DNA damage in the leukocytes of nanocomposite-exposed workers

Human exposure to nanoparticles (NPs) poses potential health risks that are modulated, for example, by the physico-chemical characteristics of NPs, the exposure route and the dose of NPs. Among 21 workers involved for many years in welding on metal surfaces and the machining of nanocomposites, we investigated the role of NPs in the induction of DNA damage. Blood samples of the exposed subjects were collected before and after their working shifts. The controls (21 individuals without occupational exposer to NPs) were sampled in parallel with the exposed ones. NP exposure concentrations were assessed using stationary and personal monitors. DNA damage, including oxidized bases and strand breaks (DNA-SB), in leukocytes was analyzed using Comet assay. The particles monitoring showed that machining was the dominant source of NPs. When compared with the controls, nanocomposite-exposed workers had significantly increased levels of both DNA damage types. In subjects performing machining, post-shift DNA-SB levels were significantly higher than those pre-shift. In welders, such an effect was not observed. Importantly, in both groups, levels of oxidatively damaged DNA were comparable in the post-shift vs. pre-shift samples. The lack of increased DNA oxidation in the post-shift samples suggests the induction of adaptive processes, probably related to long-term occupational exposure to NPs, that protect the organism against this type of DNA damage. However, despite this observation, the potential negative health impacts associated with NP inhalation cannot be ruled out.