Image: Houston Pollution Air
Emissions from petroleum and chemical plants create a haze over the outskirts of Houston. Researchers say smog is worsening allergies and asthma cases across the United States.
By
msnbc.com contributor
updated 11/4/2003 3:07:25 PM ET 2003-11-04T20:07:25

In cities across America allergies and asthma seem to be worsening. It’s not that more plants are pollinating, experts say. Rather, it’s the high levels of diesel fumes and ozone polluting the air.

In recent years, there has been burgeoning evidence that air pollutants worsen allergies and asthma, says Dr. Andre Nel, a professor in the department of immunology and allergy at the University of California at Los Angeles. And because the air is dirtier in cities, studies have shown that it’s urban dwellers who are most affected.

For allergy and asthma sufferers, this means that special attention must be paid not only to pollen counts, but also to the daily pollution index. And on bad days, exercise routines may need to be modified.

Several studies have shown ozone can exacerbate one’s allergies, says Dr. David Peden, a professor of pediatrics at the University of North Carolina School of Medicine and director of the UNC Center for Environmental Medicine, Asthma and Lung Biology.

Peden and his colleagues looked at the effects of ozone on people allergic to dust mites. Not only did ozone worsen allergy symptoms immediately, but among patients with asthma, researchers found there was a chronic inflammation of the airways that could be measured the next day.

This may explain why studies have shown people tend to show up in the emergency room one or two days after a high ozone day, Peden says. “There seems to be a time lag between the start of the inflammation and the effects that bring people to the ER.”

Other research has shown that the tiny particles in diesel exhaust can increase a person’s sensitivity to pollen or dust mites or other allergy producing antigens.

What's an allergy sufferer to do?
So what’s an allergy sufferer to do on a bad air day?

Do your best to cut down on exposure to ozone, Peden says. “In general, ozone is lower early in the morning and peaks around 4:00 to 5:00 p.m. So, you might want to exercise in the morning rather than late afternoon. That would reduce the chances of a pollution related event.”

That is, unless you’re allergic to pollen, which happens to be highest in the morning.

In that case, Peden says, you might want to exercise indoors.

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If you still want to exercise outdoors when ozone is high, it may be best to modify your workout, according to the North Carolina expert. You’re more likely to experience ill effects from ozone if you are breathing fast, Peden says.

“So you’ll experience less of an effect if you do a brisk walk rather than running,” he adds.

Interestingly, some of the worst air may be on or near freeways, Nel says. And, contrary to popular belief, the car’s air conditioner will not help.

“That will just pull in more air from the freeway,” he says. “At this stage most cars are not manufactured with an efficient filtration system for these small particles.”

Linda Carroll is a free-lance reporter based in New Jersey. Her work has appeared in The New York Times, Health and Smart Money.

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