Why does Logan have ‘the worst wintertime air’ on the Wasatch Front?

Experts say the Cache Valley’s geography and harsh winters make for worse air quality and longer inversions.

Logan • Utahns are no strangers to bad air quality, and this year’s cold winter has caused plenty of days with terrible air. But in the winter months, the air quality in Cache Valley is particularly bad, even though it has a fraction of the population of other counties along the Wasatch Front.

So why does the county have worse winter air than elsewhere in Utah?

There are a few factors, according to Randy Martin, an associate research professor at Utah State University’s Department of Civil & Environmental Engineering.

“I describe it as a bathtub,” Martin said, referring to Cache Valley. “We’re surrounded north, south, east and west by mountains with a very, very small outlet near Cutler Reservoir. So we trap the air pollutants very effectively.”

Martin said that more populated areas along the Wasatch Front, like Salt Lake County, have geographical outlets that can allow pollutants to escape more quickly than Logan. Martin said because of its geography, Cache Valley has less air to work with, so it’s easier for the valley to fill up.

Editor’s Note: This story is also available in audio form, and it was produced as part of a collaboration between The Salt Lake Tribune and Utah Public Radio.


That trapping of pollutants is commonly referred to as inversion, which is a meteorological event where warm air settles above a valley, while cold air — and pollutants in that valley — are trapped underneath with nowhere to go.

Bryce Bird, director of the Division of Air Quality within the Utah Department of Environmental Quality, said not only does Cache Valley fill up with bad air more quickly, but it also lingers for longer. This is because typically, the area has colder, snowier winters than counties to the south.

“It’s amazing that just having a few hundred feet elevation gain between the Salt Lake Valley and Cache Valley and just a little bit further north, often ... there’s more snow and then it persists longer just because the temperatures are colder,” Bird said.

Martin agreed, saying the valley has seen consistently worse air than the more populated counties to the south.

“Cache Valley this year, and historically, by historically (I mean) 15-20 years ago, has had the worst wintertime air compared to Wasatch Front,” Martin said.

Poor air quality can cause a number of health issues, particularly regarding heart and lung function, according to the Environmental Protection Agency. Bird said when air quality is poor, there is an increase in hospitalizations from asthma and heart attacks, with the latter more likely to be fatal. He added that prolonged exposure to bad air in Utah has its effect over time.

“Lung diseases that are associated with smoking we see in Utah populations where people don’t smoke,” Bird said. “And that has been correlated to lifetime exposure to air pollution.”

However, Bird said despite the state’s growing population, state and national measures to mitigate emissions are working.

In Cache, Bird pointed to a reduction in the number of wood-heating homes and car emissions testing as ways the county has controlled its air quality issues.

“All those things have actually resulted in fewer emissions in the Cache Valley than there were a few years ago, and the trend is still going down even though the population is growing,” Bird said.