Biodosimetry

Stable chromosome aberration frequencies

Stable chromosome aberrations have long been used as markers of radiation exposure but the background frequencies and factors (such as age, gender, cigarette smoking) that may modify the frequencies are not known with certainty. The currently available estimates of these baseline levels are derived from studies with relatively small sample sizes (the largest is n=385). By pooling data from sixteen laboratories around the world, we measured translocation frequencies in peripheral blood lymphocytes by fluorescence in situ hybridization whole chromosome painting among 1,400 individuals. Our data showed a curvilinear relationship between age and translocation frequency, but no association between translocation frequency and gender. We also found that cigarette smoking was associated with higher translocation frequency, and the age-related increase of translocations was greater among smokers than non-smokers (p<0.001).

We also recently assessed translocation frequencies in a subset of U.S. radiologic technologists to substantiate ionizing radiation dose estimates developed for 110,418 technologists who worked between 1916 and 1984. We observed 0.09 excess translocations per 100 CE per cGy red bone marrow dose (95% CI: -0.01, 0.2; P = 0.07), which is similar to the expected estimate based on previous cytogenetic studies conducted in other radiation-exposed populations (0.05 excess translocations per 100 CE per cGy). Despite uncertainty in the estimates of occupational red bone marrow absorbed doses, we found good general agreement between the doses and translocation frequencies, lending support for the dose assessment for this large cohort of U.S. radiologic technologists.