No Indian metro had ‘safe’ air in past 10 years: Study

MUMBAI: No major Indian city has "good" air quality. A 10-year assessment of air pollution across major urban centres has found that none of the country's top cities met safe Air Quality Index (AQI) levels at any point between 2015 and Nov 2025.

The report, prepared by Climate Trends, an environmental research firm, analysed long-term pollution patterns across 11 major cities. Delhi remained India's most polluted city throughout the period of study, with average AQI levels peaking above 250 in 2016 and hovering around 180 this year.



Despite marginal dips after 2019, the national capital never approached healthy air-quality thresholds. Vehicular emissions, industrial pollution and crop burning were major contributors, compounded by the region's geographical constraints.

Cities such as Lucknow, Varanasi and Ahmedabad which recorded persistently high average AQI values — often above 200— in first half of the decade, showed some improvement in the second half. While southern and western cities such as Mumbai, Chennai, Pune and Bengaluru recorded relatively moderate AQI levels, even they did not meet safe thresholds. Bengaluru posted lowest AQI readings in the country — between 65 and 90 — still too high for "good" category.

AQI is based on the concentration of toxic particulate matter, PM2.5 or PM10, in the air, whichever is higher.

Geography plays a significant role in prolonging pollution episodes, especially across the northern plains. "With cold north-westerly winds sweeping into the plains, minimum temperatures are set to drop further — making it even harder for pollutants to disperse," said Mahesh Palawat, vice-president at Skymet Weather.



He added that this year's weak western disturbances — extratropical storms that bring winter rain and snow to northwestern India — were inadequate and failed to trigger widespread rainfall.

"Without rain to wash pollutants out of the atmosphere, the pollution lingers for longer periods, leading to early and persistent smog-like conditions," said Palawat.

During the cold winters of the Indo-Gangetic plains, the phenomenon of "temperature inversion" — which limits vertical air movement — effectively traps pollution in the lower layers of the atmosphere. Dense city structures and tall buildings further slow wind speeds, exacerbating stagnation.

Experts stressed the need for better planning and data-driven interventions. "Technology can help address many local pollution sources within your own airshed, but this requires reliable data," said Prof S N Tripathi of IIT-Kanpur. Palak Balyan, research lead at Climate Trends said, "What India needs is sustained, long-term, science-based policy reform backed by genuine political will to take tough decisions."
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