Research to Support and Implement Recreational Water Quality Criteria (RWQC)
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In 2012, EPA issued current recreational water quality criteria (RWQC) recommendations for ambient waters, reflecting the latest scientific knowledge, public comments, and external peer review. The criteria are designed to protect the public from exposure to harmful levels of pathogens in all water bodies designated for primary contact recreational uses, such as swimming, wading, and surfing. Low concentrations of human pathogens in ambient waters, most of which originate from fecal sources, are often difficult to detect but can result in elevated risks of human illness while recreating.
To help reduce health risks associated with exposure to fecal contaminants in recreational waters, scientists in EPA's Office of Research and Development are conducting research studies to strengthen the scientific basis of existing―or to advance new―fecal contaminant detection methods, source tracking, predictive tools, and health effects assessments that support human health RWQC recommendations.
Research activities are organized into three areas: (1) fecal indicator and pathogen analytical method development to support RWQC, (2) predictive modeling to support RWQC implementation for fecal indicators and pathogens, and (3) characterization of human health risks associated with fecal indicator and pathogen measurements.
Fecal Indicator and Pathogen Method Development to Support RWQC
EPA research focuses on the development of new or improved analytical methods for high priority fecal indicators, such as rapid fecal indicator bacteria methods, coliphage, and microbial source tracking tools, as well as the science to support implementation of these methods in recreational waters.
Rapid E. coli Enumeration in Recreational Beaches
The 2012 RWQC recommends tools to rapidly enumerate (measure concentrations of) fecal indicator bacteria Enterococcus spp. using the molecular method, quantitative real-time PCR (qPCR). Research leading to these criteria demonstrated the levels of Enterococcus spp. enumerated by qPCR and showed a positive relationship with gastrointestinal illness rates among beach-goers. Despite the added value of water quality same-day notification, there is a reluctance among some states and freshwater beach management authorities to adopt the Enterococcus spp. qPCR method due to the historical use of established Escherichia coli (E. Coli) culture-based water quality standards. In response, EPA is working to develop a rapid E. coli qPCR method for site-specific analysis.
Research activities include (1) a multiple laboratory method performance assessment of EPA methods for enterococci qPCR and E. coli qPCR and (2) the development of qPCR DNA standards for multiple laboratory implementation.
Coliphage
EPA researchers are investigating the potential use of coliphage as a viral indicator for RWQC applications. Viruses cause many illnesses associated with primary contact recreation in surface waters. Compared to bacteria, viruses are typically much smaller and more persistent through wastewater treatment and in environmental waters. Coliphages may be useful for evaluating surface water quality because they may exhibit numerous desirable indicator characteristics. Therefore, the development of coliphage as a viral indicator could represent a major improvement for future RWQC and the protection of human health. However, the smaller size and lower concentrations of coliphage in ambient waters have necessitated the development of improved concentration and detection methods.
Research activities include (1) the development of a method for the concentration and quantification of F-specific and somatic coliphage in fresh and marine waters, and (2) the characterization of relationships between coliphage and other fecal indicators in recreational waters.
Microbial Source Tracking (MST)
General fecal indicators (enterococci and E. coli) typically used to assess fecal pollution do not provide information about the source(s) of contaminants. Information on fecal sources is important because the level of human health risk can change from one animal source to another and water quality managers will likely use different remediation strategies based on the source of fecal pollution. EPA has published the first nationally validated protocols for human fecal pollution characterization in recreational waters. However, little guidance is currently available on the proper application of these standardized protocols.
Research activities include (1) the development of human and other fecal source-associated methods and the science to support implementation in recreational water settings and (2) MST case studies to evaluate performance in real-world scenarios.
- EPA Science Matters Article: Microbial Source Tracking: How Did That Get in There?
Recent Technical Publications
- Evaluation of Multiple Laboratory Performance and Variability in Analysis of Recreational Freshwaters by a Rapid E. coli qPCR Method (Draft Method C) (2019). This study determined the performance of 21 laboratories in meeting proposed, standardized data quality acceptance criteria and the variability of target gene copy estimates from these laboratories in analyses of 18 shared surface water samples by a draft qPCR method developed by EPA’s Draft Method C for E. coli.
- Standardized Data Quality Qcceptance Criteria for a Rapid E. coli qPCR Method (Draft Method C) for Water Quality Monitoring at Recreational Beaches (2019). This study developed proposed standardized data quality acceptance criteria that were established for important calibration model parameters and/or controls from a new qPCR method for E. coli (EPA Draft Method C) based upon data generated by 21 laboratories.
- Advancements in Mitigating Interference in qPCR for Microbial Water Quality Monitoring (2019). Enterococcus spp. and E. coli qPCR methods were evaluated for interference rates, contributing factors resulting in increased interference in these methods, and method improvements that reduced interference.
- Whole-Genome Sequencing of Four Campylobacter strains Isolated from Gull Excreta Collected from Hobie Beach (2019). Campylobacter spp. are commensal organisms in avian species and are recognized as the leading cause of bacterial foodborne diarrheal disease worldwide. This paper reports the draft genome of two Campylobacter volucris strains, and single isolates of C. lari, and C. jejuni isolated from California gull (Larus californicus) excreta collected from a southern California beach.
- Quantification of Plasmid DNA Standards for U.S. EPA Fecal Indicator Bacteria qPCR Methods by Droplet Digital PCR Analysis (2018). This report describes the application of droplet digital PCR analysis for the quantification of a set of synthetic plasmid DNA standards that have been made available for updated EPA Methods 1609.1 and 1611.1 as well as for EPA Draft Method C for E. coli.
- Incidence of Somatic and F+ Coliphage in Great Lake Basin Recreational Waters (2018). This paper reports the use of a dead-end hollow fiber ultrafiltration single agar layer method to enumerate F+ and somatic coliphage from surface waters collected from the Great Lakes.
- Biological Weighting Functions for Evaluating the Role of Sunlight-Induced Inactivation of Coliphages at Selected Beaches and Nearby Tributaries (2018). Reports on laboratory studies of light-induced inactivation of two coliphage groups—male-specific (F+) and somatic coliphage—under various conditions in phosphate-buffered water (PBW). Strains isolated from wastewater treatment facilities and laboratory strains (MS2 and phiX174 coliphages) were evaluated.
- Comparison of Somatic and F+ Coliphage Enumeration Methods with Large Volume Surface Water Samples (2018). Coliphages are alternative fecal indicators that may be suitable surrogates for viral pathogens, but majority of standard detection methods utilize insufficient volumes for routine detection in environmental waters. This study compared three somatic and F+ coliphage methods based on a paired measurement samples collected from the Great Lakes.
- Pollution Source-Targeted Water Safety Management: Characterization of Diffuse Human Fecal Pollution Sources with Land Use Information, Strategic Water Sampling, and qPCR (2019). In this case study, human-associated MST qPCR methods were combined with low-order stream sampling, precipitation information, and a high-resolution land use-based geographic information system (GIS) mapping to characterize trends in human fecal pollution diffuse sources on a watershed scale.
- Campylobacter jejuni Colonization in the Crow Gut reveals High Deletion Within Cytolethal Distending Toxin Gene Cluster (2018). Campylobacter spp. are major causes of gastroenteritis worldwide. The virulence potential of Campylobacter shed in crow feces obtained from a roost area in Bothell, Washington was studied and compared with isolates from other parts of Washington State and Kolkata, India.
- A Human Fecal Contamination Score for Ranking Recreational Sites using the HF183/BacR287 qPCR Method (2018). In this study, a standardized HF183/BacR287 qPCR method was combined with a water sampling strategy and a novel Bayesian weighted average approach to establish a human fecal contamination score (HFS) that can be used to prioritize recreational water sites for remediation based on measured human waste levels. The HFS was then used to investigate 975 study design scenarios.
- Global Distribution of Human-Associated Fecal Genetic Markers in Reference Samples from Six Continents (2018). This study investigated the geographic distribution of five human-associated genetic markers (HF183/BFDrev, HF183/BacR287, BacHum, BacH, and Lachno2) in untreated and treated municipal wastewaters from 29 urban and rural wastewater treatment plants situated across 13 countries spanning six continents. In addition, genetic markers were tested against 280 human and non-human fecal samples from domesticated, agricultural and wild animal sources.
- Evidence of Genetic Fecal Marker Interactions Between Water Column and Periphyton in Artificial Streams (2018). An indoor mesocosm study was conducted to simultaneously measure genetic fecal indicators in the water column and in the associated periphyton when subject to wastewater point source loading.
- Extended Persistence of General and Cattle-Associated Fecal Indicators in Marine and Freshwater Environment (2018). This paper investigated the influence of water type (freshwater versus marine) and select environmental parameters (indigenous microbiota, ambient sunlight) on the decay of fecal indicator bacteria and MST markers originating from cattle manure.
- Genetic and Antibiotic Resistance Characteristics of Campylobacter jejuni Isolated from Diarrheal Patients, Poultry and Cattle in Shenzhen (2018). In this study, genetic and antibiotic resistance characteristics of Campylobacter jejuni isolated from Shenzhen, China was investigated.
- Relationships Between Microbial Indicators and Pathogens in Recreational Water Settings (2018). In this review, 73 papers generated over 40 years that reported the relationship between at least one indicator and one pathogen group or species were examined.
- Relationships and Trends of E. Coli, Human-Associated Bacteroides, and Pathogens in the Proctor Creek Watershed (2017). This study measured culturable and molecular concentrations of E. coli, a human-associated Bacteroides marker (HF183MGB), and selected water-borne pathogens and toxins (Salmonella sp. and Shiga toxin) in surface water throughout a highly urbanized watershed to determine if any relationships exist between these parameters.
- Concentration and Quantification of Somatic and F+ Coliphage from Recreational Waters (2017). This study evaluated the ability of dead-end hollow fiber ultrafiltration and single agar layer procedure to concentrate and enumerate coliphages from ambient surface waters (lake, river, marine), river water with varying turbidities, and a simulated combined sewer overflow event.
- Bacteriophages as Indicators of Faecal Pollution and Enteric Virus Removal (2017). This paper summarizes concentrations of coliphages (F+ and somatic), Bacteroides spp. and enterococci bacteriophages in human waste, non-human waste, fresh and marine waters, and treated wastewater. Fate and transport characteristics in the environment and overview of the methods available for detection and enumeration of bacteriophages are also provided.
- Occurrence of Host-Associated Fecal Markers on Child Hands, Household Soil, and Drinking Water in Rural Bangladeshi Households (2016). Using the platform of a randomized controlled trial, this study evaluated whether provision of improved sanitation hardware (toilets and child feces management tools) and associated behavior change messaging reduces fecal contamination of drinking water, child hands, and soil among rural compounds in Bangladesh. We used host-associated genetic markers of human, ruminant, and avian feces, as well as rotavirus, as outcome measures.
- Differential Decomposition of Bacterial and Viral Fecal Indicators in Common Human Pollution Types (2016). Cultivated and molecular indicators of fecal pollution originating from fresh human feces, septage, and primary effluent sewage in a subtropical marine environment were assessed with an emphasis on the influence of ambient sunlight and indigenous microbiota. Genetic and cultivated fecal indicators, including fecal indicator bacteria, coliphage, Bacteroides fragilis phage (GB-124), and human-associated genetic indicators were measured in each sample.
Predictive Modeling to Support RWQC Implementation for Fecal Indicators and Pathogens
Contamination of ambient waters by harmful levels of pathogenic microorganisms occurs through complex, poorly understood interactions involving variable microbial sources, hydrodynamic transport, and microbial fate processes. Understanding the persistence of fecal indicators provides scientific information to assess their suitability for use as human pathogen surrogates in recreational waters.
Research activities include (1) fate and transport modeling of high priority microbial contaminants in watersheds and controlled microcosm studies in fresh and marine settings; and (2) development of microbial water quality forecast modeling with Virtual Beach and process models, including software design for coliphage and other contaminants.
Recent Technical Publications and Tutorials
- Capturing Microbial Sources Distributed in a Mixed-Use Watershed Within an Integrated Environmental Modeling Workflow (2018). This paper describes the underlying equations for microbial loading rates associated with land-applied manure on undeveloped areas from domestic animals; direct shedding on undeveloped lands by domestic animals and wildlife; urban or engineered areas; and point sources that directly discharge to streams from septic systems and shedding by domestic animals.
- Functional Evaluation of Three Manure-Borne Indicator Bacteria Release Models with Multiyear Field Experiment Data (2018). This study evaluated and compared performances of three manure-borne bacteria release submodels at the field-scale. Models included the exponential release model, the two-parametric Bradford and Schijven model, and the two-parametric Vadas-Kleinman-Sharpley model.
- Using Integrated Environmental Modeling to Assess Sources of Microbial Contamination in Mixed-Use Watersheds (2018). To evaluate microbial fate and transport in watersheds, this study used a loosely configured software infrastructure in microbial source-to-receptor modeling by focusing on animal- and human-impacted mixed-use watersheds.
- Quantitative Microbial Risk Assessment Tutorial—Primer (2017). This primer organizes QMRA tutorials that describe functionality of a QMRA infrastructure, guides the user through software use and assessment options, provides step-by-step instructions for implementing a mixed-use, watershed-based QMRA, and suggests the order for reading and reviewing the tutorials.
- Quantitative Microbial Risk Assessment Tutorial—Installation of Software for Watershed Modeling in Support of QMRA (2017). Provides instructions for accessing, retrieving, and downloading software to install on a host computer in support of QMRA modeling.
- Quantitative Microbial Risk Assessment Tutorial—SDMProjectBuilder: Import Local Data Files to Identify and Modify Contamination Sources and Input Parameters (2017). Consolidates information for gaining access to software used in support of QMRA modeling.
- Quantitative Microbial Risk Assessment Tutorial—Navigate the SDMPB and Identify an 8-digit HUC of Interest (2017). Reviews some of the screens, icons, and basic functions of the SDMPB that allow a user to identify an 8-digit HUC (HUC-8) of interest from which a pour point or 12-digit HUC (HUC-12) can be chosen for a microbial assessment. It demonstrates how to identify and delineate a HUC8-8, initiate the execution of SDMPB, navigate the SDMPB, use basic functions of the SDMPB tool bar, and identify and label a HUC-8.
- Quantitative Microbial Risk Assessment Tutorial – HSPF Setup, Application, and Calibration of Flows and Microbial Fate and Transport on an Example Watershed (2017). Combines several shorter tutorials and applies them to a complete watershed basin, from source to receptor. Prior to implementation, it is recommended that users become familiar with earlier boutique tutorials since many questions may be answered more concisely by them.
- SDMProjectBuilder: SWAT Setup for Nutrient Fate and Transport (2016). This Tutorial reviews some of the screens, icons, and basic functions of the SDMPB and explains how one uses SDMPB output to populate EPA’s Soil and Water Assessment Tool (SWAT) input files for nutrient fate and transport modeling in the Salt River Basin.
- Modeling the Influence of Septic Systems on Fecal Bacteria Load in a Suburban Watershed in Georgia (2017). In this study, EPA’s SWAT was used to assess the influence of septic systems on bacterial loads in a suburban watershed.
Characterization of Human Health Risks Associated with Fecal Indicator and Pathogen Measurements
Current RWQC rely on general fecal indicator bacteria, such as enterococci and E. coli, to estimate potential public health risk associated with polluted waters. This effort addresses a broad series of human health risk research topics, including the use of epidemiology, new analytical methods to quantify pathogen exposure, and quantitative microbial risk assessment (QMRA) to estimate public health risk in recreational settings.
Research activities include (1) the comparison of infection rates, self-reported symptoms, and water quality conditions with an emphasis on novel indicators, such coliphage, rapid E. coli qPCR, and human-associated MST procedures; (2) the use of QMRA to estimate potential public health effects in recreational water settings; (3) improved recreational user information, such as swimming duration, activities, and behaviors across age groups to more accurately assess beach-goer exposure to fecal pollutants; (4) use of saliva testing procedures to compare the incidence of specific waterborne infections among swimmers and non-swimmers at recreational fresh and marine beaches; and (5) the use of an animal model to develop estimates of Campylobacter loading potential of human and avian isolates.
Recent Technical Publications
- Exposure to Human-Associated Chemical Markers of Fecal Contamination and Self-Reported Illness Among Swimmers at Recreational Beaches (2018). This study estimated the association between chemical markers of human-derived fecal pollution and self-reported illness among recreational swimmers and determined whether chemical markers were able to identify source when used in combination with conventional fecal indicators (Enterococcus).
- Asymptomatic Norovirus Infection Associated with Swimming at aTropical Beach: A Prospective Cohort Study (2018). In this study, saliva samples were collected from 1,298 participants at a beach in Puerto Rico and tested for evidence of norovirus-specific IgG responses as an indicator of incident norovirus infection. Saliva was tested for IgG responses to GI.1 and GII.4 noroviruses using a microsphere based multiplex salivary immunoassay.
- Outbreaks Associated with Untreated Recreational Water—United States, 2000-2014 (2018). This report discusses 140 untreated recreational water–associated outbreaks that caused at least 4,958 illnesses and two deaths; 80 outbreaks were caused by enteric pathogens. Public health officials from 35 states and Guam voluntarily reported the outbreaks to CDC.
- Waterborne Disease Outbreaks Associated with Environmental and Undetermined Exposures to Water—United States, 2013-2014 (2017). This report discusses 15 outbreaks associated with an environmental exposure to water and 12 outbreaks with an undetermined exposure to water reported to CDC, resulting in at least 289 cases of illness, 108 hospitalizations, and 17 deaths. All outbreaks of legionellosis reported were associated with human-made water systems, including infrastructure intended for water storage or recirculation.
- Surveillance for Waterborne Disease and Outbreaks Associated with Drinking Water—United States, 2013-2014 (2017). This report discusses a total of 42 drinking water–associated outbreaks reported to CDC, resulting in at least 1,006 cases of illness, 124 hospitalizations, and 13 deaths. Legionella, Cryptosporidium, and Giardia duodenalis, and chemicals or toxins were implicated, including the first outbreaks associated with algal toxins.
- Exposure to Human-Associated Fecal Indicators and Self-Reported Illness Among Swimmers at Recreational Beaches: A Cohort Study (2017). This study estimated associations between human-associated Bacteroides markers in water and self-reported illness among swimmers at six U.S. beaches spanning 2003-2007.
- Coliphages and gastrointestinal Illness in Recreational Waters: Pooled Analysis of Six Coastal Beach Cohorts (2017). This study estimated the association between coliphages and gastrointestinal illness and compared it with the association with culturable enterococci. Data from six prospective cohort studies that enrolled coastal beach-goers in California, Alabama, and Rhode Island were pooled.
- Acute Gastroenteritis and Recreational Water: Highest Burden Among Young US Children (2016). This study estimated the gastroenteritis risks and illness burden associated with recreational water exposure and determine whether children have higher risks and burden.
- The Water Quality in Rio Highlights the Global Public Health Concern Over Untreated Sewage Disposal (2016). This commentary discusses the global public health problem of exposures to untreated sewage and describes the need for context specific solutions to monitoring and communication and risk assessment.