Farmworkers and environmental groups sue the EPA over its July 13, 2021 re-approval of the weedkiller paraquat, alleging it puts farmworkers at increased risk of developing Parkinson's disease. They petitioned the 9th U.S. Circuit Court of Appeals to review and set aside, in whole or in part the Environmental Protection Agency (EPA) interim registration decision approving continued use of the widely used herbicide, which they claim violates the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). The Agency said there was insufficient evidence to clearly link exposure to paraquat herbicides and Parkinson's disease. On May 25, 2022, the groups filed an opening brief alleging that “EPA repeatedly understated the extent of paraquat’s adverse effects, and it failed to lawfully address the serious risks it did identify.” EPA has until July 25 to file its response. Syngenta, the key maker of paraquat, has intervened in the action, and has until August 14 to file its response.