Smoking is extremely harmful, and is associated with the development of malignant tumors, respiratory diseases, cardiovascular and cerebrovascular diseases, reproductive developmental abnormalities, diabetes and so on. 1. Malignant tumors: Tobacco contains 69 known carcinogens, which can lead to genetic mutations in the human body, thus leading to lung cancer, esophageal cancer, stomach cancer and other malignant tumors. 2. Respiratory diseases: Smoking can damage the structure and function of the respiratory tract, thus causing the occurrence of chronic obstructive pulmonary disease and other diseases. 3. Cardiovascular and cerebrovascular diseases: research shows that smoking can damage the endothelial cells of blood vessels, which leads to atherosclerosis and then causes various cardiovascular and cerebrovascular diseases. 4. Abnormalities in reproductive development: Tobacco smoke has been shown to contain a variety of substances that can affect human reproduction and development, which will adversely affect the development of the fetus. 5. Diabetes: It has been proven that smoking can cause type 2 diabetes and affect the prognosis of diabetic patients. In addition to the above, smoking can also cause other harm, if you feel unwell, please consult a doctor.