Pollutants

Pollutants

Main article: Pollutant

A pollutant is a waste material that pollutes air, water or soil. Three factors determine the severity of a pollutant: its chemical nature, the concentration and the persistence.

Sources and causes

Air pollution produced by ships may alter clouds, affecting global temperatures.

Air pollution comes from both natural and man made sources. Though globally man made pollutants from combustion, construction, mining, agriculture and warfare are increasingly significant in the air pollution equation.^[10]
Motor vehicle emissions are one of the leading causes of air pollution. China, United States, Russia, Mexico, and Japan are the world leaders in air pollution emissions. Principal stationary pollution sources include chemical plants, coal-fired power plants, oil refineries,^[14] petrochemical plants, nuclear waste disposal activity, incinerators, large livestock farms (dairy cows, pigs, poultry, etc.), PVC factories, metals production factories, plastics factories, and other heavy industry. Agricultural air pollution comes from contemporary practices which include clear felling and burning of natural vegetation as well as spraying of pesticides and herbicides^[15]
About 400 million metric tons of hazardous wastes are generated each year.^[16] The United States alone produces about 250 million metric tons.^[17] Americans constitute less than 5% of the world's population, but produce roughly 25% of the world’s CO₂,^[18] and generate approximately 30% of world’s waste. In 2007, China has overtaken the United States as the world's biggest producer of CO₂.^[21]