Vitamin A deficiency. Exposure to air pollution. If you don't smoke, don't start. If you do smoke, quit. It is never too late to stop smoking.
Research shows that the chances of developing lung cancer decreases after one quits .
Nonsmokers exposed to second-hand smoke are at an increased risk for developing lung cancer. For example, a nonsmoker married to a smoker has a 25 percent increased risk for lung cancer. Never expose children to second-hand smoke. Prolonged exposure can interfere with normal lung development and increase their risk of developing respiratory illnesses such as asthma. In the workplace, follow work and safety guidelines to reduce your exposure to second-hand smoke.