Aspen air getting gritty
Air pollution in Aspen has reached an unusual off-season peak, an environmental official says.
Last Thursday and Friday morning’s pollution readings are the highest recorded in town since April, said Lee Cassin, director of the Aspen Environmental Health department. Cassin said the particulate reading for Monday morning was unusually high as well. Particulate pollution is generally made up of airborne dust and smoke particles from various sources.
Cassin said the recent particulate pollution levels could cause health problems. She attributes the higher readings to more traffic in town in the past few days. Aspen’s particulate pollution is primarily dust raised by the wheels of vehicles, Cassin said.
Measurements are taken from an air-monitoring station on the roof of the U S Bank building at 420 E. Main St., and read remotely in the city’s offices on Hopkins Avenue. Particulate pollution is measured in millionths of a gram per cubic meter of air. Typical off-season levels in Aspen are in the neighborhood of 25, with higher levels occurring as traffic builds during ski season.
But on Thursday, Nov. 11, the 24-hour average reading was 49, and Friday, the 24-hour reading was 47.
Particulate pollution reached a peak in Aspen last April after the environmental effects of magnesium chloride were brought into question. City street crews stopped using the de-icer on the streets and used more sand to compensate, and one day’s 24-hour average particulate count reached 55.
Air pollution reaches a daily peak each morning. Last Thursday, the reading was 146 for the hour between 8 and 9 a.m. Friday the reading reached 121 during that period. The highest pollution levels of the day are most often recorded at about that time, because it’s the peak commuting hour, Cassin said. A lesser peak is reached during afternoon commuting hours. Yesterday, the peak one-hour reading was 101, also recorded between 8 and 9 a.m.
Environmental Protection Agency standards permit a municipality to have only one day per year with a 24-hour reading exceeding 150, and a town’s average daily reading for a year cannot exceed 50. Failure to keep below these levels earns a town the label of an EPA non-attainment area, and special remediation is required.
Aspen’s 24-hour readings have been far below the EPA single-day limit of 150, but last week’s daily averages of 47 and 49 are quite capable of causing health problems, Cassin said. “We see increased hospital admissions, difficulty with breathing, and increases in asthma attacks,” Cassin said, “even with levels of around 50.”
Cassin said she checks the air-quality reading first thing every morning. If the particulate reading is high, she notifies the street department, and street cleaning crews are dispatched to clear some of the dust from the streets. Main Street was washed down yesterday.
Yesterday morning, Cassin said, a distinct line was visible between the layer of dirty air over Aspen and the clean air above.
Some air pollution may be coming from more distant sources as well. Dan Matthews, a wilderness specialist for the U.S. Forest Service at the Aspen Ranger District, said several large range and forest fires which have been burning in California may have contributed to a drop in Roaring Fork Valley air quality as prevailing winds carry smoke eastward.
Matthews, who helps with an air-quality monitoring station atop Aspen Mountain, said the filters and film from that station are sent off to a lab in California, and are not particularly useful in monitoring day-to-day changes.
But Matthews also suggested that the long dry spell in the intermountain West may be a factor in air quality.
“When it rains or snows it clears the air,” Matthews said. “It’s been so long since we’ve had any precipitation that the dust is just hanging in the air.”
“I think it’s a number of factors coming into play,” Matthews concluded.
But because particulate measurements drop steeply on weekends, it’s clear that most of Aspen’s immediate problem is from traffic. Saturday’s 24-hour average was 27.5 and on Sunday the level dropped to 20.5 before jumping back up yesterday morning
Cassin said people can help bring pollution levels down by avoiding driving. Carpooling, walking, bicycling and riding a bus are all ways to accomplish that, she said.
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