It also reacts with other materials such as rubber compounds, breaking them down. In response to a lawsuit filed by the American Lung Association, the U.S. Environmental Protection Agency in July 1997 set a new stricter ozone standard of 0.08 ppm averaged over an eight-hour period.
Compliance is based on the fourth highest reading per year averaged over three years.
According to the 1990 census, there are an estimated 110 million people living in those counties. In February 2001, in response to industry lawsuits, the U.S. Supreme Court upheld the EPA's process for setting health-based standards. Efforts to roll back the stricter ozone standard were overturned. Ozone levels typically rise between May and October when higher temperatures and the increased amount of sunlight combine with the stagnant atmospheric conditions that are associated with ozone air pollution episodes. To reduce ozone air pollution, the American Lung Association supports the use of stringent controls on motor vehicle and pollution emissions produced by the commercial and industrial sources of the hydrocarbon compounds and oxides of nitrogen that form ozone.