Ambient nitrogen dioxide in 47 187 neighbourhoods across 326 cities in eight Latin American countries: population exposures and associations with urban features.

Background: Health research on ambient nitrogen dioxide (NO) is sparse in Latin America, despite the high prevalence of NO-associated respiratory diseases in the region. This study describes within-city distributions of ambient NO concentrations at high spatial resolution and urban characteristics associated with neighbourhood ambient NO in 326 Latin American cities.

Methods: We aggregated estimates of annual surface NO at 1 km spatial resolution for 2019, population counts, and urban characteristics compiled by the SALURBAL project to the neighbourhood level (ie, census tracts). We described the percentage of the urban population living with ambient NO concentrations exceeding WHO air quality guidelines. We used multilevel models to describe associations of neighbourhood ambient NO concentrations with population and urban characteristics at the neighbourhood and city levels.

Findings: We examined 47 187 neighbourhoods in 326 cities from eight Latin American countries. Of the roughly 236 million urban residents observed, 85% lived in neighbourhoods with ambient annual NO above WHO guidelines. In adjusted models, higher neighbourhood-level educational attainment, closer proximity to the city centre, and lower neighbourhood-level greenness were associated with higher ambient NO. At the city level, higher vehicle congestion, population size, and population density were associated with higher ambient NO.

Interpretation: Almost nine out of every ten residents of Latin American cities live with ambient NO concentrations above WHO guidelines. Increasing neighbourhood greenness and reducing reliance on fossil fuel-powered vehicles warrant further attention as potential actionable urban environmental interventions to reduce population exposure to ambient NO.

Funding: Wellcome Trust, National Institutes of Health, Cotswold Foundation.