SALT LAKE CITY – When winter comes to Utah and atmospheric conditions trap a soup of pollutants close to the ground, doctors say it turns every resident in the Salt Lake basin into the equivalent of a cigarette smoker.

For days or weeks at a time, an inversion layer in which high pressure systems can trap a roughly 1,300-foot-thick layer of cold air – and the pollutants that build up inside it – settles over the basin, leaving some people coughing and wheezing.

“There’s no safe level of particulate matter you can breathe,” said Salt Lake City anesthesiologist Cris Cowley.

The doctors and a lobby group of Utah mothers are blaming a company that mines nearly a mile deep in the largest open pit in the world for contributing one-third of Salt Lake County’s pollution. The rest is from tailpipe and other emissions.

They have filed a lawsuit against Kennecott Utah Copper, accusing it of violating the U.S. Clean Air Act.

The company is the No. 1 industrial air polluter along Utah’s heavily populated 120-mile Wasatch Front and operates heavy trucks and power and smelter plants. It says the claims are “without merit.”

Kennecott cites the blessing of Utah regulators for expanded operations and new controls that hold emissions steady.

Utah’s chief air regulator, however, acknowledged Kennecott is technically violating a 1994 plan adopted by the U.S. Environmental Protection Agency that limited the company to hauling 150 million tons of ore a year out of the Bingham Canyon Mine.

Utah has twice allowed the company to exceed that limit, as the company moves to expand a mine in the mountains west of Salt Lake City.

In each case, Utah sought EPA’s consent, but the EPA didn’t take any action. The lawsuit could force EPA’s hand, said Bryce Bird, director of the Utah Division of Air Quality.

Bird said the old limit would defeat changes Kennecott made to curb dust and emissions since 1994. Kennecott disputes the doctors’ figure and says it contributes about 16 percent of Salt Lake County’s overall emissions.

An examination by The Associated Press of emissions figures provided by Kennecott showpollutants ranges from 65 percent of Salt Lake County’s sulfur dioxide emissions to 18 percent of its particulates.