Surface properties of respirable silicate and aluminosilicate dusts affecting bioavailability.
Wallace-WE; Keane-MJ; Harrison-JC; Stephens-JW; Brower-PS; Grayson-RL; Vallyathan-V; Attfield-MD
Cellular and molecular effects of mineral and synthetic dusts and fibres: proceedings of the NATO Advanced Study Institute on Cellular and Molecular Effects of Mineral and Synthetic Dusts and Fibres, October 11-13, 1993, Paris, France. Davis JMG, Jaurand M-C, eds. London: Springer-Verlag, 1994 Aug; H85:369-379
The disparity between the known fibrogenic activity of quartz (14808607) particles and comparable epidemiological evidence of this pathology in mine dust were investigated by particle surface analysis and cytotoxic studies. Scanning electron microscope energy dispersive X-ray analysis (SEM/EDX) was used to determine the presence of surface coatings capable of limiting the bioavailability of the quartz component of mine dusts. Twelve coal mine dust samples were collected from United States coal mines including Pennsylvania (PA) anthracite and bituminous, Illinois (IL) bituminous and Colorado (CO) subbituminous. Homologous surface behavior was observed for 80% of the anthracite samples. In contrast, only 20% of the western PA bituminous, 46% of the central PA bituminous and 44% of the IL and CO samples were free of aluminosilicate clay coatings. The membranolytic potential of respirable quartz and kaolin dusts were compared under the conditions of incubation with L-alpha-dipalmitoyl- phosphatidylcholine (DPPC) to mimic the coating and dispersion of the alveolar surface and incubation with phospholipase-A2 (PLA2) to simulate digestive processes. Incubation with DPPC led to adsorption of surfactant and reduced erythrocyte hemolysis to control levels for quartz and kaolin. Subsequent incubation with PLA2 led to a rapid 50% digestion of the surfactant coating for both quartz and kaolin. Digestion of remaining DPPC on quartz particles proceeded more rapidly than for kaolin particles. A model composed of a dust particle with a bilayer coating of DPPC was proposed. The authors conclude that the use of mass percent of quartz content of mine dusts, which does not reflect the actual quartz particle surface bioavailability, may be the cause of inconsistent epidemiological findings for exposed coal miners. The authors further conclude that quartz and kaolin dusts have comparable membranolytic activities which are neutralized by surfactants and restored by phospholipase digestion.
Quartz-dust; Respirable-dust; Dust-analysis; Dust-particles; Mineral-dusts; Coal-mining; Coal-workers-pneumoconiosis; Silica-dusts; Surface-properties; In-vitro-study; Microscopic-analysis; X-ray-analysis
William E. Wallace, National Institute for Occupational Safety and Health, Division of Respiratory Disease Studies, Morgantown, West Virginia, USA 26505
Cellular and molecular effects of mineral and synthetic dusts and fibres: proceedings of the NATO Advanced Study Institute on Cellular and Molecular Effects of Mineral and Synthetic Dusts and Fibres, October 11-13, 1993, Paris, France