Pollution bouncing back in middle and lower Indo-Gangetic Plain: CSE

After a decline in 2020 due to the COVID-19 pandemic, West Bengal, Bihar and Odisha are seeing a resurgence in pollution

By DTE Staff
Published: Monday 10 January 2022
Photo: istock__

Pollution is bouncing back in the eastern states of West Bengal, Bihar and Odisha after a short decline due to disruption by the novel coronavirus disease (COVID-19) pandemic, according to a new analysis of regional pollution trends done by Delhi-based non-profit Centre for Science and Environment (CSE).

Most cities in the region recorded a rising trend in annual particulate matter (PM)2.5 level in 2021, after the initial drop during 2020 due to pandemic-linked lockdown phases, the analysis noted.

It also said cities in the region needed big cuts in annual average PM2.5 levels to meet clean air standards.

The analysis covered 29 continuous ambient air quality monitoring stations spread across 12 cities in the three states:

  • West Bengal: Seven stations in Kolkata, three stations in Howrah and one station each in Asansol, Siliguri, Durgapur, Haldia
  • Bihar: Six stations in Patna, three stations in Gaya, three stations in Muzaffarpur and one in Hajipur
  • Odisha: One real time station each in Talcher and Brajrajnagar

Durgapur, a big industrial hub of West Bengal, had the most polluted air in the region in 2021, with an annual average PM2.5 level of 80 microgram per cubic metre (µg/m3).

It was followed by Muzaffarpur and Patna, with annual average PM2.5 levels of 78 µg/m3 and 73 µg/m3 respectively. According to CSE:

If the real time data is taken as an indicator, in West Bengal, Durgapur needs to reduce annual average PM2.5 by 50 per cent to meet the annual PM2.5 standard, Howrah 34 per cent, Asansol 32 per cent, Siliguri 32 per cent, Kolkata 28 per cent. Haldia met the standard in 2021.  

It added that in Bihar, Muzaffarpur needed a reduction in annual average PM2.5 levels by close to 49 per cent to meet the standard, Patna 45 per cent, Hajipur 33 per cent, Gaya 18 per cent.

Odisha was the only state where Bajrajnagar and Talcher had met the annual standard with average.

CSE said ‘severely polluted’ days had not been noted in any city in the region during 2021.

The Air Quality Index (AQI) represents 24-hour average air quality data. The air quality is considered to be ‘very poor’ when the AQI is from 301-400, according to Central Pollution Control Board (CPCB) guidelines.

An AQI of 0-50 is considered ‘good’, 51-100 ‘satisfactory’, 101-200 ‘moderate’, 201-300 ‘poor’ and 401-500 ‘severe’. Above 500 is the ‘severe-plus or emergency’ category.

The share of ‘very poor’ days had been highest in Muzaffarpur at 93 in Bihar, followed by Durgapur at 71 in West Bengal, Patna with 67 days in Bihar and Howrah with 58 days in West Bengal.

Days with ‘poor’ air quality were highest in Durgapur at 71, followed by 67 in Patna, 53 in Kolkata and 51 in Howrah.

Eastern India usually sees a significant increase in the amount of nitrogen dioxide (NO2) in the air of all its cities during December, compared to the previous months of November, October and September, according to CSE.

“Brajrajnagar registered 3.6 times jump in monthly NO2 level, Kolkata registered a 2.8 times increase while Patna, Talcher, and Asansol registered a 2.5 times increase. In absolute concentration terms, Patna registered the highest monthly average of 51 µg/m3 for December. It is followed by Kolkata (50 µg/m3) and Talcher (44 µg/m3),” the analysis noted.

NO2 levels corelate well with traffic peaks in cities, according to CSE.

The non-profit recommended scaling up action across all sectors — industry, power plants, vehicles and transport, waste management, clean cooking fuel and dust control to meet the national ambient air quality standard and to prevent rebound of pollution in the region.

“This analysis of real time air quality data for the period 2019-2021 shows that the downward dip in pollution that was induced by the hard lockdown phases of the pandemic in 2020 is threatening to bounce back with the levels in 2021 already rising. But in many cases, the levels are still lower than 2019,” Anumita Roychowdhury, executive director, research and advocacy at CSE, said.

This underscored the urgency of scaling up action across all sectors to prevent further worsening and to arrest the trend in this region, she added. 

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