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CSE analyses air pollution in central India, finds Singaruli and Gwalior worst polluted cities

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CSE analysis points to early signs of rising air pollution and worsening of winter pollution in Madhya Pradesh
and Chhattisgarh

Singrauli and Gwalior have the most polluted air in the region

It is not only the northern part of India that is in the grip of severe winter pollution. Several cities in other regions – including in the central Indian states of Madhya Pradesh and Chhattisgarh — are experiencing a worsening of winter pollution, finds a latest analysis from Centre for Science and Environment (CSE).

“Even though real time air quality data is extremely limited in this region, whatever real time data is emerging from only 17 cities of these two big states indicates a growing crisis and vulnerability to winter smog. This demands early and stronger multi-sector action at a regional scale to meet the clean air targets,” says Anumita Roychowdhury, executive director, research and advocacy, CSE.

“Gaps in air quality data and lack of quality control of data make it difficult to construct reliable air quality trends and do proper risk assessment,” says Avikal Somvanshi, programme manager, Urban Lab, CSE. “The worsening of air quality in the region has not drawn adequate public attention. In winter, air quality of cities like Singrauli, Gwalior, Jabbalpur and Katna could get nearly three times worse than their annual average levels.” 

CSE has analysed air quality status in cities of Madhya Pradesh (MP) and Chhattisgarh. This is a continuation of the air quality tracker initiative of the Urban Data Analytics Lab of CSE that was started last winter. The objective of this new analysis has been to understand the trends and magnitude of winter pollution in major cities of different regions that have real time air quality monitoring systems.

This is an assessment of annual and seasonal trends in PM2.5 concentration for the period January 1, 2019 to December 12, 2021. This analysis is based on real time data available from the current working air quality monitoring stations in central India. A huge volume of data points have been cleaned and data gaps have been addressed based on the USEPA (United States Environmental Protection Agency) method for this analysis.

The analysis covers 18 continuous ambient air quality monitoring stations (CAAQMS) spread across 17 cities in the two states: two stations in Gwalior and one station each in Bhopal, Damoh, Dewas, Indore, Jabalpur, Katni, Maihar, Mandideep, Pithampur, Ratlam, Sagar, Satna, Singrauli, Ujjain, Bhilai and Bilaspur.

Air quality monitoring is still very limited in the central region. Cities in MP have data available for over two years; but real time monitors in Chhattisgarh became operational only in the latter half of 2021, which limits the possibility of assessing long term trends. Therefore, the data is indicative of the current status of air quality and seasonal variations in particulate pollution in medium and smaller cities in the region.

The analysis shows that air pollution during winter is a problem in all cities in these two states, with Gwalior and Singrauli having the worst air quality — as bad as the winter air quality of cities in the National Capital Region and Uttar Pradesh.

Nitrogen dioxide (NO2) pollution is also high in these cities, with Indore recording the highest for the region. The limited air quality data in the region indicates that it has not changed much from the 2020 levels. But due to limited historical data, it is difficult to comment on the regional air quality trends.

Key highlights of the analysis

Data quality remains poor despite automation: The central region has 18 real time monitors — 13 are operated by state pollution control boards, while five are operated by private entities: these are the Bhilai monitoring station (operated by the Bhilai Steel Plant), Satna (by Birla Cement), Maihar (by KJS Cement), Ratlam (by IPCA Lab), and Phool Bagh-Gwalior (by Mondelez India Foods). Most stations meet the minimum data availability of 75 per cent for the winter season this year (January 1-December 12, 2021). The stations that do not meet the minimum requirement are Maihar (38 per cent) and Phool Bagh-Gawlior (23 per cent).

Stations in Chhattisgarh only started operating in September (Bilaspur) and November (Bhilai), but they have reported data for more than 75 per cent of days since becoming operational.  

A quick examination of the data indicates that stations operated by industry actors tend to report very low concentration numbers or have massive data gaps compared to stations operated by state pollution control boards. The station at Satna operated by Birla Cement especially stands out for uncannily low values — in fact, the annual average for 2020 for this particular station works out to be about 50 per cent lower than what is reported by two manual stations of the city in the annual NAMP report. It is not clear why such deviation occurs in Satna’s real time monitor data.

Singrauli and Gwalior have the most polluted air in central India: Singrauli, a small town in eastern MP but designated as a critically polluted area by the Central Pollution Control Board, has the most polluted air in the region with a 2021 average of 81 ug/m3. It is followed by Gwalior and Katni that have 2021 averages of 56 ug/m3 and 54 ug/m3 respectively (see graph on PM2.5 trends in the full analysis report). The 2021 average has bypassed the 2020 average in all the major cities — Bhopal, Indore, Jabalpur and Ujjain — and it does not meet the annual standard as well. Satna has the lowest 2021 average value, but the quality of data from the city’s only station is suspect. Bilaspur, Bhilia and Maihar do not have adequate data for computation of annual values.

Singrauli has had over three months of very poor air quality days in 2021: In Singrauli, the year’s number of days with air quality in the ‘very poor’ or ‘severe’ categories stands at 95, which is identical to that of Delhi – as of November 2021 (see graph on PM2.5 AQI categorisation in the full analysis report). Singrauli has had just one severe day, though: there is a constant high pollution level in the city, but it rarely gets tipped over to ‘severe’, which generally happens due to impact of additional factors like meteorology or external pollution sources.

Major cities like Bhopal (38 days), Indore (36 days), Gwalior (72 days), Jabalpur (49 days) and Ujjain (30 days) have recorded over a month of poor or worse air quality in 2021 so far. These bad air quality days are concentrated during winter months. Cities in the east abutting the Indo-Gangetic Plains are dirtier compared to rest of the cities in the region.

High pollution episode common during winters despite low annual levels: Except Singrauli, rest of the central Indian cities have relatively low annual PM2.5 levels (requiring less than 30 per cent reduction to meet the annual standard). But during winters, episodes of high pollution are common, when weekly PM2.5 levels go as high up as 202 ug/m3 as recorded in Gwalior in November 2021 (see graph on weekly PM2.5 levels vs annual levels in the full analysis report). This winter, so far, the highest weekly level has crossed 100 ug/m3 in Singrauli (191 ug/m3), Katni (141 ug/m3), Bhopal (129 ug/m3), Jabalpur (124 ug/m3), Indore (104 ug/m3), and Damoh (101 ug/m3). The levels are marginally lower this winter compared to those in last winter.

Indore has dangerously high NO2 levels in winter: There is a significant increase in the amount of NO2 in air of all cities of central India during November (compared to that in September-October). Gwalior registered a 4.6 times jump in monthly NO2 level, while Mandideep registered a 4 times increase. In absolute concentration terms, Indore registered the highest monthly average of 83 µg/m3 for November. This is higher than the 24-hour standard for NO2. Indore is followed by Jabalpur (60 µg/m3) and Gwalior (49 µg/m3). Such high levels have not been recorded even in north Indian cities, which are generally more polluted.  

Traffic is a major contributor to pollution: All cities show peaking of hourly NO2 concentrations between 6 PM and 8 PM which coincides with the evening rush hour. Hourly NO2 levels in Gwalior increases five-fold between noon and 6 PM. The cycle is equally sharp in other cities, with 2.5-4.3 times increases in the evening (from afternoon). All cities also have a morning NO2 peak around 7-8 AM, but this is relatively smaller than the evening peak. In Indore, high NO2 levels persist till midnight indicating pollution generated by night-time truck movement in the city.

Diwali was a mega polluting event: The pollution level on Diwali night (8 PM to 8 AM) in cities in this region shot up by 1.4-3.9 times the average level recorded on seven nights preceding Diwali. Bhopal had the greatest pollution build-up on Diwali night, with a 3.9-fold increase in night-time PM2.5, followed by Ujjain that saw a 3.7 fold increase. Sagar, Bilaspur and Damoh registered very low PM2.5 levels with no impact of Diwali. In absolute concentration terms, Bhopal dominated the list of most polluted Diwali nights with a 371 µg/m3 PM2.5 level. Pollution was very high among all other major cities as well on Diwali night with Indore (342 ug/m3), Ujjain (309 ug/m3), Gwalior (281 ug/m3) and Jabalpur (209 ug/m3) crossing the 200 ug/m3 mark.

The next steps

Says Roychowdhury: “The central Indian region — that includes critically polluted industrial areas — requires urgent attention under the National Clean Air Programme. While strengthening the air quality monitoring network for proper risk assessment, action should be tightened in critically polluted areas and implementation of multi-sector clean air action plan scaled up to meet time-bound clean air targets. This is needed to prevent worsening of the public health crisis in this region.”

 (By Pratyusha Mukherjee)

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