As a bike commuter on a major city recently hit by a peak of air pollution (Paris), I've looked around for infos, and it's seems cyclists are less exposed to air pollution than motorists or even pedestrians.

Sources : http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2920084/ http://www.theguardian.com/environment/bike-blog/2014/feb/20.... http://www.minnpost.com/second-opinion/2014/03/city-cycling-...