Water Filters and Giardia

Kyoto: Hiking from Kibune to Kurama

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In conclusion, during the past fifteen years, giardiasis has beenrecognized as one of the most frequently occurring waterborne diseases inthe United States. The most common sources of water contamination includeimproperly treated municipal sewage, infected animals, and indiscriminatedefecation by outdoorsmen. Chlorine concentrations in the 0.1 mg per literto 0.5 mg per liter range are largely ineffective against Giardia at thecontact times commonly employed by municipal water utilities. The long-term solution to the problem of municipal waterborne outbreaks of giardiasiswill involve appropriate pretreatment combined with improvements in andmore widespread use of filters in the municipal water treatment process.

While both micrometer- and submicrom eter-rated filters are being employedon a limited scale for personal or household use, further evaluation ofthe efficacy of filters distributed by different manufacturers is neededto enable individuals and public health personnel to distinguish those that are safe and effective from those that are not.