HOUSTON --A federal court will allow environmental groups to pursue a lawsuit that accuses Exxon Mobil Corp. of violating federal air pollution laws thousands of times in the past five years. The U.S. District Court Southern District on Tuesday dismissed a request by the largest U.S. refiner to dismiss the lawsuit regarding its Texas facility. The lawsuit filed by Sierra Club and Environment Texas says Irving-based Exxon's Baytown refinery released 10 million pounds of illegal pollution, including cancer-causing toxins, without facing proper fines or being forced to fix equipment. The environmental groups say they are suing refineries in the Houston Ship Channel to force compliance with the federal Clean Air Act because Texas state regulators are failing to do so. They have reached a $5.8 million with Shell.