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Use of Quantitative Microbial Risk Assessment to Improve Interpretation of a Recreational Water Epidemiological Study
Citation:
Soller, J., Tim Wade, A. Ichida, S. Eftim, J. Clancy, R. McCuin, K. Schwab, G. Ramirez-Toro, S. Nappier, AND J. Ravenscroft. Use of Quantitative Microbial Risk Assessment to Improve Interpretation of a Recreational Water Epidemiological Study. Microbial Risk Analysis. Elsevier B.V., Amsterdam, Netherlands, 1:2-11, (2016).
Impact/Purpose:
A quantitative microbial risk assessment approach was used to help inform and interpret the results of an epidemiology study of the health effects of beach goers in Puerto Rico
Description:
We conducted a supplemental water quality monitoring study and quantitative microbial risk assessment (QMRA) to complement the United States Environmental Protection Agency’s (U.S. EPA) National Epidemiological and Environmental Assessment of Recreational Water study at Boquerón Beach in Puerto Rico to estimate the gastrointestinal (GI) illness levels associated with recreational water exposures. The previously reported epidemiological study had sufficient statistical power to detect an average illness rate of approximately 17 swimming associated GI illnesses per 1,000 recreation events or greater, and found no consistent relationships between water quality measured by fecal indicator bacteria (FIB) and swimming-associated illnesses (U.S. EPA, 2010a). The QMRA incorporated monitoring data for pathogens and fecal indicators collected during the epidemiological study period and calculated average swimming-associated illness levels that were approximately two GI illnesses per 1,000 recreation events. The QMRA results were consistent with the low rate of reported illnesses during the 2009 epidemiological study (i.e. <17 GI illnesses per 1,000 recreation events) and provide additional context for understanding the epidemiological results. The results illustrate that coupling QMRA with an epidemiological study at a single study site provides a unique ability to understand human health illnesses especially in conditions where water quality, as measured by traditional FIB is good and/or average illness rates are lower than can be quantified via epidemiological methods alone.
