1. Fine particulate matter crosses the blood-brain barrier
PM2.5 particles, the ultrafine pollutants that define Delhi's winter smog, are small enough to pass directly from the lungs into the bloodstream and from there into the brain. A 2023 study published in The Lancet Planetary Health found that long-term exposure to PM2.5 is associated with accelerated brain ageing and reduced grey matter volume in regions governing memory and executive function. In Indian cities, where PM2.5 levels routinely exceed WHO safe limits by ten to twenty times during peak pollution months, this is not a distant risk. It is a daily biological event.
