DRAFT
SUW1ARY OF NATIONAL ASSESSMENT
OF THE URBAN PARTICIPATE PROBLEM
Distributed At
Air Programs Regional Office Workshop
Southern Pines, N.C.
August 3-6, 1976
(This represents a portion of the
draft final report on the 14 city
TSP study conducted by GCA Corp.
for OAQPS)
Thompson G. Pace
Project Officer
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CONTENTS
Page
List of Figures iv
List of Tables vi
Acknowledgments vii
Sections
I Introduction *
General Conclusions !
Study Approach 4
Organization of the Study Report 5
II General Findings of the Study 6
Study City Analysis 6
Study of Factors Affecting Attainment 26
III Assessment of Factors Affecting Attainment 32
Background and Large-Scale Considerations 34
Particulates From Traditional Sources 51
Particulates From Nontraditional Sources 62
Monitoring Considerations 77
Relative Contributions of Various Factors 103
IV Summary i08
Problem Assessment 108
ii
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CONTENTS (continued)
Sections Page
Attainment Factors Identified in City Studies 108
Control Strategy Options 113
Framework for Control Strategy Prioritization 119
V Recommendations 122
Recommendations for Emission Control Efforts 123
Recommendations Concerning Air Quality Management
Planning 128
Issues Concerning NAAQS Review 130
(Please note - The Draft Final Report on the 14-city Suspended
Particulate study entitled "Volume I - National Assessment of
the Particulate Problem" contains Appendices A through G which
support the following material.)
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LIST OF FIGURES
No. Page
1 Geographical Distribution of 14 Study Cities 7
2 Schematic Relationship Among Five Major Factors 31
3 Average TSP, Levels by Neighborhood Type 33
4 Composite Annual Geometric Mean TSP Levels at Nonurban
NASN Sites From 1970 Through 1973 (ug/m3) 48
5 Annual. Geometric Mean Sulfate and Nitrate Levels at Non-
urban NASN Sites- 1974 50
6 Average Estimated Contributions to Nonurban Levels in the
East, Midwest, West 52
7 Relationship Between City Wide Average TSP Levels and
Traditional Source Emission Density 55
8 Traditional Source Increments in Different Site Types 63
9 The Range and Average Lead Concentrations Found at
Monitoring Sites 71
10 Average and Range of TSP Loadings Due to Tire Wear at
Different Monitoring Site Classifications 73
11 Nontraditional Source Increments at Different Site Types 73
12 Range of Heights in Typical Hi-Vol Installations 85
13 Duration of Rainfall Effectiveness in Reducing TSP Levels
at Two Birmingham Sites 94
14 Relationship Between TSP Concentrations and Wind Speed at
Three Selected Sites in Birmingham on Days With 48-Hour
Precipitation Amounts <_ 0.02 Inches 97
iv
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LIST OF FIGURES (continued)
No. Page
15 Relative Effect of Annual Precipitation on Annual TSP Level
in a Hypothetical Urban Area 101
16 Summary of Average Impact of Major Contributors to TSP
Levels 105
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LIST OF TABLES
No. Page
1 Population and Physical Setting of Case Study Cities 9
2 Study Cities by Their Dispersion and Industralization
Characteristics 10
3 Summary of Sites Exceeding Air Quality Standards 11
4 Source and Emissions Characterization of Study Cities 12
5 Composite Summary of Microscopic Analysis In 14 Cities,
yg/m3 24
6 Estimates of Average Filter Loadings by Site Classification 25
7 Composite Summary of Particle Size by Components 25
8 Estimates of Particles Smaller Than 20 urn Radius Emitted
Into or Formed in the Atmosphere (106 Metric Tons/Year) 37
9 Nonurban Levels of Sulfates and Nitrates in the 14 Study
Cities 43
10 Urban and Nonurban Levels of Sulfates and Nitrates in the
14 Study Cities 46
11 Approximate Impact (In wg/m3} of Vehicular Traffic on
Adjacent Hi-Vol Sites 67
12 General Monitoring Objectives 79
13 Average TSP Concentrations by Neighborhood Type 83
14 Variation in Monitor Height Among the 14 Cities 86
15 Number of Sites With an Estimated Impact of Local
Influences, by Neighborhood Classification 88
16 Control Priorities 121
vi
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ACKNOWLEDGMENTS
Numerous persons and organizations have made significant contributions to
this overall study effort, and GCA/Technology Division wishes to sincerely
acknowledge their participation. On-going project supervision has been
received from Thompson G. Pace, Project Officer, of EPA's Control Programs
Development Division. Professional staff members of the EPA Regional
Offices and of the state and local agencies responsible for the case study
cities have been uniformly cooperative and helpful.
Specific thanks are due to Dr. William E. Wilson and Ronald K. Patterson
of the Environmental Sciences Research Laboratory, for sharing the results
of their field research in several cities; to Dr. David S. Shearer and
Dr. Richard J. Thompson of the Environmental Monitoring and Support
Laboratory, for their analytical support; to Gerald Gipson of the Monitoring
and Data Analysis Division for providing modeling results in several cities;
and to David Dunbar, Edward J. Lillis, John D. Bachmann, and the staff of
the Monitoring and Reports Branch for their on-going review and advice.
vii
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SECTION I
INTRODUCTION
This report presents the results of a study conducted under the auspices
of the Control Programs Development Division of EPA's Office of Air Quality
Planning and Standards. Its overall purpose was to assess the national
particulate problem, based on case studies in 14 major urban areas, with
emphasis on identifying the factors involved in the attainment or non-
attainment of the National Ambient Air Quality Standards (NAAQS) for total
suspended particulates (TSP). The study was intended to improve technical
understanding of the TSP problem, to provide specific guidance to the states
in TSP problem analysis and control strategy formulation, and to develop
recommendations for EPA concerning future program direction and research
needs. Consequently, this document is directed primarily at those managers
and air quality planning specialists at EPA and the various state and local
air pollution control agencies who are concerned with the development of
TSP control programs.
GENERAL CONCLUSIONS
The study identified five factors that affect attainment and maintenance of
the total suspended particulate (TSP) ambient standards. These are con-
ceptually grouped as follows: three general categories of sources that
contribute to the TSP loading at any given point, and two factors that act
to modify the ambient levels measured. The three major categories of par-
ticulates are emissions from traditional sources, emissions from nontradi-
tional sources, and natural and transported particulates. The two modi-
fying factors are meteorology and monitoring network configuration and
siting.
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Traditional sources are those sources that have historically been of con-
cern to the air pollution control community. Fuel combustion sources,
solid waste disposal operations, and industrial process emissions, includ-
ing both stack emissions and fugitive emissions, comprise this segment.
Particulate emissions from traditional sources were found to be decreasing
in relative significance as the quantities of such emissions are reduced.
In spite of this, however, they are still the dominant problem in some
urban areas with much heavy industry. The traditional sources that remain
the greatest problem are the primary metals and mineral products industries,
as well as fugitive emissions from all traditional sources.
Nontraditional sources include particulate sources that have not been con-
trolled under existing State Implementation Plans or have been controlled
inadequately. Particulate auto exhaust emissions, rcentrainment of road
dust, fugitive dust emissions from construction and demolition operations,
dust from unpaved areas and other urban activities comprise this segment.
A principal finding of the study was that particulates from these sources
have prevented most urban areas from attaining the ambient standards at all
sites, and that, unless controlled, they will continue to do so. Given the
current downward trend in traditional source emissions, particulate matter
from nontraditional sources will pose the greater problem in the on-going
maintenance of the ambient standards.
Natural and transported particulates consist of those large-scale influences
that are the contributors to what is frequently called "background." The
long-range transport of both primary and secondary particulates, as well as
naturally occurring particulates, are included in this portion. Often these
particulate levels are inadequately considered in air quality planning, al-
though their inclusion is essential for accurate quantitative planning.
Such planning may well include regional scale strategies for reducing the
impact of these sources on ambient levels.
Meteorological factors were identified as a partial determinant of the
magnitude of ambient particulate levels. For example, precipitation can
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significantly affect annual average TSP concentration; a variation of as
much as 20 ug/m3 is seen over the normal range of precipitation values.
Although not a factor subject to control, the variations in meteorological
effects over time and in different locations must be considered in air
quality management planning. The results of this study's analyses will
help in doing this more quantitatively.
Network configuration and hi-vol siting affect the perception of particulate
levels. Variations in siting practice and network configuration make com-
parisons of values between cities and neighborhoods difficult. These varia-
tions frequently distort the overall picture and constrain problem identifica-
tion and subsequent strategy development which is essential for attainment/
maintenance. Most of these variations are, however, within the general
guidelines for monitor siting prescribed by EPA.
This study also addressed the methodological problem of quantifying the
relative contributions of the various source types and categories. It is
concluded that, at present, no single analytical technique, or any ap-
parent combination, can be simply and routinely applied to a variety of
situations to provide a reliable, unbiased determination of the nature or
origin of the collected particles. It is possible to use microscopic and
other monitoring and analytical techniques in concert to provide compre-
hensive particle identification analyses. However, the requisite analytical
sophistication and cost constrain their use for widespread screening-level
studies. Their utility is primarily in more precise study of already well-
structured problems.
The study identified a number of needs for Increased emphases and program
re-directions. From a national perspective, two major overall control and
research needs emerge:
The regional-scale burden of transported and secondary
particulates, especially sulfates, must be reduced.
A broadly supported control effort directed at urban re-
entrained dust and similar nontraditional particulate
sources will be required in order to meet the present
particulate standard.
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STUDY APPROACH
The overall approach to the study involved the identification of those
factors influencing the attainment or nonattainment of the standards, the
assessment of their significance on a national basis, and the development
of a recommended action program for EPA and the state and local control
agencies.
The primary source of new Information for this national assessment was a
series of case studies in 14 major urban AQCR's. These studies involved
analyzing, for each urban area, the air quality and emission data on TSP,
meteorological data from the National Weather Service, the control regula-
tions in the State Implementation Plans, planning materials maintained by
EPA, and published technical articles or reference materials. Each city
case study also involved a field visit to the city to conduct detailed
inspections of most of the TSP monitoring sites in the area.
Although the primary purpose of the study was not to produce new analytical
data, several specific analyses were performed. Selected hi-vol filters
from each of the 14 case study cities were analyzed by optical microscopic
techniques to provide information on the types and sources of the particles
collected. Some of these filters were reanalyzed for quality control by
the same or other microscopists and laboratories; others were analyzed by
EPA for metals and nonmetallic inorganic ions by standard NASN analytical
procedures. EPA provided information from special field studies in two of
the study cities, including wind directional monitoring, diurnal variations
in elemental composition, and particle sizing data. Data resulting from
all these analyses are compiled in Volume II of this report, and discussion
of the results is included in this volume or in the individual city volumes
as appropriate.
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ORGANIZATION OF THE STUDY REPORT
This document is Volume I of the final study report, which consists
overall of 16 separately bound volumes. It summarizes the data from
the other volumes and should be considered the primary product of
the study. Volume II summarizes the analytical data developed during
the study, and Volumes III through XVI are the working documents com-
piled for discussion purposes for each individual city. The subject of
each volume is listed below:
Volume I - National Assessment of the Participate Problem
Volume II - Particle Characterization
Volume III - Denver
Volume IV - Birmingham
Volume V - Baltimore
Volume VI - Philadelphia
Volume VII - Washington
Volume VIII - Chattanooga
Volume IX - Oklahoma City
Volume X - Seattle
Volume XI - Cincinnati
Volume XII - Cleveland
Volume XIII - San Francisco
Volume XIV - Miami
Volume XV - St. Louis
Volume XVI - Providence
The remainder of Volume I is organized as follows:
Section II - Presents the general findings of the study.
Summarizes the findings in each individual case study city
and Identifies the components of the five major factors
influencing TSP levels.
Section III - Presents the overall national assessment of
the significance of each of the five factors. Places in
perspective the components of each of these factors and
quantifies their relative contributions to air quality.
Section IV - Summarizes problem assessment techniques, the
attainment factors identified in the city studies, and the
implications of the study for control strategy development.
Section V - Provides the detailed recommendations.
Appendices - Various supportive and reference materials.
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SECTION II
GENERAL FINDINGS OF THE STUDY
The individual reviews of the TSP attainment situation in the 14 study
cities provided a wide range of general findings. Some of these find-
ings are specific to individual cities, and others are generally
applicable throughout the study cities. The analysis of these findings
among the different cities serves as the basis for an interpretation
of TSP attainment nationwide. This section summarizes the general
findings from the city case studies (reported in Volumes III to XVI)
and identifies the major factors affecting the TSP attainment problem.
STUDY CITY ANALYSIS
Selection Process
The 14 cities (AQCRs) used in the case studies were selected to repre-
sent a cross section of urban areas. Such factors as proximity to
bodies of water, topography, meteorology, degree and type of industri-
alization, fuel usage, and air quality levels were considered. As
shown in Figure 1, the study cities are dispersed around the contiguous
48 states, with many located in the East where a large portion of the
population and industry of the United States is concentrated. In nature
and density, they range from the old industrial cities of the east
coast to the newer, less congested cities of the plains and west coast,
and they include a cross section of the climatological regimes of the
nation. The cities range in size from Philadelphia, the nation's
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PROVIDENCE
PHILADELPHIA
BALTIMORE
Figure 1. Geographical distribution of 14 study cities
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fourth largest urban area, to Chattanooga, a small industrial city in
the southern mountains. Basic statistics on population, topography,
and employment for each of the 14 cities are presented in Table 1.
Two of the major factors that are important in understanding the po-
tential for a TSP problem are the industrial nature and dispersion
characteristics of an area. The industrial nature indicates the general
level of emissions from major point sources, while the diapers ion
characteristics dictate the degree to which these emissions affect am-
bient levels of particulates; Table 2 lists the 14 cities classified
according to the possible combinations of these two characteristics.
Considered under the category of dispersion characteristics are non-
urban particulate levels, extremes in rainfall, sea breezes, and topo-
graphy. Therefore, cities such as Miami, San Francisco, and Providence,
which are dominated by their proximity to the ocean, offer good disper-
sion qualities; cities with ventilation dominated by valley topography
(Chattanooga, Birmingham, and Denver) are considered to have adverse
dispersion characteristics. Industrialization was a judgmental catego-
rization based upon the level of employment in the manufacturing sector,
the nature of the manufacturing, and the density of emissions.
Table 3 summarizes air quality and Table 4 characterizes sources and
emissions for the 14 cities, which are grouped by industrialization
categories. Other tables and figures giving characteristics of the
cities are included in Appendix A.
Methodology of City Visits
The core of the city case studies was one or more field visits to each
city. Prior to visiting each study city, a variety of data summaries
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Table 1. POPULATION AND PHYSICAL SETTING OF CASE STUDY CITIES
Urban area
Philadelphia
San Francisco
Washington, D.C.
Cleveland
St. Louis
Baltimore
Seattle
Miami
Cincinnati
Denver
Providence
Oklahoma City
Birninghsa
Chattanooga
1970 population
AQCR
5, 635,406
6,639,949
2,862,912
3,383,879
2,476,757
2,078,379
1,937,371
2,435,089
1,660.495
1,252.007
1,502.601
783.403
1,045.599
689.494
Rank*
in U.S.
4
6
8
9
10
14
17
18
21
24
30
42
43
96
Central
city/county
1,948,609
715,674
756,510
1,721,300
622,236
905 ,759
1,156,633
1,267,792
924,018
514.678
560,261
526,805
644,991
255,064
Population density
par iq. ml.
SMSA
1357
1254
429
1329
547
917
337
621
644
366
1347
300
272
307
Central
city /county
15.116
15.904
12,402
9,893
10,201
11,613
- 6,350
9,763
5,780
5,418
9,896
579
3,785
2.284
Physical setting
Large bodies
of water
Delaware River
Ocean, S.F. Bay
PotonBc River
Lake Erie
Miaslssipl River
Patapsco River,
Baltimore Harbor
Puget Sound
Ocean; Everglades
Ohio River
Narragansect Bay
-
-
-
Topography
Slightly rolling
Significant hills
Slightly rolling
Flat; river valley
Slightly rolling
Slightly rolling
Significant hills
and valleys
Flat
River valley, sig-
nificant hills
Mountains to west;
rolling to east;
river valley
Slightly rolling
Flat
Valley between sig-
nificant hills
Valley between
sharp ridges
Manufacturing
employment (AQCR)
Magnitude,
thousands
603
347
53
484
279
184
139
144
195
99
201
44
92
128
Percent
of total
34.1
24 4
7 2
36.1
35.1
29.3
26.7
10.5
37.7
20.8
44.2
19.0
31.1
52.6
Saaed on Urbanised Area population.
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Table 2. STUDY CITIES BY THEIR DISPERSION AND
INDUSTRIALIZATION CHARACTERISTICS
Industrialization
Light
Moderate
Heavy
Dispersion characteristics
Favorable
Miami
San Francisco
Providence
Moderate
Oklahoma City
Washington, D.C.
Seattle
Baltimore
Cleveland
Cincinnati
Philadelphia
St. Louis
Adverse
Chattanooga
Denver
Birmingham
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Table 3. SUMMARY OF SITES EXCEEDING AIR QUALITY STANDARDS
City
Heavily
industrialized
Cleveland
Birmingham
Philadelphia
Baltimore
St. Lou la
Cincinnati
Moderately
industrialized
Chattanooga
Denver
Seattle
Providence
Lightly
Industrialized
Washington, D.C
Oklahoma City
Miami
San Francisco
Total no.
of eites
with complete
1974 data
25
13
10
29
31
25
12
22
10
21
9
14
17
17
Annual standard
No. sites exceeding
standard
Primary,
75 ng/m3
12
11
7
9
15
8
5
14
2
1
2
5
2
0
Secondary,
60 ug/m5
21
11
9
14
26
21
5
21
4
5
5
6
7
2
Highest
geometric mean,
ug/in3
175
144
122
134
158
130
101
131
105
88
102
107
66
74
24 -hour standard
No. sites exceeding
standard
Primary,
260 ng/o3
6
7
4
6
13
0
1
13
2
0
9
5
2
3
Secondary,
150 ng/n.3
15
U
8
14
3
7
7
22
5
1
9
13
8
10
% total obs.
> standard
Primary
4.7
NA
NA
0.9
1.1
0.1
0.9
NA
0.3
0
2.2
0.7
NA
0.2
Secondary
17.6
NAa
**o
7.6
8.7
4.2
6.9
NA
0.8
0.8
NA
5.5
NA
1.3
Highest
value ,
Mg/in3
534
499
624
NA
NA
296
434
565
320
173
527
NA
NA
2S6
*NA - Row data not available in format appropriate for summary.
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Table 4. SOURCE AND EMISSIONS CHARACTERIZATION OF STUDY CITIES
City
Heavily industrialized
Cleveland
B iriiingham
Philadelphia
Baltimore
St. Louis
Cincinnati
Moderately industrialized
Chattanooga
Denver
Seattle
Providence
Lightly industrialized
Washington, D.C.
Oklahoma Cltv
Miami
San Francisco
Major point
sources
Steel mills, utilities,
chemicals
Steel nills, cement
Refineries, coking.
smelting, chemicals
Steel mills, incinerators
Coking, steel mills.
grain handling
Utilities, manufacturing
Foundries, cement.
minerals
Utilities
Manufacturing
I- 1 ility, foundries
I'tUlty
Itllities, grain, asphalt
Minerals
Minerals, chemicals
Predominant fuels
Residential
Gas
Cas
Oil
Gas, oil
Gas
Gas
Electricity
Cas
on
Oil
Gas
Gas
Electricity
Gas
Industrial
Gas, coal
Gae
as
Oil, gas
Oil
Gas
Gas, coal
Cas
Cas
Oil
Oil
Caa, oil
Gas
Cas, oil
Cas
Traditional
sources,
emission
density
TPY/sq. mile
333
MIR
j &O
243
240
411
133
68
60
37
30
92
J
30
60
Compliance cements
About 1/3 of major sources in compliance,
smaller sources (including incinerators)
unknown
compliance about half complete
Most sources to compliance
Moat sources In compliance, a few under
plans for compliance
Most sources thought to be In compliance,
Missouri's compliance determination Is
not stringent
Many sources In compliance, rest (Includ-
ing several large sources) expected with!
2 years
Most source) (n compliance
Most sources in compliance
Most sources thought to be in compliance
Compliance status not certain - many
seea to be In compliance
Most sources in compliance
Most sources in compliance
Most sources in compliance
Most sources in compliance
Those fuels i-hose usage IB greater than 1/3 of local Bcu's.
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and analyses were prepared and studied, using data on air quality,
emissions, and compliance that were provided by the Project Officer
from EPA's AEROS data banks. Air quality and emission data were
studied for patterns and trends, both temporal and geographic. Emis-
sion and compliance data were used to consider patterns of enforcement
and compliance.
The primary purpose of the field visits was to study in detail the
hi-vol monitoring network and to gain a degree of understanding about
the overall nature of the study city and the general patterns of land
use, such as the relationships among industrial and residential areas.
During the field visit, the study team also consulted with technical
staff members from the appropriate pollution control agency concerning
those areas where the EPA data base was incomplete or anomalous, and a
member of the agency staff usually accompanied the visiting team on
the monitoring site study visits. Additional efforts during the study
visits in some cities involved seeking data on traffic volumes, street
cleaning practices, etc., as appropriate to the particulate air pol-
lution problem in the city. In most cases, historical hi-vol filters
from agency files were also selected and brought back for analysis.
Following the field visit, the monitoring site information was reviewed
and compiled into an overall site classification analysis. Other in-
formation and data obtained were integrated with that previously avail-
able, and an overall assessment concerning the factors affecting attain-
ment was formed. The data summaries, analyses, and conclusions relat-
ing primarily to a single city were then compiled into a working docu-
ment for each of the study cities; these documents comprise Volumes III
through XVI of this report.
13
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City Study Findings
The results and findings of the city case studies are quite varied in
detail and in breadth of applicability. Those specifically relevant to
only the individual city are presented in the separate volume for that
city. Those that are of significance for the overall conclusions of
the study are summarized here. Appendix A presents tabular summaries
of other data relevant to the various study cities.
Baltimore - A heavily industrialized city, Baltimore has had an inten-
sive pollution control program since the mid-1960s. This has contri-
3
buted to a 50 ug/m decrease in the annual average at the center-city
NASN site over this time. Nonetheless, the annual primary standard is
still exceeded at nine sites, mostly in the center city and harbor in-
dustrial areas. Under vigorous enforcement of very stringent regulations,
most of the city's major industries and the municipal incinerators have
reduced their emissions an average 70 percent; on the other hand, emis-
sions from the iron and steel industry, which comprise 85 percent of
the total point source emissions in the metropolitan area, have been
reduced only 15 percent. One steel mill clearly contributes to TSP
problems at several industrial sites; however, at the industrial site
3
with the highest annual average (134 ng/m ), local fugitive dust emis-
sions also make a significant contribution to the elevated levels.
Three or four sites located in the urban center appear to be above the
standard without any particular local source influence. Part of this
urban increment is probably due to the use of oil for residential space
heating, one category of source which is not closely regulated; however,
much of the TSF measured at these sites must simply be attributed to
the dense level of activity in the urban area. TSP levels at the center
city site are further elevated by immediately adjacent expressway
construction.
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Birmingham - The improvement in air quality has been substantial in
Birmingham, but still only two suburban sampling sites met the annual
primary standard in 1974. Values have fallen from around 300 to 145
O
^g/m at the most polluted industrial site, and commercial and other
industrial sites have shown similar decreases of roughly 50 percent.
Four industrial sites reported 1974 annual geometric means over 125
j
fig/ro because of proximity to the predominant steel industry and the
associated coking and foundry operations, which account for the bulk of
point source emissions. Stringent regulations and vigorous enforcement
have resulted through 1974 in about half the emission reduction ultimate-
ly expected, with the balance anticipated over the next 2 years as com-
pliance plans are completed. The general effect of dense urban activity
on TSP levels is not seen clearly in Birmingham because of the much
larger industrial process contribution, but may well be a problem for
future consideration.
Chattanooga - A moderately industrialized city, Chattanooga has also
experienced a significant decline in TSP levels due to a trend away
from the use of coal and, more recently, to vigorous control of indus-
trial emissions. However, five of twelve sites, all in industrial or
commercial locations, continue to exceed the annual primary standard
with annual means between 80 and 101 ug/m . Of these, two are affected
significantly by local industrial sources - a quarry and a cement
plant - and the others by general downtown commercial activity or major
traffic arteries. An overall difficulty relates to adverse topography
and meteorology; particularly stringent emission control for both in-
dustrial and fugitive sources will be needed to meet the standards
under the adverse dispersion conditions prevalent in Chattanooga.
Cincinnati - The TSP trend has been downward since the mid-1960s, with
the NASN center-city site experiencing a 70 ^g/m decrease in its annual
average. The major industries - transportation equipment, fabricated
metals, paper, chemicals, and a small power plant - have made large
15
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reductions in particulate emissions, primarily by switching from coal to
natural gas or otherwise reducing fuel combustion emissions. Nonetheless,
seven sites still exceeded the annual primary standard in 1974 at loca-
tions in the central business district (CBD) and the industrial valley,
with one site measuring 130 ug/m as an annual average. All sources are
expected to come into compliance over the next 2 years, during which
time further reductions are expected. However, full compliance may not
result in standards attainment because fugitive emissions and fugitive
dust are likely to remain a significant source of particulates at several
sites in the CBD and industrial areas unless control measures are taken.
Cleveland - Although there has been a fairly steady decrease in ambient
TSP levels since the early 1960s, 1974 levels at 12 of 25 sites in the
county violate the annual primary standard. The city is large and heavi-
ly industrialized, with an emission density of 335 tons per year per
square mile, and has the highest annual average TSP levels of the cities
studied (175 ug/m ). Primary metals, fabricated metal products, ma-
chinery and .transportation equipment are the predominant industries and,
along with the utilities, the largest sources of particulate emissions.
Control efforts have resulted in substantial emission reductions by a
few problem sources, but overall they have not been effective. Most
sources are either not under compliance schedules, not meeting conditions
of their variances, or not under agency surveillance at all. While other
factors may very well become apparent as the massive industrial contri-
bution is reduced, it seems clear that the predominant reason for non-
attainment in Cleveland is the current lack of control of industrial
emissions. These include not only major point sources but also industrial
fugitive emissions and the vehicle-entrained fugitive dust emissions
associated with industrial areas.
Denver - In contrast to most other areas studied, the Denver AQCR has
shown no definitive trends in TSP levels during the past 6 years. Des-
pite its low level of industrialization, Denver has had TSP concentrations
16
-------
well above the annual standards since levels were initially monitored
in 1957. In the long term, Denver County has shown approximately a 20
percent improvement in its air quality since 1965. However, in 1974
only one out of 22 sites, a site located in a rural area, met the secon-
dary standard; 14 of the sites exceeded the primary standard. This
general lack of attainment of the standards has been commonly attributed,
in part, to the arid climate which allows easy reentrainment of fugitive
3
dust. The highest annual mean (131 ug/m ) was recorded at a site ob-
viously influenced by fugitive dust, where 36 percent of the observations
were above the secondary 24-hour standard and 14 percent were above the
primary 24-hour standard. The impact of both fugitive dust and tradi-
tional industrial source emissions is spread throughout the region be-
cause of the poor ventilation and topographic characteristics of the
region. In addition, an inadequate data base, from which the initial
implementation planning was done, has contributed to the problem of
attainment- in the region. Several emission inventories have been com-
piled for the region over the years, but the lack of consistency be-
tween these inventories has prevented the determination of emission
trends. Despite the problem of appropriate emission data, major sources
are assumed to be generally in compliance with the regulations and the
state agency is now pursuing fugitive dust sources.
Miami - The highest ambient TSP levels in Miami have been fluctuating
near the standards for several years. The area is generally free of
major TSP point sources; the largest emitters are stone and gravel
quarrying operations. During 1974, two sites failed to meet the primary
3
standard. The higher, with an annual geometric mean of 86 ng/m , was
located in a light industrial-commercial area, on a major arterial high-
way, with an auto junkyard and a variety of other unpaved fugitive dust
sources in the immediate vicinity. The other site was at a highway in-
tersection in a rural area, near a major aggregation of cement plant
operations. A special study conducted by the Dade County agency indi-
cated, however, that the cause of the high levels was not the cement
17
-------
plants themselves, but rather the reentrainment by traffic of material
spilled on the highway by the sizable number of trucks turning at the
intersection.
Because of the general lack of point source emissions, the relative
homogeneity of the area, and particularly the consistency of the monitor
heights, Miami provided a good opportunity to study that portion of
urban ISP levels that appears to result from aggregate urban activity.
Two measures of urban activity were found to correlate well with the TSP
values at the various sites: traffic volumes and the proportion of ad-
jacent land used for streets and parking.
Oklahoma City - An institutional, light-industrial city where gas is
the predominant fuel, Oklahoma City nonetheless has five of 14 sites
where the annual primary standard is exceeded. TSP levels at the NASN
site show only a slight downward trend over time, reflecting the low
density of readily-controlled industrial sources and the inability to
comprehensively control fugitive dust. The high levels at the sites
over the standard can be attributed in part to either significant traffic
exposure, adjacent construction, or (at three of the sites in the cen-
ter city) a combination of central business district traffic and urban
renewal activity. The dry climate and high winds tend to maximize
natural entrainment of dusts, but the urban pollution problem is not
primarily due to participates from the surrounding rural area.
Philadelphia - Air quality has been steadily improving in the city;
annual average TSP concentrations at the NASN site are down over 100
ug/m since 1957. However, the annual primary standard was met at only
three of the 10 monitors operating throughout 1974. Of these three
monitors, all in residential areas of the city, only one met the secon-
dary annual standard with a value of 59 ug/m . The large improvements
in air quality have been directly paralleled by reductions in the inven-
toried emissions due to stringent controls on industry (fabricated metals,
18
-------
machinery, electrical equipment, petroleum) and large incinerators,
phasing out of small incinerators and coal burning, and fuel switching
in power plants. The lack of attainment of the standards, despite
stringent regulations and effective enforcement, reflects the generally
high level of TSP entering the city from outlying industrial activity
(40 to 50 ug/m3) and the activity associated with an urban environ-
ment, including space heating and vehicular traffic. Small residen-
tial boilers have not been under any control other than visible emis-
sion regulations. Vehicular traffic was shown to contribute up to
50 ug/m3 to the measured levels of TSP for monitors close to the street.
In addition, fugitive emissions from stockpiled materials and a grain-
handling operation were believed to be major influences on the monitor
with the highest annual mean (122 ug/m ).
Providence - A downward trend in TSP concentrations has been occurring
since the mid-1960s, and only one sampling site exceeded the annual
primary standard in 1974. A utility, municipal incinerators, and some
industrial processes - primary metals, fabricated metal products and
electrical equipment - are the largest point sources of particulate
emissions. Fuel switching and the closing of incinerators are apparent-
ly responsible for the emission reductions and the corresponding air
quality improvement, although the compliance status of a number of sources
is unknown. The one site which exceeded the annual primary standard
3
with an average of 88 ^g/m is excessively influenced by a major express-
way immediately adjacent. Oil-fired space heating is a significant
source category which has not received much attention in light of the
general standards attainment. Some portion of the overall favorable
picture may be due to a generally high average sampler height compared
to other cities and to relatively good dispersion characteristics.
St. Louis - The TSP trend has been downward since the mid-1960s with
the NASN site experiencing a decrease of 80 ng/m in its annual geometric
mean. Fifteen sites, however, violated the annual primary standard in
19
-------
1974. Transportation equipment, primary metal, fabricated metal pro-
ducts, and machinery industries are the largest sources of particulate
emissions, and fuel switching and industrial process controls have
accounted for much of the emission reductions. The majority of the
sources in the Missouri portion of the AQCR are believed by the local
agencies to be in compliance; however, the St. Louis City and County
regulations are among the least stringent of those studied. The
Illinois portion is less advanced in terms of degree of compliance, be-
cause control efforts started later, but it should become comparable to
Missouri by maintaining its program of stringent regulations and
strict enforcement. The fact that high TSP concentrations are still
being experienced despite the presumed general compliance indicates that
other factors are important. These include the relatively weak regu-
lations and the lack of source testing as a method for compliance de-
termination in Missouri, as well as the general tendency of dense cen-
ter-city sites to be systematically higher due to urban activity.
San Francisco - San Francisco is the one study city that met the annual
primary standards during 1974. Despite its large population and gen-
erally dense urbanization, the San Francisco AQCR has never had a
serious problem with particulates, due largely to the very clean back-
ground air it receives from over the Pacific Ocean and the low level of
heavy industrial activity. Air quality trends at the San Francisco
3 3
NASN site have shown a decrease of about 20 ^g/m from a high of 73 ug/m
in 1957. This decrease of over 30 percent in above background levels
is comparable to the trends reported for emission reductions. These
emission reductions occurred in part (pre-1970) because of extensive
fuel switching by the residential sector from coal and oil to gas and
electricity and (since 1969) because of controls on industrial processes
and burning of materials. These controls are no more stringent than the
average found in the cities studied, but their success is maximized by
an extensive, computerized enforcement program conducted by the Bay Area
Pollution Control District. In addition, regulations have been revised
20
-------
over time as data indicate that more stringent controls are feasible
and warranted. The combination of the above factors and the low level
of emissions (170 tons/day for the entire AQCR) meant that only two
monitors out of 17 exceeded the annual secondary standard, and no mo-
nitors violated either the 24-hour or annual primary standards. The
3
highest annual geometric mean of 74 p.g/m was measured at a station
highly influenced by fugitive dust. This monitor and many others in
the network are often subject to poor ventilation conditions because
of the valley topography; even so, the 24-hour secondary standard was
exceeded less than 1 percent of the time in 1974.
Seattle - While it also has the advantage of being a west coast city,
unencumbered with TSP transport from other areas, Seattle is further
inland than San Francisco and significant industry is concentrated in
a valley adjoining the city. However, the higher level of annual pre-
cipitation helps keep the TSP concentrations down around those measured
in the San Francisco area. Air quality levels have shown fairly steady
downward trends over the years with a 50 ^ig/m decrease in the annual
average at the NASN site since 1957. Of the 30 sites in the AQCR, the
annual primary air quality standard was exceeded at two stations and
the annual secondary standard was exceeded at another three sites. The
3
highest concentrations (60 to 105 |ag/m ) occur in the industrial valley
and the lowest levels (35 jag/m ) in the residential areas out of the
valley. Estimates of emissions indicate that most traditional source
sectors - industrial processes, fuel combustion, solid waste disposal -
have had some reductions contributing to a 40 percent overall reduction
in inventoried emissions since 1969. These changes in emissions since
1969 have not been reflected in the air quality, which has seen in-
creasing TSP levels in 1973 and 1974. The regulations under which pro-
cess sources are controlled were found to be much less stringent than
those normally applied; further major reductions could be expected if
controls were brought up to the average stringency seen in other cities.
Fugitive dust due to vehicular traffic has also been cited as one of
21
-------
the problems in the industrial valley. The monitor with the highest
3
annual mean (105 ug/m ) is located approximately 25 feet back from a
heavily traveled road; a location 100 yards back from the road has
levels about 40 percent lower.
Washington. D.C. - While Washington has never had the major TSP problem
of other cities because of its nonindustrial nature, two sites in the
city exceeded the annual primary standard in 1974. There has been a
slight downward trend since the early 1960s as coal use decreased and
higher grade fuels were substituted, but two center-city sites con-
tinued to exceed the primary standard in 1974. Control regulations are
stringent, and large emission reductions have resulted from the closing
of incinerators and fuel switching; most sources seem to be in com-
pliance. The cause of nonattainment at the two center-city sites is a
mixture of urban activities. Demolition and construction associated
with urban renewal was prevalent for several years, and has been more
recently supplemented by construction of the METRO transit system.
In comparison with other cities, traffic would appear to be an expected
problem. However, any clear demonstration of that influence is pre-
cluded by the extreme heterogeneity of monitoring site locations, with
almost all monitors located very high, very remote from the traffic,
or both.
Particle Characterization
As mentioned in Section I, optical microscopic examination was undertaken
on selected hi-vol filters from each city. The filters were selected
from several representative sites in each city and the results were sub-
jected to quality control checks. A summary of the filter analyses and
the results of the quality control are presented in Appendix B of this
volume, and a more detailed presentation is included in Volume II of
this report.
22
-------
In Table 5, the microscopy results for each city have been averaged by
the generic type of material present. These composite results show the
highest percentage component to be mineral matter. Sources of mineral
matter include windblown soil, reentrained dust from streets, fugitive
dust from construction and demolition, and such industrial sources aa
primary metals and mineral products industries and material storage
piles. Appendix B gives a more detailed breakout of these components.
The higher values for mineral matter in Denver and Oklahoma City support
the theory that fugitive dust sources are particularly important in arid
areas.
It should be emphasized that the optical microscope does not allow iden-
tification of particles smaller than about 1 urn, so the analytical data
is representative of only the supermicron portion of the particulate.
Therefore, in applying the component percentages, it was assumed that
15 percent of the mass is invisible to the microscopist. Table 6 shows
the results- of this procedure as applied to a categorization of the
components by site type for all sites studied in the 14 cities. All
filters analyzed were selected from days with average or greater loadings.
Particle Size The average particle size for each of the major visible
components is presented in Table 7. In general, mineral constituents
had the smallest particle size, and biological materials and rubber the
largest. The differences between sizes reported for the aggregate cate-
gories and the subcategories is not significant. Although the average
size of the mineral fraction, 8 ^m, is consistent with the average sizes
of the principal components, the average size reported for combustion
products, 5 um, is noticeably lower than the average size of the individ-
ual components within that group. This is because the filters on which
sizing of the individual components was done are not necessarily the
same filters that comprise the aggregate combustion products group. For
some filters the size range was reported only for the combustion products
group as a whole because the individual components comprised less than
23
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Table 5. COMPOSITE SUMMARY OF MICROSCOPIC ANALYSIS IN 14 CITIES, Percent
City
Heavily
industrialized
Cleveland
Birmingham3
Philadelphia3
Baltimore3
St. Louis
Cincinnati
Moderately
industrialized
Chattanooga
Denver
Seattle
Providence
lightly
industrialized
Washington, D.C.
Oklahoma City
Miamib
San Francisco
All cities
Minerals
Average
51
66
64
69
75
51
36
81
60
64
70
88
79
52
65
Range
28-85
14-90
6-93
52-88
21-99
24-88
3-96
62-97
30-96
28-92
39-87
63-99
75-83
29-73
3-99
Combustion
products
Average
40
22
33
25
21
44
35
7
27
22
23
8
9
29
25
Range
10-70
2-86
6-89
11-61
1-79
9-84
8-78
1-19
1-62
4-68
5-49
1-31
7-12
10-50
1-89
Biological
material
Average
1
2
1
3
<1
1
16
1
3
1
5
<1
-------
Table 6. ESTIMATES OF AVERAGE FILTER LOADINGS BY SITE CLASSIFICATION
Components
Mineral
Combustion products
Biological material
Misc. (mostly rubber)
Assumed < 1 urn
Total
3
Average loading , tig/rn
Commercial
64
27
2
9
19
120
Residential
51
19
3
5
14
92
Industrial
87
42
3
9
25
166
Undeveloped
66
6
<1
<1
13
86
Table 7. COMPOSITE SUMMARY OF PARTICLE SIZE BY COMPONENTS
Component
Minerals
Quartz
Calcite
Hematite
Combustion Products
Oil soot
Coal soot
Glassy fly ash
Biological Material
Pollen
Rubber
Average
size, p.m
( 8)
11
9
3
( 5)
13
30
12
(24)
35
(43)
Average size
range , urn
-------
5 percent of the observed particulate. The average size of the biological
material is quite large but understandable in terms of its source and
aerodynamic shape. The very large average particle size reported for
rubber, however, is somewhat harder to understand. The generation of
large rubber particles by mechanical abrasion is easily understood, but
it is difficult to explain how such large particles can be transported
over substantial horizontal or vertical distances.
Quality Control The reader is cautioned to review Appendix B regarding
the results of quality control procedures used in the microscopic examina-
tion. Briefly, it was found that the replicability of the results of
analyses of individual samples varied considerably with some results quite
far apart. However, the compositing of results from many filters to ob-
tain average results minimizes any systematic bias among microscopists
and laboratories.
SUMMARY OF FACTORS AFFECTING ATTAINMENT
The purpose of the city case studies was to identify and study the various
factors, problems, and issues concerned with attaining the TSP standards
as they were experienced in each city. Since the 14 cities cover a broad
range of city characteristics and hence represent a variety of situations
with respect to TSP air quality and its determinants, analyses of the
factors in the various cities can be drawn together for an overall assess-
ment of the TSP attainment situation in the study cities and, by extrapo-
lation, throughout the nation.
Following the analyses of the study cities, a number of factors were
identified as significant for standards attainment. Many of these had
been first identified in the preliminary literature review and were then
followed up in the city studies; a few others were identified in the
course of one or more of the city studies. The principal issues are
listed below, grouped into five major categories that will subsequently
provide a framework for the more detailed discussions in Section III.
26
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Large Scale Influences
Large scale influences include those factors that dominate an area much
larger than the urban areas being studied. They include natural, trans-
ported, and secondary particulates. The differing influences of these
factors in various urban areas can cause significant differences in the
ability to control the local TSP problem. Their effect on urban levels
is generally estimated by measuring air quality in nonurban areas. The
average nonurban particulate level for the 14 study cities is between
3 3
25 and 30 ug/m ; however, values ranged from less than 15 tig/m on the
3
west coast to roughly 35 ug/m in the metropolitan northeast. The three
major large scale factors are described below:
Natural particulates A major factor that can have signifi-
cant impact on standards attainment is the magnitude of the
natural TSP level in the incoming air masses. The west coast
cities benefit from having a very low (global) particulate
level, while cities in the central plains or the east have
additional continental contributions.
Transported primary particulates Cities in the eastern
metropolitan complex have the further problem of manmade
particulates being transported from neighboring urban areas
without space for adequate dilution. Therefore, these cities
have an impaired capability for managing their own air
quality.
Secondary particulates Levels of particulates such as sul-
fates, nitrates, ammonium, and some organic compounds, which
are generally believed to be formed as secondary particulates,
indicate again that cities in the east are receiving increased
TSP levels from other areas. These particulates are formed
both in transport and locally from sources not traditionally
controlled in TSP standard attainment strategies.
Traditional Source Factors
Much of the problem of standards attainment in several of the 14 study
cities is attributable to emissions from those sources industrial pro-
cesses, fuel combustion, incineration that have traditionally been
considered subject to pollution control efforts. Cities with heavy
27
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industrial activity were found to have citywide TSP levels averaging from
10 to 50 ng/m above the levels in cities with little or no industry;
sites particularly close to heavy industrial activity averaged up to
25 ug/m higher than other industrial sites. Specific nonattainment
factors related to traditional source emissions include the following:
Industrial emissions In several cities, widespread in-
dustrial emissions were obviously the major share of the
overall urban problem; in other cities more isolated in-
dustrial emission problems were responsible for local non-
attainment. The most apparent problems were the steel
industry, with associated coking and foundry operations,
and the various minerals handling industries, such as
cement and asphalt plants and stone and gravel quarries.
Fugitive emissions Several sites, generally near indus-
trial areas, were significantly affected by fugitive emis-
sions from such sources as materials stockpiles, coal load-
ing operations, blast furnace slips, rock crushing and
loading, and similar uncontained industrial processes.
Fuel oil combustion In several cities there was concern
over the degree of impact from oil combustion. In coastal
cities, oil is frequently used for space heating, and the
smaller residential oil burners are typically not controlled
as pollution sources. In midwestern cities where coal is
used significantly, even very major oil-fired combustion
units, such as utility boilers, may be ignored as sources
because they are cleaner than equivalent coal-fired units.
Fuel use trends One positive influence on standards attain-
ment in several cities is the on-going trend toward cleaner
fuels, especially the shift from coal to gas in small units.
This is a continuation of a trend spanning many years, fueled
by factors of convenience and economic affluence.
Lack of effective control In at least one instance, a major
factor in failing to attain the standards is the overall lack
of any effective control program or enforcement effort.
Lack of adequate time for control In some instances, failure
to meet the standards is due to having insufficient time since
the inception of control efforts for even an outstanding con-
trol program to cope with a major TSF problem.
Inadequate regulations In some cases, relatively nonstringent
regulations inhibit meeting the standards by requiring less re-
duction in emissions than is necessary to meet the standards.
28
-------
Inadequate compliance determination In most of the study
areas, the process of verifying that a source is in com-
pliance and remains so appears to be somewhat haphazard.
Most agencies have less firm knowledge on such matters than
seems desirable.
Inadequate data base In some cases, planning for air quality
management and standards attainment is inhibited by the lack
of an adequate data base. Usually involving emissions rather
than air quality data, this lack can be so extreme in some
cases that it must be construed as a major misunderstanding
as to the nature of the TSF problem being faced.
Nontraditional Factors
Even with the nonurban, large scale particulate concentrations and the
emissions from traditional sources taken into consideration, analysis of
many of the monitoring sites in the 14 study cities indicated that other
factors, not traditionally considered, were producing TSP levels that were
3
typically 25 to 30 ug/m higher than expected. Such levels could often
be attributed to specific sources such as construction activity or local-
ized fugitive dust emissions, but in many cases the elevated concentra-
tions were simply the result of the intense level of activity in urban
areas. Specific factors identified include:
Localized fugitive dust emissions A number of sites in
various cities were prevented from attaining the standard
at least in part by emissions from bare unvegetated lots,
unpaved parking areas and roadways, heavily traveled ex-
pressways, and similar local sources of entrained dust.
General urban activity In most cities, ambient TSP levels
in the densest part of the city are higher than elsewhere
with no single, obvious reason. This effect influences at-
tainment at a number of commercial and dense residential
sites in almost every city. The best immediate presumption
is that this contribution represents the combined, well-
mixed influence of higher levels of traffic , building con-
struction, pedestrian activity, and other types of urban
activity that tend to be greater in the more dense central
part of the city.
29
-------
Construction activity Several sites, often center city com-
mercial sites, were hindered in meeting the standard by dust
entrained from construction sites of various types, including
urban renewal, small building construction, and highway and
subway construction.
In addition to the above factors, which are all related to sources of
particulate emissions, other factors were found to affect the real or
apparent TSP problem. As discussed in the selection of the cities, the
meteorology and climatology of a region can help to aggravate or amelio-
rate the TSF problem; the dispersion characteristics and precipitation
levels are the most prominent influences. The design of the monitoring
network configuration and the actual placement of monitors are also im-
portant in conceptualizing what the TSP situation is. The general find-
ings from the city studies for these factors are summarized below.
Meteorology and Climatology
Dispersion conditions The overall pollutant dispersion
characteristics can have significant effects in either direc-
tion; in the southern mountain area, the attainment is clearly
more difficult because of adverse meteorology and topography,
whereas in the coastal and great plains areas the opposite is
true.
Precipitation Frequent, significant precipitation is ap-
parently a help in attaining standards, while arid condi-
tions are a detriment.
Monitoring Considerations
Inappropriate sampler heights One of the more common prob-
lems with hi-vol network design is the question of consistent,
appropriate sampler heights. If the hi-vols are strikingly
higher or lower than typical, the recorded TSP levels will be
artificially decreased or elevated in comparison to other
cities. Similarly, if there are striking height differences
within one urban area, there will be difficulties in adequately
planning for standards attainment and in accurately assessing
progress.
30
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9 Network design As the TSP levels vary from monitor to moni-
tor, and generally around the city, it is important to ensure
that those areas of maximum TSP concentration are monitored.
Some cities located monitors with the help of extensive model-
ing efforts, while others picked convenient locations.
Figure 2 is a schematic sketch of the interrelationship of these five
major groups of factors. It is intended as a minemonic device to em-
phasize that three of the factors are actual components of the particu-
late matter, while the other two are distorting influences.
TRADITIONAL
SOURCES
NONTRADITIONAL
SOURCES
LARGE-SCALE
INFLUENCES
MONITOR SITING
Figure 2. Schematic relationship among five major factors
31
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SECTION III
ASSESSMENT OF FACTORS AFFECTING ATTAINMENT
This section assesses the significance of the five major factors identified
with respect to the attainment or nonattainment of the ambient standards.
For ease of readership, much of the more extensive analytical and discus-
sion material has been collected into appendices, of which this section
can be considered a summary.
Since the air quality standard makes no distinction among particulates
from various sources, it is not possible to ascribe nonattainment to any
particular source or source category, other than to the extent that the
source or source category contributes to the measured ISP levels at the
point in question. Consequently, the assessment of the contributions from
the various factors can be seen as the determination of the contributions
of the various factors to an overall typical TSP concentration. This
viewpoint, along with a determination of how the various factors affect
variations in TSP levels, provides a useful discussion framework, which
is used throughout this section. The large number of monitoring sites
(154) visited and studied throughout the country provide a unique opportunity
for developing an understanding of the individual factors affecting the
measured TSP levels. From an analysis of the data, the city characteristics,
and the monitoring site locations, the components of the TSP at different
types of sites were estimated.
The most obvious difference among sites is the nature of the neighborhood
in which they are located. Figure 3 shows the average of the annual con-
centrations at all the sites in the 14 study cities varied by the primary
32
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ISO
10
E
100
UJ
u
50
a.
(A
RESIDENTIAL
COMMERCIAL
INDUSTRIAL
Figure 3. Average TSP levels by neighborhood type
33
-------
neighborhood classification of residential, commercial, and industrial.
Residential neighborhoods generally had TSP concentrations in the range
j
of 50 to 70 ug/m ; monitors at commercial sites recorded a wider range of
3
values, principally between 60 and 110 pig/m ; and industrial neighborhoods
3
had the highest TSP levels, averaging between 80 and 150 ng/m .
To explain not only why these TSP levels are what they are but also why
they vary as they do, the analyses conducted in this study drew upon the
general findings from the city studies discussed in Section II. These
findings identified major topics of concern for assessment of the TSP
standards attainment problem on a nationwide basis: large scale consider-
ations, traditional sources, nontraditional sources, monitoring considera-
tions, and meteorology/climatology. This categorization structures the
following discussion, which summarizes the findings of the cross-city
analyses presented in the appendices.
BACKGROUND AND LARGE-SCALE CONSIDERATIONS
In reviewing the literature, and in considering the wide range of typical
air quality levels over different parts of the country, it is apparent
that there is a significant portion of TSP levels that varies over a geo-
graphical scale much larger than any one or even a few AQCRs. On an over-
all average basis, the levels of TSP measured in nonurban areas represent
the concentration of particulates in the air masses before they arrive in
an urban area; hence the wide range of nonurban values implies that com-
parable cities, located in different portions of the country, would require
different degrees of control to attain and maintain the ambient standards.
Therefore, quantitative air quality planning requires an understanding of
these levels and how and why they occur.
Terminology
Variously, particulates either measured in or presumed to originate in
nonurban areas beyond the jurisdiction of local or state agencies have
34
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previously been labelled in one way or another under the heading "back-
ground." The usage of the term, however, when examined carefully, is found
to entail a number of somewhat different concepts. The official concept
of background is defined in the Requirements for Preparation, Adoption,
and Subraittal of Implementation Plans (40 CFR 51.13):
For purposes of developing a control strategy, background con-
centration shall be taken into consideration with respect to
particulate matter. As used in this subpart, 'background con-
centration* is that portion of the measured ambient levels of
particulate matter that cannot be reduced by controlling emis-
sions from manmade sources; 'background concentration* shall be
determined by reference to measured ambient levels of partic-
ulate matter in nonurban areas.
Unfortunately, this definition reflects to some extent the prevalent varia-
tion in usage of the word "background," and hence contradictory usage of
the term continues. Under the first part of the last sentence, in which
background is defined as the uncontrollable portion of TSP, EPA regulations
provide for rollback calculations to ascertain the degree of emission
control necessary for the attainment of the air quality standards. The
rollback formula:
, ambient - standard
reduction required = ambient . background
tacitly assumes that the background level is a lower limit below which the
ambient concentration cannot be reduced. On the other hand, in air quality
modeling efforts, the background is frequently defined as the difference
between the measured concentrations and the calculated concentrations
which includes into background any source not included in the inventory
used. In still other circumstances, an agency may choose to regard as
"background" any TSP coming across the boundary into their jurisdiction,
regardless of whether that jurisdiction extends appropriately into nonurban
areas.
35
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Contradiction in the usage of the term background also arises from the
latter part of the above citation referring to the actual measurement of
background. Following that concept, the background levels most often used
in air quality reflect measurements of the ambient air quality in some re-
mote rural area; this may possibly be within the county, AQCR, or state,
depending upon the jurisdiction of the planning agency; or may be very far
away. Where possible, these measurements are made upwind of the prevailing
flow of air so as not to sample the particulate contribution of the area.
However, what these remote monitors are actually measuring is not neces-
sarily an uncontrollable or nonmanmade level of TSP. Rather, these mea-
surements simply reflect the particulate concentrations coming into the
urban area, including not only the natural, uncontrollable particulates
but also man's contribution to the nonurban particulate levels; these lat-
ter include emissions in rural areas, particles transported from distant
urban areas, and secondary particulates.
To avoid confusion with previous use of the term background, the term
nonurban particulate will be used in this report to refer to the latter
part of the EPA definition presented above; i.e., the TSP concentration
determined by measuring the ambient levels of particulate matter in non-
urban areas. The major components of nonurban particulates are listed
below:
Natural particulate TSP contributed solely by natural pro-
cesses and thus truly uncontrollable; includes a global con-
tribution, which includes both primary and secondary par-
ticles, and a continental contribution, primarily from wind
erosion of soil.
Transported particulate - TSP levels that arise due to emis-
sions from man's activities in "upwind" urban and industrial
areas; includes both primary and secondary particulates trans-
ported from one area to another.
Local influences TSP measured at nonurban monitors that is
contributed by emissions in rural areas (dirt roads, agri-
cultural tilling, space heating, rural industrial sources)
and affected by the actual placement of the monitor (reen-
trained dust, small town activity).
36
-------
Because the term background has also connoted TSP that cannot be explained
through modeling efforts and TSP that cannot be controlled through control
of primary particulate sources, the excess of secondary particulates mea-
sured in urban areas over the levels measured in nonurban areas will also
be considered under this topic.
Natural Particulates
The emission and formation of particulates from natural sources result in
low concentrations of ambient particulates that have always existed, re-
gardless of man's influence. The most important of the natural sources of
particulates are soil and rock debris, forest fires, plants, volcanoes and
ocean salt spray; in addition, natural sources can emit gaseous pollutants
which can react to form particulates. As shown by the estimates in Table 8,
particulate emissions from natural sources and particulate formation from
naturally occurring precursors far outweigh the contribution of manmade
sources on a global scale.
Table 8. ESTIMATES OF PARTICLES SMALLER THAN 20 um RADIUS EMITTED INTO
OR FORMED IN THE ATMOSPHERE (106 metric tons/year)
Man-made
Particles from direct emissions
Particles formed from gaseous emissions
Sulfate from S02
Nitrate from NOX
Organics from hydrocarbons
Natural
Soil and rock debris
Forest fires and slash-burning debris
Sea salt
Volcanic debris
Particles formed from gaseous emissions
Sulfate from H2S
Ammonium salts from NHj
Nitrate from NOl^
Organics from hydrocarbons
Total
185 - 415
773 - 2200
958 - 2615
10 - 90
130 - 200
30 - 35
15 - 90
100 - 500
3 - 150
300
25 - 150
130 - 200
80 - 270
60 - 430
75 - 20Q
37
-------
Of the natural sources of particulate emissions, sea salt is probably the
largest emission source, but its greatest effect on TSP concentration
occurs over the oceans; its contribution to TSP levels extends over land
only a short distance. Over land, wind-entrained soil dust is the largest
direct source of particulate emissions. Gaseous emissions from natural
sources are scavenged through various chemical reactions and result in the
production of significant quantities of aerosol materials over a broad area.
Volcanic emissions can vary greatly from year to year but usually do not
contribute a large proportion of the natural particulate emissions. The
contribution of forest fires can only be estimated roughly at present;
though it appears small in Table 8, it may be considerably more important
with respect to air quality since such fires are frequently adjacent to
urban areas. Pollens, spores, and bacteria are an insignificant fraction
of the total emissions.
The primary distinction between the sources of natural particulates with
respect to TSP levels is simply their location and to some extent the
effective emission height and particle size. Generally, the natural par-
ticulate levels can be thought of as contributions fr_ni two types of
sources: global sources and continental sources. Global particulates
arise from the heated emissions from volcanoes and, to a lesser extent,
forest fires, and from secondary particulates formed from natural gaseous
emissions; these emissions are characteristically in the submicron range.
Sea salt is also often referred to as a global particulate. Continental
sources are wind erosion of rocks and soil; pollens and spores; and (over-
lapping global particulates) forest fires and secondary particulates,
especially hydrocarbons from plant exudations.
The contribution from global sources is considered relatively constant across
the North American continent in the range of 1 to 5 pg/m3; for TSP strategy
planning, the contribution from continental sources is much more important
than that from global sources. Continental particulate levels are much higher
and they vary across the continent. For example, in the Great Plains region
of the United States, wind erosion of soil is estimated to produce a larger
mass of particulates than all other sources in the nation and results in high
dust concentrations over large areas. Most duststorms occur in the spring
38
-------
but air pollution from duststorms can be a problem in other seasons as well.
The rainfall and soil erosiveness of an area are also influential with
respect to the frequency and severity of duststorms.
Transported Particulates
The term transport refers to the movement of particulates over a greater
distance than normally considered for dispersion modeling used for air
quality planning. Transported particulates include primary particles,
which are emitted directly into the air and secondary particles, which are
formed from reactions of gases in the atmosphere. While natural particu-
lates can also be transported considerable distances, this discussion of
transported particulates is meant to center on particulates that originate
from man's activities.
Transported Primary Particulates The transport of primary particulates
may be divided into two classes short-range and long-range. Long-range
transport occurs when the particulates are mixed into an air mass and
travel several hundred kilometers or more without any removal mechanisms
such as washout or rainout. This phenomenon of transport is directly re-
lated to meteorology because it requires a stable air mass moving across
the country. An interesting case study of the transport of a particular
air mass is described in Appendix C. This study demonstrates how long-
range transport can produce abnormally high values of particulates over
short periods, causing violations of the 24-hour standards. The degree
to which it affects annual means is related to the frequency of such
occurrences.
Short-range transport refers to the transport of particulates over less
distance, ranging from a few to about 100 kilometers. It is primarily
concerned with the movement of particulates across planning area bound-
aries; i.e., from the jurisdiction of one air pollution control agency
into the jurisdiction of another. This problem has been recognized in
the guidelines for the classification of areas with respect to deteriora-
tion of the air quality. For instance, an AQCR cannot be designated
Class III (degradation up to the air quality standards) if such a desig-
nation will also result in degradation of the air quality of an AQCR
designated Class I (minimum degradation).
39
-------
Obviously, short-range transport of primary particulates is of principal
concern in areas which have adjoining urban areas with insufficient rural
areas between to allow for removal or dispersion of the pollutants. Such
is the situation in the northeast where the air may sweep up past Balti-
more, Washington, and Philadelphia into New York and up to Boston. In
the study of Providence under this effort, high values of particulates,
even in the less developed areas of the AQCR, were most often associated
with winds from the direction of New York City. Meteorology is a com-
plicating factor in this analysis because of variations in windspeed and
rainfall with changing wind direction. However, it is likely that such
conditions do exist.
Over even a smaller scale, transported primary particulates are important
whenever air crosses from one region that is completely autonomous into
another area that has separate control. Such a situation was found in
Philadelphia in the course of this study. The Philadelphia Air Manage-
ment Services has complete responsibility in Philadelphia County, while
the Commonwealth of Pennsylvania Department of Environmental Resources
has responsibility for the counties surrounding Philadelphia. Since the
entire County of Philadelphia can be considered urbanized, the most re-
mote site in the network is one located in a lightly dense residential
neighborhood near the border of Philadelphia and Montgomery Counties.
This site had an annual mean of 59 ug/m in 1974, implying that there
were virtually no means of avoiding violating at least the secondary
annual standard as the air passed over the city. Another site, in a
more industrialized corner of the county but also near the industrial-
ized areas of Delaware County in Pennsylvania and Gloucester County in
New Jersey, had an annual mean of 94 ng/m . The value at this site is
especially important since it is in the southwest corner of Philadelphia
County, the direction from which most of the air crossing the county
would come.
40
-------
Transported Secondary Particulate As mentioned previously, secondary
particulates are the products of chemical reactions occurring in the at-
mosphere. They can initiate In the gas phase or as a result of reactions
between gases and already existing particles. They are a major source of
the ubiquitous Aitken nuclei, or homogenous nucleation centers, that are
essential for most of the condensation processes that take place in the
atmosphere. They are also a prime component of urban smog.
Composition The main ingredients in the formation of secondary particu-
lates are sunlight and gases such as sulfur dioxide, ammonia, nitric oxide,
water vapor, and hydrocarbons, which enter the atmosphere from both natural
and manmade sources. Secondary particulates range in size from molecular
clusters with diameters on the order of 0.005 urn to particles with diam-
2-4
eters as large as several micrometers. Field studies of urban aerosols
have shown that the highest concentration of secondary particulates is
usually in the range 0.01 to 1.0 jam. The concentration of particles in this
size range can vary directly with intensity of sunlight and concentration
of ozone.
The principal factors governing distribution by size over the respective
rates of particulate formation and removal. The smallest particles,
which are created constantly during the daylight hours, coagulate into
larger particles. The overall life cycle of secondary particulates is
difficult to determine; estimates range from 1 week to 40 days.5 In the
end, the particles are either removed from the atmosphere by precipita-
tion or dry deposition. During this period, however, they may be
transported vast distances from the source of the gaseous precursors.
Found in both urban and rural areas, secondary particulates are in general
composed of three types of chemical compounds sulfates, organics, and
nitrates - which are briefly discussed below.
Sulfates. Sulfates are ubiquitous. A large fraction of the
global aerosol is ammonium sulfate (NH^^SO^.. Sulfates such
as sulfuric acid O^SO), which is found in most urban aerosols,
41
-------
result from the reaction of 803 and water. The sulfate salts,
such as PbSO^, in turn, derive from the reactions of compounds
such as ammonia or metallic oxides with sulfuric acid droplets.
Organics. The second major constituent of secondary particulates
is produced by the reaction of hydrocarbons with oxidants (e.g.,
NC>2, 03) in the atmosphere to produce peroxide radicals. Through
a series of chain reactions, these radicals eventually form large
organic molecules which condense to form droplets or solid particles.
Primary sources of hydrocarbons in urban areas are automobile ex-
haust and industrial effluents. In some rural areas, hydro-
carbon emissions from natural sources may be significant. Ter-
penes are an example of such emissions; many terpenes are highly
unsaturated, and in some cases they can even be oxidized in the
dark by reaction with 02. The particulates formed by oxidation
of these organic vapors are sometimes the cause of the haze ob-
served in rural areas.
Nitrates. Nitrogen oxides emitted into the air can be oxidized
and react with water to form nitric acid in either vapor or drop-
let form. From this form, nitrates are created through reactions
with gaseous or solid species.
Air quality impact Secondary particulates can occur both over a long
period of transport and apparently also fairly quickl., in an urban area.
As with primary particulates, secondary particulates can be important
over both short-range and long-range transport. The long-range transport
study in Appendix C found sulfate levels three times higher than normal;
shorter transport of secondary particulates is known to contribute to
high levels in the northeast.
Annual levels of sulfates and nitrates for nonurban areas near each of
the 14 study cities are given in Table 9. Average values for each of
the industrialization classifications, for the cities in the east (of
the Mississippi River) versus the west, and for the cities in the north
(heating degree days more than 4000/year) versus the south, have been
calculated. While the heavily industrialized cities have the highest
nonurban levels of secondary particulates, this division apparently re-
sults from the geographic location of the cities. The highest levels
within each category of industrialization occur in cities east of the
42
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Table 9. NONURBAN
NITRATES
LEVELS OF SULFATES AND
IN THE 14 STUDY CITIES3
Cities
Heavily
industrialized
Cleveland
Birmingham
Philadelphia
Baltimore
St. Louis
Cincinnati
Average
Moderately
industrialized
Chattanooga
Denver
Seattle
Providence
Average
Lightly
industrialized
Washington, D.C.
Oklahoma City
Miami
San Francisco
Average
East
West
North
South
Nonurban levels
504
10
7
10
8
6
11
8.7
6
2
3
7
4.5
8
3
5
2
4.5
8
3.2
7.2
4.6
N03
1
1
1
1
1
1
1.0
2
0
0
1
0.8
1
1
1
0
0.76
1.11
0.4
0.78
1.0
Total
11
8
11
9
7
12
9.7
8
2
3
8
5.3
9
4
6
2
5.25
9.11
3.6
6.0
5.6
Best estimate averages based upon
composite values of available NASN data.
43
-------
Mississippi, where the density of industrialization is greatest, and also
in the northern cities, where space heating is more important. In the
two dichotomous breakdowns - north versus south, east versus west - the
impact of geographic location on the nonurban values is obvious. A logical
extrapolation of these data would be that nonurban secondary particulates
are highest in the northeast and lowest in the southwest.
Other Factors
As mentioned previously, two other factors are important when considering
nonurban TSP levels and the use of such levels in air quality planning.
Nonurban levels can reflect local influences that are not of concern when
planning control strategies for an urban area because the particulate mat-
ter is not actually carried into the urban area. At the same time, se-
condary particulatet formed locally in an urban area are not accounted
for in nonurban monitoring, and therefore, these urban secondary excess
levels are not appropriately incorporated in traditional air quality
planning.
Local Rural Influences - Local influences on nonurban levels can be tradi-
tional emissions such as from local space heating and rural industrial
activity; but, more likely, these local influences are artifacts of the
monitor placement so that the TSP levels are subject to reentrainment
from dirt roads, agricultural tilling, or natural wind erosion. Similarly,
TSP levels reported as nonurban levels may be from monitors located in
small, rural towns; these monitors would also be measuring the particulates
generated by man's activities (traditional and nontraditional sources) in
the town.
Emissions from dirt roads in the major counties in the study AQCRs are
discussed later under the topic of Nontraditional Sources. That analysis
suggests that the current inventories for dirt roads provides an exaggerated
picture of the importance of unpaved rural roads to the air quality in an
urban area. The current inventories suggest that emission levels due to
44
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dirt roads in urban counties are usually much higher than the total tradi-
tional source emission levels in urban areas. Obviously the air quality
impact from these sources is not equivalent to that from traditional sources;
otherwise, the TSP concentrations in rural areas would be expected to reach
or exceed those in urban areas.
Similar findings apply to the inventoried emissions for agricultural tillings.
While the emissions from tilling were never as great as those from dirt roads
in the 14 AQCR's studied, in some areas the levels are quite high; e.g., in
the San Francisco Bay Area AQCR, emissions due to tilling are inventoried at
almost 190,000 tons per year. Since tilling does not occur throughout the
year but only at certain seasons, any impact from tilling would be expected
to be short-term, perhaps causing elevated levels for a month at a time.
Urban Secondary Excess - Secondary particulates formed in the urban area
as a result of local emission sources have been ignored in control strate-
gies applied to air quality planning; i.e., control of TSP concentrations
has been approached solely by reducing directly emitted particulates. Pre-
sumably, the amount of secondary particulate formed is related to the
amount of precursors, so that higher levels of secondary particulates may
be expected to be found in the more industrialized regions. For sulfates,
the amount of space heating with fuels high in sulfur may be important in
winter.
Because of the different control approaches that are open to an individual
air pollution control agency, it is helpful to separate out the secondary
particulates formed within the jurisdiction of the agency from those formed
in transport to the region. The annual levels of sulfates and nitrates for
urban and nonurban areas in each of the 14 study cities are given in Table
10 and averages have been calculated for the same breakdowns given in
Table 9. The data in Table 10 demonstrate that air entering the city is
the predominant factor in determining the sulfate levels in a city but that
nitrate levels can increase by a factor of three in the city. Since
45
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Table 10. URBAN AND NONURBAN LEVELS OF SULFATES AND
NITRATES IN THE 14 STUDY CITIES3
Cit les
HeavtU
Industrial izcd
Cleveland
Birmlnt,tian
Philadelphia
Bait inpre
St. Louis
Clnc.ini.il i
Average
Moderately
induslrullred
Chattanoof A
Denver
Seattle
Providence
Average
Lightly
industrial j:ed
Va«ihi 1 1,1 PI . n C
Okla'iom?. Cstt
Kiani
San Frareiscr
A jera-ic
East
West
Nor en
South
Nonurban levels
SOi
10
7
1C
6
6
1<
E 7
6
»
3
7
- 5
e
3
5
2
- 3
B
1
-> 2
- 6
N03
1
1
1
1
1
1
1 0
2
0
0
1
0 6
1
1
1
I1
'. 74
i .:
' -
' " r
1 0
Total
11
s
11
9
7
12
9 i
B
-
3
e
5 3
9
6
6
2
5.35
0 11
; t
e
5 f.
Grban levels
S04
10
16
14
10
12
12
12 0
11
5
7
9
S.O
12
3
3
S
6 25
1C 7o
4
K. 1
2 0
M>3
3
3
6
3
3
3
3.2
2
3
2
2
2.3
3
j
1
2
7.0
: 67
: L
2 £
5 9
Total
13
17
IB
13
15
15
13
8
9
11
10 3
\'j
5
b
7
S 25
13
e s
li fi
5 "
Urban excess
S04
0
7
6
2
6
i
S
3
4
2
3.3
'.
t\
r
3
1 7;
2 75
: 2
: r-
3 '
N03
2
2
3
2
2
2
0
3
2
1
1 5
2
!
C
2
1 23
'. 5i
2 0
2 11
1 C
Total
2
9
7
6
8
3
S
8
6
3
5.0
£
1
S
3 0
4 33
5 2
5.C
4 0
va.uef ""
46
-------
sulfates are the predominant secondary pollutant, the average increase in
secondary participates is on the order of 60 to 70 percent. As may be
expected, the largest increases (urban excesses) are seen in the highly
industrialized areas where secondary particulate levels inside the city
average 6 ug/m above those in the nonurban setting; lightly industrialized
areas have half of this increase. On the whole, cities may have concentra-
3
tions elevated 5 to 15 vig/m due solely to sulfates and nitrates. Two
important points concerning Tables 9 and 10 are that some sulfates may
be directly emitted as primary particulate, and secondary organics may also
be significant, but adequate measurements were not available.
National Assessment
As has been shown above, particulate levels exist which are beyond the
control of individual state and local air pollution control agencies.
These levels of TSP enter the jurisdiction of an agency along, with the
air mass that, is carrying them. The particulates entering a region may
be the result of a facility a few miles upwind of the jurisdiction, of
another city 50 km away, of sources generating precursors to secondary
pollutants hundreds of miles from the region, or of natural nonurban sources
such as sea salt, pollen, and wind-driven dust. While the smaller scale
transport problems may often be adequately handled by cooperation between
adjoining state and local agencies or by EPA regional office intervention,
the larger scale influences either cannot be controlled or need direction
and planning on the national level. These larger scale problems are
addressed below.
The concentration of particulates in rural areas of the country has been
monitored for many years as part of the National Air Surveillance Network
(NASN). Figure 4 presents composites of values reported at various mmurban
NASN sites from 1970 through 1973. The data in this figure indicate the
wide range of annual means being reported. In addition to the problem of
transported primary and secondary particulates, some of the range in TSP
values is expected to be due to inconsistent and, in some cases, poor
47
-------
oo
HAWAII
Figure 4. Composite annual geometric mean TSP levels at nonurban NASN
sites from 1970 through 1973 (ng/m3)
-------
monitor siting. For instance, the high values reported at the monitors
on the west coast (California and Oregon), which would be expected to have
values half of those reported based upon global and continental particulate
levels, are recorded by monitors located on the ground. As discussed later
under reentrainment, such low siting is expected to result in highly exag-
o
gerated values. The high value of 58 yg/m reported in Indiana is due to
a nearby power plant influencing the levels in the rural area.
The impact that transported secondary particulates have on these nonurban
sites can be seen in Figure 5, which presents the nonurban sulfate and
nitrate levels for 1974. Almost no nitrates and very little sulfates are
found in the western part of the country, yet secondary particulates con-
sistently add more than 5 yg/m to the TSP loading at nonurban sites east
of the Mississippi River. These data reiterate the findings of the 14 city
case studies: secondary particulates in nonurban areas can add significantly
to the TSP burden on cities in the east arid northeast.
The transported primary particulates cannot be so easily addressed on the
national scale for several reasons. One reason is that the density of non-
urban NASN monitors is too low to provide adequate information on the change
of TSP levels between major urban areas. Such an analysis would have to
include monitors operated by state and local agencies in order to be close
to the density of monitors needed, and these data were not available on a
nationwide or even regionwide basis. Therefore, the conclusions on trans-
ported primary particulates must stand solely on the earlier discussion and
the analysi.s provided in Appendix C.
Another problem already mentioned, monitor height, not only means that
transport cannot be accurately determined but also brings many of the
reported nonurban values into question. Most of the monitors in the non-
urban network apparently are located at heights below 10 feet, with many
of them in the 3 to 6 foot range. Such monitors are more likely to be
influenced by nearby disturbances than by any particulates being transported
into the region.
49
-------
Ul
o
Q-SULFATE
£]- NITRATE (>
Figure 5. Annual geometric mean sulfate and nitrate levels at
nonurban NASN sites 1974
-------
Despite these problems., some estimate of the variations in the nonurban
levels can be made from the findings of this study. Figure 6 provides a
conceptualized diagram of the contributions to nonurban levels as one moves
across the country. Global particulates are assumed to be constant across
the country. Continental particulate is lowest on the west coast, where
the land area has not had a chance to contribute significantly, and highest
in the midwest due to the high winds and more arid conditions. The
occurrence of some off-the-ocean air masses is felt to bring down the con-
tinental contribution a little in the east.
Transported secondary particulates contribute only a few micrograms in the
west and midwest. However, in the east, nonurban levels of secondary par-
ticulates are averaging around 10 ug/m . Although the long-range transport
case study presented in Appendix C is for Oklahoma City, the impact of
transported primary particulates on annual TSP levels in the west and mid-
west is felt to be minimal. In the east where cities are more concentrated,
2
transported primary particulates are more serious, averaging about 5 ug/m
on an annual basis throughout the east but potentially much higher in the
congested northeast.
On top of all these contributions, another few micrograms have been added
to reflect the local influences occurring on a large scale basis in the
rural areas (space heating, traffic, agricultural activity, etc.). This
additional level does not include immediate impacts from nearby sources
(power plants, roads) or from possible reentrained dust due to low monitor
height.
PARTICULATES FROM TRADITIONAL SOURCES
The most obvious of the many factors affecting attainment of the TSP
standards are the particulate emissions from three major categories of
pollution sources fuel combustion, industrial processes, and solid waste
disposal operations. These three source categories have long been con-
sidered significant pollution problems, and have traditionally been the
51
-------
Ul
40
ro 30
E
z
o
u
z
o
a.
en
20
10
LOCAL
TRANSPORTED
SECONDARY
CONTINENTAL
GLOBAL
WEST
LOCAL
TRANSPORTED
SECONDARY
CONTINENTAL
GLOBAL
MIDWEST
LOCAL
TRANSPORTED
PRIMARY
TRANSPORTED
SECONDARY
CONTINENTAL
GLOBAL
EAST
Figure 6. Average estimated contributions to nonurban
levels in the East, Midwest, West
-------
primary concern of air pollution control efforts; consequently, they have
been labeled "traditional sources" for purposes of this study. This sec-
tLon summarizes the assessment made of the significance of traditional
source emissions as a factor in the nonattainment of the TSP standards;
Appendix 0 presents summaries of the data assembled and the analyses made
to develop the assessment.
In general, the impact of traditional sources on nonattainment depends
very heavily on the nature of the urban area in question. The 14 case
study areas included both cities where traditional sources totally dominate
the picture and cities where they are not now, and probably never were, a
major share of the problem. Based on analysis of aggregate emission in-
ventories, emission densities, and compliance trends, it is possible to
summarize the impact of traditional sources in the 14 case study areas
as follows:
I. Three areas, all heavily industrialized, still have a
major problem with traditional sources;
II. Three areas have reduced emissions from traditional
sources to the point where they are no longer totally
dominant, although continuing further reduction and
on-going surveillance is still required;
III. Four areas have reduced formerly moderate levels of
traditional source emissions (mostly from fuel use
for heating and light industry) to near insignificance;
IV. In four areas, traditional sources probably never
were a serious problem.
While these specific proportions are not necessarily reflected in the
overall national picture, there are certainly a number of urban areas
throughout the country in each of these categories.
A comparison was also made of the emission parameters leading to this
classification with air quality levels in the various urban areas, expressed
as city wide average TSP concentrations. With adjustments made for differ-
ing nonurban levels and secondary particulates, essentially no difference
53
-------
in typical air quality between the third and fourth categories listed
above was indicated, with the average for both groups being 35 ug/m3 above
nonurban levels (Denver was excluded as an anomaly). This approximates
the contribution of nontraditional sources as discussed later. The three
heavily-industrialized cities still dominated by traditional source emis-
sions had an average city wide ISP level of 66 ug/m above nonurban, sug-
3
gesting that about 30 ug/m is the maximum potential city wide reduction,
even with very stringent traditional source control. The three cities
(category II) that have made significant but as yet incomplete traditional
source reductions averaged 48 pg/m above nonurban levels, suggesting that
o
there is still 10 to 15 pg/m of traditional source influence on city wide
averages which could be reduced somewhat with further control of traditional
sources. Figure 7 displays the relationship between emission density and
air quality, and illustrates the clustering of the study cities into the
categories. It is important to remind the reader that these results must
be interpreted as only semi-quantitative and extrapolated with care. Al-
though it is believed they provide a good national aggregate assessment of
the role of traditional sources, this analysis does average over different
neighborhoods and over vastly different cities with significaly different
sources and control programs, and meteorology.
With respect to the three major categories of traditional sources - fuel
combustion, industrial processes, and solid waste disposal - the relative
contributions also varied significantly with the nature of the different
urban areas. The fuel combustion contribution to inventoried emissions
ranged from less than 20 percent in clean-fuel, industrialized areas to
well over 90 percent in totally nonindustrial areas, with industrial
processes accounting for most of the balance. Solid waste disposal emis-
sions were generally less than 5 percent.
Fuel Combustion
The magnitude of fuel combustion emissions depends primarily on the amounts
and types of fuels burned, but the degree to which they are or can be con-
trolled primarily depends on the installation size point sources and
54
-------
10
o>
=1
CC
<
o
z
o
u
LU
CO
CO
Q.
in
m
cc
Q.
in
UJ
o
90
80
co
to
UJ
u
£ 70
z
CATEGORY HI
0 100 20O 30O 4OO 500 6OO
TRADITIONAL SOURCE EMISSION DENSITY, tons/yeor/sq mile
Figure 7. Relationship between city wide average TSP levels and
traditional source emission density
55
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area sources - and sometimes on the type of source - electric power, in-
dustrial or residential. The overall pattern of the fuel combustion emis-
sions was generally as would be expected, with greater emissions in areas
where coal and heavy oil are more prevalent, and in areas where major
electric power or industrial combustion sources remain uncontrolled.
Substantial further reductions in particulates from these sources are
expected under present regulatory plans. In addition, there is a signi-
ficant range in the stringency of emission regulations applied to combustion
sources, so that in many areas there is room for further reductions by
tightening the standards.
One particular aspect of fuel combustion emissions control to which the
study sought an answer is the question of residential space heating. The
use of coal in residential units has declined almost to the point of in-
significance, but in coastal cities the use of oil (rather than gas) is
common, and is likely to remain so. Since small oil burners are generally
controlled only through visible emissions enforcement, if at all, the
degree to which they might contribute to the TSP probls_.n is an important
open question. In the cities selected for the study, it proved impossible
to separate the extensive residential use of oil from other fuel use and
industrial sources by means of the air quality and emission data analysis
techniques primarily used. However, it did prove possible to make a rough
estimate of the impact from heating oil based on the microscopic analysis
of hi-vol filters from the various cities. Composited results for each
city, while subject to significant caution in interpretation, did indicate
elevated levels of oil soot in those cities -Providence, Washington,
Seattle, and Baltimore where they would logically be expected. An
approximate comparison of these results with those in the other cities
i
suggests a contribution to TSP levels of no more than 5 yg/m . While
this is a small portion of the typical urban levels of 75 to 100 ug/m »
it is a significantly larger portion of the 30 to 35 yg/m "working range"
between typical nonurban levels and the secondary standard.
56
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Industrial Processes
The second major category of traditionally considered pollution sources
are industrial process losses, as distinguished from emissions from in-
dustrial fuel combustion emissions. Process emissions are divided into
stack emissions and fugitive emissions, the latter being those indirect
emissions from doors, windows, etc., material storage piles, or other
outside activity on the plant property. Historically, primary concern
has been directed at stack emissions, which are more easily identified,
quantified, and controlled, and have, in the past, been the major sources
of particulate emissions from industry.
Stack Emissions The degree of the process emission problem is dependent
on the industrialization of the area in question. In the heavy industrial
cities where control of process sources is still being pursued, these
sources, along with industrial fuel use, dominate the air pollution picture.
In those industrial cities where emissions from process sources have
been generally controlled, they tend to remain roughly half the total
inventory. The process weight regulations concerning stack emissions from
process losses are not amenable to significant tightening, and further
reductions of inventoried emissions will generally need to come from en-
forcement of existing regulations, adoption of tighter regulations for
specific types of sources, and control of fugitive emissions. The industry
categories that continue to pose the greatest stack emissions problem are
the primary metals and minerals processing industries.
Fugitive Emissions - Fugitive industrial emissions have been traditionally
recognized, but only minor control efforts have been pursued to date. In
many operations, especially where dry materials handling is prominent,
emissions are generated in processes both inside and outside of plant
facilities, but on plant property, which are either ignored or insuffi-
ciently controlled so that significant particulate emissions are generated.
For industrial processes that operate outdoors, such as coke ovens and rock
crushing operations at quarries, these pollutants are directly emitted to
57
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the ambient air. Even when such processes are enclosed, the pollutants
emitted into the working environment may escape to the atmosphere through
windows, doors, roof ventilators, or even unsealed cracks in walls. In
either case, those pollutants that enter the outside ambient air have been
defined as fugitive emissions.
Fugitive emissions result from a wide variety of circumstances, including
poor operation or maintenance of process equipment. For example, fugitive
emissions can be the result of leakage from warped doors on coke ovens as
well as the oven charging operation itself. Storage piles and handling
operations for sand and gravel, coal, grain, and other materials that are
kept in the open can become fugitive sources when a strong wind blows over
them. Similarly, dirt and gravel parking lots and roadways on industrial
property can become major sources of particulates due to either wind
erosion or traffic.
Fugitive emissions have generally been assumed to be small in comparison
to stack" emissions. However, with stack emissions coming under controls
that may provide up to 99 percent reduction, the relative importance of
fugitive emissions has been growing, and they may now comprise
a significant portion of nationwide emissions. For example, EPA has
estimated that total fugitive emissions of particulate from electric arc
furnace charging can be 5 to 50 times the amount of the stack emissions
emitted downstream of the control device.
Even if the quantity of fugitive emissions from a process is small in
comparison with the stack emissions, the low height at which they are
typically emitted means that very little dilution occurs and fairly high
ambient levels are created. Consequently, even though adequate emission
estimates are lacking, fugitive emissions appear to be a significant and
increasing problem. A very rough estimate based on comparing TSP levels
at various monitoring sites (see Appendix D) suggests their aggregate
impact in industrial neighborhoods is typically on the order of 25 pg/m .
58
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Reduction of fugitive emissions will likely require a new approach to
regulatory control of such emissions. Currently, regulations for control
of fugitive emissions are of three general types: nonspecific nuisance
regulations, quantitative property-line regulations, and regulations that
prescribe specific control measures in specific circumstances. The
majority of regulations in the country are of the first type, defining
dust as a nuisance and often requiring "reasonable precautions" to pre-
vent emissions. While flexible and capable of being strong enforcement
tools, such regulations have not in fact proven effective on an overall
basis. The other two types can be more effective, though clearly not
without serious enforcement efforts. Property-line regulations in par-
ticular require enforcement and measurement techniques that are even
more difficult than those required for stack emission sources. Although
both alternative types are apparently somewhat better than nuisance reg-
ulations, there were only limited areas where they are used, and no areas
where an extensive, effective control effort was underway.
Solid Waste Disposal
Of the several methods of solid waste disposal, Incineration and open
burning have traditionally been the most common in urban areas and, there-
fore, the most significant sources of partlculate emissions. Under pres-
sure from pollution regulations, however, the larger point sources of
solid waste disposal emissions, municipal incinerators and large Indus-
trial installations have been controlled or replaced, while the smaller
residential and commercial incinerators and open burning in dumps are
typically tightly regulated and often banned. With the continuing trend
toward landfills, recycling, and the use of combustible rubbish as a
fuel supplement, solid waste disposal is expected to continue to decline
in significance as a factor in attaining the NAAQS.
59
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Surveillance', Compliance and.Enforcement Programs
An integral part of the impact that emissions from traditional sources
may have on standards attainment is involved with the nature and effec-
tiveness of the pollution control effort applied to them. Since fuel
combustion, industrial processes and solid waste disposal have long been
viewed as important sources of particulate emissions, maintaining sur-
veillance over these traditional sources and enforcing regulations concern-
ing them have been major activities of many control agencies since their
inception. The nature of the control programs varies significantly, in-
volving various combinations of source registration, permit systems, in-
spections, and so on.
The achievements of surveillance and enforcement programs depend on the
matching of enforcement activities to the nature of the particulate emis-
sion problem. Among the 14 cities, the largest actual reductions in
emissions from traditional sources have been achieved in those cities
where surveillance and enforcement programs are comprehensive and vigorous.
The activities of such programs generally included the following: constant
surveillance and patrols, frequent inspections of problem sources, a gen-
eral knowledge of all of the traditional sources, rigorous compliance
determination, prompt action when a violation or upset occurs, issuance
of compliance orders that are strict yet reasonably attainable in the
opinion of an appeals board, and strict enforcement of compliance schedules,
The stringency of the regulations being applied is obviously important in
determining the reductions in particulate emissions actually obtained.
Study findings indicate, however, that somewhat more important are the
enforceability of the regulations, the strictness of the enforcement, and
especially the manner in which compliance is determined. The enforce-
ability of regulations affects the ease and speed with which emissions
are controlled, and is Influenced by the types of regulations in effect.
60
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For example, in dealing with numerous small incinerators, a standard
specifying certain types of equipment is much easier to enforce than an
emission standard which requires monitoring; in dealing with coke ovens,
an efficient standard is one that specifies maintenance and operating
conditions; in dealing with fugitive emissions, a source-specific regula-
tion is more effective than a general nuisance regulation. The enforce-
ability of regulations is also related to the institutional channels through
which any hearings and appeals proceed. Enforcement is more effective and
more efficient when control activities and enforcement proceedings are
conducted by the same governmental level or at least by well-coordinated
and geographically proximate agencies.
Another important concern is the matter of compliance determination. It
is not at all clear that reports of full or near compliance actually mean
that all or most traditional sources are in compliance with the regulations.
While it was not a major purpose of the present study, some understanding
of the methods used for compliance determination was obtained during dis-
cussions of overall compliance status. Only a few of the agencies conduct
or require actual stack tests and then not on a routine basis. More
commonly, compliance determination is done on the basis of walk-through
inspections and theoretical calculations based on process loads, emission
factors, control efficiency specifications, and similar data. While this
type of compliance determination is appropriate for some sources and control
measures when done by well-trained agency personnel, it Is equally inap-
propriate for other, more complex sources with untried control technology,
particularly when performed by relatively inexperienced agency personnel.
Air Quality Impact
A primary objective of the study was to develop an understanding of the
impact that traditional sources have on TSP levels. Specifically, it is
important to place traditional sources in a proper perspective with res-
pect to the problem of standards attainment. The type of analysis based
61
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on citywide levels that was presented in Figure 7 is adequate for a broad,
general perspective; however, a more careful analysis involving individual
monitoring sites was also undertaken in order to provide a more detailed
and comprehensive picture. This effort, involving over 150 hi-vol sites,
considered in detail the nature of the site neighborhoods and the air quality
levels recorded, and has provided an overall perspective which is used
throughout this section to structure the summary discussion. Figure 8
indicates the quantitative impacts in various types of neighborhoods
estimated to result from traditional source emissions. The figure estimates
the impact at residential, commercial, and industrial sites in cities with
two different levels of traditional source prominence, following the
grouping presented in Figure 7. The higher portion of the bars represent
the three cities where traditional sources are still dominant (Category I),
and the lower portion the cities where significant control has taken place
(Category II); in the other two categories, where traditional sources are
largely absent or controlled, no apparent impact was seen. With respect to
other parameters, such as meteorology, the estimates should be viewed as
representing a hypothetical average city. The traditional sources in a
heavily industrialized, not yet controlled city add 10 yg/m3 at a typical
residential site, 19 ug/m3 at a commercial site, and about 70 ng/m3 at an
industrial site. Roughly, about 20 ug/m3 of the latter may be attributed
to fugitive sources.
PARTICULATES FROM NONTRADITIONAL SOURCES
The above discussion focused on sources traditionally considered for con-
trol of ambient levels of particulate matter; i.e., sources which are
generally stationary point sources, or fugitive emissions. These tradi-
tional sources were shown to cause levels of TSP that were far in excess
of the national ambient air quality standards. However, even in cities
where TSP emissions froft traditional sources are relatively smJtll, city-
wide averages are 30 pg/m^ or more above nonurban levels, and the secon-
dary annual standard is being violated. Monitors in apparently clean
62
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75 r
50
z
Ui
o;
u
Q.
10
25
nt
RESIDENTIAL
COMMERCIAL
INDUSTRIAL
Figure 8. Traditional source increments in different
sice types
63
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areas of a city or in smaller, nonindustrial cities have measured high
TSP concentrations which cannot be explained by modeling with tradi-
tional source emissions or which fail to decrease as expected under
controls of the State Implementation Plans. These findings indicate
that a certain level of particulate in cities is caused by the concen-
trated activity in an urban area. These activities are here collec-
tively designated "nontraditional" sources; i.e., those sources not
traditionally considered in air pollution control strategies.
Nontraditional sources of particulates may be divided into two categories.
One category consists of obvious, distinct sources of emissions that have
not been normally considered as sources; these include construction
and demolition activities, emissions from tailpipes, and tire wear. The
other category refers to the more general problem of activity in the
city and the characteristics of the urban setting that allow particulates
to become entrained or reentrained.
Before the discussion of these categories, two terms merit differen-
tiation: fugitive emissions and fugitive dust emissions. Both refer
to general, nonstack emissions of particulates. However, fugitive emis-
sions (included under traditional sources) result from industrial-related
operations and escape to the atmosphere through windows, doors, and vents
rather than through a primary exhaust system. Fugitive dust emissions,
on the other hand, are generally related to natural or man-associated
dusts (particulate only) that become airborne due to the forces of wind,
man's activity, or both. Fugitive dust emissions include windblown par-
ticulate matter from paved and unpaved roads, tilled farm lands, and ex-
posed surface areas at construction sites. Natural dusts that become
airborne during dust storms are also included as fugitive dusts.
Estimates of emissions from nontraditional sources in several comprehen-
sive reports tend to indicate that the total level of particulates from
several of these activities are an order of magnitude larger than those
from traditional sources. This study did not include any major effort
64
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to develop additional emission factors; rather, it concentrated on a re-
view of the previously published literature plus analysis of air quality
data collected to determine the impact of such sources on ambient TSP.
Appendix E provides the detailed results of much of this analysis, the
following discussion summarizes the findings.
Reentrained Participates
In an urban area, particulate matter accumulates on the various city sur-
faces due to fallout, and especially heavy loads on streets can result
from dirt and mud carryout from unpaved parking lots and roads, spillage
from trucks, and sand and salt applied for snow control. This particulate
matter can then become entrained and at least temporarily suspended in the
ambient air due to wind erosion or man's activities disturbing the surface.
Natural Reentrainment - Natural reentrainment of particulates occurs when
wind is strong enough to lift particulates from the surface. Due to the
mechanics of wind erosion, such movement is more likely to be initiated
in an urban area where hard, flat surfaces are exposed to the sweeping
action of the wind. Based upon the analysis presented in Appendix F of
this report and other literature, winds above 10 to 12 miles per hour are
likely to be contributing to the TSP levels. Above this speed, the re-
entrained dust maintains the TSP level above what would be projected based
upon the balanced dilution effect of the ventilation accompanying the
wind. Therefore, the analysis in Appendix F indicates that the overall
impact neither increases or decreases the daily TSP levels. However,
cleaner surfaces (determined by comparisons after rainfall) did allow
the dilution effect to reduce levels further than when the wind was blow-
ing over dirtier surfaces (measured on days before which there was no
rainfall).
Vehicular-induced Reentrainment - The most important contribution to re-
entrainment caused by man in an urban area is the disruption of surface
65
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dust by motor vehicle activity. The wheels of the vehicles not only
Impart kinetic energy to particles on the road but also grind up the
larger, nonsuspendible particles into smaller ones and break up the co-
hesive bonds of the .dust. Such activity in an urban area occurs primarily
on paved roads with additional local impacts expected due to dirt and
gravel roads and parking lots. The amount of particulate reentrained by
motor vehicles is directly related to the amount of dirt on the road,
its suspendibility (sand versus dust), the speed of the vehicles, and
the level of activity (often expressed as ADT - average daily traffic).
Vehicular activity on paved roads - The data gathered in the course of
this study provided several opportunities for making estimates of the
impact of vehicular-induced reentrainment by comparisons of comparable
monitoring sites. The best data were the result of special studies that
had been or were being conducted by the local agencies to determine for
themselves the Impact of traffic on the measured TSP levels. Generally,
this was done by monitoring in one location but at either different
heights or distances from the road, or both. The analyses of these data
for each city are given in the individual city reports and the cross-city
analysis is provided in Appendix E.
The findings from these data indicated that there was a direct relationship
between the daily TSP concentrations and average daily level of traffic (ADT)
and an inverse relationship between TSP and the distance of the monitor from
the traffic, measured by the slant distance ( SD = «J(height) + (distance) J.
A comparison of the ADT/SD to the TSP concentration implied that a linear
relationship could be assumed to exist with good correlation.
As is discussed more extensively in Appendix E, this relationship between
ADT and slant distance has a significant Impact on the interpretation of
TSP levels measured by a hi-vol anywhere near a street with significant traf-
fic. The data assembled in this study were not quite adequate to support
development of a quantitative relationship suitable for accurate calculations;
66
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however, it Is possible to provide rough estimates of the impact of ve-
hicular traffic on nearby hi-vols. The data in Table -11 are meant to
provide approximate values suitable for identifying sites with potential
problems and roughly judging the magnitude of the problem.
Table 11. APPROXIMATE IMPACT (IN yg/m3) OF
VEHICULAR TRAFFIC ON NEARBY
HI-VOL SITES
Traffic
volume ,
(ADT)
1,000
5,000
10,000
30,000
Slant distance of hi-vol from street
(feet)
20
5
25
50
100
50
2
10
20
50
100
5
10
25
150
3
7
15
Vehicular activity on unpaved areas - In many urban areas dirt or gravel
roads and parking lots are used by individual establishments or in indus-
trial areas because of the expense of adequate paving. These areas can
be sources of dirt for carryout to paved areas and may also serve as areas
for naturally reentrained dust. In addition, vehicular activity on these
areas can bring about man-induced reentrainment.
A comparison of the published emissions from unpaved roads with those of
traditional emissions is given in Appendix E for those central counties
analyzed in the course of this study. That analysis implies that the
unpaved road emissions in counties which are not totally urbanized can
be 10 to over 30 times the emissions from traditional sources. Even in
urbanized areas, where unpaved roads are not common, the fugitive dust
from unpaved roads may be over 10 percent of the traditional emissions
in the county.
67
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Based on the discussion on reentrainment from paved roads, which indicates
that the impact of fugitive dust from vehicular activity decreases quickly
with distance, it is felt that these numbers are inappropriate for direct
use in air quality planning. If these fugitive dust emissions are treated
the same as traditional emissions and used in rollback or dispersion model-
Ing calculations, there would be excessive, undeserved emphasis placed on
these sources and a potential deemphasis of the control of traditional
sources. While these amounts of particulate may be temporarily reentrained
due to vehicular activity, they are not suspended for any length of time.
If they were, the rural areas of counties would be expected to have TSP
levels as high as those found in the cities; such is obviously not the
case. Therefore, the use, if any, of these numbers would have to be li-
mited to Inputs to models which adequately reflect the deposition and
other removal of the particulates.
Specific Urban Sources
Certain activities in urban areas have not been considered major contribu-
tors to the TSP levels and therefore have received little attention in
the formulation of control strategies for particulates. Yet these sources
may be considered true emission sources because the particulates arise
directly as a result of the individual activity rather than as a by-
product, and several recent studies have suggested that these sources
may be having more of an impact than previously thought. Of particular
interest in a crowded urban area are transportation sources - the tailpipe
emissions from automobiles and the emission of rubber due to tire wear.
In addition, construction/demolition activities that are constantly
occurring in cities add to the total TSP levels measured. Each of these
sources is discussed below.
Transportation Sources - Although particulates from the transportation
sector have been inventoried, they have seldom been regulated except
through ordinances prohibiting smoking vehicles and Federal restrictions
68
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on aircraft. Controls on motor vehicles have centered around emissions
of carbon monoxide, nitrogen oxides, and hydrocarbons, which are one to
two orders of magnitude greater than emissions of particulates. In ad-
dition, particu lates from the transportation sector have generally been
assumed to be insignificant when compared with emissions from traditional
sources. However, as emissions from traditional sources have been reduced
under implementation planning, their proportionate contribution to the TSP
problem has been reduced so that particulates from the transportation
sector have become increasingly more important.
Tailpipe emissions Attempts to separate out the contribution of motor
vehicles to the total TSP measured have centered around the use of lead
as a tracer element. In most urban environments where lead, copper, and
zinc smelters, grey iron foundries, or other major point sources of lead
are not prevalent, ambient lead levels are assumed to be due almost en-
tirely to vehicular activity. Therefore, if the ratio of TSP emissions
from tailpipes to the suspended lead emissions is known, the ambient levels
of lead can be multiplied by this ratio to provide the ambient TSP con-
tribution due to total tailpipe emissions. Based on several studies re-
viewed in Appendix E, this ratio may be assumed to range from 3 to 5 de-
pending upon the vehicle type and age mix.
Ambient lead levels are routinely measured in major cities through anal-
ysis of NASN filters, and many state and local agencies also perform their
own studies for lead. (California has an air quality standard for lead of
1.50 ug/m3 for a monthly average.) Ambient lead levels contained in the
National Aerometric Data Bank (MADE) indicate average annual concentra-
3 3
tions ranging from 0.5 to 2 ug/m with a few cities measuring 3 to 4
These lead data suggest that tailpipe emissions are contributing from 1
3
to 20 ug/m to the total participate levels measured. Data collected from
the individual cities studied under this effort indicate lead values in the
3
middle range of those reported above; i.e., around 1 ng/tn . Therefore,
it may be assumed that tailpipe emissions are generally contributing 3 to
3
5 _Lg/m to the ambient levels.
69
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Special sampling studies conducted by EPA in Miami and St. Louis as part
of this study provided data on particle sizes by elemental composition.
Results in both cities indicated that the lead particles being sampled
are extremely small. Only a small percentage are greater than 4 pm in
diameter, and the largest percentage was collected in the last impactor
stage, implying the particles had an effective aerodynamic diameter of
less than 0.25 urn. This small diameter means that the lead would be dis-
persed and transported much as a gas with very little fallout with distance.
Therefore, it may be expected to be measured at rooftop levels or even in
more remote areas.
As part of this special study conducted by EPA in Miami, 2-hour elemental
concentrations were compared with the hourly traffic counts for 1 week.
These data illustrated the expected relationship of increasing lead con-
3
centration (as high as 4.6 ug/m for a 2-hour average) with increasing
traffic, especially in the early morning when rush-hour traffic started and
before mixing height and wind speed increases caused a drop in lead
concentration.
A compilation of all the sites for which some lead data were available
provided 49 monitors from six cities (Baltimore, Miami, Oklahoma City,
Philadelphia, San Francisco, Washington) with annual average lead concen-
trations as well as individual filter analyses from several sites in the
other cities discussed above. Those monitors with annual data were grouped
according to their site classifications and then averaged to provide a
mean concentration. Because the monitoring sites had a wide range of
local influences affecting the measured lead levels, Figure 9 presents
not only the mean values for each of the site classifications but also
the range of values found. Since there were only four monitoring sites
each for the classification of rural and industrial, these averages and
ranges may not be representative of situations found in other cities.
70
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2.2
2.0
K> 1-8
2 1.4
£
% L2
UJ
z 1.0
o
o
Q O.8
UJ
-1 O.6
O.4
0.2
0
SITES)
COMMERCIAL
(28 SITES)
RESIDENTIAL
(13 SITES)
RURAL
(4 SITES)
Figure 9. The range and average lead concentrations
found at monitoring sites
71
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Tire wear - Aside from direct tailpipe emissions and reentrainment dust,
automobiles are known to generate particulates simply from the deteriora-
tion of the body and parts. Rust, corrosion, and friction of one part on
another are all known sources. However, their magnitude is small compared
with the wear that is seen on tires. In the U.S., an estimated 660,000
tons of tire-tread are worn away each year. Since over half of all vehicle-
miles traveled (VMT) is in urban areas, approximately 350,000 tons of rub-
ber are added to the urban environment every year. Considering the size
and widespread nature of this source, its impact on air quality warrants
study.
Although filters were selected from each city for microscopic analysis,
neither the selection of a few filters nor the accuracy of the microscopy
were believed to be sufficient to characterize the cities. However, the
numerous filters from among the cities were considered to be adequate for
averaging contributions according to the various classifications for the
monitoring sites.
By using the percentage contribution of rubber tire fragments to the total
visible loading on the hi-vol filter (diameter > 1 pm) and assuming ap-
proximately 85 percent of the loading was visible, average rubber load-
ings can be calculated for each site type. These average values, along
with the range of values observed, are plotted in Figure 10. This figure
shows that co-mercial sites, generally most esposed to traffic, have
the highest contribution of rubber while undeveloped or rural sites
barely measure any rubber.
In the course of the careful evaluation of the monitoring network in each
city, monitoring sites were also rated on the basis of local influences,
including paved roads. Sites with ar. expected paved road influence (10
in all) had rubber concentrations twice as high as sites for which no such
influence had been noted - 9.9 and 4.9 ug/m3 respectively.
72
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10
=1
o
T RURAL
f_(5 SITES)
Figure 10. Average and range of TSP loadings due to tire wear
at different monitoring site classifications
73
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The values found for rubber in the course of this study are several times
what were expected based on the literature reviewed. The reason for this
discrepancy is not apparent. This experiment may have been better formu-
lated than previous ones to give a good cross-section of values, or the
high levels may be an artifact of the monitoring site and filter selection.
Currently, however, there is no reason to doubt the validity of these
data.
Of some interest in planning for control is the particle size distribution
of the rubber. As shown in Table 7, the average size range of the rubber
tire fragments (13 to 135 urn) is much larger than that of any other par-
ticulate identified. Some particles were found to be 200 urn in length.
Normally, such large particles are not considered suspendible for any
length of time and are too large to be of concern for respiratory effects.
Despite their size, however, no difference was discernible in average con-
centrations of rubber by monitor height. Several monitors 50 to 100 feet
3
above ground level measured levels of rubber in the 5 to 15 ug/m range
while other, lower monitors recorded no rubber.
Construction/Demolition - The movement of materials associated with con-
struction and demolition activities usually results in the emission of
particulates into the ambient air. Major demolition programs, whether
using a ball and crane or blasting (low-yield), will emit particulates
up to a height equal to that of the building being removed. Construction
involves much more movement of materials continuously for periods of
several months to over a year. Emissions are generated by a wide variety
of operations over the duration of the construction, including land
clearing, blasting, ground excavation, and on-site traffice, as well as
the construction of the facility itself.
The study findings in Appendix E illustrate that construction activity
does have an impact on very local TSP levels but that the effect is not
readily predictable. Construction will generally elevate concentrations
downwind from the site for distances up to a mile; the amount of increase
74
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is related to the level of activity, type of activity, distance from the
activity, and control measures employed. Monitors within half a mile of
construction may have annual geometric means 10 to 15 yg/ra3 higher than
normal. Therefore, if 10 percent of the monitors in an urban area are
near construction activity, the calculated citywide average TSP level
would he 1 to 2 yg/m3 higher than otherwise expected.
These measured impacts are much less than would be expected based on a simple
interpretation of the emission levels developed for each county (see Appendix
E). Obviously, the use of those emission levels must be restricted to input
into modeling programs which adequately account for the fallout and depo-
sition of particles. Development of new emission factors to reflect the
type and degree of activity and any control measures would be more ap-
propriate than the use of the existing factors.
National Assessment
While the above discussions have not covered all topics possible under
the heading of nontraditional sources, they did center on those sources
that have been identified as probable major influences. From these
sources alone it is evident that there are contributions to the total
TSP levels simply from man's activity and that the contributions are the
highest in an urban area where man's activity is greatest. Similarly,
the closer to the activity, the larger the impact. These variations
have been addressed above for each of the sources, but an overall
combined assessment is needed to indicate the extent of the total
impact of nontraditional sources on TSP levels, and thereby on the
problem of attaining standards.
Because of the range of TSP levels that may be contributed by the various
nontraditional sources, it is not possible to identify at this stage either
the exact impact at any monitoring site or even the average impact in any
one city. Such a determination would require extensive data and modeling,
-------
most of which are not available. Rather, the intent is to provide a mea-
sure of the range of impacts that may reasonably be expected in most sit-
uations and an understanding of the relative importance of nontraditional
sources for standards attainment on a national basis. Therefore, this
conclusion should not be taken as sufficient to preclude detailed analysis
in each city but as guidance to the development of national priorities for
further planning measures.
The average and range of TSP levels attributed to tailpipe emissions and
tire wear were given in the, above analyses by site type. Recognizing
that ranges of values varied in different cities, average contributions
can still be calculated. Tailpipe emissions provided an average level
of TSP in industrial and commercial areas of 4 to 5 yg/m and approximate-
ly 3 ug/m3 in residential areas. Tire wear added rubber concentrations
of 6 ug/m3 at industrial sites, 9 ug/m3 at commercial sites» and 3 ug/m3
at residential sites.
Construction activity is more difficult to present on an average basis
because of the wide range of possibilities that may occur. Some cities
have construction underway at individual, widely dispersed locations
which are not close to monitoring sites, while others may have similar
activity but close to one or more monitoring sites. Levels of TSP due to
construction are expected to range between 0 and 15 ug/m ; the closer
the monitor, the greater the impact. If only one or two monitors out of
a network of 20 are near construction activity, a citywide average will
only be affected by 1 to 2 pg/m3 annual geometric mean. However, in some
cities major construction programs such as urban renewal and subways are
going on in concentrated areas of the city. These activities are apparently
causing higher-than-normal values at a large number of nearby monitors and
will provide elevated average values in the commercial section of the city.
While construction is obviously a localized source, the reentrainment
problem exists wherever there are roads and traffic. Since the level
76
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of reentrained matter could not be exactly determined through microscopy
or elemental analyses, as with rubber and tailpipe emissions respectively,
other measures were necessary. By calculating the excess levels at resi-
dential, commercial, and industrial sites that could not be explained
after accounting for nonurban levels and traditional sources, the total
nontraditional impact on the annual geometric mean TSP levels averaged
around 20 to 25 ug/m3 at residential sites and 30 to 35 ug/m at commer-
cial and industrial sites. By subtracting the above levels estimated to
be due to tirewear, tailpipe emissions, and construction, the average re-
3
entrainment contribution was approximately 20 pg/m at industrial moni-
tors, 18 yg/m3 at commercial monitors, and 14 ug/m at residential moni-
tors. (The higher levels at industrial monitros are likely the result of
dirtier roads in the area.) These levels of TSP were compared with those
calculated in specific studies in Miami and Providence, by using the dis-
tribution of monitor siting situations and the expected impact of reentrain-
ment at each site, and also with projected reentrainment levels based on
published reports of the ratio of tailpipe TSP to reentrainment TSP. The
same order of magnitude was found in all cases.
Figure 11 indicates the quantitative impacts on TSP levels of each of the
nontraditional sources considered above in various types of neighborhoods.
As has been stressed throughout this discussion, these are only average
values and a wide range of values can be expected when comparing particular
situations.
MONITORING CONSIDERATIONS
The monitoring of ambient TSP levels is not a causative factor in the at-
tainment of standards in the same sense as high nonurban levels or emis-
sions from either traditional or nontraditional sources. However, network
configuration and station siting do affect the extent to which measured
levels are representative. These factors also affect the overall quality
and usefulness of the data base needed for both air quality planning and
verifying attainment.
77
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40 r
30 -
^
0>
UJ
2
UJ
-------
This section compares current EPA guidance on monitoring, as found in
OAQPS Guideline No. 1.2-012, with the actual network configurations and
siting practices found during visits to more than 150 monitoring sites.
It contains an analysis of the effects of the variations in networks and
siting on measured levels and thus on standards attainment, and an anal-
ysis of the impact of deviations from EPA guidelines.
Monitoring Objectives
Table 12 from the EPA monitoring guideline document lists the objectives
that have been commonly used in designing current networks. Basically
these are the outgrowth of the original NASN objective of surveying typical
pollutant levels, with some recent additions in the areas of planning and
enforcement. Conspicuously missing from the list, however, other than
under the general rubric of research, is any concept of monitoring to
determine the nature of the air pollution problem in a given area or the
identity and location of sources having an impact in a particular situation.
Table 12. GENERAL MONITORING OBJECTIVES
Provide data for research
Provide data for air quality planning efforts
Provide data for emergency episode prevention
Monitor time trends and patterns
Monitor source compliance with regulations
Ascertain attainment and maintenance of NAAQS (population exposure)
Determine impact of specific proposed or constructed facilities on
ambient concentration
Provide data to support enforcement actions
79
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Monitoring Guidelines
The current EPA monitoring guidelines define a general structure for
discussion and planning network monitoring objectives, emphasizing the
need to design the network to meet well-defined objectives and data needs.
They prescribe the general size of monitoring effort required, emphasizing
that this must be adjusted to suit local conditions. More specifically
concerning hi-vol placement, the guidelines recommend a horizontal clear-
ance of at least 2 meters and a height range of 2 to 15 meters; this lat-
ter permits placement at any height from essentially ground level to
about 50 feet.
Network Configuration
The concept of network configuration involves the number of monitoring
sites and their geographic distribution over the area of concern. It in-
cludes "both the concept of selecting patterns of sites and areas of cities
over distances of several miles and the concept of selecting neighborhoods
over distances of a few city blocks.
Configuration Problems - In general, the monitoring networks studied in
the 14 cities did not have major problems with overall configuration.
However, two problems of some concern in several of the cities do warrant
further discussion. These problems were the general lack of stations to
measure incoming air mass concentrations and the lack of clearly defined
industrial area monitors in several cities.
The widespread lack of relatively remote stations is to some extent a
matter of policy and agency jursidiction as well as a matter of network
design. For only a very few of the urban areas studied was there an ap-
propriate station to measure the TSP loadings of incoming air masses.
Previously operated nonurban sites have been abandoned in two areas,
while in many they never existed. When necessary for air quality planning,
80
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a TSP concentration in incoming air is typically just assumed, usually
based on the NASN nonurban sites, which are frequently not appropriately
near.
This lack of adequate nonurban data is not yet a serious problem in major
industrialized urban areas, where ambient levels typically exceed the
standards substantially, so that precise knowledge of incoming levels is
not yet necessary. However, it will no doubt become increasingly proble-
matic as ambient levels approach the standards, and as improvements in
air quality require increasingly precise planning. In those study areas
where levels are nearer the standards, particularly those areas
where traditional sources are not dominant, there is already a planning
problem resulting from the lack of precise knowledge of the transition in
levels from remote through suburban into urban areas. This problem is
of additional concern in regions of the country where we find significant
levels of secondary pollutants of generally unknown origin.
The second area in which there were some problems with network configura-
tion is the matter of sites in industrial areas. In some of the heavily
industrialized urban areas studied, there were clearly defined industrial
sites, located either within the industrial area or along the margins be-
tween industrial and residential areas. At these sites, there was no
real question about the air quality influence of the industrial areas
and operations, and the trend or lack of trend in industrial emissions
was clear, In other areas, however, the sites best described as industrial
were not in fact located in or representative of the most uniformly dense
industrial areas, but rather were often influenced primarily by one nearby
industrial source. Consequently, the air quality impact of the city's in-
dustrial areas is not clearly monitored, and the effects of control efforts
are not readily seen. The reason for these problems is primarily the
nature of the industrial areas themselves. In the areas that are well
monitored, the industrial activities are typically iron and steel mills
and associated metallurgical operations, usually located in large, con-
tiguous, readily identifiable areas. In contrast, the poorly monitored
81
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areas are in long, narrow riverside flood plains and contain much more
heterogeneous industrial activity, with extensive warehousing, truck and
rail terminals mixed in. Another somewhat similar problem is the matter
of agency jurisdiction. Not accidentally, major industries are frequently
located just beyond city boundaries, either in smaller satellite munici-
palities or in unincorporated areas, and hence tend to escape thorough
coverage in a network focused upon the responsibilities of a city agency.
This is clearly a difficulty occurring in Philadelphia, where a major
heavy industrial area extends from the edge of the city along the river-
front in adjacent counties and into adjacent states.
Air Quality Patterns Based on site visits, over 150 hi-vol sites were
classified as nonurban, residential, commercial, or industrial on the
basis of the principal impact on air quality, rather than strictly on
location; that is, a site in a residential neighborhood that received a
major impact from an adjoining industrial area was categorized as indus-
trial rather than residential. A consistent pattern appeared when the sites
were grouped by the four neighborhood types. In each urban area, the
average air quality levels were lowest in the residential neighborhoods and
highest at the industrial sites. Table 13 compares average concentrations
by site type after those sites that are unduly affected by nearby sources
(in addition to an areawide influence) were removed from the data base.
Not surprisingly, industrial sites were systematically higher; traditional
sources have long been recognized as a major source of air pollution. How-
ever, it is also important to note that commercial sites were similarly
higher. This is because the potential for automotive-related pollutants
(such as exhaust particles, rubber tire particles, and other types of
reentrained street dust) is greater in commercial areas than in residential
areas due to increased vehicle miles traveled (VMT).
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Table 13. AVERAGE TSP CONCENTRATIONS BY
NEIGHBORHOOD TYPE
Cities
Category I
Cleveland
Birmingham
St. Louis
Average
Category II
Philadelphia
Baltimore
Cincinnati
Average
Category III
Chattanooga
Denver
Seattle
Providence
Average
v/o Denver
Category IV
Washington, D.C.
Oklahoma City
Miami
San Francisco
Average
No. of
sites
studied
11
13
22
10
9
12
8
6
7
8
9
14
13
11
Geonetrlc mean TSP concentration
above nonurban levels,
ug/m3
Residential
45
35
29
36
26
30
24
27
20
48
21
18
27
20
17
26
24
24
23
Commercial
86
56
41
61
48
40
36
41
42
81
33
29
46
35
30
49
36
31
37
Industrial
113
88
74
92
58
71
66
65
54
96
62
None
71
58
None
None
None
None
None
Because ambient air quality levels in different types of neighborhoods
show such distinct differences, it is important to consider network con-
figuration, especially the representation of industrial neighborhoods, in
any comparison of air quality between cities. Failure to do so might very
well result in faulty conclusions about the effectiveness of regulations,
the relative contributions of source categories, or any other objective
of the comparison.
83
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Station Siting
The selection of the actual site for placement of the hi-vol is a major
consideration. As a matter of historical practice, siting decisions have
usually been made on the basis of more practical matters, such as building
access, security, power availability, and so on. However, the principal
factors to consider on a technical basis are the effects of height and
distance from the street, and any nearby sources of particulates.
Height Effects - The primary problem with siting is the height of the hi-
vol above the ground or street level, the height issue is difficult be-
cause the traditional practice is to put hi-vols on rooftops, while the
more recent view of some is that the health-oriented spirit of the Clean
Air Act should mandate placement near the breathing zone.
Typically, hi-vol heights range from ground level to the top of many-story
buildings; Figure 12 illustrates three points on this .'ange: a
low-level (6 foot) site type routinely used in Birmingham; an unusually
high site the "Food Circus" building in Seattle at 70 feet; and a more
typical site a one-story fire station in Oklahoma City. In general,
sites of all these varieties are present in each network, but on an overall
basis there is a significant difference among cities in the average height
of the hi-vols. Table 14 shows the variations in monitor height among
the 14 cities. Clearly, variation is significant.
The distance of the hi-vol back from the nearest street is often re-
lated to the vertical height because of the relationship of general build-
ing size and neighborhood type. The typical central business district
(CBD) site on a tall building will be both vertically higher and horizon-
tally nearer to the street than a residential site, which may well be on
a one-story building but is more likely to be set back from the street a
significant distance. Distance back from the street is clearly a some-
what more flexible parameter than height, as the hi-vols can usually be
84
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(a) Low-level site (Birmingham)
(b) Elevated site (Seattle)
(a) Sites of typical height (Oklahoma City)
Figure 12. Range of heights in typical hi-vol installations
85
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moved about on a rooftop. The analyses of dust reentrainment from streets
in Appendix E found that there was some evidence that TSP levels were more
affected by variations in height than by distance back from the street.
Table 14. VARIATION IN MONITOR HEIGHT AMONG THE 14 CITIES
Cities
Heavily
industrialized
Cleveland
Birmingham
Philadelphia
Baltimore
St. Louis
Moderately
industrialized
Cincinnati
Chattanooga
Denver
Seattle
Providence
Lightly
industrialized
Washington, O.C.
Oklahoma City
Miami
San Francisco
Height of
monitors , feet
Mean
37
10
14
31
38
29
21
30
34
56
33
17
20
30
Median
25
6
13
30
19
25
19
23
20
49
28
15
18
18
The original decision in favor of placing hi-vols on rooftops rather than
at street level, first made in establishing the NASN in the early 1950s,
considered the fact that such siting would minimize the measurement of
particulate matter reentrained from the ground. (The other significant
reasons were concern over vandalism and the fact that ground-level sites
are hard to find in the CBD.) The fact that these original monitors were
deliberately placed where measurement of reentrained particles would be
minimized emphasizes the changing concept of the TSP problem. Today
86
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low-level, reentrainment-type emission sources are seen by many cities
as the reason that they cannot meet the ambient standards, but in the
1950s they were considered by most as extraneous interferences, not pol-
lution sources; the pollution sources were the heavy industries and the
large fuel combustion operations. Consequently, appropriate siting of
hi-vols is still an issue today, and the inconsistencies, both among sites
within an urban area and among networks in different urban areas, continue
to hamper not only careful data analysis but also problem definition.
Impact of Nearby Sources The exact placement of a hi-vol with respect to
other types of sources can also have a significant impact on the levels
measured. This is particularly true at sites that are at all proximate
to low-level dust eattainment sources , such as unpaved parking lots or
roads, construction activity, sources of fugitive emissions, and indus-
trial sources with much settleable particulate or low-level emission
points. The sites visited in the study were classified as to whether any
nearby source had an undue influence on the measured levels; Table 15
summarizes the number and type of sites with nearby sources. It is ap-
parent from the table that a significant fraction of the hi-vols in most
of the cities are influenced by nearby sources, and significant changes
in concentrations at these sites are dependent on controlling the nearby
source. In many cases, the source is nontraditional or is related to
fugitive dust.
Only three residential sites had special local impacts, but in the commer-
cial and industrial categories such influences were common. Ten of the 60
commercial sites had local impacts, even when a fairly stringent definition
of undue influence was used. For example, since so many commercial sites
had an obvious impact from traffic, such an influence was labeled an undue
effect only if the monitor was either unusually low and close to the street
(as in Figure 12(a)) or affected by a major street, as in the case of
samplers adjacent to expressways. Construction, a cause of special
local impacts at three sites in 1974, was identified only if it
87
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Table 15.
00
00
NUMBER OF SITES WITH AN ESTIMATED IMPACT OF LOCAL INFLUENCES,
BY NEIGHBORHOOD CLASSIFICATION
Total number of sites visited
Number with some apparent degree of
local impact
Number with degree of impact judged
major
Number with "undue" impact in context
of neighborhood definition
Average TSP levels at sites without
"undue" impact
Typical increment at sites with
"undue" impact
Residential
39
10
3
3
60 Mg/uH
15 yg/ra3
Commercial
60
36
10
10
78 ug/m3
25 ug/m3
Industrial
41
24
21
0
110 ug/m3
-
Undeveloped
14
0
0
0
-
-
Total
154
70
34
13
-
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was Immediately adjacent to the site (within one or two blocks) and if
the impact on air quality levels was apparent.
The 41 industrial sites presented a different situation. As initially
classified, essentially all the industrial sites had impacts from nearby
unpaved roadways, parking areas, trucking terminals, and other fugitive
dust sources. Consequently, it was deemed appropriate to include these
impacts in the basic concept of an industrial neighborhood, and no in-
dustrial sites were classified as having undue impacts. Some sites in
commercial neighborhoods, however, were so classified on the basis of
undue impacts from isolated industrial sources.
Air Quality Patterns Approximate impacts of nearby sources of various
types were estimated and are summarized in Appendix G. Also determined
were the impacts, of sources of fugitive emissions, generally identified
as being in the immediate vicinity of the monitor; these impacts were
discussed in the section on traditional sources.
The typical effect on air quality levels at sites with significant impact
3
from nearby sources can easily be 20 to 25 ng/m . This represents an in-
crease of at least 30 percent over the typical levels recorded at commer-
cial neighborhood sites in the 14 study cities. Data at specific sites
can vary substantially from these average values, depending on the prox-
imity of the source to the site.
Comparison of Actual Siting to Guidelines - The general conclusion regarding
siting of the monitors visited is that they are altogether too loosely
placed with respect to both height and horizontal placement. However, they
are generally within the height range specified in the EPA guidance ma-
terial, which recommends sites less than 50 feet high, and provides only
qualitative cautions concerning horizontal placement. Thus, it is con-
cluded that more definitive guidance is needed, particularly on height and
proximity to nearby sources, such as paved roads.
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Operating Frequency and Schedule
Designing the frequency and scheduling aspects of TSP network operations
is generally a matter of balancing the precision desired or required in
the resultant annual mean with any necessary resource restraints. These
decisions are not generally a major problem in designing a network and
the matter of operating schedules was not found to be, in and of itself,
a significant factor relative to standards attainment. Common practice
in the networks studied was to sample on a systematic schedule every 6th
day, following recommended EPA guidance; this is generally adequate to
produce acceptable estimates of the annual mean and the frequency of vio-
lations of the 24-hour standard.
The only significant interaction between hi-vol operating frequency and
the problems of standards attainment is a matter of having enough data to
provide adequate knowledge of the air pollution problem to be dealt with.
As an example, the analyses of meteorological parameters and TSP levels
in Section III and Appendix F, conducted to investigate the impact of
urban fugitive dust influences, were dependent on having essentially daily
hi-vol data available; in other urban areas where similar detailed anal-
yses would have been important for judging the cause of the TSP problem,
data gathered on the standard every-6-days schedule proved to be completely
inadequate for a proper analysis. This is believed to be a fairly common
failing because the very nature of particulates from urban activity makes
the problem closely interrelated with meteorology. Since the problems of
fugitive dust emissions, resuspension of material from the roadway, etc.,
are increasingly being blamed for failure to attain the standards, in-
creased sampling frequency should appropriately be a part of agencies'
attempts to define this problem adequately for planning purposes.
Summary
The degree to which monitoring considerations influence the attainment of
standards is philosophically difficult to assess. The matter of network
90
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configuration, or neighborhood selection, is difficult because there are
no clear criteria for defining proper configuration; it would necessarily
be a function of the purpose of the monitoring. The matter of individual
site placement is philosophically difficult because it gets into the vague
area of defining the dividing point between "ambient" air, where the
standards should be met, and source-oriented monitoring sites.
Network Configuration The selection of neighborhoods for monitoring re-
flects a difficult tradeoff between the various monitoring objectives.
Selecting residential neighborhoods will provide better population-exposure
coverage but will likely result in lower values than selecting commercial
neighborhoods. Industrial sites, in turn, will have higher values than
commercial sites, but will provide necessary information on the progress
of traditional source control. One obvious conclusion relating to net-
work configuration is that the latitude air pollution control agencies
necessarily have in the design of their networks can easily affect the
number of sites in the jurisdiction that attain the standards. However,
this is a concern over the relative balance between residential, commer-
cial and industrial sites in the network, which doesn't necessarily relate
to the overall effect of the control program on the aggregate exposure of
the population. One obvious approach to this, which is simple at least in
theory, is to designate smaller subnetworks for various purposes, each of
which might have a different balance of sites.
Hi-vol Siting - For certain specific sites, the difference between attain-
ing and exceeding the standard is very clearly attributable to the special
influence of some nearby source. Philosophically, this situation could be
viewed either of two ways. It could be called a sampler siting anomaly,
which should be resolved by moving the hi-vol or redesignating it a source-
oriented research station. Alternatively, it could be viewed as a site
receiving an impact from a pollution source which, though possibly temporary
or of a fugitive dust nature, is still something that should be controlled.
Which of these two interpretations is appropriate depends on the precise
nature of the site in question. Since public access has been presumed by
91
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EPA to be the criterion for defining ambient air, the key parameter is the
extent to which the public has access to the site in question. The inter-
pretation of public access may prove difficult, however. For instance, the
Dyer Street site in Providence, which exceeds the standard because of the
impact of an expressway, is located on a parcel of right-of-way land imme-
diately adjacent to the expressway. While the public technically and
legally has access to the parcel, as a practical matter the general public
has no reason to go there, and in fact there appears to be no significant
pedestrian volume.
In assessing the overall impact of undue influences from local sources,
the important factor is the proportion of sites falling in each of these
two categories. Based on the site visits and the above philosophy on
interpretation of public access, the significant majority of cases appear
to be situations where the source should be controlled, and the instances
of true monitoring anomalies which should be corrected are a small minority.
In a position somewhat between these latter two situations is the group
of sites that have significant but temporary local influences, usually
construction. These are to a certain-"degree clearly controllable fugitive
dust problems; because of their transitory nature, however, some portion
of the impact must be written off as an anomaly.
Another obvious conclusion is that, because nearby sources do affect mea-
sured air quality considerably, the siting practices of the agency can
significantly affect the number of sites indicating violations. Consid-
eration of the siting practices of the agency is thus a necessary pre-
requisite to comparing air quality values between cities.
METEOROLOGY AND CLIMATOLOGY
General Considerations
In determining which AQCRs have met or are likely to meet the national
particulate standards and which, if any, are not, it is important to keep
92
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in perspective the role of meteorology and climatology. As part of this
goal, the following discussion summarizes the impact of certain meteorological
variables and meteorological conditions on TSP levels in as quantitative a
fashion as appears reasonable at the present time.
The principal effects to be considered are discussed at length in Appen-
dix F where the range of conditions experienced by the 14 study cities is
analyzed. A brief discussion of these findings follows.
Precipitation - The effect of precipitation is twofold: (1) it cleanses
the atmosphere by capturing particles within the cloud (rainout) and by
the washout of particles below the clouds; and (2) it suppresses fugitive
dust. Precipitation is very effective in reducing TSP levels in areas
with high concentrations which have resulted from either industrial or
fugitive dust sources, and average concentrations decrease steadily with
increasing 48-hour precipitation amounts in these areas. The effect of
precipitation is greatest on the day it occurs and lasts an average
of about 2 days. In the city case studies of high-concentration areas,
concentrations measured during the last half of a 48-hour period with
precipitation _>_ 0.25 inch averaged approximately half of concentrations
measured during 48-hour periods with negligible precipitation. Concentra-
tions at typical urban sites (excluding clean residential areas) on days
with measurable precipitation were about 75 to 85 percent of average
values for the site and time of year.
Figure 13 presents a graphical summary of the findings at two sites in
one of the study cities when different levels of 24-hour precipitation are
used to classify a day as one with precipitation. Under one analysis, any
day with measurable precipitation (0.01 inch) was considered to have had
precipitation; in a second analysis, only days with at least 0.25 inch of
precipitation were considered as days with precipitation. Figure 13 shows
that, on the average, TSP levels remain depressed the day after rain at
North Birmingham; at Downtown Birmingham the levels return to near normal
more quickly. The effect of rainfall of different intensities is shown by
93
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1.50
140
I3O
1.20
1.10
1.00
O 0.90
5 0.80
0.70
0.60
>0-OI IN.
T«6)
I 2 3 4 5 OR MORE
NUMBER OF DAYS AFTER PRECIPITATION
o) NORTH BIRMINGHAM
OOI IN.
I 2 3 4 5 OR MORE
NUMBER OF DAYS AFTER PRECIPITATION
b) DOWNTOWN BIRMINGHAM
Figure 13. Duration of rainfall effectiveness in reducing TSP
levels at two Birmingham sites
-------
the difference between the two curves for each site. The occurrence of
the peak average ratio at 4 days after precipitation at North Birmingham
reflects a few very high ratios apparently associated with periods of
dry, light-wind, poor-dispersion conditions lasting for several days.
Wind Speed The effect of wind speed is also twofold. First, as the
speed of the wind increases, the effective volume of air available for
dilution increases. Thus, for constant source strengths, downwind con-
centrations are inversely proportional to wind speed. However, in the case
of particulates, total emissions are not invariant with wind speed since
the wind is the agent by which soil and dust particles are naturally en-
trained. The amount of fugitive dust entrained depends on the moisture
content and nature of the soil (or dust) and the wind speed. At speeds
below 10 to 15 miles per hour, however, the amount is basically negligible
even under dry conditions. At greater average speeds, and particularly
under gusty conditions, fugitive contributions can be substantial. Wind
speed also indirectly contributes to fugitive emissions by increasing
the rate of evaporation, and hence speeds the drying of the soil and dust
particles.
Specific analyses on the effect of wind speed were conducted in four of the
study cities using 24-hour average TSP concentrations and daily average
airport wind speeds. One of these (Birmingham) is heavily industrialized,
two (Chattanooga and Denver) are moderately industrialized, and one
(Oklahoma City) is lightly industrialized. Birmingham and Chattanooga
have above-average precipitation and low average wind speeds, Denver has
little precipitation and below-average wind speeds, and Oklahoma City
has nearly average amounts of precipitation and high average wind speeds.
The results of these studies showed that the dilution effect of wind
speed was noticeable below speeds of about 10 miles per hour in industrial
areas where major contributions were made from point sources. At higher
wind speeds and in nonindustrial urban areas, average TSP levels did not
appear to be related to wind speed. It was not possible to
95
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discover to what extent this invariance with wind speed resulted from an
interplay between dilution and wind-induced fugitive dust contributions.
However, the findings in Birmingham apparently indicate some reentrainment
of particulates at high wind speeds. As shown in Figure 14, the average
concentration decreases with increasing wind speed for speeds up to about
8 knots and then remains essentially constant. Furthermore, the decrease
of average concentration with wind speed, as shown by the dashed line, is
approximately linear from 2 to 8 knots, as would be expected if dilution
were the controlling influence. The change in slope shown at 2.5 knots
can be attributed to stagnation conditions at very low wind speeds. While
the curve for North Birmingham reflects the same relationship as that
for Downtown Birmingham, the average concentration at Mountain Brook ap-
pears to be invariant with wind speed. This difference may be explained
by the availability of particles for reentrainment being very low in the
residential areas. The industrial site, being in a dirtier area, has a
larger amount of particulate that can be reentrained.
Stability and Stagnation - The stability of the air, c- measured by the
change of temperature with height, controls the rate of vertical turbulent
diffusion and the mixing depth. It therefore is a measure of the dilution
power of the atmosphere in the vertical. The diurnal variation of wind
speed caused by the vertical transfer of momentum is closely related to
the diurnal variation in stability. Stagnating air masses permit the
accumulation of pollutants and the development of stable transport patterns,
While no special attempt was made during this study to isolate the effects
of stability or stagnation periods on TSP levels, several general state-
ments can be made. First, the highest 24-hour concentrations are observed
during stagnating conditions since by definition these are periods with
very low wind speeds and inversion conditions over at least a 24-hour
period. Under these conditions, concentrations are typically about two
or two and a half times the average values for the site and time of year,
and the 24-hour standards are most likely to be exceeded. In the more
polluted areas, levels may be increased 100 yg/m3 or more. For that
96
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IO
490
400
350
300
o
VO
250
200
ISO
100
50
NORTH BIRMINGHAM
(INDUSTRIAL)
*» NORTH BIRMINGHAM
or DOWNTOWN BIRMINGHAM
«MT. BROOK
DOWNTOWN BIRMINGHAM
- (COMMERCIAL)
^
MT. BROOK (BACKGROUND/RESIDENTIAL)
JL
JL
JL
JL
JL
JL
5678
WIND SPEED, knots
10
II
12
15 14
Figure 14.
Relationship between TSP concentrations and
wind speed at three selected sites in
Birmingham on days with 48-hour precipita-
tion amounts < 0.02 inches
-------
part of the country with the maximum number of stagnations (14), stagnations
occur on an average of 3.8 percent of the days in a year. If on these days
the average concentration is 2.3 times the annual mean, the increase in
the annual mean due to the stagnation days is approximately 5 percent.
Temperature Temperature, and seasonal temperature patterns, are the best
single indicators of space heating requirements, and hence correlate with
particulate emissions from these sources. Emissions from city to city
for the same number of degree days will vary with the type of fuel burned.
Temperature also plays a part in fugitive dust emissions by affecting the
evaporation rate of water and by its influence on the growth of vegetation.
The impact of temperature (using heating and cooling degree days) was in-
vestigated in each city and the results are reported in the individual
volume for the city. Comparisons among the various cities were made
using a regression analysis, reported later in this section. (Also see
Appendix F.)
Wind Direction On a local scale, the wind direction determines the polar
distribution of pollutants around their sources, and hence is requisite to
the understanding of source-receptor relationships and the design of source-
specific sampling networks. On a regional scale, the TSP concentration
in the air mass entering an urban area is determined by the past history
of the air mass, which is best estimated by trajectory calculations;
wind direction roses can also be helpful. While wind direction-
pollution roses were calculated and reported in many of the city volumes,
trajectory analysis was done for only one case; that analysis is given in
Appendix C.
Solar Radiation In addition to being the driving energy source for
weather systems, solar radiation relates to particulate emissions through
temperature, evaporation, and plant growth. Solar radiation can also
98
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increase the ambient TSP levels by providing the requisite energy for the
conversion of gases to secondary participates.
Combined Impact of Meteorology
Multiple regression analysis was used to estimate the effects of annual'
variations in meteorological parameters over the 5-year period from 1970
to 1974 on the annual mean TSP levels in the study cities. The three
meteorological parameters initially considered as Independent variables
were precipitation, temperature (heating degree days), and wind speed.
After initial calculations, plus reflection on the apparent lack of
short-term correlation between wind speed and TSP level except in in-
dustrial areas, it was decided to exclude wind speed from the analysis.
Allowance for a linear trend was made by designating 1970 as year 1,
1971 as year 2, and so on.
In the analysis, each site type average in each city was treated as a
separate observation. Dummy variables were used to permit different
intercepts for the several cities and the three site types, while the
meteorological effects were estimated based on data from all cities.
This approach in effect assumes that the meteorological parameters operate
in roughly the same manner throughout the country, which is clearly neither
an obvious nor a trivial assumption. Previous analyses that permitted the
meteorological effects to differ from city to city did indicate that the
effects found in the various cities were quite similar in magnitude, and
it is on this basis that the assumption was made.
The resulting equation was:
TSP = C - 2.9Y - 0.43P + 2.5T
3
where TSP = annual geometric mean concentration in fig/m
3
C = constant in ug/m
Y = year, 1 to 5
P = annual precipitation in inches
T = heating degree days in thousands.
99
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The implication of the general regression equation is that within the
3
study cities concentrations have been lowering at the rate of 2.9 ug/m
per year over the last 5 years, that an increase of 1 inch in annual pre-
3
cipitation decreases the mean concentration by 0.43 ug/m , and that an in-
crease in heating degree days of 1000 increases the mean concentration by
3
2.5 ug/m .
This result can be used to get some feel for the magnitude of the effects
of annual changes in precipitation and temperature on TSP levels. Examin-
ation of the variations in precipitation and temperature over the 5-year
period in each of the 14 study cities showed that the smallest range in
precipitation (6 inches) occurred in St. Louis while the greatest range
(27 inches) occurred in both Chattanooga and Providence. The minimum
range for heating degree days was 188 in Miami and the maximum range was
1189 in Cleveland. The implied differences in TSP levels resulting from
3
these annual variations in precipitation range from 2.6 ug/m in St. Louis
3
to 11.6 ug/m in Chattanooga and Providence, and the differences resulting
3
from variations in heating requirements range from 0.5 ug/m in Miami to
3
3.0 ug/m in Cleveland.
Although conclusions based on this equation must be considered tentative,
the relationship provides a ready means for comparing precipitation and
heating demand effects throughout the country. For example, the results
of applying the equation to the climatological precipitation pattern
(Figure F-20) can be displayed as the relative effect of differences in
total annual precipitation on the annual TSP level, as has been done in
Figure 15. In this figure a precipitation rate of about 35 inches a year
corresponds to the "0" relative effect isopleth. The maximum geographical
3
difference in the annual mean shown by the figure is approximately 35 ug/m
3
(from -25 to +10 ug/m ).
The use of the relationship between heating degree days and TSP level in
conjunction with the geographical distribution of degree days shown in
Figure F-27 suggests a maximum contribution to the annual mean from space
100
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-25
-25
+ 5
Figure 15. Relative effect of annual precipitation on annual TSP level
in a hypothetical urban area. (Estimated from regression
equation, p. 99)
-------
heating of 25 pg/m3. The spatial variation in degree days found in the
western United States has been drastically smoothed out in Figure 7-21,
so attention should really be focused on the area east of the Rockies.
The effect of space heating on TSP levels ranges from about 5 wg/m3 in
the southern tier of states to 22 vg/m3 in the most norther states. Again,
this is an attempt to generalize the effect of space heating using data
from a mix of cities with widely different fuel usage characteristics, and
the results therefore are not necessarily appropriate for any specific city.
Conclusions
Low TSP levels are to be expected in a ''standard" urban area if it is
located in a generally flat, well-exposed topographical setting where:
Entering air is clean (i.e., nonurban levels are low).
Annual precipitation is high and distributed throughout
all months of the year. (Moderate amounts of precipita-
tion roughly every third day are very effective in cleans-
ing the atmosphere and in suppressing fugitiv dust.)
Wind speeds are not extreme. (Light winds minimize dilu-
tion, and strong gusty winds generate fugitive dust under
dry conditions).
Daytime mixing depths are high and the frequency of low-
level inversions is low. (This combination maximizes
periods of good vertical daytime dispersion and minimizes
periods of poor nighttime dispersion.)
Space heating demands are minimal. (With a standard mix
of fuels, space heating emissions are proportional to
degree days.)
High-pressure weather systems do not stagnate. (Stagnant
anticyclones with accompanying light winds, a persistent
subsidence inversion, and nocturnal surface-based inver-
sions lead to accumulated high TSP concentrations and vio-
lations of the 24-hour standards.)
The frequency and character of winter precipitation is such
that street sanding is rarely, if ever, required. (On the
other hand, snow cover is highly effective in eliminating
fugitive dust.)
102
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Conversely, high TSP concentrations are to be expected in a "standard"
urban area if air entering the city already contains a substantial par-
ticulate loading, and if the location is sheltered with resulting poor
ventilation, has a cold, dry climate, and experiences frequent stagnant
high-pressure systems.
Because of complex interrelationships among meteorological parameters and
the generation, transport, dispersion, and depletion of airborne particu-
lates, however, it must be recognized that a single parameter may bring
about opposing effects and, further, that certain meteorological param-
eters tend to be linked by the nature of typical weather systems: fast
moving air dilutes and transports pollutants readily but also increases
evaporation, thus hastening the drying of soil and settled particulates,
and as a consequence the air stream may entrain particulates from the
dried surfaces; high temperatures increase evaporation, but also encourage
the growth of vegetation and eliminate the need for space heating; snow
and ice eliminate fugitive dust emissions from most surfaces, but may re-
sult in the need for extensive street sanding and hence ultimately be
responsible for an increase in urban fugitive dust emissions.
While it is possible to make certain judgments based on what are believed
to be the major effects of precipitation, heating degree days, and stag-
nation periods as done above, only a rigorous statistical analysis can
properly assess the effects of meteorological and climatological param-
eters on nationwide urban TSP levels. Such a study was beyond the scope
of the present effort, and any serious attempt to assign a TSP pollution
potential rating to individual AQCRs should await the completion of such
an analysis.
RELATIVE CONTRIBUTIONS OF VARIOUS FACTORS
By way of summary, the following discussion considers the overall average
ambient TSP level and divides it into portions considered representative
of the influences of the various major factors discussed in this section.
103
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Such an analysis is essentially a mnemonic device, averaging over many
important variables. Consequently, it should not be interpreted quanti-
tatively with respect to any particular site or urban area; a discussion
concerning how these results may be particularized to specific conditions
is presented in Appendix G.
The contributions to the overall particulate level at any point have been
classified as coming from three major categories emissions from tradi-
tional sources, emissions from nontraditional sources, and nonurban
particulates. In addition, two major categories of modifying influences
were identified - meteorological factors and monitoring considerations.
The rough qualitative impact of these factors was suggested in the sketch
in Figure 2 in Section II. The following quantification of those factors
is built around Figure 16.
Nonurban Levels The most basic contribution to the total is roughly
30 ug/m of natural and transported particulates. As discussed above,
and as seen in the small bar chart to the side in Figu i 16, this level
varies significantly among various regions of the continent. The low west
>
coast level of about 15 ug/m represents the favorable situation of being
located on the ocean and receiving air with essentially globally averaged
natural TSP levels. The mid-continent level of about 25 ug/m3 includes a
10 ug/m3 increments, representing a slight increase in secondary par-
ticulates (1 to 2 ug/m3) and a major contribution from the natural par-
ticulates accumulated as the air mass passes over the broad, relatively
dry, western portion of the continent.
The northeastern nonurban levels then contain a further 10 p.g/m incre-
ment, which consists of two major pieces. A significant increase in trans-
ported secondary particulates, the precise source of which is not thoroughly
proven, is a large share of the increment. The other share is attributed
to transported primary particulates from the major urban concentrations
of the midwest and northeast.
104
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120
liO
too
90
80
Z
o
z
Ul
o
§
u
a.
in
60
INOU9T COHU
MCS
50
40
10
UNDUE
O u
E S
§ §
oe M
I s
O
3
if
II
RES
COMM INDU9T
CAST HIOMXT WEST
Figure 16. Summary of average impact of major contributors
to TSP levels
105
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Emissions From Nontraditional Sources - The general types of nontraditional
sources identified as important are essentially the substance of human ac-
tivity in urban areas. They occur in every urban area and hence are seen
as more basic than the traditional sources, which are of only minor concern
in at least some urban areas. The overall contribution from such sources,
however, differs significantly among different neighborhoods within a single
urban area, as seen in the small bar chart in Figure 16. This contribution,
which consists primarily of the effects of tailpipe emissions, tire wear,
1
and road dust reentrainment, is about 20 ug/m in residential areas and
about 30 vg/m in commercial and industrial areas, the difference being
the greater level of traffic. The proportion of residential versus
other sites considered in averaging over the other two categories is a
matter of abstract philosophy; an average of roughly 25 ug/m3 has been
selected for use in the figure.
Emissions From Traditional Sources - The third major contributor to am-
bient levels~ traditional sourcesvaries dramatically not only
with neighborhood type but also with the general industrial nature of
the city. As was seen in Figure 8, the impact of traditional sources
3 3
can range up to about 10 ug/m and 30 ug/m at residential and commercial
3
sites respectively, and up to 50 ug/m at industrial sites. This latter
figure reflects the inclusion of fugitive emissions from industrial
sources, but the contribution of truck traffic and similar industry-
related emissions has been included with nontraditional sources. Roughly
averaging over various neighborhood types and over the spectrum of non-
3
industrial to heavily industrial cities, a value of 25 ng/m has been in-
cluded in Figure 16.
3
This addition of 25 ug/m is the same as the contribution from nontra-
ditional sources; thus on a nationwide basis, the two categories are
roughly equivalent. However, it must be kept in mind that the differences
among cities affects this balance significantly.
106
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Modifying Factors - The two major categories of modifying factors are not
so readily represented graphically. Meteorological and climatological
factors primarily can increase or decrease the average levels depending on
the various regions of the country. Quantitatively, the effect is fairly
commonly about 5 ug/m3, and in some areas 10 yg/m3.
The influence of monitoring considerations comes primarily in distorting
comparisons of measured levels among neighborhoods and cities. However,
the aggregate nationwide average of undue influence from nearby sources
2
can add a very few vig/m to the total, as Indicated in Figure 16.
107
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SECTION IV
SUMMARY
This section summarizes the findings of the study, including the study
approach to general problem assessment, the attainment factors identified,
the assessment of these factors, the control options available, and
their applicability and priority for control.
PROBLEM ASSESSMENT
This study approached the national particulate problem with many of the
same tools an individual air quality planner would use to approach an
assessment of the problem in a particular urban area. It utilized air
quality data analysis, emissions data and modeling, and analytical particle
identification; these, along with special monitoring studies, are the
techniques with which a TSP problem at any level is studied. However, the
results of this study are intended to provide general information on a
national scale rather than urban-scale planning information for the
14 study cities or any others. While the individual air quality
planner will hopefully find the results useful, they are not intended to
solve any specific problems in specific urban areas. Rather, the results
provide an additional component of technical information which will need
to be integrated and assessed in conjunction with local knowledge.
ATTAINMENT FACTORS IDENTIFIED IN CITY STUDIES
The purpose of the city case studies was to identify and study the various
factors, problems, and issues concerned with attaining the TSP standards
as they were experienced in each city. Since the 14 cities cover a broad
108
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range of city characteristics and hence represent a variety of situations
with respect to TSP air quality and its determinants, analyses of the
factors in the various cities can be drawn together for an overall assess-
ment of the TSP attainment situation in the study cities and, by extrap-
olation, throughout the nation.
Following the analyses of the study cities, a number of factors were
identified as significant for standards attainment. Many of these had
been first identified in the preliminary literature review and were then
followed up in the city studies; a few others were identified in the course
of one or more of the city studies. These issues are listed below, grouped
into categories that provide a framework for discussions.
Traditional Factors
Air pollution programs have traditionally been oriented toward the control
of fuel combustion, process emissions and incineration. Such control
programs have resulted in substantial reductions in emissions and corres-
ponding improvements in air quality in many of the 14 study cities.
While all of the cities studied have ongoing control programs for tradi-
tional sources, there were differences both in the amount of traditional
source influence and in the success of the program:
Three cities still have significant problems with traditional3
sources. Citywide air quality averages are typically 30 tig/m
higher than they are in similar cities with light emissions from
industry and fuel combustion.
Three cities have had heavy industrial sources and problems, but
have made major improvements in air quality. They still, however,
have citywide averages typically 10 to 15 ug/m3 higher than
similar cities with light emissions. There is some potential
for improvement in air quality in these cities by further reduc-
tion of traditional sources.
Four cities have had moderate emissions problems and have them
well under control. These cities must control nontraditional
sources to make further, substantial improvements in air quality.
109
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Four cities never had problems with traditional sources, except
fuel combustion for heating and power generation. Further im-
provements must come from control of nontraditional sources.
The major sources still presenting problems with attainment of standards
are in the primary metals and minerals industries. Of primary con-
cern are the fugitive emissions which are not confined and do not come
from a stack or vent. These emissions have substantial impact on air
quality; sites which were influenced by fugitive emissions averaged
3
25 ng/m higher than industrial sites affected by stack emissions only.
This is partly due to the typically low level emission point and poor
potential for dispersion. Another problem is that of area source fuel
3
combustion; fuel oil is estimated to contribute on the order of 5 ug/m
to citywide averages in some cities. A similar order of impact is realized
from the many small (minor) sources if these sources are generally con-
trolled.
Major program considerations which were determined to be a factor in
traditional source impact are the assurance of compliance with existing
regulations and, in some cases, the stringency of those regulations. This
will be discussed further under control alternatives.
Nontraditional Factors
While many cities have realized substantial improvements in air quality,
few cities have all sites below the primary standard and fewer still have
all sites below the secondary standard. This is due to the impact of
factors which have not been traditionally addressed by the air pollution
programs, such as reentrained dust, tire wear particles, dust from con-
struction, and automotive exhaust emissions. The impact of all such
general urban activity varies from a typical impact of 20 to 25 yg/m3 in
residential areas to a typical impact of 30 to 35 pg/m3 in commercial and
industrial areas; the citywide contribution is about 30 yg/m3. The com-
ponents of this contribution are discussed below.
110
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Reentrained dust The impact was found to vary with the
traffic flow and inversely to the height and distance
of the monitor from the street. The average impact on
residential monitors is estimated at 10 to 15 ug/m3
and 15 to 20 ^g/m3 at commercial and industrial sites
respectively. The composition of this component is
mostly mineral matter.
Tire rubber particles This component of nontraditional
particulates is even more variable with neighbor-
hoods. Typical impacts of 2 to 5, 5 to 10 and 3 to
7 ug/m3 were found at residential, commercial and In-
dustrial sites, respectively. Sites located par-
ticularly near heavy traffic averaged twice the levels
at other sites.
3
Construction Impacts of 15 ug/m are common only if the
construction is close to the monitoring site. Cities with
typical levels of construction have citywide impacts on
the order of 1 to 3 ug/m3.
Automotive exhaust This varies somewhat with neighborhoods^
with concentrations of 3 ug/m3 in residential and 4 to 5 ug/m
in commercial and industrial areas. This estimate is for the
primary particulate only and is generally about 20 to 25 percent
lead.
Large Scale Factors
Large scale factors are the combined influences of particulate matter
that dominate an area much larger than the urban areas being studied.
They include natural particulates and transported primary and secondary
particulates. These factors, in affecting the TSP levels in an urban area,
can cause significant differences in the controllability of the TSP
problem. Their effect on urban levels is generally estimated by measuring
air quality in nonurban areas. The average nonurban particulate level
3
for the 14 study cities is between 25 and 30 ug/m ; however, values ranged
from less than 15 ug/m on the west coast to over 35 ug/m in the densely
metropolitan east.
Transported secondary particulates make up a significant portion of non-
urban levels. Nonurban sulfate and nitrate levels range from very low
111
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3
in the midwest and west to around 10 ug/m in the northeast. Total
urban secondary levels vary up to around 15 ug/m in the north and east.
Other Related Factors
In addition to the above factors, which are to varying degrees related to
sources of emissions, other factors were found to affect the real or
apparent TSF problem. As discussed in the selection of the cities, the
meteorology and climatology of a region can help to aggravate or ameliorate
the TSP problem; the dispersion characteristics and precipitation levels
are the most prominent influences. The design of the monitoring network
and the actual placement of monitors is also important in conceptualizing
what the TSP situation is. The general findings from the city studies
for these factors are summarized below.
Monitoring considerations The siting practice of the control
agency has considerable impact on the air quality levels and
number of violations recorded. For example, 10 of the 60
commercial sites visited had local impacts fro_. nearby sources.
With one exception, all these sites violated the primary annual
standard. Also, since industrial neighborhoods were shown to
have substantially higher TSP levels, the proximity of monitors
to industrial neighborhoods is an important variable. A specific
relationship was found in the study between average daily traffic
(ADT) at a site, the slant distance of the monitor from the
street, and air quality levels. For example, based on approximate
calculations, a monitor 100 feet (slant distance) from a busy
street (10,000 ADT) might be influenced by the reentrained dust,
tire wear and exhaust by 10 ng/m3. This same relationship shows
an impact of 40 to 45 (jg/nr* if the monitor is only 25 feet from
the street.
Meteorology The study found precipitation to be an extremely
important variable; a yearly increase in rainfall of 1 inch can
cause decreases in citywide annual averages of 0.4 ng/nH. It
also concluded that average windspeeds above 10 miles per hour
could cause some resuspension of dust. The effect on air quality
would depend upon the gustiness of the wind and the condition of
the soil.
112
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CONTROL STRATEGY OPTIONS
The development of a control strategy for the attainment and maintenance
of the ambient particulate standards must depend on accurate identifica-
tion of the sources responsible for the particulate problem. Once this
identification has been established, the available control measures can
be defined, evaluated, and combined into an aggregate control strategy
which is appropriate and effective. The major single conclusion of the
study is that the control measures traditionally directed at pollution
sources are not going to be adequate in many cases, and that other, more
novel control measures directed at nontraditional sources and sources con-
tributing to nonurban levels must also be considered.
Proposing detailed control strategies or priorities for specific situa-
tions is beyond the scope of this study. Such a process must necessarily
involve the addition of significant quantities of local knowledge. None-
theless, two points should be mentioned briefly. The first involves the
relative emphasis on the three main contributions to urban TSP. If
traditional sources still contribute the major share of TSP in an area,
they are clearly the most appropriate segment to attack. Potential over-
all reductions in emissions of 75 percent or more may be expected in those
cases where sources are not yet stringently controlled. In every city,
industrial or otherwise, the nontraditional sources present a more dif-
ficult target, with reductions of 50 percent or less probable even from
truly extensive control efforts. The nonurban contributions, which are a
major influence in at least the nonindustrial cities, are the worst in the
sense of being essentially intractable at a state and local scale. The
priorities for control must consider these general differences. The
second point to remember when selecting among strategies is that there are
a number of considerations other than simply mass particulate reduction.
For instance, under the Clean Air Act mandate to protect public health,
strategies that attack smaller particles or toxic materials are preferable
to those that attack inert windblown dust; similarly, strategies that
impact the more populated regions of a city should take priority over
113
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those that would affect fewer people. When evaluating control alter-
natives, economic factors, social disruption, and enforceability must
also be considered.
Keeping in mind the need for individual consideration in each area
violating the TSP standards, the following discussion lists the types of
control measures generally considered appropriate for each of the various
sources of particulates included in the three major categories previously
outlined.
Control Measures Directed at Traditional Sources
The general pattern of control technology applicable to traditional
sources is well established; the open questions are primarily those of
application. In this sense, it is appropriate to subdivide the category
of traditional sources into four subcategories:
Major point sources
Smaller point sources
Fugitive emission sources
Fuel combustion area sources.
Stack Emissions - With some differences in emphasis, the control measures
available for both major and smaller point sources are similar.
Obtain compliance with regulations - existing efforts to
bring sources into compliance must continue, and must be
extended in those areas where current efforts are
incomplete.
Tighten compliance determination and surveillance pro-
cedures - one area of significant difference by size of
source; major sources should be stack tested at least
annually, smaller sources inspected frequently under a
tight surveillance system.
Tighten regulation stringency - after considering carefully
the local need for tighter traditional source control:
-------
Upgrade regulations for selected major sources
and smaller sources to at least require the best
control technology reasonably available (not
necessarily RACT as currently promulgated).
Incineration can be completely banned in favor
of landfilling or shredding for power generation.
Process losses covered under a general process
weight regulation can be further restricted by
adopting regulations specific to individual
problem industries.
Fugitive Emissions - Aside from the major concerns of improved surveil-
lance and enforcement, specific measures for reducing fugitive emissions
from traditional sources include special regulations beyond simple
nuisance or "reasonable precaution" regulations:
Quantitative or visible emission standards at
property lines
Operating and maintenance standards for specific
processes
Covering storage piles
Enclosing materials handling equipment
Paving roadways and loading and parking areas
Area Source Fuel Combustion - Though difficult to effectively control be-
cause of their large numbers, there is a real possibility of reducing
emissions from such sources, if the need warrants, through measures
such as the following:
Design standards for new boilers
Maintenance of oil boilers
Prohibition of coal use
Inspection and maintenance of small oil
burners
115
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Control Measures Directed at Nontraditional Sources
After agencies have taken the appropriate steps to controlling traditional
sources, and in areas where traditional sources have never been the major
problem, control strategies for the attainment of the TSF standards may
have to consider control of those nontraditional sources discussed in
Section III. Implicit in the very label "nontraditional" is the concept
that these sources have not had control measures directed at them. How-
ever, control of these sources is not so much a matter that is beyond
reach technically as it is a matter of using measures that are costly
or hard to justify or, in many cases, simply measures that are not normally
seen as pollution control measures. Examples of these types of measures
are listed below for the three major categories of such sources:
Motor vehicle exhaust
Fugitive dust from construction and demolition operations
Reentrainment of particles from roadway surfaces.
Motor Vehicle Exhaust - In urban areas where tailpipe emissions are
found to be contributing 5 to 10 ng/m to the total suspended particu-
late loading, it may be necessary to consider their control. The
available control measures for lowering tailpipe emissions are:
Reduce lead in gasoline
Reduce VMT totals in area
Reduce emission per mile through inspection and maintenance.
Construction/Demolition and Other Fugitive Dust Sources - The control
of dust from construction and demolition activities and similar acti-
vities is most often approached through the use of nuisance or reason-
able precaution regulations much as is the case with fugitive emissions
More specific control measures that can be applied include:
Watering construction site and demolition rubble
Chemical soil stabilization
Use of sequential blasting demolition.
116
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Reentrained particulates - The majority of such participates are street
duet entrained by traffic; control measures include both preventive
measures and street cleaning:
Control of dust deposition - A viable approach to controlling
reentrained particulates is reducing the amount of particulate
matter available for rcentrainment; control measures include:
Fallout - The fallout level will decrease automatically
with control of traditional source emissions.
Carryout - Dirt and mud carryout from unpaved
roads and parking lost can be reduced by require-
ments for paving or stabilization of these
areas.
Spillage - The loading on streets due to spillage from
trucks is easily regulated against, but enforcement may
be a problem. Regulations that require specific equip-
ment on trucks would probably be an improvement.
Tirewear Particulates - Reduction in the amount of
rubber tire particles could be effected by VMT re-
duction or by designing and requiring tires with better
wear characteristics.
Sanding - Because of the obvious hazard of slippery
roads, sanding and salting operations will obviously
continue. Analysis of the efficiency of sanding may
result in procedures that apply less sand more ef-
fectively; however, systematic road cleaning after
sanding operations would be more appropriate.
Street cleaning to remove deposited material - Since it is
not possible to prevent all deposition of particles on a
paved surface, an alternative or auxiliary approach to con-
trol of particle reentrainment is to remove the particles
from the surface. Control measures include:
Street cleaning
o Rotating broom sweepers
o Regenerative air blast sweepers
o Vacuum street cleaners
Street flushing with water.
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Control Measures Directed at Transported Primary and Secondary Participates
A complicating factor in any standards attainment strategy development is
the concentration of TSP in the incoming air mass. When such concentra-
tions approach or exceed the standards, there is little if anything that
an agency can do to meet the standards unless the controls are also pur-
sued for this incoming (nonurban) TSP. Obviously, there are really no
appropriate measures for the contribution of natural sources to these TSP
levels; however, those particulates directly attributed to man's activi-
ties are, to varying degrees, controllable. In certain cases attention
directed toward control of these sources may be more profitable than non-
traditional control techniques.
Transported Primary aarticulates - Those particulates that are emitted
directly as primary particulates and are then transported from one area
to another can be controlled through conventional traditional source
regulations. The difficulty arises in the development of regionwide con-
trol strategies in which one area may need to limit its emissions more
severely than necessary to simply meet the standards in that area because
of the impact on a neighboring area. Such regionwide planning may be
immediately possible on a statewide basis or may require interstate and
inter-EPA region cooperation.
Secondary Particulates - Much the same thing can be said for secondary
particulates except that many of the secondary particulates are formed in
transport over much longer distances than would normally be of concern
for primary particulates. Therefore, these control strategies must seek
national direction rather than state or interstate cooperation. However,
secondary particulates that are locally formed can presumably be locally
controlled. As indicated in Section III, urban excess secondary particu-
o
lates may add 5 ug/m to levels in the city and these particulates could
be controlled once the appropriate precursor relationships are known.
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FRAMEWORK FOR CONTROL STRATEGY PRIORITIZATION
The institution of control measures must be preceded by the careful
prioritization of available options. This section suggests a framework
for evaluating control options as a function of the scale of the problem.
There are significant differences in the general prevalence of the three
major factors traditional sources, nontraditional sources, and large-
scale consideration - and thus the applicability of their associated con-
trol options, when dealing with problems of different geographical scales.
Consequently, priorities for instituting control options are best made
within this context of differing scales.
Concept of Scale
A general assessment of the relative scale of impact of the factors affect-
ing attainment can be made. It is helpful to think of TSP problems as
affecting either a relatively small area (neighborhood), and entire urban
area or many urban areas in a general region (intercity). These are dis-
cussed below.
Neighborhood scale - TSP problems over areas a few blocks
in size occur even in the urban areas with relatively low
citywide levels; typically measured by only one hi-vol,
these problems are often caused by a relatively local
source, frequently a small industry or fugitive dust source.
Urban scale - In some urban areas, the TSP problem is to a
large extent citywide (in addition to neighborhood hot spots),
and is less likely to be due to a relatively few identifi-
able sources as on the neighborhood scale.
Intercity scale - In some portions of the country, there is
a general regional TSP problem that transcends any individual
urban area or AQCR.
Within any particular area, it is very possible to have problems in all
three of these scales simultaneously. Nonetheless, the overall control
approach to each can be generally independent and in fact, problems of
certain types typically occur primarily in one geographic scale. For
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example, nontraditional sources typically cause mostly neighborhood
problems, while traditional sources may more likely cause urban-scale
problems.
Priorities of Instituting Control Options
The previous sections have delineated various control measures that could
be instituted by agencies and suggested the general scale of applicability
of different factors affecting attainment and their associated control
measures. This section suggests the specific categories of sources for
which control measures could be applied to reduce particulate concentra-
tions at each level or scale. The source categories into which the many
types of air quality problems have been generalized are as follows:
Traditional
Major sources
Small sources
Fugitive emissions
Area source fuel combustion
Nontraditional
Resuspended dust from roadways
Fugitive dust from construction and demolition
Auto tailpipe emissions
Large scale
Transported primary particulates
Transported secondary particulate
Urban secondary excess
The following matrix (Table 16) summarizes the priorities for adopting
control measures for these categories of sources as a function of the
scale of the problem.
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Table 16. CONTROL PRIORITIES
Order of
priority
1
2
3
Regional scale of problem
Neighborhood
Fugitive emissions
Reen trained dust
Fugitive dust/
construction
Small sources
Area source fuel
combustion
Auto tailpipe
Urban secondary
excess
Major sources
Urban
Lightly
industrialized
Reentrainment dust
Auto tailpipe
Area source fuel
combustion
Urban secondary
Small excess
sources
Fugitive dust/
construction
Major sources
Heavily
industrialized
Major sources
Urban secondary
Small excess
sources
Fugitive emis-
sions
Reentrained dust
Auto tailpipe
Area source fuel
combustion
Fugitive dust/
construction
Intercity
Major sources
Transported primary
Transported
secondary
Small sources
Area source fuel
combustion
Fugitive emissions
Reentrained dust
Fugitive dust
Auto tailpipe
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SECTION V
RECOMMENDATIONS
The broad scope of this study provided an opportunity for an evaluation of
the control practices to date, an assessment of the controls that are
needed in the future, and an understanding of the obstacles that are pre-
venting the attainment and maintenance of the NAAQS for TSP. Based on
these findings, numerous recommendations have been formulated. The recom-
mendations cover a wide range of topics and are directed at various
audiences both inside and outside of EPA. Some of these recommendations
are readily apparent from this study and are, in fact, called out separately,
as in Appendix G. Others are the result of integrating all the findings
and analyses conducted over the course of the study.
The recommendations provided below run the full gamut of considerations.
They are organized by first presenting specific recommendations for emis-
sion control efforts, then more general recommendations concerning the
major upgrading of quantitative air quality management planning, and finally
recommendations regarding the current review and further development of the
NAAQS for TSP.
In general, all of these recommendations recognize the need to provide ap-
propriate justification for any new major control approach that must be
adopted. Equally important is the demonstration that proposed control
programs will result in the necessary improvements in air quality.
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RECOMMENDATIONS FOR EMISSION CONTROL EFFORTS
The following recommendations are grouped for convenience into three
groups corresponding to the three major components of urban TSP levels as
discussed previously traditional particulate sources, nontraditional
sources, and nonurban particulate levels.
Control of Traditional Sources
All urban areas do not require an equivalent degree of traditional source
control. The first set of recommendations presents control efforts con-
sidered appropriate for major industrialized urban areas having an apparent
TSP problem primarily associated with emissions from major fuel combustion,
industrial process and solid waste operations. The second and third set
of recommendations are directed at all urban areas, both those that are
heavily industrialized and those that have only a moderate to light amount
of industry and area-wide combustion of oil or coal. Such a breakdown
presumes that most of the effective programs will already meet the first
set of recommendations for local control planning. However, additional
control may still be needed under large scale planning efforts as dis-
cussed later.
1. Control of Major Point Sources
a. Limitations on emissions from fuel-burning installations
of all sizes should be tightened considerably. There is
a factor of at least A between the typical regulation and
the most stringent, yet workable, regulation; while very
stringent requirements are likely not required in many
urban areas, in major industrial areas they are clearly
needed.
b. Emission limitations applicable to major oil-burning in-
stallations should be defined separately, and more strin-
gently, than those applicable to coal combustion. A single,
uniform combustion regulation that was designed to permit
some coal combustion will unavoidably permit relatively
poorly controlled residual oil combustion, simply because
of the inherently different emissions potential of the
two fuels. There is no need for this, nor for the atti-
tude that coal-to-oil conversion should be seen as a total
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abatement of the source; oil-fired sources can and
should be controlled.
c. All major combustion sources that have undergone coal-
to-oil conversion should be tested. There are significant
differences in effectiveness when control devices de-
signed for coal fly ash are utilized on oil-fired units,
yet it appears not uncommon for the original percent-
efficiency figures to be utilized in calculating emissions
levels.
d. Emissions from industrial process losses should be
regulated on the basis of industry-specific restrictions.
The present common practice of utilizing a general process-
weight curve necessarily means that relatively-easy-to-
control processes will only be required to meet such
standards as are appropriate for the more difficult to con-
trol ones. Major processes in any given area should be
regulated with a specific emission limitation economically
and technologically tailored to that industry.
e. Compliance determination procedures in general should be
significantly strengthened, primarily by increased use
of source casting and source surveillance. In general,
the degree of assurance of stated control efficiencies,
etc., appears to be less rigorous than needed to provide
good quantitative compliance knowledge. WMle it is not
recommended that all sources be physically tested, it is
believed that a much greater level of testing is needed
than is now practiced. All large sources and all unique
sources should be tested on compliance attainment and at
intervals thereafter, either by agency personnel or by an
approved independent testing organization. Reliance on
routine engineering calculations should be permitted only
for the simplest, most routine situations. Source tests
should take care to include not only stack emissions but
fugitive emissions from processes. Systematically and
randomly scheduled visits should be made with schedules
depending upon the source size, history of complaints and
problems, and compliance status.
2. Control of Fugitive Emissions
a. EPA should develop and make available an accurate me-
thodology for inventorying the emissions and estimating
the air quality impact in the vicinity of isolated sources
of fugitive emissions, such as quarries and rock-crushing
operations. In order to include such emissions in air
quality management planning, more adequate information must
be developed.
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b. In every heavily-industrialized area, the cognizant
state and local agencies should conduct, and EPA should
support, a major survey effort to identify and inventory
fugitive emission sources. Such surveys should Include
field monitoring, extensive inspections of industrial
premises, and the rough estimation of emission quantities.
While fugitive emissions from generally-isolated indus-
trial operations (such as quarries) are relatively easy
to identify, if not quantify, it is not easy to define
the degree to which fugitive emissions from dense heavy
industrial areas are a problem. Consequently, a serious
effort to define the nature and magnitude of the problem
is required prior to dealing with it.
c. Regulations applicable to fugitive emissions from indus-
trial property should be strengthened by the itemization.
of specific control measures where possible and by the
institution of property-line air quality limitations
where required by the complexity of the area or the In-
dustrial operations involved. It is anticipated that in
cases of clear-cut, obvious sources it will be more ex-
peditious for the control agency to identify and specify
the required control measures. In contrast, in more com-
plex situations such as a major iron and steel facility, it
is anticipated that it will be more expeditious to require
the source to conduct property-line monitoring and be
responsible for the identification and implementation of
control measures on their own property so long as the
control measures required as a result of property line
monitoring are no less stringent than otherwise would be
required.
3. Control of Small Point Sources and Areawide Fuel Combustion
a. State and local agencies should reassess their point source
cutoff to ensure that a major percentage of their traditional
source inventory is receiving individual attention. Arbitrary
cutoff points of 25, 50, 100 tons/year are often used to
define point and area sources. Commonly, those cities that
have significantly reduced the emissions from major point
sources have used a high cutoff point. As the emissions have
been reduced, smaller sources are now of concern and should
be considered individually for modeling, compliance, and
enforcement purposes.
b. Regulations governing the allowable emissions from small
combustion units should be promulgated or, if already
promulgated, reviewed to_ reflect current fuel usage, fuel
availability, and control technology. Many jurisdictions
do not control small combustion units or allow emissions
higher than"necessary for a well-maintained unit.
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c. Small incinerators should be banned or should have permits
required to ensure proper control and burning under
favorable meteorological conditions.
Control of Nontraditional Sources
In contrast to the control of more conventional sources, which is primarily
a problem in industrialized areas, the management of particulates arising
from urban activity is likely to be required in essentially all urban areas
of any size. However, nontraditional sources are not such a well-defined
problem as to permit immediate and detailed control strategy planning.
Rather, no major national attack on such particulate sources is considered
appropriate for implementation until a variety of preparatory steps have
been taken. Consequently, the following recommendations concern prepara-
tion for, rather than actual implementation of, the control of urban
activity sources.
Control of Urban Activity Sources
a. EPA should develop appropriate methodologies for inven-
torying emissions from nontraditonal sources in urban
areas and support their proper utilization by state and
local agencies. To the extent possible these inventories
will take into account particle size and spatial and tem-
poral emission rates.
b. EPA should develop and provide to the states a diffusion
model which adequately takes into account particle size,
small scale diffusion, and the deposition characteristics
of the inventoried emissions. Both short-term (24-hour)
and long-term (annual) averaging models are needed which
allow for variations in parameters including precipita-
tion, ground cover, particulate loadings on roads (fluc-
tuating with street cleaning, precipitation, sanding opera-
tions), wind speed, etc.
c. EPA should develop and implement a major effort aimed at
providing, in 1 to 2 years' time, information on the costs
and effectiveness of control measures potentially appli-
cable to urban reentrainment. The effectiveness, and to
some extent the cost, should be considered in light of
the potential for public acceptance and ease of implemen-
tation. Cross-media environmental impacts should also be
addressed; e.g., street flushing for reentrainment control.
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EPA should develop and implement a public education
effort aimed at developing recognition, on the part
of appropriate bodies of public opinion and appropri-
ate government agencies, that such nontraditional
sources are of significance with respect to air quality
and are a legitimate subject of environmental concern.
Control of Large Scale Influences - Additional reductions in TSP levels
can be expected if precursors of secondary particulates are controlled,
not only within an urban area, but also "upwind" of cities. Other con-
tributions from "upwind" sources can arrive directly via transport. Plan-
ning measures to control these contributions require national direction
for implementation, but will result in a more equitable distribution of
the stringency of control measures.
1. Control of Secondary Particulates
a. EPA should continue efforts to develop and document the
mechanisms of formation and models for the prediction of
secondary particulate levels, especially sulfates and
organics, on both the meso- and macroscale. The effects
of precipitation on scavenging of precursors, stagnating
air conditions, insolation, thermal radiation, etc.,
should be adequately considered.
b. State and local agencies should take into account the
formation of secondary particulates in their formulation
of control strategies for TSP. The urban excess of
secondary particulates must be either consciously in-
cluded in the TSP level that is considered uncontroll-
able, thereby requiring further restrictions on tradi-
tional sources, or should be addressed through the con-
trol of the emission of precursor pollutants.
c. EPA should not permit the use of supplementary control
strategies or tall stacks to satisfy immediately local
air quality needs since the result may be to increase
levels of secondary particulates at sites remote from
the source. Because of the continental scale and vari-
ability of meteorology, it is not likely that such con-
trols techniques would be permitted anywhere in the
country. In fact, additional SOX controls may be needed
at some sites to help solve the TSP problem elsewhere.
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2. Transport and Primary Particulates
a. States should require air quality planning to be done
on as large a regional scale as is necessary to reach
into an area not impacted by transport. Where an auton-
OTDOUS local agency has control over only a small pare of
a problem area they should have their authority extended,
through a contract with the state, a regional compact, or
some other arrangement.
b. EPA should support research efforts directed at the better
understanding of short- and long-range transported particu-
lates. Long-range transport under specific meteorological
conditions that contribute to excessive TSP levels and
cause violations of the 24-hour standards could become
predictable so that appropriate measures could be taken.
Short-range transport needs better documentation and anal-
ysis so that the intercity contributions to high TSP levels,
leading primarily to violations of the annual standard,
can be considered for air quality planning. Comprehensive
inter-EPA regional planning may be necessary for TSP
control.
RECOMMENDATIONS CONCERNING AIR QUALITY MANAGEMENT PLANNING
The second broad area of recommendations concerns improving the states'
ability to accurately and quantitatively develop plans for the attainment
and subsequent maintenance of the ambient standards. As has been noted,
the general failure of the SIPs to attain the standards despite signifi-
cant emission reductions is in part due to inadequate data bases and, to
a less extent, to inadequate planning methodologies. This area is thus
very fruitful for action, particularly short-term EPA action.
1 . Development of Improved Data Bases
a. EPA should support data gathering efforts and computer-
ized systems by state/locals which are compatible with
NEDS and SAROAD~A number of major changes and expan-
sions in NEDS and SAROAD are currently underway, and it
is essential that these receive continued support. The
fundamental concept of a joint federal/state/local pol-
lution control system depends on consistent, accurate,
up-to-date bases readily available to all.
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b. EPA should provide a greatly expanded normrban ambient
TSP data base, either through their own monitoring ef-
forts or by encouraging and utilizing such monitors run
by the states.There is a need for a clear understand-
Ing of the variation in ambient levels as one moves from
remote nonurban areas through more proximate areas into
suburban areas, as well as a need for more detailed data
on the differences in levels between various portions of
the continent. Current networks need to be reviewed for
appropriateness, completeness, and possible local influ-
ences as discussed below.
c. EPA should conduct a study, based on existing nonurban
sites, concerning the effect of height and distance on
measured levels at such sites. Because of the long
history of many of these sites, dating back to the ear-
liest years of the NASN, they have apparently never been
studied carefully from a siting viewpoint, and in fact
many are apparently placed very close to the ground.
Since they must of necessity provide data to be extrap-
olated over scales of hundreds of miles, it should be well-
determined to what extent they reflect air masses on that
large scale, and to what extent very local impacts may be
important. The evaluation of the current network should
be conducted with the point of establishing consistently
sited monitors (height and neighborhood) and any changes
in the siting should be documented through concurrent
sampling for a period of time.
d. EPA should provide improved, more specific, network de-
sign and monitor siting guidelines for TSP monitoring
in urban areas. Although the study cities visited were
all major cities with active control programs and were
all meeting the minimum monitoring requirements, an un-
fortunate number of circumstances arose where the data
from these networks was inadequate to meet relatively
simple analysis needs. Emphases in the recommended ef-
fort should include the minimization of local effects
at sites, the development of inter-urban site standard-
ization, and the encouragement of increased monitoring
frequency for problem diagnosis purposes* The number
of sites required for an area should not be based on an
arbitrary formula but should be determined by the need
to understand the full complexities of the TSP problem.
2. Development of Improved Planning Tools
a. EPA should promote Increased use by state and local agen-
cies of special studies as planning tools. These studies
would be directed at providing analytical procedures and
control development tailored to the particular TSP
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situation and topographical, meteorological, industrial,
and social-economic characteristics of a region through
coordination with other environmental and regional plan-
ning efforts.
b. State and local agencies responsible for emission inven-
tory maintenance should reevaluate previous years' emis-
sion inventories to make them compatible with those in-
ventories currently being used. A basic understanding
of how the emissions situation has changed in the past
and the resulting impact on air quality provides the
soundest basis for future planning.
c. EPA should support the development of the microscale dis-
persion models that are required to adequately cope with
the potential need to control vehicular traffic in urban
settings as a TSP control measure. At the present, the
quantitative consideration of such matters is limited to
the type of empirical data analysis performed herein.
While essential for many purposes, this type of treat-
ment does not allow for the consideration of hypothetical
alternatives, as is necessary for control strategy
formulation.
d. EPA should develop both the conceptual framework and the
requisite computer software needed to utilize long-distance
air mass trajectory modeling as an air quality management
tool available to the stages. As increasing refinement of
control strategies is necessary, concern with background
transport, regional-scale secondary particulates, and
other large-scale considerations will become increasingly
important.
e. EPA should develop and promulgate at least informally guide-
lines for the use of particulate analysis by microscopy and
other analytical methods. The need to identify sources of
particulate matter will very likely result in an increase
in this work, and a mechanism is needed to assemble and make
available experience with the various approaches.
f. EPA should assess and provide information to states on hard-
ware available for and design of special field studies.
ISSUES CONCERNING NAAQS REVIEW
The nature of the control measures mentioned above with respect especially
to many of the "nontraditional" sources of particulates and large-scale
problems will significantly modify the nature of many pollution control
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programs. Implementation of some of the control measures will necessarily
extend the scope of control programs into areas of municipal services that
have not traditionally been involved in pollution control, and which will
necessarily be costly. Consequently, they will no doubt require extended
discussion and justification, not only in the eyes of public opinion,
elected officials, and municipal executives, but also in the eyes of many
personnel within the air pollution control community itself.
An important element in future planning concerns the actual standards them-
selves. The NAAQS are currently being reviewed by the National Academy of
Sciences for appropriateness and completeness. While the purpose of this
TSP attainment study did not involve addressing the need for standards re-
view or the ongoing review by the NAS, five specific issues became apparent
in the course of this study. These are listed below with the hope that they
will be considered in the review of the standards for TSP.
1. Particle Size - At present, the particulate standard is based
on the total mass of particulate matter suspended in the air;
there is no concern with particle size, save that the particles
be small enough to remain suspended. (Or actually, just to re-
main suspended long enough to reach the hi-vol, the proximity of
which thus becomes crucial.) Because the health effects of par-
ticles of various sizes differ significantly, and because the
size distribution of particles from various source types differs
significantly, any standard, whether an emission standard or es-
pecially an ambient air standard, that fails to recognize such
differences is unavoidably seen as oversimplified.
2. Particle Toxicity - Differential toxicity among particles of
various chemical nature is an issue very like that of particle
size. Known, obvious differences, such as the distinction be-
tween inorganic soil materials and organic coal tar derivatives,
are not Included in the basis for the present ambient standard,
except implicitly through the selection of epidemiological
evidence to support the standard. This unavoidably contributes
to the general impression that the standard is oversimplified
in letting important factors "average out." The composition of
the total particulates is already coming under review due to
recent concerns about toxic pollutants.
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Monitoring Specifications - At present, neither the NAAQS them-
selves nor the specified Federal Reference Method address the
question of how hi-vol monitors should be placed relative to
the sources of the particulate matter. While "common sense"
has probably been adequate in distinguishing between ambient
and source-oriented situations in the case of major point
sources, it is clearly not so in the case of such low-level
dispersed sources as street dust reentrainment. In order to
be seen as appropriately precise in this area, the standards
should at least take note of the effects of height and distance
from a source such as a street by specifying a reference point
where the standard applies and defining relationships by which
data from other points could be adjusted.
Time Scale of Standards - At present, the necessary recognition
of differing averaging times is handled by having standards for
both short-term and long-term (annual) averages, and this is
generally considered adequate. However, there are some phenom-
ena that operate on a longer-time period and tend to indicate
a desirability in considering longer-term values as well, such
as perhaps 5-year running averages. Such an approach would
offer one way of resolving the difficulties in handling such
features as meteorologically good and bad years in air quality
planning. It would also help in rationalizing the situation
caused by several-year temporary phenomena, such as major con-
struction, which presently are viewed as anomalies, causing
standards' violations that can be ignored because they are
temporary.
Spatial Averaging - Similar to the problem of monitoring speci-
fications is the concern over the Clean Air Act requirement
that each and every area of a city meet the air quality
standards. It can generally be assumed that every city has at
least one corner which can not meet the standards even though
the current monitoring network indicates no violations. In the
same manner, monitors may be placed so as to ignore the problem.
Average TSP levels within a certain area up to a set height may
be more appropriate.
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