Doses from the consumption of Cardiff Bay flounder containing organically bound tritium

Abstract

ICRP dose coefficients for the ingestion of organically bound tritium (OBT) by adults andchildren are intended for general application to unspecified forms in diet and maynot be applicable to intakes of a specific form of OBT. To obtain informationrelating to OBT in fish from Cardiff Bay, the retention of tritium in adult rats wasdetermined after administration as either tritiated water (HTO) or dried flounder fleshcontaining OBT. Two components of retention were obtained in each case. The firstcomponent, attributable to tritium equilibrating with body water, had a half-time ofretention of 3 days in each case, and accounted for 97% of the intake as HTOand 70% after intake of OBT in flounder. Results were consistent with rapidcatabolism of a large proportion of flounder OBT to HTO. The second component ofretention, attributable to OBT in rat tissues, accounted for 3% of tritium intake asHTO and 30% after intake as flounder OBT; the half-times of retention were10 days and 25 days, respectively. The results obtained after administration asHTO are consistent with published animal data and correlate with the ICRPassumptions for adult man of half-times of 10 days for 97% behaving as HTO inbody tissues and 40 days for 3% incorporated into OBT in body tissues. Theresults obtained after administration of flounder OBT suggest that appropriateassumptions for retention in adult man are 70% with a 10 day half-time and 30% with a100 day half-time. These assumptions result in an ingestion dose coefficient of6 × 10−11 Sv Bq−1. This compares with the ICRP value for OBT ingestion by adults of4.2 × 10−11 Sv Bq−1, based on half-times of 10 days and 40 days applied to equalproportions of retained tritium. It is proposed that a dose coefficient of6 × 10−11 Sv Bq−1 should be applied to tritium in flounders from Cardiff Bay. It is further proposed that thisdose coefficient should be applied to all ingestion intakes by adults relating to this source ofexposure, unless specific information is available showing that a significant proportion ofthe intake is HTO. The same proposals apply to dose coefficients derived here for flounderOBT consumption by children.