title: Evaluation of spontaneous DNA damage in lymphocytes of healthy adult individuals from high-level natural radiation areas of Kerala in India.
abstract: Inhabitants of the high-level natural radiation areas (>1 mSv year(-1)) of Kerala in southwest India were evaluated for basal damage (spontaneous DNA strand breaks and alkali-labile sites) by the alkaline comet assay and oxidative DNA damage (ENDO III- and hOGG1-sensitive sites) by the enzyme-modified comet assay. Of the 67 adult male subjects studied, 45 were from high-level natural radiation areas and 22 subjects were from a nearby normal-level natural radiation area (≤1 mSv year(-1)). Basal damage due to the age and residential area (normal-level natural radiation area/high-level natural radiation areas) of the donors showed significant interaction (P < 0.001) when all subjects were analyzed using a general linear model (GLM). In subgroup analysis, basal damage increased with age in subjects from the normal-level natural radiation area (P = 0.02), while a significant negative correlation (P = 0.002) was observed in subjects from high-level natural radiation areas. Further, basal damage in elderly subjects from high-level natural radiation areas was significantly (P < 0.001) lower compared to the subjects from the normal-level natural radiation area. Oxidative DNA damage was not influenced by age, smoking habit or residential area in the entire sample. However, in a subgroup analysis, hOGG1-sensitive sites showed a significant increase with age in subjects from high-level natural radiation areas (P = 0.005). ENDO III-sensitive sites increased with natural radiation exposure in subjects from high-level natural radiation areas (P = 0.02), but when stratified according to smoking, a significant increase was observed only in smokers (P = 0.01). To the best of our knowledge, this is the first study on basal and oxidative DNA damage in healthy adults of this population. However, our findings need more validation in a larger study population.
authors.affiliation: Low Level Radiation Research Laboratory, Radiation Biology and Health Science Division, Bhabha Atomic Research Centre, Kollam-691 001, Kerala, India. prvkumar06@gmail.com
authors.forename: P R Vivek
authors.initials: PR
authors.lastname: Kumar
authors.forename: V D
authors.initials: VD
authors.lastname: Cheriyan
authors.forename: M
authors.initials: M
authors.lastname: Seshadri
mesh_terms: D000328:Adult; D001417:Background Radiation / Q000009:adverse effects*; D020552:Comet Assay; D004247:DNA / Q000187:drug effects / Q000528:radiation effects*; D004249:DNA Damage; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D007194:India; D008214:Lymphocytes / Q000528:radiation effects* / Q000648:ultrastructure; D008297:Male; D010084:Oxidation-Reduction; D012907:Smoking / Q000009:adverse effects; D013910:Thorium / Q000009:adverse effects
chemical_list: D013910:Thorium; D004247:DNA