PHOENIX -- Environmental regulators say metropolitan Phoenix is under an ozone health watch Wednesday as the area's pollution levels may approach the federal health standard for air quality.
Ozone is an invisible gas created when other pollutants in the air are heated by the sun.
Experts say ozone can irritate the lungs and aggravate existing health conditions such as asthma.
Officials said people who are unusually sensitive to air quality should consider limiting their time outdoors.
They also recommended that people avoid waiting in their cars at drive-thru restaurants, unplug electronic devices that aren't being used and fuel their cars after dark or during cooler evening hours.