Alveolar macrophages in rabbits after combined exposure to nickel and trivalent chromium

Rabbits were exposed to a combination of 0.7 mg/m3 Ni2+ as NiCl2 and 1.2 mg/m3 of Cr3+ as Cr(NO3)3, to 0.6 mg/m3 of Ni2+ as NiCl2, or to filtered air for about 4 months, 5 days/week and 6 hr/day. Alveolar macrophages were recovered by lung lavage and studied by light and electron microscopy. Metabolic activity, phagocytic capacity and lysozyme activity in the macrophages were studied. After the combined exposure, the effects on lung weight, number of macrophages, and appearance of surface and number of intracellular laminated inclusions in these cells were more than additive. These effects might be explained by a combination of increased production by Ni2+ and impaired catabolism of surfactant by Cr3+. Because the metal concentrations used were not far above occupational threshold limit values, combined exposures to nickel and trivalent chromium should be considered more seriously.