CAS RN: 67-66-3

Carcinogenicity Evidence

Cancer Classification: Group B2 Probable Human Carcinogen
Weight-of-Evidence Characterization: Under the 1986 U.S. EPA Guidelines for Carcinogen Risk Assessment, chloroform has been classified as Group B2, probable human carcinogen, based on "sufficient evidence" of carcinogenicity in animals (U.S. EPA, 1998). Under the Proposed Guidelines for Carcinogen Risk Assessment (U.S. EPA, 1996; U.S. EPA, 1999), chloroform is likely to be carcinogenic to humans by all routes of exposure under high-exposure conditions that lead to cytotoxicity and regenerative hyperplasia in susceptible tissues (U.S. EPA, 1998). Chloroform is not likely to be carcinogenic to humans by any route of exposure under exposure conditions that do not cause cytotoxicity and cell regeneration.
Evaluation: There is inadequate evidence in humans for the carcinogenicity of chloroform. There is sufficient evidence in experimental animals for the carcinogenicity of chloroform. Overall evaluation: Chloroform is possibly carcinogenic to humans (Group 2B).
Chloroform is reasonably anticipated to be a human carcinogen based on sufficient evidence of carcinogenicity from studies in experimental animals
A3; Confirmed animal carcinogen with unknown relevance to humans.
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