0.15 Air, water and soil  (Page 2/7)

Volatile organic compounds (VOCs) include hydrocarbons such as methane (CH4), propane (C3H8), and octane (C8H18), and chlorofluorocarbons (CFCs) such as dichlorodifluoromethane (CCl2F2).

Hydrocarbons are released into the atmosphere in automobile exhaust and from the evaporation of gasoline. They contribute to the formation of photochemical smog . Chlorofluorocarbons were used as propellants for aerosols and as refrigerants until it was discovered they can cause depletion of the protective ozone layer. Volatile organic compound emissions can be reduced by using vapor-recovery gasoline nozzles at service stations and by burning oxygenated gasoline in automobile engines.

Suspended particulate matter consists of tiny particles of dust, soot, asbestos, and salts, and of microscopic droplets of liquids such as sulfuric acid and pesticides. Sources of these pollutants include the combustion of fossil fuel (e.g. diesel engines) and road and building construction activity. Exposure to these particles can lead to respiratory irritation, reduction of lung capacity, lung cancer, and emphysema.

Photochemical oxidants are primarily produced during the formation of photochemical smog. Ozone (O3) is a highly reactive, irritating gas that causes breathing problems, as well as eye, nose, and throat irritation. It also aggravates asthma, bronchitis, and heart disease. Ozone and other photochemical oxidants can damage or kill plants, reduce visibility, and degrade rubber, paint, and clothes. Photochemical oxidants are secondary pollutants, and can be controlled by reducing the amount of nitrogen dioxide in the atmosphere.

Radioactive substances include radon-222, iodine-131, and strontium-90. Radon is gas produced during the decay of uranium that is naturally present in rocks and building materials made with these rocks. It is known to cause lung cancer in humans. The other radioisotopes are produced by nuclear power plants (iodine-131) or are contained in the fallout from atmospheric nuclear testing (strontium-90). They can be introduced into the food chain through plants and become incorporated in the tissues of humans and other animals. Their ionizing radiation can produce cancers, especially those related to the thyroid and bone.

Hazardous air pollutants include benzene (C6H6) and carbon tetrachloride (CCl4). Benzene is a common organic solvent with numerous industrial uses. Carbon tetrachloride was formerly used as a solvent in the dry cleaning business. It is still used in industrial processes. Exposure to these compounds can cause cancer, birth defects and central nervous system problems.

Water pollutants

The eight classes of water pollutants are: infectious agents, oxygen-depleting wastes, inorganic chemicals, organic chemicals, plant nutrient pollutants, sediments, radioactive materials and thermal pollution. Infectious agents such as bacteria, viruses, and parasitic worms enter water from human and animal waste, and cause diseases such as typhoid fever, cholera, hepatitis, amoebic dysentery, and schistosomiasis, a condition marked by blood loss and tissue damage.