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

BACKGROUND: Health research on ambient nitrogen dioxide (NO(2)) is sparse in Latin America, despite the high prevalence of NO(2)-associated respiratory diseases in the region. This study describes within-city distributions of ambient NO(2) concentrations at high spatial resolution and urban characteristics associated with neighborhood ambient NO(2) in 326 Latin American cities. METHODS: We aggregated estimates of annual surface NO(2) at 1 km(2) spatial resolution for 2019, population counts, and urban characteristics compiled by the SALURBAL project to the neighborhood level (i.e., census tracts). We described the percent of the urban population living with ambient NO(2) levels exceeding WHO Air Quality Guidelines. We used multilevel models to describe associations of neighborhood ambient NO(2) concentrations with population and urban characteristics at the neighborhood and city levels. FINDINGS: We examined 47,187 neighborhoods in 326 cities from eight Latin American countries. Of the ≈236 million urban residents observed, 85% lived in neighborhoods with ambient annual NO(2) above WHO guidelines. In adjusted models, higher neighborhood-level educational attainment, closer proximity to the city center, and lower neighborhood-level greenness were associated with higher ambient NO(2). At the city level, higher vehicle congestion, population size, and population density were associated with higher ambient NO(2). INTERPRETATION: Almost nine out of every 10 residents of Latin American cities live with ambient NO(2) concentrations above WHO guidelines. Increasing neighborhood 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(2). FUNDING: Wellcome Trust, National Institutes of Health, Cotswold Foundation