Q&AZ: What Is Ozone Pollution?
Phoenix has exceeded ozone health standards 32 days since May.
A listener wanted to know what ozone is, where it comes from and what harm it can do.
"Good" ozone in the upper atmosphere protects us from ultraviolet rays.
"Bad" ozone forms near ground level from sunlight-powered chemical reactions involving emissions from cars, refineries and chemical plants.
Matt Pace is a meteorologist with the Arizona Department of Environmental Quality. He said concentrations are highest in the afternoons of long summer days.
"Typically, when we have very calm winds over the valley, when high pressure's sitting overhead, there's not a lot of mixing in the atmosphere. So all those compounds can kind of work together to form the ozone and result in higher levels of ozone," he said.
Ozone can cause lung damage, pain, coughing and shortness of breath, and can worsen respiratory diseases like asthma.
People who are sensitive to ozone should limit outdoor activities when advisories are in effect.
Numerous strategies can help reduce ozone, including telecommuting, taking mass transit, carpooling, refueling after dark and turning off car engines when stopped instead of idling.