Ozone – A Complex Problem in the Maricopa Region

Excessive ground-level ozone concentrations can be harmful to public health. Meeting the federal air quality standard for ozone is not only critical for our public health, but also for the economic vitality of our region. Over the past decade, managing and reducing regional ozone concentrations has become an increasingly complex problem.

What Is Ozone (O₃)?

Ozone is a gas you usually can’t see or smell, and it doesn’t come directly from cars, factories, or any other single source. Instead, it forms when sunlight triggers a chemical reaction between two types of pollutants—nitrogen oxides (NOx) and volatile organic compounds (VOCs)—which are released into the air by emissions from sources including vehicles, industrial and manufacturing activity, the use of paint and solvents, and even natural emissions from trees and vegetation.

Stratospheric Ozone ("good ozone")

Stratospheric ozone forms high in the atmosphere and makes up the “ozone layer” that protects the earth from harmful UV radiation.

Ground-Level Ozone ("bad ozone")

Ground-level ozone is breathed in and can trigger a variety of problems for people and the environment.

How Ground-Level Ozone May Impact 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.

What Are The Ozone Concentrations In Our Region?

The Arizona Department of Environmental Quality provides daily air quality forecasts of ozone levels in our region. The Environmental Protection Agency (EPA) also provides real-time ozone measurements through the AirNow website. Check out the Air Now Interactive Map for levels near you.

AirNow Interactive Map of Air Quality

AirNow interactive air quality map screenshot of MAG Region on June 6, 2023

The Problem

Understanding Why Ozone Concentrations Have Increased — Despite Local Reductions in Emissions — is Key to Successfully Addressing Ozone Pollution

As shown in the graphic below, while the region has seen emissions decrease dramatically since the early 2000s, ozone levels began a steep rise starting in 2017. Currently, there are some hypotheses for why ozone may be increasing, including the rapid increase in wildfire emissions. Further research is essential to fully understand the factors driving the rise in ozone concentrations in the region.

Much of the Ozone Pollution in our Region is Out of our Control

Unfortunately, there is no easy local path to attaining the federal ozone standards. MAG and EPA modeling indicate over 80 percent of the ozone in our region is from nature and sources outside our region –transported from other states or even other countries – which cannot be addressed or controlled locally.

What We Are Doing About It

As the lead air quality planning agency for our region, MAG cares deeply about the environment and public health. Along with our partners at the Arizona Department of Environmental Quality, Maricopa County, and Pinal County, the region has a strong record of advancing air quality outcomes. We were successful in achieving compliance with the 1997 and 2008 ozone standards. In fact, our collective work over the last three decades has resulted in lowering total emissions by more than 70 percent statewide—even while Arizona’s population doubled. This is due to the 93 federal, state and local control measures already in place.

Working with our partners, we continue to seek all feasible remedies to reduce ozone concentrations in our region while acknowledging the significant challenges the region faces with regard to uncontrollable ozone pollution from wildfires and from areas outside our region.

Who Does What?

MAG works with air quality agencies at the federal, state and county level to prepare air quality plans that address Clean Air Act requirements for ozone. Each agency has a specific role to play in improving air quality across the region.

Clean Air Act

Establishes federal regulatory laws to protect and improve air quality, setting the foundation for pollution control efforts.

U.S. Environmental Protection Agency (EPA)

Defines air quality standards, reviews and approves air quality plans, and ensures compliance through enforcement actions.

Maricopa Association of Governments (MAG)

Develops regional Air Quality Plans, including strategies and emission control measures, to meet Clean Air Act standards.

State of Arizona

Formulates state-specific air quality rules, adopts MAG’s regional Air Quality Plans, and manages statewide enforcement.

Maricopa and Pinal Counties

Implement and enforce local air quality regulations aligned with state and regional plans to maintain healthy air standards locally.

Who does what? Clean Air Act, EPA, ADEQ, County Air Quality, MAG responsibilities

What Can You Do to Reduce Ozone?

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

Reduce driving, carpool or use public transit. Learn more about transportation options and alternatives at ShareTheRide.com.
Avoid waiting in long drive-thru lines. Park your car and walk inside at coffee shops, fast-food restaurants, and banks. Learn about the "Care for Clean Air, Be Idle-Free!" initiative.
Refuel 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.
For more tips and information, visit Maricopa County’s “Help Keep Ozone Away, Commit to One Day!” campaign.

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. https://www.azasthma.org/resources/Documents/Asthma%20Burden%20Report.pdf.