Respiratory effects from the inhalation of hydrogen chloride in young adult asthmatics

Almost no human data exist from controlled studies using low levels of hydrogen chloride (HCl), and, with no existing HCl ambient standards in the United States, the need for human health effects research is evident. In this study, five female and five male 18 to 25-year-old asthmatic subjects were exposed to filtered air, 0.8 ppm and 1.8 ppm HCl while wearing half-face masks, during three separate 45-minute experimental sessions involving 15 minutes exercise (treadmill walking), 15 minutes rest, followed again by exercise. Baseline and postexposure pulmonary function measurements were taken including forced expiratory volume in 1 second (FEV1), forced expiratory volume (FVC), maximal flow at 50% of expired vital capacity (Vmax50), maximal flow at 75% of expired vital capacity (Vmax75), and total respiratory resistance as well as peak flow. Nasal work of breathing and oral ammonia levels also were measured preexposure and postexposure. No significant pulmonary effects were found at these HCl concentrations and exposure duration. Nasal power showed no significant differences between test atmospheres; however, in isolation a significant decrease (P less than .01) was found in measurements of inspiration with exposure to 0.80 ppm. Ammonia levels showed a significant rise postexposure after both concentrations of HCl (paired t test, (P less than .01)), not seen after air exposure. In summary, the asthmatic subjects in this study showed no adverse respiratory health effects of inhalation of low concentrations of HCl.