Plutonium 239 retention in former workers of the Thule base

In a memorandum of 1987 on a comprehensive health examination of persons employed at Thule air-base at the time of the crash of a nuclear-armed B-52 bomber in 1968, the National Board of Health suggested performing analyses for plutonium of urinesamples from 50-100 selected persons. This programme was carried out during the winter 1987-88. Collection of samples and evaluation of results were done by the National Institute of Radiation Hygiene. Department of Health Physics, National Laboratory Risoe, made the analyses. Included in the group were persons, who according to records from 1968 were judged to have had above-average potential for uptake of plutonium, as well as s number of persons, who before the summer 1987 had approached the social services and/or the Department of Dermatology, Marselisborg Hospital, with complaints of health effects attributed to the work at Thule air-base. 62 persons were included and results from the analyses of 53 24-hour-samples of urine, as well as from a number of control- and standard are presented. The technique used for the analysis had a minimum detectable activity for 239Pu of 200 μBq per sample. Consequently, according to internationally recognized models for uptake, distribution and retention of plutonium in the human organism, it is possible in 1988 to recognize an intake by inhalation in 1968 of 300 Bq 239Pu. No sample was found to contain 239Pu. So the results indicate, that any intake of 239Pu by the persons here involved, as a consequence of their work at Thule airbase in 1968, did not exceed 300 Bq. An intake of 300 Bq 239Pu can be evaluated to result in a 50-year committed dose equivalent of 20 mSv. The current dose-limit for occupationally exposed persons is 50 mSv/y. (author)