Association of Chromosome Translocation Rate with Low Dose Occupational Radiation Exposures in U.S. Radiologic Technologists

Abstract

Chromosome translocations are a well-recognized biological marker of radiation exposure and cancer risk. However, there is uncertainty about the lowest dose at which excess translocations can be detected, and whether there is temporal decay of induced translocations in radiation-exposed populations. Dosimetric uncertainties can substantially alter the shape of dose-response relationships; although regression-calibration methods have been used in some datasets, these have not been applied in radio-occupational studies, where there are also complex patterns of shared and unshared errors that these methods do not account for. In this article we evaluated the relationship between estimated occupational ionizing radiation doses and chromosome translocation rates using fluorescent in situ hybridization in 238 U.S. radiologic technologists selected from a large cohort. Estimated cumulative red bone marrow doses (mean 29.3 mGy, range 0–135.7 mGy) were based on available badge–dose measurement data and on questionnaire-reported work history factors. Dosimetric assessment uncertainties were evaluated using regression calibration, Bayesian and Monte Carlo maximum likelihood methods, taking account of shared and unshared error and adjusted for overdispersion. There was a significant dose response for estimated occupational radiation exposure, adjusted for questionnaire-based personal diagnostic radiation, age, sex and study group (5.7 translocations per 100 whole genome cell equivalents per Gy, 95% CI 0.2, 11.3, P = 0.0440). A significant increasing trend with dose continued to be observed for individuals with estimated doses <100 mGy. For combined estimated occupational and personal-diagnostic-medical radiation exposures, there was a borderline-significant modifying effect of age (P 0.0704), but little evidence (P > 0.5) of temporal decay of induced translocations. The three methods of analysis to adjust for dose uncertainty gave similar results. In summary, chromosome translocation dose-response slopes were detectable down to <100 mGy and were compatible with those observed in other radiation-exposed populations. However, there are substantial uncertainties in both occupational and other (personal-diagnostic-medical) doses that may be imperfectly taken into account in our analysis.

Radiation Organ Doses Received in a Nationwide Cohort of U.S. Radiologic Technologists: Methods and Findings

“…We previously assessed chromosome trans-location frequencies using fluorescent in situ hybridization (FISH) in separate groups of 79 and 150 radiologic technologists and evaluated the relationships between chromosome translocation rates and estimated occupational radiation doses, finding borderline statistical significance ( 39 , 40 ). We reevaluated ( 41 ) the chromosome translocation dose-response relationship in the 229 biodosimetry study participants using the RBM doses reported here. About 95% of the RBM doses in the combined groups ranged from 0.2– 100 mGy.…”

Nested Case-control Study of Occupational Radiation Exposure and Breast and Esophagus Cancer Risk among Medical Diagnostic X Ray Workers in Jiangsu of China

“…Epidemiological studies have been carried out in several countries for investigation of cancer risk among medical radiation workers, such as radiologists studied in the UK (Doll, 2005) and the U.S (Matanoski et al, 2008), radiological technologists studied in the U.S (Little et al, 2014;Moskowitz et al, 2014) and Japan (Yoshinaga et al, 1999), and radiotherapy staff studied in Denmark (Andersson et al, 1991). Breast cancer is believed to be one of the most readily caused by ionizing radiation (Snijders et al, 2012).…”

Occupational ionising radiation and risk of basal cell carcinoma in US radiologic technologists (1983–2005)

“…We were unable to locate other publications with similar analyses to compare our findings. One possible contribution to the observed higher excess risk for earlier years could be the increased X-ray energies over time due to improvements in filtering and higher energy of the beam, combined with the known greater biological effectiveness of lower energy radiation 36 37. However, the modifications in radiation energy spectrum are modest and unlikely to fully explain our observations.…”