group and individuals without asbestosis, respectively. Linear regression analysis showed that 28,4% and 50,5% of comet assay results were increased by exposure to asbestos and developed asbestosis. The results of CAT and GST were not difference between the groups. These results supports the association of genotoxic damage and the onset of asbestosis by chrysotile asbestos exposure in workers of this study.Keywords: asbestos, occupational exposure, genotoxicity. IntroductionAsbestosis is a form of pneumoconiosis caused by inhaling asbestos, a generic commercial designation for a group of naturally-occurring mineral silicate fibres of the serpentine (chrysotile asbestos) and amphibole series (actinolite, amosite, anthophyllite, crocidolite and tremolite) [1]. Inhaling any kind of asbestos fibers causes the development of intense interstitial pulmonary fibrosis, which involves an inflammatory reaction, production of collagen and the formation of granuloma [2][3][4][5].Asbestosis and other diseases related to asbestos are increasing worldwide [6,7] and several studies have shown that exposure to asbestos has contributed to occupationally-related cancer. Each year, approximately 125 million people around the world are occupationally exposed to asbestos and at least 100,000 people die because of diseases related to this exposure (for example asbestos-related lung cancer, mesothelioma, or asbestosis [1]) despite the fact that "chrysotile manufacturers, governments of asbestos-producing nations, and some asbestos miners' unions contend either that their products do not cause disease or that there is insufficient evidence to reach a reliable conclusion", as stated by Pezerat (2009) [8]. Abstract: Genotoxic effects of occupational workers exposed to asbestos can be evaluated using different biomarkers as oxidative stress enzymes in conjuction with comet assay. This study assessed changes to oxidative stress enzymatic parameters and genotoxic damage in workers occupationally exposed and non-exposed to chrysotile asbestos, who attended the outpatient Clinic of the Center for Worker Health Studies and Human Ecology (CESTEH/ENSP/FIOCRUZ) in Brazil. Chest radiography and spirometry were performed to assess clinical progression of symptoms. The traditional visual score comet assay in peripheral whole blood cells was used to assess DNA damage, and oxidative stress was evaluated by measuring catalase (CAT) and glutathione S-transferase (GST) activities. Respiratory alterations were observed in 53% of workers exposed, as determined by pulmonary function and bronchodilation, and 6 workers were diagnosed with asbestosis. The comet assay was statistically significantly higher in the exposed group and individuals with asbestosis compared to the non-exposed