An assessment of immediate DNA damage to occupationally exposed workers to low dose ionizing radiation by using the comet assay.

BACKGROUND

Several cytogenetic studies have shown an increased frequency of chromosomal aberrations for workers exposed to low dose ionizing radiation, however the dose, type of radiation and management vary among the areas of work; it is possible that this variation may generate different quantity of DNA damage, detectable within the first hours after exposure of the personnel. In this study we assessed early DNA lesions caused by exposure to low doses of ionizing radiation in 41 workers from the departments of Radiology, Nuclear Medicine and Radiotherapy and a group of 20 healthy unexposed individuals, all from the same Institution.

MATERIAL AND METHODS

Blood samples were obtained from exposed and unexposed subjects for analysis of DNA damage using the comet assay. The migration of the comet's tail was compared before and after the workday, as well as among the groups; the relationship between DNA migration and the exposure dose of the month was also obtained.

RESULTS

A significant increase in damage to DNA was seen after workday for the occupationally exposed group (p < 0.01) as compared with the samples before workday as well as with those from the unexposed group. A positive correlation was found between the monthly dose of radiation and the migration length of DNA before and after the workday (p < 0.01). There were significant differences in the length of the comet tails among workers from different departments: workers from Radiology (28.6 microm) have less DNA damage than those from Nuclear Medicine and Radiotherapy (92.5 microm, 63.4 microm respectively) departments.

CONCLUSIONS

All the workers occupationally exposed showed an increase in DNA fragmentation after the workday. The amount of radiation in all three services is different, in Nuclear Medicine and Radiotherapy the workers showed a greater monthly dose of exposure and greater DNA damage than the Radiology workers. The longer tails were observed in Nuclear Medicine where radionuclides are used; these radioactive substances are handled and administered to patients orally or intravenously by the workers, which implies a different type of exposure and radiation, this may explain the differences found in this study. Most of the DNA damage detected by the comet assay is repaired, however a part of it may result in stable chromosomal rearrangements that may represent a long-term health risk. It is important to sensitize exposed workers on their responsibility of working with radiation and the improvement of the hospital safety practices.