Substance that causes or aggravates tumors or other types of
cancer. A substance is considered carcinogen if it is (1) found to be a carcinogen or potential carcinogen by the International
Agency For
Research On Cancer, (2)
listed as carcinogen or potential carcinogen in the latest
edition of
Annual Report On Carcinogens published by the US National
Toxicology Program or, (3) is regulated by the US
Occupational Safety &
Health Administration (OSHA) as a carcinogen. Carcinogens enter a body through inhalation (of
asbestos fiber and cigarette
smoke, for example), ingestion (of heavy metals and pesticides, for example), and
absorption (of dyes and hydrocarbons, for example) through
skin.
Because the
development of cancer is through irreversible cellular
damage, no
safe dose-limit is assumed for carcinogens. In comparison,
toxic substances
cause irreversible health damage only when
exposure to them exceeds a certain
dose limit. Most
synthetic chemicals, especially
industrial solvents and
plastics, are either already-determined carcinogens or suspected carcinogens.