Слова к части II. amount[s'maunt] п количество; сум- contrary['kantren] (to) а противо-

' Air Pollution ^

A man can live without food for weeks and without water for days, but he can live without air for only a few minutes. Accordingly, air is the most immediately vital resource.

S Lesson 20 ^ 207

Since the amount of contamination until recent years was small in relation to the vastness of the atmosphere, little trouble resulted. In the last few decades, however, continuing contamination is producing con­centrations that are harmful to men, animals and olants.

Air pollution is produced by different air contaminants in different areas. By general definition, air pollution is the introduction of hazard­ous materials into the atmosphere as the result of man's activities.

Some pollutants, such as smoke from fores/t fires, may stem from
either natural or human causes. Pollution, as cjiscussed here, will imply
the possibility of control. * '*'■■/ ' *

In order to understand the problem of air pollution more fully, let us briefly examine the nature and size of our atmosphere. «Pure» air is, of course, a mixture of many kinds of gases, including about 78 per cent nitrogen, 21 per cent oxygen, less than 1 per cent argon, 0,03 per cent carbon dioxide, traces of several other gases and varying amounts of water vapour. Uo far, contrary to popular belief, the percentage of oxy­gen in the air has not been reduced significantly with the Advent of air pollution. However, man's activities are reducing the world supply of green plants which are the only sources of oxygen at an alarming rate. An acre of foodcrop plants produces far less* oxygen than the acre of forest it may have replaced.,A? цсге of jp^eAent^ftoduces no oxygen at all. Thus, some scientists feeove may eventualljdrun into oxygen deple­tion problems with the elimination of green plants) though other air problems are more^>^i^a^s4ime. 4 v'■ ^l'n - iv

The problem of air pollution is further' complicated by the existence
of inversion layers over many of the world's major cities. An inversion
layer is a layer of warmer air over a cooler surface layer.of air, and
results from an area's topographical character and proximity to water.
The inversion layer acts as an air trap, preventing air pollutants from
mixing with upper layers of air. Thus, instead of pollutants being diluted
through twelve miles of atmosphere, they may be held within several
hundred feet of the ground. 4^)} (; '

The problem of air pollution is of great social importance. Russian research workers have established, after analysing the results of hun­dreds of medical checkups that there is a definite correlation between the degree of air pollution and rates of incidence and death from bron­chitis, pneumonia and lung cancer. The researchers believe that if air pollution were decreased by 50 per cent then the incidence of these diseases would go down by 25 per cent.

208 'О Learning to Understand a Medical Text

An adequate rtumber of facts has now been established which prove that there is a connection between air pollution and the death-rate from all types of cancer.

Упражнение 5. Прочтите нижеприведенные суждения. Найдите в тексте
В предложения, более полно выражающие мысль данных суждений, И\
прочтите их вслух. 1,

1. In the last few decades continuing contamination has become harm­ful to men, animals and plants. 2. Air pollution is produced in different ways. 3. Man's activities are significantly reducing the percentage of oxygen in the air. 4. The inversion layer acts as an air trap. 5. There is a definite correlation between air pollution and the death-rate from cancer and lung diseases.

Упражнение 6. Основываясь на тексте В, назовите основные источники загрязнения воздуха в современном городе.