Radiation internal dose to the herring gull embryo due to 90 Sr in the egg

Abstract

Birds are bioindicators of anthropogenic environmental stress, including the changes caused by radioactive contamination of the ecosystems. The early stage of development is the most radiosensitive period. Therefore, it is necessary to assess embryo's exposure dose when interpreting observed radiobiological effects in birds. This is especially true for areas contaminated with Ca-like 90Sr. The levels of radionuclide accumulation in the eggshell can be extremely high, which leads to chronic embryo exposure. The objective of the study is to develop a method to calculate the dose to a herring gull embryo exposed to 90Sr distributed in egg compartments (shell, embryo body, white and yolk). To achieve the set objective, the time-dependent Sr distribution in the egg compartments was described. Alongside with that, dosimetric modeling was carried out to obtain dose factors that convert the radionuclide activity in different compartments of an egg to the embryo doses at various stages of embryogenesis. It has been shown that the accumulated dose to the herring gull embryo can be calculated based on the data on 90Sr total activity in the egg using the dose conversion factor equal to 0.44 µGy Bq− 1. Since the eggshell contains more than 90% of total 90Sr activity, the conversion from eggshell activity to the dose to the embryo would be practically the same as that from the total egg activity – 0.46 µGy Bq− 1. The main dose fraction (~ 99%) accumulates at the last stage of embryogenesis (from 13 to 26 days).