Air Pollution

What is air pollution? It is the presence of substance that is not normally part of the atmosphere’s composition. The atmosphere is composed of approximately 78 percent nitrogen and 21 percent oxygen. It also contains small amounts of other gases, such as water vapor, carbon dioxide and hydrogen. Any substance that is not part of this normal gaseous makeup is called a pollutant.
There is many kinds of air pollutants: smoke, dust, ash, pollen, various gases and other substances. Many of these come from sources other than man and his activities. They have always been present in the atmosphere. They come from activities of plants and animals and even from outer space called meteoric dust. These pollutants are seldom harmful. Indeed, they are often beneficial. Without atmosphere dust, for example, rain and show would never fall.
Nature easily handles her own forms of air pollution. Heavier pollutants soon settle out of the air. Rain one of nature’s most effective "antipollution devices", washes dust and other pollutants from the atmosphere.
Various natural cycles help maintain the atmosphere’s chemical balance. For example, animals and plants take oxygen from the air and release carbon dioxide. During photosynthesis, green plants remove carbon dioxide and give off water vapor and oxygen. Water vapor rises from the surfaces streams, lakes and seas. Excess water comes out of the atmosphere as dew, rain and snow.
Man’s activities threaten this natural system of checks and balances. Chimney, factories, airplanes and automobiles are discharging pollutants into the air at an ever-increasing rate. Many scientists fear that the cycles of the earth and the atmosphere may not to able to cope with this increased pollution.
Can air pollution kill you? There is little doubt that is at least a contributing factor in deaths from diseases such as emphysema and lung cancer. Evidence also indicates a strong relationship between air pollution and cardiovascular death, bronchitis, and all types of cancer. Death rates among elderly people or those who already have respiratory and hearth ailments increase sharply during periods of high air-pollution levels. Construction workers who inhale asbestos fibers may develop lung cancer.
In addition, we know that air pollutants irritate the eyes, throat and lungs, causing sore throats, coughing and so on. Children living in areas with high air-pollution levels have a greater incidence of asthma and eczema (a skin disease) than do children in less polluted areas.
Human beings are not the only living things harmed by air pollution. Many plants are also damaged. In fact, the effect on vegetation is often a clue to the existence of air pollutants that are not noticeable in other ways. Carbon monoxide, hydrocarbons, sulfur compounds, metals, acid and ozone are serious treats to most vegetation. Plants absorb these pollutants through their leaves. The leaves may develop holes, become discolored. Eventually they may die. This may lead to the death of the entire plant.
(Adapted from The Book of Popular Science)