Cytogenetic analysis in lymphocytes from radiation workers exposed to low level of ionizing radiation in radiotherapy, CT-scan and angiocardiography units

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Abstract

Ionizing radiation is known as a classical mutagen capable of inducing various kinds of stable and unstable chromosomal aberrations. The percentage of cells with chromosomal aberrations was analyzed in peripheral blood lymphocytes of occupationally exposed workers in radiotherapy, CT-scan, angiography and healthy controls. The incidence of all types of aberrations (gap, acentric fragment, dicentric and ring) in exposed subjects were higher than those observed in healthy controls (P = 0.0001). However, the frequency of aberrant cells with dicentric and ring chromosome in exposed subjects were not significantly different from those in controls. To see whether there is a significant difference in the incidence of chromosomal aberrations among three groups, they were compared for all types of observed aberrations. No significant difference was found between radiotherapy and CT-scan groups (P = 0.838). The percentage of aberrant cells observed, for angiography groups were significantly higher than radiotherapy (P = 0.0001) and CT-scan (P = 0.0001) group. Taken together these data suggest that the cumulative effects of low level chronic exposure to ionizing radiation is higher for those who occupationally exposed in angiography.

Highlights

► We examined chromosomal abnormalities induced by low doses of ionizing radiations. ► We compared the level of chromosome aberrations for different working conditions. ► We found that the genetic damage is higher for radiation workers in angiography. ► Cytogenetic analysis is a useful method for estimation of radiation damage.

Introduction

It is well known that ionizing radiation induce DNA double strand break (DSB) [1]. Most of DSBs repair rapidly and accurately [2]. A small number of breaks remain unrepaired and become visible in subsequent metaphase chromosomes. Several studies performed using cytogenetic analysis, report the presence of increased frequencies of chromosomal aberrations in peripheral blood lymphocytes of individuals accidentally, environmentally or occupationally exposed to cumulative low level of ionizing radiation [3], [4], [5]. However, the relationship between ionizing radiation exposure level and the elevation of the frequencies of different types of structural chromosomal aberrations is not yet completely clarified. [6]. Chromosomal abnormalities have been correlated with genetic alterations that can trigger genomic instability and development of cancer. Therefore a biomonitoring based on chromosome aberration analysis make it possible to estimate the cancer risk [7]. In order to prevent the occurrence of significant changes in the genetic pool of the whole population, it is very important to monitor hospital workers chronically exposed to radiation for many years. Moreover, recent technological advances have greatly expanded the new modalities for use of ionizing radiation in diagnostic and treatment. For example, interventional radiology such as cardiac catheterization constitutes a source of relatively high exposure (UNSCEAR 2000). Extensive use of multi-slice computed tomography has also increased radiation doses [8]. International commission on radiological protection reported that the organ dose from CT-scan can often approach or exceed that observed in atomic bomb survivors [9]. Also in the most of the radiotherapy units, 60Co was replaced with high energy linear accelerators.

In the present study we examined chromosomal abnormalities in three groups of hospital workers, working in linear accelerator section for radiotherapy (RT), multi-slice CT-scan (CT) and angiography (An) chronically exposed to ionizing radiation in comparison with matched controls. In particular, there is not enough information on genetic hazards of occupational exposure in case of working with multi-slice CT-scanner and linear accelerator radiotherapy machine. Other variable, such as the effect of donor age, gender, smoking status on the frequency of cells with chromosomal aberration were also taken into account.

Section snippets

Subjects

The study population comprised 33 technicians occupationally exposed to ionizing radiation in the units of radiotherapy, CT-scan and angiography at the Golestan and Imam Khomeini hospitals in Ahvaz, Iran. Eleven individuals working in the same hospitals without any work-related exposure to ionizing radiation considered as control group. All the subjects of exposed and controls lived in the same urban area and matched in age, gender and smoking habit. All the participants were provided with

Results

The percentage of cells with chromosomal aberrations in peripheral blood lymphocytes from three groups of radiation workers and a group of healthy controls are shown in Table 2. A total of 500 metaphases for each subject were analyzed for various chromosomal aberrations. The chromosomal aberrations like gaps, fragments, dicentric and rings which were recorded in the present study were both of chromatid and iso-chromatid type. Correlation in the percentage of aberrant cells detected between four

Discussion

The importance of cytogenetic study of peripheral lymphocytes among occupationally exposed workers even at much below the permissible level of exposure has been reported for more than 30 years. According to Upton (1982), the effects of exposure to low radiation doses accumulate in the body and may damage health after several years of exposure [11]. There are numerous studies on the induction of chromosomal aberration by radiation in the exposed workers of various fields. However to our

Conflict of interest statement

A conflicting interest exist when professional judgment concerning a primary interest such as patient's welfare or the validity of research) may be influenced by a secondary interest (such as financial gain or personal rivalry). It may arise for the authors when they have financial interest that may influence their interpretation of their results or those of others. Examples of potential conflicts of interest include employment, consultancies, stock ownership, honoraria, paid expert testimony

Acknowledgements

We would like to thank to Freshteh Dehbashi for her assistance in Laboratory, Farah Azizi malamiri for working as third observer of chromosomal aberrations. This work was supported by Deputy of research grant in Ahvaz Jundishapur University of Medical Sciences, Ahvaz, I.R. Iran.

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