Transfer of Tritium from ³H-Thymidine, ³H-Leucine, ³H-Glucose, and Tritiated Water into Mouse Tissue DNA During Long-Term Exposure

Organically bound tritium (OBT) transfers into human body via food chain. ICRP report recommends that the dose due to OBT ingestion is 2.3 times higher than that due to HTO. Thymidine is a specific precursor of DNA. There were several reports on ingestion experiments of OBT including ³H-thymidine. However, the concentrations of tritiated compounds used in those experiments were extremely high compared with environmental tritium concentration. Therefore, in this study, we used tritiated compounds with 100 times of concentration based on the highest concentration in rain after nuclear tests during the 1960's, i.e. 700 Bq tritium/l rainwater. Mice were chronically fed with each one of tritiated organic compounds, ³H-thymidine, ³H-leucine, ³H-glucose or HTO for comparison, and the excretion and distribution of tritium in mouse body and tritium uptake into DNA in each tissue were determined at 180th, 240th, and 300th day of ingestion. Almost no significant differences were found between the dose rates from DNA-bound tritium throughout long-term exposure by ingestion of tritiated organic compounds and that of HTO.