84
                           O3r=-0.76
                           CO r= 0.71
                           Benzene
                           r=0.82
               NO2 Increment: lOppb
               NOX Increment: per doubling
               NO Increment: per doubling

               NO2
               Lag ORR 1.08 [1.03, 1.13]
               Lag 0-1 RR 1.11 [1.05,1.17]
               Lag 0-2 RR 1.10 [1.04, 1.17]
               Lag 0-3 RR 1.12 [1.03, 1.20]
               Warm only Lag 0-1 RR 1.14 [1.04, 1.26]
               Cold only Lag 0-1 RR1.10 [1.03, 1.17]
               Adjusted for Benzene Lag 0-1 RR 0.99 [0.87, 1.13]

               NOX
               Lag ORR 1.07 [1.02, 1.12]
               Lag 0-1 RR 1.10 [1.05, 1.16]
               Lag 0-2 RR 1.10 [1.03, 1.17]
               Lag 0-3 RR 1.11 [1.04,1.20]
               Warm only Lag 0-1 RR 1.13 [1.03, 1.24]
               Cold only Lag 0-1 RR 1.09 [1.02, 1.16]
               Adjusted for Benzene Lag 0-1 RR 0.89 [0.77, 1.03]
                                                                                                              NO
                                                                                                              Lag ORR 1.04 [1.01, 1.07]
                                                                                                              Lag 0-1 RR 1.07 [1.03, 1.11]
                                                                                                              Lag 0-2 RR 1.06 [1.02, 1.11]
                                                                                                              Lag 0-3 RR 1.08 [1.02, 1.14]
                                                                                                              Warm only Lag 0-1 RR 1.08 [1.01, 1.16]
                                                                                                              Cold only Lag 0-1 RR 1.06 [1.01, 1.11]
                                                                                                              Adjusted for Benzene Lag 0-1 RR 0.93 [0.85, 1.01]

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             TABLE AX6.3-2 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                           EMERGENCY DEPARTMENT VISITS
 Reference, Study
Location, & Period
Outcomes, Design, & Methods
Mean Levels of NO2 &
 Monitoring Stations
Copollutant          Effects and Interpretation:
Correlations   Relative Risk & Confidence Intervals (95%)
          EUROPE and MIDDLE EAST (cont'd)
 X
 ON
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 to
          Boutin-Forzano et al.
          (2004)
          Marseille, France

          Period of Study:
          4/97-3/98
                    Outcome(s): Asthma
                    ICD-9 Code(s): NR
                    Age groups analyzed: 3-49
                    Study Design:  Case-Crossover
                    N: 549
                    Statistical Analyses: Logistic
                    regression
                    Covariates: minimal daily
                    temperature, maximum daily
                    temperature, minimum daily
                    relative humidity, maximum daily
                    relative humidity, day of wk
                    Statistical Package: NR
                    Lag:  0-4 days
                              MeanNO2:  34.9 ug/mj
                              Range: 3.0,85
                        SO2; r = 0.56   Increment: 10 ug/mj
                        O3;r=0.58
                                      Increased ER visits
                                                                      OR 1.0067 [0.9960, 1.0176] lagO
 H
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O
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TABLE AX6.3-2 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                               EMERGENCY DEPARTMENT VISITS
Reference, Study
Location, & Period
EUROPE and MIDDLE
Castellsague etal. (1995)
Barcelona, Spain
Outcomes, Design, &
Methods
EAST (cont'd)
Outcome(s): Asthma
ICD-9 Code(s): NR
Age groups analyzed: 15-64
Mean Levels of NO2 &
Monitoring Stations

Mean NO2 (ug/m3)
Summer: 104.0
Winter: 100.8
Copollutant
Correlations

SO2;r = NR
O3; r = NR
Effects and Interpretation:
Relative Risk & Confidence Intervals

Increment: 25 ug/m3
Seasonal differences
(95%)


          Period of Study:
          1986-1989
          Study Design: Time series
          # of Hospitals:  4
          Statistical Analyses: Poisson
          regression
          Covariates: long-time trend,
          day of wk, temperature, relative
          humidity, dew point
          temperature
          Seasons:  Winter:  Jan-Mar;
          Summer: Jul-Sep
          Dose-Response investigated:
          Yes
          Statistical Package: NR
          Lag: 0, 1-5 days and
          cumulative.
          Summer: lag 2 days
          Winter: lag 1 day	
IQR (ug/m3):
Summer: 48
Winter:  37

# of Stations:
15 manual, 3 automatic
Summer:
1.071 [1.101, 1.130] lag 0-5 cumulative
1.045 [1.009, 1.081] lag 0
Winter:
1.072 [1.010, 1.137] lag 0-2 cumulative
1.056 [1.011, 1.104] lag 0

Asthma visits increased across quartiles of NO2
in summer; a positive but less consistent
increase across quartiles was observed in
winter.

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             TABLE AX6.3-2 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                           EMERGENCY DEPARTMENT VISITS
 Reference, Study
Location, & Period
                                   Outcomes, Design, & Methods
Mean Levels of NO2 &   Copollutant           Effects and Interpretation:
 Monitoring Stations    Correlations   Relative Risk & Confidence Intervals (95%)
          EUROPE and MIDDLE EAST (cont'd)
 X
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O
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          Tobias etal. (1999)
          Barcelona, Spain

          Period of Study:
          1986-1989
                     Outcome(s): Asthma
                     ICD-9: NR
                     Age groups analyzed: >14
                     Study Design:  Time series
                     Statistical Analyses: Poisson
                     regression, followed APHEA
                     protocol
                     Covariates:  temperature, humidity,
                     long-term trend, season, day of wk
                     Statistical Package: NR
                     Lag:  NR
24-h-avg NO2 ug/mj

Non-epidemic days:
54.7 (20.8)
Epidemic days:
58.9 (26.7)
BS
S02
03
P x 104 (SE x 104) using Std Poisson
Without modeling asthma epidemics:
11.25 (11.79) p> 0.1
Modeling epidemics with 1 dummy variable:
1.18 (7.59) p> 0.1
Modeling epidemics with 6 dummy variables:
13.60 (1.19) p< O.I
Modeling each epidemic with dummy variable:
U.40(1.44)p<0.\

P x 104 (SE x 104) using Autoregressive
Poisson
Without modeling asthma epidemics:
13.65 (11.81)p>0.1
Modeling epidemics with 1 dummy variable:
3.28 (7.77) p> 0.1
Modeling epidemics with 6 dummy variables:
16.49 (^.01) p< 0.05
Modeling each epidemic with dummy variable:

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               TABLE AX6.3-2 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                             EMERGENCY DEPARTMENT VISITS
 Reference, Study
Location, & Period
                                 Outcomes, Design, & Methods
 Mean Levels of NO2 &
  Monitoring Stations
 Copollutant            Effects and Interpretation:
 Correlations    Relative Risk & Confidence Intervals (95%)
          EUROPE and MIDDLE EAST (cont'd)
 X
          Galan et al. (2003)
          Madrid, Spain

          Period of Study:
          1995-1998
                    Outcome(s) (ICD-9): Asthma (493)
                    Age groups analyzed: All
                    Study Design:  Time series
                    N: 4,827
                    Statistical Analyses:  Poisson
                    regression, (1) classic APHEA protocol
                    and (2) GAM with stringent criteria
                    Covariates: trend, yr, season, day of
                    wk, holidays, temperature, humidity,
                    influenza, acute respiratory infections,
                    pollen
                    Statistical Package: NR
                    Lag: 0-4 days
24-h mean:  67.1 ug/m3
SD=18.0
IQR: 20.5
Max:  147.5

# of Stations: 15
PM10; r = 0.717   Increment: 10 ug/mj
SO2;r=0.610    Asthma:
O3;r=-0.209    RR 1.013 [0.991, 1.035] lag 0
                RR 1.011 [0.989, 1.032] lag 1
                RR 1.013 [0.992, 1.034] lag 2
                RR 1.033 [1.013, 1.054] lag 3
                RR 1.026 [1.006, 1.047] lag 4

                Multipollutant model:
                NO2/SO21.031 [1.004, 1.059] lag 3
                NO2/PM101.001 [0.971, 1.031] lag 3
                NO2/Pollen 1.024 [1.004, 1.044] lag 3
                NO2/Pollen/O3 1.024 [1.005, 1.045] Poisson
                NO2/Pollen/O3 1.022 [1.005, 1.040] GAM
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            TABLE AX6.3-2 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                         EMERGENCY DEPARTMENT VISITS
 Reference, Study
Location, & Period
                                    Outcomes, Design, & Methods
Mean Levels of NO2 &
 Monitoring Stations
                    Effects and Interpretation:
Copollutant         Relative Risk & Confidence
Correlations              Intervals (95%)
          EUROPE and MIDDLE EAST (cont'd)
 X
 Oi
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          Teniasetal. (1998)
          Valencia, Spain

          Period of Study:
          1993-1995

          Seasons:
          Cold: Nov-Apr
          Warm:  May-Oct
                      Outcome(s): Asthma                24 h:
                      ICD-9 Code(s): NR                 57.7 ug/m3
                      Age groups analyzed:  >14           Cold:  55.9
                      Study Design: Time series           Warm: 59.4
                      N:  734                            1-hmax:
                      Statistical Analyses: Poisson         101.1  ug/m3
                      regression, APHEA protocol          Cold:  97.3
                      Covariates: seasonality, temperature,   Warm: 102.8
                      humidity, long-term trend, day of wk,
                      holidays, influenza                  # of Stations: 2
                      Seasons: Cold: Nov-Apr; Warm:
                      May-Oct
                      Dose-Response Investigated:  Yes
                      Statistical Package: NR
                      Lag: 0-3 days	
                      24 h:
                      O3;r=-0.304
                      S02 (24 h);
                      r = 0.265
                      SO2(lh);r= 0.261

                      Ih:
                      O3;r=-0.192
                      S02 (24 h);
                      r = 0.199
                      SO2(lh);r= 0.201
                  Increment:  10 ug/m

                  NO2 24-h avg
                  All yr 1.076 [1.020, 1.134] lag 0
                  Cold 1.083  [1.022, 1.148] lag 0
                  Warm 1.066 [0.989, 1.149] lagO

                  NO21-h max
                  Allyr 1.037 [1.008, 1.066] lagO
                  Cold 1.034  [1.004, 1.066] lagO
                  Warm 1.044 [1.002, 1.088] lagO
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              TABLE AX6.3-2 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                            EMERGENCY DEPARTMENT VISITS
Reference, Study
Location, &
Period
Outcomes, Design, & Methods
Mean Levels of NO2 &
Monitoring Stations
Copollutant
Correlations
Effects and Interpretation:
Relative Risk & Confidence Intervals (95%)
          EUROPE and MIDDLE EAST (cont'd)
 X
Tenias et al. (2002)   Outcome(s): COPD
Valencia, Spain      ICD-9 Code(s): NR
                   Age groups analyzed:  >14
                   Study Design: Time series
Period of Study:      N:  1,298
1994-1995           # of Hospitals:  1
                   Statistical Analyses: Poisson
                   regression, APHEA protocol; basal
                   models and GAM
                   Covariates: seasonality, annual
                   cycles, temperature, humidity, day
                   of wk, feast days
                   Seasons: Cold, Nov-Apr; Warm,
                   May-Oct
                   Dose-Response Investigated: Yes
                   Statistical Package: NR
                   Lag: 0-3 days
                                                            NO224-havg: 57.7 ug/m3;
                                                            Range: 12, 135
                                                            1-hmax: 100.1 ug/m3;
                                                            Range: 31,305

                                                            # of Stations: 6 manual and
                                                            5 automatic; r = 0.87
BS;r= 0.246
SO2;r= 0.194
CO; r= 0.180
O3;r=-0.192
Increment: 10 ug/m

24-havgNO2
All Year RR 0.979 [0.943, 1.042] lagO
Cold, 24-havg: RR0.991 [0.953, 1.030] lagO
Warm, 24-havg: RR0.961 [0.900, 1.023] lagO

l-hmaxNO2
All Year RR 0.986 [0.966, 1.007] lagO
Cold, 24-havg: RR0.996 [0.975, 1.018] lagO
Warm, 24-havg: RR0.968 [0.935, 1.003] lagO

Possibility of a linear relationship between
pollution and risk of emergency cases could not
be ruled out.
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               TABLE AX6.3-2 (cont'd).  RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                              EMERGENCY DEPARTMENT VISITS
 Reference, Study
Location, & Period
                                Outcomes, Design, & Methods
    Mean Levels of NO2 &
     Monitoring Stations
                      Effects and Interpretation:
Copollutant      Relative Risk & Confidence Intervals
Correlations                    (95%)
          EUROPE and MIDDLE EAST (cont'd)
 X
 oo
 H
 6
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O
 O
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 W
 O

 O
 HH
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 W
Migliaretti et al.      Outcome (ICD-9): Asthma (493)
(2005)              Age groups analyzed: <15, 15-64,
Turin, Italy          >64
                    Study Design:  Case-Control
Period of Study:      Controls: age matched with other
1997-1999           respiratory disease (ICD-9:
                    460-487, 490-2, 494-6, 500-19) or
                    heart disease (ICD-9:  390-405,
                    410-429)
                    N:  cases =  1,401
                    controls = 201,071
                    Statistical Analyses:  logistic
                    regression
                    Covariates:  seasonality,
                    temperature, humidity, solar
                    radiation, wind velocity, day of
                    wk, holiday, gender, age,
                    education level
                    Seasons: Cold: Oct-Mar; Warm:
                    Apr-Sep
                    Statistical Package: NR
                    Lag: 0-3 days and cumulative
All Participants:
24-hmean:  112.7 ug/m3,
SD = 30.2, Median =107.7

Cases:
24-hmean:  117.1 ug/m3,
SD = 30.0, Median =113.0

Controls:
24-hmean:  112.7 ug/m3,
SD = 30.2, Median =107.7

# of Stations:  10, r= 0.79
                                                                                             TSP; r = 0.8     Increment: 10 ug/mj
                                                                                             Two-pollutant
                                                                                             model
                                                                                             adjusted for
                                                                                             TSP
              Single Pollutant (NO2):
              <15 yrs 2.3% [0.3, 4.40]
              15-64 yrs 3.10% [-0.01, 7.70]
              >64 yrs 7.70% [0.20, 15.20]
              All ages 2.40% [0.5, 4.30]

              Copollutant (NO2 and TSP)
              <15 yrs 1.71% [-0.02, 5.00]
              15-64 yrs 1.20% [-0.06, 6.50]
              >64 yrs 0.91% [-0.08, 5.91]
              All ages 1.10% [-0.02, 3.82]

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                TABLE AX6.3-2 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                              EMERGENCY DEPARTMENT VISITS
   Reference, Study
  Location, & Period
Outcomes, Design, & Methods
Mean Levels of NO2 &     Copollutant            Effects and Interpretation:
 Monitoring Stations      Correlations    Relative Risk & Confidence Intervals (95%)
          EUROPE and MIDDLE EAST (cont'd)
 X
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 6
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O
 O
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          Pantazopoulou et al.
          (1995)
          Athens, Greece
                       Outcomes: All respiratory visits
                       ICD-9: NR
                       Age groups analyzed:  All ages
                       Study Design: Time series
Period of Study :  1988   N: 213,316
                       Number of hospitals: 14
                       Statistical Analyses: Multiple
                       linear regression
                       Covariates:  Season, day of wk,
                       holiday, temperature, relative
                       humidity
                       Season: Warm (3/22-9/21),
                       Cold (1/1-3/21 and 9/22-12/31)
                       Lag:  NR
          Gartyetal. (1998)
          Tel Aviv, Israel
          1993
                       Outcome(s):  Asthma
                       ICD-9 Code(s): NR
                       Age groups analyzed:  1-18
                       Study Design: Descriptive study
                       with correlations
                       N: 1,076
                       Statistical Analyses: Pearson
                       correlation and partial
                       correlation coefficients
                       Covariates:  maximum and
                       minimum ambient temperatures,
                       relative humidity and barometric
                       pressure
                       Statistical Package:  Statistix
                              NO2 24-h avg

                              Winter:  94 ug/m3, SD = 25
                              5th:  59,50th: 93,
                              95th: 135

                              Summer: 111 ug/m3,
                              SD = 32
                              5th:  65,50th: 108,
                              95th: 173

                              # of stations: 2
                              24-h mean of NOX
                              (estimated from histogram):
                              60 ug/m3; Range 50, 250
                         CO
                         BS
Increment: 76 ug/m3 in winter and 108 ug/m3 in
summer (95th-5th)

Respiratory disease admissions

Winter:  Percent increase: p = 66.8 [19.6, 113.9]

Summer: Percent increase:  P = 21.2 [-35.1, 77.5]
                                      Correlation between NOX and ER visits for
                                      asthma:

                                      All Year:
                                      Daily data r = 0.30
                                      Running mean for 7 days r = 0.62

                                      Excluding September:
                                      Daily data r = 0.37
                                      Running mean for 7 days r = 0.74

                                      38% of variance in number of ER visits explained
                                      by fluctuations in NOX. Increases to 55% when
                                      Sept. is omitted from analyses.

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TABLE AX6.3-2 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                              EMERGENCY DEPARTMENT VISITS
Reference, Study
Location, & Period
Outcomes, Design, & Methods
Mean Levels of NO2 &
Monitoring Stations
Copollutant
Correlations
Effects and Interpretation:
Relative Risk & Confidence Intervals (95%)
LATIN AMERICA
Farhat* et al. (2005)
Sao Paulo, Brazil
Outcome(s) (ICD-9): Lower
Respiratory Disease (466, 480-5)
Mean: 125.3 ug/m3
PM10;r=0.83
SO2;r=0.66
Increment: IQRof 65.04 ug/m3
          Period of Study:
          1996-1997
       Age groups analyzed:
       Study Design: Time series
       N: 4,534
       # of Hospitals:  1
       Statistical Analyses: 1) Poisson
       regression and 2) GAM - no
       mention of more stringent criteria
       Covariates: long-term trends,
       seasonality, temperature,  humidity
       Statistical Package: S-Plus
       Lag: 0-7 days, 2,3,4 day  moving
       avg
                                                                SD = 51.7
IQR: 65.04 ug/m3
                                                                # of Stations: 6
CO; r = 0.59     Single-pollutant models (estimated from
               graphs):
               LRD -17.5% [12.5, 24]

               Multipollutant models:
               Adjusted for:
               PM1016.1% [5.4, 26.8] 4 day avg
               SO2 24.7% [18.2, 31.3] 4 day avg
               CO 19.2% [11.8, 26.6] 4 day avg
               Multipollutant model
               18.4% [3.4, 33.5] 4 day avg
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              TABLE AX6.3-2 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                            EMERGENCY DEPARTMENT VISITS
 Reference, Study
Location, & Period
Outcomes, Design, & Methods
Mean Levels of NO2 &
 Monitoring Stations
Copollutant           Effects and Interpretation:
Correlations   Relative Risk & Confidence Intervals (95%)
          LATIN AMERICA (cont'd)
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          Martins* et al. (2002)
          Sao Paulo, Brazil

          Period of Study:
          5/96-9/98
                    Outcome(s) (ICD-10): Chronic
                    Lower Respiratory Disease
                    (CLRD) (J40-J47); includes
                    chronic bronchitis, emphysema,
                    other COPDs, asthma,
                    bronchiectasia
                    Age groups analyzed:  >64
                    Study Design: Time series
                    N:  712
                    # of Hospitals: 1
                    Catchment area: 13,163 total ER
                    visits
                    Statistical Analyses: Poisson
                    regression and GAM - no mention
                    of more stringent criteria
                    Covariates:  weekdays, time,
                    minimum temperature, relative
                    humidity, daily number of non-
                    respiratory emergency room visits
                    made by elderly
                    Statistical Package: S-Plus
                    Lag: 2-7 days and 3 day moving
                    avgs
                               NO2 max 1-h avg (ug/m3):
                               117.6, SD = 53.0,
                               Range 32.1, 421.6

                               IQR:  62.2 ug/m3

                               # of Stations: 4
                         O3; r = 0.44     Increment:  IQR of 62.2 ug/mj
                         SO2;r=0.67
                         PM10; r = 0.83   Percent increase: 4.5% [-6.5, 15] lag 3 day
                         CO; r = 0.62     moving avg (estimated from graph)

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               TABLE AX6.3-2 (cont'd).  RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                             EMERGENCY DEPARTMENT VISITS
 Reference, Study
Location, & Period
Outcomes, Design, & Methods
Mean Levels of NO2 &
 Monitoring Stations
Copollutant              Effects and Interpretation:
Correlations      Relative Risk & Confidence Intervals (95%)
          LATIN AMERICA (cont'd)
 X
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O
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          Ilabacaetal. (1999)
          Santiago, Chile

          Period of Study:
          2/1/95-8/31/96

          Days: 578
                    Outcome(s) (ICD-9): Upper
                    respiratory illness
                    (460-465, 487);
                    Lower respiratory illness
                    (466, 480-486, 490-494, 496,
                    519.1,033.9);
                    Pneumonia (480-486)
                    Age groups analyzed: <15
                    Study Design:  Time series
                    # of Hospitals: 1
                    Statistical Analyses:  Poisson
                    regression
                    Covariates: Long-term trend,
                    season, day of wk, temperature,
                    humidity, influenza epidemic
                    Season: Warm (Sep-Apr),
                    Cool (May-Aug)
                    Statistical Package:  NR
                    Lag: 0-3 days
                              24-havgNO2:
                              Warm:
                              Mean: 97.0
                              Median:  91.5
                              SD: 34.6
                              Range: 37.2,246
                              5th: 54.3
                              95th: 163.0

                              Cool:
                              Mean: 160.2
                              Median:  154.4
                              SD: 59.5
                              Range: 60.1,397.5
                              5th: 74.4
                              95th: 266.0

                              # of stations: 4,
                              r = 0.70,  0.88
                       Warm:         Increment: IQR
                       SO2r=0.66
                       O3 r = 0.15      All respiratory
                       PM10r = 0.71    Cool
                       PM25r=0.70   Lag2IQR: 56.4 RR 1.0378 [1.0211, 1.0549]
                                      Lag 3 IQR: 56.4 RR 1.0294 [1.0131, 1.0460]
                       Cool:           Lag avg 7 IQR: 33.84 RR 1.0161 [1.0000, 1.0325]
                       SO2 r = 0.74     Warm
                       O3 r = 0.22      Lag 2 IQR: 30.08 RR 1.0208 [0.9992, 1.0428]
                       PM10r = 0.82    Lag 3 IQR: 30.08 RR 1.0395 [1.0181, 1.0612]
                       PM25 r = 0.80   Lag avg 7 IQR: 22.56 RR 1.0251 [0.9964, 1.0548]

                                      Upper respiratory
                                      Cool
                                      Lag 2 IQR: 56.4 RR 1.0569 [1.0339, 1.0803]
                                      Lag 3 IQR: 56.4 RR 1.0318 [1.0095, 1.0545]
                                      Lag avg 7 IQR: 33.84 RR 1.0177 [0.9960, 1.0399]
                                      Warm
                                      Lag 2 IQR: 30.08 RR 1.0150 [0.9881, 1.0426]
                                      Lag 3 IQR: 30.08 RR 1.0425 [1.0157, 1.0699]
                                      Lag avg 7 IQR: 22.56 RR 0.9944 [0.9591, 1.0311]

                                      Pneumonia
                                      Cool
                                      Lag 2 IQR: 56.4 RR 1.0824 [1.0300, 1.1374]
                                      Lag 3 IQR: 56.4 RR 1.0768 [1.0273, 1.1287]
                                      Lag avg 7 IQR: 33.84 RR 1.0564 [1.0062, 1.1092]
                                      Warm
                                      Lag 2 IQR: 30.08 RR 1.1232 [1.0450, 1.2072]
                                      Lag 3 IQR: 30.08 RR 1.0029 [0.9332, 1.0779]
                      	Lag avg 7 IQR: 22.56 RR 1.1084 [1.0071, 1.2200]

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             TABLE AX6.3-2 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                          EMERGENCY DEPARTMENT VISITS
Reference, Study
  Location, &
     Period
                              Outcomes, Design, & Methods
  Mean Levels of NO2 &
   Monitoring Stations
 Copollutant           Effects and Interpretation:
 Correlations    Relative Risk & Confidence Intervals (95%)
          LATIN AMERICA (cont'd)
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          Lin etal. (1999)
          Sao Paulo, Brazil

          Period of Study:
          May  1991-April
          1993

          Days: 621
                  Outcome(s): Respiratory disease,
                  Upper respiratory illness, Lower
                  respiratory illness, Wheezing
                  ICD-9 Code(s): NR
                  Age groups analyzed: <13
                  Study Design:  Time series
                  # of Hospitals: 1
                  Statistical Analyses: Gaussian and
                  Poisson regression
                  Covariates: Long-term trend,
                  seasonality, day of wk,
                  temperature, humidity
                  Statistical Package: NR
                  Lag: 5-day lagged moving avgs
NO2 ug/mj:
Mean:  163
SD: 85
Range: 2,688

Number of stations:  3
SO2r=0.38     Increment:  NR
CO r= 0.35
PMio r = 0.40    All respiratory illness
O3r=0.15      NO2 alone RR 1.003 [1.001, 1.005] 5-day
               moving avg
               NO2 + PM10+ O3+ SO2+ CO RR 0.996
               [0.994, 0.998]

               Lower respiratory illness
               NO2 alone RR 0.999 [0.991, 1.007] 5-day
               moving avg
               NO2 + PM10+ O3+ SO2+ CO RR 0.990
               [0.982, 0.998]

               Upper respiratory illness
               NO2 alone RR 1.003 [0.999, 1.007] 5-day
               moving avg
               NO2 + PM10+ O3+ SO2+ CO RR 0.996
               [0.992, 1.000]

               Wheezing
               NO2 alone RR 0.996 [0.990, 1.002] 5-day
               moving avg
               NO2 + PM10+ O3+ SO2+ CO RR 0.991
               [0.983, 0.999]

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TABLE AX6.3-2 (cont'd).  RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                               EMERGENCY DEPARTMENT VISITS
 X
 Oi
Reference, Study
Location, &
Period

Mean Levels of NO2 &
Outcomes, Design, & Methods Monitoring Stations
Effects and Interpretation:
Copollutant Relative Risk & Confidence Intervals
Correlations (95%)
ASIA
Chew etal. (1999)
Singapore

Period of Study:
1990-1994








Outcome(s) (ICD-9): Asthma (493) 24-havg: 18.9 ug/m3,
Age groups analyzed: 3-12,13-21 SD = 1 5 .0, Max < 40
Study Design: Time series
N: 23,000 # of Stations: 15
# of Hospitals: 2
Statistical Analyses: Linear
regression, GLM
Covariates: variables that were
significantly associated with ER
visits were retained in the model
Statistical Package: SAS/STAT,
SAS/ETS 6.08
Lag: 1,2 days avgs
SO2; r = - 0.22 Categorical analysis (via ANOVA) p-value
O3; r = 0. 17 and Pearson correlation coefficient (r) using
TSP; r = 0.23 continuous data comparing daily air
pollutant levels and daily number of ER
visits

Age Group: 3-12 13-21
LagO r = 0.10 r = 0.09
p = 0.0019 p<0.00l
Lagl r = 0.12 r = 0.04
p<0.00l p = 0.0014
Lag 2 r=0.14 r=0.03
p<0.00l p = 0.0066
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          Hwang and Chan
          (2002)
          Taiwan

          Period of Study:
          1998
    Outcome(s) (ICD-9): Lower
    Respiratory Disease (LRD) (466,
    480-6) including acute bronchitis,
    acute bronchiolits, pneumonia
    Age groups analyzed: 0-14, 15-64,
    >65, all ages
    Study Design:  Time series
    Catchment area: Clinic records from
    50 communities
    Statistical Analyses:  Linear
    regression, GLM
    Covariates: temperature, dew point
    temperature, season, day of wk,
    holiday
    Statistical Package: NR
    Lag: 0,1,2 days and avgs
24-hr avg: 23.6ppb,
SD = 5.4, Range: 13.0,34.1
S02
PM10
03
CO

No correlations
for individual
pollutants.

Colinearity of
pollutants
prevented use of
multipollutant
models
Increment:  10% change in NO2 (natural
avg) which is equivalent to 2.4 ppb.  NOTE:
The percent change is for the rate of clinic
use NOT for relative risk for adverse effect.

Increased clinic visits for lower respiratory
disease (LRD) by age group

0-14 yrs
1.3% [1.0, 1.6] lag 0
15-64 yrs
1.5% [1.3, 1.8] lag 0
>65 yrs
1.8% [1.4, 2.2] lag 0
All ages
1.4% [1.2, 1.6]lagO

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              TABLE AX6.3-2 (cont'd).  RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:
                                             EMERGENCY DEPARTMENT VISITS
 Reference, Study
Location, & Period
Outcomes, Design, & Methods
Mean Levels of NO2 &
 Monitoring Stations
Copollutant          Effects and Interpretation:
Correlations   Relative Risk & Confidence Intervals (95%)
          ASIA (cont'd)
 X
 Oi
          Tanakaetal. (1998)
          Kushiro, Japan

          Period of Study:
          1992-1993
                    Outcome(s):  Asthma
                    ICD-9 Code(s): NR
                    Age groups analyzed:  15-79
                    Study Design: Time series
                    N: 102
                    # of Hospitals:  1
                    Statistical Analyses: Poisson
                    regression
                    Covariates: temperature, vapor
                    pressure, barometric pressure,
                    relative humidity, wind velocity,
                    wind direction at maximal velocity
                    Statistical Package: NR
                               NO2 24-h avg
                               9.2 ±4.6ppb in fog

                               11.5 ± 5.7 in fog free days

                               Max NO2 24-h avg <30 ppb
                          NO2; r = NR
                          SO2;r = NR
                          SPM (TSP);
                          r = 0.70
                          O3; r = NR
              Increment:  15 ppb

              Nonatopic
              OR 0.62 [0.45, 0.84]

              Atopic
              OR 0.81 [0.67,0.97]
          *Default GAM
          +Did not report correction for over-dispersion
          NR: Not Reported
          APHEA: Air Pollution and Health: a European Approach
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TABLE AX6.3-3. RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN: GENERAL

                         PRACTITIONER/CLINIC VISITS
X
ON

ON
H

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o
H

O


O
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W

O


O
HH
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W
Reference, Study
Location, & Period
Mean Levels & Monitoring
Outcomes, Design, & Methods Stations
Copollutants Effects:
Correlations Relative Risk & Confidence Intervals (95%)
NORTH AMERICA
Hernandez-Garduno
etal. (1997)
Mexico City, Mexico

Period of Study:
May 15,1992-
January 31, 1993







Outcome(s): Respiratory illness
ICD9: NR
Age groups analyzed: <\5,\5+,a\\ Number of Stations: 5
ages (0-92)
Study Design: Time series
N: 24,113
Number of Clinics: 5
Statistical Analyses: Cross-correlation,
linear regression and autoregressive
error model analyses
Covariates: Long-term trend, day of
wk, temperature, humidity
Statistical Package: SAS
Lag: 0-6
O3 Increment: Maximum NO2 concentration of all
SO2 days-Mean NO2 concentration of all days
CO
NOX <\4yrs
NO2lagO: RR 1.29 ±0.09 (p< 0.01)
NO2lag6: RR1.18 ± 0.09 (p> 0.05)

15+yrs
NO2lagO: RR 1.14 ± 0.07 (p< 0.05)
NO2lag6: RR 1.10 ± 0.06 (p> 0.05)

All ages
NO2lagO: RR 1.43 ± 0.15 (p< 0.01)
NO2lag6: RR1.29 ± 0.15 (p> 0.05)
CANADA
Villeneuve et al.
(2006)
Toronto, ON, Canada

Period of Study:
1995-2000
Days: 2,190







Outcome(s) (ICD9): Allergic Rhinitis 24-havg: 25.4 ppb, SD = 7.7
(177) IQR: 10.3 ppb, range 9.2, 71.7
Age groups analyzed: >65
Study Design: Time series Number of stations: 9
N: 52,691
Statistical Analyses: GLM, using
natural splines (more stringent criteria
than default)
Covariates: Day of wk, holiday,
temperature, relative humidity, aero-
allergens
Season: All yr; Warm, May-Oct; Cool,
Nov-Apr
Statistical Package: S-Plus
Lag: 0-6
SO2 Increment: 10. 3 ppb (IQR)
03
CO All results estimated from Stick Graph:
PM2.5
PM10_2.5 All Yr:
PM10 Mean Increase: 1.9% [-0.2, 3.8] lag 0

Warm:
Mean Increase: 0.1% [-3.2, 3.8] lag 0

Cool:
Mean Increase: 1.4% [0.0, 5.9] lag 0



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         TABLE AX6.3-3 (cont'd).  RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:  GENERAL
                                                     PRACTITIONER/CLINIC VISITS
 Reference, Study
Location, & Period
Outcomes, Design, & Methods
  Mean Levels &
Monitoring Stations
Copollutants
Correlations
                Effects:
Relative Risk & Confidence Intervals (95%)
           EUROPE
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           Hajatetal. (1999)
           London, United
           Kingdom

           Period of Study:  1992-
           1994
                     Outcome (ICD9):  Asthma (493);
                     Lower respiratory disease (464, 466,
                     476, 480-3, 490-2, 485-7, 4994-6,
                     500,503-5,510-5)
                     Age groups analyzed: 0-14; 15-64;
                     65+; all ages
                     Study Design: Time series analysis
                     Statistical Analysis:  Poisson
                     regression, APHEA protocol
                     Covariates: long-term trends,
                     seasonality, day of wk, temperature,
                     humidity
                     Seasons: Warm, Apr-Sep; Cool,
                     Oct-Mar; All yr
                     Dose-response investigated?  Yes
                     Statistical package: SAS
                     Lag: 0-3 days, cumulative
                               Allyr24-havg:
                               33.6 ppb, SD = 10.5

                               Warm: 32.8(19.8)
                               Cool: 34.5(10.1)

                               10th-90th all yr
                               percentile: 24 ppb
                     SO2;r = 0.61      Increment: 24 ppb (90th-10th percentile)
                     BS; r = 0.70       Asthma
                     CO; r = 0.72      All ages 2.1% [-0.7, 4.9] lag 0; 3.1% [-0.4, 6.7] lag 0-1
                     PM10;r= 0.73     0-14 yrs 6.1% [1.2, 11.3] lag 1; 6.9% [1.7, 12.4] lag 0-1
                     03;r=-0.10        Warm:  13.2% [5.6, 21.3] lag 1
                                        Cool: -0.1% [-6.3, 6.5] lag 1
                                      15-64 yrs 3.0% [-0.7, 6.7] lag 0; 3.1% [-1.6, 7.9] lag 0-3
                                        Warm:  3.3% [-2.0, 8.9] lag 0
                                        Cool: 2.6% [-2.3, 7.7] lag 0
                                      65+ yrs 9.9% [1.6, 18.7] lag 2; 5.3% [-3, 14.3] lag 0-3
                                        Warm:  18.6% [6.3, 32.4] lag 2
                                        Cool: -0.5%-9.6, 11.8] lag 2
                                      Lower Respiratory disease
                                      All ages 1.3% [-0.4, 3.0] lag 1; 1.2% [-0.7, 3.1] lag 0-2
                                      0-14 yrs 4.8% [1.3, 8.3] lag 2; 4.5% [0.4, 8.7] lag 0-3
                                        Warm:  1.4% [-3.8, 6.9] lag 2
                                        Cool: 7.2% [2.8, 11.6] lag 2
                                      15-64 yrs 1.1% [-1.1, 3.4] lag 2; 0.8% [-1.8, 3.5] lag 0-2
                                        Warm:  2.3% [-1.2, 5.9] lag 2
                                        Cool: 0.2% [-2.6, 3.1] lag 2
                                      65+-1.7% [-4.3, 1.1] lag 0
                                        Warm:  -1.7% [-5.9, 2.6] lag 0
                                        Cool: -1.6% [-4.8,1.8]lagO
                                      Two-pollutant model-Asthma
                                      NO2 alone 5.2% [0.8, 9.8]
                                      N02/03 6.7% [2.2, 11.4]
                                      N02/S023.9%[-1.2, 9.2]
                                      N02/PM10 5.3% [-0.6, 11.6]
                                      Two-pollutant model - Lower Respiratory disease
                                      NO2 alone 4.2% [1.1, 7.3]
                                      NO2/O34.9%[1.8, 8.2]
                                      NO2/SO22.5%[-1.1,6.2]
                                      NO2/PM103.5%[0.1,6.9]

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        TABLE AX6.3-3 (cont'd).  RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:  GENERAL
                                                    PRACTITIONER/CLINIC VISITS
 Reference, Study
Location, & Period
Outcomes, Design, & Methods
  Mean Levels &
Monitoring Stations
Copollutants
Correlations
                Effects:
Relative Risk & Confidence Intervals (95%)
           EUROPE (cont'd)
                Increment: 24 ppb (90th-10th percentile)

                Single-pollutant model
                <1 to 14 yrs
                11.0% [3.8, 18.8] lag 4
                12.6% [4.6, 21.3] lag 0-4
                15 to 64 yrs
                5.5% [2.0, 9.1] lag 6
                11.1% [6.8, 15.6] lag 0-6
                >64 yrs - too small for analysis

                Two-pollutant models
                <1 to 14 yrs
                N02&03: 7.9% [0.6, 15.8]
                N02&S02: -3.8% [11.8, 5.0]
                N02&PM10:  10.8% [0.1, 22.7]
                15 to 64 yrs
                N02&03: 4.8% [1.0, 8.8]
                NO2&SO2: 1.0% [-3.7, 5.8]
                NO2 & PM10: 0.5% [-4.9, 6.3]
 X
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 ON
 OO
           Hajat*etal. (2001)
           London, United
           Kingdom

           Period of Study:
           1992-1994
                     Outcome (ICD9):  Allergic Rhinitis
                     (477)
                     Age groups analyzed: 0-14; 15-64;
                     65+; all ages
                     Study Design:  Time series analysis
                     N: 4,214
                     Statistical Analysis:  Poisson regression,
                     GAM
                     Covariates: long-term trends,
                     seasonality, day of wk, temperature,
                     humidity, variation in practice
                     population, counts for lagged allergic
                     pollen measures, daily number of
                     consultations for influenza
                     Dose-response investigated? Yes
                     Statistical package: S-Plus
                     Lag: 0-6 days, cumulative
                                 NO224-havg: 33.6 ppb,
                                 SD=10.5

                                 # of Stations: 3;
                                 r = 0.7-0.96
                      SO2;r=0.61
                      BS;r=0.70
                      CO; r = 0.72
                      PM10; r = 0.73
                      O3;r=-0.10
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        TABLE AX6.3-2 (cont'd). RESPIRATORY HEALTH EFFECTS OF OXIDES OF NITROGEN:  GENERAL
                                                     PRACTITIONER/CLINIC VISITS
 Reference, Study
Location, & Period
                                     Outcomes, Design, & Methods
  Mean Levels &
Monitoring Stations
Copollutants
Correlations
                Effects:
Relative Risk & Confidence Intervals (95%)
           EUROPE (cont'd)
 X
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           Hajat*etal. (2002)
           London, United
           Kingdom

           Period of Study: 1992-
           1994
                     Outcome (ICD9): Upper Respiratory
                     Disease, excluding Rhinitis (460-3,465,
                     470-5, 478)
                     Age groups analyzed:  0-14; 15-64;
                     65+; all ages
                     Study Design: Time series analysis
                     Statistical Analysis:  Poisson regression,
                     GAM
                     Covariates: long term trends,
                     seasonality, day of wk, holidays,
                     temperature, humidity, variation in
                     practice population,  counts for lagged
                     allergic pollen measures, daily number
                     of consultations for influenza
                     Seasons: Warm, Apr-Sep; Cool
                     Oct-Mar
                     Dose-response investigated? Yes
                     Statistical package:  S-Plus
                     Lag: 0,1,2,3 days
                                                                      NO224havg:  33.6 ppb,
                                                                      SD=10.5
                                                                      Warm (April-Sept)
                                                                      Mean: 32.8 ppb,
                                                                      SD= 10.1

                                                                      Cool (Oct-March)
                                                                      Mean: 34.5 ppb,
                                                                      SD=10.1

                                                                      # of Stations:  3
                      SO2;r=0.61
                      BS;r=0.70
                      CO; r = 0.72
                      PM10; r = 0.73
                      O3;r=-0.10
                Increment (90th-10th percentile): All yr: 24 ppb; Warm
                season: 25.8 ppb; Cool season: 22.1 ppb

                Single-pollutant model
                Allyr
                0-14 yr 2.0% [-0.3, 4.3] lag 3
                15-64 yrs 5.1% [2.0, 8.3] lag 2
                >65 yrs 8.7% [3.8, 13.8] lag 2

                Warm
                0-14 yrs 2.5% [-0.9, 6.1] lag 3
                15-64 yrs 6.7% [3.7, 9.8] lag 2
                >65 yrs 6.6% [-1.1, 14.9] lag 2
                Cool
                0-14 yrs 1.7% [-1.1, 4.6] lag 3
                15-64 yrs 1.2% [-1.3, 3.9] lag 2
                >65 yrs 9.4% [2.8, 16.4] lag 2

                Two-pollutant models
                0-14 yrs
                N02&03:  1.7% [-0.6, 3.9]
                N02&S02:  2.2% [-0.4, 5.0]
                NO2&PM10: 1.5% [-1.7, 4.8]
                For 15-64 yrs
                N02 & 03: 4.4% [2.2, 6.8]
                NO2&SO2:  4.4% [1.6, 7.2]
                NO2 & PM10: 2.7% [-0.5, 5.9]
                For >65 yrs
                N02&03: 8.1% [3.0, 13.6]
                NO2&SO2:  8.6% [2.1,15.4]
                N02&PM10: 4.3% [-2.8, 11.8]
           * Default GAM
           + Did not report correction for over-dispersion
                                                                               NR: Not Reported
                                                                               APHEA: Air Pollution and Health: a European Approach

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 TABLE AX6.4-1. HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN:  CVD HOSPITAL ADMISSIONS AND
	VISITS: UNITED STATES AND CANADA	
                                                                                                 Effects: Relative Risk or Percent Change
                                                                                 Copollutants       & Confidence Intervals ([95% Lower,
                                                                                (Correlations)                    Upper])
 Reference, Study
Location, & Period
                                Outcomes, Design, & Methods
Mean Levels & Monitoring
         Stations
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          Burnett etal. (1997)*
          Metropolitan Toronto
          (Toronto, North York,
          East York, Etobicoke,
          Scarborough, York),
          Canada

          Study period:
          1992-1994, 388 days,
          summers only
                    Outcome(s) (ICD9): IHD
                    410-414; Cardiac Dysrhythmias
                    427; Heart failure 428. All
                    Cardiac 410-414, 427, 428.
                    Obtained from hospital discharge
                    data.
                    Population: 2.6 Million residents
                    Study design: Time series
                    Age groups analyzed: all
                    # Hospitals:  NR
                    Statistical analysis: relative risk
                    regression models, GAMs.
                    Covariates: adjusted for
                    long-term trends, seasonal and
                    subseasonal variation, day of the
                    wk, temperature, dew point
                    Seasons: summer only
                    Dose response:  Figures
                    presented
                    Statistical package: NR
                    Lag:  1-4 days	
                                                   NO2 daily 1-h max (ppb):      H+ (0.25)
                                                   Mean:  38.5                  SO4(0.34)
                                                   CV: 29                     TP(0.61)
                                                   Min: 12                     FP (0.45)
                                                   25thpercentile:  31            CP(0.61)
                                                   SOthpercentile:  38            COH (0.61)
                                                   75thpercentile:  45            O3 (0.07)
                                                   Max: 81                     SO2(0.46)
                                                                               CO (0.25)
                                                   # of Stations:  6-11

                                                   (Results are reported for
                                                   additional metrics including
                                                   24 h avg and daytime avg
                                                   (day))
                                             Results reported for RR for an IQR increment
                                             increase in NO2. T ratio in parentheses.

                                             All Cardiac Disease
                                             Single-pollutant model
                                             1.049 (3.13), daily avg over 4 days, lag 0

                                             Multipollutant model
                                             1.30 (1.68), w/NO2,O3,SO2,

                                             Objective of study was to evaluate the role of
                                             particle size and chemistry on cardio and
                                             respiratory diseases. NO2 attenuated the
                                             effect of paniculate in this study.

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 TABLE AX6.4-1 (cont'd).  HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN:  CVD HOSPITAL ADMISSIONS
	AND VISITS: UNITED STATES AND CANADA	
                                                                                                    Effects: Relative Risk or Percent Change
                                                                                   Copollutants      & Confidence Intervals ([95% Lower,
                                                                                   (Correlations)                    Upper])
 Reference, Study
Location, & Period
                                Outcomes, Design, & Methods
Mean Levels & Monitoring
         Stations
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          Burnett etal. (1999)*
          Metropolitan Toronto
          (Toronto, North York,
          East York, Etobicoke,
          Scarborough, York),
          Canada

          Study Period:
          1980-1995, 15 yr
                     Outcome(s) (ICD9): IHD
                     410-414; Cardiac Dysrhythmias
                     427; Heart failure 428; All
                     Cardiac 410-414, 427, 428;
                     Cerebrovascular Disease
                     Obtained from hospital discharge
                     data 430-438; Peripheral
                     Circulation Disease 440-459.
                     Population: 2.13-2.42 million
                     residents
                     Study Design: Time series
                     Statistical Analysis:  GAMs to
                     estimate log RR per unit changes,
                     stepwise regression used to select
                     minimum number of air
                     pollutants in multipollutant
                     models.
                     Covariates: long-term trends,
                     seasonal variation, day of wk,
                     temperature, and humidity.
                     Statistical Package: SPLUS
                     Lag(s):  0-2 day
                                                   NO2 daily avg (ppb)
                                                   Mean: 25.2
                                                   Sthpercentile: 13
                                                   25thpercentile:  19
                                                   SOthpercentile:  24
                                                   75thpercentile:  30
                                                   95thpercentile:  42
                                                   Max: 82
                                                               Multiple day avgs used in
                                                               models
                           PM2.5 (0.50)
                           PMj 0-2.5 (0.38)
                           PM10 (0.52)
                           CO (0.55)
                           SO2 (0.55)
                           O3(-0.04)
Results reported for % increase in hospital
admissions for an increment increase in
NO2 equal to the mean value.

Single Pollutant Models:
Dysrhythmias: 5.33 (1.73) 3-day avg, lag 0
Heart Failure: 9.48 (6.33), 1 day, lagO
IHD: 9.73 (8.4) 2-day avg, lag 0
Cerebrovascular disease:  1.98 (1.34),
1 day, lag 0
Peripheral circulation: 3.57(1.78), 1-day,
lagO

Multipollutant Models:
Heart failure
6.89 (w/ CO)
6.68 (w/ CO, PM2 5)
6.33 (w/ CO, PM2.5, PMj 0-2.5)
6.45 (w/ CO, PM2.5, PMj 0-2.5, PM10)
IHD
8.34 (w/ CO, SO2)
7.76 (w/ CO, SO2, PM2 5)
8.41 (w/ CO, SO2, PM2.5, PMj0-2.5)
8.52 (w/ CO, SO2, PM2.5, PMj0-2.5, PM10)
In multipollutant models, gaseous
pollutants were selected by stepwise
regression. PM variables were then added
to the model.

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 TABLE AX6.4-1 (cont'd).  HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN:  CVD HOSPITAL ADMISSIONS
	AND VISITS:  UNITED STATES AND CANADA	
                                                                                                Effects: Relative Risk or Percent Change
                                                                                Copollutants      & Confidence Intervals ([95% Lower,
                                                                                (Correlations)                    Upper])
 Reference, Study
Location, & Period
                               Outcomes, Design, & Methods
Mean Levels & Monitoring
         Stations
 X
 to
          Morris etal. (1995)
          US (Chicago, Detroit,
          LA, Milwaukee,
          NYC, Philadelphia)

          Study Period:
          1986-1989, 4 yr
                     Outcome(s) (ICD9): CHF 428.
                     Daily Medicare hospital
                     admission records.
                     Study Design: Time series
                     Statistical Analyses: GLM,
                     negative binomial distribution
                     Age groups analyzed: >65yrs
                     Covariates: temperature,
                     indicator variables for mo to
                     adjust for weather effects and
                     seasonal trends, day of wk, yr
                     Statistical Software: S-PLUS
                     Lag(s): 0-7 day
                                                  NO21 h-max (ppb)
                                                  Mean (SD)
                                                  LA: 0.077(0.028)
                                                  Chicago: 0.045 (0.013)
                                                  Philadelphia: 0.054 (0.017)
                                                  New York: 0.064(0.022)
                                                  Detroit: 0.041  (0.015)
                                                  Houston: 0.041 (0.017)
                                                  Milwaukee: 0.040(0.014)
                           SO21-hmax
                           Os 1-h max
                           CO 1-hmax

                           Correlations of
                           NOa with other
                           pollutants strong.

                           Multipollutant
                           models run.
Results reported for RR of admission for
CHF associated with an incremental increase
in NO2 of 10 ppb.

CHF:
LA:  1.15(1.10, 1.19)
Chicago:  1.17(1.07, 1.27)
Philadelphia: 1.03(0.95,1.12)
New York:  1.07(1.02, 1.13)
Detroit: 1.04(0.92,1.18)
Houston:  0.99(0.88, 1.10)
Milwaukee: 1.05 (0.89, 1.23)

RR diminished in multipollutant models
(4 copollutants).
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 TABLE AX6.4-1 (cont'd). HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN:  CVD HOSPITAL ADMISSIONS
	AND VISITS:  UNITED STATES AND CANADA	
                                                                                                     Effects: Relative Risk or Percent Change
                                                                                                      & Confidence Intervals ([95% Lower,
                                                                                                                    Upper])
 Reference, Study
Location, & Period
                                      Outcomes, Design, & Methods
  Mean Levels &
Monitoring Stations
 Copollutants
(Correlations)
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           Wellenius et al.
           (2005a)
           Birmingham,
           Chicago, Cleveland,
           Detroit, Minneapolis,
           New Haven,
           Pittsburgh, Seattle

           Study Period: Jan
           1986-Nov 1999
           (varies slightly
           depending on city)
                       Outcome(s) IS, primary diagnosis of acute
                       but ill-defined cerebrovascular disease or
                       occlusion of the cerebral arteries; HS,
                       primary diagnosis of intracerebral
                       hemorrhage.  ICD codes not provided.
                       Hospital admissions ascertained from the
                       Centers for Medicare and Medicaid
                       Services. Cases determined from discharge
                       data were admitted from the ER to the
                       hospital.
                       NIS:  155,503
                       NHS: 19,314
                       Study Design: Time-stratified case
                       crossover.  Control days chosen such that
                       they fell in same mo and same day of wk.
                       Design controls for seasonality, time
                       trends, chronic and other slowly varying
                       potential confounders.
                       Statistical Analysis: 2-stage hierarchical
                       model (random effects), conditional
                       logistic regression for city effects in the
                       first stage
                       Software package:  SAS
                       Covariates:
                       Lag(s): 0-2, unconstrained distributed lags
                                                              N02 24 h (ppb)
                                                              10th: 13.71
                                                              25th: 18.05
                                                              Median: 23.54
                                                              75th: 29.98
                                                              90th: 36.54

                                                              NO2 data not
                                                              available for
                                                              Birmingham, Salt
                                                              Lake, and Seattle
                     PM10 (0.53)

                     CO, S02

                     Correlation only
                     provided for PM
                     because study
                     hypothesis
                     involves PM
                Results reported for percent increase in
                stroke admissions for an incremental
                increase in NO2 equivalent to one IQR
                (11.93).

                Ischemic Stroke:  2.94 (1.78, 4.12), lag 0
                Hemorrhagic Stroke: 0.38 (-2.66, 3.51),
                lagO

                Multipollutant models not run.

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 TABLE AX6.4-1 (cont'd).  HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN:  CVD HOSPITAL ADMISSIONS
	AND VISITS: UNITED STATES AND CANADA	
                                                                                                Effects: Relative Risk or Percent Change
                                                                                 Copollutants      & Confidence Intervals ([95% Lower,
                                                                                (Correlations)                  Upper])
 Reference, Study
Location, & Period
                                 Outcomes, Design, & Methods
  Mean Levels &
Monitoring Stations
          Fung et al. (2005)
          Windsor, Ontario,
          Canada

          Study Period:
          April 1995-Jan 2000
                     Outcome(s) (ICD9): CHF 428; IHD
                     410-414; dysrhythmias 427.  Hospital
                     admissions from Ontario Health
                     Insurance Plan records.
                     Study Design: Time series
                     Statistical Analysis: GLM
                     N: 11,632 cardiac admission, 4.4/day
                     for 65+ age group
                     Age groups analyzed: 65+, <65 yr
                     Statistical Software: SPLUS
                     Lag(s): lag 0, 2, 3 day avg
                                                      NO21-hmax (ppb):
                                                      Mean(SD):  38.9(12.3)
                                                      Min:  0
                                                      Max: 117
                      S02 (0.22)
                      CO (0.38)
                      O3 (0.26)
                      COH (0.39)
                      PM10 (0.33)
 X
Results expressed as percent change
associated with an incremental increase in
NO2 equivalent to the IQR (16 ppb)

Cardiac:
65+ age group:
0.8(2.2, 3.9), lag 0
0.9 (-2.7, 4.6), 2-day avg (lag 0-1)
0.8 (-3.3, 5.0), 3-day avg (lag 0-2)

Effect for NO2 not observed in these data.
Association of SO2 with cardiac admissions
observed.
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 TABLE AX6.4-1 (cont'd). HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN: CVD HOSPITAL ADMISSIONS
	AND VISITS:  UNITED STATES AND CANADA	
                                                                                                  Effects: Relative Risk or Percent Change
                                                                                 Copollutants       & Confidence Intervals ([95% Lower,
                                                                                 (Correlations)                    Upper])
 Reference, Study
Location, & Period
                                Outcomes, Design, & Methods
  Mean Levels &
Monitoring Stations
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Linn et al. (2000) *
Metropolitan Los
Angeles, USA

Study Period:
1992-1995
                     Outcome(s) (ICD9):  CVD
                     390-459; Cerebrovascular 430-
                     438; CHF 428; MI 410; cardiac
                     ARR 427; Occlusive Stroke 430-
                     435. Hospital admission records
                     used to ascertain cases.
                     Study Design:  Time series
                     Statistical Analyses:  Poisson
                     regression, GAM
                     Covariates: day of wk, holidays,
                     long-term trend, seasonal variation,
                     temperature, humidity
                     Lag(s):  0-1
                     Seasons: Winter, Spring, Summer,
                     Autumn
                     Statistical Software:  SPSS, SAS
                                                    NO2 24 h (pphm)

                                                    Winter
                                                    Mean: (SD) 3.4 (1.3)
                                                    Range: 1.1,9.1
                                                    Spring
                                                    Mean(SD): 2.8(0.9)
                                                    Range: 1.1,6.1
                                                    Summer
                                                    Mean(SD): 3.4(1.0)
                                                    Range: 0.7,6.7
                                                    Autumn
                                                    Mean(SD): 4.1(1.4)
                                                    Range: 1.6,8.4
                                                                                         CO (0.84, 0.92)
                                                                                         O3 (-0.23, 0.11)
                                                                                         PM10(- 0.67, 0.8)

                                                                                         Range in
                                                                                         correlations depends
                                                                                         on the season,
                                                                                         independent effects
                                                                                         of pollutants could
                                                                                         not be distinguished.

                                                                                         # Stations: 6+
                                           Results reported as increase % increase in
                                           admission for a 10 ppb increase in NO2.
                                           SD in parentheses. Season-specific
                                           increases reported when statistically
                                           significant.

                                           CVD
                                           All Seasons:  1.4(0.2)
                                           Winter:  1.6(0.4)
                                           Spring: 0.1 (0.6)
                                           Summer: 1.1 (0.5)
                                           Autumn:  1.4(0.3)
                                           Cerebrovascular
                                           All Seasons:  0.4(0.4)
                                           Winter:  -1.3(0.7)
                                           Spring: 4.2(1.2)
                                           Summer: 0.9 (1.2)
                                           Autumn:  0.7(0.6)
                                           MI
                                           1.1(0.5)
                                           CHF
                                           1.0(0.5), winter 1.9 (0.9)
                                           Cardiac Arrhythmia
                                           0.6 (0.5)
                                           Occlusive stroke
                                           2.0 (0.5), winter 2.7 (1.0), autumn 0.1
                                           (0.05)

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 TABLE AX6.4-1 (cont'd).  HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN:  CVD HOSPITAL ADMISSIONS
	AND VISITS: UNITED STATES AND CANADA	
                                                                                                    Effects:  Relative Risk or Percent Change
                                                                                   Copollutants       & Confidence Intervals ([95% Lower,
                                                                                   (Correlations)                   Upper])
 Reference, Study
Location, & Period
                                   Outcomes, Design, & Methods
   Mean Levels &
 Monitoring Stations
         Lippmann et al.
         (2000*; reanalysis Ito,
         2003, 2004)
         Windsor Ontario (near
         Detroit MI)

         Study period:
         1992-1994 (hospital
         admissions - mortality
         study spanned longer
         period)
                      Outcome(s): IHD 410-414;
                      dysrhythmias 427; heart failure 428;
                      stroke 431-437.
                      Study Design:  Time series
                      Statistical Analysis:  Poisson regression
                      GAM.  Results of reanalysis by Ito
                      2003, 2004 with GLM are presented.
                      Lag(s):  0-3 day
                                                          NO2 24-h avg (ppb)
                                                          5th %:  11
                                                          25th %: 16
                                                          50th %: 21
                                                          75th %: 26
                                                          95th %: 36
                                                          Mean:  21.3
                      PM10 (0.49)
                      PM25 (0.48)
                      PM10_2.5 (0.32)
                      H+(0.14)
                      SO4 (0.35)
                      03(0.14)
                      SO2 (0.53)
                      CO (0.68)
                  Results reported for RR for incremental
                  increase in NO2 of 5th to 95th percentile.

                  IHD
                  1.01(0.94, 1.10), lag 0
                  Dysrhythmias
                  0.98(0.86, 1.12)
                  Heart Failure
                  1 (0.91,  1.09)
                  Stroke
                  0.99 (0.90, 1.09)
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Mann et al. (2002)*
South coast air basin
ofCA,US

Study Period:
1988-1995, Syr
                     Outcome(s) IHD 410-414; or IHD with
                     accompanying diagnosis of CHF 428;
                     or Arrhythmia 426, 427; Ascertained
                     through health insurance records.
                     Study Design: Time series
                     N: 54,863 IHD admissions
                     Age groups analyzed: <40; 40-59;
                     >60.
                     Statistical Analysis:  Poisson regression
                     with GAM, results pooled across air
                     basins using inverse variance weighting
                     as no evidence of heterogeneity was
                     observed.
                     Covariates: study day, temperature,
                     relative humidity, day of wk.
                     Lag(s): 0-2, 2-4 day moving avg
                     Software:  SPLUS
                     Seasons:  Some analyses restricted to
                     April-October
NO2 24-h avg (ppb):
Exposure assigned for
each air basin based
on health insurance
participant's zip code.

Mean(SD): 37.2
(15.7)
Range: 3.69,  138
Median: 34.8

# Stations: 25-35
O3 8 h-max
(-0.16,0.54)
CO 8-h max
(0.64, 0.86)
PM10 24-h avg
(0.36, 0.60)

Range depends
on air basin

No multipollutant
models run.
Traffic pollution
generally
implicated in
findings.
Results reported for percent increase in
admissions for a 10 ppb incremental increase
inNO2.

All IHD
1.68(1.08,2.28)
IHD w/ secondary diagnosis of Arrhythmia:
1.81(0.78,2.85)
IHD w/ secondary diagnosis of CHF:
2.32 (0.69, 3.98)
IHD w/ no secondary diagnosis:
0.46 (-0.81, 1.74)

Effect of secondary diagnosis strongest in
the 40-59 age group.
Group with secondary CHF may be sensitive
subpopulation or their vulnerability may be
due to greater prevalence of MI as the
primary diagnosis.

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 TABLE AX6.4-1 (cont'd). HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN:  CVD HOSPITAL ADMISSIONS
	AND VISITS:  UNITED STATES AND CANADA	
                                                                                                   Effects: Relative Risk or Percent Change
                                                                                   Copollutants       & Confidence Intervals ([95% Lower,
                                                                                  (Correlations)                    Upper])
 Reference, Study
Location, & Period
                                 Outcomes, Design, & Methods
  Mean Levels &
Monitoring Stations
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         Metzger et al. (2004)
         Atlanta, GA

         Period of Study: Jan
         1993-Aug312000,
         4yr
                      Outcome(s):  IHD 410-414; AMI
                      410; Dysrhythmias 427; cardiac
                      arrest 427.5; congestive heart
                      failure 428; peripheral and
                      cerebrovascular disease 433-437,
                      440,443-444,451-453;
                      atherosclerosis 440; stroke 436.
                      ED visits from billing records.
                      N: 4,407,535 visits, 37 CVD
                      visits/day
                      # Hospitals:  31
                      Age groups analyzed: adults > 19,
                      elderly 56+
                      Statistical Analysis: Poisson
                      regression, GLM. Sensitivity
                      analyses using GEE and GAM
                      (strict convergence criteria)
                      Covariates: long-term trends,
                      mean and dew point temp, relative
                      humidity (cubic splines)
                      Statistical Software:  SAS
                      Season:  Warm, April 15-October
                      14; Cool, October 15-April 14.
                      Lag(s):  0-3 day
                                                      NO21-hmax (ppb):
                                                      Median:  26.3
                                                      10th-90thpercentile
                                                      range 25, 68
                       PM10 24 h (0.49)
                       O3 8-h max (0.42)
                       SO2 (0.34)
                       CO 1 h (0.68)

                       1998-2000 Only
                       PM25 (0.46)
                       Course PM (.46)
                       Ultrafine PM (.26)
                       Water-soluble
                       metals (.32)
                       Sulfates(.17)
                       OC (0.63)
                       EC (.37)
                       OHC (0.3)

                       Multipollutant
                       models used. All
                       models specified a
                       priori.
Results presented for RR of an incremental
increase inNO2 equivalent to 1 SD (3-day
moving avg).

All CVD:  1.025 (1.012, 1.039)
Dysrhythmia:  1.019 (0.994, 1.044)
CHF: 1.010 (0.981, 1.040)
IHD:  1.029 (1.005, 1.053)
PERI: 1.041 (1.013, 1.069)
Finger wounds 1.010 (0.993, 1.027)

NO2 effect was generally attenuated in
two-pollutant models. The attenuation was
strongest in the period after 1998.

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 TABLE AX6.4-1 (cont'd). HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN:  CVD HOSPITAL ADMISSIONS
	AND VISITS:  UNITED STATES AND CANADA	
                                                                                                  Effects: Relative Risk or Percent Change
                                                                                Copollutants       & Confidence Intervals ([95% Lower,
                                                                                (Correlations)                     Upper])
 Reference, Study
Location, & Period
                                Outcomes, Design, & Methods
  Mean Levels &
Monitoring Stations
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          Moolgavkar (2000b)*
          Cook County IL, Los
          Angeles County, CA,
          Maricopa County,
          AZ

          1987-1995
                     Outcome(s) (ICD9): CVD
                     390-429; Cerebrovascular disease
                     430-448. Hospital admissions
                     from CA department of health
                     database.
                     Age groups analyzed: 20-64, 65+
                     yrs
                     Study Design:  Time series
                     N: 118 CVD admissions/day
                     # Hospitals:  NR
                     Statistical Analysis:  Poisson
                     regression, GAM
                     Covariates: adjustment for day
                     of wk, long term temporal trends,
                     relative humidity, temperature
                     Statistical Package: SPLUS
                     Lag: 0-5 days
                                                   NO2 24-h avg (ppb)
                                                   Cook County:
                                                   Min: 7
                                                   Ql: 20
                                                   Median: 25
                                                   Q3: 30
                                                   Max:  58

                                                   NO2 24-h avg (ppb) LA
                                                   County:
                                                   Min:  10
                                                   Ql: 30
                                                   Median: 38
                                                   Q3: 48
                                                   Max:  102

                                                   NO2 24-h avg (ppb)
                                                   Maricopa County:
                                                   Min: 2
                                                   Ql: 14
                                                   Median: 19
                                                   Q3: 26
                                                   Max:  56
                       PM10 (0.22, 0.70)
                       PM25 (0.73) (LA
                       only)
                       CO (0.63, 0.80)
                       SO2 (0.02, 0.74)
                       O3(-0.23, 0.02)

                       Two-pollutant
                       models (see results)
Results reported for percent change in
hospital admissions per 10 ppb increase in
NO2. T statistic in parentheses.

CVD, 65+:
Cook County
2.9(10.2), lag 0
2.3 (6.7), lag 0, two-pollutant model (PM10)
2.9 (8.1), lag 0, two-pollutant model (CO)
2.8 (8.8), lag 0, two-pollutant model (SO2)
LA County
2.3(16.7), lag 0
-0.1  (-0.5), lag 0, two-pollutant model (CO)
1.7 (8.0), lag 0, two-pollutant model (SO2)
Maricopa County
2.9 (4.1), lag 0
-0.3  (-0.3), lag 0, two-pollutant model (CO)
2.6 (3.6), lag 0, two-pollutant model (SO2)

Cerebrovascular Disease, 65+:
Cook County
1.6(3.6)
LA County
(5.7)

Effect size generally diminished with
increasing lag time. Increase in hospital
admissions (1.3 for CVD and 1.9 for
Cerebrovascular) also observed for the
20-64 age group.	

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TABLE AX6.4-1 (cont'd). HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN: CVD HOSPITAL ADMISSIONS
                            AND VISITS: UNITED STATES AND CANADA
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Reference, Study
Location, & Period Outcomes, Design, & Methods
Moolgavkar (2003) Outcome(s) (ICD9): CVD
Cook County IL, Los 390-429; Cerebrovascular disease
Angeles County, CA, 430-448 was not considered in the
Maricopa County, reanalysis. Hospital admissions
AZ from CA department of health
database.
1987-1995 Age groups analyzed: 20-64,
£_ C_l_ ~Trc,
to+ yrs
Study Design: Time series
N: 118 CVD admissions/day
# Hospitals: NR
Statistical Analysis: Poisson
regression, GAM with strict
convergence criteria (10-8),
GLM using natural splines
Covariates: adjustment for day of
wk, long-term temporal trends,
relative humidity, temperature
Statistical Package: SPLUS
Lag: 0-5 days















Mean Levels & Copollutants
Monitoring Stations (Correlations)
NO2 24-h avg (ppb) PM10 (0.22, 0.70)
Cook County: PM25 (0.73) (LA only)
Min: 7 CO (0.63, 0.80)
Ql: 20 SO2 (0.02, 0.74)
Median: 25 O3 (-0.23, 0.02)
Q3: 30
Max: 58 Two-pollutant models
NO2 24-h avg (ppb) (see results)
LA County:
Min: 10
Ql: 30
Median: 38
Q3: 48
Max- 10?
IVAdA.. J.VJ £*
NO2 24-h avg (ppb)
Maricopa County:
Min: 2
Ql: 14
Median: 19
Q3: 26
Max: 56











Effects: Relative Risk or Percent Change
& Confidence Intervals ([95% Lower,
Upper])
Results for CVD not shown but use of
stringent criteria in GAM did not alter
results substantially. However, increased
smoothing of temporal trends attenuated
results for all gases.



























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 TABLE AX6.4-1 (cont'd).  HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN:  CVD HOSPITAL ADMISSIONS
	AND VISITS:  UNITED STATES AND CANADA	
                                                                                                 Effects: Relative Risk or Percent Change
                                                                                 Copollutants      & Confidence Intervals ([95% Lower,
                                                                                 (Correlations)                   Upper])
 Reference, Study
Location, & Period
                                 Outcomes, Design, & Methods
     Mean Levels &
  Monitoring Stations
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          Peel et al. (2006)
          Atlanta, GA

          Study Period:
          Jan 1993-Aug 2000
                    Outcome(s) (ICD9): IHD 410-414;
                    dysrhythmia 427; CHF 428;
                    peripheral vascular and
                    cerebrovascular disease 433-437,
                    440,443,444,451-453.
                    Computerized billing records for ED
                    visits.
                    Comorbid conditions: hypertension
                    401-405;  diabetes 250; dysrhythmia
                    427, CHF 428; atherosclerosis 440;
                    COPD 491, 492, 496; pneumonia
                    480-486; upper respiratory infection
                    460-465, 466.0; asthma 493, 786.09.
                    # Hospitals: 31
                    N: 4,407,535 visits
                    Study Design: case crossover. CVD
                    outcomes among susceptible groups
                    with Comorbid conditions.
                    Statistical Analyses: Conditional
                    logistic regression.
                    Covariates:  cubic splines for
                    temperature and humidity included
                    in models. Time independent
                    variables controlled through design.
                    Statistical Software: SAS
                    Lag(s): 3-day avg,  lagged 0-2 day
NO2l-hmax(ppb):
Mean(SD): 45.9(17.3)
10th: 25.0
90th: 68.0
PM10 24-h avg
Os 8-h max
SO2l-hmax
CO 1-hmax

Correlations not
reported
                                                                                                 Results expressed as OR for association of
                                                                                                 CVD admissions with a 20 ppb incremental
                                                                                                 increase in NO2.

                                                                                                 Comorbid Hypertension
                                                                                                 IHD:  1.036 (0.997, 1.076)
                                                                                                 Dysrhythmia: 1.095(1.030,1.165)
                                                                                                 PERI: 1.031(0.987, 1.076)
                                                                                                 CHF:  1.037 (0.985, 1.090)

                                                                                                 Comorbid Diabetes:
                                                                                                 IHD:  1.003 (0.95, 1.059)
                                                                                                 Dysrhythmia: 1.158(1.046,1.282)
                                                                                                 PERI: 1.012 (0.947, 1.082)
                                                                                                 CHF:  1.017 (0.959, 1.078)

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 TABLE AX6.4-1 (cont'd). HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN:  CVD HOSPITAL ADMISSIONS
	AND VISITS: UNITED STATES AND CANADA	
                                                                                                 Effects: Relative Risk or Percent Change
                                                                                 Copollutants       & Confidence Intervals ([95% Lower,
                                                                                (Correlations)                    Upper])
 Reference, Study
Location, & Period
                                 Outcomes, Design, & Methods
    Mean Levels &
  Monitoring Stations
          Schwartz, (1997) *
          Tuscon, AZ

          Study Period:
          Jan 1988-Dec 1990.
                     Outcome(s) (ICD9):  CVD 390-
                     429. Ascertained from hospital
                     discharge records.
                     Study Design: Time series
                     Statistical Analysis:  Poisson
                     regression, GAM
                     Age groups analyzed: 65+
                     Covariates: long-term and
                     seasonal trends, day of the wk,
                     temperature, dew point,
                     Statistical Software:  SPLUS
                                                     NO224-havg(ppb):
                                                     Mean: 19.3
                                                     10th: 9.9
                                                     25th: 13.2
                                                     50th: 19
                                                     75th: 24.6
                                                     90th: 29.8
                        PM10 (0.326)
                        O3(- 0.456)
                        S02 (0.482)
                        CO (0.673)
                   Results reported as a percent increase in
                   admission for an increment in NO2
                   equivalent to the IQR (11.4 ppb).

                   CVD 0.69% (-2.3, 3.8)
                   Tuscon selected to minimize correlations
                   between pollutants.  Since there was no
                   association between NO2 and admissions,
                   author suggests results for CO not
                   confounded by NO2.
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Stieb et al. (2000) *
Saint John, New
Brunswick Canada

Study Period: July
1992-March 1996
                    Outcome(s): Angina pectoris; MI;
                    dysrhythmia/conduction
                    disturbance; CHF; All Cardiac.
                    ED Visits collected prospectively.
                    Study Design: Time series
                    Statistical Analyses:  Poisson
                    regression, GAM
                    N:  19,821 ER visits
                    # Hospitals: 2
                    Lag(s):  1-8 days
NO2 24-h avg (ppb)
Mean(SD): 8.9(5.5)
95th:  19
Max:  35

NO2 max (ppb)
Mean(SD): 20.2
95th:  39
Max:  82
CO (0.68)
H2S(-0.07)
O3(-0.02)
SO2(0.41)
PM10 (0.35)
PM25 (0.35)
H+(-0.25)
SO4 (0.33)
COH (0.49)
Results reported for percent change in
admissions based on a single pollutant model
for incremental increase in NO2 equivalent
to 1 IQR (8.9 ppb)

Cardiac visits:
-3.9, p-value = 0.136, lag 2, allyr
10.1, p-value = 0.051, lag 5, May-September

For specific CVD diagnoses, ARR and CHF
approached significance. NO2 was not a
focus of this paper.	

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 TABLE AX6.4-1 (cont'd). HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN:  CVD HOSPITAL ADMISSIONS
	AND VISITS: UNITED STATES AND CANADA	
                                                                                                  Effects: Relative Risk or Percent Change
                                                                                Copollutants         & Confidence Intervals ([95% Lower,
                                                                               (Correlations)                     Upper])
 Reference, Study
Location, & Period
                                Outcomes, Design, & Methods
  Mean Levels &
Monitoring Stations
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          Villeneuve et al.
          (2006)
          Edmonton, Canada

          Study Period: April
          1992-March 2002
                     Outcome(s) (ICD9): Acute
                     ischemic stroke 434, 436;
                     hemorrhagic stroke 430, 432;
                     transient ischemic attach (TIA)
                     435; Other 433, 437, 438.  ED
                     visits supplied by Capital Health.
                     N: 12,422 Stroke Visits
                     Catchment area: 1.5 million
                     people
                     Study Design: case-crossover,
                     exposure index time compared to
                     referent time. Time-independent
                     variables controlled in the design.
                     Index and referent day matched by
                     day of wk.
                     Statistical Analysis: Conditional
                     logistic regression, stratified by
                     season and gender.
                     Covariates: temperature and
                     humidity
                     Statistical Software: SAS
                     Season: Warm: April-September;
                     Cool: October-March.
                     Lag(s):  0, 1, 3 day avg	
                                                    NO224hppb:
                                                    Allyr
                                                    Mean(SD): 24(9.8)
                                                    Median: 22.0
                                                    25th: 16.5
                                                    75th: 30.0
                                                    IQR: 13.5
                                                    Summer
                                                    Mean(SD): 18.6(6.4)
                                                    Median: 17.5
                                                    25th: 14.0
                                                    75th: 22.0
                                                    IQR: 8
                                                    Winter
                                                    Mean(SD): 29.4(9.6)
                                                    Median: 28.5
                                                    25th: 22.5
                                                    75th: 35.5
                                                    IQR: 13.0
                      O3 24-h max (-0.33)
                      O3 24-h avg (-0.51)
                      SO2 25-h avg (0.42)
                      CO 24-h avg (0.74)
                      PM10 24-h avg (0.34)
                      PM2 5 24-h avg (0.41)

                      All yr correlations
                      summarized.
Results reported for an incremental
increase in NO2 equivalent to one IQR
NO2.

Ischemic Stroke, Summer
.17(1.05,
.18(1.05,
.26(1.09,
Hemorrhagi
.16(0.99,
.14(0.97,
.18(0.95,
.31),lagO
.31),lagl
.46), 3 day avg
c stroke, Summer
.37)
.35)
.46)
                                             TIA not associated with increase in NO2.
                                             Above results are strongest effects, which
                                             were observed during summer.

                                             Authors attribute NO2 effect to vehicular
                                             traffic since NO2 and CO are highly
                                             correlated.

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 TABLE AX6.4-1 (cont'd). HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN:  CVD HOSPITAL ADMISSIONS
	AND VISITS:  UNITED STATES AND CANADA	
                                                                                                  Effects: Relative Risk or Percent Change
                                                                                 Copollutants       & Confidence Intervals ([95% Lower,
                                                                                 (Correlations)                     Upper])
 Reference, Study
Location, & Period
                                 Outcomes, Design, & Methods
  Mean Levels &
Monitoring Stations
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          Wellenius et al.
          (2005b)
          Allegheny County,
          PA (near Pittsburgh)

          Study Period: Jan
          1987-Nov 1999
                      Outcome(s): CHF428.  Cases are
                      Medicare patients admitted from
                      ER with discharge of CHF.
                      Study Design:  Case crossover,
                      control exposures same mo and
                      day of wk, controlling for season
                      by design.
                      Statistical Analysis:  Conditional
                      logistic regression
                      N: 55,019 admissions, including
                      repeat admissions, 86% admitted
                      <5 times
                      Age groups analyzed: 65+ yrs
                      (Medicare recipients)
                      Covariates: Temperature and
                      pressure. Effect modification by
                      age, gender, secondary diagnosis
                      arrhythmias, atrial fibrillation,
                      COPD, hypertension, type 2
                      diabetes, AMI within 30 days,
                      angina pectoris, IHD, acute
                      respiratory infection.
                      Statistical Software: SAS
                      Lag(s): 0-3
                                                     NO224-havg(ppb):
                                                     Mean (SD) 26.48 (8.02)
                                                     5th:  15.10
                                                     25th:  20.61
                                                     Median: 25.70
                                                     75th:  31.30
                                                     95th:  4102

                                                     # Stations: 2
                      PM10 (0.64)
                      CO (0.70)
                      O3(-0.04)
                      S02 (0.52)
Results reported for the percent increase in
admissions for an increment of NO2
equivalent to one IQR (11 ppb)

CHF, single-pollutant model
4.22(2.61,5.85), lag 0

CHF, two-pollutant model
4.05 (1.83, 6.31), adjusted for PM10
-0.37 (-2.59, 1.89), adjusted for CO
3.73 (2.10, 5.39), adjusted for O3
3.79 (1.93, 5.67), adjusted for SO2

CHF admission was 3 x higher among those
with history of MI.

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 TABLE AX6.4-1 (cont'd). HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN:  CVD HOSPITAL ADMISSIONS
	AND VISITS:  UNITED STATES AND CANADA	
                                                                                                         Effects: Relative Risk or Percent Change
                                                                                     Copollutants         & Confidence Intervals ([95% Lower,
                                                                                     (Correlations)                       Upper])
 Reference, Study
Location, & Period
                                   Outcomes, Design, & Methods
  Mean Levels &
Monitoring Stations
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           Zanobetti and
           Schwartz (2006)
           Boston, MA
           1995-1999
                       Outcome(s) (ICD9): MI 410.
                       Admissions through the emergency
                       room from Medicare claims.
                       Age group analyzed: 65+ yrs
                       Study Design: Case crossover,
                       control days matched yr, mo and
                       temperature
                       Statistical Analysis: Conditional
                       logistic regression
                       N: 15,578
                       Covariates: temperature
                       (regression spline), day of wk
                       Seasons:  Hot (April-September)
                       and cold
                       Software: SAS
                       Lags: 0,  0-1 previous day avg
                                                        NO2 24-h avg ppb
                                                        5th: 12.59
                                                        25th: 18.30
                                                        Median: 23.20
                                                        75th: 29.13
                                                        95th:
                                                        90th-10th: 20.41

                                                        # Stations: 4
                       Os (-0.14)
                       BC (0.70)
                       CO (0.67)
                       PM25 (0.55)
                       PM non-traffic (0.14)
                       (residuals from model
                       of PM2 5 regressed on
                       BC)
                                                                                                                   Results reported for percent increase in
                                                                                                                   admissions for incremental increase in NO2
                                                                                                                   equivalent to the 90th-1 Oth percentiles
                                                                                                                   (20.41 or 16.80 for 0-1, previous day avg).

                                                                                                                   MI
                                                                                                                   10.21(3.82, 15.61), lag 0
                                                                                                                   12.67 (5.82, 18.04), lag 0-1, previous
                                                                                                                   day avg

                                                                                                                   Results suggest traffic exposure is
                                                                                                                   responsible for the observed effect.  Effects
                                                                                                                   more pronounced in the summer season.
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           * Default GAM

           AMI Acute Myocardial
           Infarction
           ARR Arrhythmia
           BC Black Carbon
           COH coefficient of haze
           CP Course Particulate
                       CVD Cardiovascular Disease
                       EC Elemental Carbon
                       FP Fine Particulate
                       HS Hemorrhagic Stroke
                       ICD9 International Classification of Disease,
                       9th Revision
                       IHD Ischemic Heart Disease
                       IS ischemic stroke
                                                        MI Myocardial Infarction
                                                        OC Organic Carbon
                                                        OHC Oxygenated
                                                        Hydrocarbons
                                                        PERI Peripheral Vascular
                                                        and Cerebrovascular Disease
                                                        PM Particulate Matter
                      PIH primary intracerebral
                      hemorrhage
                      PNC Particle Number
                      Concentration
                      SHS Subarachnoid
                      hemorrhagic stroke
                      TP Total Particulate
                      UBRE Unbiased Risk
                      Estimator

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TABLE AX6.4-2. HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN: CVD HOSPITAL ADMISSIONS AND
                                        VISITS:  AUSTRALIA AND NEW ZEALAND
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Reference, Study
Location, & Period
Barnett et al. (2006)
Australia and New
Zealand: Brisbane,
Canberra, Melbourne,
Perth, Sydney
Outcomes, Design, & Methods
Outcome(s) (ICD9): All CVD
390-459; ARR 427; Cardiac
disease 390-429; Cardiac failure
428; IHD 410-413; MI 410;
Stroke 430-438.
Mean Levels &
Monitoring Stations
N02 (ppb)
1-havg: 15.7,23-2
24-havg: 7.1, 11.5
IQR: 5.1
Copollutants
(Correlations)
PM10 24 h
CO24h
S02 24 h
038h
BS24h
Effects: Relative Risk or Percent Change &
Confidence Intervals ([95% Lower, Upper])
Results reported for % change in hospital
admissions associated with one IQR increase in
NO2
Arrhythmia
          Period of Study:
          1998-2001
                   Ages groups analyzed:  15-64 yrs,
                   >65yrs
                   Study Design: Time stratified,
                   case-crossover, multicity study
                   # of Hospitals: A11ER
                   admissions from state government
                   health departments
                   Statistical Analyses: Random
                   effects meta analysis,
                   heterogeneity assessed using I2
                   statistic.
                   Covariates: Matched analysis
                   controlling for long-term trend,
                   seasonal variation and respiratory
                   epidemics. Temperature (current-
                   previous day) and relative
                   humidity,  pressure, extremes of
                   hot and cold, days of wk,
                   holidays, day after holiday,
                   rainfall in some models.  Matched
                   on copollutants.
                   Statistical Package:  SAS
                   Lag:  0-3
                                                               # of Stations:  1-13
                                                               depending on the city
Matched analysis
conducted to
control for
copollutants
>65: 0.4 (-1.8, 2.6)
15-64:  5.1(2.2,8.1)
Cardiac
>65: 3.4(1.9,4.9)
15-64:  2.2(0.9,3.4)
Cardiac failure
>65: 6.9(2.2, 11.8)
15-64:  4.6(0.1,6.1)
IHD
>65: 2.5(1.0,4.1)
15-64:  0.7 (-1.0, 2.4)
MI
>65: 4.4(1.0,8.0)
15-64:  1.7 (-1.1, 2.4)
All CVD
>65: 3.0(2.1,3.9)
15-64:  1.7(0.6,2.8)

NO2 association became smaller when matched
with CO. Authors hypothesize that NO2 is a
good surrogate for PM which may explain these
associations.

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TABLE AX6.4-2 (cont'd).  HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN:  CVD HOSPITAL ADMISSIONS AND
                                             VISITS:  AUSTRALIA AND NEW ZEALAND
  Reference, Study
 Location, & Period
Outcomes, Design, & Methods
                                                               Mean Levels & Monitoring
                                                                        Stations
 Copollutants      Effects: Relative Risk or Percent Change &
(Correlations)     Confidence Intervals ([95% Lower, Upper])
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          Simpson et al. (2005b)
          Australia (Brisbane,
          Melbourne, Perth,
          Sydney).

          Study Period:
          Jan 1996-Dec 1999
         Hinwood et al. (2006)
         Perth, Australia

         Study Period:
         1992-1998
                      Outcome(s) (ICD9):  Cardiac
                      disease 390-429; IHD 410-413;
                      stroke 430-438.
                      Study Design: Time series.
                      Statistical analysis:  APHEA2
                      protocol, GAM (did not indicate
                      use of stringent convergence
                      criteria), GLM with natural
                      splines, penalized splines.
                      Random effects meta-analysis
                      with tests for homogeneity.
                      Age groups analyzed: All, 15-64,
                      65+
                      Covariates: long-term trend,
                      temperature, humidity, day of
                      wk, holidays, influenza
                      epidemics
                      Software package: SPLUS, R
                      Lag(s):  1-3 days
                      Outcome(s): All CVD
                      unscheduled admissions.
                      Obtained from discharge records
                      using ICD9 Codes.
                      Age groups analyzed: all ages,
                      65+
                      Study design:  Case crossover,
                      time stratified with 3-4 controls
                      within same mo
                      Statistical Analysis:  conditional
                      logistic regression
                      N:  26.5 daily  CVD admissions
                      Seasons:  Nov-April, May-Oct
                               NO l-hmax(ppb):

                               Mean (range):
                               Brisbane: 21.4(2.1,63.3)
                               Sydney: 23.7(6.5,59.4)
                               Melbourne: 23.7 (4.4, 66.7)
                               Perth: 16.3 (1.9, 41.0)
                               NO2 24 h (ppb)
                               Mean:  10.3
                               SD: 5
                               lOthpercentile: 4.4
                               90thpercentile: 17.1
                               NO21-h max (ppb)
                               Mean:  24.8
                               SD: 10.1
                               lOthpercentile: 13.3
                               90thpercentile: 37.5

                               # of Stations:  3
                                                                                          PM10 24 h
                                                                                          PM25
                                                                                          BS 24 h (0.29, 0.62)
                                                                                          03lh
                                                                                          C08h

                                                                                          Not all correlations
                                                                                          reported. NO2 affect
                                                                                          attenuated slightly
                                                                                          when modeled with
                                                                                          BS but not with O3

                                                                                          May be confounding
                                                                                          of NO2 effect by
                                                                                          paniculate.
                                                                                          O3lh, 8h(-.06)
                                                                                          CO 8 h (.57)
                                                                                          BSP24h(.39)
                  Single-city results reported for percent increase
                  for an increment in 1-h max NO2 equivalent to
                  one IQR. Pooled results reported for an
                  increment of 1 ppb NO2.

                  Cardiac
                  All ages: 1.0023 (1.0016, 1.0030), lag 0-1
                  15-64: 1.0015 (1.0006, 1.0025), lagO
                  >65:  1.0018(1.0011, 1.0025), lag 0-1
                  IHD
                  All ages: 1.0019(1.0010,1.0027)
                  >65:  1.0017(1.0007, 1.0027)

                  No effect for stroke.

                  Heterogeneity in CVD results among cities,
                  probably due to different pollutant mixtures,
                  may have affected the results.

                  Results reported for OR per incremental
                  increase of 1 ppb NO2.

                  All CVD (estimated from graph)
                  NO2 24 h >65:  1.005 (1.001, 1.006), lag 1

                  NO2 8 h All ages: 1.0045 (1.0012, 1.0075),
                  lagl
                  NO2 8 h >65: 1.0036 (1.001, 1.0065), lag 1

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TABLE AX6.4-2 (cont'd). HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN: CVD HOSPITAL ADMISSIONS
                                      AND VISITS: AUSTRALIA AND NEW ZEALAND
 Reference, Study
Location, & Period
Outcomes, Design, & Methods
  Mean Levels &
Monitoring Stations
 Copollutants    Effects: Relative Risk or Percent Change &
(Correlations)    Confidence Intervals ([95% Lower, Upper])
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         Jalaludin et al. (2006)
         Sydney, Australia

         Period of Study:
         Jan 1997-Dec 2001
                     Outcome(s) (ICD9):  All CVD
                     390-459; cardiac disease 390-
                     429; IHD 410-413; and
                     cerebrovascular disease or stroke
                     430-438; Emergency room
                     attendances obtained from health
                     department data.
                     Age groups included: 65+
                     Study Design:  Time series,
                     multi-city APHEA2 Protocol.
                     Statistical Analysis:  GAM (with
                     appropriate convergence criteria)
                     and GLM Models. Only GLM
                     presented.
                     Lag: 0-3
                     Covariates: daily avg
                     temperature and daily relative,
                     humidity, long-term trends,
                     seasonality, weather, day of wk,
                     public school holidays, outliers
                     and influenza epidemics.
                     Dose response:  quartile analysis
                     Season:  Separate analyses for
                     warm (November-April) and cool
                     periods (May-October).
                              NO2l-havg
                              Mean:  32.2
                              SD: 7.4
                              Min: 5.2
                              Ql: 18.2
                              Median: 23
                              Q3: 27.5
                              Max: 59.4

                              # of Stations:  14
                       BS24-havg
                       (0.35)
                       PM1024-havg
                       (0.44)
                       PM2 5 24-h avg
                       (0.45)
                       CO8-havg
                       (0.55)
                       O3 1-havg
                       (0.45)
                       SO2 24-h avg
                       (0.56)

                       Two-pollutant
                       models to adjust
                       for copollutants
                Results reported for % change in hospital
                admissions associated with one IQR increase in
                24hNO2.

                All CVD
                2.32(1.45, 3.19), lag 0
                Cardiac Disease
                2.00(0.81, 3.20), lag 0
                IHD
                2.11(0.34, 3.91), lag 0
                Stroke
                -1.66 (-3.80, 0.51) lag 0

                Effect of NO2 attenuated when CO was
                included in the model. NO2 effect most
                prominent during the cool season.

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TABLE AX6.4-2 (cont'd). HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN:  CVD HOSPITAL ADMISSIONS
                                      AND VISITS:  AUSTRALIA AND NEW ZEALAND
  Reference, Study
 Location, & Period
Outcomes, Design, &
     Methods
  Mean Levels &
Monitoring Stations
 Copollutants       Effects:  Relative Risk or Percent Change &
(Correlations)      Confidence Intervals ([95% Lower, Upper])
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         Morgan etal. (1998a)
         Sydney, Australia

         Study Period:
         Jan 1990-Dec  1994
                       Outcome(s) (ICD9): Heart
                       Disease 410, 413, 427, 428.
                       Inpatient statistics database
                       for New South Wales Health
                       Department.
                       Study Design:  Time series
                       Statistical Analysis:  Poisson
                       regression, GEE
                       # Hospitals: 27
                       Covariates: daily mean
                       temperature, dew point
                       temperature
                       Lag(s): 0-2 days, cumulative
                       Statistical Software: SAS
                        NO224-havg(ppb):
                        Mean(SD):  15(6)
                        IQR: llppb
                        10th-90th: 17

                        NO21-hmax (ppb):
                        Mean(SD):  29(3)
                        10-90th:  29  ppb

                        NO224-hmax: 52
                        NO21-hmax:  139

                        # Stations: 3-14
                        (1990-1994)
                     O3 1-hmax (-0.086)
                     PM (0.533, 0.506)

                     Correlations for 24-h
                     avg NO2
                     concentrations

                     Multipollutant
                     models
                  Results reported as percent increase in
                  admissions associated with an incremental
                  increase in 1-h max NO2 equivalent to the
                  10th-90thpercentile.

                  Heart Disease:
                  6.71 (4.25, 9.23), single pollutant, lag 0, 1-h max
                  6.68 (3.61, 9.84), single pollutant, lag 0, 1-h max

                  Results lost precision but did not change
                  substantially when stratified by age or when 24-h
                  averaging time was used.
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TABLE AX6.4-2 (cont'd). HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN: CVD HOSPITAL ADMISSIONS
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AND VISITS: AUSTRALIA AND NEW ZEALAND
Reference, Study
Location, & Period
Petroeschevsky et al.
(2001)
Brisbane, Australia

Study Period:
Jan 1987-Dec 1994,
2,922 days














* Default GAM


AMI Acute Myocardial
Infarction
ARR Arrhythmia
BC Black Carbon
COH coefficient of haze
CP Course Particulate






Outcomes, Design, &
Methods
Outcome(s) (ICD9): CVD
390-459. Hospital
admissions, non-residents
excluded.
Study Design: Time series
Statistical Analyses: Poisson
regression, APHEA protocol,
linear regression and GEEs
Age groups analyzed: 15-64,
65+

Covariates: temperature,
humidity, rainfall. Long-term
trends, season, flu, day of wk,
holidays.
Statistical Software: SAS
Lag(s): lag 0-4, 3-day avg,
5-day avg





CVD Cardiovascular Disease
EC Elemental Carbon

FP Fine Particulate
HS Hemorrhagic Stroke
ICD9 International Classification of
Disease, 9th Revision
IHD Ischemic Heart Disease
IS ischemic stroke






Mean Levels &
Monitoring Stations
NO2 1-h max (pphm)
Summer
Mean: 206
Min: 0.35
Max: 5.8
Fall
Mean: 2.56
Min: 0.70
Max: 5.85

Winter
Mean: 3.54
Min: 0.35
Max: 8.05
Spring
Mean: 3.12
Min: 0.55
Max: 15.58
Overall
Mean: 2.82
Min: 0.35
Max: 15.58
MI Myocardial Infarction
OC Organic Carbon

OHC Oxygenated Hydrocarbons
PERI Peripheral Vascular and
Cerebrovascular Disease
PM Particulate Matter








Copollutants Effects: Relative Risk or Percent Change &
(Correlations) Confidence Intervals ([95% Lower, Upper])
BSP Results reported for RR for CVD emergency
O3 admissions associated with a one-unit increase
SO2 m NO2 1-h max.

Correlation between CVD 15-64 yrs
pollutants not 0.986 (0.968, 1.005), lag 3
reported.
CVD 65+ yrs
0.990 (0.977, 1.003)


CVD all ages
0.987 (0.976, 0.998)









PIH primary intracerebral hemorrhage
PNC Particle Number Concentration

SHS Subarachnoid hemorrhagic stroke
TP Total Particulate
UBRE Unbiased Risk Estimator










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TABLE AX6.4-3.  HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN:  CVD HOSPITAL ADMISSIONS AND
                                                             VISITS:  EUROPE
 Reference, Study
Location, & Period
Outcomes, Design, & Methods
Mean Levels & Monitoring
         Stations
 Copollutants        Effects: Relative Risk or Percent Change &
(Correlations)       Confidence Intervals ([95% Lower, Upper])
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           Ballester et al. (2006)
           Multi-city, Spain:
           Barcelona, Bilbao,
           Castellon, Gijon,
           Huelva, Madrid,
           Granada, Oviedo,
           Seville, Valencia,
           Zaragoza

           Period of Study:
           1995/1996-1999,
           N= 1,096 day
                     Outcome(s) (ICD9): All CVD
                     390-459; Heart diseases
                     410-414,427,428. Emergency
                     admission from hospital records.
                     Discharge data used.
                     Study Design: Time series, meta-
                     analysis to pool cities
                     N: daily mean admissions
                     reported by city
                     Statistical Analyses: Poisson
                     regression and GAM, with
                     stringent convergence criteria,
                     meta-analysis with fixed effect
                     model.  Tested linearity by
                     modeling pollutant in linear and
                     non-linear way (spline
                     smoothing).  Linear model
                     provided best results 55% of time
                     but used in all cases to facilitate
                     comparability.
                     Covariates:  temperature, humidity
                     and influenza, day of wk unusual
                     events, seasonal variation and
                     trend of the series
                     Seasons: Hot:  May to October;
                     Cold: November to April
                     Statistical Package:  SPLUS
                     Lag: 0-3
                              NO224-havg (ug/m2):
                              Mean: 51.5
                              lOthpercentile:  29.5
                              90th percentile:  74.4

                              # of Stations: Depends on the
                              city

                              Correlation among stations: NR
                            CO 8-h max (0.58)
                            O38-h max (-0.03)
                            SO2 24 h (0.46)
                            BS 24 h (0.48)
                            TSP 24 h (0.48)
                            PM10 24 h (0.40)

                            Two-pollutant models
                            used to adjust for
                            copollutants
                   Results reported for % change in hospital
                   admissions associated with 10 ug/m2 increase in
                   N02

                   All CVD
                   0.38% (0.07%, 0.69%), lag 0-1
                   Heart Diseases:
                   0.86% (0.44%, 1.28%)

                   Effect of NO2 was diminished in two-pollutant
                   models.

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TABLE AX6.4-3 (cont'd). HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN: CVD HOSPITAL ADMISSIONS
CJQ
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Reference, Study
Location, & Period Outcomes, Design, & Methods
Lanki et al. (2006) Outcome(s) (ICD9): AMI 410.
Europe (Augsburg, Ascertained from discharge
Helsinki, Rome, records or AMI registry data
Stockholm) depending on the city.
Study Design: Time series
Study period: Statistical Analysis: Poisson
1992-2000 regression, for non- linear
confounders - penalized splines
in GAM chosen to minimize
UBRE score. Random-effects
model for pooled estimates.
N: 26,854 hospitalizations
Statistical Software: R package
Covariates: barometric pressure,
temperature, humidity.
Lag(s): 0-3 day






















AND VISITS: EUROPE
Mean Levels & Monitoring Copollutants Effects: Relative Risk or Percent Change &
Stations (Correlations) Confidence Intervals ([95% Lower, Upper])
NO2(ug/m3) PM10 (0.29, 0.64) Results reported as RR associated with an
CO (0.43, 0.75) incremental increase in NO2 equivalent to the
Augsburg: O3 (0.17, 0.38) IQR (8 ug/m2)
25th: 40.2
50th: 49.2 Range in correlations Pooled results for 5 Cities:
75th: 58.9 depends on the city 0.996 (0.998, 1.015), lag 0
98th: 88.7
Barcelona Two-pollutant models No significant results observed for analyses
25th: 34.8 for PNC with O3 and stratified by age or season for lag 0/1 .
50th: 45.0 PM10only.
75th: 60.0
98th: 86.0
Helsinki
25th: 21.8
50th: 28.7
75th: 37.6
98th: 64.7
Rome
25th: 61.9
50th: 70.6
75th: 80.4
98th: 102.5
Stockholm
25th: 16.3
50th: 22.2
75th: 28.6
98th: 45.9











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TABLE AX6.4-3 (cont'd). HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN: CVD HOSPITAL ADMISSIONS

                                       AND VISITS: EUROPE
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Reference, Study
Location, & Period
Von Klot et al. (2005)
Europe (Augsburg,
Barcelona, Helsinki,
Rome, Stockholm)

Study Period:
1992-2000




























Outcomes, Design, & Methods
Outcome(s) (ICD9): Re-admission for AMI
410; angina pectoris 411 and 413; Cardiac
diseases including AMI angina pectoris,
dysrhythmia (427), heart failure (428).
Hospital admissions database used to identify
cases.

Population: Incident cases of MI during
1992-2000 among those >35 yrs old.
N Augsburg: 1560
N Barcelona: 1134
N Helsinki: 4026

NRome: 7384
N Stockholm: 7902
Study Design: Prospective Cohort
Statistical Analyses: Poisson regression, at
risk period from the 29th day after the index
event until the event of interest, death,
migration or loss to follow-up. GLM models,
penalized spline functions for continuous
confounders. City results pooled using
random-effects model. Heterogeneity
assessed. Sensitivity analyses conducted
varying the smooth functions, convergence
criteria, and how confounders were specified.
Statistical Software: R package
Covariates: daily mean temperature, dew
point temperature, barometric pressure,
relative humidity, vacations or holidays.
Lag: 0-3 days




Mean Levels &
Monitoring Stations
NO2 24-h avg (ug/m2):
Augsburg
Mean: 49.6
5th: 30
25th: 39.7
75th: 57.2
95th: 75.3

Barcelona
Mean: 47.7
5th: 18

25th: 34.0
75th: 60
95th: 83
Hel sinki
A/T^on- "30 1
IVlColl. JU.l
5th: 13
25th: 21.2
75th: 36.7
95th: 52.9
Rome
Mean: 15.8
5th: 5.4
25th: 10.1
75th: 21.7
95th: 25.9
Stockholm
Mean: 22.8
5th: 10.3
25th: 16
75th: 28
95th: 39.4
# Stations: 1-5
Effects: Relative Risk or Percent Change
Copollutants & Confidence Intervals ([95% Lower,
(Correlations) Upper])
CO 24 h (0.44, 0.75) Results reported for RR for incremental
O38h(-0.2,-0.13) increases in same day NO2 equivalent to the
PMin ( 29 66) mean of the city specific IQR's multiplied by
PNC ( 44 83) 0-05 (8 ug/m2). Pooled results are below:

Two-pollutant models "^
but N02, CO, and PNC 1 -028 (0.997, 1 .060)
not modeled together Angina Pectoris
because they were too 1.032 (1.006, 1.058)
highly correlated. Cardiac Diseases
1.032(1.014,1.051)


Two-pollutant models show that the effect of
NO2 independent of PM10 and O3. Traffic
exhaust may be associated with cardiac
readmission.



















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TABLE AX6.4-3 (cont'd).  HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN:  CVD HOSPITAL ADMISSIONS
                                                            AND VISITS: EUROPE
  Reference, Study
 Location, & Period
Outcomes, Design, & Methods
  Mean Levels &
Monitoring Stations
 Copollutants         Effects: Relative Risk or Percent Change &
(Correlations)        Confidence Intervals ([95% Lower, Upper])
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           Atkinson etal. (1999a)
           London, England

           Period of Study: 1992-
           1994,
           N= 1,096 day
                       Outcome(s) (ICD9): All CVD 390-
                       459; IHD 410-414. Emergency
                       admissions obtained from the
                       Hospital Episode Statistics (HES)
                       database.
                       Ages groups analyzed: 0-14 yr, 15-64
                       yr, 0-64 yr, 65+ yr, 65-74 yr, 75+ yr
                       Study Design: Time series, hospital
                       admission counts
                       N: 189,109 CVD admissions
                       Catchment area:  7 million residing in
                       1600 Km2 area of Thames basin.
                       Statistical Analyses: APHEA
                       protocol, Poisson regression
                       Covariates: adjusted long-term
                       seasonal patterns, day of wk,
                       influenza, temperature, humidity
                       (compared alternative methods for
                       modeling meteorological including
                       linear, quadradic, piece-wise, spline)
                       Seasons: warm season April-
                       September, cool season remaining
                       mos, interactions between season
                       investigated
                       Dose response investigated:  yes,
                       bubble charts presented
                       Statistical Package:  SAS
                       Lag:  0-3
                                l-hmax(ppb)
                                Mean:  50.3
                                SD:  17.0
                                Min: 22.0
                                Max:  224.3
                                10th-90thpercentile: 36

                                # of Stations:  3, results
                                averaged across stations

                                Correlation among
                                stations: 0.7-0.96
                       PM10 24 h
                       C024h
                       S02 24 h
                       O38h
                       BS24h

                       Correlations of NO2 with
                       CO, SO2, O3, BS ranged
                       from 0.6-0.7
                       Correlation of NO2 with
                       O3 negative

                       Two-pollutant models
                       used adjust for
                       copollutants
                   Results reported for % change in hospital
                   admissions associated with 10th-90th percentile
                   increase in NO2 (36 ppb)

                   All CVD
                   Ages 0-64: 1.20% (-0.62%, 3.05%), lag 0
                   Ages 65+:  1.68% (0.32%, 3.06%), lag 0

                   IHD
                   Ages 0-64: 1.53% (-1.22%, 4.37%), lag 0
                   Ages 65+:  3.03% (0.87%, 5.24), lag 0

                   NO2 was associated with increased CVD
                   admissions for all ages but this association was
                   stronger among those 65+ yrs old.  Similar
                   increase associated with IHD among those 65+ yrs
                   old.

                   Monitors close to roadways were not used in the
                   study.  Correlations for NO2 between urban
                   monitoring sites were high. Authors suggest that
                   the pollution levels are uniform across the study
                   area. Authors did not investigate the interaction
                   between meteorological variables and air
                   pollution.  In two pollutant models, O3 had little
                   impact on NO2. BS moderated the association of
                   NO2 with CVD among the 65+ age group.
                   Suggestion that NO2 associations were non-linear.

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 TABLE AX6.4-3 (cont'd). HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN:  CVD HOSPITAL ADMISSIONS
	AND VISITS: EUROPE	
                                                                                                  Effects:  Relative Risk or Percent Change
                                                                                 Copollutants        & Confidence Intervals ([95% Lower,
                                                                                (Correlations)                     Upper])
 Reference, Study
Location, & Period
                                  Outcomes, Design, & Methods
  Mean Levels &
Monitoring Stations
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          Ballesteretal. (2001)*
          Valencia, Spain

          Period of Study:
          1992-1996
                       Outcome(s) (ICD9):  All CVD
                       390-459; heart diseases 390-459;
                       cerebrovascular diseases 430-438.
                       Admissions from city registry -
                       discharge codes used.
                       Study Design: Time series
                       N:  1080 CVD admissions
                       # of Hospitals: 2
                       Catchment area: 376,681
                       inhabitants of Urban Valencia
                       Statistical Analyses:  Poisson
                       regression, GAM, APHEA/
                       Spanish EMECAM protocol.
                       Both Linear and non parametric
                       model, including a loess term was
                       fitted, departure from linearity
                       assess by comparing deviance of
                       both models.
                       Covariates:  long-term trend and
                       seasonality, temperature and
                       humidity, wk days, flu, special
                       events, air pollution.
                       Seasons: Hot season May to Oct.;
                       Cold season Nov to April

                       Statistical Package: SAS
                       Lag: 0-4	
                                                     1-hmax (ug/m)
                                                     Mean:  116.1
                                                     SD: NR
                                                     Min: 21.1
                                                     Max: 469.0
                                                     median: 113.2

                                                     # of Stations: 14
                                                     manual, 5 automatic

                                                     Correlation among
                                                     stations: 0.3-0.62 for
                                                     BS, 0.46-0.78 for
                                                     gaseous pollutants
                     CO 24 h (0.03)
                     SO224h(0.33)
                     O38h(-0.26)
                     BS(0.33)
                                                                                       Two-pollutant models
                                                                                       used to adjust for
                                                                                       copollutants
Results reported for RR corresponding to a
10 ug/m2 increase inNO2

All CVD
1.0302 (1.0042, 1.0568), lagO
Heart Disease
1.0085 (0.9984, 1.0188), lag 2
Cerebrovascular Disease
1.0362(1.0066, 1.0667), lag 4

Clear association of NO2 with
cerebrovascular disease observed.
Association persisted after Inclusion of BS
and SO2 in two-pollutant models with NO2.

Cases of digestive disorders served as a
control group - null association with NO2
observed.

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 TABLE AX6.4-3 (cont'd).  HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN:  CVD HOSPITAL ADMISSIONS
	AND VISITS:  EUROPE	
                                                                                                   Effects: Relative Risk or Percent Change
                                                                                  Copollutants        & Confidence Intervals ([95% Lower,
                                                                                 (Correlations)                     Upper])
 Reference, Study
Location, & Period
                                  Outcomes, Design, & Methods
  Mean Levels &
Monitoring Stations
 X
          D'Ippolitietal.
          (2003)
          Rome, Italy

          Study Period: Jan
          1995- June 1997
                      Outcome(s) (ICD): AMI 410 (first
                      episode).  Computerized hospital
                      admission data.
                      Study Design: Case crossover, time
                      stratified, control days within same
                      mo falling on the same day.
                      Statistical Analyses: Conditional
                      logistic regression, examined
                      homogeneity across co-morbidity
                      categories
                      N: 6531 cases
                      Age groups analyzed:  18-64 yrs,
                      65-74 yrs, >75
                      Season:  Cool: October-March;
                      Warm:  April-September.
                      Lag(s): 0-4 day, 0-2 day cum avg
                      Dose Response: OR for increasing
                      quartiles presented and p-value for
                      trend.
                                                       NO2 24 h (ug/m3)
                                                       Mean(SD): 86.4(15.8)
                                                       25th: 74.9
                                                       50th: 86.0
                                                       75th: 96.9
                                                       IQR: 22

                                                       # Stations: 5
                      TSP 24 h (0.37)
                      SO224h(0.31)
                      CO 24 h (0.03)

                      No multipollutant
                      models
Results presented for OR associated with
incremental increase in NO2 equivalent to
one IQR.

AMI
1.026(1.002, 1.052), lag 0
1.026(0.997, 1.057), lag 0-2

Association observed for NO2 but TSP
association more consistent. Authors think
that TSP, CO, and NO2 cannot be
distinguished from traffic-related pollution
in general.
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          Llorca et al. (2005)
          Torrelavega, Spain

          Study period:
          1992-1995
                      Outcome(s) (ICD): CVD (called
                      cardiac in paper) 390-459.
                      Emergency admissions, excluding
                      non residents.  Obtained admissions
                      records from hospital admin office.
                      Study design:  Time series
                      Statistical analyses:  Poisson
                      regression, APHEA protocol
                      Covariates: rainfall, temperature,
                      wind speed direction
                      N: 18,137 admissions
                      Statistical software:  STATA
                      Lag(s): not reported	
                                                       NO2 24 h ug/m3:
                                                       Mean(SD): 21.3(16.5)
                      TSP (-0.12)
                      SO2 (0.588)
                      SH2 (0.545)
                      NO (0.855)

                      Multipollutant
                      models
Results reported for RR of hospital
admissions for 100 ug/m3 increase inNO2.

Cardiac admissions:
1.27 (1.14, 1.42), 1-pollutant model
1.10 (0.92, 1.32), 5-pollutant model
                                                                                                            Effect of NO2 diminished in multipollutant
                                                                                                            model.

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 TABLE AX6.4-3 (cont'd).  HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN: CVD HOSPITAL ADMISSIONS
	AND VISITS:  EUROPE	
                                                                                                    Effects: Relative Risk or Percent Change &
                                                                                                        Confidence Intervals ([95% Lower,
                                                                                                                   Upper])
Reference, Study Location,
       & Period
                                        Outcomes, Design, & Methods
  Mean Levels &
Monitoring Stations
 Copollutants
(Correlations)
 X
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          Pantazopoulou et al.
          (1995)
          Athens, Greece

          Study Period: 1988
          (Winter and Summer)
          Poloniecki et al. (1997)
          London, UK

          Study Period:
          April 1987-March 1994,
          7yrs
                         Outcome(s):  Cardiac Disease ICD
                         codes not provided. Cases ascertained
                         from National Center for Emergency
                         Service database. Cases diagnosed at
                         time of admission so they are ED visits
                         and were not necessarily admitted to the
                         hospital.
                         Study design: Time series
                         Statistical Analyses: Linear regression
                         (not well described)
                         Covariates:  Dummy variables for
                         winter mos with January as referent.
                         Dummy variables for summer mos with
                         April as referent. Day of the wk,
                         holidays, temperature, relative humidity,
                         N: 25,027 cardiac admissions.
                         Lag(s): NR
                         Outcome(s):  All CVD 390-459; MI
                         410; Angina pectoris 413; other IHD
                         414; ARR 427; congestive heart failure
                         428; cerebrovascular disease 430-438.
                         Hospital Episode Statistics (HES) data
                         on emergency hospital admissions.
                         Study Design: Time series
                         N: 373, 556 CVD admissions
                         Statistical Analyses: Poisson regression
                         with GAM, APHEA protocol
                         Covariates:  long term trends, seasonal
                         variation, day of wk, influenza,
                         temperature and humidity.
                         Season:  Warm, April-September; Cool,
                         October-March.
                         Lag: 0-1 day
                                                              NO21-h max (ug/m3):
                                                              Winter
                                                              Mean(SD): 94(25)
                                                              5th:  59
                                                              50th:  93
                                                              95th:  135

                                                              Summer
                                                              Mean(SD): 111(32)
                                                              5th:  65
                                                              50th:  108
                                                              95th:  173

                                                              # Stations: 2
                                                              NO224hppb:
                                                              Min: 8
                                                              10%: 23
                                                              Median: 35
                                                              90%: 53
                                                              Max: 198
                    CO,BS
                    No correlations
                    provided
                    Black Smoke
                    CO24h
                    SO2 24 h
                    O38h

                    Correlations
                    between
                    pollutants high
                    but not
                    specified.
               Results reported for regression coefficients
               based on an incremental increase in NO2 of
               76 ug/m3 in winter and 108 ug/m3 in
               summer (5th to 95th percentile).

               Winter (regression coefficient)
               11.2(3.3, 19.2)

               Summer (regression coefficient)
               -0.06 (-6.6, 6.5)
               Results expressed as a relative rate (RR)
               for an incremental increase of NO2
               equivalent to 30 ppb (10th-90th percentile)

               AMI:  1.0274 (1.0084, 1.0479)
               Angina Pectoris:  1.0212(0.9950, 1.0457)
               Other IHD:  0.99(0.0067,1.0289)
               Cardiac ARR:  1.0274(1.0006,1.0984)
               HeartFailure:  0.9970(0.9769, 1.0194)
               Cerebrovascular Disease:  0.9851 (0.9684,
               1.0045)
               Other Circulatory: 1.0182 (1.0000,
               1.0398)
               All CVD: 1.0243(1.0054,1.0448)
               No attenuation of NO2 association with MI
               in two-pollutant model (cool season).	

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 TABLE AX6.4-3 (cont'd). HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN:  CVD HOSPITAL ADMISSIONS
	AND VISITS:  EUROPE	
                                                                                                   Effects: Relative Risk or Percent Change
                                                                                                     & Confidence Intervals ([95% Lower,
                                                                                                                   Upper])
 Reference, Study
Location, & Period
                                    Outcomes, Design, & Methods
  Mean Levels &
Monitoring Stations
 Copollutants
(Correlations)
 X
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          Ponka and Virtanen
          (1996)
          Helsinki, Finland

          Study Period:
          1987-1989, 3 yrs
                      Outcome(s) (ICD9):  IHD 410-414; MI
                      410; TIA411; Cerebrovascular diseases
                      430-438; Cerebral ischemia due to
                      occlusion of extracerebral vessels 433;
                      Cerebral ischemia due to occlusion of
                      cerebral vessels 434; Transient ischemic
                      cerebral attack 43 5. Case ascertainment
                      was for both emergency admission and
                      hospital admissions - done via registry
                      system.
                      Study Design:  Time series
                      Statistical Analyses:  Poisson
                      regression, pollutant concentrations log
                      transformed
                      N:  12,664 all IHD admissions; 7005
                      IHD ED admissions; 7232
                      cerebrovascular hospital admissions;
                      3737 cerebrovascular ED admissions.
                      Covariates: weather, day of wk, long-
                      term trends, influenza
                      Lag(s):  1-7 days
                                                          NO2 8 h (ug/m3)
                                                          Mean(SD): 39(16.2)
                                                          Range: 4, 170

                                                          NO 8 h ug/m3
                                                          Mean(SD): 91(61)
                                                          Range: 7,467

                                                          # Stations: 2
                      SO28h
                      NO8h
                      TSPSh
                      O38h

                      NO2 highly
                      correlated with
                      SO, and TSP
                Results reported are regression coefficients
                and standard errors (SE).

                NO2 with ED admissions for transient short
                term ischemic attack
                -0.056(0.105), p = 0.59, lag 1
                NO2 with ED admissions for
                cerebrovascular disease
                -0.025 (0.057), p = 0.657, lag 1
                NO with IHD, all admissions
                0.097 0.023,p<0.00l,lagl
                NO with IHD, ED admissions
                O.lll(0.030),p<0.00l,lagl

                Significant increase  in admissions for
                transient short-term ischemic attack and
                cerebrovascular diseases for lag 6
                associated with NO2 exposure.
          Prescott et al. (1998) *  Outcome(s) (ICD9):  Cardiac and
          Edinburgh, UK

          Study period: Oct
          1992-June 1995
                      cerebral ischemia 410-414, 426-429,
                      434-440. Extracted from Scottish
                      record linkage system.
                      Study Design: Time series
                      Statistical Analysis:  Poisson, log linear
                      regression models
                      Age groups analyzed: <65, 65+yrs
                      Covariates:  seasonal and wkday
                      variation, temperature, and wind speed.
                      Lag(s):  0, 1, 3 day moving avg
                                                          N02 24 h (ppb)
                                                          Mean(SD): 26.4(7.0)
                                                          Range: 9,58
                                                          IQR:  10 ppb
                      03, 24 h
                      PM, 24 h
                      S02, 24 h
                      CO, 24 h

                      Correlations not
                      reported.
                Results reported for percent change in
                admissions based on an incremental
                increase in NO2 equivalent to the IQR of
                10 ppb.

                <65 yrs, CVD admissions
                -0.05 (-5.2, 4.5), 3 day moving avg
                65+ yrs, CVD admissions
                -0.9 (-8.2, 7.0), 3 day moving avg

                Data for lag 1  not presented

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 TABLE AX6.4-3 (cont'd). HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN:  CVD HOSPITAL ADMISSIONS
	AND VISITS: EUROPE	
                                                                                                         Effects: Relative Risk or Percent Change
                                                                                      Copollutants        & Confidence Intervals ([95% Lower,
                                                                                      (Correlations)                       Upper])
 Reference, Study
Location, & Period
                                    Outcomes, Design, & Methods
  Mean Levels &
Monitoring Stations
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           Yallop et al. (2007)

           London, England
           Study Period:
           Jan. 1988-Oct. 2001,
           >1400 days
                        Outcome(s): Acute pain in Sickle
                        Cell Disease (HbSS, HbSC,
                        HbS/pO, thalassaemia, HbS/p+).
                        Admitted to hospital for at least one
                        night.
                        Study Design:  Time series
                        Statistical Analyses: Cross-
                        correlation function
                        N: 1047 admissions
                        Covariates: no adjustment made in
                        analysis, discussion includes
                        statement that the effects of weather
                        variables and copollutants are inter-
                        related.
                        Statistical Package: SPSS
                        Lag(s): 0-2 days
                        Dose response:  quartile analysis,
                        graphs presented, ANOVA
                        comparing means across quartiles.
                                                          NR
                       O3, CO, NO, NO2,
                       PM10:
                       daily avg used for all
                       copollutants

                       High O3 levels
                       correlate with low
                       NO, low CO,
                       increased wind
                       speeds and low
                       humidity and each
                       was associated with
                       admission for pain.
                       Not possible to
                       distinguish
                       associations in
                       analysis.
                                                                                                                   Results reported are cross-correlation
                                                                                                                   coefficients. NO inversely correlated with
                                                                                                                   admission for acute pain in SCO.
                                                                                                                   CFF: -0.063, lag 0
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           * Default GAM


           AMI Acute Myocardial
           Infarction
           ARR Arrhythmia
           BC Black Carbon
           COH coefficient of haze
           CP Course Particulate
                       CVD Cardiovascular Disease
                       EC Elemental Carbon
                       FP Fine Particulate
                       HS Hemorrhagic Stroke
                       ICD9 International Classification of Disease,
                       9th Revision
                       IHD Ischemic Heart Disease
                       IS ischemic stroke
                                                          MI Myocardial Infarction
                                                          OC Organic Carbon
                                                          OHC Oxygenated Hydrocarbons
                                                          PERI Peripheral Vascular and Cerebrovascular Disease
                                                          PM Particulate Matter
                                            PIH primary intracerebral hemorrhage
                                            PNC Particle Number Concentration
                                            SHS Subarachnoid hemorrhagic stroke
                                            TP Total Particulate
                                            UBRE Unbiased Risk Estimator

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      TABLE AX6.4-4.  HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN:  CVD HOSPITAL ADMISSIONS
                                                         AND VISITS:  ASIA
 Reference, Study
Location, & Period
Outcomes, Design, &
      Methods
  Mean Levels &
Monitoring Stations
 Copollutants        Effects: Relative Risk or Percent Change &
(Correlations)       Confidence Intervals ([95% Lower, Upper])
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         Chan et al. (2006) *
         Taipai, Taiwan

         Period of Study:
         April1997-Dec 2002,
         2090 days
                     Outcome(s) (ICD9):
                     Cerebrovascular disease
                     430-437; stroke 430-434;
                     hemorrhagic stroke 430-432;
                     ischemic stroke 433-434.
                     Emergency admission data
                     collected from National
                     Taiwan University Hospital.
                     Ages groups analyzed:
                     age >50 included in study
                     Study Design:  Time series
                     N: 7341 Cerebrovascular
                     admissions among those
                     >50 yrs old
                     # of Hospitals:
                     Catchment area:
                     Statistical Analyses: Poisson
                     regression, GAMs used to
                     adjust for non-linear relation
                     between confounders and ER
                     admissions.
                     Covariates: time trend
                     variables: yr, mo, and day of
                     wk, daily temperature
                     difference, and dew point
                     temperature.
                     Linearity: Investigated
                     graphically by using the
                     LOESS smoother.
                     Statistical Package: NR
                     Lag: 0-3, cumulative lag up to
                     3 days
                         NO224-havg (ppb):
                         Mean: 29.9
                         SD: 8.4
                         Min: 8.3
                         Max: 77.1
                         IQR: 9.6 ppb

                         # of Stations:  16

                         Correlation among
                         stations: NR
                      PM10 24 h, r = 0.50
                      PM2 5 24 h, r = 0.64
                      CO8-havg, r=0.77
                      SO2 24 h, r = 0.64
                      O3 1-h max, r = 0.43

                      Two-pollutant models
                      to adjust for
                      copollutants
                  Results reported for OR for association of
                  emergency department admissions with an IQR
                  increase inNO2 (9.3 ppb)

                  Cerebrovascular:
                  1.032(0.991, 1.074), lag 0
                  Stroke:
                  0.994(0.914, 1.074), lag 0
                  Ischemic stroke:
                  1.025(0.956, 1.094), lag 0
                  Hemorrhagic stroke:
                  0.963(0.884, 1.042), lag 0

                  No significant associations for NO2 reported. Lag
                  0 shown but similar null results were obtained for
                  lags 1-3. NO2 highly correlated with PM and CO.

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TABLE AX6.4-4 (cont'd). HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN:  CVD HOSPITAL ADMISSIONS
                                                       AND VISITS: ASIA
 Reference, Study
Location, & Period
Outcomes, Design, &
      Methods
  Mean Levels &
Monitoring Stations
 Copollutants      Effects: Relative Risk or Percent Change &
(Correlations)     Confidence Intervals ([95% Lower, Upper])
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          Chang et al. (2005)
          Taipei, Taiwan

          Study Period:
          1997-2001, 5 yrs
                    Outcome(s) (ICD9):  CVD
                    410-429.
                    Daily clinic visits or hospital
                    admission from computerized
                    records of National Health
                    Insurance. Discharge data.
                    Source Population:
                    2.64 Million
                    N: 40.8 admissions/day,
                    74,509/5 yrs
                    # Hospitals: 41
                    Study Design: case crossover,
                    referent day 1 wk before or
                    after index day
                    Statistical Analyses:
                    conditional logistic regression.
                    Covariates: same day
                    temperature and humidity.
                    Season:  warm/cool (stratified
                    by temperature cutpoint of
                    20 °C)
                    Lag(s):  0-2 days	
                         NO224-havg(ppb):
                         Mean: 31.54
                         Min: 8.13
                         25th: 26.27
                         50th: 31.03
                         75th: 36.22
                         Max: 77.97

                         # of Stations: 6
                      CO 24-h avg
                      O3 24-h avg
                      SO2 24-h avg
                      PM10 24-h avg

                      Correlations not
                      reported.

                      Two-pollutant models
                      to adjust for
                      copollutants
                  OR for the association of CVD admissions with
                  an incremental increase in NO2 equivalent to
                  one IQR.

                  Warm(>20°C)
                  1.177(1.150, 1.205)
                  Cool (<20 °C)
                  1.112(1.058, 1.168)

                  NO2 effect remained in all warm season two-
                  pollutant models. Effect remained in cool
                  season two-pollutant models with the exception
                  of the model that included PM10.

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TABLE AX6.4-4 (cont'd). HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN:  CVD HOSPITAL ADMISSIONS
                                                        AND VISITS:  ASIA
 Reference, Study
Location, & Period
Outcomes, Design, & Methods
                                                                 Mean Levels &
                                                               Monitoring Stations
 Copollutants      Effects: Relative Risk or Percent Change &
(Correlations)     Confidence Intervals ([95% Lower, Upper])
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          Lee et al. (2003a)
          Seoul, Korea

          Study period:
          Dec 1997-Dec 1999,
          822 days, 184 days in
          summer
          Tsai et al. (2003a)
          Kaohsiung, Taiwan

          Study period:
          1997-2000
                     Outcome(s)(ICD10): fflD:
                     Angina pectoris 120; Acute or
                     subsequent MI 121-123; other
                     acute fflD 124.  Electronic
                     medical insurance data used.
                     Study Design: Time series
                     Statistical Methods:  Poisson
                     regression,  GAM with strict
                     convergence criteria.
                     Age groups analyzed: all ages,
                     64+
                     Covariates: long-term trends
                     LOESS smooth, temperature,
                     humidity, day of wk.
                     Season: Presented results for
                     summer (June, July, August)
                     and entire period.
                     Lag(s): 0-6
                     Outcome(s) (ICD9):  All
                     cerebrovascular 430-438; SHS
                     430; PIH 431-432; IS 433-435;
                     Other 436-438.  Ascertained
                     from National Health Insurance
                     Program computerized
                     admissions records.
                     Study Design: Case crossover
                     Statistical Analysis:
                     Conditional logistic regression.
                     Statistical Software:  SAS
                     Seasons: >20°C;<20°C.
                     N: 23,179 stroke admissions
                     # Hospitals: 63
                     Lag(s): 0-2, cumulative lag up
                     to 2 previous days
                              NO224h(ppb):
                              5th:  16
                              10th: 23.7
                              Median: 30.7
                              75th: 38.3
                              95th: 48.6
                              Mean(SD): 31.5(10.3)
                              IQR: 14.6
                              N02 (ppb)
                              Min: 6.25
                              25th:  19.25
                              Median: 28.67
                              75th:  36.33
                              Max:  63.40
                              Mean:  28.17
                                                                                     PM10,r = 0.73, 0.74
                                                                                     SO2,r= 0.72, 0.79
                                                                                     O3,r=-0.07, 0.63
                                                                                     CO, r= 0.67, 0.79

                                                                                     Range depends on
                                                                                     summer vs. entire
                                                                                     period.

                                                                                     Two-pollutant
                                                                                     models
                                                                                     PM10
                                                                                     S02
                                                                                     CO
                                                                                     03
                  Results reported for RR of IHD hospital
                  admission for an incremental increase in NO2
                  equivalent to one IQR.

                  64+, entire study period:
                  1.08(1.03, 1.14), lag 5
                  64+, summer only:
                  1.25(1.11, 1.41), lag 5

                  Results for lag 5 presented above. Lag 0 or 1
                  results largely null - presented graphically.
                  Confounding by PM10 was not observed in
                  these data using two-pollutant models.
                  Results reported as OR for the association of
                  admissions with an incremental increase of
                  NO2 equivalent to the IQR of 17.1 ppb

                  PIH admissions
                  Warm: 1.56 (1.32, 1.84), lag 0-2
                  Cool:  0.81(0.0, 1.31), lag 0-2

                  IS admissions:
                  Warm: 1.55 (1.40, 1.71), lag 0-2
                  Cool:  1.16(0.81, 1.68), lag 0-2

                  Effects persisted after adjustment for PM10,
                  SO2, CO, and O3.

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TABLE AX6.4-4 (cont'd). HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN: CVD HOSPITAL ADMISSIONS
                                                        AND VISITS: ASIA
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Reference, Study
Location, & Period
Wong etal. (1999)
Hong Kong, China
Outcomes, Design, &
Methods
Outcome(s) (ICD9): CVD:
410-417, 420-438, 440-444;
CHF428;IHD410-414;
Mean Levels &
Monitoring Stations
NO2 24-h avg (ug/m3)
Mean: 51.39

PM
SO;
03
Copollutants
(Correlations)
10, r = 0.79
•)
Effects: Relative Risk or Percent Change
& Confidence Intervals ([95% Lower,
Upper])
Results reported for RR associated with
incremental increase in NO2 equal to
10 ug/m3.
          Study Period:
          1994-1995
                    Cerebrovascular Disease 430-
                    438. Hospital admissions
                    through ER departments via
                    Hospital Authority (discharge
                    data).
                    Study Design:  Time series
                    Statistical Analyses:  Poisson
                    regression, APHEA protocol
                    # Hospitals:  12
                    Covariates: daily
                    temperature, relative
                    humidity day of wk, holidays,
                    influenza, long-term trends
                    (yr and seasonality variables).
                    Interaction of pollutants with
                    cold season examined.
                    Season: Cold (Dec-March)
                    Lag(s): 0-3 days
Range for other           CVD
pollutants: r= 0.68, 0.89.  65+yrs:  1.016(1.009,1.023)
                        All ages: 1.013(1.007, 1.020)
Two-pollutant models
                        CHF
                        1.044 (1.25, 1.063)
                        IHD
                        1.010 (0.999, 1.020)
                        Cerebrovascular Disease
                        1.008 (0.998, 1.018)

                        Interaction of NO2 with O3 observed

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TABLE AX6.4-4 (cont'd). HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN:  CVD HOSPITAL ADMISSIONS
                                                       AND VISITS:  ASIA
 Reference, Study
Location, & Period
Outcomes, Design, &
      Methods
  Mean Levels &
Monitoring Stations
 Copollutants       Effects: Relative Risk or Percent Change &
(Correlations)      Confidence Intervals ([95% Lower, Upper])
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          Yang et al. 2004a
          Kaohsiung, Taiwan

          Period of Study:
          1997-2000
                    Outcome(s) (ICD9): All
                    CVD: 410-429 * (All CVD
                    typically defined to include
                    ICD9 codes 390-459)
                    N: 29,661
                    Study Design: Case
                    crossover
                    Statistical Analysis: Poisson
                    time-series regression
                    models, APHEA protocol
                    # of Hospitals:  63
                    Seasons: authors indicate not
                    considered because the
                    Taiwanese climate is tropical
                    with no apparent seasonal
                    cycle
                    Covariates: stratified by
                    warm (>25°) and cold (<25°)
                    days, temperature and
                    humidity measurements
                    included in the model
                    Statistical Package:  SAS
                    Lag: 0-2 days
                        Min: 6.25 ppb
                        25%:  19.25 ppb
                        50%:  28.67 ppb
                        75%:  36.33 ppb
                        Max:  63.40 ppb
                        Mean: 28.17 ppb

                        # of Stations: 6
                        Correlation among
                        stations: NR
                     PM10
                     CO
                     S02
                     O38

                     Two-pollutant models
                     used to adjust for
                     copollutants

                     Correlations NR
                   OR's for the association of one IQR
                   (17.08 ppb) increase in NO2 with daily counts
                   of CVD hospital admissions are reported

                   All CVD (ICD9: 410-429), one-pollutant
                   model
                   >25°: 1.380(1.246, 1.508)
                   <25°: 2.215 (2.014, 2.437)

                   All CVD (ICD9: 410-429), two-pollutant
                   models
                   Adjusted for PM10:
                   >25°: 1.380(1.246, 1.508)
                   <25°: 2.215 (2.014, 2.437)
                   Adjusted for SO2:
                   >25°: 1.149(1.017, 1.299)
                   <25°: 2.362 (2.081, 2.682)
                   Adjusted for CO
                   >25°: 1.039(0.919,1.176)
                   <25°: 2.472(2.138,2.858)
                   Adjusted for O3
                   >25°: 1.159(1.051,1.277)
                   <25°: 2.243 (2.037, 2.471)
                   Association of CVD admissions with NO2
                   attenuated on warm days after adjustment for
                   copollutants. Association persisted on cool
                   days. Kaohsiung is the center of Taiwan's
                   heavy industry.	

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 TABLE AX6.4-4 (cont'd). HUMAN HEALTH EFFECTS OF OXIDES OF NITROGEN:  CVD HOSPITAL ADMISSIONS
                                                            AND VISITS:  ASIA
 Reference, Study
Location, & Period
                                 Outcomes, Design, & Methods
  Mean Levels &
Monitoring Stations
 Copollutants        Effects: Relative Risk or Percent Change &
(Correlations)        Confidence Intervals ([95% Lower, Upper])
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           Yeetal. (2001)
           Tokyo, Japan

           Study Period:
           July-August,
           1980-1995
                     Outcome(s):  Angina 413;
                     Cardiac insufficiency 428;
                     Hypertension 401-405; MI 410.
                     Diagnosis made by attending
                     physician for hospital
                     emergency transports.
                     Age groups analyzed: 65+ yrs
                     male and female
                     Statistical analysis:  GLM
                     Covariates: maximum
                     temperature, confounding by
                     season minimal since only 2
                     summer mos  included in
                     analysis
                     Statistical Software:  SAS
                     Lag(s):  1-4 days	
                                                                NO2 24-h avg (ppb)
                                                                Minimum:  5.3
                                                                Maximum: 72.2
                                                                Mean(SD): 25.4(11.4)
                       O3,r= 0.183
                       PM10,r = 0.643
                       SO2,r= 0.333
                       CO, r= 0.759
                    Results reported for model coefficient and
                    95% CI.

                    Angina:
                    0.007 (0.004, 0.009)
                    Cardiac insufficiency:
                    0.006 (0.003, 0.01)
                    MI:
                    0.006 (0.003, 0.01)
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           * Default GAM

           AMI Acute Myocardial
           Infarction
           ARR Arrhythmia
           BC Black Carbon
           COH coefficient of haze
           CP Course Particulate
                     CVD Cardiovascular Disease
                     EC Elemental Carbon
                     FP Fine Particulate
                     HS Hemorrhagic Stroke
                     ICD9 International Classification of
                     Disease, 9th Revision
                     IHD Ischemic Heart Disease
                     IS ischemic stroke
                                                                MI Myocardial Infarction
                                                                OC Organic Carbon
                                                                OHC Oxygenated
                                                                Hydrocarbons
                                                                PERI Peripheral Vascular and
                                                                Cerebrovascular Disease
                                                                PM Particulate Matter
                       PIH primary intracerebral
                       hemorrhage
                       PNC Particle Number
                       Concentration
                       SHS Subarachnoid hemorrhagic
                       stroke
                       TP Total Particulate
                       UBRE Unbiased Risk Estimator

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1 AKL,tL AAtO-1. MULUJL;
MEASURED BY


% Change
Author, Year (95% CI)

Lino et al. (2004)
lagl -5.0% (-9.2, -.7)


Chan et al. (2005)
4-hlag -4.5% (-8.1, -.30)
8-hlag -6.9% (-12.0, -1.8)


Wheeler et al. (2006)
MI patients [N = 12]

4hlag -26.0% (-42.1, -8.6)
COPD patients
[N = 22]
4 h lag 16.6% (0.2, 34.3)
Luttmann-Gibson
et al. (2006)
lagl 0.3% (-6.0, 6.6)

Schwartz et al. (2005)

lagl -1.6% (-7.8, 5.1)
5 JLAAlVlimrNLr JLAJ'UMJKt 1U AlVimJU> 1 l>Ui A1>L) UJLAKl KA1 tL VAK1AB1L11 Y AJ
STANDARD DEVIATION OF NORMAL-TO-NORMAL INTERVALS (SDNN)

NQj Cone (ppb) Copollutant Correlation
Analysis AVg
Location Subjects Method Time Mean (sd) Range PM O3 SO2
US, ARIC multivariable
study 4,390 adults linear regression 24 h 21(8)

83 adults
recruited from linear mixed
Taiwan cardiology effects regression Ih 33(15) 1,110 PMi00.4 -0.4 0.5


30 adults (12
MI + 22 linear mixed 18(nosd plO-p20,
Atlanta COPD) models 4h given) 7,30 PM25 0.4






32 adults 10 (no sd p25-p75,
Steubenville (>50yrs) mixed models 24 h given) 6,13 PM25 0.4 -0.3 0.3

28 elderly hierarchical
Boston adults models 24 h med 18 p25-p75, 14, 23 PM25 0.3 0.02


•>




CO





0.7




0.5










0.6


All results given for 20 ppb increase in NO2 with 24-h averaging time, or 30 ppb for 1-h averaging time. (20 ppb increases also used for averaging times between 1 and 24 h)




























-------
TABLE AX6.5-2. STUDIES EXAMINING EXPOSURE TO AMBIENT NO2 AND HEART RATE VARIABILITY AS
CJQ
r-K
to
o
o



MEASURED BY
Author, Year
Risk of ICD discharge
Peters et al. (2000a)
lagl
lag 0-4
VARIABLES RECORDED
OR (95% CI) Location

Eastern MA
1.55(1.05,2.29)
1.88(1.01,3.49)
ON IMPLANTABLE CARDIOVERTER DEFIBRILLATORS (ICDS)
NO2 Cone (ppb) Copollutant Correlation
Subjects Analysis Method Mean(sd) Range PM2.5 O3 SO2

100 cardiac logistic regression,
outpatients fixed effects 23 (no sd given) 11,65 0.6 -0.3 0.3




CO

0.7


Risk of ICD-recorded ventricular arrhythmias



X
ON
O
ON
O
H
6
o
0
H
O
O
H
W
O
O
HH
H
W
Rich et al. (2005)
all patients
lag 0-1
patients with recent arrhythmia
(< 3 days)
lag 0-1
Dockery et al. (2005)
patients with recent arrhythmia
(<3 days)
lag 0-1
Risk of ST-segment depression
>0.1mV
Pekkanen et al. (2002)
lag 2
Risk of resting heart rate
>75 bpm
Ruidavets et al. (2005)
Iag8h
Boston

1.54(1.11,2.18)
2.09(1.26,3.51)
Boston
2.14(1.14,4.03)
Finland
14.1 (3.0,65.4)
France
2.7(1.2,5.4)
203 cardiac p25-max,
outpatients case-crossover med 22 1 8, 62



307 cardiac logistic regression, p25-p95,
outpatients GEE med 23 19,34 >0.4 <-0.4 >0.4

45 cardiac linear regression, p25-max,
patients GAM med 16 12, 36 0.4

polytomous logistic
863 adults regression 16(6) 2,48 -0.3 0.7




0.6

0.3


All results given for 20 ppb increase in NO2 with 24-h averaging time.





-------
TABLE AX6.6-1. BIRTH WEIGHT AND LONG-TERM NO2 EXPOSURE STUDIES
CJQ
r-K
to
o
o
^









X
ON
O

O
J>
H
6
o
2
0
H
O
O
H
W
O
O
HH
H
W
Study Study
Author, Year Location Group

Lin et al. (2004) Taiwan Term LEW
Pregnancy
Medium NO2
High N02
Trimester 1
Medium NO2
High NO2
Trimester 2
Medium NO2
High N02
Timester 3
Medium NO2
High NO2
Seoul,
Lee et al. (2003b) Korea Term LEW

Pregnancy
Trimester 1
Trimester 2
Trimester 3
LEW
Bobak M. (2000) Czech adjusted
Trimester 1 for GA
Trimester 2
Trimester 3

Study Odds Ratio
Subjects (95% CI)
92,288 birth
cert
1995-1997
1.06(0.93,
1.06(0.89,

1.10(0.96,
1.09(0.89,

0.87 (0.76,
0.93 (0.77,
1.01 (0.88,
0.86(0.71,
388, 105 birth
cert

1996-1998 1.04(1.00,
1.02(0.99,
1.03(1.01,
0.98 (0.96,
69,935 birth
cert
1991 only 0.98(0.81,
0.99 (0.80,
0.97(0.80,




1.22)
1.26)

1.27)
1.32)

1.00)
1.12)
1.16)
1.03)


1.08)
1.04)
1.06)
1.00)
1.18)
1.23)
1.18)

Unit of Cone Range (ppb) Correlation with Other Pollutants
Analysis Averaging
Method Time Low Mid-range High PM2.5 PM10 O3 SO2 CO BS Distance

3km
Logistic
regression <26.1 26.1,32.9 >32.9


<24.3 24.3, 34.7 >34.7


<24.0 24.0, 34.4 >34.4


<23.8 23.8, 34.2 >34.2

Generalized
additive 24 h 25 31.4 39.7
model
(GAM)
Interquartile 0.66 0.75 0.77
0.81 0.77 0.78
0.8 0.76 0.82
Logistic
regression 24 h 12.2 20 31.1
50 ng
increase 0.53
0.62
0.63


-------
TABLE AX6.6-1 (cont'd). BIRTH WEIGHT AND LONG-TERM NO2 EXPOSURE STUDIES
CJQ
O
O








X
Oi
O
OO
O
>
H
6
o
0
H
O
O
H
W
O
O
HH
H
W
Study Study
Author, Year Location Group
LEW
Maroziene and Kaunas adjusted
Grazuleviciene
(2002) Lithuania for GA
Pregnancy
Medium NO2
High N02
Trimester 1
Trimester 2
Trimseter 3
LEW
Liu et al. (2003) Vancouver adjusted
First mo for GA
Last mo
Salam et al. Southern
(2005) CA Term LEW
Pregnancy CHS
Trimester 1
Trimester 2
Trimester 3
Bell M et al. LEW
(2007) CT and MA adjusted
pregnancy for GA
black mothers
white mothers


Study Odds Ratio
subjects (95% CI)
3,988 birth cert

1998 only
1.28(0.97, 1.68)
0.96 (0.47, 1.96)
1.54(0.80,2.96)
0.91 (0.53, 1.56)
0.93(0.61, 1.41)
1.34(0.94, 1.92)
229,085 birth
cert
1986-1998 0.98(0.90,1.07)
0.94(0.85, 1.04)
3,901 birth cert
1975-1987 0.8(0.4,1.4)
0.9(0.5, 1.5)
1.0(0.6, 1.6)
0.6(0.4, 1.1)
3 5 8, 504 birth
cert
1999-2002 1.027(1.002,1.051)
-12.7 (-18.0, -7.5)
-8.3 (-10.4, -6.3)


Unit of Cone Range (ppb) Correlation with Other Pollutants
Analysis Averaging
Method Time Low Mid-range High PM2.5 PM10 O3 SO2 CO BS Distance
Logistic
regression

6.2 (5.7)
10 ug increase


10 ug increase


Logistic
regression 24h 15.1 18.1 22.3 -0.25 0.61 0.72
10 ppb increase

Logistic 5 km or 3
regression 36.1 (15. .4) 0.55 -0.1 0.41 within 50 km
within
IQR 25 county

logistic
regression 17.4(5.0) 0.64 0.55
interquartile IQR 4.8
linear regression
difference in
gms
per IQR


-------
                     TABLE AX6.6-2. PRETERM DELIVERY AND LONG-TERM NO2 EXPOSURE STUDIES
OQ
to
o
o
X
O
VO
H

6
o


o
H

O

O
H
W

O
Study Study
Author, Year Location Group
Bobak 2000 Czech Preterm
trimester 1
trimester 2
trimester 3
Liu S et al. (2003) Vancouver Preterm
first mo
last mo
Maroziene and Kaunas Preterm
Grazuleviciene R
(2002) Lituania
pregnancy
medium NO2
high NO2
trimester 1
trimester 2
trimester 3
Ritz etal. (2000) southern C A Preterm
first mo
6 wks before birth
Hansen C et al.
(2006) Brisbane Preterm
trimester 1
90 days before
birth
Odds Ratio (95%
Study subjects CI)
69,935 birth cert
1991 only 1.10(1.00,1.21)
1.08(0.98, 1.19)
1.11(1.00, 1.23)
229,085 birth cert
1986-1998 1.01 (0.94, 1.07)
1.08(0.99, 1.17)
3,988 birth cert


1.25 (1.07, 1.46)
1.14(0.77, 1.68)
1.68(1.15,2.46)
1.67(1.28,2.18)
1.13(0.90, 1.40)
1.19(0.96, 1.47)
97, 158 birth cert
1989-1993 No effects for
any preg period
28,200 birth cert
2000-2003 0.93(0.78,1.12)
1.03 (0.86, 1.23)
Unit of Cone Range (ppb) Correlation with Other Pollutants
Analysis Averaging M,d_
Method Time Low range High PM2.5 PM10 O3 SO2 CO BS
Logistic
regression 24 h 12.2 20 31.1 0.62
50 ug increase


24 h 15.1 18.1 22.3 -0.25 0.61 0.72
10 ppb increase

Logistic
regression


10 ug increase 6.2 (5.7)


10 ug increase


Logistic
regression 24 h 32 40.9 50.4 0.74 -0.12 0.64


Logistic
regression 24 h 8.8(4.1) 0.32 0.13
IQR 5.2 ppb
IQR4.5ppb
Distance




13 monitors
avg










Zipcode
within
2 miles





O
HH
H
W

-------
OQ
 to
 o
 o
                          TABLE AX6.6-2 (cont'd). PRETERM DELIVERY AND LONG-TERM NO2 EXPOSURE STUDIES
                                                                                         Unit of    Cone Range (ppb)
                                                                                                                            Correlation with Other Pollutants
               Study     Study

Author, Year   Location   Group   Study Subjects
                                                          Odds Ratio (95%     Analysis   Averaging         Mid

                                                                             Method
      CI)
Time    Low   range   High PM2.5   PM10    O3   SO2    CO     BS    Distance
          Leem  et al.

          (2006)



          Trimester 1 Q2



          Trimester 1 Q3



          Trimester 1 Q4



          Trimester 3 Q2



          Trimester 3 Q3



          Trimester 3 Q4
             Inchon,

             Korea      Preterm  52,113 birth cert



                               2001-2002
                Log binomial



1.13(0.99,1.27)    regression



1.07(0.94, 1.21)



1.24(1.09,1.41)    Trend .02



1.06(0.93, 1.20)



1.14(1.01, 1.29)



1.21(1.07,1.37)    Trend <.001
                                       15.78  22.93    29.9
                                                                0.37
                                                                               0.54  0.63
                                                                   Kriging
 X
 H

 6
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 o
 H

O


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 O


 O
 HH
 H
 W

-------
TABLE AX6.6-3. FETAL GROWTH AND LONG-TERM NO2 EXPOSURE STUDIES
CJQ
r-K
to
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o










X
ON
|zl

o
H
6
o
0
H
O
O
H
W
O
O
HH
H
W
Author, Year

Salam et al.
(2005)

Pregnancy
Trimester 1
Trimester 2
Trimester 3
Mamies et al.
(2005)

Trimester 1
Trimester2
Trimester 3
1 mo before
birth
Liu et al. (2003)
Trimester 1
Trimester 2
Trimester 3
First mo
Last mo




Study Study Study Odds Ratio
Location Group Subjects (95% CI)

Southern Term 3,901 birth
CA SGA cert
<15% of
CHS data 1975-1987 1.1(0.9,1.3)
1.2(1.0, 1.4)
1.0(0.8, 1.2)
1.0(0.8, 1.2)
5 1,460 birth
Sydney SGA cert
>2sd
below 1998-2000 1.06(0.99,1.14)
national
data 1.14(1.07,1.22)
1.13(1.05, 1.21)

1.07(1.00, 1.14)
229,085 birth
Vancouver term SGA cert
national 1986-1998 1.03(0.98,1.10)
0.94(0.88, 1.00)
0.98(0.92, 1.06)
1.05(1.01, 1.10)
0.98(0.92, 1.03)




Correlation with Other
Unit of Cone Range (ppb) Pollutants
Analysis Averaging
Method Time Low Mid-range High PM2.5 PM10 O3 SO2 CO

Linear
mixedmodel 24h 36.1(15.4) 0.55 -0.1 0.69


IQR = 25


Logistic
regression 1-hmax 18 23 27.5 0.66 0.47 0.29 0.57

23.2 (7.4)
Ippb


Logistic
regression 24 h 15.1 18.1 22.3 -0.25 0.61 0.72
10 ppb






US Distance
5 km or
3 monitors
within 50 km





5km





13 monitors
Avg








-------
TABLE AX6.7-1. LUNG FUNCTION AND LONG-TERM NO2 EXPOSURE
CJQ
«j
t— t-
to
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^











J>
X
a\
i
p^
to


O
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6
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o
H
O

o
H
W
O
73
O
H H
H
W
Author, Year
Gauderman
(2004)
Difference in
lung growth
FVC
FEVj
MMEF
Moseler et al.
(1994)
with asthma
symp

FEVi

lnMEF75%

In MEF50%

lnMEF25%
no asthma symp
FEVj
lnMEF75%
lnMEF50%

lnMEF25%

Ackermann-
Liebrich et al.
(1997)
FVC


FEVi



Study Study Study
Location Group Subjects Odds Ratio (95% CI)
Lung 1757
southern CA function children

Longitudinal age 10-18
CHS -95 (-183.4, -0.6)
Correlation with Other
Unit of Cone Range (ppb) Pollutants
Analysis Averaging Mid-
Method Time Low Range High PM2.5 PM10 O3 SO2 CO B
2-stage
linear 24 h annual 0.79 0.67 -0.11

Regression Avg

IS Distance
Study monitors
in 12 towns



- 101.4 (- 164.5, -38.4) 34.6 ppb
-211 (-377.6, -44.4)

Frieberg lung function 467 children

Germany age 9- 16

0.437

-0.011

-0.022

-0.029

-0.049
0.003
0.004

0.003
Lung
Switzerland function 3, 115 adults

3 yr residents
nonsmokers -0.0123

SAPALDIA (-0.0152, -0.0094)
-0.0070

(-0.0099, -0.0041)


Linear Median
regression wkly 21.28

threshold
Parameter
estimates



j!g








2-stage 24-h
linear annual 18.9(8.5) 0.91 -0.78 0.86

Regression Avg

Parameter
estimate


10 ug




















Sonitors in
8 Study area










-------
TABLE AX6.7-1 (cont'd). LUNG FUNCTION AND LONG-TERM NO2 EFFECTS
CJQ
r-K
to
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.
X
ON
i—1
OJ


O
^
H
1
O
o
0
H
O
Cj
o
H
W
O
O
HH
H
W


Study Study
Author, Year Location Group
Schindler et al. Lung
(1998) Switzerland function
FVC home
FVC personal
FEV home
FEV personal
Peters et al. Southern Lung
(1999a) CA function

FVC all
1986-1990
FVC girls
1986-1990
FEVi all
1986-1990
FEVi girls
1986-1990
FVC all 1994
FVC girls 1994
FEVi all. 1994

FEVi girls 1994

Tager et al. Lung
(2005) Southern & function
Northern
lnFEF75 men CA

lnFEF75 women






Study Odds Ratio
Subjects (95% CI)

560 adults %change
3 yr residents -0.59 (-1)
SAPALDIA


3,293
children
CHS

-42.6(13.5)

-58.5(15.4)

-23.2(12.5)

-39.9(13.9)
-46.2(16.0)
-56.7(19.8)
-22.3(14.8)

-44.1 (16.1)

255 students
UC

Berkeley -0.029(0.003)

-0.032(0.002)




Correlation with Other
Unit of Cone Range (ppb) Pollutants
Analysis Averaging Mid-
Method Time Low range High PM2.5 PM10 O3 SO2 CO
Linear
regression Wkly avg




Linear
regression 24 h

Parameter
estimates

IQR = 25 ppb



IQR = 25 ppb






Linear
regression 22 30 40 Men 0.57
Parameter
estimates 21 27 40 Women
Results
substantially







US Distance
Personal and
Home monitors




Study monitors
in 12 tons
















Lifetime history









-------
CJQ
to
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-------
TABLE AX6.7-2 (cont'd). ASTHMA AND LONG-TERM NO2 EXPOSURE
CJQ
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X
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-------
                          TABLE AX6.7-2 (cont'd). ASTHMA AND LONG-TERM NO2 EXPOSURE
OQ
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W

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Study
Author, Year Location Study Group
Wang et al.
(1999) Taiwan Asthma

Current asthma
Ramadour M
et al. (2000) 7 communities Asthma
France ISAAC


Shima and
Adachi et al.
(2000) 7 communities Asthma
Outdoor 4th
grade girls Japan Prevalence
Outdoor 5th
grade girls
Outdoor 6th
grade girls
Indoor 4th grade
girls
Indoor 5th grade
girls
Indoor 6th grade
girls
Outdoor Asthma

Indoor Incidence
Study
Subjects
117,080
students

age 11-16
2,445
children
age 13-14
3yr
residence

905
children
age 9- 10









Odds Ratio
(95% I)

1.08
(1.04, 1.13)

Nonsignificant

Results


1.14(0.65,
2.09)
1.14
(0.63,2.13)
0.95
(0.45, 2.05)
1.63
(1.06, 2.54)
1.67
(1.06,2.66)
1.18
(0.62,2.18)
2.10
(1.10,4.75)
0.87
(0.51, 1.43)
Analysis
Method
Logistic
regression
Above/below
median
Logisitic
regression




Logistic
regression

lOppb
increase





lOppb
increase


Correlation with Other
Unit of Cone Range (ppb) Pollutants Distance
Averaging Mid-
Time Low range High PM2.5 PM10 O3 SO2 CO BS
28 24 district
median monitors


Monitors in each
11 -27 mean community




In home
20-29 30-39 >40 measurements

7-25 Monitors near
mean schools

Outdoors







-------
£
CJQ
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Study
Author, Year Location
Kim J et al.
(2004a) San Francisco

All children Bay area
All 1 yr
residents
1 yr resident
girls
1 yr resident
boys
All children
All 1 yr
residents
1 yr resident
girls
1 yr resident
boys
Gauderman W
et al. (2005) Southern CA

Lifetime asthma CHS
Asthma med use



Hwang et al.
(2005) Taiwan

Parental atopy National study
No parental
atopy








TABLE AX6.7-2 (cont'd). ASTHMA AND LONG-TERM NO2 EXPOSURE
Correlation with Other
Unit of Cone Range (ppb) Pollutants
Study Study Odds Ratio Analysis Averaging Mid-
Group Subjects (95% I) Method Time Low range High PM2.5 PM10 O3 SO2 CO
1,109 24
Asthma children 2-stage mean "low" "low"
Hierarchical
Age 9-11 1.02(0.97,1.07) model

1.04(0.98, 1.10)

1.09(1.03,1.15) IQR = 3.6NO2

1.00(0.94, 1.07)
1.04(0.97, 1.11)

1.07 (1.00, 1.14) IQR = 14.9 NOX

1.17(1.06, 1.29)

1.02(0.93, 1.11)
Logistic
Asthma 208 children regression 4wkavg 13-51

1.83(1.04,3.21) IQR= 5.7
2.19(1.20,4.01)



32,672
Asthma children 2-stage 21.5 29.6 33.1 0.34 -0.39 0.5
Hierarchical
ISAAC 0.99(0.92,1.07) model

1.02(0.95,1.10) lOppbNOx












US Distance
10 school
sites















Outside
home






Schools
within
1 km of
monitors










-------
TABLE AX6.7-3. RESPIRATORY SYMPTOMS AND LONG-TERM NO2 EXPOSURE
CJQ
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HH
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Author, Year
Garrett et al.
(1999)
wheeze
cough
short of breath
chest tightness
any symptoms
any symptoms

any symptoms
Hirsch et al.
(1999)

wheeze home

wheeze school

cough home
cough school
cough non-
atopic child


Peters et al.
(1999b)
wheeze
cough
wheeze boys

wheeze girls






Study Study
Location Study Group Subjects
148
Latrobe Valley Symptoms children
Australia Monash Q Age 7- 14
1994-1995






5,421
Dresden Symptoms children
Age 5-7,
Germany ISAAC 9-11

1995-1996
12 mo
residence





3,676
Southern CA Symptoms children
CHS Questionnaire Age 9- 16
1994









Odds Ratio
(95% CI)


1.15(0.85, 1.54)
1.47(0.99,2.18)
1.23 (0.92, 1.64)
1.12(0.81, 1.56)
1.24(0.91, 1.68)
1.12(0.93, 1.35)

2.71 (1.11,6.59)



1.13(0.93, 1.37)

0.95 (0.72, 1.26)

1.22(1.94, 1.44)
1.21 (0.96, 1.52)

1.42(1.10, 1.84)




1.12(0.86, 1.45)
1.14(0.94, 1.39)
1.54(1.04, -2.29)

0.86(0.57, 1.29)





Unit of Cone Range (ppb)
Analysis Averaging
Method Time Low Mid-range High PM2.5
Logistic
regression 6

10 ug


10 ugmean
10 ug winter
10 ug
summer
Logistic
regression 29.3 33.8 37.8



10 ug







Logistic
regression 24 h 21. 5 mean

IQR = 25 ppb







Correlation with Other
Pollutants

PM10 03 S02 CO BS Distance

In home




4 monitors




Within 1 km











Study
monitors
In 12 towns









-------
TABLE AX6.7-3 (cont'd). RESPIRATORY SYMPTOMS AND LONG-TERM NO2 EXPOSURE
CJQ
r-K
to
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o










X
ON
VO


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>
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6
o
0
H
O
O
H
W
O
O
HH
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W
Author, Year
Millstein et al.
(2004)

wheeze
wheeze Mar-Aug
wheeze Sept-Feb
Penard-Morand
et al. (2005)


wheeze past
12 mos.

Mukala et al.
(1999)

cough
cough
nasal symp winter
nasal symp winter
nasal symp spring
nasal symp spring
Pikhart et al.
(2000)
wheeze
wheeze
wheeze

Study Study Study
Location Group Subjects

Southern CA Symptoms 2,034 children

CHS Age 9- 11
1995


France 6
towns Symptoms 4,901 children

IS SAC Age 9- 11
1999-2000
3 yr residence
Helsinki Symptoms 163 children

Finland Age 3-6
1991


Prague Symptoms 3,045 children
Czech SAVIAH Age 7- 10
1993-1994


Odds Ratio
(95% CI)



0.93 (0.77,
0.79 (0.40,
0.85 (0.64,




0.87(0.75,



1.23 (0.89,
1.52(1.00,
0.99(0.58,
0.89 (0.44.
0.76 (0.56,
0.68 (0.46,
1.16(0.95,
1.07(0.86,
1.08(0.86,




1.12)
1.53)
1.14)




1.01)



1.70)
2.31)
1.68)
1.82)
1.02)
1.01)
1.42)
1.33)
1.36)

Correlation with Other
Unit of Cone Range (ppb) Pollutants
Analysis Averaging
Method Time Low Mid-range High PM2.5 PM10 O3 SO2 CO
Mixed effects
model Moly 0.28 0.39


IQR = 5.74 ppb


Logistic
regression 3 yrs


8.7, 16.1,
10 ng 16.0 25.7 0.46 0.76 0.35

GEE Wkly <8.6 8.6, 14.5 >14.5

2nd tertile Avg
3rd tertile
2nd tertile
3rd tertile
2nd tertile
3rd tertile
Multi-level
model 14.8 19 24.1
Individual
covariates
Ecological
covariates
Both covariates

US Distance
Study
monitors
In 12
towns


29
monitoring
sites,
school
address


Palms
tubes
On outer
garment








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TABLE AX6.7-3 (cont'd). RESPIRATORY SYMPTOMS AND LONG-TERM NO2 EXPOSURE
CJQ
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Study
Author, Year Study Location Group

van Strien, 2004 CT and MA Symptoms
wheeze
wheeze
wheeze
cough
cough
cough
short of breath
short of breath
short of breath
Nitschke et al.
(2006) Adelaide Symptoms
Wheeze school Australia
Wheeze home
Cough school
Cough home
Difficult breath
school
Difficult breath
home
Chest tight school
Chest tight home




Study Odds Ratio
Subjects (95% CI)

849 children
Agel2mos 1.15(0.79,1.67)
1.03 (0.69, 1.53)
1.45 (0.92, 2.27)
0.96 (0.69, 1.36)
1.33 (0.94, 1.88)
1.52(1.00,2.31)
1.59(0.96,2.62)
1.95(1.17. 3.27)
2.38(1.31,4.34)
174 asthmatic
Children, age
5-13 0.99(0.93,1.06)
2000 1.00(0.90,1.11)
1.01 (0.98, 1.04)
0.99 (0.96, 1.02)
1.11 (1.05, 1.18)
1.03(1.01, 1.05)
1.12(1.07, 1.17)
1.02(0.95, 1.09)




Unit of Cone Range (ppb)
Analysis Averaging
Method Time Low Mid-range High PM2.5
Poisson
regression 10-14 day 5.1 9.9 17.4
Q2 Avg
Q3
Q4
Q2
Q3
Q4
Q2
Q3
Q4
Zero-inflated 117
negative School 34(28) max
binomial 147
regression Home 20 (22) max
lOppb
increase








Correlation with Other
Pollutants
PM10 03 S02 CO BS Distance

In home








9 days in
class
3 days at
home










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                                              TABLE AX6.8. LUNG CANCER
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Author, Year
Nyberg et al.
(2000)
30-yr estimated
exposure



10-yr estimated
exposure





Nafstad (2004)
lung cancer
incidence




non-lung cancer



Study Study Study Odds Ratio
Location Group Subjects (95% CI)
lung
Stockholm cancer 1,042 cases
2,364
Sweden controls 1.05 (0.93,
men age
40-75 1.18(0.93,
0.90(0.71,
1.05 (0.79,

1.10(0.97,
1.15(0.91,
1.01 (0.79,
1.07(0.81,
1.44(1.05,

Norway lung caner 16,209 men
age 40-49
at entry 1.08(1.02,
followed
1972-1998 0.90(0.70,
1.06(0.81,
1.36(1.01,
1.02(0.99,
0.98 (0.88,
1.05 (0.94,
1.04(0.91,

1.18)
1.49)
1.14)
1.40)

1.23)
1.46)
1.29)
1.42)
1.99)


1.15)

1.15)
1.38)
1.83)
1.06
1.08)
1.18)
1.18)
Correlation with Other
Unit of Cone Range (ppb) Pollutants
Analysis Averaging Mid-
Method Time Low range High PM2.5 PM10 O3 SO2 CO BS Exposure
logistic From
regression 8.1 10.6 13.3 addresses
10 ug and traffic
Q2
Q3
Q4

10 ug
Q2
Q3
Q4
90th percentile
Cox Home
proportional 5.32 10.6 16 address
10 ug 1972-1974

Q2
Q3
Q4
10 ug
Q2
Q3
Q4

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TABLE AX6.9. EFFECTS OF ACUTE NOX EXPOSURE ON MORTALITY. RISK ESTIMATES ARE STANDARDIZED

                           FOR PER 20 PPB 24-H AVG NO2 INCREMENT
X
to
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H
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Reference, Study Outcome
Location, and Period Measure
Copollutants
Mean NO2 Levels Considered
Lag Structure
Reported
Method/Design
Effect Estimates
META ANALYSIS
Stieb et al. (2002), re- All cause
analysis (2003) meta-
analysis of estimates
from multiple
countries.
24-h avg ranged from PM10, O3, SO2,
13 ppb (Brisbane, CO
Australia) to 38 ppb
(Santiago, Chile).
"Representative"
concentration: 24 ppb
The lags and multiday
averaging used in these
estimates varied
Meta-analysis of
time-series study
results
Single-pollutant
model
(11 estimates):
0.8%(95%CI: 0.2,
1.5);
Multipollutant
model estimates
(3 estimates): 0.4%
(95% CI: -0.2,1.1)
UNITED STATES
Samet et al. (2000a,b
reanalysis Dominici et
al., 2003)
90 U.S. cities (58 U.S.
cities with NO2 data)
1987-1994





Kinney and Ozkaynak
(1991)
Los Angeles County,
CA
1970-1979


Kelsalletal. (1997)
Philadelphia, PA,
1974-1988




All cause;
cardiopulmonary







All cause;
respiratory;
circulatory




All cause;
respiratory;
cardiovascular,




Ranged from 9 ppb PM10, O3, SO2, 0, 1 , 2
(Kansas City) to 39 ppb CO; two-pollutant
(Los Angeles), 24-h avg models






69 ppb, 24-h avg KM (particle optical 1
reflectance), NO2,
S02, CO;
multipollutant
models


39.6 ppb, 24-h avg TSP, CO, SO2, O3 0 (AIC presented for
0 through 5)





Poisson GAM,
reanalyzed with
stringent convergence
criteria; Poisson GLM.
Time-series study.




OLS (ordinary least
squares) on high-pass
filtered variables.
Time-series study.



Poisson GAM






24-h avg NO2
(per 20 ppb):
Posterior means:
All cause:
Lagl: 0.50%
(0.09, 0.90)
Lag 1 with PM10
andS02: 0.48%
(-0.54,1.51)
All cause:
Exhaustive
multipollutant
model:
0.5% (-0.1, 1.2);
Two-pollutant with
Ox: 0.7% (0.5, 1.0)
All cause:
Single pollutant:
0.3% (-0.6, 1.1);
With TSP:
-1.2% (-2.2, -0.2)

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TABLE AX6.9 (cont'd). EFFECTS OF ACUTE NOX EXPOSURE ON MORTALITY. RISK ESTIMATES ARE

                 STANDARDIZED FOR PER 20 PPB 24-H AVG NO2 INCREMENT
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Reference, Study
Location, and Period
Outcome Measure Mean NO2 Levels
Copollutants Lag Structure
Considered Reported
Method/Design
Effect Estimates
UNITED STATES (cont'd)
Ostro et al. (2000)
Coachella Valley, CA
1989-1998





Fairley
(1999; reanalysis
Fairley, 2003)
Santa Clara County,
CA
1989-1996

Gamble (1998)
Dallas, TX
1990-1994



Dockery etal. (1992)
St. Louis, MO and
Eastern Tennessee
1985-1986


All cause; 20 ppb, 24-h avg
respiratory;
cardiovascular;
cancer; other



All cause; 28 ppb, 24-h avg
respiratory;
circulatory




All cause; 1 5 ppb, 24-h avg
cardiopulmonary




All cause St. Louis: 20 ppb;
Eastern Tennessee:
12.6 ppb, 24-h avg



PMio, PM2.5, 0-4
PM10-2.5, 03, CO





PMio, PM2.5, 0, 1
PM10-2.5, S042\
coefficient of
haze, NO3~, O3,
S02;


PMio, O3, SO2, Avg 4-5
CO; two-pollutant
models



PM10,PM2 5,804,!^, Lagl
03, S02




Poisson GAM with
default convergence
criteria. Time-series
study.



Poisson GAM,
reanalyzed with
stringent convergence
criteria; Poisson GLM.
Time-series study.


Poisson GLM. Time-
series study.




Poisson with GEE.
Time-series study.




Lag 0 day:
All cause:
5. 5% (1.0, 10.3)
Respiratory:
1.8%(-10.3, 15.5)
Cardiovascular:
3. 7% (-1.7, 9.3)
Lagl:
All cause:
1.9% (0.2, 3.7);
Cardiovascular:
1.4% (-1.7, 4. 5);
Respiratory:
4.8% (-0.3, 10.2)
All cause:
4.4% (0.0, 9.0)
Cardiovascular:
1.9% (-4.6, 9.0)
Respiratory:
13.7% (-2.0, 32.0)
All cause:
St. Louis, MO:
0.7% (-3. 5, 5.1)
Eastern Tennessee:
3. 9% (-8.7, 18.2)

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TABLE AX6.9 (cont'd). EFFECTS OF ACUTE NOX EXPOSURE ON MORTALITY. RISK ESTIMATES ARE

                 STANDARDIZED FOR PER 20 PPB 24-H AVG NO2 INCREMENT
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Reference, Study
Location, and Period
UNITED STATES (cont'd)
Moolgavkar (2003)
Cook County, IL and Los
Angeles County, CA,
1987-1995






Moolgavkar (2000a,b,c);
Re-analysis (2003).
Cook County, IL;
Los Angeles County, CA;
and Maricopa County, AZ,
1987-1995





Lippmann et al. (2000;
reanalysis Ito, 2003, 2004)
Detroit, MI
1985-1990
1992-1994





Outcome
Measure

All cause;
cardiovascular








Cardiovascular;
cerebro vascular;
COPD










All cause;
respiratory;
circulatory;
cause-specific




Mean NO2 Levels

Cook County: 25
ppb; Los Angeles:
38 ppb, 24-h avg







Cook County: 25
ppb; Los Angeles: 38
ppb; Maricopa
County: 19 ppb, 24-h
avg








1985-1990: 23. 3 ppb,
24-h avg
1992-1994: 21. 3 ppb,
24-h avg




Copollutants
Considered

PM2.5, PMio, O3,
S02, CO;
two-pollutant models







PM2.5, PMio, O3,
SO2, CO; two- and
three-pollutant
models









PMio, PM2.5,
PMio-2.5, S042\ Lf,
O3, SO2, CO;
two-pollutant
models



Lag Structure
Reported Method/Design

0, 1, 2, 3, 4, 5 Poisson GAM with
default convergence
criteria. Time-series
study.






0, 1, 2, 3, 4, 5 Poisson GAM with
default convergence
criteria in the original
Moolgavkar (2000); GAM
with stringent convergence
criteria and GLM with
natural splines in the 2003
re-analysis. The 2000
analysis presented total
death risk estimates only in
figures.


0, 1, 2, 3, 0-1, Poisson GAM,
0-2, 0-3 reanalyzed with
stringent convergence
criteria; Poisson GLM.
Numerical NO2 risk
estimates were not
presented in the re-analysis.
Time-series study.
Effect Estimates

All cause:
Lagl:
Cook County:
Single pollutant:
2.2% (1.3, 3.1); with
PM10: 1.8% (0.7, 3.0);
Los Angeles:
Single pollutant: 2.0%
(1.6, 2.5); with PM25:
1.8% (0.1, 3. 6).
GAM, Lag 1:
Cardiovascular:
Cook County: 1.1%
(-0.5, 2. 8); Los Angeles:
2. 8% (2.0, 3.6);
Maricopa Co.: 4.6%
(0.5, 9.0);
Re-analysis, GLM:
Total deaths: 2.5% (1.5,
3.6)



Poisson GAM:
All cause:
Lagl:
1985-1990:
0.9% (-1.2, 3.0)
1992-1994:
1.3%(-1.5,4.2)


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      TABLE AX6.9 (cont'd). EFFECTS OF ACUTE NOX EXPOSURE ON MORTALITY.  RISK ESTIMATES ARE
                               STANDARDIZED FOR PER 20 PPB 24-H AVG NO2 INCREMENT
  Reference, Study         Outcome
Location, and Period       Measure
  Mean NO2 Levels
    Copollutants
    Considered
 Lag Structure
   Reported
     Method/Design
   Effect Estimates
           UNITED STATES (cont'd)
           Lipfert et al. (2000a)
           Seven counties in
           Philadelphia, PA area
           1991-1995
                      All cause;
                      respiratory;
                      cardiovascular;
                      all ages; age
                      65+ yrs; age
                      <65 yrs; various
                      subregional
                      boundaries
20.4 ppb, 24-h avg
PMio, PM2.5,
PMio-2.5, SO4
O3, other PM
indices, NO2, SO2,
CO; two-pollutant
models
0-1
Linear with 19-day
weighted avg
Shumway filters.
Time-series study.
Numerous results.
All-cause, avg of
0- and 1-day lags,
Philadelphia:
2.2% (p > 0.05)
 X
 I
 to
           Chock et al. (2000)
           Pittsburgh, PA
           1989-1991
                      All cause; age
                      <74 yrs;
                      age 75+ yrs
Not reported.
PM10, N02, S02,
CO; two-, five-,
and six-pollutant
models
0, plus minus 3
days.
Poisson GLM. Time-series
study. Numerous results
All cause, lag 0, age 0-
74: 0.5% (-2.4, 3.5);
age 75+:  1.0% (-1.9,
4.0).
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TABLE AX6.9 (cont'd). EFFECTS OF ACUTE NOX EXPOSURE ON MORTALITY. RISK ESTIMATES ARE

                STANDARDIZED FOR PER 20 PPB 24-H AVG NO2 INCREMENT
Reference, Study
Location, and Period
De Leon etal. (2003)
New York City
1985-1994


Klemm and Mason
(2000);
Klemm et al. (2004)
Atlanta, GA
Aug 1998- July 2000



Gwynn et al. (2000)
Buffalo, NY



Outcome Measure Mean NO2 Levels
Circulatory and 40.6 ppb, 24-h avg
cancer with and
without contributing
respiratory causes

All cause; 51.3 ppb, max 1-h.
respiratory;
cardiovascular;
cancer; other; age
<65 yrs; age
65+ yrs


All cause; 24-h avg 21 ppb
respiratory;
circulatory


Copollutants
Considered
PMio, O3, SO2,
CO; two-pollutant
models


PM2.5, PMio-2.5,
EC, OC, 03,
SO42~,
NO3~, SO2, CO




PMio, CoH, 03, S02,
CO, IT, S042~



Lag Structure
Reported Method/Design
0 or 1 Poisson GAM with
stringent convergence
criteria; Poisson GLM.
Time-series study.

0-1 Poisson GLM using
quarterly, moly, or
biweekly knots for
temporal smoothing.
Time-series study.



Poisson GAM with
Default convergence
criteria.
Time-series study.

Effect Estimates
Gaseous pollutants results
were given only in figures.
Circulatory:
Age < 7 5: -1%
Age 75+: -2%
All cause, age 65+ yrs: avg
0-1 days
Quarterly knots:
1.0% (-4.2,6.6);
Moly knots:
3.1% (-3.0, 9.7);
Bi-wkly knots:
0.9% (-5.9, 8.2).
All cause (lag 3): 2.1%
(-0.3,4.6);
Circulatory (lag 2): 1.3%
(-2.9, 5.6); Respiratory
(lag 1): 6.4% (-2. 5, 16.2)
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TABLE AX6.9 (cont'd).  EFFECTS OF ACUTE NOX EXPOSURE ON MORTALITY.  RISK ESTIMATES ARE
                         STANDARDIZED FOR PER 20 PPB 24-H AVG NO2 INCREMENT
Reference, Study
Location, and Period Outcome Measure
Copollutants Lag Structure
Mean NO2 Levels Considered Reported
Method/Design
Effect Estimates
CANADA
Burnett et al. (2004) All cause
12 Canadian cities
1981-1999



Burnett et al. (2000), All cause
re-analysis (2003)
8 Canadian cities
1986-1996
24-h avg ranged from PM2.5, PM10-2.5, O3, 1 , 0-2
10 (Saint John) to 26 SO2, CO
(Calgary) ppb.



24-h avg ranged from PM2.5, PM10, 0,1,0-2
15 (Winnipeg) to 26 PM2.5_10, SO2,
(Calgary) ppb. Q3, CO
Poisson GLM.
Time-series study.



Poisson GAM with
default convergence
criteria. Time-series
study. The 2003 re-
analysis did not
consider gaseous
pollutants.
Lag 0-2, single
pollutant: 2.0%
(1.1, 2.9); with O3:
1.8% (0.9, 2.7).
Days when PM
indices available,
lag 1 , single
pollutant: 2.4%
(0.7, 4.1); with
PM25: 3.1%
(1.2,5.1).
Days when PM
indices available,
lag 1 , single
pollutant: 3.6%
(1.6, 5.7); with
PM25: 2.8%
(0.5, 5.2).
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          Burnett et al. (1998a),   All cause
          11 Canadian cities
          1980-1991
          Burnett et al. (1998b),   All cause
          Toronto, 1980-1994
                                 24-h avg ranged from
                                 14 (Winnipeg) to 28
                                 (Calgary) ppb.
                                 24-h avg 25 ppb.
S02, 03, CO
SO2, O3, CO, TSP,
COH, estimated PM10,
estimated PM2 5
0,1,2,0-1,0-2
examined but the best
lag/averaging for each
city chosen
0,1,0-1
Poisson GAM with
default convergence
criteria. Time-series
study.
Poisson GAM with
default convergence
criteria. Time-series
study.
Single pollutant:
4.5% (3.0, 6.0); with
all gaseous
pollutants: 3.5%
(1.7,5.3).

Single pollutant
(lagO):  1.7%
(0.7, 2.7); with CO:
0.4% (-0.6, 1.5).

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TABLE AX6.9 (cont'd). EFFECTS OF ACUTE NOX EXPOSURE ON MORTALITY. RISK ESTIMATES ARE

                 STANDARDIZED FOR PER 20 PPB 24-H AVG NO2 INCREMENT
X
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O
HH
H
W
Reference, Study
Location, and Period
Copollutants
Outcome Measure Mean NO2 Levels Considered
Lag Structure
Reported Method/Design
Effect Estimates
CANADA (cont'd)
Vedal et al. (2003)
Vancouver, British
Columbia, Canada
1994-1996


Villeneuve et al.
(2003)
Vancouver, British
Columbia, Canada
1986-1999





Goldberg et al. (2003)
Montreal, Quebec,
Canada
1984-1993





All cause; 17 ppb, 24-h avg PM10, 03, SO2,
respiratory; CO
cardiovascular


All cause; 19 ppb, 24-h avg PM25, PM10,
respiratory; PM25_10, TSP,
cardiovascular; coefficient of
canceri haze, S042\ S02,
socioeconomic status .-. ^.^
U3, L.U





Congestive heart 22 ppb, 24-h avg PM2 5, coefficient
Failure (CHF) as of haze, SO42\
underlying cause of SO2, O3, CO
death vs. those
classified as having
congestive heart
failure 1 yr prior to
death

0,1,2 Poisson GAM with
stringent convergence
criteria. Time-series
study. By season.

0,1,0-2 Poisson GLM with
natural splines.
Time-series study.







0,1,0-2 Poisson GLM with
natural splines.
Time-series study.






Results presented in
figures only. NO2
showed associations
in winter but not in
summer.
All yr:
All cause
Lag 1: 4.0%
(0.9, 7.2)
Respiratory:
LagO: 2.1%
(-3.0,7.4)
Cardiovascular:
LagO: 4.3%
(-4.2, 13.4)
CHF as underlying
cause of death:
Lag 1: 1.0%
(-5.1,7.5)
Having CHF 1 yr
prior to death:
Lag 1: 3.4%
(0.9,6.0)

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TABLE AX6.9 (cont'd). EFFECTS OF ACUTE NOX EXPOSURE ON MORTALITY. RISK ESTIMATES ARE

                 STANDARDIZED FOR PER 20 PPB 24-H AVG NO2 INCREMENT
X
to
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O
H
W

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O
HH
H
W
Reference, Study
Location, and Period Outcome Measure
Copollutants
Mean NO2 Levels Considered
Lag Structure
Reported Method/Design
Effect Estimates
EUROPE
Samoli et al. (2006) All cause,
30 APHEA2 cities. respiratory;
Study periods vary cardiovascular
by city, ranging from
1990 to 1997






Samoli et al. (2005) 9 All-cause
APHEA2 cities.
Period not reported.



Touloumi et al. (1997) All cause
Six European cities:
London, Paris, Lyon,
Barcelona, Athens,
Koln.
Study periods vary by
city, ranging from
1977 to 1992
Zmirouet al. (1998) Respiratory;
Four European cities: cardiovascular
London, Paris, Lyon,
Barcelona
Study periods vary by
city, ranging from
1985-1992
1-h max ranged from BS, PM10, SO2, O3
24 (Wroclaw) to 81
(Milan) ppb








The selected cities had None
1 -h max medians
above 58 ppb and the
third quartiles above
68.

Ranged from 37 BS, O3; two-pollutant
(Paris) to 70 (Athens) models
ppb, 1-h max





Ranged from 24 BS, TSP, SO2, O3
(Paris) to 37 (Athens)
ppb in cold season and
23 (Paris) to 37
(Athens) ppb in warm
season, 24-h avg

0 1 Poisson model with
penalized splines.









0 1 Poisson model with
either non-parametric
or cubic spline smooth
function in each city,
and combined across
cities.
0,1,2,3,0-1,0-2,0-3 Poisson
(best lag selected for autoregressive.
each city) Time-series study.





0, 1, 2, 3, 0-1, 0-2, 0-3 Poisson GLM.
(best lag selected for Time-series study.
each city)




All-cause: single:
1.8% (1.3, 2.2); with
S02: 1.5% (1.0, 2.0)
Cardiovascular:
single: 2.3%
(1.7, 3.0); with SO2:
1.9% (1.1, 2.7)
Respiratory: single:
2.2% (1.0, 3.4); with
SO2: 1.1%
(-0.4,2.6)
No numeric estimate
presented. The
concentration-
response was
approximately linear.

All-cause:
Single-pollutant
model:
1.0% (0.6, 1.3);
WithBS:
0.5% (0.0, 0.9).


Western Europe:
Respiratory:
0.0% (-1.1, 1.1)
Cardiovascular:
0.8% (0.0, 1.5)



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TABLE AX6.9 (cont'd). EFFECTS OF ACUTE NOX EXPOSURE ON MORTALITY. RISK ESTIMATES ARE

                STANDARDIZED FOR PER 20 PPB 24-H AVG NO2 INCREMENT
X
H

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o
H

O


O
H
W

O


O
HH
H
W
Reference, Study
Location, and Period
Outcome Measure Mean NO2 Levels
Copollutants
Considered
Lag Structure
Reported Method/Design
Effect Estimates
EUROPE (cont'd)
Biggeri et al. (2005)
8 Italian cities, Period
variable between
1990-1999


Anderson et al. (1996)
London, England
1987-1992


Bremneretal. (1999)
London, England
1992-1994
Anderson etal. (2001)
West Midlands region,
England
1994-1996


Prescott etal. (1998)
Edinburgh, Scotland
1992-1995

All cause; 24-h avg ranged from
respiratory; 30 (Verona) to 51
cardiovascular (Rome) ppb


All cause; 37 ppb, 24-h avg
respiratory;
cardiovascular


All cause; 34 ppb, 24-h avg
respiratory;
cardiovascular; all
cancer; all others; all
ages; age specific
(0-64, 65+, 65-74,
75+ yrs)
All cause; 37 ppb, 1-hmax
respiratory;
cardiovascular.


All cause; 26 ppb, 24-h avg
respiratory;
cardiovascular; all
ages; age <65 yrs;
age >65 yrs

Only single-pollutant
models; O3, SO2, CO,
PM10


BS, O3, SO2;
two-pollutant models


BS, PMio, O3, SO2, CO;
two-pollutant models
PMio, PM2.5,
PM25.10,BS, SO42~, O3,
S02, CO


BS, PMio, 03, S02, CO;
two-pollutant models

0-1 PoissonGLM.
Time-series study.


0, 1 Poisson GLM.
Time-series study.


Selected best from 0, Poisson GLM.
1, 2, 3, (all cause); Time-series study.
0,1,2,3,0-1,0-2,
0-3 (respiratory,
cardiovascular)
0-1 Poisson GAM with
default convergence
criteria. Time-series
study.


0 Poisson GLM.
Time-series study.

All cause:
3.6% (2. 3, 5.0);
Respiratory:
5. 6% (0.2, 11.2)
Cardiovascular:
5.1% (3.0, 7.3)
All cause (Lag 1 ):
0.6% (-0.1, 1.2);
Respiratory (lag 1 ):
-0.7% (-2. 3, 1.0)
Cardiovascular:
0.5% (-0.4, 1.4)
All cause (lag 1):
0.9% (0.0, 1.9)
Respiratory (lag 3):
1.9% (-0.3, 4.2)
Cardiovascular (lag
1): 1.9% (0.6, 3.2)
All cause:
1.7% (-0.5, 3.8)
Respiratory:
3. 3% (-1.9, 8.8)
Cardiovascular:
3.1% (-0.2, 6.4)
Results presented as
figures only.
Essentially no
associations in all
categories. Very
wide confidence
intervals.

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TABLE AX6.9 (cont'd). EFFECTS OF ACUTE NOX EXPOSURE ON MORTALITY. RISK ESTIMATES ARE
CJQ
r-K
to
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1
UJ


O

£5
H
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O
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W
O
O
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H
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STANDARDIZED FOR PER 20 PPB 24-H AVG NO2 INCREMENT
Reference, Study
Location, and Period
EUROPE (cont'd)
Le Tertre et al. (2002a)
Le Havre, Lyon, Paris,
Rouen, Strasbourg, and
Toulouse, France
Study periods vary by
city, ranging from
1 QQH 1 QCK
1 yy\j-i yyj

Zeghnoun etal. (2001)
Rouen and Le Havre,
France 1990-1995

Dab etal. (1996)
Paris, France
1987-1992
Zmirou etal. (1996)
Lyon, France
1985-1990



Sartor etal. (1995)
Belgium
Summer 1994












Outcome Measure

All cause;
respiratory;
cardiovascular






All cause;
respiratory;
cardiovascular

Respiratory


All cause;
respiratory;
cardiovascular;
digestive


All cause; age
<65 yrs; age 65+ yrs












Copollutants
Mean NO2 Levels Considered

Ranged from 15 BS, O3, SO2
(Toulouse) to 28 (Paris)
ppb, 24-h avg






24-h avg 18 ppb in SO2, BS, PM13, O3
Rouen; 20 ppb in
Le Havre

24 ppb, 24-h avg BS, PM13, O3, SO2,
CO

37 ppb, 24-h avg PM13, SO2, O3





24-h avg NO2: TSP, NO, O3, SO2
Geometric mean:

During heat wave
(42-day period): 17 ppb

Before heat wave
(43-day period): 15 ppb

After heat wave
(39-day period): 13 ppb



Lag Structure
Reported Method/Design

0-1 Poisson GAM with
default convergence
criteria. Time-series
study.





0, 1 , 2, 3, 0-3, Poisson GAM with
default convergence
criteria. Time-series
study.
0 Poisson
autoregressive.
Time-series study.
Selected best Poisson GLM.
from 0, 1, 2, 3 Time-series study.




0, 1 , 2 Log-linear regression
for O3 and
temperature.
Time-series study.











Effect Estimates

Six-city pooled estimates:

All cause:
2.9% (1.6, 4.2)
Respiratory:
3. !%(-!. 7, 8.0)

Cardiovascular:
3. 5% (1.1, 5. 9)
All cause in Rouen
(lagl): 5.5% (0.2, 11.1);
in Le Havre (lagl): 2.4%
(-3.4,8.5)
Lagl:
2.1% (3. 1,7.7)

All cause (lag 1):
1.5% (-1.5, 4.6)
Respiratory (lag 2):
-2. 3% (-15.6, 13.0)
Cardiovascular (lag 1):
0.8% (-2.7, 4.3)
Only correlation
coefficients presented for
NO2. Unlike O3, NO2 was
not particularly elevated
during the heat wave.










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TABLE AX6.9 (cont'd).  EFFECTS OF ACUTE NOX EXPOSURE ON
                         STANDARDIZED FOR PER 20 PPB 24-H AVG
                            MORTALITY. RISK ESTIMATES ARE
                            NO2 INCREMENT
Reference, Study
Location, and Period
Outcome
Measure
Mean NO2 Levels
Lag
Copollutants Structure
Considered Reported Method/Design
Effect Estimates
EUROPE (cont'd)
Hoek et al. (2000;
reanalysis Hoek, 2003)
The Netherlands:
entire country, four
urban areas
1986-1994


Hoek etal. (2001;
reanalysis Hoek, 2003)
The Netherlands
1986-1994





All cause; COPD;
pneumonia;
cardiovascular





Total
cardiovascular;
myocardial
infarction;
arrhythmia; heart
failure;
cerebro vascular;
thrombosis-
related
24-h avg median:
17 ppb in the
Netherlands; 24 ppb
in the four major
cities



24-h avg median:
17 ppb in the
Netherlands; 24 ppb
in the four major
cities




PMio, BS, SO42 , 1,0-6 PoissonGAM,
N(V, O3, SO2, CO; reanalyzed with
two-pollutant models stringent
convergence
criteria;
Poisson GLM.
Time-series study.


PMio, O3, SO2, CO 1 Poisson GAM,
reanalyzed with
stringent
convergence
criteria; Poisson
GLM. Time-series
study.


Poisson GLM:
All cause:
Lagl: 1.9% (1.2, 2.7)
Lag 0-6: 2.6% (1.2, 4.0); with BS: 1.3%
(-0.9,3.5);
Cardiovascular (lag 0-6): 2.7% (0.7,
4.7).
COPD (lag 0-6): 10.4% (4.5, 16.7).
Pneumonia (lag 0-6): 19.9% (11.5, 29.0).
Poisson GLM:

Total cardiovascular:
2.7% (0.7, 4.7)
Myocardial infarction:

0.3% (-2.6, 3.2)
Arrhythmia:
1.7% (-6.6, 10.6)
          Roemer and van
          Wijinen(2001)
          Amsterdam, the
          Netherlands
          1987-1998
              All cause
BS, PM10, 03, S02,     1,2,0-6
CO
                               Background sites:
                               24 ppb

                               Traffic sites:
                               34 ppb
Poisson GAM with
default convergence
criteria (only one
smoother).
Time-series study.
Heart failure:
7.6% (1.4, 14.2)
Cerebro vascular:
5.1% (0.9, 9.6)
Thrombo sis-related:
-1.2% (-9.6, 8.1)
Total population using background sites:
Lagl: 3.8% (1.7, 5.9);
Traffic pop. using background sites:
lagl: 5.7% (0.6, 11.0);
Total pop. using traffic sites:
Lagl: 1.7% (0.4, 3.0)

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TABLE AX6.9 (cont'd). EFFECTS OF ACUTE NOX EXPOSURE ON MORTALITY. RISK ESTIMATES ARE

                STANDARDIZED FOR PER 20 PPB 24-H AVG NO2 INCREMENT
X
H

6
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o
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O


O
H
W

O


O
HH
H
W
Reference, Study
Location, and Period
Outcome Measure
Mean NO2 Levels
Copollutants Lag Structure
Considered Reported Method/Design
Effect Estimates
EUROPE (cont'd)
Verhoeffetal. (1996)
Amsterdam, the
Netherlands
1986-1992



Fischer et al. (2003) The
Netherlands, 1986-1994
Spix and Wichman
(1 996) Koln, Germany
1977-1985
Peters et al. (2000b)
NE Bavaria, Germany
1982-1994
Coal basin in Czech
Republic
1993-1994

All cause; all ages;
age 65+ yrs




All-cause,
cardiovascular,
COPD, and
pneumonia in age
groups <45, 45-64,
65-74, 75+
All-cause
All cause;
respiratory;
cardiovascular;
cancer

l-hmaxO3:
43 ug/m3
Maximum 301




24-h avg median
17ppb
24-h avg 24 ppb; 1-h
max 38 ppb
24-h avg:
Czech Republic:
17.6 ppb
Bavaria, Germany:
13. 2 ppb
PMio, O3, CO; 0,1,2 Poisson. Time-series
multipollutant models study.
NON02!!!



PMio, BS, O3, SO2, 0-6 Poisson GAM with
CO default convergence
criteria. Time-series
study.
TSP,PM7, SO2 0,1,0-1 Poisson GLM.
Time-series study.
TSP, PMio, 03, S02, 0, 1, 2, 3 Poisson GLM.
CO Time-series study.

1-h max O3 (per
100 ug/m3)
All ages:
LagO: 1.8% (-3. 8, 7.8)
Lagl: 0.1% (-4.7, 5.1)
Lag 2: 4. 9% (0.1, 10.0)
Cardiovascular:
Age<45: -1.3% (-13.0,
12.1): age 45-64: -0.4%
(-4. 8, 4. 3); age 65-74:
4.4% (0.8, 8.0); age 75 and
up: 3. 5% (1.4, 5.6)
Lagl: 0.4% (-0.4, 1.2)
Czech Republic:
All cause:
Lagl: 2.1%(-1.7, 6.1)
Bavaria, Germany:
All cause:
Lagl: -0.1% (-3.6, 3.6)

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TABLE AX6.9 (cont'd).  EFFECTS OF ACUTE NOX EXPOSURE ON MORTALITY. RISK ESTIMATES ARE

                  STANDARDIZED FOR PER 20 PPB 24-H AVG NO2 INCREMENT
Reference, Study
Location, and Period
Outcome Measure
Mean NO2 Levels
Copollutants
Considered
Lag Structure
Reported
Method/Design
Effect Estimates
EUROPE (cont'd)
Michelozzietal. (1998)
Rome, Italy 1992-1995
Ponkaetal. (1998)
Helsinki, Finland
1987-1993
All-cause
All cause;
cardiovascular; age
<65 yrs, age 65+ yrs
24-h avg 52 ppb
24-h avg:
Median 20 ppb
PM13, S02, 03, CO
TSP, PM10, 03, S02
0,1,2,3,4
0,1,2,3,4,5,6,7
Poisson GAM with
default convergence
criteria. Time-series
study.
Poisson GLM.
Time-series study.
Lag 2: all-yr: 1.6% (0.4,
2. 9); cold season 0.3%
(-1.2, 1.8); warm season:
4.2% (1.8,- 6.6)
No risk estimate
presented for NO2.
PM10 and O3 were
                                                                                                 reported to have stronger

                                                                                                 associations.
X
Saez et al. (2002)
Seven Spanish cities,
variable study periods
between 1991 and 1996.




All cause;
respiratory;
cardiovascular





03, PM, S02, CO 0-3
24-h avg mean ranged
from 17 ppb in Huelva
to 35 ppb in Valencia.




Poisson GAM with
default convergence
criteria. Time-series
study.




All cause:
2.6% (1.6, 3.6);
with all other poll.:
1.7% (0.0, 3.3);
Respiratory:
7.1% (-14.0, 33.5)
Cardiovascular:
4.4% (-0.2, 9.2)
H

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      TABLE AX6.9 (cont'd).  EFFECTS OF ACUTE NOX EXPOSURE ON MORTALITY.  RISK ESTIMATES ARE
                               STANDARDIZED FOR PER 20 PPB 24-H AVG NO2 INCREMENT
  Reference, Study
Location, and Period
Outcome Measure     Mean NO2 Levels
Copollutants
 Considered
Lag Structure
  Reported
Method/Design
Effect Estimates
           EUROPE (cont'd)
           Garcia-Ay merich et al.
           (2000)
           Barcelona, Spain
           1985-1989
                     All cause;
                     respiratory;
                     cardiovascular;
                     general population;
                     patients with COPD
                  Levels not reported.     BS, O3, SO2
              Selected best avg lag
                 Poisson GLM.
                 Time-series study.
                  All cause:
                  General population:
                  Lag 0-3: 3.3% (0.8, 5.8)
                  COPD patients:
                  Lag 0-2: 10.9% (0.4, 22.6)
                                                                                                                                 Respiratory:
                                                                                                                                 General population:
                                                                                                                                 Lag 0-1:  3.3% (-2.3, 9.2)
                                                                                                                                 COPD patients:
                                                                                                                                 Lag 0-2:  12.1% (-4. 3,
                                                                                                                                 31.4)
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O
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           Saezetal. (1999)
           Barcelona, Spain
           1986-1989
                     Asthma mortality;
                     age 2-45 yrs
                  Levels not reported.     BS, O3, SO2
              0-2
                 Poisson with GEE.
                 Time-series study.
                  Cardiovascular:
                  General population:
                  Lag 0-3: 2.4% (-0.9, 5.8)
                  COPD patients:
                  Lag 0-2: 4. 3% (-13.6,
                  25.8)
                  RR = 4.1 (0.5,35.0)

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       TABLE AX6.9 (cont'd). EFFECTS OF ACUTE NOX EXPOSURE ON MORTALITY.  RISK ESTIMATES ARE
                                STANDARDIZED FOR PER 20 PPB 24-H AVG NO2 INCREMENT
Reference, Study
Location, and Period
Outcome Measure
Copollutants
Mean NO2 Levels Considered
Lag Structure
Reported
Method/Design
Effect
Estimates
EUROPE (cont'd)
Sunyeretal. (1996)
Barcelona, Spain
1985-1991

All cause;
respiratory;
cardiovascular;
all ages; age 70+ yrs

1-hmax: BS, SO2, O3
Median:
Summer:
51 ppb
Winter:
46 ppb
Selected best
single-day lag

Autoregressive
Poisson. Time-
series study.

All yr, all ages:
All cause:
Lagl: 1.9%(0.l
Respiratory:
3,3.1)

                                                                                                                           LagO:  1.5% (-1.9, 5.0)

                                                                                                                           Cardiovascular:
                                                                                                                           Lagl:  2.2% (0.5, 3.9)
 X
 Oi
 Oi
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 6
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O
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 O
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Sunyer and Basagana
(2001)
Barcelona, Spain
1990-1995
Sunyer et al. (2002)
Barcelona, Spain
1986-1995
Mortality in a cohort
of patients with
COPD
                                All cause,
                                respiratory, and
                                cardiovascular
                                mortality in a cohort
                                of patients with
                                severe asthma
Mean not reported
IQR8.9ppb24-h
                   1-hmax: median
                   47 ppb;
                   24-h avg median
                   27 ppb
                                                                          o, 03, CO
                   PMio, BS, S02,
                   O3, CO, pollen
0-2
                                                        0-2
Conditional logistic
(case-crossover)
                 Conditional logistic
                 (case-crossover)
Summer risk estimates larger than
winter risk estimates.
7.8% (-2.0, 18.6)
with PM10:
3.9% (-12.0,22.5)

Odds Ratio:
Patients with 1 asthma admission:
All cause:
1.10(0.80,1.51)
Cardiovascular:
1.70(0.96,2.99)

Patients with more than 1 asthma
adm:
All cause:
2.14(1.10,4.14)
Cardiovascular:
1.53(0.46,5.07)

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TABLE AX6.9 (cont'd). EFFECTS OF ACUTE NOX EXPOSURE ON MORTALITY. RISK ESTIMATES ARE

                STANDARDIZED FOR PER 20 PPB 24-H AVG NO2 INCREMENT
X
H

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O
H
W

O


O
HH
H
W
Reference, Study
Location, and Period
EUROPE (cont'd)
Diaz etal. (1999)
Madrid, Spain
1990-1992






Latin America
Borja-Aburto et al.
(1997)
Mexico City
1990-1992






Borja-Aburto et al.
(1998)
SW Mexico City
1993-1995



Loomisetal. (1999)
Mexico City
1993-1995


Outcome Measure

All cause;
respiratory;
cardiovascular







All cause;
respiratory;
cardiovascular; all
ages; age <5 yrs; age
>65 yrs





All cause;
respiratory;
cardiovascular;
other; all ages;
age >65 yrs


Infant mortality



Copollutants Lag Structure
Mean NO2 Levels Considered Reported

24-h avg TSP, O3, SO2, CO 1 , 4, 1 0
Levels not reported.








l-hmaxO3: TSP, SO2, CO; 0,1,2
Median 155 ppb two-pollutant models

8-h max O3:
Median 94 ppb
10-havgO3
(8 a.m.-6 p.m.):
Median 87 ppb
24-h avg O3:
Median 54 ppb
37.7 ppb, 24-h avg PM25,O3, SO2; 0, 1, 2, 3, 4, 5, and
two-pollutant models multiday avg





24-h avg 38 ppb PM2.5, 03 0,1,2,3,4,5,3-5




Method/Design

Autoregressive linear.
Time-series study.








Poisson iteratively
weighted and filtered
least-squares method.
Time-series study.






Poisson GAM with
default convergence
criteria (only one
smoother).
Time-series study.


Poisson GAM with
default convergence
criteria. Time-series
study.

Effect Estimates

Only significant risk
estimates were
shown. ForNO2,
only respiratory
mortality was
significantly
(p < 0.05) associated
with an excess
percent risk 8.5%.

l-hmaxO3
(per 100 ppb):

All ages:






Lag 1-5:
All cause: 2.3%
(-1.0,5.6);
Cardiovascular:
2.8% (-3.2, 9.2);
Respiratory: 4.7%
(-5.1,15.5).
Lag 3-5:
11. 4% (2.2, 2 1.4);
with PM2.5:
2.9% (-10.2, 17.8)

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TABLE AX6.9 (cont'd). EFFECTS OF ACUTE NOX EXPOSURE ON MORTALITY. RISK ESTIMATES ARE

                STANDARDIZED FOR PER 20 PPB 24-H AVG NO2 INCREMENT
X
oo
H

6
o


o
H

O


O
H
W

O


O
HH
H
W
Reference, Study Location,
and Period
Outcome Copollutants Lag Structure
Measure Mean NO2 Levels Considered Reported
Method/Design
Effect Estimates
LATIN AMERICA (cont'd)
Gouveia and Fletcher (2000b)
Sao Paulo, Brazil
1991-1993













Pereiraetal. (1998)
Sao Paulo, Brazil
1991-1992



Saldivaetal. (1994)
Sao Paulo, Brazil
1990-1991


Saldivaetal. (1995)
Sao Paulo, Brazil
1990-1991

All ages (all 1-h max: PM10, O3, SO2, CO 0, 1, 2
cause); age <5 yrs 84 ppb
(all cause,
respiratory,
pneumonia);
age 65+ yrs
(all cause,
respiratory,
cardiovascular)







Intrauterine 24-h avg 82 ppb PM10, O3, SO2, CO 0-4
mortality




Respiratory; age 24-h avg NOX PM10, O3, SO2, CO; 0-2
<5 yrs 127 ppb multipollutant models



All cause; 24-h avg NOX PM10, 03, SO2, CO; 0-1
age 65+ yrs 127 ppb two-pollutant models


Poisson GLM.
Time-series study.














Poisson GLM.
Time-series study.




OLS of raw or
transformed data.
Time-series study.


OLS; Poisson with
GEE. Time-series
study.

All ages:
All cause:
LagO: -0.1%
(-0.7,0.4)

Age 65+:
All cause:

Lag 1: 0.4%
(-0.2, 1.1)
Respiratory:
Lag 2: 1.0%
(-0.6,2.5)
Cardiovascular:
Lag 1: 0.5%
(-0.4,1.3)
Single-pollutant
model:
5.1% (2.8, 7.5);
With other
pollutants:
4.7% (1.6, 7.9)
NOX slope estimate:
0.007197
deaths/day/ppb
(SE 0.003214),
p = 0.025
NOX slope estimate:
0.0341
deaths/day/ppb
(SE 0.0105)

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TABLE AX6.9 (cont'd). EFFECTS OF ACUTE NOX EXPOSURE ON MORTALITY. RISK ESTIMATES ARE

                STANDARDIZED FOR PER 20 PPB 24-H AVG NO2 INCREMENT
X
vo
H

6
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o
H

O


O
H
W

O


O
HH
H
W
Reference, Study Location,
and Period
Outcome
Measure
Mean NO2 Copollutants Lag Structure
Levels Considered Reported

Method/Design

Effect Estimates
LATIN AMERICA (cont'd)
Cifuentes et al. (2000)
Santiago, Chile
1988-1966



Ostro et al. (1996) Santiago,
Chile 1989-1991
All cause





All cause

8-h avg 41 ppb PM25, PM10-2.5, CO, 0, 1, 2, 3, 4, 5, 1-2,
SO2, O3 1-3, 1-4, 1-5




1-h max 56 ppb PM10, O3, SO2; 1
two-pollutant models
Poisson GAM with default
convergence criteria;
Poisson GLM. Time-
series study.


OLS, Poisson.
Time-series study.
GLM model, lag 1-2:
Single pollutant: 1.7%
(0.7, 2.7); with other
pollutants: 1.5% (0.3,
2.7)
(per 25ppb 8-h avg)
Poisson, lag 1: -0.5%
(-1.1,0)
AUSTRALIA
Simpson et al. (2005a,b)
Brisbane, Sydney,
Melbourne, and Perth,
Australia
1996-1999


Simpson et al. (2000)
Brisbane, Australia
1991-1996



Morgan etal. (1998b)
Sydney, Australia
1989-1993



Simpson etal. (1997)
Brisbane, Australia
1987-1993


All cause,
respiratory, and
cardiovascular
in all ages;
cardiovascular
in age 65+ yrs

All cause,
respiratory, and
cardiovascular
in all ages;
cardiovascular
in age 65+ yrs
All cause;
respiratory;
cardiovascular



All cause;
respiratory;
cardiovascular


1-h max ranged PM10, PM25, bsp 0, 1, 2, 3, 0-1
from 16 to 24 (nephelometer), O3,
ppb CO




24-h avg: whole PM10, PM2.5, bsp, O3, 0, 1, 2, 3, 0-1
yr: 12 ppb; cool CO
season: 1 3 ppb;
warm season
9 ppb

24-h avg 13 bsp, O3 0-1
ppb; 1-h max 26
ppb



24-h avg 14 PM10, bsp, O3, SO2, 0
ppb; 1-h max 28 CO
ppb


Poisson GLM, GAM with
stringent convergence
criteria. Time-series
study.



Poisson, GAM with
default convergence
criteria. Time-series
study.


Poisson with GEE. Time-
series study.




Autoregressive Poisson
with GEE. Time-series
study.


Lag 0-1, GAM, all-
cause, single pollutant:
3. 4% (1.1, 5. 7); with
bsp: 3.1% (0.3, 5.9);
cardiovascular: 4.3%
(0.9, 7.8); respiratory:
11.4% (3. 5, 19.9)
All-cause (lag 1): 9.7%
(4.7, 14.8); respiratory:
18.8% (1.2, 39.6)



Lag 0-1, single pollutant,
all-cause: 3.0% (0.1,
6.0); cardiovascular:
2.2% (-1.7, 6.4);
respiratory: 8.6% (-0.4,
18.4)
Lag 0-1, single pollutant,
all-cause, all-yr: -1.0%
(-5.2, 3.4); summer:
-3.6% (-11. 2, 4.7);
winter: 1.2% (-4.0, 6.9)

-------
TABLE AX6.9 (cont'd). EFFECTS OF ACUTE NOX EXPOSURE ON MORTALITY. RISK ESTIMATES ARE
CJQ
r-K
to
o
o













X
i
_^.
o



O
£
H
i
O
o

0
H
O

H
W
O
O
HH
H
W


Reference, Study
Location, and Period
ASIA
Kim et al. (2004b)
Seoul, Korea
1995-1999



Lee etal. (1999)
Seoul and Ulsan,
Korea
1991-1995







Lee and Schwartz
(1999)
Seoul, Korea
1991-1995





Kwon etal. (2001)
Seoul, Korea
1994-1998






STANDARDIZED FOR PER 20 PPB 24-H AVG
Lag
Outcome Copollutants Structure
Measure Mean NO2 Levels Considered Reported

All cause 24-h avg 33 ppb. PM10, O3, SO2, CO; 1
two-pollutant models




All cause l-hmaxO3: TSP, SO2 0

Seoul:
32.4 ppb
10th %-90th %
14-55
Ulsan:
26.0 ppb
10th %-90th %

16-39
All cause l-hmaxO3: TSP, SO2 0

Seoul:
32.4 ppb
10th %-90th %
14-55



Mortality in a 24-h avg 32 ppb PM10, O3, SO2, CO 0
cohort of
patients with
congestive heart
failure




NO2 INCREMENT


Method/Design

Poisson GAM with stringent
convergence criteria (linear
model); GLM with cubic natural
spline; GLM with B-mode spline
(threshold model). Time-series
study.
Poisson with GEE. Time-series
study.









Conditional logistic regression.
Case crossover with bidirectional
control sampling.






Poisson GAM with default
convergence criteria; case-
crossover analysis using
conditional logistic regression.








Effect Estimates

Risk estimates for NO2 not
reported.




1-h max O3 (per 50 ppb):

Seoul:
1.5% (0.5, 2. 5)
Ulsan:
2.0%(-11. 1,17.0)





1-h max O3 (per 50 ppb):

Two controls, plus and
minus 1 wk:
1.5% (-1.2, 4.2)

Four controls, plus and
minus 2 wks:
2.3% (-0.1, 4. 8)
Odds ratio in general
population:
1.1% (-0.3, 2. 5)
Congestive heart failure
cohort:
15. 8% (1.8, 31.7)




-------
OQ
to
o
o
TABLE AX6.9 (cont'd). EFFECTS OF ACUTE NOX EXPOSURE ON MORTALITY. RISK ESTIMATES ARE

                STANDARDIZED FOR PER 20 PPB 24-H AVG NO2 INCREMENT
X

I

£
H

6
o


o
H

O


O
H
W

O


O
HH
H
W
Reference, Study
Location, and Period
Outcome Measure
Mean NO2 Copollutants Lag Structure
Levels Considered Reported
Method/Design
Effect Estimates
ASIA (cont'd)
Ha et al. (2003)
Seoul, Korea
1995-1999
Hong et al. (2002)
Seoul, Korea
1995-1998
Tsai et al. (2003b)
Kaohsiung, Taiwan
1994-2000




Yang et al. (2004b)
Taipei, Taiwan
1994-1998




Wong et al. (200 Ib)
Hong Kong
1995-1997



Wong et al. (2002)
Hong Kong
1995-1998


All cause; respiratory;
postneonatal (1 mo to 1
yr); age 2-64 yrs; age 65+
Acute stroke mortality


All cause; respiratory;
cardiovascular; tropical
area




All cause; respiratory;
cardiovascular;
subtropical area




All cause; respiratory;
cardiovascular




Respiratory;
cardiovascular; COPD;
pneumonia and influenza;
ischemic heart dis.;
cerebrovascular
24-h avg 33 ppb PM10, O3, SO2, 0
CO

24-h avg 33 ppb PM10, O3, SO2, 2
CO

24-h avg 29 ppb PM10, SO2, O3, 0-2
CO





24-h avg 31 ppb PM10, SO2, O3, 0-2
CO





24-h avg 25 ppb PM10, O3, SO2; 0,1,2
in warm season; two-pollutant
33 ppb in cold models
season


24-h avg 29 ppb PM10, O3, SO2; 0, 1, 2, 0-1, 0-2
two-pollutant
models


Poisson GAM with default
convergence criteria.
Time-series study.
Poisson GAM with default
convergence criteria.
Time-series study.
Conditional logistic
regression. Case-crossover
analysis.




Conditional logistic
regression. Case-crossover
analysis.




Poisson GAM with default
convergence criteria.
Time-series study.



Poisson GLM. Time-series
study.



All cause for postneonates:
0.8% (-5.7, 7.7); age 65+:
3. 8% (3.7, 3.9)
4.3% (1.6, 7.0)


Odds ratios:
All cause:
0.1% (-5. 9, 6.6);
Respiratory:
-1.0% (-22.2, 25. 9);
Cardiovascular:
-1.8% (-14.0, 12.1)
Odds ratios:
All cause:
0.6% (-3. 9, 5.2);
Respiratory:
2.5%(-13.1,20.8);
Cardiovascular:
-1.1% (-9.5, 8.0)
All cause (lag 1 ):
2. 6% (0.9, 4.4);
Respiratory (lag 0):
6.1% (-1.8, 10.5);
Cardiovascular (lag 2):
5.2% (1.8, 8.7)
Respiratory (0-1):
5.1% (1.6, 8.7);
Cardiovascular (lag 0-2):
3.1% (-0.2, 6.5)


-------
OQ
 to
 o
 o
      TABLE AX6.9 (cont'd).  EFFECTS OF ACUTE NOX EXPOSURE ON MORTALITY.  RISK ESTIMATES ARE
                                 STANDARDIZED FOR PER 20 PPB 24-H AVG NO2 INCREMENT
  Reference, Study
Location, and Period
Outcome Measure     Mean NO2 Levels
    Copollutants
     Considered
  Lag Structure
    Reported
   Method/Design
    Effect Estimates
           ASIA (cont'd)
 X
 to
           Hedley et al. (2002)
           Hong Kong
           1985-1995
           Intervention Jul 1990
           (switch to low sulfur-
           content fuel)
           Yang et al. (2004b)
           Taipei, Taiwan
           1994-1998
                      All cause;
                      cardiovascular;
                      respiratory;
                      neoplasms and other
                      causes; all ages;
                      age 15-64yrs;
                      age 65+ yrs
                   Avg moly NO2:

                   Baseline: 29 ppb

                   1 yr after intervention:
                   25 ppb
                                                      2-5 yrs after
                                                      intervention: 28 ppb
SO2 (main pollutant of
interest, 45%
reduction observed 5
yrs after intervention),
FMio,
SO42~, NO2
Moly avgs
considered
without lags
                      All cause;
                      respiratory;
                      cardiovascular;
                      subtropical area
                   24-havg31 ppb
    o, S02, 03, CO
0-2
Poisson regression of
moly avgs to estimate
changes in the increase
in deaths from warm
to cool season.
Annual proportional
change in death rate
before and after the
intervention was also
examined.
Conditional logistic
regression.  Case-
crossover analysis.
Declines observed in all
cause (2.1%, p = 0.001),
respiratory
(3.9%, p = 0.001), and
cardiovascular
(2.0%, p = 0.020)
mortality after the
intervention.

As NO2 levels did not
change before and after
the intervention, NO2
likely did not play a role
in the decline in observed
mortality.
Odds ratios:
All cause:
0.6% (-3.9, 5.2);
Respiratory:
2.5% (-13.1,20.8);
Cardiovascular:
-!.!%(- 9.5,8.0)
 H
 6
 o

 o
 H
O
 O
 H
 W
 O
 O
 HH
 H
 W

-------
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