"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 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.
Pollution can take two major forms: local pollution and global pollution. In the past, only local pollution was thought to be a problem. For example, coal burning produces smoke, which in sufficient concentrations can be a health hazard. One slogan, taught in schools, was "dilution is the solution to pollution". The theory was that sufficiently dilute pollution could cause no damage. In recent decades, awareness has been rising that some forms of pollution pose a global problem. For example, human activity (primarily nuclear testing) has significantly raised the levels of background radiation all over the world, which may lead to human health problems. Awareness of both kinds of pollution, among other things, has led to the environmentalism movement, which seeks to limit the human impact on the environment.
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."
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 sources of pollution, such as nuclear power plants or oil tankers, can release very severe pollution when accidents occur. 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, and asthma. Certain pollutants are known to cause particular illnesses: for example, mercury compounds cause Minamata disease.
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.
Toxic Release Inventory - tracks how much waste companies release into the water and air. Gives permits for releasing specific quantities of these pollutants each year.
Superfund - manages Superfund sites and the pollutants in them (CERCLA).
Scorecard.org - lots of info about pollution in the US. Just enter your zip code. Colored maps also show how bad certain types of pollution are in your area.
Rachel's Environment and Health News - Weekly news about how the polluted environment affects people, and what corporations and governments are doing (or not doing) about it. Also in Spanish.
Essential.org - Some organizations related to consumers and consumer protection, including pollution.
