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What is Ozone?

Nonattainment areas for the 2015 ozone standard

Ozone is a regional pollutant formed in the air when sunlight mixes with pollutants, mostly volatile organic compounds (VOCs) and nitrogen oxides (NOx).

VOCs are pollutants that easily evaporate in the air and are found in things such as gasoline, paints and cleaning products. NOx is created when fuel is burned from things such as cars, power plants and lawn mowers. As a regional pollutant that forms in the air, ozone may be created anywhere, not just where the NOx and VOCs are emitted.

Is ozone good or bad?

The ozone layer in the upper atmosphere helps to protect the Earth from the sun's harmful ultraviolet radiation and is good for us. However, ozone that forms at ground level can be unhealthy at certain levels. Based on recent health studies, the United States Environmental Protection Agency (USEPA) has determined that levels of ozone that measure above 70 parts per billion (ppb) over an 8-hour period outdoors is unhealthy. Above 70 ppb, ozone can cause health concerns including difficulty breathing, aggravating asthma and chronic lung irritation.

Are there areas in Michigan with high ozone levels?

Air quality in an area has not met the USEPA health-based standard is considered to be in nonattainment. For ozone, any level over 70 ppb is considered unhealthy and any area that has a three-year trend of unhealthy days is determined to be nonattainment by the USEPA. In Michigan, there are four areas of the state that are considered nonattainment for ozone: parts of Allegan and Muskegon counties, Berrien County and Southeast Michigan.

What actions are necessary for attainment?

While being in an ozone nonattainment area can seem bad, there is also an opportunity to reduce the level of harmful ozone. EGLE is tasked with finding new ways to reduce VOCs and NOx that cause ozone pollution. One way is to require companies that want to emit VOCs or NOx in the nonattainment area to find ways to reduce pollution. The result of these reductions is less ozone forming in the nonattainment area. Another way ozone pollution can be reduced is through individual action, even by people outside of the nonattainment areas.

Can I really make a difference?

Yes. Individual actions can make a big difference in the amount of ozone created. VOCs and NOx emissions are produced by a lot of everyday actions – mowing the lawn; fueling up your car, boat, or lawn mower; driving your car and even using electricity. Steps taken by individuals, every day, but especially on Clean Air Action! Days, can really make a difference.

On Clean Air Action! Days, citizens can refrain from fueling up until the evening, avoid mowing the lawn, limit driving and keep the air conditioning set just a degree or two higher to keep the ozone levels lower. For more information on Clean Air Action! Days, check out this video.

How do I know my area's ozone pollution level?

The Michigan Department of Environment, Great Lakes, and Energy's (EGLE) Air Quality Division has 25 air monitoring stations across the state to measure ozone concentrations in the air. Real time ozone monitoring data is available at

You can also sign up to receive advanced notice about Clean Air Action! Days in your area by downloading the USEPA AIRNow app or by enrolling in EnviroFlash.

West Michigan Information – West Michigan Clean Air Action

Southeast Michigan Information - SEMCOG

Statewide Information - EGLE

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