Environmental Engineering Reference
In-Depth Information
Chronic bronchitis
has many contributing factors, including a low socioeco-
nomic status, occupational exposure, and population density; smoking is a major
factor. Air pollution resulting in smoke, particulates, and sulfur dioxide is an
additional factor.
Emphysema
mortality rates in U.S. urban areas are approximately twice the
rural rates, indicating an association with air pollution levels (sulfur oxides).
Asthma and bronchitis often precede emphysema.
Lung cancer
rates are reported to be higher among the urban populations than
the rural. The dominant factor in lung cancer is smoking. Air pollution plays a
small but continuous role.
Some generalized effects of common air pollutants and their possible rela-
tionship to these diseases are of interest. Sulfur dioxide and sulfuric acid in low
concentrations irritate the lungs, nose, and throat. This can cause the membrane
lining of the bronchial tubes to become swollen and eroded, with resultant clot-
ting in the small arteries and veins. Children are more susceptible to coughs,
colds, asthma, bronchitis, and croup. Carbon monoxide can affect the cardiovas-
cular system; in high concentrations, the heart, brain, and physical activity can
be impaired. It can reach dangerous levels where there is heavy auto traffic and
little wind. Smokers are at greater risk. Acute carbon monoxide poisoning causes
a lowered concentration of oxygen in the blood and body tissues. (See the dis-
cussion on carbon monoxide poisoning earlier in this chapter.) Ozone and other
organic oxidants, known as photochemical oxidants, are produced by the reaction
of hydrocarbons and nitrogen oxides in sunlight. Ozone is believed to be respon-
sible for a large portion of the health problems associated with photochemical
oxidants.
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Ozone and other chemicals formed in smog irritate the eyes and air
passages, causing chest pain, coughing, shortness of breath, and nausea. Ozone
can cause aging and severe damage to the lung tissues and interference with
normal functioning of the lungs at levels of 0.12 ppm to greater than 0.20 ppm.
Nitrogen dioxide in high concentrations can result in acute obstruction of the air
passages and inflammation of the smaller bronchi. Nitrogen dioxide at low levels
causes eye and bronchial irritation. In the presence of strong sunlight, nitrogen
dioxide breaks down into nitric oxide and atomic oxygen, and this then combines
with molecular oxygen in air to form ozone. Particulate matter can cause eye and
throat irritation, bronchitis, lung damage, and impaired visibility.
Benzopyrene and related compounds are known to cause some types of cancer
under laboratory conditions and have been incriminated as carcinogens. Olefins
have an injurious effect on certain body cells and are apt to cause eye irritation.
Beryllium concern relates primarily to lung disease, although it also affects the
liver, spleen, kidneys, and lymph glands. Vinyl chloride is related to lung and
liver cancer. Mercury may affect several areas of the brain as well as the kidneys
and bowels. Lead is associated with retardation and brain damage, especially in
children (see separate discussion earlier). The EPA National Emission Standards
for Hazardous Air Pollutants identify vinyl chloride, lead, benzene, asbestos,
beryllium, and mercury as hazardous. Considerable evidence has been assembled
linking air pollution with adverse health effects.
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