In recent studies, we have documented that the biologic activity of quartz can be substantially reduced by surface chemistry modification with aluminum lactate treatment of the particles. In the present study, we evaluated the efficacy of aluminum lactate inhalation to reduce the biologic activity of experimental silicosis in the sheep tracheal lobe model. Four groups of 10 sheep were exposed once to either 100 ml phosphate-buffered saline (PBS) followed by aerosol inhalation of 10 ml PBS at monthly intervals (PBS-PBS group), to 100 ml PBS followed by inhalation of 100 mg aluminum lactate in 10 ml PBS (PBS-Al group), to 100 mg of quartz in 100 ml PBS followed by inhalation of 10 ml PBS (Si-PBS group), or to 100 mg of quartz in 100 ml PBS followed by inhalation of 100 mg aluminum lactate in 10 ml PBS (Si-Al group). Bronchoalveolar lavage (BAL) was repeated at monthly intervals for 6 months from before exposure (Month 0), and all sheep were autopsied at Month 6. All aerosol inhalations were carried out 24 h after BAL starting at Month 1 and monthly thereafter. In the PBS-PBS group and PBS-Al group, all BAL analyses remained at control levels and lung histology remained normal. In the Si-PBS group, BAL analyses documented significant sustained 3- to 10-fold increases in macrophages, lymphocytes, neutrophils, immunoglobulins, lactate dehydrogenase, glycosaminoglycans, lecithin, and phosphatidylglycerol, with histopathologic changes of nodular silicosis (pathologic score, 2.9 +/- 0.9) and mean retention of quartz at 2.83 +/- 0.98 micrograms/mg lung tissue.(ABSTRACT TRUNCATED AT 250 WORDS)