| BackgroundLow dose ionizing radiation(LDIR) refers to the dose of X or gamma irradiation that is less than 200 m Gy(within 1 h) or the dose rate is lower than 0.1 m Gy·min-1(the mean dose rate above1 h). The previous researches mainly focus on the adverse effects of large dose or high dose rate of IR and the health effects of acute nuclear irradiation events. A series of biological effects can be induced by ionizing radiation, such as influence on the blood system, chromosome structure, late effect and cell fate determination. However, most of the cognition for the effects of LDIR came from extrapolation of high dose radiation.With the development of science and technology, radiation technology and nuclear technology are widely used in industrial and medical fields. Medical radiation workers and industrial radiographic inspection workers have rapidly becoming the two major categories in LDIR occupational workers. The biological effects of occupationally exposed to LDIR have been controversial. Recent researches reported that LDIR can induce certain health effects. However, the results of personal dose monitoring in Chongqing municipality showed that the dose in protracted occupationally exposed radiation workers were not exceed the national standard limit. Therefore, aim at the medical radiation workers and industrial radiographic inspection workers, research on detecting the possible safety risks in occupationally exposed p become a realistic research topic.ObjectiveThis study was conducted to investigate the genetoxic damage with oxidative and antioxidative effects in radiation workers who protracted exposure to LDIR in current situation of occupational protection measures. It is not only screening for sensitive biomarkers reflecting the effects of LDIR damage, but also providing clues for methods of occupational protection.Content1. Monitoring individual dose for the radiological workers and detecting the air kerma rate at six operation sites in the workplace of industrial radiographic inspection workers.2. Basic information, questionnaire of occupational history and peripheral venous blood were collected from medical radiation workers.3. Nuclear DNA damage was detected in radiation workers, and mitochondrial DNA(mt DNA) damage was detected in industrial radiographic inspection workers.4. The oxidative-antioxidative status in blood was assessed individually for all radiation workers and controls.Methods1. The individual dose monitored was evaluated by personal thermoluminescent dosimeter(TLD), and portable inspection tour instrument was used to detect the radiation levels in workplace of industrial radiographic inspection workers.2. Chromosomal damage and DNA breakage damage endpoints in peripheral blood lymphocytes were determined using the cytokinesis-blocked micronucleus(CBMN) assay and single cell gel electrophoresis.3. Real-Time PCR was used to determine the mt DNA copy number and supercoiling formation in industrial radiographic inspection worker, long-PCR was detected for determing mt DNA integrity; RT-PCR was used to evaluate the m RNA levels of TFAM, PGC-1α, NRF1 and NRF2.4. The MDA level was detected by glucosinolates barbitone colorimetry, xanthine oxidase method was used to detect Cu Zn-SOD activity, activity of GSH-Px was detected by disulfide generation 2 nitro benzoic acid, and activity of CAT was determined by molybdenum acid colorimetric.Results1. We had collected 253 medical radiation workers and 31 industrial radiographic inspection workers, 118 controls who engaged in catering service were enrolled. Besides, 49 controls were picked out from controls as the control group for industrial radiographic inspection workers. Differences in age, gender and smoking ratio among controls and the radiation workers were not significant. All subjects were healthy, and did not receive drug therapy recently. The radiation workers were not contacted with other irradiation except for occupational exposure radiation, and the controls are not received medical irradiation in recent.2. We had collected 244 medical radiation workers and 27 industrial radiographic inspection workers. The results showed that the mean annual effect dose of medical radiation workers was 0.52 ± 0.29 m Sv/a, ranged in 0.12~4.76 m Sv/a. We found that the mean annual effect dose for medical radiation workers w 0.58 ± 0.25 m Sv/a in 2013, the average of annual effect equivalent dose of nuclear medicine type(0.72 ± 0.59 vs. 0.48± 0.32 m Sv/a,P=0.007)and diagnostic radiology type(0.60 ± 0.33 vs. 0.48 ± 0.32 m Sv/a,P=0.038)are obviously higher than other radiation working type。The annual effect dose of industrial radiographic inspection workers was 0.15 ± 0.03 m Sv/a, ranged in 0.12~0.21 m Sv/a. And the average air kerma rate at six operation sites in workplace was 0.105 ± 0.01 μGy/h. In this study, the annual effect dose of radiation workers and radiation levels in workplace of industrial radiographic inspection workers are all meet the national radiation occupationally exposure dose equivalent standard.3. Through analyzing the questionnaire of radiation occupational history of medical radiation workers, we acquired some information that the average of radition working year was 10.18 ± 9.39 years, and the nuclear medicine radiation working years(14.49 ± 11.79 years) was longest in all types. The average of daily workage hours of medical radiation workers is 6.83 ± 2.88 hours, and the mean daily workage hours of diagnostic radiation type was 8.46 ± 1.31 hours, and it was obviously longer than nuclear medicine types. X-ray was the main radiation ray in medical radiation workers, and the percentage was 75.16%.4.The medical radiation workers exhibited increased frequencies of micronucleus(MN)(3.40 ± 2.95‰ versus 2.49 ± 2.74‰,P=0.004), nuclear buds(NBUDs)(4.02 ± 2.74‰ versus 1.89 ± 1.31‰, P<0.001) and necleoplasmic bridges(NPBs)(0.20 ± 0.53‰ versus 0.07 ± 0.25‰,P=0.001) compared to controls. In all work types, the MN rate, NBUD rate and NPB rate of diagnostic radiation were obviously increased comparing to controls, the NBUDs rate of radiotherapy are significantly higher than controls. For radiation occupational history, the MN rate of the 0.38~0.54 m Sv/a annual effect dose group and >0.54 m Sv/a group were obviously elevated compared to ≤0.38 m Sv/a group(P<0.001). And the NBUD rate of 0.38~0.54 m Sv/a group was statistically higher than ≤0.38 m Sv/a group(P=0.027). The MN rate in ≥7 radiation working years group was significantly higher than <7 year group(P<0.001).5. In medical radiation workers, the correlation relationship of MN rate is significantly positive correlation with annual effective dose and radiation working years(P<0.001). NBUD rate was significantly positive correlation with daily workage hours(P=0.035). NPB has significantly positive correlation with radiation working years(P=0.011). NDI has significantly negative correlation with radiation working years(P=0.001).6. The industrial radiographic inspection workers are demonstrated obviously increased frequencies of MN(5.93 ± 4.00‰ versus 3.02 ± 2.66‰, P=0.001) and NBUDs(3.60 ± 2.24‰ versus 1.98 ± 1.21‰, P=0.001).7. Meanwhile, we had performed single cell gel electrophoresis(SCGE) test in selected 73 medical radiation workers and 102 controls. We investigated the DNA breakage damage endpoints with Tail DNA percentage(%)(19.26 ± 6.04 versus 16.74 ± 6.44, P=0.01), Tail Length(60.97 ± 14.24 versus 45.29 ± 18.69 μm, P<0.001), Tail Moment(TM)(15.23 ± 7.41 versus 11.04 ± 7.69, P<0.001) and Olive Tail Moment(OTM)(11.28 ± 4.43 versus 8.33 ± 4.49, P<0.001) are significantly increased.8. In the present study, the mt DNA copy number of the industrial radiographic inspection workers are higher than controls(40.04 ± 24.99 versus 24.86 ± 19.14, P=0.015) and the supercoiling formation value are also evidently increased(4.48 ± 2.68 versus 3.07 ± 2.78, P=0.03). The mt DNA integrity of industrial radiographic inspection workers group is decreased compared to controls(95.10 ± 9.54 versus 313.51 ± 14.58, P<0.001). The m RNA levels of TFAM, PGC-1α and NRF2 are observed higher than controls(P<0.001). NRF1 expression level is obviously higher than controls(P=0.011).9. Radiation workers occupationally exposed IR existed oxidative-antioxidative imbalance. In the medical radiation workers group, MDA level(4.14 ± 2.97 versus 2.03 ± 1.34 nmol/m L, P<0.001) and CAT activity(9.36 ± 4.67 versus 6.68 ± 3.19 U/mg Hb, P<0.001) are significantly higher than controls. Meanwhile, the MDA level of industrial radiographic inspection workers group(13.12 ± 8.69 versus 1.96 ± 1.60 nmol/m L, P<0.001) and CAT activity(8.02 ± 2.25 versus 6.48 ± 3.29 U/mg Hb, P=0.032) are obviously increased, Cu Zn-SOD activity(26.27 ± 4.99 versus 29.17 ± 3.95 U/m L, P=0.009) is significantly decreased compared to controls.ConclusionThe individual dose monitored of radiation workers and radiation levels in workplace met the state radiation protection standard. We found that radiation workers have obviously genetic damage and oxidation and antioxidant imbalance. |
PDF Full Text Request