Aerosol Synergism and Hydrate Formation—A Possible Connection

Abstract

Earlier experiments using guinea pigs and other laboratory animals have shown that aerosols of sodium chloride potentiate the irritant effects of inhaled sulfur dioxide and formaldehyde. This potentiation was not seen with other vapors such as formic acid and acetic acid; nor was it observed when water-insoluble aerosols were substituted for the sodium chloride. A simple explanation for these results would be that the potentiated vapors dissolved in the hydroscopic particulates and were thereby carried deeper into the respiratory tract. However, such an explanation does not explain the observed difference between potentiated and nonpotentiated vapors. Additionally, the retention time for dissolved vapors is too short to permit the aerosol to transport the dissolved vapor for any appreciable distance. Here it is pointed out that both sulfur dioxide and formaldehyde are hydrated in water solutions to compounds (methylene hydroxide and sulfite, respectively) that have low vapor pressures and are known to decompose only very slowly in water solution. The physical chemistry associated with the formation of these compounds may provide the desired explanation for the observed potentiating effect of inhaled sodium chloride aerosols.