Figure 1.

Relative risk (RR) for all-cause mortality (ACM) when physical activity (cycling) occurs during exposure to air pollution (at 50 μg/m³ PM_2.5). The tipping point and break-even point indicate the lowest risk, and the lack on any protective effect of exercise, respectively. According to this model, the tipping point is at cycling for <90 min/day, while the break-even point indicates that any benefit of cycling is lost for >5 h/day cycling. Reproduced from Tainio et al. (61), used by permission under Creative Commons license.