With Delhi winters coming in, the spell of late smog is most likely to stay not just outside the homes, but it could in fact, follow you inside your homes. A study by the University of Delhi's Satyawati College, Jamia Millia Islamia, and US's South Dakota University, reveal that bacterial levels were recorded to be 10 fold higher than the World Health Organization (WHO) recommended safety limits. Studies have also found that air inside the city homes have 12 times more fungal spokes than the WHO safety limits. They can cause skin allergies, respiratory issues, and anxiety. As per a 2021 study by the Energy Policy Institute at the University of Chicago (EPIC India), PM 2.5 levels for low-income and high-income households in Delhi were high during the winters. The concentrations reported 23 and 29 times higher than the WHO safe limits, respectively. These findings also suggested that high-income households were 13 times more likely to own air purifiers than low-income households.In Delhi, No One Gets To BreatheDr Kenneth Lee, who was the lead author of the study said, "In Delhi, the bottom line is - whether someone is rich or poor, no one gets to breathe clean air." Lee further adds, "It’s a complex vicious cycle. When you do not know about the pollution levels inside your homes, you do not worry about it, and hence you are less likely to take corrective actions. Only with increased awareness, demand for clean air may gain momentum.”The study also found that indoor PM2.5 levels were higher than the value reported by the nearest government monitor. The PM2.5 levels spiked in the mornings and evenings when households were most likely to be cooking. The recent study published in Frontiers in Public Health 2025 notes that long term exposure to high fungal and bacterial concentration make indoor air in several parts of Delhi as harmful as the smog outside. The study also noted that most fungal particles were smaller than 2.5 microns, this is why they can easily penetrate through your bloodstreams. The study revealed a distinct seasonal trend in indoor air quality across Delhi. Fungal levels rose steadily from winter, peaking at around 6,050 CFU per cubic metre between September and November, just before the city’s infamous smog season. Bacterial concentrations, meanwhile, climbed from winter to summer, reaching their highest levels in August before tapering off in the fall.Health complaints among residents were widespread: 33% reported frequent headaches, 23% experienced burning or irritated eyes, 22% suffered persistent coughing or breathlessness, and 18% struggled with sneezing and allergic rhinitis. Another 15% reported skin irritation and itching.Who Are At Most Risk Of Indoor Pollution?The study highlighted that children and young adults were particularly vulnerable, about 28% of children under 12 and 25% of young adults (18–30 years) experienced breathing difficulties, coughing, or allergy-related symptoms. Researchers attributed children’s higher susceptibility to developing lungs, increased physical activity, and longer indoor exposure.Women also reported more eye and skin problems, making up nearly 60% of dermatological and eye irritation cases, likely due to spending more time indoors.Conducted over a year in North Delhi, the study, “Microbial Indoor Air Quality Assessment and Health Correlations in Densely Populated Urban Areas of Delhi, India”, found that fungal and bacterial levels inside homes were several times higher than WHO’s safe limits, underscoring that Delhi’s pollution crisis extends well beyond outdoor air.
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