On July 31, 2023, the NAM filed an amicus brief urging the D.C. Circuit to vacate the EPA’s 2020 rule that sets emission standards for ethylene oxide. Ethylene oxide is frequently used to sterilize critical medical products in the United States. In a 2016 Integrated Risk Information System (“IRIS”) assessment, the EPA developed a value that estimates the health risk of inhalation exposure to ethylene oxide. The EPA used this value as a basis for setting ethylene oxide emissions standards in 2020 that limited the emissions from over 200 chemical manufacturing facilities. In 2022, the EPA issued a decision on reconsideration of its 2020 rule, reaffirming the rule and its reliance on the 2016 IRIS value.
We argued in our brief that the EPA violated the Administrative Procedure Act by using its 2016 IRIS value without following its own guidance for setting standards and providing an adequate explanation for failing to do so. Specifically, the EPA failed to follow the best available science, to take into consideration disagreement within the scientific community as to the proper approach to calculating cancer risks and to subject its 2016 IRIS value to peer review. This case is important to all chemical manufacturers who oppose using IRIS values to assess safe emission levels because such values are usually set at detect levels rather than levels that would contribute to harm. It will also have an impact on the medical community because some medical devices and instruments can only be sterilized with ethylene oxide, making the availability of the chemical necessary for safe and high-quality medical devices necessary for use in medical procedures.