Application of satellite data in air quality management: Lessons learned in India

Exposure to ambient PM_2.5 is the leading environmental health risk in India. An efficient air quality management plan requires a consistent and long-term database at high spatial and temporal scale. We have developed a satellite-based PM_2.5 data for India by filling the gaps in satellite AOD to complement the paucity in ground monitoring. The average population-weighted exposure during 2017-2021 was estimated as 52.5 μg/m³, 18.1% lower than the estimates without adjusting for the sampling gaps. The annually averaged mortality burden attributable to ambient PM_2.5 exposure during this period was estimated to be 0.45 million (95% UI: 0.36-0.55), 0.27 million (95% UI: 0.22-0.33) and 0.24 million (95% UI: 0.19-0.28) for low, medium and high sociodemographic index states, respectively. If the sampling gaps in satellite AOD is not filled, the health burden in India would be overestimated by 0.1 million (95% UI: 0.07-0.13).  We demonstrated  use of this satellite data in various air quality management practices. We have delineated 9 to 11 major seasonal air sheds in India using k-means clustering. We have found that the number of days daily PM_2.5 exceeding the national standard have decreased during 2017 to 2021 in all air sheds. We have identified the potential sites for future expansion of the ground network under the National Clean Air Program. We examined the representativeness of the existing ground monitors in the non-attainment cities. These lessons learned in India could be valuable for other developing countries with limited or no ground monitoring.