Cytogenetic Follow-Up Studies in Persons Accidentally Exposed to ⁶⁰Co γ-Rays, 10 Years After Exposure

Abstract

We have periodically analyzed the chromosome aberrations in peripheral blood lymphocytes in 8 men exposed to γ-radiation during an accident in a cobalt-60γ-ray therapeutic facility which occurred in Wuhan in Dec. 1972. Physical doses were estimated to be wtihin a range of 5–245 rads. In previous studies, we took the unstable aberrations as the indicators for cytogenetic changes. However, the frequencies of abnormalities dropped progressively as the time went on. Recently, by using microscopic and karyotypic analysis, we measured the chromosome aberrations from 8 persons 10 years after the accident. The FPG technique was also used to determine the cell division cycle and to measure the rate of sister chromatid exchanges SCE. The following results were obtained:

• 1. 20 aberrant cells were scored in 720 metaphases and a total of 16 cells contained stable types. Most of the persistent aberrations were translocations and deletions. The highest frequencies of aberrations were observed in 3 cases who received the highest radiation doses.

• 2. The distribution of metaphase in first, second and third divisions in cultures were determineed. As compared with the control, no delay in cell cycle of lymphocytes of the exposed cases was observed.

• 3. The analysis of SCE in blood lymphocytes of the exposed persons was performed. It failed to show any increase in SCE rate in comparison with the control.