AMMONIA PRODUCTION IN INHALATION CHAMBERS AND ITS RELEVANCE TO CHLORINE INHALATION STUDIES

Inhalation exposure of animals to low concentrations of chlorine (ca. 1 ppm) may be complicated by the formation of chloramines from the reaction of ammonia, evolved from animal urine and feces, with chlorine. To address this problem, ammonia levels were determined by an indophenol method during a 6-hr period, in inhalation chambers using male, Fischer 344 rats under varying conditions of air flow and animal loading. At chamber air flows of 13, 26, or 40 liters/min, ammonia concentrations were obtained at 2, 4, and 6 hr for 1, 3, or 5% animal loading. Ammonia concentrations increased with time, peaking at 6 hr; they increased with increased percentage animal loading and decreased with increased chamber air flow. At 6 hr, for 13 liters/min, and 1, 3, or 5% animal loading, ammonia concentrations were 0.46, 1.91, and 2.42 ppm, respectively. At 40 liters/min, the ammonia levels at 6 hr were 0.22, 0.39, and 1.30 ppm for 1, 3, or 5% animal loading. Chloramines were detected in a chamber containing low concentrations of chlorine and ammonia (ca. 2 ppm each) by using a modified methyl orange method. These results suggest that, depending upon the variables indicated, sufficient ammonia may be evolved from animals in an inhalation chamber to reduce the amount of free chlorine present. Taken in conjunction with the toxic action of chloramines, such reduction may affect the outcome of chronic, low-level exposures to chlorine. © 1979.