Air pollution, greenspace and active travel infrastructure impacts on stress while walking, cycling, or in motorized transport

BACKGROUND AND AIM Recent studies have shown that active travel is generally associated with lower levels of both perceived and measured stress. Specific microenvironmental conditions encountered during daily journeys, however, may lead to varying degrees of stress experienced at that moment. Our aim is to evaluate how travel mode-specific stress, as measured by Galvanic Skin Response (GSR), varies given different levels of Black Carbon (BC) and greenspace exposure, and by road type. METHODS BC and GSR were collected alongside confounders and travel information from 122 participants across 3 European cities for 3 weeks as part of the Physical Activity through Sustainable Transport Approaches (PASTA) study. Greenspace and road type were identified from the geo-locations recorded by a GPS device also worn by participants. A Bayesian Doubly Robust (BDR) estimation method via bootstrapping (which allows us to incorporate randomness originating from the random nature of the unobserved observations of GSR and to simulate the posterior distribution of GSR given the measured covariates) was employed to estimate the effect of BC, green space and road type on cycling-/walking-/motoring-specific GSR, while accounting for confounders such as physical activity, gender, and age. RESULTS BC significantly increases GSR when people are cycling or walking, but has no statistically significant effect on people in motorized transport. In reverse, greenspace and traveling on roads with active travel infrastructures (i.e. cycleways and/or pedestrian paths) both lead to lower GSR while walking and cycling, with again no effect on people in motorised transport. CONCLUSIONS Decreasing air pollution, improving active travel infrastructure and increasing greenspace along travel routes can reduce stress experienced during active travel. Reducing traffic and improving active travel microenvironments may thus further enhance benefits of walking and cycling in reducing stress in urban populations. KEYWORDS Built environment, urban planning, stress, air pollution, active travel, causal inference.