title: Efficacy of chlorine dioxide tablets on inactivation of cryptosporidium oocysts.
abstract: The ability of chlorine dioxide (ClO2) to achieve 2-log inactivation of Cryptosporidium in drinking water has been documented. No studies have specifically addressed the effects of ClO2 on C. parvum oocyst infectivity in chlorinated recreational water venues (e.g., pools). The aim of this research was to determine the efficacy of ClO2 as an alternative to existing hyperchlorination protocols that are used to achieve a 3-log inactivation of Cryptosporidium in such venues. To obtain a 3-log inactivation of C. parvum Iowa oocysts, contact times of 105 and 128 min for a solution containing 5 mg/L ClO2 with and without the addition of 2.6 mg/L free chlorine, respectively, were required. Contact times of 294 and 857 min for a solution containing 1.4 mg/L ClO2 with and without the addition of 3.6 mg/L free chlorine, respectively, were required. The hyperchlorination control (21 mg/L free chlorine only) required 455 min for a 3-log inactivation. Use of a solution containing 5 mg/L ClO2 and solutions containing 5 or 1.4 mg/L ClO2 with the addition of free chlorine appears to be a promising alternative to hyperchlorination for inactivating Cryptosporidium in chlorinated recreational water venues, but further studies are required to evaluate safety constraints on use.
authors.affiliation: Waterborne Disease Prevention Branch, Division of Foodborne, Waterborne, and Environmental Diseases, Centers for Disease Control and Prevention , Atlanta, Georgia 30329, United States.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Murphy
authors.forename: Charles N
authors.initials: CN
authors.lastname: Haas
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Arrowood
authors.forename: Michele C
authors.initials: MC
authors.lastname: Hlavsa
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Beach
authors.forename: Vincent R
authors.initials: VR
authors.lastname: Hill
mesh_terms: D000818:Animals; D002713:Chlorine / Q000494:pharmacology; D017606:Chlorine Compounds / Q000494:pharmacology*; D016785:Cryptosporidium parvum / Q000187:drug effects* / Q000254:growth & development; D004285:Dogs; D005456:Fluorescent Dyes / Q000378:metabolism; D054879:Halogenation / Q000187:drug effects; D007700:Kinetics; D008018:Life Cycle Stages / Q000187:drug effects; D061985:Madin Darby Canine Kidney Cells; D033661:Oocysts / Q000187:drug effects*; D010087:Oxides / Q000494:pharmacology*; D013607:Tablets; D013997:Time Factors
chemical_list: D017606:Chlorine Compounds; D005456:Fluorescent Dyes; D010087:Oxides; D013607:Tablets; D002713:Chlorine; C025109:chlorine dioxide