Utah cities land at No. 10 on the list for the worst air quality as of Thursday morning

KAYSVILLE — Four Utah cities landed on the list of the 10 worst cities for air quality Thursday morning.

Kaysville, Utah, was the most polluted city in the U.S. as of 5:34 a.m., according to IQAir. South Jordan, Saratoga Springs and Midvale also landed on the morning list.

This ranking has since changed. At the time of publication, the ten most polluted cities were all in California.

The rankings will continue to change. Experts say it is influenced by a number of factors.

What affects air quality?

Cold air doesn’t rise, it sinks.

So when an inversion occurs in Utah, weather experts say cold air and pollutants will be trapped in the valleys.

When you are at a lower altitude, the chances of polluted, stagnant air are usually higher. It also depends on how close you are to pollution sources such as highways and industrial sites where emissions are higher.

Heather Holmes is an associate professor of chemical engineering at the University of Utah. She compared it to skiing down the fall line of a mountain.

“It’s like the path of least resistance,” Holmes said. “Cold air will just slide down the mountain slopes and everything will end up at the lowest elevation. So it’s a mix of the elevation of your location… and then also your proximity to sources.”

She said that before sunset, when these Utah cities made the worst air quality list, the layer of air closest to the Earth’s surface was at its lowest.

So the valley we live in has a lid that pushes the air down, giving it less room to mix.

This causes the pollutants to become more concentrated.

KSL meteorologist Devan Masciulli said wind also played a role.

“It could have been a factor from Kaysville. It’s close to the highway and it may have been because the wind at that time pushed a concentration perfectly toward Kaysville and that raised their AQI to a little higher than some other locations.”

Experts said you shouldn’t be surprised if other Utah cities join the top 10 list tomorrow or at the next reversal.