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Regulators are issuing an air pollution alert for seven counties along the Wasatch Front, home to 2 million Utah residents.

A pollution-trapping inversion or icy fog has given northern Utah the nation’s worst air.

<div class=”p402_hide”>State monitors show Utah County has the worst air. It was exceeding federal standards by three times early Monday.</div>

The Utah Division of Air Quality issued the alert for Box Elder, Cache, Davis, Salt Lake, Tooele, Utah and Weber counties.

Authorities are prohibiting wood burning and urging people to limit driving.

Doctors say people _ especially pregnant women and children _ should stay indoors, or at least avoid active outdoor exercise.

Valley temperatures across northern Utah weren’t expected to break 21 degrees Monday.

Mountain temperatures are warmer, with Park City expected to reach 43 degrees.

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