title: Comparing probabilistic microbial risk assessments for drinking water against daily rather than annualised infection probability targets.
abstract: Some national drinking water guidelines provide guidance on how to define 'safe' drinking water. Regarding microbial water quality, a common position is that the chance of an individual becoming infected by some reference waterborne pathogen (e.g. Cryptsporidium) present in the drinking water should < 10(-4) in any year. However the instantaneous levels of risk to a water consumer vary over the course of a year, and waterborne disease outbreaks have been associated with shorter-duration periods of heightened risk. Performing probabilistic microbial risk assessments is becoming commonplace to capture the impacts of temporal variability on overall infection risk levels. A case is presented here for adoption of a shorter-duration reference period (i.e. daily) infection probability target over which to assess, report and benchmark such risks. A daily infection probability benchmark may provide added incentive and guidance for exercising control over short-term adverse risk fluctuation events and their causes. Management planning could involve outlining measures so that the daily target is met under a variety of pre-identified event scenarios. Other benefits of a daily target could include providing a platform for managers to design and assess management initiatives, as well as simplifying the technical components of the risk assessment process.
authors: Centre for Water and Waste Technology, University of New South Wales, Sydney, NSW 2052, Australia. rsignor.pubs@gmail.com
authors: R S
authors: RS
authors: Signor
authors: N J
authors: NJ
authors: Ashbolt
mesh_terms: D006801:Humans; D015233:Models, Statistical; D015980:Public Health Practice; D018570:Risk Assessment / Q000379:methods*; D012308:Risk Management / Q000379:methods; D014871:Water Microbiology; D014881:Water Supply / Q000592:standards*