As the wind steadily moved a storm system across the Great Basin toward Utah over the weekend, air quality worsened across the Wasatch Front.
According to U.S. Environmental Protection Agency data, air monitors detected spikes in ground-level ozone — the “bad ozone” that can impact breathing and aggravate asthma. But that doesn’t tell the whole story.
That’s because the air quality index, or AQI, provides an average over longer periods of time — eight hours for ground-level ozone and 24 hours for particulate matter like dust — meaning it may not reflect the pollution peaks during that span.
“The average itself [for particulate matter] will look lower than maybe what you’re experiencing in real time,” said Rachel Edie, an environmental scientist with the Utah Department of Environmental Quality.
Windy conditions are not unusual this time of year, said Monica Traphagan, lead meteorologist for the National Weather Service in Salt Lake, but the gusts over the weekend and on Monday were more intense and widespread than normal.
Sustained winds blew up to 40 miles per hour and gusted as strong as 57 mph, according to National Weather Service data.
Those high winds pulled ozone down from higher levels of the atmosphere, Edie said, but the air was moving too quickly for reactions to happen that would have created more ozone.
Ozone measurements stayed relatively steady based on trend data, she said.
That same trend data shows some large spikes in PM 10 pollution – tiny particulate matter like dust measuring up to 10 microns in diameter.
The EPA reported “moderate” levels of particulate matter pollution — both PM 10 and the smaller PM 2.5, which is 2.5 microns in diameter — in Box Elder, Davis and Salt Lake counties at least one day during the windstorms.
At that level, the EPA recommends people who might be “unusually sensitive” to air pollution because of asthma and other lung diseases, heart disease, age, or pregnancy consider making outdoor activities shorter and less intense.
But monitors across the Wasatch Front showed occasional jumps to higher levels.
“On these windy days, there are just so many different factors that are building into those numbers for each of those pollutants,” Edie said.
That includes if it has rained recently to reduce the amount of dust, if there is cloud cover to limit the creation of ground-level ozone and if there are dust events with high, but sporadic, measurements, she said.
Northern Utah is now in for less wind and “much cooler temperatures,” Traphagan said.
Some precipitation also is likely, she said, though snow is only likely above 8,000 feet. There also is some chance of lightning, she said.
Overall, northern Utah is likely to see some “unsettled weather” for the rest of the week, Traphagan said.
The air quality forecast predicts good air quality for Wednesday and Thursday.
But people should always check current conditions, Edie said, especially if they have asthma, their allergies are kicking up or they are otherwise sensitive to particulate matter.
And strong winds don’t necessarily mean bad air, she said, since it can move pollution out of the valley during inversions or high ozone periods.
“[Wind] can definitely be a positive,” Edie said.
Megan Banta is The Salt Lake Tribune’s data enterprise reporter, a philanthropically supported position. The Tribune retains control over all editorial decisions.