The good news is the snowstorm that caused more than 100 traffic incidents in the valley last Monday has ended, leaving mostly clear roads and blue skies over the county.

The bad news is those blue skies are going the way of the storms, leaving the traditional January inversion hovering over the valley.

The Division of Environmental Quality has asked residents to take voluntary action on New Year's Day by not using solid fuel-burning devices or open burning. Individuals were asked to reduce vehicle use by consolidating trips. Health conditions were still considered good.

"Air pollution plays a huge part in restrictive lung diseases," said Dr. Joseph Miner, director of the Utah County Health Department. "You can actually get a lot of acute diseases."

Miner described two types of lung disease. One is obstructive, in which the flow of air into a lung is obstructed by conditions including asthma, emphysema, chronic bronchitis, infections and obesity. The other is restrictive. Restrictive lung disease is marked by particles in the lung itself. Such disease may be caused by silicosis, coal dust, asbestos or infections.

Miner said in the Great London Smog of 1952, approximately 12,000 individuals died during a four-day period from exposure. Ten years later 700 died from a similar smog.

Conditions in Utah County are not expected to reach anywhere near that level, of course. But there are steps people can take to help the conditions.

Nitrogen dioxide and sulfur dioxide are two of the main compounds listed by the Environmental Protection Agency as toxic air pollutants. They are products of combustion, which greatly multiplies the effects of poor air quality. They are often associated with the temperature inversion, as the cold weather tends to keep those products closer to the earth.

That combustion comes from sources including wood- and coal-burning stoves, as well as vehicles. The majority comes from vehicles, but the amount per individual is much greater with the stoves and fireplaces.

"Burning wood or coal in one fireplace can be the equivalent of 90,000 homes burning natural gas," Miner said. "That can contribute as much to pollution as three cities the size of Provo.

"People need to be sensitive to that and not make other people breathe their smoke. Natural gas or propane are much more clean than wood or coal."

Bryce Bird, Utah's director of the Division of Air Quality, said air quality has been generally improving in recent years and attributed much of that to stricter regulations.

But one thing that cannot be regulated is the terrain. The topography along the Wasatch Front is also one of the major factors that affects the inversions.

"Phoenix is surrounded by mountains," said Dr. Michael Rhodes, director of Utah Valley Family Medicine. "But they don't get the cold with the blanket of snow, which adds to the inversion.

"They have a similar topography. Anywhere you have a large populace centered around a mountainous front you can get an inversion."

Daily Herald reporter Barbara Christiansen can be reached at (801) 344-2907 or bchristiansen@heraldextra.com. Twitter: @bchristiansen3.

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