Forty-six years after Congress passed the landmark Clean Air Act, many battles are still being fought to keep lung-burning pollutants from being poured into our skies.

One of the biggest fights is being waged 80 miles west of Philadelphia, at the huge Brunner Island electric power plant. While burning coal to crank out enough power to serve a million homes, the plant releases uncontrolled amounts of smog-causing nitrogen dioxide (known as NOx), which blows east and fouls our region's air with ozone pollution, a powerful pollutant that can damage vulnerable lungs.

The Sierra Club says Brunner Island is the single largest driver of smog-causing pollution in all of Southeast Pennsylvania. The plant spews more NOx than the combined emissions from every other facility in nine Southeast Pennsylvania counties.

What Brunner Island dumps in the air is a big reason the American Lung Association gives a failing grade to the air quality in Philadelphia and three suburban counties.

That dirty air is a real threat to hundreds of thousands of Pennsylvanians who have asthma, weak hearts, or damaged lungs. A high ozone pollution day puts extra strain on their fragile health and can send them to the hospital - or even to the morgue.

Steady exposure to high ozone is also a serious risk for very young children, with their still-developing lungs and immature immune systems.

At least a quarter of Philadelphia school children either have asthma or show signs of it, with the highest rates occurring among minorities and those who are poor.

Brunner Island will soon be able to burn natural gas in addition to running on coal. Burning only gas would be much cleaner and, in today's energy market, much cheaper. But state authorities appear willing to let Brunner Island keep burning coal without requiring it to install modern controls on nitrogen oxide, which worsens ozone pollution in downwind areas.

In fact, Brunner Island is the only coal-burning plant that's not affected by new state rules setting tighter standards on NOx pollution. That's because the rules require less pollution from plants with existing NOx equipment, but Brunner Island has never had any.

Besides rewarding Brunner Island for foot-dragging on pollution control, the hands-off treatment gives it an unfair advantage over cleaner competitors.

Brunner Island's owner, Talen Energy, says the plant meets state and federal environmental standards. The unanswered question is why those standards aren't just as tough for Brunner Island as they are for other big coal plants in the state.

Delaware and Connecticut have filed complaints with the federal Environmental Protection Agency about Brunner Island. They say the plant's downwind pollution is a big reason they can't meet their anti-smog goals.

The EPA has the authority to tell Pennsylvania environmental officials to end the Brunner Island loophole and treat it like every other big coal-burning plant in the state.

That's the right call. Brunner Island shouldn't be allowed to burn "cheap" coal that fouls the air and dumps big health costs on vulnerable people who live downwind.