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EPA proposes change to Denver area's air quality status for airborne particles

Release Date: 5/24/2002
Contact Information:
EPA 303-312-6005,

Release Date: 5/24/2002
Contact Information:
EPA 303-312-6004,

Release Date: 5/24/2002
Contact Information:
EPA 303-312-6436,

Release Date: 5/24/2002
Contact Information:
EPA 303-312-6603,

Release Date: 5/24/2002
Contact Information:
EPA 800-227-8917

DENVER – The U.S. EPA’s Denver office today announced it’s proposing to approve Colorado’s request to reclassify Denver’s air quality as acceptable for airborne particles or soot (PM10), which means the area meets national air quality standards for PM10. The Agency also intends to approve the metro area’s long-term plan to keep satisfying the requirements.

Within the past year, EPA upgraded Denver’s air quality status for smog (ozone) and carbon monoxide pollution, and the Agency approved similar air quality maintenance plans to keep those pollutants below federally mandated levels.

Denver is on the verge of becoming the first major metropolitan area in the United States to meet all national clean-air standards. To achieve this standing, the city has had to significantly slash levels of several pollutants, and has had to devise plans to keep its air free from excessive levels of those pollutants over the next 10 years.

The change in Denver’s soot status involves several Front-Range counties, including: Denver, Jefferson, and Douglas Counties, as well as parts of Boulder, Adams and Arapahoe Counties. Since 1990, the metro area was deemed to be moderately out of compliance for EPA’s national air standards for PM10, or particulate matter of 10 micrograms (one-seventh the size of a single human hair) per cubic meter of air.

Particulates are solid or semi-solid particles small enough to be suspended in the atmosphere. The major sources of these particles are generally a combination of sand and gravel from wintertime deicing, crushing/grinding operations, vehicles, wood burning, and wind-blown dust from unpaved roads, parking lots, open fields or construction sites.

Some studies indicate that particulate matter decreases the heart’s ability to respond to physical stress. When the heart cannot adapt well to changes in the heart rate, its oxygen-carrying capacity in the blood is reduced. Health threats are most serious for those who suffer from cardiovascular disease, asthma, emphysema, influenza, and bronchitis. Children and the elderly are also likely to be adversely affected by heavy concentrations of these pollutants. While Denver is meeting the minimum federal requirement for particulate levels, sensitive populations (the elderly, children and people with cardiovascular disease, asthma, emphysema, influenza, or bronchitis) may still be affected by particulate pollution at levels that are below the national standards.

Denver's geography has been one of its challenges. Because of weather patterns, the city is prone to temperature inversions that trap warm air under heavy cool air, keeping pollution stagnant over the city. While the atmosphere is much cleaner now, these inversions, and the brown haze they foster, will continue. However, the situation today is nothing like it used to be. In the late 1970s, Denver routinely violated various national air quality standards more than 200 days a year. Since January 1993, Denver has not violated PM10 requirements.

The metro area has relied on several methods to reduce PM10 pollution. For instance, the metro area instituted a strict street sanding and sweeping program. This program calls for applying non-toxic deicing solutions prior to snowstorms and reduced amounts of sand and gravel applied on streets during the storms. Sand that is applied is promptly removed shortly after a storm ends.

Other measures to curtail PM10 pollution included restricting wood burning during potentially high pollution days. Reduced wood burning cuts down on sooty emissions which add to the pollution particles already lingering in the air. Many Denver area industrial facilities have taken steps to cut particle pollution. Colorado has regulations affecting the stationary sources of particulates in the area, including specific requirements for the power plants.

Once EPA’s proposal is finalized, Denver will have more flexibility in making decisions affecting air quality. Permits for new power plants and other industrial polluters won't be as restrictive, and Federal oversight will be relaxed.

EPA will shortly publish in the Federal Register notice of its proposal to approve Colorado’s request to be designated as in compliance with national PM10 air quality requirements A 30-day public comment period on this proposed Federal rule starts on the date of publication of the proposed action.