Group 1: Carcinogenic to humans. There is sufficient evidence of carcinogenicity in humans. Group 2A: Probably carcinogenic to humans. Limited evidence in humans and sufficient evidence in animals. Group 2B: Possibly carcinogenic to humans. Limited evidence in humans and less than sufficient evidence in animals. Group 3: Not classifiable as to its carcinogenicity to humans. Inadequate evidence in humans and animals. Group 4: Probably not carcinogenic to humans. Evidence suggests lack of carcinogenicity in humans and animals.
