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Environmental Protection Agency
June 1976
Air  Pollutants
                                                                                                                                         In this century, man has increased his productive
                                                                                                                                         capability a thousandfold. New industrial processes and
                                                                                                                                         a myriad of technological innovations have improved
                                                                                                                                       our lives enormously. But we are beginning to realize that
                                                                                                                                       the cost of this progress may also be heavy. Man has
                                                                                                                                       underestimated his ability to damage the environment and
                                                                                                                                       threaten not only the welfare of himself but the lives of his
                                                                                                                                       children as well.
                                                                                                                                         In recent years scientists have begun to look at man-made
                                                                                                                                       pollution to determine where it originates, how  we can
                                                                                                                                       reduce it, and most importantly, what effects pollution has
                                                                                                                                       on human health.
                                                                                                                                         One area of utmost concern to scientists is air pollution.
                                                                                                                                       Most of what we know  about the effects of air  pollution on
                                                                                                                                       human health we have learned in the last decade. And only
                                                                                                                                       in the last five years have we begun to understand the way
                                                                                                                                       individual pollutants react with other chemicals to affect
                                                                                                                                       our health.
                                                                                                                                         Scientists are convinced that air pollution is a very real
                                                                                                                                       contributing factor to the three major types of diseases that
                                                                                                                                       cause sickness and death in our society—heart disease,
                                                                                                                                       lung disease, and cancer.
                                                                                                                                       Research has shown that air
                                                                                                                                       pollution will accelerate the
                                                                                                                                       rate of disease in those persons
                                                                                                                                       already afflicted, and earlier
                                                                                                                                       death is a very real possibility.
                                                                                                                                         The problem of air pollution
                                                                                                                                       is not limited to those
                                                                                                                                       persons who live in the
                                                                                                                                       cities or near the sources of
                                                                                                                                       pollution. Studies have
                                                                                                                                       .shown that air pollution can
                                                                                                                                       actually be hazardous to people
                                                                                                                                       who live fifty or a hundred
                                                                                                                                       miles away from the pollution
                                                                                                                                       source. This is because some
                                                                                                                                       common pollutants are
                                                                                                                                       transformed while moving through
                                                                                                                                       the atmosphere, by chemical
                                                                                                                                       reactions with sunlight into
                                                                                                                                       more hazardous pollutants, such
                                                                                                                                       as photochemical oxidants,
                                                                                                                                       which attack our lungs and
                                                                                                                                       respiratory system.
                                                                                                                                                                          Prompted by widespread public support, Congress in
                                                                                                                                                                        1970 enacted the landmark Clean Air Amendments, now
                                                                                                                                                                        usually called simply the Clean Air Act, a law which
                                                                                                                                                                        continues to be of major importance in protecting public
                                                                                                                                                                        health and welfare from air pollution.
                                                                                                                                                                          It gave the U.S. Environmental Protection Agency (EPA)
                                                                                                                                                                        responsibility for setting and enforcing standards on
                                                                                                                                                                        various types of air pollutants suspected of having an impact
                                                                                                                                                                        on public health and welfare. The Agency subsequently set
                                                                                                                                                                        air quality standards for six common classes of pollutants:
                                                                                                                                                                        sulfur oxides, paniculate matter, carbon monoxide, photo-
                                                                                                                                                                        chemical oxidants, nitrogen oxides and hydrocarbons.
                                                                                                                                                                          Following is a description of the six major air
                                                                                                                                                                        pollutants and their effects on human health:
                                                                                                                                                                        Sulfur Oxides
                                                                                                                                                                          Approximately 95 percent of pollution-related sulfur
                                                                                                                                                                        oxide emissions  in this country are in the form of sulfur
                                                                                                                                                                        dioxide, a by-product of combustion of fossil fuels such as
                                                                                                                                                                        oil and coal. The remaining 5 percent are in the  form  of  a
                                                                                                                                                                        variety of sulfur compounds that  eventually are transformed
                                                                                                                                                                        into sulfuric acid, another pollutant.
                                                                                                                                                                                                  Coal or oil-burning power
                                                                                                                                                                                                plants produce most of the
                                                                                                                                                                                                sulfur dioxide emissions, while
                                                                                                                                                                                                autos account for only about
                                                                                                                                                                                                1 percent.  Sulfur dioxide
                                                                                                                                                                                                oxidizes in the atmosphere to
                                                                                                                                                                                                form sulfates, a paniculate
                                                                                                                                                                                                form of sulfur, the effects of
                                                                                                                                                                                                which depend on particle
                                                                                                                                                                                                size, dispersion by weather
                                                                                                                                                                                                conditions, and the presence of
                                                                                                                                                                                                other pollutants which may
                                                                                                                                                                                                magnify the effects.

                                                                                                                                                                                                  The levels of sulfates  in the
                                                                                                                                                                                                air often exceed those levels
                                                                                                                                                                                                where adverse  human effects
                                                                                                                                                                                                begin to appear. Sulfate
                                                                                                                                                                                                concentrations greater than
                                                                                                                                                                                                9 or 10 micrograms per  cubic
                                                                                                                                                                                                meter of air will aggravate
                                                                                                                                                                                                asthma, lung and heart disease,
                                                                                                                                                                                                and the lung function in children.

  The effect of sulfur dioxide is magnified by the presence
of other pollutants such as photochemical oxidants and
by-products such as sulfuric acid and hydrogen sulfide.
The combination of these is known to affect the respiratory
  Many scientists also believe this exposure to sulfates
may be cumulative,  causing or increasing the likelihood of
respiratory illness such as bronchitis, emphysema, and
asthma. Studies show that children exposed to continuous
high SO., concentrations are more likely to develop
respiratory illness when high  concentrations of particulates
are present.

Participate Matter
  Total suspended particulates (TSP) is a term for the
measurement of all particles in our air, including soot,
mists, and sprays. TSP includes  a wide range  of non-toxic
materials such as dust and dirt, and many other materials
that we know or suspect to be toxic, such as  beryllium,
lead, asbestos, certain hydrocarbons which may be
carcinogenic, suspended sulfates and nitrates, and possibly,
radioactive elements.
  The amount of toxic materials in our air will vary
geographically, depending on the man-made and natural
sources in a particular area.  To date, few studies have been
conducted on the health effects of individual particles
because of the wide  range of differences in the makeup of
paniculate  concentrations. Particulate matter is studied
for the most part as  a single contaminant, and most studies
relate paniculate concentrations to death, respiratory
illness, and breathing problems in urban industrial areas
where energy supplied by fossil fuel consumption is a
major concern.
  The effects of paniculate air pollution on health are
related to injury to the surfaces of the respiratory system,
that is, to the linings of the lungs and throat. Such injury
may be temporary or permanent. It may be confined to the
surface. However, by weakening resistance to infection,
such pollutants may affect the entire body adversely.
Chemicals carried into the lungs by particulates, for
example, may cause cancer to develop on the lung lining,
which then may spread throughout the body  and prove
fatal. Inhaled lead particulates may cause lead poisoning—
manifested by nervous and blood symptoms—while causing
very little damage to the  lung itself.
  In studies of air pollution in London and New York City,
a rise in the number of deaths has been recorded when both
smoke and sulfur oxides levels were high. Studies in  Buffalo
and Nashville also showed increased death rates,
particularly among older persons, where combined pollution
from particulates and sulfur oxides were recorded. Eye
irritation from dust  particles also can be a problem in many
Carbon Monoxide
   Carbon monoxide (CO) is a colorless, odorless,
tasteless gas commonly found in our urban atmosphere in
concentrations that can be harmful to people. It is a by-
product of combustion, and the greatest single source of
this pollutant is the automobile.
   Carbon monoxide is inhaled through the lungs and enters
the blood stream by combining with hemoglobin, the
substance that normally carries oxygen to the cells. CO
combines with hemoglobin much more readily than oxygen
does. The result is that the amount of oxygen getting to the
tissues is drastically reduced in the presence of CO, and this
can have a profound effect on our health. CO also impairs
heart function by weakening the contractions of the heart
which supply blood to the various parts of the body. The
effect of this on a healthy person is to reduce significantly
his ability to perform exercise, but in a patient with heart
disease, who is unable to compensate for the decrease in
oxygen, it can be a life-threatening  situation. A person who
has a heart attack in the presence of heavy carbon
monoxide air pollution is more likely to die than if the
attack had occurred in clean air. And carbon monoxide is
also harmful to persons who have lung disease, anemia, or
cerebral-vascular disease.
   Carbon monoxide can also affect mental function at
relatively low concentrations. Visual perception and
alertness can be affected.

Photochemical Oxidants
   Photochemical oxidants are not emitted directly into the
atmosphere but are produced by a complex series of
chemical reactions initiated when certain emissions by
autos and other sources—hydrocarbons and  oxides of
nitrogen—are exposed to sunlight. Ozone, peroxyacyl
nitrate (PAN), formaldehyde, acrolein, nitrogen peroxide,
and organic peroxides are all formed in this manner. The
presence of these pollutants in the atmosphere is dependent
on sunlight, so after nightfall their concentrations are
very low.
  This type of pollution first gained attention in  the 1940's
as the main cause of smog in Los Angeles. Since that time
photochemical smog has become common in many cities.
  Photochemical oxidants are responsible for a number of
health effects in humans. They can affect the  lungs and
eyes. They may cause respiratory irritation and even
changes in lung function. They may result in eye irritation
with the familiar symptoms of tears and inflammation. At
certain concentrations they have been shown to impair the
performance of athletes, and to affect persons with asthma.
  Ozone, the main constituent of photochemical smog, is a
severe irritant  to all mucous  membranes,  and its main
health effects are on the respiratory system. It is virtually
intolerable at levels of 1 part per million. At considerably
lower concentrations (.1 to .2 ppm) which often occur in
the air of many American cities, ozone in conjunction with
other photochemical oxidants causes a variety of health
effects which are aggravated by exercise. Ozone also has an
increased effect on respiratory function in the presence of
sulfur dioxide.

Nitrogen Oxides
   Oxides of nitrogen usually originate in high-temperature
combustion processes, and to a lesser extent in chemical
   Although measurement of this pollutant in the
atmosphere is difficult, experience has shown that in
various forms, oxides of nitrogen can affect humans as well
as materials and vegetation.
   Based on occupational exposures to nitrogen dioxide by
firemen, welders, silo fillers, miners, chemists, and other
industrial workers, we know that at high concentrations this
pollutant can be fatal to humans. At lower levels of 25 to
 100 parts per million, it can cause acute bronchitis and
   The group of pollutants known as nitrogen oxides also
 can affect lung tissue and lower the resistance of laboratory
 test animals to  influenza. Scientists suspect the same effect
 may occur in humans. In one study of schoolchildren
 living near an industrial plant producing nitrogen dioxide,
 an increase in respiratory disease was noted.
   Oxides of nitrogen also can react with hydrocarbons, in
 the presence of sunlight, to form photochemical oxidants
 which, as noted elsewhere in this pamphlet, can  affect
 human lungs and eyes as well as cause respiratory irritation.

   Motor vehicles are the chief source of hydrocarbon
 emissions, with the remainder coming from evaporation of
 industrial solvents in painting, dry cleaning, and so on, and
 from gasoline marketing and incineration.
   No adverse effects on human health are directly
 attributed to hydrocarbons. However, this pollutant does
 react under sunlight, as  indicated earlier in this pamphlet, to
 form photochemical oxidants which do affect people,
 causing respiratory irritation and the stinging, watery eye
 reaction  associated with urban smog.

   Since passage of the Clean Air Act in 1970, the Nation
 has demonstrated in these ways that it can do something
 about air pollution:
   •  Sulfur dioxide concentrations nationally were reduced
 approximately 25 percent between 1970 and 1975.
   •  The national average for paniculate matter,  which
includes  dust, smoke,  and soot,  dropped  14 percent
between  1970 and 1973.
   •  Concentrations of photochemical oxidants showed
 improvement in key cities. The Los Angeles and San
 Francisco areas were cases in point.
   •  Nationwide, the percentage of air measurements
exceeding the ambient carbon  monoxide standard declined
by more  than 50 percent between 1970 and  1975.
   •  Of 20,000 major stationary sources of air pollution
(industries, power plants, municipal incinerators, etc.) by
 1975, 16 271 or 82 percent were complying with emission
regulations or were meeting an abatement schedule.
   "The Nation has made significant progress in cleaning up
the air," declared Russell E. Train, EPA Administrator,
"but there is still a long way to go. If citizens, industries, and
officials at all levels of government work hard together, we
can and will attain the health protection goals established
in the Clean Air Act. I am confident that we have both the
will and the means to do so."