Above: The difference between a clear and a hazy day, as seen from Dickey Ridge, Shenandoah National Park. National Park Service photo.
A sampling of how air pollution affects different national parks around the country.
• Joshua Tree National Park has some of the worst air quality of any park, with record high ozone levels. On clear days, visibility is 100 miles, but haze pollution can cut views to 17 miles.
• From 1999-2003, Sequoia and Kings Canyon National Parks recorded 370 days with unhealthy air from ozone pollution. Over half of the Jeffrey and ponderosa pine trees are showing some level of ozone damage.
• Ozone pollution in Rocky Mountain National Park has been higher than in urban Denver. On the haziest days, visibility at Rocky Mountain is approximately 57 miles- half the distance it should be.
• Florida has issued fish-consumption advisories in Everglades National Park due to high mercury levels in largemouth bass and other fish species.
• Scientists at Mammoth Cave National Park have documented elevated levels of mercury in bats, including one species at risk of extinction—the endangered Indiana bat.
• Estimated annual average natural visibility at Acadia National Park is 110 miles. However, air pollution reduces visibility to approximately 33 miles. Scientists measured some of the highest mercury concentrations in this park’s warm-water fish species, such as bass, perch, and pickerel.
• Great Smoky Mountains National Park- our nation's most visited national park, has spectacular overlooks that are severely impaired by haze. Scenic views in the park should extend for more than 100 miles, but air pollution cuts those views to around 25 miles.
• Big Bend National Park has some of the worst visibility of any national park in the West. Scientists believe that mercury and other toxic compounds may be contributing to reproductive failure among peregrine falcons in the park.