The Supreme Court on Monday left intact a key Obama administration environmental regulation, refusing to take up an appeal from 20 states to block rules that limit the emissions of mercury and other harmful pollutants that are byproducts of burning coal. The high court’s decision leaves in place a lower-court ruling that found that the regulations, put in place several years ago by the Environmental Protection Agency, could remain in effect while the agency revised the way it had calculated the potential industry compliance costs. The EPA finalized its updated cost analysis in April. In a statement Monday, the EPA praised the court’s decision not to review the case, saying the mercury standards are an important part of a broader effort to ensure clean air for Americans. “These practical and achievable standards cut harmful pollution from power […]