Estimation of lymphocyte radiation doses after the ingestion of radionuclides of different tropicity

Abstract

Assessment of the lymphocyte doses is relevant for solving a number of radiobiological problems, including the risk assessment of hemoblastosis (leukemia, multiple myeloma, lymphoma etc.), as well as the use of circulating lymphocytes as “natural biodosimeters”. The latter is because the frequency of chromosomal aberrations occurring in lymphocytes following radiation exposure is proportional to the accumulated dose. Assessment of doses to the circulating lymphocytes requires due account of: first, the dose accumulated by the lymphocyte progenitors in the red bone marrow; and second, the dose accumulated during lymphocyte circulation through lymphoid organs. The models presented by International Commission on Radiological Protection (ICRP-67, ICRP-100) allow calculating the dose for specific lymphoid organs based on known level of radionuclide intakes. A recently developed model of circulating T-lymphocyte irradiation takes into account all sources of exposure and age-related dynamics of T-lymphocytes: (1) exposure of lymphocyte progenitors in red bone marrow: (2) exposure of T-lymphocytes in the lymphoid organs, taking into account the proportion of resident lymphocytes and the residence time of circulating lymphocytes in the specific lymphoid organs. The objective of the study is to assess the dose coefficients allowing for the transition from the ingestion of 141,144Ce, 95Zr, 103,106Ru, 95Nb to the doses accumulated in circulating T-lymphocytes. For calculations, we used the dose coefficients from ICRP publications for specific lymphoid organs, as well as published data on the residence time of circulating lymphocytes in lymphoid organs and tissues. As a result, it was shown that the doses in circulating T-lymphocytes are higher than those in the red bone marrow, but lower than the doses to the colon wall. The dose coefficients were age dependent; the maximum values were typical for newborns. The obtained dose coefficients for 141,144Ce, 95Zr, 95Nb and 103,106Ru can be used to estimate the tissue and organ doses based on data on the frequency of chromosomal aberrations in peripheral blood lymphocytes.