Pollutant

Pollutants are substances which directly or indirectly damage us or the environment. Many of the compounds which are dangerous to the environment can also be harmful to us in the long-term and come from nuclear-fossilsources, like petroleum.

Pollutants can cause the destruction of areas of the environment which are protective to us. CFCswere carefully chosen not to be damaging to humans, but a side effect causes an effect held to be very damaging to the environment. They diffuse into the upper atmosphere where they stay for some time. When the sun's radiation does break them down, they turn into highly-reactive radicals. These catalysethe break down of the ozone layer, which protects us from cancer-causing ultraviolet radiationfrom the sun. CFCs are especially damaging because one CFC molecule can cause the breakdown of many millions of ozone molecules.

Some pollutants imbalance environmental processes by causing an excess of a compound which is already present naturally. In the United States, asbestos, a naturally occurring fibrous mineral, was one of the first hazardous air pollutants regulated under Section 112 of the Clean Air Actof 1970. Carbon dioxideis already present in the atmosphere - indeed it is vital for life on earth. Carbon dioxide helps keep the earth warm by trapping infra-red radiation, which would otherwise be reflected into space. However if there was too much of it present the earth's temperature would rise too high. It is thought that this would cause many destructive effects including the flooding of many low-lying areas, and an imbalance of the earth's weathersystem. Another example of these compounds are nitrate-containing fertilizers. When these leak into streams they cause plants and algae to grow too fast. This restricts light for plants on the river-bed and they decay. Microbes feed off the decaying plants and use up all the oxygen in the lake, causing fish and other plants to start dying off.

Many pollutants have a poisonouseffect on the body. Carbon monoxideis an example of a substance which is damaging to humans. This compound is taken up in the body in preference to oxygen, causing the body to suffocate and drop dead.

Some pollutants are not so dangerous by themselves until they combine with other naturally present compounds. The oxides of nitrogenand sulfurare released from impurities in fossil fuelswhen they are burnt. They react with water vaporin the atmosphere to become acid rain. Acid rain damages buildings and makes lakes uninhabitable.

Compounds can be bad pollutants not just by how damaging they are but also because of other factors, such as the length of time that they stay dangerous. Uraniumis a radioactiveelement used in nuclear fissionpower plants. Once it has been used it is often highly radioactive, meaning even small traces are able to cause cancerand damage unborn children. It will stay like this for many millions of years and has to be kept under adequate storage. Because of the difficulties in safely containing this element many people think it is inevitable that radiation will escape and cause damage to the environment. (disputed — see [[: talk:Pollutant#{{{1|Disputed}}}|talk page]])

See also

• Pollution
• Poison
• Chlorofluorocarbons(CFCs)
• Carbon dioxide
• Fertilizer
• Carbon monoxide

External links

• Agency for Toxic Substances and Disease Registryno:Miljøgift

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This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Pollutant Wikipedia article Pollutant.