i
EPA-450/2-76-013
August 1976
GUIDELINE SERIES
OAQPS NO. 1-2-044
GUIDELINE FOR PUBLIC REPORTING OF DAILY
AIR QUALITY—POLLUTANT STANDARDS INDEX (PSI)
US. ENVIRONMENTAL PROTECTION AGENCY
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina
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This report is issued by the Environmental Protection Agency to report
technical data of interest to a limited number of readers. Copies are
available free of charge to Federal employees, current contractors and
grantees, and nonprofit organizations - in limited quantities - from the
Library Services Office (MD35) , Research Triangle Park, North Carolina
27711; or, for a fee, from the National Technical Information Service,
5285 Port Royal Road, Springfield, Virginia 22161.
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EPA-450/2-76-013
GUIDELINE FOR PUBLIC REPORTING OF DAILY
AIR QUALITY-POLLUTANT STANDARDS INDEX (PSI)
OAQPS Number 1.2-044
August 1976
Prepared by
EPA Working Group to Develop an Air Quality Index
Contributing Agencies
U.S. Environmental Protection Agency
Office of Research and Development
Office of Air and Waste Management
Office of Planning and Management
National Oceanic and Atmospheric Administration
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PREFACE
The U. S. Environmental Protection Agency's recommended "Pollutant
Standards Index" (PSI) is the result of a joint effort on the part of
EPA's Offices of Research and Development, Air and Waste Management, and
Planning and Management. The guideline was prepared by the EPA Working
Group to Develop an Air Quality Index in response to a request from the
Federal Interagency Task Force on Air Quality Indicators of which EPA is
a member. The Federal Task Force, chaired by the Council on Environmental
Quality, \ as cresced as a result of a joint EPA/CEQ report which pointed
out existing problems resulting from the present diversity of indices used
in the Unitec States and Canada.
This guideline suggests the use of the Pollutant Standards Index
(PSI) for those local and state air pollution control agencies wishing to
report an air quality index on a daily basis. The PSI places maximum
emphasis on protecting the public health; that is, it advises the public
of any possible adverse health effects due to pollution. In order to err
on the side of public safety, the index stresses reporting on the basis
of the stations with the highest pollutant concentrations and assumes that
other unsampled portions of the community will also t.xperience high con-
centrations. In addition, its emphasis is upon acute health effects
occurring over very short time periods (24 hours or less) rather than
chronic effects occurring over months or years. It is not intended for,
and should not be used for, ranking urban areas in terms of the severity
of their air pollution problems. Such rankings require the use of many
other kinds of environmental data not incorporated in this index.
Finally, Appendix A discusses the meteorological information needs
of forecasting relative index changes. This was prepared by personnel
from the National Oceanic and Atmospheric Administration.
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TABLE OF CONTENTS
Page
PREFACE ii
1. EXECUTIVE SUMMARY 1
2. INTRODUCTION 3
3. THE EPA RECOMMENDED DAILY INDICATOR—POLLUTANT STANDARDS
INDEX (PSI) 4
3.1 Number of Pollutants 5
3.2 Calculation Method 5
3.3 Descriptor Categories 8
4. REPORTING PROCEDURES 16
4.1 Reporting the Index 17
4.2 Reporting the Federal Episode Criteria 17
4.3 Forecasting the Index 17
4.4 Flexible Media Reporting 18
5. MONITORING REQUIREMENTS 20
5.1 Need for Monitoring Uniformity 20
5.2 Network Considerations 20
5.3 Measurement Practices and Reporting Frequencies 21
5.3.1 Use of Federal Reference Methods 21
5.3.2 Carbon Monoxide, Nitrogen Dioxide, and Ozone 21
5.3.3 Sulfur Dioxide 21
5.3.4 Total Suspended Particulate 22
5.3.4.1 Staggered high-volume sampler measurements 22
5.3.4.2 Alternative measurements 23
5.3.5 Frequency of Reporting and Appropriate 23
Averaging Times
6. REFERENCES 24
7. APPENDIX A A_I
iii
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1. EXECUTIVE SUMMARY
This guideline suggests the use of the Pollutant Standards Index
(PSI) for those local and state air pollution control agencies wishing to
report an air quality index on a daily basis. The
document also includes appropriate monitoring and reporting guidance. Tha
guideline is the result of an earlier study showing that of all the air
quality indices in use today, no two are exactly the same. A potentially
serious problem of public confusion can occur in regions where neighboring
states and cities use different indices. The PSI also responds to the
request of several state and local agencies that the U. S. Environmental
Protection Agency provide them with a recommended uniform air quality index.
The recommended index incorporates five pollutants—carbon monoxide,
sulfur dioxide, total suspended particulate, photochemical oxidants, and
nitrogen dioxide—for which there are short-term (24 hours or less) health-
related National Ambient Air Quality Standards (NAAQS), and/or Federal Episode
Criteria, " and Significant Harm Levels. ' ' A sixth variable—the product of
total suspended particulate and sulfur dioxide—is computed and is included in
the index equation. This variable and also nitrogen dioxide are treated
differently than the other pollutants because they have no short-term
NAAQS. Therefore, they are reported when they exceed the Federal Episode
Criteria and Significant Harm Levels. Because of the basic design of the
index, any further pollutant requiring NAAQS, Federal Episode Criteria, and
Significant Harm Levels can be readily added.
The index uses a "segmented linear function"* to convert each air
pollutant concentration into a normalized number. The NAAQS for each
pollutant corresponds to PSI=100, and the Significant Harm Level corresponds
to PSI=500.
At a minimum, PSI reports the pollutant with the highest index value
of all the pollutants being monitored, a dimensionless number, and a
descriptor word. On days when two or more pollutants violate their
*
A segmented linear function consists of two or more straight lines,
drawn between successive coordinates ("breakpoints") where each line may
have a different slope.
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respective NAAQS, each of the pollutants should be reported. Five
descriptor words have been chosen to characterize daily air quality: "good,"
"moderate," "unhealthful," "very unhealthful," and "hazardous." In
addition, for each descriptor word, generalized health effects and cautionary
statements are provided for use when the air is characterized as "unhealthful"
or worse.
For large metropolitan areas comprised of many smaller cities and
suburbs where significant air quality differences may exist, the air
pollution control agency may wish to report separate index values for
each community. This has the advantage of showing the public how air
pollution varies over the larger metropolitan area. The pollutants would
be monitored at population-oriented locations where the maximum concen-
tration for the particular pollutant is expected to occur, and the public
within each community would be made aware of the worst air quality to
which it is exposed.
Further guidance is given on the measurements practices and monitor
siting considerations (Section 5).
PSI should not be used to rank cities. An evaluation of PSI in
7 8
eight cities ' illustrated the difficulties of attempting to compare air
quality levels in different cities using this or any other index. PSI is
designed for the daily reporting of air quality to advise the public of
potentially acute, but not chronic health effects. To properly rank the
air pollution problems in different cities, one should rely not just on
air quality data, but should include all data on population characteristics,
daily population mobility, transportation patterns, industrial composition,
emission inventories, meteorological factors, and the spatial represen-
tativeness of air monitoring sites. A correct ranking should also consider
the number of people actually exposed to various concentrations, as well
as the frequency and duration of their exposure.
Adoption of PSI should reduce the confusion due to the existence of
many indices. PSI has several advantages: (1) it is simple and can be
easily understood by the public, (2) it can accommodate new pollutants,
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(3) it is based on a reasonable scientific premise, (4) it relates to
NAAQS, Federal Episode Criteria, and Significant Harm Levels, (5) it
exhibits day-to-day variations, and (6) a qualitative trend in the index
can be forecast for periods up to a day in advance, especially during
episodic conditions.
2. INTRODUCTION
A major area of concern in the field of air pollution control is how
to best report daily air quality to the public. A recent CEQ/EPA Report
indicates that of the 55 largest U. S. metropolitan air pollution control
agencies, 33 use an air pollution index. In addition, five states and
two Canadian Provinces operate state-wide (or Province-wide) index systems.
With two minor exceptions, no two indices were found to be exactly the same.
The public confusion generated by the use of so many indices is particularly
evident in bordering states using different indices. Therefore, there is
a need to develop a uniform index to report the daily status of air
pollution.
Q
A recent paper emphasizes the need for a truly meaningful index to
have a sound scientific basis. The paper suggests that such an index
be based on the relationship between pollutant concentration and adverse
health (welfare) effects—that is, a "damage function." Unfortunately, it is
an extremely complex undertaking to relate measured air pollutant concen-
trations to the many diverse effects of air pollution—for example, aggra-
vation of disease in susceptible people, increased incidence of respiratory
illness in healthy persons, impairment of human motor function, reduced
visibility, corrosion of materials, and soiling of buildings. Arriving
at an air quality standard for a given pollutant—which is just one point
in a damage function—has required vast quantities of data, medical
advisory committees, detailed epidemiological studies, and other extensive
research. The air quality criteria documents published for the major air
pollutants ~ reflect the complexity of the process.
9
The recent paper also emphasizes the importance of an index
accounting for the adverse effects associated with combinations of
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pollutants — that is, synergism. For example, the criteria document on
sulfur oxides states that adverse health effects attributable to sulfur
oxides are intensified in the presence of particulate matter. Under-
standing synergistic effects adds greatly to the problem of obtaining a
truly meaningful air quality index. These problems stress the need for
additional research to develop pollutant-related damage functions that
take into account synergistic effects on health and welfare.
As an interim solution to these problems, this guideline recommends
a uniform index to report daily air quality, along with appropriate
monitoring guidance, This index will serve until a more meaningful air
quality index can be created. If adopted, a uniform index should end the
confusion associated with the use of many.varied indices.
3. THE EPA RECOMMENDED DAILY INDICATOR—POLLUTANT STANDARDS INDEX (PSI)
The Pollutant Standards Index (PSI or ijj) is the result of a joint
effort by EPA's Offices of: Research and Development, Air and Waste
Management, and Planning and Management. Its evolution has included
formulation of several candidate index structures, ' and the index
has undergone an extensive review process involving state and local
air pollution control agencies, public organizations, and media repre-
sentatives.
The recent CEQ/EPA compendium of air pollution indices developed an
"index classification system" to analyze and compare the various indices
used by state, Provincial, and local agencies. Indices were categorized
according to four criteria: (1) number of pollutant variables measured,
(2) calculation method used to compute the index, (3) descriptor categories
reported with the index, and (4) method of reporting (whether it is
"combined," "maximum," or "individual").
The report found that the greatest number of the indices in use
incorporate five of the six National Ambient Air Quality Standard (MAAQS)
pollutants (hydrocarbons are excluded because there are no direct health
effects associated with the pollutant. It is controlled because it is a
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precursor to the formation of photochemical oxidants.); (2) use a
segmented linear function*; (3) are based on the maximum of one of the
pollutant variables; and (4) use three to five descriptor categories.
In the following sections, the structure of PSI is presented accord-
ing to the "index classification system" categories.
3.1 Number of Pollutants
PSI includes five pollutants: carbon monoxide (CO), sulfur dioxide
(502)> total suspended particulate matter (TSP), photochemical oxidant (00
and nitrogen dioxide (N02). Primary (that is, health related) NAAQS, and/or
Federal Episode Criteria, and Significant Harm Levels exist for all five.
In addition, one pollutant product TSPxSCL is included because it has
34
both Federal Episode Criteria and a Significant Harm Level. ' As with
NOp. which has no short-term primary NAAQS, the product is reported when
the Federal Episode or Significant Harm Levels are exceeded. Finally,
because of the structure of the index, any pollutant identified in the
future for which NAAQS, Federal Episode Criteria, and Significant Harm
Levels are adopted can be added without modifying the basic form of the
index.
3.2 Calcjlation Method
A segmented linear function is used relating actual air pollution
concentrations to a normalized number. For example, PSI (t|0 equals 100
when the NAAQS for each pollutant is reached, while t> equals 500 when the
Significant Harm Level for each pollutant is reached. The normalized
number should be easier for the general public to understand because it
does not require one to know specific NAAQS concentrations or the many
different Federal Epsiode and Significant Harm Levels.
The index breakpoints are listed in metric units (Table 1) and in
parts per million (Table 2). The first breakpoint separates the descriptor
*
A segmented linear function consists of two or more straignt lines,
drawn between successive coordinates ("breakpoints") where each line may
have a different slope.
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categories "good" and "moderate." For CO and 03, the first breakpoint was
chosen at 50 percent of the primary NAAQSs. In the case of TSP and S02,
concentrations equal to their respective primary annual NAAQS were chosen
because the frequent occurrence of values greater than these concentrations
could lead to violations of their respective annual NAAQS. In an area where
a violation of either the annual primary TSP or S02 standard occurs, approxi-
mately 50 percent or more of the days will thus be classified as "moderate"
or worse. This approach minimizes the potential for public confusion which
might arise from a preponderance of days reported as "good," followed by
the report that the annual health-related standard has been violated.
The breakpoints between the primary NAAQS and Significant Harm
Levels are somewhat arbitrarily set at the Federal Episode Alert, Warning,
and Emergency Levels, except for oxidants. In the case of oxidant, 400 yg/m3
was used as the PSI breakpoint for the descriptor words "unhealthful"
and "very unhealthful" because it appears to be more consistent with the
descriptor words than the suggested administrative Alert level of 200 yg/m3.*
Figures 1 through 5 show the segmented linear function for each of the
NAAQS pollutants, and Figure 6 showsthe function for the product of TSP and
SOn. If NAAQS for new pollutants are adopted in the future, they can be
accommodated by drawing a new segmented linear function.
3.3 Descriptor Categories
PSI is primarily a health related index as shown by the descriptor
words: "good," "moderate," "unhealthful," "very unhealthful," and "hazardous,"
(Table 3). The breakpoints used to separate these descriptor words are
somewhat arbitrary. On the basis of health effects data above, it is not
possible to establish a sharp demarcation between any two descriptor words.
However, when the five pollutantswere examined in the context of severity
of health effects, their NAAQS and EPA suggested administrative Alert,
Warning, and Emergency levels tended to provide convenient breakpoints,
except for the oxidant Alert level, which was replaced with 400 yg/m3, as
discussed earlier.
*Several air pollution control agencies are using 400 yg/m3
instead of 200 yg/m3 as their Alert level with concurrence by the Environmental
Protection Agency.
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50% PRIMARY NAAQS
10 20 30 40 50
CARBON MONOXIDE (8-hour RUNNING AVERAGE), mg/m3
Figure 1. PSI function for carbon monoxide
60
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500
400
300
200
100
EMERGENCY^
LEVEL 11875
WARNING
LEVEL
ALERT
LEVEL*375
260JfPRIMARY
NAAQS
— 75 •ANNUAL PRIMARY
NAAQS
0 200 400 600 800 1000
SUSPENDED PARTICULATE MATTER (24-hour RUNNING AVERAGE, A/g/m3
Figure 2. PSI function for suspended particulate matter
1200
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500
400
§300
200
100
0
ALERT LEVEL
365
80
WARNING LEVELi
EMERGENCY,
LEVEL
ANNUAL PRIMARY NAAQS
0 500 1000 1500 2000 2500
SULFUR DIOXIDE (24-hour RUNNING AVERAGE), M9/m3
Figure 3. PSI function for sulfur dioxide
3000
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EMERGENCY
LEVEL 41000
160JTPRIMARY
NAAQS
200
400 600 800
OZONE (1-hour AVERAGE), M9/m3
1000
1200
Figure 4. PSI function for photochemical ozone
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14
500
400
EMERGENCY
LEVEL
'3000
r 300
GO
O.
WARNING
LEVEL *2260
200
ALERT,
LEVEL W1130
100
0 1000 2000 3000 4000
NITROGEN DIOXIDE (1-hour AVERAGE),
Figure 5. PSI function for nitrogen dioxide,
5000
6000
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15
500
0 100 200 300 400 500
TOTAL SUSPENDED PARTICULATE X S02 (24-hour-AVERAGE MEASUREMENT), 103
Figure 6. PSI function for product of total suspended particulate and sulfur dioxide
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16
Air pollution levels between the short-term primary NAAQS and the Alert
level for TSP, S02, and CO and 400 pg/m3 for 03 are deemed "unhealthful,"
because mild aggravation of respiratory symptoms in susceptible persons and
irritation symptoms in the healthy population occur at some point above the
short-term primary NAAQS and at and below the Alert levels for TSP, SO^, and
CO and 400 yg/m3 for 0,. ~ N09 is not reported until concentrations exceed
14
the Alert level because no short-term NAAQS has been established. Air
pollution concentrations above the Alert level but below the Warning level
are classified as "very unhealthful," while concentrations above the Warning
level are "hazardous."
These classifications are related to generalized health effects and
appropriate cautionary statements (Table 3). A single set of generalized
health effects and cautionary statements is indicated for the descriptor
words "unhealthful" and "very unhealthful." The "hazardous" category has
two sets of generalized health effects and cautionary statements. The
first set is reported when the index exceeds 300 and the second when the
index exceeds 400 indicating the increasing severity of the air pollution
levels.
In the case of T-SP and S02> short-term secondary air quality standards
also exist below their primary NAAQS. Secondary standards are designed to
protect against the adverse effects of pollution on the public welfare (animals
vegetation, materials, visibility, etc.). According to PSI, if their short-
term secondary NAAQSs are violated, the concentrations would be classified as
"moderate" or worse. While this descriptor word is valid from a health view-
point, the air quality is unsatisfactory from the standpoint of welfare
effects. Because PSI is a health-related index, the user may wish to report
on the possible welfare effects when either the short-term TSP or S02 NAAQS
is violated.
4. REPORTING PROCEDURES
PSI has been designed to be as flexible as possible in allowing air
pollution control agencies to decide for themselves the information to
include in their reports to the various media. This section examines the
recommended method of reporting the index, the reporting of the Federal
Episode Criteria, and the concept of flexible media reporting.
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17
4.1 Reporting the Index
Since each pollutant is examined separately by comparing its measured
concentration with the NAAQS, the Episode Levels, and the Significant Harm
Level, each pollutant can be reported separately. At the minimum, the
pollutant with the highest index value should be reported to advise the
public of the worst air pollution to which it is exposed. On days when
two or more pollutants violate their respective NAAQS--that is, have
PSI values greater than 100--then each of the pollutants should be reported.
The index values of the other pollutants may also be reported for complete-
ness. When the air pollution level is reported as "unhealthful," "very
unhealthful," or "hazardous," cautionary statements should also be used.
In addition, the generalized health effects can be used.
Users of PSI may wish to report on the health effects of each pollu-
tant individually, thereby providing more detailed language on each
pollutant than is available in Table 3. In preparing such information for
the public, the user is encouraged to seek appropriate medical advice
and to consult the literature.
4.2 Reporting the Federal Episode Criteria
When the Federal Episode Levels for each pollutant are exceeded, the
user should report the administrative actions associated with the Alert,
Warning, or Emergency Levels. The issuance of administrative actions
depends, of course, upon the forecast of meteorological conditions affecting
future pollution levels.
Issuance of administrative actions also apply to the product of TSP
and S0?, which has both Federal Episode Criteria and Significant Harm
2 3
Levels. ' Although available health effects information has not been
codified to tie the descriptor words to the product of TSP and SC^ the
product is included for purposes of administrative completeness.
4.3. Forecasting the Index
The forecasting of a quantitative index for periods up to a day in advancs
would be difficult without extensive meteorological data and specialized exper-
tise that some air pollution control agencies may not possess. However,
qualitative index forecasting is practicable using the National Weather
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18
Service's Air Pollution Weather Forecast Program, ' With this weather
information, along with available emissions and air quality trend data,
agencies can develop techniques or procedures to forecast the relative
change in the index by using the following word descriptors: No signifi-
ca_n_t_ _c_hancje_, decrease, or increase. The principal responsibility for
obtaining the necessary emission and air quality information lies with
the air pollution control agency using the index. The air pollution con-
trol agency would integrate the meteorological information and apply the
predictive methods to generate the forecast. The information needs for
forecasting relative index changes is discussed further in Appendix A.
4.4 Fiexj_b_l_e_ Media Reporting
The index has been designed to be as flexible as possible in reporting
the status of air quality to the public. Either short or long reports can
be used. For television, the report could read, "Today the air pollution
index is 50, the air quality is good." However, when the air pollution
becomes unhealthful, then several possible reports could be considered
for television, the news media, or telephone recordings. For example,
when oxidant pollution reaches a concentration of 280 yg/m3 (0.14 ppm), the
report could take several different forms.
(1) Today, the air pollution index is 150. The air is "unhealthful."
The pollutant 0, is responsible.
^
(2) An air pollution alert has (or has not) been called based on
the forecast for the remainder of the day (and/or) tomorrow.
(3) Repeat the above and add the following cautionary statements:
"Persons with existing heart or respiratory ailments should reduce physical
exertion and outdoor activity."
(4) The report could include everything said in (1), (2), and (3) and
then add that "unhealthful" air can cause "mild aggravation of symptoms
in susceptible persons, with irritation symptoms in the healthy population."
(5) Finally, the report could conclude with the forecast of tomorrow's
air pollution level, such as "no change in the air pollution level is
expected."
Table 3 should be referred to in preparing the air pollution status
report to the public. Figures 7 and 8 illustrate the above ozone example
-------
19
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by showing possible reports for the television and newspaper, respectively.
Both figures provide essential information, indicating the PSI value, the
critical pollutant, the health implications for the public, and the next
day's forecast. Each of the descriptor categories has been given equal
weight. The information is displayed so that it can be presented as
rapidly as possible in an easy-to-understand format.
5. MONITORING REQUIREMENTS
5.1 Need for Monitoring Uniformity
In order for PSI to be readily accepted, the data used in calculating
the index must be comparable from site to site within a region. Since
these data are to be obtained at existing air monitoring sites, certain
easily implementable practices can eliminate considerable variability in
the data. Among these are using: (1) uniformity of site types—that is,
residential, commercial, etc.; (2) Federal Reference Methods or their
equivalent; (3) standardizing sampling height and probe exposure; and (4)
good housekeeping and quality control procedures to provide high quality
data.
5.2 Network Considerations
Air pollution control agencies need not undertake additional monitoring
requirements in the implementation of PSI, but can simply select sites
from their existing network. The sites selected, however, should generally
meet two basic criteria: (1) sites should be representative of population
exposure—that is, not unduly influenced by a single emission point or
background-oriented, and (2) sites should be located in areas of maximum
concentration for the pollutant of interest, but should not be unduly in-
fluenced by any single source. Areas suitable for monitoring, by pollutant are
• TSP - populated areas substantially downwind of large sources or in
the midst of numerous area sources.
• S02 - populated areas substantially downwind of large sources or in
the midst of numerous area sources.
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21
• CO - densely populated, high-traffic volume areas, including areas
in the center city.
• 0^ - populated areas substantially downwind of areas of maximum
hydrocarbon emissions density, such as the central business district.
The site should be 100 meters or more removed from major traffic
arteries or parking lots.
• N02 - populated areas downwind of areas of high traffic density.
If a pollutant(s) is (are) measured at several locations within a
metropolitan area, it would be desirable (if possible) to base the index on
the site showing the highest reading on a given day. This would mean that
different sites would be used on different days.
For large metropolitan areas comprised of many smaller cities and
suburbs where significant air quality differences may exist, the air
pollution control agency may wish to report separate index values for
each community. This has the additional advantages of showing the public
how air pollution varies over the larger metropolitan area. Furthermore, for
example, the photochemical pollutants tend to be higher in the suburban fringe.
5.3 Measurement Practices and Reporting Frequencies
5.3.1. Use of Federal Reference Methods
Since PSI is based on the NAAQS, the Federal Reference Methods (FRM) or
equivalent should be used where possible. Such methods are consistent with
the averaging time of the primary standards. Further, continuous methods
should be used, where possible, to facilitate the reporting of the index
numbers two or three times per day.
5.3.2 Carbon Monoxide, Nitrogen Dioxide, and Ozone
The FRM for CO is based on the nondispersive infrared measurement
principle. The proposed method for N02 and the existing method for 0^
employ the chemiluminescence measurement principle and give continuous
data. A FRM or equivalent method for CO, N09, and Oo must also meet
20
performance specifications set forth in the Federal Register.
5.3.3 Sulfur Dioxide
The FRM for S02 is the pararosaniline 24-hour bubbler method. The
solution may be analyzed automatically or manually at the central labora-
tory. Serious logistics problems can arise if an index number must be
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22
calculated from multiple sites two or three times per day. Fortunately,
there are procedures for designating continuous S09 analyzers as equivalent
20
to the FRM, and from these 24-hour running averages are easily obtained.
Therefore, the use of the continuous S0? analyzer is recommended to
collect the data used in the index. If one is not available, then a
pararosaniline 24-hour bubbler method can be used if several precautions
are taken. To prevent deterioration in the sample, the sample should be
collected at ambient temperature or no warmer than 15°C if ambient tempera-
tures are below freezing. The sample should then be analyzed as soon as
possible, with no later than a six-hour de-lay from end of sampling to
analysis.
5.3.4 Total Suspended Participate
The FRM for TSP uses a high-volume sampler and specifies a midnight-
to-midnight 24-hour sample followed by a 24-hour equilibration at a
relative humidity less than 50 percent. This leads to a two-day delay
in the reported value. For index reporting, the simplest modification to
the FRM is to make the sampling time more convenient—that is, 8 a.m.-to-
8 a.m. or noon-to-noon, etc. The sample could be weighed immediately to
provide a TSP value for the index. Later a true value could be calculated
after the recommended equilibration time of 24 hours. A study in EPA
Region IV has shown that the true TSP values are usually within 10
percent of the values measured immediately after collection.21 The true
value would be recorded as the correct one, reported to the National Aero-
metric Data Bank, and used to calculate annual averages and maxima.
5.3.4.1 Staggered high-volume sampler measurements
During episode conditions, the air pollution control agency may
find it necessary to inform the public of existing conditions two or three
times per day. Therefore, several high-volume samplers could run for
24 hour periods staggered every 4 to 6 hours throughout the episode.
The sample could be weighed immediately, and that weight used in
deciding what action should be taken concerning the possible
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23
emergency. Then the filter would be equilibrated for 24 hours and
reweighed.
5.3.4.2 Alternative measurements
The paper tape sampler and the integrating nephelometer can be used
to indicate the need for overlapping high-volume sampler measurements.
The paper tape sampler has been used in most previous indices and has both
Federal Episode Criteria and a Significant Harm Level. The Coefficient
of Haze (COH) value from the paper tape sampler, however, is poorly
correlated with TSP levels. In addition, the paper taoe sampler has not
been determined to be an "equivalent method" to the FRM. Therefore, its
use should be limited to index reporting and must not be used to determine
compliance with the NAAQS for particulate matter.
A newer instrument relatively untested in routine field applications
is the integrating nephelometer. It measures the scattering of light
from small particles and correlates well with visibility and TSP measure-
ments. Both the paper tape sampler and the nephelometer can produce a
running 24-hour value which can be used as a qualitative indicator of TSP
loadings in the atmosphere.
5.3.5 Frequency of Reporting and Appropriate Averaging Times
The frequency of reporting is left up to the agency, within these
suggested ranges. It may be desirable to report the index once a day
but probably not more than three times per day. Because the high-volume
sampler has a 24-hour averaging period, agencies might consider operating
two or more high-volume samplers at the same station but with off-set
time periods, ending between 8 a.m. and 6 p.m. to provide reporting infor-
mation during the most desirable period.
If the agency desires, the paper tape sampler or integrating nephelo-
meter could be used in conjunction with the high-volume sampler to provide
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24
estimates of the most recent ambient participate loading. Thus used, the
paper tape sampler provides some guidance on whether or not to undertake
more intensive measurements during high air pollution levels.
Appropriate averaging times for which the index should be tabulated
and reported for each pollutant are:
• TSP - TSP values taken with the high-volume sampler are discrete
24-hour values. Monitoring and data collection should be on a
schedule consistent with the agency's need to report the air quality
index. Other overlapping times may be employed by those agencies
wishing to report more than one index value per day.
• S02 - The suggested reporting value is the most current 24-hour
running average since the last reporting period.
• CO - Although there are two standards for CO (8 hours and 1 hour),
the 8-hour standard is usually considered the limiting one and will
be the one violated in the vast majority of cases. The most
current 8-hour running average since the last reporting should be
used. In addition, the agency could also report the index value
associated with the highest 8-hour average during the reporting
period.
• Oo - The suggested reporting value for 0, is the highest hourly
value since the last reporting period. The reporting periods are
usually 24 hours or shorter.
• N02 - Although the standard for NOp is an annual one, there are
hourly values associated with episode criteria; therefore, using
the highest hourly value since the last reporting period is recom-
mended.
6. REFERENCES
1. Thorn, Gary, and Wayne R. Ott. Compendium Analysis, and Review of
United States and Canadian Air Pollution Indices, joint study by the
U. S. Environmental Protection Agency and the Council on Environmental
Quality, December 1975.
2. Federal Register, Vol. 36, April 30, 1971, pp. 8186-8201.
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25
3. Federal Register, Vol. 36, November 25, 1971, pp. 22390-22414.
4. Federal Register, Vol. 36, December 17, 1971, p. 24002.
5. Federal Register, Vol. 36, March 13, 1974, p. 9672.
6. Federal Register, Vol. 40, August 20, 1975, pp. 36330-36333.
7. Ott, Wayne R. and William F. Hunt., Jr. "A Quantitative Evaluation
of the Daily Air Pollution Index Proposed by the U. S. Environmental
Protection Agency." Presented at the 69th Annual Meeting of the Air
Pollution Control Association, Portland, Oregon, June 1976.
8. Hunt, William F., Jr., and Wayne R. Ott. Pollutant Standards Index
(PSI) Evaluation Study, Joint Office of Air and Waste Management and
Research and Development Report, U. S. Environmental Protection Agency,
April 1976.
9. Hunt, William F., Jr., William M. Cox, Wayne R. Ott, and Gary Thorn.
A Common Air Quality Reporting Format, Precursor to an Air Quality
Index, presented at the Fifth Annual Environmental Engineering and
Science Conference, Louisville, Kentucky, March 3-4, 1975.
10. Air Quality Criteria for Particulate Matter, USDHEW, PHS, CPEHS,
NAPCA, Washington, D.C., January 1969, No. AP-49.
11. Air Quality Criteria for Sulfur Oxides, USDHEW, PHS, CPEHS, NAPCA,
Washington, D.C., January 1969, No. AP-50.
12. Air Quality Criteria for Carbon Monoxide, USDHEW, PHS, CPEHS,
Washington, D.C., March 1970, No. AP-62.
13. Air Quality Criteria for Photochemical Oxidants, USDHEW, PHS, CPEHS,
Washington, D.C., March 1970, No. AP-63.
14. Air Quality Criteria for Nitrogen Dioxide, EPA, APCO, Washington,
D.C., January 1971, No. AP-84.
15. Thorn, G.C. and W.R. Ott, Atmospheric Environment, K3, 261(1976).
16. Thorn, G.C., W.R. Ott, W.F. Hunt, and J.B. Moran. "A Recommended
Standard Air Pollution Index," presented at 171st National Meeting
of the American Chemical Society, New York, N.Y., April 1976.
17. Knelson, John H., U. S. Environmental Protection Agency, memorandum
to Raymond Smith, U. S. Environmental Protection Agency, December 15,
1975.
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26
18. National Weather Service, Operations Manual, Air Pollution Weather
Forecasts, WSOM Issuance 75-13, Part C, Chapter 30, April 1975.
19. National Weather Service, Technical Procedures Bulletin No. 122: Air
Stagnation Guidance for Facsimile and Teletype (3rd Edition),
October 21, 1974. (Supersedes previous TPB's Nos. 52, 58, and 69).
20. Federal Register, Vol. 40, February 18, 1975, pp. 7049-7070.
21. Helms, G.F. U. S. Environmental Protection Agency, Region IV,
Atlanta, Georgia. Personal communication, December 1975.
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APPENDIX A
INFORMATION NEEDS FOR FORECASTING PSI
INTRODUCTION
The information needed to qualitatively forecast the
Pollutant Standards Index (PSI) is of two types: (1) pollutant-
related and (2) meteorological. The pollutant-related
information may include data on source locations, physical
source characteristics and emissions, •atmospheric-physio-
chemical transformation processes, and actual air quality
measurements and trends. Meteorological information that may be
included are data on synoptic weather features, on meteorological
parameters indicative of the dispersive capability of the
lower atmosphere, and of the photochemical potential. It
might also include information on the effect of local
terrain complexities upon meteorological parameters.
Together, pollutant-related and meteorological information
form the input to locally tailored predictive techniques
such as mathematical models, statistically derived methods,
or other techniques that may be applied along with subjective
judgment to some degree.
The necessary pollutant-related information is to be
obtained by the air pollution control (APC) agency having
local responsibility for issuing the Index. The National
Weather Service (NWS) is the primary agency supplying the
needs of APC agencies for meteorological information. NWS ser-
vices include issuance of advisories on air pollution
potential and air stagnations. However, some APC agencies
and/or their consultants may also collect and interpret
meteorological information to supplement that available
from the NWS.
GENERAL DATA NEEDS
The types and amounts of pollutant-related information
needed will vary depending on the particular pollutant (s)
of concern and the source to monitoring site configurations
in the particular geographical area. For example, in the
Los Angeles Basin, photochemical oxidant is the primary
pollutant of concern and since precursor sources (mainly
mobile) are widespread, the potential for maximum impact
exists over a rather large area. In contrast, in Pittsburgh
and Birmingham where suspended particulate matter from
-------
industrial ferrous emissions will most likely cause elevated
pollutant levels, the maximum impact will probably be more
localized; thus, pollutant-related information may not
have to be as extensive. It is also important to know the
diurnal, weekly, and seasonal characteristics of emissions.
For instance, carbon monoxide concentrations are closely
associated both spatially and temporally with automobile
emissions. Typical diurnal patterns reflect morning and
evening peaks in vehicular traffic. High concentrations may
shift weekly in response to changes in workday versus weekend
automotive travel patterns. Seasonal patterns may shift
in some areas with vacation travel.
Generally, an up-to-date emissions inventory should be
available for communities where PSI is to be utilized in
order to adequately assess the source to monitoring site
impact relationships. For point sources (usually > 100 tons/
year of a pollutant) information should include the source
location, pollutants emitted, emission rates, and stack
parameters. Area source data, including lesser point
emissions, are not normally as specific. Available area
emissions, in tons per year, are usually quantified by city
or county. Vehicular emissions may be estimated by com-
bining local traffic pattern information with documented
vehicle-fleet emissions rates. These emissions data are
available from the EPA National Emissions Data System
(NEDS), state planning agencies, and private sources. It
may be necessary to supplement these data with emissions
information affecting the various temporal cycles; for
instance, information on the normal operating schedules of
large point sources and on traffic volume cycles in con-
gested areas.
Trends in the concentrations of pollutants can also
be useful in predicting the PSI. Trend information
might include the day-to-day variation in peak
hourly values or 24-hour averages. Trends data should
always be evaluated relative to changes taking place or
anticipated in emissions or meteorology. Persistence of a
trend would especially aid in arriving at the PSI forecast
if no definitive changes in emissions or meteorological
features are indicated. Interpretations of trends infor-
mation, on a day-to-day basis, require care and experience
because of the fluctuations that for varied reasons tend
to occur about a mean trend.
The types of meteorological information that could be
used for forecasting the PSI have been rather well
defined through past experience with forecasting
methods developed in support of air pollution control activities
A-2
-------
This support has largely dealt with forecasting indices and episodic
conditions. The meteorological features and parameters that
are most often utilized in forecasting air quality indices
at the present time are:
• Character and Movement of Air Masses and Fronts
• Areas of Air Mass Subsidence
• Incidence, Intensity, and Height of Inversions
• Mixing Layer Height
• Prevailing Wind Direction
• Mean Wind Speed (Surface and Mixing Layer)
• Ventilation (Mixing Layer Mean Wind Speed x Mixing Heighl
• Precipitation
• Temperature
• Total Sky Cover
Of course, the emphasis placed on particular features and
parameters listed above will vary with location and pollu-
tant (s) of concern.
NWS INFORMATION AND SUPPORT SERVICES
The NWS operates a comprehensive Air Pollution Weather
Forecast Program. The program is administered from NWS
National and Regional Headquarters with operational program
elements at the National Meteorological Center (NMC) and
local Weather Service Forecast Offices (WSFO's). Details.^
of the program are contained in the-NWS Operations Manual
and Technical Procedures Bulletins. This program generates
a variety of national, regional, and local air pollution
weather forecast products which are issued to the public,
to control agencies, or to both, as appropriate.
The NMC is responsible for providing the large-scale
meteorological guidance used by field offices in the pre-
paration of advisories and other products which are parti-
cularized and tailored to specific geographic areas to user
requirements.
The air pollution weather products of NMC are comprised
of the following elements:
a. Forecast Air Stagnation Charts. Issued every
morning on facsimile, these four panel computer
based charts depict expected areas of atmospheric
stagnation (Figure 1).
b. Air Stagnation Narrative. This plain language
teletype message describing the Air Stagnation
Charts, is issued every morning.
A-3
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c. Air Stagnation Data. This computer derived tele-
type message currently consists of today's mixing
height and transport wind speeds for selected NWS
stations.
The WSFO's have responsibility for local forecast
products within designated geographic boundaries, including
the issuance of the following three basic air pollution
products:
a. Air Stagnation Advisories (ASA). Issued to the
public and control agencies when locally established
critical values of transport wind, mixing height,
and ventilation are forecast to be reached and
conditions are expected to persist for at least
36 hours, causing probable significant decrease
in air quality.
b. Special Dispersion Statements. A special product
issued only to control agencies when a potential
air pollution situation is determined by an NWS
forecaster to exist but no ASA will be issued because
such an issuance would not be in the public interest.
c. Dispersion Outlooks. A routine product issued by
all WSFO's where it has been determined that the
APC needs routine meteorological information to
facilitate day-to-day operations and adequate
manpower is available at the WSFO. The format,
content, and issuance times of this product is
determined by the WSFO and APC. The Dispersion
Outlook is issued only to the APC.
Occasionally, air pollution episodes of public concern
may occur during non-stagnant situations. These involve
predesignated episode levels that require control actions
to improve the air quality condition. In these situations,
the WSFO provides the appropriate government agencies with
the meteorological support necessary for pollution control
or abatement procedures.
In conjunction with these services, the NWS provides
supplemental, low-level upper air soundings at designated
stations upon request from agencies and/or WSFO's. This
program which provides for greater spatial and temporal
detail on dispersion conditions, especially during episodes
or potential episodes, is available for several cities.
These locations are listed below, together with the
scheduled:
A-5
-------
L_oc_d t_ip_n
Birmingham, Ala.
Charleston, W. Va.
Chicago, 111.
El Monte, Ca.
Houston, Tex.
Los Angeles, Ca.
Philadelphia, Perm.
Program
1 p>er day routine- At^k uay , week-
end and second daily observation on
call
1 per day routine week day, week-
end and second daily observation on
call
1 per day routine week day, week-
end and second daily observation on
call
2 per day routine week days except
occasionally omit afternoon sound-
ings on well ventilated days
1 per day routine week day, week-
ends and second daily sounding on
call
2 per day, 7 days a week
all observations on call
Additionally, special low-level soundings ar^ available on -m
on-call basis at the regular upper air observation facilities
near Denver, Co., New York, N.Y., Oakland, C.a . , Pittsburgh,
Pa., and Wasnington, D.C. An aircraft sounding is available
at Sacramento, Ca. Through a Cooperative effort, state A?C
agencies take soundings as needed in Seattle, Boston, Portland,
Ore., and San Jose, Ga. These are taken at special facilities
that were established by the NWS.
The NWS has, up until recently, not been too closely in-
volved nationwide in predicting conditions conducive to buildup
of photochemical pollutants. Because of recent interest and
increasing demand for such information, the NWS is in the
process of evaluating possible te^hr.iru^s with the objective e£
modifying or adding to current air pollution weather forecast
products and services.
DEVELOPMENT OF PREDICTION METHODOLOGY
The available services and inforraticn briefly described
above form the basis for developing a local community procedure
for making local qualitative forecasts of the PSI. These forecasts
r-nn h'- reasonably r.^de for periods up to a aay in udvance in terms
of No Significant Change, Increase, or Decrease. It is advisable
agencies planning to use the index along with
to have rj1" rre-nr.el on their itaf
or
ia.uij.iar
a forecast pro-
*/ith meteoro-
logical data and how these data may be applied in development
of index prediction methodology.
A-6
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Considering the wealth of information available from
the NWS, it seems logical that the issuance of an index
forecast should be scheduled at intervals complementary to
operations at the NWS. This would allow the APC agency to
have the advantage of the most current NMC weather products
and WSFO air pollution forecast services. In addition, it
would encourage further cooperation and support of the local
NWS facility. However, while it can be expected that NWS
meteorologists will be able to closely coordinate with a
local agency in arriving at index change predictions during
potential or actual episodic conditions, they will most likely
not be able to give such attention to routine day-to-day
forecasting of the index. Also, NWS personnel would not be ex-
pected to have detailed knowledge of pollutant-related factors.
Where an APC agency may have developed the expertise
necessary to make quantitative predictions of the PSI for
the following day, they should be encouraged to make these
predictions. However, it should be cautioned that making
quantitative predictions of air quality or air quality
indices should not be attempted without a reasonable expec-
tation of success based on well-tested techniques. Other-
wise, a less than satisfactory forecast record could result,
which would tend to have an adverse effect on public accept-
ance of the PSI.
Mathematical air quality simulation models have to date
not been used to any appreciable extent in index prediction.
Because of their relative complexity, cost of modifying for
local use, and time and expense that may be involved in making
day-to-day predictions, their use for predicting the index
qualitatively will initially be limited. However, where APC
agencies may progress to the point of making quantitative
forecasts, the use of models may become necessary. A
listing and brief description of possible air quality models
that could be applied are contained in OAQPS Guideline No.
1.2-031.
CURRENT USE OF METEOROLOGICAL INFORMATION IN INDEX PREDICTION
Approximately half of the 25 local agencies currently
issuing air pollution indices make forecasts of their index
a day in advance. Of these, only one third have meteoro-
logists on their staffs, while the remainder rely upon NWS
meteorologists for interpretation of meteorological data.
Three of the local agencies were selected to serve as examples
of how varying degrees of meteorological information can be
incorporated into air quality index forecasting.
A-7
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One of the more sophisticated forecast techniques, the
Air Pollution Dispersal Index, was developed six years ago
by the State of Colorado Department of Health in Denver. A
forecast is issued each morning for four time periods, a.m.
today, p.m. today, a.m. tomorrow, and p.m. tomorrow. The
technique developed by department meteorologists is based
upon concepts of mixing-heights and wind speed discussed
by Holzworth in AP-101, and employs a nomogram of wind
speed vs. mixing heights, with isolines of constant venti-
lation factor values serving to demarcate four dispersion
categories. These categories are:
2
Ventilation Factor (m /sec)
(Wind Speed x Mixing Height) Associated Dispersion
< 2000 Bad
> 2000 to 4000 Fair
> 4000 to 6000 Good
> 6000 Excellent
The mixing heights used for the "today" forecast are deter-
mined from a plot of the Denver morning upper air sounding,
the morning minimum surface temperature at Stapleton Airport
plus 3° to 4°C, and the forecast afternoon maximum temperature,
The "tomorrow" mixing heights are determined from the fore-
cast 24-hour minimum and 36-hour maximum temperature, and a
forecast of the sounding using locally-tailored analytical
techniques. All transport wind speeds are derived from
either observed or forecast NWS data. Critical factors in
Denver are the typical low-level morning inversions which
serve to deteriorate air quality and the occurrence or
forecast of rain or snow which automatically leads to a
forecast of improving air quality.
4
The City of Philadelphia Department of Public Health
uses general meteorological conditions and a NWS Air Stag-
nation Index to predict the Philadelphia Air Quality Index.
The local agency receives meteorological information twice
daily from the Philadelphia NWS office. Parameters of most
concern are wind speed, gustiness and the likelihood of a
frontal passage with its associated turbulent mixing. Wind
direction is not a vital concern since emission sources in
the city are relatively well distributed in all directions.
Specifically, the Air Stagnation Index is formulated from
the algebraic sum of several weighted meteorological para-
meters as shown in Table 1. To determine the index value,
the weights associated with each observed parameter are
summed. When at least one of the meteorological values is
-------
TABLE 1. Air Stagnation Check Sheet"
Meteorological
parameters
Value
categories
Weights
morning
wind speed
(knots)
afternoon and
evening
wind speed
(knots)
morning
mixing height
(meters)
afternoon
ventilation factor
(meter /sec)
> 10
< 10 > 8
< 8 > 6
1 6
> 11
< 11 > 9
< 9 > 6
I 6
> 1500
< 1500 > 750
^ 750 > 500
> 8000
< 8000 > 6000
< 6000 > 4000
< 4000
STOP
-1
+ 1
+ 2
STOP
-1
+ 1
+ 2
STOP
-1
0
STOP
-2
0
+1
Philadelphia Forecast Office
National Weather Service
National Oceanic and Atmospheric Administration
U.S. Department of Commerce
A-9
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associated with a "STOP," excellent dispersion is forecast.
Otherwise, dispersion is forecast according to the following
scheme:
Sum of weights Forecast dispersion
-1, -2, -3 good
0 marginally good
+1 marginally poor
+ 2 , +3 poor
However, due to the nature of the Philadelphia Air Quality
Index, a dramatic change in dispersion is required to effect
a change in the index values.
4
The Department of Public Health in Dallas uses meteoro-
logical data in a very qualitative manner. The general
weather situation is examined daily with primary importance
directed toward stagnating high pressure systems, cold frontal
passages, and prevailing wind direction. NMC trajectory
analysis data, surface weather patterns, and prognostic
charts are used in a non-rigorous manner. For example,
geographical plots of smoke and haze reports are occasionally
used to determine the area extent and approach of pollutants
due to large scale circulation patterns.
Improving conditions are forecast with the occurrence
of precipitation, a frontal passage, and increasing wind
speed. Deteriorating air quality is predicted when trajec-
tories persist from local or more distant sources or sources
areas.
A-10
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REFERENCES
1. National Weather Service, Operations Manual, Air Pollution
Weather Forecasts, WSOM Issuance 75-13, Part C, Chapter 30,
April 1975.
2. National Weather Service, Technical Procedures Bulletin
No. 122: Air Stagnation Guidance for Facsimile and
Teletype (3rd Edition), October 21, 1974. (Supersedes
previous TPB's Nos. 52, 58, and 69.)
3. U.S. Environmental Protection Agency, Guidelines for Air
Quality Maintenance Planning and Analysis, Volume 12:
Applying Air Quality Models to Air Quality Maintenance
Areas, EPA-450/4-74-012, September 1974 (OAQPS No. 1.2-031),
Research Triangle Park, N.C.
4. Thorn, G., and Wayne R. Ott, "Compendium Analysis, and Review
of United States and Canadian Air Pollution Indices,"
Joint Study by the U.S. Environmental Protection Agency and
the Council on Environmental Quality, Washington, D.C.,
December 1975.
5. Holzworth, G.C., "Mixing Heights, Wind Speeds, and Potential
for Urban Air Pollution Throughout the Contiguous United
States," U.S. Environmental Protection Agency, Research
Triangle Park, N.C. January 1972 (AP-101).
A-ll
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-450/2-76-013
3. RECIPIENT'S ACCESSION«NO.
4. TITLE AND SUBTITLE
GUIDELINE FOR PUBLIC REPORTING OF DAILY AIR QUALITY-
POLLUTANT STANDARDS INDEX (PSI)
5. REPORT DATE
August 1976
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S),
'William F. Hunt, Jr., Wayne R. Ott, John Moran
Raymond Smith, Gary Thorn, Neil Berg and Barry Korb
8. PERFORMING ORGANIZATION REPORT NO
OAQPS 1 .2-044
9 PERFORMING ORGANIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
U.S. Environmental Protection Agency
Offices of: Air & Waste Management, Research &
Development, and Planning and Management
Research Triangle Park, NC and Washington, D.C.
2AE132
11. CONTRACT/GRANT NO.
NA
12. SPONSORING AGENCY NAME AND ADDRESS
U.S. Environmental Protection Agency
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
Appendix A was prepared by the National Oceanic and Atmospheric Administration.
Authors: E.L. Martinez and Norman Possiel.
16. ABSTRACT
The U.S. EPA's Pollutant Standard Index (PSI) is the result of a joint effort
on the part of EPA's Offices of Air and Waste Management, Research and Development,
and Planning and Management. The guideline suggests the use of an air quality
index for those local and state air pollution control agencies wishing to report
an air quality index on a daily basis. The PSI places maximum emphasis on
protecting the public health; that is, it advises the public of any possible
adverse health effects due to pollution. The index incorporates five major
pollutants: carbon monoxide, oxidants, particulates, sulfur dioxide, and nitrogen
dioxide. "Good" air quality falls in the 0 to 50 range, "moderate" air quality from
50 to 100, "unhealthful" from 100 to 200, "very unhealthful" from 200 to 300,
and "hazardous" above 300.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Pollutant Standards Index
Air Quality Index
Air Pollution Index
3. DISTRIBUTION STATEMENT
Release Unlimited
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
40
20 SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
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