Effect of chlorine and monochloramine in drinking water on the developing rat fetus

Chlorine dioxide (ClO2) or monochloramine (NH2Cl) may be considered as an alternative to chlorine (HOCl) as a disinfectant in public water supplies, since chlorination produces trihalomethanes. This study was conducted to determine the effect of chlorine and monochloramine on rat fetuses. Female rats were administered 0, 1, 10 or 100 mg l−1 NH2Cl or HOCl daily in the drinking water for 2 1/2 months prior to and throughout gestation. Rats were sacrificed on Day 20 of gestation and fetuses were preserved for soft-tissue and skeletal examination. No significant increase in fetal resorptions was found in any treated group. A slight increase in skeletal variants (such as incompletely ossified or missing sternebrae, or rudimentary ribs) was seen in 10 and 100 mg l−1 HOCl groups. Soft-tissue defects, mainly improper orientation of the heart or adrenal agenesis, were observed in the 100 mg l−1 HOCl group. The percentage of total defects (skeletal and soft-tissue) was increased significantly over control in the 100 mg l−1 HOCl group; however, monochloramine did not produce any significant changes in rat fetuses at any dose level.