vvEPA
450/05 86-012
REVIEW OF THE NATIONAL AMBIENT AIR
QUALITY STANDARDS FOR PARTICULATE MATTER
UPDATED ASSESSMENT OF SCIENTIFIC
AND TECHNICAL INFORMATION
ADDENDUM TO THE 1982 OAQPS STAFF PAPER
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Strategies and Air Standards Division
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park. N.C. 27711
December 1986
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Cover Illustration. Mean concentration of components of participate
matter from dichotomous sampling (1978-79) in Portage, WI (P), Topeka,
KS (T), Kingston, TN (K), Watertown, MA (W), St. Louis, MO (SL) *(1976),
and Steubenville, OH (S). Shading represents fine fraction (< 2.5 pm),
remainder is coarse fraction up to a nominal 15 pm. These communities
are the subject of the Harvard "Six Cities Study" of the health effects
of air pollution. The cities were chosen to reflect a gradient in PM
and SOX air pollution. Although a major component of this study—
reflecting longitudinal analyses—has not been completed, the results
of cross-sectional analyses (Ware et al., 1986) and a series of
episode studies (Dockery et al., 1982) have been identified as
being among the more important recent publications for examining
the health effects of particulate matter. The data in the figure
illustrate the variations in particle mass and composition among
these cities during the period when these studies were being conducted.
Reference. Spengler, et al. (1980). Fine Particle Measurements in
Six U.S. Cities. In Proceedings of the Technical Basis for a Size
Specific Particulate Standard Speciality Conference. March 1980.
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REVIEW OF THE NATIONAL AMBIENT AIR QUALITY STANDARDS FOR PARTICIPATE MATTER:
UPDATED ASSESSMENT OF SCIENTIFIC AND TECHNICAL INFORMATION
ADDENDUM TO THE 1982 OAQPS STAFF PAPER
Strategies and Air Standards Division
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, N.C. 27711
December 1986
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11
Acknowledgments
This staff paper is the product of the Office of Air Quality
Planning and Standards. The principal authors include John Bachmann
and Jeff Cohen. The report incorporates comments from OAOPS, the Office
of Research and Development, the Office of Policy, Planning, and Evaluation,
and the Office of General Counsel within EPA and was formally reviewed hy
the Clean Air Scientific Advisory Committee.
Helpful comments and suggestions were also submitted by a number of
independent scientists, by officials from the California Air Resources.
Board, and by environmental and industry groups including the National
Resources Defense Council, the American Lung Association, the American Iron
and Steel Institute, the American Mining Congress, the Utility Air Regulatory
Group, Consolidation Coal Company, the Mining and Reclamation Council of
America, the Indiana Coal Council, Phelps Dodge Corporation, and Middle
South Services.
The authors wish to thank Teresa demons and Tricia Holland for word
processing, and Dick Atherton for graphics assistance.
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1.1 i
TABLE OF CONTENTS
Page
List of Figures iv
List of Tables iv
Executive Summary v
I. Introduction 1
A. Purpose 1
B. Background 1
C.,Approach 4
II. Air Quality Considerations . 5
A. Current PM^g Concentrations 6
B. Historical Trends in Six Cities 9
III. Critical Elements in the Review of the Primary Standards ... 12
A. Mechanisms 12
B. Concentration/Response Information 16
IV. Factors to be Considered in Selecting Primary Standards for
Particles 32
A. Pollutant Indicator 32
8. Level of the Standards 37
C. Summary of Staff Conclusions and Recommendations ..... 60
Appendix A. Summary of Recent Epidemiological Studies on
Particulate Matter A-l
Appendix B. Calculation of PM^g/TSP Relationships 8-1
Appendix C. CASAC Closure Memorandum . . . C-l
References
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IV.
Number
2-1
2-2
3-1
4-1
4-2
4-3
4-4
Number
1
2
2-1
3-1
3-2
4-1
4-2
A-l
A-2
A-3
LIST OF FIGURES
Concentrations from Dichotomous Samplers
in EPA IP Network
Trends in Seasonal Particle Fractions in Steubenville
Regional Deposition of Monodisperse Aerosols
Estimates of Thoracic Deposition of Particles
Mean Daily Mortality vs. Mean British Smoke for
Days with BS < 500 ug/m^ During 14 London Winters
Mean Change in FVC Compared to Baseline for
Children in Relation to Occurrence of Pollution
Episodes in Steubenville, Ohio, and the Ijmond
Area of the Netherlands
Adjusted Frequency of Cough for Children Living in 6
U.S. Cities vs. 4-year Average Estimated PM^o Levels
LIST OF TABLES
Updated Staff Assessment of Short-Term Epidemiological
Studies
Updated Staff Assessment of Long-Term Epidemiological
Studies
Estimated Counties Exceeding Proposed Standard Limits
Summary of Recent (1982-86) Epidemiological Studies
Providing Most Useful Concentration-Response
Information for Acute Particle Exposures
Summary of Epidemiological Study Providing Most
Useful Concentration-Response Information for
Long-Term Particle Exposures (1982-86)
Updated Staff Assessment of Short-Term
Epidemiological Studies
Updated Staff Assessment of Long-Term
Epidemiological Studies
Epidemiological Studies (1982-86) on Short-Term
Changes in Mortality and Exposure to Particles
Epidemiological Studies (1982-86) of Effects
on Mortality Due to Long-Term Exposures to Particles
Epidemiological Studies (1982-86) of Effects
on Morbidity Due to Long-Term Exposures to Particles
Page
7
10
13
35
42
46
56
Page
ix
xi
9
18
29
50
58
A-2
A-4
A-5
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EXECUTIVE SUMMARY
This paper evaluates and interprets the updated scientific and
technical information that the EPA staff believes is most relevant to
decision making on revised primary (health) national ambient air quality
standards (NAAQS) for particulate matter and is an addendum to the 1982
particulate matter staff paper. The paper assesses the factors the staff
believes should be considered in selecting the pollutant indicator and
level for the primary particulate matter standards, updating and supplementing
previous staff conclusions and recommendations in these areas to incorporate
more recent information. This assessment is intended to help bridge tne
gap between the scientific review contained in the EPA criteria document
addendum "Second Addendum to Air Quality Criteria for Particulate Matter
and Sulfur Oxides (1982): Assessment of Newly Available Health Effects
Information" and the judgments required of the Administrator in making
final decisions on revisions to the primary NAAQS for particulate matter
that were proposed in March 1984 (49 FR 10408). The staff paper and this
addendum are, therefore, important elements in the standards review process
and provide an opportunity for public comment on proposed staff recommenda-
tions before they are presented to the Administrator.
Particulate matter represents a broad class of chemically and physically
diverse substances that exist as discrete particles (liquid droplets or
solids) ranging in size from molecular clusters of 0.005 micrometers (um)
to coarse particles on the order of 100 um. The major chemical and physical
properties of particulate matter vary greatly with time, region, meteorology
and source category, complicating the assessment of health and welfare
effects as related to various indicators of particulate pollution. The
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vi
original measurement method for the particulate matter NAAQS was the "hi
volume" sampler, which collects particles of sizes up to a nominal 25-45 urn
(so called "Total Suspended Particulate" or TSP). EPA has proposed to
replace this particulate matter indicator with one that includes only
particles with aerodynamic diameters smaller than a nominal 10 urn, termed
"PMig". Although a large number of PM^g monitors are now in place, reliable
and consistent data are, at present, limited. Data from 39 sites in EPA's
IP network show long-term urban PM^g levels range between 25 and 75 ug/nr and
maximum 24-hour values range from 50 to 175 ug/m3. Higher values are
likely as more data become available. Both fine (<2.5 urn) and coarse
(>2.5 urn) particles are substantial components of PM^g mass, with a tendency
for higher coarse contributions in western US locations with higher concentra-
tions. National estimates of PM^g levels are derived from applying measured
PM10/TSP ratios to the wider TSP data set. This analysis (for 1983-85 data)
estimated that 193 counties exceeded the lower bound of the ranges proposed
.- o
for PM-^Q standards (150 ug/m 24 hour, 50 .ug/m annual) while 136 counties had
sites that exceeded the current primary TSP standards.
Particle Indicator
Based on an examination of air quality composition, respiratory tract
deposition, and health effects and related considerations, the 1982 staff
paper recommended adoption of the size specific indicator (PMig) proposed
in 1984. The present staff assessment of the more recent informaton on
respiratory tract deposition contained in the criteria document addendum
reinforces the conclusions reached in the original staff assessment in
1982. The staff finds that the recent data do not support alternative
indicators that have been suggested, which exclude all particles larger
than 10 urn. The PM^g indicator is generally conservative over the range of
tracheobronchial deposition.
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vn
Recent information suggesting enhanced tracheobronchial particle deposition
for children relative to adults provides an additional reason for an indicator
that includes particles capable of such penetration. Given these considerations
and its earlier conclusions, the staff reaffirms its recommendation to
replace TSP as the particle indicator for the primary standards with a new
indicator that includes only those particles smaller than a nominal 10 urn
in aerodynamic diameter (PM^o). The previously developed effectiveness
criteria for samplers are acceptable for regulatory purposes.
Level of Standards
The major scientific basis for selecting PM standards that have an
4
adequate margin of safety remains community epidemiological research, with
mechanistic support from toxicological and controlled human investigations.
The limitations of epidemiological studies for these purposes must, however,
be recognized. Such studies, while representing real world conditions, can
only provide associations between a complex pollutant mix measured at
specific locations and times and a particular set of observable health
points. Difficulties in conducting and interpreting^ epidemilogical studies
limit the reliance that can be placed on the results of any single study.
None of the available studies have used PM^g as a direct measure of pollution,
requi ring—where appropriate—further conversion of results to estimated
PM^Q units.
The 1982 criteria document and the criteria document addendum identify
a limited set of epidemiological studies most useful for developing quanti-
tative conclusions regarding the effects of particulate matter. This
updated staff assessment incorporates the previous evaluation of the earlier
studies as well as'the present assessment of more recent studies.
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viii
The updated staff assessment of.the short-term epidemiological data
is summarized in Table 1; levels are expressed in Doth the original
(British smoke—"BS" or TSP) and PMi0 units. The "effects likely" row denotes
concentration ranges derived from the criteria document and its addendum at'
or above which a consensus judgment suggests greatest certainty that some
effects would occur, at least under the conditions that obtained in the
original studies. The data do not, however, show evidence of clear population
thresholds but suggest a continuum of response with both the risk of effects
occuring and the magnitude of any potential effect decreasing with concen-
tration. This is particularly true for the statistical analyses of daily
4
mortality in London. Substantial agreement exists that wintertime pollution
episodes produced premature mortality in elderly and ill populations, but
the range and nature of association provide no clear basis for distinguishing
any particular lowest "effects likely" levels or for defining a concentration
below which no association remains. The recent lung function studies in
children suggest that effects are possible in the range listed in Table 1,
but the relationships are not certain enough to derive "effects likely"
levels for PMio They do suggest levels below which detectable functional
changes are unlikely to occur.
Based on this staff assessment of the short-term epidemiological data
the range of 24-hour PM^Q levels of interest are 140 to 250 ug/m . The
up'per end of the range reflects the judgment of the Administrator with
regard to the maximum level proposed in 1984 for a 24-hour standard, based
on his consideration of the earlier criteria and assessments. Although the
recent information provides additional support for the possibility of
effects at lower levels, it 'does not demonstrate that adverse effects would
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TABLE 1. UPDATED STAFF ASSESSMENT OF SHORT-TERM EPlUEfUOLOGICAL STUDIES
Effects/Study
Effects Likely
Effects Possible
No Significant
Effects Noted
o
Measured British Smoke Levels (as ug/m )
(24-hr, avg.)
Daily Mortality
in London*
1000
J
?
-
Aggravation of
Bronchitis2
250*-500*
< 250*
-
Combined
Range
250-500
<250
-
o
Measured TSP Levels (ug/nr)
(24-hr, avg.)
Small, reversible declines
in lung function in children3*
-
220*-4203
200-2504
125*4-1603
Equivalent PMi0
Levels (gg/m3)
Combined
Range5
350-600
140-350
<125
*Indicates levels used for upper and lower bound of range,
^Various analyses of daily mortality encompassing the London winter of 1958-59, 14 winters from 1958-72, in aggregate
and individually. Early winters dominated by high smoke and S02 from coal combustion with frequent fogs. From 1982 CD:
Martin and Bradley (1960); Ware et al., (1981); Mazumdar et al. (1981). From 1986 CD Addendum: Mazumdar et al. (1982);
Ostro (1984); Shumway et al., (1983); Schwartz and Marcus (1986). Later studies show association across entire range of
smoke, with no clear delineation of "likely" effects or threshold of response possible.
2Study of symptoms reported by bronchitis patients in London, mid-50's to early 70's; Lawther et al . (1970).
3Study of pollution "episodes" in Steubenville, Ohio, 1978-80; Dockery et al. (1982).
Jstudy of 1985 pollution episo'de in Ijmond, The Netherlands; Dassen et al. (1986).
^a) Conversion of BS readings to PM^j levels: Assumes for London conditions and BS readings in the range 100-500 ug/m ,
BS
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•3
occur with certainty at a PM^Q concentration of 250 ug/m . This level,
therefore, remains an appropriate upper bound. The recent data suggest
that the range of levels under consideration of alternative .standards can
be reduced to 140 ug/m3, although the original lower bound of 150 ug/rn3
is within the range of uncertainty associated with expressing the data as
PMiQ. Neither the studies used to derive this range nor the more qualitative
studies of effects in other sensitive population groups (e.g., asthmatics)
or effects in controlled human or animal studies provide convincing scientific
support for health risks of consequence below 140 ug/m3 in current U.S.
atmospheres. These qualitative data, as well as factors such as aerosol
composition and exposure characteristics, should also be considered in
evaluating margins of safety associated with alternative standards in the
range of 140 ug/m3 to 250 ug/m3.
The amended staff assessment of the more quantitative long-term
epidemiological data is summarized in Table 2. Long-term studies "are
subject to additional confounding variables that reduce their sensitivity
and make interpretation more .difficalt. The most important new study shows
a gradient of responses in children among six U.S. cities that follows the
measured gradient in particulate matter, but response comparisons for
locations with somewhat smaller pollution gradients within some of
these cities do not follow the same patterns. The results of a separate
series of studies on long and intermediate term (2-6 weeks) exposures in a
number of U.S. cities (Ostro, 1983, 1987; Hausman et. al, 1984) is more
supportive of the possibility of within city effects at comparable U.S.
exposure levels. Thus some risk of effects is possible at levels somewhat
below those suggested by the 1982 assessment, but it is uncertain given the
potential for confounding present in these more recent studies.
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TABLE 2. UPDATED STAFF ASSESSMENT OF'LONG-TERM EPIDEMIOLOGICAL STUDIES
Effects/Study
Effects Likely
Effects Possible
No Significant6
Effects Noted
Measured BS
Levels (as ug/m3
Increased
Respiratory
Disease, Reduced
Lung Function
in Children1
230-300 BS
<230 BS
'
Measured TSP Levels (ug/m3)
Increased Respiratory
Disease Symtpoms,
Small Reduction in
Lung Function in
Adults^
180*
130-180*
80-130
Increased
Respiratory
Symptoms
in Adults-*
-
60-150(110)
Increased
Res'pi ratory
Symptoms and
Illnesses in
Children4
-
60*-114
-
Reduced
Lung
Function
in
Children4
-
-
40-114
Combined
Range
>_180
60-180
<60
Equivalent
PM^Q Levels
(ug/m3)
Combined
Range**
80-90
40-90
• <40
*Indicates levels used for upper and lower bound of range.
*Study conducted in 1963-65 in Sheffield, England (Lunn et al., 1967). BS levels (as ug/m3) uncertain.
2Studies conducted in 1961-73 in Berlin, N.H. (Ferris et al., 1973, 1976). Effects level (180 ug/m3)
based on uncertain 2-month average. Effects in lung function were relatively small.
"3Study conducted in 1973 in two Connecticut towns. (Bouhuys et al. 1973). Exposure estimates reflect 1965-73 data in
Anson. Median value (110 ug/m3) used to indicate long-term concentration. No effects on lung function, but some
suggesstion of effects on respiratory symptoms.
4Study conducted in 1976-1980 in 6 U.S. cities (Ware et al., 1986). Exposure estimates reflect 4-year averages across
cities. Comparable pollution/effects gradients not noted within cities.
Conversion of TSP to PMjM equivalents for Berlin, Ansonia studies based on estimated ratio of PMjy/TSP for current
U.S. atmospheres (Pace, 1983). The estimated ratio ranged between 0.45 and U.5. Conversion for six-city study
based on site-specific analysis of particle size data (Spengler et al., 1986).
^Ranges reflect gradients in which no significant effects were detected for categories at top. Combined range
reflects all columns.
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XII
Based on this updated assessment of the long-term epidemiological data,
the staff recommends that the range of annual PM^Q levels of interest be
40 to 66 ug/m3. The upper-end of the range reflects the judgment of the
Administrator with regard to the maximum level proposed "for an annual
standard, based on his consideration of the earlier criteria and assessment.
The staff concludes that this level remains a useful upper bound. The
recent data prompt consideration of a standard level below the previous
lower bound (50 ug/m3) to values as low as 40 pg/m3. Uncertain data from
one recent study of six cities suggest that at this level some risk may
remain of respiratory effects in children, but no detectable increases in
i
pulmonary function are expected in children or adults.
When evaluating margins of safety for an annual standard, it is
particularly important to examine the results of qualitative data from a
number of epidemiological, animal, and air quality studies. These suggest
concern for effects not directly evaluated in the studies used to develop -
the ranges. Such effects include damage to lung tissues contributing to
^chronic respiratory disease, cancer, and premature mortality. The available
scientific data do not suggest major risks for these effects categories at
current ambient particle levels in most U.S. areas. Nevertheless, the risk
that both fine and coarse particles may produce these responses supports
the need to limit long-term levels of PM^Q for a variety of aerosol
compositions.
When selecting final standard levels, consideration should be given to
the combined protection .afforded by the 24-hour and annual standards taken
together. For example, a 24-hour standard at 150 ug/m3 would substantially
reduce annual levels in a number of areas below 50 ug/m3 adding to the
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xiii
protection afforded by an annual standard in areas with higher 24-hour
peak to annual mean ratios.
Because of different form, averaging procedures, size range, and
limited PM^g data, precise comparison between the above ranges of PM^Q
standards and the current primary TSP standards is not possible. A staff
analysis of Pl^g/ISP ratios applied to recent TSP data shows that the
revised lower bounds, taken together, would result in standards clearly
more stringent that the current standards. In various analyses, standards
at the lower bound of the previous range (150,50) have appeared to range
from more stringent to approximately comparable to the-present primary
standards. Standards at the upper end of the range could, however, result
in about a four-fold decrease in the number of areas exceeding the primary
standards.
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REVIEW OF THE NATIONAL AMBIENT AIR QUALITY STANDARDS FOR PARTICIPATE MATTER:
UPDATED ASSESSMENT OF SCIENTIFIC AND TECHNICAL INFORMATION
ADDENDUM TO THE 198Z OAQPS STAFF PAPER
I. INTRODUCTION
A. Purpose
This paper evaluates and interprets the most relevant scientific
and technical information reviewed in the EPA document, Second Addendum
to Air Quality Criteria for Particulate Matter and Sulfur Oxides (1982):
Assessment of Newly Available Health Effects Information (EPA, 1986) and
represents an update of the 1982 particulate matter staff paper (EPA, 1982a).
This staff paper addendum is intended to help bridge the gap between the
scientific review of recent health effects information contained in the
criteria document addendum and the judgments required of the Administrator
in making final decisions on the proposed revisions to the primary national
ambient air quality standards (NAAQS) for particulate matter (49 FR 10408).
As such, particular emphasis in this paper is placed on conclusions,
recommendations, and uncertain-ties regarding the pollutant indicator and
levels for the primary standards. While the paper should be of use to all
parties interested in the standards review, it is written for those decision
makers, scientists, and staff who have some familiarity with the technical
discussions contained in the criteria document addendum.
8. Background
1. Legislative Requirements
Since 1970 the Clean Air Act as amended has provided authority and
guidance for the listing of certain ambient air pollutants which may endanger
public health or welfare and the setting and revising of NAAQS for those
pollutants. Primary standards must be based on health effects criteria and
provide an adequate margin of safety to ensure protection of public health.
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2
As several recent judicial decisions have made clear, the economic and
technological feasibility of attaining primary standards are not to be
considered in setting them,-although such factors may be considered to a
degree in the development of state plans to implement the standards (D.C.
Cir., 1980, 1981). Further guidance provided in the legislative history
of the Act indicates that the standards should be set at "the maximum
permissible ambient air level . . . which will protect the health of any
(sensitive) group of the population." Also, margins of safety are to be
provided such that the standards will afford "a reasonable degree of
protection . . . against hazards which research has not yet identified."
(Committee on Public Works, 1974). In the final analysis, the EPA
Administrator must make a policy decision in setting primary standards,
based on his judgment regarding the implications of all the health effects
evidence and the requirement that an adequate margin of safety be provided.
2. Original PM Standards and Proposed Revisions
The current primary standards for particulate matter (to protect
public health) are 75 micrograms per cubic meter (ug/m^) annual geometric
mean, and 260 ug/m^, maximum 24 hour concentration not to be exceeded more
than once per year. The reference method for measuring attainment of the
primary standards is the "hi-volume" sampler (40 CFR Part 50, Appendix
B), which effectively collects particles in the range of up to 25-45
micrometers (urn) in diameter (so-called "total suspended particulate," or
"TSP"). Thus, TSP is the current indicator for the particulate matter
standards.
On March 20, 1984, EPA proposed changes in the standards (49 FR 10408)
based on the Agency's review and revision of the health and welfare criteria.
The proposed changes to the primary standards included:
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3
1) replacing TSP as the indicator for particulate matter with a new
indicator that includes only those particles with an aerodynamic diameter
smaller than or equal to a nominal 10 urn (PMig);
2) changing the level of the 24-hour standard to a value to be
selected from a range of 150 to 250 gg/m^ and replacing the deterministic
form of the standard with a statistical form that permits one expected
exceedance of the standard level per year; and
3) changing the level and form of the annual standard to a value to
be selected from a range of 50 to 65 ug/m^, expected annual arithmetic mean.
Given the precautionary nature of the Act, the Administrator stated
an inclination-to select the primary standards from the lower portions of the,
above ranges. The proposal notice (49 FR 10408) sets forth the rationale
for these and other proposed revisions of the particulate matter NAAQS
and background information related to the proposal.
3. Developments Subsequent to Proposal
After the close of the public comment period on the proposed standards
provisions, the Clean Air Scientific Advisory Committee (CASAC) met on
December 16-17, 1985 to review the proposal and to discuss the relevance
of certain new scientific studies on the health effects of particulate
matter that had emerged since the Committee completed its review of the
criteria document and staff paper in January 1982. Based on its preliminary
review of these new studies, the Committee recommended that the Agency
prepare addenda to the criteria document and staff paper to evaluate the
relevant new studies and consider their potential implications for standard
setting. The Agency announced its decision to prepare these addenda on
April 1, 1986 (51 FR. 11058).
A preliminary draft of this paper was reviewed by the CASAC in October 1986*
This final product incorporates the suggestions and recommendations of the
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4
CASAC as well as other appropriate comments received on the initial draft.
The CASAC closure memorandum (Lippmann, 1986) is reprinted in Appendix C.
C. Approach
The approach in this paper is to address the newly available health
effects information in the criteria document addendum (CD addendum or CDA;
EPA, 1986a) in the context of those critical elements which the staff believes
have implications for the proposed revisions to the primary particulate
matter standards. Particular attention is drawn to judgments, related to the
proposed indicator for the primary standards (i.e., PM^Q), and the proposed
ranges of interest for the level of the primary standards. Previous staff
conclusions and recommendations related to the secondary standards wi 11 not
be addressed here.
Sections II and III review important recent scientific and technical
information relevant to standard setting. Section II provides a brief
update of aspects of current and historical air quality information on
particulate matter to support discussions of the standards. Section III
addresses those essential elements of the health effects information that
require re-examination in light of the new information in the CD addendum,
which include:
1) respiratory tract deposition and clearance of inhaled particles; and
2) concentration/response relationships for both acute and long-term
exposures to particulate matter derived from community epidemiological
studies.
Drawing from the discussion in Sections II and III, Section IV
identifies and assesses the factors the staff believes should be considered
in selecting the particulate pollutant indicator and level of primary
standards. Staff conclusions and recommendations on policy alternatives
are updated and supplemented to incorporate the more recent information.
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II. AIR QUALITY CONSIDERATIONS
More than any other criteria pollutant, "participate matter" represents
a broad class of chemically and physically diverse substances. Their
principal common feature is existence as discrete particles in the condensed
(liquid or solid) phase ranging in size from molecular clusters of 0.005 urn
to coarse particles on the order of 100 urn.* The major chemical and
physical properties of particulate matter vary greatly with time, region,
meteorology, and source category. It is to be expected, then, that the
effects of given quantities of particles on public health and welfare also
will vary. This variable composition complicates the evaluation of the"
applicability of specific particle health and welfare studies for establish-
ing national ambient air quality standards. The 1982 staff paper ("SP,"
1982) (Section IV) summarized some key features of our understanding of
historical and current particulate matter composition to provide perspective
for interpretation of-the effects studies derived-from the 1982 criteria
document ("CD," 1982b). This section of the addendum updates the original
work in two areas: 1) an overview of recent measured and estimated PM^Q
concentrations and potential exposures, and 2) a summary of historical
particle size relationships associated with six U.S. cities that are the
subject of the most important new epidemiological studies.
*Where not otherwise specified, particle sizes reported in this paper
reflect aerodynamic equivalent diameter (AED). A number of terms (e.g.,
fine, coarse, inhalable, thoracic, TSP) are used to describe various fractions
of particulate matter. Many of these terms are defined by the instruments
used for measurement. The major particle indicators discussed in this
paper are defined in Appendix D of the 1982 staff paper.
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6
A. Current PM^g Concentrations
Since the original staff and CASAC recommendations for a 10 urn cut-
point for the primary particulate matter standards, a number of different
sampling devices capable of measuring this fraction (termed PM^g) have
been developed. Several hundred PM^g instruments are now being operated
in the field by state and local agencies, industries, and researchers.
Data from these sources are, however, fragmentary due in part to start-up
and reporting limitations, and the available results have not yet been
adequately screened. Thus, it is not yet possible to provide an adequate
• national assessment of PM^g concentrations.
Some idea of PM^g levels and composition across the country can,
however, be derived from later years of EPA's "Inhalable Particle" (IP)
network (Pace, 1986). Beginning in 1982, the 39 sites in this network with
dichotomous samplers were retrofitted with PM^g inlets. These sites were
chosen'to represent areas with the highest particulate matter concentrations
in the original 163 site network. As a group, they have considerably
higher TSP levels than most sites in EPA's "SAROAD" data base. Because of
the limited number and duration, however, it is virtually certain that
other locations in the nation will record similarly high or even higher
concentrations. The PM^g samplers came on line at various times in 1983 and
1984 and were operated on a 1 in 6 day sampling schedule. Thirty-eight
of the sites provide useful data during this period, with a total collection
of 11 to 113 readings per site.
With these limitations in mind, Figure 2-1 presents the annual and
maximum 24-hour values from this network in 1983-84. These data suggest
that both fine and coarse particles are major contributors to PM^g mass
across all sites, with a tendency for sites with higher concentrations to
-------
MAX 24-HOUR CONCENTRATIONS (83-84)
38 SITES IN EPA IP NETWORK
200
FP
COARSE
ANNUAL MEAN PMIO CONCENTRATIONS (83-84)
m
E
\
0)
Z
O
H
I-
<
d
H-
UJ
O
O
U
38 SITES IN EPA IP NETWORK
COARSE
Figure 2-1. PMio Concentrations from Dichotomous Samplers In EPA IP Network,
ordered by concentration, a) Maximum 24-hour PMio values with associated fine
mass. Due to limited sampling frequency, these data probably understate the
actual maxima, b) Annual means of PKjo and fine particles. Fine mass is a
substantial fraction of PMjo mass particularly in eastern sites; coarse
particles tend to constitute a large fraction at higher concentrations and
at western sites. (Pace, 1986)
-------
8
have a higher coarse fraction. This tendency holds for both maximum 24-hour
and annual data over all sites on the days with highest PM^g concentration,
the fine fraction average about 60% of PM^g mass.
The data in Figure 2-1 suggest that no more than eight sites would exceed
the lower bounds of the ranges for PM^g standards proposed in 1984. As noted
above, however, these results are likely to understate the extent of higher
concentrations across the country. To provide some sense of the nature of
such concentrations as well as potential human exposures to them, EPA
staff have developed an approach for estimating the probability of exceeding
particular PM^g values using available TSP measurements (Pace and Frank,
1984). The approach is based on a detailed examination of size fractionated
data (PMig, PMis, and TSP) across the nation (Pollack et al., 1985). To
provide a best estimate of the number of areas that would exceed particular
PM^g values, staff applied PM^g/TSP relationships associated with a 50%
probability of exceeding the specified limits to the national TSP data
set for the years 1982-84. The results shown in Table 2-1 represent the
estimated number of counties (and population residing therein) that would
exceed combined PM^g standards set at the extreme upper and lower bounds
of the proposed ranges. For comparison purposes, the effect of adding
a secondary annual TSP standard of 90 ug/m^ and the counties exceeding the
current primary TSP standards are also shown. These estimates are highly
uncertain, but give some perspective on the nature of current PM^g air
quality and potential exposures with respect to the proposed standards.
More definitive data from actual PM^g monitoring will be available in
the near future.
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9
TABLE 2-1. ESTIMATED COUNTIES EXCEEDING PROPOSED STANDARD LIMITS*
Standards No. Counties
(24 hr/annual , ug/m3) Exceeding Limit
Upper bound of P
(250/65)
Upper PM10 + TSP
Lower bound of P
(150/50)
Lower PM^Q + TSP
Current primary
(260/75)
MIQ ranges
secondary**
MIQ ranges
secondary**
TSP standards
36
73
173
176
155
Population in Counties
12 mil lion
-
60 mil lion
-
50 mil lion
*Based on 1982-84 TSP data, counties with probability of exceeding standards
(probex) _>. 0«5, 1980 census data. Geographical area exceeding limits may, in
many cases, be much smaller than county size. Accordingly, populations in
the vicinity of such concentrations are lower than the total county populations,
**90 ug/m3 annual arithmetic mean.
8. Historical Trends in Six Cities
The draft criteria document addendum indicates that two of the more
important recent publications on the effects of particulate matter are derived
from the Harvard "Six Cities" study. To aid in the assessment of these
studies, EPA commissioned an examination of the relationships between TSP
and size fractionated particle mass measurements in these cities (Spengler
et al., 1986). The results, which span some seven years of size specific
data, are useful both in examining trends and in permitting improved estimates
of historical PM^Q levels from TSP measurements. Details on the analysis,
methodology, and relationship to health study sites are contained in a
separate report (Spengler et al., 1986).
The results from Steubenville in Figure 2-2 are illustrative. Over
the six year period of record, concentrations of all particle fractions
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10
100-
90"
80-
7O-
4O"
3O '
2O-
io-
•AW \w
v V--
i 1 . . , 1 . . , 1
1979 198O
. "\Vy 'YJ \Vy
\ . \ •— '*N
a
1981 1982 1903 • 1981
1.2-
1.1-
i.o-
cu
H^ O.8-
in
^ 0.7-
cu
V 0.6-
Uj
O O.5-
^ 0.4'
ct
0.3-
0.2
0.1
-
1 ill 1
Jii I u 6 1 nuaiy/iiii 1
0 "VTvOuTTyPTin.
v n • T y v i T T . v r
T ' T
0.0 | ... | ...,...,...,
i
•
'
i
i-
i
-
i r
T
1979
1980
1981
1982
198
Figure 2-2. Trends in Seasonal Particle Fractions at Steubenville (Spengler
et al., 1986). a) From 1979 on, all size fractions show similar seasonal
trends with a general decline in all measures, b) The ratio of PMis/TSP as
measured by dichotomous sampler is, however reasonably stable over the same
period. The ratios of these fractions at other six city sites also do not
show clear trends, but in some cases the decrease in coarse particles
(> 2.5 pm) is more pronounced than that for fine, suggesting that the
historical ratios of PMio/TSP were somewhat lower.
-------
11
generally declined as source emissions declined, with some suggestion of
an increase in 1984. The PM^/TSP ratio remained reasonably stable through
this period. This suggests that the PMnj/TSP ratio of U.5 measured in
1984 would be reasonably representative of the recent historical past.
Size fraction ratios at the other five sites also showed little in the
way of trends, but the examination of trends in particle mass suggested
that the PM^g/TSP ratio in three cities (St. Louis, Watertown and Topeka)
were likely to have been somewhat lower in earlier years when TSP levels
were higher (Spengler et al., 1986). Recent (1984) PMio/TSP ratios for these
cities are Portage, WI (0.64), Topeka, KS (0.46), -St. Louis, MO (0.62),
Harriman, TN (0.66), and Watertown, MA (0.54). The report notes that the.
PM^g and some other aerometric data for certain years were obtained by use of
Beta-Gauge measurement rather than gravimetric mass. Based on an examination
of trends, no perceptible difference is noted between these two measures,
at least for determining longer-term averages.
The ratios derived from annual averages do not necessarily apply to any
particular 24-hour period. Data presented in the Spengler et al. (1986)
report (Figures IV-3 to IV-8) also include size fraction and ratio data
that encompass the 1979 and 1980 episode studies reported in Dockery et
al. (1982). On various days during the three study periods, the PM^/TSP
ratios measured by dichotomous samplers ranged between 0.4 and 0.8. Based
on the overall ratios among fractions in Steubenville (Tables V-5,6 in the
Spengler et al. report), the PMjQ/TSP ratios would be expected to be a
factor of about 0.8 to 0.9 of these PMi5/TSP ratios (see Appendix 8).
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12
III. CRITICAL ELEMENTS IN THE REVIEW OF THE PRIMARY STANDARDS
This section summarizes recent information on particle deposition
in the respiratory tract and on concentration-response relationships from
community studies. A comprehensive discussion of these and other critical
elements, including mechanisms of toxicity, effects of concern, and sensitive
populations, is contained in Section V of the 1982 staff paper (1982a).
The present summary provides a basis for later discussions of the implications
of the more recent studies for selecting the particle indicator and examining
concentration/response relationships.
A. Mechanisms: Particle Deposition
The major relevant new information reviewed in the CD^adde.ndum concerning
mechanisms related to penetration and deposition of particles in the respiratory
tract falls into the following categories: (1) extension of experimental data
on deposition and clearance of large (> 10 urn) particles; (2) assessment of
particle deposition during oronasal breathing; and (3) information on variations
in deposition and clearance for children and individuals with respiratory
illness, as well as for altered breathing patterns. Each of these areas is
briefly discussed below.
1. Thoracic Deposition of Large (> 10 urn) Particles
Figure 3-1 updates the range of available experimental data on alveolar
and tracheobronchial particle deposition presented in the 1982 CD (Figure 2,
CDA). The recent experimental deposition data on larger particles (> 10
urn) from three laboratories are represented as the individual points shown.
The CD addendum notes that the data of Svartengren (1986) reflect an atypical
inhalation pattern; accordingly, less emphasis should be placed on those
data. Nevertheless, the major thrust of the new results, taken together,
is to substantiate the original extrapolation of the upper bound of the
-------
13
o
er
u.
o
&
ui
O
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
—r—i—i i i i
RANGE OF ALVEOLAR DEPOSITION.
MOUTH BREATHING
ESTIMATE OF ALVEOLAR DEPOSITION. NOSE BREATHING
RANGE OF TRACHEOBRONCHIAL DEPOSITION.
MOUTH BREATHING
—— EXTRAPOLATION OF ABOVE TO POINT ( Q > PREDICTED
BY MILLER « «!.. (19791
o«
OB
-O+ SVARTENGHEN (1986)
OPEN SYMBOLS: TRACHEOBRONCHIAL DEPOSITION
SOLID SYMBOLS: ALVEOLAR DEPOSITION
1—I—I I I I I lllllll
0.2
PHYSICAL DIAMETER,
2.0 3.0 4.0 5.0
10 121416 20
AERODYNAMIC DIAMETER,
Figure 3-1. Regional deposition of monodisperse aerosols by indicated
particle diameter for mouthpiece breathing (alveolar, tracheobronchial) and
nose breathing (alveolar) (CDA, Figure 2). The alveolar band indicates
the range of results found by different investigators using different
subjects and flow parameters for alveolar deposition following mouth
breathing. Variability is also expected following nasal inhalation.
The tracheobronchial band indicates intersubject variability in deposition
over the range of sizes as measured by Chan and Lippmann (1980). Deposition
is expressed as fraction of particles entering the mouth (or nose). Also
shown is an extrapolation of the upper bound of the TB curve to the point
predicted by Miller et al. (1979). The extrapolation illustrates the
likely shape of the curve in this size range but is uncertain. However,
the data of Emmett et al. (1982), Heyder (1986), and Svartengren (1986)
tend to substantiate this extrapolation. In the Svartengren (1986)
studies, subjects took maximally deep inhalations at a flow of
500 cm3 s1.
-------
14
tracheobronchial deposition curve in Figure 3-1 to the point predicted by
Miller et al. (1979). With the exception of the Svartengren results, the
newer data are also reasonably consistent with the range of alveolar
deposition illustrated; taken together, however, the added points suggest
slightly higher alveolar deposition for larger particles than did the
previous data.
2. Assessment of Deposition During Uronasal Breathing
The experimental results depicted in Figure 3-1 were obtained from
studies in which the subjects inhaled through a mouthpiece. Such results
tend to overstate particle penetration under more natural oronasal breathing
conditions. Swift and Proctor (1982) attempted to quantify this overstatement
and simulate deposition under natural oronasal and oral breathing for
ventilation rates corresponding to light activity. Based on their results,
the authors predicted that little thoracic deposition would occur for
particles larger than 10 pro with natural breathing conditions'. The
CD addendum points out that this conclusion does not appear to be
consistent with the information available in 1982; moreover, the analysis
itself has been superceded by improved simulations using more recent
experimental data (Miller et al., 1984, 1986).
As indicated in the CD addendum, these latter analyses provide
significantly improved fits of the deposition data and extend both the
particle size range and ventilation patterns simulated. These results
show that the Swift and Proctor simulation and related predictions
understate thoracic deposition for particles larger than 10 urn under all
conditions and understate deposition of particles larger than 6 urn for
individuals who habitually breathe oronasally (mouth breathers) at light
activity levels. The CD addendum concludes that the more recent
-------
15
deposition data shown in Figure 3-1 "are relevant to examining the
potential of particles to penetrate to the lower respiratory tract and
pose a potentially increased risk. Increased risk may be due to increased
localized dose or to the exceedingly long half-times for clearance of
larger particles (Gerrity et al., 1983)" (p. 2-18).
3. Variations in Deposition and Clearance for Children and Other Groups
Experimental deposition data discussed above are restricted to
adults. The epiderniological evidence, however, indicates increased risk
to young children exposed to ambient particulate matter. Phalen et al.
(1985) have modeled tracheobronchial deposition of particles. Although
not accounting for prior extrathoracic removal, the results suggest a
tendency towards increased particle deposition efficiencies for the range
of particle sizes modeled (0.5 to 10 urn) in smaller (younyer) individuals
(CDA, Figure 4). Attempts to quantify age-dependent differences in
deposition will' require improved information on differences in children
related to alveolar and extrathoracic deposition, deposition over the
entire breathing cycle, and clearance patterns.
Subject characteristics, disease states, and other factors can also
alter the deposition and clearance of particles from more typically
observed ranges. Recent work by Heyder (1982) examined biological variability
of particle deposition in adults and found very small intrasubject
variability mainly due to daily variations in breathing cycle and flow
rate. The more extensive variability of deposition rate between subjects.
breathing the same aerosol was found to be less determined by the morphological
constitution of the respiratory tract than by individual ventilatory
patterns.
-------
16
Several new studies on clearance mechanisms further support previous
conclusions in the 1982 CD and Staff Paper regarding the consequences
of retarded mucous transport when impaired by disease or other insults on
residence times of inhaled particles, long-term clearance times of
insoluble particle from the alveolar region, and the regional deposition
of inhaled particles (Svartengren et al., 1986; Levandowski et al., 1985,
Garrard et al., 1985; Bailey et al., 1982; Bohning et al., 1982; Philipson
et al., 1985; Gerrity et al., 1983).
B. Concentration-Response Information
As discussed in the 1982 Staff Paper, associations between air
pollution and both acute and chronic effects have been demonstrated in
many countries and different population groups, supported by controlled
laboratory exposures of animals and humans to various components of
particulate matter (SP, section V.A,B,C; Appendix B). • Assessing
the precise level of particulate pollution associated with observed
effects on health, however, has many problems. Suspended particulate
matter is not a uniquely defined entity. The comprehensive physical and
chemical characteristics are not only hard to measure and relate to
health effects, but vary with monitoring device, geography, and time.
This variability increases the uncertainty of any extrapolations from one
set of circumstances to another, and greatly limits the utility of laboratory
studies of single substances for quantifying health risks.
Epidemiological studies can provide strong evidence for the existence
of pollutant effects, but are more limited for identifying accurate effects
levels for specific pollutants or pollutant classes. Among the more
important limitations of epidemiology as discussed in the 1982 CD are:
1) inadequate and inconsistent measurement of the exposure burden of
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17
individuals; 2) variability in the measurement of health endpoints (e.g.,
lung function, hospital admissions, frequency of symptoms) and in the
sensitivity of populations studied; 3) failure, especially in cross-sectional
studies, to control fully for confounding or covarying factors, such as
cigarette smoking and socioeconomic status; 4) difficulty in distinguishing
particles from other pollutants; and 5) inability to establish a causal
relationship, or negate one, based only on statistical associations.
Recognizing these limitations, epidemiological studies still
form the principal basis for developing concentration response assessments
for particulate pollution.. The key concentration-response information
derived from the 1982 CD is discussed in the 1982 Staff Paper and in the
1984 PM proposal notice (49 FR 10408). The following review summarizes the
recent epidemiological studies cited by the CD addendum as providing the
most reliable exposure-response information on mortality and morbidity
effects associated with acute and'chronic exposures to particulate
matter. Other recent studies that may provide reasonable evidence of
exposure-response relationships or qualitative insights are summarized in
tabular form in Appendix A. Further assessment of the epidemiological
studies as applied to selecting alternative levels for air quality standards
is presented in Section IV.
1. Acute Exposures
a) Mortality
Table 3-1 summarizes recent epidemiological studies providing the most
useful concentration response information for assessing acute exposures to
particulate matter. The initial entry reflects the newer CD addendum conclusions
regarding reanalyses of daily London mortality in relation to short-term
(24-hour) exposures to PM and S02 (Mazumdar et al., 1982; Ostro, 1984 Shumway
-------
TABLE 3-1. SUMMARY OF RECENT (1982-86) EPIDEMIOLOGICAL STUDIES PROVIDING MOST USEFUL
CONCENTRATION/RESPONSE INFORMATION FOR ACUTE PARTICLE EXPOSURES
Jbserved
ffects
Observed Concentration Range
Time
Study
increases in
daily mortality
in metropolitan
.ondon
ihort-term
•eductions in
ung function
in 330 school
:hildren,
iteubenville,
iH (330 total)
hort-term
eduction in
ung function
n 179 school
hildren in
he
etherlands
Ijmond)
1958-1972
winters
<500 BS*
>500
24-hr averages
Four
separate
study
periods of
3 weeks
following
pollution
"episodes"
in 1978-1980
Before,
during, af-
ter pollu-
tion epi-
sode Nov.
1984-Feb.
1985
1) 420 TSP 280
2) 270 TSP 460
3) 220 TSP 170
4) 160 TSP 190
(max 24 averages for
"alert" or "sham"
episode)
200-250 TSP 200-250
and RSP
(D5n < 3.5
urn)
24-hr averages
Shumway et al.
1983, Schwartz
and Marcus,
1986
Recently published studies reinforce 1982 CD, Mazumdar et
SP conclusions regarding likelihood of increased 1982, 1983;
mortality at 500 to 1000 ug/m3 for BS and SOo, Ostro 1984
with no clearly defined threshold for BS in the
range of 150 to 500 ug/m^. Year-by-year analyses
indicate significant BS-mortality associations
in most to all winters. Nature of relationships
vary significantly with model. Suggestion of
surrogate behavior.
Recent unpublished analyses confirm major
findings of the published studies with advanced
statistical techniques accounting for auto-
correlation and temperature effects. Schwartz
and Marcus findings suggest significant
association for BS at lowest levels (<100
BS), but not for S02 below about 500 ug/m .
First 3 episodes: small (2%-3%) but significant
reversible declines in FVC up to 2-3 weeks after
peak. Less consistent results for FEV. No
significant effects after 4th "sham" episode.
Baseline measurements for 1st, 4th taken on days
with high pollution. Linear regression of pooled
data for 330 children indicate significantly more
negative slopes in functions vs. TSP and SO;? across
ranges (10-270 ug/m^, 0-280 pg/m^, respectively).
Higher response in some children suggests sensitive
subgroup.
Small (3-5%) reversible declines in several Dassen et
measures of airway function (FVC, FEVj, MEF) al., 1986
during episode and 5 days later. No effect
after 26 days or shortly after a day when TSP,
RSP and S02 levels all averaged 100-150 ug/m .
Separate sub-groups of children tested on each
day. Peak TSP levels possibly understated.
al,
Dockery et al,
1982
00
Britsh Smoke s is a pseudo-mass indicator related to small particle (size less than a nominal 4.5 \im) darkness
CD, pp. 1-88 to 1-90).
-------
19
et al., 1983, Schwartz and Marcus, 1986). Among the important unresolved
issues raised regarding these London data are identification of a practical
threshold for PM-mortality associations, separating effects of PM and S02,
the changes in coefficients obtained with different subsets of data sets
and models, the effects of unmeasured variables such as other outdoor
pollutants, demographic changes over time and indoor air pollution, and the
appropriate statistical methods to account for long-term seasonal trends in
mortality (Roth et al., 1986). When considering the available evidence,
the CD Addendum finds that:
o
"the following conclusions appear-to be warranted based on the earlier
criteria 'review (U.S. EPA, 1982a) and present evaluation of newly
available analyses of the London mortality experience: (1) Markedly
increased mortality occurred, mainly among the elderly and chronically
ill, in association with BS and S02 concentrations above 1000 pg/m ,
especially during episodes when such pollutant elevations occurred for
several consecutive days; (2) During such episodes coincident high
humidity or fog was also likely important, possibly by providing
conditions leading to formation of ^$04 or other acidic aerosols;
(3) Increased risk of mortality is associated with exposure to 6S and
S02 levels; i'n the'range of 500 to 1000 ug/m , -for S02 most clearly at
concentrations 700 ug/m3; and (4) Convincing evidence indicates that
relatively small but statistically significant increases in the risk of
mortality exist at 8S (but not SOo) levels below 500 ug/m , with no
indications of any specific threshold level having been demonstrated at
lower concentrations of BS (e.g., at _<_ 150 ug/rn3). However, precise
quantitative specification of the lower PM levels associated with mortality
is not possible, nor can one rule out potential contributions of other
possible confounding variables at these low PM levels" (CDA, p. 3-9).
Analyses of deviations in daily mortality from 15-day moving means for
each of the 14 winters individually in two publications found that the
mortality-BS relationship was significant in most to all of the years
(Ostro, 1984, Mazumdar et al., 1982). In separate regressions involving a
linear model of S02 and BS jointly, a linear model of BS alone, and a quadratic
analysis of BS alone, Mazumdar et al. found that the BS-mortality relationship
was significant in 7, 14, and 13 winters respectively. In a linear regression
of year by year data for days when BS was below 150 ug/m3, Ostro found
-------
20
significant regression coefficients i.n 7 of 12 winters with a substantial
number of days with BS < 150 ug/m3, including 6 of the most recent 7 winters.
Both Mazumdar et al. and Ostro found a tendency for the regression coefficients
"to increase in later years in smoke only regressions; a trend is not apparent
in the joint smoke-S02 regression.
From a methodological perspective, the recent report by Shumway et al.
(1983) represents a significant addition to the London mortality analyses.
Their investigations developed a complex time series structure that accounted
for long-term trends in mortality as well as auto-correlation in the data.
No attempt was made to separate the effects of BS and S0£ and the effects
of the two pollutants were found to be nearly identical. Total, cardiovascular,
and respiratory mortality all increased with BS (or S02) concentration across
the range of concentrations with no discernible threshold. Slopes decreased
at higher concentrations similar to findings of Mazumdar et al. and Ostro
for smoke aTone. Temperature was also a-significant predictor with the
greatest impact when both current and 2-day lag temperature was used.
Based on analyses of alternative time-lagged models, the authors concluded
that (1) the mechanism by which these factors influence mortality has pollution
acting strongly and instantaneously, and (2) the largest fraction of variance
in daily mortality could be attributed to cyclical patterns in temperature
and pollution that had 7-21 day periods. Taken together, these conclusions
suggest that although relatively small elevations of pollution may influence
daily mortality, larger effects are more likely when the elevated concentrations
occur as part of a multi-day cycle than after short duration episodes.
In order to delineate further the degree of reliance that can be
placed on the more recent analyses outlined above (Ostro, 1984; Mazumda-r
et al., 1982; Shumway et al., 1983), EPA conducted a reanalysis of the 14
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21
winter London mortality data set (Schwartz and Marcus, 1986).* Schwartz
and Marcus controlled for the effects of autocorrelation in separate time
series regressions of daily mortality that incorporated various combinations
of temperature, humidity, SU2, and BS. They found that both "crude" (or
absolute) daily mortality as well as deviations in daily mortality from a
15-day moving mean were positively and significantly correlated with increases
in BS. Significant linear correlations of crude mortality with BS were
observed for 13 of 14 winters (deviations were significant in all 14 winters),
including 6 of the last 7 winters, during which the maximum daily BS levels
were well below 500 gg/m3. The overall effect of accounting for autocorrelation
was to increase the strength of the associations. When compared to the
previous published analyses, the magnitude of the regression coefficients
for each year were comparable to those found by Mazumdar et al, (1982) and
Ostro (1984). As in the earlier studies, Schwartz and Marcus found a
tendency for the overall regression coefficients to increase in the later
years with lower concentrations. This is also evidenced in an apparently
concave concentration-response relationships when the data for all winters
were grouped and plotted. When only days with BS < 200 ug/m3 were included in
the regression, however, the regression coefficients were more stable, with
no clear tendency to increase with time. In essence, the BS/mortality
relationship across and within individual winters appears to be concave,
with no apparent threshold at various BS levels tested in this and earlier
analyses (500 gg/m3, 250 ug/m3, 200 ug/m3, 150 gg/m3). The Schwartz and
*This paper and a summary memorandum (Marcus and Schwartz, 1986), are
reprinted in full as Appendix A to the Criteria Document Addendum. Although
not published, the paper was presented to the CASAC and the public for
review at the October 15-16, 1986 meeting. Copies were made available to
the public at the time of the meeting. Subsequently, EPA received and
considered comments on this study from industry and environmental groups
and from members of the scientific community.
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22
Marcus results thus reinforce the findings of Ostro (1984) regarding the
absence of an apparent threshold and both Ostro and Mazumdar et al., (1982)
with respect to the magnitude of the regression coefficients. The suggestion
by Mazumdar of a "quadratic" concentration-response relationship with a
threshold at 300 ug/m3 is not supported by the reanalyses.
Schwartz and Marcus also examined further the suggestion raised by
Mazumdar et al. (1982) that the effects of smoke are separable from those
of S02« In regressions involving both pollutants, the col linearity between
the two tended to deflate the apparent significance of both. However, the
overall results for all years combined and for those individual years with
lower correlations between BS and SOg (r < 0.9) show that the mortality
effects of BS remain significant and relatively large even when S02 is
included in the model, while the inclusion of BS in the model reduces the
S02 coefficients to insignificant values. Thus, while an independent
effect of S02 cannot be excluded, particularly at higher concentrations,
these analyses add weight to previous suggestions that BS is significantly
correlated with mortality independent of S02.
Based on the various studies discussed above, it is currently not
possible to derive an appropriately quantitative model for a gravimetric
particulate matter/daily mortality relationship across the range of concentrations
observed in London or to specify a concentration below which no association
remains. It is even more problematic to apply such relations to locations
other than London. However, the results of Mazumdar et al. (1982) provide
some perspective on the relative magnitude of any effects during various
winters. Using a linear model with coefficients comparable to those found
in other studies, these investigators found the mean effects of smoke
-------
23
accounted for on the order of 4 to 9% of daily mortality in London during
the early winters and about 2 to 3% in later winters.
Other recent studies discussed in the CD addendum and Appendix B of this
document examined pollutant/mortality relationships in more contemporary
atmospheres in New York City, Pittsburgh, and Athens, Greece. The Ozkaynak
et al. (1986) reanalysis of 14 years of N.Y.C. data (1963-1976) found
significant associations between excess daily mortality and PM, S02 and
temperature using time-series methods to control for autocorrelation.
Differences in the rate of change of S02 and PM indicators during the study
period allowed estimation of their separate effects. In joint regression.
analysis across all years, PM indicators (coefficient of haze and visibility
extinction coefficient) together accounted for significantly greater excess
mortality than did S02. Although their findings are considered preliminary
for risk assessment purposes, these results are of particular interest
given the'possibility that fairly contemporaneous particulate air pollution
in a U.S. urban area could be contributing to mortality (CDA p. 3-10 to
3-12).
The work of Mazumdar and Sussman (1983) in -Pittsburgh and that of
Hatzakis et al. (1986) in Athens, however, found conflicting results. The
first found significant association between particulate matter and excess
deaths in Pittsburgh, but no effect of S02, while the Athens study found an
association with SU2 but not with smoke measurements. The CD' addendum
points out that limitations in both studies with respect to measuring
particulate matter as well as methodological difficulties prevent meaningful
conclusions from these studies with respect to the effects of particulate
matter and S02.
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24
b) Morbidity
Previous conclusions regarding concentration-response relationships for
morbidity effects of daily PM/S02 exposures were based primarily on studies
of bronchitic subjects in London during the 1950's through early 1970's.
Results more relevant to contemporary U.S. conditions are presented by
Dockery et al. (1982) and summarized in Table 3-1 along with a comparable
recent study from the Netherlands (Oassen et al., 1986).
The CD addendum concludes that the repeated measurements of lung
function by Dockery et al. (1982) showed statistically significant but
physiologically small and apparently reversible group mean declines in
Forced Vital Capacity (FVC) and Forced Expiratory Volume at 0.75 seconds
(FEVg.75) associated with short-term increases in PM and S02 air pollution
(p. 3-16). The small, reversible decrements appear to persist for up to
3-4 weeks after episodic exposures to these pollutants.
The data were analyzed for each episode separately and also for pooled
results for all four study periods. Taken individually, statistically
significant declines in FVC (2-3%) were seen consistently during the first
three study periods while FEV declines were significant only for the second
and third. This suggests that significant effects on lung function occurred
in these children for those episodes with maximum 24-hour TSP levels of
220 to 422 ug/rn3. The possibility of effects below 220 ^g/rn^ can not be
dismissed, but the absence of effects on either FVC or FEV in the fourth
study period (Fall 1980) suggests that the peak TSP level measured during
that period (160 ug/m^ 24-hour maximum) might be considered as a practical
no effects level.
The interpretation of the episode results is, however, complicated by the
frequent moderate peaks in pollution that occurred at various times through
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25
each episode. TSP levels in excess of 150 ug/m^ occurred during three of
the baseline measurements in the 1978 episode, potentially diminishing the
apparent significance of any declines as measured following the subsequent
alert. Similarly, TSP levels during some "baseline" periods in the Fall 1980
study approached or exceeded those during the rest of the study. Moreover,
the presence of intermediate peaks following an alert can cloud interpretation
of the time to recovery from the functional depressions. In these respects,
the Fall 1979 study and to a lesser extent the Spring 1980 study, both with
relatively low pollution during baseline measurements, offer the clearest
results. The Spring study, however, had intermediate TSP peaks that at a
second site reached about 240 ug/m^ (Spengler et al., 1986) at about
the time of the second follow-up measurement. Since this suggests exposures
at or above those following the "sham," no firm conclusions regarding the
effects of the-first peak can be -drawn from this follow-up.
In contrast to the episode studies, the pooled regression analysis
assumed that functional response resulted from the previous day pollution
levels across the range of measured concentrations. The authors concluded
that because a significantly greater number of subjects had negative regression
coefficients for both lung function measures vs. TSP and S$2> ^uny function
might be altered across the full range of TSP and SO^ levels. As the
authors note, however, a non-linear threshold model cannot be precluded,
especially given the absence of pulmonary function effects in the Fall 1980
study. The CD addendum also notes that the regression analysis apparently
included a large number of subjects with data only from the first study
with the highest pollution and largest FVC changes. This might have unduly
affected the regression results. Ancillary regression data showing a
significant negative slope for the testing days in the Spring 1980 study
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26
(Ferris et al., 1983) suggest, however, that excluding the 1978 data would
not change the conclusions.
Although the group mean changes in lung function during individual
episodes were small (generally 2 to 4%), the pooled data suggests the
possibility that some children showed enhanced responses. The CO addendum
notes that the predicted changes in FVC per unit TSP for the upper quartile
of children was -0.386 ml/pg/m^, or 5 times higher than that for the group
mean. The distribution of individual regression slopes (Figure 3 in Dockery
et al.) indicates that approximately 5% of the children had negative slopes
of 1 ml/ug/m^ TSP or more. Some of the larger negative slopes are likely
to be due to chance or non-pollution factors such as reduced effort in
follow-up functional measurements. Some of those children, however, may
have been substantially more sensitive to pollution than the group mean.
A study of episodic exposures of children to particulate matter and
S02 conducted in the Netherlands by Dassen et al . (1986) produced results
similar to the episode component of Uockery et al . Pulmonary function
values measured during an air pollution episode in which 24-hour average
measurements of TSP, RSP* and S02 at a 6 station network all reached a
range of 200-250 ug/m^, were significantly lower (3-5%) than baseline
values measured 1-2 months earlier for the same subgroup of children. Lung
function parameters that showed significant declines on the second day of
the episode included FVC and FEV, as well as measures of small airway
function (e.g., maximum mid-expiratory flow, maximum flow at 50% of vital
capacity). Declines from baseline were observed 16 days after the episode
in a different subset of children, but not after 25 days in yet a third
subgroup. Shortly before the last set of measurements, 24-hour average TSP,
*Respirable Suspended Particles, reportedly D^Q £ 3.5 by cyclone sampler.
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27
RSP and S02 jointly reached 100-150 ug/m , suggesting that these levels
were not associated with observable functional effects (CDA, p. 3-17).
The authors note that TSP values may be somewhat low, but partially
overlapping measurements at a local network suggest they were unlikely to be
underestimated by more than 10 to 20%. Overall, collocated RSP measurements
were 0.79 to 0.94 of TSP, with network averages actually exceeding TSP
during the episode. The authors indicate rain, north winds, and snow may
have accounted for the apparent low levels of coarse particles during this
period.
In comparison with the Steubenville episodes, the pattern of pollution
t
is much less problematic. Baseline and intermediate concentrations, with
one exception, were low. Thus, the finding of a similar time course of
response (two to three weeks for recovery) provides additional support for
an extended depression in function following a single episode. The absolute
magnitude of functional changes appears somewhat greater in the Dutch
episode, but much of the difference is due to the fact that the latter
results were adjusted for lung function growth over the course> of the study
while the Steubenville results were not. A confounding aspect of the Dutch
study is the use of different subgroups during follow-up measurements.
The findings of these recent episode studies are consistent with those
of other, more qualitative, community studies identified in the 1982 staff
paper reporting pulmonary function changes in children and adults exposed to
high short-term levels of particles alone (Lebowitz et al., 1974) or in
combination with SOg (Van der Lende et al., 1975; Stebbings et al. 1979;
Saric et al., 1981).
Other recent studies on'the relationship between short-term exposures
to particles and acute morbidity effects are characterized in the CD
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28
the CD addendum as allowing no definitive interpretations at this time
(Mazumdar and Sussman, 1983; Perry et al., 1983; Bates and Sizto, 1983,
1985).
2. Long-Term Exposures
Recent cross sectional studies of the association between long-term
particulate matter concentrations and mortality are summarized in Appendix
B. While these may be of qualitative interest in supplementing prior
analyses, at present there is no basis by which to derive exposure-response
information given their unstable results, inadequate exposure characterization,
and internal inconsistencies.
i
A number of newly available studies have examined the long-term effects
of exposures to particles (with and without $62) on respiratory mechanics,
symptoms, and illness (Table A-3). The CD addendum identifies only the
Ware et al. (1986) paper (summarized in Table 3-2) as possibly providing
results by which to derive quantitative conclusions concerning exposure-effect
relationships.on morbidity. The remainder are either too preliminary to
interpret definitively (van der Lende et al., 1986) or are subject to
significant uncertainties regarding the nature of any gradients in PM
exposure levels (e.g., Pengelly et al., 1985; CEC, 1983).
Ware et al. (1986) found significant, positive associations between
some respiratory symptoms and illness in children and concentrations of
TSP, and the sulfate fraction of TSP (TSCty), and between one symptom and
SO;?. However, an examination of somewhat smaller pollution variance within
two of the cities did not produce the expected gradient in response, with
the exception of illness before age two. Pulmonary function parameters
were not associated with pollutant concentrations within the observed
ranges. The authors note that the between-city results may represent
-------
TABLE 3-2. SUMMARY OF EPIOEMIOLOGICAL'STUDY PROVIDING MOST USEFUL
CONCENTRATION/RESPONSE INFORMATION FOR LONG-TERM PARTICLE EXPOSURES (1982-86)
Jbserved
ffects Population
'ossible 10,000
increased rates 6-9 year olds
if cough, in 6 U.S.
>ronchitis, lower cities
espiratory
il Iness
to differernce
in lung function
"
City_
Portage
Topeka
Watertown
Kingston/
Harriman
St. Louis
Steubenville
Within City
Gradients:
Time
76-79
77-80
74-77
75-78
75-78
76-79
City Mean Pollution •
(in ug/m3)
TSP SO? TSO/i Comments
39
63
•46
62
94
114
12
3
18
25
68
61
5.4
5.4
8.4
9.5
11
19
Well des
cross-set
ongoing 1
Symptom,
on parenl
of elevai
vs. fall
quality i
(1 per y«
cohorts 1
adjusted
Steubenville
-Valley
-Ridge
St. Louis
-Carondelet
-Remainder
133
95
116
73
80
54
98
38
Study
gned. Preliminary Ware et
tional results from 1986
ongitudinal study.
illness data based
al recall, suggestion
ed response in spring
surveys. Nine air
egions with 3 cohorts
ar) generated 27
or analysis. Effects
for 1) age, sex,
parental education and smoking
and 2) random city, region, year
variability. S02 associated
significantly only with cough.
Within city results not consistent
with inter-city findings. Pollution
gradient maintained when adjusted
by city specific PMifl ratios
(Spengler et al., 1986).
al
ro
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3U
differences unrelated to pollution exposure such as cultural factors,
persistent differences between cities in illness or reporting rates, or
better recall of illnesses in more polluted cities. These cities tended to
be visited in the spring, while some of the cities with lower pollution
were visited in the fall when past winter illnesses were more remote.
The CD addendum concludes that the Ware et al. (1986) study:
"provides evidence of respiratory symptoms in children being associated
with particulate matter exposures in contemporary U.S. cities without
evident threshold across a range of TSP levels from 30 to 150 ug/m^
with more marked effects notable in the 60-150 ug/ro^ range in comparison
to lower levels... The medical significance of the observed increase
in symptoms unaccompanied by decrements in lung function remains to be
fully evaluated but is of likely health concern. Caution is warranted,
however, in using these findings for risk assessment purposes in view
of the lack of significant associations for the same variables when
assessed from data within individual cities included in the Ware et
al. (1986) study" (p. 3-49).
The CO addendum further notes that:
"the reported stronger associations between TSL)4 levels and other
measures of ambient air FP concentrations are highly suggestive of
possible associations between health effects observed .in the Ware
et al. (1986) study and exposure to small particles in contemporary
U.S. atmospheres.... However, full interpretation of the strength
and significance of these findings is difficult at this point, in
light of further follow-up of these children still being in progress
and the expectation that longitudinal analyses will later be carried
out which will relate health data to more extensive aerometric data
(including such data collected in later years)" (p. 3-37).
A series of studies by Ostro and coworkers (Ostro, 1983, 1987; Hausman
et al., 1984) provide qualitative indication of morbidity in adults in
U.S. cities with particulate matter concentrations overlapping those
found in the six cities study. The series of investigations encompassed
both annual and shorter term (2 week) exposures. The most recent work
(Ostro, 1987; Hausman et al., 1984) examined Health Interview Survey (HIS)
data and yielded "associations between particulate pollution and increases
in restricted activity days (RAD), respiratory related RAD, and work loss
days, as well as other, even more generalized health indicators. The most
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31
consistently significant correlations were for effects and average exposure
occurring 2 to 4 week previously (2 period lag). This somewhat puzzling
result raises some questions about the mechanism of action. It is, however,
consistent with the kind of delayed response suggested by the Steubenvilie •
and Netherlands episode studies. Additional questions raised in the CD
addendum include the nature of the HIS data, the statistical modeling used,
and the estimates of fine particle concentrations based on airport visibility
data. Only limited pollution data are provided in the published reports,
but in 1976 annual TSP levels ranged between 40 to 133 ug/m^ and the mean
estimated FP level for these cities was 22 ug/m^. Other issues include the
i
degree for which the fixed effects model accounts for city specific effects,
the role of ozone and other pollutants not included in the regressions and
consistency among other examinations of the HIS data (Portney and Mull any,
1986). The results from further analyses that address many of these
issues are expected in the near future (Ostro, 1986). At present, however,
the CD addendum concludes that these analyses:
"have found consistent associations between PM and morbidity measures
for adults tha't are reasonably consistent between and within contemporary
American cities. As such, the results tend to reinforce the plausibility
of the Ware et al. (1986) findings of associations between morbidity
measures in children and PM concentrations found in contemporaneous
American urban air sheds. However, the Ostro analyses do not allow
for the estimation of quantitative relationships between morbidity
effects and more usual 24-hr or annual average direct gravimetric
measures of participate matter air pollution (e.g., TSP, PM^Q, etc.)"
(p. 3-40).
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32
IV. FACTORS TO BE CONSinERED IN SELECTING PRIMARY STANDARDS FOR PARTICLES
This section, drawing upon the previous summary of newly available
scientific information, enumerates key factors that should be considered
by the Administrator in making decisions on the proposed revisions to
the primary standards for participate matter. The staff conclusions and
recommendations on the most appropriate policy options presented update
and supplement those made in the 1982 staff assessment. Where the original
conclusions and recommendations and supporting rationale are unchanged
by the newly available information, they are summarized without restating
the supporting discussions. Particular emphasis is placed on aspects of
t
the new information that amend or revise the original assessment. The key
standard components discussed are the pollutant indicator, averaging time,
and levels for the primary standards.
A. Pollutant Indicator
Based on the re-evaluation of available scientific information, the
staff finds that the following conclusions reached in the 1982 assessment
remain valjd:
1) A separate general particulate matter standard (as opposed to a
combination standard for particulate matter and SO;?) remains a reasonable
public health policy choice.
2) Given current scientific knowledge and uncertainties, a size-specific
(rather than chemical-specific) indicator should be used.
3) Health risks posed by inhaled particles are influenced both by the
penetration and deposition of particles in the various regions of the
respiratory tract, and by the biological responses to these deposited
materials.
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33
4) The risks of adverse health effects associated with deposition of
ambient fine and coarse particles in the thorax (tracheobronchial and
alveolar regions of the respiratory tract) are markedly greater than for
deposition in the extrathoracic (head) region. Maximum particle penetration
to the thoracic region occurs during oronasal or mouth breathing.
5) The risks of adverse health effects from extrathoracic deposition
of general ambient particulate matter are sufficiently low that particles
which deposit only in that region can safely be excluded from the standard
indicator.
6) The size-specific indicator for primary standards should represent
those particles capable of penetrating to the thoracic region, including
both the tracheobronchial and alveolar regions.
Considering these conclusions in light of data on air quality composition,
respiratory tract deposition and health effects, the need to provide protection
for sensitive individuals who may breathe by month and/or oronasally, and '
the similar convention on particles penetrating the thoracic region recently
adopted by the International Standards Organization (ISO, 1981), the staff, •
recommended that the size-specific indicator include particles less than or
equal to a nominal 10 urn "cut point."* This indicator, referred to as
"thoracic particles" in the 1982 staff paper, has been termed "PMio"
regulatory purposes.
*The more precise term is 50% cut point or 50% diameter (059). This
is the aerodynamic particle diameter for which the efficiency of particle
collection is 50%. Larger particles are collected with substantially
lower efficiency and smaller particles with greater (up to 100%) efficiency.
In practical usage, acceptable ambient samplers with this cut point provide a
reliable estimate of the total mass of suspended particulate matter of aerodynamic
size less than or "equal to 10 urn. See additional discussion regarding the
Federal Reference Method in the notice of proposed revisions (49 FR 10408).
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34
Figure 4-1 summarizes many of the more relevant aspects of the recent
particle deposition studies contained in the CD addendum and discussed in
Section III.A of this paper. The figure represents thoracic deposition of
particles under nasal and oronasal breathing as estimated by Miller et al.
(1986). Superimposed on the figure are the estimates of the band of thoracic
deposition by Swift and Proctor (1982). The latter analysis has been used
to support recommendations for an alternative particle size indicator, which
would have a "D0" of 10 urn and a 050 of approximately 6 urn. The figure
shows that such an indicator would omit the non-trivial fraction of thoracic
deposition contributed by particles larger than 10 pin for all breathing'
conditions and would also understate deposition of particles larger than
6 urn for "mouth" breathers. •
The sampler effectiveness curves for two prototype PM^g inlets also
plotted in Figure 4-1 illustrate the generally conservative nature of the
PM^o indicator"when compared to these data.' The samplers reach'100% efficiency
for particles of 7 ym and smaller, while the respiratory tract deposition
data do not quite reach 50% (in effectiveness terms). Practical, satnplers
could not, of course, realistically match this performance. Thus, a
better way to compare the deposition data with the sampler effectiveness
is to scale the data such that the maximum deposition point represents "1," or
100%. Viewed from this perspective, the maximum point for the distribution
illustrated in Figure 4-1 generally lies between 3 and 5 urn and the 50%
point tends to be in the vicinity of 10 urn. In this relative sense, the
PM^Q indicator, follows the "inlet" portion of respiratory tract penetration
pattern, but substantially overcollects fine particles smaller than 3 to 5
um relative to lung deposition. The figure indicates that most fine mass
is not deposited in the respiratory tract, while PMjg samplers would collect
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35
0.5
0.4
0.3
ui
O
0.2
ac
O
0.1
I I II UK I I i I II U.
— — — MOUTH BREATHERS
NORMAL AUGMENTERS —
0 -L
I I I I IIlll
I I I I I I H-
B
T I I I IIU.
Inlet 2
Inlet 1
I I
1.0
10.0 100 1.0
AERODYNAMIC DIAMETER,
10.0
100
Figure 4-1. Estimates of thoracic deposition of particles between 1 and
15 urn by Miller et al. (1986) for normal augmenters (solid lines) and mouth
breathers (broken lines) are.shown for minute ventilation (Ve) exceeding
the switch point of 35 L m1nl(A) and for lower Vp (B). Normal augmenters
are individuals who normal
airflow when V. exceeds about
/ MI ivi i w i i wrv«» i » 0 \ u / o i *w i HI a i
ly use oronasal breathing to augment
out 35 L min , while mouth breather
respiratory
refers to
those individuals who habitually breathe oronasal ly (Niinimaa et al., 1981).
The shaded area (B) is a composite of the computed bands of thoracic
deposition of particles less than 8 urn by Swift and Proctor (1982) for Ve
of approximately 24.6 and 15 L min.1 Also plotted are the sampler
effectiveness curves for two representative PM^g Inlets.
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36
100% of this fraction. As stated in the 1982 staff paper, given the larger
surface area in the fine mode as well as other concerns, the greater weight
given fine vs. coarse particles by a 10 gni indicator remains prudent and
appropriate.
In summary, the staff assessment of more recent information on respiratory
tract deposition contained in the criteria document addendum reinforces the
conclusions reached in the original staff assessment in 1982. In particular,
the staff finds that:
1) the recent data do not provide support for an indicator that excludes
all particles greater than 1U gm;
2) the analysis used to specify an alternative indicator with a nominal
size cut of 6 urn (Swift and Proctor, 1982) can significantly understate
thoracic deposition of particles larger than 6 gm under natural breathing
conditions;
3) the PM}Q indicator appears somewhat less conservative than previously
thought with respect to large (> 10 pm) particle deposition under conditions
of natural mouthbreathing. Nevertheless, this indicator is generally
conservative for tracheobronchial deposition; and
4) recent information suggesting enhanced tracheobronchial particle
deposition for children relative to adults provides an additional reason
for an indicator that includes particles capable of such penetration (Section
III).
Given these considerations and the earlier conclusions, the staff
reaffirms its recommendation to replace TSP as the particle indicator for
the primary standards with a new indicator that includes only those particles
less than a nominal 10 gm (PM^o).
In the previous assessment, the staff also made recommendations with
respect to the shape of sampler effectiveness curves. Analysis of the
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37
influence of outpoint and effectiveness curves under various simulated
ambient conditions have tended to show that (1) the 059 of the inlet has
the major influence, and (2) for a fixed cutpoint, the mass collected does
not vary greatly with the shape of the effectiveness curve (Rodes et al.,
1981; Van der Meulen, 1986). For this reason, and because of the difficulty
in precisely matching the most recent respiratory tract deposition estimates,
the staff concludes that, for regulatory purposes, the effectiveness criteria
developed based on the 1982 CO remain acceptable.
B. Level of the Standards
1. General Considerations
This treatment of the implications of more recent studies follows the
framework and maintains the underlying philosphy of the 1982 staff paper
as discussed therein (SP, pp. 83-89). The following general considerations
are drawn from that more complete discussion.
The major scientific basis for selecting PM standards that have an adequate
margin of safety remains community epidemiological research, with mechanistic
support from toxicological and controlled human investigations. The
«
limitations of epidemiological stu'dies for quantitative evaluation of the
health risks of particulate matter under current U.S. conditions are
detailed in the 1982 criteria document (EPA, 1982b) and its addendum (EPA,
1986) as well as in the 1982 PM staff paper (pp. 83-86). Such studies,
while representing real world conditions, can only provide associations
between a complex pollutant mix measured at specific locations and times
and a particular set of observable health points. Difficulties in
conducting and interpreting epidemiological studies limit the reliance
that can be placed on the results of any single study. Furthermore, even
the best studies often provide no clear evidence of population "thresholds."
Thus the approach of identifying specific "lowest demonstrated effects" levels
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38
for current U.S. exposures and adding margin of safety considerations is
less appropriate in this case. Instead, the approach followed in the 1982
staff paper and here is to assess the nature of health risks along a continuum
of exposure using the full range of available information. It follows
that, although the scientific literature provides substantial information
on the potential health risks associated with various mixes and levels of
particles, selection of any general particulate standard remains largely a
public health policy judgment.
Because particulate matter is a pollutant class with variable composition,
and none of the published studies have used the proposed PM^Q indicator, the
range of aerosol composition and size indices must be considered in using the
relevant epidemiological studies for developing standards. For example, in
order to translate the re-suits of historical British studies into terms
useful for setting U.S. standards, general relationships between British
smoke, readings and particle mass units (i.e., PM^Q), estimated in the 1982
staff paper are used here. Those relationships were based on available
calibration data from the study periods, incorporating reasonable assumptions
«
concerning pollution composition, relative role of particles, and the
nature of U.S. vs. British exposure regimes (SP, pp. 7-13, 96-100).
Conversions are also made between TSP concentrations measured in the U.S.
studies and corresponding PM^Q levels, in some cases using more detailed
site-specific data.
The following sections present a brief staff assessment of the
concentration/response relationships suggested by the most significant
epidemiological studies in the CD addendum. This assessment supplements
the quantitative information in the 1982 staff paper and indicates
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39
how these studies may be applied in developing ranges for final decision-making
on standards for particulate matter, as indicated by PM^Q. The presentation
also outlines a qualitative assessment of the key factors that affect the
margins of safety (risk) associated with the concentration-response relationships
derived from these studies, as translated to contemporary U.S. exposures.
The margins of safety associated with the levels of interest for PM^Q
derived from the quantitative studies should also be evaluated with respect to
any potential effects that may reasonably be anticipated from qualitative
human and animal health studies summarized in the 1982 staff paper. Short-
and long term exposure are discussed separately.
2. Short-term Exposures
a. Derivation of Range of Interest from Epidemiological Studies
i) Concentration-Response Relationships
The 1982 CD indicates that the epidemiological studies most
useful for developing quantitative conclusions regarding the effects of
short-term exposures to particulate matter include a series of studies and
analysis of daily mortality in London (Martin and Bradley, 1960; Martin,
1964; Ware et al., 1981; Mazumdar, et al., 1981) and studies of bronchitis
patients, also in London (Lawther et al., 1970).
The assessment of the earlier London mortality studies in the 1982 CO
concluded that 1) clear increases in excess daily mortality occur at BS
o
and S02 levels at or above 1000 ug/m , and 2) some indication of likely
increase in excess mortality exists in the range of 500 to 1000 ug/m^ BS
and S02, with greatest certainty of increases occurring when both pollutants
exceed 750 ug/m^ (CuA, Table 1). These estimates represent judgments with
respect to the most scientifically reliable "demonstrated effects likely
levels" for daily smoke (and SOg) and mortality at least in the context of
historical London pollution exposures.
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40
Because of the severity of the health endpoints in these studies, and
the need to provide an adequate margin of safety in standard setting, the 1982
CD and staff paper also examined these studies to determine whether the data
support the possibility of health risks at lower BS levels. This assessment
concluded that data from the earlier London studies do not provide clear
evidence of absolute population thresholds, and suggest instead a continuum
of response, with both the likelihood and extent of any effects occurring
decreasing with concentration. Thus, based on these earlier studies,
effects were judged to be "possible" at levels below 500 to 1000 ug/m3
smoke down to a practical lower bound of 150 ug/m3 (as BS) derived from
the Martin and Bradley (1960) study. The analysis stressed that because
evidence is less clear, the nature and extent of risks at lower levels are
much more uncertain.
The more recent analyses of London mortality during the winters between
1958 and 1972 cited,in the CD addendum include Mazumdar et al. (1982),
Ostro (1984), Shumway et al. (1983), and Schwartz and Marcus (1986).
In essence, these analyses add to the evidence for the possibility that
participate pollution accounted for a small but statistically significant
portion of daily mortality at levels extending well below 500 ug/m3 8S
(24-hour avg.), with no discernible threshold. Considering the findings of
these more recent studies, the staff amends its earlier assessment of the
London mortality data (SP, pp. 89-9b) with the following conclusions:
1) The finding of significant associations between BS and mortality in
the majority of the 14 winters by different investigators in published
(Mazumdar et al., 1982; 1983; Ostro, 1984) and unpublished (Schwartz and
Marcus, 1986) analyses using several approaches strengthens the plausibility
of the associations. The findings of significant associations in later
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41
"non-episodic" years when particle composition and levels began to approach
U.S. conditions is of particular significance.
2) The finding in some analyses of a trend towards increased regression
coefficients with decreased concentration and the concave shape apparent
across the range of mortality-BS data as plotted by Schwartz and Marcus
(See Figure 4-2) raises questions regarding whether the statistical association
reflects a causal relationship. The possibility that smoke may be acting
as a "surrogate" for unmeasured factor(s) at lower BS levels, as suggested
by Mazumdar et al. (1982) cannot be precluded. Non-pollution factors such
•
as weather, demographic shifts and indoor pollution exposures have been
advanced as possible alternatives (Roth et al., 1986). To date, however,
smoke/mortality relationships have retained (or even increased in) significance
when meteorological factors (temperature and humidity) are included and the
year-to-year consistency of association, particularly for BS < 200 ug/m^,
argue against the observed effect being explained by changing indoor-heating
practices in London or by long-term demographic shifts (CDA, p. 3-7).
Moreover, as Mazumdar et al. points out, BS might be a surrogate for other
particulate components rather than some as yet unanalyzed non-pollution
variable. Schwartz and Marcus (1986) suggest that the decreasing response
with higher pollution may result from the effect of higher pollution in
earlier winters being blunted by public awareness (and hence reduced exposure)
or by a tendency for the most susceptible individuals to succumb on the
earliest day of very high pollution in a multi-day episode. Some of the
curvilinear shape between BS and mortality might also be due to the non-linear
relationship between BS and gravimetric mass at lower BS levels. In a
qualitative sense, adjusting for this relationship would make the corresponding
particle mass/response relationship more linear.
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42
Daily Mortality - British Smoka (All Day* Undar 600 po/m* BS)
London Wmtara 1968-69 to 1971-72
360
326
1300
1
276
260
60 100 160 200 260 300 36O 4OO 46O 6OO
BrHWi Smoka. ng/m>
Figure 4-2. Mean daily mortality vs. mean British Smoke (BS) for days with
BS < 500 ug/m3 during 14 London winters (1958-72) (Schwartz and Marcus, 1986).
Each point represents the mean "crude" daily mortality and BS for 20 adjacent
values of BS. Grouping data points in this fashion (c.f. Ware et al.,
1981; SP, Figure 6-2) reduces scatter and reveals an apparently concave
relationship extending to the lowest observed BS levels with a decreasing
slope at higher concentrations. This is consistent with the findings of
higher regression slopes in years with lower average concentrations
(Mazumdar et al., 1982; Ostro, 1984). The concave shape may, however,
be an artifact. Some possible explanations include a non-linear relationship
between BS and gravimetric mass, reduced population exposures during
publicized high pollution episodes and correlations of BS with unmeasured
non-pollution variables that are causally related to mortality (see text).
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43
3) The approach of Shumway et al., (1983) is an important addition
to the literature that, while reinforcing the above findings, suggest
additional complexity in the potential concentration response function,
particularly with respect to the influence of temperature and nature of
temporal patterns in pollution. Temperature appears to exert a same-day
positive effect, with higher daily mortality associated with an increase
in temperature. The lag result in Shumway et al., however, also suggests
that reduced mortality is likely during a cold spell after a dip in temperature.
This phenomenon could be explained by increased outdoor-related activities
on warmer days in the winter. The Schwartz and Marcus analyses subsumes
any such lag effect of temperature in the autoregressive model. Further
analyses are desirable to examine possible interactions or non-linear
responses involving temperature, humidity, fog, and wind.speed.
4) While it is still difficult to separate the effects of S02 and 6S
on mortality, the preliminary findings of Schwartz and Marcus (1986)
support the suggestion (Mazumdar et al., 1982) that at lower S02 values
mortality effects may be associated with particulate matter alone.
5) Taken together, the analyses to date do not permit identification of
a clear "no effects" level. The lower bound derived from earlier analyses
is no longer appropriate. The individual regression analyses, however, provide
some suggestion that effects do not always achieve significance in the last two
winters when mean smoke levels were below 75 to 100 ug/m-^ (Ostro, 1984;
Schwartz and Marcus, 1986).
As the earlier assessment noted, the London data—even in more
recent winters—have inherent limitations when applied to assessing
effects in U.S. atmospheres. The pollution composition, meteorological
patterns, indoor sources, population characteristics, and other factors in
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44
London may have been uniquely responsible for the observed results. Thus,
the findings from recent reanalyses of daily mortality during 14 years in
New York City (1963-1976) (Ozkaynak and Spengler, 1985, Ozkaynak et al.,
1986) are of particular interest. The results, although preliminary,
showing associations between mortality and particle concentrations (indicated
by coefficient of haze, or CoHs, and atmospheric visibility readings) add
to the evidence for a more general association between elevated particulate
matter levels and increased mortality. This recent work reinforces earlier
qualitative findings of PM/mortality associations in New York City (Schimmel
and Murawski, 1976; Schimmel, 1978).
The 1982 CD evaluation of the Lawther et al. (1958, 1970) studies
concluded that a worsening of health status of chronic bronchitic patients
could occur on days wi,th BS _> 250-500 gg/m3 and S02 > 500-600 gg/m3. The
1982 CD also noted that associations between pollution and health status
persisted at lower levels in selected, more sensitive individuals, although
over the vigorous objection of the lead investigator (Lawther, 1986). Better
evidence for effects on morbidity at lower concentrations is provided by
the two recent studies of U.S. and Dutch children exposed during pollution
episodes with elevated 24-hour TSP and S02 levels (Dockery et al., 1982;
Oassen et al., 1986).
The U.S. study found evidence of small but significant (2-3%)
reductions in lung function (FVC, FEV^yij) in Steubenville following periods
when 24-hour TSP levels reached 220 to 420 ug/m3 and S02 reached 280 to 45b
gg/m3, but no significant changes following 24-hour TSP and S02 maxima of 160
and 190 gg/m3, respectively. The Dutch study found comparable functional
reductions during and following an episode when concentrations of TSP, RSP,
o
and S02 were each in the range of 200 to 250 gg/m (based on six monitoring
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45
sites) for 2 to 4 days, with no significant reduction shortly after a more
modest 24-hour pollution increase when levels of all 3 pollutants averaged
100 to 150 ug/m3.
Taken together, these studies suggest that functional declines associated
with episodic exposures occur rapidly and persist for up to 2 to 3 weeks
before recovery, with a tendency for larger declines to occur following
episodes with higher concentrations of smaller size particles.. This is
illustrated in Figure 4-2, which compares the Dutch findings with the
Steubenville episode (Fall 1979)° that has the most comparable air quality
patterns (see Section III.B). In both studies, functional measurements
show a substantial decline, as measured a day or two into the episode, that
persists for 16 to 18 days. Given the lack of decline in the Steubenville
"sham" (2 weeks after baseline) and the fact only two test days (episode
and 1st follow-up) showed declines in the Netherlands, it seems unlikely
that lack of interest in follow-up tests could account for the pollution
related results.
Comparison of the magnitude of response between two different investigations
with children of overlapping but different ages should be viewed with caution.
Although the results may suggest slightly larger functional changes during
the Dutch episode, it is not clear whether any differences would be
significant. With both TSP and RSP levels at 200 to 250 Mg/m3, it is
reasonable to assume intermediate to small particle indicators (PM^5 or PM^j)
levels were in the same range in Ijmond. Based on size specific measurements
of Steubenville during the Fall 1979 episode (Spengler et al., 1986) maximum
concentrations of small particles were somewhat lower in Steubenville.
Applying factors appropriate for that episode (Section II), peak PM^g
levels were on the order of 150 to 170 ug/m3. An earlier Steubenville
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46
Fill 1979
Steubenville
Ijmond t =
'Unadjusted for lung
function growth for
comparison with
Steubenville
1 week 2 weeks
Time Relative to Onset of Pollution Episode
Episode/
Alert
3 weeks
4 weeks
Figure 4-3. Mean change in FVC compared to baseline for children in relation
to occurrence of pollution episodes in Steubenville, Ohio (Dockery et al., 1982)
and the Ijmond area of the Netherlands (Dassen et al., 1986). Inserts: Air
quality during each study period. Steubenville study: Fall, 1979 episode,
184 3rd and 4th grade children with 69 tested during alert, all tested
during follow up. Netherlands study: Winter, 1985 episode, 179 children
aged 7 to 11 years, with each follow up reflecting a different group; FVC
adjusted for growth (light triangles). Arrows show results unadjusted for
growth (Brunkreff, 1986) for direct comparison with Steubenville results,
which are also not adjusted. The patterns in response for the two studies
show a remarkable similarity. The maximum unadjusted mean changes for the
Netherlands episode are comparable to slightly larger than Steubenville
(~1 t.o 2%). Although maximum TSP levels are similar for each episode (see
inserts), based on corollary measurements of PM^ (Spengler et al., 1986)
in Steubenville and RSP in Ijmond, concentrations of smaller sized particles
(as PMi$, PM^j, or PM3.5) were higher in Ijmond. SO^ peaks were", however,
higher in Steubenville.
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47
episode (Fall 1978) with levels of small particles potentially approaching
those of the Dutch episode (Fall, 1978) found comparable to larger unadjusted
maximal declines in FVC ( ~ 50 ml).
Although it is difficult to separate the effects of particles from
S02, peak levels of SOg were higher in the 1979 Steubenville study (455
ug/m3), and lower in both the Dutch (200 to 250 ug/m3) and Fall 1978 (280
ug/m3) study that had comparable to larger changes in FVC. Other pollutants
possibly associated with functional changes (03, N02) were unlikely to
confound these studies. The effects of seasonal patterns temperature or
. other meteorological factors cannot' be ruled out, but neither study found
any significant correspondence between lung function and temperature.
Other important aspects of these two studies are as follows:
1. It appears reasonable to expect that short-term changes in lung
function in children following acute exposures to particulate matter is, in
most cases, a more sensitive response than premature mortality or worsening
of bronchi tic symptoms.
2. Fairly contemporary atmospheric conditions were studied and,
particularly in the case of the Steubenville study, particle composition is
fairly representative of contemporary U.S. cities, significantly increasing
•the applicability of the results to current standard setting.
3. The observed lung function declines beneath baseline never exceeded
3 to 5% on average, and recovery apparently began after 2-3 weeks. It is
difficult to assess the significance of such reductions. Dockery et al.
note that they might be associated with aggravation of respiratory symptoms
in children with pre-existing illness. Long-term examination of Steubenville
children suggest higher rates of respiratory illnesses and symptoms compared
to other U.S. cities with lower PM levels, but no evidence for any persistent
reductions in lung function (Ware et al., 198b).
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48
The extent to which some children may be considered to be "responders"
has not yet been formally examined. Oockery et al., however, also show
that the upper quartile (25%) of children included in their pooled analysis
of lung function vs. TSP had individual regression coefficients of FVC and
FEVg.75 5 and 17 times the median, respectively, suggesting a correspondingly
greater than average decline in lung function across the range of pollution
levels. As noted in Section III.B., a smaller subset representing the
upper 5% of these children showed even more substantial negative regression
coefficients (for FVC, £ -1 ml/gg/m3 TSP). Assuming a linear response with
no threshold across the range of TSP concentrations observed in the regression
study (11 to 272 ug/m3), this group would have a predicted decline in FVC on
the order of 10 to 15%. Such calculations almost certainly overstate
the percentage of potentially sensitive children because some or all of the
larger responses may be due to a random distribution of results. (Section
III.B.). Nevertheless, this assessment suggests that functional changes of
potential concern—even on a transient basis—might occur in some small
sensitive subgroups of children.
4. Although the data suggest that decrements in lung function may
occur during or immediately following a single day of high particulate matter
levels, it is not clear whether or not multi-day episodes are required
to produce more prolonged (2 to 3 weeks) decrements. Results from controlled
human and animal toxicologies! studies provide support for mechanisms by
which short or longer term functional declines could result from particle
exposures (Table 5-2, 1982 SP). Little evidence exists, however, that would
support prolonged declines from single short-term SOg exposures at these
concentrations.
5. Although questions can be raised regarding potential variability
in lung function testing throughout the study period (especially given the
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49
youth of the subjects), it appears that state-of-the-art measurement
procedures were used as well as appropriate controls for inter-observer
bias and extreme or missing values.
6. The results of these more recent studies are consistent with
earlier more qualitative acute studies in Pittsburgh (Stebbings et al., 1975),
Tuscon (Lebowitz et al., 1974), and the Netherlands (van der Lende et al.,
1975).
ii) Translation to PMip Indicator
Table 4-1 summarizes the updated staff assessment of the more
recent and earlier available quantitative short-term epidemiological studies.
Following the approach in the 1982 staff paper, the assessment incorporates
available data and assumptions necessary to express results obtained using
different particle indicators in terms of the recommended particle indicator.
The "effects likely" row in -Table 4-1, based on the 1982 CD,
reflects the previous staff assessment and underlying rationale (SP, pp.
96-100). As discussed therein and above, effects are possible at
concentrations below those consensus "effects likely levels." In light
of the assessment of the more recent London mortality studies outlined above,
no lower bound smoke concentration is indicated in the "effects possible"
column. Due to the lack of a clear threshold in these studies, the uncertainty
in translating these results to contemporary U.S. atmospheres, and the
availability of more recent U.S. data involving potentially more sensitive
effects the staff has chosen not to attempt to derive any lower bound PMu
concentration from the London data. The approach used previously to bound
8S/PM10 relationships does not apply to lower values (< 100 ug/m3 BS), and it
is also unclear to what extent BS readings were calibrated to mass measurements
in the later years when smoke levels had declined appreciably. Thus the
lowest pollutant levels of interest in the remaining short-term studies are
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TABLE 4-1. UPDATED STAFF ASSESSMENT OF SHORT-TERM EPIOEMIOLOGICAL STUDIES
Effects/Study
Effects Likely
Effects Possible
No Significant
Effects Noted
o
Measured British Smoke Levels (as ug/m )
(24-hr, avg.)
Daily Mortality
in London*
1000
1
?
-
Aggravation of
Bronchitis2
250*-500*
< 250*
-
Combined
Range
250-500
<250
-
Measured TSP Levels (ug/m3)
(24-hr, avg.)
Small, reversible declines
in lung function in children3*
-
220*-4203
200-2504
125*4-1603
Equivalent PMiQ
Levels (ug/m3)
Combined
Range5
350-600
140-350
<125
Mndicates levels used for upper and lower bound of range.
Various analyses of daily mortality encompassing the London winter of 1958-59, 14 winters from 1958-72, in aggregate
and individually. Early winters dominated by high smoke and S02 from coal combustion with frequent fogs. From 1982 CD:
Martin and Bradley (1960); Ware et al., (1981); Mazumdar et al. (1981). From 1986 CD Addendum: Mazumdar et al. (1982);
Ostro (1984); Shurnway et al., (1983); Schwartz and Marcus (1986). Later studies show association across entire range of
smoke, with no clear delineation of "likely" effects or threshold of response possible.
2Study of symptoms reported by bronchitis patients in London, mid-50's to early 70's; Lawther et al. (1970).
3Study of pollution "episodes" in Steubenville, Ohio, 1978-80; Dockery et al. (1982).
4Study of 1985 pollution episode in Ijmond, The Netherlands; Dassen et al. (1986).
a) Conversion of BS readings to PM^Q levels: Assumes for London conditions and BS readings in the range 100-500 ug/m ,
BS
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51
250 ug/m3 (BS) and SOU gg/nr S02 (based on the earlier bronchitic studies)
and 200 to 420 (TSP) and 190 to 455 ug/m3 (S02) (based on the recent
studies of lung function in children). The recent studies provide some
suggestion of "no observed effects" levels with TSP concentrations of 100 to 160
ug/m3. The relative importance of S02 in these studies cannot be specified,
but collectively the data suggest a greater role for particles. Thus the
conservative assumption (for particles) is made that the response might have
occurred without substantial amounts of S02 present.
Conversion of the British data to PM^g equivalents is particularly uncertain,
and the approach is discussed in the earl'ier assessment (pp. 98-101). The
original upper bound of a range of interest for a 24-hour standard derived
from the Lawther study was 350 Mg/m3 as PM1Q (SP, p. 97-99). Because this
level contained little or no margin of safety, staff and CASAC recommended
that consideration of standard levels begin at lower concentrations. Accordingly,
the Administrator, considering this advice', as well as other factors, proposed
250 pg/m3 as the upper bound of the range of levels for a possible 24-hour
standard (49 FR 10408). Thus, the upper bound for the range of interest is
250 ug/m3, as PM1(J. The translation of the Steubenville and Netherlands
results to PMio is summarized in Table 4-1. Based on these results, the lowest
PMlO level of interest derived from the short-term studies can be reduced to
140 ug/m^, although the original lower bound of 150 pg/m^ is within the range
of uncertainty of the conversion. A level of 140 ug/m3 contains a large
margin of safety against exposures clearly associated with the more serious
effects of particulate matter and is at the lower end where reversible,
physiological responses of uncertain health significance may be observed.
However, the original lower-bound recommended by staff and CASAC also contains
a substantial margin of safety.
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52
b) Additional Factors to be Considered in Evaluating Margins of Safety
and Risks - Short-term Exposure?
The 1982 staff paper identified a number of factors to be considered
in developing a standard with a margin of safety. In applying the results
of the more recent studies to determine the margin of safety for sensitive
populations provided by alternative PM^Q standards in the above range, the
following additional factors should be considered:
(i) Aerosol Composition
1. As noted above, the likelihood of high ozone levels during the
U.S. and Dutch episodes seems low. Where high photochemical smog levels
are present, the observed effects of ozone on lung function (e.g., McDonnell
et al., 1983) suggest the possibility of interactive responses not accounted
for by these or the British studies.
2. When particle components differ substantially from those in the
communities studied, risk will vary. The variability of composition
(e.g., relative fraction of sulfate, nitrate, secondary organics, carbonaceous
material, and coarse particles) is high. Accordingly, the risks associated
with PM^g will vary among U.S. cities.
(i i) Exposure
Although the assessment of the mortality studies suggest any risk
of premature mortality to sensitive individuals may be small at lower
concentrations, the number of people exposed to lower concentrations is
substantially larger than the number exposed to higher levels. Table 2-1
shows that at present, the total U.S. population living in counties with
PM1Q levels in excess of 250 ug/m3 is on the order of the size of the London
population. The number in counties in excess of 150 ug/m3 is estimated at
six times larger. The increased number of sensitive individuals exposed
increases the risk that some effects will occur in the total population
exposed.
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b3
Relative exposures and indoor/outdoor pollution relationships
are an important consideration in interpreting the British studies; these
•are discussed elsewhere (SP, p. 101). With respect to the more recent
morbidity studies, for comparable outdoor concentrations, the overall exposures
to maximum 24-hour outdoor pollution in Steubenville and in the Netherlands
was likely as high as typically occurs in contemporary U.S. exposure situations
during the fall through spring seasons. Summertime exposures, would,
however, tend to be greater in many areas.
(iii) Risks For Other Sensitive Groups. Effects Not Evaluated
Consistent with evidence from toxicalogical, controlled human and.
quantitative epidemiological data, the studies used to derive ranges of
interest identify a number of groups and effects as particularly susceptible
to ambient particles: (1) premature mortality in very sensitive individuals
with chronic respiratory and cardiovascular diseases, individuals with
influenza, and'the elderly, (2) aggravation of"disease in bronchitic patients,
and (3) lung function declines in children.
While other groups may be affected by ambient particle exposures,
such as asthmatics or even younger children, the previous assessment found
no data to support the existence of significant effects below the suggested
range (SP, pp. 102-103). The most significant new information in this
regard is the finding of restricted activity in adults associated with
earlier particle exposures of 2 week or longer durations (Ostro, 1987). At
present, the results cannot be interpreted as demonstrating such effects
occur at 24-hour levels below the range of interest.
Additional short-term effects of particulate matter sugyested by
qualitative evidence, such as altered respiratory clearance, possibly
resulting in infections, are identified in the 1982 staff paper (p. 103).
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54
3. Long-Term Exposures
a) Derivation of Range of Interest.from Epidemiological Studies
Earlier cross sectional and longitudinal studies useful in establishing
ranges of interest for long-term (annual) PM^o standards are identified in
and discussed in the 1982 staff paper (pp. 57-63; 103-107) and CD. Of the
newly available studies, the CO addendum cites the Ware et al. (1986)
cross-sectional study of children in 6 U.S. cities as providing potentially
useful results for examining quantitative relationships.
In interpreting the Ware et al. (1986) study the CO addendum concludes
that there is evidence of respiratory symptoms in children associated with
particulate matter exposures without apparent threshold across the range of
measured TSP levels (CDA, p. 5-6). As for all cross sectional studies, however,
these results—though adjusted for a number of confounding factors—
should be viewed with caution. A particular concern is the apparent
absence of the expected gradient in response for-results within cities.
The lack of within city effects does not necessarily negate the results
among cities. Possible explanations include movement of the population
throughout the area (reducing the within city gradient), the presence of a
lesser gradient in smaller sized particles, or a tendency for hyperresponders
to move to cleaner areas of the city (consistent with the negative and
significant within city gradient for wheeze). Results of a separate
series of studies of long- and intermediate-term (2 to 6 weeks) exposures
indicate consistent associations between respiratory-related restrictions
in adults and PM gradients within, as well as among, a number of U.S.
cities (Hausman et al., 1984; Ostro, 1983, 1987). While these results cannot
be used to estimate quantitative relationships between morbidity effects
and PMio» the CD addendum indicates they do provide qualitative support
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55
for the possibility of within-city effects related to comparable U.S.
exposure levels. Nevertheless, until further results are available,
the within-city anomaly of the Ware et al. results as well as. other
uncertainties (e.g., parental recall in spring vs. fall) noted in Section
III.B. caution against interpreting the results as demonstrating "effects
likely" levels. Considering the assessment in the CD addendum, however,
the six city results do suggest the possibility of effects, at least in the
more polluted areas.
In deriving a range of possible effects levels from this study, it
is useful to examine the gradient in PM^Q terms, based on applying the
ratios developed by Spengler et al. (1986) to the data. Because the
staff previously recommended an expected annual mean PMio standard and
because Ware et al. (1986) found that long-term (life-time) TSP exposures
were also significantly associated with respiratory effects, the PMiu
levels are estimated in terms of multi-year averages. Figure 4-3 plots
the relationship between long-term averages in frequency of cough and
estimated PM^Q levels across the six cities. This is the same effect plotted
against annual TSP levels in the Ware et al. paper (Figure 5, COA), originally
chosen because it was most consistently associated with TSP levels across
cities.
As illustrated in Figure 4-3, three "cleaner" cities—Portage, Watertown,
and Topeka—consistently had the lowest frequencies of respiratory illnesses
and symptoms. The highest symptom prevalence rates were consistently found
in Kingston/Harriman, St. Louis and Steubenville. Based on this very
qualitative break-down, the staff concludes that the most convincing evidence
for the possibility of effects is for the latter three cities, with long-term
o
average TSP levels between 60 and 114 ug/nr and corresponding PM^Q values
between 40 and 60 pg/m3.
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56
120 ••
o
o
o
100 •
UJ
3 80
o
u
u.
o
UJ
u
I 60 t
P—I
20
10
20
30
40
50
60
ESTIMATED LONG TERM PM10 CONCENTRATION
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57
Table 4-2 amends the previous staff assessment of the the most useful
long-term epidemiological data to reflect this newer information; particulate
matter levels are expressed in both the original and converted PM^Q units.
The "effects likely" row reflects the earlier assessment based on the
pre-1982 studies. In adding the six cities results to the "effects possible"
row, it is interesting to note some consistency among the U.S. studies
with respect to concentration at which functional and symptomatic effects
occur. The Ferris et al. work (1973, 1976) suggests functional effects may
occur down to levels of 130 ug/m3 TSP, but none of these studies find such
effects at lower concentrations. The finding of symptomatic responses' in
children with no change in lung function in the range of 60 to 114 ug/m3
(as TSP) (Ware et al. 1986) is consistent with similar findings in adults
for a long term mean of 110 ug/m3 (60 to 150 ug/m^) TSP from the Bouhuys et
al. (1973) study.
The conversio'n of the earlier studies to PM^Q in Table 4-2 reflects more
recent information. In considering the earlier assessment and recommendations,
the Administrator proposed that the level of the annual standard be no
higher than 65 ug/m3 PM1Q (49 FR 10408). This, therefore, is the upper bound
of the present range of interest. The lower bound is lowered from the
previous assessment to 40 ug/m3 as PM1(J, based on the recent results of
Ware and coworkers. The staff, therefore, recommends a range of interest
O
between 40 and 65 ug/nr for decision making on an annual standard for PM^Q.
The results of the original studies, assessment of risks at lower
levels, and conversion to a common indicator all are subject to considerable
uncertainties. Furthermore, effects are not demonstrated within the ranges
listed above; the lower bounds represent conservative estimates where some
risk of effect is not ruled out by the data.
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Table 4-2. UPDATED STAFF ASSESSMENT OF LONG-TERM EPIDEMIOLOGICAL STUDIES
Effects/Study
Effects Likely
Effects Possible
No Significant6
Effects Noted
Measured BS
Levels (as ug/m3
Increased
Respiratory
Disease, Reduced
Lung Function
in Children1
230-300 BS
<230 BS
-
Measured TSP Levels (ug/m3)
Increased Respiratory
Disease Symtpoms,
Small Reduction in
Lung Function in
Adults2
180*
130-180*
80-130
Increased
Respiratory
Symptoms
in Adults3
60-150(110)
-
Increased
Respiratory
Symptoms and
Illnesses in
Children4
-
60*-114
V
Reduced
Lung
Function
in
Children4
-
-
40-114
Combined
Range
_>180
60-180 •
<60 -
Fquivalent
PMjo Levels
(ug/m3)
Combined
Range;*
80-90
40-90
<40
'
en
oo
*Indicates levels used for upper and lower bound of range..
!study conducted in 1963-65 in Sheffield, England (Lunn et al., 1967). BS levels (as ug/m3) uncertain.
2Studies conducted in 1961-73 in Berlin, N.H. (Ferris et al., 1973, 1976). Effects level (180 ug/m3)
based on uncertain 2-month average. Effects in lung function were relatively small.
3Study conducted in 1973 in two Connecticut towns. (Bouhuys et al. 1973). Exposure estimates reflect 1965-73 data in
Anson. Median value (110 ug/m3) used to indicate long-term concentration. No effects on lung function, but some
suggesstion of effects on respiratory symptoms.
4Study conducted in 1976-1980 in 6 U.S. cities (Ware et al., 1986). Exposure estimates reflect 4-year averages across
^cities. Comparable pollution/effects gradients not noted within cities.
Conversion of TSP to PMjn equivalents for Berlin, Ansonia studies based on estimated ratio of PM^g/TSP for current
U.S. atmospheres (Pace, 1983). The estimated ratio ranged between 0.45 and 0.5. Conversion for six-city study
based on site-specific analysis of particle size data (Spengler et al., 1986).
^Ranges reflect gradients in which no significant effects were detected for categories at top. Combined range
reflects all columns.
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59
b) Additional Factors to be Considered In Evaluating Margins of Safety
and Risks - Long-term Exposures
When evaluating margins of safety (TISKS) in this range, additional factors
identified in the 1982 assessment (SP, p. 106-111) should be considered.
(i) Aerosol Composition
1. S02 levels in the six cities studied by Ware et al. generally
covaried with TSP. Where high S02 levels co-exist with PM].o» the above
range would appear to be protective.
2. The six cities study is directly relevant to current U.S. atmospheres
with periodic elevations of ozone.
3. The risks of lung function and respiratory illness noted in
these long-term studies can be expected to vary with particle composition
among different regions. Although reliable comparisons of relative aerosol
toxicity on a unit mass basis are not available, the potential impact of
such variability is reduced by the fact that Ware et al. (1986) compared
cities of distinct pollution and geographic characteristics.
(ii) Risk for Other Sensitive Groups, Effects Not Evaluated
Because of the limited scope and number of long-term quantitative
studies, it is important to examine tne results of qualitative data from
epidemiological and animal studies. These studies justify concern for
other sensitive groups (asthmatics, bronchitic subjects, the elderly,
individuals with cardiopulmonary disease), and for serious effects (damage to
lung tissue from acid aerosols and mineral dusts, cancer, premature mortality)
not directly evaluated. Available data do not suggest major risks for
these effects categories or populations at current ambient particle levels
in most U.S. areas. Nevertheless, the risk that both fine and coarse mode
particles may produce these responses adds to the need to limit long-term
levels of PM^Q for a variety of aerosol compositions.
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60
C. Summary of Staff Conclusions and Recommendations
The major updated staff conclusions and recommendations made in
Section IV.A,B are briefly summarized below.
1. The staff reaffirms its recommendation to replace TSP as the
particle indicator for the primary standards with a new indicator that
includes only those particles less than or equal to a nominal 10 urn, termed
PMlQ. The previously developed effectiveness criteria for samplers are
acceptable for regulatory purposes.
2. Based on an updated staff assessment of the short-term epidemiological
data the range of 24-hour PM^g levels of interest is 140 to 250 ug/m .
The upper end of the range reflects the judgment of the Administrator with
regard to the maximum level proposed for a 24-hour standard, based on his
consideration of the earlier criteria and assessments. Although the recent
'information provides additional -support for the possibility of effects at
lower levels, it does not demonstrate that adverse effects would occur with
certainty at a PM^Q concentration of 250 ug/m . This level, therefore,
remains an appropriate upper bound. The recent data suggest that the range of
levels under consideration -of alternative standards can be reduced to 140
ug/m-*, although the original lower bound of 150 ug/m3 is within the range
of uncertainty associated with expressing the data as PMio« Neither the
studies used to derive this range nor the more qualitative studies of effects
in other sensitive population groups (e.g., asthmatics) or effects in controlled
human or animal studies provide convincing scientific support for health
risks of consequence below 140 ug/m3 in current U.S. atmospheres. These
qualitative data as well as factors such as aerosol composition and exposure
characteristics should also be considered in evaluating margins of 'safety
associated with alternative standards in the range of 140 ug/m3 to 250 ug/m3.
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61
3. Based on an updated staff assessment of the long-term epidemiological
data, 'the range of annual PM^ levels of interest is 40 to 65 ug/m . The
upper end of the range reflects the judgment of the Administrator with
regard to the maximum level proposed for an annual standard, based on his
consideration of the earlier criteria and assessment. The staff concludes
that this level remains a useful upper bound. The recent data prompt
consideration of a standard level below the previous lower bound (50 ug/m3)
to values as low as 40 ug/m3. Uncertain, data from one recent study suggest
that at this level some risk may remain of respiratory effects in children,
but no detectable increases in pulmonary function are expected in children
or adults.
When evaluating margins of safety for an annual standard, it is particularly
important to examine the results of qualitative data from a number of
•epidemiologica-1, animal, and air-quality studies. These suggest concern
for effects not directly evaluated in the studies used to develop the
ranges. Such effects include damage to lung tissues contributing to chronic
respiratory disease, cancer, and premature mortality. The available scientific
data do not suggest major risks for these effects categories at current
ambient particle levels in most U.S. areas. Nevertheless, the risk that
both fine and coarse particles may produce these responses supports the
need to limit long-term levels of PM^Q for a variety of aerosol compositions.
4. When selecting final standard levels, consideration should be
given to the combined protection afforded by the 24-hour and annual standards
taken together. For example, a 24-hour standard at 150 gg/m3 would
substantially reduce annual levels in a number of areas below 50 ug/m3
adding to the protection afforded by an annual standards in areas with
higher 24-hour peak to annual mean ratios.
-------
62
Because of different form, averaging procedures, size range, and
limited PM^Q data, precise comparisons between the above ranges of PM^y
standards and the current primary TSP standards are not possible. A staff
analysis of PMig/TSP ratios applied to recent TSP data shows that the
revised lower bounds, taken together, would result in standards clearly
more stringent than the current standards. In various analyses, standards
at the lower bound of the previous range (150,50) have appeared to range
from somewhat more stringent to approximately comparable to the present
primary standards. Standards at the upper end of the range could, however,
result in about a four-fold decrease in the areas exceeding the primary
standards.
-------
APPENDIX A. SUMMARY OF RECENT EPIDEMIOLOGICAL STUDIES ON PARTICULATE MATTER
A.I INTRODUCTION
This appendix presents a tabular summary and assessment of the community
epidemiological studies of particulate matter published since closure on
the 1982 criteria document and included in the CD addendum and not
summarized individually in Tables 3-1 or 3-2. It is intended to support
discussions in Sections III and IV of this paper. The tables follow the
organization of the criteria document and begin with studies of mortality
(Table A-l) associated with short-term exposures and are followed by and a
tabular summary of mortality (Table A-2) and morbidity (Table A-3) associated
w-ith long term exposures.
-------
TABLE A-l. EPIOEMIOLOGICAL STUDIES (1982-1986) ON SHORT-TERM CHANGES IN MORTALITY AND EXPOSURE TO PARTICLES
Data Base
Observed Effects/Comments
Study
Daily fluctuations in total
London mortality and pollu-
tion during 14 winters
(1958 - 1972) over a period
when PM (BS) and SO-, levels
declined by 80% and 50%,
respectively.
Reanalysis of above data.
Report detailing reanalysis
of above data. Mortality
data stratified by cause.
Unpublished reanalysis of
above data.
Regression coefficients averaged over 14 individual winters; 25.1% change
in mortality per mg/m3 BS vs. 1.2 % per mg/m3 SOo. Stratified quartile
analysis also indicates association primarily with BS but pollutant col-
linearity cannot be eliminated. Subset of highest pollution days shows mor-
tality increases with BS across range; with S02 only >700 gg/m3. Data cor-
rected for temperature, humidi-ty, day of week, annual, seasonal trends.
Possible over-control for temperature. Linear and quadratic models
using all BS data fit equally well. Below 300 gg/rn3, smoke explains <0.2% of
mortality variation in quadratic model, * 10% in linear model. Authors
hypothesize threshold and that quadratic model more plausible. Higher
smoke coefficients in later, less polluted years possibly explained by
statistical model, surrogate behavior.
Significant effect of BS on mortality deviations for days of BS < 150 gg/m3
in 9 of 12 winters, and in 5 of 6 later winters with no BS levels > 500
In first 6 winters, BS significantly associated with mortality on days
with BS > 150 gg/m3; not for later years (with very few observations).
Mazumdar
et al., 1982
Ostro, 1984
Temperature, humidity controlled;
with higher BS as in above study.
SO^ not included. Lower coefficients
Multiple time series analysis of detrended data controlled for autocorre-
lation. Effect of temperature significant, greatest with 2-day lag. BS and
S0£ predict mortality equally.well. Log-linear relation holds for all years -
no evident threshold or lag for pollution effect. Strongest associations
with pollution and temperature cycles of 7-21 days; shorter cycles had small
effect. Pollutants more important than temperature in predicting overall
and respiratory deaths; temperature more important in cardiovascular mortality.
Use of log pollution levels not comparable with other analyses. PM and
effects were not separated.
Shumway et al.,
1983
Autoregression models to control for time series effects (e.g., day of week,
epidemics), weather. Accounting for temperature, humidity enhances signi-
ficance of pollution in explaining mortality. BS consistently associated,
with mortality with or without S0£ included down to levels < 150-200 gg/nr
higher slopes in later years and at lower levels. S02 significant only ir
2 years with high levels. Diagnostic plots, regression results suggest
concave mortality/BS relationship.
Schwartz and
Marcus, 1986
-3.
-------
TABLE A-l. EPIDEMIOLOGICAL STUDIES ON (1982-1986) SHORT-TERM CHANGES IN MORTALITY AND EXPOSURE TO PARTICLE
(cont'd)
Data Base
Observed Effects/Comments
Study
Daily fluctuations in mor-
tality and pollution during
5 winters (1972-1977) in
Pittsburgh, Pa., characteri-
zed by variations in PM
(CoH) and S02 across 3
monitoring sites.
Daily fluctuations in
mortality (sum of circu-
latory, respiratory,
cancer). CoH, SOg, and
airport visibility during
14 years in N.Y.C. (1963-
1976) over a period when
S02 levels declined
by = 75% and CoH declined
slightly.
Daily fluctuations in
total mortality, SOg and
BS during 8 years in
Athens (197b-1982) over
a period when SOo and BS
levels declined by - 75%.
5 monitoring sites with
considerable variation in
BS, but not S02 levels.
Significant association between total and heart disease mortality
and PM, not S02, at high pollution site (CoHs * 1.25). Non-significant, in-
consistent associations at other sites. Seasonal trends, day-of-week, weather
controlled. Data filtered to account for autocorrelation. Possible over-
control for temperature. Only same-day effects considered.
Preliminary time series analysis, controlling for non-linear time trends,
found significant associations with PM indicators, S02, temperature.
Elevated CoH levels typical of period associated with 1.2-2% increase in
daily mortality. Lower end of range corresponds to coefficients reported
by Schimmel (1978) in prior analysis of same data. S02 associated with
0.3-1.5% increase in mortality. On days of regional visibility
deterioration, visibility derived extinction coefficient (surrogate for fine
particles) accounted for ~ 1% increase in mortality. S02 and PM declined
at different rates in NYC such that effects of pollutants less confounded
than in other studies. Unlike Schimmel (1978), S02 significantly correlated
with mortality. CoH and S02 measured at only 1 site; mortality estimates
somewhat sensitive to location of visibility reading (3 airports).
Unlike other studies, significant association between mortality and S02, but
not smoke, after controlling for temperature, secular, seasonal, monthly,
weekly variations and their interactions. Regression coefficient for S02
unaltered after sequential removal of days with values in excess of 500 down
to 150 ug/in . Authors inferred threshold slightly below 150 ug/m SO?.
Temporal trends controlled by subtracting expected mortality from 1956-1958
may introduce bias. Reliability of smoke measurements unclear.
Mazumdar and
Sussman, 1983
Ozkaynak and
Spengler, 1985
Ozkaynak et
al., 1986
CO
Hatzakis
et al ., 1986
-------
TABLE A-2. EPIDEMIOLUGICAL STUDIES (1982-1986) OF EFFECTS ON MUKTALITY DUE TO LONG-TERM EXPOSURES TO PARTICLES
Date Base
Results/Comment
Study
Age-and sex-specific
1969-1970 mortality in 112 U.S.
SMSAs related to annual TSP, 504
(and ozone for subset of 69 SMSAs
based on 1975 levels)
1980 U.S. mortality in U.S. SMSAs
along with annual average fine
particle (FP; < 2.5 urn), inhalable
particle (IP < 15 urn), TSP, and
504 from central monitors.
1968-1972 mortality among 45-54 year
old whites in U.S. counties and aggre-
gated in Public Use Samples (PUS).
TSP, S02, N02 values derived from
1974-1976 data.
Asthma and bronchitis mortality during
1963-1983 in Japanese industrial city
(Yokkaichi) over a period when SOX
levels, dominated by petroleum emissions,
increased up to 1967 and declined after
1970 (50% reduction by 1973; 75% by
1982). Levels of N02, TSP, oxidants
consistently low; only data from 1974-
1982 presented. Comparisons with clean,
control areas.
1969-1973 mortality among 45-74 year
olds in England and Wales. Smoke and
S02 data from 1971 and estimated his-
torical pollution exposure based on
coal consumption rates.
Attempts to improve Lave and Seskin (1978) model with additional Lipfert,
variables (diet, drinking water, residential heating fuels, migration, 1984
SMSA growth) and to evaluate collinearity in pollutant levels. As
variables added, pollution lost significance. TSP and 504 coefficients
unstable (elasticities between zero and ~6%); neither significant in
joint regression. TSP coefficient more often significant across data
sets, typically ~ 0.7 deaths/year/100,000 per ug/m3. Sulfate coef-
ficent less robust, more often non-significant. 03 coefficient fairly
stable, when significant ~ 1.3. Effects of individual pollutants
difficult to separate.
Regression analysis with control variables for % elderly, race, Ozkaynak &
population density, college education, poverty (not smoking). TSP and Spengler,
IP coefficients most often not significant. Mean 504 or FP most 1985
consistent predictors of mortality. Preliminary analysis, more
complex models await testing.
Regression analysis with 17 socio-economic (SES) and 4 weather Selvin et
control variables (no control for smoking, occupational exposure). al., 1985
Inconsistent associations; S02 most often significant, TSP and
N02 mostly negative coefficients. Interpretation of results
limited by use of retrospective exposure estimates, geographic
aggregations by groups of counties, possible overcbntrol of SES.
Asthma mortality for persons >^ 60 years old rose (in 1967) and fell Imai et
(after 1971) significantly with SOX levels. Significant increase al., 1986
in mortality due to bronchitis in persons >^ 60; after 1967,
continued increase following SOX declines in 1971; then decreased •
from 1976 on, 5 years after pollution reductions. Measurements of
SOX using lead peroxide methods limits quantification of acid
sulfate versus S02 effects.
Unlike comparable analyses of data from 1948-1964, no association
between pollution and mortality except between S02 and chronic
bronchitis, hypertensive disease and all causes of death in females.
Positive 562 results inconsistent with other studies. Suggests de-
clining effect of pollution on mortality since mid-1950's. No account
for occupational exposure, migration. BS readings not calibrated to
local mass readings; limits reliability.
Chinn et
al., 1981
-------
TABLE 'A-3. EPIDEMIOLOGICAL STUUIES (1982-1986) ON MORBIDITY EFFECTS OF LONG-TERM EXPOSURES TO*PARTICLES
Population/Exposure
Results/Comment
Study
Parental questionnaire and lung
function tests for = 3500 2nd-4th
graders in 4 sections of Hamilton,
Ontario during 1979-1982. Within-city
gradients in PM levels; multiple TSP
and size-selective particle monitors.
= 700 men and women (15-64 years)
examined between 1965 and 1984 in 3
year interval, living in 2 areas of
contasting pollution levels in the
Netherlands:
Vlaardingen Vlagtwedde
Annual means (24-hr, max)
BS S02
1965 40(185) 200(1030)
1974 40(165) 85( 362)
1984 37(124) 45(124)
BS
"very low"
"low" 16(158)
14(105) 15(117)
« 22,000 children (6-11 years old)
from 19 geographic regions in 6
European countries in 1975. Numerous
pollution monitors using different
measurement methods - collocated
monitors used to standardize
readings. Range for adjusted annual
Black Smoke 5-57 ug/nr; annual SO?
19-326 ug/m3.
No significant association between cough or episodes of bronchitis and
pollution indices after adjusting for maternal smoking, SES, gas
stove use. Peak flow and MEFy5, an index of small airway function,
significantly associated with "fine" particles. No association
between FEV and PM. Possible biases in Cascade impactor readings,
modest gradients, limit conclusions (likely included much larger
particles).
After 1st 4 follow-ups (9 years), significantly greater (= 6050
decline over time of vital capacity and FEV^ in Vlaardingen compared
with rural area. Preliminary results indicate that over 15 years,
difference in FEVj decline not significant—mainly due to lower
FEV values than expected in last 2 exams in rural area. Prevalence
of chronic phlegm and breathlessness always greater in Vlaardingen
but much smaller differences in later exams (1976-1984) when symptom
prevalence increased in rural town (consistent with lung function
chanyes)--possibly due to short episodes (5-10 days) of peak
pollution observed in rural area (24 hr. S02 = 50-80 ug/m ) during
last 2 exams
expected
More thorough data analyses and further testing
Across countries no significant differences in respiratory symptoms
related to smoke or S02. When systematic differences in health
between countries accounted for, strong associations in Italy and
Ireland between smoke and wheezing, breathlessness, cough, and non-
specific chronic lung disease. Annual levels in both those countries
between = 7-38 ug/m3 (winter means 24-54 ug/m3). No smoke effects
in other countries. Significant S02 effects in some countries.
Limited application to current U.S. PM exposures given sampling
differences, lack of calibration.
Pengelly
et al.,
1986
van
der Lende
et a I.,
1986
CEC, 1983
-------
TABLE A-3. EPIOEMIULOGICAL STUDIES ON (1902-1986) MORBIDITY EFFECTS OF LONG-TERM EXPOSURES TO PARTICLES
(cont'd)
Population/Exposure
Children < 4 years from residential
areas of contrasting SOo and dustfall
levels reporting to a clinic in
Duisburg, W. Germany
Results/Comment
Clear distinction in incidence of croup and obstructive bronchitis
between high and low pollution areas (S02 < 300 ug/nr >, dustfall
< 0.35 g/mZ.day >). Other factors (e.g., infections, distance
to clinic, degree of crowding) accounted for but effects of S02
and PM cannot be separated. Limited application to assessing
effects of U.S. particles.
Study
Muhling
et al .,
1985
3,088 residents (aged 19-70 years) of
Cracow, Poland, surveyed in 1968 and
1973, living in high pollution area
in city center (mean suspended
particle concentration = 118 ug/m^,
SOo = 114 ug/nr) versus those in
other areas (mean SP = 109 ug/m3,
S02 = 53
Air pollution by itself not a significant predictor of
bronchitis. However, effects of occupational exposure to
hazards (i.e., chemicals, irritating gases, high temperature and
humidity) on prevalence of bronchitis, chronic cough/phlegm,
reduced FEV much greater in men living in high pollution areas.
Among men with persistent cough/phlegm, more frequent exacerbations
of symptoms in high pollution areas. Little effect of pollution on
women. Attempts to test interactions among multiple variables
suggest marked pollution effects only in combination with other
factors. PM measurements not directly applicable to U.S.
levels. Cannot separate PM from
Wojtyniak
et al.,
1986
-------
APPENDIX B. ESTIMATION OF PM10 LEVELS ASSOCIATED
WITH KEY STEUBENVILLE ALERTS
This appendix details the calculations involved in converting TSP
measurements from the Steubenville alert studies into PM^g units. Two of
the four Steubenville alert studies from Dockery et al . (1982) were used in
deriving the "possible" and "no significant effects noted" levels in
Table 4-1. These were the Spring and Fall 1980 studies. The peak 24-hour
TSP levels measured in these studies were, respectively 220 ug/m^ and
160 ug/m^. Relevant information on TSP and other particle size fraction
ratios in Steubenville is summarized in the report of Spengler et al .
(1986). PM10/TSP ratias were available only for 1984-85, whereas PM15/TSP
i
ratios, as measured by dichotomous samplers, were available for portions of the
actual alert periods in Steubenville. Therefore, the general approach taken
was to estimate a range of PMio/OClb ratios (where DC^ is PM^5 as measured
by dichotomous sample) expected for Steubenville and then multiply this by
the DCi5/TSP ratio observed during the relevant alert period -to estimate the
ratio for the period, i.e.,
PM10/DC15 x DC15/TSP =* PM10/TSP (8-1)
(estimated, 1979-85 data) (observed for alert) (estimated for alert)
The range of PMio/DCl5 ratios was estimated by using 1984-85 measurements of
PM^O/TSP and PM^o/IP]^ ratios (where IPi5 is PM^5 as measured by size
selective high volume sampler) together with measurements of IPi5/DCi5 and
TSP/DCi5 made the 1979-84 period. The two approaches can be written as:
PM10/IP15 x IPl5/DCi5 = PMio/OC15 (6-2)
(measured 84-85) (measured 79-84) (estimated)
and;
PM10/TSP x TSP/OC15 = PM10/DC15 (B-3)
(measured 84-85) (measured 79-84) (estimated).
-------
R-2
The median PMio/IPi5 ratio for S.teubenville in 1984 is 0.76 (Table V-6,
Spengler et al., 1986). The median IPis/DC-is ratio for 1980-84 (5-yr average)
in Steubenville is 1/0.82 or 1.22 (Table V-5, Spengler et al., 1986). The
PMjo/0^15 estimated from equation B-2 is, therefore:
0.76 x 1.22 = 0.93.
A somewhat lower figure (0.87) can be obtained by using the 1985 PMjQ/IPis
ratio while a comparable to somewhat higher estimate can be derived from
using the IPi5/DCi5 ratio from 1980 (the year in which the episodes occurred)
in place of the longer term value. Given the absence of clear trends in the
ratios, the longer term estimate is preferred in this case. Given the
t
uncertainties in the estimates a rounded PMio/DCis ratio of 0.9 is derived from
this procedure.
Similarly, a lower bound estimate for PM^o/DC-is can be derived from
equation B-3. The median 1984 PMio/TSP ratio for Steubenville is 0.5 while
that for 1985 is 0.51 (Table V-6, Spengler et al., 1986). The median
TSP/DC15 ratio for 1979-84 (6 yr. average) is 1/0.66 or 1.5. From equation
A-3, the P^io/DCis ratio is 0.76, which rounds to 0.8. From the above
calculations, therefore, the range of estimated median PMio/0^15 ratios for
Steubenville is 0.8 to 0.9.
The PMio/TSP ratios for specific alert periods can be estimated using
these average ratios calculated above (0.8 to 0.9) together with specific
PMJ5/TSP measurements made during the alert studies. In the spring 1980
study, the peak TSP level of 220 ug/m^ occurred on or about April 21 (Figure 1,
Dockery et al., 1982). Although no particle ratios were available on that
day, the DCjs/TSP ratios for the higher concentrations days occurring just
before and after that date are approximately 0.8 (Figure IV-6, Spengler et.
al., 1986). Thus, by equation B-l, the range of estimated PMjo/TSP ratios
-------
B-3
for that alert period are:
(0.8 to 0.9) x 0.8 = 0.64 to 0.72.
To estimate the lower bound of the "possible" effects range, the lower •
PM10/TSP ratio (0.64) is used and the estimated PM1Q level is 2?0 ug/m3
x 0.64 = 140 ug/m3. Although not useful for deriving a lower bound, the
upper bound estimate would yield 220 ug/m3 x 0.72 = 160 ug/m3. These upper
and lower estimates bound the original lower bound (150 ug/m3) of the range
proposed for a 24-hour PM^g standard in 1984.
In the Fall 1980 study, in which significant effects were not observed,
the peak TSP concentration of 160 ug/m3 was reported during the baseline
measurement period on or about October 17 (Figure 1, Dockery et al., 1982).
Corollary measures indicate somewhat higher concentrations ( 200 ug/m3 as
TSP) on this date as well as on a subsequent date (about October 29) (Figure
IV-7, Spengler et al., 1986). DCjs/TSP ratios for this study period were
typically in the vicinity of 0.5 for most of the study period. Thus, the
range of estimated PM^o/TSP ratios from equation B-l is:
(0.8 to 0.9) x 0.5 = 0.4 to 0.45. ' ; '
The range of estimated peak PMjg levels asociated with this study period is
therefore:
(160 to 200 ug/m3) x (0.4 to 0.45) = 65 to 90 ug/m3.
-------
APPENDIX C
CASAC Closure Letter
-------
SAB-CASAC-87-010
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON. Q.C. 20460
December 16, 1986
OFFICE OF
_. ,, , _. THE ADMINISTB A TOW
The Honorable Lee Thomas
Administrator
U.S. Environmental Protection
Agency
Washington, DC 20460
Dear Mr. Thomas:
The Clean Air Scientific Advisory Committee (CASAC) has completed
its review of the 1986 Addendum to the 1982 Staff Paper on Particulate
Matter (Review of the NAAQS for Particulate Matter; Assessment of
Scientific and Technical Information) prepared by the Agency's Office
of Air Quality Planning and Standards (OAQPS).
The Committee unanimously concludes that this document is consistent
in all significant respects with the scientific evidence presented and
interpreted in the combined Air Quality Criteria Document for Particulate
Matter/Sulfur Oxides and its 1986 Addendum, on which the CASAC recently
issued its closure letter. The Committee believes that this document
provides you with the Jcind and amount of technical guidance that will
be needed to make appropriate revisions to the standards. The Committee's
major findings and conclusions concerning the various scientific issues
and studies discussed in the Staff Paper Addendum are contained in the
attached report.
Thank you for the opportunity to present the Committee's views on
this important public health issue.
Sincerely,
Morton Lippmann/Ph.D.
Chairman
Clean Air Scientific Advisory
Committee
cc: A. James Barnes
Gerald Emison
Vaun Newill
John O'Connor
Craig Potter
Terry Yosie
-------
SAB-CASAC-87-010
SUMMARY OF MAJOR SCIENTIFIC ISSUES AND CASAC
.CONCLUSIONS ON THE 1986 DRAFT ADDENDUM
TO THE 1982 PARTICULATE MATTER STAFF PAPER
The Committee found the technical discussions contained in the Staff
Paper Addendum to be acceptable with minor revisions.
Particle Size Indicator
The CASAC reaffirms its January 29, 1982 recommendation that a particle
size indicator that includes only those particles less than or equal to a
nominal 10 um aerodynamic diameter, termed PM^o, is appropriate for regulation
of particulate concentrations. This judgment is based on analysis of the
earlier available data, and the analysis of the recent scientific studies
discussed in the 1986 Addendum to the Air Quality Criteria for Particulate
Matter/Sulfur Oxides and the 1986 Addendum to the Particulate Matter Staff
Paper.
Implications of London Mortality Studies
Further analyses of the London mortality studies, including recent
analysis by Agency staff, suggest that:
1) the data provide no evidence for a threshold for the association
between airborne particles and daily mortality or a change of
coefficient with changes in particle composition;
2) mortality effects can be associated with PM alone (with or
without sulfur oxides);
3) there is no reliable quantitative basis for converting
Rritish Smoke (BS) readings to PM^Q gravimetric mass
at low (<100-200 ug/m3) BS levels, and hence the mortality
data are not readily useful for establishing a lower bound for
24-hour PM^o NAAQS, although the suggestion of mortality at
relatively low PM levels must be given serious consideration
in selecting a margin of safety.
Interpretation of Lung Function Studies for 24-hour Standard
Although the lung function decrements observed in children during and
after air pollution episodes are of uncertain health significance, the two
episodic lung function studies (Dockery et al., 1986? Dassen et al., 1986)
are consistent with each other and the earlier work of Stebbings. They
provide a relatively sensitive indication of possible short term physiological
responses. Given the difficulty in deriving a lower limit from the mortality
studies, these lung function studies can be useful in determining lower
bounds for a 24-hour PM^g standard.
-------
-2-
Interptetaticn of the six Cities Study for Annual Standard
In general, the Committee felt that the six cities data are useful in
establishing the Tower bound of the range for the annual standard. In
addition, the following are suggested by the data:
1) Cough and bronchitis, as defined in this study, are about twice
as prevalent in children living in cities with PM^Q in t^6
range of 40-60 ug/m3, in comparison to cities with 20-30 ug/m3;
2) Because factors other than particulate matter may affect the
inter-city differences, it is difficult to determine whether
these associations should be designated as "likely" health
effects;
3) The results are consistent with the Ostro studies in terms of
morbidity responses at long-term average particulate matter
exposures within current particulate ambient air quality
standards; and
4) The results are consistent with the Bouhuys study in terms
of symptoms without changes in pulmonary function.
Ranges for 24—hour and Annual Standards for PM]p
In its January 2, L986 letter to the Administrator, the CASAC noted
that its preliminary analyses of the jnore recent data do not indicate the
need for fundamental changes in the structure of the proposed particle
standards; however, the Committee pointed out that these new data suggest
the need to focus consideration on standards at or perhaps below the low
ends of the ranges proposed in the March 20, 1984 Federal Register Notice.
The ranges of interest then proposed were 150-250 ug/m3 for 24-hour standard,
and 50-65 ug/m3 for annual standard.
Since then, EPA staff have proposed updated ranges of interest for
both the 24-hour standard (140-250 ug/m3), and the annual standard (40-65
ug/m3), based on short-term and long-term epidemiological data, respectively.
The Committee finds these ranges of interest reasonable, given the scientific
data and related uncertainties; however, a final decision should also weigh
evidence from clinical and toxicolcgical studies as well. The Committee
agrees with EPA staff that selection of final standards must include
consideration of the combined protection afforded by the 24-hour and annual
standards taken together.
The Committee recommends that you consider setting the revised standards
at the lower ends of the proposed ranges for both the 24-hour and annual
standards. The Committee recognizes that the exact levels to be chosen
for the 24-hour and annual standards represent a policy choice, influenced
by the need to include a margin of safety. Given the uncertainty in the
supporting scientific data, the Committee cannot distinguish the 'health
effects that may be observed at different levels near the lower bound,
such as the health significance of setting the 24-hour standard at 140
ug/m3 compared to 150 ug/m3.
-------
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TECHNICAL REPORT DATA
(Please read Insmictions on the reverse before completing)
1. REPORT NO.-
EPA 450/05 86-012
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE ... . . „ , . L ,*. j j
Review of the National Ambient Air Quality Standards.
for Particulate Matter: Updated Assessment of
Scientific and Technical Information Addendum to the
Staff Paper
5. REPORT DATE
December 1986
6. PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Office of Air and Radiation
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
This paper evaluates and interprets the updated scientific and technical information
that the EPA staff believes is most relevant to decision making on revised primary
(health) national ambient air quality standards (NAAQS) for particulate matter and is
an addendum to the 1982 particulate matter staff paper. This assessment is intended
to help bridge the gap between the scientific review contained in the EPA criteria
document addendum and the judgments required of the Administrator in making final
decisions on revisions to the primary NAAQS for particulate matter that were proposed
in March 1984 (49 FR 10408). The major recommendations of this addendum include the
following:
1. The staff reaffirms its recommendation to replace TSP as the particle indica-
tor for the primary standards-with a new indicator that includes only those particles
less than or equal to a nominal 10 um, termed PM,Q.
2. Based on an updated staff assessment of the short-ternuepidemiological data,
the range of 24-hour PM,Q levels of interest is 140 to 250 ug/m .
3. Based on an updated staff assessment of the long-term epidemiological data,
the range of. annual PM,Q levels of interest is 40 to 65 ug/m3.
4. When selecting final standard levels, consideration should be given to the
combined protection afforded by the 24-hour and annual standards taken together.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COS AT I I ield/Group
Particulate Matter
Aerosols
Air Pollution
Sulfur Oxides
Air Quality Standards
18. DISTRIBUTION STATEMENT
Release to public
19. SECURITY CLASS (This Report I
Unclassified
21. NO. OF PAGES
100
20. SECURITY CLASS (THis page;
22. PRIC H
EPA Form 2220-1 (Rev. 4-77)
PREVIOUS EDITION IS OBSOLETE
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