Correction: An earlier version of this article incorrectly said that a new Environmental Protection Agency air-pollution rule targeting coal-fired power plants applies to 28 states and the District. The recently finalized rule applies to 27 states and the District; an additional state will be included in a supplemental proposal that has not been finalized. The article also misidentified a senator who, along with Sen. Mary Landrieu (D-La.), circulated a letter urging the EPA to withdraw the rule. He is Jeff Sessions (R-Ala.), not Pete Sessions. This version has been corrected.

The Environmental Protection Agency announced Thursday that it finalized rules that compel 27 states and the District to curb air pollution that travels across states by wind and weather, the first in a series of federal restrictions aimed at improving the air Americans breathe.

The Cross State Air Pollution Rule, which replaces a Bush-era regulation thrown out by federal courts in 2008, targets coal-fired power plants mainly in the eastern United States. The measure, along with a proposal aimed at cutting summertime smog in the Midwest, is projected to cost the utility industry about $2.4 billion in pollution-control upgrades over several years.

EPA Administrator Lisa P. Jackson said Thursday that the rule is “another long overdue step to protect the air we breathe and that our children breathe.”

She predicted that it will prevent as many as 34,000 premature deaths annually and generate $280 billion in benefits “that far outweigh the cost of complying with the rule.”

Jackson said the rule is projected to result in 1.8 million fewer sick days annually and allow people who suffer from respiratory ailments related to breathing pollution to spend more time outdoors in summer.

A federal judge vacated the George W. Bush administration’s Clean Air Interstate Rule (CAIR) for several reasons, questioning in part whether the emissions trading system it established would do enough to bring all states into compliance with federal air-quality standards.

Frank O’Donnell, who directs the advocacy group Clean Air Watch, said the new measures are “a good first step in cleaning up the air” but are less significant than upcoming guidelines for acceptable smog and soot levels across the country.

Utilities in several states, including Virginia and Maryland, have already begun to cut the nitrogen oxide and sulfur dioxide emissions linked to both soot and smog-forming ozone. The EPA estimates that the power sector has spent $1.6 billion to install pollution controls that helped bring emissions in line with the Bush measure.

“The utilities are basically already meeting this,” said Michael Dowd, who directs the air quality division at Virginia’s Department of Environmental Quality. He added that while the Cross State measure was helpful because it “locks into place” slightly stricter standards than CAIR, “it’s probably not going to bring any substantial real reductions from what we’re seeing now.”

Air pollution is carried downwind from one state to another. Maryland, for example, is “kind of at the wrong end of the tailpipe” when it comes to transported pollutants such as sulfur dioxide and nitrogen oxide, said Kathy Kinsey, deputy secretary of Maryland’s Department of the Environment.

“We get a lot of ozone pollution from upwind states,” she said. “This is a very important rule for us.” Maryland is concerned that the rule is not stringent enough to lower ozone pollution significantly that drifts in from states such as Pennsylvania and Ohio, Kinsey said.

James L. Connaughton, who was chairman of the Council on Environmental Quality under George W. Bush and is now an executive vice president at Constellation Energy, said Constellation has spent $1 billion on pollution control upgrades at facilities such as Maryland’s Brandon Shores power plant.

“We just went ahead and did it,” Connaughton said, adding that it was unfortunate the court ruled that the Bush proposal could not go into effect. “We lost a couple of years in air quality improvement and investment, but we’re now back on track.”

Some utility officials said the new rules and others that the Obama administration plans to enact in the coming months could force the retirement of several coal plants. That, in turn, will raise electricity costs for consumers, said American Electric Power spokesman Pat Hemlepp.

The rule will probably have its biggest impact on states such as Texas, which has challenged the idea of stricter controls on coal-fired power plants. It “will adversely affect thousands of Texas jobs creators and electricity consumers without fair notice and the opportunity to be heard,” said Sen. John Cornyn (R-Tex.).

S. William Becker, executive director of the National Association of Clean Air Agencies, said the new regulations impose tighter restrictions than did the Bush rules on sulfur dioxide emissions that create fine particles known as soot. But they resemble the former rules, he said, in that they are using an outdated smog standard that the EPA is expected to tighten later this month.

Some lawmakers are already lobbying to weaken the new smog rules. Sens. Jeff Sessions (R-Ala.) and Mary Landrieu (D-La.) are circulating a letter among their colleagues that urges Jackson to withdraw the rules because the senators have “significant concerns” about their economic impact.