The comparative toxicity of volcanic ash and quartz. Effects on cells derived from the human lung.
To evaluate the effects of volcanic ash and free crystalline silica on cells derived from the air space of the human lung, we compared the effects of these minerals on human alveolar macrophages and A549 cells, which are derived from human type II pneumocytes. The quartz was markedly cytotoxic to alveolar macrophages and A549 cells and stimulated the release of neutrophil chemotactic activity from alveolar macrophages. By contrast, volcanic ash was much less toxic to human alveolar macrophages and A549 cells and did not stimulate the release of neutrophil chemotactic activity from alveolar macrophages. The results with A549 cells were similar to findings with isolated type II pneumocytes recovered from rat lungs. Secretory IgA, IgG, and albumin, which are normally present in the air spaces of the lung, reduced the cytotoxicity of quartz in a dose-dependent manner. These results suggest that in the human lung quartz, but not volcanic ash, may cause direct damage to cells in the alveolar spaces and lead to the recruitment of phagocytes from the bloodstream to the lung.