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California Proposes Lowering NSRL for Ethylene Oxide Under Prop 65

California State House

On April 7, 2023, the California Office of Environmental Health Hazard Assessment (OEHHA) proposed lowering the "No Significant Risk Level" (NSRL) from ethylene oxide from 2 to 0.058 micrograms (µg) per day under the state’s Safe Drinking Water and Toxic Enforcement Act of 1986, also known as Proposition 65. Ethylene oxide is listed as a carcinogen under Proposition 65.

Proposition 65 requires companies to provide warning statements where their products cause an “exposure” to carcinogens and/or reproductive toxicants. The warning requirements do not apply when an exposure falls within the “safe harbor.” For carcinogens, the safe harbor is the "No significant risk level" (NSRL), or the level of exposure that would result in not more than one excess case of cancer in an exposed population of 100,000 people, assuming exposure over a 70-year lifetime.

The update to the NSRL for ethylene oxide would be made by amending Title 27, California Code of Regulations, section 25705(b). Written comments concerning this proposed regulatory action are due by May 23, 2023. In the Notice of Proposed Rulemaking, OEHHA stated that a copy of the Final Statement of Reasons for this regulatory action may be obtained, when it becomes available, on the OEHHA website at