A battle over the cancer risks of ethylene oxide air emissions from chemical plants has landed in court. The chemical maker Huntsman Petrochemical and two industry trade groups, the American Chemistry Council and the Louisiana Chemical Association, filed lawsuits Feb. 21 that challenge the US Environmental Protection Agency’s recent decision to maintain a 2020 regulation limiting ethylene oxide emissions from organic chemical manufacturing. That regulation relies on a controversial hazard assessment conducted by the EPA’s Integrated Risk Information System (IRIS) in 2016. The rule requires chemical manufacturers to reduce ethylene oxide emissions from equipment leaks, vents, and storage tanks to protect communities near industrial facilities. Industry wants the EPA to use a less protective risk assessment conducted by the Texas Commission on Environmental Quality (TCEQ). In December, the EPA rejected the TCEQ’s assessment . The EPA concluded that there is no scientific basis for changing its preference of using hazard