First, the bad news: Our air stinks!

You've probably noticed.

It's so polluted out there that you have to floss the grit out of your teeth.

Airplanes have to build up extra speed to clunk through the atmosphere hanging over the valley.

The good news: It's not as bad as it used to be.

The Division of Environmental Quality reported earlier this month that our air is cleaner than it once was, based on annual averages.

Our "temporary" inversions are another matter. When it comes to 24-hour averages and winter inversions, we are way over the EPA's newly established limits. We have about four years to clean up or the federal government will send us to our room without any federal highway and transit funds.

The Great Inversion of '07 rages on. The gunk is hanging around the valley like a ring around a bathtub. If you want to see how bad it really is, drive up to Park City, look in your rear-view mirror and ask yourself this question:

Where do we flush this place?

First, some background: Air pollution is measured two ways: (1) Concentration levels; (2) Size of the particulate matter floating in the air.

On Monday morning, Salt Lake City's air was in violation of the EPA's standards for PM (particulate matter) 2.5. That's tiny (a human hair is about 60 micrometers in width) — and tiny is bad. These particulates are so tiny that they can be breathed deeply into the lungs; the big particles that are blown into the air by storms can be filtered in the nasal passageways or in the mucous of the upper airways.

That morning, Salt Lake's air measured 70 micrograms of PM 2.5 per cubic meter of air. "This would be high even for Los Angeles," says Brigham Young University professor Arden Pope. Clean air is 10 micrograms. By early Monday afternoon, the concentration of pollution reached 100.

"It's been climbing like a rocket," said Neal Olson, an environmental scientist for the state. "It's almost as bad as I've ever seen."

A red burn day is 35 micrograms per cubic meter of air for a 24-hour average. Salt Lake has reached the red-burn level 15 times in January, 12 in the past 17 days.

There were three red days in Salt Lake-Davis County last year, by comparison. The record was set with 23 days in 2004.

In the past month, pollution concentrations have climbed so high that Olson wonders if we won't be forced to go to a next level above red — Purple. That's DEFCON 2 or 3 in air pollution talk.

The length of the inversion is approaching record levels; the amount of pollution, however, has improved.

"We hear a lot of people who haven't been here long say it's getting worse," says Rick Stott, director of the DEQ. "That's not scientifically accurate by a long stretch."

But it's bad and Stott says so. On Monday, walking around downtown Salt Lake City was about the equivalent of sitting in a living room while someone smoked a cigarette. Some people are wearing masks in public. The problem is that Utah's particulate matter is too small to be filtered by masks. But, as Olson says, "It won't hurt. If you see a different color (on the white mask), then it must be doing something."

Utah is pretty much the perfect place for dirty inversions. Normally, these pollutants would rise into the atmosphere, but cold temperatures, combined with the bowl-shaped valleys and snow, prevent them from escaping. Along comes a stationary high pressure system and a vicious cycle ensues. A layer of snow on the valley floor and the thick gunk in the air prevent the ground from warming, so the cold air (and pollutants) are trapped.

Taken together, it's a perfect recipe for a thick, chunky soup. M'm, M'm, not so good.

What can you do? Reduce your driving, which accounts for about half the pollutants. Stott likens the situation to compounding interest — "Each day of the inversion traps pollution from the previous day. What you did last week is still there in the air."

So if you eliminate one or two days of driving, or if you walk to lunch instead of drive, or combine all your errands into one trip, that's less pollution collecting in the air — and in your lungs.

Doug Robinson's column runs on Tuesdays. Please e-mail