Biological half-time in rats exposed to nickel monosulfide (amorphous) aerosol by inhalation

This study reports the biological half-time of amorphous nickel monosulfide(NiS(A)) aerosol retained in rat lungs. Wistar male rats were exposed to NiS(A) aerosols (mass median aerodynamic diameter:4.0 microns) for a single 4 h exposure, or for 7 h/d, 5 d/wk for 1 mo. The average exposure concentrations were controlled at 107 mg/m3 for the single exposure and at 8.8 mg/m3 for the repeated exposures by a dust generator consisting of a continuous fluidized bed with an overflow pipe and a screw feeder. After the exposures, the nickel contents in the rat organs, blood, and urine were measured and histopathological examinations were performed. The biological half time of NiS(A) in rat lungs was 20 h, which was extremely shorter than 21 mo of green nickel oxide (NiO(G)). There were no malignant tumors in any of the exposure groups.