Using Satellite-Derived Data to Estimate the Burden of Disease from Ambient Air Pollution in Cities Worldwide

The urban population currently accounts for more than 50% of the total global population, and is expected to reach 67% by 2050. In urban areas where air pollution is being monitored, it is estimated that more than 80% of the population are exposed to air quality levels that exceed the World Health Organization guidelines. However, information on the burden of disease from ambient air pollution at the city level remains limited. Satellite remote sensing can provide valuable data on surface pollutants globally, especially in areas with non-existent or limited ground monitoring networks. In addition, the relatively high spatial resolution of satellite retrievals enables health impact assessments to be performed at a level that can capture intra-urban heterogeneity in fine particulate matter (PM_2.5) and NO₂ concentrations. Here, we estimate the annual burden of premature mortality attributable to PM_2.5 for all ages in cities worldwide, using satellite-derived estimates at 0.1° x 0.1° resolution that has been calibrated with surface monitoring data where available, and epidemiologically-derived health impact functions used by the Global Burden of Disease 2016 Study. We also estimate the city burdens of asthma incidence attributable to NO₂ for children aged 1-18 years at 250m x 250m resolution, using surface NO₂ concentrations derived from land-use regression modelling and satellite monitoring. Among the 100 most populated cities, we estimate that the population-normalized burden of premature mortality due to stroke, ischemic heart disease, chronic obstructive pulmonary disease, lung cancer, and acute lower respiratory infections attributable to PM_2.5 vary by over a factor of five. These differences are driven by variations in both PM_2.5 concentrations and baseline disease rates between cities. The largest population-normalized burdens are estimated in cities in Russia, India, and China. For NO₂, we estimate the largest annual burdens of childhood asthma incidence per pediatric capita for Lima, Peru (690 cases), Shanghai, China (650 cases), Bogota, Colombia (580 cases), Beijing, China (560 cases), and Toronto, Canada (550 cases). The large burdens in Chinese cities are primarily driven by high NO₂ concentrations, whereas Lima, Bogota, and Toronto have relatively high pediatric asthma incidence rates, especially for the 1-4 years age group. The NO₂-attributable fractions of childhood asthma incidence range between 6-47% across all 100 cities, with values exceeding 20% in 75 cities. We also report on ongoing efforts undertaken by the NASA Health and Air Quality Applied Science Team “Indicators” Tiger Team to 1) examine temporal trends in the city-level burden of disease from PM_2.5 from 1990 to 2016, 2) assess whether existing urban sustainability indicators adequately capture air pollution impacts, and 3) develop an interactive web-based tool to communicate our findings to public stakeholders. Such city-specific information can be used for a variety of purposes by policymakers – examples include evaluating against other risk factors and informing cost-benefit analyses of air pollution and greenhouse gas mitigation strategies.