8 Exposure interventions

Evidence from epidemiological studies (Chapter 11) supports clear associations between faecal indicator organism density and exposure risk in waters contaminated with human sewage, but the utility of these pathogen indicators in bodies of water contaminated with animal waste and other non-point source pollution has been questioned (Kay et al. 1994, WHO 2001, Shuval 2003, Wade et al. 2006, Colford et al. 2007, US EPA 2009a). In this context, therefore, the results of such studies may be inconclusive, yet the reality of risks to human health associated with waterborne disease transmission remains irrefutable (Cotruvo et al. 2004, Craun et al. 2004, US EPA 2009b). Diffuse sources of contamination are commonplace; impacting both urban and rural settings in developed and developing nations alike. By some estimations, 99 per cent of all faecal contamination reaching surface waters is derived from the excreta of