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Ajo | PM-10 Nonattainment Area

County Affected:

Parts of Pima County | View on a Map >

Nonattainment Area Designation Date:

Oct. 31, 1990
(55 FR 45799)

Classification Level: 


Pollutant of Concern:

PM10 (particulate matter 10 microns or less in diameter; 1987 standards)


The concentration of PM10 in the air in Ajo has been below federal standards for several years. ADEQ has developed a redesignation request which was submitted to EPA in May of 2019. When approved, this SIP will reclassify the area as an attainment area. As part of this request, ADEQ provided an updated emissions inventory, modeling demonstration, strategy for Exceptional Events and rules for PM10 controls.

Sources of Pollutant:

  • Inactive Ajo smelter tailings pile
  • Inactive slag reprocessing facility
  • Unpaved roads
  • Cleared/vacant lot areas

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