Average daily ozone pollution levels in the Great Smoky Mountain National Park over the last eight years have been nearly two times higher than pollution levels in Atlanta, Knoxville, Nashville, and Charlotte, according to a report by the National Parks and Conservation Association. Much of the pollution drifts over to the park from coal-fired power plants and automobile exhaust and remains trapped there. The report recommends that the Tennessee Valley Authority phase out its oldest and dirtiest coal plants, which are grandfathered from current pollution-control requirements, and invest in cleaner and more efficient power sources.