Physical agents causes cancer

   Physical agents. Excessive exposure to sunlight is an important predisposing factor to cancers of the skin. The solar keratoses (thickening of epidermal cells) that occur on those portions of the body exposed to the sun are the intermediate stage between normal skin and skin cancer. These develop more frequently in farmers,sailors, and other workmen whose activities expose them to large amounts of ultraviolet radiation form sunlight. Sunbathing with prolonged and unnecessary exposure to the sun is unwise. Because of the high level of pigment in their skin, dark people are less susceptible to skin cancer than are those with a fair complexions.
   Exposure to radiation in X-rays or atomic radiation increases a person's susceptibility to cancer. When X-ray equipment was first introduced, the precautions required today were not used, with the result that those working in the field were needlessly exposed to radiation. For example, radiologists had ten times the incidence of leukemia as did physicians in general. Because of improved technology, the X-rays used today expose both radiologist and patient to a minimal amount of radiation, thus drastically reducing the risk of adverse effects.
   Excessive temperature appears to make tissues vulnerable. Cancer of the lip is quite common among pipe smokers. The heat from the pipe stem is thought to be an important factor (a promoter) in causing cancer of the lip. A testicle that has not descended into the scrotum is more likely to develop a malignant change because the body temperature inside the body is higher than in the scrotal sack.