U'~.:iei1 States Environr^r-.tai Crie-'i* -r-.o EPA ^CHj c> ~'r'•'•'•• •>
Env^cnmemai protecnor Assessment Off r^ June 1979
Agency Research Tr.,ingif '?,>••. M :.'.••; i -
<>EPA Suspended Particulate
Matter
A Report to Congress
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EPA-600/9-79-006
June 1979
Suspended Particulate
Matter
A Report to Congress
by
Lucile F. Adamson, Ph.D.
Professor, Macroenvironmental and Population Studies
Howard University
Washington, D.C. 20059
and
Robert M. Bruce, Ph.D.
Health Scientist
Environmental Criteria and Assessment Office
Office of Research and Development
Environmental Criteria and Assessment Office
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
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DISCLAIMER
This report has been reviewed by the Office of Research and Development,
EPA, and approved for publication. Mention of trade names or commercial
products does not constitute endorsement or recommendation for use.
n
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PREFACE
This report was written in accordance with Section 403(a)(l) of the Clean
Air Act Amendments of 1977, P.L. 95-95, as noted under 42 U.S.C. Section 7548.
The purpose of this report is to assess health and welfare effects caused by
suspended particulate matter in relationship to size, weight, and chemical
composition.
The report does not constitute an in-depth review of the original
published literature; rather, it summarizes, through the use of recent reviews
by well-known experts in the field, the current scientific position with
regard to knowledge of airborne particles, their effects on public health and
welfare, and the respective levels at which these effects are thought to
occur.
The Agency is pleased to acknowledge the efforts of all persons and
groups who have participated in preparing this document.
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ABSTRACT
This report is in response to Section 403(a)(l) of the Clean Air Act
Amendments of 1977, P.L. 95-95, as noted under 42 U.S.C. Section 7548. The
report covers (1) a review of the physical and chemical characteristics of
airborne particles (source, composition, and sampling site as related to
size); (2) a review of the effects of particulate matter on public welfare
(ecological, materials, atmospheric, aesthetic); (3) the status of human
exposure to airborne particles as related to source; and (4) a review of the
effects of airborne particles on human health (lung deposition, chemical
composition, interactions, and potentiating conditions).
Although there is a wide divergence of opinion among experts and
scientific groups with respect to the issues of particulates the following
can be concluded from the available information:
1. A major portion of the adverse health and welfare effects of air
pollution is due to airborne particles.
2. Although pollution levels have declined in many U.S. localities in
recent decades, there is still need for improvement in several of
our cities.
3. Additional research is needed to improve the scientific basis for
future airborne particle standards as outlined by EPA (cf. Inhalable
Particulate Research Plan, Project Officer, Dr. Roger Cortesi, EPA,
ORD).
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CONTENTS
PREFACE iii
ABSTRACT iv
FIGURES vi
TABLES vii
LIST OF REVIEWERS viii
TECHNICAL SUPPORT ix
1. EXECUTIVE SUMMARY 1
2. INTRODUCTION 7
3. CHARACTERISTICS OF AIRBORNE PARTICLES 8
3.1 PHYSICAL CHARACTERISTICS OF AIRBORNE PARTICLES 8
3.2 CHEMICAL CHARACTERISTICS OF AIRBORNE PARTICLES 12
4. AEROSOLS: SOURCES AND CONCENTRATIONS 20
4.1 SOURCES AND EMISSIONS 20
4.2 TRANSFORMATION AND TRANSPORT 27
4.3 CONCENTRATIONS 28
5. EFFECTS OF AIRBORNE PARTICLES ON HUMAN HEALTH 36
5.1 DEPOSITION OF AIRBORNE PARTICLES IN THE LUNG 36
5.2 HEALTH EFFECTS OF GENERAL AIRBORNE PARTICLE POLLUTION . 37
5.3 CONDITIONS WHICH MAY POTENTIATE HEALTH EFFECTS OF
AIRBORNE PARTICLES 45
5.4 HEALTH EFFECTS OF SPECIFIC CHEMICAL COMPOUNDS 47
5.5 HEALTH COST ANALYSES 57
5.6 DEFICIENCIES IN THE SCIENTIFIC DATA BASE 58
6. EFFECTS OF PARTICULATE MATTER ON PUBLIC WELFARE 62
6.1 ECOLOGICAL EFFECTS 62
6.2 EFFECTS ON MATERIALS 63
6.3 ATMOSPHERIC AND CLIMATIC EFFECTS 64
6.4 AESTHETIC EFFECTS 65
7. REFERENCES 67-75
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FIGURES
Page
1. Comparison of volume distributions measured by
several investigators in different locations 10
2. Estimation of TSP levels by the Hi-Vol method
under varying conditions of particulate pollution 18
3. TSP annual means at 17 urban NASN stations 30
4. Benzo(a)pyrene seasonality and trends (1966 to 1975) in
the 50th and 90th percentiles for 34 NASN urban sites. ... 31
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TABLES
1. Geometric mean and 90th percentile urban participate
concentrations in the United States, 1971-1975 14
2. Correlations of chemical content with particle size 16
3. Global estimates of particles smaller than 20 urn
radius emitted into or formed in the atmosphere 21
4. Nationwide estimates of particulate emissions, 1940-1970 . . 23
5. Recent nationwide emission estimates 1970-1977 24
6. Emission estimates for major sources of certain
airborne particles 26
7. Trends in urban metal concentrations and their
possible causes 32
8. Ratios of urban (U) to suburban (S) concentrations in
air, Cleveland, Ohio area 34
9. Health effects and dose/response relationships for
particulates and sulfur dioxide 39
10. Threshold estimates for adverse health effects
attributable to sulfur dioxide, particulate sulfate,
and total suspended particulates (TSP), short-term
exposures 40
11. Threshold estimates for adverse health effects
attributable to sulfur dioxide particulate sulfates,
and total suspended particulates (TSP), long-term
exposures 41-42
12. Variables related to the health effects of airborne
particles 44
13. Comparison of health cost studies. 59-60
VII
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LIST OF REVIEWERS
Appreciation is extended to the following persons for their efforts in
reviewing this report.
Mr. John Bachmann, Office of Air Quality Planning and Standards, U.S.
Environmental Protection Agency, Durham, N.C.
Mr. Michael A. Berry, Environmental Criteria and Assessment Office, U.S.
Environmental Protection Agency, Research Triangle Park, N.C.
Dr. Donald E. Gardner, Health Effects Research Laboratory, U.S. Environmental
Protection, Agency, Research Triangle Park, N.C.
Dr. Robert E. Lee, Health Effects Research Laboratory, U.S. Environmental
Protection Agency, Research Triangle Park, N.C.
Mr. Thomas McMullen, Environmental Criteria and Assessment Office, U.S.
Environmental Protection Agency, Research Triangle Park, N.C.
Dr. Fred Miller, Health Effects Research Laboratory, U.S. Environmental
Protection Agency, Research Triangle Park, N.C.
Ms. Beverly E. Tilton, Environmental Criteria and Assessment Office, Research
Triangle Park, N.C.
vm
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TECHNICAL SUPPORT
The following persons are recognized and acknowledged for their
invaluable services in the preparation of this document.
Ms. Dela Bates, Environmental Criteria and Assessment Office, U.S.
Environmental Protection Agency, Research Triangle Park, N.C. 27711
Ms. Vandy Duffield, Environmental Criteria and Assessment Office, U.S.
Environmental Protection Agency, Research Triangle Park, N.C. 27711
Mr. Douglas Fennel 1, Environmental Criteria and Assessment Office, U.S.
Environmental Protection Agency,.Research Triangle Park, N.C. 27711
Mr. R. Wayne Fulford, Health Effects Research Laboratory, U.S. Environ-
mental Protection Agency, Research Triangle Park, N.C. 27711
Mr. Allen G. Hoyt, Environmental Criteria and Assessment Office, U.S.
Environmental Protection Agency, Research Triangle Park, N.C. 27711
Ms. Bonnie Kirtz, Health Effects Research Laboratory, U.S. Environmental
Protection Agency, Research Triangle Park, N.C. 27711
Ms. Evelynne Rash, Environmental Criteria and Assessment Office, U.S.
Environmental Protection Agency, Research Triangle Park, N.C. 27711
IX
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1. EXECUTIVE SUMMARY
This document is submitted as a Report to Congress, mandated by Section
403(a)(l) of the Clean Air Act Amendments of 1977, P.L. 95-95, as noted under
42 U.S.C. Section 7548, concerning the health and welfare effects of airborne
particle pollution. The report provides an extended summary of these effects
primarily as described in the review by the National Academy of Sciences (MAS)
(Airborne Particles). but also as described in other recent reviews. These
reviews are: (1) Health Effects of Particulate Pollution: Reappraising the
Evidence. A. E. Bennett et al., 1978; (2) Environmental Health Criteria for
Sulfur Oxides and Suspended Particulates. World Health Organization, 1978;
(3) Fine Particulate Pollution. World Health Organization, 1977; (4) Intra-
urban Mortality and Air Quality: An Economic Analysis of Pollution Induced
Mortality. J. Gregor, 1977; (5) Total Suspended Particulates: Review and
Analysis. R. Wells, 1976; (6) Air Quality Criteria for Particulate Matter,
National Air Pollution Control Administration, 1969. The report represents an
interim summary of health and welfare effects associated with airborne particles.
A comprehensive review of health and welfare effects and other aspects is
currently being conducted as part of the revision of the particulate matter
t-
criteria document. An external review copy of the criteria document will be
available by late 1979, with final publication by late 1980. The material in
this interim report is summarized under several headings as indicated below.
Characteristics of Airborne Particles
Airborne particles include a variety of chemical substances distributed
over a wide range of particle sizes. The distinction between "fine particles"
[<2 micrometers, ((jm)] and "coarse particles" (>2 pm) is a fundamental one.
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There is now an overwhelming amount of evidence that not only are two modes
usually observed in the mass or volume distribution of well-mixed urban and
rural aerosols, but that the fine and coarse modes are normally quite diffe-
rent in chemical composition. The fine and coarse particle modes originate
separately, are transformed separately, are removed from the atmosphere by
different mechanisms, require different control techniques, have different
chemical composition, have different optical properties, and exhibit differential
penetration of the respiratory tract. Therefore, the distinction between fine
and coarse particles is of fundamental importance to any discussion of the
physics, chemistry, measurement, and respiratory tract deposition of aerosols.
The major components of the fine fraction of the atmospheric aerosol are
sulfates, ammonium ions, hydrogen ions, condensed organic matter, and trace
levels of lead. The fine fraction, as a percentage of total suspended parti-
culate matter, varies from 20 to 60 percent in urban areas. The percentage of
the fine particle fraction which is formed mainly from atmospheric photo-
chemical reactions varies from 60 to 80 percent in these urban areas (percentages
based on short-term, intensive studies). Also, several studies have shown that
potentially toxic carcinogenic species, such as polynuclear aromatic compounds,
arsenic, selenium, cadmium, and zinc, which can exist as vapors are more
concentrated in the fine particle fraction.
Materials typically found in the coarse fraction include those pro-
duced from mechanical processes such as grinding operations; rubber tire
particles and other road dust; and also wind-blown dusts, sea salt, and pollen.
Sources and Concentrations
Exposures to airborne particles are determined not only by the amount and
type of emitted pollutants, local topography, and meteorological conditions,
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but also by one's residential or occupational proximity to sources of such
pollution and the rate, depth, and mode (mouth or nose) of breathing. For
those pollutants that can accumulate in tissues, such as lead, cadmium, and
fat-soluble organic compounds, tissue levels can increase with duration and
frequency of environmental exposures.
Although the mass emissions of airborne particles from natural sources
are thought to exceed those from man-made sources, naturally derived particles
are both quantitatively and qualitatively less significant to human exposures
in the urban environment. As an example, it has been estimated that the
natural particle component of the Los Angeles aerosol is less than 30 percent
of the total. These natural particles (sea salts, dust, etc.) are also
generally less hazardous to healthy individuals than are many of the particles
from man-made sources. Indoor concentrations of airborne particles are some-
times as great or greater than outdoor concentrations, particularly in certain
occupational settings and in homes in which cigarette smokers live. Typi-
cally, urban environmental concentrations greatly exceed those of rural loca-
tions. Urban particulate pollution increased by 18 percent from 1940 through
1970, principally due to stationary fuel combustion sources and industrial
process losses. Subsequent to 1970, particulate levels began to decline. The
most significant downward trends in emissions were 33 percent for stationary
fuel combustion sources and 54 percent for industrial processes. These down-
ward trends resulted from the change from coal to natural gas and oil, the
adoption of local smoke control ordinances, and the adoption of national emission
standards. This decreasing trend that has been observed from 1970 through
1977 does not imply that all components of total suspended particulate are
decreasing. However, a number of toxicologically significant particulates
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such as trace metals and polycyclic organic matter have decreased. Prominent
among the metal components of total suspended particulate showing a decline
are vanadium, manganese, and nickel. Nationwide lead averages have declined
since 1972 due to the introduction of the lower compression engines and the
use of lower lead gasoline. This trend should continue with the shift of
usage from low-lead gasoline to no-lead gasoline.
Health Effects
There has been increasing emphasis on examining what particle size fraction
is of significance for health impacts. Recently, the EPA evaluated available
information on the disposition of particles in the human respiratory tract.
The analysis is summarized in "Size Consideration For Establishing A Standard
For Inhalable Particles." This analysis provides the theoretical basis for
designation of a size-specific airborne particle standard that would provide
for more effective control of those particles most likely to be responsible
for adverse health effects. The analysis indicates that under the most sensitive
conditions (mouth breathing) particles of up to 15 micrometers in diameter can
penetrate to the upper portions of the lung (conducting airways). This fraction,
termed inhalable particulate (IP) matter makes up roughly 50 to 60 percent of
total suspended particulate matter and includes all of the fine (<2.5 urn) and
some of the coarse (2.5 to 15 urn) mode fraction. Based on this analysis, a
major expansion of air pollution monitoring and health studies was initiated
in 1979 to monitor and evaluate the health effects of inhalable as well as
fine particulate matter.
Past studies of particulate pollution have indicated that high levels of
airborne particle pollution are correlated with increased incidence, prevalence
and severity of respiratory diseases and with increased mortality from these
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and other diseases. The minimum concentration and duration of airborne particle
exposure at which these health effects become significant cannot be precisely
specified at this time. Furthermore, due to the limitation of monitoring
methods used in these historical studies, it is difficult to correlate
health effects directly with particle size and chemical composition.
Various reviews of the available information, including a report by a
task force of the World Health Organization (1979), have concluded either that
levels approximating the present primary TSP standards are reasonable ones for
protection of public health or that there is not sufficient justification to
change these standards on the basis of present knowledge. Others have concluded
that the standards are more stringent than can be justified on the basis of
present knowledge. Additional research is needed on the chemical and physical
properties of particles in order to define better the characteristics and
magnitude of particulate exposures which are consistent with public health.
Welfare Effects
Airborne particles produce well-documented effects on public welfare
which include adverse effects on building materials and other exposed sur-
faces, atmospheric conditions, and aesthetic conditions, as well as possible
influences on global temperatures and climate. The aesthetic effects of
particulate pollution include the soiling of fabrics, buildings, and other
surfaces, cultural losses due to damage to exposed architectural and historic
artifacts, and degradation of visibility. Airborne particles have been
associated with increased cloud cover and precipitation and have been
implicated in shifts in temperature and climate. Moreover, airborne particles
can seriously damage vegetation, wildlife, and natural systems when removed
from the atmosphere by snow and rainfall. Long-range transported fine sulfates
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and nitrates acidify soils and surface waters; nitrates, organic, and
metallic substances in fine particulates can accumulate to harmful levels in
soil, water, and plants.
It can be concluded that (1) a major portion of the adverse health and
welfare effects of air pollution is due to airborne particles; (2) although
pollution levels have decreased in many localities in recent decades, there is
still need for considerable improvement in some of our cities; and (3) addi-
tional research is needed to improve the scientific basis for future airborne
particle standards.
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2. INTRODUCTION
Section 403(a) of the Clean Air Act Amendments of 1977, P.L. 95-95, as
noted under 42 U.S.C. Section 7548, requires the Administrator of the Environ-
mental Protection Agency, in cooperation with the National Academy of Sciences,
to submit before February 1979, a report to the Congress "on (1) the relationship
between the size, weight, and chemical composition of suspended particulate
matter and the nature and degree of the endangerment to public health or
welfare presented by such particulate matter (especially with respect to fine
particulate matter) and (2) the availability of technology for controlling
such particulate matter."
This report is submitted in fulfillment of the first part [403(a)(l)] of
that requirement. The form of the report is as follows:
Following the Executive Summary and the Introduction, Sections 3 through
6 present brief statements of the current scientific position with regard to
knowledge of airborne particles and their effects on public health and wel-
fare. References to prior reviews and to research reports are provided for
those readers who wish additional documentation or detail.
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3. CHARACTERISTICS OF AIRBORNE PARTICLES
3.1 PHYSICAL CHARACTERISTICS OF AIRBORNE PARTICLES
3.1.1 Size of Ambient Aerosol Particles
3.1.1.1 Aerodynamic Equivalent Diameter —Inasmuch as airborne particles are
quite variable in shape, density, and chemical properties, their size and
weight are generally characterized by an indirect measure referred to as the
aerodynamic equivalent diameter: the diameter of a spherical particle of
density 1.0 which would fall through air in earth's gravitational field at the
falling speed of the observed particle. Aerodynamic equivalent diameter is,
therefore, a function of both shape and density and is not necessarily indica-
tive of the actual diameter of the observed particle. References in this
report to particle diameter refer to this measure.
3.1.1.2 Size Distribution-'-Suspended atmospheric particles range in diameter
from a few nanometers (nm) to several hundred micrometers (urn).* The numeri-
cal distribution of particles within this range normally exhibits two or three
maxima. The bimodal distribution, with maxima at about 0.3 and 10 pm and a
minimum at about 2 pro. is most common; but trimodal distributions (with the
third peak (nuclei mode) corresponding to particles with diameters less than
0.1 jjm) are also observed in ambient aerosols. Two micrometers is often used
as the approximate demarcation point between "fine" and "coarse" particles.
Within the definition of fine particles two distinct populations can exist,
the "Aitkin nuclei" (<0.1 urn), emitted as such or formed by vapor condensation,
* This corresponds to a range from approximately the ultramicroscopic diameter
of the smaller viruses to the diameter of dust particles which are easily
visible. A nanometer is one one-thousandth of a micrometer (micron).
8
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and the "accumulation mode" particles (0.1 to 2 pm), formed chiefly by coagu-
lation and condensation of smaller particles. In fresh emissions, the Aitkin
nuclei are usually numerically predominant, whereas in well-aged aerosols most
of the fine particles are in the accumulation mode. The ratio of mass and
volume to particle size varies with the geographical location, the predominant
type of pollution (fugitive dust or photochemical products) and the age of the
aerosol. Examples of volume distribution curves for particles measured by
several investigators at different locations are shown in Figure 1. For more
information on particle size, see Chapter 2 of the National Academy of Sciences
document prepared for EPA titled Airborne Particles.
3.1.1.2 Variation of Particle Size According to Source--To a large extent,
the initial size of an airborne particle depends upon its source. Secondary
particles, formed in the atmosphere by condensation and/or chemical reactions
of gases (such as sulfuric acid or organic solvent droplets), are very small
initially. Although they rapidly grow by coagulation, most of them remain in
the submicrometer range, also referred to as the accumulation mode.
Combustion processes, including automotive operation, produce particles
which are mostly less than 1 urn in diameter, including particles of soot,
various organic materials, and lead salts from leaded gasoline combustion.
Many other chemical processes, such as sulfuric acid manufacture, also produce
submicrometer-sized particles. Other sources which produce substantial amounts
of fine particle emissions include metallurgical processes, paper mills,
cement plants, and asphalt plants.
Grinding processes and most natural processes usually produce predominantly
large particles (>2 urn). However, there is no reason to assume that they do
not also produce fine particles.
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P)
a
a
100
80
60
40
20
L.A..1969,
342 RUNS
I I I II III! I I
MPLS /
(PETERSON, 1967),'
45',7 RUNS /
COLORADO./ /
1970,3 RUNS, /
\ I
f '/ JAENICKE*. i
'.' &JUNGE*. \
k\
SEATTLE
•' // (1967) \ ,
' •• \
MPLS
(CLARK, 1965)
" 56 RUNS f f
''^•^(NOLL) V,' .-•'OKITA''..
is i ~-'-*^ i/'*' ' (1955)
i i t^wTnl -- T ill hTPt "I i i n nil i i i 11 ml 'J •
0.01
O.J
10
100
PARTICLE DIAMETER (Dq), micrometers
Figure 1. Comparison of volume distributions measured by several investigators
in different locations.1
10
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3.1.2 Physical State of Airborne Participate Matter
Airborne particles, a phrase that is used interchangeably with "ambient
aerosol," consist of both liquid and solid particles. Although these phrases
are not normally understood to encompass particles of pure water, fine particles
often serve as condensation or stabilizing nuclei and are associated mechanically
with rain, fog, mist, and hail.
Aqueous droplets of dissolved or hydrated gases or solids are included
conceptually within the definition of airborne particles. The fine particle
fraction, especially, may contain a substantial liquid component at normal
temperatures and humidities. Depending on the relative humidity, the liquid
content of the fine particle fraction will vary considerably; for example, 50
percent of the fine particle fraction is water at 80 percent relative humidity.
Many of the fine particles (0.1 to 2 urn) are hygroscopic and, in some
cases, deliquescent; and may change back and forth from the liquid to solid
state with changes in ambient humidity. Solution/solid droplets of this
nature include those of ammonium sulfate, sodium sulfate, sodium chloride, and
ammonium nitrate.
Other hygroscopic particles, while not undergoing a phase change, will
exhibit changes in size with changes in humidity. Examples are particulate
sulfuric acid, glycols, sugars, organic acids, and alcohols. Sulfuric acid
and ammonium bisulfate are aqueous solution droplets at all relative humid-
ities from 30 to 100 percent.
Because the true mass of aqueous particles is not detected by methods
which weigh or measure reflectance of filter-collected particle samples, water
is often exempted from mass measurements of particulates. Therefore, as noted
11
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above, measurements of airborne particles by these methods will underestimate
both the mass and content of aerosols containing, for example, aqueous solutions
or volatile or gaseous materials such as soluble organic compounds, nitric
2
acid, or ammonia. However, as noted above, the reverse error--the iji situ
formation of spurious particles on the collection filter due to chemical and
physical interaction of the filter with atmospheric gases—also occurs and
has been cited as a source of overestimation of the sulfate and nitrate content
3 4 50
of ambient particles. ' ' For example, two types of filters in common use
were reported to collect 10 to 20 times as much artifactual as ambient parti-
4
culate nitrate.
3.1.3. Primary and Secondary Airborne Particles
Primary particles are those that are emitted as such; secondary particles
are those formed in the atmosphere. Many of the ambient air particles are
"secondary" aerosols: particles which are formed from materials (such as
sulfur oxides and organic vapors) which are emitted as gases but which, upon
cooling or upon chemical reaction within the atmosphere, condense to form
particles. It has been estimated that secondary particles constitute as much
as one-half of urban aerosols and 25 percent of the particulate pollution in
the nation as a whole.
Primary particles (those emitted as particles) are both coarse and fine,
while most but not all secondary particles are in the "fine" size range.
3.2 CHEMICAL CHARACTERISTICS OF AIRBORNE PARTICLES
The specific chemical composition and characteristics of any atmospheric
aerosol sample will depend upon the sources of the particles and on any reac-
tion or selection that occurs during the residence time of the particle in the
12
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atmosphere. Ambient aerosols are typically mixtures of greatly diluted emissions
from numerous sources and are collected (or inhaled) after varying periods of
settling, atmospheric mixing, atmospheric chemical reactions, and exposure to
atmospheric humidity and washout. Therefore, the chemical characteristics of
different samples can be extremely variable and complex.
Some of the chemical characteristics of ambient particles which are
environmentally significant are composition, water solubility, acidity, hygro-
scopicity, deliquescence, efflorescence, and toxicity of both the atomic and
molecular components of the particle.
3.2.1 Composition
Chemical categories of airborne particles which are of particular concern
are toxic (including carcinogenic) organic compounds, inorganic fibers, toxic
metals, and inorganic acids. To a large extent, chemical analyses of aerosols
have determined atomic rather than molecular identities. A summary of the
composition of ambient aerosol samples determined by the National Air Sampling
fi-ft
Network is given in Table 1. It can be seen that, of the components
listed, sulfate is present in greatest amount, followed in order by nitrate
anion. Of the metals, average concentrations were highest for iron and lead.
Acidity of airborne particles derives primarily from the presence of
sulfuric acid, which is formed chiefly as secondary particles by oxidation of
emitted sulfur oxides. Nitric acid, which is also present, is generally in
the vapor state. Some of the sulfuric acid is neutralized by atmospheric
ammonia and other cations. Sometimes, however, it remains partially un-
neutralized even in the presence of more than enough ammonia for theoretical
g
neutralization. It has been hypothesized that coating of the acid particle;
by organic material protects them against neutralization.
13
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TABLE 1. GEOMETRIC MEAN* AND 90th PERCENTILE URBAN PARTICIPATE
CONCENTRATIONS IN THE UNITED STATES, 1971-1975
Pollutant
Suspended parti culates0
Fractions:
Nitrates6
Sul fates
Ammonium (salts)
Beryllium
Cadmium
Chromium
Cobalt
Copper
Iron
Lead
Manganese
Nickel
Titanium
Vanadium
Concentration, ug/r
Geometric mean 90th
-61
2.56
8.42
0.05
LD.f
L.D.
0.006
L.D.
0.114
1.18
0.86
0.03
L.D.
0.032
L.D.
n3
4.-i b
percent! le
-97
6.16
18.36
0.91
0.08
0.007
0.140
LD
0.37
2.32
1.78
0.92
0.034
0.08
0.07
Based on 50th percentile
90th percentile of quarterly composite measurements.
cRepresent 1792 sampling sites.
Represents 300 of the 1,792 Hi-Vol sampling sites.
ePossibly high by 70 to 90% due to artifacts.
L.D. - Less than discrimination limit.
14
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3.2.2 Composition as Related to Size
There are certain correlations between particle size and chemical com-
position, as indicated by the two summaries given in Table 2. Sulfate,
nitrate, elemental carbon, condensed organic vapors, ammonium ion, and lead
occur chiefly in the fine-particle fraction and make up the major part of that
fraction. In six U.S. cities, the mean diameter of particles containing
metals ranged from a low of 0.4 to 0.7 pm for lead and vanadium to a high of
2.4 to 3.5 urn for iron. Particle diameters for polycyclic organic matter were
found by another study to range from 0.3 to 0.5 pm.
Various metals, as indicated by Table 2, plus alkaline particles and
plant parts, occur chiefly in the coarse fraction. This fraction consists
largely of mechanically produced particles such as soil, road and tire dust,
and rock dust.
3.2.3 Effect of Sampling Method on Measured Particle Pollution --The two
classical and historically most significant approaches to measuring the mass
of airborne particles are based on gravimetric measurement of particles collected
on a filter (Hi-Vol Sampler) and on optical transmission or reflectance of
particles collected on filters (British Smoke Shade and AISI tape samplers).
The British Smoke Shade method* measures the degree of blackening of a filter
3
through which a low velocity (0.05 ft /min) stream of ambient air has been
drawn for a specified length of time. The mass of particles accumulated on
the filter is measured in terms of reflectance and converted to a mass basis
by means of a "standard smoke" calibration and ultimately reported in micrograms
per cubic meter.
The gravimetric method used most commonly in the United States has been
the High-Volume (Hi-Vol) Method. Particles from a high-velocity (40 to 60
*Hereinafter referred to as the Smoke Shade method.
15
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TABLE 2. CORRELATIONS OF CHEMICAL CONTENT WITH PARTICLE SIZE
a) Predominant Particle Size for Various Substances
Variable
Nickel
Tin
Vanadium
Antimony
Manganese
Zinc
Copper
Ammonium salts
Soot
b) Ratios of Element Distribution Between Fine and Coarse Particles
Normally fine
Sul fates
Organic (con-
densed vapors)
Lead
Arsenic
Selenium
Hydrogen ion
Normally coarse Normally bimodal
Iron Chloride
Calcium
Titanium Nitrate
Magnesium
Potassium
Phosphate
Silicon
Aluminum
20
(St. Louis Urban Aerosol, 18-day average, Aug.-Sept., 1975)
Predominantly fine
Element Fine/coarse
Predominantly coarse
Element Fine/coarse
Sulfur
Lead
8.90
3.67
Calcium
Silicon
Iron
Potassium
Titanium
0.09
0.13
0.29
0.33
0.55
16
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ft /min) ambient air stream are collected on a filter and weighed. Larger
particles, including blowing dust particles, can be entrained in the rapid air
stream and collected by this method. Therefore, except at very high levels of
fine particle pollution, and assuming constant sampler flow rate, measurements
of ambient particulate matter typically give higher values by Hi-Vol than by
the Smoke Shade method. The disparity is greatest at lower levels of parti-
culate pollution (when coarse particles represent a larger fraction of the
Hi-Vol sample). For example, an urban pollution Hi-Vol measurement of 200
3 3
pg/m was reported to correspond to a Smoke Shade reading of 100 ug/m , while
3 21
at 500 ug/m the two methods yielded approximately equal results. However,
with unusually dark particles, the Smoke Shade method can give values higher
22
than the corresponding gravimetric values. Markedly varying particulate
concentrations during the sampling period may result in Hi-Vol sample biases
because the collection efficiency decreases non-uniformly over the sampling
interval as more particles are deposited on the filter (Figure 2). Under-
estimation of particulate levels can result under conditions of constant TSP
levels (Figure 2A) and under conditions of increasing TSP levels (Figure 2B).
If particulate levels are declining (Figure 2C), an overestimation can result.
It should be kept in mind (1) that the Smoke Shade Method can under- or
overestimate the collected particulate matter depending upon whether the
particles are unusually optically light or dark since this method depends on
reflectance, whereas gravimetric methods are col or-independent; (2) that some
overestimation of particle mass by the Hi-Vol method will occur due to inter-
action of the acid gases (i.e., S02, N02, HN03) with the alkaline surface of
3 4
the glass fiber filter; ' and (3) that both methods will fail to adequately
quantify the mass of those particles that consist of air pollutants dissolved
or suspended in or on aqueous droplets.
17
-------
CONSTANT TSP WITH TIME
c
1
w"
«
ASSUMED AVERAGE FLOW RATE
-l/ZtQj + a,)
OVERESTIMATES FLOW
UNDERESTIMATES TSP
TSP
TIME
INCREASING TSP WITH TIME
c
1
co"
QC
O
u.
HIGHEST FLOW AT LOWEST TSP
LOWEST FLOW AT HIGHEST TSP
RESULT: UNDERESTIMATES TSP
TIME
DECREASING TSP WITH TIME
c
I
«n~
e
u
HIGHEST FLOW AT HIGHEST TSP
LOWEST FLOW AT LOWEST TSP
RESULT: OVERESTIMATES TSP
TIME
Figure 2. Estimation of TSP levels by the Hi-Vol method under varying
conditions of paniculate pollution.
18
-------
In addition to the above instruments that have been used routinely in the
United States and England for measuring the total mass of aerosols, impactors
afford the additional option of separating the airborne particles according to
size for subsequent chemical analysis. Impactors that separate aerosol particles
depend upon the relative balance between inertial and aerodynamic forces. In
the conventional type of aerosol impactor (e.g., cascade), an airstream turns
abruptly as it approaches a flat surface. Particles with the largest inertia
tend to maintain a straight trajectory and impact on the surface, whereas
smaller particles will follow the air streamlines and not be collected.
Inertial impactors such as these have been used extensively to collect air-
borne particles (e.g., CHESS data); however, difficulties with particle bounce,
reentrainment, and non-uniform deposition have limited their use. To reduce
particle bounce error the impaction surface may be coated with a non-volatile
grease; however, large weighing errors are often encountered using greased
surfaces. The problem inherent in collection by impaction onto surfaces is
eliminated by using a "virtual" impactor in which particles are impacted into
a slowly pumped void and in turn pulled onto a filter. The dichotomous "virtual"
85
impactor as described by Stevens and Dzubay was designed with an aerosol
inlet such that the instrument fractionated particles into <3.5 urn and >3.5 urn
with an upper limit of 20 urn. In order to provide a data base for evaluating
health effects of fine and inhalable particles, the dichotomous sampler and
the aerosol inlet were modified to give cut points of 2.5 urn and 15 urn, res-
pectively. These particles are to be collected from air samples and deposited
on Teflon filters with a 1.0 urn pore size. The monitoring network describing
the collection of these inhalable particles has been described by Rodes in
oc
an Environmental Science and Technology article by Miller.
19
-------
4. AEROSOLS: SOURCES AND CONCENTRATIONS
4.1 SOURCES AND EMISSIONS
4.1.1 Global
Particulate air pollution sources can be categorized as man-made or
natural. Man-made atmospheric particles are formed by condensation of emitted
gasses, by chemical reactions (including combustion), or by mechanical pul-
verization. Natural sources include such processes as volcanic action, ocean
spray, dusting of soil, forest fires, and the release of particulate organic
matter from vegetation. Reentrainment of dust originating from both natural
and man-made sources occurs when previously deposited particles are resuspended
by air movement or other processes.
Global estimates of particulate emissions are presented in Table 3 for
23
both man-made and natural sources. This estimate, as well as those by
24 25
Robinson and Robbins and Hidy and Brock show that on a global scale anthr-
opogenic particulate sources constitute from perhaps 5 percent to 50 percent
of the total, regardless of particle size and age. Such estimates of global
aerosol budgets include both primary and secondary particulate; however, they
do not distinguish between fine and coarse particles and cannot be applied
directly to urban regions. Most aerosol in urban regions is clearly dominated
by emissions from human activity, particularly by the production of sulfur
26
dioxide from the combustion of oil and coal. Miller et al. developed an
approach to an urban budget for the Los Angeles basin showing the relative
importance of human and naturally produced particulate matter, which includes
both primary and secondary particles.
20
-------
TABLE 3. GLOBAL ESTIMATES OF PARTICLES SMALLER THAN 20 urn
RADIUS EMITTED INTO OR FORMED IN THE ATMOSPHERE23
Type of particles Number in atmosphere,
109 kg/yr
Natural
Soil and rock debris3 100-500
Forest fires and slash-burning debris 3-150
Sea salt (300)
Volcanic debris 25-150
Particles formed from gaseous emissions
Sulfate from H2S 130-200
Ammonium salts from NH3 80-270
Nitrate from NO 60-430
Hydrocarbons from plant exudations 75-200
Subtotals 773-2,200
Manmade
Particles (direct emissions) 10-90
Particles formed from gaseous emissions
Sulfate from S02 130-200
Nitrate from NO 30-35
Hydrocarbons 15-90
Subtotal 185-415
TOTAL 958-2,616
alncludes unknown amounts of indirect man-made contributions.
21
-------
4.1.2 Nationwide
Table 4 provides historical data on nationwide estimates of total
27
participate emissions in the United States from 1940 to 1970. These data,
derived from major source categories of primary particles, indicate an average
increase of about 0.6 percent per year, from 20.7 to 24.6 million tons. This
represents an overall increase of approximately 18 percent attributed to
anthropogenic sources, primarily fuel combustion in stationary sources and
industrial process losses. Table 5 indicates that since 1970 estimated
emissions have decreased due to increased use of particulate control devices,
even though fuel use and industrial output have increased substantially.
Recent emission estimates, based on 1977 emission factors, show that total
emissions from transportation have essentially remained constant throughout
28
the 1970-1977 period. This constant trend is the net effect of the decrease
in the amount of particulate discharged per mile traveled (emission rates) and
the increase in vehicle miles traveled. In other source categories, namely
stationary fuel combustion and industrial processes, there were significant
downward trends of 33 percent and 54 percent, respectively.
Estimates for natural sources of particulate far outweigh those attribu-
ted to man on a global scale; however, on a nationwide basis estimates do not
include those particles that are formed in the atmosphere by photochemical
reactions, namely, secondary particles (e.g., sulfates). On a nationwide
basis the effective manmade impact of secondary particles is extremely
difficult to quantify.
4.1.3 Variation of Chemical Composition with Source
Although it is not generally possible to identify in detail the specific
sources of an ambient aerosol, there are characteristic chemical differences
22
-------
TABLE 4. NATIONWIDE ESTIMATES OF PARTICULATE EMISSIONS, 1940-19703
(10 tons/year)
Source category
Fuel combustion in
stationary sources
Transportation
Solid waste disposal
Industrial process
losses
Agricultural burning
Miscellaneous
Total
Total controllable
1940
9.6
0.4
0.4
8.8
1.6
6.4
27.1
20.7
1950
9.0
0.4
0.6
10.8
1.8
3.3
25.9
22.6
1960
7.6
0.5
1.0
11.9
2.1
2.1
25.3
23.2
1970
6.8
0.7
1.4
13.3
2.4
1.0
25.6
24.6
aBased on 1970 emission factors.
Miscellaneous sources not included.
23
-------
TABLE 5. RECENT NATIONWIDE EMISSION ESTIMATES 1970-1977
(10 metric tons/yr, expressed as TSP)
ro
Source Category
TRANSPORTATION
Highway vehicles
Nonhighway vehicles
STATIONARY FUEL COMBUSTION
Electric utilities
Industrial
Residential, commercial
and institutional
INDUSTRIAL PROCESSES
Chemicals
Petroleum refining
Metals
Mineral products
Oil and gas production
and marketing
Industrial organic
solvent use
Other processes
SOLID WASTE DISPOSAL
MISCELLANEOUS
Forest wildfires, and
managed burning
Agricultural burning
Coal refuse burning
Structural fires
Miscellaneous organic
solvent use
TOTALS:
1970
1.2
0.7
0.5
7.1
4.1
2.6
0.4
11.9
0.3
0.1
2.1
7.8
0
0
1.6
1.1
0.9
0.5
0.3
0.1
0
0
22.2
1971
1.1
0.7
0.4
6.6
4.0
2.2
0.4
11.3
0.2
0.1
1.9
7.4
0
0
1.7
0.8
1.1
0.7
0.2
0.1
0.1
0
20.9
1972
1.2
0.8
0.4
6.4
4.1
2.0
0.3
10.6
0.2
0.1
1.9
6.9
0
0
1.5
0.7
0.7
0.5
0.1
0
0.1
0
19.6
1973
1.2
0.8
0.4
6.5
4.4
1.8
0.3
10.3
0.2
0.1
2.1
6.4
0
0
1.5
0.6
0.6
0.4
0.1
0
0.1
0
19.2
1974
1.2
0.8
0.4
5.6
3.8
1.5
0.3
8.9
0.2
0.1
1.9
5.5
0
0
1.2
0.6
0.7
0.5
0.1
0
0.1
0
17.0
1975
1.1
0.8
0.3
5.0
3.7
1.1
0.2
6.5
0.2
0.1
1.4
3.7
0
0
1-1
0.5
0.6
0.4
0.1
0
0.1
0
13.7
1976
1.1
0.8
0.3
4.6
3.3
1.1
0.2
6.2
0.2
0.1
1.5
3.2
0
0
1.2
0.5
0.8
0.6
0.1
0
0.1
0
13.2
1977
1.1
0.8
0.3
4.8
3.4
1.2
0.2
5.4
0.2
0.1
1.3
2.7
0
0
1.1
0.4
0.7
0.5
0.1
0
0.1
0
12.4
NOTE: A zero in this table indicates emissions of less than 50,000 metric tons/yr.
-------
in emissions from different sources. Some of these chemical entities are
summarized in Table 6, which includes the results of rough emission estimates
from a number of reports.
Mobile sources are the major emitters of airborne lead (88 percent of
29
total lead emissions), most of it as chlorides and bromides. Vehicles are
also responsible for 38 percent of total anthropogenic hydrocarbon emissions,
some of which are particulate or form secondary particles. Mobile sources
31
release less than 2 percent of the sulfur oxides emitted.
Stationary fuel combustion sources emit particles containing a number of
substances of concern, including polycyclic organic matter (POM) and other
organic material, carbon (soot, which is mainly of health significance because
of its surface catalytic and adsorptive properties in relation to other pollu-
tants), and certain metals. These sources also emit 81 percent of the national
sulfur oxide emissions, most of which are assumed to be converted to particles.
Eighty percent of benzo(a)pyrene* emissions were estimated to come from coal
combustion, as compared to only 4 percent from stationary oil burning and 2
32
percent from mobile sources. Coal combustion emissions are also distinguished
33
by the fact that they include 88 percent of the nationwide beryllium emissions-
Stationary oil combustion, on the other hand, generates 83 percent of nickel
and 90 percent of vanadium emissions. Therefore, it would appear that except
in the vicinity of atypical local sources, four metals can serve as virtual
identifying markers for combustion-linked airborne particles: lead for mobile
sources, beryllium for coal, and nickel and vanadium for oil. Such source-
characteristic differences have been used in the chemical balance method to
*Benzo-a-pyrene (BaP) emissions are virtually all in the particulate state
after cooling to atmospheric temperature.
25
-------
TABLE 6. EMISSION ESTIMATES FOR MAJOR SOURCES OF CERTAIN.AIRBORNE PARTICLES
Pollutant
Smelting,
Mobile metal-
sources lurgical
Stationary
combustion, Total emissions
Coal Oil Other
Year
Tons
% of total
Particles3 4
a h
SO a'D 2
X
NO a 35
X
Hydrocarbons3' 59
e f
Benzo(a)pyrene ' 2
Metals9
Beryllium
Cadmium
Chromium
Copper
Manganese
Nickel
Lead 88-93
Titanium
Vanadium
emissions
36
13
<1
<1
3
43
68
84
74
11
2
1
of pollutant
32 2
60 13
19 7 22C
<1 <1 27d
80 4
88 6
52h
9 10J
7
11
83
83 101
9 90
1972
1972
1972
1972
1975
1970
1970
1970
1970
1970
1970
1970
1970
1970
19.8 x 106
c.
33.2 x 10°
24.6 x 106
27.8 x 106
978
170
2,200
17,000
14,000
18,000
7,300
230,000
52,800
20,000
*Ref. 3.4, Tables 4.1 and 4.2.
Emitted chiefly as gases but with substantial conversion to secondary particles.
.Other stationary fuel combustion.
Evaporated solvents.
fValues stated by authors to be only approximate.
TRef. 41.
9Ref. 33, Table 1.
•Incineration of radiators and plated metal.
•Pigment production and use.
'•'Refractory production.
26
-------
prepare an emission inventory for particles collected in the Los Angeles
area.5'35
Noncombustion stationary source emissions have identifiable components
that are characteristic of the processes involved. Thus, sulfuric acid plants
emit sulfuric acid mist; emissions from an open hearth furnace have been found
to be 89 percent iron oxide; particles from cement plants are chiefly calcium
oxide and calcium carbonate. Smelters and other metallurgical processes emit
metal-containing particles, including 84 percent of the nation's total copper
33
emissions; particles with a high proportion of bio-organic materials are
emitted by such sources as flour mills, grain elevators, and paper/pulp mills;
and aerosols collected near the sea will include substantial fractions of sea
salts.
4.2 TRANSFORMATION AND TRANSPORT
The makeup of a mixture of particles changes with time after emission.
Insofar as elapsed time is correlated with distance from the source, these
changes will be reflected in the changes with distance. The most significant
transformations with time and distance are: (1) Condensation of vapors to
form secondary particles (which produces high concentrations, near the point
of emission, of particles less than 0.1 urn diameter); (2) particle coagulation
and growth (particle interactions occurring very rapidly to produce larger
particles from the condensation particles in the "accumulation mode" (0.1 to 2
urn) which persist in the atmosphere for days and for great distances); (3)
chemic.al transformations such as oxidation of sulfur oxides and photochemical
smog formation (occurring relatively slowly, so that products of these reactions
are higher at moderate distances than at the site of emission); and (4) fallout,
27
-------
rainout, and other removal mechanisms (which cause a steady decrease in
particle mass and in mean particle diameter with increasing time and distance).
•>c
Long-range transport of sulfate and other inorganic compounds as well
37
as of polycyclic aromatic hydrocarbons has been reported. Even coarse
particles can be transported over long distances if they are injected above
the atmospheric mixing layer as by volcanoes or by air mass movements over dry
deserts. These processes of aerosol transformation and transport are described
50
in detail in Airborne Particles. Their net effect is that at increasing
distances from the source, the aerosol concentration decreases and is increasingly
dominated by accumulation mode particles with a mean diameter in the range of
0.4 to 1 urn, the nuclei having been removed by coagulation and the coarse
particles by sedimentation.
4.3 CONCENTRATIONS
4.3.1 Trends in Airborne Particle Pollution
The routine episodes of high levels of visible smoke pollution which
characterized wintertime in some U.S. cities before World War II no longer
occur. The extensive replacement of coal as a home-heating fuel and the
enforcement of local smoke emission ordinances brought about gradual decreases
from the earlier high levels of urban smoke pollution, whether from coal or
other fuels. Since the passage of the Clean Air Act of 1970 and promulga-
o
tion of the ambient air quality standards for TSP (primary, 75 ug/m ) and
several other pollutants, particulate emissions are being further reduced.
Seventy-two percent of the sites monitored showed lower airborne particle
concentrations in 1976 than in 1970. Improvement has been more marked in the
Northeast and Great Lakes regions than in the western areas of the country
28
-------
where windblown dust is often a significant aerosol constituent. The general
pattern of change between 1970 and 1976 was little change at sites where 1970
concentrations were low and improvements at sites with higher 1970 concentrations.
At 53 percent of the sites, concentrations in 1976 were greater than
those of 1975. The areas showing this reversal of the previous downward trend
were generally in the Southeast, Midwest, and West. These same areas had dry
soil conditions in 1976 due to the drought experienced by large areas of the
country at that time. It has been suggested that the resultant increase in
38
wind-blown dust was the reason for most of the increase in 1976 TSP levels.
Nationwide trends in total suspended particulate pollution are summarized for
1970-1977 in Table 5.
The gradual decrease shown by TSP data gathered at 17 of the National Air
Surveillance Network (NASN) stations during the period 1966 to 1977 is shown
in Figure 3.
The TSP curves of Figure 3 are not representative of every component of
airborne particulate matter. A recent analysis of BaP trends during the
10-year period of 1966 to 1975 was based upon 34 urban (24 coke ovens) and 3
rural sites. These trends for the urban sites (Figure 4) are consistent with
previous results indicating a steady decline of BaP.
Table 7 shows the trends of atmospheric trace metal levels in U.S. urban
areas from 1965 to 1974.33
Prominent among the metals showing a decline are vanadium, manganese, and
nickel. Nationwide lead averages have declined since 1972 because of the
lower lead content of gasolines sold in recent years.
29
-------
HIGHEST VALUES:
.227 182 306 213 183 151 144 121 158 119 100 123
100
"I
§
111
o
o
o
0.
90
80
70
60 -
LOWEST VALUES:
25 22 25 21
1966
76
Figure 3. TSP annual means at 17 urban NASN stations.
NOTE: TSP means (EPA data) from all of those stations for which
data were available for each of the years 1966-1977 were
used to derive the composite averages shown. Stations
included were Grand Canyon Nat. Park, Honolulu, Chicago,
Indianapolis, New Orleans. Arcadia Nat. Park, Baltimore,
Detroit, Cleveland, Toledo, Youngstown, Pittsburgh, Houston,
Norfolk, Shenandoah Nat. Park. Seattle, and Charleston.
30
-------
m
4
c
UJ
o
u
10
I I
90 PERCENT! LE
OF QUARTERLY MEASUREMENTS
50 PERCENT)LE
_ OF QUARTERLY MEASUREMENTS^
I
1966 67
68
69 70
TIME, year
71
72 73
74
75
Figure 4. Benzolalpyrene seasonality and trends (1966 to 1975) in the 50th
and 90th percentita for 34 NASN urban sites.63
31
-------
TABLE 7. TRENDS IN URBAN METAL CONCENTRATIONS AND
THEIR POSSIBLE CAUSES33
Metal
Observed trends
Possible causes
Fuel-Combustion-Related Metals
Beryllium
Lead
Nickel
Titanium
Vanadium
Industry-Related Metals
Cadmium
Chromium
Cobalt
Copper
Iron
Manganese
Unknown
Down last 5 years
Down
Up
Down
Down
No trend
Unknown
No trend
Down
Down
Lower lead content in gasolines
after 1969
Reduction of Ni in residual oils
Increasing use of coal in
electric utilities
Reduction of V in residual oils
Controls in metal industry
and improved incineration
practices
Unknown
Contamination from hi-vol
commutator
Improved incineration or
waste burning practices, fuel
switching, controls in steel
industry
Controls in metals industry
32
-------
4.3.2 Comparative Exposure to Airborne Particles
4.3.2.1 Urban Versus Rural Exposures
The generally higher exposures of urban residents to airborne particles
is one illustration of the impact of source proximity. For example, data from
the National Air Sampling Network in 1970 show that the mean annual average
benzo(a)pyrene concentration was 1.9 ng/m (range 0.1 to 19.3) at 120 urban
31
stations versus 0.2 (range 0.1 to 0.4) for 20 nonurban stations.
Such urban/rural differentials also exist for other constituents of
airborne particles. The urban/suburban ratios for 22 trace elements in air of
the Cleveland area are shown in Table 8. The median ratio is 2.2 and in no
case did the suburban exceed the urban concentration.
Other comparisons of urban and nonurban aerosol exposures and the apparent
effects of their differences on disease and death rates are presented and
discussed in Airborne Particles.
4.3.2.2 Indoor Versus Outdoor Residential Exposures
Because there is continual air exchange between interiors and exteriors
of homes, outdoor aerosols—particularly the fine particles—will be included
among the indoor airborne particles. However, this exchange also serves to
dissipate airborne particles generated by indoor sources. Indoor sources
include combustion processes such as those of cigarettes, furnaces, fireplaces,
and stoves, and aerosol dispensers of consumer products. Although indoor
concentrations of airborne particles, in the absence of smokers, are believed
to be usually less than those outdoors, some studies have found higher indoor
levels. It is recognized that the current emphasis upon improved insulation
and weatherstripping for homes as an energy conservation measure could have
either beneficial or adverse effects on indoor air quality, depending on
33
-------
TABLE 8. RATIOS OF URBAN (U) TO SUBURBAN (S) CONCENTRATIONS IN AIR,
CLEVELAND, OHIO AREA36
Element U/S
Element U/S
Element
U/S
Antimony
Chloride
Beryllium
Chromium
Cobalt
Bismuth
6.9
6.5
6.1
5.6
3.4
3.3
Mercury
Iron
Cadmium
Sodium
Magnesium
Manganese
Calcium
3.0
2.8
2.5
2.4
2.4
2.2
2.0
Silicon, tin
Copper, vanadium
Aluminum
Zinc
Arsenic
Selenium
Bromide
1.8
1.8
1.7
1.6
1.4
1.3
1.2
X = 2.8
34
-------
whether, as a consequence, the indoor air is more or less polluted than the
outdoor air.
39-41
Three documents recently prepared for EPA specifically address the
problem of indoor air pollution, including indoor airborne particles. Because
it is now known that indoor airborne particle concentrations sometimes are
higher than the limits allowed outdoors by the ambient air quality standard
while simultaneous outdoor concentrations are not, and because most individuals
are exposed for longer periods each day to indoor than to outdoor environments,
there is increasing concern as to the health impact of air quality in non-occupa-
tional indoor environments. Accordingly, it has been recommended that further
monitoring of indoor air quality should be carried out and that epidemiological
studies of relationships between indoor air pollution and health effects be
40
conducted. Some health studies such as the Harvard Air Pollution Health
52
Study, are already incorporating indoor monitoring.
4.3.2.3 Environmental Versus Occupational Exposures
In some occupational environments, the airborne particle concentration
greatly exceeds that of the external environment. Examples are workplaces
such as textile and paper mills, steel works, smelters, metallurgical processing
plants, coke ovens, and mines.
These high occupational exposures frequently involve exposure to higher
proportions of coarse particles than found in environmental exposures. They
are of some importance to evaluating effects of particles because they may
modify the response of an individual to airborne environmental pollution, and
because they are the source of much of our information concerning the health
effects of airborne particles.
35
-------
5. EFFECTS OF AliBME PSASfflClES «WI WRN
5.1 DEPOSITION OF AIRBORNE PARTICLES IN THE UING
Adverse health effects of airfronrae partiieiuilaibe matter ffioflHiow rd
of the particles in the respiratory tract, lira imam., Dhe mespfitnatery tbracit
-------
of the human respiratory system. The analysis also recommended that a second
particle size cut-point of <2.5 urn diameter be incorporated in the air sampling
devices, based upon considerations of the chemical composition and the size
distribution of airborne particles and on the predominant penetration of
particles <2.5 urn diameter into the gas-exchange region of the respiratory
tract. This analysis pointed out that data collected in this size range could
be used in conjuction with epidemiological health parameters to refine an
inhaled particulate standard in the future.
5.2 HEALTH EFFECTS OF GENERAL AIRBORNE PARTICLE POLLUTION
3
The present primary ambient air quality standard of 75 ug/m for particulate
matter is required on an annual basis for the protection of public health. In
the NAS document entitled Airborne Particles, scientific information concerning
the health effects of airborne particles is described. A more concise review
43
by one of the contributors to that volume has also been published. Tabular
summaries of evidence presented by different workers for particular health
44
effects are provided in the statement by the American Thoracic Society and
in Airborne Particles.
Exposure to airborne particles as it actually occurs almost always is
accompanied by simultaneous exposure to other air pollutants and to other
environmental chemicals. Although there is a tendency to regard these other
pollutants as merely obstructing the view of the scientist seeking to detect
the true effect of one particular pollutant, it must be kept in mind that the
other pollutants are probably modifying the "true" effect of the pollutant
studied and that the observed responses to the mixed but real exposure condi-
tions are the ones that are relevant to human health. As an example, where
37
-------
airborne particle pollution is coincident with sulfur oxides pollution, it is
desirable to evaluate the health effect of these pollutants jointly.
There are indications that particles contribute more heavily than sulfur
dioxide does to the health effects of this combination. For example, health
indices in London have improved during a period (1950-1970) in which particulate
pollution declined greatly along with a smaller reduction in sulfur dioxide.
In any case, there is good evidence that excessive airborne particle/SOp
pollution does cause illness and death, as well as increased prevalence,
incidence, and severity of respiratory disease and symptoms. Incidence and
progression of bronchitis and emphysema have been especially clearly linked to
such pollution. The effects are most evident in the oldest and youngest age
groups and in those people who are sick. There is also evidence of delayed
appearance and of long-term persistence of the adverse effects of airborne
particle exposures.
The fact that urban residence is associated with increased incidence of
45
cancer and that mutagenic (Ames-test positive) components are extractable
46-49
from urban airborne particles suggest the possibility that airborne
particles are also to some degree carcinogenic.
Table 9 provides estimated concentrations of particulates and sulfur
50
dioxide that may affect health. Estimates of adverse health effects attribut-
able to sulfur dioxide, particulate sulfates, and total suspended particulates
(TSP) are presented for short-term and long-term exposures, respectively, in
Tables 10 and 11, reproduced from Airborne Particles. Additional discussion
of the evidence concerning this dose-response relationship is contained in
Airborne Particles.
38
-------
TABLE 9. HEALTH EFFECTS AND DOSE/RESPONSE RELATIONSHIPS FOR PARTICULATES AND SULFUR DIOXIDE
Averaging time
for pollution
measurements
24 hour
Weekly mean
6 Winter months
Annual
Place
London
New York
City
Chicago
New York
City
Birmingham
New York
London
Britain
Britain
Buffalo
Berlin
Particles,
mg/m3
2.00
0.75
0.50
6 COHSa
3 COHS
Not stated
0.145 (+?)
0.18-0.22
2.5 COHS
0.20
0.20
0.07
0.10
0.10
0.08
0.18
S02
mg/m3
1.04
0.71
0.50
0.50
0.70
0.70
0.286
0.026
0.52
0.40
0.20
0.09
0.10
0.12
0.45b
0.73C
Effect
Mortality
Mortality
Exacerbation of bronchitis
Mortality
Morbidity
Exacerbations of bronchitis
Increased prevalence of respiratory symptoms
Increased prevalence of respiratory symptoms
Mortality
Increased prevalence or incidence of
respiratory illness
Bronchitis sickness absence from work
Lower respiratory infection in
in children
Bronchitis prevalence
Respiratory symptoms and lung func-
tion in children
Mortality
Decreased lung function
Reference
88
97
97
94
93
89
95
95
92
87
101
90
96
99-100
102-103
91
^Coefficient of Haze Units.
Dmg S03/cm2/30 days.
cmg S03/100 cm2/day.
-------
TABLE 10. THRESHOLD ESTIMATES FOR ADVERSE HEALTH EFFECTS ATTRIBUTABLE TO SULFUR DIOXIDE, PARTICULATE
SULFATE, AND TOTAL SUSPENDED PARTICULATES (TSP), SHORT-TERM EXPOSURES
Exoosure level . ua/m3
Adverse effect Research
human health approach
Mortality Epidemiology
Aggravation Epidemiology
of chronic
lung disease
Aggravation Epidemiology
of asthma
-t»
o
Aggravation of Epidemiology
combined
heart and
lung disease
Irritation of Epidemiology
respiratory
tract
Type of
estimate
Worst case
Least case
Best judgment
Worst case
Least case
Best judgment
Worst case
Least case
Best judgment
Worst case
Least case
Best judgment
Worst case
Least case
Point est
S02
30
500
300-400
119
500
365
23
>365
180-250
180
>365
365-500
340
340
340
Parti cu late
sulfate
No data
No data
No data
6
No effect
10
6
10
8-10
6
10-17
8-10
No data
No data
No data
TSP
250
500
250-300
100
>250
>250
75
>260
100
61
260
70-100
170
192
170
Safety margin, % contained
in primary standard
S02 std.
Duration 365 M9/1"3
24 hr
24 hr
24 hr
24 hr
24 hr
24 hr
24 hr
24 hr Less
24 hr
24hr
24hr Less
24 hr
2-3 days
2-3 days
2-3 days
0
37
0-9
0
37
0-37
0
than 100
0
0
than 100
0-37
0
0
0
Suspended
sulfates
(no std.)
No data
No data
No data
No data
No data
0
0
0
0
0
0
0
No data
No data
No data
TSP std.
260 ug/m3
0
92
0-15
0
Less than
0
0
Less than
0
0
Less than
0
0
0
0
100
100
100
Safety Margin = Effects threshold minus standard divided by standard x 100.
-------
TABLE 11. THRESHOLD ESTIMATES FOR ADVERSE HEALTH EFFECTS ATTRIBUTABLE TO SULFUR DIOXIDE
PARTICULATE SULFATES, AND TOTAL SUSPENDED PARTICULATES (TSP), LONG-TERM EXPOSURES
Fxnosurp IPVP!. un/m3
Adverse effect Research
human health approach
Excess Epidemiology
mortality
Increase in Epidemiology
prevalence
of chronic
bronchitis
Increased fre- Epidemiology
quency or
severity of
acute respi-
ratory ill-
ness in
otherwise
healthy
families
Increase in Epidemiology
family ill-
ness during
influenza
epidemics
Type of
estimate
Worst case
Least case
Best judgment
Worst case
Least case
Best judgment
Worst case
Least case
Best judgment
Worst case
Least case
Best judgment
S02
120-198
250
250
50-90
404
95
91
200
91
106
250
106
Suspended
sulfate
No data
No data
No data
96
20
14
9
23
9
14
18
14
TSP
135
175
175
60-100
180
100
75
200
100
126
151
151
Duration,
years
Unknown
Unknown
Unknown
3
12
5
1
3
3
1
Unknown
3
Safety margin, % contained
in primary standard
S02 std.
80 ug/m3
50-148
212
212
0-12
405
19
14
250
14
33
212
33
suspended
sul fates
(no std.)
0
0
0
0
0
0
0
0
0
0
0
0
TSP std.
75 (jg/m3
80
133
133
0-33
140
33
0
167
33
68
101
101
-------
TABLE 11 (continued).
Adverse effect Research
human health approach
Increased Epidemiology
lower
respiratory
tract infec-
tions in asth-
matics
Subtle de- Epidemiology
crease in
ventilatory
function
Type of
estimate
Worst case
Least case
Best judgment
Worst case
Least case
Best judgment
Exposure level, pg/m3
S02
32
186
91
118-131
400-500
200
Suspended
sulfate
8
20
8
9
28
11
TSP
100
No
100
75-141
200
100
Safety margin, % contained
in primary standard
Duration,
years
Unknown
Unknown
Unknown
1
9
8-9
S02 std.
80 ug/m3
0
133
14
48-64
400-525
150
Suspended
sul fates
(no std.)
0
0
0
0
0
0
TSP std.
75 ug/m3
33
—
33
0-88
167
33
Safety Margin = Effects threshold minus standard divided by standard x 100.
-------
The severity of the health effects at any given airborne particle concen-
tration and the lowest pollution level requirecTto evoke significant adverse
health effects in the most sensitive populations are not eas-ily determined.
With so many factors determining exposures (Table 12) and with so many variables
influencing the response to a given exposure, any epidemiological study of
dose/response relationships must necessarily cope with uncertainties in both
the dose and response functions. Therefore, there is some disagreement among
scientists as to the level at which airborne particle pollution becomes hazardous.
The conclusions of many of the studies cited in Tables 9-11 have been
51 ' ' " '•
questioned by Bennett et al. (report prepared for the American Iron and—
Steel Institute) generally on the basis of the fact that one or more relevant
variables were uncontrolled. The extent to which the correlations of health
effects with pollution indicated by such studies should be discredited must
remain a matter of judgment. As is apparent from the above mentioned tabulation
of related variables, it can be expected that there will be some uncontrolled
variabTes in any epidemioTogic study of the health effects of air pollution.
In addition to differing judgments as to the reliance that can be placed
on various studies with their varying levels of imperfection, there are also
sometimes differences of opinion as to how even such information as is avail-
able in a given study should be interpreted.
In addition to variations in the design and interpretation of various
studies, other factors also undermine precise assessment of the epidemio-
logical evidence. These include differences in methodology of airborne parti-
cle measurement; the possibility that health effects of exposure to air pollu-
tion may not appear or may persist until many years later; the high mobility
of the Aaerican population that causes the enviroment of a given population to- w*
be only partially representative' of exposure of that population; the changing
43
-------
TABLE 12. VARIABLES RELATED TO THE HEALTH EFFECTS OF AIRBORNE PARTICLES
Exposure factors
Response factors
Incidental factors
(Linkage factors )
1. Emissions (kind and amount)
2. Synergistic combinations
3. Topography
4. Climate, weather, humidity
5. Seasonal and diurnal changes
6. Place of residence
7. Occupation
8. Duration of exposure
9. Smoking (active and passive)
10. Physical activity
11. Breathing mode (mouth or nose)
1. Temperature
2. Physical condition
3. Concurrent disease
4. Nutritional status?
5. Prior exposure
6. Smoking history
7. Age
1. Income
2. Education
3. Social class
4. Raceb
5. Sexb
6. Sanitation
7. Health insurance
(Exp. No. 6 - 10)
(Exp. No. 6 - 10)
(Exp. No. 6 - 10)
(Exp. No. 6 - 10)
(Exp. No. 7,9,10)
(Resp. No. 2,3)
(Resp. No. 2-4)
8. Access to medical care (Resp. No. 2-4)
(Resp. No. 3, Exp. No. 6)
9. Population density
10. Ageb
(Resp. No. 2,5)
Causal exposure or response factors, through which incidental factor
may be linked to health effects of air pollution.
3Somewhat uncertain.
-------
pattern and nature of air pollution; and changing social and behavioral pat-
terns which modify the impact of such variables as race, sex, and smoking.
5.3 CONDITIONS WHICH MAY POTENTIATE HEALTH EFFECTS OF AIRBORNE PARTICLES
Associations between the health effects of airborne particles and corre-
lated variables can be categorized as three types. A number of variables
(which we will call exposure factors) can be assumed to influence causally the
extent of exposure to airborne particle pollution; variables of a second type
(response factors) directly 'influence the response of an exposed person to a
given exposure; and variables of the third type (incidental factors), while
correlated with pollution-related morbidity and mortality, are assumed to be
non-causally linked to health effects through association with one or more of
the exposure or response factors. Examples of some variables of each type are
shown in Table 12.
The factors listed in Column 1 of Table 12 directly determine the exposure
of a particular person to airborne particles. They include the nature and
amount of pollutants emitted (No. 1-2), the geographic and atmospheric factors
that determine the extent to which pollutants will accumulate in or be removed
from the ambient air (No. 3-5), and the individual determinants that vary with
personal behavior or circumstance (No. 6-11).
Some of these variables have been discussed in Sections 6.2 and 6.3.
A second category of factors (Column 2) will determine the response of
each individual to a given level of airborne particle pollution. These
response factors include external potentiating variables, such as temperature,
and physiological factors.
Since low temperature alone can cause increased mortality in the elderly,
low temperature may increase the vulnerability of the old or sick to superimposed
45
-------
air pollution exposure. Studies have shown correlations of low temperature
with airway resistance and with symptoms exhibited during air pollution
50
episodes by bronchitis patients. However, the extent to which the health
effects of temperature and of air pollution are independent or interacting is
not clear.
The physiological factors named in Column 2 (items 2 through 7) all
relate to general physical condition and therefore to the capacity of the
individual to resist pollution-imposed stress. There is abundant documentation
to show that people with concurrent respiratory disease are especially vulnerable
to air pollution and that, conversely, air pollution has decided impact on the
incidence of respiratory disease. Many epidemiologic studies have taken
advantage of these relationships by monitoring the symptomatic reaction of
respiratory disease patients or the prevalence of respiratory disease during
air pollution episodes. The quantitative aspects of these correlations,
especially the minimal level of air pollution likely to evoke an adverse
respiratory response, are still under debate.
The different responses of different age groups to air pollution are also
well documented. Although the increased vulnerability of the elderly to air
pollution may be in part related to increased cumulative exposures to prior
air pollution, it is presumably chiefly due to the decreased physical fitness
in older age groups with resultant increases in susceptibility both in disease
and to air pollution. There is also evidence that children and especially
50
infants are also more vulnerable to air pollution.
The third column of Table 12 lists some incidental factors: variables
which appear to be correlated with pollution-related morbidity or mortality
46
-------
but which are categorized here as being thus linked only indirectly, through
one or more of the more direct exposure or response factors. Possible
causal linkages are indicated in Column 4. We have suggested that factors 1-5
can most reasonably be assumed to be linked through exposure factors while
correlations of 6-10 with health effects seem more likely to be mediated by
response factors.
The linkage of income level, for example, with pollution-related health
effects can reasonably be seen as due to the decreased occupational and residen-
tial exposures to air pollution which increased income can command. Protec-
tive effects related to education, race, social class, and sex are also postu-
lated to be mediated chiefly through variations in exposure. Such categoriza-
tion of race and sex as indirect or non-causal factors is somewhat uncertain.
However, there is no clear evidence of direct effects of these variables on
response to air pollution unmediated by other exposure or response factors.
5.4 HEALTH EFFECTS OF SPECIFIC CHEMICAL COMPOUNDS
Airborne particles can be of health significance because some of their
chemical components are potentially toxic per se and also because less hazard-
ous particles, on interaction with other air pollutants or constituents, can
be transformed into more hazardous ones.
5.4.1 Intrinsically Injurious Particles
A given inhaled particle may exert an adverse health effect either through
chronic local tissue damage by an insoluble particle deposited in the deep
lung or through solution and absorption of toxic components of the particle.
Detailed understanding of the active agents and mechanisms which produce the
adverse health effects is still largely non-existent. However, several chemical
47
-------
components of the ambient aerosol are known or suspected to be contributors to
these effects, either because of epidemiological observations or because of
other information available from experimental, occupational, or clinical
studies.
5.4.1.1 Fibers—Asbestos was first recognized as an occupational health
hazard responsible for the condition known as pulmonary asbestosis and later
as an occupational carcinogen when retrospective epidemiological studies
showed that occupational exposure is strongly associated with malignancy of
the lung, pleura, peritoneum, and gastrointestinal tract. The effects typically
become manifest 20 or more years after exposure. There is increasing evidence
that the general population may also suffer from inhalation exposure to asbestos,
since asbestos fibers are found in the ambient air and pulmonary asbestos
bodies are found in post-mortem examination of a large proportion of urban
54
residents. To protect the general population from exposure to high ambient
levels of asbestos, the EPA promulgated an emission standard in 1973 which
curtailed asbestos emissions from specific industries. The projected total
reduction by 1977 from implementation of the standard was 93 percent.
5.4.1.2 Toxic Metals--Several metals which are known to be associated with
airborne particles and which are known to be toxic are of concern.
Lead is the air pollutant metal which, on a nationwide basis, is believed
to pose the greatest hazard. Airborne lead, at least 88 percent of which is
from combustion of leaded gasoline, has been associated with increased lead
29
concentrations in the blood of children and adults. Primary exposure to
airborne lead occurs from inhalation, while secondary exposure may occur
through ingestion of foods and nonfood items which are contaminated by airborne
lead. In people, lead affects the erythrocytes, the central and peripheral
48
-------
nervous systems, soft tissues (kidney, liver), and bone. The latter sequesters
95 percent of the body burden of lead. Irreversible brain damage is one of
the observed effects of overt lead poisoning in infants and children.
Biological effects which have been correlated with blood lead levels
include elevated erythrocyte protoporphyrin and mild anemia (15 to 40 ug of
lead/dl blood), peripheral nervous disorders and central nervous system damage
(50 to 60 |jg/dl), and severe neuro-behavioral impairment (80 to 120 ug/dl),
sometimes resulting in convulsions and death. The minimum "safe" level of
exposure to lead, as manifested by blood lead levels, is apparently variable
among individuals. Formerly, blood lead concentrations less than 40 ug/dl
were considered harmless. However, it has now been documented that hemato-
29
logical effects do occur at lead concentrations as low as 10 ug/dl.
Association of relatively low (<40 ug/dl) blood lead levels with learning
deficits and with lower IQ scores has also been reported. It is apparent
that current airborne lead levels may be having undetected but quite serious
effects on young urban residents. (NASN data for 1974 indicate that lead
concentrations were less than 0.5 ug/m at all nonurban stations but were 1.0
or higher at 32 percent of the urban stations.) Concern about the effects of
airborne lead has prompted the EPA to propose and promulgate an air quality
standard for lead based on health considerations. The present lead standard
3
(1.5 ug/m averaged over a calendar quarter) has as its goal a population mean
blood lead level of 15 ug/dl or less among children who do not receive signi-
ficant exposure to lead-based paints. Such an average would ensure blood lead
levels not exceeding 30 |jg/dl for 99 percent of such children.
Mercury is a highly toxic metal which occurs in air both as particles and
vapor. Toxicity is due to accumulation in nerve tissue which ultimately can
49
-------
lead to insomnia, loss of memory, and severe neurobehavioral and personality
changes. Children and the fetus are the most susceptible to mercury poisoning.
Release of mercury into the atmosphere from natural sources far outweighs the .
release from the major man-made source, coal combustion. On the average, the
ambient concentrations in the large industrial cities are well below the 1
ug/m level, and toxic airborne exposures are unlikely except in the vicinity
of point sources.
Cadmium accumulates in the body, especially in the kidney, where it has a
very long biological half-life. Cadmium dust, when inhaled at high concentra-
tions, can lead to severe kidney and lung damage. In view of the cumulative
nature of this metal and of the resulting health effects, it seems appropriate
to minimize the exposure of the general population. The average concentration
o
in the ambient air is extremely low (approximately 0.002 |jg/m ) but may reach
3 57
levels of 0.3 ug/m near industrial point sources such as smelters. The-EPA
is presently evaluating what type of regulatory action, if any, is needed to
protect public health.
Arsenic is emitted mainly by metal smelters, coal combustion facilities,
and the pesticide industry. In air, arsenic occurs mainly in particulate
form. Approximately 80 percent of absorbed arsenic is retained and widely
distributed in the tissues. Arsenic may cause both acute and chronic poisoning,
but acute poisoning is rare. Both subacute and chronic poisoning can result
from polluted air. Effects of arsenic poisoning include skin and mucous
membrane abnormalities, gastrointestinal and nervous symptoms, and disorders
of the circulatory system and the liver. In spite of the epidemiological
association between exposure to arsenic and cancer of the skin, lungs, and
50
-------
liver, a suitable animal model has not been developed that demonstrates carci-
nogenicity of arsenic. The epidemiologic studies involved exposure not only
to arsenic compounds but to high levels of sulfur dioxide (at smelters) and of
other heavy metals (at power plants). NASN reported annual average con-
centrations of arsenic in air ranging (in 1964) from nondetectable levels to
3 3
0.75 mg/m , with an overall average of 0.02 ug/m . The EPA is presently
CO
considering listing arsenic as a hazardous air pollutant.
Beryllium is considered to be one of the most toxic metals in industrial
use. The major emission source is coal combustion (88 percent of total emis-
sions). All acute cases of beryllium disease have been associated with beryl-
lium either in occupational settings or in communities adjacent to point
sources. The Committee on Toxicology of the National Academy of Sciences
concluded that a 30-day average concentration of 0.01 ug/m in ambient air was
a proven safe level since no cases of beryllium poisoning from exposures at or
59
below that level were reported. Beryllium is also reported to be carcino-
genic, although the point is presently being contested. Quarterly composite
NASN data for 1970-1975 show that the beryllium concentrations at both urban
3
and non-urban sites were below the detectable limit (0.0008 ug/m ).
General urban atmospheric pollution with manganese is occurring as man-
ganese-containing additives are substituted for lead antiknock compounds.
In view of the pneumonitis and increased mortality from pneumonia which have
in the past been caused by manganese pollution in the vicinity of point
CO
sources, it will be important to monitor closely and control within safe
limits any future increase in particulate manganese.
In summary, it can be said that of the toxic metals in airborne particles,
only lead is present in the urban general atmosphere at average concentrations
51
-------
which may be hazardous. Other toxic metals (including manganese, mercury,
cadmium, arsenic, and beryllium) are potential health hazards in the vicinity
of point source emissions.
5.4.1.3 Polycyclic Organic Matter (POM)--These compounds are adsorbed on
32
airborne particles and are included in the "benzene soluble organic fraction".
The major human health concern relating to POM is the possible causation of
cancer by one or more members of this group of organic compounds. POM is
associated with airborne particles emitted from both mobile and stationary
sources (such as diesel engines and coke ovens) during the combustion or
pyrolysis of hydrocarbons.
A detailed assessment of the health effects of POM has been recently
CO
prepared. Occupational studies have clearly demonstrated an increase in
lung cancer with exposure to POM. Epidemiological studies in community set-
tings have demonstrated, after correction for smoking, that urban residents
have a twofold greater risk for the development of lung cancer as compared to
residents of rural environments. It is assumed that POM contributes to some
unknown fraction of this increase. It is believed that the risk of lung
cancer development by exposure to POM is real, that the magnitude of that risk
to the general population cannot be accurately determined based on our current
knowledge, that it is almost certainly much less than the lung cancer risk
associated with cigarette smoking, but that in real-life situations with
concurrent exposures to cigarette smoking and other foreign chemicals, the
*BaP is the POM for which the most information concerning emissions is available.
It is used as an indicator of the presence and concentration of POM as a
class. However, the validity of this use of BaP as a surrogate for POM is
uncertain.
52
-------
63
absolute risk of POM exposure is probably magnified. Urban trend data for a
specific POM (benzo(a)pyrene)* show an 80 percent decline from 1966 to 1975.
5.4.1.4 Sulfur Dioxide/Sulfuric Acid/Sulfate Salts—In addition to the survey
of the physiological effects of airborne sulfur compounds given in Airborne
Particles, two other reviews of this subject have been recently published. '
Therefore, the effects of these substances will be only briefly discussed
here. The reader should consult the cited reviews for more detail.
Epidemiological evidence concerning the toxicity of sulfur oxides and
sulfates is complicated by the concurrent presence of other particulate matter
and other pollutants. However, it is clear that high TSP levels coupled with
high sulfur oxides can lead to sickness and fatalities. Observed increases in
morbidity and mortality during air pollution episodes are discussed below and
in the various reviews cited.
The source of most of the particulate sulfur compounds is fossil fuel
combustion, sulfur dioxide being the major form emitted. This gas is quite
soluble in water and occurs as sulfurous acid in aqueous airborne particles.
It is also oxidized to sulfuric acid, which in turn is neutralized to some
extent, forming neutral sulfates.
Much of the evidence suggesting that the sulfate aerosol contributes to
the health effects of air pollution is based on experimental work with animals.
In various studies at exposure levels of 1000 ug/m or less, sulfuric acid has
not been shown to cause increased pulmonary airflow resistence, chronic changes
in liver and lungs, kidney, and pancreas (in combination with other pollutants),
decreased carbon monoxide diffusion capacity, and cellular changes in the
bronchial mucosa. Because it is a strong acid, sulfuric acid may be expected
53
-------
to have a greater irritant effect on respiratory mucosa than do sulfate salts.
However, because of the presence of ammonia in the respiratory tract, much or
all of the inhaled sulfuric acid may be neutralized before contacting the
mucosa. The extent to which such neutralization actually occurs will depend
on several other factors, including particle size. As noted above, ambient
sulfuric acid has been shown to persist even in the presence of more than
Q
enough ammonia for complete neutralization.
Animal experiments have shown that neutral sulfate salts are also respi-
ratory irritants to varying degrees, with zinc sulfate and zinc ammonium
sulfate being highly irritating and ferric and manganese sulfates being inert.
There has been little research on the effect of sulfate salts on humans.
5.4.1.5 Other Particles—A number of other types of particles can be assumed
to contribute to the health impact of airborne particles.
Nitric acid vapor and particulate nitrates are formed, to some extent,
from nitric oxide in a manner analogous to the formation of sulfuric acid and
particulate sulfates from sulfur dioxide. Orel and Seinfeld, in a recent
report, compare the formation, sizes, and concentrations of ambient sulfate
and nitrate particles. Unlike sulfuric acid, the nitric acid that is formed
tends to remain in the gas phase, although it may be an important component of
acidic precipitation. Although it is recognized that respirable nitrates
may be of health significance, little information is available as to their
health effects.
Cigarettes are the source of much of the airborne particle exposures for
smokers and of some for non-smokers, especially in indoor environments.
Because cigarette smoke particles are small, contain adsorbed pyrolysis pro-
ducts known to be carcinogenic, are deposited and remain for extended periods
54
-------
in the smokers' lungs, and are deliberately or involuntarily inhaled at high
concentrations, they represent a special and extreme case of hazardous airborne
particles. The greater susceptibility of smokers to the adverse health effects
of airborne particles (e.g., asbestos) and to air pollution episodes is well
documented. Although one cannot assume that all of the harmful factors in
cigarette smoke are associated with particles, a substantial fraction of them
probably is.
5.4.2 Chemical Interactions with Other Pollutants
A recent report examines the role of solid/gas interactions in air pollu-
tion. Particle interactions with other air pollutants involve both surface
adsorption of pollutant gases and surface-catalyzed chemical reactions. These
processes can produce modified particles which may be either more or less
hazardous than the original ones.
5.4.2.1 Adsorption—Because many airborne particles incorporate substances
which are surface active and because they have large surface areas relative to
their mass, these particles are effective sorbents of other air pollutants.
Most POM, for example, which is normally emitted as hot vapors, condenses into
32
fine particles upon cooling. Particles can convey into the non-ciliated
portion of the lung water-soluble toxic substances that would otherwise have
CO CO
been largely exhaled or removed in the upper respiratory tract ' An analy-
sis of the southern California aerosol on four successive days showed that the
most abundant form of carbon in the particles (50 percent) was elemental
carbon. Because of their adsorptive efficiency, fine carbon particles can
synergistically increase the effects of other pollutants. The co-carcinogenic
effect of benzo(a)pyrene has been shown experimentally to be potentiated by
the presence of carbon particles with which, in automotive emissions, it is
55
-------
normally associated. Benzo(a)pyrene and other polycyclic organic matter
adsorbed on soot have been shown to be released from the particles by body
fluids.
5.4.2.2 Surface Chemical Reactions—Particles participate in various chemical
reactions with atmospheric gases. Preeminent, perhaps, are the solution by
water droplets of gases and the aggregation of other particles with these
water droplets, establishing an aqueous reaction medium where chemical trans-
formations occur. Sulfur dioxide is oxidized to sulfuric acid in the presence
of aqueous atmospheric aerosol. The rate of this reaction is dependent on
temperature, pH, and the presence of catalytic trace elements. Soluble salts
of ferrous iron, manganese, and vanadium are among those which catalyze the
oxidation of sulfur dioxide. In a further particle/gas interaction, the
sulfuric acid droplets can then be neutralized by atmospheric ammonia.
There are epidemiological and experimental indications that adverse
health effects of sulfur dioxide at concentrations normally present in the
ambient air are largely or entirely dependent on the coincidental presence of
particles. The interaction causing this synergism is presumably due both to
the particle-catalyzed oxidation of sulfur dioxide in the environment and to
sulfur dioxide oxidation which occurs after dry-particle transport of the
adsorbed gas into the warm, humid atmosphere of the respiratory tract. Syner-
gistic effects of sulfur-dioxide and particle exposures are discussed in
50
Airborne Particles. Sulfur dioxide has also been reported to increase
72
synergistically the carcinogenic activity of benzo(a)pyrene particles.
Other aspects of particle surface chemistry are suggested by the report
73
of Linton et a!.; for example, in coal fly ash, numerous elements including
lead, chromium, manganese, sulfur, iron, potassium, sodium, lithium, and
56
-------
vanadium have strongly enhanced surface concentrations and Teachabilities
relative to those of the glassy particle matrix. Lead, for example, while
present at a concentration of 0.06 percent on the basis of bulk analysis, had
a surface concentration of 4 percent and was highly Teachable. Preliminary
studies also established the surface predominance of lead, bromine, chlorine,
sulfur, phosphorus, potassium, and sodium in automobile exhaust particles.
The non-uniformity was attributed to volatilization-condensation processes.
Since it is the particle surface which contacts and is extracted by body
fluids upon ingestion or inhalation, this non-uniformity will have the effect
of increasing the effective dose resulting from inhalation of airborne parti-
cles.
5.5 HEALTH COST ANALYSES
With regard to the development of recommended guidelines for the protec-
tion of public health, there has been much discussion relating to the desir-
ability and magnitude of safety factors, the desirability of regulating parti-
cular types or sizes of particles, the extent to which air quality standards
should be designed to protect especially vulnerable groups,* and to the economic
benefits to be derived. To provide data related to the latter consideration
(cost/benefit trade-offs), a number of studies have attempted to estimate the
74
costs of air pollution. A report by Herman presents a survey of studies
published between 1967 and 1977 concerning the health costs of air pollution.
It concludes that sulfur oxides and particles are a more serious threat to
health than are other
*Such groups might include the aged, the sick, children, those with above-
average levels of outdoor activity, and that 10 percent of the healthy popula-
tion (Airborne Particles) which is reported to exhibit exaggerated responses
to sulfur dioxide exposure. The Clean Air Act requires protection of
such susceptible groups.
57
-------
air pollutants. It was stated that "no study surveyed for this report dissents
directly or indirectly from the conclusion that sulfur oxides and particulate
matter impose the greatest health costs on the American population." A tabular
comparison of health cost studies was given in the report by Herman. Those
parts of the table summarizing studies which were concerned mainly with sulfur
oxide and particle pollution are presented here in Table 13. Estimates from
the various studies of the health penalty imposed by these pollutants are
given in the eighth row of the table.
Because such studies attempt to assign monetary valuations to essentially
indeterminate costs such as lost earnings as well as to more tangible expenses
such as medical costs, and because they usually do not include such real but
non-quantifiable effects as the psychic and emotional penalties of disease and
premature death, they are admittedly only coarse approximations.
5.6 DEFICIENCIES IN THE SCIENTIFIC DATA BASE
Much needed information concerning the effects of airborne particles on
public health and welfare is not available. A recent report by the Inhalable
Particles Research Committee outlines the most urgent research needs. These
include: (1) definitive animal toxicology experiments establishing acute and
chronic effects resulting from individual and multiple pollutant exposures not
admissible with human subjects, (2) comprehensive clinical studies of physio-
logical responses in human volunteers to low level individual and multiple
pollutant exposures, and (3) expanded collection and evaluation of epidemio-
logical data in communities selected so that relationships between particle
pollution and observed health effects can be described.
58
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TABLE 13. COMPARISON OF
Reference
Year(s) studied
Pollutant(s)
Illness
Death
Measurement
of
pollutant(s)
Dose-response
function
Population
at risk
Results:
addi tional
cases of
disease
or death
Results:
do' 1 ar
estimate( s)
DM ini tion
of estimate
Stu&P Of
estimate
72
Lave and Seskin
1963
sulfates
participates
respiratory disease,
cardiovascular disease,
and cancer
yes
no measurement;
50% improvement
assumed
inferred frum previous
epidemiological
studies
nationwide
50% abatement would
cut i 1 Inpss and death
from respiratory dis-
ease 25%, cancer 15%,
and cardiovascular
disease 10%"
Savings' respi ratory-
S1.222M; canc£r-$390M;
cardiovascular-$468M
medical costs and
lost earnings
nationwide
73
Jaksch and Stoevener
1969-1970
particulates
respiratory diseases,
allergies, skin diseases,
circulatory, digestive,
genitourinary disorders,
eye diseases
no
18 Portland monitors;
24-hour readings every
4 days; isopleths drawn,
values assigned to people
taking account of differ-
ent exposures due to
home, work, travel
regression analysis: age,
sex. marital status, no.
in household, race,
fitness, drinking,
smnking, occupation,
humirti ty , temperature ,
1 pol lution measure
?,500 Portland residents
20 micrograms per cubic
meter increase to 80
microgram particulate
levels had "minimal
effect" on cost of
outpatient visits
addi tional 3. 5C per
visit or $1000 per year
medical costs only
ISO, 000 members of
Mi ser-Permanenle
Mt-dica 1 Care Program in
Portland , Oregon
74
Waddell
1970
sul fur dioxide,
particulates, sulfates
irritation symptoms,
heart and lung (elderly),
asthma, acute lower
respiratory, chronic
bronchitis
yes
used the average
26% improvement in
pol lution levels
reported for 1970
death: 26% abatement
reduces death rate 2.33%
(estimated from Lave &
Seskin 50%-4.5% relation);
i 1 1 ness: reductions
estimated from CHESS
data
Irritation-50M, asthma-4M,
heart & lung-4M, acute
lower-50M, ch. bronch.-6M
i 1 1 ness: reductions:
irritation: 75-100%,
heart and lung: 10-30%,
others: 10-50%
S0.7-4.4B death:--
$0.9-3.26 illness--
savings if 26% reduction
in air pol 1 ution
i 1 Iness and death:
medical costs and lost
earnings
approximately 1S5H people
-urban population
nationwide
75
Finklea et a! .
1970
sulfates
heart and lung disease,
lower respiratory (LRD)
disease (chi Idren) ,
chronic respiratory
disease (CRD), asthma
yes
NASN sulfate readings
extrapolated to four
types of population
density (less than 2500
per city to more than
2M); 1-24 monitors per
type in each of 9 regions
dose-response functions
constructed for acid
sulfate aerosols from a
number of studies, includ-
ing CHESS; "best judgment"
rather than mathematical
fit used
heart and lung--3.7M,
4. 1M asthmatics, 35. 2M
children. 137. 4M--
premature death
13,000 excess deaths,
44. 7M aggravated heart and
attacks, 0.376M excess LRO
0.565M nonsmoker excess
CRO symptoms
—
--
Nat ionwide
76
Johnson et al. (EPA)
.1970
sul fur dioxide,
sulfates, particulates
Acute resp. --influenza ,
a. bronchi ti s , pneumonia
Chronic resp. --emphysema, c.
bronchitis,, bronchiecstasis,
c. interstitial pneumonia
no
anrva 1 SMSA averages
of each pol lutant;
168 SMSAs; center-city
NASN readings.
excess disease rates
from 9 CHESS study
communities appl ied
to SMSAs with same
combi nat ion a^d
levels of pol lutants
48. 8N center-city res.
Acute: 1,901 .000 rases
(adult--17-65);
5,863.000 cases (childreO
Chronic: 679.000 (adult)
Acute: S4/5. 9 n.i 1 1 ion
Chronic: $104.6 mil 1 ion
medic a co>ts . lost
earnings , house*' fe
disability, lost school
IC'8 center c i t >es
48. S mi 11 ion people
59
-------
HEALTH COST STUDIES74
77
Liu and Yu
1970
sulfur dioxide,
participates
yes: not specified
yes
S02:
19G8-70 SO, averages
in 40 SMSA$ where average
exceeded 25 micrograms per
cubic meter; one per SMSA,
particulates: 1968-70
averages from same SMSAs
illness-calculated from
lf>2 CHISS observations
using "Monte Carlo" method
death-reqress ion anal>sis:
^ cue? *b, income, educa-
tion, ^ weather variables
explains 82% of death rate
78
Carpenter et al .
1972
sulfur dioxide,
particulates
respiratory and
heart disease
no
pollutant measurements
used to classify neighbor-
hoods according to three
levels of SO- and partic-
particulates in Allegheny
County (encompasses
Pittsburgh)
regression analysis: sex.
ape , occupation , smoki ng ,
neighborhood median
income, how hospital bill
paid, whether surgery
performed. % occupancy
of hospital , race. 3
measures of pollution
5
Gregor
1968-1972
sulfur dioxide,
particulates
no
yes
sulfur dioxide: 5-year
mean of annual averages
measured at 5-49 stations;
particulates: 5-year mean
of annual averages,
42-47 stations; means for
each census tract in
Allegheny Co. (Pittsburgh)
regression analysis:
% adults with high school
education, population
density, precipitation,
temperature, 2 pollution
measures
79
Heintz, Hershaft, Horak
1973
sulfur dioxide, sulfate
compounds, particulates
same as Waddel 1
same as Waddel 1
same as Waddel 1:
no measurement;
assumed 26% improvement
in pol lution level s
same as Waddel 1 , see
"Results" below
80
Lave and Seskin
1979 (projected)
sul fur .oxides,
particulates
al) illness
yes
smallest SO reading.
ari thmet ic Sean of
participate readings
taken biweekly in 1960-1961
and 1969 in each of
112-117 SMSAs
regression equation:
2 pollution variables.
% of people 65 and over,
income, population density,
% non-white explains
83% of the death rate
40 S^SAs. 1pp. 64 million 32,600 patients in 28
(1970 Statistical Abstract) hospitals
app. 950,000 Allegheny
County residents
same as Waddell
SO, and paM iculatf s
account for- apg. 1% of
total death rate
S0? accounts for 7% of
excess illness rate.
participates ?8%
deMh-41.930.6 mi 11 inn
iIlness-1249.5 million
i 1 ! ness-medical costs .
lost earnings, "psychic"
costs
appro* i mat P '/ 64 T- i H ion
people in 40 SMSAs
133.600 additional
hospital-days, plus
1-3.5 days longer in
hospital suffered by
residents of more
polluted neighborhoods
$9.9 mi 11 ion extra
hospital ization costs
in 1972
medical costs only
32.600 rpvpiratory and
hpart hospital patients
in Al iegheny County
1% SO,, and particulate
reduction in 1968-1972
would have reduced death
rate .01-. 06/100. 000 for
younger than 45; .1-.5,
45-64; .3-12.6. 65*
potential sav ing of
17. 5 mi 11 ion per year
"wi 1 ) inqnes^ to pav"-
*200 for 1/1000 reduction
in annual chance of dying
Allegheny County
(Pittsburgh area)
residents
26% ihatemeiil '-educes
death rate 2.33%
i 1 Iness savings:
see Waddel 1
dealh-$3.2 bi U ion
i 1 lnes-»-$C S hi 11 ion:
savings it 26% reriuct-
tion in a>r pollution
h.iddei 1 f iqurps updated
tn account for rising
wages, population
increase, etc
appro* imatelv 155
mi 1 1 i on- urban
popul^t ion nat ionwide
tPA-prnjected ^o and 88%
levels "t particulates
and su'fur oxiaes bs 19~9
would reduce U.S. death
and iMness
V.b. & t; i T! i.in > -u - ;M)-
1079 ("V -if I'.'/: i- ••
medica 1 co^l s p'~c JVL te
tc 19'9. i1«^cciinteri ^t
medical L.-st^ . "^i^t
earninqs. and nuuse*' f
equivalent earnings
nationwide
°«,
e
60
-------
To support the health oriented research there is need for more detailed
characterization of particulates - sizes, quantities, composition, and distri-
bution—plus a better understanding of the physical and chemical transforma-
tions of particles between their emission and their deposition in lungs and on
soils, foilage, etc. Finally, fundamental to all the above research is the
refinement of techniques capable of measuring those properties of particulate
pollution that emerge as important.
61
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6. EFFECTS OF PARTICULATE MATTER ON PUBLIC WELFARE
The effects of airborne particles on public welfare consist, chiefly, of
adverse effects on plants, animals, and soils; on materials; on visibility and
other aesthetic conditions; on meteorological conditions; and possibly on
climate. ; .
6.1 ECOLOGICAL EFFECTS
Airborne particles can cause injury to vegetation. The type of injury
which may occur is dependent on particle size and composition. Excessive
deposits of dust particles, such as those from cement plants, can cause crusts
to form on the leaves, twigs, and flowers of plants if moisture is present.
The presence of the crust prevents sunlight from reaching the leaves, thus
inhibiting the process of photosynthesis. Studies of these phenomena have
been made in the vicinities of dust-emitting cement kilns and are extensively
reviewed in Airborne Particles.
The stomata in the leaves may become clogged if they are on the upper
leaf surface. Depending on their chemical composition, dusts can cause direct
injury to leaves and flowers. Particles containing fluorides, magnesium
oxides, and soot-containing particles have been shown to cause vegetational
injury.
Fine particulate matter (ambient aerosol) is the principal conveyer of
acid in the atmosphere. The effects of acidic precipitation on ecosystems
are briefly reviewed in Airborne Particles and more extensively in the
numerous contributions to a Symposium on Acid Precipitation. Acidic
precipitation, containing sulfuric, nitric, and hydrochloric acids, can
62
-------
severely inhibit the growth and health of trees and other plants both by
direct contact and by acidification of the soil. The effects on domestic
plants can have substantial agricultural as well as natural ecological
impact.
Several analyses of the effects of acidic precipitation on specific
78
ecosystems have been presented. For example, Schofield estimated that fish
populations have been adversely affected by acidification in approximately 75
percent of the high-elevation Adirondack lakes. Some of these lakes are now
so acidic that fish cannot survive.
Toxic material in airborne particles can also injure terrestrial animals.
An example is the fluoride poisoning which has been observed in cattle and
79
horses grazing near point sources (such as aluminum processing plants).
Lead poisoning of wildlife, domestic animals, and aquatic organisms is
29
reviewed in Air Quality Criteria for Lead.
6.2 EFFECTS ON MATERIALS
The damaging effects of particulate matter on materials are extensively
reviewed in Airborne Particles. These effects are due not only to the
attack of chemically active components such as sulfuric and nitric acids but
also to the action of adsorbed or dissolved gaseous pollutants, including
sulfur oxides, nitrogen oxides, hydrogen sulfide, ammonia, and ozone. The
effects include corrosion of metals, deterioration and discoloration of paint,
erosion of stone and masonry, fading and embrittlement of plastics, fading and
weakening of textiles, and peeling of asphalt surfaces. An estimate of 3.8
billion dollars as the annual cost of such damage is cited. This estimate did
not include costs associated with surface soiling.
63
-------
80
Using an economic model of household behavior, Watson and Jaksch
estimated welfare gain from less soiling using empirical estimation of a
physical soiling function, a behavioral frequency-of-cleaning function, and
total current expenditures for cleaning derived from two earlier studies. A
behavioral frequency-of-cleaning function and estimates of total cleaning
expenditure were obtained by analyzing data gathered for Philadelphia, including
data from a cross section survey of 1090 households. Although the results are
limited by the empirical data, this preliminary analysis for 123 SMSA's* found
that the benefits of less soiling when the federal primary particulate standard
is attained would range from $537 to $3816 million per year in 1971 dollars.
When soiling benefits and health and materials benefits (obtained from other
studies) were combined and compared with control costs, Watson and Jaksch
found tentatively that the secondary annual particulate target (60 micrograms
per cubic meter) would provide the largest net benefit.
6.3 ATMOSPHERIC AND CLIMATIC EFFECTS
Absorption and scattering of sunlight by aerosol particles cause decreased
visibility and decreased intensity of the sunlight which reaches the ground.
It has been estimated that such scattering and absorption are responsible for
a radiation loss of 20 percent in parts of the rural midwest, an effect of
potentially great agricultural impact. Absorption and reflection of sunlight
by the aerosol and by particle-enhanced cloud cover may also be responsible,
to some degree, for the recent cooling trends in regional and global climate.
Although the significance of this effect on climate is still uncertain, it may
prove to be of importance.
^Standard Metropolitan Statistical Areas.
64
-------
Airborne particles influence cloud formation and rainfall by serving as
condensation nuclei. The effect is well documented in areas downwind from
urban and industrial locations. It is estimated that many urban centers cause
an increase in downwind precipitation of 5 to 15 percent.
These effects of airborne particles on visibility, insolation, cloud
cover, global temperature, and precipitation are discussed and documented in
detail in Airborne Particles.
6.4 AESTHETIC EFFECTS
Aesthetic and nuisance effects of airborne particles include such phenom-
ena as the general soiling of clothing, buildings, and other exposed surfaces,
the association of unpleasant odors with airborne particles, the obscuration
of scenic vistas, the cultural loss incurred by degradation of exposed archi-
tectural and historical artifacts, and the diminished opportunities for pleasant
outdoor activity, including recreational enjoyment of natural ecosystems.
Although the costs of these effects are not normally quantifiable, it is
apparent that they are significant and are a major factor in public assessment
81
of the undesirability of airborne particle pollution. The 1969 criteria
81
document, Air Quality Criteria for Particulate Matter, presented the conclu-
sion that total suspended particulate (TSP) levels above 70 mg/m (annual
geometric mean) evoke public awareness and/or concern.
6.5 Trends in Visibility
Recent studies suggest that fine particulate sulfates may be a principal
cause of visibility reduction associated with air pollution in areas as
82 83 84
diverse as Los Angeles, the eastern U.S., and the southwest.
65
-------
Widespread atmospheric hazes observed throughout the eastern U.S. are apparently
83
increasing with regional SO emissions. Trijonis and Yuan analyzed visibility/
A
pollution relationships at 12 northeastern sites. They found that visibility
is not substantially better in non-urban areas than in metropolitan areas of
the northeast, averaging only 9 to 12 miles. From the middle 1950's to the
early 1970's, visibility exhibited only slight downward trends in large
metropolition areas but decreased on the order of 10 to 40 percent at
surburban and nonurban locations. Over the same period, visual range declined
remarkably during the third calender quarter relative to other seasons, making
the summer months the worst season for visibility. Examination of meteoro-
logical trends at some sites indicates a slight decrease in maximum daily
average temperature and a slight increase in humidity, but these are not
sufficient to account for the visibility trends. Additional work is needed to
determine whether the visibility changes influenced the climate trends.
66
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75
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/9-70-Q06
4. TITLE AND SUBTITLE
, SUSPENDED PARTICULATE MATTER:
A Report to Congress
7. AUTHOR(S)
Dr. Lucile Adamson, Howard Univ., Washington, D.C.
Dr. Robert Bruce
8. PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Environmental Criteria and Assessment Office
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, N.C. 27711
3. RECIPIENT'S ACCESSION NO.
5. REPORT DATfc
June 1979
6. PERFORMING ORGANIZATION CODE
10. PROGRAM ELEMENT NO.
1HA882
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
Office of Research and Development
U.S. Environmental Protection Agency
Washington, D.C. 20460
13. TYPE OF REPORT AND PERIOD COVERED
TYPE Q
Final
14. SPONSORING AGENCY CODE
EPA-600/CO
15. SUPPLEMENTARY NOTES
fliis report is in response to Section 403(a)(1) of the Clean Air Act as Amended
August 1977. The report covers: 1) a review of the physical and chemical characteris-
tics of airborne particles (source, composition, and sampling site as related to size);
2) a review of the effects of particulate matter on public welfare (ecological, materi-
als, atmospheric, aesthetic); 3) the status of human exposure to airborne particles as
related to source; and 4) a review of the effects of airborne particles on human health
(lung deposition, chemical composition, interactions, and potentiating conditions).
Although there is a wide divergence of opinion among experts and scientific groups
with respect to the issues of particulates (cf. Appendix A), the following can be
concluded from the available information:
1. High levels of airborne particles have been associated with episodes of high
pollution during the past, especially in the United Kingdom and the United States.
2. Although pollution levels have declined in many U.S. localities in recent
decades, there is still need for improvement in several of our cities.
3. Additional research is needed to improve the scientific basis for future
airborne particle standards as outlined by EPA (cf. Dr. Cortes 1 in the Culver Pilot
Study of Particulate Matter).
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
aerosols ecology public health smog
airborne wastes emission smoke
air pollution fibers soot
ashes fly ash respiratory system
carcinogens inorganic acids visibility
combustion products metals smelting
corrosion mist
nr
;irllPiHiIPpIrticu1a4s
m\
04A
04B
06A
13B
metallurgical processes
07B
07C
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Report/
UNCLASSIFIED
21. NO. OF PAGES
76
20. SECURITY CLASS I This page)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (Rev. 4-771
'S CBSO'_E-E
76
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