4502760161
August 1976
THE HEALTH IMPLICATIONS
OF
PHOTOCHEMICAL OXIDANT AIR POLLUTION
TO YOUR COMMUNITY
». 1. 08817
U.S. Environmental Protection Agency
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
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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.
Publication No. EPA-450/2-76-016
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INTRODUCTION
In many communities throughout the country, citizens frequently
breathe the air pollutant "photochemical oxidant" in levels which medical
research has shown to be potentially dangerous to their health. Levels
of this air pollutant in most areas of the country can also cause substan-
tial damage to .many forms of vegetation and to a number of valuable
materials such as rubber products, painted surfaces, and fabric dyes.
Practically no city, town or community of the country fully escapes the
effects of photochemical oxidant in the air.
New and expanded efforts are underway to help bring about control
of photochemical oxidant and reduce its impact on the general public.
However, many people may not fully understand the need for these programs
and what can be accomplished through them. This short paper seeks to
better clarify the photochemical oxidant situation for State and local
government officials such as State legislators, mayors, city councilmen,
and community air pollution control officials who have a vital role to
play in reducing the health threat from this air pollutant.
BACKGROUND
In 1971 photochemical oxidant was formally recognized by the
Environmental Protection Agency as a nationwide air pollution problem.
To protect the public from its harmful effects, a national ambient air
quality standard was set April 30, of that year. This standard placed a
legal limit on the amount of photochemical oxidant that could be present
in the air after July 1975 (with some provisions for extending this
deadline for two years), based on the best available scientific evidence
of health and other adverse effects.
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Since 1971 many problems have been encountered as federal, State,
and local governments have attempted to implement air pollution control
programs which would ensure that the standard would be met. Even today,
there are relatively few places in the country that do not, at least
occasionally, experience photochemical oxidant levels in excess of the
standard. These problems were expected since the standard was set at a
very low concentration level, roughly half of which is often present
because of the natural background in many locations. However, medical
experts believed that the low concentration was justified based on the
available health data and because Congress had stipulated that a national
ambient air quality standard must provide protection for all segments of
the population and include an adequate margin of safety.
Undoubtedly the standard has become a controversial issue. While
very few will disagree that this air pollutant in high concentration
levels causes serious adverse health effects, some people have questioned
the need for a standard as restrictive as the present one. Likewise,
others have questioned the basis on which the current standard was
established. Questions such as these have evolved because the data on
human health effects from exposure to low levels of photochemical oxidant
are very sparse and hence the conclusions to be drawn from these data
are somewhat controversial. Therefore, universally acceptable conclusions
cannot always be reached over such effects, and one must turn to the
wisdom and judgment of qualified experts from the medical sciences to
interpret the available data.
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In 1974, Congress commissioned the National Academy of Sciences
(NAS) to review and update the information on health effects from air
pollution, including those effects caused by photochemical oxidant.
After reviewing and interpreting the available data, these highly qualified
scientists from the various scientific and technical fields concluded:
In general, the evidence that has been accumulated
since the promulgation of the Federal ambient air quality
standards by the EPA Administrator on April 30, 1971,
supports those standards. Hence on the balance, the (NAS) /-,\
panels found no substantial basis for changing the standards. '
Although the above conclusion applied to all national standards, in
specifically addressing photochemical oxidant, the NAS noted that even
with the current standard, the risk to the general population may not be
negligible, and that there is evidence which suggests that there may not
be a completely safe level of this air pollutant for all people. A
similar conclusion has more recently been reached by members of the
World Health Organization (WHO).^
Thus, there are many medical people who are convinced that photo-
chemical oxidant in very low concentration levels can cause substantial
health effects to the general public. During the current sessions of
Congress in which Clean Air Act amendments were being considered, industry
spokesmen presented arguments against the present standard for photochemical
oxidant. Senator Domenici appeared to reflect the predominant feelings
among members of the Senate and House committees which reported out
Clean Air Act amendments when he noted that:
After listening to testimony from the medical
community and reviewing the National Academy of Sciences
report, the Senate Public Works Committee turned a
deaf ear to industry attacks on the standard. '
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Unfortunately, it is easy to become so engrossed in the controversy
over health effects from low levels of photochemical oxidant, that the
real-world situation is overlooked. In many American cities, citizens
are frequently exposed to photochemical oxidants--not at levels near the
standard where some controversy exists over the health effect—but at
levels two to five times higher than the standard where the risk of
suffering adverse effects is much higher and better demonstrated.
To put this into better perspective, the numerical value of the
photochemical oxidant standard is .08 ppm (parts per million) hourly
average, not to be exceeded more than once per year. In somewhat simpler
terms this means that: except for one hour each year, the amount of
photochemical oxidant in the air (averaged over a one hour period)
should not exceed 8 parts oxidant per 100,000,000 parts air. In many
American cities, particularly during the summer months, hourly levels of
this air pollutant frequently range between .20 ppm and .30 ppm and have
exceeded .40 ppm in some places. Thus, while arguments continue over
the health effects caused by relatively low levels of photochemical
oxidant, millions of Americans are breathing what is considered by many
medical experts to be dangerously high levels. The available medical
evidence shows that by reducing these high levels, even by relatively
small amounts, substantial health benefits can be gained. Furthermore,
technology which is reasonable in terms of its economic and social
consequences, is available and can be applied to gain many of these
benefits. Unfortunately, in the highly populated areas with maximum
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oxidant levels, there is little "danger" in the forseeable future that
oxidant reductions will even approach the .08 ppm national standard that
has generated some debate. Thus, that debate is somewhat academic.
BRIEF REVIEW OF HEALTH EFFECTS
Many elected officials may not be fully aware of the health effects
which current levels of photochemical oxidant can cause. While a full
discussion of all of the health effects data is not attempted in this
paper, a brief summary of findings from recent studies conducted by the
National Academy of Sciences, the World Health Organization, and other
medical institutes should help officials to appreciate the need for
reducing elevated levels of photochemical oxidant in their States and
communities.
Before going into further detail, a few terms which may be somewhat
unfamilar need to be defined. Photochemical oxidant is a group of
compounds found as pollutants in the atmosphere all of which are character-
ized by their oxidizing properties. While there are a large number of
compounds which can fall into this group, the one which occurs most
abundantly, and for which most is known, is ozone. Another important
chemical species measured as oxidant is a group of compounds referred to
as PAN (peroxyacyl nitrates).
It is very difficult to obtain an accurate measurement of all the
photochemical oxidant compounds in the air. Therefore, most air sampling
stations only measure ozone which generally composes over 90% of the
total photochemical oxidant in the air. Consequently the terms ozone
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and photochemical oxidant are sometimes used interchangeably. Many of
the health studies, however, have been based on ozone effects rather
than on total photochemical oxidant, and in fact, little is known about
the health effects of many specific photochemical oxidant compounds
other than ozone and PAN. Moreover, some of the other oxidants are
stongly suspected to be dangerous to humans.
The ,two previously referenced reports from the National Academy of
Sciences and World Health Organization, along with recent reports from
the National Research Council^ ' [which is composed of The National
Academy of Sciences, National Academy of Engineering and The Institute
of Medicine] and the Environmental Health Resource Center of the Illinois
(5)
Institute for Environmental Quality ' contain a wealth of medical data
showing that health effects can accompany current levels of photochemical
oxidant in many American cities. The information below has been extracted
from these documents, which are available for those wishing to further
explore the health effects of this air pollutant.
It is estimated that between five and ten percent of the general
population suffer from some form of chronic disease. As hourly concen-
trations approach .20 ppm, ozone has been clearly associated with aggra-
vating such diseases as asthma, chronic heart and lung disease, and
certain anemias. Some asthma sufferers begin to experience significantly
more attacks when hourly levels of ozone are around .15 ppm. People
that are very sensitive to air pollution begin to suffer adverse effects
at even lower concentrations. It is well documented that people who
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suffer from cardiopulmonary diseases such as asthma, emphysema, or
allergies require many hours to recover from ozone-caused attacks.
Ozone can destroy or weaken red blood cells. For example, increased
sphering (shape changing) of red blood cells in humans has been observed
after only 30 minutes of exposure to ozone at .25 ppm. Since ozone
measurements in the atmosphere are normally reported in terms of an
hourly average concentration (rather than 30 minutes) and because similar
damage to blood cells in animals has been observed at much lower concen-
trations, there is evidence that such damage can occur in some humans
when hourly ozone levels are considerably below the .25 ppm value. This
effect is of particular concern to people who may already have fragile
blood cells. In this regard about 12% of the black male population is
thought to suffer from G6PD deficiency, a disease which restricts the
reproduction of red blood cells. Thus, in such people any cell damaged
or destroyed by ozone is not readily replaced by normal body function.
Similarly, people who suffer from vitamin E deficiency because of socio-
economics, dietary habits, medication, illness, or other reasons, may
also suffer additional stresses from breathing ozone.
Although it is often thought that photochemical oxidant affects
only the sick or elderly, normal healthy people have also been observed
to suffer adverse effects from exposure to this air pollutant. In
Japan, during a smog episode in which hourly oxidant (ozone) levels
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reached .24 ppm, young school children suffered a number of adverse
effects including difficulty breathing, nausea, headaches, coughing
spells, eye irritation, throat pains, and periods of general ill feeling.
This is a level which is reached in many American cities during summer
months.
Carefully controlled laboratory experiments in this country have
shown that ozone interferes with the normal function of the lung in
healthy adults causing such effects as decreased air ventilatory functions,
biochemical changes, substantial soreness, coughing, chest tightness,
mucous expectoration, wheezing, nausea, pharyngitis, laryngitis and
malaise. In normal healthy adults, these observations have not been
demonstrated to occur below .25 ppm; however, it must be noted that
these are effects when ozone is the only air pollutant present. Members
of the National Academy of Sciences^ point out that some of these
effects can be expected to occur in the real world at ozone levels
considerably below that observed in the laboratory test. This is because
in addition to being a very toxic material, ozone is known to have
synergistic properties (i.e., the health effects are much more pronounced
when ozone and other common air pollutants are breathed simultaneously
than when breathed alone). Thus ozone can aggravate some of the health
effects that are actually caused by other air pollutants and can cause
the effects to occur at lower levels of these pollutants than would
happen if no ozone were present. Likewise, the presence of other air
pollutants can synergistically affect the observed health effects noted
during pure ozone studies.
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A number of medical researchers have demonstrated that the effects
of ozone are strongly aggravated during periods of exercise. Thus,
while a person may not feel the effects of ozone while sitting or resting,
his capability to perform tasks which require exercise can be greatly
reduced by ozone. For example, healthy high school athletes have been
observed to exhibit a decrease in performance as levels of ozone in the
air increase. Statistical analysis of these data shows that this decrease
can be detected as ozone levels reach around .12 ppm, and sharply worsen
as ozone levels become higher. Thus, high levels of this air pollutant
can affect the life style of people, perhaps without their awareness.
(4)
The National Research Council in its report^ ' noted that people tend to
limit activities which require strenuous exercise when oxidant pollutant
is high.
The Occupational Safety and Health Administration (OSHA) has deter-
mined that the air in the working environment should not average more
than .10 ppm ozone during an 8 hour work day. Normally, OSHA standards
are much higher than ambient air standards because the former are designed
to protect healthy adult workers rather than the general public. Thus,
it is sobering to note that in many American cities, ambient levels of
this air pollutant that are breathed by all people, exceed the level
that has been determined to be unsafe for normal healthy adult workers.
Other effects that have been observed in healthy humans at ozone
levels found in many parts of the country, include increased coughing,
irritations of the respiratory system, and decreased visual acuity
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(especially night vision). At levels even slightly below the current
standard, eye irritation can be experienced (not from ozone, but from
PAN and other photochemical oxidants) and increased headaches can
accompany levels near the current standard.
There are also indirect health effects and direct non-health effects
from exposure to photochemical oxidants. One researcher has reported a
significant increase in the number of automobile accidents during periods
of high levels of photochemical oxidant. The National Academy of Sciences
has estimated that damage from this air pollutant to farm crops, forests,
and material products can be as much as three billion dollars a year.
Such damage is not confined solely to areas surrounded by highly industrial
centers, as is evident from reports that the tobacco crop in the relatively
rural State of North Carolina has substained several million dollars
damage already this year from ozone in the air, much of which is trans-
ported from urban areas outside the State.
For obvious reasons, there are limitations to the type of experiments
that can be conducted with humans. For example, young children, the
elderly, and people with severe chronic illnesses cannot be subjected to
experiments which may impair their health. Yet, these groups of people
may suffer most from exposure to photochemical oxidants. It is also
difficult to obtain a measure of the effects on humans from repeated
exposure over a long period of time.
To help answer questions which cannot be answered through human
experiments, scientists have tested a variety of animals, in chambers
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where the levels of ozone can be carefully controlled and maintained for
long periods of time. Animal studies are commonly used to indicate
likely effects of substances on humans. The results from these studies
have created considerable concern among medical experts over exposure to
high concentrations of ozone for short periods of time, and exposure to
low concentrations for relatively long periods.
At levels1 and durations of exposure comparable to those experienced
in many areas of the country, serious health effects have been observed
to occur in animals. Among these are chromosome changes, permanent
damage to the elastic recoil properties of lungs, decreased fertility,
increased mortality, serious birth defects, and a very disturbing possible
link with lung cancer.
Two observations made in animal studies are of vital concern to
medical experts. One of these is that ozone appears to much more severely
affect very young animals than the adults of the species. This, coupled
with recent reports from scientists in Japan that very young human
children have been observed to experience lung airway resistance from
breathing ozone at .04 ppm, one-half the current U.S. standard, is
extremely disturbing because such effects have not been observed in
human adults at concentrations this low. The second disturbing observa-
tion from animal studies is that in very low concentrations (.08 ppm)
for several hours, ozone can reduce the capability of body defenses of
animals to fight off infectious bacteria. In this regard, The Illinois
Institute for Environmental Quality has concluded:
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Since ozone has recently been shown to predispose
the lungs to infection, increase vascular resistance,
and affect the young more readily than adults, children
must be carefully considered, especially because of
their constant outdoor activities.^ '
Medical research has not, as yet, established a direct relationship
between the effects observed in animals and the expected effects in
humans. In many historical Situations, however, the causes and effects
of various diseases have been found to be similar in both humans and
animals.
Medical experts outside this country have also concluded that
levels of photochemical oxidant must be kept low in order to provide
protection to the general public. Argentina (.10 ppm), Canada (.08
ppm), Japan (.06 ppm), and Romania (.005 ppm) have established very
stringent standards for this air pollutant (averaging time for all the
above standards is one hour except Romania which uses a thirty minute
average). Other countries can be expected to establish national standards
soon in light of work accomplished by the World Health Organization to
help them reach such decisions. The chairman of the panel for photochemical
oxidant from this organization has reached the following conclusion:
It is apparent that any primary protection standard
between .05 and .10 ppm will provide the narrowest margin
of safety against some possible detrimental effects in the
more susceptible segments of the population. There would
seem to be little justification for exceeding .10 ppm for
a primary protection standard, and the fact that the thres-
hold limit value for occupational exposures in the United
States is .10 ppm should reinforce the conclusion that this
is the upper limit for aoRrimary protection standard for
the general population.^ '
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THE EFFECT OF REDUCING CURRENT OXIDANT LEVELS
As noted in the reports from the National Academy of Sciences, the
National Research Council and World Health Organization, many of the
health effects from photochemical oxidant have been found to be dose-
response related. This means that at some given level, called the
threshold, some people are observed to begin to experience an effect.
Then as levels increase above the threshold, the initial sufferers begin
to experience more severe effects, while other people begin to feel the
symptoms experienced by the initial group at the lower levels. Thus as
the levels increase both the severity of the effects and the number of
people affected increase.
Ideally, it would be desirable to maintain the level of photochemical
oxidant or any other air pollutant well below any identified threshold
value. Unfortunately, for many health effects the threshold value of
oxidant is not known. From the previous discussion, however, it seems
clear that for many of the effects, the threshold is considerably below
the levels of photochemical oxidant currently being experienced in many
areas of the country. Consequently, by beginning now to reduce the
level of photochemical oxidant to which people are exposed, health
benefits can be realized, even if the threshold value for every health
effect is not reached right away.
An idea of how photochemical oxidant reduction can provide health
benefits is contained in a recent report on "Mobile Source Goals Beyond
1980" prepared by a Joint Task Force of the Federal Agencies for the
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President's Energy Resources Council. ' In this report several health
effects from photochemical oxidant were studied. Dose-response relation-
ships for six symptoms were developed, which included aggravation of
heart and lung disease, aggravation of asthma, incidence of chest pain,
headaches, eye irritation, and incidence of coughing spells. From the
work by this task force the aggregate effects from these six symptoms
were found to be reduced by over 90% in cases where peak photochemical
oxidant levels were reduced from .30 ppm to .15 ppm (a 50% improvement
in air quality). Thus, in this case, even though the .08 ppm standard
would not be met, substantial health benefits could be gained. Since
many of the other health effects are probably related in a similar
manner and clearly have thresholds below current photochemical oxidant
levels, benefits for other than the above six symptoms could also be
expected.
The concept that reducing current levels of photochemical oxidant
will provide health benefits is not new or unique with this paper.
Similar findings have been made by a number of knowledgeable scientists,
including members of the National Academy of Sciences, ' academic
scholars, ' ' and independent panels of medical experts.'' ' In general
these scientists report that the earlier these reduction programs can
begin, and the larger the amount of reduction that can be obtained, the
greater will be the health benefits. Similar conclusions have also been
reached for reducing material and vegetation damage.
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THE FORMATION OF PHOTOCHEMICAL OXIDANT IN THE ATMOSPHERE
The subject of controlling (or reducing the levels of) photochemical
oxidant is very technical and has almost developed a language of its
own. Yet, to understand the reasons behind various approaches to controlling
this air pollutant requires some knowledge of how oxidants are formed in
the atmosphere, and why they have become such a nationwide problem.
Photochemical oxidants are usually not emitted directly into the
atmosphere by any source, but are formed through chemical reactions
between other types of air pollutants, which are sometimes called precur-
sors. These reactions require sunlight as a source of energy. The rate
at which photochemical oxidant is formed depends upon the mixture of
precursor air pollutants present as well as sunlight intensity. The
reactions can be very dynamic in nature. That is, an oxidant can be
formed and then react with some other compound to form a new molecule
which can later be decomposed to again form oxidant.
This complex atmospheric chemistry occurs as the air mass moves
across the country, generally from west to east. In this movement,
which sometimes can stagnate for several days at one place, precursor
pollutants are added to the air as it passes over sources of these
pollutants, most of which are located in the immediate vicinity of urban
areas. The net result of this process is that the level of photochemical
oxidant present in a given urban area can be influenced by sources of
the precursor pollutants in the immediate area, and by sources in other
urban areas many miles away over which the air has previously passed.
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To complicate matters further, some of the precursors react very
rapidly after being emitted into the air, while others can remain in the
air for relatively long periods of time before the oxidant forming
reactions take place. Consequently, pollutants which enter the air as
it passes over a city, can then later lead to high levels of photochemical
oxidant in rural areas which may be essentially free of man-made sources
of air pollution. Also ozone and other oxidants which form in the air
over cities can be entrapped in an inversion layer, transported aloft
for many miles, then later be dispersed to the ground at some point many
miles downwind. This latter effect was recently demonstrated by the
highly publicized da Vinci test conducted in St. Louis. In this test
ozone generated over the city became entrapped in an inversion layer.
Using a highly instrumented ballon, this pocket of high ozone concentration
was tracked as it remained aloft (at about 2500 feet) and moved eastward
away from St. Louis. When the inversion layer broke up, the ozone
dispersed and caused violations of the standard in the middle of a wheat
field 150 miles from St. Louis.
For the above reasons, photochemical oxidant air pollution tends
not to be just a localized problem around smoke stacks, but is usually
spread across large areas. To control this air pollutant, requires
utilization of the factors over which man has some control—that being
the manmade precursor pollutants which are emitted into the air and
later react to form photochemical oxidant.
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The two primary precursor air pollutants which lead to the formation
of photochemical oxidant are hydrocarbon compounds and oxides of nitrogen.
Historically, the major thrust for controlling photochemical oxidant has
been through limiting the amount of hydrocarbon compounds emitted into
the air. These compounds are emitted by a large number of diversely
located sources including automobile exhaust, gasoline evaporation from
handling and storage facilities, petrochemical plants, dry cleaning
facilities, degreasing operations, paint shops, solvent facilities,
along with many products commonly used in day-to-day living. There are
also natural sources of hydrocarbon such as oil seepage, pine trees and
rotting foliage.
There has been some implication that controlling manmade hydrocarbon
emissions may not be effective in reducing photochemical oxidant levels
because the air contains an abundant amount of hydrocarbon which is
emitted from natural sources. However, after reviewing the avai.able
(14)
data, the National Academy of Sciencesv ' recently concluded that the
evidence indicates that at a maximum, only .05 to .06 ppm of the oxidant
found in the air can be attributed to non-manmade (or natural) sources
of hydrocarbons.
In laboratories throughout this country and abroad, many tests have
been conducted in a device called a "smog chamber" to determine the
process by which photochemical oxidant is formed. This device is simply
a chamber in which environmental factors such as temperature, sunlight
intensity and the amounts of various air pollutants can be carefully
controlled to simulate the real-world atmosphere. Results from such
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tests, which have been conducted in government, university and industry
laboratories, have uniformly and consistently revealed that when the
mixture of reactive hydrocarbons* and nitrogen oxides is similar to that
normally found in the air over major urban areas (that is the ratio of
reactive hydrocarbons to nitrogen oxides is less than about 30 to 1)
reducing the amount of reactive hydrocarbon present is a very effective
means of lowering the amount of photochemical oxidant formed. Where the
mixture is similar to that normally found in the air over rural areas
(i.e., above ratio greater than about 30 to 1) reducing the amount of
hydrocarbon may be somewhat less effective in reducing photochemical
oxidant levels.
Results from the "smog chamber" data and well established chemical
laws have lead most air pollution control experts to conclude that the
most effective means of reducing current levels of oxidants is through
controlling the hydrocarbon compounds that are emitted into the air by
sources in and around major urban areas. By so doing, the oxidant which
is formed over these areas can be reduced as can the oxidant and precursor
pollutants that are transported outside the urban area.
Another very important reason for focusing control of hydrocarbon
emissions on major urban areas is that oxidant levels are sufficiently
high in such areas that current control technology will be effective in
reducing these levels. On the other hand, for those areas where oxidant
* Reactive hydrocarbons are those which react very rapidly in the
atmosphere as distinguished from other hydrocarbons which react somewhat
slower.
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levels are usually relatively low (such as rural areas or isolated small
towns), but occasionally may exceed the standard, there is some uncertainty
over how effective localized control programs would be.
The California Institute of Technology recently completed a study^ '
which shows that over the last ten years, controlling hydrocarbon
emissions has proven very effective in reducing the level of photochemical
oxidant in the Los Angeles Basin. During this time period the average
daily emissions of reactive hydrocarbon in the Basin have been reduced
by 18% through various control programs, while over the same time period
the average hourly oxidant levels across the Basin were reduced by 19%.
Also, it was found that programs to reduce hydrocarbon emissions have
been extremely effective in reducing the number of times hourly oxidant
levels reach very high values (over .20 ppm). When the data are statis-
tically examined, a clear trend is established which reveals that whenever
programs were implemented to reduce hydrocarbon emissions (such as new
standards for automobile exhaust) corresponding reductions in the levels
of photochemical oxidant were experienced.
It is often argued that trends in Los Angeles may not necessarily
represent what can be accomplished at other locations. However, in the
San Francisco Bay Area, which has historically experienced considerably
lower levels of photochemical than those in Los Angeles, the same type
relationship exists between hydrocarbon emission control programs and
photochemical oxidant concentrations as noted above for Los Angeles.
Although somewhat less convincing because of limited air sampling data
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and emission inventories, there are strong indications that a number of
non-California cities have also experienced reductions in oxidant
levels through hydrocarbon emission control program. Sampling data
collected in Cincinnati, Denver, Philadelphia, St. Louis, and Washington,
D.C. from 1964 through 1973 reveal a general downward trend in the
levels of photochemical oxidant. The percentage change in peak concentra-
tions for these cities is not too unlike that found in Los Angeles and
San Francisco. Specific emission inventories over the time period are
not available for the non-California cities, however, each has experienced
some form of hydrocarbon emission control. For example, automobiles
produced between 1963 and 1967 emitted 20% less hydorcarbons than pre-
1963 models. Likewise, cars produced since 1968 have experienced syste-
matic reductions in hydorcarbon emissions, so that a new 1973 model
emitted (on the average) about 68% less hydrocarbons than a pre-1963
model.
Because of growing concern over the repeated number of times ozone
watches had to be issued, the State of Illinois recently undertook an
independent study to determine the most effective way to control ozone
in that State. After a lengthy review of the entire ozone situation,
(12)
the basic conclusion reached^ ' was that emphasis should be placed on
the reduction of hydrocarbon emissions in urban areas. Similar conclu-
sions have also been reached by other States.
CONTROL PROGRAMS
In a typical urban area, hydrocarbon emissions come from a large
number of sources which are usually located somewhat randomly throughout
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the area. The type of sources are usually quite different in each urban
area. For example, in one location oil refineries may produce most of
the hydrocarbon emitted into the air, while in another, automobile
exhaust may be the largest contributor. Because of the wide differences
in types of sources found in various cities it is not possible to outline
a single control program which can be used for every city. Rather, it
will be necessary to examine each city individually to determine the
sources, amounts, and types (fast or slow reacting) of hydrocarbon
emissions before an effective control program can be established for
that particular city. For this reason, extensive cooperation between
governments at all levels will be necessary if the oxidant problem is to
be solved. Through effective planning and rational judgment, programs
can be developed to reduce the threat of photochemical oxidant to the
health and welfare of the nation, without creating chaos in the life
style of the general public. The understanding, wisdom and leadership
of elected officials are essential in the movement to clean up the air
citizens breathe. Without the support of these officials, no air pollution
control program can be fully effective.
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Reference List
1. "Air Quality and Automobile Emissions Control - A Report by the
Coordinating Committee on Air Quality Studies", Volume 2, National
Academy of Sciences, Prepared for the Committee on Public Works, U.S.
Senate, September 1974, U.S. Government Printing Office.
2. "Environmental Health Criteria for Photochemical Oxidants", World
Health Organization, Draft Report EHE/EHC/WP/75.5, March 20, 1975.
3. Domenici, Pete V., U.S. Senator "The Clean Air Act Amendments of
1976: Balancing the Imponderables," Congressional Record, March 22,
1976, S3900.
4. "Ozone and Other Photochemical Oxidants", National Research Council,
Washington, D.C., 1976.
5. "Health Effects and Recommended Alert and Warning System for Ozone",
The Environmental Health Resource Center, Institute for Environmental
Quality, State of Illinois, Document Number 75-17, July, 1975.
6. "Air Quality Noise and Health Report of a Panel of the Interagency
Task Force on Motor Vehicle Goals Beyond 1980", March, 1970, available
through the Office of the Secretary of Transportation, Publications
Section, TAD-443.1, Washington, D.C.
7. "Air Quality and Automobile Emissions Control - A Report by the
Coordinating Committee on Air Quality Studies", Volume 4, National
Academy of Sciences, Prepared for the Committee on Public Works, U.S.
Senate, September 1974, U.S. Government Printing Office.
8. Downing, Paul B., Controlling Oxidants in Los Angeles, Environmental
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