Background: 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 <1.0mGy to 45.0mGy/year. The areas with external gamma radiation dose >1.5mGy/year are considered as High-Level Natural Radiation Areas (HLNRA) and ≤ 1.5mGy/year are Normal Level Natural Radiation Area (NLNRA).

Objective: 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.

Materials and methods: 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(XRCC1 Arg399Gln), X-ray repair cross complementing 3 (XRCC3 Thr241Met], Protein kinase, DNA-activated, catalytic subunit (PRKDC) (X-ray repair cross-complementing group 7, XRCC7 G/T), nei like DNA glycosylase 1 (NEIL1 G/T) and DNA ligase 1 (LIG1 A/C) was carried out using PCR based restriction fragment length polymorphism (PCR-RFLP) followed by silver staining.

Results: Our results showed no significant difference in genotype frequencies in HLNRA vs NLNRA at three of the five SNPs studied i.e. XRCC1 Arg399Gln (χ²₍₂₎ = 5.85, p = .054), XRCC3 Thr241Met (χ²₍₁₎ = 0.71, p = .339), PRKDC (XRCC7 G/T) (χ²₍₂₎ = 3.72, p = .156), whereas significant difference was observed at NEIL1 G/T (χ²₍₂₎ =8.71, p = .013) and LIG1 A/C (χ²₍₂₎ = 7.66, p = .022). The odds of heterozygote to homozygote genotypes in HLNRA relative to NLNRA at XRCC1 Arg399Gln (OR = 1.96, 95% CI: 1.13–3.40), XRCC3 Thr241Met (OR = 0.73, 95% CI: 0.41–1.31), PRKDC (XRCC7 G/T), (OR = 0.81; 95% CI: 0.48–1.38), NEIL1 G/T (OR = 0.54; 95% CI: 0.31–0.96) and LIG1 A/C (OR = 1.62; 95% CI: 0.97–2.69) was also not significantly different in HLNRA vs NLNRA, except at XRCC1 and NEIL1.

Conclusion: The genotype frequencies at three of these SNPs i.e. XRCC1 Arg399Gln, XRCC3 Thr241Met and PRKDC (XRCC7 G/T) were similar, whereas NEIL1 G/T and LIG1 A/C 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.

背景： DNA修复基因上的单核苷酸多态性（SNP）被认为是潜在的放射敏感性生物标记。印度西南部喀拉拉邦的沿海地带在其沙滩中有少量独居石分布，其中含有Th-232及其衰变产物。因此，该区域的辐射水平从每年<1.0mGy到45.0mGy。外部伽玛辐射剂量> 1.5mGy /年的区域被视为高水平自然辐射区（HLNRA），≤1.5mGy /年的区域被视为正常水平自然辐射区（NLNRA）。

目的：在本研究中，试图评估慢性低剂量照射对喀拉拉邦海岸的NLNRA和HLNRA人群DNA修复基因多态性的影响。

材料和方法：从246名健康的随机个体（NLNRA，N  = 104； HLNRA，N  = 142）的静脉血样本中分离基因组DNA ，并对5个SNP进行基因分型，例如X射线修复交叉互补1（XRCC1 Arg399Gln）， X射线修复交叉互补3（XRCC3 Thr241Met），蛋白激酶，DNA激活的催化亚基（PRKDC）（X射线修复交叉互补第7组，XRCC7 G / T），与DNA糖基化酶1（NEIL1 G / T）和DNA连接酶1（LIG1A / C）使用基于PCR的限制性片段长度多态性（PCR-RFLP）进行，然后进行银染。

结果：我们的结果表明在三个研究即5个SNP的在HLNRA VS NLNRA基因型频率没有差异显著XRCC1 Arg399Gln（χ ² _（2） = 5.85，p  = 0.054），XRCC3 Thr241Met（χ ² _（1）  = 0.71 ，p  = 0.339），PRKDC（XRCC7 G / T）（χ ² _（2） = 3.72，p  = 0.156），而在观察显著差异NEIL1 G / T（χ ² _（2） = 8.71，p  = 0.013）和LIG1 A / C（χ ² _（2） = 7.66，p  = .022）。在XRCC1 Arg399Gln（OR = 1.96，95％CI：1.13–3.40），XRCC3 Thr241Met（OR = 0.73，95％CI：0.41–1.31），PRKDC（XRCC7 G / T）（OR = 0.81； 95％CI：0.48–1.38），NEIL1 G / T（OR = 0.54； 95％CI：0.31-0.96）和LIG1 A / C（OR = 1.62； 95％CI：0.97–除了XRCC1和NEIL1，HLNRA与NLNRA的差异也没有显着差异（2.69）。

结论：XRCC1 Arg399Gln，XRCC3 Thr241Met和PRKDC（XRCC7 G / T）这三个SNP的基因型频率相似，而NEIL1 G / T和LIG1 A / C在HLNRA和NLNRA人群之间存在显着差异。但是，在该研究领域中，需要在更大的队列中使用更多数量的SNP进行进一步的研究。