EPA 823-R-07-006 

REPORT OF THE EXPERTS SCIENTIFIC WORKSHOP ON CRITICAL 

RESEARCH NEEDS FOR THE DEVELOPMENT OF NEW OR REVISED 

RECREATIONAL WATER QUALITY CRITERIA 

Airlie Center 

Warrenton, Virginia 

March 26-30, 2007 

U.S. Environmental Protection Agency 

Office of Water 

Office of Research and Development 

June 15, 2007 
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U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 i 

DISCLAIMER

This document has been reviewed in accordance with U.S. Environmental Protection Agency 

policy and approved for publication. Mention of trade names or commercial products does not 

constitute endorsement or recommendation for use. Furthermore, this document is a summary of 

the views of the individual workshop participants and approval for publication does not signify 

that the contents reflect the views of the Agency and no official endorsement should be inferred. 
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U.S. Environmental Protection Agency Experts Scientific Workshop

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ACKNOWLEDGMENTS

EPA would like to thank the experts and others who participated in the Experts Scientific 

Workshop on Critical Research Needs for the Development of New or Revised Recreational 

Water Quality Criteria. Their dedication and hard work at the workshop and following the 

workshop to produce these proceedings are greatly appreciated. 

Workshop Chair: 

Denise Keehner, USEPA 

Workshop Experts: 

Nicholas Ashbolt, USEPA 

Thomas Atherholt, New Jersey Department of Environmental Protection 

Michael Beach, Centers for Disease Control and Prevention 

Bart Bibler, Florida Department of Health 

Alexandria Boehm, Stanford University, California 

Rebecca Calderon, USEPA 

Jack Colford, University of California, Berkeley 

Elizabeth Doyle, USEPA 

Alfred Dufour, USEPA 

Lee Dunbar, Connecticut Department of Environmental Protection 

Lora Fleming, University of Miami School of Medicine and Rosenstiel School of Marine and 

Atmospheric Sciences, Florida 

Charles Hagedorn, Virginia Tech 

Joel Hansel, USEPA 

Lawrence Honeybourne, Orange County Health Care Agency, Santa Ana, California 

Donna Francy, U.S. Geological Survey 

Roger Fujioka, University of Hawaii, Manoa 

Toni Glymph, Wisconsin Department of Natural Resources 

Mark Gold, Heal the Bay, California 

Paul Hunter, University of East Anglia, U.K. 

Dennis Juranek, Centers for Disease Control and Prevention (retired) 

David Kay, University of Wales, U.K. 

Sharon Kluender, Wisconsin State Laboratory of Hygiene 

Erin Lipp, University of Georgia 

Graham McBride, National Institute of Water and Atmospheric Research, New Zealand 

Charles McGee, Orange County Sanitation District, California 

Samuel Myoda, Delaware Department of Natural Resources 

Charles Noss, USEPA 

Robin Oshiro, USEPA 

James Pendergast, USEPA 

Mark Pfister, Lake County Health Department, Illinois 

John Ravenscroft, USEPA 

William Robertson, Water, Air and Climate Change Bureau, Health Canada 

Stephen Schaub, USEPA 
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Mark Sobsey, University of North Carolina, Chapel Hill 

Jeffrey Soller, Soller Environmental, California 

Michael Tate, Kansas Department of Health and Environment 

Peter Teunis, RIVM (National Institute of Public Health and the Environment), Netherlands 

Gary Toranzos, University of Puerto Rico, Rio Piedras 

Timothy Wade, USEPA 

John Wathen, USEPA 

Stephen Weisberg, Southern California Coastal Water Research Project 

David Whiting, Florida Department of Environmental Protection 

Richard Zepp, USEPA 

Workshop Organizing Committee: 

Shari Barash USEPA 

Rebecca Calderon USEPA 

Elizabeth Doyle USEPA 

Alfred Dufour USEPA 

Samantha Fontenelle* USEPA 

Mark Gibson* ICF International 

Patricia Harrigan USEPA 

Peggy Himes Great Lakes Environmental Center 

Rick Hoffmann USEPA 

Audrey Ichida* ICF International 

Beth Leamond USEPA 

Patrick McCool Great Lakes Environmental Center 

Charles Noss USEPA 

Kevin Oshima USEPA 

John Ravenscroft* USEPA 

Grace Robiou USEPA 

Cynthia Roberts USEPA 

Stephen Schaub USEPA 

Timothy Wade USEPA 

John Wathen USEPA 

* Workshop proceedings document managers 

Appendix B includes a complete list of all persons who attended the workshop and their 

affiliations and contact information, including workshop experts, EPA resource personnel, and 

meeting support personnel (note takers, meeting facilitator, logistics staff). 

Report cover photo credits: 

Charles Hagedorn, Virginia Tech, Blacksburg 

Lawrence Honeybourne, Orange County Health Care Agency, Santa Ana, California 
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June 2007 v 

TABLE OF CONTENTS

DISCLAIMER...................................................................................................................................................................I

ACKNOWLEDGMENTS .................................................................................................................................................III

TABLES AND FIGURES................................................................................................................................................. IX

ACRONYMS.................................................................................................................................................................. XI

INTRODUCTION .............................................................................................................................................................1

1. APPROACHES TO CRITERIA DEVELOPMENT ...........................................................................................................9

1.1 BENCHMARKS FOR CRITERIA DEVELOPMENT ...................................................................................................11

1.2 INTEGRATION OF WORKSHOP COMPONENTS.....................................................................................................12

1.3 SUMMARY OF CURRENTLY AVAILABLE WATER QUALITY CRITERIA SETTING APPROACHES ...........................13

1.3.1 WHO Approach for Water Quality Criteria Setting..............................................................................13

1.3.2 EU Approach for Water Quality Criteria Setting ..................................................................................15

1.3.3 EPA 1986 Water Quality Criteria Setting .............................................................................................16

1.3.4 Summary of Proposed Criteria Development Approaches....................................................................18

1.3.5 Other Approaches Considered ..............................................................................................................20

1.4 SUMMARY OF CRITICAL ISSUES TO BE RESOLVED IN APPLYING AVAILABLE WATER QUALITY CRITERIA 

APPROACHES ...................................................................................................................................................20

1.4.1 Summary of Application of WHO Approach for U.S. Criteria Setting.................................................21

1.4.2 Summary of Application of EU Approach for U.S. Criteria Setting.....................................................23

1.4.3 Summary of Application of EPA 1986 Approach for U.S. Criteria Setting..........................................23

1.5 SUMMARY OF RESPONSE TO WORKGROUP CHARGE QUESTIONS ......................................................................24

1.6 CONCLUDING REMARKS ...................................................................................................................................33

2. PATHOGENS, PATHOGEN INDICATORS, AND INDICATORS OF FECAL CONTAMINATION .....................................35

2.1 APPLICATION OF MICROBIAL/BIOMARKER PARAMETERS .................................................................................37

2.2 TIERED TOOLBOX MONITORING APPROACH .....................................................................................................38

2.3 PARAMETERS FOR HAZARDOUS EVENT POLLUTION MONITORING....................................................................39

2.3.1 Microbiological Parameters ..................................................................................................................39

2.4 TRADITIONAL FECAL INDICATORS (COLIFORMS & ENTEROCOCCI) ....................................................................40

2.5 ALTERNATIVE FECAL INDICATORS ...................................................................................................................41

2.5.1 Bacteria .................................................................................................................................................41

2.5.2 Bacteriophages ......................................................................................................................................43

2.5.3 EU Project Summary of Tracers ...........................................................................................................46

2.6 PATHOGENS AND PATHOGEN INDICATORS........................................................................................................47

2.7 CHEMICAL BIOMARKERS OF FECAL CONTAMINATION......................................................................................49

2.7.1 Fecal Sterols..........................................................................................................................................49

2.7.2 Caffeine.................................................................................................................................................49

2.7.3 Optical Brighteners and Other Sewage Markers ...................................................................................50

2.8 RESEARCH NEEDS.............................................................................................................................................51

2.8.1 Within a 1 to 3 Year Timeframe ...........................................................................................................51

2.8.2 Longer-term Research Goals.................................................................................................................52

3. METHODS DEVELOPMENT .....................................................................................................................................57

3.1 INTRODUCTION .................................................................................................................................................59

3.2 CLASSES OF INDICATORS ..................................................................................................................................60

3.3 EVALUATING NEW METHODS FOR EXISTING INDICATORS................................................................................62

3.3.1 Health Risk Evaluation .........................................................................................................................62

3.3.2 Establishing Equivalency between New and Standard Methods...........................................................63

3.4 PERFORMANCE CRITERIA..................................................................................................................................63

3.5 EVALUATION PROCESS FOR ALTERNATIVE (NEW) INDICATORS........................................................................66
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3.6 EVALUATING SOURCE IDENTIFICATION METHODS - PROFICIENCY AND EVALUATION......................................67

3.6.1 Library-independent Methods ...............................................................................................................67

3.6.2 Non-microbial Methods ........................................................................................................................68

3.6.3 Library-Based Methods.........................................................................................................................68

3.7 MODIFICATIONS TO THE EVALUATION PROCESS WHEN INDICATORS ARE USED FOR OTHER APPLICATIONS....68

3.8 RESEARCH NEEDS.............................................................................................................................................69

4. COMPARING RISK (TO HUMANS) FROM DIFFERENT SOURCES ............................................................................75

4.1 INTRODUCTION .................................................................................................................................................77

4.2 SUMMARY OF WORKGROUP DISCUSSIONS AND REFLECTIONS ON WORKGROUP-SPECIFIC CHARGE AND 

QUESTIONS ......................................................................................................................................................80

4.3 OPTIONS FOR APPROACHES AND IMPLEMENTATION CONSIDERATIONS.............................................................82

4.4 RESEARCH NEEDS.............................................................................................................................................83

4.4.1 Epidemiological Studies........................................................................................................................83

4.4.2 Quantitative Microbial Risk Assessment ..............................................................................................85

4.4.3 Etiologic Agents....................................................................................................................................86

4.4.4 Fate and Transport.................................................................................................................................87

4.4.5 Determine the Occurrence of Pathogens in Affected Recreational Waters...........................................88

4.4.6 Bather Studies .......................................................................................................................................89

4.4.7 Additional Research..............................................................................................................................89

5. ACCEPTABLE RISK.................................................................................................................................................91

5.1 INTRODUCTION .................................................................................................................................................93

5.2 MAIN CONCLUSIONS AND OBSERVATIONS........................................................................................................93

5.2.1 Whether the Term ‘Acceptable Risk’ is Still the Most Appropriate Term............................................93

5.2.2 Public Involvement in ‘Acceptable Risk’ Decisions.............................................................................94

5.2.3 ‘Acceptable Risk’ Levels for the General Population...........................................................................95

5.2.4 ‘Acceptable Risk’ Levels for Vulnerable Subgroups............................................................................97

5.2.5 What are the Current Levels of Protection from Existing Criteria? ......................................................99

5.2.6 Potential Synergies for Health Protection between Revised Recreational Water Criteria and 

Standards for Drinking Water Sources and Shellfish Harvesting Waters ..........................................100

5.2.7 Areas of Discord .................................................................................................................................100

5.3 RESEARCH NEEDS...........................................................................................................................................100

6. MODELING APPLICATIONS FOR CRITERIA DEVELOPMENT AND IMPLEMENTATION ........................................105

6.1 INTRODUCTION ...............................................................................................................................................107

6.1.1 Water Quality Notification..................................................................................................................107

6.1.2 Sanitary Investigation Models..............................................................................................................109

6.2 HOW MODELS ARE CURRENTLY BEING USED.................................................................................................110

6.2.1 Sanitary Investigation Models..............................................................................................................110

6.2.2 Water Quality Notification Models.....................................................................................................111

6.2.1 Communication of Modeled Information to the Public and Recreational Water Managers ...............113

6.3 ADVANTAGES AND DISADVANTAGES OF MODELING ......................................................................................114

6.3.1 Advantages of Modeling .....................................................................................................................114

6.3.2 Disadvantages of Modeling.................................................................................................................115

6.4 MODEL DEVELOPMENT AND EVALUATION .....................................................................................................117

6.4.1 Initiating Model Development for Water Quality Notification...........................................................117

6.4.2 Model Development for Water Quality Notification ..........................................................................117

6.4.3 Data Needs for Simple Sanitary Investigation Model Development...................................................119

6.4.4 Cost Estimates.....................................................................................................................................119

6.4.5 Understanding the Uncertainty and Measuring Success of Statistical Models....................................119

6.5 RESEARCH NEEDS...........................................................................................................................................120

6.5.1 Short-term Research Needs (2 to 3 years)...........................................................................................121

6.5.2 Longer-term Research Needs (8 to 10 years)......................................................................................123

7. IMPLEMENTATION REALITIES .............................................................................................................................129
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7.1 APPLICATION TO SPECIFIC PROGRAM AREAS..................................................................................................131

7.1.1 Beach Monitoring and Water Quality Notification Programs.............................................................131

7.1.2 NPDES Permitting Programs ..............................................................................................................135

7.1.3 Monitoring and Assessment for CWA §303(d) and §305(b) ..............................................................136

7.1.4 Total Maximum Daily Load Program.................................................................................................139

7.1.5 Important Differences Between Workgroup Members as to Views/Observations..............................140

7.2 EVALUATION OF ALTERNATIVE APPROACHES FOR CRITERIA DEVELOPMENT ................................................140

7.2.1 WHO Approach ..................................................................................................................................141

7.2.2 EU Approach.......................................................................................................................................143

7.2.3 Existing U.S. Model – 1986 Criteria...................................................................................................144

7.2.4 Alternative Approaches.......................................................................................................................145

7.3 RESEARCH NEEDS...........................................................................................................................................145

7.3.1 Near-term (Next 1 to 3 Years).............................................................................................................146

7.3.2 Long-term (Beyond 3 Years) ..............................................................................................................147

APPENDIX A: CHARGE TO THE EXPERT WORKGROUP MEMBERS ........................................................................ A-1

APPENDIX B: PARTICIPANT LIST............................................................................................................................. B-1

APPENDIX C: TRANSLATION OF EPIDEMIOLOGY TO DISEASE BURDEN BY WHO AND EU................................... C-1

APPENDIX D: SUMMARY OF THE EUROPEAN COMMISSION DIRECTIVE................................................................ D-1

APPENDIX E: INDICATOR TERMINOLOGY............................................................................................................... E-1

APPENDIX F: SUMMARY OF MEASUREMENTS CURRENTLY PLANNED FOR THE DOHENY AND MALIBU

 BEACH (CALIFORNIA) EPIDEMIOLOGY STUDY..................................................................................F-1

APPENDIX G: DEVELOPMENT OF DETERMINISTIC MODELS.................................................................................. G-1
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TABLES AND FIGURES

TABLE 1. WHO CLASSIFICATION MATRIX FOR INTEGRATING MICROBIAL WATER QUALITY AS

MEASURED BY ENTEROCOCCI DENSITY WITH SANITARY INSPECTION CATEGORY............................14

TABLE 2. NUMERICAL MICROBIOLOGICAL WATER QUALITY ASSESSMENT CLASSIFICATION FOR FRESH 

(INLAND) AND MARINE (COASTAL AND TRANSITIONAL) BATHING WATERS FOR THE 24 EU 

MEMBER STATES...............................................................................................................................16

TABLE 3. SUMMARY OF EPA’S 1986 RECOMMENDED WATER QUALITY CRITERIA FOR BACTERIA AND

2004 RULE.........................................................................................................................................17

TABLE 4A. SUMMARY OF PROPOSED CRITERIA DEVELOPMENT APPROACHES: STRENGTHS AND

LIMITATIONS .....................................................................................................................................18

TABLE 4B. SUMMARY OF THREE PROPOSED CRITERIA DEVELOPMENT APPROACHES: BENCHMARKS ...............19

TABLE 5. COMPARING RISKS (TO HUMANS) FROM DIFFERENT PATHOGEN SOURCES .......................................78

TABLE 6. RESEARCH NEEDS AND RANKINGS FROM FIVE “ACCEPTABLE RISK” WORKGROUP MEMBERS .......103

TABLE E-1. DEFINITIONS FOR INDICATOR AND INDEX MICROORGANISMS OF PUBLIC HEALTH CONCERN ........E-1 

TABLE F-1. SUMMARY OF MEASUREMENTS CURRENTLY PLANNED FOR THE DOHENY AND MALIBU

BEACH (CALIFORNIA) EPIDEMIOLOGY STUDY................................................................................. F-1

TEXT BOX E-1. DEFINITIONS OF KEY FECAL INDICATOR MICROORGANISMS...........................................................E-1 

FIGURE 1. FLOW DIAGRAM OF HOW THE WORKGROUP COMPONENTS CONTRIBUTE TO THE

DEVELOPMENT OF NEW OR REVISED RECREATIONAL WATER QUALITY CRITERIA.............................3

FIGURE 2. CLEAN WATER ACT: WATER QUALITY STANDARDS OVERVIEW........................................................5

FIGURE 3. FLOW DIAGRAM OF HOW THE WORKGROUP TOPICS CONTRIBUTE TO THE DEVELOPMENT AND 

IMPLEMENTATION OF NEW OR REVISED RECREATIONAL WATER QUALITY CRITERIA ......................13

FIGURE 4A. ENTEROCOCCI (MPN/100 ML) SAMPLED EVERY 10 MINUTES AT A BEACH IN CALIFORNIA ...........108

FIGURE 4B. SUBTROPICAL MARINE BEACH (MIAMI, FLORIDA): 48 HOURS SAMPLING ......................................108

FIGURE 5. THE POSSIBLE FATES OF MICROBES (FECAL INDICATORS AND PATHOGENS) IN

ENVIRONMENTAL WATER AND SEDIMENT ......................................................................................124

FIGURE C-1. A PROBABILITY DENSITY FUNCTION OF FECAL INDICATOR DISTRIBUTIONS MEASURED AT A 

RECREATIONAL WATER SHOWING PROBABILITY OF EXPOSURE (Y AXIS) VERSUS LOG10 

FECAL STREPTOCOCCI CONCENTRATION.........................................................................................C-2

FIGURE C-2. THE DOSE-RESPONSE RELATIONSHIP DERIVED FROM KAY ET AL. (1994) (A) AND THE

FUNCTIONAL FORM USED TO DERIVE THE 2003 WHO GUIDELINE VALUES (B)..............................C-2

FIGURE C-3. COMBINING THE DOSE-RESPONSE CURVE AND THE PDF TO PRODUCE A RELATIVE DISEASE

BURDEN ASSESSMENT FOR ANY BEACH OR REGION........................................................................C-3
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ACRONYMS 

7Q10 the lowest streamflow for 7 consecutive days that occurs on average once 

every 10 years 

AWQC ambient water quality criteria 

ASABE American Society of Agricultural and Biological Engineers 

ATP adenosine triphosphate 

BEACH Act Beaches Environmental Assessment and Coastal Health Act of 2000 

BMP Best Management Practices 

CAFO concentrated animal feeding operation 

CDC Centers for Disease Control and Prevention 

cfu colony forming unit 

CSO combined sewer overflow 

CWA Clean Water Act 

DNA deoxyribonucleic acid 

DU designated use 

EHEC enterohemorrhagic E. coli

EPA U.S. Environmental Protection Agency 

EU European Union 

FDA U.S. Food and Drug Administration 

FFU focus forming units 

GC/MS gas chromatography-mass spectrometry 

GI gastrointestinal 

GIS geographic information systems 

GM geometric mean 

HACCP Hazard Analysis Critical Control Point 

HEV hepatitis E virus 

HIV/AIDS human immunodeficiency virus/acquired immune deficiency syndrome 

HPLC high performance liquid chromatography 

HSPF Hydrological Simulation Program-Fortran 

ILSI International Life Sciences Institute 

IMS immunomagnetic separation 

ISO International Organization for Standardization 

L Liter 

mL Milliliter 

MPN Most Probable Number 

MST microbial source tracking 

NASBA nucleic acid sequence based amplification 

NEEAR National Epidemiological and Environmental Assessment of Recreational 

Water Study 

NOAA National Oceanic and Atmospheric Administration 

NPDES National Pollutant Discharge Elimination System 

NPS non-point source program 

NWS National Weather Service 

PCR polymerase chain reaction 

pfu plaque forming unit 
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POP probability of precipitation 

POTW publicly owned [wastewater] treatment works 

QMRA quantitative microbial risk assessment 

qPCR quantitative polymerase chain reaction 

RCT randomized controlled trial 

RDS relative standard deviation 

RMSE root mean square error 

RNA ribonucleic acid 

SAFE Swimming Advisory Forecast Estimate 

SCCWRP Southern California Coastal Water Research Project 

SD standard deviation 

SETAC Society of Environmental Toxicology and Chemistry 

SRC sulphite-reducing clostridia 

SSM single sample maximum 

SSO sanitary sewer overflow 

STEC shiga-toxin producing E. coli 

SWMM Storm Water Management Model 

TMA transcription-mediated amplification 

TMDL total maximum daily load 

UAA Use Attainability Analysis 

U.K. United Kingdom 

URI upper respiratory illness 

U.S. United States 

USGS U.S. Geological Survey 

UV ultraviolet light 

WQS Water Quality Standards 

WHO World Health Organization (United Nations) 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 1 

INTRODUCTION 

Purpose of the Workshop

Since the U.S. Environmental Protection Agency (hereafter EPA or the Agency) last published 

recreational water quality criteria in 1986, there have been significant advances, particularly in 

the areas of molecular biology, microbiology, and analytical chemistry. EPA believes that that 

these new scientific and technical advances need to be factored into the development of new or 

revised Clean Water Act (CWA) Section 304(a) criteria for recreation. To this end, EPA has 

been conducting research and assessing relevant scientific and technical information to provide 

the scientific foundation for the development of new or revised criteria. The enactment of the 

Beaches Environmental Assessment and Coastal Health (BEACH) Act of 2000 (which amended 

the CWA) required EPA to conduct new studies and issue new or revised criteria, specifically for 

Great Lakes and coastal marine waters. 

From March 26 through 30, 2007, EPA convened a group of 43 national and international 

technical, scientific, and implementation experts from academia, numerous states, public interest 

groups, EPA, and other federal agencies, at a formal workshop to discuss the state of the science 

on recreational water quality research and implementation. 

The purpose of the workshop was for EPA to obtain individual input from members of the broad 

scientific and technical community on the “critical path” research and science needs for 

developing scientifically defensible new or revised CWA §304(a) recreational ambient water 

quality criteria (AWQC) in the near-term. Near-term needs were defined as specific research 

and science activities that could be accomplished in 2 to 3 years so that results are available to 

EPA in time to support the development of new or revised criteria. The new or revised criteria, 

which would be available from EPA in roughly 5 years (2012), must be scientifically sound, 

protective of the designated use, implementable for broad CWA purposes, and when 

implemented, provide for improved public health protection. (See Appendix A for the full 

charge to the experts.) The Agency wants to develop this new or revised criteria in a highly 

participatory framework within the next 5 years based on the best available science. 

Workshop Design

The Experts Scientific Workshop on Critical Research and Science Needs for the Development of 

New or Revised Recreational Water Quality Criteria was designed to be similar in organization 

and format to the Society of Environmental Toxicology and Chemistry (SETAC) Pellston 

Workshops, where technical experts in a particular subject area are invited to participate and 

evaluate current and prospective environmental issues. A Pellston-type workshop typically 

brings together between 40 to 50 technical experts from academia, business, government, and 

public interest groups. Experts are semi-sequestered for up to a week to facilitate focused 

discussions and individual and collaborative writing of a draft summary report by the end of the 

workshop. Subject leaders are then responsible for consolidating, editing, producing, and 

distributing the final (formal) workshop proceedings. 
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Participant Affiliation Balance 

In addition to U.S. and international experts drawn from academia, public interest groups, and 

numerous state and other federal agencies, EPA selected several experts from within EPA to 

serve in the workgroups (see Appendix B for participant list). The 43 experts serving in 7 

subject areas were supported by a total of 9 EPA resource personnel, 10 note takers, 3 logistics 

contractors, and a professional facilitator. The proper balance between EPA presence and 

outside experts was crucial for keeping the discussions on track with EPA’s needs from the 

workshop while providing ample opportunity for the external experts to voice their opinions and 

intellectually explore topics of interest to EPA. 

Agenda Overview 

The workshop began on Sunday evening, March 25, 2007, with a logistics meeting for the 

workgroup chairs, EPA staff, and note takers. The plenary sessions on Monday served to orient 

participants regarding CWA §304(a) AWQC and EPA’s needs from the workshop discussions 

and these proceedings. Monday afternoon the seven workgroups met for the first time to discuss 

interpretation of the charge questions (Appendix A). On Tuesday, all workshop participants met 

in a plenary session, which was followed by workgroup sessions throughout the day. The 

agenda facilitated and encouraged the workgroups to meet with each other to discuss common 

and overlapping issues. At the end of the day the workshop participants met again in plenary to 

hear report-outs from each workgroup chair that described their progress for the day. 

Because the seven workgroup topics have many overlapping issues, it was important for the 

groups to communicate as needed so they could both stay informed of and build on each other’s 

discussions. In addition to several joint breakout sessions, the workgroup chairs also shared all 

of their meals to discuss ongoing progress. On Wednesday, the workshop participants met once 

again in a plenary session to discuss overall progress followed by workgroup breakout sessions 

where each group continued discussions and began writing a draft workgroup report. The 

workgroups continued writing on Thursday. Friday morning, each workgroup turned in a 10 to 

20 page draft report and their respective chairs provided an overview of each report regarding the 

major themes discussed and critical research needs in a final plenary session. 

Seven Workgroup Topics 

The seven workgroup topics are presented in seven chapters in this report. The relationships 

between these and other topics are graphically represented in Figure 1. In Figure 1 shaded boxes 

correspond to the seven workgroups. The alternatives boxes in Figure 1 refer to various possible 

indicators that a toolbox approach could provide for each of the CWA applications. The charge 

questions helped the workgroups to define the scope of their discussions. The experts were 

asked to provide their individual insights on the state of the science as well as critical path 

research that could be completed by EPA in the next 2 to 3 years. A short description of each 

workgroup and the tasks EPA asked them to discuss follows. 
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June 2007 3 

Figure 1. Flow Diagram of How the Workgroup Components 

Contribute to the Development of New or Revised Recreational 

Water Quality Criteria. 

1. Approaches to Criteria Development – focus on a toolbox approach as well suggest 

other potential approaches for new or revised criteria development. 

2. Pathogens, Pathogen Indicators, and Indicators of Fecal Contamination – discuss the 

strengths and limitations of indicators of fecal contamination, pathogen index 

microorganisms, and specific pathogens for development of new or revised recreational 

AWQC. 

3. Methods Development – discuss methods for quantifying indicators and pathogens, such 

as culture-based methods, molecular-based methods (e.g., quantitative polymerase chain 

reaction [qPCR]), and faster culture-based methods and their applicability for AWQC. 

4. Comparing Risks to Humans from Different Sources – discuss the relative risks of 

illness to humans in waters contaminated with human fecal material versus animal fecal 

material. 

5. Acceptable Risk – discuss the level of risk to various populations that would be 

associated with numeric AWQC. EPA was interested in the science necessary to inform 

the policy decision regarding the target risk range and the process through which the 

policy decision could be reached. 

6. Modeling Applications to Criteria Development and Implementation – discuss 

predictive modeling approaches and their potential applications in implementation of 

AWQC. 

Criteria Development

Chapter 1

Indicator(s)

Chapter 2

“Acceptable 

Risk”

Chapter 5

Implementation

Realities

Chapter 7

Method(s)

Development

Chapter 3

Risks to Humans

from Different 

Sources

Chapter 4

Assessment

(based on

monitoring

data)

NPDES

Permitting

Primary

Contact

Waters

Alternatives for 

Water Quality 

Notification

TMDLs Predictive 

Modeling

Chapter 6

Other

Indicators

Alternatives

Alternatives
U.S. Environmental Protection Agency Experts Scientific Workshop

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7. Implementation Realities – identify and consider factors that influence implementation 

of criteria for each of the CWA uses (beach monitoring and notification, development of 

National Pollutant Discharge Elimination System [NPDES] permits, assessments to 

determine use attainment, and development of total maximum daily loads [TMDLs]. 

Background 

Clean Water Act §304(a) Recommended Criteria 

What are EPA’s Recommended §304(a) Criteria? 

CWA §304(a) AWQC are (typically) expressed as numeric concentrations of pollutants. These 

are essentially the numbers that EPA recommends that States and Tribes adopt in setting their 

own Water Quality Standards (WQS) to protect waters for specified designated uses. State and 

Tribal WQS, once approved by EPA, are the effective standards used in CWA regulatory and 

non-regulatory programs. Figure 2 provides an overview of CWA WQS. 

States and Tribes classify waters by their designated use,1

 which includes “primary contact 

recreation.” States and Tribes typically define primary contact recreation to encompass 

recreational activities that could be expected to result in the ingestion of, or immersion in, a 

waterbody (such as swimming, water skiing, surfing, or any other recreational activity where 

ingestion of, or immersion in, the water is likely). 

CWA §304(a): 

• AWQC often are described as concentrations in the water column and generally have a 

time and duration component. 

• AWQC could be expressed as an annual average concentration that should not be 

exceeded; a daily value or seasonal concentration that should not be exceeded; or a value 

that should not be exceeded, on average, more than one time every 3 years (for acute 

aquatic life criteria). 

• AWQC are often associated with EPA-approved analytical methods. This is partly 

because without EPA-approved methods to measure concentrations in effluent, States are 

reluctant to adopt criteria in WQS that are then used in NPDES permits (see more below). 

States typically adopt the recommended criteria into their WQS (i.e., regulations promulgated 

using state rulemaking processes [similar to Federal regulation development]). 

What do States do with these EPA-recommended Numbers and how are they used by States? 

Increasingly, because of the dynamics of State rulemaking processes and public and regulated 

community involvement, States are reluctant to adopt EPA’s recommended criteria unless the 

 1

 CWA designated use (DU) classifications are narrative statements describing appropriate intended human 

and/or aquatic life and other quality objectives for waterbodies. 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 5 

Figure 2. Clean Water Act: Water Quality Standards Overview. 

underlying science supports the desired environmental result and the criteria can be implemented 

for all aspects of their CWA Programs. 

Under CWA §304(a)(9), EPA is required to publish new or revised water quality criteria for 

pathogens and pathogen indicators (including a revised list of testing methods, as appropriate) 

for the purpose of protecting public health in coastal recreation waters. Coastal recreation waters 

In general, States and Tribes have four options (§303(c)): 

• Adopt EPA §304(a) criteria 

• Modify §304(a) criteria to reflect regional considerations 

• Develop their own criteria (scientifically defensible) 

• Adopt narrative criteria where numeric criteria cannot be determined 

Also: 

• EPA reviews changes to State or Tribal criteria for protection of the designated use 

and scientific defensibility 

• State and Tribal criteria are not effective for CWA purposes until approved by EPA 

• In the case of multiple DUs, criteria must support the most sensitive use 

• State-adopted and EPA-approved State and Tribal WQS form the regulatory 

compliance numbers for CWA purposes 

CWA Water Quality Standards are composed of 3 parts: 

• Designated use (DU) 

• Ambient water quality criteria (AWQC) to support the DU 

• Antidegradation provisions to protect existing uses and high quality waters 

Designated Use (§303(c)) 

• Use Attainability Analysis (UAA) 

required if fishable/swimmable uses 

not assigned 

• Economic and social impacts may be 

considered

Criteria for 

protection of 

aquatic wildlife 

EPA AWQC for protection of human health 

• Criteria based on DU 

• Separate criteria for each pollutant (§304(a)) 

• EPA AWQC are guidance only
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 6 

are marine and Great Lake waters designated by States for use for swimming, bathing, surfing, or 

similar water contact activities. Under CWA §303(i)(1)(B), States are then required to adopt 

new or revised WQS for those pathogens and pathogen indicators for which EPA’s new or 

revised criteria have been developed. States must submit these standards to EPA for approval or 

disapproval. EPA approves the standards if they are scientifically defensible and protective of 

the designated use.

Once approved, State WQS become effective for CWA purposes. This means that the Stateadopted §304(a) criteria become regulatory standards and are used for several different CWA 

purposes, including the following: 

• §303(d) listings. Under §303(d) of the CWA, States prepare lists of waters that are 

impaired and need TMDLs; States develop the lists every 2 years and submit them to 

EPA for approval. If States determine that waters are not meeting applicable water 

quality standards (whether from point or non-point sources of pollution), States are to 

identify those waters as “impaired” under §303(d). 

• TMDL calculations for impaired waters must be prepared to implement the applicable 

State WQS.

• NPDES permits, which are issued after State WQS are in place for a pollutant, must 

have discharge limits as stringent as necessary to meet such WQS. EPA’s analytical 

methods are often used to measure compliance with permit limits. 

• Public Notification at Beaches. Under the BEACH Act of 2000, eligible coastal and 

Great Lakes States may apply for and receive BEACH Act grants for their beach 

monitoring and public notification programs. Those States use their recreational contact 

WQS to determine whether to close an area for swimming or issue a swimming advisory. 

Toolbox Approach 

EPA’s recommended AWQC have to be applicable at a national level. A toolbox approach is 

under consideration because of the potential for greater flexibility in selecting situationallyappropriate indicators/methods and increased options for implementation, which is desirable for 

nationally applicable criteria. A toolbox allows for the use of varied techniques and approaches 

to achieve public health protection. 

A preliminary working definition of the Toolbox approach for recreational water quality criteria 

might be the following: 

The toolbox approach is a set of potential microbiological (i.e., a microbe plus a specified 

enumeration method) and/or physico-chemical assays that could be employed alone, or in 

certain combinations, to protect and restore the recreational use of waters. The contents 

of the toolbox (the “tools”) would be used by State public health and water quality 

agencies for beach advisory/closing program purposes and for all other Water Quality 

Standard related regulatory purposes under the CWA. The level of risk (or public health 

protection) would be the same regardless of which tool is used. 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 7 

Although the toolbox concept allows a context for considering feasibility and applicability of 

different indicator and method combinations in developing new or revised recreational criteria 

under CWA §304(a), it is critical that there is an understanding of the relationship among the 

different methodologies for proper implementation of the criteria. For example, if EPA 

recommended one type of indicator for one set of uses (e.g., culturable enterococci) and also 

recommended the use of a DNA-based method (e.g., enterococci qPCR) for other uses, then 

there would have to be an understanding of the meaning of those multiple measures (i.e., 

linkage) in the context of the overall CWA §304(a) program. Without a clear understanding of 

the linkage and context of different methods the entire “toolbox” concept becomes 

unmanageable from a regulatory perspective. 
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U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 9 

CHAPTER 1 

APPROACHES TO CRITERIA DEVELOPMENT 

Joel Hansel, Chair, USEPA 

Mark Gold, Heal the Bay, California 

David Kay, University of Wales, U.K. 

John Ravenscroft, USEPA 

William Robertson, Water, Air and Climate Change Bureau, Health Canada 

Jeffrey Soller, Soller Environmental, California 

David Whiting, Florida Department of Environmental Protection 
[this page intentionally left blank] 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 11 

1.1 Benchmarks for Criteria Development 

The workgroup was charged with answering 21 questions and providing a range of alternatives 

for the development of new or revised national recreational ambient water quality criteria 

(AWQC; see Section 1.5 for summary response). The following six potential approaches that 

could be used or adapted for an approach to develop new or revised criteria were initially 

discussed: (1) EPA’s 1986 approach, (2) World Health Organization (WHO), (3) European 

Union (EU), (4) Hazard Analysis and Critical Point Analysis (HAACP), (5) Heal the Bay’s 

Beach Report Card, and (6) EPA’s Air Quality Index. The workgroup members concentrated the 

discussions on the three approaches that were deemed most appropriate for consideration in the 

context of Clean Water Act (CWA) Section 304(a) ambient water quality criteria (AWQC), 

namely, the WHO approach (with possible modifications), the EU approach (adopted 2006), and 

a modified version of EPA’s 1986 criteria. Before the workgroup defined the approaches and 

determined the potential application of the three alternative approaches, workgroup members 

agreed that it was critical to identify desirable attributes or benchmarks for the criteria. The 

benchmarks or attributes that were identified are summarized below. 

1. The criteria are health-based. The workgroup demonstrated a preference that the criteria 

be as directly as possible anchored to health effects demonstrated in epidemiology 

studies. 

2. The criteria should demonstrate utility for and be compatible with all of the CWA 

§304(a) criteria (as amended by the Beaches Environmental Assessment and Coastal 

Health Act of 2000 [BEACH Act]) needs, including water quality assessment for public 

notification at beaches in a timely manner, assessment for impaired waters listings, 

development of total maximum daily load (TMDL) development and implementation, 

and development of National Pollution Discharge Elimination System (NPDES) permits. 

3. The criteria should be scientifically defensible for application in a wide variety of 

geographical locations (climatic conditions), including fresh and marine waters, and 

temperate, subtropical, and tropical waters. 

4. The criteria be sufficiently robust and flexible so that they can be configured to protect 

the public health of those exposed to recreational water impacted by sewage effluent, 

concentrated animal feed operation (CAFO) contaminated runoff, non-point sources (e.g., 

agriculture [non-CAFO], urban runoff) and waters not impacted by anthropogenic 

sources. 

5. The criteria should be sufficiently robust and flexible so that they can be configured to 

provide regulators the ability to protect susceptible (sensitive) subpopulations such as 

children and immunocompromised individuals. Commonality was found among 

workgroup members that protecting the health of children was of paramount concern. 

6. The criteria are associated (linked) with analytical methods that are reliable, robust, and 

provide reproducible results. 

7. The criteria should protect primary contact recreation in freshwaters, marine waters, 

temperate, subtropical, and tropical waters equally. Similarly, the criteria should provide 

equal protection those exposed to effluent, urban runoff, and/or non-point source runoff 

impacted waters via primary contact recreation. 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 12 

The workgroup members agreed that all seven of the above attributes are critical considerations 

for criteria development. In assessing the potential application of each of the proposed 

alternatives, it is important to keep in mind that criteria applied to these alternatives are assumed 

to be consistent with all of the above attributes (or at least most of them) before the final 

frameworks and criteria are developed. The likelihood that some of these attributes will not be 

met in the near-term seems to make the WHO or EU approaches more suitable for 

implementation. 

The workgroup expressed the opinion that EPA should release the new or revised criteria and 

implementation guidance concurrently to provide clarity to States on how the criteria should be 

used for regulatory and public notification needs. 

1.2 Integration of Workshop Components 

A summary of the interactions between the various subject areas addressed in this workshop is 

presented in Figure 3. In Figure 3 shaded boxes correspond to the seven workgroups. The 

alternatives boxes in Figure 3 refer to various possible indicators that a toolbox approach could 

provide for each of the CWA applications. Briefly, the Pathogen/Pathogen Indicator workgroup 

proposes indicators that may have utility for criteria development (see Chapter 2). In doing so, 

they consulted with the Methods Development workgroup members (see Chapter 3) to assure 

that validated methods are or could be available and usable for the implementation of the 

proposed parameter. Different methods have different specificities for identifying whether the 

source of fecal contamination is human- or animal-based. The Comparing Risks workgroup 

provided information on the relative risks to human health from different sources of fecal 

contamination (Chapter 4). Once identified, the pathogen/pathogen indicator and the associated 

method are used during the criteria development process. Another critical component in the 

criteria development process is the identification of a risk level. Information from the 

Acceptable Risk workgroup (see Chapter 5) on how to develop “acceptable risk” thresholds is 

used in this context during the criteria development process. The Modeling workgroup discussed 

how predictive modeling can be used to inform criteria approaches and to provide information on 

water quality notification (Chapter 6). Once these pieces were integrated, an initial check was 

conducted against the suggestions and concerns of the Implementation Realities workgroup (see 

Chapter 7) members to help ensure that the potential for criteria development does not conflict 

with actual “on the ground” implementation. 

As discussed in the Introduction to these proceedings, recreational AWQC are used for a number 

of purposes. First, these criteria are used to make assessment determinations under CWA 

§305(b) and §303(d).2

 Within this regard and depending on the framework, a number of 

alternate indicators or methods may be used to assist in making the determination as to the 

overall quality of a waterbody and the compliance with the underlying criteria. Second, these 

criteria are used to determine permit limits for NPDES permit holders and for TMDL purposes. 

Finally, these criteria are used to determine the acceptability of the water for direct primary 

contact recreation. Conceptually, alternative indicators, including models, could also be used for 

these purposes. 

 2

 http://www.epa.gov/owow/tmdl/tmdl0103/ 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 13 

Criteria 

Development

Indicator(s)

“Acceptable 

Risk”

Implementation

Realities

Method(s)

Development

Risks to Humans

from Different 

Sources

Assessment

(based on

monitoring

data)

NPDES

Permitting

Primary

Contact

Waters

Alternatives for 

Water Quality 

Notification

TMDLs Predictive 

Modeling

Other

Indicators

Alternatives

Alternatives

Figure 3. Flow Diagram of How the Workgroup Topics 

Contribute to the Development and Implementation of New or 

Revised Recreational Water Quality Criteria. 

1.3 Summary of Currently Available Water Quality Criteria Setting Approaches 

The three alternatives that were identified by the workgroup were a modified WHO approach, 

the EU approach, and a modified version of the EPA 1986 approach because all of these 

approaches are largely based on peer reviewed epidemiology studies and some version of each of 

these frameworks are in use currently in at least one country. 

Workgroup members generally agreed that all three criteria development approaches are feasible 

providing the criteria meet the becnhmarl/attributes listed above. Although the workgroup 

briefly discussed other approaches such as the EPA’s Air Quality Index, HAACP, and Heal the 

Bay’s Beach Report Card approaches, none of these approaches were deemed to be appropriate 

for the desired purposes for a variety of reasons, including lack of applicability for criteria 

development. 

1.3.1 WHO Approach for Water Quality Criteria Setting 

The WHO has been concerned with health issues associated with recreational water 

environments for many years and has published several influential reports that represent a well 

accepted view among international experts (Prüss, 1998). The WHO approach provides a basis 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 14 

for standard setting in light of local and regional circumstances, such as the nature and 

seriousness of local endemic illness, exposure patterns, and competing health risks that are not 

associated with recreational water exposure. 

The WHO approach is based on the perspective that recreational water quality and protection of 

public health are best described by a combination of sanitary inspection and microbial water 

quality assessments (the WHO [2003] Guidelines use enterococci as the fecal indicator of 

choice; see Table 1). This approach considers possible sources of pollution in a recreational 

water (“sanitary inspection category” in Table 1), as well as observed levels of fecal pollution 

(“microbial water quality assessment category” in Table 1), and combines them into a five-level 

classification scheme for recreational water environments. To date, the classification system has 

been used primarily to “grade” recreational waters and to provide an assessment for regulatory 

compliance purposes. This approach however, also could be adapted for other CWA §304(a) 

applications such as NPDES permitting and TMDL development. 

The microbial water quality assessment criteria are based on a banded system, where the band 

divisions are equivalent to a risk of acquiring gastrointestinal (GI) illness for (A) <1 case in 100 

exposures, (B) <1 case in 20 exposures, (C) <1 case in 10 exposures, and (D) >1 case in 10 

exposures. The 95th percentile value was selected as an appropriate descriptor of the microbial 

probability density function because it is easily understood to be the probability of encountering 

Table 1. WHO Classification Matrix for Integrating Microbial Water 

Quality as Measured by Enterococci Density with Sanitary Inspection 

Category. 

SOURCE: WHO, 2003. 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 15 

polluted water and focuses on water quality that is likely to cause illness (i.e., greater probability 

of illness associated with increasing density of human sources of fecal pollution). The WHO 

levels of risk for the bands described above were selected based on a series of science policy 

decisions in consultations with numerous international experts and were intended to be 

reasonable for both the developed and developing world. The expectation in the United States is 

that the “acceptable risk” (see Chapter 5) levels would be similar or more protective than the risk 

levels adopted by other developed countries. The methodology used to derive the 2003 WHO 

Guideline values is summarized in Appendix C. 

The sanitary inspection category is intended to classify the risk of illness caused by fecal 

pollution in a recreational waterbody, although human fecal pollution will tend to drive the 

overall sanitary inspection category derived for an area. WHO experts believe that the three 

most important sources of human fecal contamination of recreational water environments for 

public health purposes are typically sewage, riverine discharges, and direct contamination from 

bathers. Sanitary inspections are required to address those sources as well as others, and 

inspections should take on a tiered approach, dependent on the level of perceived risk and its 

uncertainty. For example, if human and domestic fecal pollution is considered low based on land 

uses, but fecal indicator counts are relatively high, further exploration of the source(s) and their 

relative risks would be recommended. This higher level of examination (tier) may utilize more 

expensive methods and approaches and further cycles (tiers) of investigation as necessary. 

Based on the results of the sanitary inspections, recreational waters are ranked (from very low to 

very high) with respect to evidence for the degree of influence of fecal material. 

1.3.2 EU Approach for Water Quality Criteria Setting 

The EU broadly adopted the 2003 WHO Guidelines in formulating the 2006 Bathing Water 

Directive. A summary of the European Commission Directive is provided in Appendix D. The 

approach incorporates the following fundamental elements: 

• The EU starts with the WHO risk assessment framework, but does not include the 

sanitary inspection category information for the purposes of recreational water 

classification. Instead, it uses only the microbial water quality assessment information to 

characterize the probability of exposure to human pathogens. 

• The EU approach used the WHO microbiological criteria for marine waters and applied 

the same risk assessment framework to new epidemiological data to derive standards for 

fresh recreational waters. 

• The EU approach allows sample discounting. Under discounting, numeric excursions 

above the water quality standards that are predicted and/or measured do not count against 

the waterbody for compliance determination (i.e., such values are discounted from the 

data set prior to calculation of the 95th percentile, but only 15% of scheduled samples can 

be so discounted). Sample discounting is allowed when a predictive model, source 

reduction plan, and communication management system are in place to inform the public 

about short-term pollution events derived during predictable conditions (e.g., rainfall). 

The EU Bathing Water Directive (7/EU/EEC; dated February 15, 2006) is currently being 

translated by Member States for implementation (EP/CEU, 2006). The Directive establishes 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 16 

separate numerical microbiological criteria for fresh (inland) and marine (coastal and 

transitional) bathing waters for the 24 EU Member States (Table 2). The numerical values are 

based on epidemiological studies reported by Kay et al. (1994) and Wiedenmann et al. (2006)—

the former was used by WHO in formulating their Guidelines (Kay et al., 2004; WHO, 2003). 

Table 2. Numerical Microbiological Water Quality Assessment Classification for 

Fresh (Inland) and Marine (Coastal and Transitional) Bathing Waters for the 24 EU 

Member States. 

Inland (Fresh) Waters 

Indicator Excellent Good Sufficient 

(Intestinal) enterococci (cfu/100 mL) 200* 400* 360** 

E. coli (cfu/100 mL) 500* 1,000* 900** 

Coastal and Transitional (Marine) Waters 

Indicator Excellent Good Sufficient 

(Intestinal) enterococci (cfu/100 mL) 100* 200* 200** 

E. coli (cfu/100 mL) 250* 500* 500** 

Notes: * = Based on a 95th percentile evaluation; ** = Based on a 90th percentile evaluation to 

reduce the risk of statistical anomalies when using a small data set, which also allows lower limit 

values for enterococci and E. coli densities in inland waters to be classified as sufficient versus 

good microbiological water quality. 

Source: Adapted from EP/CEU (2006). 

1.3.3 EPA 1986 Water Quality Criteria Setting

In the late 1970s and early 1980s, EPA conducted public health studies evaluating several 

organisms as possible indicators, including total and fecal coliforms, E. coli, and enterococci. 

The studies showed that enterococci and E. coli are the best predictors of GI illness 

(gastroenteritis) in sewage effluent-impacted freshwaters, while enterococci were the best 

predictor in sewage-impacted marine waters. Gastroenteritis describes a variety of diseases that 

affect the GI tract and are rarely life-threatening; self-limiting symptoms include nausea, 

vomiting, stomachache, diarrhea, headache, and fever. Based on these studies, EPA published a 

criteria document, Ambient Water Quality Criteria for Bacteria – 1986, recommending the use 

of these bacterial indicators in ambient water quality criteria values for the protection of primary 

contact recreation (US EPA, 1986). Table 3 summarizes the Water Quality Standards for 

Coastal and Great Lakes Recreation Waters Rule (US EPA, 2004) that requires States and 

Tribes to adopt the 1986 AWQC for Bacteria. 

States and Tribes generally define their designated use of “primary contact recreation” to 

encompass recreational activities that could be expected to result in the ingestion of, or 

immersion in, water, such as swimming, water skiing, surfing, or any other recreational activity 

where ingestion of, or immersion in, the water is likely. 

EPA derived standards that implied an acceptable excess illness probability of 0.8% in swimmers 

exposed in freshwater and 1.9% in swimmers exposed in marine waters. EPA’s 1986 bacteria 

criteria document indicates the illness rates are “only approximate” and that the Agency based 

the 1986 values that appear in Table 3 on these approximations. 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 17 

Table 3. Summary of EPA’s 1986 Recommended Water Quality Criteria for Bacteria and 

2004 Rule 

Geometric Mean Single Sample Maximum Allowable Density Indicator SwimmingAssociated 

Gastroenteritis 

Rate per 1,000 

Swimmers

Steady State 

Geometric Mean 

Indicator 

Density 

Designated 

Beach Area 

Moderate: 

Full Body 

Contact 

Recreation 

Lightly Used: 

Full Body 

Contact 

Recreation 

Infrequently 

Used: Full 

Body Contact 

Recreation 

Freshwater

Enterococci 8 33 61 78 107 151 

E. coli 8 126 235 298 409 575 

Marine Water

Enterococci 19 35 104 158 276 501 

Source: US EPA (2004). 

EPA’s 1986 bacteria AWQC document provides geometric mean densities as well as four 

different single sample maximum values (representing values below which an increasing 

percentage of single values are expected to fall if the geometric mean of samples from the 

waterbody is equal to the geometric mean criteria). The 1986 bacteria AWQC document 

categorizes the single sample maximum values based levels of beach usage as follows: 

“designated bathing beach” for the 75% (most conservative) confidence level, “moderate use for 

bathing” for the 82% confidence level, “light use for bathing” for the 90% confidence level, and 

“infrequent use for bathing” for the 95% confidence level. The lowest confidence level 

corresponds to the highest level of protection. 

In the 1986 AWQC context, single sample maximum criteria are water quality assessment tools 

that provide a sense of when the water quality in a waterbody is not consistent with the AWQC. 

Insights based on single observations are very difficult because of the expected variability of 

fecal indicators. For instance, if the long-term geometric mean concentration of enterococci in 

the water at a marine beach is 35/100 mL and the log standard deviation is 0.4, then there is an 

18% chance that the concentration of enterococci in a single sample would be over 158/100 mL. 

The higher the single sample maximum, the lower the probability that a single sample exceeding 

that value would occur as part of the normal random variability of samples (US EPA, 2006). 

Since publication of the 1986 criteria, many States have expressed concern that the current fecal 

indicator/illness rate relationships identified in the epidemiology studies leading up to the 1986 

criteria are not appropriate or representative of all U.S. waters. For example, States have 

concern that the most appropriate indicator in tropical waters may be different than in temperate 

waters, and that appropriate levels of indicators may be different in waters where human fecal 

waste predominates animal waste. Other identified issues are as follows: 

• lack of clear, timely, and flexibile guidance regarding use of the single sample maximum 

values and differing risk levels; 

• no EPA-approved analytical methods for use in wastewater for the indicator bacteria; 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 18 

• lack of data to correctly assess the applicability of the 1986 bacteria criteria to flowing 

waters; and 

• lack of data to quantify the risk associated with contributions from nonhuman sources of 

fecal contamination as well as lack of flexibility to adjust the criteria for water bodies that 

do not receive human sources of fecal contamination. 

1.3.4 Summary of Proposed Criteria Development Approaches 

Workgroup members developed a summary of the three proposed criteria development 

approaches, including strengths and limitations (Tables 4a and 4b). 

Table 4a. Summary of Proposed Criteria Development Approaches: 

Strengths and Limitations 

Criteria 

Approach 

Science 

Supporting 

Approach 

Strengths Limitations 

World Health 

Organization 

(WHO, 2003) 

Fleisher et al., 

1996 

Kay et al., 1994, 

2004 

WHO, 1999 

Wyer et al., 1999 

• Flexible 

• Most comprehensive of 

available methods 

• Adopted by other countries 

• Incentives for beaches to 

upgrade 

• Allows more site appropriate 

protection of health 

• Sanitary inspection 

component is qualitative; not 

quantitative 

• Greatest data needs 

• Would need to adapt 

potentially complex system to 

wide range of conditions in 

U.S. 

• Potential implementation 

issues 

European Union 

(EP/CEU, 2006) 

Fleisher et al., 

1996 

Kay et al., 1994, 

2004 

Wiedenmann et 

al., 2006 

WHO, 1999, 

2003 

• Flexible 

• Relatively straightforward 

• Incentives for beaches to 

upgrade 

• Adopted by other EU 

Member States 

• Discounting system has no 

direct precedent in the U.S. 

• Would need to devise robust 

and acceptable discounting 

scheme 

• Potential implementation 

issues 

Current U.S. 

Criteria 

(US EPA, 1986) 

US EPA, 1983, 

1984 

• Relatively straightforward 

• Currently in place in most 

states, new implementation 

issues less likely 

• Fewest data requirements 

• Allows less flexibility 

• Single sample max (75th 

percentile) has been criticized 

from implementation 

perspective 

• Credibility concerns in many 

parts of the U.S. 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 19 

Table 4b. Summary of Three Proposed Criteria Development Approaches: 

Benchmarks 

Criteria 

Approach Criteria Attribute Approach Compatible with Attribute 

Health-based Yes 

CWA §304(a) applications 

Most challenging – unclear how different 

grades for beaches would be interpreted 

with respect to impaired waters; for 

example, TMDLs would need to be 

considered. 

Geographic variability Not with current indicator, ongoing 

research could fill gaps 

Point vs. non-point No, epidemiological data would be 

needed 

Multiple subpopulations Could be, but in current configuration 

children not analyzed separately 

Uniform risk across waterbody types Yes 

World Health 

Organization 

(WHO, 2003) 

 

Linked to method that is validated Yes currently, but will also depend on 

future indicators 

Health-based 

Yes, but differential risks from different 

sources of fecal contamination is not 

included, thus, this approach is less 

health-based than WHO approach 

CWA §304(a) applications Yes, but challenging for same reasons as 

WHO approach 

Geographic variability Not with current indicator, ongoing 

research could fill gaps 

Point vs. non-point No 

Multiple subpopulations Could be, but in current configuration 

children not analyzed separately 

Uniform risk across waterbody types Yes 

European Union 

(EP/CEU, 2006) 

 

Linked to method that is validated Yes currently, but will also depend on 

future indicators 

Health-based 

Yes, but concern about single sample 

standard, also concerns that differential 

risks from different sources of fecal 

contamination are not included 

CWA §304(a) applications Yes 

Geographic variability No 

Point vs. non-point No 

Multiple subpopulations No 

Uniform risk across waterbody types 

No, fresh and marine recreational waters 

have different “acceptable risks”; this 

could be addressed in new or revised 

criteria 

Current U.S. 

Criteria 

(US EPA, 1986) 

Linked to method that is validated Yes currently, but will also depend on 

future indicators 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 20 

1.3.5 Other Approaches Considered 

As noted previously, the workgroup considered a number of other frameworks and approaches 

that might be applicable to criteria development, including the following: 

• Hazard Analysis and Critical Control Point Principles (HACCP); 

• Heal the Bay Beach Report Card; and 

• EPA Air Quality Index. 

The EU, EPA (1986) criteria, and the WHO approaches are already being used for the intended 

purpose, either in the United States or other countries. The other possible approaches listed 

above have not been applied in a regulatory framework for proposed water regulation and would 

need to be thoroughly assessed to determine their utility or applicability to derive recreational 

water quality criteria. The workgroup members felt that it was beyond their ability to conduct 

such an assessment at this time. One workgroup member noted that the Heal the Bay approach 

was never intended for use in all regulatory purposes and would not be recommended for such. 

1.4 Summary of Critical Issues to be Resolved in Applying Available Water Quality 

Criteria Approaches 

No matter which recreational water quality criteria development approach is selected, a number 

of research needs have to be met before criteria development can reach completion. Additional 

epidemiological studies that take into account marine waters, subtropical and tropical waters, 

urban runoff, and non-point sources of contamination will need to be completed in the next 2 to 3 

years to provide the health effects data necessary if nationally applicable are to be developed. 

Further testing of quantitative polymerase chain reaction (qPCR) methods to detect enterococci 

and/or any additional proposed indicators under the conditions listed above also is critical. The 

epidemiological studies should also include (1) culture-based methods in addition to molecular 

methods for enterococci; (2) culture and molecular-based methods for E. coli in fresh water 

studies because national freshwater criteria and numerous States currently use E. coli in 

recreational criteria and including E. coli would maintain a level of consistency with the existing 

CWA §304(a) guidance; and (3) sensitive subpopulations to the extent feasible, including 

children at a minimum. 

Other research gaps that can be filled in the next few years include, but are not limited to, fate 

and transport of molecular-based indicator organisms in wastewater treatment plants and in the 

ambient aquatic environment. Workgroup members expressed a significant concern about the 

issue of conservation of measurable genetic material throughout the treatment process because of 

the regulatory ramifications in the NPDES, water quality assessment, and TMDL programs of 

moving to molecular-based criteria. 

Another research need is for effective predictive models for beach water quality forecasting to 

notify the public of the potential health risks of recreational water contact. The current use of 

single sample assessments using culture-based methods has proven to be largely ineffective for 

public notification of beaches purposes because of the time required for sample processing (i.e., 

sample transportation to a laboratory, 18 to 24 hour incubation time, and time required for results 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 21 

to reach and be evaluated by a decision maker). In addition to their development, the models 

need to be adequately field verified and calibrated. Ideally, regional models can be developed, 

but if predictive models can only be developed on a site specific basis over the next 3 years, the 

data needed to develop, field verify, and calibrate the models should not be cost prohibitive to 

collect. At a minimum, recreational beach managers should consider a simple, predictive rainfall 

model to more effectively protect public health. 

Workgroup members emphasized that a sanitary investigation3

 approach to characterize 

drainages to primary contact recreational waters would prove useful for at least the WHO criteria 

development framework. A simple to implement, quantitative-based sanitary investigation, in 

conjunction with the health risk data from the proposed additional epidemiology studies, may 

enable the development of source specific risk parameters for criteria development. To clarify 

expectations for these surveys, a standardized and relatively simple approach would need to be 

developed that includes fecal bacteria source characterization (publicly owned [wastewater] 

treatment works [POTWs], storm drain outfalls, CAFOs, on-site wastewater treatment systems 

[“septic systems”], agriculture, etc.) on a drainage-wide basis, distance of sources to primary 

contact recreational waters, flow, developed area in the drainage, and the frequently high 

variability in water quality from day to day. Additional sanitary investigation components such 

as source identification and source tracking4 may not need to be implemented unless there is a 

need in the regulatory process to implement a TMDL or to protect the public health of swimmers 

at chronically polluted beaches. 

The following summary assumes that all of the approaches encompass and achieve the 

benchmarks outlined in Section 1.1 to the extent feasible. 

1.4.1 Summary of Application of WHO Approach for U.S. Criteria Setting

The general framework described by the WHO (2003) would be applicable to U.S. criteria 

setting in the near-term given that the following research is conducted and science policy 

decisions are made: 

 3

 This is similar to Canada’s “Environmental Health and Safety Assessment” in Appendix A of Guidelines for 

Canadian Recreational Water Quality (MNHW, 1992). Although the WHO (2003) uses the term “sanitary 

inspection,” some workgroup members expressed concern that use of that specific term or the related term “sanitary 

survey” might imply adoption of all the protocols for sanitary inspections/surveys from other contexts. Thus, the 

term “sanitary investigation” was selected for use in these proceedings to minimize preconceived assumptions 

regarding the nature of the sanitary investigation and is used to refer to a quantitative approach to gauge watershed 

susceptibility to fecal influence. However, “sanitary inspection” is used when the WHO approach is described. 

4

 Although there is not universal acceptance of definitions for microbial source tracking and microbial source 

identification, the Methods workgroup discussions assumed the following working definitions: source identification 

is determination of the type of animal (sometimes human versus nonhuman, sometimes more specific) that produced 

the fecal contamination. It does not include determining where in the watershed that material came from, but it does 

suggest what to look for upstream. Source tracking is determination of the actual source of fecal matter, such as a 

leaking pipe, a septic system, or a cow pasture. It typically involves using some of the marker techniques associated 

with source identification, but not necessarily. Source tracking can also be achieved through extensive spatial 

sampling with existing indicators or (for example) through use of dye tablets in septic systems. 
U.S. Environmental Protection Agency Experts Scientific Workshop

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1. Analyze epidemiological data to determine the values of water quality that correspond to 

the identified levels of “acceptable risk” for the indicator of fecal contamination using the 

selected method(s). 

2. Identify a suitable indicator of fecal contamination or suite of fecal indicators 

(particularly for subsequent tiers of investigation). This information needs to be 

epidemiologically based. 

3. Identify “acceptable risk” levels. Choosing an “acceptable risk” level is a policy decision 

that is informed by science (e.g., epidemiology studies). See Chapter 5 for a discussion 

of the process through which an “acceptable risk” level could be chosen. 

4. Derive a quantitative sanitary investigation category rather than a qualitative process; 

also, the sanitary investigation should be standardized nationwide. 

5. Statistically validate the linkages between different indicator/method combinations for 

different CWA §304(a) purposes to facilitate translation between the various 

indicator/methods. 

6. Consider and develop a recreational water quality reclassification scheme, if appropriate. 

If such a reclassification scheme is appropriate, a management system would be 

necessary to facilitate implementation of beach advisories and to ensure informed choice 

regarding beach use. 

7. Develop a public information management system and a beach signage provision. The 

purpose of these programs would be to represent bathing water characteristics derived 

from a “bathing water profile” and historical water quality. 

8. Institute a monitoring program to acquire bathing water quality data for numerical 

compliance assessment purposes. 

9. Release CWA §304(a) criteria guidance and associated implementation guidance 

concurrently. 

To apply the WHO (2003) approach for future criteria setting, the following issues will need to 

be considered in detail and expanded: 

1. Develop a process to determine how waterbodies get listed as impaired. 

2. Determine the appropriate number of categories for microbial and sanitary investigation 

categories. 

3. Possibly change several qualitative determinations in the framework (i.e., very good, 

good, fair) to less descriptive terms (i.e., Category I, Category II, etc.). 

4. Develop a process for categorization of NPDES dischargers (consideration for default to 

most restrictive category). 

5. Determine how to use different indicator/method combinations for CWA §304(a) 

applications and translate to each other to ensure equivalent levels of protection. 

6. Determine whether health risks from nonhuman fecal sources are substantially different 

than from human sources. 

7. Determine what is the most appropriate metric for expressing the water quality criteria 

(geometric mean, upper percentile, a combination of those and/or other) 
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8. Determine how to make water quality public notification decisions (this is likely a 

function of the indicator/method combination[s] that are employed and the strength of a 

predictive model). 

9. Develop a well described and vetted quantitative sanitary investigation guidance; here the 

workgroup members suggested a tiered approach that allows for varying levels of effort 

based on likely benefit from the assessment (high and low risk should be easier to assess 

[i.e., beaches downstream from POTWs or urban catchments would be high risk, and 

beaches downstream of catchments with 100% natural sources would be low risk]). 

Although completion of the sanitary investigation does not need to be required, surface 

waters would default to the most restrictive criteria until such time as a completed 

investigation provides justification for changing the applicable criteria. 

10. Develop a well described and vetted recreational water quality reclassification scheme. 

1.4.2 Summary of Application of EU Approach for U.S. Criteria Setting 

The general framework described by the EU (EP/CEU, 2006) would be applicable to U.S. 

recreational water quality criteria setting given the same research and science policy decisions as 

described above for the WHO except (1) a classification scheme based on a quantitative sanitary 

investigation would not be necessary because the sanitary inspection category is not used to 

determine the beach classification, and (2) it would not be necessary to determine whether health 

risks from nonhuman sources of fecal contamination are substantially different than from human 

sources, because the beach classification is based on microbial densities only.. 

To apply the EU approach for future criteria setting the same issues described above will need to 

be considered in detail and expanded, with the following exceptions: 

1. Reform the microbial categories to fit U.S. waters, do not include the “sufficient” 

category of EU Directive EEC/7/2006. 

2. Determine if a discounting scheme is necessary and appropriate (e.g., elimination of 

monitoring data for compliance purposes), and if so, then there is a need to determine 

how to make it most protective of public health. 

1.4.3 Summary of Application of EPA 1986 Approach for U.S. Criteria Setting 

The current EPA (1986) framework described previously would be applicable to new or revised 

U.S. criteria development with the following modifications: 

1. Develop additional indicators and analytical methods that would be applicable to tropical 

and temperate waters and also for use in wastewater. 

a. Base additional indicators and methods on health risks (i.e., occurrence would be 

correlated with rates of illness from epidemiological studies). 

b. Ensure that the revised criteria framework specifies the appropriate 

indicator/methods combination for the various waters. 
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2. Consider more timely methods for beach monitoring and water quality notification. 

Currently, there is no scientific evidence supporting beach water quality determinations 

based on, at best, day-old (culture-based) data. 

a. If molecular-based methods are used, then fate and transport data for that 

indicator using that method would be needed. 

b. If molecular-based methods are limited to beach monitoring and water quality 

notification, then these methods must be linked somehow to the methods used for 

the other CWA purposes. Currently, very limited data are available for this 

purpose. 

c. If predictive modeling is used in water quality notification programs, the models 

need to be adequately field-verified and calibrated. 

3. Risk threshold 

a. Any final recommendation for CWA §304(a) criteria must be health-based and 

derived from the available epidemiological data. 

b. If a single sample criteria is used, it should be of similar stringency to any other 

measure used (e.g., geometric mean) and the single sample criteria should account 

for the expected frequency of exceedance (e.g., if the single sample criteria is 

based on a 95th percentile, a 5% exceedance should be allowed without invoking 

compliance ramifications). 

c. Consider risk to sensitive subpopulations (e.g., children) in the determination of 

the risk threshold. 

d. The risk of illness should be the same for swimmers in all types of waters (i.e., 

marine, fresh, temperate, tropical, etc.) exposed to all types of fecal contamination 

sources (e.g., point, non-point). 

e. Secondary contact recreation waters: 

i. Acquire data to show health risks associated with limited, but defined 

levels of contact and/or incidental exposure. 

ii. Data can be from epidemiological studies or estimated using quantitative 

microbial risk assessment (QMRA). 

iii. Develop a more accurate descriptor of what constitutes secondary contact. 

4. CWA §304(a) AWQC recommendations and associated implementation guidance should 

be released concurrently. 

1.5 Summary of Response to Workgroup Charge Questions

See Appendix A for the complete (original) charge questions. 

1. What approaches exist currently for setting limits of pollutants that may be relevant for 

developing nationally recommended recreational water quality criteria? Consider 

approaches used for other kinds of pollutants in water, in other environmental media, 

and by other countries as well as approaches being implemented by States. What are 

the pros and cons of each of these approaches?

• European Union Revised Bathing Water Directive 2006/7/EC 
U.S. Environmental Protection Agency Experts Scientific Workshop

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• Hazard Analysis and Critical Control Point Principles 

• Heal the Bay Beach Report Card 

• EPA Air Quality Index 

• EPA Ambient Water Quality Criteria for Bacteria – 1986

• WHO Guidelines for Safe Recreational Water Quality Environments. Volume 1 

Coastal and Fresh Waters 

The EU (EP/CEU, 2006), (US EPA) 1986 criteria, and the WHO (2003) approaches are already 

being used for the intended purpose, either in the United States or other countries. The other 

possible approaches listed above have not been applied in a regulatory framework for proposed 

water regulation and would need to be assessed to determine their utility or applicability to 

derive new or revised recreational water quality criteria. 

2. Which of these approaches is most applicable and appropriate for developing 

nationally recommended recreational water quality criteria in the near-term? Why is 

this approach on balance considered the most applicable and appropriate?

Workgroup members identified the following critical benchmarks for water quality criteria 

development: 

• Be applicable to human health effects; 

• Fulfill the needs of Clean Water Act (CWA) and meet the associated regulatory 

purposes (monitoring, permitting, total maximum daily loads [TMDLs], and 

§303(d)); 

• Address geographic variability (i.e., tropical, subtropical, and temperate regions); 

• Address potential differences between point and non-point sources of fecal 

contamination and associated risk; 

• Consider risks to susceptible subpopulations, primarily children; and 

• Be based upon methods that are reliable and reproducible. 

Based on these benchmarks, workgroup members further identified three approaches for further 

consideration—European Union Revised Bathing Water Directive 2006/7/EC (EP/CEU, 2006), 

EPA Ambient Water Quality Criteria for Bacteria – 1986, and the 2003 World Health

Organization Guidelines for Safe Recreational Water Quality Environments. Volume 1 Coastal 

and Fresh Waters. Table 4a summarizes the advantages and disadvantages of each approach and 

is provided in Section 1.3.4. 

3. For those approaches identified as applicable and appropriate, what is the science that 

supports the approach? Is that science sufficient and of adequate quality?

Epidemiological research identified to support the best selected approaches was: 

• European Union Revised Bathing Water Directive (2006/7/EC; EP/CEU, 2006) 

o Fleisher et al. (1996) 
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o Kay et al. (1994) 

o Weidenmann et al. (2006) 

o Wyer et al. (1999) 

• EPA Ambient Water Quality Criteria for Bacteria - 1986 

o US EPA (1983) 

o US EPA (1984) 

• World Health Organization 2003 Guidelines for Safe Recreational Water Quality 

Environments. Volume 1 Coastal and Fresh Waters 

o Fleisher et al. (1996) 

o Kay et al. (1994) 

All members of the workgroup agreed that the research reports listed above support the 

respective approaches but some members questioned whether the research identified above was 

adequate to meet all of the identified benchmarks. They also agreed that additional 

epidemiological and modeling work needed to be performed in order to successfully implement 

any of the approaches above for future new or revised recreational water quality criteria 

development in the United States. 

4. Are there any critical research and science needs that should be addressed in 

developing or selecting an appropriate approach? Can this research be completed n 

time to be used in criteria development in the near term?

The workgroup members identified the following research and science needs to support the 

suggested approaches. 

• Information on the geographic applicability of fecal indicators for assessing health 

risks at tropical and subtropical fresh and marine recreational bathing areas impacted 

by point and non-point sources of fecal contamination (see Chapters 2, 3, and 4; 

research on sensitive subpopulations should also be incorporated into this need [see 

Chapter 5]); 

• Ability to discriminate between human and nonhuman sources of fecal 

contamination; 

• Information on sources of runoff (e.g., concentrated animal feeding operations 

[CAFOs]) from both marine and fresh recreational waters; 

• How much water are bathers ingesting while swimming?; and 

• Fate and transport of indicators (and pathogens) in the aquatic environment. 

Workgroup members also identified the following possible long-term research needs: 

• Comparison of prospective cohort and randomized control trial epidemiological 

studies; 

• Identification of pathogens (viruses, bacteria, or parasites) responsible for GI illnesses 

at bathing beaches; 
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• Health impacts following exposures over multiple days; 

• Significance of non-GI illnesses (dermal, aural, nasal); and 

• Comparison of severity of illnesses related to exposure to human and animal 

(domestic and wildlife) fecal contamination (see Chapter 4). 

Although workgroup members identified these long-term research needs there were some 

differences of expert opinion on the essentiality of these needs. In conjunction with these 

research needs, workgroup members also noted the necessity to clarify the objectives of 

environmental health assessments (sanitary investigations) and microbial source tracking 

methods. 

 

5. Is a “toolbox” approach appropriate for developing new or revised recreational criteria 

in the near-term? Why or why not?

The Approaches to Criteria Development workgroup members interpreted the concept of a 

toolbox approach differently. Some members believed that shifting from the current (US EPA, 

1986) criteria approach to either the WHO (2003) or EU (EP/CEU, 2006) model approach would 

constitute a type of toolbox approach. For example, the sanitary investigation as used within the 

WHO approach could be considered to be an additional tool in the implementation of the new or 

revised criteria. Others believed the toolbox approach meant the use of alternative or additional 

fecal indicators or pathogen methods. In either case, the implementation of the toolbox approach 

was dependent upon additional epidemiological studies being conducted that may or may not be 

possible within the near-term (2.5 to 3 years). 

Predictive models could be an integral part of the toolbox. Models that have been both validated 

and calibrated are critical for accurately predicting recreational waters that exceed criteria. 

Improved notification via forecasting models is likely to protect public heath better then the use 

of single sample criteria based on current indicators measured by culture methods. 

6. What are the pros and cons of selecting a “toolbox” approach?

There was commonality of workgroup member opinions in regards to several of the pros and 

cons related to the use of a toolbox approach. 

Most of the workgroup members believed that a toolbox approach would help address some of 

the issues with geographic variability. For example, the use of different fecal indicators that 

demonstrate improved indicator/illness rate relationships in subtropical or tropical waters would 

reduce the likelihood of these waters inappropriately being listed as impaired under the CWA. 

The use of some form of sanitary investigations, as within the WHO (2003) approach, would 

potentially allow for discounting those waters that were identified as having limited or no 

anthropogenic fecal loading, thereby avoiding those waters being listed as impaired 

inappropriately. 
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The cons associated with a toolbox approach were primarily related to the current lack of data on 

the fecal indicator/illness rate relationships for additional methods. There was also some concern 

expressed about the difficulty in incorporating the toolbox approach to account for the use of 

different indicators for different CWA §304(a) needs. There was also concern about the 

feasibility of establishing requisite and defensible linkages between the various indicator/method 

combinations that could comprise the toolbox. 

7. What are the desired features or characteristics that would make a “toolbox” approach 

appropriate?

Any additional fecal indicator or pathogen measure within the toolbox would need to have 

proven indicator/illness rate relationships, or at a minimum, have a linkage to another indicator 

that does. The characteristic of being interrelated (correlated) with each other would be of 

particular use, especially if one was going to be used to support one aspect of the CWA §304(a) 

needs and the other was being used to support another §304(a) need. 

The toolbox approach should support more then just one aspect of the CWA §304(a) needs. Any 

of the tools within the toolbox should be validated, either by predictive modeling or by 

correlation to other tools within the toolbox. Additionally, if a management action is initiated on 

the results of a particular tool within the toolbox (e.g., a beach closure based on qPCR) the 

follow up action should also be based upon the same tool (beach opened based on qPCR), to the 

extent possible. 

8. Would a “toolbox” approach achieve additional public health protection as compared 

to another approach? Why or why not? 

 

Yes, as mentioned above, the additional tools within the toolbox could potentially improve the 

assessment of waters (e.g., reduce the listing of tropical or subtropical waters as impaired due to 

the poor indicator/illness relationship for these waters) or the appropriateness of beach advisories 

or closures. 

9. Criteria for secondary contact recreation could be part of a “toolbox.” What 

approaches would be appropriate for developing criteria for secondary contact 

recreation? 

Workgroup members defined secondary contact as limited or incidental contact. As such, 

workgroup members believed that the same approach could be used for waters designated as 

secondary contact as used for primary contact, meaning that epidemiologically-based health data 

could be used to define acceptable exposure limits. QMRA could also be used for these 

purposes to supplement available epidemiological information. 
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10. What are critical research and science needs in developing or selecting an appropriate 

approach for secondary contact recreation? 

Additional epidemiological studies may be needed under secondary contact conditions. These 

epidemiological studies should address the same data needs as those proposed in support of the 

primary recreation criteria. Alternatively, QMRA could be used if exposure data are available. 

Can this research be completed in time to be used in criteria development in the nearterm? 

It is possible, but unlikely given the current demands for additional epidemiological work in 

support of the primary contact designated use. However, a QMRA study could be conducted 

during this timeframe. 

11. What are the implementation considerations of the different approaches for CWA 

purposes (1) beach monitoring and notification, (2) development of NPDES permits, 

(3) assessments to determine use attainment, and (4) development of TMDLs? 

All three approaches—the (EPA) 1986 criteria, EU (EP/CEU, 2006), and WHO (2003) 

approaches—would require additional epidemiological studies to implement. Given additional 

epidemiological data with additional indicators, it is possible that each approach could 

potentially be implemented and could support multiple CWA §304(a) needs. As noted above, 

using multiple indicators for different purposes is a cause of concern. 

Are there practical considerations that could preclude, or greatly limit, the use of an 

approach in routine, regulatory implementation (e.g., field sampling issues, laboratory 

challenges, staff training, etc.)? 

 

If future epidemiological studies do not identify additional indicator tools that would improve the 

indicator/illness relationship for a broader geographic range, the (EPA) 1986 model would be a 

much less desirable option than either the WHO (2003) or EU (EP/CEU, 2006) approach. Both 

the EU and WHO approaches apply a discounting scheme, so the failure of near-term 

epidemiological studies to identify more robust indicator tools does not preclude the 

implementation of these approaches for the development of new or revised recreational water 

quality criteria. 

Geographic Applicability

1. Is a single criterion available that is appropriate for the diverse range of geographic 

conditions? Why or why not?

No. Different regions of the country have different potentials for regrowth, persistence, 

indicator/pathogen die off rates (UV exposure), and indicator/illness rate relationships. The 

literature supports the conclusion that additional indicators will be necessary to accurately 

identify those recreational waters that are at risk across all geographic regions of the country. 
U.S. Environmental Protection Agency Experts Scientific Workshop

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Workgroup members felt that future epidemiological studies should include additional indicators 

to improve the indicator/illness relationship across all geographic areas of the United States. 

2. Is a toolbox approach appropriate for different geographical conditions? Why or why 

not? 

Yes, for the reasons noted in the response to Question #1 above. 

3. What would a “toolbox” that addresses geographical differences look like? 

The toolbox might include alternative or additional indicators that better predict, either 

individually or in combination, the indicator/illness relationship. Alternatively, the toolbox 

might include environmental health and safety assessments (sanitary investigations) that allow 

for the discounting of waters that appear as impaired based upon the indicator results, but for 

which the impairment judgments are not supported by demonstrable impacts (elevated indicators 

from wildlife or sediment sources only). The toolbox approach also could be used to allow 

different indicators and be used for different CWA §304(a) purposes. 

4. What are critical research and science needs in developing or selecting an approach 

that will appropriately factor-in diverse geographical conditions? 

Additional epidemiological studies are needed that provide improved indicator/illness rate 

relationships for all regions of the United States. These additional epidemiological studies 

should focus on recreational waters that are under a variety of potential pathogen sources (e.g., 

sewage, urban runoff, non-point sources, non-anthropogenic sources). Where possible, the 

various potential sources of pathogens should be considered within a single epidemiological 

study rather than each being considered in separate studies. This might be possible by examining 

waters that have varying sources depending upon rainfall or climatic conditions. For example, 

California beaches that have urban runoff sources during wet weather but no known point or 

non-point sources during dry weather. 

To pursue the 2003 WHO approach, a quantitative environmental health and safety assessment 

(i.e., sanitary investigation) tool would have to be developed in order to support the 

categorization of recreational waters as to their risk of potential fecal contamination. To have 

greater confidence in the WHO model, research is needed to determine if the notion that fecal 

contamination from non-anthropogenic sources is of lesser human health risk that anthropogenic 

sources. 

Expression of Criteria

1. Given the diverse needs of the CWA programs and the overarching goal of protecting 

and restoring waters for swimming, what protection is provided by establishing a 30-

day “average” value as the criteria? 

There was some commonality of workgroup member opinion on this issue. Several members 

felt that the criteria would best be expressed as a geometric mean and/or a standard deviation or 
U.S. Environmental Protection Agency Experts Scientific Workshop

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95th percentile. Several members believed that these values would have to be site specific in 

order to be protective. If formatted correctly, an average value is as protective as any other 

single measure. 

What additional protection (if any) is provided by a daily or instantaneous maximum 

value? 

The added value provided by an instantaneous maximum value is dependent upon the 

indicator/illness rate association. Short-term variability associated with the current indicators 

limit the usefulness of single sample maximum values; however, using qPCR or other non 

culture-based methods may improve the utility of single sample values. Additional 

epidemiological data is needed to assist in making this determination. One problem is that the 

formulation of the current single sample maximum is such that it is more stringent than the 

geometric mean, and this has caused substantial confusion among States. 

From a scientific standpoint, is one measure better scientifically than another for 

particular purposes (e.g., mean value for purposes of identifying waters and daily 

maximum for beach monitoring and notification purposes)? Why? 

It depends on how the new or revised criteria are derived and the assumptions made about the 

variability in water quality. There is some scientific merit to the continued use of single sample 

maximum values for some CWA purposes. This is of particular interest with respect to public 

health protection; however, there was not agreement among the workgroup members on this 

point. 

2. What are pros and cons of expressing the criteria differently for the various CWA 

program needs? 

As currently used, single sample maximum values are not effective for beach monitoring 

purposes. This may change somewhat if the shift from culture-based methods to non culturebased methods improves the issues with variability and indicator/illness rate relationships. 

There is potential to use single values, whether culture- or non-culture based, in predictive 

models for beach monitoring. The geometric mean, standard deviation, or 95th percentiles show 

promise for multiple CWA programs. So long as there is data from epidemiological studies that 

demonstrates the one expression of the criteria is equally as protective as another, there would be 

no problem with using different expressions of the criteria for different CWA purposes. 

3. What are the implications of instantaneous or daily values for public health 

protection? If we don’t currently have a good understanding of this, what are the 

critical research and science needs to answer the questions? 

Currently there is very little data to support the use of instantaneous or daily values derived from 

culture-based methods from Day 1 to predict the need to post or close recreational waters on Day 

2. There are recent epidemiological data (Wade et al., 2006) that indicates that qPCR (non 

culture)-based indicator methods may be effective for same day notification at some beaches. 
U.S. Environmental Protection Agency Experts Scientific Workshop

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Group members identified several critical research needs that would potential improve the utility 

of an instantaneous or daily value (see Chapter 1). 

4. If EPA were to set criteria at a mean concentration over 30 days and not recommend a 

single sample maximum, do we understand the illnesses that could occur on a single 

day (where the level would still lead to compliance with the 30-day average)? 

In general, workgroup members agreed that the probability of illness on any single day is not 

understood. Some reasons for this are as follows: 

• the variance in water quality in any particular water body could be significantly 

different than the criteria from which it was derived; 

• the variability of indicator could change between beaches and temporally; and 

• if the exposure-response curve is based on a geometric mean, the interpretation of a 

single sample is difficult. 

With research, a single sample maximum could be used to estimate the probability of illness on a 

particular day. 

5. If the science is “not there,” what are the critical research and science needs to answer 

this question? 

Critical research and science needs centered on expanding epidemiological studies based on 

qPCR (and other indicators and methods) to other situations (e.g., example marine beaches or 

non-point pollution sources). 

6. What are the implementation considerations for CWA purposes of failing to address 

(and addressing) differences geographically in the criteria and failing to include (and 

including) a single sample maximum value for (1) beach monitoring and notification, 

(2) development of NPDES permits, (3) assessments to determine use attainment, and 

(4) development of TMDLs? Are there practical considerations that could preclude, or 

greatly limit, the usage in routine, regulatory implementation (e.g., field sampling 

issues, laboratory challenges, staff training, etc.)? 

To address this question it was separated into the following two components: (1) failing to 

address geographical differences, and (2) failing to include a single sample maximum for various 

purposes identified in the CWA. 

(1) Failure to recognize that the current criteria may not be applicable to tropical and 

subtropical beaches could present an unacceptable risk to bathers in these recreational 

waters. 

(2) Single sample maximum NPDES permits – compliance tools such as NPDES permits 

require single sample maximums and need to continue that approach. 

Regarding States’ designated use attainment, single sample maximum values are not necessarily 

required and in fact may not be necessary. These types of criteria could be useful for beach 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 33 

monitoring and water quality notification. Regarding TMDLs, single sample maximum values 

do not seem applicable for TMDLs for indicator bacteria. 

1.6 Concluding Remarks

The workgroup members did not specifically prefer one criteria approach over another primarily 

because it is believed that additional data that will become available from epidemiological 

studies within the next 2 to 3 years and how those data will inform the criteria development 

process is not yet known. For example, it is not known what new information will be available 

based on new indicators and/or methods and how that information might inform a sanitary 

investigation component of a WHO-based criteria approach. 

Further, it was the opinion of workgroup members that there may be differences in the ability to 

implement each of the three approaches if all of the various criteria attributes are not met. For 

example, workgroup members felt that the 1986 EPA approach with a new or different indicator 

and/or method would not be satisfactory if most or all of the criteria attributes were not met. 

Workgroup members also felt that the same set of circumstances may not preclude the use of the 

WHO or EU approach. With respect to the use of a toolbox-based approach where different 

indicators are used for different CWA §304(a) applications, workgroup members expressed 

concern about the feasibility of developing health-based linkages (as described above) as would 

be required by either the WHO or EU approaches. Thus, at this time, no workgroup member was 

definitively able to recommend one approach over another; however, the workgroup members 

agreed that the choice of approaches must be deferred pending the outcome of ongoing and nearterm research. 

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CHAPTER 2 

PATHOGENS, PATHOGEN INDICATORS, AND 

INDICATORS OF FECAL CONTAMINATION 

Nicholas Ashbolt, Chair, USEPA 

Roger Fujioka, University of Hawaii, Manoa 

Toni Glymph, Wisconsin Department of Natural Resources 

Charles McGee, Orange County Sanitation District, California 

Stephen Schaub, USEPA 

Mark Sobsey, University of North Carolina, Chapel Hill 

Gary Toranzos, University of Puerto Rico, Rio Piedras
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U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 37 

2.1 Application of Microbial/Biomarker Parameters

The charge of the Pathogen, Pathogen Indicators, and Indicators of Fecal Contamination 

workgroup was to identify critical research and science needs in the development of new or 

revised criteria for recreational waters, including total maximum daily load (TMDL) 

implementation, and National Pollutant Discharge Elimination System (NPDES) implementation 

using microbial and chemical indicators. The discussions were limited to constituents for which 

methods are currently available or expected to be available within the next 3 years and focused 

around the following four issues: 

1. Fecal matter indicators (as surrogates for gastrointestinal [GI] and non-GI illnesses); 

2. Pathogens and their index organisms (GI and non-GI illnesses); 

3. Application of fecal indicators, pathogen index organisms, and pathogens in combination 

for criteria development; and 

4. Application of all the above for all categories of waters, climatology, and geographical 

considerations. 

Currently, implementation of ambient water quality criteria (AWQC) for the four Clean Water 

Act (CWA) applications require monitoring fecal bacterial indicators to assess the degree to 

which the water is contaminated with sewage and sewage-borne pathogens with respect to the 

accepted risk for exposure. Development of the existing (US EPA, 1986) AWQC for 

recreational waters were based on epidemiological studies that related concentrations of fecal 

indicator bacteria at recreational waters impacted primarily by point sources of human sewage. 

Since development of the currently used 1986 AWQC, research has shown that this narrow 

health effects-based standard (i.e., epidemiological studies at beaches with point sources of 

human sewage) is limited in that it does not take into account differences in geographical 

conditions, ecology of microorganisms, and varying sources of fecal indicator bacteria. In this 

regard, the expected relationship between illness and indicator organism densities would be high 

if the source of contamination is human sewage, moderate if the source was a mixture of human 

and animal feces, or lower if the source is the result of replication of the indicator bacteria in the 

environment, such as in soil, sediments, storm drains, or on plants or aquatic vegetative matter. 

Initially, replication of fecal indicator bacteria was reported in tropical areas (e.g., Hawaii, 

Guam, Puerto Rico) but has now been documented in subtropical areas such as south Florida and 

even temperate areas (Great Lakes States). A further but untested complication in interpreting 

fecal indicator bacteria results may arise due to different rates of pathogen inactivation in the 

environment relative to fecal indicators across different geographic and climatic regions. 

It is for the above reasons that experts in the field of microbial water quality generally agree that 

the principles of microbial ecology must be considered in water quality assessment. 

Understanding and applying these principles requires an assessment of the sources of fecal 

contamination, selection of the appropriate methods used to assess these sources, a connection 

between the intended AWQC application, and the fecal and/or pathogen indicator or pathogen 

measured and an analysis of that indicator’s fate and transport. Because of this understanding, 

workgroup members suggested a tiered assessment of a watershed, starting with traditional fecal 

indicators (conservative measures), and progressing to select a suite of indicators of 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 38 

contamination (providing source specificity and contaminant load information). A 

characterization of contaminant inputs through a sanitary investigation of the watershed and the 

waterbody being assessed should be undertaken, specifically assessing hazardous events, such as 

rainfall-induced runoff or wastewater treatment failure. Key information would pertain to a 

cataloguing of point sources (e.g., sewage effluent) and non-point sources (e.g., animals, runoff, 

on-site septic systems, environmental regrowth) so that a comparative risk assessment can be 

made based on the concentrations of standard (traditional) monitoring fecal indicators (i.e., E. 

coli, enterococci) and the expected presence of human pathogens. This initial assessment should 

assist in understanding the relationship between the contamination and epidemiological studies 

(indicator levels and risks of illness) mentioned elsewhere in these proceedings. In order to 

select appropriate indicators, a tiered toolbox approach was preferred by workgroup members 

rather than promoting use of one particular indicator over another. 

2.2 Tiered Toolbox Monitoring Approach 

An initial cataloguing of fecal pollution sources should include a review of existing monitoring 

data and a sanitary investigation to assess contaminant levels and sources that impact a given 

recreational water site. Based on that information, the indicator used in monitoring or the 

predictive modeling tool most appropriate for each CWA AWQC application and contamination 

source would be selected for the situation. Water quality assessment for each recreational water 

site should begin with the simplest analyses and assessment and move on to the most appropriate 

(specific or targeted) indicator for that site or purpose. More refined tools to differentiate 

between human, domestic animal, or environmental sources of fecal contamination could 

subsequently be used if deemed necessary. 

If a sanitary investigation determines that fecal pollution is human or animal origin, then E. coli

or enterococci could be used in the tier one water quality assessment because many pathogens 

can be expected to multiply in human and animal intestines. If the source of the “fecal” indicator 

organisms is determined to be from the environment (i.e., from growth in soil/sand, sediment, or 

water), then E. coli and enterococci may be inappropriate because most pathogens are not 

capable of environmental multiplication. As a result, the monitoring for this tier would need to 

be a fecal organism/chemical that does not amplify in the environment, such as spores of 

Clostridium perfringens or male-specific (F+) coliphages measured by culture- or molecularbased methods, specific members of the Bacteriodes bacteria measured by a molecular method, 

or use of a chemical indicator of fecal material. 

For a subsequent tier of monitoring, infectivity and/or molecular methods could be used for 

specific groups of pathogens such as, for bacterial pathogens (shiga-toxin producing E. coli

[STEC] or Salmonella), for protozoa (Cryptosporidium or Giardia), and for representative 

human sewage-borne viruses (enteroviruses, adenoviruses, polyomaviruses, or noroviruses). 

Location-specific data should be archived for potential use in future predictive modeling that 

might allow for management of site-specific fecal contaminants. Finally, if possible, archiving 

samples for further characterization and national comparison of new indicators, and/or pathogens 

and their respective methods would be advantageous assuming a national repository database and 

sample archive facility could be established. 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 39 

Several non-GI illnesses have been associated with recreational uses of water but these are not 

addressed by monitoring for fecal indicator microorganisms or chemicals because the etiological 

agents for these waterborne diseases come from non-sewage sources. Examples include animal 

urine (Leptospira spp.), shedding from human skin (Staphylococcus aureus), or microorganisms 

that are naturally present in freshwater environments (Aeromonas hydrophila, Naegleri fowlerii, 

Legionella pneumophila). Further, several human pathogenic Vibrio species (V. cholerae, V. 

vulnificus, V. parahaemolyticus, V. alginolyticus) are indigenous to marine and brackish waters. 

Because reliable indicators have not been developed for non-GI etiological agents, the best 

approach to address aquatic non-enteric pathogens is to characterize the aquatic conditions that 

increase the risk for these pathogens. For pathogenic Vibrio spp., this includes saline waters of 

warmer temperature and waters that contain high levels of nutrients. 

2.3 Parameters for Hazardous Event Pollution Monitoring 

The first approach to investigate a hazardous event (sewage discharge, rainfall impact, etc.) 

would be to assay for fecal indicators (appropriate for a climatic/geographic area of concern, see 

Section 2.4). The primary indicators of fecal contamination are E. coli or enterococci; however, 

based on the classification from an initial sanitary investigation, alternatives may include 

Clostridium perfringens or F+ coliphages (dependent on a robust method being confirmed). 

These must be demonstrated to relate to a possible health outcome (see Section 2.4). When 

information is required on source characterization, then additional microbial indicators (see 

Section 2.5) are generally preferred over chemical biomarkers (see Section 2.7). 

 

Focused sampling during and after higher risk periods is important when information from the 

sanitary investigation (which may include system models) is used to predict such risk. For these 

applications, the context of the likely pathogen group(s) should dictate the type of indicator to 

assay. For example, for rainfall in an area possibly impacted by on-site septic systems, viruses 

are considered the most mobile pathogen group so use of virus model organisms, such as the F+ 

coliphages, would be informative. For sites contaminated by concentrated animal feeding 

operations (CAFOs), reasonable pathogen index tests include shiga-toxin producing E. coli or 

Cryptosporidium. This approach assumes that some background level of the targeted group is 

known for the area of concern (see Section 2.8, research needs). 

2.3.1 Microbiological Parameters 

The Beaches Environmental Assessment and Coastal Health (BEACH) Act of 2000 requires 

States with coastal or Great Lakes recreational waters to adopt the current (US EPA, 1986) 

criteria for E. coli and enterococci. In November 2004, EPA promulgated a final rule that put 

federal standards in place for the 21 coastal states that had not adopted the 1986 criteria or 

established criteria as protective of human health as EPA’s 1986 criteria. However, these federal 

criteria apply only to coastal states and Great Lakes waters. In many cases, a fecal coliformbased standard still applies to many states having only inland waters. It is important to note that 

the results of the epidemiological studies used to generate the 1986 criteria for coastal and Great 

Lakes waters may not be directly applicable to all inland waters. 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 40 

2.4 Traditional Fecal Indicators (Coliforms and Enterococci) 

Consideration of the environmental context for which these traditional indicators are used is 

critical to the interpretation of the results. For example, wastewater treatment/disinfection may 

be effective in reducing the number of these traditional fecal indicators but ineffective in 

reducing/inactivating some pathogens of concern (Blatchley et al., 2007). Some industrial 

treatment systems may contain/enable replication of high number of “fecal indicators,” which are 

not necessarily associated with fecal sources (Degnan, 2007; Gauthier and Archibald, 2001). 

Ambient water and soils in tropical environments may be conducive to the growth of 

environmental strains of E. coli and enterococci (Fujioka and Byappanahalli, 2001). A similar 

situation was found in temperate Australian waters (Ashbolt et al., 1997; Barnes and Gordon, 

2004; Davies et al., 1995) and these indicators have also been found to persist in U.S. beach 

sand/sediments (Whitman et al., 2006). 

The range of strains of fecal indicators identified by traditional culture-based methods may differ 

from those identified by enzyme-based and quantitative polymerase chain reaction (qPCR 

[molecular])-based methods. Further, the strains more associated with fecal matter are not 

differentiated from the environmental strains by all of these methods. There are commercially 

available systems that can aid in the discrimination of strains; however, less expensive typing 

kits do not accurately provide such discrimination for environmental strains. It is important to 

note then when quantifying fecal indicator organisms, different methods target different strains. 

For example, cells stressed by wastewater disinfection processes may be enumerated using MPN 

(Most Probable Number) methods but excluded by methods enumerated by colony forming unit 

(cfu) methods. When current qPCR methods are used, both viable and non-viable cells are 

detected. In addition, the number of gene targets may vary per cell and therefore do not provide 

comparable information to culture-based results. 

 E. coli 

Of the traditional fecal indicators (see also Appendix E, Text Box E-1), only E. coli has been 

shown in epidemiological studies to consistently relate to health outcomes for freshwater 

recreational water users (Cabelli et al., 1982; Wade et al., 2003; Wiedenmann et al., 2006). In 

marine/estuarine waters, E. coli is more readily inactivated than enterococci and appears to 

correlate less well to health risk than enterococci for saline water environments. 

Subtyping of different strains of E. coli (library-dependent microbial source tracking methods) 

appears to be very site-specific if useful at all. Thus, it is not generally suggested as an effective 

way forward to separate environmental sources of E. coli from fecal sources across the United 

States (see Section 2.5). 

Enterococci 

The enterococci are the major group of fecal indicators that have a clear link to GI illness and 

upper respiratory disease in bathers in marine and fresh recreational waters (Kay et al., 2004). 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 41 

There are, however, several shortcomings in the use of current methods for enterococci. Most 

importantly, there is a range of different Enterococcus spp. detected by current methods. Based 

on unpublished Californian studies (Stephen Weisberg, SCCWRP, personal communication, 

2007), greater fecal specificity may result from specific identification and enumeration of E. 

faecalis or E. faecium or molecular-based methods targeting specific genes within these species 

(e.g., ribosomal RNA or enterococcal cell surface-associated protein and its gene Esp) (Lehner et 

al., 2005; Liu et al., 2006). However, no robust method is currently available that readily 

provides such information, nor has this concept been verified at other U.S. recreational water 

sites (Anderson et al., 1997). 

2.5 Alternative Fecal Indicators 

2.5.1 Bacteria 

 Clostridium perfringens 

C. perfringens is a member of the sulphite-reducing clostridia (SRC), which are spore-forming 

anaerobic bacteria excreted in human and animal fecal matter, but unlike other SRC, do not 

appear to grow in the aquatic/soil environment. These bacteria have been used as fecal indicator 

organisms for decades. Australian and North Carolina studies show C. perfringens levels in 

humans comparable to levels found in dog and feral pig feces, but low levels in cattle, sheep, 

horses, and birds (Leeming et al., 1998; Mark Sobsey, University of North Carolina, Chapel Hill, 

personal communication, 2007). Importantly, because C. perfringens does not appear to grow in 

aquatic/soil environments, it has potential to be useful as a fecal indicator for tropical 

environments such as in Hawaii where growth of E. coli and enterococci in soil/sand, sediment, 

and water make those indicator organisms less useful (Byappanahalli and Fujioka, 1998; Hardina 

and Fujioka, 1991; Roll and Fujioka, 1997). For example, in ambient streams in Hawaii, 

concentrations of fecal coliforms, E. coli, and enterococci consistently exceed recreational Water 

Quality Standards due to contribution by extra enteric sources (Hardina and Fujioka, 1991, 

Luther and Fujioka, 2004). Thus, monitoring inland and coastal waters for C. perfringens

provides reliable data for sewage contamination and is used by the Hawaii State Department of 

Health to confirm a sewage contamination event (Fujioka and Byappanahalli, 2001). 

The presence of C. perfringens (spores) in water, therefore provides evidence of existing 

human/urban fecal contamination, which may reflect either recent or historical fecal 

contamination from humans or animals. Although methods have been available for some time, 

confirmation of a robust and consistent method approach should be developed. For example, the 

advantages of heat-treating samples (or not) to remove background vegetative cells and induce 

spore germination remains unclear. 

The environmental resistance of C. perfringens spores has both advantages and disadvantages in 

their application as a fecal indicator, pathogen indicator, and as an indicator of wastewater 

treatment efficacy. Collectively, these make C. perfringens spores better indicators of persistent 

and treatment-resistant pathogens, such as Cryptosporidium oocysts (resistance to chlorine) and 

adenoviruses (resistant to UV radiation). However, they can be so persistent in the environment 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 42 

that they may not indicate the presence of pathogens coming from recent (contemporary) fecal 

contamination. 

Recent studies on the partitioning of C. perfringens and other fecal indicator microbes in 

environmental waters, such as E. coli and coliphages, indicate differences in the extent of their 

association with settleable particulate matter (Characklis et al., 2005; Krometis et al., 2007). To 

date, limited data have been collected on any potential relationship between C. perfringens

counts and recreator health outcomes (see Section 2.8). 

 Bacteroides 

Bacteroides spp. are members of the normal microbiota of warm blooded animals and studies 

have shown them to be among the most prevalent genera in feces (Holdeman et al., 1976). 

Because they are strict anaerobes that grow in the GI tract of humans and animals, they do not 

survive for long periods of time under aerobic conditions (Kreader et al., 1998). However, their 

survival under different redox potential conditions (e.g., sediments) has not been thoroughly 

studied. Recent research based on molecular methods has demonstrated that some isolates may 

be strictly associated with human feces (Walters et al., 2007). If this is the case, these 

microorganisms also have the potential to be used for microbial source tracking (MST) 

applications. 

Studies have indicated human versus bovine specificity in certain 16S rRNA genes therefore, 

16S rRNA Bacteroides genes have been used as an index of human or animal contamination in 

Europe and the United States. The ability to differentiate sources of fecal contamination is very 

attractive when it comes to determining risk as a result of exposure via recreational waters. The 

molecular methodology has been shown to be robust and applicable in the United States and 

Europe, though it remains to be seen if this robustness holds across temperate versus tropical or 

subtropical zones of the world. Some results from Hawaii and Europe indicate that these 

methods may be useful under those climatic conditions (Betancourt and Fujioka, 2006; Seurinck 

et al., 2006). Either way, it is unclear whether quantification of human/animal fecal loads will be 

consistent or indeed possible using these molecular-based methods. 

Though data from molecular techniques have shown that there is specificity in the human versus 

animal strains, the fact that both human and animal feces contain a diverse population of 

Bacteroides spp. may limit the usefulness of some detection methods. Methods that focus on 

one target may have reduced sensitivity as a result of the lower concentrations of a specific 

Bacteroides strain. Data have shown that Bacteroides spp. does not survive for long periods of 

time in the environment; thus, Bacteroides detected by qPCR in ambient waters includes a high 

percentage of inactivated microorganisms. The fact that qPCR detects both live and dead 

organisms needs to be considered when data are applied in different contexts (e.g., different 

AWQC applications). That is, qPCR detection is linked to the time the nucleic acid remains 

within the cell without being degraded. EPA data have demonstrated that the DNA remains 

undegraded for up to 20 days (Kevin Oshima, USEPA, Office of Research and Development, 

personal communication, 2007) in the inactivated unlysed cells. This may be equivalent to the 

survival of some enteric pathogens under environmental conditions. Thus, the presence of 

Bacteroides may have possible use as an indicator of health effects. Because the concentration 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 43 

of Bacteroides spp. in feces is much higher than other fecal bacteria, once the persistence of 

PCR-detected types is better understood, it may also be useful for TMDL applications, although 

this possibility needs further evaluation. 

The molecular methodology for the detection of general and human-specific Bacteroides spp. is 

already being tested and has proven to be robust (Gawler et al., 2007; Walters et al., 2007). 

Thus, if detection methods are validated in the United States there is an excellent opportunity for 

short-term advances in quickly adapting the use of this alternate indicator for the rapid analyses 

of recreational waters and fecal source identification. 

2.5.2 Bacteriophages 

 Coliphages 

Bacteriophages (viruses) that infect E. coli and possibly other closely related coliform bacteria 

are called coliphages. There is a long history of research documenting the possible uses of 

phages as indicators of fecal contamination (Grabow et al., 1998). Coliphages were first 

proposed as indicators of the presence of E. coli bacteria and are taxonomically very diverse, 

covering the following six virus families: three families of double-stranded DNA viruses 

(Myoviridae, Styloviriae, Podoviridae), two families of single-stranded DNA phages 

(Microviridae and Inoviridae), and one family of single-stranded RNA viruses (Leviviridae). 

Coliphages that infect via the host cell wall of E. coli are called somatic coliphages (including 

families Myoviridae, Styloviriae, Podoviridae, and Microviridae). Male-specific (also called F+) 

coliphages (Inoviridae and Leviviridae) infect by attaching to hair-like appendages called F-pili 

protruding from the host bacterium surface. 

Somatic phages have been explored as fecal, treatment efficacy, and health effects indicators. 

However, little is known about the specificity of their occurrence in human or animal feces. 

Furthermore, their considerable taxonomic diversity and the lack of readily available and 

convenient methods to distinguish or specifically detect the different groups has made it difficult 

to determine which, if any, are effective fecal, treatment efficacy, or health effects indicators. In 

a recent study by Colford et al. (2007), somatic coliphages were not predictive of human health 

risks from bathing in marine recreational water largely impacted by non-point sources of fecal 

contamination. Furthermore, there is very little information on the sources and ecology of the 

somatic coliphages, especially for the different taxonomic groups. With rare exceptions, they are 

detected as a broad group with no effort to identify specific taxonomic groups or relate or 

attribute these different taxonomic groups to specific sources of human or animal fecal 

contamination or possibly non-fecal environmental sources. 

Male-specific coliphages have been studied extensively as fecal indicators and for 

water/wastewater treatment/disinfection efficacy. Furthermore, F+ RNA coliphages can be 

distinguished genetically (via nucleic acid detection methods) or antigenically (via 

immunological methods), into four distinct subgroups: I, II, III, and IV. There is reasonably 

good evidence that Groups II and III are associated primarily with human fecal waste and that 

Groups I and IV are associated primarily with animal fecal waste (Furuse et al., 1975; Hsu et al., 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 44 

1995; Osawa et al., 1981) in the United States. Male-specific coliphages have been included in 

some epidemiological studies of recreational water. In the recent study by Colford et al. (2007) 

at a marine recreational water site impacted primarily by non-point source fecal contamination, 

F+ coliphages were the only microbial indicator whose levels were associated with risks of 

swimming-associated illness. 

 Strengths of Coliphages as Indicators 

Advantages of both somatic and F+ coliphages as fecal indicators include their (1) presence in 

relatively high concentrations in sewage; (2) relatively high persistence through wastewater 

treatment plants, compared to typical bacterial indicators like E. coli and fecal coliforms 

(coliphages may behave similarly to human viruses during wastewater treatment); and (3) ability 

to be detected in relatively small (100 mL) to medium (1,000 mL) volumes of fecally 

contaminated water. 

Coliphages can be detected by relatively simple, affordable, and robust culture methods—several 

of which have been standardized and collaboratively tested as EPA, EU, and ISO (International 

Organization for Standardization) water methods. However, the EPA methods for somatic and 

F+ coliphages have been fully validated only for groundwater and not for ambient surface waters 

or wastewaters. Recent research also describes a rapid, simple, and affordable method to detect 

and group infectious F+ coliphages by short-term (3-hour) enrichment culture, followed by quick 

(<1 minute) detection of positive cultures by a simple immunological (particle agglutination) 

method scored by simple visual examination (Love and Sobsey, 2007). The method can be 

conducted in an MPN format to quantify concentrations of the different F+ coliphage groups (F+ 

DNA and F+ RNA Groups I, II, III, and IV). 

These findings indicate that robust, simple, rapid, and low-cost F+ coliphage methods could be 

implemented within the 2 to 3 year time frame if correlations to health targets are observed in 

epidemiological studies. It would be valuable if water samples from upcoming EPA and 

SCCWRP (Southern California Coastal Water Research Project; see also Appendix F) marine 

recreational water epidemiological studies are collected and archived for analysis by these 

emerging qPCR methods once they are fully developed and validated. In addition, research is 

suggested to compare the performance of methods for rapid coliphage detection by short-term 

enrichment-particle agglutination and qPCR and to consider the advantages and disadvantages of 

these two methods for application to recreational water quality monitoring. 

 Limitations of Coliphages as Indictors 

Although effective methods are available to recover, detect, and quantify coliphages, limitations 

and unsolved problems with these methods remain. The single agar layer method (EPA Method 

1601) for enumeration of coliphages by counting plaques is limited to sample volumes of about 

100 mL. Analyzing larger volumes is cumbersome and consumes considerable materials, such 

as Petri plates. Although the enrichment culture-spot plate method can be used to conveniently 

analyze sample volumes of up to 1 L, the method makes it more difficult to resolve coliphage 

mixtures when more than one type of coliphage is present in the enriched sample volume. In 

some cases, one coliphage will grow faster and to a higher concentration. This makes it difficult 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 45 

to detect and isolate minority coliphages that grow more slowly and to lower concentrations. 

However, detection of all of the different coliphages present as a mixture in enriched sample is 

possible by either nucleic acid or immunological (particle immunoagglutination) methods. 

The ecology of both somatic and F+ coliphages remains poorly documented and inadequately 

understood. Information is lacking on bacterial host range, sources, occurrence, and behavior 

(survival, transport, and fate) in different geographical regions having different climates 

(temperate, subtropical, and tropical) and in waters and wastewaters of different microbial 

quality. 

F+ coliphages can also be detected by molecular-based methods, including conventional and 

qPCR methods, according to recent studies. Careful review of these studies suggests that there 

may be deficiencies in the ability of these qPCR methods to detect the broad range of F+ DNA 

and F+ RNA coliphages and their subgroups. Nevertheless, research is now in progress to 

further improve F+ RNA qPCR by developing and performance-validating primer sets for all 

four genogroups of F+ RNA coliphages (Stephanie Friedman, EPA Environmental Effects 

Research Laboratory Laboratory, personal communication, 2007). Reliable methods have not 

been developed for genetic analysis and characterization of different somatic coliphage 

taxonomic groups. 

Very few studies have been conducted to evaluate F+ coliphages as predictive indicators of 

human health risks from recreational use of water. The most extensive study was conducted by 

Colford et al. (2007). That study showed no health relationship for somatic coliphages, but a 

weak relationship for F+ coliphages examined by two different assay methods—an MPN version 

of EPA Method 1601 (enrichment-spot plate method) and EPA Method 1602 (saline agar layer 

plaque assay). However, these methods have not been performance characterized and fully 

validated for use in fresh and marine recreational waters according to EPA collaborative study 

protocols. Additional studies of this type are needed to clarify their potential criteria uses. 

 Bacteroides phages 

Bacteroides phages, viruses that specifically infect Bacteroides spp., have been tested as 

indicators of fecal material in Spain and more recently in the U.K. The former used a method 

(bacterial host) that was tested in some labs in the United States but further efforts were not 

made as a result of the perceived difficulty in dealing with anaerobic methodology. Attempts to 

use the B. fragilis strain VPI 3625 showed low occurrence of these phages in the United States 

(Chung and Sobsey, 1993). Spanish data initially supported the use of B. fragilis HSP40, which 

is specific to phages that only occur in human feces. More recent British work indicated human 

specificity and high phage counts for a newer Spanish host Bacteroides (GB-124), thus providing 

the opportunity for determining human fecal contamination and virus transport using a rapid and 

inexpensive phage method (Ebdon et al., 2007). 

Strengths of Bacteroides Phages as Indicators 

The methods for the detection of Bacteroides spp. phages are inexpensive and their presence 

indicates human fecal contamination. In addition, there is research that indicates specific 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 46 

Bacteroides hosts are susceptible to phages that are possibly useful for MST, which would be 

beneficial for its use for CWA §304(a) criteria (Chung and Sobsey, 1993; Ebdon et al., 2007). 

Limitations of Bacteroides Phages as Indicators 

The diversity of phages including their specificity for human host strains is not yet well 

characterized over a range of locations. This type of data could be easily obtained in 2 to 3 

years, but if it is discovered that there is wide variability in their validity for MST, then their 

attractiveness for use in national AWQC would be reduced. Many laboratory personnel may not 

have the experience required to work with anaerobic microorganisms; however, little additional 

laboratory equipment would be required. Because detection methods have not been standardized 

in the United States, it would likely take several years to develop standardized methods for 

enumeration of Bacteroides phages in water samples. 

2.5.3 EU Project Summary of Tracers 

Several microbes and chemicals have been considered as potential tracers to identify fecal 

sources in the environment. However, to date, no single approach has been shown to accurately 

identify the origins of fecal pollution in all aquatic environments. In a European multilaboratory study, different microbial and chemical indicators were analyzed in order to 

distinguish human fecal sources from nonhuman fecal sources using wastewaters and slurries 

from diverse geographical areas across Europe. Twenty-six parameters, which were later 

combined to form derived variables for statistical analyses, were obtained by performing 

methods that were achievable in all the participant laboratories and include the following: 

enumeration of fecal coliform bacteria, enterococci, clostridia, somatic coliphages, F+ RNA 

phages, bacteriophages infecting Bacteroides fragilis RYC2056 and Bacteroides

thetaiotaomicron GA17, and total and sorbitol-fermenting bifidobacteria; genotyping of F+ RNA 

phages; biochemical phenotyping of fecal coliform bacteria and enterococci using miniaturized 

tests; specific detection of Bifidobacterium adolescentis and Bifidobacterium dentium; and 

measurement of four fecal sterols. A number of potentially useful source indicators were 

detected (bacteriophages infecting B. thetaiotaomicron, certain genotypes of F+ bacteriophages, 

sorbitol-fermenting bifidobacteria, 24-ethylcoprostanol, and epicoprostanol), although no one 

source identifier alone provided 100% correct classification of the fecal source. Subsequently, 38 

variables (both single and derived) were defined from the measured microbial and chemical 

parameters in order to find the best subset of variables to develop predictive models using the 

lowest possible number of measured parameters. To this end, several statistical or machine 

learning methods were evaluated and provided two successful predictive models based on just 

two variables that provided 100% correct classification—(1) the ratio of the densities of somatic 

coliphages, and phages infecting Bacteroides thetaiotaomicron to the density of somatic 

coliphages and (2) the ratio of the densities of fecal coliform bacteria and phages infecting B.

thetaiotaomicron to the density of fecal coliform bacteria. Other models with high rates of 

correct classification were developed but they required higher numbers of variables (Blanch et 

al., 2006). 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 47 

2.6 Pathogens and Pathogen Indicators 

Many beach regulators and scientists believe that there are significant opportunities to utilize 

specific pathogens or pathogen indices to better understand or characterize potential health risks 

from recreational exposures. Some reasons for not doing so, however, remain—especially that 

pathogen numbers are generally significantly lower and more variable than fecal indicator 

organisms. Nonetheless, pathogens could be utilized to accurately determine risks as there have 

been a number of studies that define actual human dose-response from oral exposures such as 

may be encountered during swimming. Enteric pathogens are found in raw and even treated 

sewage so there is merit in using them in water quality monitoring to assess the risks from 

exposure. Also, it is possible that an entire “class” of pathogen risks can be determined by the 

presence of an “index pathogen” representing that group. The current capabilities of molecular 

methods to detect, identify, and enumerate pathogens has increased regulators’ and stakeholders’ 

interest in seeing these applied to ambient water quality monitoring to better protect public 

health. 

There are a number of criteria related capabilities that may be provided by use of specific 

pathogen or index pathogen monitoring, such as the following: (1) determination of specific 

pathogen residuals from sewage discharges, the data from which could then be used to conduct 

quantitative microbial risk assessment (QMRA) studies to assess relative levels of public health 

concern at a beach; (2) establishment of “model” pathogens and index pathogens that could be 

used to assess risks from new or reemerging pathogens (an example would be the use of a virus 

model to assess the recreational risks from avian influenza [H5N1] because this virus can be 

released from infected human and animal feces [especially waterfowl] and can directly or 

indirectly contaminate recreational waters); and (3) determination of levels of pathogens that can 

subsequently be used in QMRA studies to inform decision making relative to whether or not a 

beach should be closed or reopened after a closure. 

There are currently two approaches to pathogen detection, identification, and enumeration, (1) 

the traditional culture-based techniques that are especially useful in determining viability of the 

sampled materials; and (2) the molecular-based methods (PCR, antibody-based, and metabolicbased) that generally cannot distinguish between viable and non-viable pathogens, but which 

may be quite useful in further differentiating or speciating pathogens in water samples. The 

culture-based methods are useful for recreational waters in that they can determine if there is a 

viable disease risk from exposure while the molecular methods may not be capable of discerning 

viability. 

Moreover, the culturable isolate can be further characterized for the presence of human virulence 

genes and compared to clinical isolates in waterborne disease outbreaks. In contrast, molecularbased methods may not be capable of discerning viability although the presence of virulence 

genes can also be assayed by molecular methods. Because molecular methods do not recover the 

entire microorganism, further characterization of that microorganism is limited. 

Specific tracking of host sources using molecular techniques for pathogens can be very useful in 

setting TMDLs, as it can help identify the source of the pathogen and its magnitude. Recent 

improvements in molecular science applications have brought about a capability to 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 48 

simultaneously sample and evaluate large numbers of pathogens (e.g., microarray technology). 

Microarray technology still requires high concentrations of pathogens for detection. However, 

ambient waters generally contain pathogen levels below the limits of detection and are unevenly 

distributed in the water matrix. Thus, research is needed to determine how to best apply these 

advanced technologies for characterizing enteric and non-enteric disease contaminants, their 

levels, and potential risks associated with their presence in recreational waters. 

Workgroup members expressed some concerns about using either specific pathogens or pathogen 

class indices as a first tier monitoring requirement for infectious disease risks in a recreational 

water setting. First, pathogens are typically present in low concentrations in treated sewage, 

receiving waters, and also in recreational waters; therefore, high volumes of water need to be 

sampled, which is time consuming, costly, and contributes to analytical variability. Second, 

pathogen presence is typically sporadic in a community as many waterborne diseases may not be 

endemic, but are rather transient/episodic so they do not represent a constant contaminant source 

of fecal pathogens to monitor. Third, there is a variable component in terms of fecal 

contributions from humans and various animal sources in ambient waters that may have an 

impact on determining recreational exposure risks. Typically, a number of the bacterial 

pathogens (e.g., toxigenic E. coli, Campylobacter) are found in both humans and animals, but 

there may be differences in strain virulence or infectivity potential from different sources. 

Likewise, there are a number of protozoan pathogens that cross-infect animal species and 

humans (Giardia spp. and Cryptosporidium parvum). On the other hand, human enteric viruses 

have a much more limited host range and except for a potential few (e.g., hepatitis E virus 

[HEV]), animal sources of enteric viruses are not a major public health concern in recreational 

waters. Lastly, it is important to note that at any given time only a small portion of the human 

population may be infected and excreting any specific pathogen or index pathogen. Thus, large 

wastewater treatment systems may always contribute a small level of pathogens of concern while 

septic systems or small treatment systems may not have enough contribution from the infected 

population to ensure that those effluents would contain specific pathogens of concern to use as a 

routine measure of contamination—even if the disease organisms are endemic in the population. 

Also, many types of pathogens are associated with a seasonality or periodicity to their 

occurrence in a given population. 

It is reasonable to use specific pathogens or their index organisms (or model organisms) in a 

toolbox or tiered approach to monitoring if considered as other than as a first tier measure of 

fecal contamination. In a toolbox approach, the determination of the presence and concentration 

of specific pathogens or their index organisms could be useful to characterize risks once it has 

been determined that there is a trigger level of fecal contamination at a given recreational water 

site. Dose-response data for a number of the primary pathogens from oral exposures is available 

and these data would help more narrowly define exposure risks for a detected pathogen. Because 

of the costs, time for analysis results, and expertise needed to test specific pathogens or index 

organisms, these measurements would be the last set of measurements applied to monitoring of 

recreational sites for determining potential sources. The specific pathogen monitoring tools for 

other AWQC applications (e.g., TMDLs) could allow States to determine sources and 

concentrations of the pathogens for particular upstream contamination events. Also, pathogens 

could be incorporated into future NPDES permit limits and be used in the future to assess 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 49 

wastewater treatment plant discharges for specific pathogens of concern downstream and to 

provide a better understanding of the efficacy of treatment and disinfection processes. 

2.7 Chemical Biomarkers of Fecal Contamination 

Various shortcomings have been identified in relying solely on indicator bacteria or 

pathogen/index microorganisms for CWA criteria uses. Methods for MST in aquatic 

environments have been developed and discussed above that distinguish animal from human 

sources in the United States and in Europe (Blanch et al., 2006). However, for some specific 

tiered approaches in sanitary investigations, certain chemical biomarkers of sources may provide 

timely or higher resolution information in fecal source tracking. Some of the most promising are 

discussed below. 

2.7.1 Fecal Sterols

The most commonly known fecal sterol, coprostanol (5β-cholestan-3β-ol), is largely produced in 

the digestive tract of humans and dogs by microbial hydrogenation of cholesterol (Leeming et 

al., 1996). The term “sterols” is generally used for all sterols and stanols (i.e., “fecal sterols”) 

and is also a more specific term denoting a steroidal alcohol with at least some degree of 

unsaturation. 

Two pathways have been proposed for the biotransformation of cholesterol to coprostanol, one in 

the gut and the other in natural sediments. The α-configured form (cholestanol) is the most 

thermodynamically stable of the reduction products and is found ubiquitously in the 

environment; whereas coprostanol is largely of fecal origin, but some reisomerization can yield 

low levels in natural sediments. Both forms are easily resolved by gas chromatography-mass 

spectrometry (GC/MS) analysis. 

An important advance in using these fecal sterols has been the realization that it is critical to 

measure both the ratios and absolute concentration of at least four of these related compounds to 

attribute fecal source contributions between humans, herbivores, and birds (Ashbolt and Roser, 

2003). Coprostanol alone has never really been embraced as an indicator for sewage pollution 

because its presence is not considered as indicative of a health risk due to multiple sources and 

low level environmental production in sediments. 

The fecal sterol biomarker technique offers many diagnostic and quantitative advantages when 

used in conjunction with traditional techniques for detecting sewage pollution. When careful 

data interpretation is undertaken, fecal sterol analysis, although expensive and complex, has 

resolved problems of source attribution in urban and rural environments not possible with use of 

traditional fecal indicator bacteria and coliphage assays (Roser and Ashbolt, 2007). 

2.7.2 Caffeine 

Caffeine has been extensively examined as a tool for assessing human influence on aquatic 

systems. Although caffeine is metabolized when consumed, a small amount (<10%) of ingested 

caffeine remains intact when excreted (Peeler et al., 2006). Most work in the past decade has 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 50 

focused on heavily polluted systems and efficiency of caffeine removal in sewage treatment 

plants, although with improvements in techniques and the lowered detection limits, the scope of 

application has broadened to include stream, wetland, estuarine, and groundwater systems. 

A major disadvantage is that caffeine is often present in the urban environment from numerous 

plant species debris as well as from human “dumping” of coffee wastes. Further, the current 

methods used (specific extraction and GC/MS analysis) are relatively complex and expensive. 

Nonetheless, based on the recent work of Peeler et al. (2006) in southwest Georgia, caffeine 

appears immediately below wastewater discharge sites and within towns, but not in rural 

watersheds. Overall, aquatic concentrations of caffeine are typically less than for fecal sterols, 

but caffeine tends to stay in solution, whereas the sterols associate with fine particulates. 

2.7.3 Optical Brighteners and Other Sewage Markers 

Recent sewage contamination may be readily identified in waters by the presence of ammonium, 

turbidity/particle counts, phosphate, odor, and a range of organics present. Depending on the 

sensitivity and AWQC applications, some of these analytes may provide value in fecal source 

identification. 

One relatively inexpensive and sensitive fecal source identification method is fluorometry 

(Hartel et al., 2007). Fluorometry identifies human fecal contamination by detecting optical 

brighteners (also called fluorescent whitening agents) in water. Optical brighteners are 

compounds added primarily to laundry detergents, and because these brighteners emit light in the 

blue range (415 to 445 nm), they compensate for undesirable yellowing in clothes (Kaschig, 

2003). In the United States, 97% of laundry detergents contain optical brighteners (Hagedorn et 

al., 2005). Because household plumbing systems mix effluent from washing machines and 

toilets together, optical brighteners are associated with human sewage in septic systems and 

wastewater treatment plants. However, in order to use optical brighteners to detect human fecal 

contamination properly, they must be combined with use (counts) of fecal indicator bacteria. For 

example, effluent from a wastewater treatment plant contains optical brighteners, regardless of 

how effective the treatment processes have been at removing or inactivating pathogens. Thus, 

data on the presence of optical brighteners without accompanying data on viable fecal indicators 

does not provide information on the potential health risk from pathogens. 

However, results of studies that have combined fluorometry with counts of fecal bacteria have 

been contradictory. Although various reports have documented a strong fluorescent signal and 

high numbers of fecal enterococci, cases of no correlation between fluorometry and counts of 

fecal bacteria have also been reported (Hartel et al., 2007). One key confounder has been the 

presence of organic matter that fluoresces and interferes with fluorometry. Yet, this interference 

can be reduced by adding a 436-nm emission filter to the fluorometer, which may reduce 

background fluorescence by over 50%. As long as the fluorometer used is equipped with a 436-

nm filter, it appears that targeted fecal indicator sampling combined with fluorometry can be a 

relatively inexpensive method for identifying human fecal contamination in water. 
U.S. Environmental Protection Agency Experts Scientific Workshop

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In summary, chemical biomarkers appear to have niche applicability for those with the resources 

and expertise to use them and where such biomarkers are advantageous, such as where other less 

expensive MST options have shown to be unsatisfactory or provide ambiguous results. 

2.8 Research Needs 

2.8.1 Near-term (1 to 3 Years)

1. Validate the range and species or sub-species diversity qPCR assays identify, and how 

they may relate to health outcomes for recreational exposures (also using archived 

epidemiological study material) (high priority). 

a. Example priority list of organisms: enterococci, Bacteroides, C. perfringens, E. 

coli, F+ RNA coliphages, and somatic coliphages

2. Investigate the potential for speciation of enterococci to identify fecal-specific (preferably 

human) from environmental strains, then apply results to future MST and 

epidemiological studies (high/medium priority). 

3. Ensure that archived samples (collected from epidemiological/specific studies) are 

suitably sorted and stored (to maintain their integrity) for future viability as well as 

molecular-based method comparison or validation studies for candidate 

indicators/methods (high priority). 

4. Validate C. perfringens (SRC) assay’s robustness over a range of water and sediment 

sample characteristics and correlate health effects relationships to this indicator (high 

priority). 

5. Determine if there are Bacteroides analytical targets that are human-specific and validate 

their use over a range of geographic areas, diverse populations, climates, and water 

quality conditions to correlate levels to health targets (high priority). 

6. Conduct health and epidemiological studies with as wide a range of microorganisms 

(indicators/MST organisms) as possible to identify risk correlations for a range of 

pathogens/indicators (including bacteriophages) from various nonhuman sources; at a 

minimum would include E. coli, enterococci, enterococci-qPCR, coliphages, 

Bacteroides-PCR, C. perfringens; where possible, Bacteroides phage GB-124, 

enterohemorrhagic E. coli (EHEC); and check for absence of human Norovirus-qPCR, 

adenovirus-qPCR, Pan-enterovirus-qPCR, polyoma viruses (high priority). 

7. Conduct health and epidemiological studies with microorganisms from nonhuman 

sources such as Leptospira spp. in fresh and S. aureus and pathogenic Vibrio spp. in 

marine recreational waters and determine appropriate indicators for these pathogens 

(medium priority). 

8. Conduct epidemiological studies incorporating the measurement of pathogens of interest 

(along with indicators) as monitoring tools in sewage in order to determine the 

correlations of the occurrence of these pathogens to indicators, and to better understand 

their association with diseases at downstream recreational locations. For instance, while 

it is strongly suggested that enteric viruses are major contributors to illness from 

swimming, there have not been prospective epidemiological studies to actually support 

this association. Use serology (also consider collecting saliva and possibly fecal 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 52 

samples) to help identify the etiological agents from sewage that are impacting on 

recreational water sites (high priority). 

a. Conduct similar studies in recreational waters (above refers to studies in sewage) 

(medium priority). 

9. Systematically identify and evaluate more reproducible, accurate, and cost effective 

methods to sample and identify priority pathogens or their index organisms (including the 

total adenoviruses, [e.g., Groups A-F and adenovirus 40/41], but also JC virus, and 

Norovirus) in ambient waters (medium priority). 

10. Determine if there are any appropriate sewage associated bacterial pathogens that can 

adequately serve as an index of any of the currently known sewage-borne bacterial 

organisms to use on a more routine basis in recreational water criteria. For example, 

determine if monitoring recreational waters for Salmonella spp. bacteria and phages of 

Salmonella can fulfill the criteria of a pathogen index for sewage-borne bacterial 

pathogen can be developed (medium/low priority). 

11. Conduct microbial fate and transport studies to determine relationships between 

traditional and new fecal indicators, index pathogens, and priority pathogens in treated 

effluents and in downstream recreational waters to compare and validate their 

applicability for specific criteria uses (high/medium priority). 

2.8.2 Longer-term Research Goals

The research below may take longer than 2 to 3 years of research to complete. These are not

presented in order of priority. 

1. Review archived samples to look for trends in evolution of viruses (new or cyclic reemergence of viruses) and the efficacy of current indicator targets used by molecular 

methods for health based correlations. 

a. Develop predictive models to understand the conditions that promote the 

emergence or re-emergence of new pathogens. 

2. Continue to conduct additional epidemiological studies on non-point sources of fecal 

contamination and assess illness relationships to pathogen/indicators. 

3. Continue to conduct sewage surveillance for pathogens as a means of public health 

surveillance and informing pathogen monitoring programs for CWA purposes. 

4. Develop robust method for speciation of enterococci with a view to identify fecal-specific 

(preferably human) from environmental strains; then apply to future MST and 

epidemiological studies (assuming initial studies suggest that this should be explored 

further). 

5. Conduct studies on beaches to characterize the usefulness of total adenoviruses (Groups 

A-F), adenovirus 40/41, JC virus, and Norovirus to meet recreational water quality 

criteria purposes. 

6. Conduct health/epidemiological studies to identify a range of pathogens/indicators from 

various nonhuman sources of fecal contamination. 
U.S. Environmental Protection Agency Experts Scientific Workshop

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CHAPTER 3 

METHODS DEVELOPMENT 

Stephen Weisberg, Chair, Southern California Coastal Water Research Project 

Alfred Dufour, USEPA 

Charles Hagedorn, Virginia Tech 

Sharon Kluender, Wisconsin State Laboratory of Hygiene 

Erin Lipp, University of Georgia 

Robin Oshiro, USEPA 
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3.1 Introduction 

The Methods Development workgroup focused on addressing the following four key questions: 

1. What are the attributes and criteria for deciding whether a new method or indicator is 

ready for adoption by EPA? 

2. What kinds of studies are necessary to quantify those attributes? 

3. Are there any new indicators/methods for which those studies have been conducted and 

that are ready for adoption? 

4. What studies (or modifications to planned studies) are most critical for EPA to implement 

in the next 3 years to support adoption of new methods/indicators in a criteria 

development framework? 

A critical starting point for the workgroup members was recognition that the evaluation of 

methods and/or indicators needs to be considered in context of the Clean Water Act (CWA) 

applications in which they would be used. The following five primary uses were identified by 

workgroup members: 

• Routine beach monitoring to support public health warning notification systems; 

• Routine beach monitoring data to support total maximum daily load (TMDL) decisions; 

• Rapid methods to track the progress of a sewage spill as it moves downstream or 

downcoast to improve the beach closure determinations; 

• Compliance assessments conducted at the terminus of National Pollutant Discharge 

Elimination System (NPDES) discharge pipes; and 

• Trends assessments to determine whether water quality conditions at a site are changing 

over time. 

The workgroup focused on the first two applications beacause members felt that they are most 

relevant to EPA’s desire to redefine their current recreational water quality criteria. However, 

several workgroup members also recognized the relevance of the other applications so a short 

section is included (see Section 3.7) that illustrates the similarities and differences in the method 

evaluation process for these other CWA uses. 

For water quality notification systems, two principal issues were identified that need to be 

addressed. The first is that current laboratory measurement methods require up to 24 hours to 

enumerate indicator bacteria. Contaminated beaches remain open during this processing period, 

but indicator bacteria may already have returned to acceptable levels by the time laboratory 

results are available and warning signs are posted. Continued advances and improvements in 

molecular- and immunological-based techniques provide new opportunities for measuring 

bacteria more rapidly. Although current (traditional/standard) methods rely on bacterial growth 

and metabolic activity, these new methods allow direct measurement of cellular attributes, such 

as genetic material or surface immunological properties. By eliminating the necessity for a 

lengthy incubation step, some of these methods have the potential to provide results in less than 

4 hours, enabling managers to take action to protect public health (i.e., post warnings or close 

beaches) on the same day that water samples are collected. This assumes that samples can be 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 60 

processed at the beach or that the time required for transportation to a laboratory is brief. For 

same day posting to be achieved, the results of the tests also have to be delivered to and 

evaluated by beach managers in a timely manner. 

The second issue workgroup members identified is that present standards used to evaluate 

recreational water quality data are based on a “one-size-fits-all model,” relying on use of a single 

indicator (e.g., enterococci at marine beaches) and a single standard for all recreational waters. 

There is growing recognition that enterococci measured on the beach may derive from many 

sources, including humans, domesticated animals, indigenous wildlife (including shore and 

migratory birds), and regrowth in sand, sediments, or on biofilms. The health risk to humans 

varies depending on which of these sources is responsible for the measured enterococci. As 

such, existing warning systems do not provide an equal level of health risk protection at all 

beaches. Moreover, the costly cleanup processes associated with the TMDL programs are not 

necessarily focused on the beaches that represent the greatest public health risk. There are 

additional concerns that cleanup activities, and associated costs, are being targeted at beaches 

where enterococci concentrations that exceed standards result from natural sources and 

processes. 

EPA could consider two means of adjusting their criteria framework to address one-size-fits-all 

concerns. The first adjustment is to develop additional indicators to replace, or to augment in a 

tiered fashion, the existing enterococci indicator as it is now used at marine beaches (US EPA, 

1986). These new indicators would be more specific to human sources and better related to 

human health risk than the existing indicator. 

The second potential adjustment is to adopt a framework similar to that of the World Health 

Organization (WHO, 2003), in which watershed characterization studies are used to adopt sitespecific standards. These site-specific standards would be based on perception of health risk 

resulting from the types of fecal sources in the watershed and the proximity of those sources to 

the beach. The Methods workgroup members felt strongly that source identification methods 

needed to be a key tool in characterizing risk and that further evaluation of source identification 

methods needed to be conducted if they are to be used in this context. 

This chapter is organized around describing the approach that would be used for assessing 

methods/indicators in the following three contexts: (1) replacement of existing methods with 

more rapid methods, (2) replacement of existing indicators with those that are more specific to 

human sources of fecal contamination, and (3) determination of source identification methods 

that can be used to characterize risk in the development of site-specific standards. Within each 

section, the adequacy of evaluations of methods/indicators is discussed and the most immediate 

research activities that would provide the greatest benefit to EPA for modifying monitoring 

and/or indicators within the next 5 years are highlighted. 

3.2 Classes of Indicators 

The evaluation of methods is a critical element in bringing new technology to the measurement 

of water quality. Current evaluation protocols were developed for cultural methods for 

enumerating bacterial indicators of fecal contamination. The evaluation usually included method 
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attributes regarding the performance of the method, such as specificity, accuracy, and precision. 

Further evaluation that addressed how the method performed in and between laboratories 

included multi-laboratory testing that determined how robust a method might be (i.e., how poorly 

can the method be performed and still produce useful results?). The question that arises is 

whether the current protocols for evaluating membrane filter culture-based methods are suitable 

for evaluating new methods that are being proposed for measuring water quality. Some of the 

new or alternative methodologies that are available for testing water quality include molecularbased methods, such as quantitative polymerase chain reaction (qPCR), nucleic acid sequence 

based amplification (NASBA), and transcription-mediated amplification (TMA). These methods 

amplify nucleic acid sequences to high levels such that they can be easily detected. Other 

methods use antibodies to which fluorescent compounds are attached. The fluorescent-tagged 

antibodies then attach to specific microbes and are “counted” in a flowcytometer. The preceding 

methods “count” dead and live bacteria and thus differ significantly from currently used 

quantitative cultural methods. 

Some recent methods do measure viable microbes in an indirect manner. For example, enzymebased methods measure substrate utilization employing compounds that fluoresce when 

metabolized by specific bacteria. Comparison of the fluorescence to a standard curve allows a 

“count” to be established. Another method measures adenosine triphosphate (ATP) using a 

bioluminescence measuring instrument to determine the amount of ATP that is produced only 

from viable bacteria. 

In the current context, there are indicators available or in late stages of development that are 

ready for evaluation to determine if they are appropriate for use in routine beach monitoring. 

Some can be measured with the technology described above while others can be measured with 

currently available methodologies. 

Leading candidates are indicators and detection methods that can be used to replace current 

culture-based indicators of water quality (i.e., enterococci and E. coli). For instance, nucleic acid 

sequences from enterococci have been used to measure the density of enterococci in bathing 

beach water. Some aspects of the performance of this method have been completed. As 

described above, enterococci have also been quantified using a fiber optic/fluorescent antibody 

detection method, an enzymatic/substrate method, and a method that measures ATP. None of 

the latter methods have been evaluated with respect to either their performance characteristics or 

for robustness. Similarly, molecular-based methods that measure viruses (e.g., adenoviruses) 

that might replace currently used indicators of recreational water quality have not had their 

performance evaluated. If these indicators are shown to be effective in their performance, they 

will be candidates for use in epidemiological studies to determine how well their densities in 

recreational waters relate to swimmer health. 

Another class of microbes and other analytes are related to identifying the source of fecal 

contamination that might affect beach microbial water quality. Other markers include genes 

such as the Esp gene from enterococci, which might be specifically associated with human feces; 

male-specific (F+) coliphage that can indicate whether water has been contaminated by humans 

or animals; and chemical markers such as optical brighteners, caffeine, coprostanol, and urobilin 

that may be associated with human use or are the end-products of human metabolism (see also 
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Chapter 2). Optical brighteners are measured quite easily with a spectrofluorometer, while 

caffeine, coprostanol, and urobilin require more complex instrumentation, such as a high 

performance liquid chromatography (HPLC) instrument. Measuring genomic markers is less 

complicated and does not require a thermocycler to perform a PCR test. The varied nature of 

these source identification markers may require modification of the performance evaluation 

criteria to accommodate the different characteristics of these source specific analytes. For 

instance, the range of applicability and practicality may be more important than the accuracy and 

precision characteristics of these chemical or genomic source identification approaches. 

The last class of indicators that may be ready for evaluation as indicators of fecal contamination 

are those that may have been rejected previously, for whatever reason, but should be considered 

again because of the availability of new information about their occurrence in water or because 

of new methods for their detection. Other potential indicators may be candidates because they 

are species within a group indicator, such as the enterococci and clostridia, and individual 

species may better indicate the quality of a waterbody. It is likely that this class of indicator will 

fit well into the current paradigm for characterizing microorganisms that might be used for 

routine recreational water quality monitoring. 

3.3 Evaluating New Methods for Existing Indicators 

Workgroup members felt that after a method passes defined performance criteria, it must be 

evaluated for its application as an equivalent (or superior) water quality tool compared to the 

current assays. An example of when this approach might be used is the transition from culturebased enterococci detection to detection by a rapid (molecular-based) assay. 

The workgroup identified two major approaches to conduct this evaluation, (1) determining the 

relationship to health risks based on epidemiological studies or (2) establishing equivalency to an 

existing water quality tool. 

3.3.1 Health Risk Evaluation

Workgroup members felt that determining the relationship to health risk is the best approach to 

evaluating a new method. An epidemiological study that can associate human risk with a new 

method is the preferred approach. The new detection method will ideally show an improved 

relationship to illness and will therefore be more protective of public health than the current 

approach that relies on indicator detection. Likewise, if the new method offers other 

improvements over the existing method (e.g., more rapid, less costly, etc.), then its relationship 

with human health should be at least as good as the current indicator. 

The health risk evaluation should also be used when the target of the new method differs 

significantly from the current system. For example, a culture-based enterococci assay does not 

measure the same thing as a polymerase chain reaction (PCR)-based assay, which detects DNA 

rather than culturable (viable) cells. In these cases, a direct comparison of methods (as described 

below) may not be appropriate or possible. 
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3.3.2 Establishing Equivalency between New and Standard Methods

The equivalency validation approach assumes that for methods with similar targets (e.g., viable 

cells), the performance of the new method can be compared to that of the existing method 

without the need to determine health risk directly. Given the cost and time involved in large 

scale epidemiological studies, the equivalency approach can be performed for many new 

methods. The EPA should determine how dissimilar the method targets can be and still be 

evaluated by this approach. For example, cellular activity-based assays (e.g., immunomagnetic 

separation and ATP bioluminescence [IMS/ATP]) and membrane-filtration assays both measure 

viable cells, even though the end points are different. The workgroup members suggested that 

this activity-based assay is similar enough to be evaluated through equivalency validation. This 

level of flexibility is important because of the limited number of epidemiological studies that can 

be carried out in the near- or long-term. 

The current EPA (2003) protocol, EPA Microbiological Alternate Test Procedure (ATP) 

Protocol for Drinking Water, Ambient Water, and Wastewater Monitoring Methods, provides a 

suitable vehicle for performing these evaluations. The EPA recommends approval of a proposed 

method if it is similar or better than the approved method (the “gold standard”) for 80% of the 

matrices tested. Currently, only culture-based methods can be included as an alternate test 

procedure; therefore, consideration should be given by the EPA on the comparability of other 

methods (as mentioned above). 

Along these lines, California has adopted equivalency validation between methods with different 

targets (i.e., culture-based versus PCR-based). This protocol, Beta Testing of Rapid Methods for 

Measuring Beach Water Quality (SCCWRP, 2007), provides guidelines for comparing between 

methods. Similar to EPA, this validation compares method performance between multiple 

sample types and laboratories and also sets acceptable variability between results at 0.5 log 

(based on within method variability previously reported [Griffith et al., 2006; Noble et al., 

2003]). Additionally, the precision should be equal to or better than for the existing methods. 

Many workgroup members felt that EPA’s protocol is too prescriptive because it disallows 

applications for methods that are not culture-based. In the future, for example, should the IMSATP test be found to have a health risk-based association, EPA should consider allowing its 

comparison to culture-based methods since both assay for live organisms, albeit not exactly via 

the same mechanism (membrane-filtration colonies or Most Probable Number [MPN] results 

versus ATP occurrence). By the same token, workgroup members felt that the California 

protocol was too relaxed in that genetic methods were compared to culture-based methods for the 

purposes of acceptance of the former. Because these methods do not measure the same targets 

(DNA versus membrane-filtration colonies), this was perceived as comparing “apples to 

oranges” as the criteria for making such comparisons are not yet well established. 

3.4 Performance Criteria

Regardless of which of the two evaluation approaches is chosen (health risk-based or method 

equivalency-based), performance criteria for the method should be completed, and preferably 

before using the method in an epidemiological study to obtain heath risk-based association data. 
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Workgroup members consider the following to be the major parts of performance criteria: 

repeatability, accuracy, specificity, sensitivity, robustness, range of applicability, and 

practicality. These performance criteria are summarized below. 

Repeatability asks the question: if a test is repeated, will the results be the same? Note, this does 

not take into account the degree of error with regard to how well the test does at identifying its 

target (accuracy). For example, if a person is throwing darts at a target, repeatability is the 

measure of how often the darts hit a specific place. Repeatability does not measure whether one 

hits the center of the target or not—that is accuracy (see more below). Repeatability is 

sometimes referred to as precision and can be expressed both on an absolute scale (i.e., standard 

deviation) and on a relative scale (i.e., relative standard deviation [RSD]). The RSD (sometimes 

referred to as coefficient of variation) is calculated as the standard deviation divided by the 

mean, expressed as a percent. For the purpose of summarizing data, both standard deviations 

and RSDs should be calculated. Generally, RSDs are most appropriate for summarizing 

precision when variability increases as concentration increases. To provide an indication of the 

effect of multiple matrices on precision, standard deviations should be calculated separately for 

each matrix as well as for the method over all matrices. In addition to within and among 

matrix/matrices for repeatability, it is important to test intra- (within lab) and inter-laboratory 

(among labs) repeatability to ensure consistency. 

Accuracy measures the degree to which the method identifies its target. It is defined as the 

degree of agreement between an observed value and an accepted reference value. Accuracy 

includes random error (precision) and systematic error (recovery) that are caused by sampling 

and analysis. Using the above dart example, this would be the number of times that the dart hits 

the “bulls-eye.” 

Specificity includes the false positive and false negative rates. The false positive question asks if 

the method is significantly more likely or less likely to detect non-target organisms or other 

sample constituents that would be reported as the target organism by the analyst when compared 

to the reference method. To assess whether the false positive rates are significant, replicates 

known to contain non-target organisms that could be falsely identified as the target organism 

should be analyzed. The determination that the samples do not contain the target organism 

should be based on a third independent standard method. For example, if the target organism is 

cultured E. coli, the test should be used against, at a minimum, other enterobacteria, and, 

depending on what the test is, potentially Gram positive organisms as well. If the test is for 

genetic material, then the primers and probes should be tested against GenBank to look for 

potential false positives from non-E. coli species with the same sequences. Specificity also asks 

the false negative question regarding whether the new method is significantly more or less likely 

to exhibit non-detections for samples with the target organism or to exhibit results that are biased 

low when compared to the reference method. To assess whether the false negative rates are 

significantly different between methods, replicates known to contain target organisms should be 

analyzed. As in false positive studies, the determination that the samples do not contain the 

target organism should be based on a third independent standard method. For example, if the 

target organism is genetic material from E. coli, then a method for culturable E. coli can be used. 
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If the culture method is able to detect E. coli, then the genetic method should, in general, also 

detect E. coli. 

Estimates of false positive and negative rates as percentages can be calculated as follows: 

1. false positive rate = # false positives/(# of true negatives + false positives) × 100%; and 

2. false negative rate = # false negatives/(# true positives + false negatives) × 100%. 

The sensitivity of a test is the analytical detection limit of the test (the smallest amount detectable 

using the method). For chemical methods, the sensitivity may be defined as the minimum 

amount of a particular component that can be determined by a single measurement with a stated 

confidence level. Generally, these refer to instrument analysis; thus, it is the lowest quantity of a 

substance that can be distinguished from the absence of that substance (a blank). For microbial 

methods, sensitivity is the limit of detection of a particular method. In general, methods are not 

used at this level since confidence around that level is lower and more subject to user error. 

The robustness of a test is the degree to which the method can perform in the presence of 

incorrect inputs or stressed conditions. More simply, how poorly can a method perform and still 

produce useful results? For example, does the method perform as intended in the hands of a 

semi-novice user (e.g., a qPCR method performed by a person familiar with molecular-based 

methods including PCR but not qPCR)? If the test is for cultured microorganisms, can it detect 

stressed organisms in ambient waters (e.g., the EPA E. coli methods have a 2-hour resuscitation 

step at a lower temperature for stressed organisms)? Robustness is not a measurable attribute per 

se but must be considered and applied for overall method performance. 

The range of applicability should also be considered as it answers the question: is the test 

reliable on a nationwide basis (e.g., does it work equally well in temperate and tropical climes, in 

the Great Lakes and other inland waters, etc.), in the presence of inhibitors (e.g., turbidity, 

alkalinity, organics [humic acids]), and in a variety of matrices (e.g., sewage, septic tanks, urban 

runoff, agricultural waste, known animal sources)? In general, the range of applicability does 

not apply to matrices other than the one for which the test was designed; that is, a recreational 

water quality method should not be expected to perform equally well for sewage sludge. Like 

robustness, this is not a measurable attribute but must be considered and applied for overall 

method performance. 

Workgroup members felt that practicality should also be considered when considering a method. 

This issue is largely addressed in Chapter 7 (Implementation Realities workgroup). However, 

four main issues were considered important enough to be mentioned here—capital cost, training 

cost, per sample cost, and additional sampling requirements. Capital costs include the upfront 

costs such as equipment purchase and the actual space required for the test. For example, when 

performing genetic testing, aside from the equipment needed (e.g., platform [specific machine], 

laminar flow hoods, dedicated pipettors), space is needed, ideally in separate rooms, for reagent 

preparation (material not containing any genetic materials). Space is also needed for the two 

types of sample preparation, those containing high target sequence DNA concentrations such as 

DNA standards and calibrator samples, and those containing expected low target sequence DNA 

concentrations (e.g., filter blanks and water samples)—the latter of which should also be in 
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separate laminar flow hoods. Training costs are those incurred prior to routine testing so that the 

user can perform the test within the performance criteria of the test; these may include 

participation in a workshop for hands-on experience or completing a training module. The other 

two issues regard routine use of the test. A high per sample cost may become an issue if a large 

volume of tests need to be completed on a routine basis. Additional sampling is generally an 

effort that results from rapid testing. For example, if an early morning sample yields, after 4 

hours, a positive result resulting in beach closure, it may then lead to additional sampling to 

determine if the beach still needs to be closed in mid-afternoon. It should be noted that many 

laboratories (at least in California) do not object to capital or training costs, but take issue with a 

high per sample cost or with additional sampling requirements. 

3.5 Evaluation Process for Alternative (New) Indicators

Currently, recreational water quality is assessed with a single indicator with a single threshold 

(i.e., a “one-size-fits-all” approach). Under consideration is the implementation of alternative 

indicator(s) that are better associated with human health risk than the enterococci. These 

alternative indicators could theoretically replace the current standard but still be used in a onesize-fits-all approach or could be targeted for specific applications (e.g., one indicator may be 

best associated with risk in tropical marine waters, another in temperate marine waters, and 

another in freshwaters). Regardless of the final implementation, any new proposed indicator will 

need to be vetted through performance based standards. 

The system of approving an alternative indicator will follow the same process as outlined for the 

assessment of any indicator or method, although there will be key differences. 

• Any proposed indicator and/or method should be evaluated for the following 

performance characteristics: 

o repeatability (i.e., precision); 

o accuracy; 

o sensitivity; 

o specificity (false positive/false negative); 

o robustness; 

o range of applicability; and 

o practicality. 

• After performance characteristics have been demonstrated and the indicator and 

associated method has been determined to have adequate performance, it then should be 

evaluated for its use and application in a water quality criteria, including: 

o relationships to health risks must be established based on epidemiological studies 

covering an array of beach types and/or geographic areas; and 

o because of lack of comparable standards, a new indicator cannot be evaluated based 

upon equivalency to an existing method. 

This approach would establish the basis for alternative (new) indicators, and leads into the 

possibility that such indicators could also serve in a role as source identifiers. 
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3.6 Evaluating Source Identification Methods – Proficiency and Evaluation

When bacterial levels in recreational waters exceed adopted State Water Quality Standard, the 

potential risk to the public health requires local authorities to post advisories or close swimming 

areas, risking significant losses in local revenue. The goal of microbial source tracking (MST), 

as applied to U.S. waters, is to accurately identify the contributors and, if possible, the relative 

proportions of fecal pollution from all potential sources, or at least the major contributors. 

Proper use of MST can assist watershed managers in implementation of best management 

practices (BMPs) that can reduce fecal inputs, thereby limiting or reducing public health risk. 

Two major classes of microbe-based and one class of chemical-based MST methods are 

currently being developed and utilized in surface waters across the world (Blanch et al., 2006; 

Stoeckel and Harwood, 2007). Although there has been significant progress in the MST field 

over the past decade, variability among performance measurements and validation approaches in 

laboratory and field studies has led to a body of literature that is very difficult to interpret, both 

for scientists and for end users (Stewart et al., 2003; Stoeckel et al., 2004). This section lists and 

defines/describes performance characteristics that should be uniformly applied across MST 

studies, although selection of which criteria from the following list to use will vary somewhat 

based on the target. All methods and MST projects need to include some considerations for 

representative sampling, sampling frequency, sample volumes required, and the number and 

choice of source categories. Although the use of a toolbox approach has been important in MST 

studies, there is a desire to develop an appropriate tiered approach to avoid costs and time from 

using multiple methods simultaneously. Within the MST community, and largely as a result of 

the method comparison studies, library-independent methods are currently the priority, while 

chemical-based methods appear to be desirable for rapid screening and presence-absence tests 

(with perhaps quantification in the future). Library-based methods still have a role in MST, but 

only in those circumstances where detailed information is needed, such as many TMDL-based 

studies. 

3.6.1 Library-independent Methods (also Reported as Sample-level Classification) 

Examples (not comprehensive) include both molecular approaches (Bacteroidales, E. coli toxin, 

Enterococcus Esp gene, direct measurement of source-specific viruses (polyoma, adenoviruses, 

enteroviruses, phages, etc.) and microbe-based approaches (Clostridium perfringens [alternative 

indicator], source-related clostridia, source-related enterococci, sorbitol fermenting 

bifidobacteria [human], Rhodococcus copraphilus [grazing animals], human-specific 

bacteriophages, phage typing, etc.). 

Method evaluation includes the following eight performance criteria: 

 

1. Accuracy is defined as the true positive or success rate—if a method identified the 

presence of the target in 98 out of 100 blind samples, the accuracy would be 98%; 

2. Rates of false negatives and false positives of the target are used to describe specificity; 

3. The analytical detection limit of the test is used to describe sensitivity; 

4. The level of target-host specificity and the range of target-host distribution; 

5. Efficiency of recovery of the target from different environments; 
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6. The reproducibility of analytical results, both inter- and intra-laboratory; 

7. The suitability of marker detection (and/or quantification) to meet study-specific 

objectives; and 

8. Detection of several of the above, especially #4 and #5, can be referred to as robustness. 

3.6.2 Non-microbial Methods (also Called Chemical Methods) 

Examples of non-microbial indicators include, but are not limited to, optical brighteners, hostderived DNA (e.g., eukaryotic mitochondrial DNA), fecal sterols/stanols, and source-specific 

fecal compounds such as caffeine and pharmaceuticals for humans. 

The performance criteria in numbers 1 through 8 above, excluding #4 and #5, apply to nonmicrobial methods. For chemicals, the analytical detection limit of the test is usually applied to 

describe both sensitivity (#3) and the efficiency of recovery of the target from different 

environments (#5). 

 

3.6.3 Library-based Methods (also Called Isolate Matching) 

Examples of library-based methods include but are not limited to both molecular approaches 

(pulsed-field gel electrophoresis [PFGE], ribotyping, PCR with different primer sets, etc.) and 

phenotype-based approaches (antibiotic resistance analysis [ARA], biochemical, etc.). 

The performance criteria in numbers 1 to 3 from library-independent methods (above) are 

applicable for library-based methods. In addition, the following four criteria apply: 

1. Jackknife (also reported as holdout or cross-validation) analysis and the pulled-sample 

test (recently described as internal proficiency) should be done on each and every library 

(Stoeckel and Harwood 2007); 

2. Library should shave clones removed to reduce redundancy, based on the precision of the 

typing method; 

3. External proficiency or blind tests to determine both size and representativeness of the 

library should be done as the library is developed; and 

4. The benefit-over-random statistic should be used when accuracy is determined, and 

should be performed on both the library and the external proficiency (or blind) set. 

3.7 Modifications to the Evaluation Process When Indicators are used for Other 

Applications

Indicators are used in many different contexts. Routine beach monitoring, the most time-critical 

use of indicator bacteria is described extensively in other chapters of these proceedings. This 

section briefly addresses other (secondary) uses of indicators. Another use of indicators is as an 

early warning system that would provide evidence for an imminent human health risk, such as a 

sewage spill. They can also provide evidence of returning to acceptable ambient water quality 

conditions as designated by the criteria. It is important that the methods be highly specific and 

robust. Because of the potential for illness in exposed populations, it is extremely important that 
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this use of an indicator be associated with great specificity and robustness. Specificity in this 

case refers to the ability of a method to detect an indicator with certainty that the indicator is not 

giving a false positive response (i.e., an organism or analyte that responds similarly to the target 

organisms, but is not the target organism). Similarly, target microbes that do not provide a 

positive response are indicated as false negatives and too many of these could result in a false 

sense of security that would be highly unacceptable from a public health perspective. 

Robustness in this case means that the method can be abused and still function properly. 

Methods of this type are usually used under extreme conditions where the correct result must be 

obtained in a very short time period. 

Another use of indicators is for compliance monitoring purposes, such as monitoring sewage 

treatment effluent for EPA’s NPDES Program. Important characteristics for indicators used for 

such compliance monitoring are precision and specificity. The precision is necessary because 

sewage treatment plants would receive a fine(s) if limits of the permit are exceeded. The 

specificity, both false negative and false positive responses, are important for the same reason 

mentioned above and may influence the way beaches are managed. 

Trend assessments are used to determine whether water quality conditions at a site are changing 

with time. The most important characteristic is precision that contributes to the ability to detect 

small changes over time (i.e., whether the water quality is decreasing or improving over time). If 

the water quality decreases then bathing may no longer be allowed. Conversely, if the water 

quality improves sufficiently then bathing may be re-allowed. 

3.8 Research Needs

Several lines of research should be pursued in order to implement improved methods for (1) 

rapid detection of current water quality indicators, (2) implementing alternative indicators that 

are more protective of public that the current indicators, or (3) determining source (human or 

nonhuman) at beaches. This set of research priorities is based upon the current state of available 

methods and the projected feasibility of implementation in near-term (1 to 3 years) and mid-term 

(2 to 5 years) or longer timeframes. Although these are listed in priority order, the workgroup 

members felt that they largely expand on efforts that EPA or its potential partners have already 

initiated and all are achievable in the next 3 years. Appendix G summarizes currently planned 

measurements for use in the upcoming Doheny and Malibu Beach (California) epidemiology 

study. 

1. Systematic evaluation of performance criteria for library-independent source 

identification methods (for use in source characterization [i.e., human versus nonhuman 

fecal contamination] and in MST) (timeline: 1 to 2 years). 

Workgroup members felt that EPA should fast-track studies to evaluate the performance 

criteria of source-specific microbial targets. 

A series of controlled trials representing a variety of geographical areas should be 

conducted to evaluate promising methods. Studies should include samples spiked with 

known source fecal matter from multiple hosts as well as environmental samples 
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collected from areas with known dominant sources of fecal contamination. Samples 

should be assayed by the test methods in several laboratories using blinded controls. 

These protocols would be similar to those used in the Griffith et al. (2003) studies that 

EPA co-sponsored approximately 5 years ago, but which need to be updated as new 

methods have developed and existing methods refined. 

Although there are many potential methods that could be included in such studies, the 

workgroup members identified the following as the most important: 

1. enterococci Esp gene; 

2. E. coli virulence genes; 

3. human enteric viruses (molecular detection); 

a. DNA-based – adenoviruses and polyomavirus; 

b. RNA-based – enterovirus and norovirus; 

4. Methanobrevibacter smithii (nifH gene); 

5. Clostridium perfringens; 

6. coliphage; and 

7. Bacteroides human-specific markers. 

The last two methods are also being planned for use in EPA’s upcoming (2007) health 

risk (epidemiological) study. The workgroup members felt that the coliphage and 

Bacteroides methods are more advanced than the others and endorses their inclusion in 

source identification studies. 

In coordination with trials over various geographic areas, candidate methods should also 

be evaluated from the perspective of persistence of genetic or chemical or microbial 

targets in both primary and secondary habitats (sediments) over longer time periods 

(multi-year). Although this may be a longer term goal, eventually all methods that appear 

to be suitable for use regulatory or management-level decisions will need such to be 

examined over time periods sufficiently long so that there is confidence that the desired 

targets do not change, or that changes can be captured and dealt with if they do occur. 

2. Evaluation of chemical indicators for human sewage (timeline: 2 to 3 years). 

Several possible chemical markers of sewage have been reported and have the potential 

to be used in a rapid to real-time assessment of source. Coordinated studies to evaluate 

the performance criteria over multiple labs are needed to implement these assays. 

The following analytes should be included in near term evaluation studies: 

1. optical brighteners; 

2. coprostanol; and 

3. caffeine. 
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At least one multi-laboratroy evaluation study of optical brighteners is currently being 

developed by individual investigators (Hartel et al., 2007). 

3. Continued evaluation of rapid assays for the detection of enterococci in human health risk 

(epidemiological) studies (timeline: 1 year and beyond). 

Rapid detection of current water quality indicators are proposed to allow same day 

evaluation of water quality. To implement these assays, continued evaluation of the 

health risk relationship is needed. For qPCR (Enterococcus), more epidemiological 

studies from a range of beach types are needed before implementation. Additionally, 

other rapid assays for enterococci have been developed and should be evaluated in 

upcoming and future epidemiological studies. 

Methods under consideration for enterococci detection include the following: 

 

Immediate (timeline: 1 to 2 years): 

• qPCR (detection of DNA); and 

• TMA (detection of RNA). 

Mid-term (timeline: >2 years; require additional performance evaluation): 

• IMS/ATP (detection of activity); 

• RAPTORTM (antibody-based detection)5

; and 

• enzymatic detection. 

4. Evaluation of alternate indicator candidates in human health risk (epidemiological) 

studies (timeline: 1 year and beyond). 

Potential alternate indicators (i.e., to replace enterococci and E. coli) that have already 

been vetted for performance criteria should be included in any future epidemiological 

studies of recreational waters to determine their relationship with health risk. 

The following indicators should be evaluated within the next two years: 

• Bacteriodales human specific markers; and 

• F+ coliphage (antibody). 

Other candidates indicators should be added for evaluation as they meet required 

performance criteria (as listed above) 

5. Optimization of sampling, recovery, and processing methods for efficient concentration, 

processing and detection of rapid, alternative or host specific indicators (Time line: 1 

year and beyond). 

 5

 http://www.resrchintl.com/raptor-detection-system.html 
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Additional methods need to be optimized for source specific microbial targets. Studies 

should address issues such as optimization of sample volume, processing/concentration 

methods, and extraction/purification methods (especially for targets expected to occur at 

low numbers in the environment). 

Furthermore, research addressing straightforward techniques to enumerate Enterococcus 

faecium and faecalis, rather than the larger Enterococcus group that is presently 

measured, are needed as the individual species are more likely to be associated with 

human sewage/feces. Performance-based criteria tests are also needed for these species. 

References 

Blanch, AR; Belanche-Munoz, L; Bonjoch, X; Ebdon, J; Gantzer, C; Lucena, F; Ottoson, J; 

Kourtis, C; Iversen, A; Kuhn, I; Moce, L; Muniesa, M; Schwartzbrod, J; Skraber, S; 

Papageorgiou, GT; Taylor, H; Wallis, J; Jofre, J. 2006. Integrated analysis of established and 

novel microbial and chemical methods for microbial source tracking. Applied and Environmental 

Microbiology 72(9): 5915-5926. 

 

Griffith, JF; Weisberg, SB; McGee, CD. 2003. Evaluation of microbial source tracking methods 

using mixed fecal sources in aqueous test samples. Journal of Water and Health 1: 141-151. 

Hartel, PG; Hagedorn, C; McDonald, JL; Fisher, JA; Saluta, MA; Dickerson, JW, Jr.; Gentit, 

LC; Smith, SL; Mantripragada, NS; Ritter, KJ; Belcher, CN. 2007. Exposing water samples to 

ultraviolet light improves fluorometry for detecting human fecal contamination. Water Research:

In press.

Noble, RT; Weisberg, SB; Leecaster, MK; McGee, CD; Ritter, K; Walker, KO; Vainik, PM. 

2003. Comparison of beach bacterial water quality indicator measurement methods. 

Environmental Monitoring and Assessment: 81: 301-312. 

SCCWRP (Southern California Coastal Water Research Project). 2007. Beta Testing of Rapid 

Methods for Measuring Beach Water Quality. Technical Report 506. Available at: 

ftp://ftp.sccwrp.org/pub/download/PDFs/506_beta_testing.pdf. 

Stewart, JR; Ellender, RD; Gooch, JA; Jiang, S; Myoda, SP; Weisberg, SB. 2003. 

Recommendations for microbial source tracking: Lessons learned from a methods comparison 

study. Journal of Water and Health 1: 225-31. 

Stoeckel, DM; Mathes, MV; Hyer, KE; Hagedorn, C; Kator, H; Lukasik, J; O’Brien, TL; Fenger, 

TW; Samadpour, M; Strickler, KM; Wiggins, BA. 2004. Comparison of seven protocols to 

identify fecal contamination sources using Escherichia coli. Environmental Science and 

Technology 38: 6109-6117. 

Stoeckel, DM; Harwood, VJ. 2007. Performance, design and analysis in microbial source 

tracking studies. Applied and Environmental Microbiology 73(8): 2405-2415. 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 73 

US EPA (U.S. Environmental Protection Agency). 1986. Ambient Water Quality Criteria for 

Bacteria – 1986. EPA440/5-84-002. Washington, DC: US EPA. 

US EPA. 2003. EPA Microbiological Alternate Test Procedure (ATP) Protocol for Drinking 

Water, Ambient Water, and Wastewater Monitoring Methods – Guidance. EPA-821-B-03-004. 

Washington, DC: US EPA. 

WHO (World Health Organization). 2003. Guidelines for Safe Recreational Water 

Environments. Volume 1 Coastal and Fresh Waters. Geneva, Switzerland: WHO. 
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CHAPTER 4 

COMPARING RISK (TO HUMANS) FROM DIFFERENT SOURCES 

Dennis Juranek, Chair, Centers for Disease Control and Prevention (retired) 

Rebecca Calderon, USEPA 

Jack Colford, University of California, Berkeley 

Elizabeth Doyle, USEPA 

Graham McBride, National Institute of Water and Atmospheric Research, New Zealand 

Samuel Myoda, Delaware Department of Natural Resources 
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4.1 Introduction

Fresh and marine recreational waters and beaches may be impacted by human and/or animal 

feces from point and non-point sources. Studies have recently been completed by EPA on 

assessing rapid water quality indicators and their ability to predict swimming-associated illness 

at freshwater beaches impacted by publicly (and privately) owned (sewage/wastewater) 

treatment works (POTW) systems. Similar EPA studies are currently planned (starting summer 

of 2007) to assess the risk of illness for people who swim in marine recreational waters impacted 

by POTW systems (point sources of fecal contamination). Thus, in the near future additional 

information should be available on risk of illness for bathers at marine beaches largely impacted 

by human sewage. Plans are also underway by the Southern California Coastal Water Research 

Project to assess swimming risks at least one marine beach that is impacted by non-point source 

sewage that likely contains a mixture of human and animal feces. However, there remains a 

paucity of data on the risk of illness for swimmers at beaches exclusively (or primarily) impacted 

by feces from animals. The absence of such data makes it difficult to interpret the health 

significance of the frequent and persistent elevated fecal indicator levels in such waters that have 

been attributed to animals in many locations throughout the United States. 

It is widely believed that human feces pose a larger health risk than animal feces to swimmers 

and other primary contact recreational water users. This belief derives from the basic concept 

that virtually all enteric pathogens of humans are infectious to other humans, while relatively few 

of the enteric pathogens of animals are infectious to humans. Possible exceptions are bird flu 

virus and swine hepatitis E virus (HEV). Workgroup members regarded the evidence for swine 

HEV transmission by water to be very weak and felt that it could disregarded in terms of risk 

assessments during the next 2 to 3 year EPA planning period. Bird flu was discounted as a major 

concern for swimmers because it was felt that if an outbreak of bird flu was recognized in birds 

or humans in the United States, early public health recommendations would include directives 

for people not to swim in waters that might be impacted by bird or human feces, including 

chlorinated public pools. 

Counterbalancing the concept that animal feces may pose a lower risk is recognition that animals 

do harbor many bacterial and protozoan pathogens that pose a human health hazard and that 

some of these pathogens, such as enterohemorrhagic E. coli (EHEC), can cause serious, 

potentially life-threatening illness in humans. In addition, animal feces are often directly 

deposited in freshwater that receives no treatment before reaching bathing areas. The 

concentration of both feces and pathogens may be sufficiently high at beach locations at various 

times to pose a significant health risk to swimmers. 

The bottom line is that there are few data to demonstrate whether animal feces pose a lower, 

greater, or equivalent health risk to bathers than human feces. If there is a difference, it would be 

helpful to know the magnitude of that difference in order for EPA to make appropriate public 

health recommendations. The only way to get a better sense of the health risk for swimmers 

posed by animal feces is to conduct targeted studies. Some types of studies (epidemiological and 

quantitative microbial risk assessment [QMRA] studies) would produce quantitative estimates of 

risks while others (fate and transport, pathogen loads in water, etc.) would provide supporting 

information or stand alone qualitative information about risk. 
U.S. Environmental Protection Agency Experts Scientific Workshop

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It is recognized that there are many different types of animals and that the pathogen risks posed 

by feces from these animals are different. These differences, as well as the different pathways 

(point, non-point, fecal deposition on land versus in water, etc.) that feces reach bathing areas, 

have to be taken into account in weighing risk. Workgroup members approached the issue by 

developing Table 5 in order to rank the likely risks from different sources of fecal contamination 

and to help prioritize which bather/animal-fecal-risk interface studies should be undertaken first. 

The initial workgroup member discussion focused on assessing the universe of pathogen sources 

of interest to recreational waters. Workgroup members developed a table (Table 5) in which the 

major sources of fecal contamination categories are in rows. The major rows are wildlife, 

agricultural animals, domestic animals (pets), human/sewage, and what the workgroup termed 

“secondary environments” (i.e., soil, sand, and sediments). The wildlife row is subdivided into 

aquatic birds and all others. The agricultural animals are divided into poultry and other (largely 

comprised of domestic livestock such as cattle, sheep, and pigs). The human/sewage is divided 

Table 5. Comparing Risks (to Humans) from Different Pathogen Sources.a

Source Viruses Protozoa Bacteria 

Wildlife 

Aquatic birds N L L-M 

Other (e.g., deer) N M M #2 priority 

Agricultural animals 

Poultry N N M-H 

Other (e.g., cattle, sheep) N M M-H #1 priority 

Domestic animals 

Pets (e.g., dogs, cats) N L L 

Fecal shedding by bathers #3 priority 

 Adults L L L 

 Children H H H 

Sewage

No treatment (combined sewer 

overflows) H H H 

No treatment (separate storm 

sewer overflows) ?* ?* ?* 

Secondary treatment** H H M 

Plus chlorine** H H L 

Plus UV 

M-H 

(L with 

increased 

energy) L 

Secondary environments*** L L M a Does not have an explicit fate and transport component 

* Risk largely depends on amount of human feces present 

** Focus of most (U.S.) recreational water epidemiological studies 

*** Sediment suspension and contact with beach sand 

N = estimated no or negligible risk, L = estimated low risk, M = estimated medium risk,

H = estimated high risk 
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into untreated sewage, secondary treatment sewage, chlorinated sewage, and UV-treated sewage. 

Fecal shedding by bathers (adults and children) is considered separately. 

The columns are defined by broad microorganism groups of viruses, protozoan and bacteria. By 

an expert opinion process (within the workgroup) each cell of the table was given a risk estimate 

of no (zero) or negligible risk (N), low, medium, and high (L, M, H). The types of 

characteristics discussed included infectious dose, numbers of pathogens per gram of stool from 

infected animals, implication of source in waterborne disease (extended discussion on foodborne 

disease and vector-borne disease), persistence and survival in the environment and finally an 

assumption that sources are in close proximity to a primary contact recreational area. The N, L, 

M, H risk designations in the table cells represent the workgroup’s “best guesses” and assumed 

that animal feces was deposited in freshwater relatively closed to bathing sites. The workgroup 

did not specifically address pathogen “die-off” associated with fecal deposition on land 

(spring/summer temperatures resulting in pathogen drying, transport from soil to water affects on 

viability, etc.). It was felt that many of these types of data are available and that the table could 

be updated with real data at a later date as a separate project. It was recognized that updating the 

table with published data might change the values in one or more risk rankings of the table cells. 

With rare exception, viruses are species-specific. Essentially, all enteric oral/fecally transmitted 

viruses that infect humans are of human origin. For all of the animal viral sources of pollution, 

the viral cells were given a zero or negligible risk (indicated by “N” entries in Table 5). All the 

human sources were given a high risk estimate with the exception of UV-treated sewage. UVtreated sewage at current levels has up to a 0.5-log reduction of viruses and hence this cell was 

assigned a medium risk. More energy intensive UV irradiation may provide up to a 4-log viral 

reduction and result in a low risk ranking. Sentinel viruses for this group include enteroviruses, 

hepatitis A virus, norovirus, rotovirus, and adenoviruses. The major protozoan pathogens of 

concern are Giardia and Cryptosporidium. Given the current knowledge of infectious dose, the 

long survival in the environment, many of the animal cells within the table were given a low, 

low-to-medium, or medium risk level. As with the viruses, all the human cells within the table 

were given a high risk rating with the exception of UV-treated sewage. The bacteria had similar 

ratings to the protozoa ranging from low-to-medium and again, the human sources were all 

assigned a high ranking with exception of chlorine- and UV-treated sewage that received a low 

risk ranking. 

Bather density was divided into adults and children (recognizing that children could be divided 

into specific age groups) with the assumption that hygiene and accidental fecal discharges were 

much more likely to occur in children than adults. Thus, for adults, a low risk ranking was 

assigned across the columns and a high risk ranking was assigned for children. 

Based on the few studies done on secondary environments, viruses and protozoa were given a 

low risk rating, while bacteria were given a medium rating. 
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In developing Table 5, workgroup members noted the following discussion points: 

1. Current epidemiological literature suggests that the symptomatic profile of swimmingassociated illnesses indicates primarily viral illnesses. 

2. Certain pathogens such as EHEC have a low probability of occurrence but are associated 

with severe a health outcome. 

3. Information available to the workgroup suggested that nonhuman fecal sources impacted 

freshwater sources more than marine water sources. 

4. Combined sewer overflows (CSOs) were considered as untreated sewage. 

5. Separate storm sewer overflows initially were put in the domestic animal row but 

subsequent discussion of recent studies suggested that they could have a human 

component in many communities. 

In discussing the future research needs related to the development of new or revised recreational 

water quality criteria, the workgroup members defined the ultimate goal to be a determined 

quantitative risk estimate for each fecal source (row). The benchmark by which risks should be 

compared is the secondary and chlorine treated sewage row that is currently the focus of recently 

completed EPA National Epidemiological and Environmental Assessment of Recreational 

(NEEAR) epidemiological studies for freshwater and the planned marine water studies. The 

following research projects were suggested to meet that objective of determining a sound and 

defensible risk estimate for each row of Table 5. 

4.2 Summary of Workgroup Discussions and Reflections on Workgroup-specific 

Charge and Questions 

The charge to the workgroup was to consider the impact of waterborne pathogens from various 

sources, both human and nonhuman, on the health risk resulting from exposure to fecal 

contamination in recreational waters. Workgroup members considered the impact of the issue on 

beach monitoring and notification and the classification of waterways as impaired. The 

discussions were wide-ranging. Discussions began with the consideration of the relationship of 

likelihood of illness due to nonhuman sources to likelihood of illness predicted by the use of 

epidemiological data from human exposure to POTW-impacted waters using fecal indicators. 

Possible approaches to modifying the application of regulatory approach using considerations of 

infectivity to pathogens among species were debated. The location of fecal sources relative to 

the site of monitoring and the potential of animals to move off-site were also discussed. These 

topics are all reflected in the potential research activities proposed and discussed in this chapter. 

Six charge questions were provided to the workgroup (see Appendix A) to help stimulate 

discussion, and to identify key issues for consideration. A brief synopsis of responses to the 

questions is presented below. 

• Question 1: Is setting criteria based on a treated human point source such as a POTW 

protective, under-protective or overprotective of other potential sources of human pathogen? 

Why or why not? Are there data to support this conclusion? 
U.S. Environmental Protection Agency Experts Scientific Workshop

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Whether the criteria are protective would depend on the effectiveness of treatment in reducing 

the levels of pathogens and the relative reduction in indicator organisms. Secondary wastewater 

treatment with chlorination could provide a false sense of security for protozoa and viruses. This 

reflects the higher degree of effectiveness of chlorine in killing/deactivating bacteria relative to 

viruses and protozoa. Given that current indicators are bacteria and would be reduced to a 

greater extent than viruses and protozoa, low indicator levels might suggest that waters impacted 

by POTWs were relatively pathogen-free when they still contained a significant virus and 

protozoan load. Data are available to characterize the relative effectiveness of disinfection 

techniques across classes of waterborne pathogens and indicator organisms. 

• Question 2: Based on the “state of the science,” what conclusions or assumptions are 

reasonable to make about risks to humans exposed to human fecal contamination, non-point 

source contamination from animal sources, and mixed sources (e.g., combined sewer 

overflows [CSOs] and (separate) storm sewer overflows)?6

 

Workgroup members felt that it is reasonable to assume that exposure to fecal contamination 

from untreated human waste posed the highest risk. Treated sewage was judged to be of lower 

concern, although it was more similar in risk to untreated human waste than to nonhuman 

sources. In general, treated and untreated sewage should be treated similarly for the purposes of 

evaluating risk. Discussion of CSOs led to the conclusion that they should be considered 

similarly to untreated sewage in terms of public health concern. Although separate storm sewer 

overflows were initially considered to be similar to animal waste in nature, there was a 

recollection of data in the literature (Haile et al., 1999) noting the occurrence of a significant 

occurrence of human pathogenic viruses in stormwater effluent and associated health effects 

merits further investigation. Aquatic avian sources were considered to be of low public health 

concern. Other wildlife and agricultural animal (including poultry) feces were deemed to be of 

moderate concern. 

• Question 3: To what extent is it reasonable to apply risk estimates from POTW-influenced 

beaches to non-POTW beaches? Do we understand scientifically whether this would lead to 

overprotection? What science would be important to understanding this? 

A portion of the answer to this question is reflected in the responses to Questions 1 and 2 above. 

The propensity to over- or under-protect would depend upon the source of the waste impacting 

the site. Non-point sources that largely reflect nonhuman sources of fecal contamination would 

probably be overprotected by studies in POTW-impacted locations. Mixed sources or untreated 

human sources may be inappropriately characterized by the POTW-dominated data. The 

workgroup’s generalizations are reflected in Table 5. Addressing the public health significance 

of CSOs and separate storm sewer overflows are problematic because of the site-specific nature 

of the extent to which they vary by site characteristics. Although the importance of dilution of 

pathogens and indicator organisms in runoff events was discussed, no conclusion was reached 

about its significance. 

 6

 It is important to note that the workgroup was specifically charged (see Appendix A) to address (separate) 

storm sewer overflows and not sanitary sewer overflows, the latter of which are often discussed in conjunction with 

CSOs and commonly using the acronym “SSO.” For this reason, workgroup members decided to not use the 

acronym SSO anywhere in the chapter. 
U.S. Environmental Protection Agency Experts Scientific Workshop

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• Question 4: Assess whether there is a possibility of overprotection due to a compounding of 

risks from multiple factors (such as the current definition of gastrointestinal [GI] illness [i.e., 

no fever]; more sensitive molecular-based methods; assuming that POTW risks = nonhuman 

fecal contamination source risks, etc.). 

This question was referred to the Acceptable Risk workgroup (see Chapter 5). 

• Question 5: How should EPA evaluate risk that may have a low probability of occurrence 

but a significant risk, if it occurs?

This question was considered by workgroup members to be unlikely to be adequately 

represented by completed epidemiological studies due to the low incidence (or detection) of 

pathogens that are associated with severe health outcomes. However, this important public 

health issue might be addressed using quantitative microbial risk assessment (QMRA) methods 

or by using large-volume filtration in future epidemiological studies. 

• Question 6: What are the key data gaps and uncertainties needed to support criteria 

development in the near term? 

The research needs and their prioritization are presented in a separate section (4.4). 

Epidemiological studies were given a high priority, with QMRA as an important adjunct. 

Additional epidemiological studies were encouraged by workgroup members because the data 

produced directly measure outcomes of interest (e.g., GI illness) and the data produced are more 

directly comparable to data being obtained for human health risks at marine beaches largely 

impacted by human sewage. Thus, epidemiological studies were preferred to the extent that they 

were possible and were viewed as an anchor for QMRA studies. However, it was recognized 

that it may be difficult to find freshwater recreational sites with sufficient bather activity to 

provide adequate sample sizes for an epidemiological study. If suitable sites cannot be found, 

then modeling the risk using QMRA techniques based on available epidemiological information 

would provide quantitative risk estimates that could help with short-term decision making on 

health risks. Similarly, if pathogen-source combinations in Table 5 cannot be conducted, it may 

be possible to use QMRA to provide quantitative risk estimates. 

4.3 Options for Approaches and Implementation Considerations

The considerations in the followings section are not applicable to the current U.S. approach (i.e., 

US EPA, 1986; see also Chapter 1) because there is no way to take into consideration the charge 

to this workgroup on comparing risk to humans of fecal contamination from different sources. 

The following considerations are applicable to both the European Union (EP/CEU, 2006) and 

WHO (2003) approaches to criteria development. The sanitary investigations are important for 

the topics discussed by this workgroup. Simultaneous use of multiple indicator organisms or a 

tiered approach may be necessary. 
U.S. Environmental Protection Agency Experts Scientific Workshop

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4.4 Research Needs 

1. Prioritize the next generation of studies. The purpose of these studies is to (1) revisit the 

ratings using a more through literature review and (2) gain as much information as 

currently exists on the magnitude of the fecal pathogen source problem across the United 

States. 

a. Quantify the magnitude of difference in the risk of illness from different exposure 

sources (see Table 5) to see if they are different from POTW-impacted waters. 

i. Initial estimate of risk – populate the table with infectious dose data and 

likely number of organisms excreted in stool per gram to characterize 

fecal source rank. 

ii. Magnitude across the United States 

1. Number of impaired waters 

2. Number of beaches affected by the sources (number of affected 

bathers if available) 

iii. Identify potential fresh and marine recreational sites for each of the fecal 

pathogen sources (rows) for future epidemiological studies. Priority 

should be given to freshwater sites. 

2. Identify and characterize potential sites for future epidemiological studies using the 

following sources of information: 

a. National Pollution Discharge Elimination System (NPDES) – provides location of 

all point source dischargers and their levels of discharge 

b. CWA §303(d) list and §305(b) reports 

c. Sanitary investigations and microbial source tracking to confirm site 

characterization 

d. Compile information (via literature review and/or site-specific) about pathogen 

loads in non-point source water impacted by all sources of fecal contamination 

(human and animal), characterizing with respect to pathogens and indicators in 

freshwater versus marine water. 

4.4.1 Epidemiological Studies

Workgroup members agreed that epidemiological studies are the most desirable approach to 

define and quantify health risks to humans swimming in fecally contaminated waters. Although 

many epidemiological studies have been previously conducted at point source-impacted beaches, 

very few such studies have been published on non-point source-impacted recreational waters. 

The relationship between current water quality indicators and health outcomes that is currently 

used in regulating beaches was developed from studies at point source-impacted beaches where 

water quality indicator levels correlated with swimming-associated illness (US EPA, 1986). It is 

plausible that the relationship between water quality indicators and health is different at nonpoint source-impacted sites since indicator levels may be high due to animal (e.g., birds, other 

wildlife) or other sources that do not increase the risk of human illness. Some workgroup 

members felt that it is appropriate to conduct epidemiological studies at non-point sourceimpacted sites to better define risk and guide future regulations. 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 84 

Some workgroup members noted that epidemiological studies cannot be performed in all of the 

various types of non-point source-impacted waters for which there is a need to know risk. In 

many of these types of sites, other techniques (such as QMRA) will necessarily have to be used 

(see Section 4.4.2). The choice of the specific sites (beaches, rivers, lakes) in which to conduct 

epidemiological studies could be guided by the risk rankings developed in Table 5. These 

rankings include the types and concentrations of pathogens present, the number of affected 

waters across the United States, the number of people who are exposed to such sites, and the 

number of sites affected by regulatory restrictions under the CWA §303(d) guidelines. 

Two principal study designs have been used in prior beach epidemiological studies—the 

randomized controlled trial (RCT) and the prospective observational cohort. The RCT has been 

primarily used in European studies and the observational cohort in many countries. Workshop 

participants discussed the relative strengths and limitations of each study design. With respect to 

the issue of health risks in non-point source-impacted waters, the workgroup members actively 

discussed the advantages of each design and felt that each had merit. Because of the required 

sample size (i.e., number of swimmers) is much less for an RCT, workgroup members could 

envision situations in which an RCT could be employed in future non-point source 

epidemiological studies. Workgroup members did note that in the United States it would be 

more likely for such an epidemiological study to receive human subjects approval if the 

enrollment scheme were altered from the RCT that has been used in several European studies. In 

Europe, subjects are typically recruited and enrolled in the studies at sites distant from the beach 

and then brought to the study sites. Workgroup members discussed an alternate design for 

consideration in the United States; specifically, enrolling willing persons who are about to enter 

the water and randomizing them to either swim or not swim that day. As in all epidemiological 

studies, aggressive exposure measurements of the water ingested and measures of water quality 

(e.g., indicators of fecal pollution) to which the swimmer is exposed would be critical. In nonpoint source sites where adequate numbers of swimmers could be enrolled, the prospective 

cohort design could be used for epidemiological studies. Workgroup members felt that it would 

be very helpful at some point to use both study designs simultaneously on one beach. This 

would allow for a direct comparison of the results and help guide future epidemiological studies. 

1. Epidemiological studies (highest priority is to conduct studies at beaches impacted by 

different types of non-point sources of fecal contamination [see Table 5]) 

a. Randomized control trials (for consideration at beaches with low numbers of 

bathers) 

i. European design should be modified for use in the United States 

(suggestion – randomize people about to swim into groups that will swim 

or not swim) 

ii. Potential problem – identifying appropriate numbers of participants may 

be more difficult for inland (predominantly fresh) recreational waters than 

marine waters 

iii. Estimated necessary sample size – 1,500 people/site 

b. Prospective observational cohort study 

i. Potential problem – identifying sufficient numbers of participants may be 

more difficult for inland recreational waters than marine waters 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 85 

ii. Estimated necessary sample size – 5,000 to 10,000 people/site (200 to 400 

people/day) 

iii. Wide range of exposures needed 

4.4.2 Quantitative Microbial Risk Assessment 

Several workgroup members advocated for QMRA studies in developing new or revised 

recreational ambient water quality criteria (AWQC). In part because QMRA can be used to rank 

the relative risks of different situations, such as sites impacted by animal versus human fecal 

wastes, and where no direct epidemiological information is available. QMRA studies can also be 

instructive in recreational areas where such studies have already been completed. 

QMRA is increasingly used to characterize risk to humans from exposure to contaminated water 

when engaging in “contact recreation,” especially swimming, but also other forms of water 

contact such as water skiing. It translates the environmental occurrence of pathogens and the 

volume of water that individuals are exposed to into a probability of infection or illness. Inputs 

with known variability are described by statistical distributions from which many random 

samples are taken, often using a “Monte Carlo” calculation procedure, to derive a risk profile.7

 

The following four step process is used: (1) identifying the important pathogens (“hazards”); (2) 

determining human exposures to contaminated water, via ingestion or inhalation; (3) 

characterizing dose-response, using data available from clinical trials, illness surveillance, and 

outbreak data; and (4) mathematically characterizing the risks and communicating risks and 

attendant uncertainties. 

For step 1, a suite of sentinel pathogenic microorganisms should be considered for each situation 

as they are considered to cover the range of illnesses that could arise in the United States, such as 

the following: 

• viruses – norovirus, Hepatitis A virus, caliciviruses, enteroviruses, rotavirus, 

adenoviruses; 

• bacteria – EHEC, Campylobacter spp., Salmonella spp., Shigella spp.; and 

• protozoa – Giardia cysts, Cryptosporidium oocysts. 

The setting for each site of interest will dictate which of these pathogens should be used. For 

example, a recreational site impacted only by animal wastes should not need to include viruses. 

Adenoviruses will need to be included where aerosols may be inhaled (e.g., by water skiers). 

For step 2, information on water ingestion and exposure rates, along with duration of the 

recreational activity, are combined with the concentration of pathogens in the water to obtain a 

 7

 EPA’s Office of Water has developed a “complete draft” of a Protocol for Microbial Risk Assessment based 

on the EPA-ILSI (ILSI, 2000) Revised Framework for Microbial Risk Assessment (http://www.ilsi.org/file/

mrabook.pdf) and which is consistent with the chemical risk assessment paradigm. The Agency has initiated a 

review to insure it meets risk assessment needs for all water-based media. Contact Stephen Schaub, EPA Office of 

Water (see Appendix B), for information on the Protocol for Microbial Risk Assessment. 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 86 

dose—all these variables being described by statistical distributions. Information on the origin, 

quantity, and fate and transport of wastes deposited on a land surface and into waterways is of 

prime importance in determining the distributions of pathogens in the water that is subsequently 

ingested or inhaled. 

For step 3, several dose-response analyses have been reported and may be used, albeit with 

caution. In particular, the form of the “dose” used in a clinical trial needs to be made consistent 

with the form used to describe the dose ingested or inhaled.8

 Also, uncertainty in the doseresponse equation, in the form of credible intervals, can be captured by the calculation process. 

In step 4, risk profiles may be derived, in the form of a cumulative distribution function—this 

will be particularly useful for examining the risks associated with rare but highly significant 

illness (e.g., EHEC). This also enables uncertainty measures to be calculated. Comparing 

relative risks for different sites should be done by comparing risk profiles, rather than by 

comparing single risk “numbers.” 

1. QMRA provides a range of possible illnesses or risks, allows comparisons across all fecal 

pathogen sources (see Table 5), and number of illnesses by a modeling approach (highest 

priority is to conduct assessments at beaches impacted by different types of nonpoint sources [see Table 5]). There was discussion among workgroup members 

regarding the strengths and limitations of conducting QMRA versus epidemiological 

studies (see Eisenberg et al., 2006); QMRA: 

a. Is a potential alternative, adjunct, or precursor to epidemiological studies 

b. Can evaluate infection and illness 

c. Could evaluate sentinel (index) pathogens such as: 

i. Bacteria (EHEC, Campylobacter, Salmonella, Shigella) 

ii. Protozoa (Giardia, Cryptosporidium) 

iii. Viruses (norovirus, Hepatitis A, caliciviruses, enteroviruses, rotavirus, 

adenoviruses) 

d. Can consider inhalation as an additional route of exposure if data are available 

iv. Adenoviruses 

2. QMRA is a good way to compile information (via literature review and/or site-specific) 

about pathogen loads in source waters impacted only by animal sources (with an 

emphasis on freshwater) and to characterize pathogens and indicators. 

4.4.3 Etiologic Agents

Workgroup members felt it important to emphasize that there is a glaring lack of knowledge 

about the incidence with which specific pathogens cause swimmer-associated illnesses at both 

non-point source- and point source-impacted beaches. Identification of such pathogens as the 

actual cause of illness in swimmers would provide important information for developing new or 

 8

 For example, a rotavirus clinical trial will report dose as FFU (focus forming units); there may be many virus 

particles for each FFU. 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 87 

revised recreational AWQC (or State Water Quality Standards) to enhance the protection of 

public health. In order to go forward with currently available technologies, the diagnosis of 

viruses could be made by exclusion of bacterial and protozoan pathogens causes of illness. 

Additionally, such information would be essential inputs into QMRA models to be used at 

recreational sites (or types of sites) where epidemiological studies cannot be conducted due to 

expense or insufficient numbers of swimmers. Because advances in modern techniques in 

microbiology now make a more complete identification of specific pathogens possible, 

workgroup members felt that the epidemiological studies currently underway and planned 

provide a unique opportunity to collect specimens (stool, saliva, and/or blood) from swimmers 

(and non-swimmers as controls) with which to identify the responsible waterborne pathogens. 

Such data would be complementary to the data collected in studies of pathogen occurrence in 

water that are presented elsewhere in this chapter and these proceedings. Workgroup members 

suggested that both types of pathogen occurrence information (in humans, in water) be collected 

during future epidemiological studies in order to minimize cost and maximize the utility of the 

information. 

1. Identify etiologic agents of swimming-associated illness. 

2. Pilot approaches for identifying etiologic agents in planned and ongoing epidemiological 

studies. 

3. Classify etiologic agents in ill swimmers by broad groupings (i.e., viral, bacterial, 

protozoan). 

4. Develop and evaluate sample collection techniques (stool, salivary antibodies, blood). 

All of the above could be done as an adjunct to epidemiological studies. 

4.4.4 Fate and Transport

Because direct pathogen detection is not feasible on an ongoing basis, a surrogate measure 

relating water quality conditions to human health risk is required. When developing the 

appropriate indicator(s) to use in this approach, knowledge of the fate and transport 

characteristics of the pathogens and indicator(s), both individually and as they relate to each 

other is critical. 

Individually, fate and transport is significant because only those pathogens that are present and 

viable in a given waterbody pose a potential public health risk. These pathogens are typically 

divided into the following three major categories: viruses, bacteria, and protozoa. Because the 

microbiological characteristics of each of these groups are significantly different, it is not 

unreasonable to assume that their fate and transport characteristics will vary (perhaps 

significantly) as well. 

The most simplistic route of pathogen transport is direct deposition. Once the pathogen(s) 

(assumed to be carried in the feces of warm blooded mammals) is excreted over or in the water, 

the question is twofold—how long will the pathogen be viable and available (i.e., persist in the 

water column). 
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Indirect deposition of feces introduces a more complex situation. First, the fecal properties of 

different mammals can vary substantially. One of the primary differences (aside from pathogen 

and indicator density) is moisture content. That is, very “wet” feces is more likely than “dry” 

feces to introduce pathogens into the aquatic environment. After defecation, the distance of the 

feces from surface water plays an important role as well. Driven by precipitation and transported 

primarily via surface runoff, the pathogens are typically washed into the surface water either by 

sheet flow or are collected and discharged through a storm water collection system. During this 

transport, they are subjected to a variety of environmental factors—including, but not limited to, 

UV disinfection, predation, temperature—that affect the proportion that will ultimately end up in 

surface water in which people are recreating. 

Another category of indirect deposition includes point source discharges, such as POTWs, CSOs, 

concentrated animal feeding operations (CAFOs), and other NPDES permitees. In addition to 

the issues identified above, the effect of the treatment processes that these effluents are subjected 

to plays a role in fate and transport of the pathogens. 

Resuspension from sand, soil, or sediment (i.e., secondary environments) can also play an 

important role in pathogen fate and transport. There may be a reservoir of indicator(s) and/or 

pathogens that could be reintroduced into the water column. Additionally, regrowth of either the 

indicator(s) or pathogens could represent a source and/or confound the risk 

assessment/prediction. 

Ideally, the indicator(s) chosen as the surrogate for the pathogens will have the same fate and 

transport characteristics of the pathogens themselves. However, since this is unlikely, it is 

important to know and relate the characteristics that are specific to the indicator(s) and the 

pathogens so that the measurement of the indicator can be correlated to the concentration of the 

viable pathogens in the water and ultimately to public health risk. 

A number of studies have been published on the fate and transport of many waterborne 

pathogens and current indicator organisms. Therefore, a literature review to identify any data 

gaps so that additional studies may be designed and also to inform QMRA studies would also be 

useful. 

1. Conduct fate and transport studies for indicators and sentinel (index) pathogens. 

2. Conduct literature review to identify data gaps and to inform QMRA. 

3. Identify indicators that have the similar fate and transport characteristics as pathogens. 

4. Should include assessment of risk of pathogens and indicators being resuspended from 

sand, soil, and sediments (secondary environments). 

4.4.5 Determine the Occurrence of Pathogens in Impacted Recreational Waters

The pathogen occurrence and pathogen concentrations in water impaired by animal feces in one 

or more non-point study site(s) (e.g., beach impacted by [non-CAFO] agricultural animal runoff; 

Table 5, priority #1) could be compared with pathogen load in planned POTW-impacted marine 

epidemiological studies. It is also proposed that investigators consider using high-volume, 

tangential-flow water filtration methods that were recently developed for assessing bioterrorism 
U.S. Environmental Protection Agency Experts Scientific Workshop

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threats to drinking water. This technology was designed to simultaneously capture very low 

concentrations of viruses, bacteria, and parasites in 10 to 100 L of water using a single collection 

apparatus (filter and pump). Although the equipment and pathogen recovery methods were 

initially designed to work on finished drinking water, there has been additional research to adapt 

the process for use on raw water supplies. The raw water application of this technology may be 

sufficiently understood for its employment in current or planned studies within the next 2 to 3 

years. If the methods have not yet been adequately evaluated for this purpose, EPA may wish to 

encourage fast tracking their development for use in recreational water epidemiological and 

related field studies. Use of the large volume filtration tools might also be helpful to assess risks 

associated with low probability events that have serious health consequences (e.g., EHEC). 

1. Determine the occurrence of pathogens in affected waters using the high volume filtration 

currently being developed for counter bioterrorism purposes. 

4.4.6 Bather Studies

Bathers themselves can be a source of both indicator organism and pathogens in recreational 

waters (Elmir et al., 2007). Workgroup members suggested the following studies to determine 

the magnitude of this problem and/or the conditions at recreational sites in which this would be a 

problem. 

 

1. Conduct additional studies on the impact of bathers on levels of indicator organisms and 

as a source of infectious pathogens for other bathers. 

2. Develop better tools for assessing bather density. 

3. Incorporate bather density into the study design and analysis of future recreational water 

epidemiological studies. 

4. Conduct additional studies on human shedding in a controlled setting with a focus on 

young children. 

5. Incorporate bather contribution to indicators and pathogens in QMRA studies. 

4.4.7 Additional Research (Either Short- or Long-term Depending on EPA Prioritysetting) 

The following research would also enhance many of the ongoing and future efforts described in 

this chapter and elsewhere in these proceedings. 

1. Include epidemiological data in predictive modeling efforts. This would broaden the use 

of both epidemiologic and modeling data. Many recreational epidemiological studies 

collect an extensive set of environmental data. Whether this is sufficient to accomplish 

environmental modeling is unknown. Both modelers and epidemiologists should discuss 

the feasibility of this effort. 

2. Develop a method for accurate exposure assessment among swimmers. Exposure 

assessment in terms of water contact and quantity of water swallowed or inhaled is an 

area of potential misclassification in observational epidemiologic studies. The following 

would improve exposure assessment in epidemiologic studies: 
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a. Develop individual sampling devices. 

b. Develop methods and conduct studies to determine the quantity of water ingested 

and inhaled in recreational settings. Consider studying secondary recreational 

contact for potential comparison. 

References 

Eisenberg, JNS; Hubbard, A; Wade, TJ; Sylvester, MD; LeChevalier, MW; Levy, D; Colford, 

JM, Jr. 2006. Inferences drawn from a risk assessment compared directly with a randomized trial 

of a home drinking water intervention. Environmental Health Perspectives 114: 1199-1204. 

Elmir, SM; Wright, ME; Abdelzaher, A; Solo-Gabriele, HM; Fleming, LE; Miller, G; 

Rybolowik, M; Shih, M-TP; Pillai, S; Cooper, JA; Quaye, EA. 2007. Quantitative evaluation of 

bacteria released by bathers in a marine water. Water Research 41: 3-10. 

EP/CEU (European Parliament/Council of the European Union). 2006. Directive 2006/7/EC of 

the European Parliament and of the Council of 15 February 2006 Concerning the Management of 

Bathing Water Quality and Repealing Directive 76/160/EEC. Official Journal of the European 

Union L64: 31-51. Available at: 

http://europa.eu.int/eurlex/lex/LexUriServ/site/en/oj/2006/l_064/l_06420060304en00370051.pdf. 

Haile, RW; Witte, JS; Gold, M; Cressey, R; McGee, C; Millikan, RC; Glasser, A; Harawa, N; 

Ervin, C; Harmon, P; Harper, J; Dermand, J; Alamillo, J; Barrett, K; Nides, M; Wang, GY. 1999. 

The health effects of swimming in ocean water contaminated by storm drain runoff. 

Epidemiology 10(4): 355-363. 

ILSI (International Life Sciences Institute Risk Science Institute). 2000. Revised Framework for 

Microbial Risk Assessment. Washington, DC: ILSI. 

US EPA (U.S. Environmental Protection Agency). 1986. Ambient Water Quality Criteria for 

Bacteria – 1986. EPA440/5-84-002. Washington, DC: US EPA. 

WHO (World Health Organization). 2003. Guidelines for Safe Recreational Water 

Environments. Volume 1 Coastal and Fresh Waters. Geneva, Switzerland: WHO. 
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June 2007 91 

CHAPTER 5 

ACCEPTABLE RISK

Paul Hunter, Chair, University of East Anglia, U.K. 

Michael Beach, Centers for Disease Control and Prevention 

Lora Fleming, University of Miami School of Medicine and Rosenstiel School of Marine 

and Atmospheric Sciences, Florida 

Peter Teunis, RIVM (National Institute of Public Health and the Environment), Netherlands 

Timothy Wade, USEPA 
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5.1 Introduction 

This workgroup was primarily charged to reassess the extent to which existing microbiological 

criteria protect the health of swimming populations, and whether or not this is appropriate for 

current U.S. society. In particular, the workgroup was asked to consider the case of vulnerable 

(susceptible or sensitive) subpopulations and whether current levels of public health protection 

are sufficient for these people. The workgroup was also asked to consider whether it would be 

possible that improvements in recreational water quality criteria would be sufficient to improve 

public health protection for drinking water, recreational water, or consumption of shellfish. 

Group members decided to organize the main questions under the following headings: 

• Whether the term “acceptable risk” is still the most appropriate term. 

• Public involvement in “acceptable risk” decisions 

o To whom should any risk from recreational water contact be “acceptable”? 

o How can we get public involvement in the decision making process over what is and 

what is not “acceptable”? 

o How best to communicate risk with and educate the general public about risks from 

recreational water. 

• “Acceptable risks” to the general population 

o Whether the current methods for assessing risk from recreational water exposure are 

sufficient and if not, what new methods may be appropriate? 

o Whether risks differ between marine and freshwaters and whether it is “acceptable” to 

have different levels of protection for people bathing in these different waters. 

o Whether the current approach, based on protecting people from enteric illness is 

sufficient, or whether “acceptable risk” decisions need to take into account nonenteric illness. 

o Whether risks are different to people swimming in tropical, subtropical and temperate 

waters. 

• “Acceptable risks” for vulnerable subgroups 

o Define the main vulnerabilities. 

o Determine what risks are greater in vulnerable subgroups and whether general 

recreational water standards are sufficient to protect these groups. 

• What are the current levels of protection from existing criteria? 

• Potential synergies for health protection between revised recreational water criteria and 

standards for drinking water and shellfisheries. 

5.2 Main Conclusions and Observations 

5.2.1 Whether the Term “Acceptable Risk” is Still the Most Appropriate Term

There was commonality amongst the workgroup members that the term “acceptable risk” is 

flawed and should be avoided during the process of creating recreational water criteria. The term 
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June 2007 94 

“acceptable” was felt to elicit responses related to “acceptable to whom?” and had the 

connotation that swimmers accepted the risk and there was some level of informed decision 

making during the process. Although a variety of suggestions for replacing “acceptable” were 

elicited (e.g., tolerable, appropriate, excess, increased), no agreement on terminology was 

reached. However, workgroup members felt that any new term should be simple, easily 

understood, and inclusive rather than paternalistic in nature. Workgroup members also felt that 

EPA should develop a policy that includes public interaction during the criteria development 

process. 

This approach to determining “acceptable risk” should be broadly inclusive of impacted groups 

(e.g., swimmers, taxpayers who pay for beaches to be open) throughout the process. This would 

mean that EPA’s decision making and criteria development process should include information 

on how impacted groups would determine the level of “acceptable risk” and how those risks and 

the concept of protective criteria would be best communicated. This would require that EPA’s 

criteria development process (1) be clear, transparent, and communicated to all stakeholders; (2) 

factor in and include input and data collected from impacted groups; (3) include a data-informed 

communication package to educate impacted groups when the new criteria are released; and (4) 

develop a plan for assisting state and local authorities with future communication of the concepts 

of “acceptable risk” and the meaning of beach closures and advisories to the public. Such an 

effort would require collaboration with sociologists and anthropologists to assess risk perception 

and risk communication research and apply this to development of appropriate assessment tools 

for determining key elements necessary for criteria development, release, and interpretation. 

Rapid integration of this information into ongoing EPA criteria development would be expected 

to build or improve partner involvement and acceptance of the new criteria.

5.2.2 Public Involvement in “Acceptable Risk” Decisions

Including public involvement in the criteria setting process would require that impacted groups 

are first informed about the process and then information solicited about how these groups make 

“acceptable risk” decisions and how tolerant these groups would be of risk associated with 

recreational swimming area use. Key research questions include the following: (1) What does 

the public understand currently? (2) What does the public think of when one uses the term 

“acceptable risk”? (3) How does the public interpret existing criteria and beach 

closures/advisories? (4) How does/should EPA communicate this risk? and (5) What level of risk 

would the public accept? The voluntary nature of recreational swimming needs to be clearly 

explained and put in context with other routinely and voluntarily accepted risks (e.g., driving to 

the beach, eating at local restaurants, smoking). The breadth of illness associated with 

swimming and types of illness to be reduced by new or revised recreational water quality criteria 

needs to be clear. Workgroup members felt that current criteria were not well understood by the 

public or beach managers so that indicator cutoff values (i.e., beach closures) connoted zero risk 

and “safe” water rather than an understanding of the concept of “acceptable risk.” These groups 

should be allowed to provided input on factors used in the decision making process (i.e., 

reduction of illness in children being a decision point). Workgroup members appreciate that 

EPA will ultimately be making the decisions and setting criteria but felt that a more informed 

and communicative path for this decision making is critical to future acceptance of these new or 

revised criteria. 
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Workgroup members suggested that EPA conduct the following activities: 

1. Begin building a transparent communication plan to inform impacted groups about 

ongoing criteria development. 

2. Rapidly initiate studies to assess how impacted groups understand and perceive the risks 

associated with recreational water use and what level of voluntary risk would be 

“acceptable,” followed by evaluation of final communication materials. 

3. Develop a multi-year plan to communicate the criteria development process to impacted 

groups and a communication plan for educating impacted groups about the new criteria. 

4. Assist state and local officials in developing data-based risk communication plans for 

communicating information on criteria interpretation and beach closures/advisories to the 

public. 

5.2.3 “Acceptable Risk” Levels for the General Population

 Method for Assessing Risk 

Workgroup members identified epidemiological (both randomized control and prospective 

observational cohort designs) and quantitative microbial risk assessment (QMRA) studies as the 

main methods for assessing risk. Some workgroup members noted that while QMRA is widely 

used and relied on by EPA for drinking water applications, it does not seem to be as widely used 

for recreational waters (with the exception of the work done by Jeffrey Soller). To broadly 

evaluate the gastrointestinal (GI) illness risk associated with the numerous potential pathogens 

found in recreational waters, epidemiological studies were viewed as more appropriate, although 

workgroup members believed the EPA should investigate expanding the role of QMRA (see also 

Chapter 4). One distinction noted was that although epidemiological studies are good at 

assessing the generally common and self-limiting risks associated with swimming in fecallycontaminated waters, they are not well-suited for investigating rare but potentially severe (and 

potentially life-threatening) illnesses that may be associated with recreational water exposure 

such as enterohemorrhagic E. coli (EHEC). For these special cases, workgroup members felt 

QMRA approaches may be the best way to assess risk and address potential outbreak situations. 

Other cases where QMRA could be useful would be for evaluating specific risks associated with 

specific waterborne pathogens (although not necessary rare) such as Cryptosporidium, 

Norovirus, and Shigella. A third method that has not yet been widely applied to assess risk from 

recreational waters is dynamic infectious disease modeling (with the exception noted above). 

These models are a form of QMRA, but specifically account for factors such as the immune 

status of the population (susceptible, infected, immune), rates of secondary transmission of 

illness, and other parameters. 

Workgroup members also noted that epidemiological studies can identify illness, but not 

infections, whereas QMRA studies can predict infections, but have more uncertainties associated 

with translating infections into an estimation of illness. Although epidemiological studies 

provide valuable results, there may be some confusion in their interpretation and application; for 

example, most studies of recreational waters to date have been conducted at beaches with known 

human sources of fecal contamination and results may not apply to other sites. EPA needs to 
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clearly explain the purpose of such studies (current, planned, and previous studies), their focus, 

and limitations. 

 Marine versus Freshwater 

Workgroup members did not see any reasonable rationale for different “acceptable risk” levels in 

marine and fresh recreational waters. Although the current “acceptable risk” levels based on 

EPA’s Ambient Water Quality Criteria [AWQC] for Bacteria – 1986 are different for fresh and 

marine waters (gastroenteritis rate of 8 per 1,000 swimmers in freshwaters and 19 per 1,000 in 

marine waters), workgroup members believed this to be an arbitrary decision that was not well 

founded. Workgroup members agreed that there could be different indicators, or different levels 

for the same indicator across marine and fresh recreational waters, but those levels should relate 

to the same estimate of risk. Furthermore, justifying differences in risk to the public and 

stakeholders based on type of water would continue to be confusing and problematic. 

There was some further discussion about how to account for differences in baseline levels of 

illness that could exist across locales and whether use of a relative risk scale instead of an excess 

(or attributable risk) scale may be a better way of addressing such differences. There is a distinct 

difference between doubling an absolute risk versus doubling a relative risk (see Section 5.2.5). 

 Enteric versus Non-enteric 

Workgroup members felt that criteria based on pathogen indicator levels derived to protect 

against GI illness would not necessarily protect against all non-enteric illnesses, with the possible 

exception of certain upper respiratory illnesses (URIs) transmitted via the fecal-oral route. At 

least one study (Fleisher et al., 1996) observed exposure-response relationships with fecal 

streptococci (enterococci) and URI; workgroup members believed there was potential for 

pathogens causing such illnesses (e.g., adenoviruses) to be transmitted via fecally-contaminated 

waters. The workgroup members felt that most causes of other non-enteric illnesses (e.g., rash, 

earache) were most likely to be caused by environmental or naturally occurring conditions and/or 

pathogenic microorganisms unrelated to fecal contamination (e.g., Naegleria infection, noncholera Vibrios) and therefore would not be explicitly controlled by criteria based on protection 

for GI illness (WHO 2003). 

There was uncertainty about EPA’s role in protecting against such illnesses, particularly those 

that are not anthropogenic. However, there are some risks that were unclear. For example, 

cyanobacteria concentrations can be influenced by nutrients and human impact, and may also be 

a cause of swimming-associated skin infections, respiratory infections, or long-term chronic 

conditions such as liver cancer (Chorus and Bartram, 1999; Fleming et al., 2002). 

Workgroup members felt that earaches (otitis externa or “swimmers ear”) were probably the 

most debilitating of the commonly occurring swimming associated non-enteric illnesses. 

However, they also felt that there was no evidence that such infections (often caused by 

Pseudomonas) were associated with fecal indicator bacteria, and therefore AWQC or State 

Water Quality Standards based on fecal indicators would not afford public health protection for 
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those illnesses. Workgroup members also felt that other indicator bacteria, or other types of 

indicators, are not currently available to protect swimmers from most non-enteric illnesses. 

Workgroup members agreed that when a beach was closed due to fecal contamination then 

potential non-enteric swimming associated illnesses would also be prevented, although this 

would be inadvertent and it is not clear how often or under what circumstances this would occur 

(e.g., Do currently used indicators correlate with the presence of cyanobacteria or 

Pseudomonas?). 

 Tropical and Subtropical versus Non-tropical Recreational Waters 

Workgroup members identified the possibility that tropical and subtropical recreational waters 

may have to be approached differently from temperate waters because of issues such as regrowth 

and significant spatial or temporal variability of both indicator organisms and pathogens in the 

water and soils, substantially different ecosystems and climatic conditions (including heavy 

rains), and possibly the presence of a greater range of “exotic” pathogens. In addition, persons 

may experience longer term seasonal exposures in tropical and subtropical recreational waters 

due to the warm waters throughout the year. Finally, it is highly likely that the background rate 

of GI diseases is higher in tropical and subtropical populations (Payment and Hunter, 2001). 

It is important to note that workgroup members believe that people in tropical and subtropical 

areas should not be exposed to greater health risks from exposure to recreational waters than 

people in more temperate areas. 

Relative risk measures, unlike excess risks, express risk as a proportion of baseline risk and thus 

correct for varying background levels. Workgroup members discussed other ways to describe 

risk in place of an “acceptable risk” framework, including illnesses prevented as a result of 

implementing criteria (as done by the U.S. Food and Drug Administration [FDA]). Workgroup 

members felt that there was need for risk communication in this area so that risks are fully and 

accurately communicated. 

5.2.4 “Acceptable Risk” Levels for Vulnerable Subgroups

 Definitions 

In considering vulnerable human populations with regards to the health risks from exposure to 

recreational water, workgroup members distinguished between two major categories of 

vulnerability, (1) persons at different life stages, and (2) persons with suppressed immune 

function. 

 What is Different? 

Life stage connotes that for a variety of reasons, humans vary in their level of vulnerability to the 

health risks associated with exposure to recreational water over their life span. In particular, the 

discussion focused on the possible increased vulnerability of children, pregnant women (and 

their fetuses), and the elderly. Workgroup members felt that children are at a greater increased 
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June 2007 98 

risk compared to all other life stages because of their behavior and possibly because of naïve 

immune status. Because all members of the population pass through life stages, classifying 

childhood as a life stage instead of simply a subpopulation strengthens the argument for 

explicitly considering children when developing AWQC. Regarding behavior, children probably 

have higher exposures; that is, they are more likely to consume both marine and freshwater. 

Moreover, young children have significant hand-to-mouth and fecal-oral behavior that may lead 

to the consumption of contaminated substances. Very young children may also be more 

vulnerable to pathogens in recreational waters because they have never been exposed to these 

pathogens previously. Of note, preliminary, unpublished data from recent studies by EPA 

(NEEAR; Timothy Wade, EPA Office of Research and Development, personal communication, 

2007) as well as results from other published studies appear to demonstrate an increased risk of 

GI illness and possibly respiratory illness for children from exposure to recreational waters, 

although this has not yet been formally reviewed. 

Pregnant women (and their fetuses) and the elderly may be at increased risk for more severe 

consequences from acquiring GI diseases from exposure to recreational waters. Pregnant women 

and their fetuses may be at greater risk from certain recreational water pathogens (e.g., coxsackie 

B virus associated with fetal infection when acquired close to delivery, and enterovirus 

associated with certain fetal malformations). Furthermore, pregnant women may be at increased 

risk for significant dehydration and its consequences if they do acquire a GI infection resulting 

from contact with recreational water. Finally, although the elderly were believed to be less 

exposed due to decreased high intensity swimming behavior, it might be possible that the 

decreased immune function associated with increasing age might make them more vulnerable to 

infection and illness. 

Workgroup members also identified a potentially large subpopulation of persons with suppressed 

immune function, ranging from persons with HIV/AIDS to persons undergoing chemotherapy 

and using other immunosuppressive medications. Of note, a portion of the latter subpopulation 

could be completely unaware of their suppressed immune function. As a group, persons with 

suppressed immune function would be at increased risk compared to the healthy population of 

acquiring diseases from a range of opportunistic pathogens found in recreational waters, such as 

Cryptosporidium, Toxoplasma, and Vibrio parahemolyticus. Furthermore, persons with 

suppressed immune function may be at increased risk of more severe consequences from these 

diseases as well as from the effects of dehydration—a secondary ramification of GI diseases. 

Tourists and visitors were identified by workgroup members as a unique potentially vulnerable 

group to increased health risks associated with exposures to recreational waters. Similar to small 

children, these people may be previously unexposed to the range of pathogens in a new 

recreational water environment, and as such, more susceptible to both acquiring the infection and 

disease—possibly with more severe health consequences. Given that many of these people are 

on vacation, they may experience greater exposure to recreational waters.9

 Further, given that 

significant tourist travel is to tropical and subtropical areas, there may be additional risks from a 

range of exotic pathogens and potentially unique ecosystem conditions found in tropical and 

subtropical recreational waters. 

 9

 Tourists may spend long periods of time in the water over several days, whereas local users may have shorter 

exposures that are spread further apart. 
U.S. Environmental Protection Agency Experts Scientific Workshop

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Overall, workgroup members believed that the apparent increased risk for children for acquiring 

GI and possibly other diseases from exposure to both fresh and marine recreational waters should 

drive the health risk assessment of any future recreational water criteria development efforts, 

assuming the current and future research continue to demonstrate their apparent increased risk. 

Workgroup members emphasized that future recreational water criteria set on health risks and 

exposures of adults would not be sufficiently protective for children. As mentioned previously, 

because of differences in susceptibility between adults and children (and other subpopulations as 

well) a given numeric criteria translates to different risk levels for each subpopulation. 

Therefore, it is impossible to protect adults and children equally. The workgroup members felt 

that data on children should be explicitly considered for deriving the “acceptable risk” level in 

the development of new or revised recreational water quality criteria, with the understanding that 

the associated risk level for adults would then be even lower. 

Workgroup members felt that the increased risk to immunosuppressed people should not be an 

important factor in setting any future recreational water criteria because the factors associated 

with the increased risk of disease in this vulnerable subpopulation are not controllable or 

achievable through management of recreational water sites. Rather, an emphasis should be made 

on improved risk communication with immunosuppressed groups and health care professionals 

to inform them about risks associated with recreational water use and, in consultation with their 

health care provider, assessment of the need to avoid recreational water exposure. 

5.2.5 What are the Current Levels of Protection from Existing Criteria? 

It is not certain how accurate the current levels of protection are. “Magic” numbers like 8 or 19 

cases of gastroenteritis in 1,000 swimmers can “take on a life of their own,” increasing the risk 

of distraction from the basic objective—providing best effort to protect swimmers. This 

provides a compelling reason for not deriving and using a single numeric value for the targeted 

risk for new or revised AWQC. Risk levels from preliminary unpublished data from the EPA 

NEEAR study seems to agree with WHO (2003) B category waters (i.e., 1 illness per 20 

swimmers) (see Table 1, Chapter 1; Timothy Wade, EPA Office of Research and Development, 

personal communication, 2007). Pathogens associated with threshold indicator levels in current 

(US EPA, 1986) AWQC may differ from those in 2007; the population established in 1986 also 

may have different susceptibility due to differences in immunity to current pathogens in 1986 

versus 2007. Aside from protection against enteric illnesses, it seems likely that enterococci 

levels below current standards also provide some protection against upper respiratory tract 

infections. 

Instead of absolute levels of risk, workgroup members felt that the preventable fraction is a better 

measure for the level of protection. This includes information on the background level of risk 

against which the risk associated with recreational water use must be compared. Presence of 

other major exposure routes may mask any beneficial effects of lowering risks due to 

recreational bathing. Thus, an absolute reduction in illness from recreational water may not be 

reflected in a similar reduction in total cases in the community if people simply become infected 

by other transmission routes. On the other hand, disease reduction may be even greater if 

secondary cases are also prevented. Most recreational water exposures are experienced by a 

minority of the population who are repeatedly (chronically) exposed. 
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It is also possible that part of the primary contact-associated infections is caused by bather-tobather transmission. This independent, direct fecal contamination would be unaffected by 

monitoring programs designed to limit sewage contamination. Further studies are needed to 

understand the role of bather shedding in disease transmission and microbial water quality 

indicator levels. 

In a trade-off situation, acceptability of risk is partially determined by its source; that is, 

pathogen-shedding by fellow swimmers is difficult to control and may be more readily accepted 

than contamination by treated sewage effluent or agricultural runoff, whose risks are usually 

considered less acceptable. More important than trying to enforce compliance with a fixed 

standard level of risk, is the need to work toward continual improvement in public health 

associated with recreational water use. 

5.2.6 Potential Synergies for Health Protection between New or Revised Recreational 

Water Criteria and Standards for Drinking Water Sources and Shellfish Harvesting 

Waters

Workgroup members considered that any change in recreational water criteria that led to 

improved public health protection would not negatively impact on the risks from drinking water 

or shellfish consumption. However, some workgroup members did express concern about any 

change that would encourage further recreation in waters intended to be used for drinking water 

production or for shellfish harvesting. When people bathe they invariably contaminate the water 

to some extent with potential pathogens. Such pathogens may then be concentrated within 

shellfish or contaminate drinking water supplies and pose a health risk to others. 

5.2.7 Areas of Discord

Although workgroup members accepted that the phrase “acceptable risk” was widely used, they 

realized that there were difficulties in its general acceptance. However, no alternative to the 

phrase was thought to be “acceptable” to all workgroup members. Although the phrase 

“tolerable risk” is now being used more frequently internationally, it was still not tolerated by all 

members of the workgroup. 

5.3 Research Needs 

1. Risk perception studies to inform the risk communication strategy for the criteria 

rollout and focus groups to evaluate the risk communication strategy 

a. Assess public understanding of relative versus absolute risk. 

b. Key research questions include the following: (1) What does the public 

understand currently? (2) What does the public think of when one uses the term 

“acceptable risk”? (3) How does the public interpret existing criteria and beach 

closures/advisories? (4) How does/should EPA communicate this risk? and (5) 

What level of risk would the public accept? 

2. Define the data and conditions where a directed monitoring program would be 

necessary to protect against certain non-enteric (non-GI) illness. 
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a. Such research would probably require pathogen-specific studies, and a possible 

role for QMRA. 

3. EPA should investigate expanding the role of QMRA, particularly for investigating 

rare but potentially severe (and life-threatening) illnesses that may be associated with 

recreational water exposure such as EHEC (e.g., E. coli O157:H7). 

a. Define data needed for the QMRA modeling for special/outbreak cases and also 

for background/regular situations. 

b. Engage EPA experts in QMRA in recreational water research. 

c. Explore approaches to integrate QMRA (and/or dynamic modeling) to better 

understand recreational risk, especially situations with rare, but potentially severe 

outcomes. 

4. Conduct methodologic comparisons in tropical and subtropical recreational waters and 

if appropriate, conduct epidemiological studies. 

Methodological and ecological studies need to be conducted in tropical and subtropical 

recreational waters because of issues such as regrowth, significant spatial and temporal 

variability of both indicator organisms and pathogens in the water and soils, substantially 

different ecosystems and climatic conditions (including heavy rains), and possibly a 

greater range of exotic pathogens. These studies would determine the impact of these 

environmental factors on the use of proposed indicators organisms to be used for 

monitoring and regulatory purposes. Depending on the results of these studies, 

assessment of the need for epidemiologic studies specifically in tropical and subtropical 

recreational waters should be performed. This information will be essential to determine 

whether the same recreational water criteria as used elsewhere in the United States are 

also appropriate in these waters. Information on risks in such waters will help ensure 

appropriate risk communication to healthcare providers, public and environmental health 

managers, and residents of and visitors to tropical and subtropical areas concerning the 

risks of tropical and subtropical recreational waters. 

5. Ensure that future epidemiological studies obtain data on and existing studies are 

reviewed for risk to children. 

Children appear to be at increased risk for acquiring GI illness and possibly other 

illnesses from exposure to recreational waters; therefore, workgroup members felt future 

recreational water criteria should be based on the health risk to children. If existing 

standards are deemed not to provide sufficient protection to children then additional 

information will be needed to establish new or revised criteria that are thought to provide 

sufficient protection. Such information will also be essential to provide risk information 

to parents and others responsible for children. 

6. Review prior data to evaluate whether additional epidemiological studies are needed to 

determine the risk of severe disease to pregnant women and their fetuses, to the elderly, 

and to immunosuppressed individuals. 

There is evidence that pregnant women (and their fetuses), the elderly, and 

immunosuppressed people may suffer more serious disease and/or more serious health 
U.S. Environmental Protection Agency Experts Scientific Workshop

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consequences from recreational bathing waters. If these data show that there may be 

increased risks, then the incorporation of these subpopulations as specific target 

populations in future epidemiological studies should be considered. Information on risks 

in such waters will help ensure appropriate risk communication to healthcare providers, 

public, and environmental health managers, and these potentially increased risk groups 

from recreational waters. 

7. Determine how risks in tourists and visitors differ from those in residents. 

There is some evidence that risk may be greater for tourists and visitors than for residents 

local to a recreational water; thus, current estimates may underestimate the actual risk and 

so give inappropriately lax criteria (Payment and Hunter, 2001). Consideration should be 

given to the design and implementation of future epidemiological studies to address risk 

in tourists and visitors. It may also be possible to review data from previous studies to 

determine if there are increased risks to tourists. Information on risks in such waters will 

help ensure appropriate risk communication to healthcare providers, public, and 

environmental health managers, and tourists with exposure to recreational waters. 

8. Ecology of swimming-related waterborne pathogens, including studies on the role of 

bather shedding on transmission of illness and microbial water quality indicators 

Further studies are needed to understand the role of bather shedding in disease 

transmission and microbial water quality indicator levels. How efficiently are pathogens 

transmitted through swimming or bathing? This could be an experimental study, partly, 

augmented by epidemiology (serology, or microbial source tracking in a small study 

population). 

9. How many illnesses are prevented by beach closures? 

Studies of the number of illnesses prevented by beach closures would be primarily a 

modeling/statistical exercise. First, the procedures/modeling assumptions should be 

agreed upon. It could be done relatively easily in a QMRA-type of study. 

Table 6 provides a summary of how each workgroup member ranked the above research needs in 

relation to overall importance (1 to 5), relevance to EPA, and estimated time needed to complete 

the project. 
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Table 6. Research Needs and Rankings from Five “Acceptable Risk” Workgroup Members. 

Description Importance Relevance to EPA Near- and/or Long-term 

Conduct risk perception studies to inform 

the risk communication strategy for the 

criteria rollout and focus groups to 

evaluate the risk communication strategy 

(#1) 5 5 5 5 5 5 5 5 5 5 

N and 

L N N N N 

Assess public understanding of relative 

versus absolute risk (#1) 1 2 1 3 3 1 1 1 3 3 

N and 

L N N N L 

Define the data and conditions where a 

directed monitoring program would be 

necessary to protect against certain nonenteric (non-GI) illness (#2) 3 3 2 3 3 3 3 2 3 3 

N and 

L N L N L 

Define data needed for the QMRA 

modeling for special/outbreak cases also 

for the background/regular situation (#3) 3 4 3 3 5 3 4 3 3 5 

N and 

L L N N N 

Engage QMRA in recreational water 

research (#3) 2 3 3 3 5 2 3 4 3 5 

N and 

L N N N N 

Explore approaches to integrate QMRA 

(and/or dynamic modeling) to better 

understand recreational risk, especially 

situations with rare, severe outcomes (#3) 4 2 4 3 4 4 2 4 3 4 

N and 

L L N N N 

Conduct future epidemiological studies in 

tropical and subtropical bathing waters 

(#4) 4 4 2 5 5 4 4 2 5 5 N N N L L 

Ensure that future epidemiological 

studies obtain data on and existing 

studies are reviewed for risk to children 

(#5) 5 4 5 5 5 5 4 5 5 5 N N N L N 

Review prior epidemiological studies to 

determine the risk of severe disease to 

pregnant women and their fetuses (#6) 2 2 1 3 5 2 2 2 5 4 L L L L L 

Review prior epidemiological studies to 

determine the risk of severe disease to the 

elderly (#6) 1 2 1 3 5 1 2 2 5 4 L L L L L 

Review evidence about whether or not 

immunosuppressed individuals are at 

increased risk from recreational bathing 

waters (#6) 4 3 1 4 5 4 3 2 5 3 L N N N N

Determine how risks in tourists and 

visitors differ from those in residents (#7) 4 5 2 4 4 4 5 2 4 5 N N L N L 

Conduct studies on the role of bather 

shedding on transmission of illness and 

microbial water quality indicators (#8) 5 5 5 4 5 5 5 5 5 5 N N N L N 

Determine the ecology of swimmingrelated waterborne pathogens (#8) 3 4 3 5 3 3 4 3 5 5 L L L L L

Determine how many illnesses are 

prevented by beach closures?(#9) 4 4 4 5 3 4 4 4 5 5 

N and 

L N N N N

Scoring for importance: score 1 not at all important to 5 highly important 

Relevance to EPA: score 1 not at all relevant to 5 highly relevant 

For time: N (within next 2 to 3 years); L (within next 10 years) 
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References 

Chorus, I; Bartram, J (eds). 1999. Toxic Cyanobacteria in Water: A Guide to their Public Health 

Consequences, Monitoring and Management. London: E & FN Spon and Geneva, Switzerland: 

World Health Organization (WHO). 

Available at: http://www.who.int/water_sanitation_health/resourcesquality/toxcyanobacteria.pdf. 

Fleisher, JM; Kay, D; Salmon, RL; Jones, F; Wyer, MD; Godfree, AF. 1996. Marine waters 

contaminated with domestic sewage: Nonenteric illnesses associated with bather exposure in the 

United Kingdom. American Journal of Public Health 86: 1228-1234. 

Fleming, LE; Rivero, C; Burns, J; Williams, C; Bean, J; Shea, K; Stinn, J. 2002. Blue green algal 

(cyanobacterial) toxins, surface drinking water, and liver cancer in Florida. Harmful Algae 1(2): 

157-168. 

Payment, PR; Hunter, PR. 2001. Endemic and epidemic infectious intestinal disease and its 

relation to drinking water. Pp. 61-88 in: Fewtrell, L; Bartram, J (eds) Water Quality Guidelines, 

Standards and Health. Risk Assessment and Management for Water-related Infectious Disease.

London: IWA Publishing. 

US EPA (U.S. Environmental Protection Agency). 1986. Ambient Water Quality Criteria for 

Bacteria – 1986. EPA440/5-84-002. Washington, DC: US EPA. 

WHO. 2003. Guidelines for Safe Recreational Water Environments. Volume 1 Coastal and 

Fresh Waters. Geneva, Switzerland: WHO. 
U.S. Environmental Protection Agency Experts Scientific Workshop

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CHAPTER 6 

MODELING APPLICATIONS FOR CRITERIA AND IMPLEMENTATION 

Alexandria Boehm, Chair, Stanford University, California 

Donna Francy, U.S. Geological Survey 

Mark Pfister, Lake County Health Department, Illinois 

John Wathen, USEPA 

Richard Zepp, USEPA 
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6.1 Introduction 

The Modeling workgroup was charged with determining how models might be incorporated into 

future recreational water criteria development and implementation. Workgroup members did not 

explicitly consider total maximum daily loads (TMDLs) in the discussion because models are 

already being used in TMDLs for pathogens throughout the United States. The discussion 

focused on what was generally felt to be the most important novel applications of models in new 

or revised recreational ambient water quality criteria. 

In the context of recreational water quality criteria, a perfect model would allow prediction of 

fecal indicators, pathogens, or risk as a function of source presence and strength relative to 

physical, chemical, biological, and human variables. 

There is limited understanding regarding the sources of microorganisms and their fate and 

transport in the aquatic environment, so the use of deterministic, process-based models (see 

Appendix G) in criteria development and implementation is not practical for most U.S. water 

quality managers within the next five years (2012). Rather, simple heuristic, statistical models 

that do not necessarily require an understanding of processes and mechanisms are more 

realistic for criteria development and implementation within the next 5 years. This is not to 

say that substantial research should not go into refining understanding of sources, fate, and 

transport of pathogens and pathogen indicators and their spatial and temporal variability in water 

and sediments. Thus, workgroup members suggested that a substantial research effort go into 

understanding these processes in watersheds and near-shore waters as this will have profound 

impacts of development of future (“next generation”) recreational water quality criteria (see 

Section 6.5).

Workgroup members saw two roles for models in the development and implementation of nearterm (five years) new or revised criteria: (1) recreational water quality notification models and 

(2) models to support sanitary investigations (hereafter referred to as “sanitary investigation 

models” for simplicity). Recreational water quality notification models are already in use in the 

Great Lakes and have proven to be effective and popular with the public (Francy and Lis, 2007; 

Olyphant, 2004; Whitman, 2007). There are a handful of sanitary investigation tools and models 

that are accessible to recreational water managers throughout the country (e.g., 

DigitalWatershed, the BASINS3 system). The main focus of this chapter is water quality 

notification models because these are easily accessible to a wide range of recreational water 

managers in the near-term. However, because workgroup members viewed the sanitary 

investigation model as an area of near-term research activities and investigation, with possible 

applications in the near-term development of new or revised criteria and/or implementation, 

discussion of sanitary investigation models was included as well. 

6.1.1 Water Quality Notification

Numerous research studies in the peer reviewed literature show that a single sample standard 

implemented in conjunction with assays that require incubation longer than a few hours results in 

less accurate management decisions (Francy and Darner, 2006; Hou et al., 2006; Kim and Grant 

2004). That is, by the time results from analysis of a water sample are available and a water 
U.S. Environmental Protection Agency Experts Scientific Workshop

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quality notification is issued, the microbial water quality may have changed. This is due to the 

inherent variability in indicator bacteria levels over timescales shorter than a day (see Figures 4a 

and 4b), as measured by culture-based assay, both with selective membrane-filtration media and 

350

300

250

200

150

100

Enterococci (MPN/100 mL)

50

12:00

10/22/05

18:00 00:00

10/23/05

06:00

Figure 4a. Enterococci (MPN/100 mL) Sampled Every 10 

Minutes at a Beach in California. (The reference background 

denotes the range of single sample exceedance.) SOURCE: A.B. 

Boehm, unpublished data (ENTEROLERT assay). 

Figure 4b. Subtropical Marine Beach (Miami, Florida): 48 

hours Sampling. SOURCE: Amir Abdelzaher, Samir Elmir, Lora 

Fleming, Kelly Goodwin, Helena Solo-Gabriele, John Wang, Mary 

Wright, University of Miami, personal communication, 2007. 
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defined substrate technologies such as Quanti-Tray (IDEXX, Westbrook, Maine). Note, 

variability in indicator levels as measured by nucleic acid-based assays (like quantitative 

polymerase chain reaction [qPCR]) has not been well characterized in the peer reviewed 

literature. The variability in Figures 4a and 4b is not unusual in environmental waters because 

“patchiness” is an inherently natural phenomena. A water quality notification model can be 

used to augment monitoring data and provide more timely and accurate recreational water 

quality notification to better protect the public from exposure to waters not in compliance 

with water quality criteria or standards. 

Summary of near-term research needs (i.e., the next 2 to 3 years) specific to water quality 

notification include (see Section 6.5 for further information) the following: 

1. Day-to-day water quality notifications should not be issued using a single sample 

standard in conjunction with a microbial assay that takes longer than a few hours due to 

time-lag notification errors as discussed above. Simple, heuristic or statistical water 

quality notification models are one way to improve water quality notification accuracy. 

2. Immediate research needs include the following: 

a. Testing whether models can be used to predict health outcomes during upcoming 

epidemiological studies in California and in Alabama and Rhode Island and 

retrospectively for the Great Lake epidemiology study in the Great Lakes (Wade 

et al., 2006) (that is, risk = f[temperature, tides, waves, etc.]); 

b. Developing and testing simple notification models on different recreational water 

types with a wide range of sources and geographical locals; 

c. Exploring the feasibility of developing regional models that apply to more than 

one recreational water; 

d. Training recreational water managers; and 

e. Creating a user-friendly portable package for developing local models. 

6.1.2 Sanitary Investigation 

Quantitatively determining the potential for a waterbody to be impaired with human pathogens is 

essential if the European Union (EU; EP/CEU, 2006) or World Health Organization (WHO, 

2003) approach to criteria development is undertaken (i.e., sanitary investigation is integrated 

into the criteria). This potential could be determined using a “toolbox approach” in conjunction 

with water quality notification models or sanitary investigation models. In the first case, the 

water quality notification model results can be used to learn about the factors that influence 

water quality in recreation waters; for example, high rainfall and wave action from a given 

direction and of a given height might lead to greatest impairment. The occurrence of these 

environmental conditions can be used to trigger sampling for “toolbox” approaches such as 

analyses for human-specific or bird-specific markers and human pathogens to “rule in” or “rule 

out” high probability of human pathogen presence. In the second case (sanitary investigation 

models), simple, quantitative sanitary investigation models that relate watershed attributes to 

probability of human pathogen impairment may be developed. 
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Summary near-term research needs (i.e., the next 2 to 3 years) specific to sanitary 

investigation models include (see Section 6.5 for further information) the following: 

1. Simple, heuristic or statistical models that correlate watershed activities (presence of 

wastewater/sewage treatment plant effluents, agricultural activities, and domesticated 

animals) and attributes (slope, soil type, climate, soil moisture) can be used to determine 

the susceptibility of a waterbody to pathogen impairment. 

2. Research should be conducted to better understand how watershed activities and 

attributes relate to pathogen presence in streams and receiving waters and include the 

following: 

a. factors that modulate septic tank impact on waterbodies; 

b. factors that modulate contributions of animal wastes to pathogen and pathogen 

loads to waterbodies; 

c. sources in urban landscapes (e.g., broken/leaky sewer pipes, combined sewer 

overflows [CSOs], runoff); and 

d. effect of meterological factors (e.g., rainfall, evapotranspiration, etc.) on nonpoint sources. 

6.2 How Models are Currently Being Used 

6.2.1 Sanitary Investigation Models 

Sanitary investigation models that explore the relationship between land use, watershed 

attributes, and water quality are already in place and have been used in TMDL implementation 

(criteria implementation); however, they have not been specifically applied to criteria 

development. Creating a TMDL-like model for a waterbody prior to impairment may be viewed 

as proactive rather than reactive. Such models in use include deterministic models like 

Hydrological Simulation Program-Fortran (HSPF) and Storm Water Management Model 

(SWMM) for watershed loading, and CE-QUAL models for pathogen fate and transport (US 

EPA, 2002). Feedback from some environmental engineers and consultants who apply these 

models to pathogen and fecal indicator transport suggests they provide highly uncertain 

predictions for pathogen and indicator concentrations and fluxes (Ali Boehm, Stanford 

University, personal communication, 2007). 

If sanitary investigation models are to be used for criteria development (i.e., prioritizing or 

discounting procedure for various type of sources), then models that are quantitative yet simple 

must be available to managers who do not have the resources to run full-scale simulations. 

These quantitative simple models need to relate land use activities and patterns to the likelihood 

of human pathogen presence. The ability to rule in or rule out the presence of human pathogen 

sources in a watershed would be useful to recreational water managers—especially if the EU or 

WHO approach to criteria development is undertaken. The relationship between land use 

patterns and microbial water quality has been investigated quantitatively along the California 

coast (Handler et al., 2006), lakes of South Carolina (Siewicki et al., 2007), North Carolina 

(Mallin et al., 2000), and Georgia (Fong et al., 2005; Vereen et al., 2007). In Australia, the 

relationship between land use and watershed attributes and pathogens and pathogen indicators 
U.S. Environmental Protection Agency Experts Scientific Workshop

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has been applied to numerous catchments using what is termed “pathogen catchment budgets 

(PCBs)” (Ferguson and Croke, 2005; Ferguson et al., 2007). A sanitary investigation model, for 

example, might indicate that a completely undeveloped watershed with no agriculture has very 

low probability of producing runoff containing human pathogens and could potentially place a 

water body in a “low concern” tier in criteria similar to the EU or WHO approaches (see Tables 

1 and 2, Chapter 1). Such models are being developed and used in the U.K. for criteria 

implementation and development (David Kay, University of Wales, U.K., personal 

communication, 2007; Kay et al., 2005, 2007). 

6.2.2 Water Quality Notification Models 

Water quality notification models that are most commonly used are simple heuristic models that 

relate rainfall to water quality. More complex models currently in use for informing advisory 

and closure decisions are exclusively statistical models that are used in conjunction with 

historical water quality data. The models draw on a body of past recreational water monitoring 

water quality data and temporally-associated physical parameters. The models are developed by 

assessing and exploring data for parameters that correlate most strongly with variations in water 

quality detected over the course of monitoring for pathogen indicators. Promising variables are 

selected, regression models are tested, and the models are refined on the basis of the results 

obtained using single variables and/or sets of variables. 

Another type of “model” for water quality notification is the Heal the Bay Beach Report Card 

grading system (http://www.healthebay.org/brc/statemap.asp), which provides grades for water 

quality that are updated daily and formulated using more than one water quality measurement. 

Given the major uncertainty and variability in measured microbial water quality (e.g., Figures 4a 

and 4b), this is highly preferable compared to using a single sample to drive public water quality 

notifications. 

One workshop participant (not from the Modeling workgroup) suggested that neural network 

models be used to model water quality for notification. Neural networks relate independent 

variables to a dependent variable non-linearly and have been used to model fecal coliforms in 

some waterbodies (Kumar and Jain, 2006; Neelakantan et al., 2002). However, the Modeling 

workgroup members agreed that neural network models would not be accessible to the majority 

of U.S. recreational water quality managers and public health officials in the near-term (5 years). 

In addition, neural network models have not been used previously for water quality notification, 

so they are probably not going to be useful in the near-term. They are, however, worth 

examining in the future. 

Simple statistical models have been developed for Great Lakes and West Coast recreational 

waters that link fecal indicator concentration with meteorological and water quality 

data/information, and include the following: 

• water quality and dynamic hydrologic variables (e.g., water temperature, turbidity, 

currents, wave height, tide level or range, lake height); 

• optical property data (e.g., UV and visible irradiance, light scattering, cloud cover); 

• meteorological parameters (air temperature, wind speed/direction, rainfall, pressure); and 
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• other factors (e.g., bird counts near a recreational water, number of swimmers in the 

water, video counts of swimmers and wildlife, flow/discharge from a storm drain or 

nearby creek). 

These models have been used very successfully in three states in the Great Lakes to predict the 

likelihood of exceedance of the current (US EPA, 1986) indicator bacteria criteria for public 

water quality notification. The models have been shown to be effective in predicting indicator 

concentrations for compliance and for making timely public health decisions relative to 

recreational water advisories and beach closures. 

The short-term predictions derived from these statistical models have been referred to as 

“nowcasting.” Nowcasting has been described in the peer reviewed literature (Boehm et al., 

2007; Francy et al., 2002, 2003; Hou et al., 2006; Nevers et al., 2005). The variables that are 

used to correlate with indicator concentrations vary depending on the type of setting of the 

recreational water. Among the descriptive variables assessed to date, turbidity, rainfall, tides, 

and wave height have been found to be among the most highly-correlated. The success of these 

models has been evaluated by their effectiveness in predicting days when current EPA limits 

have been exceeded and comparing predictions with bacteria concentrations from monitoring on 

a given day. 

Statistical tools such as Swimming Advisory Forecast Estimate (SAFE) and SwimCast 

(http://www.earth911.org/waterquality/) for Lake Michigan and nowcasting models for Lake 

Erie are being used to warn the public about potentially unhealthy conditions in recreational 

waters. Project SAFE is a statistical model used for the five recreational waters in Lake and 

Porter Counties that extend to the west of the Burns Ditch outfall (Ogden Dunes, West, Wells 

Street, Lake Street, and Marquette Beaches). These beaches are directly affected by 

contaminants in the Burns Ditch outfall, particularly during prevailing north wind conditions. 

Project SAFE models provide a far better real-time estimate of E. coli counts than advisories 

based on single sample monitoring, and are generated for the five beaches simultaneously. 

Similar applications are being developed for other Great Lakes recreational waters. Another 

instance of statistical model use is the Ohio Nowcast system. The U.S. Geological Survey 

(USGS) and Cuyahoga County Board of Health are implementing a pilot Nowcast project to test 

the use of a statistical model at Huntington Beach, Bay Village, Ohio (Francy and Lis, 2007). 

Nowcast was used as a tool for recreational water closure decisions for the first time in Ohio in 

2006. If the testing goes well, the Nowcast model will be used in subsequent years at other Lake 

Erie recreational waters. 

In all cases where models are being used in the Great Lakes, the modeling is being used to 

augment microbial water quality monitoring that is being continued as required by the National 

Beach Guidance and Required Performance Criteria for Grants (US EPA, 2002). In Lake 

County Illinois (SwimCast) all recreational waters are monitored each day in the morning and 5 

days per week in the afternoon at locations used for obtaining data for statistical modeling. In 

Indiana (SAFE model) recreational waters are monitored once a week. In Ohio (Nowcast) 

monitoring occurs 4 days per week at most Lake Erie recreational waters; and at Huntington 

Beach, monitoring was increased to 7 days per week during 2006 to provide a large data set to 

test the accuracy of the Nowcast system. 
U.S. Environmental Protection Agency Experts Scientific Workshop

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Hou et al. (2006) and Frick and Ge (submitted) have taken other important steps in developing 

useful statistical tools for use in recreational water quality notifications. Currently used models 

are based on long time-series records because models developed from large data sets are 

generally considered better than models developed from smaller data sets. However, large data 

sets are developed over time, so this approach is “static.” Because conditions at recreational 

waters are highly dynamic and change from year-to-year and as the season progresses, these 

authors’ models use a dynamic approach in which the descriptive variables are updated 

periodically. 

6.2.1 Communication of Modeled Information to the Public and Recreational Water 

Managers

Information on modeled projections of water quality has been communicated to the public 

through the use of a range of communication media and in a variety of information formats. 

Internet postings, radio spots, and local signs have all been employed in communicating the 

output of regression model-based advisories. Model outputs intrinsically include an estimate of 

error. This is expressed in the Nowcast program in a manner similar to the familiar weather 

forecast probability of precipitation (POP). That is, the likelihood of an exceedance of water 

quality standards for a given day is expressed as a percentage. In SwimCast, the modeled 

estimate of fecal indicator concentrations is provided with the average prediction and the upper 

and lower bounds of the 99th percent confidence limit of the projected figure. Because the value 

of that number to the general public is limited, a risk explanation is reported based on this 

statistical prediction in terms of a text description (e.g., low risk if entire confidence interval is 

below the single sample maximum criteria). 

Information on beach water quality can be provided to the public through a tiered approach. The 

first tier involves communicating a red or green light; that is, simply informing the public on 

whether or not the recreational water is currently posted with a water quality advisory. The 

second tier is to provide additional information for those who desire to be more informed and 

could include posting the measured water quality, environmental water quality data, and the 

resultant numerical prediction on a website. The third tier is to provide detailed information on 

the Nowcast system and explain how statistical models are developed and tested, which can also 

be provided on a website or summarized in fact sheets distributed to the public at the recreational 

water. A tiered system allows the recreational water user the ability to choose their desired level 

of information. 

Effective communication to the recreational water manager and state and local public health 

agency representatives is essential for acceptance of a Nowcast or similar system. Presenting the 

science behind statistical modeling in a simple and concise manner at periodic workshops and 

meetings is the first step toward gaining acceptance. Because the Nowcast system is different 

from conventional water quality notification systems already in place (i.e., using the previous 

day’s measured bacterial indicator concentration), local officials may be apprehensive in 

accepting the new technological approach. Thus, demonstrating to local agencies that the 

Nowcast system provides a more accurate assessment of water quality conditions may be 

required before acceptance and implementation is achieved. 
U.S. Environmental Protection Agency Experts Scientific Workshop

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6.3 Advantages and Disadvantages of Modeling 

The main advantage of modeling for water quality notification is that modeling can provide 

accurate and timely notification of water quality, whereas day-to-day monitoring cannot. Such 

modeling may be as simple as a heuristic model or a letter grade for recreational water. More 

complex models, such as those already in place in the Great Lakes, use multiple regression 

modeling or similar tools. 

An advantage of using a simple sanitary investigation model that relates land use activities and 

patterns to microbial water quality is that a manager may be able to rule in or rule out the 

presence of human pathogen sources in a watershed to relax criteria, as is proposed in the EU 

(EP/CEU, 2006) and WHO (2003) approaches to criteria development. 

6.3.1 Advantages of Modeling

• Statistical/regression fecal indicator estimation models are relatively easy to create for an 

individual with knowledge of statistics and may in some cases only require one variable 

to adequately describe/predict the pathogen indicator. Several government or private 

entities currently maintain hydro-meteorological equipment and sensors (e.g., USGS, 

National Oceanic and Atmospheric Administration [NOAA]) with readily accessible realtime data via the Internet, which could be used at no cost to the recreational water quality 

manager if deemed appropriate for the specific recreational water. Collected descriptive 

variables can either be continuous or categorical. Once developed and put into place, 

statistical models are also easy to use with minimal training required for the recreational 

water managers and operators. 

• Predictions from a sanitary investigation model may allow managers to rule in or rule out 

human pathogen sources in their watershed and hence relax water quality criteria using 

an EU or WHO criteria approach. Land use and watershed attributes may be readily 

available for incorporation into such a model (e.g., Digital Watershed, see 

http://www.iwr.msu.edu/dw/). 

• Water quality notification predictions may be made “near” real-time if required data 

elements (input variables) exist. This alleviates the delay currently experienced by 

culturable methods (18 to 24 hours for E. coli or at least 24 hours for enterococci). Even 

with the advent of rapid qPCR (molecular-based) methods, there will continue to be time 

associated with collection, sample preparation, analysis, and results evaluation. For 

example, sample preparation adds an estimated minimum of 2 hours in addition to the 

analysis time. In addition, only the most intensively used waterbodies will likely be 

monitored with a frequency that will make the best use of the timely results from the use 

of these methods. 

• Collection and analysis delays for both culture- and non culture-based methods currently 

have and potentially will continue to result in false negative (Type II) advisory/closure 

errors (e.g., contaminated recreational waters remain open). This is due to the inherent 

variability of fecal bacteria densities—even over time scales as short as every 10 minutes 

(see Figures 4a and 4b). Statistical models created for various recreational waters in the 

Great Lakes have been successfully used to correctly advise/notify the recreational water 

user of current fecal indicator conditions. Proper public notification should result in 
U.S. Environmental Protection Agency Experts Scientific Workshop

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improved public health outcomes and is the major benefit of statistical modeling. It has 

been well received (instills confidence) by the public and recreational water managers 

and operators at currently used recreational water locations. 

• For recreational waters that have daily (or multiple day per week) monitoring of a fecal 

indicator and other hydro-meteorological data, costs for creating a statistical model will 

be low relative to other monitoring/advisory costs. For many recreational waters, initial 

model creation will require additional water quality monitoring for fecal indicators 

because it is imperative that the data set on which the model is based include a full range 

of fecal indicator concentrations for the specific location. However, once the statistical 

model is created and is validated, the need for daily or weekly monitoring could be 

reduced, potentially reducing monitoring costs. 

• Once the statistical model has been created, both the data-element collection and actual 

prediction can be automated using current technologies. Although automation initially 

increases costs (i.e., equipment and programming), personnel costs should be reduced 

over time. 

• Many recreational waters are monitored infrequently due to economic reasons or 

logistical issues (e.g., difficulty of sampling on weekends). Statistical modeling, if 

relatively automated, will improve water quality notification activities at these locations, 

often during highest use days. 

• When associated variables become known during model development, a deeper 

understanding and knowledge of the potential reasons driving increased fecal indicator 

concentration should assist the recreational water operator (and other interested parties) 

with future assessments and sanitary investigation work. Simple linear relationships can 

help to identify potential sources of fecal indicator bacteria (i.e., waterfowl counts versus 

E. coli measurements) and can be used to help design monitoring and microbial source 

tracking studies. 

• Currently used statistical models are based on recreational water quality criteria and thus 

meet Beaches Environmental Assessment and Coastal Health (BEACH) Act of 2000 and 

recommended Clean Water Act (CWA) §304(a) single sample maximum allowable fecal 

indicator density requirements. Because previous studies have demonstrated that the 

currently-used bacterial indicators are statistically associated with acute GI illness, 

predictions based on these pathogen indicators should be protective of public health. 

• Statistical models could possibly be used to forecast poor conditions at recreational 

waters using forecasted descriptive variables available from NOAA. 

• The statistical approach is flexible and could be applied to prediction of other criteria 

besides the current culturable E. coli- and enterococci-based criteria. However, new data 

would be required to calibrate the models if the criteria changes and this could be a 

disadvantage (see more below). 

6.3.2 Disadvantages of Modeling

• Because water quality notification models are based on real-time data, prediction 

accuracy may be diminished by poorly collected or inappropriately maintained 

equipment. Quality assurance and quality control procedures must be in place for all 
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required input data elements. Recreational water managers and operators (or other 

individuals) must be diligent in ensuring that proper collection and data management 

techniques are used. 

• Because current water quality notification models utilize statistical techniques, a 

relatively large (n = 75) and rigorous data set is required to develop the model. Both 

dependent and assumed descriptive variables should be collected at least 3 to 4 

days/week during the recreational water season (if possible). Additionally, the data set 

should contain a variety of sampling events to capture temporal variability (morning and 

afternoon) and under both wet and dry weather conditions. It is also necessary to attempt 

to sample and collect the full range of fecal indicator concentrations for a specific 

recreational water to help ensure accurate future predictions. 

• Politicians, government officials, recreational water operators and managers, and the 

public may be apprehensive to accept the concept or the need for a modeling-based water 

quality notification system. Initial support may be difficult to obtain and a local 

“champion” would be beneficial to advance the concept. The workgroup members noted 

that once a model is created and accurate predictions are demonstrated, this apprehension 

would lessen substantially over time. 

• Statistical water quality notification models are based on previously collected data and 

historical associations. Unanticipated events such as sewage spills, large increases in 

wildlife populations, changes in shoreline from extreme weather events, or new non-point 

sources of fecal contamination may reduce the predictive ability of the model. If 

numerous under- or over-predictions occur, additional data collection activities would be 

warranted to determine whether the model would need to be modified. 

• Statistical water quality notification models appear to be most useful at recreational water 

locations that have occasional but infrequent exceedances of current bacterial water 

quality criteria. Recreational waters with consistently low or high fecal indicator 

concentrations may be very difficult to model. Additionally, the need for modeling will 

be harder to justify as currently accepted monitoring designs may be a preferable and 

cheaper method. 

• Simple statistical models, whether for recreational water quality notification or sanitary 

investigations, are generally not sufficient for use as deterministic models (e.g., bacterial 

fate and transport) or to provide load estimates for use in developing TMDLs. 

• Current statistical water quality notification models are based on recreational water 

criteria and thus meet BEACH Act and recommended CWA §304(a) single sample 

maximum allowable fecal indicator density requirements. However, if ambient water 

quality criteria for bacteria change, all currently used statistical models will need to be 

modified to reflect and predict the new criteria. This will result in new costs in the 

redevelopment and modification of an existing model to incorporate the changed 

relationships of predictive variables to indicator concentrations. In addition, because 

fecal indicators are used to predict health risk, the model is only as good as the indicator 

used. 

• There is some confusion as to whether a model output should be measured against a 

single sample standard and/or a 30-day geometric mean standard. Input from workshop 

participants revealed that these criteria are used differently around the country with 

monitoring data. Output from water quality notification models should be used with the 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 117 

single sample standard and not the 30-day geometric mean standard because it is not clear 

that model outputs should be averaged for comparison with the 30-day geometric mean 

standard. Guidance needs to be provided on this issue if new or revised recreational 

water quality criteria will support the use of models. 

• Because water quality is inherently variable, even over a 10-minute scale (see Figures 4a 

and 4b), how to collect data to develop and validate models needs to be carefully 

considered. In the Great Lakes, composite sampling is conducted. Guidance for any new 

or revised criteria that recommend models would need to address this. 

• There was some concern from the Implementation Realities workgroup that recreational 

water advisories or closures instigated by model output would count against them for 

CWA §303(d) listings or other CWA applications. Guidance for any new or revised 

criteria that recommend models would need to address this concern. 

• Models are site-specific and must be developed for various recreational sites, the same 

way water quality monitoring must be conducted at specific sites. 

• Sanitary investigation models have not been used before for water quality criteria 

development. 

6.4 Model Development and Evaluation

6.4.1 Initiating Model Development for Water Quality Notification 

Prior to initiating statistical model development at any recreational water site, a review of all past 

monitoring and watershed data should be completed. In some cases, enough data may exist to 

analyze associations between the environmental variables and indicator densities. For example, 

some states and local agencies collect data on air and water temperature, rainfall, amount of 

algae wrack, and/or tide level during compliance water monitoring. This type of ancillary data 

can be used to develop preliminary models and determine if any relationships between indicators 

and readily available environmental variables exist. This may guide additional monitoring needs 

and variables to be assessed. As always should be the case, strict quality assurance and quality 

control practices are to be followed to ensure that a high quality data set has been or will be 

collected. Additionally, a good understanding of the potential sources and extent of fecal 

contamination should be determined to aid in choosing sample locations and frequencies. This 

type of information can be obtained from recently conducted sanitary investigations, historical 

observations from local water resource managers, and/or visits to the recreational water site. 

6.4.2 Model Development for Water Quality Notification

Statistical models have relatively easy to obtain data needs. Data collection should include 

observations that cover the range of hydrometerological conditions that are expected to impact 

the recreational water. Sampling should be conducted, at the very least, by collecting at least 

two recreational seasons of data. A minimum of one recreational season will be necessary for 

model creation, while the second is used to gather additional data and for model evaluation. 

Water should be collected four or five times each week and the data set should contain a variety 

of sampling events to capture temporal variability (morning and afternoon) under both wet and 

dry weather conditions. It is also necessary to attempt to sample and collect the full range of 
U.S. Environmental Protection Agency Experts Scientific Workshop

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fecal indicator concentrations for a specific recreational water to ensure accurate future 

predictions. If current monitoring is conducted on a weekly or monthly basis, serious 

consideration should be given to increasing data collection requirements as it will take a much 

longer time period (i.e., 5 years) to develop the model. Generally, a relatively large (n = 75) and 

rigorous data set is required to develop a water quality notification model. Recreational 

locations that have consistent good or bad water quality are not good candidates for statistical 

models. Rather, sites with mixed water quality conditions are the best candidates for statistical 

models. A representative sample of the waterbody (multiple point grab samples or composite 

samples for larger recreational areas) should be analyzed for concentrations of fecal indicator 

bacteria, such as E. coli and enterococci, determined by use of an EPA-recommended method. 

The descriptive variables for each recreational waterbody will differ from site-to-site. More 

precise and frequent measurements may lead to better statistical models but also lead to 

increased costs. However, increased equipment use does lead to automated processes, greater 

reliability of measurements, and reductions in personnel time. 

Water quality notification models use a variety of descriptive variables and all are based on 

statistical correlations between descriptive variables and indicator organisms. Wave height has 

been shown to have a positive association with fecal indicator bacteria at some beaches and thus 

is often included as an independent variable in water quality notification models. Wave height 

can be estimated visually, measured with a graduated rod, or with pressure transducers. Wave 

height estimates can also be obtained from an off-site external source, such as a NOAA buoy. 

Turbidity has also been proven to be a useful factor for use in predictive models. Turbidity can 

be measured with a field turbidimeter or in situ by use of a turbidity sensor. Models of marine 

recreational water sites may also include tides (Boehm and Weisberg, 2005; Hou et al., 2006). 

Insolation, a measure of solar radiation, has been shown to be a useful predictor for fecal 

indicator bacteria models, since fecal indicator bacteria are sensitive to sunlight (Boehm et al., 

2002). Insolation can be measured using a pyranometer on site or provided by external sources 

(such as NOAA). Rainfall, as well as wind speed and direction, have been included in predictive 

models. These data can be measured in situ using a weather station or obtained from a reliable 

source such as operating meteorological stations, which are often located at airports (NOAA, 

2007). Streamflow rates from nearby tributaries (USGS, 2007) and effluent discharge rate 

information from wastewater treatment plants may also be useful factors for inclusion in a 

predictive model. The number of birds at the recreational water might also prove useful factors 

for inclusion in a model. Some models presently in use in the Great Lakes for water quality 

notification use the amount of biological wrack or algal mats as model inputs. Overall, the 

factors/variables included in a model will be site-specific. A thorough review of factors that 

might be included in a water quality notification model is outlined in Boehm et al. (2007). Water 

quality notification models that are most commonly used are simple heuristic models that relate 

rainfall to water quality (Ashbolt and Bruno, 2003). 

Two types of output may be produced by statistical models. The first and obvious output is the 

predicted microbial concentration and its associated confidence limits. A second output variable 

is the probability of exceeding an appropriate target value; for example, the probability of 

exceeding the single sample maximum recreational water quality criteria (Francy and Darner, 

2006). Either output may be used to issue advisories or closings of a recreational water site. 
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June 2007 119 

6.4.3 Data Needs for Simple Sanitary Investigation Model Development

Because the sanitary investigation model has not been implemented previously for water quality 

criteria development, data needs are based on characteristics that are important to models used 

for TMDL implementation. A waterbody manager would need data on land use within a 

watershed, types and numbers of domesticated and wild animals, publicly (and privately) owned 

(wastewater) treatment works (POTW) discharges and their degree of treatment and effluent 

characteristics, number and types of on-site septic systems, type and age of sewage 

infrastructure, presence of CSO and sanitary sewer overflows (SSO) systems, soil characteristics, 

and watershed slope. At minimum, such a model could generate a quantitative score of “very 

likely” to “not probable at all” regarding the possibility of having human pathogens present. 

6.4.4 Cost Estimates 

There is a wide range of cost estimates for the development, validation, and maintenance of 

statistical model programs. For all programs, the assumption is that an indicator monitoring 

program is already in place for the recreational water and computer hardware and statistical 

software are available. The following are 3 examples of costs for statistical modeling programs 

for 2 recreational seasons (60 observations per season), starting from the least to most expensive 

programs. 

1. Using existing data from other sources, such as meterological data from the National 

Weather Service (NWS) and wave height data from NOAA. Expenditures include data 

compilation and model development (200 hours of computer time). 

2. Using existing meterological data from other sources, measuring turbidity, wave heights, 

and number of birds at the time of sample collection. Expenditures include the purchase 

of a turbidimeter and standards ($1,200), field measurements (30 hours), and data 

compilation and model development (200 hours). 

3. Installing in situ site-specific instruments for measurements of wave heights, turbidity, 

wind direction and speed, and rainfall amounts. Expenditures include the purchase and 

installation of equipment (a one-time cost of $15,000 to $20,000), maintenance of 

equipment ($2,000/year for replacement and manufacturer calibration of equipment and 

80 hours), and data compilation and model development (200 hours). 

6.4.5 Understanding the Uncertainty and Measuring Success of Statistical Models 

The natural complexity of environmental systems means that it is difficult to develop complete 

mathematical descriptions of relevant processes, including all of the intrinsic mechanisms that 

govern their behavior. Model evaluation is defined as the process used to generate information 

to determine whether a model and its analytical results are of sufficient quality to serve as the 

basis for decision making (CREM, 2003). Once a statistical model is constructed, it is important 

to describe its usefulness or success. A regression model is built using a “training” data set 

comprised of dependent and independent variables (Boehm et al., 2007). The ability of the 

model to predict the dependent variable using independent descriptive variable inputs within the 

training data set can be described by a root mean square error (RMSE). A coefficient of 

determination (R2

) can also be used and is interpreted as the percent of the variation of the 
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June 2007 120 

independent data set described by the model. However, the workgroup members agreed that this 

was not the best metric for evaluating model performance. A third metric for testing the 

performance of a model is to examine the number of Type I and Type II errors that result. 

Assuming the null hypothesis is that a recreational water is in compliance with a water quality 

regulation and should be open to the public, a Type I error occurs when a recreational water is 

closed or posted with a warning when it should not be (i.e., false positive), while a Type II error 

occurs when a recreational water is not posted or closed when it should be based on the water 

quality regulation (i.e., false negative). These two types of errors can be summed to determine 

the total errors. The number of such errors is a function of the specific policy used by 

recreational water managers in making water quality notification and closure decisions. 

Model evaluation must be conducted using a data set with which it was not trained before it can 

be applied as a predictive tool. Model evaluation is defined as the process used to generate 

information to determine whether a model and its analytical results are of a quality sufficient to 

serve as the basis for a decision (CREM, 2003). It can only be completed if an appropriate 

evaluation data set of independent and dependent variables not used to train the model is 

available. The success of a model during evaluation is described by the root mean square error 

of prediction, which has the same mathematical formation as the RMSE. The number of Type I 

and II errors, as well as the total error rate is also calculated. The model’s performance is then 

compared with the current method for assessing recreational water quality (i.e., using the 

previous day’s measured bacterial indicator concentration). 

At a Lake Michigan recreational waterbody during 2004 (Olyphant, 2004; Pfister, 2007), 

swimmers were exposed to a health threat without warning on three occasions and kept out of the 

water when it was safe on only one occasion when a water quality model was used to make 

recreational water closure decisions. In contrast, swimmers would have been exposed to a health 

threat without warning on 19 occasions and kept out of the water when it was safe on 12 

occasions if daily morning monitoring data alone had been used to notify the public of health 

risks. 

Because every model contains simplifications, predictions derived from the model can never be 

completely accurate and the model can never correspond exactly to reality (CREM, 2003). After 

model validation (e.g., those that have been shown to correspond to field data), an additional 

year of data can be added to the model development process and a new model with another year 

of data is developed for use in subsequent years. 

The information about model evaluation presented above is an overview. The peer reviewed 

literature should always be examined for new ideas and thoughts about model evaluation. 

6.5 Research Needs 

Research needs for simple, statistical models are categorized below regarding near-term 

activities (2 to 3 year horizon) of immediate relevance to implementation and development of 

new or revised rcriteria in recreational waters to long-term research activities, such as elucidation 

of processes affecting pathogen/indicator fate and transport, development of non-point source 

models for catchments or watersheds, and deterministic models for TMDL development. There 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 121 

were differences of opinion among workgroup members about how important TMDL model 

development is for the long-term for criteria development and implementation. 

6.5.1 Near-term Research Needs (2 to 3 years) 

There is an immediate need to conduct research for development of models that can be used for 

water quality notification. Statistical (or empirical) models are most promising for this purpose 

because they are relatively cheap and simple, and readily accessible to most recreational water 

quality managers (see Chapter 7). Statistical models link microbial concentrations with 

meteorological and water quality data/information. Recent research has lead to the development 

of useful statistical models for some Great Lakes recreational beaches (Francy and Darner, 2006; 

Francy et al., 2003; Frick et al., 2005; Olyphant, 2005; Whitman and Nevers, 2004; Whitman et 

al., 2006) and marine coastal beaches (Hou et al., 2006). Although these statistical models have 

successfully predicted criteria exceedances under a variety of environmental conditions, 

statistical modeling studies must be extended to a variety of other recreational waters to evaluate 

fully the utility of this approach. 

Near-term research needs for water quality notification include the following: 

1. Day-to-day water quality notifications should not be issued using a single sample 

standard in conjunction with a microbial assay that takes longer than a few hours due to 

notification errors. Simple, heuristic or statistical water quality notification models can 

help avoid notification errors (all 5 workgroup members [5/5] agree). 

2. Immediate research needs include the following: 

a. Testing whether models can be used to predict health outcomes during upcoming 

epidemiology studies at Doheny Beach (California) and in Alabama and Rhode 

Island, and as well as the already completed epidemiology studies done in the 

Great Lakes (described by Wade et al., 2006) (high priority [5/5]); 

b. Developing and testing simple notification models on different recreational water 

types with a wide range of sources and geographical locals (high priority [5/5]); 

c. Exploring the feasibility of developing regional models that apply to more than 

one recreational water (low priority [5/5]); 

d. Training recreational water managers (high priority [3/5], low priority [2/5], 

there was disagreement on whether this belonged on the research list); 

e. Creating an excellent user-friendly portable package for developing local models 

(high priority [5/5]); and 

f. Developing dynamic predictive modeling methods (refers to models where 

variables are constantly updated over time) (high priority [2/5], medium 

priority [2/5], low priority [1/5]). 

1. Linking statistical models to health effects. One approach would be to concurrently 

conduct modeling studies along with planned epidemiological studies that will be conducted by 

EPA and the Southern California Coastal Water Research Project during the upcoming year in 

California, Alabama, and Rhode Island. In addition to measurements of microbial 

concentrations, appropriate data for model development should be collected during the 
U.S. Environmental Protection Agency Experts Scientific Workshop

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epidemiological studies (e.g., turbidity, irradiance, wind speed/direction, wave height, tides, 

temperature). 

Another approach would be to retrospectively develop statistical models for sites of past 

epidemiological studies in the Great Lakes, where appropriate data relevant to statistical 

modeling have already been collected (or can be obtained from existing meteorological data). 

For example, statistical models have been developed for Huntington Beach, Ohio, and West 

Beach, Indiana—both of which are sites of past NEEAR epidemiological studies (Haugland et 

al., 2005; Wade et al., 2006). 

2. Developing statistical models for different types of recreational waters. To test the 

feasibility of the statistical modeling approach, research is needed in recreational waters that are 

impacted by different sources of biological contaminants (non-point or point sources such as 

POTWs) and that are described by a wide range of meteorological and water quality variables. 

Waters that are significantly impacted by POTWs or non-point agricultural sources will be 

accorded the highest priority in site selection because past studies have shown that these sources 

are most likely to adversely affect human health. Sites located in the following regions should 

be considered for this research: 

• West Coast (open ocean and confined beach); 

• East Coast (open ocean and confined beach); 

• Gulf Coast; 

• inland lakes/reservoirs; 

• rivers with designated primary contact recreational use; and 

• tropics and subtropics. 

3. Dynamic approaches to statistical modeling. Currently used models are based on long 

time-series records that take at least 2 years to obtain. The regression constant and coefficients 

are held constant when the model is used to predict (generally Nowcast) conditions. Once 

established, the models are changed only at the end of season to incorporate new data. Other 

recent research suggests that model performance may be improved by using a dynamic approach 

in which the descriptive variables are updated periodically with data generated within a limited 

recent period—usually on the order of 30 to 60 days. Using the dynamic modeling approach, the 

predictions of bacterial concentrations have been significantly improved (Frick and Ge, 

submitted; Hou et al., 2006) and the time period for model development may be reduced. An 

alternative approach would be the development of a sliding seasonal band of data using multiyear data from the period surrounding the date of interest. Additional research is required to 

refine this approach, either though use of previously obtained data sets or data obtained at sites 

that will be used for the first two activities (i.e., linking statistical models to health effects and 

developing statistical models for different types of recreational waters). 

4. Communicating and training modeling techniques. Various activities can improve the 

communication of modeling techniques and results to the public and training recreational water 

managers, including the following: 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 123 

• creating a user-friendly portable package for developing local models; 

• training for running statistical models for recreational water managers; and 

• including recreational water managers on the decision process and polling them regarding 

their perception of its usefulness/feasibility. 

Training is an important component towards acceptance and implementation of statistical models 

by recreational water managers and public health agencies. In a November 2003 workshop held 

as part of the Great Lakes Beach Association Annual Conference in Green Bay, Wisconsin, 

recreational water managers expressed as a high priority the need for informed training on 

statistical models and other recreational water monitoring activities. Similarly, training is being 

provided by EPA Region 5 on statistical model and sanitary survey (investigation) development 

in April 2007 at the request of recreational water managers. 

5. Explore the feasibility of developing regional models (e.g., for southern Atlantic coast 

recreational waters). At present, simple water quality notification models are site-specific. The 

feasibility of using a regional scale model that predicts water quality regionally, within a large 

waterbody, for example, should be explored. 

Near-term research needs (next 2 to 3 years) for sanitary investigation models include the 

following: 

1. Simple, heuristic, statistical/conceptual models that correlate watershed activities (e.g., 

presence of treatment plant effluents, agricultural activities, domesticated animals) and 

attributes (e.g., slope, soil type, climate, soil moisture) can be used to determine the 

probability of a waterbody having inputs of human pathogens (all [5/5] agree). 

2. Research in the near-term should be carried out to better understand how watershed 

activities and attributes relate to pathogen presence in streams and receiving waters, 

including the following: 

a. factors that modulate septic tank impact on waterbodies (high priority [1/5] 

medium priority [1/5], low priority [3/5]); 

b. factors that modulate contributions of animal wastes to pathogen and pathogen 

loads to waterbodies (high priority [5/5]); 

c. sources in urban landscapes such as broken/leaky sewer pipes, CSOs, stormwater 

and urban runoff (high priority [5/5]); and 

d. effect of geographical and climatic setting on non-point source delivery (high 

priority [5/5]). 

6.5.2 Longer-term Research Needs (8 to 10 years) 

A variety of research needs are required to be able to develop an excellent model that would 

allow prediction of fecal indicators or human pathogens. Additionally, important sources, and 

fate and transport processes will need to be elucidated. These research needs will require a 

longer time horizon for completion and are summarized below. 
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1. Processes that affect fate and transport of pathogens and fecal indicators for 

incorporation into deterministic models and improving statistical models indicators. 

This long-term research effort involves the development of data and descriptors of 

processes that are required in deterministic models that predict fate and transport effects 

on pathogen concentrations in recreational waters. Process information can also be used 

to help define appropriate variables to use in statistical models. Such research would 

focus on partitioning of microorganisms to suspended and bottom sediments and sands, 

mortality of pathogens and indicators, zooplankton grazing on fecal indicators and 

pathogens, and the possibility of bacteria proliferation in the environment. Some of these 

processes are shown in Figure 5. In addition to these processes, a better understanding of 

mobilization of pathogens and pathogen indicators from sources within a watershed (i.e., 

from animal feces) and source strength from POTWs and CSOs are needed (high 

priority[5/5]). 

2. Research on GIS layers relevant to modeling. In order to develop viable models, 

recent and relevant GIS data need to be readily available and usable for models (e.g., 

POTW locations, recent land use categories, storm sewer locations). Digital Watershed 

Microbe

Predator

Inactivated microbe

Particle

Particle-bound

microbe

Water Column

Sediment

Transport Transport

Predation

Growth

Resuspension

Sorption

Desorption Inactivation

Sedimentation

Predation Growth Inactivation

Figure 5. The Possible Fates of Microbes (Fecal Indicators and Pathogens) in 

Environmental Water and Sediment (the fate of nucleic acids may be different; 

this figure does not include those sources). SOURCE: Adapted from Olivieri et 

al. (2007). 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 125 

is one example of a GIS-based software that can be used to provide inputs for 

deterministic models such as L-THIA (high priority [1/5], medium priority [4/5], [1/5]

does not think this is a research need). 

3. Combining deterministic models with statistical models. This research involves using 

outputs from deterministic models as inputs for statistical models that would be used for 

water quality notification and sanitary investigation purposes (high priority [0/5], 

medium priority [5/5]). 

4. Forecasting using statistical models. This research will seek to expand current efforts 

(e.g., by Frick and Ge, submitted) to use forecasted variables (such as wind speed and 

direction, precipitation, wave height, and turbidity, if available) to forecast concentrations 

of biological contaminants in recreational waters (high priority [2/5], medium priority 

[1/5], low priority [2/5]). 

5. Development of deterministic models of pathogen and fecal indicators for criteria 

implementation and development (high priority [3/5], medium priority [2/5] there 

was concern that these would not be really used by recreational water managers and that 

this is already being done if resources permit).

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CHAPTER 7 

IMPLEMENTATION REALITIES 

Lee Dunbar, Chair, Connecticut Department of Environmental Protection 

Thomas Atherholt, New Jersey Department of Environmental Protection 

Bart Bibler, Florida Department of Health 

Lawrence Honeybourne, Orange County Health Care Agency, Santa Ana, 

California 

Charles Noss, USEPA 

James Pendergast, USEPA 

Michael Tate, Kansas Department of Health and Environment 
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EPA requests that experts consider implementation realities when providing input to all specific 

and general questions throughout this document. 

The Implementation Realities workgroup members were charged with providing input to EPA 

and the experts participating on the other six workgroups concerning the practical implications of 

incorporating any proposed changes to the recreational bacteria criteria into State Water Quality 

Standards (WQS) and subsequent impacts on existing water quality management programs. To 

this end, the workgroup members met frequently with and actively participated in the 

deliberations of the other workgroups over the course of the workshop. Implementation issues 

and concerns are therefore incorporated into the individual workgroup chapters throughout these 

proceedings. This chapter provides a summary of the major areas of concern identified by the 

Implementation Realities workgroup during the deliberations resulting from the workgroup’s 

internal discussions as well as discussions with other workshop participants. 

At the most basic level, the success of implementing any new initiative depends on providing 

resources and guidance that are adequate to accomplish the stated objectives. Where additional 

effort is needed, either additional resources must be obtained or existing resources must be 

diverted from other activities. Workgroup members attempted to evaluate resource needs as a 

critical component of implementing new bacteria criteria across a broad spectrum of 

programmatic responsibilities from conducting necessary research to educating stakeholders and 

gaining acceptance of the public and regulated entities of program changes, to actual impact on 

the day-to-day implementation of water quality management programs. 

The results of the discussions are presented in three sections. First, an evaluation of the four 

principal program areas where recreational bacteria criteria are currently employed: (1) water 

quality beach notification and advisory programs; (2) National Pollutant Discharge Elimination 

System (NPDES) permitting, including regulation of wastewater treatment facilities, urban 

stormwater, and combined sewer overflow and sanitary sewer overflow (CSO/SSO) discharges; 

(3) monitoring and assessment programs required for compliance with Clean Water Act (CWA) 

§303(d) and §305(b) purposes; and (4) development of total maximum daily loads (TMDLs) for 

waters identified as not meeting State WQS. The second section provides an evaluation of the 

implementation concerns that must be addressed that relate specifically to three potential 

approaches for the development of new or revised recreational water quality criteria. The third 

and final section identifies the specific areas of research that workgroup members considered to 

be most critical to facilitating implementation efforts. 

7.1 Application to Specific Program Areas

7.1.1 Beach Monitoring and Water Quality Notification Programs 

The objective of this program is to provide accurate and timely information to the public 

regarding the health risks associated with participating in recreational activities at marine and 

freshwater beaches. Significant concerns have been expressed regarding both the accuracy and 

timeliness of the information currently provided. 
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The most pressing need for regulatory authorities who conduct beach monitoring programs is to 

get better information to the public as quickly as possible regarding the safety of the recreational 

water. There is currently a minimum 24 hour delay between the time when a water sample is 

collected, tested, and when the results of the test are available. Thus, decision makers only know 

what the quality of the bathing water was like yesterday. 

“Rapid Tests” 

Research in the past few years has resulted in the development of molecular-based tests that can 

provide results in just a few hours following the initiation of the test compared to 24 hours for 

the currently used culture-based tests. 

Rapid tests have several benefits. They shorten the time from when an unsafe water condition 

occurs (an “exceedance”) to when the test reveals the existence of an exceedance. This provides 

a capability to shorten the time it takes to post an advisory or to close the beach during unsafe 

conditions. The reduced test period thereby reduces the public health risk. The shorter test 

period also shortens the time it would take to remove the advisory and/or reopen the beach when 

water quality returns to a safe condition. Thus, the period of “loss of beneficial use” is also 

reduced. Because test results can be obtained in a shorter period, it is possible that they could be 

used to aid fecal pollution source identification efforts such as in identifying a problem in a 

specific location by enabling more samples to be analyzed in a shorter period of time. 

Although there is a desire to use the new, rapid tests in beach monitoring programs, several 

issues related to their use must first be resolved. First and foremost, it must be shown that these 

new “molecular” methods provide a level of human health protection equal to or above that 

provided by the currently used tests. States need to know that there is a beneficial reduction in 

illness to justify the costs of adopting and implementing a new test methodology. 

While rapid tests are sometimes referred to as “real-time” tests, they are not in fact real-time tests 

as there is still a delay of several hours between water sampling and test results. The public may 

still be exposed to potentially unsafe water for some period of time, albeit likely a shorter time 

period compared to current culture-based methods used to measure indicator organism levels. 

The rapid tests will not shorten the time required to collect water samples and deliver them to the 

test laboratory (typically 4 to 5 hours or longer), nor will they shorten the time required to 

convey test results to the appropriate authorities and the public (1 to 2 hours or more). 

Many States only have the resources to sample periodically (e.g., weekly, monthly) as opposed 

to daily. The new tests are not likely to provide authorities with resource savings sufficient to 

analyze water quality more frequently. However, the ability to obtain test results faster may 

raise the expectation of the public or regulatory mangers that, since the tests are faster, additional 

samples can or should be collected and tested—even when this may not be possible due to 

resource constraints. Taking full advantage of the benefits associated with more rapid tests will 

likely require additional resources for increased monitoring. 

Before any new test can be used broadly, the EPA will have to adopt and validate a standardized 

method for its use. State and local public health officials use the results of monitoring to make 
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health-based decisions to close or open a beach, or to issue or lift a beach advisory. These 

officials need to know that the analytical method they use provides reliable results; therefore, 

they only endorse methods that have already been validated by EPA. 

Further, to be able to bring a faster test into routine use, issues related to test equipment, training, 

laboratory capacity, and certification of laboratories will need to be resolved. The initial capital 

cost and any ongoing operation and maintenance costs need to be calculated and compared to 

that of the currently used tests. Regardless of how “good” the more rapid tests are, if they are 

too expensive, regulatory authorities may not be able to afford them. 

In addition, because the test endpoints of molecular-based tests are different than culture-based 

tests, a new regulatory scheme may need to be adopted to accommodate the new water quality 

criteria. See the discussion in Section 7.1.2 for further information on this topic. 

For the public and local authorities, a period of time may be required to gain “acceptance” of the 

new indicator. 

In general, any change in current monitoring practices (e.g., sampling type, frequency, location) 

necessitated by a change in recreational water quality criteria will need to be carefully considered 

relative to benefits offered because it will involve resource issues and many implementation 

concerns. 

Predictive Modeling 

Changes in microbial indicator counts in recreational waters are typically controlled to a large 

extent by a variety of meteorological and water quality factors. Data for many of these factors 

(e.g., wind, rainfall, etc.) can be obtained in real or near-real time. By monitoring and 

identifying which of these factors control indicator count changes, it is possible to create 

“predictive models” (see Chapter 6). Such models are essentially mathematical equations that 

have the “controlling” meteorological and/or water quality parameters as components. A 

“robust” model that is validated by comparison of predicted indicator concentrations to a 

sufficient number of actual concentrations is able to successfully predict, within a stated degree 

of precision, when unsafe water conditions will exist more accurately than the currently used 

culture-based assays are able to do. 

Predictive modeling offers great promise because it estimates when there may be a problem prior

to the bather exposure. The use of predictive models may also reduce the need for rapid testing. 

Furthermore, they can be employed daily, providing information beyond that available from 

periodic microbial monitoring. However, it is important to note that predictive models are not 

themselves criteria. Predictive models are tools that can be used to evaluate compliance with 

criteria. 

Models are only as good as the data used in their construction. If critical data are not available, a 

valid model cannot be developed until those data are obtained. As discussed in Chapter 6, the 

amount of data, especially microbial monitoring data, required to develop a predictive model 

within a stated confidence level may be significant. In general, model development may require 
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significant time and resources depending primarily on the availability of data on indicator 

densities and associated predictive variables (e.g., antecedent rainfall, wind direction, wave 

height, etc.). 

Currently developed predictive models appear to be site-specific. A predictive model developed 

for one beach or location is not likely to be usable at other beaches or locations because the 

effect of a predictive variable such as wind direction on indicator densities will be different at 

each beach. Therefore, for each “problem” beach or location, a separate model (i.e., set of 

predictive equations) is likely to be required. 

Competing financial resources may make modeling a low priority. For example, limited funds 

may have to be used for higher priority tasks such as improving impaired waters (e.g., fecal 

source identification). 

Any proposed use of modeling results for compliance purposes is likely to present 

implementation difficulties. Model results may not be always accepted as “proof” of a water 

quality standards violation because of the inherent uncertainty associated with model results. 

That is, regulators are likely to require actual monitoring data rather than modeling output for 

compliance purposes, particularly if non-compliance may lead to legal enforcement action. 

Regulators as well as members of the public often perceive monitoring as accurate and modeling 

as estimates. 

Statistical models are currently used in some States to assess compliance with their water quality 

standards for purposes other than beach monitoring. If there is a change in the criteria (as would 

occur if a new indicator is adopted) then corresponding model would have to be modified, which 

would require additional resources. 

It is important to note that modeling should not supplant routine water quality monitoring, which 

will always be needed to detect unanticipated events such as a sewer line break. Thus, regular 

monitoring provides an ongoing, direct measure of microbial water quality. Monitoring also 

provides data to help improve the precision of model predictions. 

General Considerations 

Workgroup members felt that any new or revised recreational water quality criteria need to allow 

for a binary (pass/fail) decision (e.g., close or not close a beach), must be a numeric, and must be 

based on a health risk determination for water quality notification/closure purposes. The criteria 

for reopening a closed beach or removing an advisory should be the same as that used for the 

initial closure or advisory. New or revised criteria must be expressed in a way that the 

authorities using the criteria are able to fully explain the criteria and their health risk basis, in a 

readily understandable way to the public. 

New or revised criteria should have some “flexibility”; for example, there may be State-specific 

circumstances and the criteria will need to be able to be used in all such circumstances. At the 

same time, the new or revised criteria need consistency so that the public has confidence that 

their health is being protected. 
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Any new or revised criteria should be tied to a specific method unless “equivalency” of the new 

method to a previously used (and validated) method can be demonstrated to facilitate 

implementation (see Chapter 3 for further information). 

The development of guidance to implement new or revised criteria should occur simultaneously 

with the development of the criteria. The implementing authorities will need assurance that the 

new criteria will be effective in ensuring that public health goals are met. 

Finally, the successful implementation of new or revised criteria will very likely result in the 

need for increased funding for microbial source tracking (see also Chapters 2 and 3) and for 

beach management programs. 

7.1.2 NPDES Permitting Programs 

The purpose of the NPDES permitting program is to insure that point source discharges of 

pollutants to waters of the United States achieve the statutory required level of treatment and do 

not cause waters to exceed State WQS after discharge. This is accomplished by imposition of the 

more stringent of either technology-based or water quality-based limits on discharge quality and 

mandating discharge monitoring at a frequency adequate to insure compliance with permit limits 

and conditions. 

Tiered Approach 

Water quality criteria might be expressed in a tiered approach; that is, that the criteria include 

multiple attributes, each of which apply for a specific purpose. With respect to NPDES permits, 

the tiered approach should be workable as long as one attribute of the criteria is specifically 

developed for NPDES requirements. This would necessitate choice of a pathogen indicator that 

achieves NPDES needs (see more below). 

In addition, NPDES effluent limits are developed with an implicit exceedence rate. NPDES 

permitting guidance for water quality-based effluent development is based on a wasteload 

allocation that is calculated based on an exposure condition that represents the upper 99th

percentile of conditions (e.g., conditions occurring under rare low flows such as the 7Q10 [the 

lowest streamflow for 7 consecutive days that occurs on average once every 10 years]) when 

point source discharges have the greatest impact on water quality conditions. As a result, it is 

important that water quality criteria include an allowable exceedance frequency to facilitate 

permit limit derivation. This is particularly important for deriving permit limits for pathogen 

indicators in wet weather conditions because the flow conditions at the time of discharge can be 

extreme and represent rarely occurring situations. 

Pathogen Indicators 

Changes in pathogen indicators from the current ones (E. coli and enterococci) will significantly 

affect implementation, especially if the change results in a different indicator being used for 

TMDL modeling than for permitting or uses an indicator that cannot reflect the efficacy of 

wastewater (sewage) treatment practices (disinfection). At a minimum, the indicator used for 
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NPDES permitting needs to be sensitive to disinfection so that the permitting authority can 

determine that the NPDES regulated facility is adequately disinfecting its discharge. If the 

indicator cannot do so, then there will be a need for different indicators for ensuring the 

discharge achieves water quality standards and the wastewater is properly disinfected. Another 

way to accomplish this is to develop an approach that translates between the various indicators. 

Analytical Methods 

There is concern that molecular-based methods may not adequately verify that wastewater 

disinfection has been effective. This concern is based on research that shows the qPCR 

(quantitative polymerase chain reaction) signal does not decrease post-chlorination. Many State 

public health codes require disinfection of human waste and the analytical method used for 

NPDES permitting needs to be able to measure disinfection. As a result, a molecular-based 

method may not be suitable to fulfill all NPDES needs. 

 

It is also important for implementation that the analytical methods be tested in a wastewater 

matrix and approved for use in wastewater. NPDES regulations require that effluent monitoring 

be conducted using either an EPA-approved analytical method or an analytical method specified 

in the permit. In the latter situation, the permit documentation needs to defend the use of the 

method. However, many States do not have the technical experience to defend analytical 

methods or have legal restrictions on the use of alternative methods and thus must rely solely on 

use of EPA-approved methods. 

Resources 

Many NPDES regulated dischargers conduct analysis of their wastewater on-site. The existing 

laboratory expertise of these dischargers may not be sufficient to conduct analyses for new 

pathogen indicators (e.g., molecular-based methods). The start up cost of purchasing equipment 

for conducting the new analyses and additional training for staff poses a resource drain for both 

the dischargers and the regulatory authority that must provide oversight. Should the dischargers 

choose to contract out their laboratory analysis, they will need to pay to ship the samples to the 

contract laboratories, which is also a resource drain. 

Finally, many states require that laboratories be certified for analysis with certification being 

specific to the parameter being analyzed. Therefore, States will need to amend their laboratory 

certification program to include the new pathogen indicators. This is also a resource drain on 

States. 

7.1.3 Monitoring and Assessment for CWA §303(d) and §305(b) 

The purpose of this program is to provide an accounting of the condition of the Nation’s waters, 

identify those that do not meet current State WQS for focused mitigating action, and to track 

progress in improving the overall quality of the Nation’s water resources. 

Assessment and listing based on the current ambient water quality criteria (AWQC) have 

disproportionately focused State resources on what are often perceived as minimal to non-
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existent public health issues. States have expressed frustration at being effectively handcuffed 

by strict application of the criteria and the inability to adjust assessment findings based on other 

data indicating the health risk is significantly lower than implied by the criteria exceedance. 

Such factors include evidence that elevated indicator levels are not due to human sources of fecal 

contamination and hydrologic factors that preclude recreational exposure, such as during or 

immediately after high rainfall events. Areas where improvements can be made in the new or 

revised criteria and implementation guidance associated with the criteria includes monitoring, 

criteria, guidance, and (inland) flowing waters. 

Monitoring 

Workgroup members felt that new or revised recreational AWQC must include a clear discussion 

regarding linkages between an advisory/closure decision at a beach and assessment of use 

attainment. Beach advisories/closure decisions may, but need not necessarily, be linked to such 

assessments. There may be instances where beach advisories or notifications are made based on 

models, or special circumstances (such as sewer line breaks) that should not be counted as nonattainment for assessment purposes. In a similar vein, if the beach advisory regulations are more 

stringent than State WQS, the advisory in and of itself should not constitute non-attainment 

unless the State chooses to list that beach as impaired on that basis. 

Ambient Water Quality Criteria 

Alternative AWQC or methodologies that more precisely define health risk would be highly 

useful in improving assessments—in particular indicators of human versus nonhuman pathogens. 

The criteria and implementation guidance need to recognize the potentially lower risk of 

pathogens from nonhuman sources and provide a way for addressing and discounting pathogen 

and indicator data not associated with anthropogenic sources of fecal contamination. 

The criteria must also be sufficiently flexible for assigning attainment of use based on limited 

data sets, particularly for inland waters. Often, States only collect data on a monthly, bimonthly, or annual basis and compare these data to previously collected data to assess trends. 

The problem will be exacerbated for assessment purposes if new or revised criteria are adopted. 

It could take years to develop a statistically significant data set. 

If the format of the new or revised criteria requires a specific number of samples to be collected 

in a set timeframe, States will be challenged as they are with the current criteria (e.g., 5 samples 

over a 30-day period). Criteria that allow assessment samples collected at any frequency to be 

statistically manipulated to the appropriate exposure frequency would allow States to maintain 

their current monitoring approaches while appropriately applying the criteria. 

Also, for ease of State implementation, new or revised criteria need to allow for some reasonable 

excursion frequency. Criteria expressed as a percentile value (e.g., cannot exceed criteria more 

than x% of time) would provide an incentive to conduct additional sampling so as to not have the 

assessment rely on one or two samples and would facilitate implementation for assessment 

purposes. 
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If the European Union (EU; EP/CEU, 2006) or World Health Organization (WHO, 2003) 

approach for criteria development is followed, there needs to be a clear distinction between the 

criteria that is needed to protect human health and what is considered to be supplemental 

guidance. For instance, is it possible to have a “good” beach or a “very good” beach and still be 

considered non-impaired? Apparently, “good” meets the criteria while “very good” is a desired 

higher level of microbial water quality. Such discussion should be in supplemental guidance 

rather than in the criteria. 

If a rapid method is selected as the indicator, the speed of a rapid method offers no additional 

benefit relative to assessment, unless the rapid method provides more precision/better protection 

to benefit public health. Therefore, a rapid method may offer the benefit of more rapid water 

quality notification, but has little positive effect on the overall assessment process that is 

conducted on data collected over a 2 year period. 

Workgroup members expressed concerns with establishing a new or revised recreational water 

quality criteria linked to a sanitary investigation. If a WHO-type criteria model is chosen that 

includes use of a sanitary investigation to modify the criteria and allow for nonhuman sources of 

fecal contamination, the frequency of performing that investigation would need to be identified 

in assessment guidance. There was a strong preference among workgroup members that the 

frequency be longer than the two year assessment cycle for State’s issuance of assessment 

information pursuant to §303(d) and §305(b) of the federal CWA. The available information for 

the sanitary investigation did not specify the frequency for repeating such investigations. 

Lastly, for assessment purposes, there needs to be some way to translate between previously used 

indicators and any new indicator(s) so information from past monitoring is not lost. If a 

“translator” is not available, it might take several years to build up enough information to 

conduct a statistically valid assessment for pathogen indicators. 

Guidance 

If new criteria indicator/methodology combinations are adopted, issuance of guidance for 

implementation will be imperative. With the likelihood of rapid molecular-based test methods, 

sanitary investigations, and so on, guidance will need to accompany the criteria to help States 

understand how to apply the new or revised criteria and thus achieve State acceptance. 

Flowing Waters 

Flowing freshwaters (e.g., streams, rivers) present some unique challenges that have not been 

addressed with previous epidemiological studies of recreational waters. Therefore, if new or 

revised criteria include application to flowing freshwaters, consideration needs to be given to an 

allowance for different values/applications of the criteria to reflect the differences in hydrologic 

regime (e.g., extreme high flows) through one of the following: 

• higher criteria that applies in extreme events; or 
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• changes to the use/criteria when the use is not taking place (e.g., when recreation is 

unlikely to occur such as during winter months or during or immediately after heavy 

rainfall). 

Lastly, an indicator applicable to flowing freshwaters needs to be identified. As stated elsewhere 

in these proceedings, E. coli appears to be a more appropriate freshwater indicator of fecal 

contamination than enterococci. E. coli are a subset of fecal coliform bacteria while enterococci 

bacteria are a separate group of enteric bacteria. More recent water quality data generated using 

E. coli can be more easily compared to earlier water quality data generated using fecal coliform 

bacteria than can more recent water quality data generated using enterococci bacteria. 

7.1.4 Total Maximum Daily Load Program 

The purpose of this program is to establish the maximum pollutant load that a specific 

waterbody can assimilate and apportion that load among sources of that pollutant to the 

waterbody, leading to the development of a management plan that when fully implemented will 

result in reducing those loads to the extent that State WQS are achieved and maintained. 

TMDLs for bacteria designed to achieve consistency with the current (US EPA, 1986) criteria 

are typically difficult to develop and explain to stakeholders because expressing pollutant 

loadings of bacteria or pathogens in terms of mass is nonsensical. Pathogens or pathogen 

indicators are not measured as mass but rather as cell counts (e.g., colony forming units [cfu]). 

Developing wasteload allocations for point sources and load allocations for non-point sources in 

mass units does not make sense to the vast majority of TMDL practioners and those responsible 

for implementing bacteria TMDLs. For this reason, alternative means of expressing loading 

reductions (e.g., “percent reduction,” “load duration curve-based,” “reference watershed” 

methods) have been used by many States. TMDL development for waters impaired by excessive 

indicator bacteria densities is further complicated in that the necessary load reductions are 

typically strongly linked to hydrologic factors and intermittent sources such as stormwater 

runoff. Establishing a static steady-state design condition, as is frequently done for other types 

of pollutant impairments, is not possible for bacteria due to the significant wet weather eventdriven characteristics of many bacteria-impaired waters. 

Workgroup members viewed criteria expressed in numerical terms as a practical necessity to 

implementing any revised recreational use criteria in TMDL programs due to the need to 

quantify loadings. Implementation realities dictate that the criteria be expressed in terms that 

facilitate calculation of an acceptable daily loading under a range of hydrological conditions. 

The criteria has to be a number (as opposed to a category/classification) to make implementation 

in TMDL programs feasible. The workgroup experts expressed a diversity of opinions over the 

benefits of a geometric mean or other statistic versus single sample maximum criteria with 

specified exceedance frequency for water quality assessment and TMDL purposes. Some prefer 

use of single sample maximum (SSM) while others prefer geometric mean largely reflecting 

current practice in their particular State. If the new or revised criteria are expressed as a single 

value, the benefits of allowing for that value to be exceeded at some stated frequency for TMDL 

and assessment purposes cannot be overstated. EPA should expect intense resistance from 

Sstates if future criteria guidance proposes criteria expressed as a “never to be exceeded” value. 
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An acceptable exceedance frequency is critical to facilitate design of treatment requirements and 

best management practices (BMPs) to implement the TMDL as well as accounting for rare 

extreme event-driven conditions not practical to mitigate. Providing States (and other 

stakeholders) with evidence that the criteria incorporate flexibility to accommodate the 

variability inherent in bacterial densities in natural systems would greatly facilitate acceptance 

and subsequent implementation efforts. 

Criteria that distinguish between human and nonhuman sources of fecal contamination would 

also make TMDL development significantly easier. The ability to make allocation decisions 

would be enhanced and public acceptance of the TMDL implementation requirements would be 

achieved much more readily if additional confidence could be provided in estimates of source 

category loading. Further, the ability to adjust TMDLs based on more accurate source separation 

and to make allowances that “discount” the contribution of certain lower risk sources (e.g., nonanthropogenic) or sources from which the contributed risk may be lower (e.g., wildlife) would 

encourage States to move forward to adopt the criteria into their WQS. If the criteria or 

implementation protocol includes a sanitary investigation there should be guidance provided to 

encourage consistency in sanitary investigation methodologies among States. This guidance 

might be a combination of minimum expectations and general framework for what constitutes an 

acceptable sanitary investigation. A mandate to provide confirmation of investigation results 

through alternative means (e.g., microbial source tracking, use of more human-specific 

indicators) may also be acceptable provided the cost and technical difficulty are not prohibitive 

or use of this additional step is only required in selected instances where the results of the 

investigation are not conclusive. 

7.1.5 Important Differences Between Workgroup Members as to Views/Observations 

Workgroup members had a diversity of opinions over the benefits of a geometric mean-based as 

opposed to AWQC based on SSM for certain water quality assessment and TMDL purposes. 

Some preferred the use of a SSM-based standard, while others preferred the use of a geometric 

mean-based standard. One of the times of potential concern is when an individual sample result 

may be over the SSM but the data set does not exceed the geometric mean. The concern is that 

some event may have occurred during that time and the public could potentially be at risk; 

however, it is also possible that the result is a one-time occurrence and the public is not at a 

greater risk than at other locations that meet the geometric mean-based criteria. 

7.2 Evaluation of Alternative Approaches for Criteria Development 

This section describes the implementation considerations for each of the three alternative 

approaches for the development of new or revised recreational water quality criteria that were 

proposed and discussed at the workshop (see Chapter 1). Some of the concerns regarding 

implementation that are common to all three approaches include the following: 

• level of discriminatory power/sensitivity of a method; 

• if rapid method is used, difficulty in implementation in some places (e.g., holding time); 

and 
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• if site-specific epidemiological studies are needed, most States will be unlikely to fund 

these studies. 

Many of the above concerns, as well as the concerns described in the following sections, would 

be eliminated if the following statements were true: 

• epidemiological studies demonstrate that indicator organisms are sufficiently correlated 

to human health risk; 

• studies provide a scientific basis for discounting risk to human health from wildlife 

sources of fecal contamination; 

• criteria included flexibility to account for the reduced exposure (and thus, lower risk) of 

use at extreme conditions (e.g., high flow); 

• relationships between advisories and impairments were more clearly defined in EPA 

guidance; 

• level of disinfection necessary to provide adequate pathogen reduction/inactivation in 

human sewage was determined; and 

• criteria applied for NPDES purposes included flexibility to account for wet weather 

conditions. 

7.2.1 WHO Approach 

The WHO approach provides a range of risk levels and accounts for differences in relative risk 

resulting from site-specific considerations of sources of indicator organisms based on the results 

of a sanitary inspection performed prior to the assessment of monitoring results. The following 

implementation concerns are not specific to any specific application of the WHO model, but 

rather reflect the general use of this approach. 

 

The WHO (2003) approach to criteria development relies on identification of the potential for 

human sources of fecal contamination to impact a beach or other recreational water area. Many 

pathogens are host-adapted and so human fecal sources may contain many pathogens not found 

in feces from non-human animals (e.g., Salmonella typhi, Vibrio cholerae, Cryptosporidium 

hominis, Entamoeba, many viruses). Thus, it is essential to have available a reliable 

methodology to distinguish between human and natural sources (e.g., wildlife only) of pathogens 

for use of the WHO model. As part of this, the methodology should also be able to either 

quantify that the risk from natural sources is low or provide some way to characterize the risk 

from natural sources as being acceptable. It is important to characterize or quantify the risk from 

natural sources rather than to completely discount it because this risk needs to be included in 

beach advisory decisions. For example, if pathogens from sea lions pose a risk to humans, then 

it is important to post an advisory on a beach where sea lions reside. However, it would not be 

necessary to consider this risk in determining impairment because sea lions are a “natural” 

source and most environmental agencies would not view development of a plan to eliminate sea 

lions as consistent with their overall mission. 

It is also important to be able to quantify the risk from domestic animals and livestock and 

include this risk if a WHO-based approach is pursued. Although these sources of fecal 
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contamination are nonhuman in nature, these animals live in close proximity to humans and may 

carry human (zoonotic) pathogens in their feces(e.g., E. coli O157:H7, Cryptosporidium parvum;

see also Strauch and Ballarini, 1994). Use of the WHO model will require including the 

likelihood of these sources impacting beaches and other recreational water areas. As a result, it 

becomes important to quantify risks of exposure to fecal material of these animals. 

 

The WHO approach appears to be amenable for use with multiple pathogen indicators (e.g., the 

toolbox). If multiple pathogen indicators are used in application of the WHO model, then all the 

considerations related to use of both molecular and culture methods that were discussed for each 

CWA application above apply. In addition, if multiple WHO model tables are used, it may be 

advantageous to develop separate tables for lakes and flowing waters because exposure in these 

two situations are different. 

There are several implementation issues that arise if the WHO model is applied using a qPCR 

analytical method. The first issue is the capacity of States and NPDES dischargers to adopt and 

use a qPCR method, as initially, there may be insufficient laboratory capacity to conduct the 

method. Specific concerns with respect to NPDES facilities are discussed in the preceding 

Section (7.12) on the NPDES permitting program. Additionally, it is reasonable to expect that 

the initial costs per sample will be substantially higher than for the currently used culture-based 

methods, which poses an additional cost to States and NPDES facilities. 

The second implementation issue with respect to qPCR is its apparent inability to confirm that 

disinfection is being properly applied. As discussed previously, NPDES permits need to both 

assure that WQS are achieved and that State disinfection requirements are being met. If qPCR 

method is used to apply the WHO approach, then another indicator using culture-based methods 

will be needed in NPDES permits to demonstrate adequate disinfection. 

Another implementation issue is the use of sanitary investigations based on the WHO approach. 

However, the protocols for a sanitary investigation should not be overly prescriptive to the point 

of making the investigation resource-prohibitive. There is a need to define the minimum 

elements of a sanitary investigation to ensure that it is reliable. Application of the criteria needs 

to invoke trust by the public. If there is too much variety in sanitary investigations, then the 

public will perceive that the investigations have no technical rigor and which will undermine use 

of the WHO model. In addition, States will need to develop the capacity to conduct sanitary 

investigations on every waterbody with recreational uses, which constitutes a resource burden. 

Finally, States need sufficient time to conduct sanitary investigations by the time the new or 

revised criteria are adopted into their WQS. 

The WHO approach includes columns that characterize different risk (see Table 1, Chapter 1). 

Two of the columns include water characterizations of “very good” but are associated with 

different risk. The model should be applied with only one “acceptable risk” level. If there is 

more than one acceptable category of good, it implies there is more than one “acceptable risk” 

level. This makes it difficult to explain to the public, difficult to enforce, and difficult to make 

decisions on the lower risk level. Any further distinction between “good” and “very good” 

outcomes should be voluntary. 
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It is possible that States will issue advisories in situations that are not considered as CWA 

impairments. This can occur when a state public health agency wants to impose a higher degree 

of protection than the state environmental agency, or at beaches where there are wildlife sources 

that pose risk. It is uncertain how such a situation would work with the WHO model, and this 

would need to be developed. 

The WHO model uses ranges of pathogen densities. This allows States to select which specific 

value to use, and thus result in inconsistencies on thresholds to close or open beaches between 

various states. It is much more preferable for the criteria to specify one threshold rather than a 

range. However, it was discussed that while the range may be difficult to implement in a 

regulatory fashion, it may more realistically describe the precision of epidemiological-based 

criteria applied to a wide range of waters coupled with the precision of indicator measurement. 

Finally, it appears that empirical models of pathogen densities can be used with the WHO model, 

as long as one threshold is used rather than a range. 

7.2.2 EU Approach 

The EU approach provides defined criteria at a single risk level but allows for adjustment of the 

assessment result based on a sanitary investigation performed following review of monitoring 

results. 

Like the WHO (2003) approach, the EU (EP/CEU, 2006) model uses sanitary inspections; 

however, unlike the WHO approach, the EU model uses the inspections to rationalize that 

monitoring results above the criteria levels do not indicate an elevated risk to human health. 

Thus, the rigor of any type of sanitary investigation that may be required for an approach based 

on the EU approach seems to be greater than for WHO-based approaches (i.e., requires a more 

detailed site assessment). A workgroup participant indicated that for some waters a desktop 

GIS-based methodology could constitute a sufficient sanitary survey for many bathing waters 

(Paul Hunter, University of East Anglia, U.K., personal communication, 2007). 

As was the case for the WHO model, there are implementation concerns regarding the time and 

capacity for conducting sanitary investigations, and the ability to distinguish between risks from 

human and nonhuman sources of fecal contamination. Specifically, States will need to know 

how good are the techniques to distinguish between risks from human and nonhuman sources, 

and what is the degree of risk from nonhuman sources. Thus, the discussion of the WHO 

approach on these topics likewise applies to the EU approach. 

As one way to implement the EU model, EPA could use a “pristine” watershed as a baseline. In 

this situation, EPA would look at pathogen indicator counts at baseline flows and use these 

values to determine how to adjust concentrations. 

The EU model process presents opportunities to be more transparent to the public than the WHO 

approach. States could seek public involvement in determining how to conduct the sanitary 

investigation/discounting process. 
U.S. Environmental Protection Agency Experts Scientific Workshop

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One impediment to implementation of the EU approach is how domestic and agricultural animals 

are addressed. It appears that these sources can be excluded; however, these fecal contamination 

sources may have a potential risk to human health. 

The EU model characterizes beaches using the 95th percentile of a set of microbial water quality 

data. This seems to prevent making short-term decisions for beach closure or reopening unless 

beach managers use some sort of predictive modeling. This is an implementation concern given 

the aforementioned (see Chapter 6) data needs of models. Not all recreational water sites can 

currently develop a model due to limited data. If there is no model, then decisions would likely 

be based on a data set over a period of time, rather than a specific data point, which would 

require interpretation for beach monitoring for closing or opening decisions. 

Like the WHO approach, the EU approach includes columns that characterize different risk (see 

Table 2, Chapter 1). The model should be applied with only one “acceptable risk” level. If there 

is more than one acceptable category of good, it implies there is more than one “acceptable risk” 

level. This makes it difficult to explain to the public, difficult to enforce, and difficult to make 

decisions on the lower risk level. Any further distinction between “good” and “very good” 

outcomes will make implementation difficult in some jurisdictions. 

7.2.3 Existing U.S. Model – 1986 Criteria 

The existing model provides defined criteria at a single risk level but does not provide for 

adjustment based on other sources of information such as sanitary investigations or source 

identification. 

The original basis for the (EPA) 1986 criteria were freshwater and marine water epidemiological 

studies conducted at a limited number of sites with restricted geographic extent and waterbody 

type (lake beaches and marine beaches). Therefore, a concern exits that single value criteria may 

not be applicable to all waters across the United States—for instance, inland flowing waters, 

tropical waters, or freshwaters under tidal influence. In the development of new or revised 

criteria, epidemiological data or quantitative microbiological risk assessment (QMRA) for as 

wide a variety of fresh and marine waters as is possible should be used. 

If single value criteria are to be developed, as was the case for the 1986 criteria, it is vital to use 

as many indicators as necessary to best characterize the microbiological quality of the water. 

There is a variety of opinion as to the most appropriate indicators for fresh and marine waters. 

However, there is evidence that E. coli is the most suitable indicator for flowing freshwaters 

while enterococci, either by culture- or molecular-based methods, is most suitable for marine 

waters; however, the workgroup did not reach a common opinion on the evidence. 

A major criticism of the 1986 criteria was the lack of approvable test methods for wastewater 

effluent. If new indicator organisms or test methods are identified for the new criteria, approved 

test methods must be developed for all potential needs such as NPDES permitting and ambient 

water quality monitoring. 

 
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The 1986 criteria provide minimal implementation guidance. Due to most States’ interpretation 

of the criteria in their WQS, the criteria tend to be treated as requiring compliance at all times 

and in all waters. This interpretation has caused considerable problems in the assessment and 

TMDL arenas. Any new or revised criteria must include implementation guidance that allow for 

methods to address issues such as extreme flows and nonhuman sources of fecal contamination. 

EPA needs to provide more scientific data and information to States for implementation of 

pathogen indicator criteria. States have concerns regarding the effectiveness of existing sewage 

treatment capabilities on new indicator organisms. In switching from enterococci or E. coli as an 

indicator, there is concern that disinfection designs may not meet permit limits based on the new 

indicator criteria. This issue needs to be addressed by EPA so that the State programs will have 

consistent, valid, and scientifically defensible responses when these concerns are raised during 

the implementation of new WQS. 

7.2.4 Alternative Approaches 

Two additional potential approaches to consider in the development of new or revised 

recreational water quality criteria include the following: 

1. An alternative hybrid approach could blend the single value criteria with facets of the WHO 

(2003) and EU (EP/CEU, 2006) models to allow for demonstration of mitigating (or 

discounting) factors to be completed by a fixed date after criteria adoption. This has the 

advantage in preventing waters from being CWA §303(d)-listed based solely on excursions 

above a single value criteria. If the water was ultimately listed, it could be de-listed at a later 

date if it were demonstrated that mitigating factors prevented designated use attainment. 

2. The largest implementation concern with the single value (EPA) 1986 criteria is regarding 

assessment. An alternative approach to developing new criteria could incorporate the 

existing 1986 criteria with the following implementation provisions: 

• a provision to discount non-compliance with the single value criteria after investigation 

of the contributing watershed to confirm the absence of nonhuman sources and lower risk 

than implied by the criteria exceedance; 

• criteria/use inapplicability during extreme high flow events; and 

• a process to exclude natural sources of fecal indicator organisms (i.e., indicators specific 

to human sources are not present), according to the corresponding risk to human health. 

7.3 Research Needs 

Research is clearly needed to provide support for implementing any alternative approach to 

criteria development, expression, or application. A key concern is the role research results play 

in the ability of State and federal regulators to explain and gain public acceptance of changes in 

existing CWA programs. Opportunities to leverage the value of individual research programs by 

employing data collection designs that may be useful to answer multiple questions should be 

exploited. 
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7.3.1 Near-term (Next 1 to 3 Years) 

Beach Monitoring 

1. Provide a quantitative protocol to identify the types of nonhuman sources of fecal 

contamination. For example, other than molecular-based fecal source identification 

techniques, are there methods (e.g., sanitary investigations) to track nonhuman sources 

such as waterfowl, dogs, horses, and other anthropogenic sources? The WHO and EU 

approaches to criteria development provide for “discounting” exceedances if it can be 

determined they are of nonhuman origin through a sanitary inspection. If risks from 

nonhuman sources can be adequately quantified, sanitary inspections could be used to 

support decision making. 

2. Determine the risk from different types of nonhuman sources of fecal contamination 

(e.g., domestic and indigenous wildlife). Although the new or revised criteria would 

need to address all potential risks, a delineation of the categories of risk made available to 

the public would improve water quality notification and informed consent aspects of 

implementation. Specifically, the perceived risk associated by the public with elevated 

concentrations of indicators derived from indigenous sources (e.g., deer, birds) may be 

more acceptable than sources of domestic origin (e.g., cattle, poultry). The public may 

wish to make an informed decision about usage relative to specific pathogens such as 

enterohemorrhagic E. coli (EHEC) that are potentially associated with agricultural land 

usage. 

3. Determine under what conditions a sanitary investigation would be sufficient (as opposed 

to microbial source tracking). This research is most important if the WHO and EU 

approaches are being considered. 

4. Identify minimum elements that a sanitary investigation should include. Again, the focus 

should be on the minimum elements necessary for a reliable sanitary investigation. If the 

requirements for a sanitary investigation are too onerous, they will become resourceprohibitive and of minimal value. Assess the reliability, accuracy, and validity (etc.) of 

the various types of sanitary investigations. Without some sort of standardized 

investigation criteria, inconsistencies will result in the implementation of the criteria and 

create potential variances in health risk levels at beaches. 

5. Predictive modeling offers the prospect of benefits to beach management that are 

sufficiently significant such that it should be explored further. An identification of data 

needs is required for such models. For water quality notification purposes, models 

should be developed and calibrated to assure a minimum confidence level. 

NPDES 

 

1. Conduct studies to develop a methodology to compare the correlation of the culturebased methods and the qPCR (molecular-based) method. Identify how or where the same 

level of protection can be provided, even if implementation is different. Any requirement 

to use non culture-based methods may have significant impacts on NPDES permit 

monitoring programs. Non culture-based methods may not adequately assess treatment 

processes or determine permit compliance. 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 147 

2. Develop an improved understanding of disinfection using the different indicators. 

Determine how well each indicator is in measuring disinfection effectiveness, including 

determination of the viability of the organisms (pathogens and indicators) following 

various disinfection processes (e.g., chlorination, UV light). 

3. Determine risks of exposure from intermittent microbial pollution discharges, CSOs, 

urban runoff, and concentrated animal feeding operations (CAFOs). 

4. Evaluate the effectiveness and cost of stormwater and agricultural BMPs as related to 

pathogens and microbial contaminants. This evaluation should be made in concert with 

epidemiological studies/QMRA analyses that will determine the risk from different types 

of sources (urban and agricultural runoff, indigenous and domestic animals, regrowth). 

5. Evaluate the efficacy, costs, and benefits of disinfection for the purposes of supporting 

eventual promulgation of a disinfection rule. It is anticipated that disinfection could 

eventually be promulgated as a mandatory treatment technology nationwide as it already 

is in many States. Specifically, research is needed to support levels of disinfection 

necessary to provide adequate pathogen reduction/inactivation. 

Use Attainment 

1. Research to determine the risk from different types of nonhuman sources of fecal 

contamination (e.g., domestic and indigenous) is needed to better quantify the risk from 

nonhuman sources so that when implemented at recreational waters, those risks are better 

accounted for. 

2. Develop criteria or methodologies that more precisely define the health risk associated 

with pathogen exposure in recreational waters. 

Overall 

1. Conduct research so that monitoring using indicators can help to distinguish human from 

nonhuman sources of fecal contamination. 

2. Conduct epidemiological/QMRA studies on flowing recreational waters. Current (1986) 

criteria were based on epidemiological studies conducted in relatively static waterbodies. 

Additional studies are needed to assess risks in flowing waters. This has significant 

implications for criteria development for inland U.S. waterways. 

3. Need to better understand the health-basis for allowable exceedance frequency. 

Additional explanation is needed to justify percentile criteria differences between WHO, 

EU, and EPA (1986) criteria development approaches (e.g., use of 95th or 90th percentile). 

4. Conduct research to better understand how to measure the impact of regrowth and 

persistence in sediments of indicator bacteria on water quality. The source of some 

problems of high pathogen indicator levels may at times be due to regrowth rather than 

urban runoff, animals, birds, biofilms, ocean circulation, etc. 

7.3.2 Long-term (Beyond 3 Years) 

NPDES 

• Develop a viability assay for the viral and protozoan portion of effluent. 
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June 2007 148 

Overall 

• Develop methodologies that are pathogen-specific. 

References 

EP/CEU (European Parliament/Council of the European Union). 2006. Directive 2006/7/EC of 

the European Parliament and of the Council of 15 February 2006 Concerning the Management of 

Bathing Water Quality and Repealing Directive 76/160/EEC. Official Journal of the European 

Union L64: 31-51. Available at: 

http://europa.eu.int/eurlex/lex/LexUriServ/site/en/oj/2006/l_064/l_06420060304en00370051.pdf. 

Strauch, D; Ballarini, G. 1994. Hygienic aspects of the production and agricultural use of animal 

wastes. Journal of Veterinary medicine Series B 41: 176-228. 

US EPA (U.S. Environmental Protection Agency). 1986. Ambient Water Quality Criteria for 

Bacteria – 1986. EPA440/5-84-002. Washington, DC: US EPA. 

WHO (World Health Organization). 2003. Guidelines for Safe Recreational Water 

Environments. Volume 1 Coastal and Fresh Waters. Geneva, Switzerland: WHO. 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 A-1 

APPENDIX A: CHARGE TO THE EXPERT WORKGROUP MEMBERS 

PURPOSE 

The purpose of the Pellston-type1

 Experts Scientific Workshop on Critical Research and Science 

Needs for the Development of Recreational Water Quality Criteria is for EPA to obtain 

individual input from members of the broad scientific and technical community on the “critical 

path” research and science needs for developing scientifically defensible new or revised Clean 

Water Act (CWA) §304(a) recreational water quality criteria in the near-term.2

 

BACKGROUND

An important goal of the CWA is to protect and restore waters for swimming. Section 304(a) of 

the Act directs EPA to publish “advisory water quality guidance on the effects of the presence of 

pollutants in water on health and welfare.” These recommendations are referred to as §304(a) 

criteria. Under §304(a)(9) of the CWA, EPA is required to publish water quality criteria for 

pathogens and pathogen indicators to protect swimmers from illnesses associated with 

pathogenic microbes in coastal and Great Lakes waterbodies. 

In adopting new or revised water quality standards, States must adopt criteria that are 

scientifically defensible and protective of the use, but they have flexibility to do so by adopting 

EPA’s recommended criteria, adopting criteria to reflect site-specific conditions, or adopting 

other criteria that are scientifically defensible. In the case of criteria EPA publishes under 

§304(a)(9), States with coastal and Great Lakes waters are required to adopt EPA’s new or 

revised criteria for pathogens and pathogen indicators into State Water Quality Standards 

(WQS). 

Once adopted into State WQS, water quality criteria express the desired ambient condition of the 

water to protect a designated use. State WQS are used for various CWA purposes or programs 

that identify and address the sources of pollution with the goal of attainment of the criteria, 

including National Pollutant Discharge Elimination System (NPDES) permits, water body 

assessments to determine use attainment, and development of Total Maximum Daily Loads 

(TMDLs). In addition, these WQS used by States in beach monitoring and water quality 

notification programs. 

 1

 A workshop similar in organization and format to the Society of Environmental Toxicology and Chemistry 

(SETAC) Pellston Workshops where technical experts in a particular subject area are invited to participate and 

evaluate current and prospective environmental issues. A Pellston-type workshop brings together between 40 to 50 

technical experts from academia, business, government, and public interest groups. Experts are sequestered for a 

week and expected to contribute to a summary report. Subject leaders are then responsible for consolidating, 

editing, producing, and distributing the workshop proceedings. 2

 Near-term requirements: in order for EPA to develop criteria in the near-term, the indicators/methods/tools 

upon which they are based must be currently available, have undergone scientific peer review and validation, and 

ready for day-to-day implementation in State public health/environmental laboratories within the next 2 to 3 years. 

New or revised criteria must be based on indicator/methods that are easy to use and interpret. 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 A-2 

Historically, EPA’s recommended criteria for protecting people who recreate in water have been 

based on fecal matter in recreational waters. In the 1960s, the federal government recommended 

using the indicator bacteria, fecal coliforms, as the primary contact recreational3 criterion. In the 

late 1970s and early 1980s, EPA conducted public health studies evaluating several organisms as 

possible indicators, including fecal coliforms, E. coli, and enterococci. The studies showed that 

enterococci are a good predictor of gastrointestinal (GI) illnesses in fresh and marine recreational 

waters, and E. coli is a good predictor of GI illnesses in fresh waters. As a result, EPA published 

in 1986 revised criteria (EPA’s Ambient Water Quality Criteria for Bacteria – 19864) for primary 

contact recreation recommending the use of E. coli for fresh recreational waters (criteria set as a 

geometric mean of 126 colony forming units [cfu]/100 mL) and enterococci for fresh and marine 

recreation waters (criteria set as geometric means of 33/100 mL in freshwater and 35 cfu/100 mL 

in marine water). These recommendations replaced EPA’s previously recommended bacteria 

criteria for fecal coliforms of 200 cfu/100 mL. EPA’s criteria recommendations use “indicator” 

bacteria. Most strains of E. coli and all enterococci do not cause human illness (that is, they are 

not human pathogens); rather, they merely indicate fecal contamination, and the assumption is 

that pathogens co-occur with incidences of fecal contamination. 

Since EPA issued its recreational criteria over 20 years ago, there have been significant scientific 

advances, particularly in the areas of molecular biology, microbiology, and analytical chemistry. 

EPA believes that these new scientific and technical advances need to be factored into the 

development of new or revised CWA §304(a) criteria for recreation. To this end, EPA has been 

conducting research and assessing relevant scientific and technical information to provide the 

scientific foundation for the development of new or revised criteria. The enactment of the 

Beaches Environmental Assessment and Coastal Health (BEACH) Act of 2000 (which amended 

the CWA) required EPA to conduct new studies and issue new or revised criteria, specifically for 

Great Lakes and coastal marine waters. 

OVERALL CHARGE TO THE EXPERTS

Experts are asked to provide their individual knowledge and insight that will help EPA define the 

critical path research and science needs, recognizing the “state of the science” and the reality that 

research that cannot be completed within 2 to 3 years will not be helpful in EPA’s near-term 

criteria development efforts. Experts should focus their efforts at this Workshop on identifying 

near-term research and science needs that will allow EPA to publish new or revised criteria in 

roughly 5 years. (While EPA understands that experts may wish to offer perspectives on 

research and science needs for the development of future or “next generation” criteria, this is not 

the primary purpose of this Workshop.) “Next generation” criteria refer to criteria EPA may 

publish in the longer term; that is, in approximately 10 to 15 years, pursuant to CWA 

§304(a)(9)(B). Section 304(a)(9)(B) directs EPA to review and, as necessary, revise the 

§304(a)(9) criteria 5 years after EPA publishes the initial criteria, and every 5 years thereafter.) 

 3

 Primary contact recreation includes activities that could be expected to result in ingestion of water or 

immersion. These activities include swimming, water skiing, surfing, and other activities where contact and 

immersion in water is likely. 

4

 US EPA. 1986. Ambient Water Quality Criteria for Bacteria - 1986. EPA440/5-84-002. Washington, DC: US 

EPA. 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 A-3 

Although not the focus of this Workshop, EPA is aware of stakeholder concerns regarding 

implementation issues associated with the existing (EPA) 1986 criteria and the desire on the part 

of some stakeholders for EPA to address these issues in the interim (i.e., before EPA publishes a 

new or revised recommended criteria). In recognition of these concerns, experts in the 

“Implementation Realities” Workgroup are encouraged to identify aspects of the 1986 criteria 

which have been cited as problematic, and, to the extent that these issues can be remedied 

through new or revised criteria, offer individual input for EPA to consider in the criteria 

development efforts.5

 

The new or revised criteria must be scientifically sound, protective of the designated use, 

implementable for broad CWA purposes, and when implemented, provide for improved public 

health protection. By scientifically sound, EPA means that the criteria must be based on the 

science and peer reviewed studies available at the time the criteria are developed. By protective 

of the use EPA means that the criteria must establish the desired ambient condition of the water 

to protect the designated use (e.g., primary contact recreation) given to the waterbody. EPA’s 

new or revised criteria must also serve the broad purposes for which CWA criteria are intended, 

including beach monitoring and water quality notification programs, development of water 

quality based effluent limits for National Pollutant Discharge Elimination System (NPDES) 

permits, waterbody assessments to determine use attainment, and development of total maximum 

daily loads (TMDLs), where needed. Lastly, the new or revised criteria, when implemented, 

should also provide for improved public health protection and States must be satisfied that the 

underlying science is sound and that the numeric values of allowed pollutant in recreational 

waters will achieve the desired environmental result. 

On the last day of the Workshop, the chairs for the individual breakout topic groups will provide 

EPA with sections of a draft Expert Report. Each of these sections will summarize the 

individual input provided by the experts and collected by the Chairs throughout the week’s 

discussions. The Chairs will be asked to summarize commonalities and differences in the input 

provided by participants, and list out the projects and activities that the individual experts 

identified as critical to the development of new or revised CWA §304(a) criteria in the near-term, 

recognizing that research that cannot be completed in 2 to 3 years will not be useful in near-term 

criteria development efforts. (The workgroup chairs may also summarize any research and 

science needs identified by the experts for developing “next generation” criteria.) 

The draft Report will include a summary of expert views on the following topics: appropriate 

pathogens or pathogen indicators, along with available and appropriate methods; single versus 

“toolbox” criteria approach; implementation issues; and most importantly, identification of 

critical technical issues and uncertainties that could be addressed with near-term research. 

EPA contractual support will be available to the Chairs during the workshop to provide 

assistance in preparing the draft Report. After the workshop, EPA contractual support will be 

available to the Chairs to finalize their component of the Report in 1-month’s time. EPA will use 

 5

 To the extent that experts come to some conclusion on how to better implement the 1986 criteria, EPA 

intends to track these issues separately in order to not depart from the primary purpose of the meeting which is to 

obtain input on critical research needs for the development of the near-term criteria. 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 A-4 

the Report as it develops a critical path science plan that will guide research activities over the 

next 2 to 3 years. 

 

Presented in the following sections of this document are key questions on seven major 

overarching issues pertaining to criteria development and implementation. A threshold issue that 

impacts the deliberations of all groups is whether EPA should consider a fundamental change in 

its approach to recommending recreational criteria; for example, switch from a single criterion in 

all places to a diversified toolbox or tiered approach, using multiple criteria, or several tools 

supporting a single criterion, or some other combination. 

Break-Out Group #1: Approaches to Criteria Development (See Chapter 1)6

 

Single versus “Toolbox” Approach: A single criterion and/or method may not adequately 

address all CWA needs. One approach for new or revised criteria may consist of several “tools” 

(i.e., indicators, methods, intrinsic geographic factors, etc.) to fulfill all of the specific CWA 

needs. For example, it could involve using molecular methods and rainfall models for beach 

monitoring and water quality notification, and possibly other method-indicator combinations for 

other CWA uses—provided that all criteria and methods are comparable in terms of level of 

protection provided. For example, the definition of an impaired recreational water in terms of 

the number of people that would get sick when the water is not in compliance cannot differ from 

the illness rate that triggers a beach advisory or closing. 

The following set of questions is intended to guide a robust discussion among the experts in this 

group. The results of this discussion will improve the understanding of the advantages and 

disadvantages of various approaches to criteria development. 

1. What approaches exist currently for setting limits of pollutants that may be relevant for 

developing nationally recommended recreational water quality criteria? Consider 

approaches used for other kinds of pollutants in water, in other environmental media, 

and by other countries as well as approaches being implemented by States. What are the 

pros and cons of each of these approaches? 

2. Which of these approaches is most applicable and appropriate for developing nationally 

recommended recreational water quality criteria in the near-term? Why is this approach 

on balance considered the most applicable and appropriate? 

3. For those approaches identified as applicable and appropriate, what is the science that 

supports the approach? Is that science sufficient and of adequate quality? 

4. Are there any critical research and science needs that should be addressed in developing 

or selecting an appropriate approach? Can this research be completed in time to be 

used in criteria development in the near-term? 

5. Is a “toolbox” approach appropriate for developing new or revised recreational criteria 

in the near-term? Why or why not? 

6. What are the pros and cons of selecting a “toolbox” approach? 

 6

 Because breakout group numbers do not correspond to chapter numbers in these proceedings, chapter 

numbers are referred to for easier reference. 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 A-5 

7. What are desired features or characteristics that would make a “toolbox” approach 

appropriate? 

8. Would a “toolbox” approach achieve additional public health protection as compared to 

another approach? Why or why not? If unknown, what science would need to be 

completed in order to determine whether a “toolbox” approach would achieve additional 

public health protection? 

9. Criteria for secondary contact recreation could be part of a “toolbox.” What 

approaches would be appropriate for developing criteria for secondary contact 

recreation? Would this approach be different from that used to develop primary contact 

recreation criteria? Why and why not? 

10. What are critical research and science needs in developing or selecting an appropriate 

approach for secondary contact recreation? Can this research be completed in time to be 

used in criteria development in the near term? 

11. What are the implementation considerations of the different approaches for CWA 

purposes (1) beach monitoring and notification, (2) development of NPDES permits, (3) 

assessments to determine use attainment, and (4) development of TMDLs? Are there 

practical considerations that could preclude, or greatly limit, the use of an approach in 

routine, regulatory implementation (e.g., field sampling issues, laboratory challenges, 

staff training, etc.)? 

Geographical Applicability: Options for ensuring criteria are appropriate in a diverse range of 

recreational waters include EPA recommending geographically different approaches, numbers, 

or indicators, applicable to different regions (e.g., fresh and marine waters, coastal and inland 

waters, tropical/subtropical and temperate waters) or types of waterbodies (e.g., lakes and 

flowing waters). 

 1. Is a single criterion available that is applicable for the diverse range of geographic 

conditions? Why or why not? 

 2. Is a “toolbox” approach appropriate for different geographical conditions? Why and 

why not? 

 3. What would a “toolbox” that addresses geographical differences look like? 

 4. What are critical research and science needs in developing or selecting an approach that 

will appropriately factor-in diverse geographical conditions? 

Expression of Criteria: EPA is currently assessing the degree to which criteria should be 

expressed as the mean concentration over a period of time (e.g., 30 days) and/or as a daily or 

instantaneous maximum value. 

1. Given the diverse needs of the CWA programs and the overarching goal of protecting 

and restoring waters for swimming, what protection is provided by establishing a 30-day 

“average” value as the criteria? What additional protection (if any) is provided by a 

daily or instantaneous maximum value? From a scientific standpoint, is one measure 

better scientifically than another for particular purposes (e.g., mean value for purposes 

of identifying impaired waters and daily maximum for beach monitoring and notification 

purposes)? Why? 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 A-6 

2. What are pros and cons of expressing the criteria differently for the various CWA 

program needs? 

3. What are the implications of instantaneous or daily values for public health protection? 

If we don’t currently have a good understanding of this, what are the critical research 

and science needs to answer these questions? 

4. If EPA were to set criteria at a mean concentration over 30 days and not recommend a 

single sample maximum, do we understand the illnesses that could occur on a single day 

(where the level would still lead to compliance with the 30 day average)? 

 5. If the science is not there, what are the critical research and science needs to answer this 

question? 

6. What are the implementation considerations for CWA purposes of failing to address (and 

addressing) differences geographically in the criteria and failing to include (and 

including) a single sample maximum value for (1) beach monitoring and notification, (2) 

development of NPDES permits, (3) assessments to determine use attainment, and (4) 

development of TMDLs? Are there practical considerations that could preclude, or 

greatly limit, the usage in routine, regulatory implementation (e.g., field sampling issues, 

laboratory challenges, staff training, etc.)? 

Break-Out Group #2: Implementation Realities (See Chapter 7)

Although EPA wants the experts to consider implementation realities when providing input to all 

general and specific questions throughout this document, the following set of questions are 

intended to guide a robust discussion among the experts about implementation issues and how 

science and research could ease implementation. 

1. What are the essential implementation considerations as EPA develops new nationally 

recommended recreational water quality criteria for CWA purposes: (1) beach 

monitoring and notification, (2) development of NPDES permits, (3) assessments to 

determine use attainment, and (4) development of TMDLs? 

2. What are the major lessons learned in implementing the (EPA) 1986 criteria? What 

worked well and not so well? How could we avoid repeating past “mistakes” that lead to 

delays in adoption or difficulties in implementing these criteria? 

3. Which approaches to criteria development have the most potential for success in 

implementation when new or revised criteria are adopted into State water quality 

standards? Why? 

4. What are general features or characteristics that would make new or revised criteria 

easy to interpret and implement for states when adopted into State water quality 

standards? Why? 

5. Would a “toolbox” approach be easier or more difficult to interpret and implement? 

What are desirable characteristics of a “toolbox” criterion from an implementation 

perspective? 

6. If new or revised criteria are provided as a range of values instead of a single value, 

what implementation concerns are triggered (e.g., can a range of values be used when 

developing NPDES permit limits or TMDL calculations)? 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 A-7 

7. What are critical path research and science needs that would enhance implementation of 

new or revised criteria in the near-term? 

Break-Out Group #3: Pathogens, Pathogen Indicators,7

 and Indicators of Fecal Contamination 

(See Chapter 2)

Indicator Approach: EPA previously developed criteria based on indicators of the potential 

presence of human pathogenic organisms; that is, based on indicators of fecal contamination. 

Other possible approaches such as pathogen index microorganisms and specific pathogens are 

discussed below. 

The following set of questions is intended to guide a robust discussion among the experts toward 

the identification of critical research and science needs in the development of criteria based on 

pathogens, pathogen indicators or indicators of fecal contamination. It is essential that this group 

focus discussions on only those pathogens, pathogen indicators or indicators of fecal 

contamination where methods are ready now for day-to-day use in State public health and 

environmental labs or where methods will be ready for day-to-day use in these labs within the 

next 3 years. 

A. Fecal matter indicators (as surrogates for gastrointestinal and non-gastrointestinal 

diseases): 

1. What are the benefits and shortcomings for continuing to implement the current fecal 

indicators (E. coli and enterococci) to meet each of the CWA §304(a) criteria uses 

(beach notification, TMDLs, NPDES permits, listing of impaired waters) to protect 

swimmers health from (a) gastrointestinal disease? (b) upper respiratory tract disease? 

(c) other diseases (skin, ear, eye disease)? Should other CWA §304(a) uses be tied to 

health outcomes? 

2. Are there other microbial fecal indicator(s) that can be used to better meet each of the 

CWA §304(a) criteria uses and provide improved protection against diseases (e.g., 

Bacteroides spp., Clostridium perfringens, coliphages or other phages)? Why? 

3. Are there any chemical biomarker fecal indicators (e.g., fecal stanols, detergents, 

whiteners, caffeine) that can be used to better protect public health and meet all CWA 

purposes than the current indicators of fecal contamination? 

4. What critical research would improve or widen the selection of fecal indicators available 

for the criteria? 

B. Pathogens and their Index organisms (gastrointestinal and non-gastrointestinal disease): 

1. Would a specific pathogen or index microorganism approach present an improvement in 

health protection over fecal indicators for each CWA use if applied as §304(a) criteria? 

If yes, then see question #2. If no, what research could be done to support this 

 7

 A specific pathogen belonging to a broader group of pathogens which would serve as a surrogate for the 

presence and/or health risks for that group (e.g., Cryptosporidium serving as a surrogate for all parasitic protozoa); 

or an indicator microorganism whose presence is correlated to the presence of a broad group of pathogens (e.g., 

spores of Clostridium perfringens serving as a surrogate for human or dog parasitic protozoa). 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 A-8 

approach? (also for skin, upper respiratory tract, ear, eye disease criteria 

considerations) 

2. What are the advantages and disadvantages of this approach? 

3. What might be the most appropriate pathogens or index organisms? Why? 

4. What data support a dose-response relationship between a particular pathogen or its 

index in recreational water and any disease outcome? 

5. The BEACH Act requires that EPA conduct research and develop new or revised water 

quality criteria for “Pathogens and Pathogen Indicators.” The Act defines a pathogen 

indicator as a substance that indicates the potential for human infectious disease. How 

might the term “index microorganism” relate to the statutory term pathogen indicator? 

6. What is the critical research to make the selection of pathogen/ index organisms 

available for the new or revised criteria and for the next generation criteria? 

Application of Alternatives: The following two sections present some possible applications of a 

mix of approaches that may increase the potential to improve monitoring, better express health 

risks from swimming exposures, and be more comprehensive in their use to meet all criteria 

needs and provide more efficient and cost effective procedures. 

C. Application of fecal indicators, pathogen index organisms, and pathogens in combination for 

criteria:

1. If none of the above three groups of surrogates can meet all CWA §304(a) criteria needs, 

is there any combination of the three that would provide an acceptable criteria 

approach? 

2. What specific combined applications would have merit in meeting criteria needs? 

3. Would the combined applications best utilize an analytical toolbox approach or a tiered 

analytical approach? 

4. Would the criteria endpoint reflect a general gastrointestinal disease target or a dose 

response estimate base on more limited disease symptoms reflecting the metrics used? 

5. What research is important to make the selection of combinations available for the new 

or revised criteria and the next generation criteria? 

6. Can adoption of the WHO/Annapolis Protocol approach8

 that combines sanitary 

reconnaissance survey information along with microbial assessment to develop 

surrogates of fecal contamination (predictive modeling) on the day to manage water 

advisories provide improved health gains over current criteria? Are there sufficient 

examples of this approach to develop new/improved use of indicators/surrogates in the 

near term? 

 8

 WHO (World Health Organization). 2003. Guidelines for Safe Recreational Water Environments. Volume 1 

Coastal and Fresh Waters. Geneva, Switzerland: WHO. 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 A-9 

D. Applications of all the above for all categories of waters, climatology, and geographical 

considerations:

1. Will the choices of individual, combined, or tiered fecal indicators, index organisms or 

pathogen indicators, or pathogens selected from above be capable of working for each or 

all of the following: 

a) Freshwaters (flowing and lakes/ponds)? Marine waters? POTWs? TMDLs? 

b) Temperate waters? Tropical waters? 

c) High matrix waters (high in solids)? Special conditions? 

2. What science or research is important in the near term to make the determination in 

Question D1? 

Break-Out Group #4: Methods Development (See Chapter 3)

The 1986 criteria are based on a culture method (EPA Method 1600) for the detection of fecal 

indicators in ambient waters. The Agency has been considering the use of newer methods, such 

as qPCR and faster culture-based methods, for inclusion in new or revised criteria. EPA is 

interested in input on what other methods or tools are available and should be considered for 

developing criteria/standards that would meet all CWA purposes. 

The following set of questions is intended to guide a robust discussion among the experts toward 

the identification of critical research and science needs in the development of detection methods 

for the new criteria. It is essential that this group focus discussions on those methods (and 

pathogens, pathogen indicators or indicators of fecal contamination) that are ready now for dayto-day use in State public health and environmental labs or would be ready for day-to-day use in 

these labs within the next 3 years. 

1. Are there quantitative methods other than membrane-filtration/Most Probable Number 

(MF/MPN) methods that measure active organisms that EPA should consider for water 

quality criteria development? 

2. Are there data to support other molecular methods for beach microbiological monitoring 

purposes? Which molecular methods are most fully developed in your view? 

3. Are there data to support other methods targeting non-microbiological surrogates of 

beach fecal pollution? Which methods are most fully developed in your view? 

 4. How important is time-to-results in method selection from the perspective of public 

 health protection? 

5. What further work needs to be done to ensure that the qPCR method or other promising 

(molecular) methods are considered valid for all CWA purposes? 

6. What are the pros and cons of the use of molecular methods in each of the CWA 

applications? 

7. If some tools are available for certain CWA uses only (e.g., for beach monitoring and 

notification) how could other methods be “linked” to the qPCR method so that they are 

scientifically sound and easily implementable? If only qPCR has been validated through 

epidemiological studies to predict health effects, what other studies could be done to link 

qPCR to other methods/indicators that may be more appropriate for §304(a) uses? 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 A-10 

8. Depending on the method used, how could contamination at the beach be linked to all 

potential fecal sources of contamination? If the source of the contamination was a 

treated point source, could the method be linked to the necessary source to address the 

contamination? 

9. Current culture-dependent methods and qPCR are linked to health risks using 

epidemiological studies. How would future methods (resulting from rapid technical 

advances) be calibrated to health risks without new epidemiological studies? 

10. What applications of water quality criteria would culture methods, including EPA 

Methods 1600 and 1603, be most suitable for and why? 

11. What further work needs to be done to ensure that other culture methods are considered 

for CWA regulatory purposes? If the science is not there, what are the critical path 

science or research needs to be used in this aspect of criteria development in the nearterm? 

12. What new methods and analytical technologies may be useful to begin to investigate in 

order for these to potentially be available in the development of “next generation” 

criteria (i.e., 10 or more years in the future)? 

13. Can other tools (e.g., models, sanitary surveys) be developed to enhance the insight 

provided by water quality indicators? 

14. What characteristics of analytical methods are essential for the methods used in both 

wastewater and ambient water? 

15. What are implementation considerations for CWA purposes (1) beach monitoring and 

notification, (2) development of NPDES permits, (3) assessments to determine use 

attainment, and (4) development of TMDLs? Are there practical considerations that 

could preclude, or greatly limit, the usage in routine, regulatory implementation (e.g., 

field sampling issues, laboratory challenges, staff training, etc.)? 

Break-Out Group #5: Comparing Risks (to Humans) from Different Sources (See Chapter 4)

New or revised criteria should be protective of waterborne organisms that are pathogenic to 

humans whether the source is human waste or animal waste. The following set of questions is 

intended to guide a robust discussion among the experts toward the identification of critical 

research and science needs to better understand the relationship between the risks posed by 

exposure to human and animal wastes in recreational waters so that this may be considered in the 

development of new criteria. 

 1. Is setting criteria based on a treated human point source such as a publicly (or privately) 

owned (sewage/wastewater) treatment work (POTW) protective, under-protective or 

overprotective of other potential sources of human pathogen? Why or why not? Are 

there data to support this conclusion? 

2. Based on the “state of the science,” what conclusions or assumptions are reasonable to 

make about risks to humans exposed to human fecal contamination, non-point source 

contamination from animal sources, and mixed sources (e.g., combined sewer overflows 

and storm sewer overflows)? 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 A-11 

3. To what extent is it reasonable to apply risk estimates from POTW-influenced beaches to 

non-POTW beaches? Do we understand scientifically whether this would lead to 

overprotection? What science would be important to understanding this? 

4. Assess whether there is a possibility of overprotection due to a compounding of risks 

from multiple factors (such as the current definition of GI illness [i.e., no fever]; more 

sensitive molecular methods; assuming that POTW risks = non-human source risks, etc.) 

5. How should EPA evaluate risk that may have a low probability of occurrence but a 

significant risk, if it occurs? 

6. What are the key data gaps and uncertainties needed to support criteria development in 

the near term? 

Break-Out Group #6: Acceptable Risk (See Chapter 5)

Population to be Protected: EPA is currently reassessing the extent to which criteria protect 

swimming populations, including some vulnerable subpopulations (e.g., immunocompromised 

individuals, elderly, and children) against various types of waterborne diseases (GI and non-GI) 

caused by pathogens. 

The following set of questions is intended to guide a robust discussion among the experts toward 

the identification of critical research and science needs to better understand what protections new 

criteria would provide and for what populations/subpopulations. 

1. Is the science there now to understand the degree and extent of protection that nationally 

recommended criteria for the general population would provide to vulnerable 

subpopulations (e.g., immunocompromised individuals, elderly, and children)? Is the 

science there now to understand whether nationally recommended criteria (based on the 

types of epidemiological studies EPA and others have conducted to date) provide 

protection against all types of major waterborne diseases? If not, for which subgroups, 

pathogens, and waterborne illnesses is the science lacking? What types of studies would 

be needed to answer these types of questions about the degree of public health protection 

provided by nationally recommended criteria? 

2. What methodologies or approaches for assessing human health risk or hazard should 

EPA consider as it develops new criteria? Why? 

 3. What are the pros and cons of using GI illness rates associated with differing levels of 

fecal contamination as the foundation for developing nationally recommended criteria? 

 4. Is there any scientifically-based reason to establish different “acceptable” risk levels for 

fresh water versus marine water? 

 5. Is the phrase “acceptable risk” from the (US EPA) 1986 criteria the best terminology or 

should we consider other terminology (e.g., tolerable or appropriate risk level)? 

 6. What science, if any, would be helpful to EPA in making decisions about what amount 

and type of human illness from recreation should be considered acceptable? 

 7. What is the level of human health protection provided by the implementation of the 1986 

criteria? Is it really no more than 8 to 10 GI illnesses (with fever) per 1,000 in fresh 

water and 19 GI illnesses (with fever) per 1,000 in marine waters, or, are we really 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 A-12 

protecting people from more than GI illness (with fever)? What science is needed to 

understand what protection is provided by the implementation of the 1986 criteria? 

Protection of Humans from Drinking Water and Fish and Shellfish Consumption: EPA is 

currently assessing the degree to which recreational criteria can and should be developed to not 

only protect people from illnesses associated with recreation, but also to protect people from 

illness caused by drinking contaminated recreational water or consuming fish and shellfish found 

in contaminated recreational water. 

 1. Will criteria that protect swimmers from swimming-related illnesses caused by pathogens 

 also protect people who drink the water or eat fish or shellfish from the same water? Is 

 the science sufficient to support a determination that recreational criteria will also 

 protect drinking water uses and shellfish uses? 

 2. What additional science is needed to ensure that recreational criteria protect people 

 from illnesses associated with recreation and also protect people from illnesses caused 

 by drinking contaminated recreational water or consuming fish and shellfish found 

 in contaminated recreational water? 

 3. Is the science there now to understand and characterize the degree of protectiveness for 

all these elements? 

 4. If the science is not there, what are the critical path science or research needs to address 

this? 

Break-Out Group #7: Modeling Applications for Criteria Development and Implementation (See 

Chapter 6)

Predictive modeling may be useful as a tool to help with the development of site-specific 

recreational water quality criteria, and the implementation of criteria. Presently, EPA is not 

considering models in its plans for new or revised criteria in the near-term. However, in 

recognition that some states and municipalities currently use models effectively in beach 

notification programs, EPA solicits input from experts regarding the potential use of models as 

tools to aide implementation of the new or revised criteria, and further requests input on critical 

research and science needs in this area for future criteria development. 

 1. What potential role could estimating techniques (or models) play in criteria 

development? In the setting of site-specific criteria for recreational waters? 

 2. What potential role could estimating techniques (or models) play in implementing 

nationally recommended criteria for recreational waters? 

 3. What are advantages and disadvantages of using models, instead of direct measurement 

(monitoring), in water quality management? And in particular, in management of 

recreational waters? 

 4. What factors should be considered in integrating modeling with current monitoring 

regimes, or in changing monitoring regimes to include or support modeling? 

 5. What is the “state of the science” in modeling to support recreational water quality 

criteria development and implementation? 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 A-13 

 6. What model evaluation procedures are used to insure the quality of predictive models for 

recreational water quality? 

 7. How does uncertainty in modeling compare to uncertainty in monitoring? How can 

uncertainty be accurately represented and considered in risk analysis and public health 

decisions? 

 8. Do differences in the nature of the respective uncertainties inherent in modeling versus 

monitoring require different means of addressing these uncertainties? For instance, 

issue an advisory on the basis of modeled results, but clear the advisory only on the basis 

of sampling. 

 8. What models would be most useful for certain “uses” of criteria (i.e., beach notification, 

assessment, permitting, TMDLs)? How would modeling be used together with 

monitoring to cover all “uses” of criteria? 

 9. In models that are currently being used to predict levels of indicator bacteria, how are 

advisory/closure decisions being made using model results, and how are the results 

and/or the risk being communicated to the public? Do paradigms currently exist that 

would be applicable to the communication of modeled information on likely water 

quality? 

 10. Given the differences between fresh water and marine water environments in terms of 

physical predictive factors, what are the respective challenges of the two environments 

relative to developing predictive models? What are the differences in data requirements, 

likely effectiveness of models, and resources required to develop and implement useful 

models for the full range of intended purposes? 

 11. What are the critical path research and science needs EPA should pursue to further 

enhance the capabilities and effectiveness of models in the development/implementation 

of new or revised criteria? Why? 

 12. What critical path research and science needs EPA should pursue to consider modeling 

in the development of next generation criteria? Why? 
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U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 B-1 

APPENDIX B: PARTICIPANT LIST

Experts by Workgroup 

Approaches to Criteria 

Development Implementation Realities 

Joel Hansel, Chair Lee Dunbar, Chair 

Mark Gold Thomas Atherholt 

David Kay Bart Bibler 

John Ravenscroft Lawrence Honeybourne 

William Robertson Charles Noss 

Jeffrey Soller James Pendergast 

David Whiting Michael Tate 

Pathogens, Pathogen Indicators, and 

Indicators of Fecal Contamination Methods Development 

Nicholas Ashbolt, Chair Stephen Weisberg, Chair 

Roger Fujioka Alfred Dufour 

Toni Glymph Charles Hagedorn 

Charles McGee Sharon Kluender 

Stephen Schaub Erin Lipp 

Mark Sobsey Robin Oshiro 

Gary Toranzos 

Comparing Risk (to Humans) 

from Different Sources Acceptable Risk 

Dennis Juranek, Chair Paul Hunter, Chair 

Rebecca Calderon Michael Beach 

Jack Colford Lora Fleming 

Elizabeth Doyle Peter Teunis 

Graham McBride Timothy Wade 

Samuel Myoda 

 

Modeling Applications to Bacteria Criteria 

Development and Implementation

Alexandria Boehm, Chair 

Donna Francy 

Mark Pfister 

John Wathen 

Richard Zepp 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 B-2 

Contact Information – Experts 

(Alphabetical) 

Nicholas Ashbolt (Chair) 

USEPA 

513-569-7303 

Ashbolt.Nick@epa.gov 

Thomas Atherholt 

New Jersey Department of Environmental 

Protection 

609-984-2212 

tom.atherholt@dep.state.nj.us 

Michael Beach 

Centers for Disease Control and 

Prevention 

770-488-7763 

mjb3@cdc.gov 

Bart Bibler 

Florida Department of Health 

850-245-4240 

Bart_Bibler@doh.state.fl.us 

Alexandria Boehm (Chair) 

Stanford University, California 

650-724-9128 

aboehm@stanford.edu 

Rebecca L. Calderon 

USEPA 

919-966-0617 

calderon.rebecca@epa.gov 

Jack Colford 

University of California, Berkeley 

510-642-9370 

jcolford@berkeley.edu 

Elizabeth Doyle 

USEPA 

202-566-0056 

doyle.elizabeth@epa.gov 

Alfred Dufour 

USEPA 

513-569-7330 

dufour.alfred@epa.gov 

Lee Dunbar (Chair) 

Connecticut Department of Environmental 

Protection 

860-424-3731 

lee.dunbar@po.state.ct.us 

Lora Fleming 

Departments of Epidemiology and Public 

Health and Marine Biology and Fisheries, 

University of Miami School of Medicine 

and Rosenstiel School of Marine and 

Atmospheric Sciences, Florida 

305-243-5912 

LFleming@med.miami.edu 

Donna Francy 

U.S. Geological Survey 

614-430-7769 

dsfrancy@usgs.gov 

Roger Fujioka 

University of Hawaii, Manoa 

808-956-3096 

roger@hawaii.edu 

Mark Gold 

Heal the Bay, Santa Monica, California 

310-451-1500 

mgold@HealTheBay.org 

Toni Glymph 

Wisconsin Department of Natural Resources 

608-264-8954 

Toni.Glymph@Wisconsin.gov 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 B-3 

Charles Hagedorn 

Virginia Tech 

540-231-4895 

chagedor@vt.edu 

Joel Hansel (Chair) 

USEPA 

404-562-9274 

hansel.joel@epa.gov 

Lawrence Honeybourne 

Orange County Health Care Agency, 

Santa Ana, California 

714-433-6015 

lhoneybourne@ochca.com 

Paul Hunter (Chair) 

University of East Anglia, U.K. 

+ 44 1603 591004 / 593061 

Paul.Hunter@uea.ac.uk 

Dennis Juranek (Chair) 

Centers for Disease Control and 

Prevention (retired) 

770-457-2056 

ddjuranek@comcast.net 

David Kay 

University of Wales, U.K. 

+44 1570 423565 

dvk@aber.ac.uk 

Sharon Kluender 

Wisconsin State Laboratory of Hygiene 

608-224-6262 

hesk@mail.slh.wisc.edu 

Erin Lipp 

University of Georgia 

706-583-8138 

elipp@uga.edu 

Graham McBride 

National Institute of Water and 

Atmospheric Research, New Zealand 

+64 7 8560726 

g.mcbride@niwa.co.nz 

Charles McGee 

Orange County Sanitation District, 

California 

714-593-7504 

CMCGEE@OCSD.COM 

Samuel Myoda 

Delaware Department of Natural Resources 

& Environmental Control 

302-739-9939 

Samuel.Myoda@state.de.us 

Charles Noss 

USEPA 

919-541-1322 

noss.charles@epa.gov 

Robin Oshiro 

USEPA 

202-566-1075 

oshiro.robin@epa.gov 

James Pendergast 

USEPA 

202-566-0398 

pendergast.jim@epa.gov 

Mark Pfister 

Lake County Health Department, Illinois 

847-377-8028 

MPfister@co.lake.il.us 

John Ravenscroft 

USEPA 

202-566-1101 

ravenscroft.john@epa.gov 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 B-4 

William Robertson 

Water, Air and Climate Change Bureau, 

Health Canada 

613-957-1505 

Will_Robertson@hc-sc.gc.ca 

Stephen Schaub 

USEPA 

202-566-1126 

schaub.stephen@epa.gov 

Mark Sobsey 

University of North Carolina, Chapel Hill 

919-966-7303 

sobsey@email.unc.edu 

Jeffrey Soller 

Soller Environmental, Berkeley, California 

510-847-0474 

jsoller@sollerenvironmental.com 

Michael B. Tate 

Kansas Department of Health and 

Environment 

785-296-5504 

MTate@kdhe.state.ks.us 

Peter Teunis 

RIVM (National Institute of Public Health 

and the Environment), Netherlands 

+31 30 274 2937 

Peter.Teunis@rivm.nl 

Gary Toranzos 

University of Puerto Rico, Rio Piedras 

787-773-1743 

gatoranzos@uprrp.edu 

Timothy Wade 

USEPA 

919-966-8900 

wade.tim@epa.gov 

John Wathen 

USEPA 

202-566-0367 

wathen.john@epa.gov 

Stephen Weisberg (Chair) 

Southern California Coastal Water Research 

Project 

714-755-3203 

stevew@sccwrp.org 

David Whiting 

Florida Department of Environmental 

Protection 

850-245-8191 

David.D.Whiting@dep.state.fl.us 

Richard Zepp 

USEPA 

706-355-8117 

zepp.richard@epa.gov 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 B-5 

Contact Information – EPA Resource 

Personnel 

(Alphabetical) 

Shari Barash 

202-566-0996 

barash.shari@epa.gov 

Samantha Fontenelle 

202-566-2083 

fontenelle.samantha@epa.gov 

Patricia Harrigan 

202-566-1666 

harrigan.patricia@epa.gov 

Rick Hoffmann 

202-566-0388 

hoffmann.rick@epa.gov 

Denise Keehner (Workshop Chair) 

202-566-1566 

keehner.denise@epa.gov 

Beth Leamond 

202-566-0444 

leamond.beth@epa.gov 

Kevin Oshima 

513-569-7476 

oshima.kevin@epa.gov 

Cynthia Roberts 

202-564-1999 

roberts.cindy@epa.gov 

Grace Robiou 

202-566-2975 

robiou.grace@epa.gov 

Lauren Wisniewski 

202-566-0394 

wisniewski.lauren@epa.gov 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 B-6 

Contact Information – Support Personnel 

(Alphabetical) 

Note Takers 

Alexis Castrovinci 

ICF International 

703-934-3313 

acastrovinci@icfi.com 

Kristine Cornils (Implementation 

Realities) 

ICF International 

(202) 257-4591 

kcornils@icfi.com 

Mark Gibson 

ICF International 

703-934-3242 

mgibson@icfi.com 

Audrey Ichida 

ICF International 

703-934-3154 

michida@icfi.com 

Rebecca Kauffman 

ICF International 

781-676-4011 

rkauffman@icfi.com 

Joseph Keithley 

ICF International 

703-934-3438 

jkeithley@icfi.com 

Michelle Moser 

ICF International 

703-934-3887 

mmoser@icfi.com 

Ami Parekh 

ICF International 

703-934-3173 

aparekh@icfi.com 

Laura Tuhela-Reuning 

ICF International 

 (740) 965-1999 

lmtuhela@owu.edu 

Kerry Williams 

ICF International 

703-218-2707 

kwilliams@icfi.com 

Facilitator 

Jan Connery 

ERG 

781-674-7322 

Jan.Connery@erg.com 

Logistics 

Patrick McCool 

GLEC 

231-941-2230 

pmccool@glec.com 

Peggy Himes 

GLEC 

231-941-2230 

phimes@glec.com 

Malkia Perry 

ERG 

703-633-1646 

Malkia.Perry@erg.com 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 C-1 

APPENDIX C: TRANSLATION OF EPIDEMIOLOGY TO DISEASE 

BURDEN BY WHO AND EU

In a series of five international expert consultations that took place between 1996 to 2001, the 

World Health Organization (WHO), together with partner organizations, including the EPA, the 

Commission of the European Communities, and a group of independent experts, have developed 

a methodology for expressing the exposure-risk relationship for recreational water. This 

approach is outlined in detail in Chapter 4 of the WHO’s (2003) Guidelines for Safe 

Recreational Water Environments. Volume 1 Coastal and Fresh Waters (see also Kay et al., 

2004). The broad framework is summarized below as a basis for burden of disease calculations. 

Stated briefly, the approach is based on the following two assumptions: 

1. that the statistical distribution of the fecal indicators (i.e., given a sufficiency of samples 

through a compliance period such as a bathing season) which predict illness in 

recreational waters is described by a log10-normal probability density function (pdf); and 

2. that the pdf for any beach can be combined with the dose-response curve to produce a 

unique disease burden for a specific location. 

Given a fixed dose-response curve, the relative disease burden (or proportion of the exposed 

population that becomes ill) for any beach, region or jurisdiction can be calculated from the 

parameters of the pdf, principally its geometric mean (GM) value (i.e., the mean of the log10

transformed bacterial counts) and the standard deviation (SD) of the log10 transformed bacterial 

counts. The mathematical basis of these calculations is outlined in WHO (2003), while Kay et 

al. (2004) and Wyer et al. (1999) provide a discussion on the impacts of different GM and SD 

assumptions. 

Figure C-1 illustrates a theoretical pdf for any beach. The cleaner the water, the further to the 

left the peak of the pdf will be. Figure C-2 provides the dose response curves reported in Kay et 

al. (1994) that were used in deriving the standards in WHO (2003). Plot C-2a is projection of the 

dose-response curve beyond the actual data range of >157 (intestinal) enterococci per 100 mL. 

In fact, the projection of this relationship to exposures above about 150 enterococci would not be 

justified because the empirical data acquired during the U.K. randomized sea bathing trials was 

restricted to lower exposures. Figure Plot C-2b assumes that the excess probability of illness 

does not continue to increase as enterococci exposure increases above the levels experienced in 

the sea bathing trials. This was chosen as the dose-response curve in the derivation of the 2003 

WHO Guidelines as a pragmatic approach. It should be recognized, however, that it may 

represent an underestimate of the true disease burden if the curve does not, in fact, flatten as 

suggested in this diagram. 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 C-2 

Figure C-1. A Probability Density Function of 

Fecal Indicator Distributions Measured at a 

Recreational Water Showing Probability of 

Exposure (Y Axis) versus Log10 Fecal 

Streptococci Concentration (later termed 

enterococci).

Figure C-2. The Dose-response Relationship 

Derived From Kay et al. (1994) (a) and the 

Functional Form Used to Derive the 2003 WHO 

Guideline Values (b). See Kay et al. (2004) for a 

more detailed explanation. 

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.0 1.5 2.0 2.5 3.0 3.5 4.0

log10 enterococci (per 100 ml)

0

5

10

15

20

25

30

-2 -1 0 1 2 3 4

log10 faecal streptococci (cfu/100 ml)

log10 Mean = 1.176

log10 SD = 0.751

a 

b 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 C-3 

Figure C-3 combines the pdf of Figure C-1 with the dose-response curve of Figure C-2 to 

produce a relative disease burden prediction as a proportion of the exposed population. The 

mathematical basis of this process is provided in Kay et al. (2004). 

Figure C-3. Combining the Dose-response Curve and the pdf 

to Produce a Relative Disease Burden Assessment for any 

Beach or Region. 

4

0

1

2

3

4

5

-3 -2 -1 0 1 2 3

log10 enterococci (per 100 ml)

Mean = 0.9337 (geometric mean = 9 enterococci per 100 ml)

Standard Deviation = 0.8103

95th percentile = 2.2672 (185 enterococci per 100 ml)

Excess probability of illness = 0.05

Probability density function

Dose response curve

Proportion with illness

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 C-4 

The computation of gastrointestinal (GI) illness rates in the population is accomplished as 

follows. The pdf is described by: 

2

2

2

( )

2

1

s

c m

e

s

y − − = π

Where c is the log10 transformed enterococci concentration, y is the normal curve height, and m

is the mean enterococci concentration. The associated probability of exposure across a given 

range of enterococci concentration (i.e., ca to cb,) for a given distribution is expressed by: 

∫ Φ =

cb

ca

dc (c) y

which is the area under the normal pdf curve between the limits ca and cb. The proportion of 

bathers with GI illness is then calculated from the area under the curve described by: 

z = py

where p is the probability of GI illness (gastroenteritis) from the dose-response relationship with 

the upper limit set at 158 enterococci per 100 mL; that is: 

p = 0.20102 (c − 31.9) − 2.3561

and z is the corresponding proportion of the normal curve height, y. The associated probability 

of GI illness across the range of enterococci concentrations, ca to cb, is then expressed by the 

following integral: 

∫ Φ =

cb

ca

dc (c) z

For the WHO (2003) Guidelines derivation, the integration of these areas was performed using 

iterative algorithms as outlined in Khabaza (1965). The algorithm was checked against standard 

tabulations of the normal pdf curve (Lindley and Miller, 1968) and an accuracy of at least four 

significant figures was obtained over the specified range of the normal pdf. 

References 

Kay, D; Fleisher, JM; Salmon, RL; Jones, F; Wyer, MD; Godfree, AF; Zelenauch-Jacquotte, Z; 

Shore, R. 1994. Predicting the likelihood of gastroenteritis from sea bathing – Results from 

randomized exposure. The Lancet 344: 905-909. 

Kay, D; Bartram, J; Pruss, A; Ashbolt, N; Wyer, MD; Fleisher, JM; Fewtrell, L; Rogers, A; 

Rees, G. 2004. Derivation of numerical values for the World Health Organization guidelines for 

recreational waters. Water Research 38: 1296-1304. 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 C-5 

Khabaza, IM. 1965. Numerical Analysis. London: Pergamon Press. 

Lindley, DV; Miller, JCP. 1968. Cambridge Elementary Statistical Tables. Cambridge: 

Cambridge University Press. 

WHO (World Health Organization). 2003. Guidelines for Safe Recreational Water 

Environments. Volume 1 Coastal and Fresh Waters. Geneva, Switzerland: WHO. 

Wyer, D; Kay, D; Fleisher, JM. 1999. An experimental health-related classification for marine 

waters. Water Research 33(3): 715-722. 
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U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 D-1 

APPENDIX D: SUMMARY OF THE EUROPEAN COMMISSION 

DIRECTIVE 

Revised Bathing Water Directive (EP/CEU, 2006) 

The Directive sets out requirements for the following: 

(a) the monitoring and classification of bathing water quality; 

(b) the management of bathing water quality; and 

(c) the provision of information to the public on bathing water quality. 

It is meant to apply to identified European Union (EU) bathing waters used by “large numbers” 

of bathers which must be assessed against the criteria in Table 2 in Chapter 1 of these 

proceedings (using the previous 3 or 4 years of sampling data) though establishment of a 

sampling program to acquire data from each bathing water at locations where a bathing water 

“profile” suggests the greatest risk of pollution and/or the greatest numbers of bathers might be 

expected (Article 3.3b). Member States must monitor each bathing water in accordance with a 

monitoring calendar established at the start of the bathing season (Article 3.4). The monitoring 

calendar can be suspended during “abnormal” conditions and samples taken during “short term 

pollution” may be disregarded (Article 3.6) provided that Member States comply with the 

additional provisions outlined below. 

Bathing waters are legally required to achieve “sufficient” microbiological status by 2015 

(Article 5.3), although the numerical values will be reviewed in 2008 (Article 14). 

However, bathing waters classified as “poor” in Table 2 may still remain in compliance with this 

Directive provided that Member States shall ensure that the following conditions are satisfied 

(Article 5.4a (i-iv)): 

adequate management measures, including a bathing prohibition or advice against 

bathing, with a view to preventing bathers’ exposure to pollution and identification of the 

causes and reasons for the failure to achieve “sufficient” quality status is undertaken by 

Member States; and adequate measures to prevent, reduce or eliminate the causes of 

pollution; and in accordance with Article 12, alerting the public by a clear and simple 

warning sign and informing them of the causes of the pollution and measures taken, on 

the basis of the bathing water profile. 

Member States must establish their bathing water profiles by March 24, 2011, which will be 

reviewed as specified in Annex III of the Revised Bathing Water Directive. 

Article 12 further describes information which must be made available to the public at the 

bathing water and communicated promptly by means of a sign, which includes: 

• the current bathing water classification and any bathing prohibition or advice against 

bathing; 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 D-2 

• a general description of the bathing water, in non-technical language, based on the 

bathing water profile established in accordance with Annex III; 

• in the case of bathing waters subject to short-term pollution: notification that the 

bathing water is subject to short-term pollution; 

• an indication of the number of days on which bathing was prohibited or advised 

against during the preceding bathing season because of such pollution, and a warning 

whenever such pollution is predicted or present; 

• information on the nature and expected duration of abnormal situations during such 

events; 

• whenever bathing is prohibited or advised against, a notice advising the public and 

giving reasons; 

• whenever a permanent bathing prohibition or permanent advice against bathing is 

introduced, the fact that the area concerned is no longer a bathing water and the 

reasons for its declassification; and 

• an indication of sources of more complete information in accordance with paragraph 

2. 

In addition, “Member States shall use appropriate media and technologies, including 

the Internet, to disseminate actively and promptly the information concerning bathing 

waters referred to in paragraph 1 and also the following information in several 

languages, when appropriate” (Article 12.1 and 12.2). 

Where a bathing water is subject to short-term pollution the public should also be informed on 

the following (Article 12.4d): 

• conditions likely to lead to short-term pollution; 

• the likelihood of such pollution and its likely duration; and 

• the causes of the pollution and measures taken with a view to preventing bathers’ 

exposure to pollution and to tackle its causes. 

Member States are required to disseminate this knowledge using geo-referenced information and 

signage at bathing waters beginning March 24, 2008. 

Member States are free to simply use the numerical standards in Table 2. However, they may 

take advantage of the opportunity to discount samples collected during short-term pollution 

events provided they have produced a bathing water profile and have complied with the 

requirement to provide public information specified in Article 12, which requires real time water 

quality prediction. No more than 15% of planned samples that are predicted to be of poor quality 

(i.e., resulting in public advisories) can be discounted in this manner prior to the calculation of 

the compliance statistics. 

References 

EP/CEU (European Parliament/Council of the European Union). 2006. Directive 2006/7/EC of 

the European Parliament and of the Council of 15 February 2006 Concerning the Management of 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 D-3 

Bathing Water Quality and Repealing Directive 76/160/EEC. Official Journal of the European 

Union L64: 31-51. Available at: http://europa.eu.int/eur-lex/lex/LexUriServ/site/en/oj/2006/ 

l_064/l_06420060304en00370051.pdf. 
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U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 E-1 

APPENDIX E: INDICATOR TERMINOLOGY

Table E-1. Definitions for Indicator and Index Microorganisms of Public Health Concern.*

Group Definition 

Indicator A group of organisms that demonstrates the efficacy of a 

process, such as total heterotrophic bacteria or total coliforms 

for chlorine disinfection 

Fecal indicator A group of organisms that indicates the presence of fecal 

contamination, such as the bacterial groups fecal coliforms or 

E. coli; thus, they only infer that pathogens may be present 

Index and model organisms A group/or species indicative of pathogen presence and 

behavior respectively, such as E. coli as an index for 

Salmonella and F-RNA coliphages as models of human enteric 

virus behavior in the environment 

Pathogen indicator A specific pathogen belonging to a broader group of pathogens 

which would serve as a surrogate for the presence and/or health 

risks for that group (e.g., Cryptosporidium serving as a 

surrogate for all parasitic protozoa), or an indicator 

microorganisms whose presence is correlated to the presence of 

a broad group of pathogens (e.g., spores of Clostridium 

perfringens serving as a surrogate for human or dog parasitic 

protozoa) 

*See Text Box E-1 for definitions of microbial groups (adapted from Ashbolt et al., 2001). 

Text Box E-1. Definitions of Key Fecal Indicator Microorganisms 

Coliforms: Gram-negative, non spore-forming, oxidase-negative, rod-shaped facultative anaerobic 

bacteria that ferment lactose (with β-galactosidase) to acid and gas within 24 to 48 hours at 36±2°C. Not 

specific indicators of fecal pollution. 

Fecal coliforms: coliforms that produce acid and gas from lactose at 44.5± 0.2°C within 24±2 hours, 

also known as thermotolerant coliforms due to their role as fecal indicators. 

Escherichia coli (E. coli): thermotolerant coliforms that produce indole from tryptophan, but also 

defined now as coliforms able to produce β-glucuronidase (although taxonomically up to 10% of 

environmental E. coli may not). Most appropriate group of coliforms to indicate faecal pollution from 

warm-blooded animals. 

Fecal streptococci (FS): Gram-positive, catalase-negative cocci from selective media (e.g., azide 

dextrose broth or m Enterococcus agar) that grow on bile aesculin agar and at 45°C, belonging to the 

genera Enterococcus and Streptococcus possessing the Lancefield group D antigen. 

Enterococci: all fecal streptococci that grow at pH 9.6, between 10° and 45°C, and in 6.5% NaCl. 

Nearly all are members of the genus Enterococcus, and also fulfil the following criteria: resistance to 

60°C for 30 minutes and ability to reduce 0.1% methylene blue. The enterococci are a subset of fecal 

streptococci that grow under the conditions outlined above. Alternatively, enterococci can be directly 

identified as micro-organisms capable of aerobic growth at 44±0.5°C and of hydrolysing 4-

methlumbelliferyl-β-D-glucoside (MUD, detecting β-glucosidase activity by blue florescence at 366nm), 

in the presence of thallium acetate, nalidixic acid, and 2,3,5-triphenyltetrazolium chloride (TTC, which is 

reduced to the red formazan) in the specified medium (ISO/FDIS 7899-1 1998).

Sulphite-reducing clostridia (SRC): Gram-positive, spore-forming, non-motile, strictly anaerobic rods 

that reduce sulphite to H2S. 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 E-2 

Clostridium perfringens: as for SRC, but also ferment lactose, sucrose and inositol with the production 

of gas; produce a stormy clot fermentation with milk; reduce nitrate, hydrolyse gelatine, and produce 

lecithinase and acid phosphatase. Bonde (1963) suggested that all SRC in receiving waters are not 

indicators of fecal pollution; thus, C. perfringens is the appropriate indicator. 

Bacteroidales: a family of strictly anaerobic bacteria present in the guts of warm-blooded animals. The 

family to which Bacteroides belongs. 

Bacteriodes: Gram-negative, mainly straight Bacteroides species that are: (a) obligately anaerobic, chain 

saturated, anteiso-methyl, and iso-methyl branched acids, (b) saccharolytic, producing acetate and 

succinate as the major metabolic end products; (c) contain enzymes of the hexose monophosphate shuntpentose phosphate pathway; (d) have a DNA-base composition in the range 40-48 mol% GC; (e) 

membranes contain sphingolipids, and contain a mixture of long-chain fatty acids; (f) possess 

menaquiones with MK-10 and MK-11 as the major components; and (g) contain meso-diaminopimelic 

acid in their peptidoglycan. This definition restricts the Bacteroides to the following ten species: B. 

fragilis, B. thetaiotaomicron, B. vulgatus, B. ovatus, B. distasonis, B. uniformis, B. stercoris, B. eggerthii, B. merdae, and B. caccae, with B. fragilis as the type strain. The Bacteroides, along with Prevotella and 

Porphyromonas, form one major subgroup in the bacterial phylum Cytophaga-Flavobacter-Bacteroides. 

This phylum diverged quite early in the evolutionary lineage of bacteria, and thus the Bacteroides, although Gram-negative organisms, are not closely related to the enteric Gram-negatives such as 

Escherichia coli.

Bacteriodes phages: Those viruses (bacteriophages) that use Bacteroides as a host for replication. 

References

Ashbolt, NJ; Grabow, WOK; Snozzi, M. 2001. Indicators of Microbial Water Quality. Pp: 289-

316 in: Water Quality: Guidelines, Standards and Health Fewtrell, L; Bartram, J. (eds.). London: 

IWA Publishing. 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 F-1 

APPENDIX F: SUMMARY OF MEASUREMENTS CURRENTLY PLANNED 

FOR THE DOHENY AND MALIBU BEACH (CALIFORNIA)

EPIDEMIOLOGY STUDY 

Table F-1. Summary of Measurements Currently Planned for the Doheny and Malibu 

Beach (California) Epidemiology Study. 

Indicator Method Investigator 

Traditional 

 Enterococci IDEXX 

South Orange County 

Wastewater Authority (SOCWA)

Enterococci Membrane-filtration (MF) SOCWA 

 Fecal coliforms MF SOCWA 

E. coli MF or IDEXX 

Southern California Coastal 

Water Research Project 

(SCCWRP) 

 Total coliforms MF SOCWA 

Rapid Traditional 

Enterococci 

Quantitative polymerase chain 

reaction (qPCR) Noble 

Enterococci qPCR Stewart 

Enterococci PCR-Luminex Stewart 

Enterococci Transcription-mediated 

amplification/nucleic acid 

sequence-based amplification 

(TMA/NASBA) Moore 

Enterococci Immunomagnetic separation (IMS) Bushon 

E. coli qPCR Noble 

E. coli IMS Bushon 

E. coli IMS Jay 

Marker Genes

Entero-Raptor, Esp gene qPCR-Raptor Harwood/Lim 

Enterococci Esp gene qPCR Scott 

E. coli virulence genes qPCR Sadowsky 

Bacteroides human marker qPCR Field 

Bacteroides human marker qPCR Wuertz 

Phage

Phage Culture Stewart 

Phage Culture Sobsey 

Rapid phage Antibody Sobsey 

Human Virus

Adenovirus qPCR Sobsey 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 F-2 

Indicator Method Investigator 

Enterovirus qPCR Stewart 

Hepatitis A virus qPCR Fuhrman 

Norovirus qPCR Stewart 

Norovirus qPCR Sobsey 

Polyomavirus qPCR Harwood 

Community Profiling

Bacteroides 

thetaiotamicron Sequencing Moorthy 

Heliobacter pylori Sequencing Moorthy 

Campylobacter jejuni Sequencing Moorthy 

Clostridium perfringens Sequencing Moorthy 

Salmonella enteritica 

serovar Typhimurium Sequencing Moorthy 

Shigella dysenteriae Sequencing Moorthy 

Shigella flexneri Sequencing Moorthy 

Shigella boydii Sequencing Moorthy 

Bacterial Markers

Bacteroides thetaiotamicron qPCR Noble 

Bacteroides thetaiotamicron PCR Leddy 

Multiple methanogens PCR Ufnar 

Methanobrevibacter smithii PCR-Luminex Stewart 

Methanobrevibacter smithii qPCR Stewart 

Legionella spp. qPCR Gast 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 G-1 

APPENDIX G: DEVELOPMENT OF DETERMINISTIC MODELS

The discussion of the modeling workgroup members included the present and future use of 

statistically-based models. This relates to the fact that they are currently being used to 

supplement monitoring information and can be implemented in a resource-effective manner in 

existing beach advisory programs. In general, deterministic models have not been included in 

the main part of this discussion (see Chapter 6) because it was the common opinion of the 

workgroup members of the modeling workgroup that their application represents a longer-range 

measure that might be considered in the context of research and development beyond the 2 to 3 

year (near-term) window envisioned by the current criteria development effort; however, there 

were differences of opinion on the importance of this relative to development of new or revised 

recreational water quality criteria. 

Although not discussed in detail at this workshop, deterministic process-based models represent 

an entire range of additional modeling tools that could be used to inform water quality criteria 

development and implementation over the range of criteria framework options that have been 

discussed during the course of this conference. Applications of such models to beach 

environments are discussed in the EPA report Review of Potential Modeling Tools and 

Approaches to Support the BEACH Program, (US EPA, 1999). They range from those that are 

simply based on precipitation to newer models that consider other factors such as sediment 

resuspension, hydrodynamics, microbial growth and decay, and non-point source basin scale 

inputs. For example, a process-based deterministic model has been recently used to predict fecal 

indicator concentrations in coastal reaches of southern Lake Michigan (Liu et al., 2006) and 

Huntington Beach, California (Boehm et al., 2005; Grant et al., 2005). Deterministic models 

also are being used in the development of total maximum daily loads (TMDLs) for pathogens 

and in evaluations of non-point and sources of biological contaminants in watersheds. 

In this appendix, deterministic models for evaluating pathogens in watersheds are briefly 

discussed. TMDLs often have to consider non-point sources from watersheds. This discussion 

is not intended to be comprehensive; rather, it is designed to illustrate the range of tools available 

to this area of consideration. 

Commonly used TMDL models allow users to discretize the watershed spatially and bacteria 

loads spatially and temporally, although this capacity is limited. As discussed in ASABE (2006), 

the models are also limited in their ability to simulate bacterial life cycles and bacteria 

concentrations. Even with their limitations, these models are useful when developing 

TMDLs if for no other reason than their use provides educational opportunities for both 

stakeholders and modelers throughout the TMDL process. The load duration method of 

developing TMDLs provides a good representation of overall water quality and needed 

water quality improvement, but intra-watershed bacteria contributions must be 

determined through supplemental sampling or through subsequent hydrologic and water 

quality modeling. Identified research needs include improved bacteria source 

characterization procedures and supporting data, and specific modeling advances. 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 G-2 

New models are now becoming available for evaluating non-point sources of pathogens derived 

from watersheds and catchments. 

• The L-THIA model (http://www.ecn.purdue.edu/run-off/lthianew/) combined with GISreferenced inputs from Digital Watershed are being used as tools to evaluate runoff of 

fecal coliform and fecal streptococcus (enterococci) in watersheds. Digital Watershed 

(http://www.iwr.msu.edu/dw/) allows the user to view the watershed tributary to any 

given point in the continental United States, on an 8-digit or (in parts of the Midwest) a 

12-digit HUC code level of detail. L-THIA calculates the surface and groundwater 

impacts of current land use, land use changes and potential best management practices 

(BMPs) for quality and quantity for the bacteria. L-THIA will be directly linked to 

STORET water quality and SSURGO soils databases within a year. In the Midwest it is 

also available as a web-based GIS tool at the 12-digit HUC code level through the 

watershed delineation tool at http://pasture.ecn.purdue.edu/~watergen/. 

• The SPARROW model (SPAtially Referenced Regression on Watershed attributes) 

(http://water.usgs.gov/nawqa/sparrow/index.html) is being used to investigate the sources 

and fate of fecal contamination in streams and to assess the effects of the spatial 

resolution of the stream network and landscape data on model parameters and 

predictions. SPARROW has been used to evaluate the following indicators: fecal 

coliforms, E. coli, C. perfringens, somatic coliphage, F+ RNA phage, and the bacterial 

pathogen Campylobacter. The explanatory data for the SPARROW models include land 

use and other data that describe the climatic, hydrologic, and physical conditions of the 

catchments. The models also reveal the effects of climate, soils, and instream processes 

on the transport of fecal contaminants. 

• LSPC is the Loading Simulation Program in C++, a watershed modeling system that 

includes streamlined Hydrologic Simulation Program Fortran (HSPF) algorithms for 

simulating hydrology, sediment, and general water quality on land as well as a simplified 

stream transport model. LSPC has been used in Alabama for developing pathogen 

TMDLs (see http://www.epa.gov/athens/wwqtsc/Toolbox-overview.pdf and 

http://www.epa.gov/ATHENS/wwqtsc/html/lspc.html). 

In addition to these models, a 1999 EPA report describes other potential models that can be used 

for evaluating non-point sources of biological contaminants from catchments. These include, for 

example, HSPF. HSPF is one of the models that is included in the BASINS3 watershed model 

system that is maintained by EPA (http://www.epa.gov/waterscience/BASINS/). 

References 

ASABE (American Society of Agricultural and Biological Engineers). 2006. Modeling bacteria 

fate and transport in watersheds to support TMDLs. Proceedings from the ASAE Annual 

Meeting. Paper 062295. 

Boehm, AB; Keymer, DP; Shellenbarger, GG. 2005. An analytical model of enterococci 

inactivation, grazing, and transport in the surf zone of a marine beach. Water Research 39(15): 

3565-3578. 
U.S. Environmental Protection Agency Experts Scientific Workshop

June 2007 G-3 

Grant, SB; Kim, JH; Jones, BH; Jenkins, SA; Wasyl, J; Cudaback, C. 2005. Surf zone 

entrainment, along-shore transport, and human health implications of pollution from tidal outlets. 

Journal of Geophysical Research 110: C10025. 

Liu, L; Phanikumar, M; Molloy, S; Whitman, RL; Shively, D; Nevers, D; Schwab, D; Rose, J. 

2006. Modeling the transport and inactivation of E. coli and enterococci in the near-shore region 

of Lake Michigan. Environmental Science and Technology 40(16): 5022-5028. 

US EPA (U.S. Environmental Protection Agency). 1999. Review of Potential Modeling Tools 

and Approaches to Support the BEACH Program. EPA-823-R-99-002. Washington, DC: US 

EPA.