Long-Term Continuous Exposure to Sulfuric Acid Mist in Cynomolgus Monkeys and Guinea Pigs

Groups of cynomolgus monkeys were exposed io sulfuric acid mist at concentrations varying from 0.38 to 4.79 mg/cu m. Particle size varied from submicronic to 4μ, mass median diameter (MMD). Groups of guinea pigs were exposed at 0.10 or 0.08 mg/cu m with MMD of 2.8, and 0.8μ, respectively. Exposures were continuous for 78 weeks in monkeys and 52 weeks in guinea pigs. The results signified no deleterious effects due to sulfuric acid mist exposure of guinea pigs. In cynomolgus monkeys, concentrations of 2.43 and 4.79 mg/cu m with particles of 3.60μ and 0.73μ MMD, respectively, were sufficient to produce definite deleterious effects on pulmonary structures and deterioration in pulmonary function. At lower concentrations the effects on pulmonary structures or deterioration in pulmonary function were less pronounced or absent. Microscopic changes observed were principally characterized by focal epithelial hyperplasia and focal thickening of the bronchiolar walls.