Pfm-lSO!!*
EPA 600/1-81-Q33
April 1981
EFFECTS OF PARTICULATE AIR POLLUTION ON ASTHMATIC SUBJECTS
by
Robert A. Kinsman, Ph.D.
Hyman Chai, M.D.
David W. Dickey, M.A.
Richard Jones, Ph.D.
Call 1s G. Morrill, Ph.D.
Ginger B. Perry, B.5.
Sheldon L. Spector, M.D,
Phillip C. Weiser.Ph.D.
National Jewish Hospital/National Asthma Center
Denver, Colorado
Contract No. 68-02-3208
Project Officer
Dorothy C. Calafiore, Ph.D.
Human Studies Division
Health Effects Research Lab
US Environmental Protection Agency
Research Trianqle Park, NC 27711
HEALTH EFFECTS RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
US ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, NC 27711
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TECHNICAL REPORT DATA
i?Uast -tad Imtmtcnoru on tnt rtvtrst btjort completing
!. 'yOflT NO, 2.
FPA-finn/l-RI-n^T npn Ponnrt
3. RECIPIENT'S ACCSSSIOto-NO.
. PB81-I90514"
*. TTLE ANO 5U3TlTLi
Effects of Particulate Air Pollution on Asthmatic
Subjects
S. REPORT OATH -
April 1981
«. PERPORMINO ORGANIZATION COOK
7. A
R.A.Kinsman, H.Chai, D.W.Dickey, R.Jon°.n, C.G.Morrill,
G.B.Perry, S.L.Spector, a*;d P.C.Weisei
8. PErtFOHMING ORGANIZATION REPORT NO.
9. feflPCRMING ORGANIZATION NAMS A(MO ACUrtSSS
National Jewish Hospital/
National Asthma Center
Denver, Colorado
10. PROGRAM CLIENT NO.
C9XA1C
11. CONTRACT/GRANT NO.
Contract No. 68-02-3208
13. SPONSORING AGENCY NAMS ANO ADORESS
Health Effects Research Laboratory (RTP,NC)
Office of Research and Development
US Environmental Protection Agency
Research Triangle Park, NC 27711
11 TYP« OP REPORT ANO PERIOD COVERED
14. SPONSORING AGENCY CO06
EPA-600/n
IS. SUPPLEMENTARY NOTES
Project Officer: Dorothy C. Calafiore, Ph.D.
abstract 1
While ouch remains to be understood, Individuals with respiratory
disease appear to be affected by high Tevels of air pollution as indicated
by subjective reports, clinic and hospital visits, and morbidity. Suspended
particulates make uo a substantial part of urban air pollution, and specific
components of particulates, such as sulfates and nitrates, when combined
with moisture, form acids with properties potentially irritating to the
lung. The available research literature has not clearly implicated the
components of suspended particulates wnich do exert an Intnediat# effect upon
the health status of individuals with respiratory disease.
The present study focuses upon the acute or short-term effects of
suspended particulates upon asthmatic individuals. It has Incorporated
several uniiwe features. First, extensive medical characterization of
each subject's asthma was available, and Individuals with other respiratory
or medical conditions were not included. Secondly, recent advance* in
methods of particulate measurement, baseo upon dlchotomous sampling of
particulates via virtual impactor techniques, were incorporated In the
study. Thirdly, the daily health status of the asthmatic subjects was
considered to be a concept that is best defined by deploying three different
types of measurements, selected In order to triangulate on the more
immediate health effects of air pollution upon the asthmatic subjects. This
report considers the period January through March, 1979 when IPM and' most
other pollutants were at their highest and most fluctuating levels in
Denver.
17. «6V WORDS ANQ OC
CUMKNT ANALYSIS
*• OESCR1PTOBS
b.lOENTIFIERS/OPEN ENOED TERMS
c. COSATt Field/Gioup
-is. ^I$U7'0N iTATSMftNT
RELEASE to public
19. SECURITY CLASS (ThuRipcm
UNCLASSIFIED
21. NO. OF PAGES
•"). SECURITY CLASS iThu paftf
UNCI ASSrFTFI)
33. PRICE
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DISCLAIMER
This report has been reviewed by the Health Effects
Research Laboratory, U.S. Environmental Protection
Agency, and approved for publication. Mention of
trade names or commercial products does not con-
stitute endorsement or reconwendation for use.
ii
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FOREWORD
The many benefits of our modern, developing, industrial society are ac-
companied by certain haiards. Careful assessment of the relative risk of
existing and new nan-made environmental hazards is necessary for the es-
tablishment of sound regulatory policy. These regulations serve to enhance
the quality of our environment in order to promote the public health and wel-
fare and the productive capacity of our Nation's population.
The Health Effects Research Laboratory, Research Triangle Park, conducts
a coordinated environmental health research program in toxicology, epidem-
iology, and clinical studies using human volunteer subjects. These studies
address problems in air pollution, non-ionizing radiation, environmental
carcinogenesis and the toxicology of pesticides as well as other chemical
pollutants. The Laboratory participates in the development and revision of
air quality criteria documents on pollutants for which national ambient air
quality standards exist or are proposed, provides the data for registration
of new pesticides or proposed suspension of those already in use, conducts
research on hazardous and toxic materials, and is primarily responsible for
providing the health basis for non-ionizing radiation standards. Direct sup-
port to the regulatory function of the Agency is provided in the form of
expert testimony and preparation of afficavits as well as expert advice to
the Administrator to assure the adequacy of health care and surveillance of
persons having suffered imminent and substantial endangerment of their health.
The study documented in this repui L .jas undertaken to identify specifi-
cally the effect of inhalable particulate matter on the exacerbation of asthma
symptoms. It was designed to incorporate several unique features. First, the
dichotomous sampling of particulate matter by recently developed air measure-
ment technology was employed. While this new technology represented an ad-
vance in exposure measurement, this study (as have other epidemiologic inves-
tigations) suffered the limitation of fixed site exposure measurement. A
second unique feature was the three-prong approach to health status measure-
ment. Subject responses were evaluated by two objective measurements (pul-
monary function tests and mechanically recorded medication usage) as well as
by the usual subjective patient-reported symptoms. Objective measurement of
medications used by subjects was for the first time possible by the newly
developed nebulizer chronologs designed to record aerosolized bronchodilator
usage. Thus, this study offered EPA's Health Effects Research Laboratory
new methods for evaluating ambient pollution levels and subject responses, in
addition to providing a limited amount of data needed for the preparation of
the forthcoming fine particulate criteria document.
F. G. Hueter, Ph.D.
Director
Health Effects Research Laboratory
iii
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ACKNOWLEDGEMENT
We gratefully acknowledge the technical assistance of Sharon Robinson,
Patricia Schor, and Robert Gibson during this study. Carolyn Wangaard,
Cynthia Cooper, Marilyn DeGroot, and Deborah Newton dedicated consider-
able time to conducting methacholine inhalation challenges and performing
antigen skin tests necessary for the medical characterization of the
asthmatic participants involved.
The Colorado Department of Health Air Pollution Surveillance Section co-
operated throughout this project, maintaining the two air pollution monitor-
ing stations located in East and West Denver. We particularly appreciate
the cooperation of Steve Arnold, Senior Air Pollution Specialist from that
office.
Chemical analyses of the inhaled particulate matter samples were provided
by Northrop Services, Inc. in Research Triangle Park, NC, and we thank
John Tisch of Northrop for his assistance ir. regard to these analyses.
Most notably, Dr. Dorothy Calafiore, our project officer at the Environ-
mental Protection Agency, was an invaluable aid to us, ready to help
facilitate any aspect of the project under her control.
Finally, we thank the volunteers who participated in this project as sub-
jects. For months, they were required to maintain careful daily records,
to perform daily pulmonary function tests, and to return to one of the
two Denver stations weekly for additional testing and debriefing. Their
consistent cooperation and their willingness to tolerate such inconven-
ience for no direct personal gain continues to be a source of gratification
to us; their patient cooperation was the critical factor in making this
work possible.
iv
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CONTENTS
Page
Disclaimer ii
Forword
Acknowledgement "*v
List of Tables vi
List of Appendices vii
1. Abstract 1
2. Introduction 3
3. Methods 6
3.1 Subjects 6
3.2 Measurements Employed 10
3.2.1 Environmental Variables 10
3.3.2 Health Status Measurements 13
3.3 Procedure . . .• 16
3.4 Data Management 17
3.5 Statistical Analyses 18
4. Results 27
4.1 Environmental and Meteorologic Variables 27
4.2 Health Statui?. Measurements 30
4.3 Health Status Measurements in Relation to Environmental
and Meteorologic Variables 35
4.3.1 Univariate Correlational Analyses 35
4.3.2 LEAPS AND BOUNDS Multiple Linear Regression
Analyses by Individual Subiects 37
4.3.3 Aggregate LEAPS AMD BOUNDS Multiple Linear
Regression Analyses for Groups 39
4.3.4 Application of the Random Effects Model 40
5. Discussion 42
6. Recommendations 46
7. References 50
8. Appendix A 54
9. Appendix B 56
10. Appendix C 59
11. Appendix D . 63
v
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LIST OF TABLES
Page
3.1 Descriptive Data for 24 Asthmatic Subjects Involved in the
Analyses 7
4.1 Monthly Means and Standard Errors for Inhaled Particulate
Matter (IPM) 28
t
4.2 Monthly Means and Standard Errors for Gaseous Air Quality
and Meteorologic Variables ... 29
4.3 Correlations Among the Environmental Variables 31
4.4 Means and Standard Errors for the Health Status Measurements . 33
4.5 Means and Standard Errors of the Correlation Coefficients
Among Health Status Measurements 34
4.6 Correlations Between Environmental Variables and Health
S .tus Measurements 36
4.7 Summary Table for LEAPS AND BOUNDS Multiple Linear Regres-
sion Analyses for the 24 Individual Subjects 38
4.8 Two-Tailed P-Values from Wilcoxon Signed Ranks Tests Per-
formed Across Subjects 41
vi
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LIST OF APPENDICES
APPENDIX A — AIRWAYS OBSTRUCTION SYMPTOM RATING SCALE
APPENDIX B — COVARIATE ANALYSES SUMMARY TABLES
Table B-l Two-Tailed P-Values from Wilcoxon Signed Ranks Tests
Performed Across Subjects for 12 and 24 Hour Lagged
Health Status Measurements
Table B-2 Two-Tailed P-Values from Tests of Significance on
Covariates Performed Across Subjects
APPENDIX C — FREQUENCY DISTRIBUTIONS FOR HEALTH STATUS MEASUREMENTS
Table C-l Frequency Distribution for Peak Expiratory Flow Rates
Table C-2 Frequency Distribution for Symptom Rating
Table C-3 Frequency Distribution for Nebulizer Usage
APPENDIX D — FREQUENCY DISTRIBUTIONS FOR ENVIRONMENTAL AND METEOROLOGIC
VARIABLES
Table D-l Frequency Distribution for Carbon Monoxide
Table D-2 Frequency Distribution for Sulfur Dioxide
Table D-3 Frequency Distribution for Ozone
Table D-4 Frequency Distribution for Temperature
Table D-5 Frequency Distribution for Barometric Pressure
Table D-6 Frequency Distribution for Fine Mass
Table D-7 Frequency Distribution for Coarse Mass
Table D-8 Frequency Distribution for Fine Sulfates
Table D-9 Frequency Distribution for Coarse Sulfates
Table D-10 Frequency Distribution for Fine Nitrates
Table D-l1 Frequency Distribution for Coarse Sulfates
vl 1
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1. ABSTRACT
This study evaluated the relationship between inhaled particulate
matter (IPM) and the health status of adult asthmatic patients residing
1n the Denver metropolitan area. All subjects lived within a radius of
2.5 miles of one of our two air pollution monitoring stations (East and
West Denver).
Using dichotomous, virtual impactor samplers, IPM was collected
daily for two 12-hour periods (7 AM to 7 PM; and 7 PM to 7 AM), provid-
3 -
ing meas'jr-rierts (ug/m ) of IPM total mass, IPM sulfates (S0^~), and
IPM Mtrates (NOg") for coarse (2.5 - 15 nm in aerodynamic diameter) and
f1r:e (<2.5 jjin) fractions. Hourly measures of carbon monoxide (CO), sulfur
dioxide (SC^)-. and ozone (0^) also were obtained. Temperature (°K) and
barometric pressure (in. Hg) were available at a single site (West Denver).
Health status of the asthmatic subjects was indexed by twice daily
(7 AM and 7 PM) measurements of peak expiratory flow rates (PEFR), sub-
jective report of airways obstruction, and continuous recording of as-
needed (PRN) aerosolized bronchodilators by a nebulizer chronolog.
Aralyses focused on the time period during which the highest and
most variable levels of air pollution occurred and the quality control of
the a:r pollution data were best assured (January through March, 1979).
In al* analyses, the preceding 12-hour levels of IPM were related to the
subsecuent health status measurements, while 12-hour gaseous air pollutants
and meteorologic variables bracketed the health status measurements.
1
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Initial multiple linear regression analyses were performed by LEAPS AND
BOUNDS for individuals end groups. Since the initial LEAPS AND BOUNDS re-
gression analyses did not take into account between-subjects variation, a
final phase involved analyses using a random effects model in which the
regression coefficients were considered random variables across subjects.
Of the air pollution variables, only fine nitrates, an IPM component that
was occasionally high in Denver relative to other American cities, were
associated with increased symptom reports by the subjects and increased
aerosolized bronchodilator usage. Due to the number of comparisons made,
this result needs to be viewed as tentative and potentially attributable
to chance.
The relative strengths and limitations of the study are discussed.
This report was submitted in fulfillment of Contract No. 68-02-3208
by National Jewish Hospital/National Asthma Center under the sponsorship
of the U.S. Environmental Protection Agency. The report describes work
completed during the contract period December 7, 1978 to May 15, 1930.
2
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2. INTRODUCTION
While much remains to be understood, individuals with respiratory
disease appear to be affected by high levels of air pollution as indicated
by subjective report, clinic and hospital visits, and morbidity.'^0 Sus-
pended particulates make up a substantial part of urban air pollution, and
specific components of particulates, such as sulfates and nitrates, when
combined with moisture, form acids with properties potentially irritating
to the lung.
The available research literature has not clearly implicated the com-
ponents of suspended particulates which do exert an Immediate effect jpon
the health status of individuals with respiratory disease. A recent ex-
•»1
tensive review' concluded that the minimum "24 hour average levels of
total suspended particulates at which increased incidence of illness in
bronchitic patients is discernible are levels in exces? of ... about 350
yg/m3 in the presence of sulfur dioxide of about [.16 ppm]." These levels
12 13
are ba^ed on studies by Lawther and Waller in London and other urban
areas of Great Britain. For asthma, the controversial CHESS studies^4*15
have been the most ambitious projects to date that have focused on sus-
pended particulates, but these studies have not provided definitive ans-
wers on the effects of various levels of suspended particulates on health.
Moreover, the single aspect of health status Involved 1n the CHESS studies
concerned the reported incidence of breathing difficulty characteristic
of asthma attacks.
3
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The present study focuses upon the acute or short-term effects of sus-
pended particulates upon asthmatic individuals. On a conceptual basis,
asthmatic subjects should be among the most highly sensitive of individuals
to the more immediate irritant properties of suspended particulates and
other irritant air pollutants because of the inherent hyperreactivity of
16-18
the airways of asthmatics to known irritants.
The present study has incorporated several unique features. First,
extensive medical characterization of each subject's asthma was available,
and individuals with other respiratory or medical conditions (e.g., bron-
chitis or emphysema) were not included. Medical characterization for most
subjects included skin tests with allergens (grasses, trees, weeds, and
house dust), and airways hyperreactivity, indexed either by methacholine
IS 19
inhalation challenge * or demonstrated reversibility of airways ob-
struction upon inhalation of a bronchodilator medication, or both. Thus,
the potentially confounding role of allergic factors upon airways ob-
struction could be explored by separating the asthmatic subjects according
to allergic predisposition, while the level of airways hyperreactivity
could also be used to explore any differing response to the air pollution
variables.
Secondly, recent advances in methods of particulate measurement,
based upon dichotomous sampling of particulates via virtual impactor
techniques,^"24 were incorporated in the study. These procedures enabled
two fractions of inhaled particulate matter (IPM) to be measured: A coarse
fraction, including IPM with an aerodynamic diameter between 2.5 and 15 vm;
and a fine fraction, with an aerodynamic diameter less than 2.5 ym. The
fine fraction of IPM may be particularly likely to trigger airways
4
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obstruction in asthma because of the deposition of these fine particles
throughout the airways, and the potentially irritant qualities of the
26 2 7
chemical components with which they are often associated. * In this
regard, supplemental chemical analyses focused upon the sulfate (SO^-)
and nitrate {NO3") components of IPM within the fine and coarse fractions.
The health effects of 1PM measures were examined against a background of
other environmental (carbon monoxide, sulfur dioxide, and ozone) and
meteorologic (temperature and barometric pressure) factors.
Thirdly, the daily health status of the asthmatic subjects was con-
sidered to be a concept that is best defined by employing three different
types of measurements: (A) a physiological measurement, i.e., peak ex-
piratory flow rate (PEFR), (B) a subjective measurement, i.e., report of
the severity of airways obstruction symptoms, and (C) a behavioral measure-
ment, i.e., discretionary usage of as-needed (PRN) aerosolized broncho-
dilators. These thref: measurements were selected in order to triangulate on
the more immediate health effects of air pollution upon the asthmatic
subjects.
This report considers only the period of January through March, 1979
when IPM and most other pollutants were at their highest and most fluctu-
ating levels in Denver, although all subjects were followed until June, 1979.
After the end of March, 1979, the particulate levels were generally low and
showed fewer variations, and information missing from one monitoring station
(West Denver) and a suspected equipment malfunction at the other station
(East Denver) precluded use of particulate data.
5
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3. METHODS
3.1 SUBJECTS
From an Initial panel of 60 volunteers, 41 wel 1-characterized asthmatic
subjects were selected and carefully followed for approximately five months,
January 1 to June 10, 1979. All lived within 2.5 miles of one of two air
pollution monitoring stations, an East Denver station {National Jewish
Hospital) and a West Denver station (National Asthma Center). Two subjects
were dropped from the study due to lengthy absences from the Denver metro-
politan area which were not anticipated at the outset. Of the remainder,
24 subjects, 12 at each station, met a criterion of 60% complete data with-
in the target period of January, 1979 through March, 1979, after eliminating
daily measurement periods when upper respiratory infections (URI's) were
reported and periods when subjects were out of the Denver metropolitan area
for more than three hours during a 12-hour measurement period. All subse-
quent analyses focused upon these 24 subjects that met these criteria. The
17 subjects eliminated were not unique with respect to any demographic or
medical measurement. Table 1 (shown on pages 7 and 8) provides detailed
demographic and medical information about the 24 subjects (9 males and 15
females) accepted for analyses. All were takinci a theophylline preparation
or an oral beta agonist on a -agular schedule as a basic bronchodilator,
while 8 subjects also supplemented this medication regimen with daily or
alternate day oral corticosteroids. In addition, all subjects took an
6
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TABLE 3.1 DESCRIPTIVE DATA K)R 24 ASTHMATIC SUBJECTS INVOLVED IN THE ANALYSES
A) East Denver Station
Age
'atient (Years) Sox
Methaclioline*
(Threshold Dose)
(my/ml)
Skin.
Tests
As-Needed
Broncho-
_ 30
520 + 30
Asbestos and
Creosote
L.S.
28
F
.31
+
Medihaler
None
370 + 30
390 + 20
H.S.
4a
F
.31
Alupent
None
280 + 20
370 + 30
D.T.
26
M
2.50
-
Alupent
Alternate
Day
390 t 100
400 ~ 120
B.W.
26
M
.62
+
Bronkometer
None
370 J 50
380 + 60
Cigarette Sinoke
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TABLE 3.1 - Continued
(C) West Denver Station
Methacholinea As-Needed Peak Flow11 Peak Flowe Reported
Age (Threshold Dose) Skin Broncho- Steroid (1/min) (l/min) Irritant
Patient (Years) Sex (mg/nil) Tests1' dilatorc Medication (AM) (PM) Lxpoiure
O.B.
22
F
.15
tf roiikosol
Alternate
Day
340 ~ 30
370 + 40
M.B.
24
F
.15
~
Bronkosol
None
360 + 60
360 + 50
Chemical Cleaners
B.L.
48
F
.62
-
Bronkosol
None
270 ~ 30
270 + 30
C.H.
47
N
.31
-
Alupent
None
440 ~ 40
450 + 40
T.M.
21
F
Not Done
+
Alupent
Alternate
Day
430 ~ 70
470 + 60
C.H.
27
F
.07
+
Alupent
None
280 ~ 60
290 ~ 60
B.N.
32
F
.15
Bronkometer
Ai Lerrjte
Day
390 ~ 20
380 + 30
P.S.
24
M
Not Done
Not Done
Bronkosol
None
480 ± 30
480 + AO
S.S.
25
F
.07
-
Alupent
None
370 ~ 60
410 + 50
Developing
Solution
R.S.
60
F
.07
-
Alupent
None
190 ~ 60
260 + 70
A.V.
28
F
.15
-
Alupent
None
190 + 50
300 + 80
P.U.
45
F
1.25
+
Alupent
Hone
400 ~ 60
400 ~ 60
aPossible threshold levels (mg/ml) in the standardized methacholine inhalation challenge procedure are:
.07. .15, .31, .62, 1.25, 2.50, 5.00, 10.00, and 25.00.
"Skin test reactions were positive (~) to one or more of the following antiqens: Mixed wtieds, mixed grasses, mixed
trees, and/or house dust. Negative (-) indicates that there were no positive skin test reactions for any antigen.
cBrand names of the aerosolized bronchodilators taken on an as-needed (PRN) basis are shown.
•Jhcm values ~ SD from January 9 - March 28 for 7 AM.
eHean values SO from January 9 - March 28 for 7 PH.
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aerosolized bronchodilator on a discretionary, as-needed (PRN) basis to
relieve episodes of acute breathing difficulty.
Prior to acceptance for the study, the subjects were screened to con-
firm the diagnosis of asthma. All had perennial symptoms of asthma as de-
I O
fined by the American Thoracic Society. Methacholine inhalation chal-
lenges, conducted according to the recommendations of the National Institute
of Allergy and Infectious Disease Panel on Standardization of Bronchial In-
19 20
halation Challenge Procedures, ' were given to 20 of the subjects, and
all had positive results, consistent with a diagnosis of asthma. Four of
the 24 subjects were not given methacholine challenges, at their physician's
requests. However, for all subjects, hyperreactive airways disease was
also confirmed by marked variations in twice-daily peak expiratory flow
rates (PEFR) during a 5- to 7-day prescreening period, by medical history,
and by physical examination. Prick tests with mixed weeds, mixed grasses,
mixed trees, 3nd house dust were given to 23 of the 24 subjects accepted
21
for the analyses. Four of the 23 subjects reacted positively (indicating
the presence of Ige) to mixed trees, 7 to mixed grasses, 7 to mixed weeds,
and 6 to house dust. Ten of the subjects reacted negatively to all antigen
skin tests.
All subjects were given a chest x-ray during prescreening to rule out
the existence of pulmonary conditions other than asthma, and an electro-
cardiogram to exclude individuals with heart disease or related
cardiopulmonary problems. All of the subjects were nonsmokers, however,
five reported being exposed to irritants at their work or in their homes.
Finally, prescreening by brief psychological testing eliminated those
subjects likely to overuse as-needed (PRN) aerosolized hronchodilators
9
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when airways obstruction is not present, or to use these PRN aerosolized
bronchodilators in arbitrary ways independent of the levels of airways
obstruction. The specific psychological instrument employed was the MMPI
Panic-Fear Personality Scale used to identify and exclude patients with
excessively high characterological anxiety known to be associated with PRN
22 23
overuse and arbitrary use. *
3.2 MEASUREMENTS EMPLOYED
Two classes of measurements were obtained twice each day: (A) envi-
ronmental and Meteorologic Variables (average temperature and barometric
pressure); and (B) Health Status Measurements, including peak expiratory
flow rates (PEFR), use of as-needed (PRN) aerosolized bronchodilators, and
report of the airways obstruction symptoms characteristic of asthma.
3.2.1 Environmental Variables
The environmental variables considered included: (A) coarse and fine
fractions of inhaled particulate matter (mass, nitrates, and sulfates), (B)
gaseous air pollutants (sulfur dioxide, carbon monoxide, and ozone), and (C)
meteorologic measurements (temperature and barometric pressure).
Inhaled Particulate Matter (IPM). The principal environmental vari-
ables were two fractions of inhaled particulate matter (IPM) which were
simultaneously monitored at the East (National Jewish Hospital, 3800 East
Colfax Avenue) and West (National Asthma Center, 1999 Julian Street) Denver
stations. Identical dichotomous samplers using virtual impactor tech-
niques were used at each station to measure two IPM fractions, a fine
fraction consisting of particulates <2.5 um in aerodynamic diameter, and
a coarse fraction consisting of particulates between 2.5 and 15 pm in
10
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aerodynamic diameter. Via the dichotomous samplers, IPM for both fractions
were collected on glass wool slides during two daily 12-hour collection peri-
ods, i.e., from 7 AM to 7 PM (7 PM) and from 7 PM to 7 AM (7 AM). The glass
wool slides were inspected visually in Denver to insure their integrity
(e.g., no tears, etc.) and shipped bi-monthly to Northrop Services, Inc.
(Research Triangle Park, NC) for IPM analyses. The glass wool slides were
* • «
weighed and subjected to ion exchange chromatography analyses to determine
the IPM sulfate (S0^~) and nitrate (NO^ ) mass concentrations for botn the
29
fine and coarse IPM fractions. In summary, the IPM measures that were
obtained included mass (ug/m ), sulfates (ug/nr), and nitrates (ug/m ) for
the fine and coarse IPM fractions during each 12-hour period.24'28
For IPM, quality control considerations required that dichotomous
sampler flow rates be ch??ked by an independent acent at the outset of the
study period (December, 1978), and by the Colorado Department of Health in
December, 1978 and February, 1979. The dichotomous sampler trays were
checked weekly while the dichotomous samplers were in operation, and proper
sealing and alignment of the trays were verified on a bi-weekly basis at
the time that new trays were loaded into the samplers. Visual checks of
the glass wool slides were made to assure their Integrity prior to shipping
to Northrop for analyses.
Gaseous Air Quality. Gaseous air pollutant measurements, including
sulfur dioxide (St^). carbon monoxide (CO), and ozone (Oj), were obtained
hourly by the Colorado Department of Health through their continuous monitor
1ng program. In order to bracket each health status measurement period
for the gaseous air quality measurements, each day was divided into two
12-hour periods, 12 AM to 12 PM (bracketing 7 AM) and 12 PM to
-------
12 AM {bracketing 7 PM). Average values, expressed in parts per
million (ppm), were obtained for each of these periods.
All measurements of the gaseous air quality variables were made using
continuous automated methods, with data collection made by a computer-
operated telemetered data acquisition system. Intake manifolds for air
sampling were consistent with Environmental Protection Agency design cri-
teria,3^ with the intake ports being uniform in elevation, from i5 to 20
feet above the ground at botn stations.
Sulfur dioxide was measured with Thermo Electron Model 43 pulsed fluo-
rescerice analyzers. Carbon monoxide was monitored using Beckman Model 866
nondispersive infrared analyzers. Ozone was measured using ethylene chemi-
luminescent McMillan 110 equipment. All analytical methods for gaseous
air quality measurements were designated equivalent under Federal
32
specifications.
For the gaseous air quality measurements, quality assurance procedures
were utilized to assure compatability with National Bureau of Standards
reference standards through methods employed by the Colorado Department of
Health. All gaseous analyzers were calibrated with a multipoint cali-
bration at the outset of the study period, and received daily purge and span
checks on the values to help assure identification of malfunction on a day-
to-day basis. During data processing, the gaseous air quality data were
visually audited by Colorado Health Department personnel, to identify any
unreasonable values.
Meteoroloqic Measurements. Hourly temperatures fJK) were available
from the Colorado Health Department Welby monitoring station, approximately
two miles equidistant from the East and West Denver stations. Average values
-------
were obtained for the 7 AM and 7 PM periods. Four daily barometric pressure
measurements (in. Hg.) adjusted to sea level equivalencies, were obtained
from the West Denver station (7 PM, 1 AM, 7 AM, and 1 PM). Barometric
pressures were checked every day against values provided by the National
Weather Bureau at Stapleton International Airport. The average barometric
pressure was obtained by averaging the value for the period of interest and
the two barometric pressure values from six hours before and six hours after
that period.
3.3.2 Health Status Measurements
The effects of the inhaled particulate matter, gaseous air pollutants,
temperature, and barometric pressure upon the health status of asthmatics
were evaluated by obtaining twice daily measureinents of three health status
variables: (A) Physiological: Pulmonary function measurements; (B)
Behavioral: Usage of as-needed (PRN) aerosolized bronchodilators; and (C)
Subjective: Ratings of the symptoms of airways obstruction. Each of these
health status measurements provides an unique index of the potential effects
of IPM upon individuals with hyperreactive airways disease.
Physiological: Pulmonary Function Measurements. Each subject was
equipped with, and trained to use, a Mini-Wright Peak Flow Meter (Armstrong
Industries, Inc., Northbrook, IL). This small, portable device reliably
measures the peak expiratory flow rate (PEFR) ~ the maximum flow rate
(liters/min) achieved during a forced expiration following a full inspiration.
As airways obstruction increases, PEFR values decrease.
On eac'i occasion (7 AM and 7 PM), the subject used the Mini-Wright
Peak Flow Meter (Mini-Wright) three times, with a one-minute rest between
13
-------
expirations. The three PEFR values (read from a gauge on the Mini-Wright)
were recorded at the bottom of their morning (or evening) log.
Quality control procedures were also established for the Mini-
Wrights.^ During the study, the peak flow readings on the Mini-Wrights
were checked weakly against the readings on a standard adult Wright Peak
Flow Meter (Std-Wright), using a reproducible flow source. This flow source
consisted of a gallon plastic bottle fitted with a compressed air source,
a large respiratory valve which could be operated manually to release pres-
sure and hence flow through the Std- or Mini-Wright. By interchanging two
valves fitted with fixed (but different) resistors and by delivering a range
of pressures up to 12 pounds/square inch to the flow meters, peak flows
between 75 and 800 1/min could be generated. Mini-Wright readings versus
Std-Wright readings fell along the same linear regression line regardless of
whether the flows were generated by the pressurized bottle or a Brooks rota-
meter using a constant flow source. The relationship between actual flow
and Std-Wright readings allowed the values from both types of peak flow
meters to be corrected by a constant to reflect actual flow. The adequacy
of the Mini-Wrights was supported by the remarkable reproducibility and
consistent readings for each Mini-Wright over the period of the study, al-
though, as noted, small variations in uncorrected readings did occur
among Mini-Wrights for the same flow.
To supplement the twice-daily PEFR values obtained by the Mini-Wrights,
once each week the subjects returned to their assigned station and more ex-
tensive spirometric pulmonary function measurements were obtained using a
Medistor spirometer (Cybermedic, Inc., Boulder, CO). These weekly pulmonary
function measurements were supervised by a trained pulmonary function
14
-------
technician, and provided measurements of PEFR, forced vital capacity (FVC),
first-second forced expiratory volume (FEV^), and mid-maximum expiratory
flow rate (MMEF).
Behavioral: Usage of As-Needed (PRN) Aerosolized Bronchodilators. A11
subjects were equipped with a nebulizer chronolog (Advanced Technology Pro-
ducts, Inc., Denver, CO) to measure usage of as-needed (PRN) aerosolized
bronchodilators. Usage measurements were also confirmed by having the sub-
ject record the time and amount for each occasion of nebulizer use on the
daily logs.
The nebulizer chronolog is a small instrument (about one-half a
cigarette package in size) that attaches to any commercially manufactured
aerosolized bronchodilator (e.g., Bronkosol, Bronkometer, Alupent). The
nebulizer chronolog consists of a battery-operated, crystal-controlled time-
piece capable of logging up to 256 nebulizer usages with a resolution of
four minutes and ar. accuracy of + one minute per month. A nebulizer chrono-
log interpreter (a micro-computer) provided a printed report of the nebulizer
usage times stored within the nebulizer chronolog, upon demand. Each week,
when the subject returned to the East or West Denver station, the nebulizer
chronolog was removed from the aerosolized bronchodilator cartridge, inter-
preted, and reset. To assure as reliable a measurement as possible of neb-
ulizer usage, subjects in the study were required to agree to use only that
aerosolized bronchodilator equipped with the nebulizer chronolog, and to
deposit any existing, supplementary aerosolized bronchodilators at one of
the two stations prior to data collection.
Subjective: Ratings of the Symptoms of Airways Obstruction. The
morning (7 AM) and evening (7 PM) logs required the subject to rate nine
15
-------
discrete symptoms of breathing difficulty, each on a 5-point scale of
severity (1 = not at all severs; 5 » extremely severe). The symptoms in-
cluded in this Airways Obstruction Scale have been found to be component
35
symptoms of airways obstruction in asthma, and together provide a symptom
score with a potential range of 37 points (9 to 45). The composition of
the symptom scale is shown in Appendix A.
3.3 PROCEDURE
Prior to data collection, all subjects were trained to use the daily
log books, both morning (7 AM) and evening (7 PM), the Mini-Wright Peak
Flow Meters, and t.he aerosolzied bronchodilators equipped with the nebulizer
chronologs. This pretraining period complied with the protocol of the study
precisely, and consisted of five (minimum) to seven (maximum) days for all
subjects.
The two stations (East Denver station: National Jewish Hospital, 3800
East Colfax Avenue; West Denver station: National Asthma Center, 1999
Julian Street) are located in Denver on an east-west line, approximately
five miles apart. Both stations were identical i?t equipment and function
for both air pollution and health status monitoring. During data collection,
the procedures were separated into (A) Daily and (B) Weekly requirements.
Daily. On a daily basis, each subject completed the morning log be-
tween 6 AM and 8 AM (7 AM) prior to taking any daily, scheduled medications.
Upon completion of the morning log, the subject used the Mini-Wright three
times, with an interval of one to two minutes between each measurement. The
PEFR values, read from a gauge on the Mini-Wright, were entered on the morn-
ing log. Upon completion of the log, information about mobility and ac-
tivity (past 12 hours), subjective ratings of airways obstruction, and PEFR
-------
were available. The morning log, Including PEFR measurements, required only
about five to ten minutes to complete. An identical procedure was followe.1
for the evening log completed between 6 PM and 8 PM (7 PM) each day. The
health status measurements obtained were available to be related to IPM
values for the preceding 12-hour period.
Finally, usage of as-needed (PRN) aerosolized bronchodilators was
registered by the nebulizer chronologs, supplemented by patient records of
usage written on the logs.
Meekly. Once each week, each subject reported to the East or West
Denver station, returning with the aerosolized bronchodilator equipped with
the nebulizer chronolog, and the daily log book. The nebulizer chronolog
was interpreted, and all occasions of usage of the nebulizer were recorded
and entered into a running record. The daily log book was examined to
assure that it was being completed diligently, and any problems in record-
keeping were resolved at this time. Finally, the nebulizer chrcnolog was
reset, and the log book replenished for the next week.
The subject then underwent the weekly pulmonary function testing,
supervised by a trained pulmonary technician, using a Medistor spirometer.
3.4 DATA MANAGEMENT
Two classes of data, (A) Environmental and Meteorologic Variables,
and (B) Health Status Measurements were coded onto computer forms, and a
computer-based file established and maintained on the University of Colorado
(Boulder) CDC 6400 computer system.
The environmental variables were reported as two separate classes.
IPM variables were recorded as 12-hour totals conforming to AM (7 PM to 7 AM)
and PM (7 AM to 7 PM) periods. These included mass, sulfates, and nitrates
17
-------
*
divided into fir-- atv coarse fractions, and were reported 1n pg/m . The
second class of environmental variables was the gaseous pollutants which
"were collected hourly over tne 12-hour periods: 12 midnight to 12 noon
(bracketing the 7 AM period) and 12 noon to 12 midnight (bracketing the 7 PM
period). These included carbon monoxide, sulfur dioxide, and ozone, and
were reported in ppm. Temperature data were converted to averages calculated
for 12-hour morning (7 PM to 7 AM [7 AM]) and evening (7 AM to 7 PM [7 PM])
periods. Barometric pressure was converted to average values at 7 AM or 7 PM,
based on the barometric pressure at the time of interest and the six hours
before and after that time.
For the health status measurements, each subject's record was scanned
prior to analyses to eliminate those days during the study when (A) the
subject reported being outside the metropolitan Denver area for more than
three hours during any 12-hour period, and/or (B) reported an upper respira-
tory infection at the time the log was completed. Due to failure to service
the dichotomous samplers, an eight-day period of IPM collection was lost
during February (February 13 to February 21).
3.5 STATISTICAL ANALYSES
3.5.1 Statistical Hypotheses
The objectives of the statistical analyses were to test tfos study's
null hypotheses pertaining to the effects of air pollution upon each of !he
three health status measurements, namely that:
(1) Elevated pollution levels do not significantly increase
the severity of reported airways obstruction symptoms;
(2) Elevated pollution levels do not signif5cant)y decrease
peak expiratory flow rates; and that
18
-------
(3) Elevated pollution levels do not significantly increase the
usage of as-needed (PRN) aerosolized bronchodilators.
Separate analyses were made for the 7 AM and 7 PM health status
measurements relating the health status measurements to the IPM collection
and other environmental and meteorologic variables for the appropriate 12-
hour period. Two series of analyses were performed to test the hypotheses,
using (A) LEAPS AND BOUNDS multiple linear regression, and (B) a random
effects model. Despite the directional nature of these hypotheses, in all
analyses two-tailed tests were used since many comparisons were to be made.
The potential existed for health status measurements to be correlated
serially more strongly between either consecutive 12-hour measurements or
24-hour measurements. As a preliminary step to both series of analyses,
these serial correlations were checked for both the 12- and 24-hour lags
for each of the health status measurements. While for both lags, all serial
correlations were statistically significant for each of the health status
measurements, the serial correlation between consecutive 12-hour measurement
periods was the strongsst (see Appendix B for p-values for both lag periods)
and was selected as the covariate in both analyses so as to remove this lag
effect.
3.5.2 LEAPS AND BOUNOS Multiple linear Regression Analyses
The first series of analyses involved correlations and the application
of multiple linear regression by LEAPS AND BOUNDS for individuals and
group averages. Averaged health status measurements were obtained by
averaging data from the 12 subjects at each station. For each subject, a
mean response was calculated and then subtracted from his/her observations
to remove a possible subject effect. This was done for each response
-------
variable, separately for AM and PM time periods. Then, at each time point
(7 AM and 7 PM for each day of the study period), data were averaged across
all subjects having data for that time point.
For this initial series, since the data were not Gaussian, transforma-
tions to normality were used to minimize the effect of outliers and to pro-
duce more robust tests of the hypotheses. Thus, the first step in the
analyses was to apply a nonparametric normalizing transformation sometimes
referred to as "normal scores." All variables used in the analyses, both
health status measurements and environmental and meteorologic variables,
were transformed separately by ranking the data from the smallest to the
largest value. Accordingly, if R is the rank of a variable from N observa-
tions, this variable is assigned the transformed value of:
where $ denotes the cumulative distribution function of a standard normal
distribution (mean 3 0; standard deviation =1).
The purpose of this normalizing transformation was to prevent spurious
correlations caused by a few extremely outlying data points. Additionally,
standard methods can be used to calculate p-values from the transformed
data where these methods are inappropriate for highly-skewed data.
Three types of statistical analyses were then conducted.
(A) Correlational Analyses. Using transformed data, correlations
were calculated between each Individual environmental and meteorologic
variable and each health status measurement, using all available data for
20
-------
each pair of variables. From these analyses, for each environmental and
meteorolopic variable, 12 correlations resulted, defined by three health
status measurements (PEFR, subjective report of airways obstruction, and as-
needed aerosolized bronchodilator usage), two time periods (7 AM aid 7 PM),
and two stations (East and West Denver). Given no relationship between an
environmental variable and the set of 12 health status measurements, the
p-values would be expected to be distributed uniformly between zero and
one. Given any relationship, these p-values would tend to cluster toward
zero. A test of the hypothesis that the p-values are uniformly distributed
37
(no relationship) is available by using Fisher's method of combining prob-
abilities for several mutually independent tests:
K 2
-2 > E in Pl * x
i = i 2K
where K is the total number cf tests, and p^ is any p-value. The statistic
is distributed as chi square with 2K degrees of freedom.
Based on these preliminary correlational analyses and Fisher's test
for combining the probabilities of several mutually Independent tests, the
variables to be used in the ne;;t phase of the analyses were selected. These
subsequent analyses involved multiple linear regressions for individuals
and groups of 12 subjects assigned to each of the stations (East and West
Denver).
(B) Multiple Linear Regression Analyses for Individuals. Using the
best environmental and meteorologic variables identified by the preceding
correlational analyses, multiple linear regression analyses were conducted
21
-------
for each health status measurement on a subject-by-subject basis. These
analyses used the LEAPS AND BOUNDS algorithm of Furnival and Wilson.38 The
39
program was adapted to include Akaike's Information Criterion (AIC) as a
method to select the best set of predictors for each health status measure-
ment. As noted, since daily data are serially-correlated, the value of
each health status measurement from the preceding 12-hour measurement period
40
was used as a predictor variable. This lagged variable acts as a covariate,
removing a significant portion of the serial correlation and reducing the
error variance. When included in the LEAPS AND BOUNDS algorithm as a
possible predictor, it may or may not be selected as being among the best
predictors by the AIC criteria. If not selected, the serial correlation is
weak. If selected, the effect of the serial correlation is largely removed.
If there are P possible predictor variables in the Lt'APS and BOUNDS
D
regression, there are 2 possible subsets. In such extreme multiple com-
parison cases, there is no way known to determine the true significance
levels. The p-values output by the program can only be used as guides and
not interpreted as true values. For this reason, only variables which were
significant at the p < .01 level were considered.
(C) Agoregate Multiple Linear Regression Analyses for Groups. Multiple
linear regressions by LEAPS AND BOUNDS were then done for the 12 subjects
from each station considered as a group, using the best and most pertinent
set of environmental variables based on the analyses described above. For
each health status measurement, the best set of predictors was identified by
the AIC criteria.
3.5.3 Application of a Random Effects Model
A potential weakness of the initial series of regression analyses by
22
-------
LEAPS AND BOUNDS is that it disregards between-subjects variability. The
second series of analyses therefore involved a random effects model which
takes into account between-subjects variability, and also explored potential
additional sources of bias, including weekends, temperature, barometric
pressure, and seasonality, which could affect tests of the statistical
hypotheses.
In this second series of analyses, the regression coefficients were
considered to be random variables across subjects, and the null hypothesis
was that the mean effect of air pollution variables was zero. A normalizing
transformation of the data was not used, but the residuals were checked and
found to be reasonably Gaussian.
The first step of the analysis was to fit the following model:
Yt = 6o + ~ et <"
where i denotes the 12-hour time lag of each subject's response variable.
When either Y or Y is missing, this time was dropped from the regression.
U li™ 1
The regression coefficient Si is then estimated by a simple linear regres-
sion. In the random effects model, ei is assumed to be a random variable
across subjects. The hypothesis to be tested is that the mean effect across
subjects is zero. If the assumption of a Gaussian distribution of B) across
subjects is in doubt, as in the present case, the appropriate test is the
nonparametric Milcoxori signed rank test. This test is performed by rank-
ing the absolute values of the regression coefficients for subjects, and
summing the ranks of the negative coefficients ard of the positive
coefficients.
23
-------
For these analyses, the 12-hour lag was retained as a covariate, and
additional covariates were considered:
(1) Weekend-not weekend
(2) Temperature
(3) Barometric pressure
(4) Seasonality
As a preliminary step, the first three of these potential covariates
were tested using the model:
Yt = 6o + + Et (2)
The weekend-not weekend variable was coded one for weekend and zero
for weekdays. When Y^, or Xt were missing, this time was dropped.
The p's were estimated by multiple linear regression for each subject, and
the coefficient 2?. tested across subjects as above using the Wilcoxon
signed rank test. This tests the potential effect of with time lag
effect removed.
Seasonality was tested using the model:
Yt = 60 + BlYt-i + &2 C0S (2,rt/365) + e3 sin (2trt/365) + et (3)
where the index t denotes the day. This is the fundamental frequency of
one cycle per year fitted over part of a year. The time shape of a season-
ality function will not be exactly a sine wave, but over a quarter of a year,
this should give a good approximation of the seasonality effect. Because
the data consist of only a part of a year, and because some data are missing,
the sine and cosine functions are not orthogonal, and must be fit by multiple
linear regression methods. If there is no seasonal effect, the random
24
-------
effects model states that the mean values of both b2 and b3 across subjects
are zero. The estimates from subject j, b2 ^ and b3 ^ are correlated,
so the appropriate test assuming a bivariate Gaussian distribution is
9 41
Hotel!ing's T . For n subjects, let:
n-1
? (b2^ - b2)2 T. (b2^ - b2) (b3^ - b3)
j=l
sym
; (b3-6s)2
(4)
be the estimated 2 by 2 covariance matrix of the cosine and sine coefficients
estimated across subjects, and sym denotes that the matrix is symmetric.
Hotelling's is:
¦ n[ b2B3]
-1
(5)
which is a scalar. This can be tested using F tables, as:
n-2 j2 ^ P
2(n-l) " * 2,n-2
(6)
The results of the random effects tests for the four covarlates are
shown in Table 2 of Appendix B. The only significant result is a weekend
PM effect for nebulizer use, indicating that there is an increase in neb-
ulizer usage during the day on weekends. This covariate was included in
subsequent analyses Involving PM nebulizer usage.
The final analyses used model 3 to test each of the nine pollutants
one at a time, except that for PM nebulizer use the extra covariate for the
25
-------
weekend effect was Included, where Xt represents the value of the pollutant.
The Wilcoxon signed rank test was used to test the significance of the
regression coefficients.
26
-------
4. RESULTS
4.1 ENVIRONMENTAL AND METEOROLOGIC VARIABLES
Monthly moans (and standard errors) for the environmental and meteor-
ologic variables are presented In Tables 4.1 and 4.2 (shown on pages 28 and
29) for the East and West Denver stations. For each variable, two means
are shown, one for the collection period ending at 7 AM (7 AM) and one for the
othc - collection period ending at 7 PM (7 PM). Daily fluctuations 1n the
environmental and meteorolocjic variables across the full three-month period
are summarized in the frequency distributions presented in Appendix D. For
both stations, average values for fine and coarse IPM were high and variable
during the months of January and February compared with March levels. In
general, the East Denver station, located at the busiest intersection 1n
Denver, had notably higher 7 AM fine IPM mass levels than the West Denver
station, a difference that was particularly noticeable 1n January and
February. For the IPM components, fine and coarse IPM sulfates, and
fine IPM nitrates were also generally higher for the 7 AM collection period,
and higher at the East than the West Denver station. For these variables,
a continuous decrease in monthly mean levels was discernible from January
through March. Average coarse IPM nitrate levels were generally low
throughout the study period, and at both stations.
For the gaseous air quality measurements, mean carbon monoxide and
sulfur dioxide levels reflected certain tendencies similar to those of the
IPM variably, showing higher levels at the East Denver station. These
-------
fABLE 4.1 MONTHLY MEANS AND STANDARD ERRORS FOR INHALED PARTICULATE MATTER (1PM>
Time Fine Mass Coarse Mass Fine Sulfates Coarse Sulfates fine Nitrates Coarse Nitrates
Station Month N Period (i^g/m ) (iig/m ) (ug/m ) (i>g,'m ) (vg/m ) (Mg/m )
January 23
7 AM
36.5 + 5.6
29.5 ~ 4.8
3.80 t 0.70
0.45 + 0.07
2.22 + 0.80
0.07 + 0.03
7 PM
31.4 t 4.2
42.1 + 6.9
4.00 + 0.54
0.45 + 0.08
1.89 4 0.62
0.02 4 0.01
February 20
7 AM
35.4 ~ 6.5
42.9 ~ 5.3
3.03 i 0.71
0.27 ~ 0.04
3.33 4 1.33
0.02 + 0.01
7 PH
21.7 ~ 2.8
29.2 ~ 6.4
2.53 + 0.42
0.31 4 0.08
0.83 4 0.41
0.05 + 0.03
March 23
7 AH
14.1 I 1.3
23.2 ~ 2.4
1.95 « 0.29
0.45 + 0.08
0.41 + 0.20
0.05 4 0.02
7 PM
16.9 4 1.1
28.2 ~ 2.6
2.52 4 0.38
0.49 4 0.10
0.28 4- 0.11
0.06 + 0.03
January 23
7 AH
26.2
~ 3.3
24.0
1 32
2.72 4 0.35
0.48 ~ 0.07
1.88
+ 0.57
0.05 4 0.01
7 PM
23.9
4 3.2
29.5
4 4.1
2.89 4 0.32
0.60 + 0.09
1.50
* 0.35
0.16 4 0.08
February 20
7 AM
26.0
t 4-3
30.4
+ 4.4
2.41 4 C.44
0.59 ~ 0.11
2.21
4 0.73
0.30 4 0.15
7 PM
16.9
i 23
34.1
4 4.3
1.92 4 0.42
0.64 4 0.10
1.02
+ 0.45
0.33 + 0.14
fbrclt 28
7 AM
II.9
i 1-2
19.5
4 2.9
1.65 4 0.20
0.32 4 0.06
0.38
4 0.18
0.03 4 0.01
7 W1
11.5
4 1,0
18.4
4 1.9
1,75 4 0.31
0.30 4 0.0ft
0.2£i
+ 0.10
0.01 + 0.00
-------
TABLE 4.2 MONTHLY MEADS AND STANDARD ERRORS FOR GASEOUS AIR QUALITY AND METEOROLOGIC VARIABLES
Gaseous Air Quality Variables
Meteorologlc Variables
Time Carbon Monoxide Sulfur Dioxide Ozone
Station Month N Period {CO; ppra) (SO^; pptn) {O3; ppm)
Temperature Barometric Pressurea
(°K) (in. Hg)
January
23
7
AM
6.8 + 0.8
.0125 + .0020
.0054 +
.0008
264 + 1
29.84 +
.03
7
PH
7.9 + 0.8
.0125 + .0019
.0066 +
.0009
266 ~ 1
29.83 ~
.02
February
20
7
AM
5.5 ~ 0.8
.0095 + .0016
.0079 ±
.0020
267 + 1
29.91 +
.04
7
PM
7.1 + 0.6
.0093 + .0008
.0089 +
.0014
274 ~ 1
29.92 ~
.04
March
28
7
AM
4.4 t 0.3
.0065 + .0007
.0194 f
,0017b
274 ~ 1
29.93 +
.03
7
PM
5.8 i 0.3
.0063 + .0004
.0278 +
.or,?ih
278 + 1
29.93 +
.03
ro
to
January
23
7
AM
4.0 + 0.6
.0082
+
.0014
.0096
t
.0014
264
,+. '
29.84
+
.03
7
PM
3.4 _~ 0.5
.0081
+
.0011
.0134
+
.0013
266
± 1
29.83
+
.02
February
20
7
AM
3.1 + 0.6
.0071
+
.0012
.0144
+
.0019c
267
* 1
29.91
+
.04
7
PM
2.5 + 0.3
.0071
+
.0001
.0175
+
.0018c
274
* 1
29.92
+
.04
March
28
7
AM
1.0 ~ 0.31
.0041
+
.0008
.0194
+
.0017b
274
+ 1
29.93
•f
.03
7
PM
1.3 t 0.^
.0029
+
.0004
.0278
~
.0021b
278
+ 1
29.93
.03
a'jra-level equivalent barometric pressure provided by the IIS Weather Service at Stoiileton International Airport.
To nlify 630/760.
to equipment failure, ozone was monitored at only the Hest station during March; osone data from the
West Denver station were used for both stations durinn this month.
CH = 12
-------
levels generally were decreasing from January through March. By contrast,
mean levels of ozone, while consistently low, show a definite increase across
months.
Morning (7 AM) temperatures rose from an average of 264°K (-9°c) to
274°K (+1°C), while average evening (7 PM) temperatures increased from 266°K
(-7°C) to 278°K (+5°C) during the same period.
Monthly average 7 AM and 7 PM barometric pressures (sea level equivalent)
were consistently at approximately 29.9 in. Hg across the three months.
Table 4.3 (shown on pages 31 and 32) presents the correlation matrix
for the environmental and meteorologlc variables for both stations during
the 71 days available for the three-month period studied. For both stations,
fine and coarse IPM mass shared approximately 25% common variance. Fine IPM
mass was also moderately related to the gaseous air quality variables (in-
versely to ozone), and to fine IPM sulfate and nitrate levels at both
stations. By contrast, while coarse IPM mass showed the same relationships
to the gaseous air quality measurements, its relationships to fine and coarse
IPM sulfates and nitrates were consistently low. Fine IPM mass values were
always correlated with temperature (r's ranging from +.40 to +.50). In con-
trast, coarse IPM mass levels were nearly independent of temperature.
4.2 HEALTH STATUS MEASUREMENTS
Table 4.4 (shown on page 33) presents the raw 7 AM and 7 PM means
and standard errors for each health status measurement for both stations. To
evaluate the relationships among the three health status measurements, indi-
vidual correlations were obtained for each subject. The average correlations
among the health status measurements at each station are shown in Table 4.5.
(shown on page 34).
30
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TABLE 4.3 CORREtATIOHS AMONG TUf ENVIRONMENTAL VARIABLES*'b
East Station
Carbon Sulfur Temper- Barometric Fine Coarse Fine Coarse Fine Coarse
Monoxide Dioxide Ozonec ature Pressure Mass Mass Sulfates Sulfates Nitrates Nitrates
Larton
Monoxide
.64
- .58c
.02
-.28
.66
.50
.46
.30
.46
.26
Sulfur
Dioxide
-.48
-.22
-.26
.65
.33
.57
.24
.47
.28
Ozone
.06
.04
-.38
-.23
-.36
1
ro
-.'5
-.35
Temperature
.14
-.52
.07
-.09
.19
-.£>0
.15
Barometric
Pressure
-.30
-.04
-.33
-.18
-.30
-.16
Fine Mass
.52
.74
.11
.81
.21
Coarse Mass
.10
.10
.26
.17
T ine Sui fates
.33
.73
.19
Coarse Sulfates
.10
.47
fine Nitrates
.24
Coarse (titrates
-------
TABLE 4.3 - Continued
Uest Station
Carbon Sulfur Temper- barometric Fine Coarse Fine Coarse fine Coarse
Munoxith.* Dioxide fconer- ature Pscssure Hjss Moss Sulfates Sulfites Nitrates Nitrates
Carbon
Monoxide
.54 -.55
- .23
-.31
.56
.66
.41
.48
.49
.27
Sulfur
Uloxitle
.48
-.29
-.11
.SO
.35
.50
,4!i
.51
.41
Ozone
.49
-.06
-.36
-.47
-.44
-.38
-.38
-.20
Tewperature
.14
-.5?
.26
-.60
-.18
-.53
-.31
Itarcmetric
Pressure
-.06
.07
-.29
-.32
-,2i
-.06
Fine Hass
.48
.61
.54
,7!i
.43
Coarse Hass
-.05
.15
.10
.12
fine Sulfate*
¦ 56
.77
.30
Coarse Sulfites
.63
.56
Fine Nitrates
.54
Coarse Nitrates
4fo? N * 60, r ¦ .30 at p < .01.
bFor If • 35, r - .39 at p * .01.
CN - 34; .11 other H's - 64 to 70
-------
TABLE 4.4 MEANS AND STANDARD ERRORS FOR THE
HEALTH STATUS MEASUREMENTS9
PEFR
Station Period (1/mln)
East 7 AM 361 + 3
Denver 7 PM 397 + 4
West 7 AM 346+4
Denver 7 PM 371 + 3
Health Status Measurement
Nebulizer Usage
Symptom Rating (Occasions/12-hour
(Scale: 9 to 45) period)
12.4+0.1 0.8+0.1
11.7+0.1 1.0+0.1
13.0 + 0.2 1.6 + 0.1
11.9+0.1 1.2+0.1
aData expressed as mean + SEM; data from January 9 - March 28.
33
-------
TABLE 4.5 MEANS AND STANDARD ERRORS OF THE CORRELATION COEFFICIENTS
AMONG HEALTH STATUS MEASUREMENTS
Station Period Health Status Measurement Symptom Rating Nebulizer
Usage
East
Denver 7 AM
7 PM
West
Denver
7 AM
7 PM
PEFR
Symptom Rating
Nebulizer Usage
PEFR
Symptom Rating
Nebulizer Usage
PEFR
Symptom Rating
Nebulizer Usage
PEFR
Symptom Rating
Nebulizer Usage
.47 + .07a -.26 + .05b
+.33 + .04'
.44 + ,08a -.14 + .06
+.22 + .06
-.58 + .04 -.11 + .06
+.21 + .04
-.51 + .06a -.16 + .03
+.27 + .06
ap < .001, for r with df ¦ 80.
kp < .02, for r with df » 80.
cp < .05, for r with df ¦ 80.
-------
While certain moderate relationships exist among the health status
measurements, there is actually notable variation in the magnitude of the
relationships. For example, PEFR was clearly negatively related to sub-
jective ratings of airways obstruction for both time periods (7 AM and
7 PM) at both stations (average r's between -.44 and -.58). On an indi-
vidual basis, 12 of the 24 subjects had correlations of at least -.60,
while two had correlations of almost +.20. The average relationships be-
tween nebulizer usage and the objective measurements of airways obstruction
(PEFR) were always negative and quite low (-.26 to -.11), although the
relationships for individual subjects ranged from -.57 to +.29. Finally,
nebulizer usage was somewhat more reliably related to subjective ratings
of airways obstruction than to PEFR, indicating a tendency for subjects to
use their nebulizers more frequently when they reported more airways
obstruction.
4.3 HEALTH STATUS MEASUREMENTS IN RELATION TO ENVIRONMENTAL AND METEOR-
0L0GIC VARIABLES
4.3.1 Univariate Correlational Analyses
Table 4.6 (shown on page 36) presents the correlations calculated be-
tween each environmental variable by station and the average health status
measurements of the 12 subjects. These were done for both time periods
(7 AM and 7 PM) at each station based on all of the available data during
the January through March period. The probabilities associated with each
correlation were calculated (p-values), enabling Fisher's test, shown at
the bottom of the table for each environmental and meteorologlc measure, to
be calculated to test the hypothesis that the p-values were uniformly
distributed.
35
-------
TABLE 4.6 CORRELATIONS BETWEEN ENVIRONMENTAL VARIABLES AND HEALTH STATUS MEASUREMENTS
Health
Status
Measure-
ment
Time
Period
Carbon
Monoxide
Sulfur
Dioxide
Ozone
Temper-
ature
Barometric
Pressure
Fine
Mass
Coarse
Hass
Fine
Sulfates
Coarse
Sulfates
Fine
Nitrates
Coarse
Nitrates
(A) East Station
Peak Flow
7 AN
.240
.110
-.297
-.091
-.31)
.150
.005
.191
-.050
.217
-.104
7 PM
.025
.007
-.291
.053
-.017
-.060
-.085
-.050
-.045
-.150
-.152
Symptoma-
7 AH
-.133
.037
.048
-.112
.092
-.048
-.111
-.067
.180
-.054
.082
tology
7 PH
.016
.0%
.271
-.361
-.192
.178
.077
.196
-.022
.464
.092
Nebuli zer
7 AM
-.092
-.052
.081
-.116
-.039
-.029
-.081
.092
-.164
-.062
.160
Usage
7 PM
-.186
-.056
.236
-.244
.003
-.071
-.077
-.110
-.269
.023
-.073
(B) Uest Station
Peak Flow
7 AM
-.215
-.221
.190
.231
.230
-.254
-.0U7
-.193
.119
-.356
-.208
7 PM
-.003
.154
-.102
-.187
.069
.035
.076
-.011
.247
.006
-.003
Symptoma-
7 AH
.109
.104
.042
-.08i
.002
.031
-.064
.066
-.065
.214
.017
tology
7 PH
.148
-.147
.011
.126
.040
.011
.010
-.014
-.135
-.165
.064
Nebulizer
7 AH
.061
-.053
-.046
-.165
-.063
.047
-.062
.070
.012
.198
.165
Usage
7 PH
.116
-.115
.051
-.187
.092
-.060
-.222
.053
-.290
.146
-.095
Z « -Zjljln pj4 -
31.15
24.46
31.59
52.91b
29.55
22.18
19.93
21.75
36.74c
57.80b
23.68
d •
"2^1n Pj is distributed as * mIth Zn df, where n * number of correlation coefficients for which p-values
were calculated.
b v
* 24 » 43.3 at p ¦ .ui.
Cx?24 « 36.4 al p ' .05.
-------
Inspection of the correlations and their signs in Table 4.6 shows that
there was Inconsistency in the pattern of correlations amonq the health
status measurements across both stations. By inspection, this inconsistency
obtained for each of the environmental and meteorologic variables, although
Fisher's tests indicated that a significant relationship obtained among the
associated p-values for the correlations for coarse IPM sulfates and fine
IPM nitrates. It would be expected that PEFR would be negatively related
to both of these IPM components, while subjective reports of airways ob-
struction and increased nebulizer usage consistently would be positively
related, given a clear effect of these IPM components upon the health status
of the asthmatic subjects. For the subjects at the West Denver station,
this pattern was closely approximated, but the pattern was not demonstrated
at the East Denver station.
On the basis of these preliminary analyses, both fractions of 1PM
sulfates and nitrates were retained for the subsequent multiple linear re-
gression analyses, while gaseous air quality, meteorologic, and fine and
coarse IPM mass variables were all excluded.
4.3.2 LEAPS AND BOUNDS Multiple Linear Regression Analyses by Individual
Subjects
The extensive series of multiple linear regression analyses using
both fractions, coarse and fine, for IPM sulfates and nitrates for the 24
individual subjects are summarized in Table 4.7 on page 38. The analyses
summarized involved both time periods (7 AM and 7 PM) and each health
status measurement. The counts shown 1n the table Indicate the number of
times a specific IPM variable appeared amonn the best predictors of the
multiply linear regression model. The predictor variables also included
-------
TABU 4.7 SUHMr TABLE FOR LEAPS MO BOUNDS MULTIPLE LINEAR REGRESSION ANALYSES
FOR THE 24 INDIVIDUAL SUBJtlTS
7 AM 7 PK
v^rUhio Symptom Nebu11ier Symptom Netiu! I zcr
" le PEFR Rating Usage PEFR Rating Usage
dumber
Name
N/Group
+
-
No
+
-
No
~
-
Ho
4
-
No
~
-
No
+
-
NO
1
Previous Health
Status Measurement
24
7
0
17
10
0
14
S
0
16
11
0
13
11
a
13
8
0
16
2
f ine Sulfates
24
2
0
22
J
i
a
I
a
23
2
1
21
2
i
21
1
2
21
3
Coarse Sulfates
24
2
2
20
1
0
23
0
i
21
3
0
21
3
2
19
0
1
23
4
Fine Nitrates
24
0
2
22
2
0
22
1
2
21
2
2
20
4
l
19
2
1
21
5
Coarse Nitrates
24
I
1
22
a
0
24
I
0
23
0
0
24
I
0
23
2
0
22
» * Variable appeared In significant regression with positive coefficient.
- • Variable api*
-------
the previous heaUh status measurements, in an attempt to exclude (and
account for) an effect attributable to changes in the health status of the
subjects that was not due to air pollution during the past 12 hours.
With the possible exception of the previous health status measurement,
the individual multiple linear regression analyses included r.o predictor
variables that improved upon no regression or the best univariate regres-
sion. This was true for each health status measurement. Host notably, IPM
measurements of fine and coarse sulfates and nitrates rarely predicted the
health status of individual subjects, and generally were inconsistent in
direction (sign of the regression coefficient) among individuals when they
appeared at all.
4.3.3 Aggregate LEAPS AMD BOUNDS Multiple Linear Regression for Groups
In the aggregate multiple linear regression analyses, the 12 subjects
assigned to each station were considered as a group. For each health status
measurement (PEFR, subjective report of airways obstruction, and nebulizer
usage), there are four aggregate regressions defined by two stations (East
and West Denver) and two time periods (7 AM and 7 PM). In all cases, the
model conformed to the analyses for individuals, usinq the previous health
status measurement, and fine and coarse IPM sulfates and nitrates as the
predictor variables.
Only two of the IPM components appeared as best predictors in these
analyses. Coarse I"M sulfates were positively associated with PEFR
(p < .01) for the 7 AM period and negatively associated with nebulizer
usage (p < .001) for the 7 PM period at the West Denver station. Both of
these relationships are paradoxical, suggesting a beneficial effect of coarse
IPM sulfates on the health status of the subjects on these two occasions.
-------
The paradoxical nature of these relationships and the failure of coarse IPM
sulfates to appear within the regressions at the East Denver station or at
the other time period suggest that the relationships are due to chance.
Fine IPM nitrates appeared as a best predictor three times, negatively
for 7 AM PEFR's (p < .0001) and positively for 7 PM nebulizer usage (p < .01)
at the West station, and positively for the 7 PM subjective report of airways
obstruction (p < .0001) at the East station. Note that these relationships
between fine IPM nitrates and the health status measurements, while always in
a direction indicative of a clear health effect upon the subjects, did not
consistently occur across both time periods and for each of the two stations.
4.3.4 Application of the Random Effects Model
For this model (pages 22-26), weekend was selected as an additional co-
varlate. The p-values for the two-tailed Wilcoxon signed rank test are
shown in Table 4.8, shown on page 41, testing the regression coefficients
for each air pollution variable. The signs indicate larger rank sums of the
positive and negative regression coefficients. For pollution to have an
adverse effect, the sign should be positive for symptomatology, negative
for peak flow, and positive for nebulizer use. The srallest p-value is
.0229 in the direction indicating an adverse effect of fine nitrates on
symptomatology. The second smallest p-value is .0249, indicating that fine
nitrates were also associated with increased usage of aerosolized broncho-
dilators. While both these results were in the expected direction, the
results must be considered cautiously. Results support the preceding LEAPS
AND BOUNDS multiple linear regression analyses, suggesting that fine IPM
nitrates may have influenced nebulizer usage and symptom reports, while no
other air pollutant adversely affected health status.
-------
TAfflE 4.8 TWO-TAtltO P-VAtOfS fftON UltCOXOtt SIGHED RANKS TESTS PERFORKL0 ACROSS SUBJECTS'
Station
Health Status
Time
Carbon
Sulfur
Overall
Overal1
F1 ne
Coarse
ffne
Coarse
Measurement
Period
Monoxide
Dioxide
Ozone
Fine Mass
Coarse Mass
Sulfates
Sulfates
Nitrates
Nitrates
Ejst
Peak flow
7 AM
.3394+
.2661+
.3013-
.1763+
.2036+
.6221+
.2036-
.4238+
.4238+
Denver
7 PM
1.0000=
.9097+
.3394-
.8501-
.3804-
.6221+
.9097-
.2661-
.6778+
Symptomatology
7 AM
.3013-
.3804-
.5693-
.3013-
.3804-
.23 34 +
.0269+
.1514+
.9697+
/ PM
.6/72+
.3194 +
.6221+
.2334+
.8501+
.0522+
.9697-
.0122+
.4238+
Nebuliler
7 AT1
.7002-
.4H1-
.2783+
.4131-
.5195-
.3652 +
.7002-
.5771+
.7646+
Usage
7 PH
.6221-
.9697+
.6377+
.79JO+
.9097+
.1294 +
.8501+
.1763+
.2334+
West
Peak Flow
7 AM
. 1099-
.0049-
.0269+
.1294-
.8501-
.1294-
.5166+
.0269-
.7910+
Denver
7 PM
.4238+
.0122+
.1763-
.2661+
.5693+
.8501+
.1514+
.3394+
.3804+
SyiW>lc»n.itolo9y
7 AM
•6??t+
. 79)0+
.111)0)-
¦ 423U-
.t/72-
.9697+
.5186-
.1099+
.1099-
7 PM
.B50J+
.0425-
1.0000=
.3394-
.5186+
.3804-
.0/71-
1.0000=
.8501+
Nebulizer
7 AM
,6221+
.3013+
.5186-
.9097+
.6772-
.1514+
.2036+
.0425-
.3394+
Usage
7 PM
.9697-
.4697-
.9697+
.8501+
.7334-
.4238+
.4238-
.1763+
.4238-
Com-
Peak Flow
7 AM
.6680-
.8262-
. 7031)+
.6106-
.6680*
.7311-
.66UO-
.1434-
.7634+
bined
7 PM
.66064
.0366+
.1355-
.7108+
.5522-
.5682+
.7817+
.5562+
.7176+
Symptomatology
7 AM
1.0000=
.5282+
.6306-
.8075-
.7571-
.8157+
.8019+
.0229+
.7539-
7 PM
.6152+
.8047-
.6306+
1.0000"
.7003+
.8262+
.3364-
.1011+
.7108+
Nebulizer
7 AH
.5300+
.5300+
.580'Ji
.6546-
.7193-
.0650+
.6507+
.04)5+
.7336+
Usage
7 PM
.6344-
.6267-
.6525+
.5879+
.5232-
.0604+
.6152-
.0249+
.5997+
As described tn the te*t (pal** 24 and 25), the 12-hour lag for health status iiK-jsurw.-nts and weekend were selected
as covariates from among lag, weekend. barometric pressure, ten^erat.iro, and seasonality for tliese analyses. The
symbols " + ," and indicate whether the positive or negative rank sum is larger in fi" Uilcoxon procedure.
-------
5. DISCUSSION
Of all the atmospheric pollutants studied, only the fine IPM nitrate
fraction gave any indication of a relationship to the health status of the
asthmatic subjects. As seen in Table 4.8, in the final series of analyses,
increased fire IPM nitrates tended to be associated with Increased subjective
reports of airways obstruction and increased aerosolized bronchodilator usage
when all subjects were combined. Because of the number of comparisons made,
theseresults, while in the expected direction indicative of an effect, may
well be attributed to chance. We did, however, select a conservative
approach to help guard against chance results by using two-tailed statistical
tests for clearly directional a priori hypotheses. Neither any other frac-
tion of IPM, any gaseous air quality variable, nor any meteorologic
measurement produced any consistent effect on the health status of asthmatic
subjects. The determination of any threshold at which a change in health
status occurs is thus precluded by the nature of these results.
Any discussion would be incomplete without a presentation of the in-
herent strengths and limitations of this particular investigation. One
obvious strength Is the a priori runner in which the study was designed,
and the prospective nature in which it was conducted. Another is the
rigorous medical characterization of our asthmatic subjects with respect
to (A) allergic factors, (B) airways hyperreactivity, (C) medical history,
and (D) the absence of any other form of cardiopulmonary abnormality. Con-
cerning each subject's response to allergenic factors, two points need
42
-------
emphasis. First, each subject's allergic status was determined by skin tests
with mixed grasses, mixed trees, mixed weeds, and house dust. Second, the
seasonal allergens were monitored daily and were found to be almost non-
existent during the entire three-month period the study encompassed. This
assured that allergic factors, rather than air pollution per se, did not
affect the health status measurements.
A third and Important strength of the present study was that the
asthmatic subjects' health status was evaluated by three types of measure-
ments: A physiological measurement — peak expiratory flow rate; a sub-
jective measurement — subjective report of airways obstruction; and a
behavioral measurement — as-needed (PRN) aerosolzied bronchodilator usage.
How each of these measurements should be affected by environmental pollution
was predicted on an a priori basis, thus diminishing the likelihood of draw-
ing false Inferences from the statistical analyses. Additionally, since
the airways caliber as Indexed by PEFR can be influenced by aerosolized
bronchodilator usage, continuous monitoring of aerosolized bronchodilators
was an integral part of this study. Such a behavioral measurement not only
reflects the health status of asthmatic subjects; but, beyond that, dis-
cretionary usage of these medications can influence prodoundly any direct
measurement of airways caliber. It should be noted that the nebulizer
chronologs used in this study were of an original design, and their re-
liability reguired back-up by the subjects' own written records of nebulizer
usage. A more technically advanced version of the nebulizer chronologs is
now available which corrects for principal sources of unreliability (e.g.,
rare accidental triggering, occasional Interference due to static electric-
ity) observed in this study. Finally, also of importance 1n this study's
43
-------
design was the inherent replicability introduced by establishing two separate
monitoring stations in the same metropolitan area. Tiiis accorded added
reliability in terms of pollution data accuracy, while providing a means for
an independent validation of any observed pattern of results.
Several limitations should be listed in regard to the practical execu-
tion of this study. First, as shown in Appendix D, there were only six or
seven "dirty" 12-nour periods (above 70 ug/m^ for fine IPM sulfates and
nitrates). Clearly, more such "dirty" days were needed to ascertain the
actual effect of air pollution on health status. Furthermore, it should be
stated that, although the N03~ levels reported here are relatively high com-
42 =
pared with those in other U.S. metropolitan areas, S0^ levels are notice-
29
ably lower than data reported for other areas. This is particularly in-
teresting in view of the fact that nitrates were the single environmental
variable possibly associated with reports of increased airway obstruction
and increased nebulizer usage. With regard to gaseous air pollutants, carbon
monoxide is the only one included in our analysis that is fairly high vis-a-
vis U.S. air quality standards. Ozone and sulfur dioxide are very low in
10 11 44-46
comparison to other metropolitan areas. ' ' Optimally, the study
should have included the entire high air pollution season, which in Denver
extends approximately from early November to mid-March.
Another possible drawback was the manner in which medical status data
were treated. Our a priori decisions required that data collected while a
subject was reporting an upper respiratory infection (URI) be eliminated,
since airways caliber in asthmatic patients is known to be affected by these
infections, certainly a potential confound for this study. However, it is
possible that URI's in asthmatics might be associated with periods of
44
-------
higher air pollutton levels, although a post-hoc analysis failed to reveal
any such relationship. Also, a further possibility to be considered in
future studies is that URI's may sensitize asthmatic subjects to Irritant
inhaled matter.^ These considerations suggest that detailed records should
be kept of reported URI's and that these data should be included .. the over-
all analysis or should be explored independently.
A final drawback should be considered. The decision was made a priori
to exclude data collected when subjects had ventured outside the metropolitan
Denver pollution bubble for more than three hours of any 12-hour period.
This decision, unfortunately, resulted in the elimination of some data that
were recorded during periods of peak pollution levels (6 AM to 8 AM and 6 PM
to 8 PM) merely because the subject was away from the area during the middle
of the day or overnight. However, the approach represented a serious attempt
to insure that subjects' resided and remained within a defined radius of the
station where air pollution was monitored. These efforts to insure proximity
to the fixed monitoring station may, in fact, represent the best compromise
until the technology becomes available to track exposure to a broad range
of pollutants by use of personal monitors.
The unique impact of each of these considerations upon the results
has been impossible to determine, although in various combinations, they
may conceivably have had a profound effect on the final outcome reflected
by this report. Consequently, appropriate weight should be given to each
of these considerations in any future studies.
45
-------
6. RECOMMENDATIONS
Establishing realistic standards for daily particulate air pollution
levels depends partly upon careful evaluation of the relationship between
health status and the pattern of air pollution that occurs. In this study,
asthmatic individuals were studied. The inherent hyperreactivity of their
airways puts these individuals among the people potentially most sensitive
to irritant IPM components. However, the necessary prospective studies are
difficult to design and to construct. The difficulties can arise from con-
founding variables (e.g., airborne allergens), from the impracticability of
controlling the Independent variables (air pollution levels), and from
problems inherent in the measurerent of the dependent variables (heal:h
status). Several recommendations are appropriate.
First, in any study of this kind, careful prescreening and trailing
are required of the volunteer subjects. Prescreening Is needed to char-
acterize the subjects medically, and particularly to identify those that
appear most likely to persevere. In this study, logs were required to be
completed twice dally, pulmonary function tests were also required each
day, and the subjects were required to return to their station weekly for
additional testing and debriefing. Selection of responsible and committed
subjects 1s essential to ggod collection of data, even at the risk of
violating certain assumptions about "good" sampling procedures. In the
present stuoy, we began with a panel of 60 volunteers, and by adhering to
thorough selection procedures accepted 41 subjects. Of those finally
-------
accepted, 39 stayed with us throughout a period of almost six months. Cer-
tain obstacles must be overcome to assure that reliable subjects are accepted
1n such a study. At a minimum, these Include:
(1) Complete explanation of what will be required on a daily
basis, for how long, and for what time period;
(2) Prescreening requirements that need to be fulfilled (e.g.,
medical examination. X-ray, etc.);
(3) A pretest run, Identical in every way with what will be
required on a daily basis for the duration of the study;
(4) Discouragement of participation 1f there Is any Indication
of potential noncompliance with the protocol. Such Indi-
cators include failure to keep appointments during pre-
screening, hesitation about making a commitment to remain
in the metropolitan area throughout the period of study,
failure to complete the logs reliably during prescreening,
reluctance to conplete most of the required medical tests,
and so on.
Careful prescreening, subject selection, and training are essential
prerequisites of lengthy studies of this kind.
Secondly, any single measurement of health status has its pitfalls.
By themselves, daily pulmonary function measurements can be Influenced by
as-needed (PUI) medications that asthnatic patients often use to relieve
airways obstruction. Singly, subjective reports of airways obstruction
symptoms are always suspect. Taken alone, behavioral measurements, such
as discretionary PRN medication usage or doctor's office visits, may either
fait to reflect actual changes in airways caliber or they may occur so
47
-------
rarely as to be nearly meaningless. Taken together, however, these rceasure-
ments help to triangulate upon health status and enable the prediction of
relationships (both negative and positive) with air pollution levels to be
specified on an a priori basis. Future studies might consider employing a
similar method to triangulate on the concept of daily health status of
asthmatic patients.
Thirdly, there is virtually no control over the independent variables
(i.e., IPM or other air pollution levels), yet in order to ascertain any
impact upon the health status measurements, a sufficient supply of days
with high and variable levels of IPM 1s needed. In practical terms, in a
city like Denve *, which has a seasonal air pollution period, this means
that the entire period of high air pollution should be included in any
future study. It may even be-desirable to prolong the measurement period
by including a second full air pollution season. A single, well-conducted
large scale study could well be less costly than a series of smaller, less
definitive studies.
Fourthly, for certain asthmatic Individuals (I.e., those with aller-
gically triggered asthma), airborne allergens can profoundly influence
health status, leading to decreased airways caliber, increased usage of as-
needed (PRN) medication, and subjective reports of increased airways ob-
struction. Such allergic factors, if not considered, potentially can con-
found the interpretation of any results. In any future study with asthmatic
patients, medical characterization, as done in the present study, should
include allergy skin tests to identify those individuals likely to be
affected by airborne allergens, while pollen counts can identify those
periods during which specific airborne allergens occur locally. Additionally,
48
-------
standardized methacholine inhalation challenges help to characterize asth-
matic patients, and provide an Index of the degree of airways hyperreactivity
that nay yet prove useful in identifying asthmatic individuals who are
particularly responsive to the Irritant properties of IPM.
Finally, given the fact that suspended particulates are of interest,
dichotomous samplers and supplemental chemical analyses appear to have
advanced particulate measurement techniques, enabling measurement of IPM
fractions with differing deposition within the airways and having potentially
different concentrations of specific IPM components. Our current results,
while at best only suggestive in regard to health effects, also indicate that
the concentration of specific IPM components differed substantially in Denver
between coarse (2.5 to 15 ym aerodynamic diameter) and fine (< 2.5 ym)
fractions. The fine fractions of IPM sulfates and nitrates appear quite
Interesting, notably because of a possible health effect, but also because
o w,he1r deposition in the airways and the varying relative concentrations
at which they occur in each fraction. The dichotomous samplers therefore
provide an important technique for future studies.
49
-------
7. REFERENCES
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3. Martin AE: Mortality and morbidity statistics and air pollution.
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6. Lave LB, Seskin EP: Air pollution and human health. Science 169:
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7. Heiman H: Episodic air pollution in metropolitan Boston. A trial
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8. lawther PJ, Brooks A6F, et al_.: Day to day changes 1n ventilatory
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12. Lawther PJ, Waller RE: Henderson M: Air pollution and exacerbations
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13. Waller RE: A1r pollution and community health. Journal of the Royal
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16. Farr RS, Spector SL: What is asthma? In Petty TL (Ed.), The
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17. Szent1vany1 A: The 6-adrenerg1c theory of the atopic abnormality
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18. American Thoracic Society Committee on Diagnostic Standards for
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and X-ray fluorescence spectrometer. Environmental Science arid
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Ann Arbor, Michigan, 1977, p. 95.
27. Loo BW, Jakievlc OM, Goulding FS: Dichotomous virtual impactors for
large scale monitoring of airborne particulate matter. In Liv BYH
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Research Triangle Park, North Carolina, 1978.
29. Stevens RK, Dzubay TG, Russwurm G, fLt al_.: Sampling and analysis of
atmospheric sulfates and related species. Atmospheric Environment
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Carolina, 1977.
32. List of Designated Reference and Equivalent Methods. EPA Publication,
Research Triangle Park, North Carolina, 1979.
33. Quality Assurance Manual for the Colorado Department of Health, A1r
Pollution Control Division, Denver, Colorado, 1978.
34. Morrill CG, Dickey DW, Welser PC, et §1.: Calibration and stability
of Standard and Mini-Wright Peak Flow Meters. Annals of Allergy,
in press.
35. Kinsman RA, Dahlem NW, Spector SL, et al_.: Observations on subjective
symptomatology, coping behavior, and medical decisions in asthma.
Psychosomatic Medicine 29:102, 1977.
36. Bradley JV: Distribution Free Statistical Tests. Englewood Cliffs,
Prentice Hall, 1968.
37. Fisher RA: Statistical Method for Research Workers. 9th Ed.,
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3C. Furnlval GH, Wilson RW: Regression by leaps and bounds. Technometrlcs
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39. Akaike H: Information theory and an extension of the maximum likelihood
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principle. Jji Petrov BN and Csaki F (Eds.). Second International Sym-
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40. Wold HOA: Ends and means in econometric model building. l£ Almquist
and Wiksell (Eds.), Probability and Statistics. New York, John Wiley,
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41. Anderson JW: Introduction to Multivariate Statistical Analyses. New
York, John Wiley, 1958.
42. Stevens RK: Personal communication.
43. Linn WS, Jones MP, Backmayer EA., et al_.: Short-term respiratory
effects of polluted ambient air: A laboratory study of volunteers 1n
a high oxidant community. American Review of Respiratory Diseases 121:
243, 1980.
44. Holland WW, Bennett AE, Cameron IR, et a]_.: Health effects of par-
ticulate pollution: Reappraising the evidence. 4. Exposure to
particulate pollution: Morbidity in adults. American Journal of
Epidemiology 110:580, 1979.
45. Holland WW, Bennett AE, Cameron IR, et al.: Health effects of par-
ticulate pollution: Reappraising the eTTdence. 6. Chess Studies.
American Journal of Epidemiology 110:616, 1979.
46. Scientific and technical data base for criteria and hazardous pollutants:
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reactivity to nitrates in subjects with influenza. American Review
of Respiratory Diseases 121:233, 1980.
53
-------
APPENDIX A
AIRWAYS OBSTRUCTION SYMPTOM RATING SCALE
54
-------
AIRWAYS OBSTRUCTION SYMPTOM RATING SCALE
Rate the present severity of each of these symptoms of breathing difficulty
(1 ¦ Mot at all severe; 5 » Extremely severe). Circle the appropriate phrase.
A. Not at all
short of breath
1
8. No mucous
congestion at all
2
A little
short of breath
2
A little
mucous
congestion
Quite short
of breath
Quite a bit
of rocous
congestion
Considerably
short of Lreath
Considerable
mucous congestion
Extremely
short of breath
Extreme mucous
congestion
C.
D.
E.
Not at ill hard
to breathe
1
No chest
congestion at all
1
No chest
tightness at all
A little hard
to breathe
Quite hard
to breathe
Considerably hard
to breathe
Extremely hard
to breathe
2 3 4 S
A little chest Quite a bit of Considerable chest Extreme chest
congestion chest congestion congestion congestion
2 3 * 5
A little chest Quite a bit of Considerable chest Extreme chest
tightness chest tightness tightness tightness
f. Chest not filled
up at all
1
G. Not at all
uncomfortable
H. Not coughing
at all
I. Not wheezing
at all
Chest a little
filled up
2
A little
uncomfortable
Chest quite
filled up
Chest considerably
filled up
3
Quite
uncomfoi table
Coughing a little Coughing
quite a bit
2 ?
Wheezing a little Wheezing
quite a bit
Considerably
uncomfortable
Considerable
coughing
4
Considerable
wheezing
Chest extremely
filled up
5
Extremely
uncomfortable
5
Extreme
coughing
5
Extreme
wheezing
55
-------
APPENDIX B
COVARlATE ANALYSES SUMMARY TABLES
56
-------
TABLE B-l TWO-TAILED P-VALUES FROM WILCOXON SIGNED RANKS TESTS
PERFORMED ACROSS SUBJECTS FOR 12 AND 24 HOUR LAGGED
HEALTH STATUS MEASUREMENTS
Health Status
Station
Measurement
Time Period
12-Hour Lag
24-Hour Lag
East
Peak Flow
7 AM
.0005+a
.0015+
Denver
7 PM
.0034+
.0068+
Symptomatology
7 AM
.0210+
.0068-
7 PM
.0020+
.0161+
Nebulizer Usage
7 AM
.0068+
.0510+
7 PM
.0093+
.0537+
West
Peak Flow
7 AM
.0005+
.0034+
Denver
7 PM
.0005+
.0015+
Symptomatology
7 AM
.0020+
.0049+
7 PM
.0015+
.0161+
Nebulizer Usage
7 AM
.0010+
.0015+
7 PM
.0015+
.0015+
Combined
Peak Flow
7 AM
.0000+
.0000+
7 PM
.0000+
.0000+
Symptomatology
7 AM
.0001+
.0001+
7 PM
.0000+
.0004+
Nebulizer Usage
7 AM
.0000+
.0000+
7 PM
.0000+
.0001+
aA "+" or indicates direction in the Wilcoxon procedure as
demonstrated by relative magnitude of the positive and negative
rank sums.
57
-------
TABLE B-2 TWO-TAILED P-VALUES FROM TESTS OF SIGNIFICANCE ON COVARIATES
PERFORMED ACROSS SUBJECTS3
Sta- Health Status
Time
Barometric
Weekend
tion Measurement
Period
Temperature
Pressure
Effect
Seasonality
East Peak Flow
7AM
• .1099-
.3013-
.9097+
.1650
Denver
7PM
.8501-
.3804+
.7910+
.3517
Symptomatology
7AM
.4697+
.1099+
.0923+
.6286
7PM
.3013-
.2661-
.8501+
.5001
Nebulizer Usage 7AM
.8311-
1.0000=
.2783-
.8053
7PM
.4697-
.7910+
.0010+
.4426
West Peak Flow
7AM
.1099+
.1294+
.6772+
.3322
Denver
7PM
.2036-
.5186+
.1099-
.5798
Symptomatology
7AM
.7334-
.7334-
.3804-
.9908
7PM
.1099+
.8501+
.1294+
.8958
Nebulizer Usage 7AM
.4238-
.9097-
.3013+
.5248
7PM
.3073-
.6221+
.0771+
.7516
Com- Peak Flow
7AM
.5602-
.5840+
.6152+
.5460
bined
7PM
.8414-
.8047+
.7443-
.1894
Symptomatology
7AM
.5522+
.6680+
.5919+
.7886
7PM
.6075+
.6382-
.8210+
.7643
Nebulizer Usage 7AM
.7475-
.5641-
.5300+
.8987
7PM
.8339-
.6861+
.0001+
.4155
aA Wilcoxon signed ranks test was used for each test of significance
for temperature, barometric pressure, and weekend effect. Hotel ling's
2
T was used to test simultaneously the two coefficients which comprise
seasonality. The symbols, M+," and indicate whether the
positive or negative rank sums is larger in the Wilcoxon procedure.
58
-------
APPENDIX C
FREQUENCY DISTRIBUTIONS FOR HEALTH STATUS MEASUREMENTS
59
-------
TABLE C-l FREQUENCY DISTRIBUTION FOR PEAK EXPIRATORY
FLOW RATES (l/MIN)a
East Denver Station West Denver Station
7AM 7PM 7AM 7PM
<175
29
35
61
17
175-200
33
32
39
18
200-225
16
9
38
22
225-250
69
32
51
42
250-275
60
20
41
41
275-300
92
26
63
65
300-325
61
30
32
53
325-350
120
91
57
87
350-375
90
88
73
68
375-400
115
174
98
120
400-425
45
94
52
54
425-450
52
65
80
59
450-475
35
26
49
61
475-500
34
48
61
68
500-525
13
40
11
19
525-550
19
41
7
14
550-575
21
24
2
3
575-600
26
45
0
1
600-H1gh
0
9
0
1
Missing
155
151
225
267
(1/Min)
Mean
SD
SEM
356
99
3
394
106
3
343
*06
4
368
91
3
aData for the period of January 1 - March 31.
60
-------
TABLE C-2 FREQUENCY DISTRIBUTION FOR SYMPTOM RATING3
(SCALE: 9 to 45)
Scale Values
East Denver
7AM
Station
7PM
West Denver
7AM
Station
7PM
9
266
366
282
351
10
110
122
80
85
11
71
78
46
52
12
79
61
43
51
13
72
54
52
39
14
104
66
50
40
15
52
32
36
31
16
25
25
18
23
17
47
59
32
37
18
32
14
100
56
19
25
8
15
12
20
9
3
10
3
21
4
4
10
4
22
4
2
8
4
23
5
4
6
5
24
1
4
2
2
25
5
2
5
2
26
0
0
3
0
27
3
4
16
5
28
0
0
0
1
29
0
0
0
0
30
0
0
0
1
31
1
1
0
1
0
I
34
1
0
0
0
36
1
45
1
4
0
0
0
1
0
0
Mean 12.5 11.7 13.0 11.9
SO 3.7 3.5 4.5 3.8
SEM 0.1 0.1 0.2 0.1
aOata for the period January 1 - March 31.
61
-------
TABLE C-3 FREQUENCY DISTRIBUTION OF NEBULIZER USAGE3
(0CCASI0NS/12-H0UR PERIOD)
No. of Occasions
East Denver
Station
West Denver
Station
7AM
7PM
7AM
7PM
0
617
658
352
409
1
100
68
109
130
2
125
86
154
139
3
18
24
71
60
4
44
50
60
30
5
5
19
27
18
6
16
13
11
6
7
3
0
5
3
8
3
5
5
3
9
1
5
3
1
10
1-
5
1
1
11
0
0
0
0
12
1
5
0
0
13
0
1
1
0
14
0
0
0
0
15
0
1
0
0
16
0
0
0
0
17+
1
1
1
0
Missing
145
143
280
280
Mean
0.8
1.0
1.6
1.1
SD
1.6
2.0
2.5
1.5
SEM
0.1
0.1
0.1
0.1
aData for the period January 1 - March 31.
62
-------
APPENDIX D
FREQUENCY DISTRIBUTIONS OF ENVIRONMENTAL
AND METEOROLOGIC VARIABLES
63
-------
TABLE D-l FREQUENCY DISTRIBUTION OF CARBON MONOXIDE (PPM)a
PPM
East Denver
Station
West Denver
Station
7AM
7PM
7AM
7PM
< 0.5
0
0
3
6
0.6 -
1.5
8
1
29
31
1.6 -
2.5
9
1
20
19
2.6 -
3.5
15
11
8
10
3.6 -
4.5
20
15
6
9
4.6 -
5.5
12
17
7
5
5.6 -
6.5
9
10
5
2
6.6 -
7.5
4
14
1
1
7.6 -
8.5
2
4
2
0
8.6 -
9.5
1
6
2
0
9.6 -
10.5
0
5
1
1
10.6 -
11.5
1
1
0
0
11.6 -
12.5
5
3
0
0
>12.5
3
2
0
0
Mean
5.3
6.6
2.8
2.4
SD
3.2
2.8
2.3
1.8
SEM
0.3
0.3
0.2
0.2
N
89
90
34
84
a12-hour averages; data for the period January 1 - March 31.
64
-------
TABLE D-2 FREQUENCY DISTRIBUTION OF SULFUR DIOXIDE (PPM)a
PPM
East Denver
Station
West Denver
Station
7AM
7PM
7AM
7PM
<.0015
5
1
8
9
.0016
- .0045
19
12
33
36
.0046
- .0075
27
33
24
17
.0076
- .0105
7
19
10
13
.0106
- .0135
11
8
6
7
.0136
- .0165
8
7
2
2
.0166
- .0195
5
0
0
2
.0196
- .0225
1
2
0
1
.0226
- .0255
2
1
3
0
.0256
- .0285
1
2
0
0
>.0286
1
2
1
0
Mean
.0087
.0089
,O06n
.0059
SO
.0070
.0062
.0053
.0044
SEM
.0007
.0007
.0006
.0005
N
87
87
87
87
a12-hour averages; data for the period January 1 - March 31.
65
-------
TABLE D-3 FREQUENCY DISTRIBUTION OF OZONE (PPM)a
PPM
East Denver Station
West Denver
Station
7AM
7PM
7AM
7PM
<.0040
18
10
6
3
.0041
- .0080
16
17
13
6
.0081
- .0120
8
16
24
14
.0121
- .0160
6
6
16
1,3
.0161
- .0200
2
1
8
12
.0201
- .0240
0
0
10
16
.0241
- .0280
1
1
3
7
.0281
- .0320
0
0
3
3
.0321
- .0360
0
0
3
6
.0361
- .0400
0
0
1
4
.0401
- .0440
0
0
1
2
>.0441
0
0
0
2
Mean
.0068
.0080
.0144
.0158
SD
.0051
.0048
.0085
.0106
SEM
.0007
.0007
.0009
.0011
N
51
51
88
88
a12-
hour averages;
data for the period January 1
- March 31.
66
-------
TABLE D-4 FREQUENCY DISTRIBUTION OF TEMPERATURE (°K)a
°K Fast Denver Station West Denver Station
7 AH • 7PM 7AM 7PM
<253.2
253.3
-
255.7
255.8
-
258.2
258.3
-
260.7
260.8
-
263.2
263.3
-
265.7
265.8
-
268.2
268.3
-
270.7
270.8
_
273.2
273.3
-
275.7
275.8
-
278.2
278.3
-
280.7
280.8
-
283.2
283.3
_
285.7
285.8
-
288.2
1
0
4
1
8
3
7
7
3
4
3
9
9
4
16
5
10
13
14
12
9
10
4
7
1
7
0
5
0
3
1
0
4
1
8
3
7
7
3
4
3
9
9
4
16
5
10
13
14
12
9
10
4
7
1
7
0
5
0
3
Mean 269 273 269 273
SD 7 8 7 8
SEM 1 ! ! j
N 89 90 89 90
a12-hour averages; data for thee period January 1 - March 31.
67
-------
TABLE D-5 FREQUENCY DISTRIBUTION OF BAROMETRIC PRESSURE (in. Hg)a
in. Hg
East Denver
Station
West Denver
Station
7AM
7PM
7AM
7PM
<29.57
2
1
2
1
29.58 - 29.62
2
1
2
1
29.63 - 29.67
2
4
2
4
29.68 - 29.72
3
7
3
7
29.73 - 29.77
12
7
12
7
29.78 - 29.82
7
13
7
13
29.83 - 29.87
8
7
8
7
29.88 - 29.92
9
9
9
9
29.93 - 29.97
9
5
9
5
29.98 - 30.02
8
9
8
9
30.03 - 30.07
6
7
6
7
30.08 - 30.12
8
4
8
4
30.13 - 30.17
6
5
6
5
30.18 - 30.22
A
8
4
8
30.23 - 30.27
1
2
1
2
30.28 - 30.32
1
0
1
0
Mean
29.92
29.92
29.92
29.92
SO
.17
.17
.17
.17
SEM
.02
.02
.02
.02
N
88
89
88
89
aAverages for two discrete times within each 12-hour period; data for
the period January 1 - March 31.
68
-------
TABLE D-6 FREQUENCY DISTRIBUTION OF FINE MASS (ug/m3)a
3
vtg/m East Denver Station V.'ast Denver Station
7AM 7PM 7AM 7PM
< 5.0
5.1 - 10.0
10.1 - 15.0
15.1 - 20.0
20.1 - 25.0
25.1 - 30.0
30.1 - 35.0
35.1 - 40.0
40.1 - 45.0
45.1 - 50.0
50.1 - 55.0
55.1 - 60.0
60.1 - 65.0
65.1 - 70.0
70.1 - 75.0
75.1 - 80.0
80.1 - 85.0
85.1 - 90.0
>90.1
4
0
7
7
18
17
13
18
13
18
8
4
2
7
3
1
0
2
2
2
1
2
3
2
2
1
2
0
0
0
2
0
0
0
1
0
2
1
4
4
17
19
18
21
11
20
7
6
9
4
4
2
1
0
4
2
2
1
0
2
3
1
0
0
1
0
2
0
0
0
0
0
0
0
0
0
Mean
SD
SEM
N
27.4
25.0
2.7
83
23.2
15.3
1.7
82
21.1
16.5
1.8
83
17.0
11.8
1.3
82
aTotals for a 12-hour collection period; data for the period
January 1 - March 31.
69
-------
TABLE D-7 FREQUENCY DISTRIBUTION OF COARSE MASS (ug/m3)a
v g/m3
East Denver
Station
West Denver
Station
7AM
7PM
7AM
7PM
< 7.0
9
4
14
7
7.1
_
14.0
10
5
14
12
14.1
-
21.0
9
13
14
17
21.1
-
?8.0
12
9
12
20
28.1
-
35.0
22
13
5
11
35.1
-
42.0
10
10
10
5
42.1
-
49.0
4
5
7
3
49.1
-
56.0
3
8
3
1
56.1
-
63.0
5
9
2
2
63.1
-
70.0
1
1
1
2
70.1
-
77.0
2
1
1
0
77.1
-
84.0
1
0
0
i
84.1
-
91.0
1
0
0
6
91.1
-
98.0
0
2
0
i
98.1
-
105.0
1
0
0
c
>105.1
0
2
0
0
Mean
30.6
37.9
24.2
25.7
SD
21.6
27.0
17.5
17.6
SEM
2.4
3.0
1.9
1.9
N
83
82
83
82
aTota1s for a 12-hour collection period; data for the period
January 1 - March 31.
70
-------
TABLE D-8 FREQUENCY DISTRIBUTION OF FINE SULFATES (pg/m3)a
3
vg/m East Denver Station West Denver Station
7AM
7PM
7AM
7PM
< .400
3
2
3
1
.401
-
.800
6
5
5
9
.801
-
1.200
11
5
14
14
1.201
-
1.600
8
11
14
10
1.601
-
2.000
6
3
13
7
2.001
_
2.400
7
9
13
7
2.401
-
2.800
7
6
2
8
2.801
-
3.200
4
5
2
3
3.201
-
3.600
4
3
2
4
3.601
—
4.000
2
1
1
4.001
-
4.400
1
3
2
3
4.401
_
4.800
2
2
0
4.801
-
5.200
1
2
3
5.201
-
5.600
1
1
2
1
5.601
-
6.000
3
0
1
6.001
_
6.400
1
0
2
0
6.401
-
6.800
1
1
0
2
6.801
-
7.200
1
0
1
1
7.201
-
7.600
1
1
0
7.G01
.
8.000
1
0
0
0
8.001
-
8.400
1
0
0
0
8.401
.
8.800
1
0
0
0
8.801
-
9.200
0
1
0
0
>9.201
3
2
1
0
Mean 2.86 2.89 2.22 2.18
SD 2.80 2.15 1.74 1.49
SEM 0.34 0.26 0.19 0.17
N 70 67 81 75
totals for a 12-hour collection period; data for the period
January 1 - March 31.
71
-------
TABLE 0-9 FREQUENCY DISTRIBUTION OF COARSE SULFATES (pg/m3)a
yg/m
3
East Denver
Station
West Denver
Station
7AM
7PM
m
7PM
< 0 -
.100
9
11
14
7
.101 -
.200
9
10
8
11
.201 -
.300
9
11
9
6
.301 -
.400
16
5
9
8
.401 -
.500
9
9
15
11
.501 -
.600
7
3
7
11
.601 -
.700
3
2
3
2
.701 -
.800
2
4
5
7
.801 -
.900
2
4
2
5
.901 -
1.000
1
3
2
3
1.001 -
1.100
1
1
2
2
1.101 -
1.200
o'
2
1
0
>1.201
2
2
4
3
Mean
0.40
0.43
0.46
0.49
SO
0.33
0.38
0.39
0.33
SEM
0.04
0.05
0.01
0.04
N
70
67
81
76
aTotals for a 12-hour collection period; data for the period
January 1 - March 31.
72
-------
TABLE D-10 FREQUENCY DISTRIBUTION OF FINE NITRATES g/m3)a
y g/m
East Denver Station
West Denver Station
7AM
7PM
7AM
7PM
< 0
- .400
43
39
45
36
.401
- .800
9
12
11
20
.801
- 1.200
3
3
6
3
1.201
- 1.600
2
1
4
2
1.601
- 2.000
0
1
1
1
2.001
- 2.400
1
2
1
4
2.401
- 2.800
0
1
1
2
2.801
- 3.200
0
2
1
2
3.201
- 3.600
1
1
0
1
3.601
- 4.000
0
1
0
1
4.001
- 4.400
3
0
1
1
4.401
- 4.800
0
2
1
0
4.801
• 5.200
0
0
3
0
5.2G1
- 5.600
0
0
1
0
5.601
- 6.000
1
0
0
0
6.001
- 6.400
0
0
0
1
6.401
- 6.800
0
0
1
1
6.801
- 7.200
2
0
1
0
>7.201
5
2
3
0
Mean
1.79
0.95
1.34
0.93
SO
3.93
1.94
2.41
1.32
SEM
0.47
0.24
0.27
0.15
N
70
67
81
75
aTota1s for a 12-hour collection period; data for the period
January 1 - March 31,
73
-------
TA3LE D-U FREQUENCY DISTRIBUTION OF CCARSE NITRATES (ug/m3)a
tiS/m3
East Denver Station
West Denver
Station
7AM
7PM
7AM
7PM
0
- .060
59
57
55
46
.061
- .120
2
4
7
3
.121
- .180
1
1
6
2
.181
- .240
0
0
4
5
.241
- .300
2
1
1
1
.301
- .360
2
I
2
¦>
.361
- .400
3
0
1
3
.421
- .480
0
2
0
3
.431
- .540
0
1
0
2
.541
- .600
0
0
2
0
.601
- .660
1
0
0
0
.•>61
- .720
0
0
1
2
.721
- .780
0
0
1
4
> .781
0
0
1
0
Mean
0,05
0.04
0.12
0.16
SO
o.:?
0.11
0.36
0.25
SEW
0.02
0.01
0.04
0.03
N
70
67
31
76
^Totals for 1 12-hour collection period; data for the period
January 1 - March 31.
------- |