Arsenic and inorganic arsenic compounds are human carcinogens, classified as weight-of-evidence Group A under the EPA Guidelines for Carcinogen Risk Assessment. Evidence on potential carcinogenicity from animal studies is 'inadequate,' and the evidence from human studies is 'sufficient.' Arsenic trioxide and potassium arsenite are classified as having 'sufficient' human evidence because human studies that specifically identify those compounds have been conducted and show evidence of causal association. Specific evidence on the potential carcinogenicity of o-arsenic acid, arsenic disulfide, arsenic pentoxide, arsenic trichloride, arsenic trisulfide, cupric acetoarsenite, lead arsenate, and potassium arsenate from animal studies of human studies is 'no data.' Only limited animal studies exist on calcium arsenate, sodium arsenite, sodium arsenate, potassium arsenite, and arsenic trioxide. However, since arsenic compounds are chemically convertible to the carcinogenic form(s) both in vitro and in vivo, and the exact species of inorganic arsenic that is directly carcinogenic in humans is not known, all the above inorganic species of arsenic are of equal concern. The potency factor (F) for inorganic arsenic compounds is estimated to be 142/(mg/kg/day), (derived from human epidemiology data), placing them all in potency group 1 according to the CAG's methodology for evaluating potential carcinogens.

Cover title. "June 1988." Includes bibliographical references. Microfiche.