Rapid industrialization and population growth has led to significant increases in emissions and air pollution to dangerous levels in India.  To address this challenge, the Indian government implemented the National Clean Air Programme (NCAP) to reduce emissions of fine particulate air pollutants in cities which fail to meet the Indian air quality standards (i.e., non-attainment cities). Though cities have seen noticeable decreases in fine particulate concentrations since the implementation of the program, a Princeton-led study finds that a significant portion of the improvements in air quality result from favorable meteorological conditions that are unlikely to persist as the climate changes.  

In this study, Dr. Yuanyu Xie, Prof. Denise Mauzerall, and their research team used the  recently expanding national surface continuous PM monitoring data (2017-2022) available from the Indian Central and State Pollution Control Boards (CPCB and SPCB) and ran regional model simulations to evaluate the effectiveness of NCAP policies in non-attainment cities.  

The results showed an 8.8% per-year decrease of PM2.5 pollution in the six non-attainment cities from 2017 through 2022.  In 2022, four of these cities met the NCAP target and achieved over 20% reductions relative to 2017 levels of PM2.5 pollution.  However, the authors note that although primary PM2.5 emissions appear to be decreasing, emission of key PM2.5 precursors (SO2, NOx, and NH3) have not been decreasing and have even increased in some locations since 2017. 

“India, along with other countries in the global South, face the dual challenge of rapid industrialization with resulting simultaneous increases in air pollutant and greenhouse gas emissions,” says Mauzerall. “Co-benefits for air quality, health and climate will result from on-going efforts in India to move away from coal and towards renewable energy.  Substantial additional mitigation action beyond current air pollution control policies, especially measures that simultaneously mitigate greenhouse gas and air pollutant emissions, such as energy system decarbonization, electrification and reductions in agricultural waste burning, are essential to achieve healthier air quality and contribute to slowing the rate of global climate change.”