“Smoke from chullahs and passive smoking are major triggers for lung cancer among non-tobacco users. Many Indian cities, including Kolkata, consistently record air quality levels far above safe limits, and this long-term exposure significantly raises lung cancer risk, even among those who have never smoked. “Particulate matters may trigger COPD or asthma but can’t cause cancer,” he said.Ruby General Hospital oncologist Sanjoy Roy said around one-third of lung cancer patients he encountered had no tobacco use history.“ They are now being diagnosed more frequently and earlier , say even a decade ago,” added Ganguly.Certain genetic mutations associated with lung cancer were more commonly seen in non-smokers and women, said Krishnan. But because these individuals do not fit the ‘typical’ lung cancer profile, symptoms are frequently overlooked or misattributed to allergies, asthma, infections or stress.