ABSORPTION KINETICS OF URANIUM TRI-N-BUTYL PHOSPHATE IN THE RAT - IMPLICATIONS FOR OCCUPATIONAL EXPOSURE

The absorption kinetics for uranium into blood after deposition as tri -n-butylphosphate (UTBP) in the rat lung were combined with human data on particle deposition and clearance from the ICRP Publication 66 res piratory tract model and information from the most recent ICRP biokine tic model for uranium to predict the consequences for exposure of work ers. These predictions suggest that, (1) the biokinetics of UTBP are s imilar to those for a Type F compound as defined by ICRP, (2) the dose coefficient is essentially independent of the aerosol size and isotop ic composition, (3) the mass of uranium equivalent to the ALI can vary by 13 fold depending upon the isotopic composition, (4) intakes of ur anium as UTBP other than chronic intakes as highly enriched forms shou ld be restricted on the basis of the chemical toxicity of uranium, (5) the assessment of intake by urine bioassay measurements should be int erpreted with caution unless the exposure conditions are well defined and (6) severe kidney damage is unlikely at intakes corresponding to t he ALI or daily limit.