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SALT LAKE CITY — Ozone is a threat to Utah air quality that primarily develops over the summer, but John Horel believes it is often forgotten because of how opaque ozone can be, compared to inversion, pollution or wildfire smoke.
Ozone forms when nitrogen oxides and volatile organic compounds "break apart" with sunlight and heat, as noted by the Utah Division of Air Quality. Vehicles, buildings and various other products can contribute to this.
The division says the "harmful air pollutant" can form hazy skies; however, Horel, chairman of the University of Utah Department of Atmospheric Sciences, says that's not always the case.
"In the wintertime, when it's dreary and we're dealing with ice fog and all those kinds of things, people recognize that and they're typically going to take more action. ... The same thing with summer smoke," he says. "But ozone is out there on the clearest of days."
That is why he's thrilled about a new website that helps to make Salt Lake County's ozone situation much more visible. The website reports air quality data collected from Utah Transit Authority TRAX light-rail trains and, eventually, 15 electric buses traversing routes across the Salt Lake Valley.
County officials launched the website on Thursday and say it will offer "real-time, neighborhood-level air quality data" ranging from particulate matter to ozone.
"This information can be used by the public, it can be used by our scientists. It's indeed game-changing," said Salt Lake County Mayor Jenny Wilson.
The website was created years after the project launched in 2021. The Utah Legislature, Salt Lake County and various other government entities and organizations contributed money to add monitors — each system costing about $40,000 — to the buses. UTA had already installed similar monitors on TRAX trains beginning in 2014.
Most air quality monitors and air quality data focuses on particulate matter, including PM 2.5, which is how pollution from wintertime inversions or wildfires is measured. But the censors attached to buses and trains also collect ozone pollution, which is harder to detect, Horel said.
Bus and train air quality monitors fit something called the federal equivalent method for measuring ozone, which is usually too expensive for homeowners to use, he explained. There are a handful of air quality monitors across the state tracking ozone, but none offer a wide range of location data as the county program.
"For the summertime ozone situation, the data is really not replicated through other networks," Horel told KSL.com.
There are some limitations. The data is dependent on when buses and trains operate and they do not run during the early morning hours. They also don't cover every part of the valley and data may not pick up microclimate variations throughout the county.
However, Horel says it still offers a critical window into an air quality threat far less monitored and noticeable than particulate matter. The hope is to turn that data into studies to better understand Salt Lake City's ozone situation, including when it's happening, where it's happening and any associated impacts.
I think when we see the data and we can capture it over time, policymakers are in a better position to know where to invest resources.
–Salt Lake County Mayor Jenny Wilson
Some of this is already underway.
The National Oceanic and Atmospheric Administration and National Science Foundation helped fund a major study of ozone creation across the Wasatch Front that will take place this summer. It will be led by some of the same researchers who uncovered high bromine levels coming from a magnesium plant in Tooele County.
The results of the study may not be known for a few years, but the project aims to "enable better understanding of the factors that lead to high ozone."
As for the new website, Wilson says she hopes residents will use it to make decisions on when to stay indoors or go out. The county will continue to watch for trends — to identify areas with worse air quality than others — that could lead to policy decisions down the road.
Yet, much like ozone, it's unclear what those policy decisions could be.
"I think when we see the data and we can capture it over time, policymakers are in a better position to know where to invest resources," she said. "We really want to probe why we see areas that are facing higher pollution and then make good policy decisions."
