Umbra on the Health Impacts of Biking in Traffic
by Michael Graham Richard, Gatineau, Canada on 09.30.05
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 PollutionFor 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.
I bike in the northeast. Sticking to the bike path, though a little out of the way for my commute, keeps me away from the many dangers of interacting with traffic. Pollution from vehicles isn't really a factor in a bike's only environment. The real dangers are wet leaves and unleashed pitbulls.
good post. nice to see you are back to accurate reporting.
for a while there one couldn't tell the facts from the editorial content.
"good post. nice to see you are back to accurate reporting. for a while there one couldn't tell the facts from the editorial content."
Not quite sure what that means (especially since we're not reporters and always had both opinions and facts), but, uh, thanks, I guess.
I think the risk of being hit on a bicycle are overstated. I don't have hard numbers, but it seems that the incidents you hear about are cases where the rider was doing non-recommended things, like riding at night with no lights, in dark clothing on the wrong side. If you are going to bike-commute, you have to be a little smart about it and not think of it as 'going for a little bike ride.' Wear a helmet, bright clothing, use lights, follow the rules of the road and drive defensively (what if that guy pulls out from the alley.) I bike-commute a little -- 1000-1200 miles/year.
Research on auto pollution published in 1977 probably uses data from a couple of years before. This was before widespread use of catalytic converters and definitely before the introduction of modern fuel injection and pollution control systems in cars. I'm not sure how reliable those studies would be 30 years down the road.
Cheng-Jih Chen,
Good point. I'd temper it by saying that even if they are cleaner, there are now a lot more cars on the roads, so it adds up. Also, diesel trucks haven't changed as much as cars as far as emissions.
Actually, the risks of riding depend on the area. Here in Phoenix, you practically need to use a tank to travel on the road with how bad these drivers are . Motorcyclist fatalities happen on a near daily basis, and bikes are much better off.
As to the pollutants you face on a bike, here's my question, since you're in the process of getting physical exercise at the same time, does that offset the health risks posed by the air around you?
I would agree that the bike accident rate is related to location and the local drivers, but i think it is more greatly affected by the bicyclists themselves. Choose where you bike, e.g. if there is a parallel secondary road to a main thoroughfare, take it as it will have less traffic, less pollution and probably better scenery. Take non-road paths when possible like a path through a park or dedicated bike paths. And if you have to share the road with cars, act like one, that is, don't blow through stop signs, red lights, follow the traffic rules and if you need to take the lane, do it. Signal your intentions with hand signs. Look carefully for cars in coming out of driveways, alleys etc. and check parked cars for people about to open their doors.