The proposed revisions will address two categories of particulate matter: fine particles which are particles 2.5 micrometers in diameter and smaller; and "inhalable coarse" particles, which are particles between 2.5 and 10 micrometers (PM10-2.5).

Air quality monitoring device collects fine particles (PM2.5) near Klamath Falls, Oregon. Photo by Jim Gillam, The Chimney Sweep News

Particulate matter (PM) is a complex mixture of extremely small particles and liquid droplets. Particulate matter can be directly emitted, as in smoke from a fire, or it can form in the atmosphere from reactions of gases such as sulfur dioxide.

Adoption of these proposals, perhaps as soon as September 2006, is expected to cause more areas to be designated as “non-attainment” by the EPA. Areas not meeting federal minimum air quality standards are required to enact measures intended to improve air quality enough to meet those standards. Communities facing air quality problems often choose to restrict residential woodburning and installation of woodburning appliances.

Nonattainment designations made in December 2004 are now effective for 39 areas comprised of 208 counties across the country [see map].

map courtesy of U.S. Environmental Protection Agency

The proposed revisions include the significant reduction -- by nearly 50 percent -- of EPA's maximum level of fine particles (PM2.5) allowed for short-term exposure.

“It’s going to take diligence on everyone’s part to meet this new standard,” said Larry Calkins, an air quality specialist with the Oregon Department of Environmental Quality. “It’s going to be very stringent and it’s going to be a hard thing to meet.”

In addition, EPA is proposing a stricter standard for inhalable coarse particles, or PM10-2.5. The standard would apply to airborne mixes of coarse particles that come from sources such as high-density traffic on paved roads and industry. The proposed standard would not apply to mixes of coarse particles that do not pose much risk to public health, such as windblown dust and soils and agricultural and mining sources.

Numerous studies have associated fine particulate matter with a variety of respiratory and cardiovascular problems, ranging from aggravated asthma, to irregular heartbeats, heart attacks, and early death in people with heart or lung disease. Particle pollution can also contribute to visibility impairment.

EPA has had national air quality standards for fine particles since 1997 and for coarse particles 10 micrometers and smaller (PM10) since 1987.

EPA is seeking comments on a number of alternative levels for the PM standards, including retaining the current standards. The agency will take public comment for 90 days following publication of the proposal in the Federal Register and will hold three public hearings. This proposed rule does not address all of the issues involved in implementing a new standard, such as designating what areas are or are not attaining any new standard, and determining the best and most cost-effective implementation strategies. EPA and the states will address those in later actions.