Toxicity of monochloramine in rat: an alternative drinking water disinfectant

Monochloramine (NH2Cl) is under consideration as an alternative to chlorine as a disinfectant in public water supplies, to avoid trihalomethanes formation. This study was conducted to investigate the toxicity of NH2Cl (0, 1, 10, 100 mg/l) in drinking water. Glutathione (GSH) content in rat blood was decreased significantly after 4 mo treatment, and the decreases were consistent throughout the treatment period. Treatment groups showed a slight increase in blood osmotic fragility. After acute administration (3 ml) of 20 and 40 mg NH2Cl/l, blood GSH levels were increased as early as 15 min and the increases were consistent up to 1 h. After 2 h exposure, however, the GSH content returned to the control value. At 3 mo, red-blood-cell count and hematocrit were decreased significantly, while after 10 mo treatment significant decreases in hemoglobin concentration and mean corpuscular hemoglobin were observed. Monochloramine administered in drinking water for 3 mo increased the incorporation of [3H]thymidine into nuclei of rat kidney and spleen in the 1- and 10-mg/l groups, while the incorporation in testes was increased only in the 100-mg/l group. The body weight of rats was decreased significantly in the highest treatment group after 3 mo treatment, and the decrease persisted throughout the period studied. An examination of blood chloroform content in all the groups after 4, 6, 9, and 12 mo showed no significant changes compared to the control.