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Kidney Week

Abstract: FR-PO966

Detection of Chlorite in Dialysis Water, an Unrecognized Safety Issue

Session Information

  • Patient Safety
    November 03, 2017 | Location: Hall H, Morial Convention Center
    Abstract Time: 10:00 AM - 10:00 AM

Category: Patient Safety

  • 1501 Patient Safety


  • Casey, Edward T., Orlando VAMC, Orlando, Florida, United States
  • Crowley, Susan T., Veterans Health Administration, West Haven, Connecticut, United States
  • Birdsong, Jeffrey, Orlando VAMC, Orlando, Florida, United States
  • Palevsky, Paul M., University of Pittsburgh, Pittsburgh, Pennsylvania, United States

Chlorine dioxide (ClO2) is increasing used by medical facilities as a water disinfectant to mitigate risk of environmental Legionella infection. When exposed to water, ClO2 generates chlorite (ClO2-), which may produce similar toxicity for dialysis patients as chlorine exposure. Although dialysis water is routinely tested for total residual chlorine that will detect chlorine, chloramines and ClO2, these methods will not detect residual chlorite. No specific safe level for residual chlorite has been established.


Our medical center injects ClO2 into the water supply due to Legionella concerns. Measurements of ClO2 and ClO2- were taken throughout the medical center, including dialysis water, on a weekly basis using a Nelco ChlordioX Plus instrument. Feed water ClO2 target level was 0.3-0.8 ppm, ClO2- maximum was 1 ppm. Water for dialysis is provided using portable RO with two pre-treatment granulated activated charcoal (GAC) filters. ClO2 and ClO2- testing was performed from the sampling port between the two GAC filters. After 8 months of undetectable levels, we detected 0.04 mg/L ClO2- from 1 of 4 portable RO units, with undetectable levels of ClO2. The GAC filters are replaced quarterly and had been replaced 7 weeks prior detection of ClO2-. Following replacement of the GAC, repeat testing showed undetectable levels of ClO2- and ClO2.


When ClO2 is used as a disinfectant for Legionella mitigation, it breaks down to yield chlorite, chlorate and chloride ions. While chlorate and chloride are effectively removed by GAC in dialysis water pretreatment, chlorite removal is not complete. We detected residual chlorite despite the GAC replacement 7 weeks earlier. After replacing the GAC filters, repeat sampling did not detect residual chlorite. Thus, the GAC appeared to remove ClO2 appropriately, but became saturated with chlorite well before the scheduled GAC replacement date. Although ClO2 is detected using the standard testing for total chlorine, chlorite is not. The effects of chronic low level exposure to chlorite are unknown, but potentially could lead to erythropoietin stimulating agent resistance and/or increased red blood cell destruction. Dialysis providers should be aware of this hazard, and recognize that more intensive monitoring and more frequent replacement of GAC may be required when ClO2 is present in municipal or hospital water.