New Delhi: As Delhi’s air quality deteriorated to the severe category on Friday (November 13), a new review of five decades of Indian research has highlighted the scale of the country’s air pollution crisis: 169 of 184 epidemiological studies examining the health impacts of air pollution reported at least one adverse health association.The systematic review, released by the Centre for Research on Energy and Clean Air (CREA), examined peer-reviewed studies published between 1975 and 2025. It found that 91.8% of the studies reported increased health risks associated with exposure to air pollution, spanning respiratory and cardiovascular diseases, pregnancy complications, impaired child growth, diabetes, cancer, mental and neurocognitive disorders, kidney diseases and mortality.The findings come as Delhi’s air quality once again reaches dangerous levels. The Central Pollution Control Board (CPCB) recorded the city’s Air Quality Index (AQI) at 403 on Friday (November 13) morning, placing it in the ‘severe’ category. As per this report by Reuters Delhi also overtook Lahore to become the world’s most polluted city, according to Swiss air-quality monitoring group IQAir.The international ranking uses a different AQI methodology from India’s CPCB and measures air quality levels based on the concentration of toxinsThe review’s findings also challenge the idea that the health consequences of air pollution are confined to urban centres. Of the 40 studies that examined rural populations, 38 reported at least one adverse health association.The review covered outdoor, household, indoor and occupational exposure to pollutants, including PM2.5 or fine particulate matter (particles measuring 2.5 micrometres or less in diameter) and PM10 (particles that are 10 micrometres or less in diameter and small enough to be inhaled into the respiratory system) black carbon, organic carbon, heavy metals and gaseous pollutants such as sulphur dioxide, nitrogen dioxide, ozone and carbon monoxide.Government-funded studies also report adverse health associationsThe review found that the evidence of adverse health associations was not limited to research conducted by independent organisations. Of the 46 government-funded studies included, 44 reported increased health risks. Similarly, 77 of 81 studies with government institutional affiliations reported adverse health associations.The institutions involved include the Ministry of Environment, Forest and Climate Change (MoEFCC), Ministry of Health and Family Welfare (MoHFW), Indian Council of Medical Research (ICMR), Central Pollution Control Board (CPCB), All India Institute of Medical Sciences (AIIMS), Department of Science and Technology (DST), University Grants Commission (UGC), and Council of Scientific and Industrial Research (CSIR).Also read: Diwali Night Exposes What Delhi Breathes the Rest of the YearRespiratory diseases were the most frequently studied health outcome, appearing in 86 studies. Sixteen studies examined mortality and 11 investigated cardiovascular diseases. Other studies examined diabetes, pregnancy-related complications, low birth weight, impaired child growth, tumours, blood disorders, mental health conditions, sleep disorders, eye diseases and chronic kidney and bone diseases.Delhi accounted for the largest number of studies at 26, followed by Punjab with 13, Maharashtra and Uttar Pradesh with 11 each, and West Bengal with 10.Where is the environment minister?The findings arrive amid public scrutiny of the government’s response to the recurring air pollution crisis.As per this report by The Print, The Students’ Federation of India (SFI) and Delhi University, staged a protest at the varsity’s Arts Faculty on Thursday (November 12) against the worsening air quality in Delhi. Separately, a group of environmentalists and activists sought a meeting with Union Environment Minister Bhupender Yadav and central government officials to push for urgent, sustained measures to tackle the pollution crisis.The SFI raised concerns about deteriorating air quality and alleged a lack of transparency in pollution monitoring, citing reports of missing data during peak pollution hours.The Wire previously reported that neither Union environment minister Bhupender Yadav nor Delhi environment minister Manjinder Singh Sirsa publicly addressed the growing pollution rates nor the missing Delhi Diwali-night monitoring data or the questions raised by the reports.This comes amid a wider online conversation questioning the minister’s role and whereabouts.A post on social media platform Instagram that was widely shared questioned where Yadav was amid the pollution crisis in the country. Another post on Instagram by the Cockroach Janta Party (CJP) questioned if India even had an environment minister.CREA calls for wider pollution-control measuresThe CREA review also points to the need to look beyond particulate matter when framing air pollution policies.While 32 studies examined PM2.5, seven researched gaseous pollutants such as nitrogen oxides, sulphur oxides, ozone and carbon monoxide.The review said studies examining gaseous pollutants also reported statistically significant adverse associations, including increased mortality, hospital and emergency visits for acute respiratory conditions, asthma-related admissions and impaired lung function.Also read: 1 in 15 Lost Pregnancies in South Asia Is Due To Air Pollution, Study FindsSulphur oxides and nitrogen oxides can also contribute to the formation of secondary PM2.5 through atmospheric chemical reactions. According to CREA, sulphate and nitrate particles formed through these processes account for approximately one-fourth of India’s PM2.5 concentrations.CREA has called for updated National Ambient Air Quality Standards (NAAQS), stricter emission standards for both particulate and gaseous pollutants, and sector-specific targets to reduce exposure from outdoor and household sources.In a statement, Manoj Kumar, an analyst at CREA, said air pollution mitigation required a multipollutant approach, including emission reductions from industries, power plants, residential cooking and other combustion activities.He also called for the revision of the National Clean Air Programme (NCAP), with PM2.5-specific targets.