March PM10 and Temp Data Available
This March’s PM-10 particulate air pollution levels were more than double the average level for February, according to reports from the City’s Environmental Health Department. 

“March was also a great example of how PM-10 levels drop when it snows, and snow covers dust on the streets,” said Lee Cassin, director of Environmental Health. “The levels go up right away when roads dry out and traffic grinds up the dirt.”

This graph shows how levels dropped whenever it snowed in Aspen.




PM-10 levels also tend to drop on weekends when traffic is lower and rise on weekdays. The average level in March was 26 millionths of a gram of PM-10 in each cubic meter of air. The federal health standard is 150, though much lower levels are now known to cause health effects. PM-10 causes increased rates of hospitalization, respiratory illness, and death rates, even at moderate levels. The worst day in March had a level of 43.

It snowed on 11 days in March and the snow cover dropped from 30 to 20 inches. Both high and low temperatures in March were warmer than historical levels. Nationwide, March was cooler in the south and warmer in the north.

“One of the interesting recent weather phenomena is the increased incidence of ‘red dust events’ which causes the snow to melt much faster, since it makes the snow absorb more solar radiation,” said Kim Peterson, director of the City’s Canary Initiative. “When combined with warmer spring temperatures, the effect on snowpack is to make the snow disappear even faster.”

March did not have any major dust events, but there have already been two red dust warnings issued by the Colorado Department of Public Health and Environment so far in April. In these events, dust from Arizona and Utah, worsened by roads and associated development and land clearance, blows to Aspen when winds are strong. Scientists can pinpoint the origin of the dust by both its geology and by back-tracing where the winds were from when the dust reached Aspen.

The dust also causes problems for water treatment plants that must remove the large amounts of fine dust. The incidence of these dust events appears to be increasing in the last few years. According to the Southern Utah Wilderness Alliance (SUWA), some of the worst dust storms have caused snow to melt weeks earlier in the spring. SUWA cites grazing, oil and gas development, and off-road vehicles as major surface disturbing activities that destabilize the dust and allow it to be carried to Colorado.

For more information on air quality in Aspen, visit For information on Aspen’s global warming programs, go to

Posted on Friday, April 16, 2010