PRESS RELEASE | ADEQ Announces Pima County Ajo Planning Area Officially Meets Federal Clean Air Standard for PM-10

ADEQ officials announced today that the U. S. Environmental Protection Agency (EPA) approved its request to redesignate the Ajo planning area in Pima County to reflect that it meets the federal health-based standard for particulate matter of ten microns or less (PM-10) in size. EPA’s redesignation of the Ajo planning area to attainment became effective September 3, 2020.

“ADEQ’s Air Quality Division worked with our partners at Pima County Department of Environmental Quality, EPA and the regulated community to develop permanent emissions reduction strategies to ensure the Ajo planning area meets and will continue to maintain federal air quality standards well into the future,” said ADEQ Air Quality Division Director Daniel Czecholinski. “More people in Arizona are breathing cleaner air, as evidenced by Ajo’s redesignation to attainment.”

Even as Arizona’s economy and population has grown, Arizona has seen a more than 60 percent reduction of emissions since the Clean Air Act went into effect in 1990.

“It is great to know that the air quality improvements over the last decade warrant the redesignation by EPA. Pima County Department of Environmental Quality (PDEQ) worked diligently with EPA and ADEQ to complete all the necessary steps to successfully move the area from nonattainment to the maintenance plan,” said Ursula Nelson, PDEQ Director. “PDEQ will be conducting inspections in Ajo to ensure continued compliance with air quality requirements.”

In May 2019, ADEQ submitted a revision to the Arizona air quality State Implementation Plan (SIP), along with a request for EPA to redesignate the Ajo nonattainment area to attainment. The clean air quality record, implemented control strategies, and projections of future emissions included in the plan all demonstrated the area is expected to continue to record good air quality and maintain the PM-10 standard through 2031.

“EPA is pleased to work with ADEQ and Pima County to redesignate the Ajo area to attainment,” said EPA Pacific Southwest Regional Administrator John Busterud. “Thanks to the efforts of Arizona state and local officials and the public, the residents of Ajo are now breathing cleaner, healthier air.”

Ajo is the site of a former copper smelter and mine. Emissions from those operations as well as nearby tailings and slag storage areas contributed to elevated levels of particulate matter. In 1990, EPA designated Ajo as not meeting the National Ambient Air Quality Standards for PM-10 based on recorded violations of the standards at an ambient monitoring station in the area.

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