Animal Waste, Water Quality and Human Health

290Animal Waste, Water Quality and Human Health8.2.6 Mathematical modelingIn additional to categorizing direct and indirect contamination sources, a propersanitary survey also provides the framework for the collection of environmentalconditions which may be associated with influxes of faecal indicator organismsand pathogens. Correlations between environmental conditions such as rainfall,turbidity, and stream direction/speed may be explained through statisticalanalysis (Kay et al. 2005). The development of statistical models capable offorecasting or ‘nowcasting’ surface water quality based on a predetermined setof environmental conditions is known as predictive modeling (Nevers &Whitman 2005, Francy 2009).Predictive models, although conceptually simple, are a powerful statistical tooldeveloped for the assessment of rivers at various scales (from site-specific toanational scale) and coastal waters which are gaining prevalence in globalassessment schemes (Olyphant et al. 2003, Feio et al. 2009). Once operational,these tools are of value to water users, allowing them to make informed choicesabout behaviours to reduce exposure risk (Boehm et al. 2007, McPhail &Stidson 2009). Coastal beaches in the United States and Scotland successfullyrun predictive models for the protection of public health (Nowcast, http://www.ohionowcast.info/index.asp; Swimcast, http://www.lakecountyil.gov/Health/want/SwimCast.htm; and Beachline, http://www.sepa.org.uk/water/bathing_waters/bathing_signs.aspx).8.2.7 Limitations of current methodologiesAlthough there have been many successes in the development andstandardization of compliance monitoring schemes, the present approaches stillsuffer from limitations due to sampling reliability and source identification(Whitman & Nevers 2004). These limitations may influence their capacity toprotect public health from waterborne zoonotic disease, especially whenregulation is based primarily, or exclusively, on the detection of faecal indicatororganisms, whose reliability in reflecting the presence of pathogens has beenquestioned (Haack et al. 2008).8.3 OPPORTUNITIES FOR EXPOSURE REDUCTIONRoutine monitoring (based on faecal indicator organisms), sanitary surveys andspatial distribution studies, complemented by research initiatives (microbialsource tracking, modeling based on environmental parameters) can provideadequate information to initiate targeted remediation efforts within the