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Summary of the Public Health Goal for Chlordane

A Public Health Goal (PHG) of 3 x 10-5 mg/L (0.03 ppb) is developed for chlordane in drinking water. Chlordane (C10H6Cl8) is a broad spectrum insecticide mainly used to control termites and pests on field crops; all uses are now prohibited in the United States (U.S.). It is extraordinarily persistent and it bioconcentrates in the environment; trace levels are expected to occur in the environment for 10 or more years after last use. Animal studies in rats and mice provide sufficient evidence for the carcinogenicity of chlordane; incidences of liver carcinomas, adenomas and hemangiomas are increased. Epidemiological studies provide inadequate evidence due to methodological and other limitations. Chlordane is considered by the U.S. Environmental Protection Agency (U.S. EPA) as a probable human carcinogen (Group B2), whereas the International Agency on Research on Cancer (IARC) classifies it as possibly carcinogenic (Group 2B). On the basis of cancer risk calculations employing a cancer slope factor of 1.3 (mg/kg-day)-1, and assuming the de minimis theoretical excess individual lifetime cancer risk level of one case per one million exposed persons (1 x 10-6), a PHG of 3x10-5 mg/L (0.03 ppb) for chlordane is developed. The PHG value of 0.03 ppb is also considered to contain an adequate margin of safety (at least 6,700) for noncarcinogenic adverse effects including potential adverse effects on the developing endocrine system with low exposures.