What is air pollution?

of the industrial nations. The major pollutants produced by these sources are carbon monoxide, carbon dioxide, hydrocarbons(compounds of carbon and hydrogen), and nitrogen oxides(compoundsof nitrogen and oxygen). Nitrogen oxides can react in the presence of sunlight to produce a form of oxygen called ozone(O3). Ozone is the chief component of photochemical smog, which is a common form of air pollution.

• Fuel combustion used for heating or cooling in factories contributes significantly to air pollution. Electric power plants that burn coal or oil also release pollutants into the atmosphere. The major pollutants from these sources are nitrogen oxides, sulphur oxides(compounds of sulphur and oxygen), and carbon dioxide.
• Industrial processes produce a wide range of pollutants. Oil refineries discharge ammonia, hydrocarbons,organic acids and sulphur oxides. Metal smelting plants give off large amounts of sulphur oxides and particles containing lead and other metals. Plants that produce plastic foam are a major source of chlorofluorocarbons(CFC's),compounds of chlorine,fluorine and carbon.
• Burning of solid wastes often creates a very visible form of air pollution-thick,black smoke. The burning of garbage, leaves and other refuse is banned in most countries.
• Other sources of pollution include chemical sprays and organic chemicals used to start fires on charcoal grills. Forest fires also contribute to air pollution. In developing countries, the burning of forests and grasslands to clear areas for farming is a major source of air pollution.
• Natural sources also contribute to air pollution. Microbes in the guts of cattle and in rice paddies break down plant materials and release an odourless gas called methane, a type of hydrocarbon.

Effects of air pollution

• Health. When people breathe polluted air, the impurities can irritate thair air passages and their lungs. Particles often remain in the lungs and can worsen such respiratory ailments as asthma and bronchitis. Radon can cause lung cancer if inhaled in large quantities.Certain chemical compounds can cause cancer and birth defects. Ozone can aggravate emphysema(lung disease in which victims have difficulty breathing,especially when exhaling), and reduses resistance to colds and pneumonia. In addition, carbon monoxide interferes with the transfer of oxygen from the lungs to body tissues.
• Agriculture.  Air pollutants can stunt the growth of crops, harm livestock and destroy crops as well. Forests also are damaged by air pollution.
• Atmosphere. Some pollutants are not poisonous but can cause damage by altering the earth's atmosphere. For example, the amount of carbon dioxide in the atmosphere has been increasing since the early to mid-1800's, chiefly as a result of the burning of coal,oil and other carbon-containing fuels. Carbon dioxide allows sunlight to reach the earth and warm its surface, but it prevents some surface heat from escaping out of the atmosphere. This greenhouse effect may produce significant climatic changes, which could destroy many kinds of plants and animals.

Chlorofluoro carbons break down the layer of ozone in the earth's upper atmosphere. This layer protects plants and animals from harmful ultraviolet rays.

• Other effects. Most materials deteriorate faster when exposed to the pollutants present in the air. concrete and stone are dissolved by air pollutants. Metals corrode faster than usual. plastics,rubber and fabrics are also damaged by air pollutants.

Air pollution is closely realted to other forms of pollution. Sulphur dioxide and nitrogen oxides can react with water dropplets in the air to produce acid rain. Acid rain pollutes lakes and streams and in high concentrations, can harm soil fertility.