Highest Second Dally
He Maximum.

Max Site

by County

Source: Aerometsic Information Retrieval System (AIRS)

Ozone Air Quality Concentrations, 1990

This map shows how ozone air quality concentrations varied by county in 1990. Counties
in blue and green had 1990 air quality better than the level of the ozone air quality standard.
There were 89 counties (in yellow, orange, and red) that had air quality worse than the level
of the ozone standard. The air quality indicator shown is the second daily maximum 1-hour
average ozone concentration at the peak site in each county.

17


CO Loves
ppm

eos
Yes
me 13
mc 17
= 7

Highest Second Max
S-Hr Avg-

Max site

by County

Source: Aerometric Information Retrieval System (AIRS)

Carbon Monoxide Air Quality Concentrations, 1990

This map shows how carbon monoxide air quality concentrations varied by county in 1990.
Counties in blue and green had 1990 air quality better than the level of the carbon monoxide
8-hour air quality standard. There were 23 counties (those in yellow, orange, and red) that had
air quality worse than the CO standard. The air quality indicator shown is the second maximum

nonoverlapping 8-hour average concentration at the peak site in each county.

11


Number of Days
> 85 Degrees

wit - 29 Days
wy 30 - 99 Days

mi >= 100 Days

Number of Days with Maximum Daily Temperature Greater Than 85
Degrees Fahrenheit in the Eastern United States, 1990

This map shows the number of days that the maximum daily temperature exceeded 85°F
as measured at National Weather Service WBAN stations. Nationally, the summer of 1990
was the fifteenth warmest summer since 1895. In contrast with 1988, the frequency of days
with temperatures greater than 85°F is much lower in the northeastern and north central states.

21


Some Perspective

When focusing on current air quality
status, it is important not to overlook some
of the earlier efforts in air pollution control.
Emission estimates are useful for examining
long-term trends (see Figure). Between 1970
and 1990, lead emissions clearly show the
most impressive decrease (-97 percent), but
there were also improvements in emissions
of total particulate (-59 percent), sulfur oxides
(-25 percent), carbon monoxide (41 percent),
and volatile organic compounds (-31 per-
cent). Volatile organic compounds and
nitrogen oxides are ozone precursors. Only
emissions of nitrogen oxides showed an in-
crease (+6 percent). It is important to realize
that the reductions occurred even in the face
of economic growth.

National Ambient Air Quality
Standards (NAAQS)

In this atlas, the measures of air quality
displayed for a particular pollutant are
directly related to the National Ambient Air
Quality Standard (NAAQS) for that pollut-
ant; the term “air quality standard" in this
atlas refers to these NAAQS. Air quality
standards are currently in place for six pol-
lutants: carbon monoxide (CO), lead (Pb),
nitrogen dioxide (NO2), ozone (Os), particu-
late matter with aerodynamic size less than

or equal to 10 microns (PM-10) and sulfur
dioxide (SO3) (see Table). A micron is equal
to a millionth of a meter.

Carbon monoxide is a colorless, odor-
less, poisonous gas that is a product of
incomplete fuel combustion. The main source
of CO in cities is motor vehicle exhaust; other
sources are wood-burning stoves, incinera-
tors, and industrial processes.

Lead emissions to the atmosphere come
primarily from non-ferrous smelters, battery
plants, and lead additives in gasoline. A
major environmental success story is the
dramatic reduction of lead in the air caused
by the lowering of lead levels in gasoline

Comparison of 1970 and 1990 Emissions

Metric tons/year (millions) Metric tons/year
(thousands)
120 250 1
100 200
80
150
60
100
40
0 4 0
TP SOx CO NOx VOC Pb

1970 —B 1990


a s
Sf . by County

é

Source: Aerometsic Information Retrieval System (AIRS)

Exceedances of the Ozone Air Quality Standard, 1988

This map displays ozone exceedances in 1988 at the peak site in each county, estimated
as required by the ozone standard. A total of 258 counties contained ozone monitoring sites
that did not meet the ozone air quality standard (i.e., estimated exceedances of 1.1 or greater).

Meteorological conditions during the hot, dry summer of 1988 were conducive to ozone for-
mation.

18


at
“et

tty:

+ mor

Sulfur Dioxide Monitoring Network

This map displays the location and type of the 741 monitoring sites, in 369 counties,
that reported sulfur dioxide data for 1990. Most of these sites are population-oriented monitoring
sites in urban areas, while the major sulfur oxides emissions sources (e.g., smelters and coal-
fired power plants) tend to be in less populated areas.

24


Number of Days
> 85 Degrees

m1 - 29 Days
my 30 - 99 Days

m >= 100 Days

Number of Days with Maximum Daily Temperature Greater Than 85
Degrees Fahrenheit in the Eastern United States, 1988

This map shows the number of days that the maximum daily temperature exceeded
85°F as measured at National Weather Service WBAN stations. Hot, dry, stagnant meteorological
conditions are conducive to the formation of ground-level ozone. Nationally, the summer
of 1988 was the third hottest summer on record since 1895.

20


NO2 Level

ppm
we <= 027
mm < .053
gy “080
we <TM -106
m?> 106
Highest Arithmetic Mean

Max Site
by County

Source: Aerometrte Information Retrieval System (AIRS) ,

Nitrogen Dioxide Air Quality Concentrations, 1990

This map shows how nitrogen dioxide air quality concentrations varied by county in
1990. Los Angeles County (shown in yellow) is the only county in the United States that
did not meet the NO2 air quality standard in 1990. The air quality indicator shown is the
annual arithmetic mean nitrogen dioxide concentration at the peak site in each county.

15


Highway Travel

The interstate highway system is shown
superimposed on 1988 total vehicle miles
traveled (VMT), by state. From 1970 to 1990,
total VMT increased 92 percent.

2500,

2000

1500

1000

Miles Traveled
Billions

<25
me < 50

wy < 100
m < 150
mw < 200
m= 200

U.S. VMT Growth

Total Vehicle Miles Traveled 2127
@ilions)
177A ened had
1527,
ual Pe
132 Jpoonoodt joood
1110 VM
1970 1975 1980 1985 1990


PM-10 may be thought of as dust and
soot suspended in the air. Principal PM-
10 sources include industrial sources, wood-
burning stoves, urban dust, and open burning
for forest management and agricultural
purposes.

Sulfur dioxide is formed from the
burning of sulfur-containing fuel, mainly coal
and oil, and also from metal smelting and
other industrial processes. It is a major
precursor to acidic deposition (acid rain).

There are two types of standards—
primary and secondary. Primary standards
protect against adverse health effects; sec-
ondary standards protect against welfare
effects, such as damage to farm crops and
vegetation and damage to buildings. Be-
cause different pollutants have different
effects, the NAAQS are also different. Some
pollutants (PM-10 and SO2) have standards
for both long-term (annual) and short-term
(24-hour) averaging times. The short-term
standards are designed to protect against
acute, or short-term, health effects, while the
long-term standards were established to
protect against chronic health effects.

Air Quality Monitoring

State and local government monitoring
stations across the nation collect direct

measurements of pollutant concentrations.
Air quality data are submitted to EPA’s
Aerometric Information Retrieval System
(AIRS) by State and local governments and
various federal agencies. The vast majority
of these measurements represent the country’s
heavily populated urban areas.

EPA and other federal agencies also
operate some air quality monitoring sites on
a temporary basis as a part of air pollution
research studies.

In 1990, almost 4100 monitoring sites
reported air quality data for the six NAAQS
pollutants to AIRS (see Table and Figure).
The national monitoring network conforms
to uniform criteria for monitor siting, instru-
mentation, and quality assurance.

Each monitoring site is classified into
one of three categories: NAMS, SLAMS, or
SPMS. The NAMS, or National Air Moni-
toring Stations, were established to ensure
a long-term national network for urban-area-
oriented ambient monitoring information and
to provide a systematic, consistent data base
for air quality comparisons and trends
analysis. The SLAMS, or State and Local
Air Monitoring Stations, were established to
allow State or local governments to develop
monitoring networks tailored more to their
immediate ambient air monitoring needs. The


and, beginning in 1975, the required use of
unleaded gasoline in cars.

Nitrogen dioxide is a poisonous, brown-
ish gas that is a precursor to ozone and to
acidic precipitation. The major sources of
nitrogen oxides emissions are motor vehicles
and fuel combustion sources such as electric
utilities and industrial boilers.

Ozone, unlike the other five pollutants,
is not emitted directly into the air, but is
created by sunlight acting on the precursor
pollutants nitrogen oxides and volatile or-
ganic compounds. The sources of these
precursors are diverse. They include gaso-
line vapors, chemical solvents, fuel combus-
tion products, and even consumer products.
Because ozone levels are influenced in part
by meteorological conditions, such as hot
weather, recent year-to-year ozone trends
have been more variable than trends for other
pollutants.

The discussions of ozone in this atlas
refer to ground-level, or tropospheric, ozone
and not to stratospheric ozone. Ozone in the
stratosphere, miles above the earth, is a
beneficial screen from the sun’s ultraviolet
rays. Ozone at ground level, in the air we
breathe, is a health and environmental
concern, and is the primary ingredient of
what is commonly called smog.

National Ambient Air Quality Standards
(NAAQS) in Effect in 1992

POLLUTANT PRIMARY SECONDARY
(HEALTH RELATED) (WELFARE RELATED)

Type of Standard Level Type of Standard Level
Average Concentration? Average Concentration®

co Shou? 9 ppm No Secondary Standard
(10 g/m?)
41-hour? 35 ppm No Secondary Standard
(40 no/m?)
NO, Annual 0.053 ppm |Same as Primary Standard
Arithmetic (100 g/m)
Mean
©, Maximum 0.12 ppm | Same as Primary Standard
Daily t-hour (235 pg/m)
Average®
Pb = Maximum 1.5 g/m | Same as Primary Standard
Quarterly
Average
PM-10 Annual 50 gm? | Same as Primary Standard
Arithmetic
Mean?
24-hour 150 g/m? | Same as Primary Standard
SO, Annual 80 p/m?
Arithmetic (0.03 ppm) 3-hour® 1300 pg/m?
Mean (0.50 ppm)
24-hour? = 365. wom?

a Parenthetical value Is an approximately equivalent concentration.
b Not to be exceeded more than once per year.

¢ The standard is attained when the expected number of days per
calendar year with maximum hourly average concentrations above
0.12 ppm Is equal to of less than 1, as determined according to
‘Appendix H of the Ozone NAAQS.

d- Particulate standards use PM-10 (particles less than 10 in diameter)
as the indicator pollutant, The annual standard is attained when the
‘expected annual arithmetic mean concentration is less than or equal
to 50 yg/m?; the 24-hour standard Is attalned when the expected
number of days por calendar year above 150 ugim? is equal to or
less than 1; as determined according to Appendix K of the PM
NAAQS.



Source: Aerometric Infarmation Retrieval System (AIRS)

Ozone Monitoring Network

This map displays the location and type of the 812 ozone monitoring sites, in 467 counties,
that reported air quality data for 1990. Ozone is not emitted directly into the air, but is created
by sunlight acting on the precursor pollutants nitrogen oxides and volatile organic compounds.
The sources of these precursors are diverse; examples include vehicle exhaust, gasoline vapors,
chemical solvents, fuel combustion products, and even consumer products.

16


Population

This map shows the U.S. population
in 1990, by county. Emissions reductions
were achieved even though U.S. population
increased 23 percent during the last 20 years.

260
240
220
200
180

160

Population
by County
<25000

wa «50000

ma «75000
<150000

wae 250000

wa "250000

U.S. Population Growth

Total Population (Millions)
203) 227: 249)
1970 1980 1990



PM-10 Monitoring Network

This map displays the location and type of the 1,279 monitoring sites, in 572 counties,
that reported PM-10 data for 1990. The PM-10 network has replaced the earlier network that
measured total suspended particulate (TSP). Major PM-10 sources include industrial emissions,
wood-burning stoves, open burning for forest management and agricultural purposes, and
urban dust.

22


United States Office of Air Quality 400-K-92-002

Environmental Protection Planning and Standards May 1992
Agency Research Triangle Park NC 27711
Air

Air Quality Atlas



WB 03-co-pmio W@ 03-co-puio-wo2

Nonattainment Areas

Areas not meeting air quality standards
are called “nonattainment areas.” This map
shows counties that (as of October 1991) con-
tain areas designated nonattainment under
the Clean Air Act Amendments of 1990.

B o3 co puio = ME 03-co— ME 03-pmio  co-pmio

+ soz © Pb

Number of
Pollutant Nonattainment Areas
Carbon Monoxide (CO) 42
Nitrogen Dioxide (NO}) 1
Ozone (03) 98
Lead (Pb) 12
Particulates (PM-10) 70
Sutfur Dioxide (SOs) 50



Source: Asramettic Information Retrieval System (AIRS)

Pollutant Standards Index (PSI)

The PSI is a simple measure of air
quality. This map shows the number of days
with the PSI greater than 100 (unhealthful)
for the NAAQS pollutants during 1990, by
county.

PSI Descriptor
Oto 50 Good
51 to 100 Moderate
101 to 199 Unhealthful
200 to 299 Very Unhealthful
300 and above Hazardous



Number of Monitoring Sites Reporting to

AIRS in 1990
Pollutant Number of Sites
Carbon Monoxide (CO) 491
Nitrogen Dioxide (NO,) 330
Ozone (O3) 812
Lead (Pb) 406
Particulates (PM-10) 1,279
Sulfur Dioxide (SO,) 741
TOTAL 4,059

SPMS, special purpose monitors, are stations
used by State and local agencies to fulfill
very specific or short-term monitoring goals.
The type of each monitoring site is identified
on the individual pollutant monitoring
network maps.

Most of the air quality information in
this atlas is based on two indicators: actual
measurements of pollutants in the ambient
air, and the number of times that the levels
of the air quality standards were exceeded.
The Pollutant Standards Index (PSI) is also
used to show how air quality varies across
the United States. The PSI is a uniform air
quality index developed for the daily report-
ing of air pollution concentrations in most

major U.S. cities. A standard color sequence
is employed when this air pollution infor-
mation is reported to the public. The PSI
colors were selected for all the air quality
maps in this atlas to provide a readily
identifiable and consistent color scheme
throughout. The “cooler” PSI colors (blue
and green) indicate air quality that is “bet-
ter’ than the level of the corresponding air
quality standard. The “warmer” PSI colors
(yellow, orange, and red) denote air quality
levels that do not meet the NAAQS for that
pollutant. The air quality maps are comple-
mented by maps that display meteorologi-
cal, population, and transportation data.

Example Monitoring Site


m Over 10

Estimated
Exceedances-
Max Site

by County

Source: Aerometsic Information Retrieval System (AIRS)

Exceedances of the Ozone Air Quality Standard, 1990

This map displays the exceedances of the ozone air quality standard in 1990 at the peak
site in each county. A total of 115 counties contained ozone monitoring sites that did not
meet the ozone air quality standard. Meteorological conditions in 1990 were not as conducive

to ozone formation as conditions in 1988.

19


802 Level
aims
me 183

m 365

un <= 548
me <= 730
m? 730

Highest Second Max
24-Hr Avg-
Max site
1 by County
3 y
‘2 Te

oS

Source: Aerometrlc Information Retrieval System (AIRS)

Sulfur Dioxide Air Quality Concentrations, 1990

This map shows how sulfur dioxide air quality concentrations varied by county in 1990.
Only one county (Allegheny County, PA) had air quality that did not meet the sulfur dioxide
24-hour air quality standard in 1990. The air quality indicator shown is the second maximum
24-hour average sulfur dioxide concentration at the peak site in each county.

25


Introduction

A picture truly is wortha thousand words.
The eye can assimilate and process a vast
amount of information at one time, quickly
discerning important characteristics through
direct visual comparisons of relationships
among areas. This atlas presents maps that
show the nation’s air quality monitoring net-
work and how air quality varies across the
country. Some of the maps have been included
in other EPA publications; others are appear-
ing here for the first time.

Most air pollution comes from human
activities such as factories, power plants, com-
mercial and residential sources, and cars,
buses, and other transportation sources. The
Clean Air Act provides the framework for
EPA, state, and local efforts to protect air
quality by controlling emissions from these
activities. Air pollution can also result from
natural sources such as forest fires and active
volcanos.

Because the number and type of pol-
lution sources vary from one place to an-
other, air quality also varies geographically.
Meteorological and topographical factors also
affect air quality by reducing the cleansing
ability of the atmosphere. Air inversions,

for example, are common in many areas of
the country (especially in the fall and win-
ter). They trap pollution ina relatively shal-
low layer near the ground. Stagnating
high-pressure systems in the summer can
also cause deteriorated air quality. Urban
areas located in valleys can have air quality
problems when pollutants get trapped and
accumulate over time. (See the cover fora
US. topographical map.) All of these fac-
tors, in the presence of pollution sources, can
contribute to the spatial variation in air quality
seen on the maps in this atlas.

Some of the maps display the extent
and coverage of the air quality monitoring
network in the United States. Other maps
identify areas in which measured air quality
levels did not meet the current National
Ambient Air Quality Standards (NAAQS) in
1990, as well as areas that experienced good
air quality, ie., levels significantly below the
NAAQS. This atlas focuses on air concen-
trations that are direct measurements of pol-
lutant concentrations at monitoring sites
throughout the country. Pollutant emission
values are based on best engineering esti-
mates of the total tonnage of these pollutants
released into the air annually.


Source Aerometric Information Retrieval System (AIRS)

Lead Monitoring Network

This map displays the location and type of the 406 monitoring sites, in 184 counties,
that reported lead data for 1990. Non-ferrous smelters, battery plants, and lead additives
in gasoline are the major sources of lead emissions to the air. The use of unleaded gasoline

and the phase-out of leaded gasoline have substantially reduced ambient lead levels in urban
areas.

12


Nitrogen Dioxide Monitoring Network

This map displays the location and type of the 330 monitoring sites, in 163 counties,
that reported nitrogen dioxide data for 1990. Most of these sites are in major urban areas.
Nitrogen oxides are an important precursor to ozone and to acidic precipitation. The two
major sources of nitrogen oxides are fuel combustion and highway vehicles.

14


For More Information on Air Quality: This atlas was prepared by the
Technical Support Division of the U.S. Environmental Protection Agency. The Division
also prepares an annual report entitled National Air Quality and Emissions Trends Report
which is directed toward both the technical air pollution audience and the interested
general public. Copies of these reports may be obtained from the Data Analysis Section
(MD-14), U.S. Environmental Protection Agency, Research Triangle Park, North Carolina
27711.

About the Cover: The cover map displays the topographical features of the contiguous United States.
Topography can affect air quality by trapping air pollutants in valleys, by channelling
wind flows, and by its secondary effects on precipitation. Data Source: Defense
Mapping Agency


PM-10 Level
ugim3

wc 75

m < 150
ge “225
me <= 300
m? 300
Second Max
2-H Ave

Max Site
by County

Source: Aeramotric Information Retrieval System (AIRS)

PM-10 Air Quality Concentrations, 1990

This map shows how PM-10 air quality varied by county in 1990. Counties in blue
and green had 1990 air quality better than the level of the 24-hour PM-10 air quality standard.
Thirty-three counties (in yellow, orange, and red) had air quality worse than the level of the
PM-10 standard in 1990. The air quality indicator shown is the second maximum 24-hour
average PM-10 concentration at the peak site in each county.

23


400-K-92-002

Air Quality Atlas

U.S. ENVIRONMENTAL PROTECTION AGENCY

Office of Air and Radiation
Office of Air Quality Planning and Standards
Technical Support Division
Research Triangle Park, North Carolina 27711

May 1992



Source: Aerametric Intormation Retrieval System (AIRS) ~

Carbon Monoxide Monitoring Network

This map displays the location and type of the 491 monitoring sites, in 236 counties,
that reported carbon monoxide data for 1990. The main source of CO in cities is motor vehicle
exhaust; other sources are wood-burning stoves, incinerators, and industrial processes.

10


PB Level
gina

<= .80

ms 150
a <= 2.30
ms 3.00
m> 3.00

Highest Quarterly Avg-
Max site
by County

Sm
we D

Source: Aerometite Information Retrieval System (AIRS)

Lead Air Quality Concentrations, 1990

This map shows how lead air quality concentrations varied by county in 1990. Counties
in blue and green had 1990 air quality better than the level of the lead air quality standard.
The twelve counties (those in yellow, orange, and red) that had air quality worse than the
level of the lead standard reflect the impact of localized lead sources. The air quality indicator
shown is the maximum quarterly arithmetic mean concentration at the peak site in each county.

13