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Summary of the Public Health Goal for Diethylhexyl Phthalate (DEHP)

A Public Health Goal (PHG) of 12 ppb is developed for diethylhexyl phthalate (DEHP) in drinking water. DEHP is a phthalic acid ester used primarily as a plasticizing additive in the production of polyvinyl chloride resins. DEHP has a very low degree of acute toxicity, with oral LD50 values ranging from 26 to greater than 34 g/kg in a variety of species. Toxicity studies have shown the liver and testes to be the principal target organs. DEHP has also been reported to cause adverse reproductive and developmental effects in laboratory animals. Chronic oral administration of DEHP has been associated with a dose-dependent increase in hepatocellular carcinomas in a National Toxicology Program (NTP) bioassay using B6C3F1 mice and Fischer 344 rats, as well as in industry-sponsored repeat studies conducted with additional doses and biochemical analyses for peroxisome proliferation. Both the International Agency for Research on Cancer (IARC) and the California Department of Health Services (DHS) have found DEHP to demonstrate sufficient evidence for carcinogenicity in experimental animals. Using data from an oncogenicity study in rats, the DEHP drinking water concentration associated with a de minimis theoretical lifetime excess cancer risk level of 10-6 was calculated to be 0.012 mg/L (12 ppb) based on the linear method and an LED10 of 33.4 mg/kg-day (human equivalent). Using the non-linear method with the same LED10,a value of 230 ppb was calculated. Based on reproductive and developmental toxicity, a noncarcinogenic value of 100 ppb can be calculated. The Office of Environmental Health Hazard Assessment (OEHHA) adopts the lowest value of 12 ppb as the PHG for DEHP in drinking water because of the current uncertainty in the potential for DEHP to cause cancer in humans.