The decision by a federal appeals court reverses a 2020 EPA decision to not regulate perchlorate, a rocket fuel and explosive chemical that interferes with the thyroid gland and hormone production, presenting an acute risk for pregnant people and infants. The compound has been found to contaminate potable water near military installations and contractor facilities. The chemical was discovered in drinking wells in the 1990s, prompting public outcry for federal regulation.

EPA initially said it would not regulate the compound in 2008, then reversed course in 2011, arguing it could be regulated under the Safe Drinking Water Act (SDWA). The agency then failed to follow through on that determination, and a previous lawsuit resulted in a settlement that extended the runway for EPA to propose a standard until 2018. In 2020, the agency revoked its 2011 determination under President Trump and the current EPA staff affirmed that decision, prompting the current lawsuit by environmental groups.

The court concluded that the EPA has the statutory authority to override the agency’s determination that the chemical must be regulated under the SDWA. (Reuters, The Hill, Independent, Bloomberg Law, E&E $)