Smaller Towns in Eastern India Record Higher Pollution in Winter: Report

Patna: Smaller towns in eastern Indian states experienced higher levels of pollution during the winter season of 2022-23, according to the latest air quality analysis by the Centre for Science and Environment (CSE), a non-profit organisation based in New Delhi. 

The CSE's analysis, released on Tuesday, revealed that cities in West Bengal, Bihar, and Odisha are increasingly falling victim to toxic particulate pollution during winter, with the problem spreading rapidly to smaller cities and towns in the region.

The assessment also pointed out that though the bigger cities in the region – like Patna and Kolkata -- that are part of the National Clean Air Programme (NCAP) have witnessed a marginal improvement in the winter average of their PM2.5 levels compared to the previous two winters, their levels are still high. 

The smaller towns of Bihar -- Begusarai, Bettiah and Siwan in particular -- have recorded the worst winter air in the region, with their seasonal average exceeding 200 micrograms per cubic metre (µg/m³). Nitrogen dioxide (NO2) pollution is also high in the cities and towns of the region, with Arrah in Bihar recording a staggering 113 µg/m³ monthly average for November, the report said.

“This analysis is a stark reminder of the rapid spread of pollution. More cities and smaller towns are scaling the pollution height and dotting the pollution map. This once again vindicates the need for strong state-wide and regional management of air pollution. This is needed to control local pollution sources, including vehicles, industry, open burning and construction dust, as well as the impact of upwind pollution sources on downwind cities and towns,” said Anumita Roychowhdury, executive director of Research and Advocacy, CSE, in a press release.   

This analysis covers 50 continuous ambient air quality monitoring stations (CAAQMS) spread across 32 cities in the three eastern states.

The CSE’s study highlighted that the eastern states experienced the most polluted winter season since 2019-20. The average PM2.5 level across nine cities of east India with functional CAAQMS stations stood at 97 µg/m³ this winter. The PM2.5 level was 6% higher compared to the average of the previous three winters.

The daily peak of the season was recorded on January 1, 2023, and the daily regional average stood at 173 µg/m³. The peak was 24% higher compared to the 2021-22 winter peak and 8% higher compared to the mean peak of the previous three winters.

Most cities have experienced worsening of winter PM2.5 levels: West Bengal’s winter average PM2.5 this year is 14% higher than the previous winter. Bihar registered a 26% and Odisha a 44% increase in the winter average compared to the previous one, the report said.

On a long-term basis, Bihar registered an 18% and Odisha a 4% rise from the mean level of the previous three winters. However, the seasonal air quality in West Bengal this winter is 4% better than the mean of the last three winters.

In absolute concentration terms, Bihar, with an average PM2.5 level of 134 µg/m³, was the most polluted state in the east. It is followed by West Bengal with an average PM2.5 level of 84 µg/m³; Odisha came third with 63 µg/m³.

According to CSE’s report, peak pollution is dangerously high in all eastern states: In absolute concentration terms, Bihar’s daily peak PM2.5 level of 287 µg/m³ was the highest among the three states. West Bengal’s peak was 152 µg/m³ and Odisha’s 112 µg/m³.

In the long term, the seasonal peak in West Bengal this winter has been 1% better than the mean of the previous three winter peaks. Bihar registered a 26% increase, and Odisha a 14% increase in their peaks compared to the mean of the previous three winter peaks.

Smaller cities of Bihar are most polluted in the region. Begusarai was the most polluted city in the east, with an average PM2.5 level of 275 µg/m³. It was followed by Siwan with 203 µg/m³, Bettiah (202 µg/m³), Katihar (188 µg/m³), and Saharsa (180 µg/m³). Notably, the top 20 most polluted cities of the east are in Bihar.

In West Bengal, Asansol, with a winter average of 102 µg/m³ was the most polluted city; it is followed by Howrah (92 µg/m³) at the second spot. Talcher (75 µg/m³) was the most polluted in Odisha. However, Somvanshi added, “Since only two cities in the state have real-time monitors with adequate data for assessment, it is not possible to capture the larger landscape.”

Haldia in West Bengal was the least polluted city among the three states with a PM2.5 average of 46 µg/m³, followed by Siliguri in West Bengal and Manguraha in Bihar with winter averages of 60 µg/m³ and 66 µg/m³, respectively.

Among major cities in the east, Patna registered the highest increase in winter pollution this time. Patna in Bihar and Talcher in Odisha were the worst performers and registered an increase of 39% and 41% from the previous year, respectively. These were followed by Asansol in West Bengal and Gaya in Bihar, which recorded an increase of 38% and 37%, respectively.

Haldia and Durgapur in West Bengal are the only two cities that have shown improvement in air quality this season compared to the corresponding period in the previous year. Durgapur registered the maximum improvement -- 30% lower PM2.5 levels compared to the previous year; Haldia clocked a 19 per cent dip.

There was a significant increase in NO2 concentrations during November compared to October and September. NO2 comes entirely from combustion sources and, majorly from vehicles. Patna registered the most significant increase -- 2.9 times -- with the maximum build-up of NO2 between September and November 2022. Katihar and Rajgir each registered a 2.6 times increase in NO2. Motihari, Kolkata and Howrah registered a 2.3 times hike.

In absolute concentration terms, Arrah in Bihar registered the highest NO2 average of 113 µg/m³ (see Graph in the detailed report). It is followed by Bhagalpur with 98 µg/m³ and Siwan with 89 µg/m³.