Global PM2.5 Watch is based on research by an international team at the World Bank. It uses a machine learning model to estimate fine particulate air pollution (PM 2.5) for 34,000 cities worldwide. Global PM2.5 Watch updates every 24 hours, providing daily data from October 2018 to one week before today’s date. It employs open data from the IQAir network, the European Space Agency’s TROPOMI satellite platform; the Copernicus ERA5 weather database; EDGAR (Emissions Database for Global Atmospheric Research); climate region identifiers from Köppen-Geiger maps; elevation data from the MERIT-DEM database, and identifiers for latitude bands and coastal locations.