EDITORIAL: URBAN SOUTH ASIA IS LIKELY THE WORLD’S REGION MOST AFFECTED BY AIR POLLUTION THAT NOT ONLY IMPACTS PULMONARY AND RESPIRATORY SYSTEMS, IT AFFECTS THE BRAIN ALSO
Vinod Mubayi
India’s capital New Delhi has long “enjoyed” a dubious top-ranking; it is the world’s most polluted capital city in terms of air quality. Air pollution is usually measured in terms of the ambient air concentration of small particulate matter known as PM2.5, i.e., particulate matter with a mean aerodynamic diameter of 2.5 microns (micrometers) or less that is readily inhaled and enters the bloodstream along with many other organs of the body that poses serious consequences for cardiovascular, pulmonary and respiratory health. Recent medical studies indicate that PM2.5 particles have deleterious impacts on the brain too.
According to the Swiss firm IQAir, New Delhi is the world’s most polluted capital city in the with an annual PM 2.5 concentration of 91.8 micrograms per cubic meter. This value is more than 18 times higher than the World Health Organization’s (WHO) standard for the PM 2.5 annual safe limit of 5 micrograms per cubic meter. It is also more than twice India’s annual standard for the PM 2.5 safe limit of 40 micrograms per cubic meter, which is considerably less stringent than that of the WHO.
PM2.5 limits vary globally, but major standards include the WHO’s standards (5 µg/m? annual, 15 µg/m? daily), the U.S. EPA’s current National Ambient Air Quality Standards (NAAQS) set at 9.0 µg/m? annually (revised in 2024) and 35 µg/m? for 24-hours, and stricter California standards, highlighting that even levels below some national limits pose health risks, impacting respiratory and cardiovascular health.
In the fall and winter months when wind speeds drop, air quality routinely turns from poor to severe to just plain hazardous. But, even though the Delhi National Capital region may be the worst affected, there are a large number of major urban conglomerations in South Asia ranging from Peshawar and Lahore in Pakistan to Delhi, Lucknow, Patna and Kolkata in India all the way east to Dhaka in Bangladesh that are to varying degrees impacted by severely polluted air and whose inhabitants bear the noxious consequences.
In fact, even coastal cities like Mumbai (formerly Bombay) that were thought to be protected from stagnant polluted air by the action of the prevailing sea breeze are now beginning to experience otherwise. For a period in October 2025, newspapers reported that Mumbai’s air quality matched the stifling haze that covers the national capital. The Air Quality Index (AQI) across different parts of the state of Maharashtra (Mumbai is its capital city) turned from “poor” to “very poor”.
The main reason for the air quality predicament that urban South Asia finds itself in is not far to seek: it is source emissions dominated by the emissions from cars and trucks, followed by emissions from industrial activity such as thermal power plants and brick kilns and construction activity. To put it bluntly, we are choking on our own excreta from the development models we chose. We copied the U.S. in the private car and truck mode of transporting people and goods and are now paying the price in terms of catastrophic health impacts.
Atmospheric scientist Prof. Gufran Beig, Chair Professor, National Institute of Advanced Studies, IISC-Campus, Bengaluru, India puts the matter succinctly in a recent article that is worth quoting at length:
“It’s not stubble burning or firecrackers: Delhi is choking on its own emissions
When the air stands still, stagnation sets in, ventilation collapses, and the system is left with no buffer to protect public health. When the weather naps, there is nowhere left to hide. Yet, we continue to blame the weather instead of our emissions.
Scientifically, the Severe AQI episode reflects the city’s condition. It represents Delhi’s true picture, its own emissions, laid bare.
There is no stubble burning in Delhi’s neighboring states, no firecrackers accompanying festivals, and the winter chill has not yet peaked. Yet, Delhi’s AQI surged to Severe (from December 13, 2025 onward). Why did this happen, and what does it teach us? This AQI may soon recede to Very Poor, but it will return, playing hide-and-seek for at least another month. Despite the hourly capping of PM 2.5 at 380 µg/m? (equivalent to AQI 500), software glitches, and other much-discussed constraints, the AQI nearly hit 500, revealing a grim reality and offering a sobering lesson.
Such extremes occur when pollution consistently persists at peak levels for prolonged periods (24-48 hours or more), irrespective of the time of day. Put simply, wind speeds across Delhi and its wider airshed dropped close to zero. This meant nothing was coming in and nothing was going out. Vertical dispersion was also restricted by a shallow inversion layer, approximately 500-700 meters deep. As a result, emissions from fixed point sources linger where they were released, creating localized pollution hotspots instead of spreading, simply because there was almost no wind. But it’s the dynamic sources of pollution, widespread across the city, that are driving the sharp dip in Delhi’s air quality.
Scientifically, the Severe AQI episode reflects the city’s condition. It represents Delhi’s true picture, its own emissions, laid bare. These events reveal how heavily Delhi relies on daily atmospheric dilution to maintain its AQI below Severe, and how this dependence creates an illusion about the true culprit: Local source emissions. More worryingly, stagnation episodes are projected to become more frequent because of climate change. When the air stands still, stagnation sets in, ventilation collapses, and the system is left with no buffer to protect public health. When the weather naps, there is nowhere left to hide. Yet, we continue to blame the weather instead of our emissions.
When the atmosphere temporarily loses its capacity to clean itself — even for just a couple of days — the true magnitude of Delhi’s emissions becomes starkly apparent. It is revealed as a monumental and self-inflicted crisis. That’s the key insight this episode revealed. Our estimates for Delhi NCT show that nearly half the emissions of PM2.5, the particles that inflict the greatest harm, come from transport (43 per cent), with waste burning at 15 per cent, residential and industrial emissions each at 13 per cent, and only 8 per cent from resuspended dust, besides others. The priority for action is, therefore, clear for policymakers.
The math is simple. In such extreme stagnant conditions, if Delhi cuts its local emissions by 50 per cent, pollution levels drop by roughly 50 per cent. When the weather changes, the same logic applies — but emission reductions must happen across the entire airshed. To effectively reduce pollution, focus on coordinated, sustained, long-term action on source emissions, not short-term optics such as smog towers, cloud seeding, water sprinkling, or air purifiers”
In addition to vehicular and industrial-residential emissions from within its own geographic territory, secondary aerosols formed by emissions from coal-fired power plants that may be located several hundreds of miles away are also significant contributors to PM2.5 air pollution in the Delhi NCR as well as in other metro cities. Gases emitted from the combustion of coal such as nitrogen oxides (NOx) and sulfur oxides (SOx) undergo chemical reactions in the atmosphere to form harmful compounds such as ammonium nitrate and ammonium sulfate that are then transported over long distances and impact urban air quality.
Journalist Sophiya Mathew writing in the Indian Express, New Delhi, newspaper of December 30, 2025 referred to an “analysis released earlier this month by the Centre for Research on Energy and Clean Air (CREA), ammonium sulfate alone accounts for nearly one-third of Delhi’s annual PM2.5 load, rising sharply during the post-monsoon winter months when pollution episodes are at their worst.”
Mathew pointed out “India is currently the world’s largest emitter of sulfur dioxide (SO?), largely due to coal-based power generation”, that accounts for the largest amount of electric power generation in the country. Mathew indicates that “In July 2025, the government exempted nearly 78% of coal-fired thermal power plants from installing flue gas desulphurization (FGD) systems, weakening SO? control at the source. The government cited three studies that said SO? levels around plants are well within norms. Experts, however, say this is inaccurate.”
Health Impacts of Toxic Air
Dr. Sudheer Kumar Shukla, an environmental scientist and sustainability expert, who currently serves as head-think tank at Mobius Foundation, New Delhi has outlined the health impacts of toxic air in a recent article published on December 12, 2025. He points out:
“Air pollution in India is no longer a winter irritant confined to the northern plains. It has become a persistent, nationwide public health emergency that affects every demographic group and nearly every organ system. Across the Indo-Gangetic plain, and increasingly in fast-growing urban centers elsewhere, dangerous concentrations of particulate matter are shaping disease patterns, slowing childhood development and silently reducing life expectancy.
India’s air quality crisis is both widespread and deeply entrenched. Of the 256 cities monitored in 2025, 150 exceeded the national PM 2.5 standard as per a report by the Centre for Research on Energy and Clean Air. For most urban residents, breathing unhealthy or hazardous air is now a routine part of the year. The Indo-Gangetic plain remains the worst affected. In 2025, Delhi recorded seasonal PM 2.5 levels of 107–130 µg/m3—far above India’s 24-hour limit of 60 µg/ m3and the World Health Organization guideline of 15 µg/ m3
The health burden of toxic air is stark. According to the Air Quality Life Index (AQLI) of the University of Chicago’s Energy Policy Institute, nearly 46% of Indians live in regions where air pollution significantly reduces life expectancy. In Delhi, current PM 2.5 exposure translates into a loss of more than eight years of life when measured against WHO standards. Across northern India, the losses range between 3.5 and seven years.
The mortality toll is equally worrying. In 2023, air pollution contributed to nearly two million deaths nationwide, as per the State of Global Air Report, 2025, primarily from cardiovascular disease, stroke, COPD and diabetes. Pollution-linked mortality has risen by 43% since 2000, underscoring the cumulative effects of long-term exposure.
Cardiovascular harm: PM 2.5 particles penetrate deep into the lungs, cross into the bloodstream and provoke systemic inflammation. Multi-city epidemiological studies in India show an 8% increase in annual mortality for every 10 µg/m? rise in long-term PM 2.5 exposure. Elevated exposure is linked to hypertension, atherosclerosis, myocardial infarction, arrhythmias and ischemic stroke. In a country already struggling with high cardiovascular disease rates, polluted air acts as a potent, invisible accelerant.
Respiratory illness: Respiratory illnesses remain the most visible consequence of toxic air. Nearly 6% of Indian children now suffer from asthma. Clinical data from AIIMS [All India Institute of Medical Sciences] reveals that a modest 10 µg/m? increase in PM 2.5 can cause a 20–40% spike in pediatric emergency visits for respiratory distress. Children exposed to high pollution levels show a 10–15% reduction in lung capacity—a deficit that may persist into adulthood. Among adults, COPD, chronic bronchitis and recurrent respiratory infections are increasingly common, especially for those living near roads, industries, landfills and construction sites.
Neurological impacts: Emerging scientific evidence shows that air pollution affects the brain as seriously as it affects the lungs and heart. PM 2.5 particles can cross the blood–brain barrier, triggering neuroinflammation and oxidative stress. Studies from Indian cities link pollution exposure to poorer academic performance, impaired memory and slower cognitive development among children.”
New Health Study on Brain Damage from PM2.5 exposure
A very important recent study entitled “Ambient Air pollution and the Severity of Alzheimer’s Disease Neuropathology” by Boram Kim, Kaitlin Blam, Holly Elser, Sharon X Xie, Vivianna M Van Deerlin, Trevor M Penning, Daniel Weintraub, David J Irwin, Lauren M Massimo, Corey T McMillan, Dawn Mechanic-Hamilton, David A Wolk, and Edward B Lee has been published recently in the Journal of the American Medical Association (JAMA): JAMA Neurol. 2025 Nov 1;82(11):1153–1161.
The aim of this study was to examine relationships between PM 2.5 exposure, dementia severity, and dementia-associated neuropathologic change. The study was motivated by several other studies that have shown that exposure to air pollution, or more specifically fine particulate matter with aerodynamic diameter less than 2.5?m (PM2.5), is associated with an increased incidence of dementia, impaired cognitive function, and accelerated cognitive decline.
“This cohort study used data associated with autopsy cases collected from 1999 to 2022 at the Center for Neurodegenerative Disease Research brain bank, University of Pennsylvania. Data was analyzed from January to June 2025.
One-year average PM2.5 concentration prior to death or prior to last CDR-SB assessment was estimated using a spatiotemporal prediction model at residential addresses. 602 cases with common forms of dementia and/or movement disorders and elderly controls were included. The study examined relationships between PM2.5 exposure, dementia severity, and dementia-associated neuropathologic change.
To summarize, the study explored the relationships between air pollution, neuropathology, and dementia. The findings were that in this cohort study of 602 autopsy-confirmed individuals, exposure to higher levels of fine particulate matter air pollution (PM2.5) was associated with more advanced Alzheimer’s disease neuropathologic change (ADNC) and more advanced clinical measures of dementia. The association between PM2.5 exposure and clinical dementia severity appeared to be statistically mediated by ADNC leading to the conclusion that higher PM2.5 exposure may exacerbate Alzheimer’s disease neuropathologic change and cognitive dysfunction in the setting of dementia.”
Response of Indian Govt and Regulatory Bodies: Evasion and Denial
Meanwhile, what is the response of the authorities in the Indian capital, the organs of the state agencies, whose normal remit would be to take steps to reduce PM2.5 air pollution. The Minister of State for Environment and Climate Change, Kirti Vardhan Singh, is reported to have stated in the Lok Sabha (lower house of the Indian Parliament) on December 18, 2025 that “There is no direct correlation between higher Air Quality Index (AQI) levels and lung diseases, with no ‘conclusive data’ to establish such a link.”
To call such a person ignorant or worse is merely to state the obvious. He is just a small cog in a machine operated by world-class ignoramuses headed by the Vishwaguru (World Guru) himself.
Mr. Singh was responding to a question from BJP parliamentarian Laxmikant Bajpayee, who sought to know if the government was ‘aware’ of studies and medical tests that linked “prolonged hazardous AQI levels” in Delhi/ National Capital Region to lung fibrosis, and an irreversible reduction in lung capacity and if the government had any ‘solution’ to save Delhi residents from pulmonary fibrosis, COPD, emphysema, reduced lung function and continuously declining lung elasticity.
The Minister, however, only gave a single-sentence response on the absence of ‘direct correlation’. In response to a related question from an opposition party Congress MP, Mr. Singh reiterated—as he did in earlier weeks— that ‘no conclusive data’ existed to establish a direct correlation of death ‘exclusively’ by air pollution and that health effects from air pollution were a “synergistic manifestation” of food habits, occupational habits, socioeconomic status, medical history, immunity and heredity.
The Minister explained the steps taken by the government to address air pollution — the establishment of the Commission for Air Quality Management (CAQM) in 2020 and how it had issued “95 statutory directions” to abate air pollution in the region. However, India’s Supreme Court termed the CAQM’s actions a “total failure” at curbing pollution in the Delhi NCR.
In the Rajya Sabha (upper house of Parliament), Minister of State for Health Prataprao Jadhav asserted in response to another question that there were “No deaths due to air pollution” and, following the advice of his colleague Kirti Vardhan Singh, repeated the same nonsense that “Health effects of air pollution are a synergistic manifestation of factors which include food habits, occupational habits, socio-economic status, medical history, immunity, heredity, etc. of the individuals.”
In fact, there is a wealth of medical data as well as many studies documenting the thousands of deaths from air pollution in India.
Another BJP politician, Delhi Environment Minister Manjinder Singh Sirsa, is reported to have said on January 1, 2026 that the national capital recorded its best air quality in eight years in 2025. The absurdity of this statement should be obvious to anyone living in the Delhi NCR but this kind of nonsense passes through the media unchallenged. The only rebuke came from the opposition party AAP that accused the BJP of having “no real intention of addressing the worsening pollution emergency.”
Denial and evasion seem to be the only tools left to the ruling politicians and government functionaries to avoid taking meaningful steps to address the problem.
Conclusion
As Dr Sudheer Shukla stated in his previously quoted article: “India’s air quality crisis is both widespread and deeply entrenched. The scientific evidence is overwhelming, and the health impacts are undeniable.”
A further tragedy is that the most deleterious impacts of urban air pollution are experienced by the lowest income communities who are forced to live on the pavements or in slums exposed to the most severe emission hotspots like roads, garbage dumps euphemistically called landfills, and construction sites. Dr Shukla rightly said: “Air pollution in India mirrors existing social and economic inequalities. The country must now recognize clean air as a fundamental right essential to equitable growth.”
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