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posted by martyb on Thursday November 10 2016, @07:32AM   Printer-friendly
from the no-heavy-breathing dept.

Traffic-related air pollution in cities can be a significant health hazard in regions close to traffic areas. The hazard is particularly acute for those who primarily move through the area using their legs, namely runners, walkers, and cyclists, because the more energy they expend, the harder they breathe, and the more air they inhale. However, the harder they work, the faster they commute, so for a given distance traveled they are subject to less exposure time. The biomechanics of walking has been studied for many decades. Most of the research deals with energy expenditure and back in the 1950s it was observed that a person adopts a natural speed of walking that corresponds to a minimal expenditure of energy for a given distance. However, how hard someone breathes is not proportional to their energy expenditure, so the rate at which they naturally walk or cycle is not necessarily the rate they should move to minimize pollution intake.

Alexander Y. Bigazzi, from the University of British Columbia, wondered what the tradeoffs were and whether one could minimize their health risk by modifying their travel speed. He found that a minimum dose speed (MDS) could be determined that is from 2-6 km/h for walking and 12-20 km/h for cycling. This is a moderate level of activity of about 3-5 METs (Metabolic Equivalent of Tasks).

The study, published in the International Journal of Sustainable Transportation, builds on Bigazzi's earlier work, which found that exposure to airborne VOCs [volatile organic compounds] was 100 to 200-per-cent higher on high-traffic arterial routes and roads through industrial areas.

Blood levels of toxicants were 40 to 100-per-cent higher than normal in cyclists after riding just six to nine kilometres on heavily used urban streets. No difference in toxicant levels was detected in cyclists that used low-traffic streets.

[Continues...]

The abstract from the paper:

A higher active travel speed has offsetting impacts on air pollution inhalation dose through higher breathing rate but shorter exposure duration. The net effect of speed choice on inhalation dose for pedestrians and bicyclists has not been established. This paper derives equations for pedestrian and bicycle steady-state minimum dose speed (MDS). Parameter distributions from the literature are applied to a synthetic population of travelers to calculate individual MDS. Results strongly support the existence of a definable MDS, which is near observed travel speeds for urban pedestrians and bicyclists. For a wide range of travelers the MDS is 2–6 km/hr while walking and 12–20 km/hr while bicycling, decreasing with road grade at a rate similar to observed speeds. On level ground, pedestrian and bicycle MDS corresponds to a moderate intensity physical activity level (3–6 MET). Small deviations from the MDS have little effect, but large deviations (by more than 10 km/hr for bicycling) can more than double inhalation dose over a fixed distance. It appears that pedestrians and bicyclists choose travel speeds that approximately minimize pollution inhalation dose, although pollution is unlikely a primary motivation.


Original Submission

 
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  • (Score: -1, Troll) by Anonymous Coward on Thursday November 10 2016, @03:00PM

    by Anonymous Coward on Thursday November 10 2016, @03:00PM (#425140)

    unsure how this helps sticking things in a rectum

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