Ethylbenzene exposure in North America - an update

Abstract

Chronic ethylbenzene exposures and attendant potential health risks for United States children and prospective parents were first evaluated under the United States Environmental Protection Agency’s Voluntary Children’s Chemical Evaluation Program. Using updated data and methods, a 2015 reevaluation observed declines in ethylbenzene releases and concentrations in ambient and indoor air. Both assessments identified inhalation as the dominant exposure route and smoking as the greatest contributor, with dietary intake much lower. Children’s exposure concentrations were similar to that of adults, but their intakes were higher. Neither breastfeeding nor toy mouthing was a significant source. This report updates the previous assessments, summarizing current ethylbenzene concentrations in air and foods, exposures during the use of household and consumer products, nationally representative biomonitoring data, including expanded demographic groups, and a new survey of worker exposures in styrene production facilities. General population ethylbenzene exposures appear to have declined for all age groups. The ethylbenzene/styrene chain of commerce contributes an estimated 0.1% to total air emissions and 7%-12% to dietary concentrations. Total estimated ethylbenzene intakes are consistent with biomonitoring data. Lactational transfer is not a significant exposure pathway for breastfed infants. Production workers’ exposure is well below occupational guidelines. Updated exposure estimates for each pathway suitable for potential health risk assessment are proposed.

Kinetically-derived maximal dose (KMD) indicates lack of human carcinogenicity of ethylbenzene

“…In contrast, the central tendency for styrene exposure levels was 0.1 ppm (434 µg/m 3 ), with 1 ppm (4343 µg/m 3 ) as the upper bound. These data indicate a high degree of conservatism in using styrene exposure levels in ethylbenzene/styrene production workers as an approximation of ethylbenzene exposure, and even greater conservatism when those data are used to estimate ethylbenzene exposure among the general population (Kester and Morgott 2023 ).…”

“…Until and unless future work on ethylbenzene carcinogenesis convincingly falsifies that conclusion, research on the toxicity of ethylbenzene that is applicable for human risk assessment should be focused on ethylbenzene exposures that approximate foreseeable human exposure levels, which are more than three orders of magnitude below the KMD identified here. The most recent, comprehensive evaluation of ethylbenzene exposure (Kester and Morgott 2023 ) showed that in styrene production facilities, personal exposure concentrations to ethylbenzene collected over the 20-year period 2000 to 2020 were typically below the limit of detection (LoD). In contrast, the central tendency for styrene exposure levels was 0.1 ppm (434 µg/m 3 ), with 1 ppm (4343 µg/m 3 ) as the upper bound.…”