Air and HealthThere is accumulating evidence that air pollution is producing harmful effects in man. Many studies reveal that air pollution may cause reduced visibility, eye irritation, and respiratory irritation. Some medical studies link air pollution with lung cancer, emphysema and other diseases. The severity of symptoms of illness increases proportionately with concentration of pollutants in the air. The first effects of air pollutants are likely to lead to discomfort. Though not associated with the development of disease, even in sensitive groups, these effects are capable of disturbing the comfort of the population in residential or industrial areas. This level is the one at which eye irritation occurs. Also in this category are levels of pollutants that damage vegetation and reduce visibility. A more serious level of pollutants, or possibly combination of pollutants, is likely to lead to insidious or chronic diseases or to significant alteration of important physiological function in a «sensitive group» such as the aged or sufferers from chronic respiratory or heart disease. Pollution would not necessarily be a risk for persons in good health. But under conditions of intense pollution, this «sensitive group» may die. Three episodes of acute air pollution have been characterized by sudden death. These tragedies occurred in Belgium's Meuse Valley in 1930, in Donora, Pennsylvania, in 1947, and in London in 1952. In each case a heavy fog settled over the area and did not lift; in each case the phenomenon was produced by a temperature inversion or a layer of warm air over a layer of cold air, and in each case there was a heavy concentration of smoke and pollutants. During these periods, 63 deaths in Meuse Valley, 20 deaths in Donora, and 3.000 deaths in London were attributed to air pollution. Most of those who died were elderly people already suffering from diseases of the respiratory or circulatory systems. This disaster in London was a major factor in hastening the Clean Air Act of 1956. The emission of dark smoke from industrial chimneys was prohibited for the whole country. Three general types of substances are known to pollute the atmospheres of all industrial environments: chemical, radioactive and biological. Chemical pollutants are the major concern because of expanding industrial, automobile and domestic wastes. However, radioactive pollutants add to the total radiation exposure in both urban and rural air. Biological dusts and pollens likewise may cause effects, especially in persons who react to them with hay fever, asthma, and other allergies. Упражнение 1. Просмотрите текст еще раз и назовите факторы, способствующие загрязнению воздуха. Упражнение 2. Найдите в тексте ответы на следующие вопросы и зачитайте их: 1. What effect is air pollution producing in man? 2. What are the first effects of air pollution? 3. Who were the victims of three episodes in Meuse Valley, Donora and London? 4. What did the Clean Air Act prohibit? 5. What substances are known to pollute the atmospheres of industrial environments? .
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