The Supreme Court appeared split on Wednesday over whether the Environmental Protection Agency erred when it adopted first-ever regulations requiring power plants to cut emissions of mercury and other toxic air pollutants. The regulations would cost $9.6 billion in annual costs, according to EPA estimates. But the agency said it was appropriate to consider only public health risks—not industry costs—when it decided to regulate coal- and oil-fired generation plants. That decision was the crux of 90 minutes of oral argument. The court was considering a section of the Clean Air Act that said the EPA “shall” regulate utilities’ emissions of the hazardous air pollutants if it found that such regulation “is appropriate and necessary.” The agency said it took costs into account later when it determined exactly how to […]