The Ozone Out There in Phoenix

Air Pollution Advisory Days in AZ

Phoenix freeways
Getty Images/Morey Milbradt

Those of us who live in the Valley of the Sun also know that it can be the Valley of Bad Air. Pollutants cause a brown cloud to hang over the valley, and there are several Ozone Alert Days each year, especially when it gets hot. What is an Ozone Alert, why does it happen and whom does it affect? Here are the answers to your ozone questions.

What is Ozone?

Ozone is a colorless gas that is in the air. Ozone exists naturally in the Earth's upper atmosphere, where it shields the Earth from the sun's ultraviolet rays. When ozone is also found close to the Earth's surface it is referred to as ground-level ozone. At this level, it is a harmful air pollutant.

Why is Ozone a Problem?

Repeated exposure to unhealthful levels of ground-level ozone affects lung tissue. Ozone is an irritant that can cause choking, coughing and stinging eyes. Ozone damages lung tissue, it may exacerbate respiratory disease, and ozone makes people more susceptible to respiratory infections.

While anyone who is active or works outdoors is affected by unhealthful ozone levels, children and the elderly are especially vulnerable to ozone.

What Causes Ground-Level Ozone?

Ground-level ozone is formed by a reaction between certain chemicals and nitrogen when there is sunlight. These chemicals are created by automobiles, trucks, and buses; large industry; utility companies; gas stations; print shops; paint stores; cleaners; and off-road equipment, such as aircraft, locomotives, construction equipment, and lawn and garden equipment.

What is an Ozone Alert Day?

These are also called High Pollution Advisory Days, and they may be declared by the Arizona Department of Environmental Quality when ozone levels are forecast to reach unhealthy levels.

What is Arizona Doing to Reduce Ground-Level Ozone?

There are several air quality improvement programs in place in Arizona:

  • Cleaner burning gasoline is sold in the Phoenix-metro area during the summer months.
  • Vapor Recovery Systems control emissions of gasoline vapors when you fill your gas tank.
  • Enhanced Vehicle Emissions Testing Program
  • The Clean Air Campaign encourages the use of alternative forms of transportation and other pollution-reducing strategies.
  • Maricopa County's Trip Reduction Program requires Valley employers with 50 or more employees to encourage their employees to carpool or use public transportation.

What Can You Do to Help Reduce Dangerous Ozone Levels?

Valley residents are encouraged to:

  • Reduce their driving.
  • Limit engine idling.
  • Carpool, bus, telework.
  • Refuel after dark.
  • Refrain from using gasoline powered garden equipment or charcoal BBQs.
  • Schedule painting projects during the cooler months, and when painting, use water-based products.

Additionally, active adults, children, and individuals with respiratory problems should limit prolonged outdoor exposure.

Our pollution issues don't only exist in the summertime. We have winter High Pollution Advisory Days, too. During those days, the Residential Restriction Woodburning Ordinance will be in effect. At that time, people must refrain from using any non-approved wood-burning devices (fireplaces). Some pellet stoves or other wood stoves may be exempt from the restriction, but those must be registered with the county for the exemption. People who violate the ordinance may receive a fine. During the winter Pollution Advisory Days, of course, the same suggestions regarding carpooling and people who have respiratory problems should be considered.

You can get more information about restrictions during high ozone advisory days and what Maricopa County is doing to keep our air safe at Clean Air Make More. There you can sign up to receive air quality notices via text or email. You can also get detailed daily information from the Arizona Department of Environmental Quality online or by calling the ADEQ Air Quality Forecast Hotline at 602-771-2367.