Ethylene oxide is a small, colorless gas that has played an outsized role in modern industry and medicine. It sterilizes medical equipment that cannot be cleaned with heat, keeps certain spices and cosmetics free of microbes, and is used to make antifreeze, plastics, textiles, and detergents. But alongside its benefits comes a stark reality: ethylene oxide is a proven human carcinogen, and long-term exposure can increase the risk of breast cancer, lymphoid cancers, and other serious illnesses. For years, communities in Illinois and Georgia have been at the center of lawsuits against sterilization companies accused of releasing dangerous amounts of the chemical into surrounding neighborhoods. Now the litigation has arrived in California, with residents near Sterigenics facilities in Vernon and Ontario raising concerns that are supported by official government records documenting violations and emissions.
The South Coast Air Quality Management District (AQMD) began investigating Sterigenics in Vernon after community complaints and its own monitoring revealed worrisome levels of ethylene oxide in the air. AQMD’s public investigation page makes clear that regulators treated the facility as a potential health hazard requiring close scrutiny. The records show that the agency did not stop at monitoring; it moved quickly to enforce controls, demanding reductions and putting Sterigenics on notice that its operations were under watch. This was not a routine inspection—it was a response to emissions of a known carcinogen in one of the most densely populated regions in the country.
By May 2022, AQMD’s warnings had escalated into formal violations against the Vernon facility. In its violation report, the agency described multiple failures by Sterigenics to maintain air pollution controls and operate permitted equipment, leading to a substantial release of ethylene oxide. These included not keeping equipment in good operating condition and using unpermitted storage tanks, thereby putting residents at risk. The violation notice ordered corrective measures and highlighted the need for immediate changes. For lawyers and residents alike, this was a turning point: official government documents now confirmed that emissions had crossed the line into regulatory violations.
Just a few months later, in October 2022, AQMD cited Sterigenics again—this time at its Ontario facility in San Bernardino County. The violations there mirrored the problems in Vernon, reinforcing that the issue was not isolated to a single plant. The Ontario records documented elevated emissions and regulatory breaches, making clear that ethylene oxide was escaping into the surrounding community. AQMD’s enforcement actions demanded reductions and corrective steps, setting the stage for broader questions about whether Sterigenics’ practices posed a systemic risk across California.
Los Angeles County Public Health added its weight to the matter, issuing a joint enforcement action and a community notification about ethylene oxide emissions in Vernon. The department’s notice warned residents about the presence of a carcinogen in their neighborhood and explained what was being done to reduce exposure. This communication was significant because it came from a public health authority, not just an air regulator, and it acknowledged openly that people had reason to be concerned. For attorneys representing nearby residents, this type of public health warning provides important documentation linking community exposure to potential health outcomes.
AQMD monitoring records show that outdoor air measurements near the Sterigenics facility in Vernon detected ethylene oxide in the surrounding neighborhood. Levels near the plant reached up to 20 parts per billion (ppb), while community samples were at typical background concentrations. To put this in perspective, the U.S. Environmental Protection Agency has calculated that continuous lifetime exposure to just 0.0001 ppb corresponds to a one-in-a-million increased cancer risk. This means some measurements were hundreds of thousands of times higher than the federal one-in-a-million cancer benchmark, highlighting why local agencies treated the situation as urgent and why residents are alarmed.
Ethylene Oxide Chemical Structure
At the federal level, the Environmental Protection Agency’s January 2025 interim registration review decision offered a different angle. The EPA reaffirmed that ethylene oxide is carcinogenic to humans and acknowledged the risks to communities living near sterilization facilities. Yet its thresholds for acceptable exposure were higher than the strict standards used by agencies like the CDC and ATSDR. Where local agencies and public health departments treated ethylene oxide as an urgent risk, EPA’s approach reflected a balancing act between health science and industrial feasibility. For those following the litigation, this contradiction matters: it creates a gap between what local records show as immediate violations and what federal standards might still classify as permissible.
The arrival of litigation in California brings all of these threads together. Plaintiffs can now point to official AQMD violation notices in Vernon and Ontario, public health warnings from Los Angeles County, and EPA’s own acknowledgment that ethylene oxide is a carcinogen. These records form the backbone of legal claims, showing not only that emissions occurred but that regulators documented them and recognized the risks. In Illinois, similar records played a decisive role in lawsuits that ended with major settlements. In California, the groundwork is being laid in the same way, with government documents serving as evidence of both emissions and regulatory concern.
What makes the California situation especially important is its scale. Vernon is a heavily industrial city just south of downtown Los Angeles, surrounded by working-class neighborhoods. Ontario sits at the edge of the Inland Empire, a region that has grown rapidly and is home to millions. The presence of sterilization facilities in these locations means large populations may be affected by even small releases of ethylene oxide. For residents, the litigation is not about abstract regulations but about the air they breathe and the risks they carry home to their families.
The contradictions between agencies add fuel to the legal debate. AQMD and Los Angeles County Public Health have treated ethylene oxide as a matter of urgent enforcement, issuing violations and warnings. EPA, while recognizing the carcinogenicity, has set higher thresholds that many see as less protective. The CDC and ATSDR, meanwhile, continue to stand by much stricter health benchmarks. These differences will be central in California courtrooms, where lawyers argue not only over whether emissions occurred but over what standards should define unacceptable risk.
Ethylene oxide litigation in California is still at an early stage, but the foundation has already been laid by government records. AQMD violations, county health notices, and EPA reviews provide the kind of documentation that courts rely on. For residents, the stakes are personal. For regulators, the stakes are about credibility and enforcement. And for Sterigenics, the stakes may be financial and reputational, as California joins the growing list of states where the company must answer for its emissions. The government records show clearly that ethylene oxide has been released, that rules have been broken, and that communities have been warned. Litigation simply takes the next step—asking what justice and accountability should look like when a known carcinogen drifts into the air people breathe.
Sources
South Coast AQMD – Sterigenics Emissions Investigation (Vernon, CA): https://www.aqmd.gov/home/news-events/community-investigations/sterigenics
South Coast AQMD – Violations Issued to Sterigenics Facility in Vernon (May 2022): https://www.aqmd.gov/docs/default-source/news-archive/2022/sterigenics-may6-2022.pdf
South Coast AQMD – Violation at Sterigenics Facility in Ontario (Oct 2022): https://www.aqmd.gov/docs/default-source/news-archive/2022/sterigenics-nov-oct20-2022.pdf
Los Angeles County Public Health – Joint Enforcement Action / Community Notification on EtO Emissions: https://publichealth.lacounty.gov/eh/docs/safety/joint-enforcement-action-community-notification-ethylene-oxide-emissions-sterigenics-vernon.pdf
EPA – Interim Registration Review Decision for Ethylene Oxide (Jan 2025): https://www.epa.gov/system/files/documents/2025-01/eto-interim-registration-review-decision-case-2275.pdf
Disclaimer
This article is for informational purposes only and is not intended as legal or medical advice. If you believe you have been exposed to ethylene oxide or any other hazardous chemical, consult a qualified medical professional immediately. For emergencies involving potential toxic releases, fire, or explosion hazards, call 911 without delay.