Combustion Generated Nickel Species Aerosols: Role of Chemical and Physical Properties on Lung Injury

Systematic manipulation of furnace temperature, residence time, and dilution air was used to study the formation of submicrometer nickel oxide (NiO) or nickel sulfate hexahydrate (NiSO 4 ) particles in a horizontal, laminar flow tube reactor. Chemical speciation, morphological changes, and aerosol size distributions were measured using x-ray diffraction, transmission electron microscopy, and diffusion mobility analysis, respectively. A technique was developed to use these submicrometer nickel species aerosols in animal inhalation studies. Representative aerosols were administered to C57BL/6J mice by intratracheal instillation or whole-body inhalation to study the effect of submicrometer particles on pulmonary injury. For instillation, NiO particles having a geometric mass mean diameter ( d pg ) of 40, 300, and 1000 nm were generated by pyrolysis of nickel nitrate hexahydrate aerosol suspended in physiological saline and administered at a dose corresponding to 3, 30, 300, or 3000 w g Ni/kg body weight. Bronchoalveolar lavage fluid was collected 18 hr after instillation and analyzed for total and differential cell counts, cell viability, and total protein. For inhalation experiments, an acute, whole-body exposure was conducted, exposing mice to 6, 24, 48, or 72 hr of continuous submicrometer NiO aerosol ( d pg = 50 nm; 340 w g Ni/m 3 ) or 24, 48, or 72 hr of NiSO 4 aerosol ( d pg = 60 nm; 420 w g Ni/m 3 ; d pg = 250 nm; 480 w g Ni/m 3 ). Exposure to NiO produced no significant lung injury when either instilled or inhaled, whereas inhaled NiSO 4 caused significant increases in protein content and neutrophil count in lavage following 48 or 72 hr of exposure. These findings suggest that submicrometer NiSO4 aerosols generated in combustion processes are more acutely injurious to the lung than an equivalent mass of NiO aerosol.