Excretion of Pu-238 during Long-term Chelation Therapy by Repeated DTPA Inhalation.

ABSTRACT: An individual underwent an extensive diethylenetriaminepentaacetate (DTPA) chelation therapy that started several months after plutonium incorporation, most likely by inhalation of a soluble compound. After receiving multiple intravenous infusions of DTPA, the patient continued the treatment by pulmonary delivery of aerosolized DTPA. The purpose of the present work is to provide and discuss the bioassay data obtained during the DTPA aerosol therapy and compare them with those under the DTPA infusion therapy that have been largely interpreted elsewhere. As with DTPA given intravenously, each delayed DTPA inhalation increased the clearance of plutonium not only in urine but also in feces, thus demonstrating the ability to remove plutonium retained by extrapulmonary tissues. Also, the slow decline of increased plutonium urinary elimination together with enhanced fecal excretion are two features coherent with the contribution of intracellular chelation to overall decorporation. The therapeutic benefit of DTPA inhalation appeared lower than with DTPA infusion, most likely due to a lower amount of DTPA reaching the systemic compartments where plutonium chelation predominates. The results suggest that DTPA administration through aerosol could be an alternative to the invasive procedure using a needle, i.e., intravenous injection/infusion, when protracted decorporation therapy is needed following transuranic internalization. Indeed, the patient may be more inclined to undergo a chelation treatment for a longer period because taking DTPA by inhalation may make it less cumbersome and painful.

Interpretation of Enhanced Fecal and Urinary Plutonium Excretion Data under a 2-y Regular DTPA Treatment Started Months after Intake.

ABSTRACT: In a worker who had internalized plutonium, most likely through inhalation of a somewhat soluble compound, an extensive diethylenetriaminepentaacetate (DTPA) treatment regimen was initiated several months after contamination. Numerous radiotoxicological analyses were performed in both fecal and urinary specimens collected, sometimes for three consecutive days after DTPA administration. Activity measurements showed the continued effectiveness of DTPA intravenous infusions in removing plutonium from tissues of retention even if the treatment regimen started very belatedly after contamination. In the present case, the activity excreted through urine within the first 24-h after a DTPA infusion contributed only about half of that activity excreted within the first three days (i.e., the cumulative activity of the first three 24-h urine collections). In addition, the careful study of the data revealed that DTPA-induced excretion of plutonium via fecal pathway significantly contributed to the overall decorporation. The intracellular chelation of plutonium may be responsible for this enhanced excretion of activity in feces as well as for the delayed and sustained increased clearance of activity in urine. The authors would suggest that the occupational physicians offer to individuals who internalized moderately soluble or soluble plutonium compounds undergo a long-term DTPA treatment, especially when it is not initiated promptly after intake. Under this scenario, measurements of plutonium in successive urine and fecal collections after treatment should be required to get a better estimate of the therapeutic benefit. Also, intracellular chelation and fecal route should be taken into account for better interpretation of radiotoxicological data and modeling of plutonium kinetics under delayed DTPA treatment.

Collective dosimetry to distinguish occupational exposure to natural uranium from alimentary uranium background in bioassay measurements.

PURPOSE: To assess occupational exposure from uranium bioassay results which are low and impacted by dietary intakes. MATERIAL AND METHODS: First, the bioassay results of a group of workers exposed to UO2 were compiled along with results of a control group. A Bayesian approach was developed to account for dietary intakes in the calculation of the committed effective dose from occupational exposure of a group of workers. RESULTS: Significant differences in uranium bioassay between the exposed and control groups were found establishing an occupational contamination of the exposed group of workers. Because uranium alimentary excretion estimated from the control group is very variable leading to unreliable individual dose assessment, a collective dosimetric approach was chosen. Applying the Bayesian method, all annual committed effective doses for the exposed group were estimated to be below 0.5 mSv with 95% confidence. CONCLUSIONS: The Bayesian method presented here is well designed to derive best estimate and dose distribution for a group of workers when a contamination is difficult to discriminate from a natural background or alimentary excretion.