Comparative pulmonary fibrogenic potential of selected particles

The comparative intrapulmonary fibrogenic potential of a number of chemically and physically characterized ashes and dusts was studied. Sprague-Dawley rats were exposed through intratracheal instillation to 5, 15, or 45 mg of stack-collected coal fly ash, electrostatic precipitator hopper-collected coal fly ash, bag-house filter-collected coal-oil mixture fly ash, Dowson and Dobson quartz, heated montmorillonite clay, and Mt. St. Helens volcano ash. Following a 3-month postexposure period, the animals were killed and subjected to histological examination. Some fibrosis was produced by all the ashes. However, the effects differed both qualitatively and quantitatively among the various exposure groups. The most severe fibrosis was found in the quartz-treated animals, followed in order of intensity by the heated clay, volcano, ash, hopper coal ash, stack coal ash, and coal-oil mixture ash. No effects were found in the saline-exposed control rats.