Just what we've always expected, driving in a 2011 BMW X5 is safer and healthier than riding your bike along city streets. According to the Chronicle, "A new study published in the journal Environmental Health Perspectives showed a link between biking in heavy traffic and heart health risks, with cyclists having heart irregularities in the hours after their exposure to a variety of air pollutants on busy roads." Kind of like how being behind the trigger it safer for you than being in front of the barrel. Got it.
Diesel buses, trucks (the worst offenders, it seems), and cars emit "fresh exhaust" that have "particles are small enough to lodge deep in the lungs," which land right in the faces of cyclists. Which seems pretty obvious.
The solution? Equally obvious. "Avoid busy streets," recommends the study's authors.