The U.S. Environmental Protection Agency today finalized Clean Air Act regulations that will slash hundreds of thousands of tons of pollutants from coal-fired power plants that drift across state borders.

Ohio Power Company's Mountaineer coal-fired power plant in West Virginia sends air pollutants across the river into Ohio. [AEP]?

The Cross-State Air Pollution Rule is intended to protect over 240 million Americans living in the eastern half of the country once it takes effect on January 1, 2012.

Environmental and public health groups and state air quality agencies praised the new rule, while the coal industry cried that economic damage would result.

The Cross-State Air Pollution Rule replaces and strengthens the 2005 Clean Air Interstate Rule, CAIR, which the U.S. Court of Appeals for the DC Circuit ordered the EPA to revise in 2008. The court allowed CAIR to remain in place temporarily while the environmental agency worked to finalize today's replacement rule.

"No community should have to bear the burden of another community's polluters, or be powerless to prevent air pollution that leads to asthma, heart attacks and other harmful illnesses," said EPA Administrator Lisa Jackson. "These Clean Air Act safeguards will help protect the health of millions of Americans and save lives by preventing smog and soot pollution from traveling hundreds of miles and contaminating the air they breathe."

Carried long distances by wind and weather, power plant emissions of sulfur dioxide, SO2, and nitrogen oxide, NOx, cross state lines. The pollutants react in the atmosphere and contribute to harmful levels of ground-level ozone, known as smog, and fine particles, usually called soot, which are linked to illnesses and premature deaths and prevent many cities and communities from enjoying healthy air quality.

The Cross-State Air Pollution Rule will improve air quality by requiring power plants to cut SO2 and NOx emissions. By 2014, this rule and other state and EPA actions will reduce SO2 emissions by 73 percent from 2005 levels, the EPA estimates. NOx emissions will drop by 54 percent.

Pollution swirls throughout the eastern United States. Neil Donahue, a chemistry professor at Carnegie Mellon University, told the "Pittsburgh Post-Gazette" newspaper that smoke from a Pittsburgh-area power plant can ride the wind east and then south along the East Coast, then travel west to Baton Rouge where it blows north through the Midwest before prevailing winds may carry it right back to Pennsylvania.

In this way, Pennsylvania receives air pollution from 15 states as distant as Missouri, Georgia and Michigan.The EPA estimates that the rule will protect communities that are home to 240 million Americans from smog and soot pollution, preventing up to 34,000 premature deaths, 15,000 nonfatal heart attacks, 19,000 cases of acute bronchitis, 400,000 cases of aggravated asthma, and 1.8 million sick days a year beginning in 2014.