Hazy skies prompt alert in valley

Air quality officials aren't using the H word, but they now blame a dust storm in southeastern Arizona for the ugly, brown air that blanketed Southern Nevada on Thursday.

It wasn't a haboob per se, but the skies over the Las Vegas Valley and the Boulder City area filled with enough dust to prompt a pollution alert from the Clark County Department of Air Quality.

Department officials said unhealthful levels of particulate pollution were detected in the early afternoon, and they urged children, seniors and people with chronic respiratory problems to stay indoors.

A haboob, which in Arabic means "strong wind," is a type of intense dust storm pushed outward by the leading edge of a thunderstorm as it collapses.

The phenomenon is fairly common in the deserts of Arizona but wasn't widely referred to as a haboob until recently, when the term was popularized by several dramatic dust storms in the Phoenix area.

Tucson and other parts of southeastern Arizona were hit by a dust storm of their own on Wednesday afternoon. Then, shortly after midnight, air monitors in the Boulder City area began to register a sharp rise in airborne particulates.

By Thursday morning, pollution levels were starting to reach unhealthful levels in Boulder City and the Las Vegas Valley.

The haze significantly reduced visibility across the valley, obscuring mountains and dimming or even erasing the resorts on the Strip behind a brown cloud. After lingering for most of the day, it was pushed out by the wind Thursday evening.

Mike Sword, air quality engineering manager for the county, said weather mapping strongly suggests the cloud came from southeastern Arizona. Readings from air monitors back that conclusion, he said, because the haze appeared to contain mostly dust, not the finer particles carried in the smoke from wildfires.

Particulate pollution can aggravate respiratory diseases. Symptoms of exposure may include coughing, wheezing and shortness of breath.

Air quality compliance officer Jack Bingham was out working in the haze Thursday morning.

"This is not a day when you want to be driving around in an air quality truck," he said. "People look at you and roll down their windows at stop signs to talk to you about what's going on."

Contact reporter Henry Brean at hbrean@reviewjournal.com or 702-383-0350.