Animal Waste, Water Quality and Human Health

302Animal Waste, Water Quality and Human Health2000 associated with unfiltered Loch Katrine water and 140 cases in Aberdeenin 2002 associated with suboptimal filtration of River Dee water. Previousevidence has also suggested an association between consumption of unfilteredwater from Loch Lomond and cryptosporidiosis (Smith et al. 1993). Datawere analyzed from laboratory-confirmed cases of cryptosporidiosis collectedfrom 1997 through 2003 to determine risk factors. An association wasidentified between the incidence of cryptosporidiosis and consumption ofunfiltered drinking-water. This association supports public education effortswith respect to exposure risks and the exclusion of animals, domestic or wild,from the vicinity of water supplies as a means of controlling outbreaks ofcryptosporidiosis.8.4.7 Mitigation in the absence of a definitivehost attributionEven in the absence of a clearly defined host, one can imagine potential risks andpossible actions to assess and reduce those risks. A multi-barrier approach mayenhance protection of human health from source to water contact exposure(Robertson & Yasvinski 2006). As a first step, a sanitary or environmentalhealth and safety survey will assist in cataloging all potential sources ofcontamination, safety hazards, and user activity patterns which will create ablueprint on which to base management strategies for exposure interventions.The second step involves applying or implementing barriers to reduce risk(either reducing sources or preventing human contact during periods of elevatedrisk) (Robertson & Yasvinski 2006). In these cases monitoring water quality viaprimary or secondary water quality indicators is only part of the investigativeprocess. Results of any analytical tests must be taken in the proper context andin light of historical evidence of disease. Weight of evidence may serve as aproxy for indicators when direct monitoring of the water body is not feasible.8.5 CASE STUDIESIn this section three case studies are presented which illustrate the efficacy ofvarious human exposure intervention measures. The studies utilized variousassessment schemes to implement interventions as presented in this chapter:source attribution leading to improved drinking-water treatment, physicalalterations and disinfection to reduce bathing-water quality failures, andinformative signage based on predictive models to reduce exposure risk atScottish bathing beaches. While by no means comprehensive, they are good