Exposure to 3H-lysine during lactation causes longer retention of organically bound tritium in the lens of mouse eyes

To investigate differences in the long-term retention of organically bound tritium among organs depending on the time of ingestion, we administered drinking water containing 50 MBq L^{-1 3}H-lysine to mice in four groups at specific stages of development for 3 weeks. Mice born to dams that had ingested ³H-lysine solution throughout pregnancy, mice fed maternal milk from dams administered ³H-lysine during lactation, adolescent mice that had ingested ³H-lysine during the growing stage, and mice that had ingested ³H-lysine during adulthood were sacrificed at the same age of 20 weeks. Subsequent measurements of tritium concentrations in organs revealed that, among the groups corresponding to different developmental stages, concentrations of organically bound tritium in the eye lens of mice fed milk from dams that had ingested ³H-lysine solution were higher than those in mice in the other three groups, whereas those in liver and muscle were higher in mice administered ³H-lysine during adulthood. These findings indicate that the hazardous effects associated with environmental tritium derived through ingestion need to be evaluated with a consideration of the stage of development at the time of exposure. To date, however, this approach has yet to be implemented in the system of radiological protection adopted by the International Commission on Radiological Protection.