Effect of Possible Smog Irritants on Human Subjects

Various aerosols and gaseous mixtures were administered to adult male volunteer subjects by two methods, one using a mask, the other involving a chamber large enough for all subjects to occupy at the same time. The main effects of sulfur dioxide gas and sulfuric acid mist inhaled in this way were an increase in airway resistance and appearance of rales, with rhinorrhea and lacrimation. Two subjects exposed to sulfuric acid mist developed long-lasting bronchitic symptoms; the addition of water vapor increased the mean particle-size of the surfuric acid mist and intensified its irritant effects. These acid substances were neutralized and their irritant effects abolished by adding either ammonia gas or magnesium oxide smoke to the atmosphere. While acrolein and crotonaldehyde were highly irritant, formaldehyde was less so; acetaldehyde and its higher homologues were almost nonirritant. It was evident that neither the concentration of sulfur dioxide nor the total aldehyde content of an atmosphere is an adequate index of its irritant action, especially on people handicapped by disease or old age.