Dose to red bone marrow of infants, children and adults from radiation of naturalorigin

Abstract

Natural radiation sources contribute much the largest part of the radiation exposure of theaverage person. This paper examines doses from natural radiation to the red bone marrow,the tissue in which leukaemia is considered to originate, with particular emphasis on dosesto children. The most significant contributions are from x-rays and gamma rays,radionuclides in food and inhalation of isotopes of radon and their decay products.External radiation sources and radionuclides other than radon dominate marrow doses atall ages.The variation with age of the various components of marrow dose is considered,including doses received in utero and in each year up to the age of 15. Dosesin utero include contributions resulting from the ingestion of radionuclides bythe mother and placental transfer to the foetus. Postnatal doses include thosefrom radionuclides in breast-milk and from radionuclides ingested in other foods.Doses are somewhat higher in the first year of life and there is a general slowdecline from the second year of life onwards. The low linear energy transfer (LET)component of absorbed dose to the red bone marrow is much larger than the high LETcomponent. However, because of the higher radiation weighting factor for thelatter it contributes about 40% of the equivalent dose incurred up to the age of15.