New federal greenhouse gas emission regulation could expose a raft of smaller emitters to litigation, a nominee for a key post in the Environmental Protection Agency told lawmakers Thursday. The potential for smaller emitters to be regulated under the Clean Air Act is one reason why business groups warn that EPA regulation of greenhouse gases could create a cascade of legal and regulatory challenges across a much broader array of sectors. The Obama administration has said that isn't their intent. Regina McCarthy, nominated to be EPA's Director of Air and Radiation, told lawmakers that even while the government has flexibility...