DefinitionParticulate matter that measures 2.5 micrometers in diameter or less is often called PM2.5. Particulate matter 10 (PM10) measures one-seventh the width of a strand of human hair, so one can imagine just how small PM2.5 really is. PM2.5 is composed of metals, allergens, nitrates, sulfates, organic chemicals, soil, and dust that are emitted from sources such as combustion products, soot from fireplaces, and blowing dust from construction sites and agricultural activities. PM2.5 levels are generally higher during the winter months due to weather, temperature, and inversions. The United States' Environmental Protection Agency (EPA) PM2.5 standard states that daily averaged PM2.5 levels should not exceed 35 micrograms per cubic meter, while annually averaged PM2.5 levels should not exceed 12 micrograms per cubic meter^1^.[[br]]
# Environmental Protection Agency (2016). National Ambient Air Quality Standards (NAAQS). Retrieved November 18, 2016 from the EPA: [https://www.epa.gov/criteria-air-pollutants/naaqs-table].
NumeratorThis indicator report contains the following views:
# Percent of days above the National Ambient Air Quality Standards (NAAQS)
# Number of person-days above the NAAQS
# Average annual ambient concentrations of PM2.5
# Percent of population living in counties exceeding NAAQS
DenominatorWhere applicable, population based on U.S. Census Bureau estimates for July 1 of each year.
Data Interpretation IssuesData on PM2.5 levels are only available where air monitors exist. The Environmental Protection Agency (EPA) and Utah's Department of Environmental Quality (DEQ) have scientifically determined where in Utah PM2.5 is likely to exceed the standard. Geographies reported will vary based on measurement type.
Data for this report represent ambient air, or outside air quality. The relationship between ambient concentrations and personal exposure can vary significantly depending upon the pollutant, activity patterns, and micro-environments.
Data for this report came from the EPA; therefore, it may differ slightly from data to other sources. One reason for a possible difference is that this data includes [http://www3.epa.gov/region9/air/quality/events.html exceptional events], which includes air pollution generated from fireworks, construction, fires, and other sources.
Why Is This Important?PM2.5 can get deep inside the lungs and cause a variety of symptoms, such as painful breathing, chest tightness, headache, and coughing. PM2.5 can exacerbate respiratory infections, trigger asthma attacks and symptoms, and cause temporary reductions in lung capacity. Respiratory symptoms are more likely to occur when PM2.5 levels exceed the EPA's standard, but are possible when PM2.5 levels are below the standard, especially in sensitive populations. PM2.5 has been found in some studies to be associated with an increased risk of chronic lung disease^1^.
In addition to these adverse outcomes, PM2.5 can influence the environment in ways that will eventually affect human health. Fine particles cause haze which reduces visibility. The long-term effects of PM2.5, which settles in the soil, natural water sources, forests, and agricultural areas, are still to be determined.
Whether or not climate change has an effect on PM2.5 concentration has yet to be determined. However, as temperatures increase, PM2.5 concentration has been shown to increase in the United States, but this is not the general consensus of the scientific community. Researchers seem to agree that as precipitation increases, PM2.5 levels will decrease since it "clears" the air^2^. If precipitation events are seen to increase with climate change, it is reasonable to conclude that PM2.5 levels may decrease. PM2.5 concentrations could also be affected by air stagnation events (i.e., inversions). If air stagnation events increase in frequency with climate change, PM2.5 levels are likely to rise because these events trap the pollution at the Earth's surface^2^. More research is needed to accurately quantify to what extent PM2.5 levels will be affected by a changing climate.[[br]]
# Utah Department of Environmental Quality (2011). Choose clean air: particulate matter (PM10 & PM2.5). Retrieved March 19, 2012 from the Division of Air Quality: [http://www.cleanair.utah.gov/pollutants/particulateMatter.htm].
# Jacob, (D.J. & Winner, D.A. (2009). Effect of climate change on air quality. Atmospheric Environment, 43(1), 51-63.McInerney, B. (2005). What will happen if snow melts earlier? (PowerPoint slides). Retrieved from Brian McInerney at firstname.lastname@example.org.
Other ObjectivesPhysical exercise is essential to maintaining good health. In order to do this safely, refer to daily PM2.5 levels by checking them at [http://www.cleanair.utah.gov]. If PM2.5 levels are high, consider exercising indoors. If outdoor exercise is unavoidable during high PM2.5 levels, consider light to moderate activity such as walking.
How Are We Doing?Several of the most urban counties in Utah have days that do not comply with the PM2.5 standard. This may be due in part to Utah's unique geography and seasonal conditions. PM2.5 levels increase seasonally in the winter and often due to inversions. Utah's Department of Environmental Quality (DEQ) is working to decrease the number of days over the PM2.5 standard.
What Is Being Done?The Utah Department of Environmental Quality (DEQ) is working to decrease Utah's PM2.5 emissions to comply with national standards. Because the majority of particulate matter is caused by automobile emissions, DEQ encourages the public to use mass transit and to stay indoors on days with high pollution levels, which you can check at [http://www.health.utah.gov/utahair]. In addition, DEQ has studied the effects of high particulate matter levels on children playing outside at recess so that schools may make informed decisions about when to keep children indoors.
The DEQ's 3-day air quality forecasting program uses a red, yellow, and green stoplight color code to inform the public about how they can help keep pollution levels low. A green day informs the public that pollution levels are low, and they can safely drive and spend time outside. A yellow day suggests citizens consider limiting their driving to reduce pollution levels. A red day strongly encourages the public to reduce driving and other polluting activities to prevent pollution levels from exceeding the health standard.
Ultimately, Utah's air quality depends on each individual taking steps to reduce the amount of energy being used and pollution being emitted.