This paper identifies opportunities to refine OECD’s indicators of air pollution and population exposure to air pollution, and their periodic production for OECD and G20 countries. First, a comprehensive review is conducted of the publicly available ground-level air monitoring data for the selected countries, including their geographic coverage, data quality, comparability, etc. Second, the paper evaluates the potential applications of ground monitoring measurements for the construction of policy-relevant and internationally comparable indicators across OECD and G20 countries. Given the limited public availability of data and the incomplete geographic coverage in countries outside of Europe and North America, this paper concludes that such data are not suitable for the development of the OECD indicators of air pollution and population exposure to air pollution that need to be harmonised across countries and over time. A hybrid approach is instead recommended as a superior alternative that draws on both satellite data combined with a chemical transport model calibrated using ground-based measurements.