Air pollution has been suggested to cause genetic damage from investigations of many biological markers that measure cytogenetic damage in humans. Here, we evaluated the genotoxic effects of ambient air pollution by investigating the extent of cytogenetic damage in human blood lymphocytes from rural and industrial female residents of Shenyang city, China, using micronuclei assays and polymorphic analyses of metabolic enzyme and DNA repair genes. After adjustment for potential confounding factors including DNA polymorphisms, industrial female residents were found to have a higher micronuclei frequency. These results provide evidence that micronuclei assays are a sensitive indicator to air pollution-induced genotoxic effects in humans.