Diagnostic X-ray examinations and increased chromosome translocations: evidence from three studies

Abstract

Controversy regarding potential health risks from increased use of medical diagnostic radiologic examinations has come to public attention. We evaluated whether chromosome damage, specifically translocations, which are a potentially intermediate biomarker for cancer risk, was increased after exposure to diagnostic X-rays, with particular interest in the ionizing radiation dose-response below the level of approximately 50 mGy. Chromosome translocation frequency data from three separately conducted occupational studies of ionizing radiation were pooled together. Studies 1 and 2 included 79 and 150 medical radiologic technologists, respectively, and study 3 included 83 airline pilots and 50 university faculty members (total = 155 women and 207 men; mean age = 62 years, range 34-90). Information on personal history of radiographic examinations was collected from a detailed questionnaire. We computed a cumulative red bone marrow (RBM) dose score based on the numbers and types of X-ray examinations reported with 1 unit approximating 1 mGy. Poisson regression analyses were adjusted for age and laboratory method. Mean RBM dose scores were 49, 42, and 11 for Studies 1-3, respectively (overall mean = 33.5, range 0-303). Translocation frequencies significantly increased with increasing dose score (P < 0.001). Restricting the analysis to the lowest dose scores of under 50 did not materially change these results. We conclude that chromosome damage is associated with low levels of radiation exposure from diagnostic X-ray examinations, including dose scores of approximately 50 and lower, suggesting the possibility of long-term adverse health effects.

Fig. 1

Translocation frequency as a function of the cumulative diagnostic red bone marrow radiation dose score (n = 362). The trend line with 95% upper and lower confidence bounds is from multivariable Poisson regression analysis, specified for ages 60–<65 and FISH method 2. [0.04 excess translocations/100 CE/10 bone marrow dose score units (95% CI: 0.02, 0.06; P < 0.001); R² = 0.7]. Dose score approximates mGy

Fig. 2

Translocation frequency with successive truncation of cumulative diagnostic red bone marrow radiation dose score ranges at 50 or less, 20 or less and 10 or less. Trend lines with 95% upper and lower confidence bounds are from multivariable Poisson regression analyses and are specified for ages 60–<65 and FISH method 2. a ≤50 dose score units [0.05 excess translocations/100 CE/10 bone marrow dose score units (95% CI: 0.001, 0.1; P = 0.04); R² = 0.7]. b ≤20 dose score units [0.08 excess translocations/100 CE/10 bone marrow dose score units (95% CI: −0.02, 0.2; P = 0.1); R² = 0.7]. c ≤10 dose score units [0.3 excess translocations/100 CE/10 bone marrow dose score units (95% CI: 0.05, 0.5; P = 0.02); R² = 0.7]. Dose score approximates mGy