Plutonium content of human placental tissues after occupational exposure

The placenta and umbilical cord were obtained following a normal live delivery from a volunteer donor who had received an accidental inhalation intake of plutonium 12 years prior to her pregnancy (Case 0777). Her employer estimated the intake to be about 73 Bq Class W plutonium. Based on bioassay results and clearance models in use at that time, they calculated her body content at the beginning of pregnancy to be about 5.6 Bq with an average concentration of approximately 60 mBq kg-1. The placenta and cord from this pregnancy, along with the placenta and cord from a donor with no known exposure to plutonium (Case 0835), were divided and assayed for plutonium by ultrasensitive fission track analysis at two collaborating laboratories. Placental 239Pu concentration values obtained by the two laboratories for Case 0777 agreed within a factor of 2 and were several-fold greater than for the control, Case 0835, as well as values that had been reported by others for unexposed populations. There was no elevated concentration of plutonium in the umbilical cord from the exposed person. The data yielded values of 0.16 and 0.27 for placental to maternal concentrations (CPI:CM) that were of the same order of magnitude as the value of 0.1 the ICRP calculated for intakes before pregnancy.