3F: The Wasatch Front is Making Progress on PM_2.5 Levels

Small particulate matter (PM) measuring 2.5 microns or less across the Wasatch Front is monitored at several locations in order to assess air quality. As is widely known, airborne particulate matter is a large concern because Utah’s air is impacted by weather patterns, population growth, wildfire smoke, pollution from various industries and transportation, and topography all intersect to create challenges to Utah’s air quality. Higher levels of PM_2.5 affect human health but also affect how the state is perceived by visitors and recreators from outside the state.

PM_2.5 is one of the measurements that the Environmental Protection Agency uses to determine whether Utah is attaining healthy levels of cleaner air. During the past decade, legislation, management and policy, air quality monitoring, and upgrades to industries that have historically contributed to air pollution have been working together to improve Utah’s air. One of the interesting observations of PM_2.5 levels over the last decade is that while population has grown
along the Wasatch Front, overall PM_2.5 levels have declined. This shows that such collaboration has
produced some positive results; however, as shown in Figure 3.F.1, it must be noted that northern Utah’s airsheds are only a bad (i.e. stagnant) winter away from excessive violations (see 2021 and 2023).

This past wildfire season was one of Utah’s busiest in years in terms of human-caused wildfires (Figure 3.F.2). There are some interesting correlations between days when PM_2.5 levels were higher and times when the air was filled with trapped smoke due to weather patterns. This was particularly true for events in mid-July and early August (Figure 3.F.3). Some of that smoke came from Utah’s fires, but some was also attributed to wildfires burning in other states. While Utahns must continue to work together to improve our state’s contributions to air pollution and manage the size of Utah wildfires, we are still sometimes subject to outside influences on our air quality.

Additionally, on Feb. 24, 2024, the U.S. EPA announced a revision to the annually averaged PM_2.5 standard, lowering from 12 μg/m³ to 9 μg/m³. As shown in the Figure 3.F.4, over the past 3-year averaging period, several monitoring locations showed year-to-year violations of the new standard, but only the Near Road location in the central Salt Lake City valley showed consistent and regulatory-enforceable exceedance of the 3-year average relative to the new annual standard.