Functional changes in the lungs of guinea pigs exposed to sodium sulfite aerosols

Abstract

Guinea pigs were exposed head only for 1 hr to submicrometer sodium sulfite aerosols (mass median aerodynamic diameter = 0.36 μm, σ g = 2.96) at 474, 669, and 972 μg SO 3 2−/m 3. Respiratory mechanics were measured in unanesthetized animals before, during, and after exposure. Dose-related increases in resistance and decreases in compliance were observed. At 972 μg SO 3 2−/m 3, the sodium sulfite aerosol caused a 50% increase in resistance and a 19% decrease in compliance. These changes were still present 1 hr after the end of exposure. The results were used to assess the irritant potency of sodium sulfite aerosol. Another group of guinea pigs was exposed whole body for 1 hr to the same aerosol at 0, 204, 395, and 1152 μg SO 3 2−/m 3. Immediately after the exposures, lung volume, diffusion capacity for carbon monoxide (DL CO), and wet lung weight were evaluated in anesthetized, tracheotomized animals. As compared to controls, total lung capacity, vital capacity, functional residual capacity, residual volume, and DL CO were all decreased with increasing concentrations of sodium sulfite. Dose-related increases in wet lung weights were also observed. These results were compared with the irritant responses of animals exposed to zinc oxide and sulfur dioxide mixed under different conditions of temperature and humidity.