HARRISBURG, Pa. (AP) — U.S. Steel has agreed to settle a lawsuit that accused the Pittsburgh-based steel producer of violating federal clean air laws by operating plants without its desulfurization controls for more than three months, emitting clouds of sulfurous gas into surrounding towns. Environmental groups Clean Air Council and PennEnvironment said the settlement was filed in federal court Monday for a judge to review. They put the value of the settlement at $42 million, including $37 million worth of improvements to U.S. Steel’s Mon Valley Works plants. The groups say an additional $5 million penalty is one of the largest-ever nationally in a citizen-enforced lawsuit under federal clean air laws.