"Pollution" refers to harmful environmental contaminants and to the act or process of polluting the environment. Generally the process needs to result from human activity to be regarded as pollution. Even relatively benign products of human activity are liable to be regarded as pollution, if they precipitate negative effects later on. The nitrogen oxides and ozone produced by industry are often referred to as pollution, for example, although the substances themselves are not harmful. In fact, it is solar energy (sunlight) that converts these compounds to smog.
Whether something is pollution can depend on context. Blooms of algae and the resultant eutrophication of lakes and coastal ocean is considered pollution when it is fueled by nutrients from industrial, agricultural, or residential runoff.
Although carbon dioxide is not toxic—and actually stimulates plant growth—because it is a greenhouse gas that fosters global warming, carbon dioxide is sometimes referred to as pollution, in particular that produced by the combustion of fuels for human use. More often and more properly carbon dioxide from such sources are labelled neutrally as "emissions."
Traditional forms of pollution include air pollution, water pollution, while a broader interpretation of the word has led to the ideas of ship pollution, light pollution and noise pollution.
Serious pollution sources include chemical plants, oil refineries, nuclear waste dumps, regular garbage dumps (many toxic substances are illegally dumped there), incinerators, PVC factories, corporate animal farms creating huge amounts of animal waste. Some of the more common contaminants are: lead (like in lead paint), chromium, zinc, arsenic, benzene.
Pollutants are thought to play a part in a variety of maladies, including: cancer, lupus, immune diseasess, allergies, asthma.
The United States Environmental Protection Agency was supposed to establish "acceptable" levels of exposure to contaminants. One of the ratings chemicals are given are carcinogenicity, or how likely they are to cause cancer. Levels range from, not carcinogenic, likely carcinogen, known carcinogen, and unknown. But scientists are finding out that most of these levels are far too high and people should be exposed less to them. The CalEPA Office of Environmental Health Hazard Assessment has a list of more reasonable levels. (OEHHA)
The US has many departments responsible for tracking various pollutants.
Regulation and Monitoring
Additional Resources
See also: pollutant, petroleum, renewable energy, toxicology