Estimation of Radiation Dose from Ingested Tritium in Humans by Administration of Deuterium-labelled Compounds and Food

Radiation doses from organically bound tritium (OBT) in foods have been a major concern near nuclear facilities. The current dose coefficient for OBT is calculated using a standard model from the International Commission on Radiological Protection, in which some biokinetic values are not based on human metabolic data. Here, the biokinetics of ingested OBT, and radiation doses from them, were estimated by administering labelled compounds and foods to volunteers, using a deuterium (D) tracer as a substitute for tritium. After the administration of D-labelled glucose, alanine, palmitic acid, or soybean, the D/H ratios in urine were measured for up to 119 days, and the biokinetic parameter values were determined for OBT metabolism. The slow degradation rates of OBT could not be obtained, in many volunteers administered glucose and alanine. The estimated committed effective dose for 1 Bq of tritium in palmitic acid varied from 3.2 × 10 to 3.5 × 10 Sv Bq among volunteers and, for those administered soybean, it varied from 1.9 × 10 to 1.8 × 10 Sv Bq. These results suggest that OBT, present in some ingested ingredients, gives higher doses than the current dose coefficient value of 4.2 × 10 Sv Bq.