The pathogenesis resulting from inhaled particulate pollutants centers around their effects upon the macrophage. An analysis of pathogenesis must proceed in two stages: first, determining how particles kill macrophages, and second, determining how this relates to fibrogenesis. Silica (silicon dioxide) alters the secondary lysosomal membrane, making it permeable to the contained lysosomal enzymes. Silica surfaces alter the lysosomal membrane through hydrogen bonding. Asbestos produces similar effects but not to the extent shown by silica. Fibrogenesis occurs through macrophage damage and release of as yet unknown factors.