Many types of cancer are caused by exposure to carcinogenic (cancer-causing) substances that can be avoided. Often, a change in lifestyle or habits can reduce your risk. Prevention, such as quitting smoking, is critical in reducing your risk of cancer. 

Lung Cancer

Cigarette smoking causes 90% of lung cancers. It is the most common habit that raises cancer risk. If you stop smoking, your risk of getting cancer decreases immediately.  Eventually, the risk becomes nearly the same as the risk for non-smokers. Smoking is not the only cause of lung cancer, however. A small percentage of people may develop lung cancer even if they don’t smoke, either because there is a family history of the disease or for other reasons that are not yet clear.

Other Types of Cancer

There are other risk factors for certain cancers. These risk factors may be substances, environmental factors, or lifestyle habits, such as:

  • chemicals (for example, pesticides)
  • excessive consumption of alcohol
  • too much sunlight (skin cancer)
  • obesity
  • exposure to radiation
  • certain viruses (such as those associated with cervical and liver cancer)

For many cancers, the causes remain unknown.


Last Updated June 2020