New Research Suggests Separation Key to Protecting Cyclists From Pollution

Cyclists who ride on bike boulevards in Portland inhale 19 to 45 percent less pollution, a new study finds. Photo: Wikipedia
Cyclists who ride on bike boulevards in Portland inhale 19 to 45 percent less pollution, a new study finds. Photo: Wikipedia

The fresh air and physical activity that come with cycling are great for your health. But for urban cyclists, one downside is that it comes with a potentially harmful dose of air pollution.

For years, studies have examined how cyclists and pedestrians are affected by air pollution in urban areas. According to Portland State University researcher Alex Bigazzi, who recently completed a literature review of dozens of studies on the issue, results have been all over the map when it comes to who experiences the most pollution — drivers, pedestrians, cyclists, or even transit riders. But when you account for the fact that bicyclists are exercising, and therefore inhaling two to five times as much air, Bigazzi says it’s pretty clear cyclists are absorbing more toxic chemicals.

A new pair of research studies point to a possible solution. Studies from Portland State University and Harvard found that cyclists are exposed to less pollution when they are provided with facilities that help separate them from cars.

Using bike trailers outfitted with equipment to measure air quality, Harvard researchers recently examined different pollution levels in the Boston area on three types of bicycling facilities: on-street bike lanes, shared bike-bus lanes, and off-road bike paths running parallel to roads (side paths). They found that cyclists who traveled on side paths separated from traffic by grass or trees inhaled 33 percent less harmful emissions, compared to those who rode on on-street bike lanes.

Meanwhile, a team of researchers at Portland State University compared pollution outcomes for cyclists traveling on major arterials and cyclists traveling along bike boulevards — low-traffic, neighborhood streets that are designed to prioritize bike traffic. In the study, subjects riding on both types of facilities were asked to exhale into a respirator bag. Their breath was then analyzed in a lab. They found cyclists riding on bike boulevards inhaled 19 to 45 percent fewer pollutants.

Bigazzi, who was also a lead author on the Portland study, says his research helps make the case for separate facilities for cyclists.

“There are specific things we can do to reduce the pollution risks while maintaining the health benefits,” she said. “And that’s specifically separating bicyclists from cars.”

  • Scott Sanderson

    I often worry about this because I ride a bicycle in Chicago every day. Is there any evidence wearing a mask helps?

  • Richard Mlynarik

    “Side paths separated from traffic by grass or trees” is where it’s at — remember to always practice Safe Streetsblog Cycletracking and only ride on golf courses. Suitable for “eight to eighty”. FORE!

  • Mcass777

    I have read that athletes take in more oxygen but keep it in their body for a shorter time because they breathe so fast. That and increased mucus production which traps pollution and allergens could help lessen the effects of pollution- who knows!

  • Komanoff

    I’m glad your lede qualified “harmful dose of air pollution” with “potentially.” The average on-road auto emits less than 1/20 the harmful emissions (CO, VOC’s, NOx) of autos in the 1970s and early 1980s, before the tailpipe controls mandated in the 1970 Clean Air Act finally kicked in. Except for the occasional gross-emitter diesel truck (and those too have gotten far cleaner), tailpipe emissions from motor v’s no longer present a clear and present danger to us cyclists who have to share the road with them, in my considered view.

    Old notions die hard, and I guess beating the air pollution drum is still a potent argument against automobiles. But as a science guy, I think it’s better to stick to arguments with real teeth, not just good optics. There are dozens of reasons for bike lanes and bike paths. I would put healthier breathing far down the list.

  • ? The same equipment should be placed inside car interiors for comparison. There have been past studies showing that interiors hold a lot of pollution and thereby expose drivers and passengers to elevated concentrations.

  • Chris J.

    Whenever I’m stuck in the same block as one of those noxious diesel trucks in a stretch of city blocks timed for cyclists (e.g. on Valencia in San Francisco), I’ll usually pull over and wait for it to get a couple traffic-light cycles ahead of me. I know breathing that stuff has got to be terrible for you.

  • Andy B from Jersey

    This really isn’t news. Plenty of other studies have shown these same patterns.

    HOWEVER it depends what pollutant you are measuring. Fine diesel particulates are known to be much more concentrated on arterial roadways with heavy diesel trucks and buses and much less a block over that might serve as a bicycle boulevard. By comparison, from what I’ve read, NOx disperses much more evenly in the lower atmosphere and you don’t have such noticeable concentrations on arterials despite the concentration of motor vehicles there.

    Trees are also knows to be an effective filter for particulates as well. A large tree can have many acres of surface area on its leaves and the mere contact of those particulates on the leaves is enough to take it out of the atmosphere.

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