Ethylene oxide

Ethylene oxide was first synthesized in 1859 and found industrial importance as an intermediate for making ethylene glycol (antifreeze), surfactants, and polyester fibers [1]. Its sterilizing properties — it kills bacteria, viruses, and spores at low temperatures — made it essential for sterilizing heat-sensitive medical devices including catheters, surgical tools, and medical implants that would be damaged by steam autoclaving. Approximately 50% of all sterile medical devices in the US are sterilized with ethylene oxide [2]. Commercial sterilization facilities — distinct from hospital in-house sterilizers — have been operating in industrial and suburban areas across the country, and their emissions were largely unmonitored for decades. In 2018, following OSHA inspection revelations at a Sterigenics facility in Willowbrook, Illinois, residents discovered their community had cancer risks from EO air emissions that were among the highest in the nation [3]. Similar facilities in Georgia, Texas, and other states were subsequently found to have significant community exposure issues.

Occupational inhalation in medical sterilization facilities and in ethylene oxide chemical production is the dominant high-dose exposure route [1]. Before tighter controls, workers at commercial sterilization facilities received chronic low-level EO exposures that substantially elevated their cancer risk. Community air near sterilization facilities is the primary non-occupational pathway — EO is a gas at room temperature and disperses from facility emissions into surrounding neighborhoods [2]. Hospital workers who work near in-house medical sterilizers have occupational exposure if sterilizer chambers are not properly sealed and ventilated. The chemical is also used in agricultural fumigation [3].

Ethylene oxide is a known human carcinogen (IARC Group 1) — the highest classification [1]. The evidence base includes multiple well-designed occupational cohort studies showing elevated lymphoid cancers (non-Hodgkin lymphoma, lymphocytic leukemia) and breast cancer in workers with EO exposure. The mechanism is direct DNA alkylation — EO is a direct-acting mutagen that forms N7-hydroxyethylguanine DNA adducts, generating G-to-A transition mutations [2]. The EPA's cancer unit risk estimate for EO is one of the highest of any regulated air pollutant, meaning even relatively low ambient concentrations represent meaningful lifetime cancer risk. OSHA's permissible exposure limit for EO was tightened in 1984 following recognition of the cancer risk [3].

Workers at medical device sterilization facilities — both large commercial operators and hospital central supply departments — carry the highest occupational EO cancer risk [1]. Community members who live within a mile of commercial EO sterilization facilities face elevated cancer risk from ambient air exposure — EPA mapping has identified dozens of such communities across the US [2]. Workers in ethylene glycol, surfactant, and polyester production facilities also have occupational EO exposure.

Check EPA's Air Toxics Screening Assessment (NATA) tool and your state's air toxics database to determine if a commercial sterilization facility near you has flagged elevated EO cancer risk [1]. If so, request your local air quality management district to conduct stack testing and monitoring and push for facility compliance with EPA's strengthened National Emission Standards for Hazardous Air Pollutants (NESHAP) for sterilization facilities [2]. Hospital workers: ensure your facility's EO sterilizer rooms have proper ventilation, interlocked chamber door systems, and continuous air monitoring. Pursue alternatives to EO sterilization for devices that can be sterilized by other methods — vaporized hydrogen peroxide and gamma irradiation are alternatives for some device types [3].