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12 Lawrence K. Wang et al.

ments were printed and used as the basis for establishing ambient air quality standards.
Now, the validity of these criteria, as well as other related data and reports, has become
open to question by industry-appointed lawyers, doctors, and others. They defend that
pollution does not differ from any other substance contacted by living matter: Small
concentrations and dosages may be beneficial, whereas excessive amounts are usually
harmful. The problem lies in deciding what “excessive” means. (In an extreme sense,
this term relates not only to living plants and animals but also to material objects, as
there are those who claim that all matter, including rocks and so forth can be shown to
be living.)
It goes without saying that air pollution is harmful to all living things and their envi-
ronment. Air pollution can be a contributing factor to chronic bronchitis, emphysema,
and lung cancer. It can increase the discomfort of those suffering from allergies, colds,
pneumonia, and bronchial asthma. It also can cause dizziness, headaches, eye, nose and
throat irritations, increased nasal discharges, nausea and vomiting, coughing, shortness
of breath, constricted airway passages, chest pains, cardiac problems, and poison in the
stomach, bloodstream, and organs.
Many of the air pollution effects observed on people and animals come from disaster
occurrences. In these situations, in which SO , particulates, and other pollutants were
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present in high concentrations, illness and death rates rose. In the Meuse Valley, the
Belgian disaster victims were mainly older persons with heart and lung problems. In
Donora, Pennsylvania, nearly half of the town’s population became ill, severity increas-
ing with age. Those who died were older persons with cardiac or respiratory problems.
In London, a similar situation occurred, and in addition a number of prize animals being
exhibited in London at that time died or were adversely affected. In one London
episode, 52 of 351 animals were severely affected with acute bronchitis, emphysema,
or heart failure, or combinations of these.
Plants vary widely in their resistance to pollution damage. Certain species are very
resistant to one pollutant and highly sensitive to another, whereas in other species, the
reverse could be true. Other contributing factors include plant age, soil, moisture,
nutrient levels, sunlight, temperature, and humidity. In general, plants are more sensi-
tive to air pollution than humans. Using SO as an example, plants that are particular-
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ly affected by this pollutant include alfalfa, barley, cotton, wheat, apple, and many soft
woods. Resistant crops are potatoes, corn, and the maple tree. Chronic injury occurs at
concentrations of 0.1–0.3 ppm SO ; acute injury occurs above 0.3 ppm. Damage can
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range from retarded growth to complete destruction of the vegetation. Aesthetic as well
as true economic cost can have definite associations with this problem. Laboratory
studies have shown that nearly all pollutants can have adverse effects on plants. It is
important to note that in a noncontrolled situation, it is difficult to determine whether
damage is caused by air pollution, crop disease, bacteria, insects, soil nutrient defi-
ciencies, lack of moisture, or mechanical damage because the effects of many of these
can appear similar.
Material damage resulting from air pollution can be extensive because nearly
everything is bathed continuously in air. Corrosion and erosion of metals is a common
example. To list a few problems, pollution deteriorates painted surfaces, oxidizes rub-