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Poor air quality along the Wasatch front has prompted a health warning and triggered wood-burning bans in a half-dozen counties through Tuesday.

The Utah Division of Air Quality issued an "orange," unhealthy grade on Monday for Sale Lake, Davis, Utah, Cache, Duchesne and Uintah counties.

The National Weather Service says cold temperatures have trapped the pollution in valleys where little relief is expected until another front moves in toward the end of the week.

Health officials are urging the elderly, the young and those with heart or respiratory conditions to avoid prolonged outdoor activity. Motorists should avoid travel and step up use of mass transit to limit hydrocarbon emissions.

A voluntary wood-burning ban is in effect for Weber, Box Elder and Tooele counties where moderate levels of particulates have triggered a "yellow" grade.