XRCC1 and colorectal carcinoma: Taken together, the individuals, who are with XRCC1 194Arg allele and heavy smoking history, or who carry XRCC1 399Arg/Gln or 399Gln/Gln genotype and have a heavy smoking or drinking habit, have the increased risk for CRC in the population of Han nationality in Jiangsu Province of China which also shows a positive correlation with exposure dose of tobacco, but these XRCC1 polymorphisms could not be independent risk factors in smoking or drinking population.