Glossary / Health hazards
Carcinogen
A carcinogen is a substance, mixture or agent that causes cancer or increases how often cancer occurs in exposed people or animals. Classification rests on the strength of evidence, not on how potent the chemical is.
Explanation
Cancer from chemical exposure usually appears many years after the exposure began. That long delay is why carcinogens are treated cautiously: by the time harm is visible, the exposure that caused it may be decades in the past, and a single short exposure may tell you very little.
Under the GHS and OSHA HazCom (29 CFR 1910.1200), carcinogenicity is a health hazard class. Category 1 covers known or presumed human carcinogens, with sub-categories 1A and 1B reflecting whether the evidence comes mainly from humans or from animals. Category 2 covers suspected human carcinogens. Carcinogens carry the health hazard pictogram and the signal word Danger or Warning depending on category.
Several outside bodies also publish lists. IARC sorts agents into groups 1, 2A, 2B and 3, and the National Toxicology Program and Proposition 65 keep their own lists. These lists do not always agree, because each uses different evidence rules and was last updated at a different time.
A classification describes hazard, not risk. Risk depends on dose, duration, route and how well exposure is controlled. A carcinogen handled in a closed system with good controls can pose far less risk than a weaker one handled carelessly.
What to do and watch for
- Look for the health hazard pictogram and the words may cause cancer or suspected of causing cancer on the label.
- Substitute a non-carcinogenic material wherever you can, since lowering exposure is harder than removing the hazard.
- Check whether OSHA has a specific standard for the substance, which may add monitoring and medical surveillance duties.
Where it appears on an SDS
- Section 2: Hazard identification. The GHS carcinogenicity category and the H350 or H351 hazard statement are listed here, with the pictogram and signal word.
- Section 11: Toxicological information. Toxicological information summarizes the evidence and often names IARC, NTP or OSHA listings for the substance.
SDS content and wording vary by supplier. This page is general reference and does not replace the current SDS for your product.