Application and refinement of the WHO risk framework for recreational waters in Sydney, Australia

Abstract

Local adaptation of the World Health Organisation (WHO) Farnham approach to managing pathogen risk in recreational waters was readily achieved given the extensive microbiological beach data for Sydney, and a clear understanding of applying the 'Annapolis Protocol' sanitary survey component to beach classification. Daily enterococci counts were predicted by rainfall (>10 mm in 24 h or >5 mm over 4-5 days), or by wind direction/speed, sunlight and tide during dry periods. Quantitative microbial risk assessment models (maximum risk exponential model for gastroenteritis and adenovirus exponential model for respiratory illness) fitted the United Kingdom epidemiological data and show potential for use. Flexibility in interpreting what is important for local conditions is essential, illustrated by replacing the general descriptions in the Farnham report with more ridged values for stormwater-impacted beaches. Hence, a user-friendly format for bather risk management, based on key environmental predictors of faecal pollution (such as rainfall, wind direction and tide) should largely replace the need for regular and costly microbiological testing; providing risk estimates in real time and allowing immediate control measures, such as signage or temporary beach closures. Ongoing testing resources should be directed to understanding the source(s) of faecal contamination, comparing enterococci/enteric virus survival under warm Australian conditions and spot checks for recalibration of environmental factors.