Population-weighted and area-weighted ambient PM2.5 and O3 concentrations in China from 2015 to 2024

Abstract China has experienced declining fine particulate matter (PM2.5) and persistent ozone (O3) concerns, but national geographic averages do not describe the concentration distribution where people reside. We conducted an ecological geospatial analysis using annual approximately 1 km ChinaHighAirPollutants PM2.5 and O3 rasters and WorldPop population-count rasters for 2015 to 2024. CHAP values were matched to WorldPop cell centres, and population-weighted ambient concentrations were compared with unweighted geographic means. At 0.2 degree resolution, descriptive linear annual slopes characterized local pollutant trends. Population-weighted PM2.5 declined from 53.06 to 31.25 micrograms per cubic metre (41.1%), whereas the corresponding O3 metric increased from 77.06 to 96.75 micrograms per cubic metre (25.6%). The population-weighted minus geographic-mean difference narrowed for PM2.5 from 5.77 to 2.43 micrograms per cubic metre and widened for O3 from 1.01 to 2.72 micrograms per cubic metre. At the prespecified 0.5 micrograms per cubic metre per year slope threshold, 97.38% of valid blocks had declining PM2.5 and rising O3. The same pattern remained predominant across alternative thresholds. These results describe a broad divergence in population-weighted ambient PM2.5 and O3 concentrations and support reporting both population-weighted and geographic summaries in integrated air-quality assessment.