Biomonitoring equivalents for DDT/DDE

Biomonitoring Equivalents (BEs) are defined as the concentration or range of concentrations of a chemical or its metabolite in a biological medium (blood, urine, or other medium) that is consistent with an existing health-based exposure guideline such as a reference dose (RfD) or tolerable daily intake (TDI). BE values can be used as a screening tool for the evaluation of population-based biomonitoring data in the context of existing risk assessments. This study reviews available health based risk assessments and exposure guidance values for DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane, CAS #50-29-3) and related metabolites and degradation products DDE (1,1-dichloro-2,2-bis(p-chlorophenyl)ethane, CAS #72-55-90) and DDD (1,1-dichloro-2,2-bis(p-chloro-phenyl)ethane) based on both non-cancer and cancer risk assessments from the Food and Agriculture Organization/World Health Organization (FAO/WHO), the United States Environmental Protection Agency (US EPA), and other organizations. Laboratory data on distribution and toxicokinetics of DDT and metabolites and estimates of human elimination half-lives were used to estimate BE values (lipid-adjusted blood, serum, or plasma concentrations) corresponding to the various non-cancer exposure guidance values and cancer risk-specific doses. The BE values based on non-cancer risk assessments range from 5000 to 40,000ng/g lipid for the sum of DDT, DDE, and DDD. The BE values corresponding to a 1E-05 cancer risk level for DDT and DDE based on the US EPA assessment are 300 and 500ng/g lipid, respectively. Sources of uncertainty relating to both the basis for the BE values and their use in evaluation of biomonitoring data are discussed. The BE values derived here can be used as a screening tools for evaluation of population biomonitoring data for DDT and related compounds in the context of the existing risk assessment and can assist in prioritization of the potential need for additional risk assessment efforts for DDT relative to other chemicals.