is no suggestion that the current radiation risk estimates for cancer at low levels of exposure are appreciably in error. Uncertainty regarding the size of this risk remains as indicated by the width of the confidence intervals.

Because of the absence of individual dose estimates in most of the cohorts, studies of occupational exposures in medicine and aviation provide minimal information useful for the quantification of these risks.

Because of the uncertainty in occupational risk estimates and the fact that errors in doses have not formally been taken into account in these studies, the committee has concluded that the occupational studies are currently not suitable for the projection of population-based risks. These studies, however, provide a comparison to the risk estimates derived from atomic bomb survivors. As with survivors of the atomic bomb explosions, persons exposed to radiation at Mayak and at Chernobyl should continue to be followed for the indefinite future.

Studies of medical and dental occupational exposures do not currently provide quantitative estimates of radiation-related risks, due to the absence of radiation dose estimates.