Animal Waste, Water Quality and Human Health

384Animal Waste, Water Quality and Human Healthgiven mode of exposure (see Question 15) will be less, leading to decreasedprobability of infection. Question 8 is phrased as a statement to be completed,that is, “Dilution from Source to Exposure Site is…” with four possibleresponses offered. Those responses, and the relative risk assigned to them are:slight ( 500-fold) relative risk = 0.002The weights used are proportional to the means of the ranges of dilution specified.Question 9: Likelihood of mobilisation. Increased mobilisation of contaminantswill increase the load reaching the water body of concern. Mobilisation can beaffected by agricultural practices, for example, tile-drain systems are the mostfrequently reported route by which liquid manure can contaminate surface watercourses, but a range of other factors and practices affect mobilisation, forexample, the slope and direction of land and how it affects run-off, irrigationpractices, vegetation and so on. as discussed by Goss & Richards (2008).Question 9 is framed as a phrase to be completed: “The likelihood ofmobilisation is …” with four possible responses offered. Those responses, andthe relative risk arbitrarily assigned to them, are:high relative risk = 1medium relative risk = 0.1low relative risk = 0.01very unlikely relative risk = 0.001Questions 10 and 11: Effectiveness, and reliability of risk mitigating actions areincluded in recognition that sufficient knowledge exists to be able to reduce riskof contamination of surface water by various practices and actions, but only ifthey are reliably implemented. Such actions include “streambank retirement”,fences near waterways to prevent animal ingress, bridges over water courses toallow animals to cross without entering the water. The answers to both questionsare based on subjective assessments. Question 10 is framed as a statement to becompleted: “The effectiveness of risk mitigating factors is …“with five possibleresponses, as follows:absolute relative risk = 0extremely high relative risk = 0.0001high relative risk = 0.01medium relative risk = 0.1low relative risk = 1