India’s pollution hotspots: Delhi’s plight is severe, but the crisis is national and year-round

File photo

A new nationwide analysis has revealed that Delhi is the most polluted state or Union Territory in India, with residents exposed to dangerously high levels of fine particulate matter throughout the year.

The findings underscore a severe public health crisis that is no longer confined to major cities or winter months, but has become a persistent, countrywide issue.

According to satellite-based assessment by the Centre for Research on Energy and Clean Air (CREA), the capital recorded an annual population-weighted average PM2.5 concentration of 101 micrograms per cubic metre (µg/m³).

This staggering figure is 2.5 times higher than India’s national ambient air quality standard and a shocking 20 times the World Health Organization’s (WHO) recommended guideline.

The CREA report paints a grim picture of a national emergency, indicating that 447 out of 749 districts analysed breach the annual PM2.5 safety limit. Crucially, the study employed population-weighted data, which represents the actual exposure of people to the pollutant, rather than just ambient air quality.

While Delhi’s plight is severe — with all 11 of its districts featuring among the country's top pollution hotspots — the crisis is far more widespread. The research identifies the entire Indo-Gangetic airshed, of which Delhi is a part, as the most polluted region in the nation.

An airshed is a geographical area that shares the same air due to common weather patterns and topography, which traps and circulates pollutants across state borders.

Perhaps more alarmingly, the CREA assessment signals a major emerging concern in the country’s northeast, a region traditionally perceived as cleaner. The Assam-Tripura airshed now shows persistently elevated concentrations, ranking as the second-most polluted airshed after the Indo-Gangetic plains.

Districts in Assam and Delhi together account for nearly half of India’s 50 most polluted districts, with states like Haryana and Bihar also featuring prominently. The report from CREA stresses that dangerous pollution levels represent a year-round national crisis.

The analysis of seasonal patterns reveals a familiar cycle of pollution peaks and troughs, but offers little comfort. Pollution peaks in the winter, affecting 82% of all districts and drops during the monsoon, only to surge again post-monsoon.

This pattern, experts say, underscores that meteorological conditions provide only temporary relief, while persistently high baseline emissions remain the core of the problem. The northeast’s airshed, for instance, continues to exceed safe levels even during the monsoon, confirming that the issue is driven by sustained emissions, not just seasonal weather.

The report challenges the current city-centric approach to air quality management. CREA analyst Manoj Kumar explained that the number of airsheds in India can vary from nine to 11 depending on the season, illustrating the complex, interconnected nature of the problem.

The findings highlight an urgent need to move beyond city-based air quality planning to a broader, coordinated airshed-based governance framework. Such an approach would recognise how pollution travels across district and state borders, making isolated clean-air policies in cities like Delhi largely ineffective against a regional tide of contaminants.

The CREA indicated that plans are underway to soon release daily satellite-derived PM2.5 maps, which could provide near real-time data to better inform policy and public awareness. For now, the data presents an unequivocal verdict: India’s clean air challenge is a vast, interconnected battle that demands a unified national strategy.