The Sterilizer Next Door: Ethylene Oxide Emissions and Community Cancer Risk
By Paul E. Rosenfeld, M.S., Ph.D., Principal Environmental Chemist, RoseyFields LLC, Santa Monica, California
A workhorse chemical with a serious downside
Ethylene oxide (EtO) is used to sterilize roughly half of all sterile medical devices in the United States because, unlike heat or radiation sterilization, it does not damage sensitive medical equipment, but it is also a highly potent carcinogen whose fenceline emissions from sterilization facilities have prompted a wave of nationwide community exposure litigation and regulatory action. RoseyFields LLC’s air dispersion modeling and human health risk assessment practice includes ethylene oxide emissions analysis for commercial sterilization and chemical manufacturing facilities.
EPA’s 2016 risk reassessment as the regulatory turning point
In 2016, EPA’s Integrated Risk Information System substantially increased its cancer risk estimate for EtO inhalation, based on updated epidemiological analysis, a revision that increased the estimated cancer risk associated with a given ambient EtO concentration by roughly 30 to 60 times the agency’s prior estimate and triggered nationwide reassessment of facilities previously considered low-risk (US EPA, IRIS: Ethylene Oxide, 2016).
Why the 2016 reassessment reshaped community risk maps overnight
Because EPA’s National Air Toxics Assessment models community cancer risk using the agency’s own IRIS toxicity values, the 2016 EtO potency revision caused numerous census tracts near sterilization facilities to newly appear as elevated-cancer-risk areas in EPA’s own modeling, even though no additional EtO had actually been emitted, a distinction crucial to explaining to a lay jury or judge why community concern emerged when it did.
The epidemiological basis for EtO’s carcinogenicity
IARC classifies ethylene oxide as carcinogenic to humans (Group 1), based on evidence of lymphoid and breast cancer in exposed worker cohorts, and the compound acts as a direct-acting alkylating agent capable of causing DNA damage at the point of contact, a mechanistic profile that helps explain effects at lower exposure concentrations than many other airborne carcinogens (IARC, Ethylene Oxide, Vol 100F).
EPA’s 2024 sterilization facility emissions rule
In 2024, EPA finalized a rule under the Clean Air Act tightening emissions standards for commercial sterilization facilities, requiring most existing facilities to reduce EtO emissions by more than 90 percent, a regulatory action explicitly grounded in the updated 2016 cancer potency assessment and years of subsequent community exposure litigation and advocacy (US EPA, Commercial Sterilization Facilities Rule, 2024).
Reconstructing historical exposure before continuous fenceline monitoring existed
Because EtO fenceline monitoring is a comparatively recent regulatory requirement, community exposure litigation frequently requires reconstructing historical emissions using facility permit records, sterilization cycle logs, and equipment specifications, then applying AERMOD dispersion modeling calibrated to the specific facility’s historical operating parameters to estimate concentrations at nearby residences over the relevant exposure period.
Why chronic, low-concentration exposure is the central scientific question
Unlike an acute release event, EtO sterilization facility litigation typically involves years or decades of continuous low-concentration fenceline emissions, requiring an exposure assessment structured around chronic daily intake and EPA’s IRIS-derived unit risk factor rather than a single peak-concentration analysis.
The community response pattern seen nationally
Following the 2016 EPA reassessment, communities near sterilization facilities in Illinois, Georgia, Michigan, Pennsylvania, and elsewhere organized around the newly identified elevated cancer risk, prompting facility closures, community relocation assistance programs, and litigation in multiple states, a pattern reflecting how a single federal toxicological reassessment can generate coordinated impacts across a geographically dispersed industry.
Distinguishing occupational from community EtO exposure
Sterilization facility workers historically faced substantially higher EtO exposures than nearby residents, and OSHA’s occupational permissible exposure limit of 1 ppm as an 8-hour time-weighted average reflects a workplace standard distinct from the far lower ambient concentrations at issue in fenceline community exposure litigation, requiring exposure assessments to clearly distinguish the two populations and their applicable benchmarks (OSHA, 29 CFR 1910.1047).
Why EtO litigation will likely continue expanding
With EPA’s 2024 rule still working through a multi-year facility compliance timeline, and with community cancer-cluster investigations near sterilization facilities continuing in multiple states, ethylene oxide is likely to remain an active area of environmental exposure litigation for years. RoseyFields.com walks through Dr. Rosenfeld’s ethylene oxide exposure assessment work in more detail.
References
1. US Environmental Protection Agency. Toxicological Review of Ethylene Oxide. Integrated Risk Information System (IRIS). Washington, DC: US EPA; 2016.
2. IARC Working Group on the Evaluation of Carcinogenic Risks to Humans. Ethylene Oxide. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Vol 100F. Lyon, France: International Agency for Research on Cancer; 2012.
3. US Environmental Protection Agency. National Emission Standards for Hazardous Air Pollutants: Miscellaneous Organic Chemical Manufacturing and Commercial Sterilization Facilities. 40 CFR Part 63. Fed Regist. 2024;89(58):20670-20785.
4. US Environmental Protection Agency. 2018 AirToxScreen: Ethylene Oxide Risk Estimates. Washington, DC: US EPA.
5. Occupational Safety and Health Administration. Ethylene Oxide. 29 CFR § 1910.1047. Washington, DC: US Department of Labor.
6. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Ethylene Oxide. Atlanta, GA: US Department of Health and Human Services; 1990.
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8. US Food and Drug Administration. Ethylene Oxide Sterilization for Medical Devices. Silver Spring, MD: US FDA.
9. National Institute for Occupational Safety and Health. Ethylene Oxide: Occupational Exposure. Cincinnati, OH: CDC.
10. US Environmental Protection Agency. Fenceline Monitoring Requirements for Ethylene Oxide Commercial Sterilizers. Washington, DC: US EPA.
11. Rosenfeld PE. RoseyFields LLC: Ethylene Oxide Air Dispersion Modeling and Risk Assessment. Santa Monica, CA: RoseyFields LLC; 2026.
12. Steenland K, Stayner L, Deddens J. Mortality analyses in a cohort of 18,235 ethylene oxide exposed workers: follow up extended from 1987 to 1998. Occup Environ Med. 2004;61(1):2-7.
13. US Environmental Protection Agency. Clean Air Act National Emission Standards for Hazardous Air Pollutants. 40 CFR Part 63.
14. US Environmental Protection Agency. Toxicological Review of Benzene (Noncancer Effects). Integrated Risk Information System (IRIS). Washington, DC: US EPA; 2003.