It is fundamental that a given cancer case cannot be attributed with absolute certainty to a prior ionizing radiation exposure, whatever the level of exposure. It is possible to estimate the probability of a causal relationship based on data and models that have been inferred from group statistics. Two types of information are needed to make these probability calculations: natural cancer incidence rates and risks of cancer induction from ionizing radiation. Cancer incidence rates for the United States are available in the report of the Surveillance, Epidemiology and End Results (SEER) program of the National Cancer Institute. Estimates of the risk of cancer induction from ionizing radiation have been published by the Advisory Committee on the Biological Effects of Ionizing Radiation (BEIR) of the National Academy of Sciences, the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), and the International Commission on Radiological Protection (ICRP). Using the parameters discussed above, the probability of causation formulation estimates the probability that a person who develops a particular cancer after a known quantifiable radiation exposure has the cancer as a result of the exposure. In 1985, the National Institutes of Health, responding to a U.S. Congressional mandate, published radioepidemiologic tables using the probability-of-causation method.
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