The winter is yet to settle in, but Delhi is already choking with pollution - the fifth largest killer in India. In October, the pollution was four times the normal level. The crowds in the city's hospitals and clinics have gone up by around 30% - most of the patients are children and senior citizens. Dr Vivek Nangia, Director of Pulmonology at Fortis Hospital, Vasant Kunj, says most people don't understand that air pollution can cause lung cancer, brain hemorrhage and stroke.