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Summary of the Public Health Goal for 1,4-Dichlorobenzene (1,4-DCB)

A Public Health Goal (PHG) of 0.006 mg/L (6 ppb) is developed for 1,4-dichlorobenzene (1,4-DCB) in drinking water. The PHG is based on carcinogenic effects observed in experimental animals A National Toxicology Program (NTP) study cited in the development of the PHG provided evidence of hepatocarcinogenicity in both male and female mice. For the calculation of the PHG, cancer potency estimates were made following the 1996 proposed draft guidelines of U.S. EPA for carcinogenic risk assessment in which linearized multistage model is fit to the experimental data in order to establish lower 95% confidence bound on the dose associated with a 10% increased risk of cancer (LED10). The PHG was calculated assuming a de minimis theoretical excess individual cancer risk level of 10-6 from exposure to 1,4-DCB. Based on these considerations, OEHHA calculates a PHG of 0.006 mg/L (6 ppb) for 1,4-DCB in drinking water.