New Delhi: Delhi ranked as the sixth most polluted city in India in October 2025, according to the latest Monthly Air Quality Snapshot released by the Centre for Research on Energy and Clean Air (CREA) on Tuesday. The report, based on data from continuous ambient air quality monitoring stations (CAAQMS), provides a detailed overview of air pollution levels across 249 cities nationwide, highlighting alarming deterioration in air quality across the Indo-Gangetic Plain (IGP), particularly in the National Capital Region (NCR).

Among the top-ranked cities for poor air quality, Dharuhera, in Haryana’s Rewari district, emerged as the most polluted, with a monthly average PM2.5 concentration of 123 micrograms per cubic meter (µg/m³). Dharuhera exceeded the National Ambient Air Quality Standard (NAAQS) limit on 77% of the days in October. Within the month, the city experienced two days classified as ‘Severe’ and nine days in the ‘Very Poor’ category, signaling critical public health concerns.

Following Dharuhera, the next most polluted cities included Rohtak, Ghaziabad, Noida, Ballabgarh, Delhi, Bhiwadi, Greater Noida, Hapur, and Gurgaon. Notably, four cities each from Haryana and Uttar Pradesh featured in the top 10, reflecting a concentrated regional air quality crisis within the NCR. Delhi’s own average PM2.5 concentration for October was recorded at 107 µg/m³, a nearly threefold increase from 36 µg/m³ in September, signaling a rapid decline in air quality over just one month.

Year-Round Pollution Beyond Stubble Burning

While stubble burning in neighbouring states often dominates media coverage as a major contributor to Delhi’s air pollution during the winter months, the CREA study noted that in October, such burning contributed less than 6% of Delhi’s PM2.5 levels. The sharp rise in pollution indicates that year-round emissions, including vehicular traffic, industrial activity, construction dust, and domestic fuel usage, play a significant role in deteriorating air quality. The findings underscore the need for long-term mitigation strategies beyond seasonal interventions like the Graded Response Action Plan (GRAP), which primarily targets winter pollution spikes.

Detailed Air Quality Trends

The air quality classifications for October reveal a stark shift from the previous month. Cities in the ‘Good’ category (PM2.5 levels of 0–30 µg/m³) fell dramatically from 179 in September to 68 in October, while those in the ‘Satisfactory’ range (31–60 µg/m³) increased from 52 to 144. This shift suggests that a significant number of cities that had previously enjoyed moderate air quality now face higher pollution levels.

Cities in the ‘Moderate’ bracket (61–90 µg/m³) rose from 4 to 27, nine cities entered the ‘Poor’ category (91–120 µg/m³), and one city, Dharuhera, fell into the ‘Very Poor’ range (121–250 µg/m³). These numbers reflect a nationwide deterioration in air quality, particularly in regions with dense populations, high vehicular activity, and industrial emissions.

Cleanest Cities in October

On the positive end of the spectrum, Shillong in Meghalaya emerged as the cleanest city in October, with an average PM2.5 concentration of just 10 µg/m³. Other cities with relatively clean air included four from Karnataka, three from Tamil Nadu, and one each from Sikkim and Chhattisgarh. Out of the 249 cities monitored, 212 recorded PM2.5 levels below India’s NAAQS of 60 µg/m³, though only six cities met the World Health Organization’s (WHO) daily safe guideline of 15 µg/m³, highlighting the difficulty of achieving globally recommended air quality standards in India’s urban centers.

Implications for Public Health

The spike in PM2.5 levels has serious public health implications. Fine particulate matter is known to penetrate deep into the lungs and bloodstream, contributing to respiratory illnesses, cardiovascular diseases, and premature deaths. The CREA report emphasizes that even cities not directly affected by stubble burning can experience high pollution levels due to local emissions, making a holistic, year-round approach essential for improving air quality.

Experts suggest that tackling air pollution in the NCR and surrounding regions requires a multi-pronged strategy, including:

1. Reducing vehicular emissions through electric mobility adoption, stricter fuel standards, and traffic management.
2. Controlling industrial and construction dust by enforcing stricter compliance with emission standards.
3. Promoting cleaner domestic fuel usage in households, especially in urban centers.
4. Continuous monitoring and early warning systems to manage acute pollution events.
5. Urban planning measures, including green cover expansion and city zoning reforms, to reduce pollution hotspots.

Regional Patterns of Air Pollution

The CREA snapshot further highlights the disproportionate impact of air pollution in the IGP and NCR. Cities like Ghaziabad and Noida, both of which are industrial hubs with high traffic volumes, consistently rank among the most polluted urban centers in India. Haryana’s Rewari district, particularly Dharuhera and Rohtak, exhibits extreme pollution partly due to industrial clusters and proximity to Delhi, compounding the air quality crisis for the national capital.

Meanwhile, the relatively clean cities, including Shillong, parts of Karnataka, Tamil Nadu, and Sikkim, benefit from lower population densities, better vegetation cover, and fewer industrial emissions, illustrating the stark regional disparity in air quality across India.

Conclusion

The CREA report paints a sobering picture of India’s urban air pollution, with Delhi ranking sixth nationally, behind cities like Ghaziabad, Noida, Rohtak, and Dharuhera. The findings demonstrate that while seasonal factors such as stubble burning contribute to spikes in PM2.5, persistent local emissions remain the primary driver of poor air quality throughout the year.

Experts emphasize that a long-term, sustained approach is essential to combat pollution, including stronger regulatory enforcement, cleaner energy transitions, and behavioral changes among citizens. Without such measures, cities in the NCR, including Delhi, risk chronic exposure to hazardous air, affecting public health, quality of life, and economic productivity.

The stark contrast between India’s most polluted and cleanest cities also underscores the need for knowledge sharing and policy replication. Lessons from relatively clean urban centers could guide initiatives in heavily polluted regions to mitigate the health and environmental impact of deteriorating air quality.

As India heads into the winter months, when air pollution traditionally worsens due to meteorological factors, the CREA report serves as a timely warning: year-round action on emissions is critical to safeguard public health and improve the livability of Indian cities.