Utah is home to some of the most beautiful mountain valleys and desert expanses in the world. Yet the same breathtaking landscapes have a direct effect on the quality of air in Utah.
Genesis of an inversion
When valley floors hold lots of snow, temperatures plummet, and a high pressure system parks overhead, leaving cold air on the ground with nowhere to go. It can’t rise because cold air doesn’t rise, it sinks. Just above it, the sun rapidly heats up the air, creating a warm blanket that pins the cold air below it to the valley floor. This is an inversion. And as long as there is lots of cold air and snow on the ground, and lots of sunlight above, the inversion will remain. 
The animated gif to the right illustrates the trapping effect that the layer of warm air has over the valley.
“Think of an airshed as the available air that you have to live in. We're stuck with that 1500 or 2000 foot layer of air. That's all we have. We can't go get more air to pollute. We have to live within our means inside that airshed. Not only do inversions trap and concentrate fine particulates at dangerous levels, they create them as well. When conditions are right, these inversions play host to a newly-discovered chemical reaction where certain chemical compounds in the air are joined to become fine particles or PM2.5. In other words, an inversion can actually create its own pollution.” 
The animated gif to the right illustrates the notion of an 'Airshed'. The available air collects in the valleys while at higher elevations the atmosphere is continually cleared out.
Winter versus Summer
During winter inversions, much of the pollution is visible. In the summer, we experience high levels of pollution as well, but it is not as visible. During the hot, sunny, still days of summer Utah is prone to the creation of ozone statewide.
We are still trying to understand why this is. According to Utah State University Environmental Engineering Professor Randy Martin, “[Oil and gas] exploration and production puts a lot of precursor species (PM 2.5) in the atmosphere.” Ozone is created when fossil fuels are burned, releasing nitrogen oxides and volatile organic compounds. When these fine particles are exposed to sunlight they go through a series of chemical reactions to create ozone. “Some of the ozone concentrations we see [in the Uintah Basin] are higher than you'll see in Los Angeles in the summertime.”  
While the highest layer of our atmosphere contains ozone that protects us from the sun’s harsh rays, when the ozone is concentrated in our airshed it can lead to premature death, asthma, bronchitis, heart attack, and other cardiopulmonary problems.