Another high-pollution advisory has been issued for metro Phoenix as ozone levels are expected to exceed the federal health standard for air quality.
Wednesday marks the third consecutive day the advisory has been issued.
People with respiratory problems are advised to limit their outdoor activities on days of elevated ozone levels.
Regulators say people also are encouraged to drive only when necessary, use carpools or public transportation, and avoid gas-powered lawn equipment and drive-thru lines.
Ozone forms when vehicle exhaust and chemical solvents combine with heat and sunlight.
