Asthma and Ozone

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What is ozone?

Ozone is the primary pollutant of concern during the summer months, sometimes referred to as smog.

Ozone is formed by the sun’s rays and heat acting upon pollution in the atmosphere.

  • Ozone is formed when hydrocarbons (aka volatile organic compounds or VOCs) and nitrogen oxides (NOx) chemically react in the presence of sunlight and heat.
    • Hydrocarbons are emitted from automobiles, gasoline stations, paint, degreasers, cleaning fluids, and many other sources.
    • Nitrogen oxides are emitted by automobiles, power plants, and other combustion processes.
    • Concern is ground level ozone that we breathe in. Stratospheric ozone layer is 15 miles above the earth surface and protects us from harmful UV rays.

When are ozone levels the highest?

  • Ozone is primarily a problem during the summer, when days are long and hot.
  • Ozone levels are generally highest in the hot afternoon hours.
  • The highest ozone levels occur during the summer when strong sunlight, high temperatures, and stagnant meteorological conditions combine to drive the chemical reactions and trap the air in the region for several days.

Who is most sensitive to ozone?

Populations that are especially sensitive to ozone include:

  • Children
  • Seniors
  • Those with chronic lung or heart conditions (e.g. asthma, cystic fibrosis, congenital heart disease)
  • People who work or exercise outdoors

What does ozone do to the lungs?

Breathing in ozone irritates the cells that line your lungs and can cause inflammation. Our lungs are able to heal, but repeated ozone exposure over time may lead to more serious health effects including:

  • Development of COPD or asthma
  • More severe respiratory infections
  • Decreased lung function

What are the symptoms of ozone exposure?

Signs that your body is reacting to ozone include: difficulty breathing, chest tightness, coughing, increased allergy or asthma symptoms, and eye, nose, or throat irritation.

What can individuals do to protect their health during ozone season?

General recommendations for outdoor physical activity during ozone season

  • The best time for outdoor summer physical activity is before noon or after 6:00 p.m.
  • If you are physically active between noon and 6:00 pm:
    • Consider light to moderate activity (e.g., walking instead of running).
    • Consider indoor activities.
  • If you have any symptoms, Discuss physical activities with your doctor, especially if you have lung disease or a heart condition.
  • Check ozone levels before outdoor activities ( or
  • The website can help you make decisions to protect your health on bad air quality days
    • This website provides health information and recommendations based on the Air Quality Index developed by the U.S. Environmental Protection Agency (EPA).
    • The website includes current pollution levels in areas throughout the state, information on symptoms the general population and sensitive groups may experience, and recommendations on what you can do to protect your health.

Ozone tracking tool

  • It is important to learn what level of air pollution you are sensitive to

  • Learn what level of pollution you are sensitive to using the ozone tracking tool
    • Check ozone levels before outdoor activities ( or
    • Pay attention to any symptoms you experience
    • Record ozone levels and any symptoms you experience on the ozone tracking sheet

What can I do to reduce my contribution to the ozone problem?

  • Reduce trips taken in the car- trip chain, use public transport, avoid driving during rush hour, and look for other ways to travel
  • Don’t idle your car
  • To help residents plan ahead and adjust their activities during periods of high pollution, DAQ provides air quality alerts through its UtahAir app (available for free download in both the Apple and Android apps stores), website (, toll-free messages (1-800- 228-5434), and regular email alerts (

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