The Atlantic:

New research has found that bicycle commuters inhale more than twice the amount of black carbon particles as pedestrians making a comparable trip. That healthy bike ride to and from work might be getting you out of a car, but it’s not getting you out of the way of the automobile emissions.

The study, led by Professor Jonathan Grigg from Barts and the London School of Medicine, looked at bicycle and pedestrian commuters in London to determine whether different modes of travel exposed commuters to higher levels of black carbon. By comparing levels of carbon in the lungs of five healthy bicycle commuters to the levels of five healthy pedestrian commuters, the researchers found a large disparity. The bicycle commuters had 2.3 times more black carbon in their lungs. They claim that the probability of this happening by chance is less than one percent.