LOUISVILLE, Ky. (WDRB) -- Mammoth Cave National Park is one of the most polluted national parks in the U.S., a new study finds.

The park, which includes 52,000 acres, underground cave systems and parts of the Green and Nolin rivers in southcentral Kentucky, got a “D” rating for healthy air and an “F” for haze that limits scenic views. 

Those ratings, based on air pollution, ranked Mammoth Cave as the 10th “most harmed” park, according to the report released Tuesday by the National Parks Conservation Association. The nonprofit organization advocates for the park system through research and lobbying in Washington, D.C.

Mammoth Cave was one of 12 parks that scored a “D” or lower in at least one of three categories, although it received a “B” rating on the impact of climate change.

The report paints a bleak picture of how air pollution has affected the nation’s federal park system. The analysis found three of every four parks have periodic levels of “unhealthy” air quality – and all parks have had vistas reduced due to haze.

In most parks, about 40 percent of views are cut short, the report found. No park had a lower rating than Mammoth Cave, where “a natural view is almost impossible to come by, even on the clearest days.”

The group attributes the pollution to coal-fired power plants, automobiles and the emissions from the energy industry. It recommends President Barack Obama make “common sense revisions” to a federal rule meant to limit air pollution at national parks and wilderness areas.

Such revisions being proposed include, among other changes, giving each park its own clean air plan.

Two California parks – Sequoia and Kings Canyon – tied for the most affected areas, while Denali National Park and Preserve in Alaska was the least impacted. The Great Smoky Mountains in eastern Tennessee and western North Carolina ranked one spot below Mammoth Cave, at No. 11.

“Without action, the situation is unlikely to change soon -- under current plans, some parks aren’t predicted to have clean air for centuries,” the report says.

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