Unless the winds blow and the skies unexpectedly pour rain, folks in Salt Lake, Davis, Utah, Tooele and Weber counties can expect a series of "red" air quality days, according to the man who makes the color call.

Bob Dalley, manager of the air monitoring center for the Department of Environmental Quality, says ozone-laden air is showing up late this year. Friday was the first "red" day, complete with health warnings for those who are young, old or have a condition that makes them susceptible to bad air, such as people with asthma.

But he expects to issue the same warning at least through Monday if the hot weather and summertime high pressure system stay the same.

Blame it on ozone buildup.

Last year, there were 14 red-air days and they began much earlier. "This is a little late to be getting into these high ozone levels," Dalley says "We've had enough moisture, cooler temperatures and clouds" to keep the ozone below health-concern thresholds.

Ozone is a chemical oxidant and a respiratory irritant. It can trigger asthmatic reactions. The same chemical-oxidation process that cracks old tires irritates lung tissue and damages cells. As it does that, it releases histamines that cause swelling and restrict air passages. While it triggers problems for those with pre-existing breathing conditions, it can also damage tissue in otherwise healthy people exposed to it.

Ozone isn't emitted as a pollutant. Instead, precursor chemicals from automobiles, industry emissions and other sources start a photochemical process when they're exposed to high temperatures and sunlight, Dalley says. That creates a different set of chemicals, including ozone, that can have an impact on health.

Health effects start showing up at around .085 parts per million for an eight-hour average. Friday's reading on the Wasatch Front was .084. "At that level, some usually sensitive people probably experienced problems yesterday," he says. And as the level rises, so will the number of other people who feel the negative effects.

It can express itself as tightening of the chest when someone exercises outdoors, for instance. People with heart disease are also vulnerable.

Young lungs are vulnerable because they're still developing, and the chemical action can damage them.

It isn't ozone, however, that you see as you approach the valley. Some of that is particulate matter from hazy smoke blowing off fires in California, Nevada and southern Utah. At this point, Dalley says, the levels are not such that they're causing health concern. In the total volume of air it's significant, but not near the ground where people are trying to breathe.

The department's telling those who are susceptible to ozone to stay indoors and anyone who doesn't have to drive not to. But even people who must drive on red days can help, says Dalley. They can reduce their own impact on the air by doing their errands at one time, instead of making several trips. A cold-starting car emits more pollution than one that's warmed up. If you must drive to work, walk to lunch. Mowing the lawn is a bad idea not only for pollution but from an overexertion point of view in this heat.

The whole day needn't be lost, though. In the mornings, when it's a little cooler, you can exercise, Dalley says. But the ozone will start to build and between 1-7 p.m. is at its highest daily level.

Oddly enough, the cars that help cause ozone buildup will also consume it a little as the day cools down again for the evening, but as it breaks up into the atmosphere, it's setting up the whole cycle again.

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E-mail: lois@desnews.com