Division of Air Quality

Northern Wasatch Front Ozone Nonattainment Area

This page contains information about summertime ozone in the Northern Wasatch Front nonattainment area and an interactive emission inventory for the area. You can use thisInteractive Inventory to explore and learn about different emission sectors and sources (SCCs) within the Northern Wasatch Front, and where the emissions originate that drive the local ozone formation.

What is summertime ozone?

You’re probably familiar with the Wasatch Front’s wintertime PM2.5 pollution, but Utah’s urban center also experiences harmful air pollution – ozone – during the summertime. Ozone is a highly reactive gas that causes damage to human lung tissue. Ground-level ozone is generated when precursor pollutants – Volatile Organic Compounds (VOCs) and Oxides of Nitrogen (NOx) – interact with sunlight. The Northern Wasatch Front region experiences ozone concentrations that exceed Environmental Protection Agency’s (EPA) air quality thresholds.
A stacked bar chart titled "Number of Days 8-hr Ozone Daily Max > 0.070 ppm" for Salt Lake City, UT, from 2000 to 2024. The vertical axis shows the number of days, and the horizontal axis lists the years. Each bar represents the total number of days in a year that ozone levels were above the standard. The bars are color-coded by Air Quality Index levels: orange for "Unhealthy for Sensitive Groups," red for "Unhealthy," and dark red for "Very Unhealthy." The chart indicates high year-to-year variability in air quality. The year with the most high-ozone days was 2021 (42 days), while the years with the fewest were 2010 and 2014 (7 days each). Other years with high counts include 2006 and 2007 (40 days each). The data shows that the majority of days above the standard fall into the orange "Unhealthy for Sensitive Groups" category.
Ozone exceedance days in the Wasatch Front.
Source

The Northern Wasatch Front Nonattainment Area

In August 2018, the EPA designated areas of the Wasatch Front as a nonattainment area for ozone based on the 2015 National Ambient Air Quality Standard of 70 ppb. The area includes Salt Lake, Davis, as well as portions of Weber and Tooele counties. Since the Northern Wasatch Front failed to meet the 70 ppb threshold by August 2021, the area was reclassified to “Moderate” nonattainment status. As part of this designation, Utah was required to develop and submit a moderate State Implementation Plan (SIP), which included a description of how the state reduced emissions in order to meet the air quality standard.

However, as the area failed to attain the standard by the moderate attainment date of August, 2024, the area may be further redesignated as a “Serious” nonattainment area. As a result of this more stringent designation, the state will again need to develop a serious SIP amendment showing how the state will further reduce NOx and VOC emissions throughout the nonattainment area. If the area is redesignated to serious status, a new SIP will be due to the EPA on January 1, 2026.

Map of northern Utah highlighting the Northern Wasatch Front Ozone Nonattainment Area in blue. The highlighted region includes all of Salt Lake County (including Salt Lake City) and Davis County, the western portion of Weber County (including Ogden), and the eastern portion of Tooele County (including the city of Tooele and the southern portion of the Great Salt Lake).

FAQs

MAPS: Ozone-forming pollutant sources in Utah

Sources of ozone precursor emissions range from vehicles to industrial mining operations, from leaf blowers to oil refineries. Learn more about the sources of pollution that cause ozone formation in your legislative district using the interactive maps.

Emissions are from the Division of Air Quality’s 2017 emissions modeling platform.

Questions?

Ryan Bares ([email protected])
Lexie Wilson ([email protected])