BOWLING GREEN — A plan by the U.S. Environmental Protection Agency to exempt some older coal plants from tough air-quality standards could hurt Mammoth Cave National Park, according to the National Parks Conservation Association.

The group is urging the EPA not to allow the exemption, citing a report released this month that it would allow emissions of 243 percent more nitrogen oxides "than the best pollution controls would allow."

The NPCA is an independent organization with a mission "to protect and enhance America's national parks for present and future generations," according to a statement posted on its Web site.

The group says Western Kentucky Energy has two small plants near Henderson that would harm the park without better pollution controls.

Western Kentucky Energy environmental manager Thomas Shaw told the Daily News in Bowling Green that the plants are currently in compliance with EPA standards and the company hasn't asked for an exemption.

"It's hard to say whether or not we would be in compliance with any future (regulations) because we don't know what they are," Shaw said.

Nitrogen and volatile organic compounds can combine to form ozone, which is already a problem at Mammoth Cave.

"But over the last four or five years, we've really seen a decline in our ozone levels," said Bobby Carson, the park's acting chief of science and resource management.

He said health risks are down, "but we still need to work on ozone for the good of public welfare."

"We have some 30 native species in the park that are sensitive to ozone," he said. "So we are still seeing plants damaged by ozone."