title: Quantitative microbial risk assessment combined with hydrodynamic modelling to estimate the public health risk associated with bathing after rainfall events.
abstract: This study investigated the public health risk from exposure to infectious microorganisms at Sandvika recreational beaches, Norway and dose-response relationships by combining hydrodynamic modelling with Quantitative Microbial Risk Assessment (QMRA). Meteorological and hydrological data were collected to produce a calibrated hydrodynamic model using Escherichia coli as an indicator of faecal contamination. Based on average concentrations of reference pathogens (norovirus, Campylobacter, Salmonella, Giardia and Cryptosporidium) relative to E. coli in Norwegian sewage from previous studies, the hydrodynamic model was used for simulating the concentrations of pathogens at the local beaches during and after a heavy rainfall event, using three different decay rates. The simulated concentrations were used as input for QMRA and the public health risk was estimated as probability of infection from a single exposure of bathers during the three consecutive days after the rainfall event. The level of risk on the first day after the rainfall event was acceptable for the bacterial and parasitic reference pathogens, but high for the viral reference pathogen at all beaches, and severe at Kalvøya-small and Kalvøya-big beaches, supporting the advice of avoiding swimming in the day(s) after heavy rainfall. The study demonstrates the potential of combining discharge-based hydrodynamic modelling with QMRA in the context of bathing water as a tool to evaluate public health risk and support beach management decisions.
authors.affiliation: Norwegian University of Life Sciences (NMBU), P.O. Box 5003, N-1432 Ås, Norway. Electronic address: fasil.eregno@nmbu.no.
authors.forename: Fasil Ejigu
authors.initials: FE
authors.lastname: Eregno
authors.affiliation: Norwegian University of Life Sciences (NMBU), P.O. Box 5003, N-1432 Ås, Norway; Norwegian Institute for Water Research (NIVA), Gaustadalléen 21, 0349 Oslo, Norway.
authors.forename: Ingun
authors.initials: I
authors.lastname: Tryland
authors.affiliation: Norwegian Institute for Water Research (NIVA), Gaustadalléen 21, 0349 Oslo, Norway.
authors.forename: Torulv
authors.initials: T
authors.lastname: Tjomsland
authors.affiliation: Norwegian University of Life Sciences (NMBU), P.O. Box 5003, N-1432 Ås, Norway.
authors.forename: Mette
authors.initials: M
authors.lastname: Myrmel
authors.affiliation: Norwegian University of Life Sciences (NMBU), P.O. Box 5003, N-1432 Ås, Norway.
authors.forename: Lucy
authors.initials: L
authors.lastname: Robertson
authors.affiliation: Norwegian University of Life Sciences (NMBU), P.O. Box 5003, N-1432 Ås, Norway.
authors.forename: Arve
authors.initials: A
authors.lastname: Heistad
mesh_terms: D001493:Bathing Beaches / Q000706:statistics & numerical data*; D003458:Cryptosporidium; D004781:Environmental Exposure / Q000032:analysis / Q000706:statistics & numerical data*; D004926:Escherichia coli; D005872:Giardia; D006801:Humans; D057446:Hydrodynamics; D008962:Models, Theoretical; D009664:Norway / Q000453:epidemiology; D011634:Public Health; D011891:Rain; D018570:Risk Assessment; D012722:Sewage / Q000382:microbiology; D014871:Water Microbiology; D014876:Water Pollution / Q000706:statistics & numerical data*
chemical_list: D012722:Sewage
keywords: Bathing water; Hydrodynamic modelling; Microbial risk assessment; Public health