Radiation carcinogenesis - past, present and future

The widespread use of penetrating X-rays and radium in treating disease in the early 1900s led to the recognition of a cancer risk in many organs and tissues following high radiation doses which caused gross tissue damage. There was, however, a delay of about 50 years before it became clear that there was a risk of radiation-induced cancer from irradiation at lower doses which do not cause acute effects. For most organs and tissues, evidence of the risk of radiation-induced cancer and its relationship to radiation dose has depended on prolonged and accurate medical surveillance of large groups of people who have been exposed in the past to known amounts of external radiation or internally incorporated radionuclides. It is now believed that any radiation dose is capable of inducing cancer and that the probability of its occurrence, but not its severity, depends on the radiation dose. In radiation protection terminology it is termed a <>. The development of knowledge of the risks of radiation-induced cancer and its application in setting protection standards both for the working population and for members of the public are described in this paper. Uncertainties in risk estimation are also considered and how future work can improve knowledge of the relationship between radiation dose and the risk of cancer. (author). 34 refs., 8 tabs