WASHINGTON  Acting under federal court order, the Obama administration proposed new air-quality rules on Tuesday for coal-burning power plants that officials said would bring major reductions in soot and smog from Texas to the Eastern Seaboard.

The Environmental Protection Agency is issuing the rules to replace a plan from the administration of President George W. Bush that a federal judge threw out in 2008, citing numerous flaws in the calculation of air-quality effects.

Gina McCarthy, head of the E.P.A.’s air and radiation office, said the new rules would reduce emissions of sulfur dioxide and nitrogen oxides by hundreds of thousands of tons a year and bring $120 billion in annual health benefits. Those benefits, Ms. McCarthy said, include preventing 14,000 to 36,000 premature deaths, 23,000 nonfatal heart attacks, 21,000 cases of acute bronchitis, 240,000 cases of aggravated asthma and 1.9 million missed school and work days.

The rule would substantially reduce the unhealthy smog that shrouds American cities, especially during heat waves like the one now enveloping much of the East.