Assessing air quality during India's National Clean Air Programme (NCAP): 2019-2023

Did air quality improve during India's National Clean Air Programme (NCAP)? Since its inception in 2019, 131 cities were designated as non-attainment cities, requiring comprehensive data collection on ambient concentrations, emission sources, emission intensities, and source contributions. Clean air action plans were developed with the goal of achieving a 40% reduction in PM10 pollution by 2026 compared to 2017 annual averages or reaching the national standard. Central government funding significantly boosted ambient monitoring capacity in all cities, increasing it by 3-4 times through the installation of at least one manual or continuous monitoring station per city to track pollution levels. The unitless air quality index from the daily bulletins recorded a drop of 13% between 2019 and 2023, which cannot be accorded to a single pollutant. Presence of PM10 as the conditional pollutant in the daily AQI bulletins doubled during this period, in contrast to reports saying 95 of the 131 cities have improved PM10 pollution levels. Delhi, the most polluted capital city in the 2023 world rankings, showed no significant change in annual average PM 2.5 concentrations. An agro-climatic airshed level assessment of TROPOMI satellite retrievals shows an increase in the atmospheric loading of gaseous SO2 and NO2 emissions and a change in the residual aerosol index signifying an increase in particulate emissions from combustion sources. Moving forward, tracking NCAP progress will require at least a tenfold increase in monitoring capacity, establishment of multi-pollutant emissions baselines, and a shift in evaluation to regional airshed scales to provide a better spatial representation of emission activities extending beyond city limits.