'It's A Nationwide Crisis': April 2025 Data Shows Most Indian Cities Exceed WHO Air Pollution Limits
Experts warn India’s toxic air is now a nationwide health emergency, urging WHO-aligned standards and climate-linked clean air action.
Published : May 13, 2025 at 4:53 PM IST
By Surabhi Gupta
New Delhi: In April 2025, there was a bittersweet conclusion about the air in India. Most of the country breathed air well within the limits of India's National permissible standards, according to the latest data from the monthly ambient air quality snapshot by the Centre of Research on Energy and Clean Air.
Among the 248 cities where air quality is being monitored, 227 did not exceed the national permissible level for PM2.5—60 µg/m³. However, only seven cities achieved the World Health Organisation (WHO) significantly stricter guideline of 15 µg/m³.
This contrast illustrates a long-standing challenge India faces, which is that the National Ambient Air Quality Standards (NAAQS) of India, last revised in 2009, may no longer meet the obligation to protect public health.
Byrnihat Tops the Pollution Charts
The small industrial town of Byrnihat in Assam was the most polluted city in India in April 2025, with a monthly PM2.5 average of 119 µg/m³—essentially double the national standard and nearly eight times the WHO level limit. Byrnihat was in 'Very Poor' for 13 full days, an air quality classification that is known to significantly impact respiratory and cardiovascular health.
Even more concerning, Byrnihat is not a part of India’s National Clean Air Programme (NCAP), which currently includes 132 cities identified for targeted pollution reduction efforts. “The fact that Byrnihat isn’t even under the NCAP lens tells you how fragmented our approach to air quality remains,” said an environmental policy expert with knowledge of the programme.
Delhi, Again in the Top Five
Delhi, India's most infamous air pollution hotspot, ranked fifth with a PM2.5 average of 77 µg/m³. The rest of the month saw just 16 days in 'Moderate', 9 in 'Poor', and 5 in 'Satisfactory'.
This shows slight improvement compared to April 2024; however, the air was far from clean. While Ghaziabad and Gurgaon also found their way to the top 10-most polluted cities list, it only goes on to emphasise the air-quality challenges faced by the region for a long time and have persisted.
Bihar: An air crisis for another notch
Siwan, Rajgir, Hajipur, Aurangabad, and Sasaram, five of India's 10 most polluted cities this April, are in Bihar. Most of these cities are in the 'Moderate' category, although they routinely violate Indian and WHO norms for air quality. This speaks of the pattern: pollution is no longer just a city problem but one that is creeping into small, fast-growing towns with little environmental regulation or public health infrastructure.
Cleaner Air In Southern Cities
Gadag in Karnataka took pride as the cleanest city of India in April, with a monthly PM2.5 average of just 6 µg/m³. The cleanest cities list was dominated by the south, four in Karnataka and two in Tamil Nadu, along with outliers like Aizawl (Mizoram), Agartala (Tripura), Vrindavan (Uttar Pradesh), and even the coastal Andaman and Nicobar Islands.
What Do Experts Say
Selomi Garnaik, climate and energy expert at Greenpeace India, told ETV Bharat that data corroborates Greenpeace India’s two recent reports, 'Spare the Air 2' and 'Beyond North', that air pollution is no longer just a northern cities' issue.
"It’s a nationwide crisis, with toxic air spreading across regions once considered relatively clean. Again, we can not afford to look at air pollution in isolation anymore. The overlap with extreme heat, especially in urban areas, is creating a dangerous mixture of health risks. This is not just an environmental issue, it is a public health and climate justice emergency," Garnaik said.
She said that communities that have contributed the least to this crisis, like outdoor informal workers, are being hit the hardest. "India must revise its national air quality standards in line with WHO guidelines, and integrate air pollution control with heat action plans and broader climate adaptation strategies. Clean air is not a privilege, it is a right, and it must be protected with the urgency it deserves," she said.
Manu Singh, an environmentalist, said the April 2025 air quality assessment reveals a stark spatial asymmetry in particulate matter exposure across India, underscoring the urgent need to recalibrate national regulatory thresholds.
"With over 90% of monitored cities surpassing WHO’s annual PM2.5 guideline by April itself, it is scientifically untenable to continue relying on the outdated 2009 National Ambient Air Quality Standards (NAAQS)," he said.
"The chronic exceedance of safe exposure levels in rapidly urbanising northern and central belts signals not only a regulatory gap but a looming epidemiological crisis. Unless India transitions towards WHO-aligned, health-based standards and decentralises mitigation through localised air quality governance, the differential exposure burden will perpetuate environmental injustice and public health vulnerability," he said.
The Overshoot Warning
A crucial metric in the April report is the concept of “overshoot days”, the point in the year after which pollution levels are so high that even near-zero emissions for the rest of the year wouldn’t allow compliance with annual safety limits.
By April, 248 out of 273 monitored cities had already overshot the WHO’s annual PM2.5 guideline. In contrast, only one city, Byrnihat, exceeded India’s annual permissible average of 40 µg/m³. The disparity calls into question the adequacy of India’s existing standards.
“This is not just a matter of statistics. It’s a public health crisis,” said a senior scientist from the Central Pollution Control Board (CPCB), requesting anonymity. “Our national standards must evolve if we are to meaningfully protect citizens.”
NCAP’s Limited Reach
The report’s data suggests that air pollution is no longer restricted to the usual suspects like Delhi or Kanpur. Yet, many of the worst-performing cities are still outside the ambit of the NCAP. As of now, there are no dedicated pollution control action plans for several non-NCAP cities with dangerously high PM2.5 levels. Experts warn that without decentralised, state-driven initiatives and a substantial revision of the NCAP framework, India risks widening the clean-air inequality between regions.
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