Under the Clean Air Act, the U.S. Environmental Protection Agency (EPA) has established air quality standards to protect public health and the environment. EPA has set national ambient air quality standards (NAAQS) for the six primary air pollutants. These include: carbon monoxide (CO), lead (Pb), nitrogen dioxides (NO2), ozone (O3), particulate matter (PM10 and PM2.5), and sulfur dioxide (SO2).
When an area does not meet the air quality standard for one of the NAAQS pollutants, the area may be subject to the formal rulemaking process that designates the area as nonattainment. The Clean Air Act requires states with areas failing to meet the NAAQS to produce a state implementation plan (SIP).
A SIP is an enforceable plan developed at the state and local level that explains how the area will comply with the NAAQS according to the Clean Air Act. The SIP is the cumulative record of all air pollution strategies, state statutes, state and local rules, and local ordinances implemented under Title I of the Clean Air Act by governmental agencies within the state.
In general, a SIP will include historical background information, a description of the nonattainment area, an assessment of air quality conditions and ambient air quality data for the area, an emissions inventory of sources of pollutants, control strategies, an attainment demonstration, and contingency provisions.
The first Arizona SIP submittal was in 1972. Because there have been so many changes to federal, state and local air quality programs over the past 30 years, there is not a single definitive document that contains all of the SIP requirements. Rather than re-writing the entire SIP regularly, parts of the SIP are simply revised as needed.
Revisions are necessary when new federal or state requirements are enacted, when new data improves modeling techniques, when a specific area's attainment status changes, or when an area fails to reach attainment.
Revisions to Arizona's SIP must be submitted to the EPA by the director of the Arizona Department of Environmental Quality (ADEQ) on behalf of the governor. Once approved by EPA and published in the Federal Register, the provisions contained in the SIP revision become enforceable by the federal government as well as by the appropriate governmental entities of Arizona. The cumulative and complete record of SIP revisions that have been approved by EPA and federally enforceable in Arizona is called the "applicable Arizona SIP".
Attainment Status
Portions of Maricopa County have been designated nonattainment for three pollutants: particulate matter (PM10), carbon monoxide (CO) and ozone (O3).
Maricopa County PM10 Nonattainment Area
On June 6, 2007, EPA found that the Phoenix metropolitan area failed to attain the 24-hour PM10 NAAQS by the December 31, 2006, attainment deadline. This failure triggered a special requirement under Section 189(d) of the Clean Air Act to submit a SIP revision to EPA by December 31, 2007, which provides for annual reductions of PM10 or PM10 precursors of not less than 5 percent of the most recent emissions inventory, until the PM10 NAAQS is attained.
Maricopa County along with the state, the Maricopa Association of Governments (MAG) and 24 various local cities and towns developed a plan to reduce PM10 emissions by 5 percent each year until the area meets the PM10 NAAQS. The plan was submitted to the EPA by December 31, 2007.
The primary sources of particulate pollution in the area are construction activities, paved road dust, unpaved roads and parking lots, agricultural activities, windblown dust from disturbed vacant lots, construction sites, and agricultural fields, fires and open burning, dust from offroad recreational vehicles, leaf blowers, and exhaust from cars.
Maricopa County CO Nonattainment Area
On April 8, 2005, EPA redesignated the Phoenix metropolitan area to attainment for CO and approved the attainment demonstration and maintenance plan which shows maintenance of the CO NAAQS through 2015. The Phoenix metropolitan area was originally designated as a moderate CO nonattainment area under the Clean Air Act Amendments of 1990, with an attainment date of December 31, 1995. As a result of the area's failure to reach attainment by the end of 1995, EPA reclassified the area as a serious nonattainment area in 1996, with a new attainment date of December 31, 2000. The Phoenix metropolitan area has not had an exceedance of the CO NAAQS since 1996. Cars and other gasoline-powered motor vehicles cause more than 75 percent of the area's CO.
Maricopa County 1-hour Ozone Nonattainment Area
On June 14, 2005, EPA redesignated the Phoenix metropolitan area to attainment of the 1-hour ozone NAAQS, the primary component of smog, and approved the attainment demonstration and maintenance plan which shows maintenance of the 1-hour ozone NAAQS through 2015. Phoenix has not exceeded the 1-hour ozone NAAQS in the last eight years, despite its growth into one of the country's major metropolitan areas. The 1-hour ozone NAAQS was revoked by EPA on June 15, 2005. However, certain control measures developed and implemented for the 1-hour NAAQS are required to remain in place to ensure continued progress toward attainment of the new 8-hour NAAQS.
Maricopa County 8-hour Ozone Nonattainment Area
On June 15, 2004, the EPA designated a 4,880 square mile area located mainly in Maricopa and Pinal Counties as an 8-hour ozone nonattainment area.
EPA's rule for implementing the new 8-hour ozone NAAQS requires that the nonattainment area meet the NAAQS by 2009. An 8-hour ozone plan for the Maricopa Nonattainment Area was submitted to the EPA by the June 15, 2007 deadline. The plan demonstrates that the 8-hour ozone NAAQS will be met by the ozone season of 2008, with measures that have been implemented before the ozone season of 2008.
On March 12, 2008, EPA strengthened the 8-hour ozone NAAQS. Specifically, EPA revised the level of the NAAQS to 0.075 parts per million (from 0.084 ppm).
States must make recommendations to EPA no later than March 2009 for areas to be designated attainment, nonattainment and unclassifiable. EPA will issue final designations of attainment, nonattainment and unclassifiable areas no later than March 2010. Nonattainment areas must submit SIPs outlining how they will reduce pollution to meet the standards by a 2013 (if EPA issues designations in 2010).
For more information:
The Arizona Department of Environmental Quality's Air Quality Plans
 website contains recent relevant documents pertaining to Arizona nonattainment and attainment areas with maintenance plans.
EPA Region 9's Arizona Air Actions
website contains recent EPA air quality actions for Arizona.
EPA Region 9's Air Quality State Implementation Plan (SIP)
website contains EPA action logs for the federally enforceable applicable SIPs in Arizona. Action logs list the state and local air pollution regulations that EPA has incorporated into the applicable SIP under section 110 of the Clean Air Act. |
