Pollution was high across all regions of India during last winter: Study

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Air pollution (Representative pic)

New Delhi: Particulate pollution increased and stayed elevated with varying intensities across all regions of India during the just-concluded winter, according to an analysis carried out by an environmental NGO.

Peak pollution was alarmingly high and synchronized, despite large distances within the regions – especially in the northern and eastern plains, says the study conducted by the Centre for Science and Environment (CSE) during the period October 15, 2021 and February 28, 2022.

The all-India winter air quality analysis showed that even though the overall regional averages of PM2.5 levels were lower than the previous winter in most regions, the winter smog episodes recorded severe spikes in several regions.

“Clearly, the winter pollution challenge is not limited to mega cities or to one specific region. It is now a widespread national problem that requires urgent and deliberate action at a national scale,” said Anumita Roychowdhury, CSE’s Executive Director, Research and Advocacy.

She advocated “quicker reforms and action” in key sectors of pollution – vehicles, industry, power plants and waste management to bend the annual air pollution curve and daily spikes.

This analysis is based on publicly available granular real time data (15-minute averages) from the Central Pollution Control Board’s (CPCB) official online portal Central Control Room for Air Quality Management, the CSE said.

The data is captured from 326 official stations under the Continuous Ambient Air Quality Monitoring System (CAAQMS) spread across 161 cities in 26 states and union territories.

Among the key highlights were that the eastern region of the country is as polluted as Delhi-NCR. 

The winter average of PM2.5 in eastern plains, that also include the newly-monitored 19 cities and towns of Bihar, was the same as that of Delhi-NCR, the CSE said.

Six Bihar towns feature in the top 10 most polluted cities this winter, with Siwan and Munger at the top.

In the northern plains, Ghaziabad, Delhi, Faridabad, and Manesar are third, fifth, seventh and tenth in the list.

Even though the seasonal average in smaller cities of Bihar rivals the mega-cities of NCR, their peak pollution during smog episodes are comparatively milder.

The NCR cities have experienced the most severe daily (24-hr average) PM2.5 levels with Ghaziabad being the worst hit.

Delhi, Noida, Faridabad, Greater Noida, and Gurugram are among the worst peak pollution (24-hr average) this winter.

The PM2.5 winter average of the eastern region is over three times the average of the cities in southern India and 22 per cent more polluted than north Indian cities.

Within the east, the Bihar sub-region is the most polluted.

From the peak 24-hr PM2.5 level perspective, north Indian cities have recorded the highest daily pollution levels on an average.

Within north, Delhi-NCR remains the most polluted sub-region with their worst days being almost five times the average.

Its peak pollution is also almost five times higher the average peak of northeastern India cities (region with lowest peak pollution) and about 60 per cent higher than the average peak of eastern cities (region with the worst regional average). 

The study also showed that average winter pollution of 2021-22 was lower than that of the previous winter, according to the CSE.

The regional PM2.5 levels this winter is lower compared to previous winter across all regions with some variation. 

Air quality on an average was 12 per cent cleaner this winter compared to previous winter based on an average of 136 cities that have valid daily PM2.5 concentration data for over 75 per cent of days of both winters (15 October to 28 February).

Most improvement on average was noted in northeast region (33 per cent) while western region cities showed the least improvement (8 per cent).

North Indian cities on an average have recorded 11 per cent lower PM2.5 level this winter, but the improvement in sub-region of Delhi NCR is smaller — just about 8 per cent.

Delhi-NCR also saw a marginal increase in the average peak 24-hr pollution.

The peak pollution rose significantly from the baseline among the cities in the south (24 per cent) and central Indian cities (7 per cent) despite the overall fall in the winter average.

Smaller cities of Bihar recorded higher pollution during winter than big cities of Delhi-NCR, the study showed.

Siwan in Bihar was the most polluted city in India this winter with seasonal average of 187 ug/m3.

In fact, 13 cities of Bihar feature in top 25 cities with the highest levels in winter. Delhi-NCR had 11 cities in the list.

Hisar in northern Haryana was the only city in the top 25 outside the sub-regions of Bihar and NCR.

From peak winter pollution perspective, NCR cities completely dominate the list of most polluted with significantly worse 24-hr averages compared to the rest of the country. Ghaziabad has witnessed the worst peak (24-hr average) among all the cities this winter with a level of 647 ug/m3 (almost 11 times the Indian standard).

Aizwal in Mizoram and Shillong in Meghalaya were the least polluted cities in the country.