Portland State University Ph.D candidate Alex Bigazzi has been biking around Portland with a $300 homebuilt air quality monitor. His goal: to get a sense of how much pollution he was breathing and how to minimize exposure to harmful fumes. Bigazzi has recently been sharing his findings around Portland.
Michael Andersen at Bike Portland reports today that Bigazzi’s first tip is to not ride very fast:
The biggest contributor to pollution intake, Bigazzi found, isn’t actually how dirty the air around you is. It’s how much of it you breathe.
“Ventilation completely dominates the exposure differences,” Bigazzi said. “The exposure differences are not that big.”
That creates an interesting mathematical puzzle: the harder your body works, the more pollution you breathe in. But the faster you move, the less time you’ll spend in the dirty air.
So assuming you’re headed to a place where the air is cleaner than it is along a roadway (Precision Castparts commuters, take note), here’s a curve Bigazzi constructed that shows the optimum speed to ride for various bikeway slopes. It’s expressed in kilometers per hour; the 17.5 kph “minimum ventilation speed” for a flat 0 percent grade is 11 mph.