Comparative inhalation toxicity of nickel subsulfide to [formula omitted] rats and B6C3F 1 mice exposed for 12 days

Abstract

Groups of F344 N rats and B6C3F 1 mice were exposed to aerosols of nickel subsulfide (Ni 3S 2) 6 hr/day for 12 days not including weekends. Actual exposure concentrations were within 3% of target (target = 10.0, 5.0, 2.5, 1.2, 0.6, and 0.0 mg Ni 3S 2/m 3). Nickel lung burdens of exposed rats and mice increased linearly with exposure concentration. Two male rats and all mice exposed to 10.0 mg Ni 3S 2/m 3 died before the end of the exposures. Exposure to Ni 3S 2 had no effect on the natural killer cell activity of mouse spleen cells. Lesions in rats and mice related to inhalation of Ni 3S 2 were found in the nasal epithelium, lung, and bronchial lymph nodes. The most extensive lesions were found in the lung and included necrotizing pneumonia. Emphysema developed in rats exposed to 5.0 or 10.0 mg Ni 3S 2/m 3, while fibrosis developed in mice exposed to 5.0 mg Ni 3S 2/m 3. Degeneration of the respiratory epithelium and atrophy of the olfactory epithelium of the nose occurred in rats exposed to as low as 0.6 mg Ni 3S 2/m 3 and mice exposed to 1.2 mg/m 3. Results indicate that inhalation exposure of rats and mice to Ni 3S 2 aerosol concentrations near the current threshold limit value (TLV) for nickel compounds (1 mg/m 3 for Ni metal and roasting fume and dust and 0.1 mg/m 3 as Ni for soluble compounds) can produce lesions in the respiratory tract. Atrophy of lymphoid tissues (spleen, thymus, and bronchial lymph nodes) was found in animals of the highest exposure concentration. Degeneration of the testicular germinal epithelium was also observed in mice and rats that survived 5.0 or 10.0 mg/m 3 exposure concentrations.