Arizona officials say residents must be vigilant about air quality as warmer temperatures start to usher in dangerous ozone pollution.
Maricopa County Air Quality Director Bill Wiley issued a warning to local residents this month marking the beginning of the area's ozone season.
Wiley says ozone pollution is more widespread in the summertime because pollutants and nitrogen oxides react more easily with heat and sunlight.
Last year, there were 29 days when one or more air quality monitors exceeded the federal ozone health standard in Maricopa County.
The Arizona Department of Environmental Quality also issued eight pollution advisories and 33 health watches for ozone last year.
Ozone pollution is odorless and colorless. It poses a direct threat to people with respiratory problems.
Driving less and conserving electricity helps reduce pollution.
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