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Pacific Southwest, Region 9

Serving: Arizona, California, Hawaii, Nevada, Pacific Islands, Tribal Nations

Phoenix Area Ozone Actions: Fact Sheet

NOTE: This content is no longer being updated. The most up to date information can be found in Federal Register Notices and Approved Air Quality Implementation Plans in Region 9.

Reclassification of the Phoenix metropolitan ozone nonattainment area to serious

October 27, 1997
Today’s action:

EPA is finalizing its determination that the Phoenix metropolitan area failed to meet the health-based 1-hour air quality standard for ground-level ozone (smog) by its Clean Air Act deadline of November 15, 1996. As a result of this determination, the area's air quality status for ozone is reclassified from moderate to serious, triggering new planning and control requirements. A new plan for meeting the health-based 1-hour standard will be due in December of 1998. The new deadline for meeting the standard is November 15, 1999.

EPA cannot grant the State's request to extend the 1996 attainment date by one year. Under the Clean Air Act, an area can experience no more than one exceedance of the standard during the attainment year in order to qualify for an extension. There were 7 exceedances recorded at air quality monitors in the Phoenix area in 1996. Therefore, we must reclassify the area.

Phoenix’s Air Quality:

EPA's finding is based on Phoenix air quality data monitored from 1994 through 1996. During this three-year period, the nonattainment area experienced 21 days of unhealthy air with a peak ozone value of 0.145 parts per million (ppm). The 1-hour ozone standard is 0.12 ppm. Most of the exceedances were recorded in the eastern part of the metropolitan area.

Today's action does not indicate that ozone air quality is worsening in the Phoenix area. In fact, thanks to the area's continuing efforts to implement a wide variety of measures to reduce pollution, ozone levels in the Phoenix metropolitan area have remained relatively stable over the past five years, a great achievement given that the area's population increased by more than 250,000 since 1990.

The State and the local community have worked hard to improve Phoenix's air quality. The steps taken just in 1997 include joining the federal reformulated gasoline program and developing a more stringent clean burning gasoline program for 1998. The area also has the country's leading vehicle emissions inspection program, a travel reduction program, a new voluntary lawnmower replacement program, mandatory conversion of government fleets to alternative fuels, incentives for conversion of private fleets to alternative fuels, incentives for the construction of public fueling facilities, and new stringent limits on industrial solvents that will begin in 1998. EPA will work with the State and local communities and business and environmental interests to assist them in developing additional cost-effective ways to reduce air pollution.

EPA recently revised the federal ozone standard from 0.12 parts per million (ppm) averaged over 1 hour to 0.08 ppm averaged over 8 hours. Based on current air quality data, Phoenix does not meet the new 8-hour standard. However, because planning and controls for the new 8-hour standard will not start for several years, areas such as Phoenix that exceed the 1-hour ozone standard must continue to implement controls for the 1-hour standard in order to assure continued progress toward cleaner air. Attaining the 1-hour standard should contribute greatly to attaining the 8-hour standard.

Impact of ozone on public health:

Exposure to ambient ozone concentrations, even at relatively low levels, can cause respiratory symptoms such as a reduction in lung function, chest pain, and cough. Repeated exposure can make people more susceptible to respiratory infection and lung inflammation, and can aggravate pre-existing respiratory diseases.

Children are most at risk from exposure to ozone because they are active outside, playing and exercising, during the summertime when ozone levels are at their highest. The elderly and those with respiratory diseases such as asthma are also at high risk.

Long-term exposure to ozone can cause irreversible changes in lung structure, which can lead to chronic respiratory illnesses such as emphysema, chronic bronchitis, and/or premature aging of the lungs.

Public comment on proposal:

EPA received 21 comments on its proposed determination, nearly all opposing the reclassification. Comments were received from Governor Hull, the Arizona Legislative Leadership, Senator Kyl, Representative Shadegg, the Arizona Department of Environmental Quality, Maricopa County, several cities in the Phoenix area, numerous business groups, and one environmental group.

Many commenters expressed concern about the new measures required under a serious classification, especially those imposed on stationary sources. EPA will work with the State and local agencies and the regulated community to clarify how these requirements apply.

Commenters also suggested that air quality data from special purpose monitors should not have been considered in evaluating whether to give the area an extension of the attainment date, even though data from these monitors are reliable. EPA, however, believes that all reliable monitoring data should be considered in determining whether an area is meeting the air quality standards.

Some commenters said that EPA should allow Arizona to focus only on the tighter new 8-hour standard rather than continuing to work toward meeting the 1-hour standard. Continued focus on the 1-hour standard, however, is necessary because planning to meet the new standard is several years away.

Next steps:

EPA's final determination will be published in the Federal Register one to two weeks from the date of signature. The notice explains the determination and responds to the comments made during the public comment period.

A copy of the final notice is available here:

For more information:

For more information, please call Colleen McKaughan, Associate Director, air Division, U.S. EPA Region 9 at (520) 498-0118; or Wienke Tax, air Quality Planner for Arizona, U.S. EPA Region 9 at (415) 947-4192.

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