4989
d Slates
Environmental Protection
•icy
March 1977
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EOT
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A Little
Background
17OOPA77019
"The Nation's
' commitment to clean
air has taken many
forms. But over the past
several years, the
evolution of Federal
legislation and regulation
has shaped and
increased a cooperative
effort among Federal and
State control agencies,
industry, and a
concerned and informed
public. Especially as a
result of the 1970 Clean
Air Amendments, a
considerable expenditure
of time, material, and
funds has been brought
to bear on solutions to
the technological and
social problems needed
to assure protection of
public health and welfare
from the adverse effects
of air pollution.
The States, backed by
Federal assistance, have
developed wide-ranging
regulatory, enforcement,
and administrative
programs to reduce
emissions of air pollution
from a great variety of
sources. These
abatement efforts have
been augmented by
direct Federal regulation
and enforcement of
control measures
directed toward certain
types of pollutants and
industrial sources, as
well as the Federal
program to reduce air
pollution emissions from
new motor vehicles.
As more and more
information becomes
available, it also
becomes possible to
assess with increasing
assurance what the
success of these
programs has been and
to describe more fully
and accurately the trends
in the quality of the
Nation's air. Based on a
study by the
Environmental Protection
Agency, National Air
Quality and Emissions
Trends Report, 1975, we
can provide some
reasonable answers to
the question, "What has
all of this effort
accomplished?"
And the answer quite
simply is that the quality
of the Nation's air has
improved. Over the past
five years considerable
progress has been made
toward achieving the
National Ambient Air
Quality Standards
established by the
Environmental Protection
Agency, under the 1970
Clean Air Amendments,
to protect our public
health and welfare.
In the remaining pages,
we shall present, in
simplified form, some of
the information from the
study. (Those desiring to
review the full, detailed
technical and statistical
analysis, may obtain a
copy from the U.S.
Environmental Protection
Agency, Office of Air
Quality Planning and
Standards, Research
Triangle Park, N.C. 27711.)
An analysis of special
interest, done for the
first time, is an estimate
of changes in population
exposed to high air
pollution levels. This has
been done for the
country for particulate
matter where more
information was
available, and for
selected areas for other
pollutants.
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The Air Quality
Trends
• The
Results
^yieasurements of
'^'actual air pollution
levels in the air are made
throughout the country
by State and local
agencies. The number of
locations where these
measurements are made
varies with different State
and metropolitan areas;
also some pollutants are
measured at fewer
locations than others,
and have been measured
for fewer years.
Using the information
provided by the States,
changes were studied for
those pollutants for
which EPA has set air
quality standards—total
suspended particulates,
sulfur dioxide,
photochemical oxidants,
carbon monoxide, and
nitrogen dioxide. Trends
in the levels of these
pollutants were
determined on a national
basis and on a regional
basis. Most of the
information covers the
period 1971-1975,
although other time
periods were considered
in some cases where
more, or less, information
may have been available.
Following the general
results, some additional
detail is provided for
particulates, sulfur
dioxide, carbon
monoxide, and oxidants.
(Not enough information
is yet available to provide
detail for nitrogen
dioxide in a non-
technical fashion, and
the reader is referred to
the original study for that
information.)
• In 1975, 28 million
fewer people
throughout the country
were exposed to
particulate levels
above the health-
related air quality
standard than had
been exposed in 1970.
This is a decrease of
38 percent.
• In the greater New
York Metropolitan area,
7 million fewer people
in 1974 were exposed
to particulate levels
above the health-
related standard than
had been exposed in
1971.
• By 1975, average sulfur
dioxide levels in urban
areas had dropped 30
percent since 1970.
This improvement
took place most rapidly
in the 1970-1973
period. Since then,
with much of the
emission reduction
having been
accomplished, and
with some movement
toward greater use of
high sulfur fuels where
possible, without
exceeding the air
quality standard, trends
have tended to level off.
• Long-term oxidant data
for much of the
country is somewhat
limited. But short-term
trends for the eastern
part of the United
States for 1973-1975
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show some decline in
levels exceeding the
air quality standard.
• In the Los Angeles Air
Basin, there has been
a considerable
reduction in the
number of days on
which the health-
related oxidant
standard has been
exceeded.In the mid-
60's, people in the
Basin were exposed to
levels above the
standard on an average
of 176 days a year. By
the mid-70's, this
exposure was down to
an average of 105 days
a year.
• Some 80 percent of the
locations where carbon
monoxide is measured
across the Nation
show improvements in
levels of this auto-
related pollutant, with
the rate of
improvement more
pronounced in
California where auto
emission standards
have been somewhat
more stringent than
the Federal standards.
• Trends in nitrogen
dioxide levels were
mixed. Levels in the
Los Angeles Basin
declined between 1971
and 1975. but in other
parts of the country
where information is
available, levels have
declined in some
locales, increased in
others, and show no
particular trend for still
others.
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Some Details . . .
About Particulates
Trends in particulate
' levels since 1970 show
a general improvement at
a rate of four percent per
year, with the result that
38 percent fewer people
throughout the country
now are exposed to
levels higher than the
health-related air quality
standard.
Improvement rates have
differed in various parts
of the country, with
higher rates being found
in the Northeast and
Great Lakes areas, and
more level rates in some
western States where
natural particulate matter
poses problems.
Despite the
improvements, total
suspended particulates
still remain a problem.
Approximately 28 percent
of the Nation's
population are still living
in areas where the annual
standard is exceeded.
Because of this, some
States may be required
to adopt new measures
to take care of problems
that still exist.
Measurements have been
made of levels of
particulate matter in the
air for more locations
and for a longer time
than any other air
pollutant. Thus, there is
enough information
available to make it
possible to estimate
nationwide trends in
population exposure.
The information available
was sufficient to allow
such an analysis to be
made for most areas of
the country, covering
some 165 million of the
total population.
In 1970, 74 million people
were exposed to levels
above the health-related
air quality standard for
particulate matter. By
1975 this number had
dropped to 46 million —
an improvement of 28
million fewer people, or
38 percent, exposed to
levels above the
standard.
Moreover, as would be
expected from the trends
in measured air quality
levels, reduced
exposures generally
occurred at all
concentration levels.
In the greater New York
Metropolitan area,
measurements have been
made of particulate
matter at a large number
of locations extending
back over many years.
Thus, it is possible to
make especially detailed
studies of trends in
population exposures to
particulates.
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National Trends, Yearly Average Particulate Levels, 1971 -1975
110
100
20
10
Year 1971
1972
1973
1974
1975
LJere we see the year-by-year
'change in the levels
measured throughout the
country. The bottom red line
shows typical average levels for
the cleaner locations, the white
line shows the overall average,
and the top red line shows
the typical average levels for the
dirtier locations. A general
improvement can be seen for all
categories. The cleaner
locations, while improving, are
not doing so at as great a rate.
The overall average shows
greater improvement. The dirtier
areas show the greatest
improvement. This is consistent
with planned pollution control
programs. Those locations
where the yearly average air
quality control standards
already were met are not so
much concerned with further
reductions, but rather with
maintaining air quality. Those
with the greatest problems,
because of previously
uncontrolled sources, have
needed, and achieved, greater
emissions reductions and
greater rates of air quality
improvement.
Trend in National Population Exposure to Particulate Matter Levels
Above the Health-Related Standard
70
'71
72
73
74
75
45%
43%
)
37%
Represents 8.2 million people
(5% of Base = 165 million)
32%
30%
28%
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Between 1971 and 1974,
annual average levels
were reduced 25 percent
resulting in 71 percent
fewer people living in
areas exposed to levels
in excess of the health-
related air quality
standard. And the
number of repeated
exposures to high daily
levels also was reduced.
The numbers of those
more likely to be
adversely affected by
high air pollution levels—
the elderly and the
school aged — living in
the high pollution area—
also dropped sharply.
Although a slightly
higher proportion of the
elderly population lives in
areas of elevated
paniculate levels, the
overall rates of
improvement are similar
for the total population,
for the school aged,and
for the elderly.
Number of People Living
in Areas of New York
Exceeding the Annual
Particulate Standard
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110(ig/m3
New York Population Exposure to Daily Particulate
1971
N.J.
Areas where daily TSP
concentrations exceed
secondary NAAQS
< 5% ol the time
5-10*
10-20%
I 20 - 30%
I >30%
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Area, 1971 and 1974
1974
Nole Isoplelh maps are based on spalial interpolation Irom data
measured al 103 monitoring sites Local TSP may vary because ol
meteorology, topography, and emissions
Levels, 1971 and 1974
1974
In 1971, 19 percent of
' the land area was
exposed to levels higher
than the health-related air
quality standard. But, in
1974, less than four
percent was blanketed by
air containing levels this
high.
"The percent of people
' exposed to daily
particulate levels in the
New York area are shown
here for 1971 and 1974.
With much smaller areas
blanketed by high levels
in 1974, many fewer people
were exposed to the higher
levels. For example, in
1971, some 58 percent of
the total population lived
in areas where levels
exceeded the welfare
related standard. But, by
1974, this had dropped to
15 percent.
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Some Details . . .
About Sulfur Dioxide
I evels of sulfur dioxide
'—in the air over the
Nation's urban areas
have decreased by an
average of 30 percent
from 1970 to 1975. Most
of this improvement took
place rapidly in the
1970-1973 period. Since
then, levels have been
fairly constant because
many areas had reached
levels that met the
ambient air quality
standard and because of
some movement toward
greater use of high
sulfur fuels where
possible, without
exceeding the air
quality standard.
In some few cases, there
seem to have been slight
increases during 1975
because of changes in
fuel use patterns. In Los
Angeles, for instance,
even though sulfur
dioxide levels are low,
there has been an
increase because of
recent changes in fuel
use associated with a
curtailment of the use of
natural gas for industrial
purposes in that area.
Similar patterns appear in
parts of the Northeast.
From a national
viewpoint, the urban
sulfur dioxide problem
has diminished so that
only a small number of
areas now exceed the air
quality standard for
sulfur dioxide. But, of
course, continued
vigilance will be required
to maintain this favorable
situation.
On the other hand, a
number of single sources
of sulfur dioxide still
exist outside of major
urban areas. These
individual sources, such
as smelters, pose the
greatest threat to the air
quality standards for
sulfur dioxide at the
present time.
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National Trends in Yearly Sulfur Dioxide Levels, 1971-1975
10
Llere we see the year-by- year
''changes in the levels of
sulfur dioxide levels measured
at all individual locations in the
country. The bottom red line
shows the typical average level
for the cleaner locations, the
white line shows the overall
average, and the top red line
shows the typical average for
the more polluted locations. A
general improvement can be
seen. Improvement at the
cleaner locations is much less
evident, while the overall
average shows greater
improvement, and the more
polluted locations show the
greatest improvement. This
pattern is to be expected
because the cleaner areas did
not have as far to go, while
those areas needing the
greatest improvement show the
greatest improvement.
1971
1972
1973
1974
1975
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Some Details .
About Carbon
Monoxide
The primary source for
' emissions of carbon
monoxide in most U.S.
cities is the automobile.
Nationally, some three-
fourths of the carbon
monoxide comes from
transportation sources.
But in some urban areas,
transportation can be
responsible for as much
as 99 percent of the
emissions, and any city
with heavy enough traffic
may have a potential
problem from carbon
monoxide. In some
cases, the problem may
be highly localized —
affecting perhaps only
the area around a few
street corners. In other
cases, the problem may
be spread throughout the
center-city area and near
major commuter
corridors. In any event,
improvements in levels of
carbon monoxide in the
air will almost always be
directly related to control
of emissions from
automobiles.
Throughout the country,
carbon monoxide levels
have not been measured
at as many locations and
for as long a period of
time as'particulates and
sulfur dioxide. This
means that it is not as
easy to determine
national trends in carbon
monoxide levels in the
air. California, however
has been making such
measurements
10
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extensively for a longer
time, so trends there can
be checked more easily.
And these can be
compared with those in
other parts of the country
to see whether they
agree.
When this is done, the
overall picture clearly
shows improvement.
In California, over a
three-year period, lower
carbon monoxide levels
were measured at 81
percent of the sampling
locations. For the
remainder of the country,
this improvement was
found at 78 percent of
the locations.
In California, carbon
monoxide levels
decreased at a rate of
about 7 percent per year.
In the rest of the country,
the decrease was at a
rate of about 5 percent a
year. Because California
has more stringent
automobile control
regulations, this
difference should be
expected.
11
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Some Details . .
About Oxidants
Qxidants (or
hotochemical
oxidants) are not emitted
directly into the air from
air pollution sources.
This group of chemicals
is formed in the air by
chemical reactions
between hydrocarbons—
such things as gasoline
vapors and cleaning
solvents—and nitrogen
oxides—which are
formed from the nitrogen
and oxygen in the air
whenever any kind of
burning takes place. The
reactions producing
oxidants are strongly
stimulated by sunlight,
but however formed,
oxidants are an important
air pollutant having
adverse effects on public
health and welfare.
Oxidants have long been
a major air pollution
problem in Los Angeles,
and other parts of
California. They have
become increasingly
important in other parts
of the country as motor
vehicle traffic —a major
source of hydrocarbons
and nitrogen oxides —has
increased, and as levels
of other contaminants
have dropped. However.
because oxidants —
outside of California—
have been recognized as
a serious problem only
during recent years, there
is not enough
information on levels in
the air extending far
enough back to allow
national trends to be
determined, although
some clues can be
found.
Summertime oxidant
levels in eastern cities
seem to be lower over
the past three years.
In California, there has
been a general
improvement. A decline
has occurred in San
Francisco over the past
ten years. In San Diego,
levels declined by some
40 percent over the past
ten years. Most of this
decline occurred during
the first five years of the
period, but recent
patterns have been
mixed, so that there has
been no net change over
the past five years.
In the Los Angeles area,
measurements of
oxidants have been made
at a large number of
locations, over a long
period of time. This
allows for a more
detailed examination of
trends in air quality
levels and, even more
usefully, in changes in
the exposure of the
population to high levels
of this contaminant.
Over a 10-year period,
people in the Los
Angeles Basin
experienced a dramatic
decline in the number of
days they were exposed
to oxidant levels above
the health standard. In
the two-year period
1965/66 people were
exposed an average of
176 days a year. By
1969/70, this had dropped
to 144 days a year. And
by 1973/74 this exposure
was down to 105 days a
year. Not only did the
number of days
decrease—so also did
the total time during
which a person was
exposed. In terms of total
hourly exposure, people
in Los Angeles were
exposed to oxidant levels
above the health-related
standard an average of
1050 hours a year in
1965/66, but by 1973/74
this exposure had fallen
to an average 525 of
hours a year—a
reduction in exposure of
one-half.
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Percent of Days on
Which Oxidants
Exceeded the Health-
Related Standard in
Los Angeles
LJere we see the trend
' in the percentage of
days in the Los Angeles
area on which the health-
related air quality
standard was exceeded.
In 1965/66, more than half
of the Basin was
blanketed with air
exceeding the standard
on more than half of the
days of the year. By
1973/74, this has been
reduced to only a small
area. This small area
remains as the result of a
combination of two
factors. A significant
reduction in emissions of
hydrocarbons that react
rapidly has taken place in
the Los Angeles Basin.
This has resulted in
sizeable improvements in
oxidant air quality in the
general vicinity of where
the reductions occurred.
On the other hand, there
still exist emissions of
sizeable quantities of
hydrocarbons that react
more slowly. Movement
of these slower reacting
materials toward the
eastern portions of the
Basin, coupled with
population growth in
these areas, has resulted
in increased high levels
in some eastern parts of
the Basin. An area where
the standard was
exceeded on fewer than
20 percent of the days
has emerged and grown.
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Trends in Population
Exposure to Oxidants
in Los Angeles,
1965-1974
LJere we see what
** percent of the Los
Angeles population was
exposed to various levels
ot oxidant above the
health-related standard
for various amounts of
time. For example, in
1965/66, a little over 50
percent (53%) were
exposed to levels above
the standard on at least
50 percent of the days. In
1973/74, the percentage
of the population with
the same exposure was
down to less than five
percent.
The standards still are
being exceeded for
virtually the entire
population for a least
some small fraction of
days, so there still is
much work to be done.
But, the improvements
are an encouraging
testimonial to the efforts
that everyone has made.
- 50%
J20%-50°.
• 20°--
>,
\ \ % '<$ %
1 x standard
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The Emissions
Trends
The
• Results
A nother way of
** measuring pollution
control progress is to
estimate the changes in
amounts of pollution
being put into the air.
Measures of the levels in
the air relate most
directly to people and to
the effects that air
pollution has on health
and welfare. Estimates of
amounts emitted relate
more directly to the
sources, and can show
where control has been
most effective and what
sources still need most
attention.
Estimates are made for
five major pollutants:
particulate matter, sulfur
oxides, oxides of
nitrogen, hydrocarbons,
and carbon monoxide.
Since oxidants are not,
for the most part, emitted
directly, estimates of
these would be
meaningless. But since
hydrocarbons are a major
ingredient in the
formation of oxidants,
estimates of these
emissions provide
important information in
determining the
effectiveness of control
measures.
P\uring the period 1970
'-'through 1975, for the
Nation —
• Particulate emissions
from all sources are
down by 33 percent.
• Sulfur oxides
emissions from all
sources are down by 4
percent.
• Nitrogen oxides
emissions from all
sources are up by 7
percent.
• Hydrocarbon
emissions from all
sources are down by 9
percent.
• Carbon monoxide
emissions from all
sources are down by
15 percent.
These figures do not take
into account the fact that
all emissions would have
been higher had there
been no pollution
controls in effect.
Summary of National Emission Estimates
Millions of Tons a Year
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1970 26.8 34.2 22.7 33.9 113.7
1971 24.9 32.3 23.4 33.3 113.7
1972 23.4 36.7 24.6 34.1 115.8
1973 21.9 35.6 25.7 34.0 111.5
1974 20.3 34.1 25.0 32.9 103.3
1975 18.0 329 24.2 30.9 96.2
15
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Some
Details
Darticulate emissions
'were reduced mainly
by installation of control
equipment on industrial
processes, because of
less coal burning by non-
utility stationary sources,
by installation of control
equipment by electric
utilities that burn coal,
and because of a
decrease in the burning
of solid waste. The
extent of emission
reductions by industrial
processing also was
increased as a result of
economic recessions
that curtailed production
by some industries. This
is particularly evident
from 1974 to 1975.
Sulfur oxides emissions
declined slightly from
1972 through 1975.
Although not shown,
emissions from electric
power generating plants
increased somewhat
through 1973, and then
levelled off. In spite of
the overall relatively
slight declines in
emissions, the air quality
trends showed us that
levels in the air over
urban areas have
decreased considerably
over the past few years.
This difference arises
because high sulfur fuels
have been shifted from
use in urban areas to use
in a growing number of
sources outside of
densely populated areas,
where fewer people live
and there are fewer other
sources.
Nitrogen oxides
emissions have increased
mainly because of
increased emissions
from electric utilities and
from mobile sources.
Emissions from electric
utilities rose because of
increased electric
generation, which
requires the use of more
fuel. Nitrogen oxides
emissions from mobile
sources have increased
due to increases in the
number of vehicle miles
travelled by all highway
vehicles. For the
automobile portion of the
highway vehicles,
emissions have been
essentially constant
since 1972 because
Federal emission
standards that went into
effect with the 1972 cars
have tended to balance
the increase in total
miles travelled.
Hydrocarbon emissions
have gone down only
slightly. Significant
reductions have been
obtained from highway
vehicles as a result of
the Federal emission
standards. But these
reductions have been
partially offset by
increases in industrial
process emissions and
losses of gasoline and
other hydrocarbon vapors
from evaporation at
filling stations and other
points in the marketing
chain, and from the use
of various solvents. The
increases reflect a
general increase in the
consumption of these
products.
Carbon monoxide
emissions have
decreased mostly
because of the Federal
emission standards on
motor vehicles and
because of less burning
of solid waste. Some
industrial emissions also
have been reduced
because of decreases in
production, and the
phasing-out of some
obsolete processes.
All photos in this publication from
EPA's Documerica collection
U S GOVfMNMfNl PRIN1INC Off ICC 1971 O -??! 430
16
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Calculated Total Emissions of Criteria Pollutants by Source Category,
1970 through 1975
Particulate Matter Hydrocarbons
Nitrogen Oxides
Carbon Monoxide
70 71 72 73 74 75
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Processes
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