During the nineteenth century, among the mine workers of the Schneeberg and Jachymov mines, now in Czechoslovakia, cases of lung cancer were detected in greater frequency than in the surrounding areas. It was later found out that these mines contained various radioactive substances which were the cause of cancer.
Experimentally also, prolonged exposure of laboratory animals to X-ray or other radioactive substances has been shown to produce cancer. Many inexperienced technicians working with X-ray machines in the past, were found to develop cancer of the skin over the hands and even developed leukaemia commonly called ‘blood cancer’. Bone cancers were noted to have occurred more frequently in girls who were engaged in watch factories to paint dials of watches with luminous paint which contained radioactive material. Leukaemia and other cancers have been shown to have occurred among many Japanese who were exposed to the atom bomb explosions.
Solar radiation has its share in the causation of cancer. In Australia, New Zealand and some parts of the USA, skin cancers are common and this is attributed to the adverse effect of sun’s rays.
Chronic Irritation Can Cause Cancer
A slight but constant injury over a period of many years, has been known to lead to cancer of that part of the body. A jagged edge of a broken tooth rubbing against the tongue, gall stones rubbing constatly against the gall-bladder, the smoking short clay pipes used by labourers in Europe, have led to cancers of tongue, gall-bladder, and the lips, respectively. In the Godavari region of Andhra Pradesh, many men and women smoke locally rolled cigars (chutta) with the burning end inside the mouth. Some of these people are known to develop cancer of the mouth.
Kangri cancer among the Kashmiris develops over the skin of abdomen and thigh. This is due to the constant injury by the hot kangri, which is an earthen pot containing burning coal kept underneath the garments directly in contact with the skin. The dhoti cancer below umblicus seen among Maharashtrian men and women has been attributed to chronic irritation leading to cancer.