Retention in young pigs of organically bound tritium given during pregnancy and lactation

A sow was given organically bound tritium (OBT) in food consisting of potato, milk and algal powder at a specific activity of 577 Bq·g^-1 from 84 days before until 42 days after delivery. Shortly after birth, some piglets were exchanged with those from a non-contaminated sow to determine the amount of activity incorporated in utero and during lactation. The specific activity of tissue OBT at birth was about equal to that of food. The piglets given OBT only during suckling attained about the same tissue OBT activity as those exposed during pregnancy. Replacement of activity occurred more rapidly in parenchymal organs than in muscle, skin, and bone. Estimates of total tissue dose indicate that after OBT feeding, OBT contributes about 5-10 times more to this dose than HTO. Compared to the experiment in which HTO had been given in drinking water, the dose from OBT in food was about 40%. Under realistic conditions of water and OBT food intake, the total dose would thus probably not exceed more than 1.5 times that from HTO only. Although most long-lived tissue OBT is probably located distally from radiosensitive targets, some tissues might be at risk if the tritium is close to radiosensitive sites. Transfer factors of OBT to liver and muscle are calculated to be 0.03 and 0.01, respectively.