title: Effect of cyanuric acid on the inactivation of Cryptosporidium parvum under hyperchlorination conditions.
abstract: Cyanuric acid (CYA) is a chlorine stabilizer used in swimming pools to limit UV degradation of chlorine, thus reducing chlorine use and cost. However, CYA has been shown to decrease the efficacy of chlorine disinfection. In the event of a diarrheal incident, CDC recommends implementing 3-log10 inactivation conditions for Cryptosporidium (CT value = 15 300 mg·min/L) to remediate pools. Currently, CYA's impact on Cryptosporidium inactivation is not fully determined. We investigated the impact of multiple concentrations of CYA on C. parvum inactivation (at 20 and 40 mg/L free chlorine; average pH 7.6; 25 °C). At 20 mg/L free chlorine, average estimated 3-log10 CT values were 17 800 and 31 500 mg·min/L with 8 and 16 mg/L CYA, respectively, and the average estimated 1-log10 CT value was 76 500 mg·min/L with 48 mg/L CYA. At 40 mg/L free chlorine, 3-log10 CT values were lower than those at 20 mg/L, but still higher than those of free chlorine-only controls. In the presence of ∼100 mg/L CYA, average 0.8- and 1.4-log10 reductions were achieved by 72 h at 20 and 40 mg/L free chlorine, respectively. This study demonstrates CYA significantly delays chlorine inactivation of Cryptosporidium oocysts, emphasizing the need for additional pool remediation options following fecal incidents.
authors.affiliation: †Waterborne Disease Prevention Branch, Division of Foodborne, Waterborne, and Environmental Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, United States.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Murphy
authors.affiliation: †Waterborne Disease Prevention Branch, Division of Foodborne, Waterborne, and Environmental Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, United States.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Arrowood
authors.affiliation: †Waterborne Disease Prevention Branch, Division of Foodborne, Waterborne, and Environmental Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, United States.
authors.forename: Xin
authors.initials: X
authors.lastname: Lu
authors.affiliation: †Waterborne Disease Prevention Branch, Division of Foodborne, Waterborne, and Environmental Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, United States.
authors.forename: Michele C
authors.initials: MC
authors.lastname: Hlavsa
authors.affiliation: †Waterborne Disease Prevention Branch, Division of Foodborne, Waterborne, and Environmental Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, United States.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Beach
authors.affiliation: †Waterborne Disease Prevention Branch, Division of Foodborne, Waterborne, and Environmental Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, United States.
authors.forename: Vincent R
authors.initials: VR
authors.lastname: Hill
mesh_terms: D000818:Animals; D002713:Chlorine / Q000494:pharmacology*; D016785:Cryptosporidium parvum / Q000187:drug effects* / Q000254:growth & development; D004203:Disinfection; D004285:Dogs; D054879:Halogenation / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D061985:Madin Darby Canine Kidney Cells; D033661:Oocysts / Q000187:drug effects; D016877:Oxidants / Q000737:chemistry; D010084:Oxidation-Reduction / Q000187:drug effects; D013997:Time Factors; D014227:Triazines / Q000494:pharmacology*
chemical_list: D016877:Oxidants; D014227:Triazines; D002713:Chlorine; C004632:cyanuric acid