How Ozone Impacts the Maricopa Region

Clean air is critical to our health, economy, and quality of life. By failing to meet the federal standards for clean air, our regional economy could lose millions of dollars each year, and your health is at serious risk.

AirNow Interactive Map of Air Quality
AirNow interactive air quality map screenshot of MAG Region on June 6, 2023

What is ozone?

You can’t see it or smell it. Ozone is formed through chemical variations between natural and man-made emissions of nitrogen oxides (NOx) and volatile organic compounds (VOCs). Sunlight is also needed to form ozone.

Stratospheric Ozone ("good ozone")

Stratospheric ozone forms high in the atmosphere when intense sunlight causes oxygen molecules (O2) to break up and re-form as ozone molecules (O3). These ozone molecules form the ozone layer and are commonly referred to as "good ozone."

Ground-Level Ozone ("bad ozone")

Ground-level ozone forms just above the earth’s surface and impacts human, plant, and animal respiration. Ground-level ozone is an irritant and is bad for your health. Arizona’s weather plays a big role in forming ground-level ozone.

Who does what?

MAG takes its role as the lead air quality planning agency for the Phoenix-Mesa metropolitan region very seriously. But air quality is regulated by federal law and other agencies enforce and implement air quality measures.

Who does what? Clean Air Act, EPA, ADEQ, County Air Quality, MAG responsibilities
Clean Air Act Maricopa County Pinal County EPA State of Arizona ADEQ MAG

Clean Air Act

Ozone standards come from the Federal Clean Air Act, passed in the early 1970s. Its most recent revisions were done over 30 years ago, in 1990. The purpose of the Act is to set a public health standard for clean air.

Environmental Protection Agency (EPA)

Regulations for the Clean Air Act are under the authority of the EPA. The EPA sets air quality standards and enforces them. It is responsible for approving state air quality plans. If the EPA determines a plan does not include reasonable measures, the EPA may step in and determine what needs to be done.

Maricopa Association of Governments

MAG's responsibility for air quality planning goes hand in hand with its job of transportation planning. Air quality and transportation are tightly linked, given that vehicles are the biggest local contributor to air pollution. MAG creates the air quality plans that demonstrate "conformity" with the EPA's regulations under the Clean Air Act (meaning the plan "conforms" to air quality standards). While MAG is responsible for air quality plans, it has no enforcement powers or authority to pass laws or rules.

Arizona Department of Environmental Quality

This state agency sets state rules and enforces them. ADEQ issues permits and inspects facilities to ensure they operate within the permit's terms.

Maricopa County / Pinal County

Counties set local rules and enforce them, issue permits, and ensure businesses remain in compliance.

The Problem

Maricopa regional air quality fails to meet the national clear air standards

Air quality in the Valley fails to meet the national standard for clean air, and that means we are exposed to unsafe levels of ozone in the air we breathe.

Why It Matters

How does ozone impact your health?

how ozone effects your health

Ground-level ozone can:

  • Make it more difficult to breathe deeply
  • Cause shortness of breath and pain when taking a deep breath
  • Cause coughing and a sore, scratchy throat
  • Inflame and damage the airways
  • Aggravate lung diseases such as asthma, emphysema, and chronic bronchitis
  • Increase the frequency of asthma attacks
  • Make the lungs more susceptible to infection
  • Continue to damage the lungs even when the symptoms have disappeared
  • Cause chronic obstructive pulmonary disease (COPD)

Some people are more sensitive to ozone than others. Sensitive groups include children, older adults, and people with lung diseases such as asthma, emphysema, and chronic bronchitis. Even healthy adults who are active outdoors can experience ozone's harmful effects.

How does ozone impact our economy?

We need to meet the federal standard by 2024 to avoid federal intervention and serious consequences to our economy.

Ozone nonattainment is expensive
  • Not meeting the current federal standard is costing our region an estimated $100 million each year.
  • Failing to meet the standard will mean costly requirements for most new and expanding industrial businesses in the region.
  • Increased federal requirements may slow new business growth.

What We Are Doing About It

As the region's air quality planning agency, MAG is leading the solution to our ozone challenge. Through collective efforts, MAG and our state and local government partners have improved air quality in our region over the last 20 years, even with a fast-growing population. However, there is still more work to be done.

Air quality and transportation planning go hand in hand. A well-planned and well-funded transportation system reduces congestion and lowers emissions, two important steps toward cleaner air. Learn more about the critical role of the half-cent sales tax and planned future transportation investments.

How the Prop 479 reduces ozone

On October 18, 2023, the Maricopa ozone nonattainment area in Arizona, along with 16 other ozone nonattainment areas in 10 additional states, was included in a final EPA rule finding that these areas have failed to submit a plan to address EPA ozone requirements for moderate nonattainment areas. The finding of a failure to submit was excepted and is one step in a multistep process. We continue to work with our partners at the Arizona Department of Environmental Quality, and Maricopa and Pinal counties, to seek all feasible remedies with the EPA to reduce ozone concentrations in our region as expeditiously as possible. Read more about our response to the EPA ruling here.


What Can You Do to Reduce Ozone?

There are many small steps you can take to help reduce ozone in our region.

  • Drive as little as possible: carpool or use public transit. For information on transportation alternatives, visit Valley Metro's
  • Fuel your vehicle after dark or during cooler evening hours.
  • Use low-VOC (Volatile Organic Compounds) or water-based paints, stains, finishes and paint strippers.
  • Delay big painting projects until high pollution advisories or health watches have passed.
  • Make sure containers of household cleaners, garage and yard chemicals and other solvents are sealed properly to prevent vapors from evaporating into the air.
  • Eliminate wood burning in fireplaces, stoves, chimineas, and outdoor fire pits.
  • Avoid using leaf blowers.
  • Conserve electricity.
  • Make the switch from gasoline to electric or battery powered lawn and garden equipment. For information on the Mowing Down Pollution and Commercial Lawn and Garden Programs, visit
Reduce ozone by using public transportation, telecommute, and car pool

Reference List

American Lung Association in Arizona. "The 2016 Arizona Asthma Burden Report," 2016. Accessed June 9, 2023.