Qualité de l’air à Salt Lake City

Is Salt Lake City polluted?

Salt Lake City air quality has never met federal attainment levels for ozone or 24-hour PM2.5 pollution.¹ This severe nonattainment status has resulted in consistent “F” ratings for both measures. According to the 2019 State of the Air report, the Salt Lake City area, which includes Provo and Orem, ranked 7th out of 217 metropolitan areas for worst 24-hour particle pollution, and 11th out of 228 metropolitan areas for worst ozone pollution.

These ratings place Salt Lake City in a similar position to Los Angeles for 24-hour PM2.5 and Denver for ozone pollution.

Excessive Salt Lake City air pollution is particularly harmful to the county’s sensitive groups, including children, the elderly, and those with heart and lung disease like COPD, asthma, and lung cancer. Currently, 601,131 residents fall into this category of being especially threatened by the city’s unhealthy PM2.5 and ozone levels.

Seasonal fluctuations play a significant role in Salt Lake City air pollution. Temperature inversions in the winter trap polluted air, preventing its normal dispersal. As a result of this weather effect, winter months can experience more than five times the PM2.5 concentration as in summer months.

If Salt Lake City air quality is only understood from the perspective of annual averages, it would appear that the city has US AQI “good” air quality. In 2019, Salt Lake City AQI was 25 for the year, safely within federal levels. Such sweeping averages, however, obscure pollution events which often afflict the city, giving way to unhealthy air pollution days.

Between 2016 and 2018, Salt Lake City experienced a weighted average of 25.7 days of unhealthy ozone and 11.5 days of unhealthy PM2.5. The US government targets a weighted average of no more than 3.2 days of unhealthy pollution a year.

For other federally regulated criteria pollutants, including PM10, SO₂, NO₂ and CO, Salt Lake City meets standards.

How bad is the air quality in Salt Lake City?

Despite long-term reductions in particle pollution and ozone of recent decades, air quality in Salt Lake City remains among the worst in the United States. The last three years, moreover, have seen increases in unhealthy ozone days and annual PM2.5 levels.

Brigham Young University researchers found that Utah air pollution reduces the average resident’s life by anywhere from 1.1 to 3.5 years.² Loss of life is assessed across the population and reveals adverse impacts on all Utah residents rather than just sensitive groups who are more likely to experience health implications. An estimated 75 percent of Utahns lose 1 year of life or more as a result to state air pollution levels, while another 23 percent lose 5 years or more.

A similar study conducted by MIT found that there are nearly 450 deaths in Utah annually as a result of air pollution.³ As the Salt Lake City county represents one third of the state's population, it’s reasonable to assume that at least 150 of these deaths occur there.

While premature mortality is a concrete measure to use to relate to the bad air quality in Salt Lake City, most residents will at one time or another experience other adverse health effects, including irritation to the nose, throat, and eyes, coughing, wheezing, chest pain, heart arrhythmia, and shortness of breath.

Use the real-time Salt Lake City health advisories provided at the top of this page to guide preventative actions to reduce pollution exposure.

What causes air pollution in Salt Lake City?

Motor vehicles represent the largest source of pollution emissions in Salt Lake City, a trend common in a majority of locations across the United States. 55 percent of all the city’s emissions are attributable to vehicular traffic.⁴

Homes and businesses are the second leading cause of emissions at 27 percent. Emissions here represent home and building space heating, water heating, and wood burning. In the winter, the share of emissions from wood burning grows to become the majority of home-related emissions.

Non-road combustion sources, including construction equipment, airplanes, boats, and lawnmowers, make up 10 percent of the city’s emissions, followed by industry, which comprises the smallest sector of emissions at 8 percent.

In the winter, Salt Lake City increased AQI levels are often the result of temperature inversions. In normal conditions, air is warmest near the ground and cools with gains in elevation. During a temperature inversion, ground-level air is colder than the air directly above it. When this happens, the warm air layer prevents the cooler air from rising and dispersing, thus causing polluted ground-level air to accumulate.

The geography of the city, at the basin of the Wasatch Mountains, Oquirrh Mountains, and Traverse Mountains, can exacerbate this effect by trapping cold air in the Salt Lake Valley and shielding the city air from strong winds that could help clear out inversions.⁵

Survey the Salt Lake City air pollution map to discover the impact of local emission sources like domestic heating and transportation on PM2.5.

When is Salt Lake City’s worst air quality?

Winter months in Salt Lake City tend to be the most polluted. In 2019, December, January, and November represented the highest AQI months in Salt Lake City, with index ratings of 60, 57, and 39 (respectively). Conversely, June, May, and April are Salt Lake City’s cleanest months with AQI ratings of 10, 10, and 11.

Seasonal air pollution trends in Salt Lake City’s result from geography and climate. In the winter, cold ground-level air becomes trapped under warmer air above as a result of temperature inversions. In this event, the pollutants in the cooler air also become trapped, unable to rise and disperse into the atmosphere, causing pollution to linger and build until the weather changes.

Inversions in the city often occur after a snowstorm, when snow cover contributes to cold ground level air, or shortly after dusk and throughout the night, when there’s no direct sunlight.

While seasonal and daily trends lend insights to changing air quality levels in Salt Lake City, nothing is more accurate than real-time data regarding current conditions. Salt Lake City real-time and forecast air quality data is displayed at the top of this city page.

Why does Salt Lake City create so much air pollution?

Fossil fuel is responsible for creating much Salt Lake City air pollution. One study estimated that roughly 85 percent of harmful emissions are the result of fossil fuel combustion, largely owing to home and building heating and traffic.

Improvements to the air quality in SLC to date have been primarily attributable to more-efficient, lower-emission vehicles on the road in part as a result of tightening vehicle emission standards. These reductions have come despite a growing population and an increase in vehicle registrations.

Some of the most effective ways for further reducing Salt Lake City air pollution include legislative measures that seek to grow the share of electric or low-emission vehicles, improve building efficiency, eliminate subsidies for oil and gas companies, expand alternative transportation, and shift towards cleaner energy sources.

Utah governor. Gary Herbert has sought to grow renewable energy and transition towards electric vehicles and greener modes of transport through nearly $100 million in appropriations and incentives. These aggressive proposals could make strides in reducing the amount of pollution emissions owing to Salt Lake City itself.⁶

+ Article Resources

[1] American Lung Association. (2019). State of the air – 2019.
[2] Errigo I., et al. (2020). Human health and the economic costs of air pollution in Utah.
[3] Caiazzo F, et al. (2013). Air pollution and early deaths in the United States. Part I: Quantifying the impact of major sectors in 2005.
DOI: 10.1016/j.atmosenv.2013.05.081
[4] Envision Utah. (2020). Background: Air quality in Utah.
[5] Utah Department of Environmental Air Quality. (2020). Inversions.
[6] Healthy Environment Alliance of Utah. (2020). Bill tracker 2020.