After some record air pollution levels this winter over the Phoenix metropolitan area, health officials are worried that ozone problems could be next.
"It may be that we simply go from one high-pollution season to another," said Steve Owens, director of the Arizona Department of Environmental Quality.
A stubborn air inversion helped trap particles of smoke and dust over the Phoenix metro area since fall and the area violated federal standards for coarse-particulate pollution 47 times on 29 days since early October.
Violations occurred on just 19 days during the previous five years combined.
But the onset of warmer temperatures now is loosening the inversion, allowing the particulates to escape and dissipate, and the Phoenix area hasn't exceeded federal air standards since Feb. 17.
But officials say particulates and ozone are caused by different factors, a continuation of this winter's weather pattern doesn't bode well for summer air quality.
Owens said his office has been warned to expect hotter-than-usual conditions in the months ahead. High temperatures help grease the chemical reaction that forms ground-level ozone, a precursor to smog.
Continued drought and calm conditions would offer little to keep a stew of ozone from forming and settling over the Valley.
"The same conditions (from this winter) would certainly lend themselves to ozone problems," said Bob Pallarino, air-monitoring specialist for the U.S. Environmental Protection Agency. "We could certainly see a tough year."
Ozone exists naturally in the upper atmosphere, helping shield against the sun's harmful ultraviolet rays. But ozone that forms near the ground is an invisible, odorless irritant that causes stinging eyes, coughing and can aggravate respiratory disease.
Long-term exposure stiffens lung tissue in the same manner that repeated sunburn leads to leathery, wrinkled skin.
Ozone season typically begins in early April as temperatures climb, and peaks during the heat of summer in July and August.
Tailpipe emissions are the biggest culprit for ozone, which forms through a chemical reaction as nitrogen oxides and volatile organic compounds are released into the air.
The Phoenix metro area exceeded federal guidelines for ozone pollution on 13 days last summer.
"As the population grows ... we get a buildup of pollutants," said Bob Kard, director of Maricopa County's Air Quality Department. "It's going to be a constant battle to keep us from violating federal ozone standards."