Radiation cancer, safety standards and current levels of exposure

Cancer can be induced by radiation in any tissue where cancer occurs naturally. The observation that antenatal diagnostic radiography causes a small but definit increas in childhood cancer is as good evidence as could be expected in support of the scientific expectation that there would be no threshold of dose for carcinogenesis. A linear relation between radiation dose and frequency of of induced cancer is a necessary assumption for a system of radiological protection but is not necessarily a reasonable basis for realistic assessments of cancer risk. Indeed there are radiobiological and epidemiological reasons to the contrary. If the linear hypothesis is accepted then at the present time in the UK the routine practice of medicine is of about 2 orders of magnitude more important in causing cancer than environmental pollution by discharge of radio-activity. The acceptability of radiation safety standards for occupational exposure may be justified by comparison of radiation cancer risks with risks from fatal accidents in the safer industries. The acceptability of the corresponding standards for members of the public seems to require more public discussion of the concept of negligible risk. Emotional reactions to uncontrolled releases of radio-activity are based at least in part on a failure to appreciate the hypothesis of linearity.