Purpose: To evaluate the cumulative gamma -radiation personal exposure by a
nalysing lymphocyte chromosome translocations using FISH painting and to co
mpare FISH-derived biodoses with those derived from retrospective physical
dose reconstruction in residents receiving chronic low dose-rate gamma -irr
adiation while living in radio-contaminated buildings.
Materials and methods: Chromosome translocation frequencies were evaluated
by scoring 933 3077 metaphases under fluorescence microscope for each of th
e five male and four female exposed individuals after they had relocated fr
om the radioactive environment for 34 and 82 months. FISH painting was cond
ucted using kits of whole-chromosome probes for chromosomes 1, 2 and 4 in o
range and 3, 5 and 6 in green and counter-stained with 4',6-diamidino-2-phe
nylindole (DAPI). The retrospective dose estimation termed Taiwan Cumulativ
e Dose (TCD) was conducted by assessment using detailed information of hist
orical exposure and the environmental radioactivity for each apartment duri
ng previous residency.
Results: A total of 20 244 well-prepared metaphases were scored. Biodoses w
ere calculated from the translocation frequencies and physical doses were e
stimated from detail questionnaires for each individual. The translocation
frequencies measured ranged from 2.2 x 10(-3) to 26.8 x 10(-)3 translocatio
ns per cell and the dose equivalent from 52.2 to 992.2 mSv. A good correlat
ion was observed between the physical and biodoses. A plot of TCD against F
ISH-derived doses produced D-fish = 0.65 D-rCD, when fitted by a linear mod
el, and D-fish = 0.53 D-rCD + 1.26 x 10(-4) D-TCD(2), when fitted with a li
near quadratic model. Given the scatter in the data and the extremely small
quadratic dose contribution, neither model could be ruled out.
Conclusion: Chromosome translocations provide a valid method of dose estima
tion in extremely protracted low dose-rate gamma -radiation exposure. Valid
ation of the TCD method by FISH-measured translocations supports the use of
TCD for epidemiological studies.