Ambient nitrogen dioxide exposures in Latin American cities

Abstract

Background and Aim: Ambient nitrogen dioxide (NO₂) is a ubiquitous urban air pollutant emitted by fossil fuel combustion. Exposure to NO₂ is associated with respiratory disease and all-cause mortality. Health research on ambient NO₂ is sparse in Latin America, despite high urbanization and the high prevalence of NO₂-associated respiratory diseases in the region. This study aims to describe highly-granular population exposures to ambient NO₂ and urban characteristics associated with NO₂ exposure within 326 Latin American cities. Methods: We leveraged estimates of annual surface NO₂ at 1km² spatial resolution, population counts from national census bureaus, and urban characteristics compiled by the SALURBAL project for the year 2019, aggregating all data to the neighborhood (i.e. census tract) level. We described the percent of the urban population living in neighborhoods with ambient NO₂ levels exceeding WHO Air Quality Guidelines (annual, 10 µg/m³). We used multilevel models to describe associations between neighborhood-level ambient NO₂ concentrations and population and urban characteristics at the neighborhood and city levels. All models were adjusted for country and included all characteristics concurrently. Results: We examined 47,251 neighborhoods in 326 cities representing eight Latin American countries. Of the ≈236 million urban residents observed, 85% lived in neighborhoods with ambient annual NO₂ 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 NO₂. At the city level, higher congestion, population density, and intersection density were associated with higher ambient NO₂. Conclusions: Almost nine out of every 10 residents of Latin American cities are exposed to ambient NO₂ concentrations above WHO guidelines. Increasing neighborhood greenness and reducing city-level congestion warrant further attention as potential actionable urban environmental interventions to reduce urban population exposure to ambient NO₂. Keywords: nitrogen dioxide, air pollution, exposure, Latin America, urban environment