Social and urban determinants of school commuting in Barcelona and its relationship with air quality around schools

Introduction: Active commuting to school has been promoted as a measure to reduce both children's sedentarism and air pollution around schools. The aim of this study is to describe school commuting patterns in children aged 2-14 years in Barcelona (Spain), analyse their determinants and assess the relationship with NO2 levels at schools. Methods: We conducted a cross-sectional study using data from the 2021 Barcelona Health Survey (n = 380 children) and linked home and school addresses to geographical information, including the city's NO2 map. We defined two types of school commuting: (i) active commuting to school (ACS; walking and cycling) and polluting commuting to school (PCS; car and motorcycle). We analysed the association with potential social and urban determinants through prevalence ratios (PR) and their 95 % confidence intervals (CI) using Poisson regression models with robust variance. Results: In Barcelona, 70.4 % of children engaged in ACS, and 12.1 % used PCS. Proximity to school emerged as the most significant determinant of ACS. PCS was strongly associated with both residential neighbourhood socio-economic status and commuting distance. Compared to children living within 750 m of the school, those living between 750 and 1500 m had a PR of 4.41 (95 % CI = 1.62-11.99) of PCS and those living over 1500 m away had a PR of 14.24 (95 % CI = 6.18-32.80). Areas with a higher prevalence of ACS also tended to have higher NO2 levels at schools, showing an imbalance between exposure and contribution to traffic related air pollution across geographical areas. Conclusions: To ensure that all students may engage in ACS, local policies promoting proximity to schools are strongly recommended.