The following are pollutants of most concern in Utah. The EPA regulates many of them.
Particulate matter (PM) is made of very small dust and soot particles. PM2.5 along with PM10 is of greatest concern because of its size–about one-fortieth the width of a human hair. PM2.5 can become trapped in the lungs and exacerbate or cause negative health conditions. PM is likely to reach unhealthy levels on winter days with little wind when temperature inversions trap emissions in for days at a time.
Causes: PM2.5 is composed of both primary and secondary particulate. Primary particulate, which makes up 25 percent of the overall problem, is emitted directly from a source such as soot. Secondary particulate, the majority of PM2.5, is created by a combination of precursor emissions that come from tailpipes, smokestacks and chemicals to form PM2.5 during atmospheric mixing. Major sources include power plants, automobiles, diesel engines, fireplaces, dust, construction, mining and agricultural activities.
Utah’s mountain valleys and wintertime temperature inversions combined with emissions, creates unusual chemical and photochemical conditions that lead to the formation of PM2.5. PM2.5 particles are less than or equal to 2.5 micrometers in diameter. They are measured in micrograms per cubic meter or µg/m3. The health-based standard of 35 µg/m3 can be likened to one grain of table salt in a one liter bottle filled with air.