KOLKATA: In 2021, PM2.5 - the tiniest of pollutants that play havoc with human lives - had for the first time touched the annual national ambient air quality standard of 40 g/m³ (microgram per cubic meter) in Kolkata. Compared to 2018, the dip in PM2.5 was 6.4%, revealed a study on air quality in six non-attainment cities in Bengal, including Kolkata, Howrah, Barrackpore, Durgapur, Haldia and Asansol.
PM2.5, because of its size, can travel straight into the bloodstream through the lung. The noxious chemicals riding on these particles trigger numerous health issues including cancer. "Meteorology played a huge role in the reduction in PM2.5 count but some decisive ground-level activities based on the understanding of a large number of data sets and research also paid rich dividends," said West Bengal Pollution Control Board chairman Kalyan Rudra. The ground-level activities include very tight satellite monitoring of crop-residue burning and immediate alert from its command centre at PCB to the district, sub-division, and block-level officers with latitude-longitude specifications.
PCB has put up 150 sensor-based real-time air quality monitoring stations, some of which are strategically placed along the borders. "With the help of IIT-Delhi, the data analysis now affirms that nearly 53% of pollutants of the city are coming from outside, nearly 21% from Bangladesh," said Rudra. "Kolkata being at the fag end of the Indo-Gangetic Plain (IGP), one of the worst airsheds globally, had the natural disadvantage of attracting pollutants of IGP, as they tend to take course of the river. Thus we need airshed specification plans. We have to control local emission inventories," said PCB member secretary Rajesh Kumar.
The study revealed almost all non-attainment cities, except Haldia, had a significant drop in pollutants. We are closely monitoring Haldia and trying to find ways to reduce pollution level, said Kumar. However, coarser particulate pollutants like PM10 still remained above the annual permissible standard of 60 g/m³ across six cities in Bengal.
