` ` We still have a long way to go , '' says American Lung Association official . NASA data show substantial reduction in nitrogen dioxide . NASA scientists recommend reductions to more - efficient cars , and emissions cuts . Nitrogen dioxide is separate from greenhouse gases , which were n't included in this report .
`` We still have a long way to go , '' says American Lung Association official . NASA data show substantial decreases in nitrogen dioxide . 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 .