Benzene is a commodity chemical used primarily in the production of plastics and other chemical products. It's also a known human carcinogen. Benzene causes various types of leukemia, lymphoma, and blood diseases.

Recent studies from China and Great Britain establish that benzene can cause various hematological cancers and blood diseases at extraordinarily low doses -- a few ppmy (part per million years). A part per million year (ppmy) of benzene is a cumulative dose of just 1 ppm.

OSHA's permissible exposure limit for benzene is 1 ppm. It can still cause harm at this level, so the American Conference of Governmental Industrial Hygienists (ACGIH) has recommended a threshold limit value of .5 ppm, and the National Institute for Occupational Safety and Health (NIOSH) has set a Recommended Exposure Limit of 0.1 ppm.

These are very small amounts of benzene. Only one cup of benzene evaporated in a football field-size building (300' x 165' x 14') produces a 3.3 ppm vapor level, which is 3.3 times the OSHA standard, 6.6 times the ACGIH standard, and 33 times the NIOSH standard.

Benzene is commonly found in the environment. Industrial processes are the main sources of benzene in the environment. Benzene levels in the air can increase from emissions from burning coal and oil, benzene waste and storage operations, motor vehicle exhaust, evaporation from gasoline service stations, and use of industrial solvents. Since tobacco contains high levels of benzene, tobacco smoke is another source of benzene in air. Industrial discharge, disposal of products containing benzene, and gasoline leaks from underground storage tanks can release benzene into water and soil.

Benzene can pass into air from water and soil surfaces. Once in the air, benzene reacts with other chemicals and breaks down within a few days. Benzene in the air can attach to rain or snow and be carried back down to the ground.

Benzene in water and soil breaks down more slowly. Benzene is slightly soluble in water and can pass through the soil into underground water. Benzene in the environment does not build up in plants or animals.