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What is Ozone?

ozone formation from EPAThere are two kinds of ozone. Good ozone is above the earth’s surface and shields us from the sun’s ultraviolet rays. Bad ozone, or ground-level ozone, is closer to the ground and happens when chemicals and pollution from gas-powered engines interact with sunlight. Ozone is most likely to reach unhealthy levels on hot sunny days in urban environments, but can still reach high levels during the colder months. Ozone can be carried long distances by wind and affect sensitive vegetation and ecosystems, including forests, parks, wildlife refuges and wilderness areas.

Protect your health and reduce pollution

The key to reducing ozone is to reduce the emissions that create it.       

  • Limit or reschedule outside activities. Think about spending more time indoors where ozone levels are usually lower. If you must be active outdoors, try to schedule activity before Noon or after 7 p.m.
  • Skip the car ride. Combine errands and use public transit, bike, or walk. If you walk or bike, do so early in the morning or later in the evening. Do not idle.
  • Postpone mowing. Gas powered lawn and garden equipment contributes to ozone-forming emissions.
  • Check on friends, relatives and neighbors. People with respiratory problems such as asthma, the elderly, and children are most affected by air pollution. 
  • Maintain healthy behaviors. Drink lots of water; Eat balanced meals; Exercise indoors on high-ozone days; Don’t smoke; Listen to your body and contact a healthcare provider if you are experiencing health symptoms.
  • Sign up for air pollution advisories and wood burning restrictions alerts.

Ozone and Health

Breathing ozone can cause:

  • shortness of breath
  • wheezing and coughing
  • chest pain when taking deep breaths

It also can reduce lung function and harm lung tissue. Ozone can worsen bronchitis, emphysema, and asthma, leading to increased medical care.

Who is at risk?

People most at risk from breathing air containing ozone include people with asthma, children, older adults, and people who are active outdoors, especially outdoor workers. In addition, people with certain genetic characteristics, and people with reduced intake of certain nutrients, such as vitamins C and E, are at greater risk from ozone exposure.

    Learn More

    Check today's air quality (

    Ground-level ozone basics from the EPA (

    Ozone and your health from the CDC (