Comparing probabilistic microbial risk assessments for drinking water against daily rather than annualised infection probability targets

摘要

Some national drinking water guidelines provide guidance on how to define ‘safe’ drinking water.nRegarding microbial water quality, a common position is that the chance of an individualnbecoming infected by some reference waterborne pathogen (e.g. Cryptsporidium) present in thendrinking water should ,1024nin any year. However the instantaneous levels of risk to a waternconsumer vary over the course of a year, and waterborne disease outbreaks have beennassociated with shorter-duration periods of heightened risk. Performing probabilistic microbialnrisk assessments is becoming commonplace to capture the impacts of temporal variability onnoverall infection risk levels. A case is presented here for adoption of a shorter-duration referencenperiod (i.e. daily) infection probability target over which to assess, report and benchmark suchnrisks. A daily infection probability benchmark may provide added incentive and guidance fornexercising control over short-term adverse risk fluctuation events and their causes. Managementnplanning could involve outlining measures so that the daily target is met under a variety ofnpre-identified event scenarios. Other benefits of a daily target could include providing a platformnfor managers to design and assess management initiatives, as well as simplifying the technicalncomponents of the risk assessment process.