The Human Body Retention Time of Environmental Organically Bound Tritium Preliminary analysis of results from a volunteer study

摘要

Tritium in the UK environment causes low radiation doses to the public, but uncertainty exists in thedose coefficient for the organically-bound component of tritium (OBT). This can affect the assessment ofeffective doses to representative persons. Contributing to that uncertainty is poor knowledge of the bodyretention time of OBT and how this varies for different OBT compounds in food. This study was undertaken tomeasure the retention time of tritium by volunteers after eating sole from Cardiff Bay, which may contain OBTfrom discharges from the GE Healthcare Ltd. plant. Five volunteers provided samples of excreta over periods upto 150 days after intake. Preliminary analysis of the results suggests retention of total tritium with body halftimesranging from 4 to 11 days, with no evidence of a significant contribution due to retention with a longerhalf-time. This range covers the half-time of 10 days used by the ICRP for tritiated water. The short timescalecould be due to rapid hydrolysis in body tissues of the particular form of OBT used in this study. Implications forthe dose coefficient for OBT are that the use of the ICRP value of 4.2 10~(-11) Sv Bq~(-1) may be cautious in thisspecific situation, and the value of 1.6 10~(-11) Sv Bq~(-1) used by the ICRP for tritiated water might even be moreappropriate. These observations on dose coefficients are separate from any implications of recent discussion onwhether the tritium radiation weighting factor should be increased from 1 to 2.