Leukemias and blood dyscrasias following exposure to chlordane and heptachlor.

We present 25 new cases of blood dyscrasia, including leukemias, production defects, and thrombocytopenic purpura, generally following home termite treatment with the chlorinated hydrocarbon pesticides chlordane and heptachlor (C/H). These newly reported cases are consistent with 34 previously published case reports associating blood dyscrasias with C/H exposure. Additionally, the newly reported leukemias are consistent with epidemiologic evidence of excess risk of leukemia and other cancers in C/H-exposed populations and with the carcinogenic action of C/H in animals. The importance of case reports in warning of the association of blood dyscrasias to C/H exposure is emphasized. Until the voluntary halt in production in July 1987, millions of homes in the United States were treated with chlordane and heptachlor for termites even though their agricultural uses were phased out in 1978, largely on the grounds of "imminent hazard" because of carcinogenicity. In view of the recognized myelotoxicity, carcinogenicity, and other chronic toxic effects of these pesticides, a national program for monitoring all homes treated is urgently needed to detect persistent contamination.