By Chris Adams

The Obama administration proposed Wednesday to tighten the allowable limit of ozone in the air, a bid to curtail the rising problem of asthma and other respiratory ailments but one that faces strong opposition from industry groups and Republicans on Capitol Hill.

The U.S. Environmental Protection Agency proposed a new standard for ground-level ozone _ known as smog _ to be set between 65 and 70 parts per billion, as measured by air-quality monitors. That's a drop from the current 75 parts per billion, a standard that was set in 2008.

Ozone forms in the atmosphere when emissions of nitrogen oxides and other compounds from automotive and industrial sources bake in the sun. It leads to poor air quality and the warnings for at-risk people _ children and elderly among them _ to stay indoors.

Among other things, ozone exposure can cause respiratory problems such as difficulty breathing and airway inflammation.

By reducing the level of ozone in the air, the EPA said it hopes to better protect both Americans' health and the environment, as ozone also stunts growth of plants and trees.

"Bringing ozone pollution standards in line with the latest science will clean up our air, improve access to crucial air quality information and protect those most at risk," said EPA Administrator Gina McCarthy, adding that "whether we work or play outdoors, we deserve to know the air we breathe is safe."

The EPA's calculations found that lowering the standard will provide "significantly better protection for children" and prevent from 320,000 to 960,000 asthma attacks and from 330,000 to 1 million missed school days per year by 2025; it will also reduce deaths and missed work days, the EPA said.

The new standard is just in the proposal stage, and the EPA will take public comments on it for 90 days; the EPA intends to issue the new standard by October 2015.

As part of the process, the EPA is also asking for comments about whether it should be trying to bring the standard even lower, to 60 parts per billion, a move advocated by health and environmental groups.

After the rule is finalized, states and counties will have several years to comply by mandating changes in local industries, traffic or other pollution sources. Counties in California _ which have unique geography and serious air-quality problems _ will have longer.

By 2025, EPA projections show that the vast majority of U.S. counties would meet the new standard, given changes and reductions already underway. Not counting California, only nine counties would exceed the 70 parts-per-billion standard, and 68 would exceed a 65 parts-per-billion standard. Those include Tarrant County, Texas, and other counties scattered across the industrial Midwest and the Southwest.

"When it comes to reducing this pollutant, we have done it before, and we are on track to do it again," McCarthy said in a conference call with reporters.

The move was generally supported by environmentalists and health experts, although they urged the administration to drop the standard even more.

Harold P. Wimmer, president and chief executive of the American Lung Association, said in a statement the proposal was "a step that is long overdue" but that "we are concerned that EPA did not include 60 ppb in the range, though it was the clear recommendation of independent scientists as well as health and medical societies. ... We will continue to push the agency to adopt standards based on the scientific evidence."

But the action was met with fierce resistance from industry groups and Republicans in Congress, who said that the standard would hurt the economy and that it was just the latest in a list of EPA proposals they plan to attack next year when they control both the House of Representatives and the Senate.

Soon-to-be Senate Majority Leader Mitch McConnell, R-Ky., said in a statement, "Many expect that it could become the most expensive regulation in American history and devastate job creation _ at a time when Americans are already struggling. ... This rule lacks balance and appears to be more about politics than anything else. The new Congress will review the rule and take appropriate action."

And House Majority Leader Kevin McCarthy, a Republican from California's Central Valley, criticized the administration for pushing too far, despite progress already made in recent years. He promised "aggressive oversight" of the action.

(c)2014 McClatchy Washington Bureau