What is PM10?

Particulate matter is the term given to the tiny particles of solid or semi-solid material found in the atmosphere. Particulates ranging in size from less than 0.1 micrometer to 50 micrometers are called Total Suspended Particulates (TSP). Particles larger than that range tend to settle out of the air. Particulate matter 10 micrometers in diameter and smaller is considered inhalable. This particulate matter is commonly called PM10.

By far, the majority of anthropogenic (man-made) particulates are in the 0.1 to 10 micrometer diameter range. Particles larger than 10 micrometers are usually due to "fugitive dust" (sand and dirt blown by winds from roadways, fields, and construction sites) and contain large amounts of silica (sand like) materials. PM10 particulates, on the other hand, are generally created during a burning process and include fly ash (from power plants), carbon black (from automobiles and diesel engines), and soot (from fireplaces and wood stoves). The PM10 particulates from these sources contain a large percentage of elemental and organic carbon which play a major role in haze phenomena and health effects.

Particles less than 2.5 micrometers are major contributors to visibility-related problems in both urban and rural areas. Along the Wasatch Front the effects of this particulate pollution can be seen as the thick brownish haze that gets trapped in our northern valleys in summer, and particularly winter months.

Elevated PM10 and TSP levels are generally associated with high density urban areas or localized mountain valleys where industry, automobiles, woodburning, sanding and unpaved roads are common sources. The monitoring effort in Utah will be increasingly focused on areas of the state that have high levels of PM10 attributable to anthropogenic sources.

Impacts in Utah

Utah began dealing with the issues involved in complying with the PM10 standard in 1987, although initial monitoring of PM10 began in 1985. Currently 4 Utah counties are designated non-attainment for PM10. These counties are Salt Lake, Davis, Weber and Utah. Box Elder County is not one of them. The State is in the process of developing control strategies to comply with federally mandated PM10 levels. Benzo-a-pyrene, a known carcinogen, is an example of this type of gaseous or semi-gaseous pollutant.