Air Pollution

Air pollution is the accumulation in the atmosphere of substances that, in sufficient concentrations, endanger human health or produce other measured effects on living matter and other materials.

Among the major sources of pollution are power and heat generation, the burning of solid wastes, industrial processes and especially transportation. The six major types of pollutants are carbon monoxide, hydro carbons, nitrogen oxides, particulates, sulfur dioxide and photochemical oxidants.

Smog has seriously affected more persons than any other type of air pollution. It can be loosely defined as a multisource, widespread air pollution that occurs in the air of cities.

As a coal economy has gradually been replaced by a petroleum economy, photochemical smog has become predominant in many cities. Its unpleasant properties result from the irradiation by sunlight of hydrocarbons and other pollutants in the air. Irradiation produces a long series of photochemical reactions. The product of the reactions include organic particles, ozone, aldehydes and organic acids. Sulfur dioxide, which is always present to some extent, oxidizes and hydrates to form sulfuric acid and becomes part of the particulate matter. Automobiles are polluters even in the absence of photochemical reactions. They are responsible for much of the particulate material in the air. They also emit carbon monoxide, one of the most toxic constituents of smog.

All types of smog decrease visibility and with the possible exception of ice fog are irritating to the respiratory system.

Statistical studies indicate that smog is a contributor to malignancies of many types. Photochemical smog produces eye irritation and lacrimation and causes severe damage to many types of vegetation, including important crops. Acute effects include an increased mortality rate, especially among person suffering from respiratory and coronary ailment.