title: Lack of increased DNA double-strand breaks in peripheral blood mononuclear cells of individuals from high level natural radiation areas of Kerala coast in India.
abstract: The high level natural radiation area (HLNRA) of Kerala is a 55km long and 0.5km wide strip in south west coast of India. The level of background radiation in this area varies from <1.0mGy/year to 45.0mGy/year. It offers unique opportunity to study the effect of chronic low dose/low dose-rate radiation directly on human population. Spontaneous level of DNA double strand breaks (DSBs) was quantified in peripheral blood mononuclear cells of 91 random individuals from HLNRA (N=61, mean age: 36.1±7.43years) and normal level natural radiation area (NLNRA) (N=30, mean age: 35.5±6.35years) using gamma-H2AX as a marker. The mean annual dose received by NLNRA and HLNRA individuals was 1.28±0.086mGy/year and 8.28±4.96mGy/year, respectively. The spontaneous frequency of DSBs in terms of gamma-H2AX foci among NLNRA and HLNRA individuals were 0.095±0.009 and 0.084±0.004 per cell (P=0.22). The individuals from HLNRA were further classified as low dose group (LDG, 1.51-5.0mGy/year, mean dose: 2.63±0.76mGy/year) and high dose group (HDG, >5.0mGy/year, mean dose: 11.04±3.57mGy/year). The spontaneous frequency of gamma-H2AX foci per cell in NLNRA, LDG and HDG was observed to be 0.095±0.009, 0.096±0.008 and 0.078±0.004 respectively. Individuals belonging to HDG of HLNRA showed marginally lower frequency of DSBs as compared to NLNRA and LDG of HLNRA. This could be suggestive of either lower induction or better repair of DSBs in individuals from HDG of HLNRA. The present study indicated that 5.0mGy/year could be a possible threshold dose for DSB induction at chronic low-dose radiation exposure in vivo. However, further studies on DNA damage induction and repair kinetics are required to draw firm conclusions.
authors.affiliation: Low Level Radiation Research Section, Radiation Biology and Health Sciences Division, Bio-Science Group, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India; Homi Bhabha National Institute, Anushakti Nagar, Mumbai 400 094, India.
authors.forename: Vinay
authors.initials: V
authors.lastname: Jain
authors.affiliation: Low Level Radiation Research Section, Radiation Biology and Health Sciences Division, Bio-Science Group, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India.
authors.forename: P R Vivek
authors.initials: PR
authors.lastname: Kumar
authors.affiliation: Low Level Radiation Research Section, Radiation Biology and Health Sciences Division, Bio-Science Group, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India.
authors.forename: P K M
authors.initials: PK
authors.lastname: Koya
authors.affiliation: Low Level Radiation Research Section, Radiation Biology and Health Sciences Division, Bio-Science Group, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India.
authors.forename: G
authors.initials: G
authors.lastname: Jaikrishan
authors.affiliation: Low Level Radiation Research Section, Radiation Biology and Health Sciences Division, Bio-Science Group, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India. Electronic address: birajalaxmi@yahoo.co.in.
authors.forename: Birajalaxmi
authors.initials: B
authors.lastname: Das
mesh_terms: D001417:Background Radiation / Q000009:adverse effects*; D053903:DNA Breaks, Double-Stranded / Q000528:radiation effects*; D004781:Environmental Exposure / Q000032:analysis*; D064368:Healthy Volunteers; D006657:Histones / Q000235:genetics*; D006801:Humans; D007194:India; D007963:Leukocytes, Mononuclear / Q000473:pathology / Q000528:radiation effects*; D008297:Male; D011829:Radiation Dosage; D011870:Radiologic Health; D011874:Radiometry; D011897:Random Allocation; D018570:Risk Assessment
chemical_list: C468783:H2AX protein, human; D006657:Histones
keywords: Chronic exposure; DNA double strand breaks; Gamma-H2AX foci; High level natural radiation area; Normal level natural radiation area; Peripheral blood mononuclear cells