Wheeze! 28 days of really bad air

The number of days that residents of Salt Lake and Davis counties had to breathe unhealthy air and were asked to limit their driving and wood burning reached an all-time high of 28 during the annual Winter Air Quality Alert program.

In a report released Thursday, the Utah Department of Environmental Quality also said Utah and Weber counties saw a record amount of "red," or poor air-quality days during the program, which started in 1992 and runs from Nov. 1 to March 1 every year.

In January, Utah experienced a near record-setting number of 18 consecutive days of poor air quality, with temperatures below freezing, a condition that can — and did — create an inversion. When cold, dense air in a valley is trapped by high pressure and warmer air above, the resulting inversion puts a "lid" on air movement, trapping pollutants that can be harmful to humans.

"That just allowed those particulates to build up," said Mike Seaman, meteorologist with the National Weather Service in Salt Lake City.

Specifically, the DEQ looks at the levels of a microscopic particulate pollutant called PM 2.5, which is made up mostly of automobile exhaust, followed by near equal amounts of pollution from industry, wood-burning stoves and fireplaces, and businesses.

In the past, the DEQ would declare a "red" day if the level of PM 2.5 reached 65 micrograms per cubic meter. Last December, that standard changed, following a federal mandate.

"We're calling red at 35 micrograms," said DEQ spokeswoman Donna Kemp Spangler. "We want to have healthier air."

Kemp Spangler said there are enough health studies that justify the tougher air-quality standard. She said it means people who are more sensitive to pollution in the air will know sooner that the air quality outside may be reaching a point that could be hazardous to their health.

The State Health Department has guidelines for ways at-risk people should react to red days and the less alarming "yellow" days when PM 2.5 levels are lower but still a health concern.

"We know that high air-pollution days are associated with an increase in emergency-room visits," said Libbey Chuy, the health department's asthma-program specialist. After a red day, Chuy said, there is usually a rise in the absentee rate at schools.