A comparative study of genotoxicity endpoints for women exposed to different levels of indoor radon concentrations

Abstract

Background and purpose

Radon and its radioactive progenies are the most important source of ionizing radiation of natural origin, being classified as a Group 1 carcinogen. The aim of this study is to investigate the genotoxic effects of a wide range of indoor radon concentrations, as well as the kinetics of the process of repairing DNA-induced lesions by a challenging dose of gamma irradiation.

Material and methods

Female subjects residing in the Băiţa-Ştei radon priority area were selected as the exposed group. The reference group was comprised of women from the same county (Bihor), but located in an area with an average indoor radon concentration typical of the county from which they were taken. Radon concentration values of 300 Bq/m³ and 148 Bq/m³, respectively, were chosen as a threshold in order to capture the impact of radon exposure between the groups. The alkaline comet assay was used in order to measure the DNA damage, as well as the repair kinetics at 2 and 24 h after 2 Gy challenging doses of gamma irradiation using peripheral blood lymphocytes. From the serum of the subjects, the oxidative damage by 8-hydroxydeoxyguanosine as well as the PARP induction was evaluated. The chromosomal aberrations were evaluated using the Cytokinesis Block MicroNucleus Assay.

Results

A statistically significant increase was observed in terms of DNA-induced lesions assessed by comet assay for the exposed group compared to the reference group. A positive correlation was obtained between DNA damage and the annual effective dose, respectively with the radon progenies concentrations. A statistically significant difference was also observed for the frequency of the micronuclei between the exposed – reference groups. Significantly faster repair kinetics of DNA-induced lesions was recorded for the first 2 h after gamma irradiation in the reference group compared to the exposed group. Using the threshold of 300 Bq/m³ for radon concentration, faster kinetics of DNA damage repair for people exposed to low radon concentrations, compared to those exposed to higher concentrations for the second phase of DNA repair kinetics was observed.

Conclusion

An increased radiosensitivity of lymphocytes, as well as slower repair kinetics, may be associated with exposure to higher indoor radon concentrations.

Keywords:

• Comet assay
• micronuclei
• indoor radon concentrations
• repair kinetics
• 8-OHdG
• PARP

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Romanian National Authority for Scientific Research and Innovation, CNCS-UEFISCDI, by the project [PN-II-RU-TE-2014-4-1009].

Notes on contributors

Tiberius Dicu

Tiberius Dicu, PhD is a Lecturer at the Faculty of Environmental Science and Engineering of the Babeş-Bolyai University, Romania. He has published over 40 articles, most on residential radon exposure. He is the Technical Manager within ‘Constantin Cosma’ Radon Laboratory (LiRaCC) and the president of the Association of Radon Professionals in Romania.

Piroska Virag

Piroska Virág, PhD, Senior Scientific Researcher and Head of the Radiotherapy, Radiobiology and Tumor Biology Laboratory of The Oncology Institute ‘Prof. Dr. I. Chiricuţă’ and Associated Professor at the Faculty of Biology of the Babeş-Bolyai University. Manager and participant in several scientific projects based on Radiobiology studies, especially in the field of the effects of low-dose radiations on normal cells.

Ioana Brie

Ioana Brie, MD, PhD, is a Senior Specialist in Radiotherapy and Scientific Researcher in Radiobiology. She is experienced in the evaluation of DNA lesions and their repair, mainly related to their potential as predictive biomarkers in clinical radiotherapy.

Maria Perde-Schrepler

Maria Perde-Schrepler, MD, Senior Researcher at The Oncology Institute ‘Prof. Dr. Ion Chiricuţă’, leader and participant in several researches studying the cytogenetic effects of radiation (gamma, X-ray, UVB) on several cells and tissues.

Eva Fischer-Fodor

Eva Fischer-Fodor, PhD, Senior Researcher at The Oncology Institute ‘Prof. Dr. Ion Chiricuţă’; experienced in blood mononuclear cell-based genotoxicity testing and a background of over 40 indexed papers on metal-induced in vitro biologic effects.

Bogdan Victor

Bogdan Victor is an expert in Medical Physics at the Institute of Oncology ‘Prof. Dr. Ion Chiricuţă’, Cluj-Napoca, having broad experience in radiation physics, dosimetry and biodosimetry. Apart from his engagement in the daily set up of radiotherapy planning for patients, he is also involved in radiobiology research by ensuring the planning for irradiation of cell cultures and small laboratory animals.

Alexandra Cucoș

Alexandra Cucoş, PhD, Senior Researcher and Head of the ‘Constantin Cosma’ Radon Laboratory, Babeş-Bolyai University, manager of several international and national research projects studying indoor radon exposure in Romania.

Bety-Denissa Burghele

Bety-Denissa Burghele, PhD, a Senior Researcher within the ‘Constantin Cosma’ Radon Laboratory, Babeş-Bolyai University, is experienced in radon measurements and risk assessment.