SALT LAKE CITY -- Northern Utah remains under a week-long health alert from air pollution trapped inside mountain valleys.
Authorities say no relief is in sight after pollution levels spiked Monday.
New Year's Day opened with as many as 73 micrograms of fine soot per cubic meter in Weber County. That's nearly three times the federal standard, according to air monitors maintained by the Utah Division of Air Quality.
Pockets of air pollution can be found across western states. The U.S. Environmental Protection Agency says Salt Lake City, Phoenix, Las Vegas and central California are suffering from the country's worst air.
Utah regulators are banning wood burning, urging people to drive less and warning people with heart or respiratory problems to stay indoors. Most of the pollution comes from tailpipe emissions.