Physical and chemical factors, autoimmune diseases, respiratory infections, and abnormal growth of normal cells in the lung tissue can lead to pulmonary nodules. The details are as follows: 1. Physical and chemical factors stimulation: special occupational groups such as carpenters, sand or stone factory workers, a large number of inhalation of dust, wood dust deposited in the lungs, the long time progress can lead to lung nodules. 2. Autoimmune diseases: autoimmune diseases such as systemic lupus erythematosus can be involved in the lungs, easy to occur lung nodules. 3. Respiratory infections: lung infections cause inflammatory reactions in the lung tissue, forming granulomas, which may calcify or harden in the lungs with the passage of time, resulting in lung nodules. 4. Activation of lung proto-oncogenes: When lung proto-oncogenes are activated, the abnormal growth of normal cells in the lungs will lead to malignant lung nodules, which will eventually progress to lung cancer. The occurrence of lung nodules is related to many factors, if you have asymptomatic lung nodules, you should consult a doctor in time and follow up regularly.