Cytogenetic monitoring of nuclear workers occupationally exposed to ionising radiation

Genotoxicity Associated with 131I and 99mTc Exposure in Nuclear Medicine Staff: A Physical and Biological Monitoring Study

Nuclear medicine staff are constantly exposed to low doses of ionizing radiation. This study investigated the level of genotoxic effects in hospital employees exposed to routinely used ¹³¹I and ^99mTc in comparison with a control group. The study compared the results of physical and biological monitoring in peripheral blood lymphocytes. The effects of confounding factors, such as smoking status and physical activity, were also considered. Physical dosimetry monitoring revealed differences in the individual annual effective dose as measured by finger ring dosimeter and whole-body dosimeter between the ¹³¹I- and ^99mTc-exposed groups. The DNA damage studies revealed differences between the groups in terms of excess premature chromosome condensation (PCC) fragments and tail DNA. Physical activity and smoking status differentiated the investigated groups. When assessed by the level of physical activity, the highest mean values of tail DNA were observed for the ^99mTc group. When assessed by work-related physical effort, excess PCC fragments were significantly higher in the ¹³¹I group than in the control group. In the investigated groups, the tail DNA values were significantly different between non-smokers and past or current smokers, but excess PCC fragments did not significantly differ by smoking status. It is important to measure exposure to low doses of ionizing radiation and assess the potential risk from this exposure. Such investigations support the need to continue epidemiological and experimental studies to improve our understanding of the mechanisms of the health effects of radionuclides and to develop predictive models of the behavior of these complex systems in response to low-dose radiation.

Cytogenetic analysis (buccal micronucleus cytome assay) of radioactive waste management workers

The Russian Federation is implementing a program for dismantling nuclear-powered submarines and nuclear service vessels decommissioned from the Navy. Program personnel may be exposed to mutagenic and carcinogenic factors, including ionizing radiation. Improved preclinical health diagnostics are desirable, for timely identification of health effects, optimization of preventive measures, and medical interventions. We used an improved version of the buccal micronucleus cytome assay (BMCyt) to conduct cytogenetic status assessment of 59 employees of the Far Eastern Center for Radioactive Waste Management (DalRAO). We observed a statistically significant increase in the frequency of buccal epithelial cells with cytogenetic abnormalities (2.31‰ versus 1.15‰) and a small decrease in the apoptotic index (42 % versus 44 %) in the exposure group vs. controls. An accumulation index of cytogenetic disorders (the ratio of cells with nuclear abnormalities to cells in apoptosis) was determined and significant differences were found between the exposure and control groups. The proposed approach is simple, non-invasive, and highly informative for monitoring the health status of personnel exposed to complex factors in the working environment.

Establishment of Dose-response Curves for Dicentrics and Premature Chromosome Condensation for Radiological Emergency Preparedness in Thailand

The in vitro dose calibration curves using conventional biological dosimetry – dicentric chromosome assay (DCA) and premature chromosome condensation (PCC) assay – were performed for the first time in Thailand for reconstruction of radiation dose in the exposed individuals. The peripheral blood lymphocyte samples from healthy donors were irradiated with ¹³⁷Cs source at a dose rate of 0.652 Gy/min to doses of 0.1, 0.25, 0.5, 0.75, 1, 2, 3, 4, and 5 Gy for DCA technique, and 5, 10, 15, 20, and 25 Gy for PCC technique. The blood samples were cultured and processed following the standard procedure as prescribed in the International Atomic Energy Agency report with slight modifications. The yield of dicentrics with dose from at least 1000 metaphases or 100 dicentrics was fitted to a linear quadratic model using Chromosome Aberration Calculation Software (CABAS, version 2.0) whereas those of PCC rings with dose from 100 rings was fitted to a linear quadratic equation at doses from 0 to 15 Gy. These curves will be useful for in vitro dose reconstruction and can support the preparedness for overexposure to radiation among public or occupational workers and eventual radiological accident in Thailand.

Consecutive results of blood cell count and retrospective biodosimetry: useful tools of health protection regulation for radiation workers

BACKGROUND

Industrial radiography is known to be one of the most vulnerable lines of work among the range of different radiation work. According to the relevant law in Korea, every worker registered in this work should check their blood cell counts every year in addition to their thermoluminescent dosimeter (TLD) doses. Since the law was enacted, however, few follow-up studies have been carried out based on the obtained results.

OBJECTIVES

To ascertain the clinical usefulness of complete blood cell count (CBC) results and suggest a proper protocol of health protection for radiation workers.

METHODS

After reviewing all the consecutive results of CBC and TLD doses from radiation workers registered nationwide, we selected two groups of high-risk radiation workers, CBC-high risk (CBC-HR) and TLD-high risk (TLD-HR) groups. A control group of unexposed healthy adults was also included. We compared the absorbed doses calculated by cytogenetic biodosimetry among those three groups, and examined possible confounding factors for each group.

RESULTS

Both groups of high-risk radiation workers, CBC-HR and TLD-HR, showed higher chromosome aberrations than the control group. In the control group, previous medical history of a CT scan increased the frequency of chromosome aberrations. In contrast, the frequency of chromosome aberrations in the high-risk radiation workers was affected not by the previous CT history but only by the duration of their work.

CONCLUSIONS

We ascertain that reviewing consecutive results of blood cell counts and cytogenetic biodosimetry are useful complementary tools to TLD doses for health protection regulation. Several confounding factors including work duration and previous medical history need to be considered for the interpretation of biodosimetry results.