The U.S. Court of Appeals for the District of Columbia Circuit severed challenges August 24 to the Environmental Protection Agency’s mercury and air toxics standards for power plants, separating arguments over the new source performance standards set by the agency from other challenges to the regulation. The order means that the court will hear three separate challenges to the agency’s air toxics standards for power plants, but all of the legal challenges will be heard on the same day. Petitioners challenging the standards must file their opening brief by October 23.