Chromosome dosimetry and occupational radiation exposure.

Chromosome analyses were carried out on lymphocytes from 11 persons with annual exposures to gamma rays below the occupational limit of 50 mSv, employed in a hospital department of radiotherapy and nuclear medicine. Cytogenetic damage indicated radiation exposure significantly above background in six cases. In four of them a dose estimate between 30 and 275 mSv with 95% confidence was derived, reflecting their accumulated occupational exposures. In one case a partial body exposure to about 30% of lymphocytes was inferred and inquiries revealed previously unknown radiotherapy. In order to avoid misinterpretation of cytogenetic data, reliable chromosome dosimetry requires that the individual's radiation history must be known