Negative effect of long-term inhalation of toner on formation of 8-hydroxydeoxyguanosine in DNA in the lungs of rats in vivo

We assessed the effects of long-term inhalation of toner on the pathological changes and formation of 8-hydroxydeoxyguanosine (8-OH-Gua) in DNA in a rat model. Female Wistar rats (10 wk old) were divided evenly into a high concentration exposure group (H: 15.2 mg/m(3)), a low concentration exposure group (L: 5.5 mg/m(3)), and a control group. The mass median aerodynamic diameter of the toner was 4.5 mu m. The rats were sacrificed at the termination of a 1-yr or 2-yr inhalation period. Pathological examination was performed on the left lung, and the level of 8-OH-Gua in DNA from the right lung was measured using a high-performance liquid chromatography (HPLC) column. The pathological findings showed that lung cancer was not observed in any of the exposed or control groups, though pleural thickening and small foci of collagen were observed in toner-exposed rat lungs. Inhalation of the toner for 1 and even 2 yr did not induce the formation of 8-OH-Gua in DNA in rat lungs. These data suggest that long-term inhalation of toner may not induce lung tumors.