Analysis of Alpha Particle Autoradiographs of Bone Samples from Adults and Children in the UK at Natural Levels of Exposure

Abstract

Alpha particle autoradiography of autopsy bones samples at natural levels of exposure reveals that the activity present is dominated by 210Po, the majority of which is assumed to be present by ingrowth from 210Pb. Contrary to the standard ICRP model for bone, the 210Pb so produced appears to be released from bone and free to migrate into both marrow and adjacent tissue. Consequently, the alpha radiation dose to red marrow is considerably higher than has previously been assumed and comparable to that from low LET radiation. The samples analysed were obtained from West Cumbria and other parts of Northern Britain and were taken from four adults and seven children. The average 210Po activity values in bone and marrow were found to be 1.46 ± 0.13 and 0.33 ± 0.04 Bq.kg-1 in adults and children respectively. The average 226Ra activity values were much lower in these samples: 0.033 ± 0.013 and 0.020 ± 0.006 Bq,kg-1in adults and children respectively. Errors quoted are those in the mean. The resultant doses to red marrow, dominated completely by 210Po within the marrow, are 780 and 176 µSv.y-1 for both adults and children respectively. These should be compared with estimates of low LET dose of 1 mSv.y-1 for both adults and children. Plutonium activity values, in neighbouring bone samples, were determined elsewhere by radiochemical methods and were considerably lower; below 0.01 Bq.kg-1 for adults and below 0.002 Bq.kg-1 for children.