Pollution puts region on alert

Warnings issued as weather system traps stagnant air

Todd Hartman, Rocky Mountain News

Published February 10, 2007 at midnight

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A lingering weather system has trapped high levels of air pollution over the Denver region, prompting health officials to issue warnings to even healthy people to limit outdoor activities.

Air quality monitors have recorded unprecedented amounts of tiny particles in the air since Wednesday. It's not due to any new source of pollution but to a weather pattern that has trapped stagnant air over Denver and a lack of winds to push it out.

Health warnings could last through the weekend, according to regulators at the Colorado Department of Public Health and Environment.

"We're under a multiday episode," said Mike Silverstein, a top regulator at the state's air quality division. "It's a significant situation from a public-health perspective. We're advising that all of our residents take precautions, not just the sensitive populations."

Those precautions are twofold: limit exerting yourself or exercising outdoors, when you could inhale the tiny particles deeper into your lungs; and limit driving and wood burning to cut down on soot levels in the air.

The weather system - known as a temperature inversion, when cold air is sealed over the area - also exacerbated foggy conditions the past few days. The fog and particle pollution combined to make skies even hazier than during a typical inversion.

"We do have these meteorological conditions from time to time, but it's an infrequent event," Silverstein said.

Monitors from the southern suburbs to downtown have recorded levels of tiny particles unseen since 1997, when the Environmental Protection Agency required that state regulators begin tracking them.

Denver long had struggled with larger, or "coarse," particulates, often tied to street sanding in winter. But this is the first time the region has seen such high levels of tiny particulates over an extended period of time.

A downtown monitor Thursday recorded levels of 57 parts per billion. One at Chatfield hit 60, and another at National Jewish Medical and Research Center, 1400 Jackson St., showed a level of 49 parts per billion.

All were above the EPA health standard of 35 ppb, averaged over a 24-hour period.

That standard was strengthened in September after scientists, armed with years of studies showing that tiny particles can penetrate deep into the lungs and wreak havoc on the heart and breathing as well as shorten a person's lifespan, advised the EPA that the previous standard of 65 ppb was too loose.

In recent days, with the weather pattern stagnant over the Denver area, the region has seen hourly levels of tiny particulates soar far higher than ever before - reaching levels approaching 100 parts per billion, surprising regulators.

"Even to get values in the 30s was fairly rare, and now we're seeing levels that exceed the old standard (of 65)," Silverstein said.

Something in the air

• What's a particulate? A kind of air pollution that is, essentially, soot. Fine particulates are linked to wood-burning stoves, car and truck exhaust, and industry emissions from power plants and factories.

• How is it measured? Tiny particulates are considered a health risk when levels average 35 parts per billion or higher over a 24-hour period.

• What are the health effects? Studies have shown a link between exposure to tiny particles and premature death and aggravation of lung and heart ailments.

hartmant@RockyMountainNews.com or 303-954-5048

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