The most common cause of lung cancer is smoking, but many people who have never smoked also develop lung cancer. One possible reason could be related to kitchen fumes. Chinese cooking habits often involve high-temperature frying and stir-frying. After frying in hot oil, the higher the temperature, the more harmful substances are in the fumes, which over time could lead to lung cancer. Some patients develop lung cancer due to air pollution; secondhand smoke is also a significant cause. For example, if a husband smokes, the likelihood of his wife developing lung cancer is more than 200% higher than in the general population, indicating that smoking harms not only the smoker but also their nearest and dearest family members. Additionally, there are other potential causes including psychosomatic factors such as chronic insomnia, depression, decreased immunity, genetic factors, and more.