These are called nonattainment areas. The new amendments set deadlines for nonattainment areas to reduce emissions of the offending pollutants to levels that meet the federal standards. The deadline for each county or region depends on the severity of the problem as defined by the U. S. Environmental Protection Agency. In addition, areas which already meet federal air quality standards must take specific steps to ensure that local and statewide air quality do not deteriorate. Michigan's worst air pollution problem continues to be ground-level ozone also known as photochemical smog.
Ozone is an invisible, irritating gas consisting of three oxygen atoms.
The extra atom makes the ozone molecule highly unstable and reactive. This reactivity is a problem because it breaks down substances - not only materials, but biological tissues and cells as well. Ground level ozone is harmful to human health. Sensitivity to ozone's effects is greater in some people, especially children, elderly people and people with lung or heart ailments. Even healthy people exercising outdoors may experience pulmonary discomfort when ozone concentrations reach the national standard of 0.12 parts per million.