It's been dustier than usual in Anchorage this week. Tuesday the city had the highest level of particulates for the year, said Steve Morris, the city's air quality expert. The level averaged 87 on the federal Environmental Protection Agency's air quality index at a monitoring site near Tudor Road, he said. Fifty to 100 is considered "moderate" air quality. Under 50 is good.
Wednesday was better.
Annually, the air quality drops from about April 10 to 25th, Morris said, except on cloudy or rainy days.
On clear days, the low temperatures at night cause a temperature inversion that traps the dust stirred up by commuter traffic, said Morris. When the air warms up in mid-morning, the inversion breaks up, and the dust levels drop.
So the highest levels of dust are between about 6 and 10 a.m., Morris said.
The particulates are mostly pulverized road materials, he said.