SALT LAKE CITY (AP) – An icy fog trapping pollutants in the Salt Lake region was bad enough Tuesday to slow airport traffic to a crawl by cutting visibility.
Northern Utah marked its 23rd winter day of health alerts for toxic air, surpassing a number for last winter that was the worst in a decade, the state’s air-quality monitor said.
The Salt Lake region and parts of California were ranked Tuesday as having the nation’s worst air by the U.S. Environmental Protection Agency, which tracks pollution at http://www.airnow.gov.
The culprit is a high-pressure system that’s forcing cold, stagnant air to settle in mountain valleys, allowing tailpipe and other emissions to build up. No relief is in sight.
Northern Utah is having more health-alert days this winter, but the levels of pollution are lower than last winter, said Bo Call, air monitoring manager for the Utah Division of Air Quality.
Soot counts approached 60 micrograms per cubic meter in Salt Lake and Davis counties Tuesday, nearly double the federal health limit.
Pollution levels tend to settle overnight before building up during day when the chemistry of smog gets a boost from sunlight reflecting off snow cover, Call said.
“It’s not that the air is cleaner in the morning. It’s just moving around more,” he said.
The atmospheric lid trapping pollutants lowers in the day, concentrating emissions near ground, he said.
A heavy fog developed Tuesday morning over the Salt Lake City International Airport, cutting visibility sharply enough to require vehicle escorts for aircraft moving between runways and terminals, said Barbara Gann, an airport spokeswoman. The number of flight delays wasn’t immediately available.
Weather forecasts show no break in the pattern that has northern Utah locked under a blanket of air pollution, even as the mountains surrounding Salt Lake City bask in sparkling clean air.
The valley air pollution was on display as 22,000 people arrive in Salt Lake City for the largest trade show for outdoor gear and apparel. The Outdoor Retailer Winter Market runs through Saturday.