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Air Quality Program

Ozone (O3)

Ozone high in the Earth's atmosphere protects us from the sun's harmful radiation. But ozone at ground level is air pollution, and is harmful to people and plants. Ozone is formed when air pollution — nitrogen oxides and volatile organic compounds (VOCs) — from vehicles, industry, and other sources react with each another in sunlight and hot temperatures. It is an ingredient of smog.

Health Effects

Ground-level ozone irritates the eyes, nose, throat, and respiratory system. It's especially bad for those with chronic heart and lung disease (like asthma, bronchitis, and emphysema), children and elderly, as well as pregnant women.

What You Can Do To Reduce and Avoid Ozone Pollution

When pollution rises on hot days:

  • Cut down on strenuous physical activity outside.
  • Stay inside until it cools down outside.
  • Don't drive unless you have to. Share a ride, take the bus, ride your bike, or walk when you can. If you must drive, combine your trips.
  • Refuel your car or truck after dusk. Don't top off your tank.
  • Limit engine idling.
  • Put off using gasoline-powered lawn and garden equipment until the hot spell is over.
  • Don't fire up the barbecue or fire pit.
  • Conserve electricity. Set your air conditioner at a higher temperature.
  • Save that painting project for later. Don't use paint or other products that release solvent gases.

National Ambient Air Quality Standard (NAAQS) for Ozone

In 2015, EPA adopted a more protective ozone standard from 0.075 parts per million (ppm) to 0.070 ppm. Washington submitted to EPA its recommendation about which counties or areas do not meet (are not in attainment or "non-attainment") the new standard. Ecology also submitted a response to comments received during the public comment period. Based on air monitoring data, most of Washington meets the standard. However, Ecology recommends that Benton, Franklin, and Walla Walla Counties are listed as unclassified because we have only monitored ozone in the Tri-Cities for one year, instead of three years as required.


Pollutant Level Remarks
Ozone 0.070 ppm
(parts per million)
Annual 4th-highest daily maximum 8-hour concentration, averaged over 3 years


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Ozone video