Suitability of new and existing ambient ethylene oxide measurement techniques for cancer inhalation risk assessment.

Ethylene oxide (EtO) is an industrial gas that was recently reassessed to pose significant additional cancer risk at low ambient concentrations. The objective of this study is to evaluate the capabilities of existing and novel techniques to measure ambient EtO at concentrations relevant for assessing cancer risk. We present the first comparison of background ambient EtO measurements between the standard offline TO-15 techniques and two new cavity ringdown spectroscopy (CRDS) instruments, the Picarro G2920 Ethylene Oxide Gas Analyzer and the Entanglement Technologies AROMA-ETO, at a site in Atlanta, GA. Then, we analyzed background EtO measured at EPA NATTS sites across the US. Finally, we used TO-15 measurement data to assess EtO cancer risk at three near-source sites. We find that the TO-15 method has low precision for collocated samples (NME ranges from 24% to 63%), and measurements made with TO-15 pressurized samplers are biased 27% low compared to those from TO-15 passive samplers. Both CRDS methods are biased low compared to TO-15 methods (88% and 31% low bias for Picarro and AROMA, respectively), and TO-15 methods observe a seasonal peak during summer (June to September) whereas Picarro observes no seasonal trend. From our near-source assessment, we find only one site with notable elevation in cancer risk prior to EtO controls installation. Our results suggest that measurement techniques need further development to accurately assess near-source EtO cancer risk. Because different techniques measure distinct EtO trends, EtO cancer risk studies that rely on current measurement capabilities should subtract simultaneous background observations from near-source observations measured by the same method to account for these real or artificial background trends.