Hopke et al. 2022, Face masks and pollutant exposure during active travel

Scoping review of 16 studies of face masks for reducing air-pollution exposure in pedestrians and cyclists. Well-fitting masks reduced inhaled particulate — N95 respirators most effectively, surgical masks moderately, and simple cloth masks poorly or not at all — and the health-outcome studies reported improved cardiovascular markers (lower blood pressure, higher heart-rate variability) and lung function with mask use in polluted air. Fit is decisive: a poor seal sharply cuts filtration. The evidence base is small and dominated by walking and commuting rather than running. Limited.