Doctors say people — especially pregnant women and children — should stay indoors, or at least avoid active outdoor exercise under the sickening yellowish haze. Elderly people with heart disease are most at risk, Moench said.
"If you can see it, you don't want to breathe it. Think about what's going into your body," Salt Lake City pediatrician Ellie Brownstein said. "It's essentially like smoking. Instead of breathing clean air, you're breathing particles that make it harder for your lungs to function and get oxygen."
Snow cover amplifies the phenomena called a temperature inversion — Salt Lake City was a foggy freezer box Wednesday at 18 degrees, while Park City basked in sunny 43-degree weather. The warmer air aloft acted like a lid on the frigid valley air, leaving it with no place to go.
For weeks, industrialized cities in northern China have been dealing with bouts of sickening smog several times more toxic than Utah's. But by U.S. standards, Utah's pollution index is off the charts with readings routinely exceeding a scale that tops out at 70 micrograms a cubic meter. The EPA sets a standard for clean air at no more than 35 micrograms.
"People think the health implications are limited to asthma — that's only a drop in the bucket," Moench said. "For every pregnant woman breathing this stuff, this is a threat to her fetus through chromosome damage. It sets people up for a lifelong propensity for all sorts of diseases."