Cancer risk from low-level ionizing radiation: the role of age at exposure.

This article examines methodological issues related to epidemiologic investigations of the influence of age at exposure on radiation risk estimates; the epidemiologic literature on the role of age at exposure in radiation-cancer associations; and biological mechanisms that may account for associations observed in these studies. There is substantial evidence that young children, and especially the fetus, are highly vulnerable to ionizing radiation. Investigations also suggest that sensitivity may increase at the oldest ages of exposure. Further attention to modifying factors in radiation-cancer associations, such as age at exposure, may help to protect workers and the public by improving our understanding of sensitivity variation within populations.