Stormy weather gave the Valley’s dirty air a good scrubbing this winter, adding detail to mountain views and reducing levels of a dangerous pollutant.
The region’s infamous brown cloud has returned along with the sunny skies, however, reminding residents of the ongoing battle against lung-damaging particulate matter.
"When you can see the brown cloud hanging over the Valley, it doesn’t take a whole lot of technical training to figure out that there’s an air pollution problem that needs to be addressed," said Steve Owens, director of the Arizona Department of Environmental Quality. "Things aren’t going to be quite as clear or quite as nice as they were over the last few weeks. But if we get more rain and things cool down again, we’ll go back to the way we were."
As the gray clouds causing last week’s rain began moving out on Friday, the air was all but devoid of the persistent smoggy haze typical for this time of year. Out-of-state visitors who attended the Desert Classic Duathlon in the McDowell Mountain Regional Park north of Fountain Hills were stunned by the green desert and beautiful weather, park supervisor Rand Hubbell said.
"Our vistas of the Mazatals and the Superstitions from the park have just been spectacular," said Hubbell, a Scottsdale resident.
A lid of warm air normally hovers over the Valley during the winter, trapping colder air below and allowing a build-up of pollutants from motor vehicle tailpipes and other sources.
Unstable air from recent storms has disturbed this pattern over the last two or three months, moving the browner air out of the Valley, said Chris Breckenridge, a meteorologist with the National Weather Service in Phoenix.
Raindrops also scour out the pollutants, bringing them to the ground and washing them away, he said. Because of that, the first rain through the brown cloud "is probably not the cleanest water you’d want to find," he said.
Forecasters expect more sunshine and stable air this week — leading to a corresponding rise in particulate pollution levels from "good" to "moderate" levels.
The brown cloud is made up mostly of particles of oil, soot, tire rubber and other matter less than 2.5 millionths of a meter in diameter (known as PM-2.5) — about the size of a single grain of flour. Common dust is another, slightly larger, type of particulate matter known as PM-10.
The two types of particulate matter are dealt with separately by government officials charged with minimizing the problem. Scientists believe both types cause lung maladies ranging from asthma to cancer.
The U.S. Environmental Protection Agency found in December that Arizona is in compliance with health standards for PM-2.5.
But the state faces tough sanctions and may lose federal highway funds in the future if air quality monitoring machines show high levels of PM-10 in the next two years.
Three weeks ago, Owen’s department asked the EPA’s forgiveness for exceeding federal dust standards during an Aug. 13 dust storm. The federal agency has yet to decide whether to penalize Arizona for the high reading.
In the meantime, county and state authorities are trying to ramp up dust control measures, hire more air quality officials and enforce pollution laws. On Monday, Owen announced a $43,000 penalty against New West Materials, LLC, for failing to control dust at its Mesa facility near Loop 202 and Val Vista Drive.
Citing a link between poor visibility and health concerns, the state also began operating a Web site a year ago on which computer users can gauge the haze without even going outside. In addition to live camera shots, the site — www.phoenixvis.net — also provides general air quality information.