Subchronic toxicity study of ozonated and ozonated/chlorinated humic acids in Sprague-Dawley rats: a model system for drinking water disinfection

Abstract

Male and female Sprague-Dawley rats were administered drinking water containing humic acids either non-disinfected for following ozonation (O{sub 3}) or ozonation/chlorination (O{sub 3}/Cl{sub 2}) for 90 consecutive days. Test animals drank either of two concentrations of humic acids, 0.25 and 1.0 g/L total organic carbon (TOC), while controls received phosphate-buffered, distilled water. No consistent significant treatment-related effects were observed in body weight gain, organ weights, food or water consumption, or hematological and clinical chemistry parameters. No target organs were identified from the histopathological examination of the tissues. The most significant observation, an increase in liver to body weight ratio for the male animals in the 1.0 g/L O{sub 3}/Cl{sub 2} humic acid group, was not observed in any other group, nor was it corroborated via any biochemical measurements or histopathological analysis. Kidney lesions, primarily chronic progressive nephropathy, were a common observation in both controls and treated groups with no apparent relationship to either humic acid concentration or the disinfection process.