Air Quality Status in Pima County

Air quality has improved significantly in Pima County over the past two decades. This is due primarily to lower emissions resulting from federally mandated stationary source and motor vehicle emission standards; increased fuel economy and vehicle emission technology improvements, and countywide dust control ordinances. The increasing availability for residents to walk, bike or use transit instead of driving also has helped. Continuing to improve air quality in the region, however, remains a challenge based on the need to meet more stringent federal air quality standards.

Ground-level ozone and particulate matter are of key significance in the area, as levels of these air pollutants have exceeded the total concentrations recommended by the federal health standard in recent years.

The U.S. Environmental Protection Agency (EPA) sets National Ambient Air Quality Standards (NAAQS) to protect public health and welfare; oversees regulations to reduce emissions of toxic air pollutants; and enacted the Regional Haze Rule to protect visibility and air quality at national parks and wilderness areas, such as Saguaro National Park in Tucson.

  • The region currently meets attainment designation for NAAQS air pollutants, except for the Rillito moderate particulate matter (PM10) nonattainment area. The Ajo moderate PM10 nonattainment area was redesignated attainment on Sept. 3, 2020, putting in place an initial 10-year maintenance plan through 2031.
  • Air quality monitors, managed by the Pima County Department of Environmental Quality, recorded a violation of the ozone standard in 2018, based upon a three-year rolling average of results from 2016-2018. The U.S. EPA is scheduled to review the ozone standard starting in 2020 and will make a subsequent designation of the region’s status
  • The Tucson Air Planning Area carbon monoxide (CO) limited maintenance plan ended July 10, 2020, finalizing a 20-year plan of maintaining attainment with CO standards.