The Center for Biological Diversity, the Clean Air Council, and the National Parks Conservation Association filed an opening brief November 30 in the U.S. Court of Appeals for the District of Columbia Circuit arguing that the Environmental Protection Agency must, under the Clean Air Act, set air quality standards despite scientific uncertainty. The group is seeking a court order to vacate an agency final rule released in April that retained existing NOx and SOx secondary standards, which could force the agency to establish additional standards.