Study of radiation damage with the radiation workers by low dose irradiation

Objective To explore the sensitivity index of radiation injury of radiation workers was analyzed and investigate whether the body changes and radiation doses of workers exposed to low-dose radiation have a dose-effect relationship. Methods The occupational health monitoring data of radiology staff were analyzed by retrospectively. Results Individual dose monitoring data, interventional radiology workers had the highest average cumulative annual dose, 0.86mSv. Lens opacity has a high detection rate, Compared with the control group, the lymphocyte count was increased. Annual cumulative dose reached 2.04 mSv, and single cycle average dose reached 1.62 mSv, dicentric chromosome was detected.


Introduction
Following the discovery of X-rays in 1895 by German physicist Wilhelm Conrad Röntgen and of radioactivity the following year by French physicist Henri Becquerel, medical, industrial, and military uses of radiation technology were developed that eventually led to a marked increase in human population exposure to ionizing radiation. With the wide application of radiation technology in the medical eld, more than 70% of the radiation comes from the medical application of radiation.
Radiation injury, tissue damage or changes caused by exposure to ionizing radiation-namely, gamma rays, X-rays, and such high-energy particles as neutrons, electrons, and positrons. Sources of ionizing radiation may be natural (e.g., radioactive substances such as the element radium or the radioisotopes potassium-40 and carbon-14) or man-made (X-ray machines, nuclear reactors, particle accelerators, nuclear weapons, etc.).
Through the displacement of electrons (ionization), ionizing radiation effectively disrupts molecular bonds. In living organisms, such disruption can cause extensive damage to cells and their genetic material. A characteristic type of DNA damage produced by ionizing radiation, even by a single radiation track through a cell, involves closely spaced, multiple lesions that compromise cellular DNA repair mechanisms. Although most of the cells sustaining such radiation-induced damage may be eliminated by damage response pathways, some cells are capable of escaping these pathways, propagating, and eventually undergoing malignant transformation, a crucial step in cancer development. (1) Cancer risk is increased roughly in proportion to the amount of energy deposited in tissue (radiation dose, usually quanti ed in units of gray [Gy] or milligray [mGy], where 1 Gy corresponds to 1 joule of energy per kilogram of tissue). However, organs and tissues differ in their sensitivity to radiation carcinogenesis (cancer-causing ability). Cancer risk further varies by type of ionizing radiation, by gender, by age at exposure, by age and time following exposure, and by lifestyle factors, such as reproductive history and exposure to other carcinogens (e.g., tobacco smoke). On average, the bulk of radiation dose to individuals comes from natural background sources that have changed little over the span of human existence.
Assessment of the health impact of ionizing radiation requires an understanding of the interactions of radiation with living cells and the subsequent reactions that lead to injury. (2,3) The biomedical effects of ionizing radiation have been investigated more thoroughly than those of any other environmental agent. Evidence that harmful effects may result from small amounts of such radiation has prompted growing concern about the hazards that may be associated with low-level irradiation from the fallout of nuclear weapons, medical radiography, nuclear power plants, and other sources.
Screening from 2016 to 2017 based on the radiation exposure dose of radiation workers, through the statistical analysis to investigate the interventional radiology, diagnostic radiology, radiotherapy, industrial aw detection, the different type of work such as nuclear medicine, different length of service and whether there is any contact between the average dose dose -effect relationship, provide the basis for provide the corresponding intervention measures.

Material And Method
A total of 976 radiological workers who underwent occupational health monitoring were randomly selected as subjects. The average age was (37.52 ± 9.84) years, and the average length of service was (12.11 ± 9.96) years. Which work in the X-ray diagnosis of 560 cases of radiation workers, 57.38% (men and women than 1.33:1), radiation therapy, 155 cases, 15.88% (men and women than 0.96:1), 158 cases of interventional treatment accounted for 16.19% (men and women than 2.01 :1), nuclear medicine 60 cases, 6.15% (men and women than 2.33:1), industrial aw detection 43 cases, 4.41% (men and women than 4.38:1).There was no signi cant difference in age, gender and length of service among the subjects (P > 0.05).

Clinical Examination
According to the occupational health management measures for radiation workers, the examination contents include general medicine, neurology, dermatology and ophthalmology. The lens was fully dilated with compound topic amide eye drops, and the lens was examined under slit lamp microscope.

Laboratory Examination
WBC and PLT were the main indicators of peripheral blood. Venous blood was collected and analyzed by MEDONIC CA620, a fully automatic hematomata. Personal dose monitoring of radiation can be done by eld monitoring or TLD monitoring. Cytogenetic test: analysis of chromosomal aberration rate and micronucleus rate of peripheral blood lymphocytes, chromosomal aberration rate and micronucleus rate of peripheral blood lymphocytes by 1640 culture medium for 48 h and 72 h respectively. The chromosome aberration rate was analyzed for 200 mitotic phases per person, and the lymphocyte micronucleus rate was analyzed for 1000 lymphocytes per person. (5)(6)(7)(8)(9) Results Determination Personal dosimetry was performed on the personal dosimeter worn by the radiological workers. The blood routine results were determined according to GB 98-2002 health standards for radiological workers.
Statistical analysis SPSS 20.0 was used for data analysis, and chi-square test was used for rate comparison. P < 0.05 was considered statistically signi cant.

Result
Mean annual cumulative dose Radiological workers of different types of work: interventional radiology workers: 0.86 mSv, radiological diagnosis: 0.37 mSv, radiotherapy: 0.13 mSv, industrial inspection: 0.33 mSv, and nuclear medicine: The detection rates of leukocyte and platelet decrease, lens opacity and lymphocyte micronucleus were compared.
There was no signi cant difference in the leukocyte lowering rate among different groups (P > 0.05).
The difference in platelet lowering rates among radiological workers engaged in diagnostic and therapeutic radiology was statistically signi cant. There was a statistically signi cant difference in platelet lowering rates between the radiosurgery and interventional therapy workers.
The difference in the rate of lens opacity was statistically signi cant. Using the radiotherapists as the control group, it was found that there was a difference in the detection rate of lens turbidity among the radiotherapists engaged in interventional therapy, nuclear medicine and industrial inspection, and the difference was statistically signi cant. See Table 1   Table 1 comparison of leucocyte and platelet decrease, lens opacity detection rate and lymphocyte micronucleus rate in radiological workers of different types of work Groups according to working-age. There was no statistically signi cant difference between the reduction rate of WBC and the reduction rate of PLT among the radiological age group(P>0.05);The lymphocyte micronucleus rate was in groups 0-10 and 10-20.10 ~ 20 groups were compared with: > 20 groups. Group 0 ~ 10 and group > 20 P<0.01 ,there were signi cant differences among different age groups; The workers with more than 20 years of working experience had the highest rate of chromosomal aberrations. See Table 2  Peripheral radiation workers from 2015 to 2017 as test results, the radiation workers as the control group, there was no statistically signi cant differences between groups (P > 0.05). See Table 3

Chromosome Aberration Analysis
Chromosomal aberrations were analyzed in 3,025 radiological workers, the results are shown in Table 6. This suggests that the chromosome aberration analysis is an important index in occupational health monitoring of radiological workers.

Discussion
The effects of long-term low dose ionizing radiation on human body are attracting more and more attention. It is generally believed that long-term and small doses of occupational radiation can lead to radiation workers in all aspects of the damage, in which the division of vigorous, metabolic vigorous cells are more sensitive to radiation. Therefore, the hematopoietic system of human body is the sensitive target system of radiation, and the change of peripheral blood image is the early manifestation of radiation damage.
Studies have shown that peripheral blood lymphocytes are more sensitive to ionizing radiation, resulting in decreased white blood cell count, lens opacity, and increased micronucleus rate and chromosome aberration rate of peripheral blood lymphocytes. Many scholars have analyzed and discussed the body damage caused by long-term low-dose irradiation of radiation workers (mainly taking four indexes of WBC count, PLT count, lens opacity detection rate, chromosome aberration rate and micronucleus detection rate as the observation and analysis indexes), but the results are not consistent. (10)(11)(12) This study proved that the radiation effect did not show obvious regularity with the change of radiation dose among the radiation workers. Although there were differences in the effects, the differences were not statistically signi cant, and the dose-effect relationship among the radiation workers in was not found.
The lymphocyte micronucleus rate was in groups 0-10 and 10-20.10 ~ 20 groups were compared with: > 20 groups.0 ~ 10 groups and 20 > groups (P < 0.01), and there was a signi cant difference among the age groups. The chromosome aberration rate was highest in people with more than 20 years of working life.
In summary, the workers with a longer working-age have longer working hours and heavy workload, which leads to prolonged cumulative exposure time and increased exposure dose, which may aggravate the radiation damage of the body.
The lymphocyte count was higher than that of the control group. Whether there is a certain excitation effect of low dose irradiation on the immune system needs further discussion.

Conclusion
Radiation workers have certain radiation damage, and the focus is on those engaged in interventional radiology. The chromosome aberration rate was highest in people with more than 20 years of working life. Annual cumulative dose reached 2.04 mSv, and single cycle average dose reached 1.62 mSv, dicentric chromosome was detected, it suggests that the chromosome aberration analysis is an important index in occupational health monitoring of radiological workers.
The lymphocyte count was higher than that of the control group, whether there is a certain excitation effect of low dose irradiation on the immune system needs further discussion.
Setting of new regulatory exposure limits, improving workers' radiation dosimetry, administration of stable iodine, running an occupational health tracking system, and improving occupational medicine and preventative care. Those interventions were not only vital for preventing unnecessary radiation, but also for managing other general health issues such as mental health, heat illness and infectious diseases.