Tropical cities are experiencing rapid growth but lack routine air pollution monitoring to develop prescient air quality policies. A targeted sampling of recent (2000s to 2010s) observations of air pollutants from space-based instruments over 46 fast-growing tropical cities quantified significant annual increases in nitrogen dioxide (NO2) (1 to 14%), ammonia (2 to 12%), and reactive volatile organic compounds (1 to 11%) in most cities, driven almost exclusively by emerging anthropogenic sources rather than traditional biomass burning.
They estimated annual increases in urban population exposure to air pollutants of 1 to 18% for fine particles (PM2.5) and 2 to 23% for NO2 from 2005 to 2018 and attribute 180,000 (95% confidence interval: −230,000 to 590,000) additional premature deaths in 2018 (62% increase relative to 2005) to this increase in exposure. These cities are predicted to reach populations of up to 80 million people by 2100, so regulatory action targeting emerging anthropogenic sources is urgently needed.
Technical Description of Figure(s):
Trends (2005-2018) in NO2 and reactive NMVOCs, using HCHO as a proxy, in rapidly growing cities in the tropics. Circle colors are the relative trends, and sizes are values at the start of the record (baseline). Outlines identify significant trends at the 95% confidence interval (CI). Warm colors indicate positive trends, and cool colors indicate negative trends. The trend in reactive NMVOCs at Antananarivo in Madagascar is gray because of the low temporal coverage.
Scientific significance, societal relevance, and relationships to future missions:
The long-term data records from Aura OMI are a vital resource for human health studies that require long-term and high-quality data of air pollutants. OMI data of NO2, HCHO and UV, with their near global coverage, are regularly used in these studies.
OMI NO2: NASA Standard Product version 4.0 (https://doi.org/10.5067/Aura/OMI/DATA2017; last accessed 18 March 2021).
OMI HCHO: Quality Assurance for Essential Climate Variables version 1.3 (https://doi.org/10.18758/71021031; last accessed 18 March 2021).
Vohra et al. (2022). Rapid rise in premature mortality due to anthropogenic air pollution in fast-growing tropical cities from 2005 to 2018. Science Advances, 8, 14. https://doi.org/10.1126/sciadv.abm4435.