XRCC1 and cyclic hematopoiesis: This study aimed to determine the type and frequency of chromosomal alterations, evaluate the levels of CIN and CH, and establish their associations with polymorphic variants at exon 5 (A→G) in the GSTP1 gene and at exons 6 (C→T) and 10 (G→A) in the XRCC1 gene in a group of ten farmers who had been occupationally exposed to pesticides in the town of Aquitania, Colombia, and in ten unexposed individuals.