Biomonitoring Equivalents (BE) dossier for trihalomethanes

Measurements of whole blood concentrations of trihalomethanes (THMs) have been reported in persons in the general population. Risk assessments based on administered doses of THMs have been conducted for both cancer and non-cancer health endpoints by the US Environmental Protection Agency; however, no health-based standards exist for interpreting measured blood concentrations of THMs. Existing physiologically based pharmacokinetic models for laboratory rats, dogs, and humans were used to estimate the average blood concentrations consistent with the points of departure, reference doses (RfDs), and, where applicable, cancer potency estimates to provide biomonitoring equivalents (BEs) for these exposure guidance values. The models were also used to characterize the short term variations in blood concentrations that could result from various exposure regimens, even when exposures remain consistent with the underlying RfDs. The BE values derived in this exercise can be used as one component of a screening-level assessment of future population biomonitoring THM data.