Nick Ashbolt

US Environmental Protection Agency, USA

WEBCAST AVAILABLE

Dr Nicholas J. Ashbolt is a Title 42 Senior Research Microbiologist with the National Exposure Research Laboratory, U.S. EPA Cincinnati (since January 2007). Previously he was Head of the School of Civil and Environmental Engineering at the University of New South Wales (UNSW) Sydney, where he continues as an Adjunct Professor as well as at the University of Cincinnati. He has 25 years of experience in environmental microbiology, with a focus on the fate and transport of environmental pathogens. Over the last 10 years he has worked in joint Australian-Sweden and European programs developing methods to interpret pathogen data with the aid of quantitative microbial risk assessment within an urban water sustainability framework. This work has contributed to the risk-based approach adopted in the recently published WHO guidelines for recreational, drinking and reuse waters. He has published 31 book chapters, 112 journal papers and over 100 conference proceedings since he joined UNSW in 1994. His research at EPA is focused on distribution system biofilm pathogen risks and application of QMRA to aid in setting criteria for drinking and recreational waters.

Abstract: Predicting pathogen risks to aid beach management: the real value of QMRA

There has been an ongoing dilemma for agencies trying to set criteria for safe recreational waters, in how to provide for an overall (season) assessment of a beach versus guidance for day-to-day management. In essence the overall ‘safe’ criterion level, typically derived from epidemiologic studies of sewage-impacted beaches, is used as some percentile value for a single sample or a moving median of a limited number (e.g. five per month) of routine samples, which are reported the day after beach exposure has occurred! Internationally, good examples exist where predictive regression models (based on rainfall, wind speed/direction, etc.), which are empirically fitted for a particular beach, estimate on the day if the target fecal indicator density is likely to be met. However, at recreational swimming sites largely impacted by non-sewage sources of fecal indicators, there is concern that the epidemiologic-derived relationship to the indicator may weaken. Furthermore, recent epidemiologic evidence supports the use of qPCR-derived measures of Bacteroides as well as more traditional fecal indicators, but we understand less about the environmental fate of these molecular targets and bather risk. Hence, modeling pathogens and indicators within a quantitative microbial risk assessment framework can  provide a way to explore various scenarios of fecal contamination and hydrologic events, such as from waterfowl, agricultural animals, resuspended sediments and from the bathers themselves. Examples will be provided that suggest that more site-specific targets derived by QMRA could provide a useful alternative, which may then be managed to via predictive models or more traditional microbiological sampling.