Ethylene Oxide (EtO) Emissions Investigation

South Coast AQMD began investigating facilities that emit Ethylene Oxide (EtO) in March 2022, following the U.S. Environmental Protection Agency’s (U.S. EPA) reconsideration of the potential toxicity of EtO. U.S. EPA has recently been collecting new information about emissions from facilities that handle EtO throughout the country.

South Coast AQMD is taking action to identify sources and reduce emissions. These actions include:

  • Air monitoring efforts at the facilities and near the surrounding community.

  • Proposition 65 Notice disclosure if applicable.

  • A complete investigation into the facilities’ equipment and compliance with South Coast AQMD rules, regulations and permit requirements.

  • Evaluation of immediate actions to be taken by the facilities to reduce leaks or fugitive emissions, including leak and source testing.

  • Begin rulemaking that will result in stricter requirements for EtO emissions from sterilization facilities.

About Ethylene Oxide

EtO is a flammable, colorless gas used in many industries to make products including antifreeze, textiles, solvents, detergents, and adhesives. Ethylene oxide also is used to sterilize medical equipment, which is the primary activity at Sterigenics. Exposure to EtO can irritate the eyes and respiratory system and damage the nervous system. Short-term exposure to EtO may cause headaches, weakness, nausea, vomiting, diarrhea, difficulty breathing, eye and skin burns, and reproductive effects. Long-term exposure to EtO over a number of years increases the risk of certain cancers including lymphoid cancer and, for females, breast cancer.


EtO sterilization and aeration facilities are subject to local, state, and federal regulations. South Coast AQMD Rule 1405 (PDF) - Control of Ethylene Oxide Emissions from Sterilization and Related Operations.

During South Coast AQMD's monitoring efforts at several commercial EtO sterilization facilities, the agency became aware of fugitive emissions from sources that were not previously known. South Coast AQMD’s investigation has identified that existing pollution controls will need to be upgraded and measures will be needed to reduce fugitive emissions.

Rule 1405 was amended on December 1, 2023 to strengthen requirements for sterilization and storage facilities. The updated rule applies to 15 sterilization facilities which are required to upgrade existing or add new pollution controls and implement measures to monitor and minimize stack and fugitive emissions. Additionally, storage facilities that receive products sterilized by EtO may also be required to monitor emissions at the fenceline. More details related to Rule 1405 requirements can be found on the Rule 1405 page

Ongoing Investigations

South Coast AQMD is investigating EtO emissions from the following facilities.

More Information

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