Shifting Gears

Special to The Times

HEALTHY people who want to cut down on buying $3-a-gallon gas might consider the perks and perils of getting out of their cars and onto their bikes.

There are obvious benefits to riding a bicycle -- such as saving money, not polluting and getting regular exercise to help ward off obesity, heart disease and perhaps even cancer.

But riding a bike in a congested and polluted city amid bigger vehicles puts the rider at risk for accidents and for sucking down the very pollution they're helping to reduce. Pollution can even trigger heart attacks in some out-of-shape or sensitive individuals.

In fact, as long as you're generally healthy -- if you don't have heart disease, diabetes or lung problems -- and if you learn to ride in a defensive and safe manner, the risks of riding are outweighed by the boon of exercise, experts say.

"The long-term benefits, in my opinion, would vastly outweigh the short-term risks of cycling," says Dr. Robert Brook, an assistant professor of cardiology at the University of Michigan, Ann Arbor.

Societal attitudes toward biking and misunderstandings about safety "perpetuate this myth that cycling on regular roads is deadly," adds League of American Bicyclists instructor Dan Gutierrez of Long Beach.

The National Center for Statistics and Analysis reported that 33,134 people in autos, and 4,500 pedestrians, died in crashes in 2004 -- but there were only 725 cyclist fatalities. Even so, Gutierrez says, fatalities don't tell the whole story. And a skilled cyclist can ride with a much lower accident risk than an untrained one.

Gutierrez, who teaches a 12-hour course on how to ride bikes in traffic, says cycling as if you're a vehicle -- so-called "vehicular" or "integrated traffic" cycling -- will remove most of the ways you can be harmed while riding in traffic.

Aside from the typical safety gear such as helmets and gloves, Gutierrez recommends riding on roads that have two lanes going in one direction -- so that cars can easily pass you -- and learning to look out for hazards such as potholes (easy enough to dodge unless it's raining) and places where the gutter meets the road. The street's asphalt will sink an inch or two next to the concrete gutter, and this can grab your front wheel.

But the biggest danger to riders, Gutierrez says, is the "door zone" -- the space next to parked cars where car doors are prone to swing open unannounced. He cites one New York study in which 16% of bicycle messengers reported such door trouble.

"It's much better for a cyclist to ride for their own safety than rely on the whims of drivers," he says.

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Creating a comfort zone

If bike commuting takes off, these risks could drop. A study published in 2003 found that motorists were less likely to collide with cyclists when more people rode bikes. This may be because drivers become more comfortable with cyclists on the roadways when they see more of them.

Diane Trout, 34, of Pasadena has read books on how to bike safely and has taken their advice to heart. As she cycles to work at Caltech, she makes sure drivers think of her as a vehicle, albeit a slow one, sharing the road. "Occasionally I feel a little nervous, but that's usually when I'm not behaving like a slow-moving vehicle," she says.

L.A.'s dirty air might also give a would-be biker pause, and with some justification: It's bad for you.

In a study published in 2005, Brook looked at the effects of pollution -- especially ultra-fine particles that are made up of carbon and metals -- on blood pressure. He and his colleagues subjected 23 people to air pollution levels within acceptable ranges and compared them with people who were breathing clean air.

The group breathing bad air experienced a 5% to 10% rise in blood pressure, which is not enough to impair a healthy person but enough to cause a problem for people who are older or who have certain heart and lung ailments, he says.

As with any exercise program, "if you're prone to asthma or respiratory or heart diseases or have diabetes, you should consult a physician first," says Michael Jerrett, an epidemiologist at USC. "Of course, biking is a tremendous form of exercise," he adds. And, it turns out, in addition to being a health-promoting activity, riding on a bike may subject you to less foul air.

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The air inside

About a dozen studies since the early 1990s have shown that people in vehicles -- even children in school buses -- get two to five times higher concentrations of various pollutants than either pedestrians and cyclists do, says engineer and avid cyclist Thomas Scheffelin of California's Air Resources Board in Sacramento.

Part of the reason might be that riders aren't in the thickest traffic; pollution is higher on highways and falls off quickly with distance. Experts also suggest that car vents suck in air near the height that vehicles spew their exhaust.

"Air gets inside cars almost instantly," Scheffelin says. "When you get behind a big diesel truck, pollution readings spike instantly."

For example, a 2004 study of 691 car drivers, mass transit riders, motorcyclists and cyclists published in the New England Journal of Medicine revealed that sitting in traffic increased people's risk of a heart attack by almost three times for a motorist but less than two times for a cyclist. (Neither risk was terribly alarming: Strenuous exercise in unpolluted air increases people's heart attack risk by about six times, a risk that regular exercise can diminish.)

Though the risk may be lower for a cyclist, it does still exist. Researchers in Copenhagen found that cyclists riding in traffic sucked in 47% more ultra-fine particles than when they rode in the lab (and that more pollution resulted in more DNA damage in their white blood cells.)

A cyclist's fitness will affect the size of the risk, Jerrett says, because it will affect how much pollution they take in and the dirty air's risk to them -- because those who are out of shape breathe in deeper.

And, he adds "you have to balance that and the health benefits" of regular exercise and a trimmer body.

Jerrett recommends riding away from congested roads and timing trips to avoid rush hour.

"And rain knocks a lot of those particles out of the air," he adds, which makes winter biking in L.A. a healthier prospect -- in some ways.

As Gutierrez warns, those potholes are hard to see in a downpour.

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