My brother died from lung cancer when he was 45. Never smoked a day in his life.
My grandmother also died of complications from lung cancer. She never smoked, but as I was sitting in her house talking about how she never smoked, my eyes were irritated and the smoke of smell from her leaky old fireplace insert was annoying. I wondered at the time if that may have contributed and if I had done more to make sure that her house was smoke free if that might have helped keep her from getting sick.