Internal alpha-particle emitters: their dose to bone marrow and the foetus

Children’s exposure to high-LET α-radionuclides is dominated by that from natural sources. If we consider the dose to bone marrow in childhood and the in utero dose to haemopoietic tissue, the important short-lived radionuclides of interest are those derived from radon and its immediate decay products (figure 1). For the long-lived α-radionuclides, Po and Ra are by far the most important, the former arising mainly from the decays of the β-emitters Pb and Bi. In contrast, the activity concentration of man-made α-emitters in the human body is extremely low. For example, even in the vicinity of the British Nuclear Fuels Sellafield site, the activity concentration of plutonium measured in children’s teeth is a few mBq kg only, around 1,000 times lower than that for naturally occurring Po at several Bq kg (O’Donnell et al. 1997).