High levels of air pollution were observed in the western part of Bengaluru Urban and in a few areas in Greater Bengaluru, said a report released by the Centre for Study of Science, Technology and Policy (CSTEP) on Monday. Satellite-based products were used to study the spatial patterns, hotspots, and rural–urban contrasts of particulate matter 2.5 (PM2.5) in Delhi and National Capital Region, Kanpur, and Bengaluru in 2019. PM2.5 is a tiny pollutant suspended in the air with a size of less than or equal to 2.5 microns. It causes several health issues and a large population of the Indian subcontinent lives in areas where the PM2.5 levels exceed the safe limits. “Across Bengaluru urban and rural areas, the annual mean PM2.5 ranged between 35 and 55 µg m-3. Rajarajeshwari Nagar and South zone recorded the highest PM2.5, followed by the west zone, Bommanahalli and Dasarahalli. Clusters of high PM2.5 were identified in Dasarahalli, Rajarajeshwari Nagar, west zone, south zone, Bommanahalli, Mahadevapura, and Yelahanka. PM2.5 hotspots were also identified in Greater and Bengaluru Rural regions,” said the report titled “Satellite-Based Mapping and the Quantification of PM2.5 in India”. These figures were reported from areas with stone crushing units and open biomass burning. However, PM2.5 levels in Delhi-NCR and the Kanpur region were found to be three times higher than that of Bengaluru. High PM2.5 levels were observed in Delhi’s east, southeast, and northeast areas and Shahdara as well as in Gurugram, Faridabad, Nuh, Palwal, and Bharatpur. High PM2.5 levels were recorded in the Kanpur city. Most urban zones of the Kanpur region were identified as PM2.5 hotspots, the study said. Methods to obtain high-resolution PM2.5 pollution maps include satellite-based estimates, modelling and dense measurement networks. Using satellite-based products to estimate PM2.5 can help generate high-resolution gridded spatial maps at a significantly lower cost. Dr Sreekanth Vakacherla, one of the authors of the report and a senior research scientist at CSTEP, said regulatory air pollution monitoring in India was mostly limited to urban areas. “It is difficult to capture the intricate spatial variations of PM2.5 without a dense network of monitors. Satellite-based products could bridge this gap. However, there are challenges and limitations in converting the satellite columnar aerosol optical depth (AOD) into surface PM2.5, such as the non-availability of satellite AOD during cloudy days and the lack of non-urban PM2.5 measurements,” he said. AOD is the measure of aerosols like urban haze, smoke, dust and particles distributed within a column of air from an instrument.
