title: Assessing protozoan risks for surface drinking water supplies in Nova Scotia, Canada.
abstract: Protozoa, such as Cryptosporidium parvum and Giardia lamblia, pose a human health risk when present in drinking water. To minimize health risks, the Nova Scotia Treatment Standards for surface water and groundwater under the direct influence of surface water require a 3-log reduction for Giardia cysts and Cryptosporidium oocysts. This study determined the protozoan risk of municipal surface source waters in Nova Scotia, through the use of a pre-screening risk analysis of water supplies, followed by subsequent water quality analysis of the seven highest risk supplies. The water supplies were monitored monthly for 1 year to obtain baseline data that could be used for a quantitative microbial risk assessment (QMRA). The QMRA model outcomes were compared to the Health Canada health target of 10(-6) disability-adjusted life years/person/year. QMRA modeling shows that the treatment facilities meet the required log reductions and disability-adjusted life year target standards under current conditions. Furthermore, based on the results of this work, Nova Scotia should maintain the current 3-log reduction standard for Giardia cysts and Cryptosporidium oocysts. The results of this study show that a pre-screening step can help to inform water sources that are particularly vulnerable to protozoan contamination, which can lead to more focused, cost-effective sampling, and monitoring programs.
authors.affiliation: Department of Civil and Resource Engineering, Dalhousie University, Halifax, NS, Canada B3J 1Z1 E-mail: graham.gagnon@dal.ca.
authors.forename: Wendy
authors.initials: W
authors.lastname: Krkosek
authors.affiliation: Department of Civil and Resource Engineering, Dalhousie University, Halifax, NS, Canada B3J 1Z1 E-mail: graham.gagnon@dal.ca.
authors.forename: Victoria
authors.initials: V
authors.lastname: Reed
authors.affiliation: Department of Civil and Resource Engineering, Dalhousie University, Halifax, NS, Canada B3J 1Z1 E-mail: graham.gagnon@dal.ca.
authors.forename: Graham A
authors.initials: GA
authors.lastname: Gagnon
mesh_terms: D016785:Cryptosporidium parvum / Q000502:physiology*; D060766:Drinking Water / Q000469:parasitology* / Q000592:standards; D016829:Giardia lamblia / Q000502:physiology*; D009674:Nova Scotia; D033661:Oocysts / Q000502:physiology; D018570:Risk Assessment; D012621:Seasons
chemical_list: D060766:Drinking Water