To investigate the pathogenicity of
nickel oxide (NiO), hamsters received life-span exposures to that compound (approximately 55 mg/m3) seven hours per day, five days per week. Heavy pulmonary
nickel oxide burdens resulted in
pneumoconiosis but in no significant carcinogenicity, specific toxicity, or mortality. Two-month exposures of hamsters to
nickel-enriched
fly ash (
NEFA) or
fly ash (FA)
aerosols (approximately 185 mg/m3) resulted in a deep lung burden of about 5.7 mg, dark discoloration of lungs, heavily dust-laden macrophages, and significantly higher lung weights than in controls, but only minimal inflammatory reaction and no deaths. The
NEFA contained 9%
nickel; FA contained 0.03%
nickel. Exposure to
aerosols of
NEFA (70 or 15 mg/m3; 6%
nickel) or
FA (70 mg/m3; 0.3%
nickel) for 20 months had no effect on
body weight or life-span of the animals. Lung weights and volumes of the high-
NEFA- and FA-exposed animals were higher than those of the low-
NEFA group and controls. The incidence and severity of interstitial reaction and bronchiolization were significantly higher in the dust-exposed groups than in the controls. The severity of dust deposition, interstitial reaction, and bronchiolization was significantly lower in the low-
NEFA group than in the high-
NEFA and FA groups. Our findings revealed no significant
nickel-specific toxicity/carcinogenicity in hamsters exposed to
aerosols of
nickel oxide or
NEFA, but exposure to high concentrations of the
oxide resulted in nonspecific dust
pneumoconiosis.