Winter pollution levels and trends point to a national air quality crisis, says CSE’s latest analysis

• Analysis contains detailed assessment of all regions – north, south, east, west, central and northeast
• Bihar and Delhi-NCR top the pollution charts. The eastern region, dominated by the newly monitored towns of Bihar,records particulate pollution higher than the corresponding average of north India during winter. Smaller towns and cities of Bihar more polluted than most cities of north India
• Among NCR cities, Ghaziabad worst hit.Aizawl and Shillong the least polluted cities in the country
• Cities of north-eastern region havethe lowest particulate level among all regions. Butits key cities have experienced sharp spike during winter
• This national crisis requires urgent and time bound multi-sector action at a regional scale to control emissions from vehicles, industry, power plants waste, household fuels and other local sources to meet the clean air targets  

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New Delhi, March 16, 2022: An all-India winter air quality analysis done by Centre for Science and Environment (CSE) says particulate pollution spiked and stayed elevated with varying intensity across all regions during the winter of 2021-22 (15 October to 28 February). 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. Peak pollution was alarmingly high and synchronized, despite large distances within the regions –especially in the northern and eastern plains. 

The analysis has been done for the 2021-22 winter air quality tracker initiative of CSE’s Urban Data Analytics Lab. “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. This requires 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,” says Anumita Roychowdhury, executive director, research and advocacy, CSE. 

“As availability of real time air quality data has improved in several regions with expansion of the air quality monitoring systems, it has become possible to assess the regional differences and the unique regional trends. This can help to inform the regional clean air action,” says Avikal Somvanshi, programme manager, Urban Data Analytics Lab, CSE. 

This air quality tracker initiative has helped to benchmark the winter air quality for peer-to-peer comparison within each region and inter-regional differences. 

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 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. 

Key highlights 

Regional profile of winter pollution shows the easternregionisas 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. 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) PM_2.5 levels with Ghaziabad being the worst hit. Delhi, Noida, Faridabad, Greater Noida, and Gurugram are among theworst peak pollution (24-hr average) this winter. 

The PM2.5 winteraverage of the eastern regionisover 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).  

Says Somvanshi: “It is important to note that mega cities are not the most polluted in any of the regions -- it is the smaller and upcoming cities that are becoming pollution hotspots. This is even more evident in the winter peak daily pollution data.” 

Average winter pollution of 2021-22 is lower than that of the previous winter: The regional PM_2.5levels 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 PM_2.5 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 westernregion 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: 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 dominatethe 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 winterwith a levelof 647 ug/m³ (almost 11times the Indian standard). 

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

Winter air quality in the northernregion

The northern region includes 60 cities with real time monitoring facilities, spread across the states of Punjab, Haryana, Chandigarh, Delhi-NCR, Rajasthan and UP: 56 of these cities have been functional in 2020 winter as well. Geographically, this region represents the North Central Plains.  

• Cities with an increasing trend: 12 cities in the region show an increasing trend, i.e. both winter average and peak increased compared to their previous winter. Bhiwani in Haryana saw a staggering jump of 145 per cent in the winter average and 89 per cent increase in peak. It was followed by Hapur in UP that registered 129 per cent increase in winter average and 117 per cent increase in peak. Other cities that show increase include Ballabhgarh, Kota, Jaipur, Khanna, Udaipur, Patiala, Muzaffarnagar, Jalandhar, Charkhi Dadri, and Faridabad.
• Cities with a mixed trend: 18 cities in the region show a mixed trend, i.e. their winter average has declined but the peak pollution increased compared to their previous winter or visa-versa. Manesar, Ambala, Ludhiana and Kaithal show an increase in their winter average but registered lower peak pollution. Ajmer, Jodhpur, Mandi Gobindgarh, Palwal, Gurugram, Panchkula, Narnaul, Meerut, Ghaziabad, Kanpur, Noida, Agra, Bhatinda, and Greater Noida saw decline in their winter average but registered higher peaks compared to last winter. Greater Noida has the most divergent trend as its winter average declined by 31 per cent but its peak is 23 per cent higher.
• Cities recordinga declining trend: 26 cities show a declining trend, i.e. both winter average and peak decreased compared to their previous winter. Srinagar in Jammu & Kashmir saw the highest decline with a drop of 63 per cent in their winter average and 33 per lower peak. Delhi also registered decline but marginal. Its winter average declined by 8 per cent and peak by 2 per cent. Other cities with declining trend include Pali, Rupnagar, Alwar, Panipat, Hisar, Jind, Karnal, Amritsar, Bahadurgarh, Bagpat, Kurukshetra, Yamuna Nagar, Sirsa, Rohtak, Sonipat, Bhiwadi, Chandigarh, Dharuhera, Bulandshahr, Mandikhera, Moradabad, Fatehabad, Lucknow, and Varanasi.
• Most polluted cities: Most polluted city in the region during winter was Ghaziabad with winter average of 178 μg/m³ followed by Delhi that had a winter average of 170 ug/m³. Next eight spots are all occupied by neighboring NCR cities, namely Faridabad, Manesar, Bagpat, Noida, Gurugram, Meerut, and Hapur. Cities of NCR completely dominated the list of the most polluted. Hisar is the most polluted city in the north outside NCR with winter average of 142 ug/m³ followed by Firozabad, Moradabad and Vrindavan -- all in the immediate vicinity of NCR.
• Least polluted cities: Srinagar is the cleanest city in the north. Palwal in Haryana, Bhatinda in Punjab and Alwar in Rajasthan are the other cities with relatively lower winter average. Interestingly, the peak pollution exceeded the standard of 60 μg/m³ in all the cities. 

Winter air quality in the eastern region

The eastern region includes 28 cities spread across Bihar, West Bengal, Jharkhand and Odisha. Geographically, this region represents the Eastern Plains and Eastern Highlands.  

• Cities with an increasing trend: Two cities in the region show increasing trend, i.e. both winter average and peak increased compared to their previous winter. Hajipur in Bihar saw a jump of 51 per cent in the winter average and 54 per cent increase in peak. Talcher in Odisha registered 1 per cent increase in winter average and 16 per cent increase in peak.
• Cities with a mixed trend: Muzaffarpur is the only city in the region that shows a mixed trend, i.e. its winter average declined but peak pollution increased compared to its previous winter or visa-versa. Its winter average increased by 3 per cent but its peak was 4 per cent lower.
• Cities with a declining trend: Nine cities in the region show a declining trend, i.e. both winter average and peak decreased compared to their last winter. Brajrajnagar in Odisha saw the most decline with a drop of 57 per cent in their winter average and 61 per lower peak. Kolkata also registered decline -- winter average declining by 21 per cent and peak by 27 per cent. Other cities with declining trend are Patna, Howrah, Gaya, Asansol, Durgapur, Haldia, and Siliguri.
• Most polluted cities: Most polluted city in the region was Siwan in Bihar with winter average of 187 μg/m³. In fact, small cities of Bihar completely dominate the list of most polluted and occupy the top 17 spots. Durgapur with winter average of 103 ug/m³ was the most polluted city in West Bengal. Patna and Kolkata occupied 18th and 23rd position on the chart.
• Least polluted cities: Brajrajnagar in Odisha and Siliguri in West Bengal recorded the lowest winter average in the region. Brajrajnagar is the only city in the region with peak pollution under that 24-hr standard. 

Winter air quality in the westernregion

The region includes 15 cities spread across Gujarat and Maharashtra. All cities have data for both winter seasons. Geographically, this region represents the arid west, Northern Deccan plateau and the Konkan Coast.  

• Cities with an increasing trend: Three cities in the region show increasing trend, i.e. both winter average and peak increased compared to their previous winter. Ankleshwar in Gujarat saw a jump of 20 per cent in the winter average and 52 per cent increase in peak. Nagpur in Maharashtra registered 9 per cent increase in winter average and 78 per cent increase in peak. Nashik in Maharashtra registered 7 per cent increase in winter average and 10 per cent increase in peak.
• Cities with a mixed trend: Four cities in the region show mixed trend, i.e. their winter average declined but peak pollution increased compared to their previous winter or visa-versa. Chandrapur had the most divergent trend with winter average increasing by 32 per cent but its peak was 24 per cent lower.
• Cities with a declining trend: Eight cities in the region show declining trend, i.e. both winter average and peak decreased compared to their last winter. Aurangabad saw the most decline with a drop of 59 per cent in their winter average and 75 per lower peak. Mumbai also registered decline -- winter average declined by 14 per cent and peak by 22 per cent. Other cities that show declining trend include Pune, Kalyan, Ahmedabad, Navi Mumbai, Solapur and Nandesari.
• Most polluted cities: Most polluted city in the region was Ankleshwar with seasonal average of 101 μg/m³. Next two spots were occupied by Vapi and Kalyan.
• Least polluted cities: Aurangabad and Nandesari recorded the lowest winter average in the region. Chandrapur and Solapur rounded up the list of three least polluted. 

Winter air quality in the central region

The region includes 17 cities spread across Madhya Pradesh and Chhattisgarh -- 15 of these have data for both winters. Geographically, this region represents the Central Highlands.  

• Cities with an increasing trend: Three cities in the region show increasing trend, i.e. both winter average and peak increased compared to their last winter. Bhopal saw a jump of 11 per cent in the winter average and 138 per cent increase in peak. Indore registered 3 per cent increase in winter average and 20 per cent increase in peak. Satna registered no change in winter average but 6 per cent increase in peak.
• Cities with a mixed trend: Four cities in the region show mixed trend, i.e. their winter averaged declined but peak pollution increase compared to their last winter or visa-versa. Sagar had most divergent trend with winter average increased by 10 per cent but its peak was 50 per cent lower. Other cities with mixed trend in the region are Maihar, Damoh, and Mandideep.
• Cities with a declining trend: Eight cities in the region show declining trend, i.e. both winter average and peak decreased compared to their last winter. Gwalior saw the most decline with a drop of 39 per cent in their winter average and 4 per lower peak. Other cities with declining trend are Pithampur, Dewas, Singrauli, Jabalpur, Katni, Ratlam, and Ujjain.
• Most polluted cities: Most polluted city in the region was Srigrauli with winter average of 115 μg/m³. The next two spots were occupied by Katni and Jabalpur. Bhopal with peak 24-hr level of 407 ug/m³.
• Least polluted cities: Satna and Bhilai recorded the lowest winter average in the region. But the data from these two cities is of suspicious nature as the monitoring stations are owned and operated by industry and not the state pollution control board. 

Winter air quality in the southernregion

Southernregionrecorded the lowest regional PM_2.5 average this winter but it also registered almost 24 per cent increase in regional average peak pollution compared to previous winter. Industrial towns of south namely Gummidipoondi in Tamil Nadu and Gadag in Karnataka, also appear in the worst 10 cities for peak pollution (24-hr value).

The region includes 35 cities spread across Andhra Pradesh, Karnataka, Kerala, Puducherry, Tamil Nadu and Telangana. Geographically, this region represents the southern Deccan plateau, Western Ghats, and the Malabar and Coramandal coasts.  

• Cities with an increasing trend: Six cities in the region show increasing trend, i.e. both winter average and peak increased compared to their previous winter. Davanagere saw a jump of 142 per cent in the winter average and 133 per cent increase in peak. Coimbatore and Kochi are the major cities with increasing trend. Other cities with increasing trend in the region are Gadag, Yadgir, and Hubballi.
• Cities with a mixed trend: Seven cities in the region show mixed trend, i.e. their winter averaged declined but peak pollution increase compared to their last winter or visa-versa. Gummidipoondi in Tamil Nadu had the most divergent trend with winter average decreasing by 44 per cent but its peak was 362 per cent higher from its low base. Chennai also recorded mixed trend with winter average decreasing by 18 per cent but its peak was 24 per cent higher. Other cities with mixed trend in the region are Ramnagara, Madikeri, Puducherry, Raichur and Mangalore.
• Cities with a declining trend: 20 cities in the region show a declining trend -- both winter average and peak decreased compared to their previous winter. Chamarajanagar in Karnataka saw the highest decline with a drop of 45 per cent in their winter average and 52 per lower peak. Bengaluru and Hyderabad show marginal decline in their winter average and peak values. Other cities with declining trend are Tirupati, Chikkaballapur, Mysuru, Bagalkot, Kannur, Kozhikode, Kalaburagi, Rajamahendravaram, Amaravati, Thrissur, Thiruvananthapuram, Visakhapatnam, Vijaypura, Koppal, Chikkamagaluru, Kollam, and Shivamogga.
• Most polluted cities: Most polluted cities in the region was Kalaburgi and Hyderabad: both had a winter average of 58 μg/m³. They are followed by Visakhapatnam.
• Least polluted cities: Chamarajanagar and Chikkamagaluru in Karnataka recorded the lowest winter average in the region. Karnataka has the least polluted cities of the region followed by Kerala. 

Winter air quality in the northeasternregion

The region includes six cities. Geographically, this region represents the Eastern Himalayas and Brahmaputra Plains.  

• Cities with a declining trend: All cities in the region show a declining trend, i.e. both winter average and peak decreased compared to their previous winter. Aizawl in Mizoram saw the most decline with a drop of 50 per cent in their respective winter averages and 51 per cent lower peak. Agartala (Tripura) registered least change with its winter average declining by 7 per cent and peak level declining by 16 per cent..
• Most polluted cities: Most polluted city in the region includes Guwahati with a winter average of 81 μg/m³. This is followed by Agartala that registered a winter average of 77 μg/m³.
• Least polluted cities: Aizwal and Shillong recorded the lowest winter average in the region. Hill stations are relatively less polluted than cities in river valleys and foothills. Aizawl and Shillong had the lowest levels compared to the all other cities of all regions this winter. But cities and towns even with low seasonal average have suffered high spikes in daily levels. 

What are our takeaways from this analysis?

Says Roychowdhury: “The widely divergent trend in pollution levels across regions is strongly influenced by local geoclimatic conditions, meteorology and the intensity of pollution. But the emerging trend points towards a national air quality crisis. While the regions are battling to meet the national ambient air quality standards, winter conditions are aggravating the problem further. Even though the pandemic conditions have arrested the trend overall trend in most regions, there is still a mixed trend. Despite having a relatively lower annual average pollution levels the peak pollution during winter can spike. This indicates the influence of cool and calm winter conditions and also the regional influence.” 

Adds Somvanshi: “While cities require their respective clean air action plans for controlling local pollution, the effort will have to be scaled up for the region to control pollution from widely dispersed sources across the urban and rural landscape. The multi-sector plan has to address vehicles, industry, power plants, household pollution, waste burning and more. This granular tracking of regional and local pollution needs to inform policy making and the compliance framework for air quality management to meet the clean air targets.” 

For more information, interviews etc: Sukanya Nair, sukanya.nair@cseindia.org, 8816818864