Interpretation of Enhanced Fecal and Urinary Plutonium Excretions Under a 2-year Regular DTPA Treatment Started Months after Intake: A Case Report.

Abstract Background: Internal contamination with plutonium is a potential hazard for workers handling this alpha-emitting transuranic element. The only medical approach available for reducing potential health effects is to promote plutonium excretion by chelation therapy with diethylenetriaminepentaacetic acid (DTPA). Because of its poor distribution in plutonium retention tissues, DTPA should be initiated as early as possible after contamination to achieve maximum chelation when plutonium is still circulating. Treatment efficacy is usually evaluated by measuring the alpha activity in urine collected in the first 24 hours following DTPA administration as it is widely assumed that plutonium-DTPA complexes are very predominantly cleared within 24 hours.Case presentation: In a worker who had internalized plutonium-238 most likely through inhalation of a soluble compound, an extensive DTPA treatment regimen was initiated several months after contamination. Numerous radiotoxicological analyses were performed in both fecal and urinary specimens collected sometimes for three days after DTPA administration.Conclusions: Activity measurements showed the continued effectiveness of DTPA intravenous infusions in removing plutonium from tissues of retention even if the treatment regimen started several months after contamination. In the present case, the activity excreted through urine in the first 24 hours after a given DTPA administration was only about half of the total urinary plutonium excretion collected over three consecutive days. 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 which 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 plutonium compounds somewhat soluble to undergo a chronic DTPA treatment, especially when it is not initiated promptly after intake. Under this scenario, regular 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 kinetic under DTPA treatment.