title: Human health risk implications of multiple sources of faecal indicator bacteria in a recreational waterbody.
abstract: We simulate the influence of multiple sources of enterococci (ENT) as faecal indicator bacteria (FIB) in recreational water bodies on potential human health risk by considering waters impacted by human and animal sources, human and non-pathogenic sources, and animal and non-pathogenic sources. We illustrate that risks vary with the proportion of culturable ENT in water bodies derived from these sources and estimate corresponding ENT densities that yield the same level of health protection that the recreational water quality criteria in the United States seeks (benchmark risk). The benchmark risk is based on epidemiological studies conducted in water bodies predominantly impacted by human faecal sources. The key result is that the risks from mixed sources are driven predominantly by the proportion of the contamination source with the greatest ability to cause human infection (potency), not necessarily the greatest source(s) of FIB. Predicted risks from exposures to mixtures comprised of approximately 30% ENT from human sources were up to 50% lower than the risks expected from purely human sources when contamination is recent and ENT levels are at the current water quality criteria levels (35 CFU 100 mL(-1)). For human/non-pathogenic, human/gull, human/pig, and human/chicken faecal mixtures with relatively low human contribution, the predicted culturable enterococci densities that correspond to the benchmark risk are substantially greater than the current water quality criteria values. These findings are important because they highlight the potential applicability of site specific water quality criteria for waters that are predominantly un-impacted by human sources.
authors.affiliation: Soller Environmental, LLC, 3022 King St, Berkeley, CA 94703, USA. Electronic address: jsoller@sollerenvironmental.com.
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Soller
authors.affiliation: Soller Environmental, LLC, 3022 King St, Berkeley, CA 94703, USA.
authors.forename: Mary E
authors.initials: ME
authors.lastname: Schoen
authors.affiliation: ICF International, LLC, 9300 Lee Highway, Fairfax, VA 22031, USA.
authors.forename: Arun
authors.initials: A
authors.lastname: Varghese
authors.affiliation: ICF International, LLC, 9300 Lee Highway, Fairfax, VA 22031, USA.
authors.forename: Audrey M
authors.initials: AM
authors.lastname: Ichida
authors.affiliation: Stanford University, Department of Civil and Environmental Engineering, Environmental and Water Studies, Stanford, CA 94305-4020, USA.
authors.forename: Alexandria B
authors.initials: AB
authors.lastname: Boehm
authors.affiliation: ICF International, LLC, 9300 Lee Highway, Fairfax, VA 22031, USA.
authors.forename: Sorina
authors.initials: S
authors.lastname: Eftim
authors.affiliation: U.S. Environmental Protection Agency, Office of Research and Development, 26 West Martin Luther King Drive, Cincinnati, OH 45268, USA.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Ashbolt
authors.affiliation: U.S. Environmental Protection Agency, Office of Water, Office of Science and Technology, 1200 Pennsylvania Avenue, NW, Washington, DC 20460, USA.
authors.forename: John E
authors.initials: JE
authors.lastname: Ravenscroft
mesh_terms: D000818:Animals; D001419:Bacteria; D016983:Enterococcus; D004784:Environmental Monitoring; D019453:Escherichia coli O157; D005243:Feces / Q000382:microbiology*; D005767:Gastrointestinal Diseases / Q000382:microbiology; D006801:Humans; D011336:Probability; D018570:Risk Assessment; D013552:Swine; D014481:United States; D014871:Water Microbiology; D014873:Water Pollutants / Q000032:analysis; D014876:Water Pollution; D060753:Water Quality; D014881:Water Supply
chemical_list: D014873:Water Pollutants
keywords: Faecal contamination; Microbial source apportionment; Quantitative microbial risk assessment; Recreational water