Characterization of Background Exposures to Ethylene Oxide in the United States: A Reality Check on Theoretical Health Risks for Potentially Exposed Populations near Industrial Sources

Ethylene oxide (EO) is an industrial chemical and sterilant that is released into ambient air from natural and unregulated anthropogenic sources that contribute to background exogenous exposure and from regulated industrial sources that contribute to additional exogenous exposure for near-facility populations. Metabolic processes contribute to substantial background endogenous exposures to EO, complicating the interpretation of the relation between total background exposure and the health significance of added industrial exogenous exposure. In 2021, Kirman and colleagues characterized the total and endogenous equivalent background concentrations for U.S. populations, which are substantially greater than the USEPA 2016 EO cancer reassessment risk-specific concentrations (0.00011–0.011 ppb), suggesting that the consideration of background exposure could be used as a reality check for the utility of the reassessment in managing EO risk for industrially exposed populations. New exposure biomarker data and background ambient concentration data for EO have become available since the 2021 assessment and are used here to refine the estimates of U.S. population total and endogenous equivalent background EO concentrations. Refined equivalent background concentrations as well as total equivalent exposure estimates for U.S. smokers provide context as to the health significance of near-industry population added exposure and a reality check for the utility of USEPA and TCEQ risk-specific concentrations in managing and communicating EO risk.