A new federal proposal to clean up the nation’s air would not only help people breathe easier, but would also help meet the goals for cleaner Bay water by 2025.

The EPA on Nov. 26 proposed tightening the air pollution standard for ground-level ozone, the key component of smog, from 75 parts per billion to a range of 65 to 70 parts per billion by 2025. It is also taking comments on a standard of 60 ppb.

The standard is aimed at protecting public health, but it would help Bay cleanup efforts by forcing reductions in nitrogen oxide emissions, which contribute to the formation of smog and are also a significant source of nitrogen entering the Chesapeake.

Lewis Linker, modeling coordinator with the EPA’s Bay Program Office in Annapolis, said a rough estimate was that, if enacted, the proposal would result in a reduction of a “couple of million pounds of nitrogen that goes into the Bay.”

As of the end of 2013, the Bay region needed to achieve 55 million additional pounds of nitrogen reductions to meet the 2025 target of roughly 192 million pounds, according to EPA figures. So the ozone rule might achieve nearly 4 percent of the needed reductions.

More precise estimates will be available after the EPA determines the level at which to set the new ozone standard, and when the Bay Program completes updates to the models it uses to estimate Bay pollution in 2017.

Air pollution controls have played a huge role in nitrogen reductions to the Chesapeake. Estimates from the Bay Program indicate that about a third of the nitrogen reductions to the Chesapeake since 1985 have stemmed from increasingly stringent air pollution regulations.

Recent research by scientists at the University of Maryland Center for Environmental Science suggest those figures may underestimate the reductions realized from air pollution controls.

Those controls, aimed at reducing acid rain, ozone, particulate pollution, tailpipe emissions and other pollutants, have slashed the amount of nitrogen emissions that fall on the Bay’s watershed by more than half.

“It’s been a real wind at our back,” Linker said. “This additional increment of reduction is going to be an additional help if the proposal goes forward.”

Industry groups and some members of Congress have lashed out at the rule as too expensive. Jack Gerard, president of the American Petroleum Institute, said the new standards would have “potentially enormous costs to the economy, jobs and consumers.”

But in proposing the new standards, the EPA said health benefits would outweigh costs. Ozone is a particular threat to the young, elderly and those with respiratory ailments.

It estimated that an ozone standard of 70 ppb would produce annual health benefits of $6.4 billion to $13 billion, and a standard of 65 ppb would produce health benefits of $19 billion to $38 billion. Annual costs are estimated at $3.9 billion for a standard of 70 ppb, and $15 billion for a standard of 65 ppb.

The benefits include avoiding asthma attacks, heart attacks, missed school days and premature deaths, among other health effects.