In vitro toxicity of cobalt and hard metal dust in rat and human type II pneumocytes

Abstract

It has been demonstrated that hard metal dust, which consists of a mixture of cobalt and tungsten carbide, is more toxic toward mouse peritoneal and rat alveolar macrophages than pure cobalt (Co) or lungsten carbide (WC). The aim of this study was to investigate the toxic effects of Co and hard metal dust on alveolar epithelial type II cells (AT-II), and to compare these with alveolar macrophages. Freshly isolated rat and human AT-II and rat alveolar macrophages were exposed for 18 hr to particles of Co, WC or ConxiC. As an index for cell toxicity, release of lactate dehydrogenase was measured. For rat AT-II, TD50 values per 105 cells were 672 μg (95% C.I.= 264-1706 μg) for pure Co and 101 μg (95% C.I.=59-172 μg) for Co in Co/WC mixture. For rat alveolar macrophages, TD50 values per 105 cells were 18 μg (95% C.I.=15-24 μg) for pure Co and 5 μg (95% C.I.=5-6 μg) for Co in Co/WC mixture. WC only caused an increase in lactate dehydrogenase at high concentrations. No toxicity was found in human AT-II for either Co, WC or Co/WC. These results indicate that 1) rat AT-II are less sensitive to Co than rat alveolar macrophages, 2) human AT-II are less sensitive to Co than rat AT-II, 3) the toxicity of Co is increased by the presence of WC.