Umbra on the Health Impacts of Biking in Traffic
Grist Magazine's Umbra Fisk, in the tradition of Cecil Adams, answers reader mail on various subject. The last edition of her column was about a question from someone who was wondering "if the benefits [of bike commuting] (exercise, sunshine, free and fast transport) are outweighed by the negatives (primarily breathing in diesel and other exhaust, but I'd also throw in the risk of almost getting run over, despite the cheap thrills)." Interestingly, Umbra finds that "while you may be hurting your health by biking in urban traffic, you are not hurting it as badly as you could be." This is explained by the way pollutants (benzene, toluene, ethylbenzene, xylene and nitrogen oxides) are scattered on the road: "The nasties are densest at the middle of the traffic zone, and less intense on the edges. [...] studies show you get the biggest hit of the nasties when you're inside a car. Sure, a personal Mobile Emissions Source appears hermetic, but it's an illusion: MES occupants are very close to sucking on the tailpipe of the MES just ahead of them. In a bus, riders' lungs are a bit above these sources. And bikers and pedestrians are on the outskirts."Our very own Warren McLaren has found this interesting excerpt from the Complete Bicycle Commuter by Hal Zina Bennett (Sierra Club Books, 1982, p.88):
Bicycling and Air Pollution::The Wheel Deal by Umbra Fisk
For bicyclists to be more susceptible to air pollutants than motorists would seem logical, but at least one scientific study suggests that just the opposite might be true. For research published in 1977 by the Department of Transportation, blood levels of carbon monoxide and other air pollutants in automobile and bicycle commuters were measured. Blood samples were compared for the two groups on a day-to-day basis.
The bicycle commuters showed levels of pollutants in their blood that were lower than their fellow automobile commuters'. Although the researchers gave no explanation of their findings, Dr. John Samson, who interpreted the data, speculates that the cyclists' more active respiratory systems did a better job of expelling air pollutants than did the relatively sedentary systems of the people sitting passively in their cars.
The tests for this project were conducted in Washington, D.C., during smog-alert days, and the cyclists, although they fared better than the motorists in theblood tests, did suffer more from eye and throat irritation. Most cyclists, however, reported that their irritation subsided half an hour after their rides.