Modification of pulmonary silicotic reaction in rats exposed to coal fly ash.

Quartz exposure resulted in an increase in the wet weight, dry weight and collagen contents of lungs. Animals inoculated comparable amounts of fly ash revealed a statistically insignificant increase in these parameters. In silicotic rats exposed to fly ash the increase in the wet weight, dry weight and collagen contents of lungs was reduced in comparison to silicotic animals unexposed to coal fly ash. Histological examination of lungs revealed the development of silicotic granulomata with reticulin and collagen fibre formation. The difference in the development of these lesions was less pronounced when a blindfold comparison was made between the silicotic animals, exposed or unexposed to coal fly ash. The increased activity of LDH in the bronchoalveolar lavage (BAL) of rats exposed to quartz alone was mitigated significantly in silicotic animals subsequently exposed to coal fly ash. The protein content of the BAL increased significantly more in quartz-fly ash exposed animals than in rats exposed to either dust alone. The total cellular elements of the BAL were increased in rats exposed to quartz alone (p less than 0.005). The results demonstrate that fly ash exposure can significantly modify the development of a silicotic pulmonary reaction.