Classes of Agents Associated with Carcinogenesis

1 Group A Human carcinogens Sufficient evidence from epidemiological studies to support a causal association between exposure to the agents and cancer 

2B Group C Possible human carcinogens Absence of human data with limited evidence of carcinogenicity in animals 

3 Group D Not classifiable as to human carcinogenicity Agents with inadequate human and animal evidence of carcinogenicity or for which no data are available 

4 Group E Evidence of noncarcinogenicity for humans Agents that show no evidence for carcinogenicity in at least two adequate animal tests in different species or in both adequate epidemiologic and animal studies 

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