Haryana’s Dharuhera topped the list of India’s most polluted cities in October, with Delhi close behind at sixth, according to the latest PM2.5 air quality assessment by the Centre for Research on Energy and Clean Air (CREA).
Notably, all ten of the most polluted cities in October were located within the National Capital Region (NCR), according to the assessment, which was based on data from continuous ambient air quality monitoring stations (CAAQMS).
In October, Dharuhera recorded an average PM2.5 level of 123 µg/m³, while Delhi’s monthly average stood at 107 µg/m³, three times higher than its September average of 36 µg/m³. Interestingly, the report noted that stubble burning accounted for less than 6 per cent of the pollution load, suggesting that year-round emission sources remain the dominant drivers of poor air quality in the region.
As per the National Ambient Air Quality Standards (NAAQS) set by the Central Pollution Control Board (CPCB), the permissible 24-hour average for PM2.5 is 60 µg/m³, while the annual average should not exceed 40 µg/m³.
India’s air quality assessment: Key takeaways
The report shows the number of cities with ‘Good’ air quality (0–30 µg/m³) plummeted from 179 in September to just 68 in October. Cities in the Indo-Gangetic Plain, especially the Delhi-NCR region, recorded the worst air, which explains the thick blanket of toxic gas now enveloping the region.
The top 10 worst-polluted cities were: Dharuhera, Rohtak, Ghaziabad, Noida, Ballabgarh, Delhi, Bhiwadi, Greater Noida, Hapur, and Gurugram; all belonging to Delhi NCR.
Uttar Pradesh and Haryana dominated the list, with four cities each in the top 10. Dharuhera, with a monthly average PM2.5 concentration of 123 µg/m³, breached the NAAQS limit on 77 per cent of days. The city recorded two ‘Severe’ and nine ‘Very Poor’ days in October.
'South India leads with the cleanest cities'
In contrast, Shillong, Gangtok and Mysuru were the least-polluted, and the top 10 cleanest cities included four from Karnataka, three from Tamil Nadu, and one each from Meghalaya, Sikkim, and Chhattisgarh.
Of the 249 cities assessed, 212 recorded PM2.5 levels within India’s permissible limit of 60 µg/m³, but only six met the World Health Organisation’s far stricter daily safe limit of 15 µg/m³.
“Winter and festive periods don't create India's pollution problem, they expose it,” said Manoj Kumar, analyst at CREA, in a release. “These seasonal spikes merely amplify baseline pollution levels that remain dangerously high throughout the year. This predictable surge is substantially preventable if we prioritize sector-specific emission cuts with clear accountability mechanisms. Instead, policy responses remain reactive and seasonal, failing to address the year-round sources driving this crisis,” he added.
What is PM2.5?
Short for particulate matter, PM refers to a mix of tiny particles in the air, such as dust, soot, smoke, dirt, and liquid droplets. PM2.5 denotes those with a diameter of 2.5 microns or smaller, about 30 times thinner than a human hair. Invisible to the naked eye, these particles linger in the air for long periods and, once inhaled, penetrate deep into the lungs and bloodstream. Of all air pollutants, PM2.5 poses the greatest threat to human health, say experts.