Biomonitoring equivalents for ethylene thiourea

Ethylene thiourea, or ETU, is used in the rubber industry and is a degradation product and impurity in some fungicides. The general public may be exposed to low concentrations of residues of ETU in a variety of ways, including food treated with ethylene bis-dithiocarbamate (EBDC) fungicides or migration from rubber products. Biomonitoring of ETU in urine is useful for an assessment of integrated exposures to ETU across different sources and routes of exposure. In this evaluation, we review available health-based risk assessments and toxicological reference values (TRVs) for ETU and derive Biomonitoring Equivalent (BE) values for interpretation of population biomonitoring data. BEs were derived based on existing TRVs derived by Health Canada, yielding a BE of 27 μg of total ETU/L in urine associated with the Acceptable Daily Intake (ADI) and 6.7 μg/L associated with a 1e-6 cancer risk. These BEs are based on an analytical method that involves a digestion step to liberate conjugated ETU, thus producing ‘total’ ETU in urine. The BE values derived in this manuscript can serve as a guide to help public health officials and regulators interpret population based ETU biomonitoring data in a public health risk context.