Tucker-JD; Kleinerman-R; Ha-M; Bhatti-P; Hauptmann-M; Sigurdson-A; Sram-RJ; Beskid-O; Tawn-EJ; Whitehouse-C; Lindholm-C; Kodama-Y; Nakamura-N; Vorobstova-I; Oestreicher-U; Stephan-G; Yong-L; Bauchinger-M; Chung-H-W; Darroudi-F; Roy-L; Barquinero-J; Livingston-G; Schmid-E; Blakey-D; Voisin-P; Littlefield-G; Edwards-A
Biological monitoring of radiation doses in humans can contribute important estimates of exposure, especially when physical measurements are unavailable. Translocations have been the most widely applied biomarker of past radiation exposure in epidemiologic studies because of well-characterized does-response curves and the persistence of translocations detectable many years later. Establishing baseline levels of translocations will contribute to the usefulness of this endpoint in cased of accidental exposure. It is well accepted that the frequency of chromosome aberrations increases with radiation exposure and age, but the effects of gender, ethnicity and lifestyle (e.g. smoking) on background translocation yields is not known with certainty. Pooled analyses of translocation data in unexposed individuals have been conducted, but the largest study included only 385 subjects. Background aberration frequencies were overwhelmingly influenced by age, but the effect of age as modified by gender and cigarette smoking remains unclear. Here we expanded the number of subjects with the goal of establishing control levels of translocation frequencies by age, gender, ethnicity and smoking status. Fifteen laboratories in North America, Europe and Asia contributed data on 1,822 unexposed individuals, with a minimum of 200 cell equivalents (CE) per subject. Ages ranged from newborn (cord blood) to 85 years. The study populations was 37% female, 40% reported ever smoking, and 77% Caucasian, 13% Black, 8% Asian, and 2% were other ethnicity. Age was the strongest predictor of translocation frequency (p<0.001). The mean number of translocations was 0.03/100 CE (95% CI=0.02-0.04) for newborns and 1.7/100 CE (95% CI =1.4-2.0) for subjects 75 years and older. Translocation frequencies per 100 CEs were similar for men and women up to age 50, when they diverged, with women having higher frequencies than men. Smokers had higher translocation frequencies than non-smokers (p < 0.001) after adjustment for gender, ethnicity, and laboratory. We noted significant variation by laboratory in all analyses. We were unable to separate the effect of ethnicity on translocations from inter-laboratory variation. More work is needed to understand the different age responses in different populations.
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