Effects of inhaled ammonium sulfate on benzo[a]pyrene carcinogenesis.

The effect of inhaled ammonium sulfate on benzo[a]pyrene carcinogenesis in the lungs of Syrian golden hamsters was studied. Exposure to ammonium sulfate at an airborne concentration 20 times average United States ambient levels resulted in a significant depression (p less than 0.05) of benzo[a]pyrene carcinogenesis in the first 6 mo of the study. However, at 2 yr, the termination of the study, there were no differences in cancer incidence between groups receiving benzo[a]pyrene and benzo[a]pyrene plus ammonium sulfate. In addition, at the concentration studied, inhaled ammonium sulfate did not significantly increase the incidence or severity of pneumonitis or pulmonary fibrosis in the hamster. However, this inhalation did increase the incidence of emphysema but not the severity. The decreased incidence of cancer during the first 6 mo of this study in animals receiving both benzo[a]pyrene and ammonium sulfate suggests that interaction between sulfate and benzo[a]pyrene does occur, but is insufficient to afford long-term protection against the development of cancer. No enhancement of carcinogenesis by benzo[a]pyrene occurs in the presence of inhaled sulfate.