Biking to work faster–or speed-walking to your subway stop–can give you a little extra exercise, but it also means you’ll be sucking in more pollution from passing cars and buses as you get short of breath from your exertion.
In a recent study, a researcher calculated exactly how fast to travel to limit exposure to pollution: around seven to 12 miles an hour on a bike, (and one to four miles an hour if you’re walking). If you go about six miles per hour faster on your bike, you can breathe in about twice as much bad air.
The paper gets even more specific; if you’re a female cyclist under 20, for example, your ideal speed is 7.76 miles an hour.
“I think it’s something people should be considering, but at the same time, I don’t think they need to overly fixate on what exact speed they should be going,” says author Alexander Bigazzi, who teaches civil engineering and community planning at the University of British Columbia.
“I think it’s more about people being aware that when they’re vigorously exercising, the volume of air they inhale over a trip is going to be several times larger than if they were going at a slower pace,” he says.
The paper calculated how speed helps–by getting you to a destination faster, and out of polluted air–along with the volume of air riders or pedestrians are likely to breathe.
Though electric bikes weren’t part of the study, it’s possible they could also help reduce exposure to pollution, though they also reduce the benefits of exercise. Driving wouldn’t necessarily help; one small experiment suggested that people in cars are actually exposed to more pollution than someone on a bike or on the sidewalk.
What might help most, at least temporarily, is choosing a different route that avoids the most traffic, says Bigatti. But he also acknowledges that cyclists need better access to busy roads.
He thinks cities should consider air pollution, along with other factors, as they plan networks of bike lanes. “Crash risks for cyclists, stress, noise pollution, and air pollution all should factor into our design of bicycle networks in cities,” he says.