Vol.12 (2022) No. 1 ISSN: 2088-5334 The Evaluation of Frequencies of Cytogenetic Biomarkers in Lymphocyte of Residents from High Natural Radiation Area in West Sulawesi, Indonesia Mukh Syaifudin a,* , Dwi Ramadhani a , Sofiati Purnami a , Nastiti Rahajeng a , Siti Nurhayati a , Harry Nugroho Eko Surniyantoro a a Center for Technology of Radiation Safety and Metrology, National Nuclear Energy Agency of Indonesia, South Jakarta, 12440, Indonesia Corresponding author: * mukh_syaifudin@batan.go.id Abstract— Residents living in high natural radiation areas may pose health consequences such as cancer. The study aims to evaluate the frequencies of cytogenetic biomarkers covering micronuclei (MN), nucleoplasmic bridge (NPB), and nuclear bud (NBUD) with the cytokinesis-block micronucleus (CBMN) assay. This cross-sectional study was done on 51 blood lymphocytes from the resident of Mamuju, West Sulawesi, Indonesia that was done according to standard procedure. After being stained with Giemsa solution, these biomarkers were observed on about 1,000 binucleated cells. The results showed a low frequency of MN (0.0162 in 36,091 cells) and extremely low frequencies of other biomarkers (0.00019 and 0.00061 for NPB and NBUD, respectively) in the study area, whereas these were 0.0225 MNs in 15,000 cells, and 0.00013 and 0.00120 for NPB and NBUD, respectively, in the control area. MNs and NBUDs were lower in the study area compared to control. No statistically significant differences (p>0.05) in NPB were found between the two areas, but not for NBUD. The frequencies of MN and NPB in female is higher than that of male in both areas. In the control group, males experienced a decrease in the number of NPB to 0.7 times compared to females, and every extra one year of age, 1.047 times more NBUDs were found. None of the confounding factors was influenced in the study group. It was concluded that there is no impact of high natural radiation to the local residents based on cytogenetics evaluation, with a note that further studies on a higher number of samples and other relevant biomarkers are required. Keywords— Natural Radiation; Cytogenetic Biomarkers; MN; NPB; Mamuju. Manuscript received 25 Jul. 2020; revised 25 Feb. 2021; accepted 17 Mar. 2021. Date of publication 28 Feb. 2022. IJASEIT is licensed under a Creative Commons Attribution-Share Alike 4.0 International License. I. INTRODUCTION Every human is exposed continuously to radiation such as sun, light, ultraviolet, microwave, ionizing radiation, and others. They are also exposed to various amounts of naturally ionizing radiation depending on where they live. This radiation covers four sources: radionuclides in the earth, cosmic radiation from external space, radioactivity inside the human body such as K-40, and radon as the biggest contributor [1]. Exposure to cosmic rays and naturally occurring radon has become unavoidable. Radon in houses type is also a problem of growing concern [2]. There is always a risk of damage to cells or tissue from exposure to any amount of or long-term exposure to ionizing radiation [3]. Therefore, improvements in the evaluation strategies in that area are valued as mandatory. Cytogenetic analyses have been used to assess the effects of ionizing radiation in a wide variety of organisms. It is based on quantifying asymmetrical chromosome alterations (dicentrics, rings, and fragments) in phytohemagglutinin- stimulated T-lymphocytes in the first mitosis after radiation exposure [4]. Another highly standardized strategy that can also be utilized for measuring various biomarkers of hereditary harm in lymphocytes is cytochalasin-blocked MN (CBMN) assay [5], [6]. The appearance of micronuclei (MN) in human T lymphocytes indicates accumulated genetic alterations ensuing from unconstrained chromosome breakage or loss [7], [8]. MN will originate at the anaphase stage from insulation chromosome or chromatid fragments as an impact of disrepair of deoxyribonucleic acid (DNA) or unrepaired DNA breaks [6]. MNs are frequently utilized as indicators of genotoxicity caused by various xenobiotics, either chemical [9] or physical [10] agents. Even though it is not radiation-specific, laborious, and subject to scorer bias, 263