Evaluation of the influence of chronic low-dose radiation on DNA repair gene polymorphisms [<i>XRCC1</i>, <i>XRCC3, PRKDC (XRCC7), LIG1</i>, <i>NEIL1]</i> in individuals from normal and high level natural radiation areas of Kerala coast

<b>Background:</b> Single Nucleotide Polymorphisms (SNPs) at DNA repair genes are considered as potential biomarkers of radio-sensitivity. The coastal belt of Kerala in south west India has a patchy distribution of monazite in its beach sand that contains Th-232 and its decay products. Thus, radiation levels in this area vary from &lt;1.0mGy to 45.0mGy/year. The areas with external gamma radiation dose &gt;1.5mGy/year are considered as High-Level Natural Radiation Areas (HLNRA) and ≤1.5mGy/year are Normal Level Natural Radiation Area (NLNRA). <b>Objective:</b> In the present study, an attempt was made to evaluate the influence of chronic low dose radiation exposure on DNA repair gene polymorphisms in NLNRA and HLNRA population of Kerala coast. <b>Materials and Methods:</b> Genomic DNA was isolated from venous blood samples of 246 random, healthy individuals (NLNRA, N = 104; HLNRA, N = 142) and genotyping of five SNPs such as X-ray repair cross complementing 1(<i>XRCC1 Arg399Gln),</i> X-ray repair cross complementing 3 (<i>XRCC3 Thr241Met</i>], Protein kinase, DNA-activated, catalytic subunit (<i>PRKDC)</i> (X-ray repair cross-complementing group 7, <i>XRCC7 G/T),</i> nei like DNA glycosylase 1 (<i>NEIL1 G/T)</i> and DNA ligase 1 (<i>LIG1 A/C)</i> was carried out using PCR based restriction fragment length polymorphism (PCR-RFLP) followed by silver staining. <b>Results:</b> Our results showed no significant difference in genotype frequencies in HLNRA vs NLNRA at three of the five SNPs studied i.e. <i>XRCC1 Arg399Gln</i> (χ²₍₂₎ = 5.85, P = 0.054), <i>XRCC3 Thr241Met</i> (χ²₍₁₎ =0.71, P = 0.339), <i>PRKDC</i> (<i>XRCC7</i> G/T) (χ²₍₂₎ = 3.72, P = 0.156), whereas significant difference was observed at <i>NEIL1 G/T</i> (χ²₍₂₎ =8.71, P= 0.013) and <i>LIG1</i> A/C (χ²₍₂₎ = 7.66, P = 0.022). The odds of heterozygote to homozygote genotypes in HLNRA relative to NLNRA at <i>XRCC1</i> Arg399Gln (OR =1.96, 95% CI: 1.13-3.40), <i>XRCC3</i> Thr241Met (OR =0.73, 95% CI: 0.41-1.31), <i>PRKDC (XRCC7 G/T),</i> (OR =0.81; 95% CI: 0.48-1.38), <i>NEIL1 G/T</i> (OR =0.54; 95% CI: 0.31-0.96) and <i>LIG1 A/C</i> (OR =1.62; 95% CI: 0.97-2.69) was also not significantly different in HLNRA vs NLNRA, except at <i>XRCC1</i> and <i>NEIL1.</i> <b>Conclusion:</b> The genotype frequencies at three of these SNPs i.e., <i>XRCC1 Arg399Gln, XRCC3 Thr241Met</i> and <i>PRKDC</i> (<i>XRCC7 G/T</i>) were similar, whereas <i>NEIL1 G/T</i> and <i>LIG1 A/C</i> showed significant difference between HLNRA and NLNRA population. However, further research using more number of SNPs in a larger cohort is required in this study area.