Monday marked one full week of cold, awful air. Not since Jan. 15 has the atmosphere in the capital been good quality — and it's not expected to improve substantially until Wednesday or Thursday.

"We've had seven consecutive days of 'red"' — hazardous air conditions, Neal Olson, environmental scientist with the Utah Division of Air Quality, said Monday.

"We had a break on the 21st and 22nd, when we went to a yellow," or moderately polluted conditions. The five days prior to that were all red alert days.

During red alerts, the 24-hour average level for the finest particles, called PM-2.5 particulates, is above the EPA's health standard of no more than 35 micrograms per cubic meter. Wood and coal stoves and fireplaces must not be used, and state officials ask residents to reduce vehicle use.

On yellow air quality days, people are asked to voluntarily forgo burning wood or coal and to cut down on vehicle use. On green days these restrictions are lifted.

Before Dec. 18, 2006, the standard was 65 micrograms, but since then it has been 35. Air pollution in Salt Lake City was measured at an unhealthy 69.4 micrograms on Monday.

But glimpsed through the dense smog, hope is shimmering on the horizon.

"By Wednesday we should be getting some colder air aloft," Len Randolph, meteorologist at KSL, said Monday. "Yesterday Cache Valley got a little relief." While pollutants dropped there, the clearing did not extend beyond Cache.

Colder temperatures aloft could stir the atmosphere, thinning the haze. "That'll help a bit," Randolph said. "That's not going to clear it all out."

A small storm is expected on Thursday, he added. "We'll just have to see whether it's going to be strong enough to blow it out of here."

While air quality has been unhealthy every day, that doesn't mean the level was consistently bad all day long. Sunday night the pollution concentration "actually dropped quite a bit," said Cheryl Heying, planning manager for the Division of Air Quality.

The night was relatively warm, causing the ceiling of the inversion to lift to a higher level of the atmosphere. With the cap lifted to a higher level, the gunky air spreads out further. "The pollution kind of disperses a bit," she said.

Besides wretched air conditions, Salt Lake residents are suffering from a barely precedented cold snap.

"We've been 32 or below since the 12th of January," said Randolph. As of Monday, Salt Lake City was in its fourth-longest stretch of temperatures at or below the freezing point (32 degrees), since record-keeping began in 1928.

If Monday's temperature did not rise above the expected high of 32, according to Randolph, the city will have tied another cold-spell record.

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E-mail: bau@desnews.com