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PR | Boundary Recommendation Process


ADEQ Encourages Public Participation in Boundary Recommendation Process for the U.S. Environmental Protection Agency Revised National Ambient Air Quality Standard for Fine Particulate Matter (PM2.5)

PHOENIX (March 26, 2024) – Arizona Department of Environmental Quality (ADEQ) officials announced today initiation of its process to develop boundary recommendations for the State of Arizona, as required by the U.S. Environmental Protection Agency (EPA) revised National Ambient Air Quality Standards (NAAQS) for fine particulate matter, known as PM2.5. ADEQ is the lead agency assisting the Arizona Governor in providing EPA with the boundary recommendations (see Arizona Revised Statutes 49-405). All states are required to submit their boundary recommendations by Feb. 7, 2025.

The boundary recommendations process involves determining geographic areas to designate as either:

  • Meeting the revised PM2.5 standard (called attainment), 
  • Not meeting, or contributing to another area not meeting, the standard (called nonattainment), or 
  • Unclassifiable based on available information. 

ADEQ Air Quality Division Director Daniel Czecholinski said, “ADEQ is looking forward to working with our local communities and affected stakeholders to identify areas of nonattainment where fine particulate matter control measures will be implemented to ensure protection of public health.”

To develop the boundary recommendations, ADEQ will carefully consider EPA’s five factors: air quality monitoring data, emissions and emissions-related data, meteorology, geography/topography, and jurisdictional boundaries, as well as informal and formal public and stakeholder input.

ADEQ expects to host a number of public information sessions and workshops about both the area designation process and then, its initial boundary recommendations, from Spring 2024 through Fall 2024. ADEQ will then seek public input on its draft boundary recommendations through a formal public notice, comment period and hearing expected to occur by October 2024. ADEQ will submit its final boundary recommendations, including responses to public comments, to the Arizona Governor by January 2025 for review, approval and submission to EPA by Feb. 7. 2025. 

EPA makes the final decision about which areas in Arizona, and the country, to designate as attainment, nonattainment, or unclassifiable with respect to its new, more stringent, PM2.5 standard. EPA is expected to begin making its final area designations in 2026.

ADEQ encourages interested parties to get involved and sign up to receive information and updates about the boundary designation process, including meeting opportunities, by subscribing to ADEQ’s PM2.5 Boundary Designations email list | Subscribe >

Background & Resources

On Feb. 7, 2024, EPA revised the annual primary (health-based) standard for PM2.5 by reducing the allowable concentration measured in outdoor air averaged over a year during a three year period from 12 µg/m3 to 9 µg/m3, while leaving the 24-hour average standard of 35 ug/m3 and secondary (welfare-based) standards unchanged. EPA’s decision to revise the PM2.5  annual standard to 9 µg/m3 will improve public health protection across the country. EPA estimates health benefits from the revised standard will include up to 4,500 avoided premature deaths, 800,000 avoided cases of asthma symptoms, and 290,000 avoided lost work days (in 2032). The net public health benefits could be as high as $46 billion (in 2032).

What is PM2.5?

PM2.5 is not a single pollutant. PM2.5 is the term used to describe a mixture of solid particles and liquid droplets in the air with a diameter less than 2.5 micrometers. PM2.5 is about 30 times smaller than the diameter of a human hair.

Where does PM2.5 come from? 

PM2.5 can be emitted directly or may result through the chemical reaction of gasses and vapors in the atmosphere. Combustion can produce PM2.5 emissions.  Some sources of PM2.5 pollution include: vehicle tailpipes, power plants, industrial processes, residential fireplaces, wood-burning stoves and wildfires.

What is the NAAQS review process?

Under the Clean Air Act, EPA is required to review the NAAQS every five years to ensure that they are adequate to protect public health or welfare based on the most recently available scientific evidence. When EPA reviews the NAAQS, it assembles a panel of scientific experts to review the standards and the science on which they are based. This scientific panel makes recommendations to the EPA Administrator, who makes final decisions regarding NAAQS reviews. The NAAQS review process is lengthy and open to public review and input. Get detailed information about the federal particulate matter standards | View EPA Website >

Read about EPA’s 2024 Revised Primary (Health-Based) NAAQS for PM2.5 and ADEQ’s boundary recommendation process | Learn More >


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