`` It happened everywhere , not just in a few areas . `` We still have a long way to go , '' says American Lung Association official . The U.S. Environmental Protection Agency has proposed new rules that would require the nation's largest coal-fired power plants to cut emissions of carbon dioxide and other greenhouse gases by 30 percent from 2005 levels within five years. NASA scientists attributes reductions to more-efficient cars , smokestack emissions cuts . Nitrogen dioxide is separate from greenhouse gases , which were n't measured in this report .
`` We still have a long way to go , '' says American Lung Association official . The U.S. Environmental Protection Agency has proposed new rules that would require the nation's largest coal-fired power plants to cut emissions of carbon dioxide and other greenhouse gases by 30 percent from 2005 levels within five years. NASA scientists attributes reductions to more-efficient cars , smokestack emissions cuts . Nitrogen dioxide is separate from greenhouse gases , which were n't measured in this report .