The Arizona Department of Environmental Quality has extended a health watch for ground-level ozone in the Phoenix metro area through Sunday.
Ground level ozone is formed by a chemical reaction heat from sunlight, nitrogen oxides and volatile organic compounds.
Ozone can irritate lungs and aggravate existing health conditions such as asthma, and people who are unusually sensitive to air quality should consider limiting their time outdoors.
Health officials recommend the following tips:
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