Causes of Cancer

Several types of cancer, including cancer of the lungs, mouth, pharynx, skin and colon, can be prevented to varying degrees. What is required is efforts to reduce smoking, alcohol consumption, carcinogenic substances in the working environment, human-caused exposure to ionizing radiation (such as that used for radiography), ultraviolet radiation (from sunlight), overweight and radon in the environment. Efforts to reduce smoking would have the greatest effects by far, as about 25% of all cancer cases among men and 15% among women result from smoking. For example, smoking causes 85% of all lung cancer cases. Carcinogenic substances in the working environment cause about 3–5% of all cancer cases. Diet and exercise are also believed to be very important in the development of cancer, but this is difficult to quantify.
How can cancer be prevented?
Primary prevention targets the known risk factors for certain types of cancer, which are described under the targets for risk factors. Prevention aims at eliminating or reducing the exposure of the population or individuals to these risk factors. Attempts can be made to prevent a few types of cancer by screening: breast cancer, cervical cancer and cancer of the colon. Nevertheless, prevention through screening requires effective treatment at the preliminary stages of each type of cancer. Screening does not reduce the number of people with cancer but can reduce mortality. Screening for breast cancer, cancer of the colon and cervical cancer can reduce mortality from these types of cancer in the relevant age groups by an estimated 20%, 15% and 50%, respectively.