Some days the smog in the Great Smoky Mountains, the country’s most-visited national park, is worse than the pollution in Atlanta. As the South’s population has soared, the region has become home to more cars and SUVs and the demand for coal-fired energy to power amenities like air conditioning has skyrocketed. The governors of Tennessee and North Carolina are urging Georgia’s governor to join a pact that would allow park officials to review pollution permits for industries. And an eight-state initiative is completing a $4 million study of how emissions across the eastern U.S. affect the Smokies. But some enviros say the states and feds are responding far too slowly to the problem.