Eight of the 10 most populated cities in India this winter season were in the Delhi National Capital Region and Uttar Pradesh, a report, released by the Centre for Science and Environment on Wednesday, showed.

In fact, eight of these were cities in Uttar Pradesh, with Ghaziabad and Bulandshahr taking the top spots. Delhi was ranked fifth, and Bhiwadi in Rajasthan, at number 10, was the only exception. Kanpur and Lucknow occupied sixth and ninth positions on the chart, according to the CSE analysis.

This analysis by CSE took into account data from 99 cities across the country, where data availability for two consecutive winters meets the minimum criteria for 75% of days between October 1 and January 31.

When ranked from the most to the least polluted cities, 23 of the places were found to be in north India. While Mysuru is the least polluted, followed by Satna in Madhya Pradesh and Kochi in Kerala, Ghaziabad is the most polluted city in the northern belt, the report said. Satna and Maihar in Madhya Pradesh and Mysuru in Karnataka were the cleanest cities in the country.

Additionally, the report identified the Delhi-NCR region as the most polluted cluster with Ghaziabad Bulandshahr, Greater Noida, Noida, and Delhi leading the pack.

Read the full report here

The levels of PM2.5, the most threatening particulate matter, worsened in 43 out of 99 cities whose winter air in two years, 2020 and 2019, was compared by the Centre for Science and Environment. Out of the 99 cities, only 19 have experienced “substantial improvement” in their winter air quality compared to the previous winter. Chennai is the only mega city included in this pool, according to the study.

The report also took into account the impact of the restrictions imposed last year to contain the spread of the coronavirus pandemic. It said that after a countrywide lockdown was enforced in March, several cities recorded lower levels of pollution during the summer and monsoon months. But by winter, the PM2.5 concentration had back to pre-cororonavirus levels.

“This bouncing back of pollution post-lockdown unmasks the high impacts of local and regional pollution,” said Anumita Roychowdhury, CSE’s executive director in charge of research and advocacy. “This demands quicker regional reforms to curb pollution from vehicles, industry, power plants and waste burning to curb the winter pollution and also sustain annual improvement at a regional scale with speed.”

The cities which saw the worst rise in pollution levels between from 2019 to 2020 include, Gurugram, Lucknow, Jaipur, Visakhapatnam, Agra, Navi Mumbai, and Jodhpur. Kolkata is the only mega city in this group.

In about 37 cities that are otherwise showing stable or declining seasonal average, their peak pollution levels rose significantly during winter, the report said. These include Aurangabad, Indore, Nashik, Jabalpur, Rupnagar, Bhopal, Dewas, Kochi, and Kozhikode.

On the other hand, in North India, other cities including Delhi have experienced the reverse, which means, an increase in seasonal average but decline in seasonal peak, it added.