Animal Waste, Water Quality and Human Health

320Animal Waste, Water Quality and Human Healthaspects (based on national, provincial, state or local water quality guidelines), Yet,they are primarily or exclusively based on compliance with faecal indicatororganism (FIO) levels. It is not feasible to test for every type of human pathogenthat may be present in an aquatic environment. This is due to their great diversity,spanning the phylogenetic spectrum from viruses and bacteria to protozoa andworms, and due to the fact that detection methods are often difficult and costly(WHO 1999). Therefore, FIO are used as proxy-indicators of increasedprobability of pathogens’ presence (US EPA 1986, WHO 1999, WHO 2003).The ideal characteristics of microbial water quality indicators are outlined below:• their population density (without proliferation) should give a reasonableestimate of the likelihood of pathogen presence and should be positivelycorrelated with the potential health risks associated with exposure;• their presence should be exclusively and consistently associated with thesource of the actual pathogens;• compared to the most resistant pathogens that may be present at significantlevels they should demonstrate a similar level of resistance to environmentalstress;• their characteristics should support accurate quantification which can beachieved through simple and inexpensive detection methods;• their presence should be harmless to humans and animals; and,• they can be detected by laboratory methods in a short time period (i.e. hours)and provide consistent results (WHO 1997).In spite of their global usage, several constraints have been noted with respect tocurrent standards and guidelines based on FIO. For example:• management actions are retrospective and take place after the exposure hasoccurred (due to the time delay in obtaining results of bacteriologic tests)(Whitman et al. 1999, US EPA 2007);• highest health risks are attributed to human faecal contamination, followedby high-density cultivation of certain livestock, while the indicators may bederived from other, multiple sources (Chapter 11) and (Stavros 2003, Nevers& Whitman 2004, US EPA 2005);• there is a lack of inter-laboratory and global standardization with regard toanalytical data;• beach classification using indicator organisms alone results in a designationof either safe or unsafe with no provision for incremental increases in healtheffects (WHO 1999, Rees 1999);• faecal indicator organisms may not correlate well with the presence of somepathogenic organisms (Lund 1996, Lemarchand & Lebaron 2003); and,