Radiation Dose to Mouse Liver Cells from Ingestion of Tritiated Food Or Water

Tritium incorporated into tissues and DNA of mice was studied after daily ingestion of tritiated food or tritiated water. The tritiated food used was a commercial preparation mixed with brine shrimp that had been reared in tritiated sea water. After ingestion of tritiated food or water for up to 22 d, the specific activity of 3H in tissues was measured as tissue-free-water 3H, tissue-bound 3H, and DNA-bound 3H. Carbon-14 glucose was added to food and drinking water to compare the 3H intake from food with that from water. The specific activity of 3H in tissues was then corrected by the specific activity of 14C in tissues to determine the 3H incorporation from the same amount of ingested food and water. DNA-bound 3H after the ingestion of tritiated food was 4.6 times higher than that of tritiated water, while tissue-bound 3H was 2.2 times higher. The radiation dose to liver from 3H incorporated through food was twofold higher than from tritiated water, which was mainly from the high incorporation of 3H into DNA. Our results demonstrated that the dose calculation based on tissue-free-water 3H alone would under-estimate the radiation exposure of the human population exposed to tritiated food.