New federal auto emission and fuel standards announced Monday should help clear Maryland's summer smog and even aid the cleanup of the Chesapeake Bay, according to state environmental officials. The U.S. Environmental Protection Agency said the "Tier 3" rules it finalized limiting tailpipe emissions and sulfur in gasoline should reduce harmful pollution, prevent thousands of illnesses and premature deaths and improve the mileage of cars and trucks. Robert M. Summers, Maryland's environment secretary, said reducing vehicle emissions should mean healthier air to breathe in the state "for generations to come." "These actions will also provide a significant benefit to the Chesapeake Bay, as approximately one-third of its nitrogen issues are caused by air pollution," Summers added, in a statement released by EPA. George S. Tad Aburn, chief of air management for the state Department of the Environment, said reducing the sulfur content in gasoline should help ease the sate's smog. Less sulfur in fuel will enable vehicles' catalytic converters to work better, he explained, so they'll remove more nitrogen oxides from exhaust that go into forming ground-level ozone. By tightening vehicle emissions nationwide, EPA also will help Maryland because Virginia and other neighboring states do not now require their new vehicles to meet pollution standards set by California, as Maryland does. With as much as 70 percent of Maryland's smog blowing in from out of state, reductions elsewhere should reduce the amount reaching Marylanders, Aburn said. He called EPA's action a "huge deal" for Maryland.