The U.S. Environmental Protection Agency (EPA) recently announced final amendments to the Miscellaneous Organic Chemical Manufacturing National Emission Standards for Hazardous Air Pollutants (NESHAP), known as MON, to reduce hazardous air pollutants. The final MON amendments are expected to reduce emissions of hazardous air pollutants from the source category by 107 tons per year, which includes reductions in ethylene oxide emission of approximately 0.76 tons per year.

This final action addresses EPA’s obligation under the Clean Air Act to conduct the residual risk and technology (RTR) review for the miscellaneous organic chemical manufacturing source category. EPA evaluated the risks posed by air toxics from this source category and determined cancer risks for this source category to be unacceptable.

To reduce risks to an acceptable level, EPA has finalized additional requirements for process vents, storage tanks, and equipment in ethylene oxide service. In addition to reducing ethylene oxide emissions, the MON amendments include updates to requirements for flares controlling ethylene oxide emissions, or emissions from processes that produce olefins and polyolefins, heat exchange systems, and equipment leaks. Once these requirements are implemented, EPA has determined that risks will be acceptable and will provide an ample margin of safety to protect public health.

Ethylene oxide is one of 187 hazardous air pollutants regulated by the EPA. It is a flammable, colorless gas used to make other chemicals that are used in making a range of products, including antifreeze, textiles, plastics, detergents, and adhesives. Ethylene oxide also is used to sterilize equipment and plastic devices that cannot be sterilized by steam, such as medical equipment.

EPA has been taking steps to address ethylene oxide emissions after its 2018 National Air Toxics Assessment found that ethylene oxide emissions may be contributing to potentially elevated cancer risk in some areas around the country. Since then, EPA has been taking a two-pronged approach to evaluate these emissions. First, the agency is reviewing existing Clean Air Act regulations for industrial facilities that emit ethylene oxide. Second, because the process for revising regulations takes time, EPA is gathering additional information on ethylene oxide emissions and is working with state and local air agencies to determine whether more immediate emission reduction steps may be warranted.

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