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Event driven exposure and risk analysis for norovirus in drinking water

Abstract:

Risk Assessment studies that rely on mean exposure levels and ignore dynamic environmental features such as source water pathogen concentration and drinking water treatment levels, may not provide accurate risk estimates. This work presents a methodology to characterize the fluctuations in source water quality due to rainfall driven norovirus loadings, applied to a river case study modeled on the Ohio River. The simulated norovirus concentrations over a period of 340 days in source water ranges from 10-5 to 104 Viruses/L . The frequency and duration of these high concentration events could not be statistically captured using a simulated weekly sampling program, suggesting the need for higher frequency monitoring and/or model based analysis of sampling data. Using the simulated time series of norovirus concentration in treated water the pbkp_redicted annual mean rate of disease per 10, 000 persons was 0.0762 cases. The point risk estimates using a mean exposure concentration approach were significantly lower(10-3-10-2 per 10000 persons). These results suggest that accurate norovirus risk estimates from exposure to drinking water need to account for short term fluctuation in source water concentration and treatment efficiency. 2010 © American Water Works Association WQTC Conference Proceedings All Rights Reserved.