Biomonitoring Equivalents for interpreting mandelic and phenylglyoxylic acid in urine resulting from exposures to styrene and ethylbenzene.

Styrene and ethylbenzene are chemicals used in the plastic and rubber industry and are present in cigarette smoke. Regulatory authorities have developed toxicological reference values to conduct risk assessments for potential exposures. The extent of exposures to ST and ETB can be assessed via biomonitoring of shared metabolites mandelic acid and phenylglyoxylic acid in urine. The metabolism of ST and ETB and the excretion of MA and PGA in urine following controlled inhalation exposures in humans has been studied. In this evaluation, we derive Biomonitoring Equivalents (BEs) for interpretation of general population biomonitoring data. BEs are defined as the concentration or range of concentrations of a chemical or its metabolite in a biological medium (blood, urine, human milk, etc.) that is consistent with existing health-based TRVs such as a reference concentration. The BE values derived in this manuscript are screening values that can help public health officials and regulators interpret biomonitoring data for styrene and ethylbenzene. Examples of interpretating existing biomonitoring data available from the National Health And Nutrition Examination Survey are provided, with additional considerations given to understanding potential sources of confounding associated with body mass index and sex.