A number of people have asked me about automobile fumes and whether I worry about breathing exhaust as I ride my bike to work. There seems to be a widespread assumption that cyclists are exposing themselves to high levels of pollutants by riding their bikes alongside automobiles. Contrary to popular belief, it’s motorists who are getting the worst of it.
At least two studies have shown motorists are exposed to far more pollutants than cyclists, in some cases by more than fourfold. The following figures are from a widely quoted study conducted in the Netherlands in 1995¹.
|Cyclists (µg/m3)||Motorists (µg/m3)|
|Carbon monoxide (CO)||2670||6730|
|Nitrogen dioxide (NO2)||156||277|
A 2004 Australian study, published in the Health Promotion Journal of Australia, confirms what was found in the older Dutch study. It looked at benzene, toluene, ethylbenzene, xylene and nitrogen dioxide, and again found motorists are exposed to much higher concentrations of these pollutants than cyclists.
This seems counter-intuitive since we cyclists are out in the open air, directly exposed to tailpipes, while motorists are inside their sealed vehicles with conditioned air. But, since most automobile vent systems are not filtered or completely sealed, motorists are exposed to pollutants from the stream of cars in front of them, as well as the pollutants that leak into the passenger compartment from their own engines and fuel systems.
So while cyclists should be proud of the fact that they’re sparing the air by riding their bikes, they can also breathe easy knowing they’re sparing themselves a big dose of toxic pollutants they’d otherwise be breathing if they were riding in a car.