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Many of the compounds which are dangerous to the environment can also be harmful to humans in the long-term range and come from mineral and fossil sources or are produced by humans themselves.

Pollutants can cause the destruction of areas of the environment which are essential to us. CFCs were carefully chosen not to harm humans, but they are damaging to the environment. They diffuse into the upper atmosphere where they stay for some time. When the radiation of the sun breaks them down, they turn into highly reactive radicals. These catalyse the break down of the ozone layer, which protects us from ultraviolet radiation from the sun. UV radiation can cause skin cancer. CFCs are especially damaging because one CFC molecule can cause the breakdown of many millions of ozone molecules.

Some compounds like asbestos, carbon dioxide or nitrates occur naturally and might be essential for life. These compounds can be released or are produced by humans, causing an imbalance of the natural processes. 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 Act of 1970. Carbon dioxide is 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 weather system. 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 poisonous effect on the body. Carbon monoxide is 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 in severe cases may lead to death.

Some pollutants became dangerous by reaction with other naturally occurring compounds. The oxides of nitrogen and sulfur are released from impurities in fossil fuels when they are burnt. They react with water vapor in the atmosphere to become acid rain. Acid rain damages buildings and makes lakes uninhabitable.

Another form of pollution is radioactive contamination. It occurs when highly active radioisotopes are released into the environment. Examples of radioactive contamination is the Chernobyl explosion in the USSR and the overground atom bomb tests of several nations including USA, USSR, United Kingdom and France . Some people think that radioactive waste could be released into the environment.

• Pollution
• AP 42 Compilation of Air Pollutant Emission Factors
• Poison
• Chlorofluorocarbons (CFCs)
• Carbon dioxide
• Fertilizer
• Carbon monoxide

• Agency for Toxic Substances and Disease Registry