Letter to the Editor: Assessment of Genomic Instability in Medical WorkersExposed to Chronic Low-dose X-rays in Northern China

摘要

Thanks very much for the attention and constructive comments of Dr Rithidech, Mortazavi, andBrooks. In our article, we assessed the level of DNA damage, chromosomal aberrations (CAs),cytokinesis-block micronucleus (CBMN) assay, gene expression profiling, and antioxidant leveldetermination. And we found that the levels of DNA damage, CA, and CBMN were all significantlyincreased. Moreover, the gene expression and antioxidant activities were changed in theperipheral blood of men exposed to low-dose X-rays. Based on the above research results, weconclude that genomic instability is associated with the duration of low-dose ionizingradiation (IR) exposure in medical workers. Our conclusions were not only inferred from theanalyses of cytogenetic data. In our article, it is not perfect that we choose at least 100metaphases cells for each individual to analyze CA rate. But our results were consistent withprevious studies that CA frequency increased in medical workers occupationally exposed tolow-dose X-rays.1 In our article, the exposure group consisted of 175 healthy individuals who had beenoccupationally exposed to low levels of X-ray radiation. The control group included 159nonexposed workers who were selected from the same hospital. Therefore, the level ofbackground radiation received by the exposure and control groups was same. And it is notnecessary to consider the high level of radon in northern China. The cumulative effective doseof exposed group with the duration of ≤10 years ranged from 2.81 to 178.73 mSv (18.28 ± 16.29mSv), those with the duration of 10 to 20 years ranged from 25.43 to 369.45 mSv (92.11 ± 85.62mSv), and those with >20 years ranged from 48.64 to 416.43 mSv (185.15 ± 143.51 mSv). Wecan find that there was a positive correlation between the working years and cumulativeeffective dose. Therefore, we think it is reasonable to use working years to categorize the subjects.2 We are also trying to find more accurate indicators to relate biological damage toradiation dose levels. In our article, normality was confirmed with the Kolmogorov-Smirnovtest, and the homogeneity of variance was confirmed with the Levine test. The cytogenetic datawere logarithmically transformed to obtain more normal distributions, and log-transformednormal distributions were then confirmed with the Kolmogorov-Smirnov test. A crosstabsχ2 test was used to analyze the demographic characteristics and CA and CBMNresults of the exposure and control groups. A Student t test was performed todetermine the statistical significance of percentage of total fluorescence in the tail(TDNA%), tail moment (TM), Olive Tail Moment (OTM), and oxidative stress biomarkers betweenthe exposure and reference groups. We believe that the above information can support a strongcorrelation between genomic instability and duration of low-dose radiation exposure of medicalworkers who work in interventional radiology diagnostics.