Evaluation of the potential immunotoxicity of chlorinated drinking water in mice1These experiments were conducted in partial fulfillment of the requirements for the MSPH degree (A.S.F.) from the Department of Environmental Sciences and Engineering, School of Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.12Disclaimer: This report has been reviewed by the Environmental Protection Agency's Office of Research and Development, and approved for publication. Approval does not signify that the contents necessarily reflect the views of the Agency nor does mention of trade names or commercial products constitute endorsement or recommendation for use.2

Recent epidemiological studies have reported associations between the consumption of chlorinated drinking water and various types of human cancer; in addition, exposure to chlorine (Cl-) in drinking water has been reported to suppress certain immune functions in laboratory animals. The current studies were conducted to extend our knowledge of the effects of drinking water exposure to Cl-. Female C57BL/6 mice were administered hyperchlorinated drinking water (7.5, 15, or 30 ppm Cl-) for 2 weeks prior to sacrifice for evaluation of spleen and thymus weights, the plaque-forming cell (PFC) response, hemagglutination (HA) titer, and lymphocyte proliferation (LP). Significant reductions in organ weights and immune response were observed in the positive control groups (i.e. dexamethasone- or cyclophosphamide-exposed mice). No consistent differences were observed between the Cl--exposed animals and vehicle control mice for the evaluated parameters. Thus, under the conditions of these experiments, 2 weeks of exposure to hyperchlorinated drinking water had no apparent adverse effects on immune function.