Cyclists taking a longer route to their destination to avoid traffic and its associated air pollutants are not really avoiding the latter, according to a new study from Colorado State University.
The study tracked 45 bicycle and car commuters in Fort Collins, and measured their exposure to multiple dangerous air pollutants -- carbon monoxide, black carbon, and particulate matter. It found that although cyclists were able to reduce their mean exposure to black carbon and carbon monoxide by using alternate routes, the length of time spent on these routes negated any real benefit.
The report findings read, “Longer commute times, regardless of route type, tend to increase cumulative exposures; this difference was especially evident for cycling. Even though cyclists’ mean particulate exposures were reduced on alternative routes, the longer duration of these routes increased cyclist’s cumulative exposures relative to driving."
As alternative routes took longer to bike, cumulative exposure increases offset the reduction in mean exposure. Bikers also breathe heavier and faster than other commuters, which “probably results in at least a doubling of their estimated inhaled exposure relative to driving,” according to the reports authors.
Although they advise not to ditch the bike because “the benefit of increased exercise is likely to outweigh the risks because of increased air pollution intake”, the authors say their findings do reveal an “important uncertainty” in the net health impacts of cycling versus driving.
The report says for cyclists to have better overall health benefits, “smarter cycling infrastructure is needed”. It suggests that future town planners can achieve larger reductions in pollution exposure by building greater separation between cyclists and drivers.
"Although Fort Collins is an exceedingly bike-friendly city, its cycling infrastructure consists mostly of on-road bike lanes—meaning cyclists are still exposed to a lot of car traffic even when they take alternative routes instead of main roads."