Pott and the path to prevention.

Two hundred years ago, Percival Pott, a London surgeon, recognized that chimney sweeps were particulary liable to develop scrotal cancer and attributed the disease to exposure to soot. By so doing, he described the first environmental cause of cancer and started the chain of events that led to the first experimental production of cancer, the first synthesis of a carcinogen, and the first isolation of a carcinogen from a natural substance. Following these laboratory successes, the main object of cancer research has been to discover the fundamental characteristics of the cancer cell and the mechanism of the cancer cell and the mechanism of its production and relativly few investigations have studied the conditions under which cancer is produced in man. Recently, however, it has been recognized that we can often prevent cancer by modifying the conditions of life without detailed knowledge of the mechanism of carcinogenesis. All but a few rare cancers vary in incidence with place or time or with both and nearly all this variation can be shown to be environmental in origin. We already know enough to prevent most cancers of the mouth, oesophagus, larynx, lung, bladder, and skin in W. Europe and N. America, most cancers of the mouth in Asia, and most liver cancers in Africa. We have clues to the causation of cancer of the cervix uteri, breast, and colon and we should learn how to prevent all these cancers before long. Many new hazards could be prevented by controlling the introduction of new carcinogenic chemicals into the environment while others could be detected quickly by improved methods of epidemiological enquiry. But even so, acute clinical observers, like Pott, will continue to be needed for many years.