Ethylene Oxide Exposure in U.S. Populations Residing Near Sterilization and Other Industrial Facilities: Context Based on Endogenous and Total Equivalent Concentration Exposures

Patrick J Sheehan,Eric D Winegar,Heather N Watson,Christopher R Kirman,Ryan C Lewis,James S Bus

doi:10.3390/ijerph18020607

Abstract

Given ubiquitous human exposure to ethylene oxide (EO), regardless of occupation or geography, the current risk-specific concentrations (RSCs: 0.0001–0.01 ppb) from the U.S. Environmental Protection Agency (EPA) cancer risk assessment for EO are not useful metrics for managing EO exposures to the general U.S. population. The magnitude of the RSCs for EO are so low, relative to typical endogenous equivalent metabolic concentrations (1.1–5.5 ppb) that contribute ~93% of total exposure, that the RSCs provide little utility in identifying excess environmental exposures that might increase cancer risk. EO monitoring data collected in the vicinity of eight EO-emitting facilities and corresponding background locations were used to characterize potential excess exogenous concentrations. Both 50th and 90th percentile exogenous exposure concentrations were combined with the 50th percentile endogenous exposure concentration for the nonsmoking population, and then compared to percentiles of total equivalent concentration for this population. No potential total exposure concentration for these local populations exceeded the normal total equivalent concentration 95th percentile, indicating that excess facility-related exposures are unlikely to require additional management to protect public health.

Highlights

Published: 12 January 2021In 2016, the U.S Environmental Protection Agency (EPA) Integrated Risk InformationSystem (IRIS) assessment of ethylene oxide (EO) estimated risk-specific concentrations (RSCs) of 0.0001 to 0.01 parts per billion by volume, associated with a 10−6 to 10−4 increase in inhalation cancer risk, respectively [1]
This study proposes and evaluates the utility of a total exposure metric incorporating both background endogenous and exogenous EO exposures to help inform the health significance of excess ambient air exposures to EO
Samples were collected at various distances from the facility to characterize the reference ambient air EO concentrations from nonindustrial sources, which, in turn, would help inform what fraction of the EO in air in the vicinity of a facility might be related to facility emissions

Summary

Introduction

Published: 12 January 2021In 2016, the U.S Environmental Protection Agency (EPA) Integrated Risk InformationSystem (IRIS) assessment of ethylene oxide (EO) estimated risk-specific concentrations (RSCs) of 0.0001 to 0.01 parts per billion by volume (ppb), associated with a 10−6 to 10−4 increase in inhalation cancer risk, respectively [1]. Ambient air samples were collected at selected locations, in the vicinity of emitting U.S. facilities, to characterize EO concentrations for local populations. Samples were collected at various distances from the facility to characterize the reference ambient air EO concentrations from nonindustrial sources (background concentrations), which, in turn, would help inform what fraction of the EO in air in the vicinity of a facility might be related to facility emissions. EO concentration in ambient air was nationally (0.13 ppb) calculated for EO monitoring at 27 monitoring locations, as part of the EPA’s NATTS and UAT monitoring program stations, sampled between October 2018 and September 2019 [5]. The overall mean for EO concentration for local background EO concentration (0.14 ppb) for the eight industrial facilities evaluated was calculated for 27 individual locations sampled at various times between September 2018 and August 2020 (Table 4). The national and local background monitoring programs contained the same number of monitoring locations, were sampled in overlapping time-periods and provided equivalent results.

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Conclusion