|RICE, NANCY - Minnesota Department Of Health|
|ANDERSON, ANITA - Minnesota Department Of Health|
|STOKDYK, JOEL - Us Geological Survey (USGS)|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/8/2020
Publication Date: 10/21/2020
Citation: Burch, T.R., Rice, N., Anderson, A.C., Stokdyk, J.P., Borchardt, M.A. 2020. Quantitative microbial risk assessment for waterborne pathogens in non-disinfecting community and non-community wells in Minnesota. Meeting Abstract. Oct 13-14, 2020.
Technical Abstract: Non-disinfecting community and non-community wells are an important source of drinking water in the state of Minnesota, and the US Environmental Protection Agency has established an acceptable risk threshold of 1×10-4 infections/person/year for waterborne pathogens in public drinking water systems. However, the actual risk that drinking water consumers are exposed to is poorly understood because the requisite epidemiological studies are usually prohibitively expensive to conduct at the necessary scale. This study attempts to predict risk associated with 11 waterborne pathogens for non-disinfecting community and non-community wells in Minnesota using quantitative microbial risk assessment (QMRA) coupled with site-specific pathogen occurrence studies for each of 174 wells sampled during a 2-year time period. Results indicate that the range of risk estimates in this sample of wells is quite wide, varying from a 0% to a 100% chance of infection annually across system types (community vs. non-community) and phases (i.e., year 1 vs. year 2). Predicted risk for individual pathogens in median wells was generally low and almost always equal to 0, whereas predicted risk for all pathogens combined in median wells was often relatively high (3.1×10-2, 1.3×10-8, 1.1×10-1, and 2.4×10-2 infections/person/year for community phase 1, community phase 2, non-community phase 1, and non-community phase 2 wells, respectively). Furthermore, population-weighted means of risk predictions were generally higher than predicted risks for median wells, indicating that total risk in the population of consumers is likely driven by a small number of extreme exposure events in “problem” wells. Overall, risk predictions from this study suggest that the risk of waterborne infection and illness in Minnesota’s non-disinfecting community and non-community wells is higher than the USEPA’s acceptable risk threshold.