Results:

• At the global average for air pollution from particulate matter (i.e., PM2.5 concentration 22 μg/m3), the benefits of physical activity outweigh air pollution exposure even at extreme levels of active travel.
• Air pollution would have to reach PM2.5 concentration 95 μg/m3, a level only present in 1% of cities worldwide, in order for half an hour of cycling to have greater health risks from air pollution than benefits from physical activity.

Methods:

• This study used health impact modeling to estimate the influence of physical activity from active transportation and air pollution exposures on all-cause mortality. PM2.5 was selected as the indicator of air pollution exposure because it is commonly used in health impact modeling and has a significant health burden.
• This study estimated the “tipping point,” or point after which an increase in active travel would no longer result in health benefits, and “break-even point,” or the point at which risk from air pollution outweighs the benefits of active transportation.