Public Health Concentrations (PHC) for Chlorthal-dimethyl (DCPA) and its Degradates Monomethyl Tetrachloroterephthalic Acid (MTP) and Tetrachloroterepththalic Acid (TPA) in Groundwater

This report describes the Office of Environmental Health Hazard Assessment (OEHHA) derivation of the public health concentrations (PHC) for chlorthal-dimethyl (DCPA) and its environmental degradates monomethyl tetrachloroterephthalic acid (MTP) and tetrachloroterepththalic acid (TPA) in groundwater.  The PHCs derived were 2 and 7 parts per billion (ppb) for DCPA, and 2500 ppb for TCA to be used for the sum of MTP and TCA concentrations.  This report included the risk characterization of human consumption of drinking water at the detected levels for a lifetime.  OEHHA conducts this evaluation under the California Pesticide Contamination Prevention Act (PCPA) (DPR, 2017a).  The California Department of Pesticide Regulation (DPR) initiated the evaluation process to determine if the detected levels of MTP and TPA would “pollute” the groundwater.  The term pollute is defined in Food and Agriculture Code Section 13142(j)1 as “to introduce a pesticide product into the groundwaters of the state resulting in an active ingredient, other specified ingredient, or a degradation product of a pesticide above a level that does not cause adverse health effects, accounting for an adequate margin of safety.”