Nonattainment Area

A metropolitan areaDetermined by the U.S. Census, based on population and density. More – such as Maricopa County – that has failed to meet the National Ambient Air QualityStandards set up by the Environmental Protection Agency to measure the health impacts of air pollution. EPA established standard measures for six pollutants: carbon monoxide, ozone, particulate matter, lead, sulfur dioxide and nitrous oxide. The transportation provisions of the Clean Air Act focus on ozone and carbon monoxide standards. More requirements.