Carcinogen classification schemes

To rank the relative hazards of chemicals considered to be potential carcinogens, governmental agencies and other bodies have developed a variety of approaches. All of these approaches are based on essentially the same types of carcinogenicity data but apply different scientific judgments to the data resulting in significant variation among the ranking systems. This article provides a summary of the most commonly used systems and the rationales used to place chemicals into the carcinogen categories of each system. Approaches included are the United Nations Globally Harmonized System of Classification and Labeling of chemicals, the classification systems of the EC Scientific Committee on Occupational Exposure Limits, the German MAK Commission, the WHO International Agency for Research on Cancer, the United States Environmental Protection Agency, the US Occupational Safety and Health Administration, the US National Toxicology Program, the US National Institute of Occupational Safety and Health, and the US American Conference of Government Industrial Hygienists.