Aspen Air Quality Better than Most Western Slope Towns

Aspen’s air quality experienced one of the cleanest years on record in 2008, according to the Colorado Department of Public Health and Environment. The agency recently released its annual report of air quality levels in towns throughout Colorado. 


“The report compares levels in Aspen with other towns in the state and country and shows trends in pollution levels over time,” explained Environmental Health Director Lee Cassin, who added the agency’s record keeping began in 1988. “Aspen’s levels were cleaner than those of other mountain and Western Slope towns, but not as clean as some Front Range areas.”


Aspen’s worst air quality day had 65 millionths of a gram of PM-10 in each meter of air, compared to the federal standard of 150. That is better than Crested Butte, Steamboat, Breckenridge, Pagosa Springs, Delta, Parachute, Rifle, Durango, Grand Junction or Telluride. On the other hand, several places had better PM-10 air quality than Aspen, including Colorado Springs, Boulder, Longmont and some of Denver’s monitoring sites. These are rough comparisons because local weather conditions strongly affect readings, and Aspen’s and other monitors’ locations have changed over time.



PM-10 is particulate air pollution, almost all from traffic, which grinds up dirt on roads, with small amounts coming from wood burning and restaurant grills. PM-10 is associated with increased illness, hospitalization and death rates even at moderate PM-10 levels like those experienced in Aspen.


Since Aspen’s high PM-10 levels are caused almost exclusively by vehicle traffic, reducing vehicle trips is the key to lowering PM-10 levels. Measures that have been taken by the City to lower traffic and PM-10 levels include paid parking, which partly pays for free transit service in town, expanded valley bus service, Dial-a-rides, HOV lanes, and free all-day parking for carpoolers. 


PM-10 is the only air pollutant historically measured in Aspen, but starting this winter, the Aspen Environmental Health Department will also be measuring ozone levels.


“That is because the highest ozone reading ever measured on the Western Slope was recorded on Aspen Mountain,” Cassin said. “The goal of the new monitoring program is to see what ozone levels are like in towns where people live.”


Ozone has several significant health effects, including decreases in lung function and painful breathing. It is not directly emitted by any sources; rather, it forms in the air from other pollutants that combine to make ozone, so ozone levels are often higher “downwind” from pollution sources. The most likely sources of ozone in our area are emissions from gas drilling and production, as well as traffic.


Aspen’s ozone monitor will be installed in December near the golf course. 


Copies of the report are available in the Environmental Health Department on the second floor of City Hall at 130 S. Galena in Aspen. For more information on air quality in Aspen, visit

Posted on Wednesday, November 25, 2009