Is it better to cycle or drive a car in polluted air?
Avid cyclist and KPCC listener Scott Chan has a question:
Chan lives in Alhambra and works in downtown L.A. His commute is just 8 miles, but he’s concerned enough about fast-moving traffic that he drives to his job, then switches to a bike to travel between meetings for his nonprofit.
Here’s his fear: “There’s a lot of exhaust,” he said. “Sometimes I’m pushing it, and I’m breathing more. My hunch is that it’s really bad for my lungs.”
The expert weighs in
Ed Avol is a professor of preventive medicine at the University of Southern California Keck School of Medicine. He specializes in traffic pollution and respiratory health.
“First, I think it’s important for everybody to realize that probably none of us get enough exercise. There’s such an issue now with obesity, diabetes and general health that getting out and exercising — be it walking, riding, etc. — is really important to your health for a number of reasons,” Avol said.
“It is true that on the busiest streets you do get more pollution exposure than if you’re riding through a quieter neighborhood. There have been a number of studies showing that in the main, it’s better for you to still ride to get that exercise — use your bicycle — than not. Even in air polluted areas,” he said.
L.A. is one of those areas. It routinely tops the American Lung Association’s annual list of most polluted cities for ozone, or smog. In 2016, it also ranked fourth for year-round particle pollution.
So while L.A.’s mild climate and sunny skies make it ideal for bicycling, Chan is right to be concerned about his health. Breathing ozone irritates lungs. It’s that burning sensation from taking a deep breath.
And particle pollution is worse. Breathing it in can increase the risk of lung cancer and also cause heart attacks, strokes, even premature death.
How can I reduce the impacts of air pollution when cycling?
Stay off busy streets
“You want to try to avoid the particles and the gases when you can,” Avol said. “That usually means distance from a roadway. So the farther away you are, the better off you are. Here in L.A., as you get farther away from a busy street, you start to get closer to the next busy street. And so it’s always a challenge to try and find that median point.”
“There's no magic bright line that you can say I'm on this side, I'm OK, if I'm on that side, I'm in trouble," Avol said. "There's sort of a gradual decreasing as you move away, but we're talking about hundreds of yards, roughly speaking, rather than 10 or 20 feet. But given the choice, you'd much rather be a quarter mile or a half mile away from the freeway. If you can go through the quieter neighborhood is much preferable in terms of your exposure and your health.”
Consider the wind
In L.A., the wind generally develops in the morning and it blows from the ocean across the land, so it’s west to east.
“But at night it reverses,” Avol said. “So during the daytime, you’re better off being on the beach side, but at night, being on that side is a little potentially more dangerous in terms of your health.”
Watch the clock
The best time to ride is 5 a.m. or 6 a.m., before traffic gets going and the sun comes up.
Avol advised avoiding rush hour because air pollution is elevated, especially near busy streets, but if that’s unavoidable, again, try a street with less traffic.
Avoid the heat
“Heat is a very powerful stress. It makes you work harder, breathe harder, so you’d like to avoid the hotter parts of the day,” Avol said. “How hard you’re working directly relates to how much you’re breathing. The deeper you breathe, the further down into your airways you draw that air."
"What’s on those particles [in the air] and what those particles are made of may affect your health, so that’s the issue with taking deep breaths and breathing,” he said.
Don't overdo it
Bicycling less than 90 minutes or two hours is probably a benefit for your health rather than taking a car, he said. But 90 minutes or two hours is the cutoff. That’s when the the benefits of exercise and the harm of air pollution begin to trade off.
The bottom line
“Ride your bike,” Avol advised, “because studies have shown that even riding your bike when it’s sunny, when it’s warm, you do get exposed, but if you look at the risks and the health tradeoffs, the exposure is still worth it."
That brings us back to Scott Chan. How does he feel now that he’s gotten the green light to pedal his heart out?
Chan said it was "super good news," especially since he already has other concerns while biking, including whether people in cars know how to safely drive around bicyclists.
“And that’s one less concern now, so I’m super happy,” Chan said.
Got questions about getting around in L.A.? Send us an email at TheRide@kpcc.org or post on our Facebook page, TheRideOnTheRadio.