OFFICE OF WATER 820-F-12-058

Recreational Water Quality 

Criteria
NOTICES

This document has been drafted and approved for publication by the Health and Ecological 

Criteria Division, Office of Science and Technology, United States (U.S.) Environmental 

Protection Agency (EPA), and is approved for publication. Mention of trade names or 

commercial products does not constitute endorsement or recommendation for use. 

FOREWORD

Under §304(a)(l) of the Clean Water Act (CWA) of 1977 (P.L. 95-217) the Administrator of the 

EPA is directed to develop and publish water quality criteria (WQC) that accurately reflect the 

latest scientific knowledge on the kind and extent of all identifiable effects on health and welfare 

that might be expected from the presence of pollutants in any body of water, including 

groundwater. CWA §304(a)(9) directs the Administrator to publish new or revised WQC for 

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

based on the results of the studies conducted under §104(v) of the CWA, for the purpose of 

protecting human health in coastal recreation waters. Coastal recreation waters (“coastal waters”) 

are defined under §502(21) of the CWA as the Great Lakes and marine coastal waters (including 

coastal estuaries) that are designated by a state for use for swimming, bathing, surfing, or similar 

water contact activities. This document includes WQC recommendations for pathogens and 

pathogen indicators based on the results of the studies conducted under §104(v) of the CWA for 

both coastal recreational waters and other waters designated for primary contact recreation 

(“non-coastal waters”). As such this document is published pursuant to §304(a)(1) and 

§304(a)(9) of the CWA and it includes EPA’s recommended final recreational water quality

criteria (RWQC) for the protection of primary contact recreation in both coastal and non-coastal 

waters, based upon consideration of all available information relating to the effects of fecal 

contamination on human health, including the studies conducted under CWA §104(v). 

The term "water quality criteria" is used in two sections of the CWA: §304 (i.e., §304(a)(1) and 

304(a)(9)) and §303(c)(2). The term has a different program impact in each section. CWA §304 

criteria are developed by EPA based on the latest scientific information on the relationship that 

the effect of a constituent concentration has on particular aquatic species and/or human health. 

They are a non-regulatory, scientific assessment of effects on human health or aquatic life. The 

criteria recommendations presented in this document are such scientific assessments. The term 

“criteria,” as used in §303(c)(2), refers to elements of state water quality standards (WQS), 

expressed as constituent concentrations, levels, or narrative statements, representing a quality of 

water that supports a particular use. When criteria are met, water quality will generally protect 

the designated use. If WQC uses are adopted by a state or promulgated by EPA WQS under 

§303, they become the relevant standard for developing permit limits, assessing waters, and 

developing total maximum daily loads (TMDLs) for waters that do not meet the WQS. It is not 

until their adoption as part of state WQS that 303(c) criteria have a regulatory impact.

In establishing WQC for adoption in WQS, states could establish numerical values based on 

EPA’s §304(a) recommendations, or the 304(a) recommendations modified to reflect sitespecific conditions, or other scientifically defensible methods. In all cases, the criteria adopted by

states must be scientifically defensible and protective of designated uses. Guidelines to assist in 
modifying the criteria recommendations presented in this document are contained in the Water 

Quality Standards Handbook (U.S. EPA, 2012a). This handbook and additional guidance on the 

development of WQS and other water-related programs of this agency have been developed by

EPA. 

The contents of this final document include only EPA recommendations and additional 

information for use by states in developing or implementing RWQC. This document does not 

establish or affect legal rights or obligations. It does not establish a binding norm and cannot be 

finally determinative of the issues addressed. Agency decisions to approve or disapprove WQC 

adopted into state WQS in any particular situation will be made by applying the CWA and EPA 

regulations on the basis of specific facts presented and currently available scientific information. 
Table of Contents

Notices................................................................................................................................ 2

Foreword............................................................................................................................. 2

Appendices.......................................................................................................................... 5

Acronyms............................................................................................................................ 6

1.0 Executive Summary...................................................................................................... 1

1.1 Contents of this Document ........................................................................................1

1.2 EPA’s Recommended §304(a) Water Quality Criteria..............................................4

2.0 Applicability and Scope of the 2012 RWQC................................................................ 6

3.0 Basis of the 2012 RWQC.............................................................................................. 9

3.1 Indicators of Fecal Contamination.............................................................................9

3.1.1 Enumeration Methods in RWQC..................................................................... 10

3.2 Linking Water Quality with GI Illness and Health..................................................12

3.2.1 Historical Perspectives in Criteria Development............................................. 12

3.2.2 Human Health Endpoint .................................................................................. 13

3.2.3 Relationship Between Water Quality and Illness ............................................ 15

3.2.4 Developing Enterococci Measured by Culture Criteria and Comparable Values 

for Culturable E. coli and Enterococcus spp. Measured by qPCR............. 20

3.3 Scope of Protected Population.................................................................................29

3.4 Waterbody Type ......................................................................................................32

3.5 Sources of Fecal Contamination..............................................................................34

3.5.1 Zoonotic Potential............................................................................................ 35

3.5.2 Differential Health Risks from Human versus Nonhuman Sources................ 35

3.6 Expression of Criteria ..............................................................................................37

3.6.1 EPA’s 1986 Ambient Water Quality Criteria for Bacteria .............................. 37

3.6.2 The 2012 RWQC ............................................................................................. 38

3.6.3 Criteria Magnitude, Duration, and Frequency for CWA Purposes.................. 39

3.6.4 Application of State WQS based on EPA’s 2012 RWQC for NPDES 

Permitting, 303(d) Listing, TMDL Development, and Beach Notification 

Programs..................................................................................................... 40

3.6.5 Practical Considerations for Implementing State WQS based on the 2012 

RWQC........................................................................................................ 41

4.0 Recreational Water Quality Criteria ........................................................................... 41

5.0 Supplemental Elements for Enhanced Protection of Recreational Waters................. 42

5.1 Beach Action Value (BAV).....................................................................................43

5.2 Rapid Method: Enterococcus spp. as measured by qPCR (EPA Method 1611)....43

6.0 Tools to Support States and Tribes in Evaluating and Managing Recreational Waters 

and for Considering Alternative Water Quality Criteria........................................... 45

6.1 Tools for Evaluating and Managing Recreational Waters.......................................46

6.1.1 Sanitary Survey................................................................................................ 46

6.1.2 Predictive Models ............................................................................................ 47

6.2 Tools for Developing Alternative Criteria...............................................................47

6.2.1 Epidemiological Studies .................................................................................. 48

6.2.2 Quantitative Microbial Risk Assessment......................................................... 49

6.2.3 Alternative Indicators or Methods................................................................... 50

References......................................................................................................................... 52
Appendices

APPENDIX A. Translation of 1986 Criteria Risk to Equivalent Risk Levels for Use with New 

Health Data Developed Using Rapid Methods for Measuring Water Quality, U.S. EPA 2011.

APPENDIX B. NEEAR data used for comparison to EPA's epidemiological studies from the late 

1970s and early 1980s

APPENDIX C. Analysis of NEEAR culture data: combining marine and fresh waters.
Acronyms

BAV beach action value

BEACH Beaches Environmental Assessment and Coastal Health

cce calibrator cell equivalent

CDC U.S. Centers for Disease Control and Prevention 

cfu colony forming units

CI confidence interval

CSO combined sewer overflow

Ct cycle threshold 

CWA 

DNA

Clean Water Act 

deoxyribonucleic acid

E. coli Escherichia coli

EPA Environmental Protection Agency

E.U. European Union

FIB fecal indicator bacteria, which includes fecal coliforms, E. coli, enterococci, or 

Enterococcus spp.

GI gastrointestinal

GM geometric mean

HCGI highly credible gastrointestinal illness

mL milliliters 

MPN most probable number

NEEAR National Epidemiological and Environmental Assessment of Recreational Water 

NGI NEEAR-GI illness

NOAEL no observed adverse effect level

NPDES National Pollutant Discharge Elimination System

PC prospective cohort

PCR polymerase chain reaction

QMRA quantitative microbial risk assessment 

qPCR quantitative polymerase chain reaction

RCT randomized control trial

RT reverse transcriptase

RWQC recreational water quality criteria

SCCWRP

SSM

Southern California Coastal Water Research Project

single sample maximum

States states, tribes, and territories of the United States

STV statistical threshold value

TMDL total maximum daily load

TSM technical support material

U.S. United States 

WERF Water Environment Research Foundation

WHO 

WQBEL

WQC

WQS

World Health Organization (United Nations) 

water quality-based effluent limits

water quality criteria 

water quality standard(s)

WWTP wastewater treatment plant
1

1.0 Executive Summary

The CWA, as amended by the Beaches 

Environmental Assessment and Coastal Health 

(BEACH) Act in 2000, requires the U.S. EPA 

under §104(v) and §304(a)(9) to conduct studies 

associated with pathogens and human health 

and to publish new or revised WQC

recommendations for these pathogens and 

pathogen indicators based on those studies. This 

document was prepared following an extensive 

review of the available scientific literature and 

evaluation of new information from studies EPA 

conducted pursuant to CWA §104(v) and after 

public notice and comment on the 2011 draft 

RWQC. This document provides EPA’s 

recommended CWA §304(a) RWQC for states, 

lays out the science related to the 2012 RWQC, 

describes how these scientific findings were used 

during the development of the 2012 RWQC, and 

describes the water quality methods associated 

with the 2012 RWQC. It also includes 

information for states that would prefer to adopt 

WQC that differ from EPA’s 2012 RWQC 

recommendations. The additional information is 

intended to assist those states in developing 

alternative WQC that are scientifically defensible 

and protective of the primary contact recreational 

use.

1.1 Contents of this Document

Section 1 provides an executive summary and 

introductory information regarding the history of 

EPA’s WQC recommendations and the CWA. 

Section 2 provides an overview of the most 

recent scientific findings used to support the 

criteria and explains the scope of the 2012 

RWQC. The studies and projects EPA conducted 

as part of the 2012 RWQC development are 

described in the Critical Path Science Plan and 

other documents (U.S. EPA 2010a, 2010b; see 

appendices A, B, and C). The projects align into 

the following major categories: epidemiological 

studies, QMRA, site characterization studies, indicators/methods development and validation 

What is new or different in the 2012 RWQC) 

compared to the 1986 Criteria?

 The 2012 RWQC consists of both a 

geometric mean (GM) and a statistical 

threshold value (STV).

 The 2012 RWQC are now comprised of a 

magnitude, duration, and frequency of 

excursion for both the GM and STV. 

 The 2012 RWQC were developed based on 

the studies utilized in creating the 1986 

WQC as well as more recent scientific 

information including the National 

Epidemiological and Environmental 

Assessment of Recreational Water 

(NEEAR) data.

 EPA is including two sets of recommended 

criteria values that protect the designated 

use of primary contact recreation.

 The criteria recommendations for marine 

and fresh waters are no longer based on 

different illness rates.

 There are no longer different criteria 

recommendations for different use 

intensities. 

 EPA is providing information for states that 

want to adopt WQS based on a quantitative 

polymerase chain reaction (qPCR) method 

that EPA has developed and validated.

 EPA is providing states with Beach Action 

Values (BAVs) for use in notification 

programs. 

 EPA is providing additional information on 

tools for assessing and managing 

recreational waters, such as predictive 

modeling and sanitary surveys.

 EPA is providing information on tools for 

developing alternative RWQC on a sitespecific basis, such as epidemiological 

studies in both marine and fresh waters and 

quantitative microbial risk assessment 

(QMRA). 
2

studies, modeling, level of public health protection, and literature reviews. EPA also considered 

relevant studies conducted by independent researchers.

Section 3 describes the science that was considered during the development of the 2012 RWQC. 

This includes indicators of fecal contamination and enumeration methods, linking water quality

and health, scope of protected populations, types of waterbodies, sources of fecal contamination, 

and the expression of the 2012 RWQC. 

In the 2012 RWQC, EPA recommends using the fecal indicator bacteria (FIB) enterococci and 

Escherichia coli (E. coli) as indicators of fecal contamination for fresh water and enterococci for 

marine water. Section 3.1 explains that EPA recommends culture-based methods be used to 

detect the presence of either indicator and that states adopt standards for these indicators as 

measured by culture methods, expressed in colony forming units (cfu). Section 3.1 also includes 

information and recommendations for states that would like to adopt standards for Enterococcus 

spp., as measured by a rapid qPCR method. Because of the limited experience with this method 

and concerns with interference, EPA recommends that states evaluate qPCR performance in 

ambient waters in which it would be employed prior to developing new or revised standards 

based on the qPCR method. EPA will provide separate guidance on how to evaluate qPCR 

performance.

Section 3.2.1 provides a historical overview of how WQC that protect the designated use of 

primary contact recreation have changed throughout the past century. Scientific advancements in 

microbiological, statistical, and epidemiological methods have demonstrated that culturable 

enterococci and E. coli are better indicators of fecal contamination than the previously used 

general indicators, total coliforms and fecal coliforms. Fecal contamination in recreational waters 

is associated with an increased risk of gastrointestinal (GI) illness and less often identified 

respiratory illness. As such, fecal contamination and its indicators are considered “pathogen 

indicators,” as defined by §502(23) of the CWA.

Section 3.2.2 discusses the various human health endpoints that EPA and others have examined 

in epidemiological studies. Additionally, EPA’s two different GI illness definitions are 

discussed. EPA’s 1986 criteria recommendations correspond to a level of water quality that is 

associated with an estimated illness rate expressed in terms of the number of highly credible 

gastrointestinal illnesses (HCGI) per 1,000 primary contact recreators. EPA’s NEEAR study

used a more comprehensive definition of GI illness, referred to as NEEAR-GI (NGI). Because 

NGI is broader than HCGI (i.e., NGI includes diarrhea without the requirement of fever), more 

illness cases were reported and associated with aquatic recreation in the NEEAR study using the 

NGI definition of illness, at the same level of water quality observed using the previous illness 

definition (i.e., HCGI).

Section 3.2.3 provides an overview of the epidemiological studies conducted by EPA as part of 

the NEEAR study. Seven studies were performed at temperate beaches primarily impacted by

wastewater treatment plants (WWTPs) discharging effluent from treated municipal sewage. 

Three of those beaches were marine water and four were fresh water. Studies also were 

performed at two additional beaches: a temperate beach in Surfside, South Carolina impacted by 
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urban runoff sources, and a tropical beach in Boquerón, Puerto Rico. EPA also considered 

epidemiological studies from other research efforts in developing these recreation criteria. 

Section 3.2.4 describes the process EPA used to derive the culturable enterococci criterion value 

and comparable illness rates for E. coli measured by culture and Enterococcus spp. measured by

qPCR thresholds. Based on the selected illness rates, EPA derived qPCR values for 

Enterococcus spp. comparable to the culture-based values for both marine and fresh waters, 

computed from the regression model derived from the NEEAR epidemiological study in marine 

and fresh waters. 

Section 3.3 discusses subpopulations that participated in recreational activities in the NEEAR 

study. Children aged ten years and younger showed a higher rate of illnesses than adults in fresh 

water, but did not for marine water exposures. The sample sizes in the epidemiological data were 

not large enough to evaluate potential differences for persons over 55 years of age, pregnant 

women, or other vulnerable individuals. EPA’s 2012 RWQC recommendations are based on the 

general population, which includes children. Because children may be more exposed and/or more 

sensitive to pathogens in recreational waters, it is important to have effective risk communication 

outreach to mitigate their exposure to contaminated recreational waters. EPA is also providing 

BAVs that are the 75th percentile value of a water quality distribution based on these new 

criteria. These values, while not recommended for determining use attainment, are provided for 

states to use as a precautionary tool to provide an early alert to beachgoers, including families 

with children. 

Section 3.4 describes EPA’s review of the available information comparing coastal (including 

Great Lakes and marine) and non-coastal (including flowing and non-flowing inland) waters to 

evaluate whether EPA should recommend that states use the 2012 RWQC in developing 

recreational WQS in all waterbody types. Based on EPA’s evaluation of the body of information 

described in section 3.4, EPA recommends the 2012 RWQC for use in both coastal and noncoastal waterbodies. While some differences may exist between coastal and non-coastal waters, 

the recommended indicators, enumeration methods, and criteria values are scientifically

defensible and protective of the primary contact use in coastal and non-coastal waters. Therefore, 

EPA’s 2012 RWQC recommendations are national recommendations for all waterbody types 

designated for swimming, bathing, surfing, or similar water contact activities (referred to 

throughout this document as “primary contact recreational use”).

Section 3.5 describes EPA’s evaluation of how different fecal sources may influence risks to 

human health. Human pathogens are often present in animal fecal matter, and thus, there are 

risks associated with recreating in animal-impacted waters. However, quantifying that level of 

risk associated with animal fecal material is difficult, and the methods necessary to distinguish 

between human and nonhuman fecal sources, with the appropriate level of confidence, are still 

under development. Thus, EPA believes that the 2012 RWQC are protective of public health, 

regardless of the source of fecal contamination. EPA is not developing recommendations that 

take source of fecal contamination into account. Rather, states interested in adopting different 

standards to address the variability in human health risks associated with different sources of 

fecal contamination on a site-specific basis should refer to section 6, where EPA describes 

methods for developing site-specific standards.
4

Section 3.6 describes the statistical expression of the 2012 RWQC. As part of the 2012 RWQC, 

EPA is recommending criteria expressed using two components: the GM and the STV. For each 

of the sets of criteria values, EPA computed the STV based on the water quality distribution 

observed during EPA’s epidemiological studies. The STV approximates the 90th percentile of the 

water quality distribution and is intended to be a value that should not be exceeded by more than 

10% of the samples used to calculate the GM. Because densities of FIB are highly variable in 

ambient waters, distributional estimates are more robust than single point estimates.

Section 4 presents EPA’s recommended WQC consisting of the magnitude, duration, and 

frequency of excursions for enterococci and E. coli as measured by culture-based methods. EPA 

provides two sets of recommended criteria, each of which correspond to two different illness 

rates. The designated use of primary contact recreation would be protected if either set of criteria 

recommendations in section 4.0 are adopted into state WQS and approved by EPA. 

Section 5 provides additional elements for states’ use to enhance public health protection. These 

elements include BAVs and values for Enterococcus spp. as measured by qPCR.

Section 6 describes the additional tools that can be used to manage recreational waters and derive 

site-specific criteria. The tools listed in section 6 will not only provide states with additional 

tools for revising their WQS for primary contact recreation, but will also help states gain a better 

understanding of their surrounding watersheds and of appropriate management strategies. 

Section 6.1 describes sanitary surveys and provides an overview of predictive models. Section 

6.2 provides an overview of options for states to develop site-specific criteria. Tools described in 

section 6 will be further developed and explained in technical support material(s) (TSM) that are 

being developed by EPA. EPA will publish multiple TSM focusing on these tools as they are 

available. 

Appendices are also included that describe data and information used to evaluate the linking of 

water quality and health. Appendix A provides a translation of the illness rates associated with 

the1986 criteria to equivalent illness rates for use with new health data developed using rapid 

methods for measuring water quality. Appendix B includes a comparison of NEEAR culturable 

water quality and health effects to EPA’s epidemiological studies from the 1980s. Appendix C is 

an analysis of the NEEAR marine and fresh water data for culturable enterococci.

1.2 EPA’s Recommended §304(a) Water Quality Criteria 

An important goal of the CWA is to protect and restore waters for swimming. Section 304(a) of 

the CWA directs EPA to publish and, from time to time, revise the WQC to accurately reflect the 

latest scientific knowledge on the identifiable effects on health and welfare that might be 

expected from the presence of pollutants in any body of water, including groundwater. These 

recommendations are referred to as §304(a) criteria. Under §304(a)(9) of the CWA, EPA is 

required to publish WQC for pathogens and pathogen indicators based on the results of the 

studies conducted under §104(v), for the purpose of protecting human health in coastal recreation 

waters, which are defined as marine and Great Lakes waters designated under CWA §303(c) for 
5

use for swimming, bathing, surfing, or similar water contact activities (referred to throughout the 

document as primary contact recreation). 

CWA §304(a) criteria do not reflect consideration of economic impacts or the technological 

feasibility of meeting pollutant concentrations in ambient water. The 2012 RWQC 

recommendations are based on data and scientific conclusions on the relationship between FIB 

density and GI illness. These criteria recommendations may be used by the states to establish 

WQS, and if adopted in state WQS and approved by EPA, will ultimately provide a basis for 

controlling the discharge or release of pollutants and assessing waterbodies. Additionally, the 

criteria also provide guidance to EPA when promulgating WQS for states under CWA §303(c), 

when such actions are necessary. 

When states adopt new or revised WQC into WQS, they must be scientifically defensible and 

protective of the designated uses of the waterbodies. EPA’s regulation 40 CFR §131.11(b)(1) 

provides that “In establishing criteria, states should (1) Establish numerical values based on (i) 

304(a) Guidance; or (ii) 304(a) Guidance modified to reflect site-specific conditions; or (iii) 

Other scientifically defensible methods.” EPA’s 2012 RWQC recommendations describe the 

desired ambient water quality conditions to support the designated use of primary contact 

recreation. 

EPA has a long history of using FIB for protecting people who use recreational waters. In the 

1960s, the U.S. Public Health Service recommended using fecal coliform as FIB, and EPA 

recommended fecal coliform bacteria in 1976 (U.S. EPA, 1976). In the late 1970s and early 

1980s, EPA conducted epidemiological studies that evaluated the use of several organisms as 

possible indicators of fecal contamination, including fecal coliform, E. coli, and enterococci 

(Cabelli et al., 1983; Dufour, 1984). These studies showed that enterococci are good predictors 

of GI illnesses in marine and fresh recreational waters, and E. coli are good predictors of GI 

illnesses in fresh waters. As a result, EPA published EPA’s Ambient Water Quality Criteria for 

Bacteria – 1986 (hereafter referred to as “the 1986 criteria”). The 1986 criteria document 

includes EPA recommendations to use enterococci for marine and fresh recreational waters (a 

GM of 33 enterococci cfu per 100 mL in fresh water and 35 enterococci cfu per 100 mL in 

marine water) and E. coli for fresh recreational waters (a GM of 126 E. coli cfu per 100 mL) 

(U.S. EPA, 1986). The 1986 recommendations replaced EPA’s previously recommended fecal 

coliform criteria of 200 fecal coliform cfu per 100 mL (U.S. EPA, 1976). In the 2004 BEACH 

Act Rule, EPA promulgated WQS for coastal recreational waters in the 21 states that had not yet 

adopted standards as protective of human health as EPA’s 1986 criteria recommendations (U.S. 

EPA, 2004).

Like past EPA recommendations for primary contact recreational uses, the 2012 criteria are 

based on indicators of fecal contamination. A pathogen indicator, as defined in §502(23) of the 

CWA, as amended by the BEACH Act, is defined as follows: “a substance that indicates the 

potential for human infectious disease.” Most strains of enterococci and E. coli do not cause 

human illness (that is, they are not human pathogens); rather, they indicate the presence of fecal 

contamination. The basis for recommending criteria that use bacterial indicators of fecal 

contamination is that pathogens often co-occur with indicators of fecal contamination. 
6

EPA recommends that states make a risk management decision regarding illness rate which will 

determine which set (based on illness rate selected) of criteria values are most appropriate for 

their waters. The designated use of primary contact recreation would be protected if either set of 

criteria (including a GM and related STV) shown in Table 1 is adopted into state WQS and 

approved by EPA. EPA recommends states apply this risk management decision statewide. Note 

that criteria for either enterococci or E. coli can be used for fresh waters. Selecting a mixture of 

the GM and STV that are associated with different illness rates is not scientifically defensible 

since the STV is derived from the water quality distribution as defined by the GM.

Table 1. Recommended 2012 RWQC.

Criteria 

Elements

Estimated Illness Rate (NGI): 

36 per 1,000 primary contact 

recreators

OR

Estimated Illness Rate (NGI): 

32 per 1,000 primary contact 

recreators

Magnitude Magnitude

Indicator 

GM

(cfu/100 mL)a

STV

(cfu/100 mL)a

GM

(cfu/100 mL)a

STV

(cfu/100 mL)a

Enterococci 

– marine 

and fresh 35 130 30 110

OR

E. coli

– fresh 126 410 100 320

Duration and Frequency: The waterbody GM should not be greater than the selected GM 

magnitude in any 30-day interval. There should not be greater than a ten percent excursion 

frequency of the selected STV magnitude in the same 30-day interval. 

a

EPA recommends using EPA Method 1600 (U.S. EPA, 2002a) to measure culturable enterococci, or another 

equivalent method that measures culturable enterococci and using EPA Method 1603 (U.S. EPA, 2002b) to measure 

culturable E. coli, or any other equivalent method that measures culturable E. coli.

EPA is also providing information for developing site-specific criteria that measure enterococci 

using EPA’s Enterococcus spp. qPCR Method 1611 (U.S. EPA, 2012b). For the purposes of 

beach notification, EPA encourages the use of a BAV, which approximates the 75th percentile of 

a water-quality distribution based on the desired GM. See section 5.1 and 5.2 for ‘Supplemental 

Elements.’

2.0 Applicability and Scope of the 2012 RWQC

EPA’s 2012 RWQC are for all waters in the United States including marine, estuarine, Great 

Lakes, and inland waters that are designated for primary contact recreation. Primary contact 

recreation typically includes activities where immersion and ingestion are likely and there is a 

high degree of bodily contact with the water, such as swimming, bathing, surfing, water skiing, 

tubing, skin diving, water play by children, or similar water-contact activities. 

Since EPA last published recommended RWQC in 1986, scientific advances have been made in 

the areas of epidemiology, molecular biology, microbiology, QMRA, and methods of analytical 

assessment. EPA’s evaluation and consideration of these new scientific and technical advances 
7

in the development of the 2012 RWQC strengthens the scientific foundation of EPA’s criteria 

recommendations to protect the designated use of primary contact recreation. 

In accordance with §104(v) of the CWA, as amended by the BEACH Act, EPA developed and 

implemented a research plan to ensure that state-of-the-art science would be available to support 

the development of the 2012 RWQC recommendations. To facilitate the identification of 

research required to develop the 2012 RWQC, EPA held a five-day scientific workshop in 2007 

to obtain a broad range of external scientific input. Forty-three domestic and international experts 

provided input on near-term research requirements that would be needed in the next two to three 

years to further develop the scientific foundation of new 2012 RWQC and implementation 

guidance. The report from this workshop, Report of the Experts Scientific Workshop on Critical 

Research Needs for the Development of New or Revised Recreational Water Quality Criteria 

(U.S. EPA, 2007a), included chapters from the seven breakout groups, including: (1) approaches 

to criteria development, (2) pathogens, pathogen indicators, and indicators of fecal 

contamination, (3) methods development, (4) comparison of the risks of different contamination 

sources to humans, (5) acceptable risk, (6) modeling applications for criteria development and 

implementation, and (7) implementation realities.

The report from the Experts Scientific Workshop provided a core part of the information EPA 

used to develop the Critical Path Science Plan for the Development of New or Revised 

Recreational Water Quality Criteria (U.S. EPA, 2007b). The Critical Path Science Plan, which 

was peer reviewed, includes 32 projects that EPA completed for the development of the 2012 

RWQC. All projects included in the Critical Path Science Plan, were completed and considered 

during the process of developing the 2012 RWQC. Projects included epidemiological studies to 

provide data correlating illness with indicators, site-characterization studies to facilitate QMRA, 

indicator and methods development and validation, water quality modeling, literature reviews, 

and additional studies to support the recommended criteria values and associated level of public 

health protection. EPA specific-projects included efforts in the following areas:1

 Epidemiological Studies and QMRA

o 2003–2004 Temperate fresh water: four beach sites on the Great Lakes

o 2005–2007 Temperate marine: three beach sites: Alabama, Rhode Island, 

Mississippi

o 2009 sites: Puerto Rico (tropical), South Carolina (urban runoff)

o QMRA for fresh water impacted by agricultural animals

 Site Characterization Studies

o Development of site characterization tool for QMRA applications

o Expanded data collection at epidemiological study locations to support modeling 

and QMRA

o Site selection evaluation for Puerto Rico and South Carolina epidemiological 

studies

o Study to better understand spatial and temporal variability

o Pilot sanitary survey in the Great Lakes

 Indicators/Methods Development and Validation Studies

 

1 EPA’s Recreational Water Quality Criteria website: 

http://water.epa.gov/scitech/swguidance/standards/criteria/health/recreation/
8

o Evaluate multiple indicator/method combinations to develop quantifiable 

relationships

o Study the effects of sample holding time, storage, and preservation

o Performance of qPCR signal in ambient water and wastewater (fate and transport)

o Develop, refine, validate, and publish new ambient and wastewater methods

o Publish a rapid test method that has been validated by multiple laboratories

o Evaluate the suitability of individual combinations of indicators and methods for 

different CWA purposes

o Develop new and/or evaluate previously published source-identifying assays

o Evaluate genetic markers for human, bovine, chickens, and gulls

 Modeling

o Pilot test Virtual Beach Model Builder

o Refine and validate existing models for fresh water beaches

o Refine and validate other existing models for marine beaches

o Develop technical protocol for site-specific application of predictive models

 Recommended Level of Public Health Protection

o Evaluate 1986 recommendations for culturable enterococci and E. coli compared 

to data collected in EPA studies and non-EPA studies

o Evaluate applicability of EPA Great Lakes epidemiological data to inland waters

o Evaluate available children’s health data 

 Literature Reviews

o State-of-the-science reviews of published studies to characterize relative risk from 

different fecal sources

o State-of-the-science review on occurrence and cross-infectivity of specific 

pathogens associated with animals

o Comparison and evaluation of epidemiological study designs of health effects 

associated with recreational water use

EPA conducted epidemiological investigations at U.S. beaches in 2003, 2004, 2005, 2007, and 

2009, and as a group these investigations are referred to as the NEEAR study. The NEEAR study

enrolled 54,250 participants, encompassed nine locations, and collected and analyzed numerous 

samples from a combination of fresh water, marine, tropical, and temperate beaches (U.S. EPA, 

2010a; Wade et al., 2008, 2010). 

EPA provided assistance and technical support to several additional projects: the Water 

Environment Research Foundation (WERF) workshop, Experts Scientific Workshop on Critical 

Research and Science Needs for the Development of Recreational Water Quality Criteria for 

Inland Waters, to consider the significance of the differences between inland and coastal 

recreational waters (WERF, 2009); and the Southern California Coastal Water Research Project

(SCCWRP) for epidemiological studies at the California beaches of Doheny (Colford et al., 

2012), Avalon, and Malibu.

Finally, EPA also considered other research and studies relevant to the development of the 2012 

RWQC. These studies included epidemiological studies, research on the development of new and 

improved water quality indicators and analytical methods, approaches to QMRA, water quality

predictive modeling, and microbial-source tracking. EPA considered all available data from the 
9

open literature and water quality data received from SCCWRP on studies they conducted with 

technical support from EPA at Doheny, Avalon, and Malibu beaches. These SCCWRP studies 

were generally consistent with the NEEAR study findings. These studies are discussed further in 

section 3 of this document.

3.0 Basis of the 2012 RWQC 

To develop the 2012 RWQC, EPA considered indicators of fecal contamination, methods for 

detecting and enumerating such indicators, the relationship between the occurrence of FIB in the 

water and their human health effects, the populations to be protected by the 2012 RWQC, 

waterbody types, sources of fecal contamination, and how the 2012 RWQC should be expressed 

in terms of a magnitude, duration, and frequency. EPA also considered all of the comments 

received on the December 2011 draft RWQC document (EPA, 2011). EPA’s responses to 

comments will be available separately. In response to comments asserting that the allowable 

illness rate in the 2011 draft RWQC was too high, EPA conducted additional analyses of the 

NEEAR data. These analyses and EPA’s recommendations are presented in sections 3.0 and 4.0. 

3.1 Indicators of Fecal Contamination

Public health agencies have long used FIB to identify potential for illness resulting from 

recreational activities in surface waters contaminated by fecal pollution. EPA based its 1986 

criteria for recreational marine and fresh waters on observed illness levels in swimmers and 

corresponding levels of bacterial indicators of fecal contamination, specifically enterococci and 

E. coli for fresh water and enterococci for marine water. Although most strains of FIB are not 

pathogenic, they demonstrate characteristics that make them good indicators of fecal 

contamination (i.e., often of fecal origin and simple methods of detection) and thus, indirectly

indicate the potential presence of fecal pathogens capable of causing GI illnesses. As such, FIB 

are “pathogen indicators” as that term is defined by CWA §502(23) –“a substance that indicates 

the potential for human infectious diseases” – even though they are not generally thought of as 

“pathogen indicators,” as that term is typically used by the scientific community as direct 

indicators of pathogens. EPA is not publishing criteria for “pathogens” because the state of the 

science was not sufficient at the time of completion of these RWQC. In addition, there are 

numerous pathogens that cause the full range of illnesses associated with primary contact 

recreation. Pathogen-specific enumeration methods for environmental waters were not available 

at the time of the NEEAR study, and thus health relationships with specific pathogens were not 

established (U.S. EPA, 2010c, 2010d).

Microorganisms that are potential indicators of fecal contamination are normally present in fecal 

material. Not all of these indicators, however, have a clear relationship to illness rates observed 

in epidemiological studies. As discussed in section 3.2.3, two microorganisms that have 

consistently performed well as indicators of illness in sewage-contaminated waters during 

epidemiological studies are enterococci in both marine and fresh water and E. coli in fresh water 

measured by culture (Prüss, 1998; Wade et al., 2003; Zmirou et al., 2003). Additionally, two 

recent epidemiological studies also demonstrate the utility of E. coli as an indicator as 

recommended in the 1986 criteria (Marion et al., 2010; Wiedenmann, 2006). Together the 

available body of information supports EPA’s 2012 RWQC recommendations to use enterococci 
10

and E. coli as indicators of fecal contamination. See section 6.2.3 for discussion of the use of 

alternative indicators, such as E. coli measured by qPCR, which EPA has not specifically 

included in the 2012 RWQC. 

3.1.1 Enumeration Methods in RWQC

Indicators of fecal contamination are detected and enumerated using a variety of methods. Thus, 

the chosen indicator and method combination is critical for determining a criterion value. The 

important linkage between the organism and the method is captured throughout this document by

the use of the term “indicator/method” to refer to this combination. 

FIB can be enumerated using various analytical methods including those in which the organisms 

are grown (cultured) and those in which their deoxyribonucleic acid (DNA) is extracted from an 

environmental sample, amplified, and quantified (using qPCR). These different enumeration 

methods result in method-specific units and values. One culture-based method, membrane 

filtration, results in the number of colonies that arise from bacteria captured on the membrane 

filter per volume of water filtered. One colony can be produced from one or several cells 

(clumped cells in the environmental sample). Another culture-based method, the defined 

substrate method, produces a most probable number (MPN) per volume. MPN analyses estimate 

the number of organisms in a sample using statistical probability tables, hence the term “most 

probable number.” Bacterial densities MPN are based on the combination of positive and 

negative test tube results that can be read from an MPN table (U.S. EPA, 1978). Culture-based 

approaches for the enumeration of FIB, such as MPN and membrane filtration, generate results 

following the culturing of a particular microbe for 18–24 hours, and in the case of MPN do not 

result in a direct count or concentration density of the bacteria being enumerated but rather rely

on probabilities. Results from qPCR analyses are reported in units that are calculated based on 

the target DNA sequences from test samples relative to those in calibrator samples that contain a 

known quantity of target organisms (Haugland et al., 2005; Wade et al., 2010)2. 

The results from each of these enumeration techniques (i.e., culture and qPCR) depend on the 

method used. Each analytical technique focuses on different attributes of the fecal indicator and 

results in a “signal” specific to that technique. For example, culture-based methods 

fundamentally depend on the metabolic state (i.e., viability and activity) of the target organisms 

for effective enumeration. Only the culturable sub-set of the target indicator is detected using 

culture-based techniques. Alternatively, qPCR-based approaches detect specific sequences of 

DNA that have been extracted from a water sample, and results contain sequences from both 

viable and non-viable forms of the targeted indicator. In the context of the 2012 RWQC, the 

results for enterococci determined using the culture-based methods are not the same as the results 

for EPA’s Enterococcus spp. qPCR Method 1611 (U.S. EPA, 2012b). These results are not 

directly interchangeable and require an explanation of each method’s results, as they relate to the 

reported health effects (i.e., epidemiological relationships; see section 3.2). 

 

2 Note that in some EPA NEEAR study publications, the term calibrator cell equivalent (cce) has been shortened to 

cell equivalent (ce). EPA considers these terms to be synonymous and in all cases calibrator cells were used. EPA 

used the delta-delta comparative cycle threshold (Ct) calibration model for estimating cce or ce in all NEEAR study 

data (U.S. EPA, 2012b). 
11

FIB, such as enterococci and E. coli, enumerated by culture-based methods, have an association 

with GI illness from exposure to ambient recreational water as demonstrated previously (Cabelli 

et al., 1982; Cabelli, 1983; Calderon et al., 1991; Dufour 1984; Marion et al., 2010; Wade et al., 

2003, 2006, 2008, 2010; Wiedenmann et al., 2006). Wade et al. (2008, 2010) did not show a 

statistically significant correlation of illness rates with culturable enterococci as was shown in 

the studies conducted in the 1980s. However, the NEEAR study did reaffirm an association with 

health as indicated by increased illness above the 1986 criteria values. The early and more recent 

studies conducted by EPA and others therefore support the establishment of WQC based on 

culturable indicators (see section 3.2.4). Thus, culturable indicators are scientifically defensible 

and are retained as the basis for the 2012 RWQC. FIB enumerated by culture-based methods also 

provide a historical association with previous water-quality data in states that already have WQS 

based on those indicators. 

EPA is also providing information on how to use a more recently developed qPCR method. 

Enterococci measured by EPA’s Enterococcus spp. qPCR Method (U.S. EPA, 2012b) showed a 

statistically significant correlation with GI illness among primary contact recreators in both 

marine and fresh recreational waters impacted by human fecal contamination (Wade et al., 2006, 

2008, 2010). The technical literature demonstrates that enumeration of enterococci using this 

technique can provide results more rapidly than culture-based methods with results available the 

same day (Griffith and Weisberg, 2011). 

As with other methods, the qPCR methodology may be affected by interference3from substances 

in different environmental matrices such as surface waters. Mitigation approaches discussed in 

EPA’s Enterococcus spp. qPCR Method 1611 have been identified that show promise for 

reducing the effects of interference in particularly problematic water samples, including those 

that occurred in the tropical marine NEEAR study (Haugland et al., 2012; U.S. EPA, 2012b). 

Although the fresh water NEEAR study sites in the Great Lakes and four temperate marine 

beaches demonstrated minimal to no interference, EPA’s overall testing of this qPCR method 

with different types of ambient waters and use by other laboratories has been limited. 

Kinzelman et al. (2011) reported minimal incidences of unacceptable interference with EPA 

Enterococcus spp. qPCR Method 1611 in Great Lakes coastal waters using a more stringent 

definition of interference; however, increased incidences were observed in some inland water 

locations. The highest frequency of incidences was seen at sites that were dominated by nonpoint source pollution. Mitigation techniques, such as purification of the sample or follow-up 

sample extract dilution, were able to resolve the interference in some of the samples; however, 

these additional steps resulted in an increase in the amount of time necessary to generate results. 

Other researchers have also reported inhibition or other types of interference in samples using 

non-EPA qPCR methodologies (Noble et al., 2010). 

 

3

Interference is any process that results in lower quantitative estimates than expected or actual values. Interference 

can result from sample inhibition of the polymerase or binding of substances to the DNA, which prevents either the 

primers from binding or polymerase function. EPA Enterococcus spp. qPCR Method 1611 (U.S. EPA, 2012b) has a 

sample processing control assay that is performed on each sample to identify unacceptable levels of interference 

(defined as a 3-Ct unit shift compared to corresponding control samples).
12

EPA believes that overall testing of the qPCR method with different types of ambient waters, and 

by different laboratories, remains limited and anticipates that there may be situations at some 

locations where the performance of the qPCR method may be inconsistent. EPA therefore 

suggests that states evaluate the qPCR method with respect to laboratory performance and 

sample interference in their prospective waters prior to developing new or revised standards 

relying on this method. EPA will provide additional guidance on how to evaluate qPCR method 

performance at a later date. 

3.2 Linking Water Quality with GI Illness and Health 

This section discusses the information that EPA considered during the course of evaluating the 

association between measures of water quality and potential human health effects from exposure 

to fecal contamination. There are many scenarios where human-derived fecal contamination can 

impact a waterbody. The relationship between the presence of FIB and any of the enteric 

pathogens that cause illness in humans can be highly variable, but has been described 

mathematically as used in QMRA (Schoen and Ashbolt, 2010). The following four subsections 

describe the lines of evidence EPA used to derive recommended criteria levels. The historical 

perspectives subsection briefly discusses previous approaches to the development of WQC in the 

U.S. The human health endpoint subsection explains how the definition of illness is important for 

understanding the meaning of the associated 2012 RWQC illness rate levels. The water quality

and illness subsection presents the results of epidemiological studies that EPA considered when 

developing the 2012 RWQC. The criteria values development subsection discusses the basis of 

the 2012 RWQC values.

3.2.1 Historical Perspectives in Criteria Development

EPA’s previously recommended RWQC (i.e., the 1986 criteria) and the 2012 RWQC are based 

on the observed association between the density of FIB and GI illnesses. FIB levels have long 

served as the surrogate measure of fecal contamination and thus the presence of pathogens that 

are commonly associated with fecal material. 

In the 1960s, the U.S. Public Health Service recommended using fecal coliform bacteria as the 

indicator of primary contact with FIB. Studies conducted by the U.S. Public Health Service 

reported a detectable health effect when total coliforms density was about 2,300 per 100 mL 

(Stevenson, 1953). In 1968, the National Technical Advisory Committee translated the total 

coliform level to 400 fecal coliforms per 100 mL based on a ratio of total coliforms to fecal 

coliforms and then halved that number to 200 fecal coliforms per 100 mL (U.S. EPA, 1986). The 

National Technical Advisory Committee criteria for recreational waters were recommended by

EPA in 1976.

In the late 1970s and early 1980s, EPA conducted a series of epidemiological studies to evaluate 

several additional organisms as possible indicators of fecal contamination including E. coli and 

enterococci. These epidemiological studies showed that enterococci are a good predictor of GI 

illnesses in fresh and marine recreational waters, and E. coli is a good predictor of GI illnesses in

fresh waters (Cabelli et al., 1982; Cabelli, 1983; Dufour, 1984). 
13

The 1986 criteria values represented the desired ambient condition of the waterbody necessary to 

protect the designated use of primary contact recreation. Those values were selected in order to 

further carry forward the same level of water quality associated with EPA’s previous criteria 

recommendations to protect the primary contact recreation use, which were for fecal coliform 

(U.S. EPA, 1976). For that effort, the enterococci and E. coli criteria values from the existing 

fecal coliform criteria were translated using the GM values for the FIB established in the 

previous epidemiological studies (see Text Box 1, below) (Dufour and Schaub, 2007). The single 

sample maximum (SSM) component of the 1986 criteria was computed using the GM values and 

corresponding observed variances in the FIB obtained from water quality measurements taken 

during the epidemiological studies from the late 1970s and early 1980s. Four different SSM 

values (recommended to be used with different recreational use intensities) were provided and 

corresponded to different percentiles of the water quality distribution around the GM. 

The 1986 criteria values resulted in different water quality values and associated illness rates for 

marine and fresh waters because the marine and fresh water epidemiological studies reported 

different GMs for the FIB associated with the level of water quality corresponding to EPA’s 

fecal coliform criteria recommendations. 

Text Box 1. Translation of 1960s criteria to 1986 criteria.

For example, using the equation in Text Box 1, the marine enterococci 1986 criterion was 

calculated as follows:

B = 20 cfu per 100 mL (observed GM enterococci) 

C = 200 cfu per 100 mL (old fecal coliform criterion) 

D = 115 cfu per 100 mL (observed GM of fecal coliforms) 

Therefore, A = 35 cfu per 100 mL. 

Using the observed relationships between the FIB densities and GI illness, EPA estimated in 

1986 that the predicted level of illness associated with the criteria was 8 HCGI per 1,000 primary

contact recreators in fresh water (see section 3.2.2) and 19 HCGI per 1,000 primary contact 

recreators in marine waters (U.S. EPA, 1986).

3.2.2 Human Health Endpoint

EPA’s 1986 criteria values correspond to a level of water quality associated with an estimated 

illness rate that is expressed in terms of the number of HCGI. The HCGI case definition is “any

one of the following unmistakable or combinations of symptoms [within eight to ten days of 

The 1986 criteria values (A) were derived as follows

 A = (B*C) / D

Where

B is the observed GM enterococci (from epidemiological studies)

C is the criterion for fecal coliform (200 cfu per 100 mL)

D is the observed GM fecal coliform (from epidemiological studies)
14

swimming]: (1) vomiting (2) diarrhea with fever or a disabling condition (remained home, 

remained in bed or sought medical advice because of symptoms), (3) stomachache or nausea 

accompanied by a fever.”

EPA’s NEEAR epidemiological studies used a different and updated definition of GI illness, 

defining a case of GI illness as “any of the following [within ten to 12 days after swimming]: (a) 

diarrhea (three or more loose stools in a 24 hour period), (b) vomiting, (c) nausea and 

stomachache, or (d) nausea or stomachache and impact on daily activity” (U.S. EPA, 2010a). 

This illness definition is referred to as NGI and is the definition of illness associated with the 

2012 RWQC. 

The NGI case definition was broadened in that diarrhea, stomachache, or nausea is included 

without requiring the occurrence of fever. Viruses are thought to be the etiologic agent 

responsible for most of the GI illnesses that are contracted in recreational waters impacted by

sources of human fecal contamination (Cabelli, 1983; Sinclair et al., 2009; Soller et al., 2010a) 

and viral gastroenteritis does not always present with a fever. Thus a GI illness case definition 

that does not require fever should allow studies to more accurately capture cases caused by

viruses. 

In addition, the NEEAR study extended the number of days following the swimming event in 

which illness may have been observed to account for pathogens with longer incubation times. 

For example, the incubation of Cryptosporidium spp. can be up to ten days, thus participants 

contacted after eight days may not have developed the case definition symptoms. By calling 

participants after ten to 12 days, the study design allowed for illness caused by pathogens 

associated with longer incubation periods to be included as cases. Similar GI definitions are now 

widely used nationally and internationally (Colford et al., 2002, 2007; Payment, 1991, 1997; 

Sinigalliano et al., 2010; Wiedenmann et al., 2006).

Because the NGI definition is broader than HCGI, more illnesses qualify to be counted as 

“cases” in the epidemiological studies than if the older HCGI definition were applied. Therefore, 

at the same level of water quality, more NGI will be observed than HCGI illnesses. The relative 

increase in rates of GI illness between the studies (i.e., HCGI versus NGI) is directly attributable 

to the changes in how illness was defined and not due to an actual increase in the incidence of 

illness among primary contact recreators at a given level of water quality. 

EPA estimated how the GI illness rate associated with the two GI illness definitions can be 

compared using the difference between (a) non-swimmer illness rates from the pre-1986 

epidemiological data, and the (b) non-swimmer illness rates from the NEEAR study (U.S. EPA, 

2011). The mean non-swimmer HCGI rate from pre-1986 epidemiological studies was 14 

illnesses per 1,000 non-swimmer recreators, while the non-swimmer recreators mean NGI rate 

from the NEEAR study was 63 illnesses per 1,000 non-swimmer recreators. Thus an illness rate 

of 8 HCGI per 1,000 primary contact recreators is estimated to be equivalent with an illness rate 

of approximately 36 NGI per 1,000 primary contact recreators (estimated translation factor of 4.5 

NGI per HCGI4). See Appendix A for more information. 

 

4

8 HCGI/1,000 primary contact recreators x 4.5 HCGI / 1 NGI = 36 NGI/1,000 primary contact recreators
15

Of all the adverse health effects considered, the NEEAR epidemiological studies found the 

strongest association with GI illnesses (see section 3.2.3). In addition to NGI, the NEEAR 

epidemiological studies evaluated other health endpoints that could have been caused by 

pathogens found in fecal matter. These included the following:

1. “Upper respiratory illness,” which was defined as any two of the following: sore throat, 

cough, runny nose, cold, or fever;

2. “Rash,” which was defined as a rash or itchy skin;

3. “Eye ailments,” which were defined as either an eye infection or a watery eye;

4. “Earache,” which was defined as ear pain, ear infection, or runny ears; and

5. “Infected cut,” which was defined as a cut or wound that became infected.

Results from the NEEAR study, and previous epidemiological studies, indicate that criteria based 

on protecting the public from GI illness via the use of FIB will prevent most types of recreational 

waterborne illnesses. In general, these other illnesses occur at a lower rate than GI illness (as 

defined by any widely accepted definition) (Fleisher et al., 1998; Haile et al., 1999; McBride et 

al., 1998; Wade et al., 2008). For example, Wade et al. (2008) reported a mean overall GI illness 

incidence of 7.3 percent, upper respiratory infection incidence of 5.7 percent, rash incidence of 

2.7 percent, and eye irritations and infections of 2.9 percent. Kay et al. (1994) and Fleisher et al. 

(1998) reported 14.8 percent GI illness in swimmers and 9.7 percent in non-swimmers, 4.7 

percent incidence of respiratory infection in swimmers and three percent in non-swimmers, and 

4.2 percent incidence of ear ailments in swimmers and 4.8 percent and non-swimmers. 

Non-EPA studies in waters not impacted by WWTPs reported correlations between other health 

endpoints and water quality. For example, Sinigalliano et al. (2010) reported symptoms of 

human subjects randomly assigned to marine water exposure with intensive environmental 

monitoring, and compared them against other subjects who were not exposed. Their results 

demonstrated an increase in GI, respiratory, and skin illnesses among bathers compared to nonbathers. Among the bathers, a relationship was observed between increasing FIB and skin illness, 

where skin illness was positively related to enterococci enumeration by culture-based methods.

3.2.3 Relationship Between Water Quality and Illness

For decades, epidemiological studies have been used to evaluate how FIB levels are associated 

with health effects of primary contact recreation on a quantitative basis. The 1986 criteria 

recommendations are supported by epidemiological studies conducted by EPA in the late 1970s 

and early 1980s. In those studies, enterococci and E. coli exhibited the strongest correlation to 

swimming-associated gastroenteritis (specifically HCGI, as discussed in section 3.2.2). Because 

enterococci and E. coli correlate with illness, EPA recommended E. coli as the indicator to be 

measured in fresh water and enterococci as the indicator to be measured in both marine and fresh 

water. Both indicators continue to be used in epidemiological studies conducted throughout the 

world, including in the European Union (E.U.) and Canada (EP/CEU, 2006; MNHW, 1992). The 

World Health Organization (WHO) recommends the use of enterococci as water-quality

indicators for recreational waters (WHO, 2003). Meta-analyses and systematic reviews of 

epidemiological studies conducted worldwide indicate that these indicators generally provided 

substantial improvements over the indicators that were favored previously, such as total and fecal 

coliforms (Prüss, 1998; Wade et al., 2003; Zmirou et al., 2003). 
16

EPA NEEAR epidemiological study design and conclusions.

EPA conducted the NEEAR epidemiological studies at U.S. beaches in 2003, 2004, 2005, 2007, 

and 2009 and reported the results in a series of research articles (U.S. EPA, 2010a; Wade et al., 

2006, 2008, 2010). The NEEAR study was a prospective cohort (PC) epidemiological study that 

enrolled participants at the beach (the cohort) at a number of study sites and followed them for 

an appropriate period of time to compare incidence of illness (i.e., NGI) between the exposed 

(swimmers) and unexposed groups. This type of study can also include exposure response 

analyses if varying degrees of exposure are present. The PC design used in the NEEAR study

was an enhancement of the cohort design previously employed by Cabelli (1983), Dufour 

(1984), and numerous others (Calderon et al., 1991; Cheung et al., 1990; Colford et al., 2005, 

2012; Corbett et al., 1993; Haile et al., 1999; McBride et al., 1998; Prieto et al., 2001; Seyfried et 

al., 1985; von Schirnding et al., 1992).

EPA investigators considered several different epidemiological study designs, but only the 

randomized controlled trial (described below) and PC designs were viewed as potentially viable 

methods by EPA’s external expert advisory panel to address the specific goals of the study. The 

goals of the study were to obtain and evaluate a new set of health and water quality data at a 

number of beaches for the new rapid, state-of-the-art methods and to use the results to support 

the development of new or revised criteria for the protection of primary contact recreation. The 

NEEAR PC design enhanced and improved upon the PC design used for studies employed in the 

development of the 1986 criteria (U.S. EPA, 1986). 

Characteristics of the NEEAR study’s design were used to establish criteria to select the seven 

beaches studied between 2003 and 2007: 

1. The beach was an officially designated recreational area near a large population center;

2. The beach had an attendance large enough to support an epidemiological study (i.e., 300–

400 attendees/day);

3. The age range of the swimmers was broad (i.e., includes children, teenagers, and adults);

4. The beach generally met the state or local WQS with a range of indicator densities;

5. The range of indicator density was related to occasional contamination by an identified 

human source of pollution (point-source); and

6. The swimming season was at least 90 days long.

For more information about the beach selection criteria, enrollment, administration of the health 

survey, and other details on the study design, please see Wade et al. (2006; 2008; 2010). 

Wade et al. (2008, 2010) also described the details on the statistical models used for the NEEAR 

analysis. Statistical tests were conducted using several approaches and models to determine 

whether the odds ratios for the different fresh water and marine beaches were statistically 

different. Covariate analyses are discussed in U.S. EPA (2010a). Additionally, regression models 

were used to determine the strength and the significance of the relationship between the indicator 

measures and health effects. Nearly all the studies conducted in recent years have used similar 

statistical models, usually logistic or log-linear models (Colford et al., 2012; Fleisher et al., 1993; 

Haile et al., 1999; Kay et al., 1994; McBride et al., 1998; Prieto et al., 2001; Seyfried et al., 

1985).
17

As a result of the statistical analyses, EPA concluded that the Enterococcus spp. levels measured 

by qPCR using EPA Method 1611 (U.S. EPA, 2012b) and GI illness data from the NEEAR 

epidemiological studies of WWTP-impacted marine and temperate fresh water study sites could 

be combined. A direct comparison of the slope parameters shows no significant difference (p = 

0.44) between the marine and fresh water beaches. The results indicated that for the majority of 

the range of exposures observed, there were no statistically significant differences in the 

estimated risk levels for marine and fresh waters (see Appendix C; U.S. EPA, 2011). 

For the NEEAR epidemiological study design, EPA collected data from seven WWTPinfluenced marine and temperate fresh water beaches at intervals throughout the day at different 

water depths, resulting in 18 daily samples. The GM of the daily samples provided a single daily 

water quality value for the health relationship analysis (U.S. EPA, 2010a). The association 

between the GM of enterococci samples collected at 0800 hours and GI illness was nearly 

identical to the daily GM of all samples collected. This association is important from an 

implementation perspective because the results indicate that a sample taken at 0800 hours could 

be used for beach-management decisions on that day.

A number of FIB were examined in the NEEAR study (see Table 2). The occurrence of GI 

illness in swimmers was positively associated with exposure to levels of enterococci enumerated 

with EPA’s Enterococcus spp. qPCR Method 1611 in marine and fresh water (U.S. EPA, 2012b; 

Wade et al., 2008, 2010). GI illness in swimmers at marine water beaches was also associated 

with exposure to levels of anaerobic bacteria of the order Bacteroidales enumerated with EPA’s 

Bacteroidales qPCR method (Wade et al., 2010). 

The association between GI illness and enterococci measured by culture in the NEEAR study

was positive, but not as strong as the qPCR relationship to illness. No associations between 

adverse health outcomes and any of the other fecal indicator organisms were observed in either 

the fresh water or marine beach studies. Culturable E. coli was not included in the NEEAR 

epidemiological studies because EPA focused on evaluating a single indicator that could be used 

by states in both marine and fresh waters. Although culturable E. coli samples were not included 

in the NEEAR epidemiological studies, other researchers confirm that culturable E. coli is 

associated with GI illness, and remains a useful indicator of contamination in fresh waters (Prüss, 

1998; Marion et al., 2010; Wiedenmann et al., 2006).

In addition to the seven temperate, WWTP-influenced beaches, EPA conducted PC 

epidemiological studies at two other beaches in 2009: a temperate beach in Surfside, South 

Carolina that is impacted by urban runoff sources but has no WWTP sources, and a tropical 

beach in Boquerón, Puerto Rico. Boquerón was selected as an epidemiological study site to 

specifically examine the health relationships of the indicators in a tropical setting. For both 

studies the FIB levels and illness rates were found to be low (U.S. EPA, 2010a). Results from 

EPA studies at the urban-runoff and tropical beaches are consistent with NEEAR study results 

from other geographical areas and other sources are consistent with EPA’s understanding of risk 

associated with fecal indicators (i.e., low illness rate and low FIB counts). Thus, EPA believes 

these criteria recommendations are scientifically defensible and protective of the use regardless 

of source or climate.
18

Table 2. Fecal indicator organisms and enumeration methods tested in the NEEAR 

epidemiological studies.

EPA Epidemiological 

Study Indicator/Methods Tested in Study

Great Lakes 

Enterococcus spp. measured by qPCR, enterococci measured 

by culture, Bacteroidales measured by qPCR

Marine (2007)

Enterococcus spp. measured by qPCR, enterococci measured 

by culture, E. coli measured by qPCR, Bacteroides 

thetaiotamicro (potentially human associated) measured by 

qPCR, Bacteroidales, male-specific coliphage measured by

antibody assay, Clostridium spp. measured by qPCR

Tropical

Same indicator/methods as 2007 marine, but no coliphage or 

Clostridium spp.

Urban Runoff

Same indicator/methods as 2007 marine, but no coliphage or 

Clostridium spp.

Other Epidemiological Studies.

Findings from epidemiological studies conducted by non-EPA researchers were also reviewed 

and considered to the maximum extent possible during the development of the 2012 RWQC, 

including all available data from the open literature, as well data from SCCWRP’s 

epidemiological studies in Southern California (see below for description of these studies). 

Numerous epidemiological investigations have been conducted since the 1950s to evaluate the 

association between illness rate to recreational water users and the concentration of suitable fecal 

indicators (reviewed in U.S. EPA, 2009b). These studies have been conducted in Australia, 

Canada, Egypt, France, Hong Kong, Israel, the Netherlands, New Zealand, Spain, South Africa, 

the U.S, and the United Kingdom. Most of these studies investigated waters that were impacted 

or influenced by wastewater effluent. Several groups of researchers have compiled information 

and generated broad and wide-ranging inferences from these epidemiological studies (Prüss, 

1998; Wade et al., 2003; Zmirou et al., 2003). For example, a systematic review and metaanalysis of 27 published studies evaluated the evidence linking specific microbial indicators of 

recreational water quality to specific health outcomes under non-outbreak (endemic) conditions. 

These studies concluded that: (1) good indicators of fecal contamination and demonstrated 

predictors of GI illness in fresh waters are enterococci and E. coli, and enterococci in marine 

water, but not fecal coliform; and (2) the risk of GI illness is considerably lower in studies where 

enterococci and E. coli densities were below levels established by EPA in 1986 (Wade et al., 

2003). 

Recently, SCCWRP conducted a series of PC epidemiological studies in Southern California, at 

Doheny, Avalon, and Malibu beaches. Many specific characteristics of the SCCWRP studies 

were designed to be similar to prior EPA and SCCWRP studies (Colford et al., 2007; Wade et 

al., 2006, 2008, 2010). EPA received the data for the analysis conducted at Doheny beach 

(Colford et al., 2012), a recreational marine beach impacted by urban runoff. The Doheny beach 

study evaluated health-risk relationships between GI illness and enterococci using qPCR-based 

(three different qPCR assays analyzed) and culture-based enumeration methods. Results 

indicated that when urban runoff with potentially containing human enteric viruses flowed freely 
19

into the marine water (berm open), the results were comparable and consistent with NEEAR 

marine WWTP-impacted beaches. Additionally, when the FIB source was more diffuse (berm 

closed), the relationship between enterococci and GI illness was not as strong as the relationship 

observed when the berm was open. These diffuse source results are similar to those observed in 

the NEEAR Surfside beach study (U.S. EPA, 2010a).

A PC epidemiological study at an Ohio reservoir (a fresh water inland beach) provided an 

indicator-illness relationship for E. coli (Marion et al., 2010). In this small-scale study, E. coli

levels (EPA Method 1603; U.S. EPA, 2002b, 2010e) were associated with GI illness in a 

statistically significant manner. As indicated previously, E. coli demonstrated a statistically

significant association with HCGI in EPA’s epidemiological studies in the late 1970s and early 

1980s (Cabelli, 1983; Dufour, 1984). 

Several epidemiological studies have been conducted using study designs that differ from the 

NEEAR design, such as those referred to as randomized control trials (RCT) or randomized 

exposure trials (see below). The RCT is an epidemiological study in which the study subjects are 

randomly allocated to groups to receive an experimental procedure or intervention. For 

recreational water exposures, the groups are bathers and non-bathers (swimmers vs. nonswimmers). The bathers are given instructions detailing their time in the water and specific 

activities, such as immersing their heads in the water. Similar to a PC study, bathers and nonbathers must be followed for an appropriate time to evaluate illness incidence and to determine 

the potential effect of other biases and potential confounders. Exposure-response analyses may

then be conducted. 

RCT study designs are preferred by some researchers because they are intended to (1) better 

account for the possibility that those who do not bathe choose not to do so based on factors other 

than water quality; (2) associate individuals and the incidence of illness with the water quality at 

the time and place of bathing, potentially reducing misclassification bias; and (3) account for 

non-water-related risk factors (Kay, et al., 1994). One of the most significant limitations of RCT 

is that the exposures in the study are not necessarily representative of those experienced by the 

general population. 

EPA reviewed and considered the results from these RCT studies to the maximum extent 

possible. For example, the WHO and European Union (E.U.) used RCT epidemiological studies 

to support their recommended water quality values (EP/CEU 2006; WHO, 2003). The RCT 

studies were conducted over four bathing seasons (summers) at a different marine beach each 

season in the United Kingdom. Trends in the gastroenteritis (equivalent to GI illness) rate with 

increasing enterococci exposure were not significantly different between sites, and thus data 

from the four beaches were pooled (Kay et al., 1994). The source of FIB in this study was 

reported as domestic sewage. Gastroenteritis was defined as “all cases of vomiting or diarrhea or 

all cases of nausea, indigestion, diarrhea or vomiting that was accompanied by a fever”. Rates of 

gastroenteritis were significantly higher in the exposed group than the unexposed group and 

adverse health effects were identified when fecal streptococci, of which enterococci are a 

subgroup, density exceeded 32 per 100 mL (Fleisher et al., 1998; Kay et al., 1994). Another E.U. 

randomized control trial at five fresh water bathing sites in Germany recommended guidance 

values based on the no observable adverse effects levels (NOAELs) for gastroenteritis of 100 E. 
20

coli cfu per 100 mL or 25 enterococci cfu per 100 mL (average values) (Wiedenmann et al., 

2006).

Additional RCT studies evaluated include Epibathe, a public health project funded under E.U. 

Framework Programme 6 to produce “science support for policy,” which began in December 

2005 and ended in March 2009. The imperative for this research effort was to improve the 

relative paucity of E.U. data describing the health effects of controlled exposure (head 

immersion) in E.U. fresh waters and Mediterranean marine waters. Both aquatic environments 

provide important recreational resources throughout the E.U. (European Commission-Epibathe, 

2009). Epibathe comprised a series of marine and fresh recreation water epidemiological studies 

conducted in 2006 and 2007 in Spain and Hungary, respectively. Four riverine recreational sites 

were evaluated in Hungary and four coastal sites were evaluated in Spain. All sites were in 

compliance with the European standards specified in the E.U. bathing Water Directive (EP/CEU, 

1976). For E.U. marine waters (Spain and the United Kingdom RCT studies), the clearest trend 

in increasing illness rate with water quality was evident using enterococci measured by culture. 

For fresh waters (German and Hungary RCT studies), the clearest indicator-illness relationship 

between GI symptoms and water quality was seen by a threshold density of E. coli measured by 

culture. Both analyses (marine and fresh water) suggest elevations in GI illness in the controlled 

exposure (head immersion) cohorts. The authors concluded that the empirical field studies and 

combined data analysis suggested that the WHO or E.U. WQS recommendations did not need to 

be revised. 

Finally, an RTC epidemiological study at a Florida marine beach not impacted by a WWTP was 

considered. In this study, investigators found that swimmers randomized to head immersion were 

approximately twice as likely to develop a skin rash when swimming in water with culturable 

enterococci levels greater than or equal to 40 cfu per 100 mL than swimmers exposed to levels 

less than 40 enterococci cfu per 100 mL (Fleming et al., 2008; Sinigalliano et al., 2010).

Not all epidemiological studies show clear or consistent correlations between indicator levels and 

health outcomes. For example, in a 1989 PC epidemiological study at high-energy (surfing) 

marine beaches impacted by sewage outfalls and stormwater overflows in Sydney, Australia, GI, 

symptoms did not increase with increasing counts of fecal coliform or enterococci, however, 

swimmers did exhibit increasing respiratory, ear, and eye symptoms with increasing levels of 

FIB (Corbett et al., 1993). In a second independent study, respiratory and GI illnesses increased 

with increasing densities of enterococci (Harrington et al., 1993). In a PC epidemiological study

at Mission Bay, California, impacted by non-point sources of fecal contamination, only malespecific coliphage had a correlation with illness (Colford et al., 2005). 

3.2.4 Developing Enterococci Measured by Culture Criteria and Comparable Values for 

Culturable E. coli and Enterococcus spp. Measured by qPCR 

The 2012 RWQC values for culturable levels of enterococci for marine and fresh waters and E. 

coli for fresh waters, if adopted in state WQS and approved by EPA, would be protective of the 

primary contact recreational use. The NEEAR study provided data to establish RWQC values for 

culturable enterococci and to help estimate an illness rate associated with those values. The 

NEEAR -based data were analyzed in several ways, some of which differed from the reported 
21

NEEAR qPCR-based approach. EPA conducted these analyses, in part, to provide a comparison 

with the data analysis underlying the 1986 criteria for recreational waters. 

The illness definition used in these analyses is consistent with those reported in the NEEAR 

study (i.e., NGI), rather than the illness definition (i.e., HCGI) used with the 1986 criteria (refer 

to section 3.2.2). To facilitate comparisons between the results from 1986 and the 2012 criteria, 

illness rates from 1986 (in terms of HCGI per 1,000 primary contact recreators) were translated 

to NGI rates using a translation (factor of 4.5) of the definition of NGI to HCGI (U.S. EPA, 

2011). See section 3.2.2.

The following is a description of EPA’s analytical approaches to develop recommended criteria 

values for enterococci measured by culture and comparable values for culturable E. coli and 

Enterococcus spp. measured by qPCR using EPA Method 1611 (U.S. EPA, 2012b). EPA was 

constrained to criteria values above the level of quantification (i.e., 20 cfu per 100 mL for 

culturable methods) (ASTM, 2012). Approach 1 analyzed the association between health and 

water quality for culturable enterococci using the NEEAR regression analysis. A statistically

significant illness-exposure response relationship was not observed across the full range of 

exposures (Wade et al., 2008, 2010). Approach 2 evaluated NEEAR swimming-associated 

illness rates for exposures above and below the 1986 GM criteria values. These results indicated 

that illness rates were higher when the criteria were exceeded compared to when those criteria 

were not exceeded. Approach 3 compared the NEEAR study illness rates to those from 1986. 

This analysis confirmed that swimming-associated illness rates in NEEAR marine and fresh 

water studies were similar to each other and to those from the 1986 fresh water studies. 

Approach 4 analyzed the NEEAR data using the 1986 analytical approach. The results provided 

a linkage between NEEAR culturable enterococci data and GI illness. Approach 5 extended 

Approach 2 to consider whether there are significant differences in GI illness rates at enterococci 

densities lower than the 1986 criteria. The results indicate that water quality in the range of 30 to 

35 enterococci cfu per 100 mL are the lowest water quality values reported to show statistically

significant differences in swimming-associated illness rates. 

Taken together, these approaches along with the level of water quality described by the 1986 

criteria provide the lines of evidence EPA is using to recommend either the culturable 

enterococci GM criteria values of 30 or 35 cfu per 100 mL. The mean illness rates associated 

with the 2012 RWQC water quality recommendations are approximately 32 cases of NGI per 

1,000 primary contact recreators for a culturable enterococci GM criterion of 30 cfu per 100 mL 

and 36 cases of NGI per 1,000 primary contact recreators for a culturable enterococci GM 

criterion of 35 cfu per 100 mL, in both marine and fresh water. These illness rates were used to 

estimate equivalent criteria values for culturable E. coli and supplemental water quality values 

for enterococci using EPA’s Enterococcus spp. qPCR Method 1611 (U.S. EPA, 2012b).

Approach 1.

Culture-based measures of enterococci collected in the NEEAR study were analyzed using the 

same rigorous statistical approach applied to the qPCR data (Wade et al., 2008, 2010). Although 

a weak association between illness and water quality for culturable enterococci was observed 

using this approach, the exposure-response relationship was not statistically significant over the 

entire range of observed water quality measured by culturable enterococci using the marine and 
22

fresh water beach datasets (Wade et al., 2008, 2010). Therefore, EPA is not relying 

quantitatively on those exposure-response relationships for the 2012 RWQC because the 

regression coefficients would not have sufficient predictive value. 

Approach 2.

EPA evaluated illness rates when swimmers are exposed to water quality levels either above or 

below the 1986 criteria values. Data from EPA’s fresh water NEEAR study sites indicated that 

swimmers exposed above the 1986 criteria value of 33 cfu per 100 mL had higher risks than nonswimmers or swimmers exposed below this value (Wade et al., 2008). At EPA’s marine water 

NEEAR study sites, approximately 16 percent of the marine study days exceeded the 1986 

criteria enterococci GM value of 35 cfu enterococci per 100 mL. On those study days, the odds 

of diarrhea, respiratory illness and earache were elevated among swimmers compared to nonswimmers (Wade et al., 2010). EPA used the NEEAR study results (Wade et al., 2008, 2010) to 

compare the swimming-associated risk on days when enterococci levels were above and below 

33 cfu per 100 mL and 35 cfu per 100 mL for fresh and marine sites, respectively. Those data 

also indicate that on days when the 1986 criteria GM values were exceeded, illness rates were 

similar at marine and fresh water sites (Figure 1a). 

Approach 3.

EPA compared the full distribution of marine and fresh water swimming-associated illness rates 

observed in the NEEAR study to that of the corresponding 1986 criteria illness rates. The 

NEEAR study data (right side of Figure 1b) suggest that the marine swimming-associated illness 

rate and fresh water swimming-associated illness rate are similar to each other and to the 1986 

fresh water rate. In contrast, the 1986 marine swimming-associated illness rate was considerably

higher than the 1986 fresh water illness rate (left side of Figure 1b). 

a) b)

Figure 1. Swimming-associated illness rates observed during EPA’s epidemiological 

studies. a) risk on days with GM above 35 cfu per 100 mL at marine sites and above 33 cfu 

per 100 mL at fresh water sites; b) swimming-associated illness observed during 1986 and 

NEEAR study. Note: Boxes in Figure 1b represent the 25th to the 75th percentiles, the lines 

within the boxes indicate the median values, and the whiskers represent the 10th and 90th

percentiles.
23

EPA then evaluated whether culturable enterococci data from the marine and fresh water 

NEEAR sites could be combined. The observed culturable enterococci data for each NEEAR 

beach were plotted and analyzed (Figure 2). There was substantial overlap in the densities of 

enterococci observed at beaches, even though there were statistically significant differences 

between beaches. However, statistically derived beach groups (represented by variations in 

shading in Figure 2) were not aligned strictly by their salinity classification, supporting the 

finding that there is not a compelling distinction between marine and fresh water (see Appendix 

C). The literature is consistent with this finding and indicates that of the factors influencing 

enterococci fate in the environment, there is evidence that sunlight, temperature and predation 

are more important in controlling enterococci concentrations than salinity (Noble et al., 2004). 

Figure 2. NEEAR marine and fresh water culturable water quality results. White, grey, and 

hatched boxes represent statistically different groups. Fresh water beach sites are Huntington 

Beach (HB), Silver Beach (SB), West Beach (WB), Washington Park (WP); marine water beach 

sites are Edgewater Beach (EB), Fairhope Beach (FB), Goddard Beach (GB), Boquerón Beach 

(BB). Note: Boxes in Figure 1b represent the 25th to the 75th percentiles, the lines within the 

boxes indicate the median values, and the whiskers represent the 10th and 90th percentiles.

Approach 4.

EPA conducted another analysis to develop a culture-based linkage between the NEEAR and 

1986 studies. EPA could not reanalyze the 1980s data using the NEEAR statistical approaches 

because the raw data from those earlier studies are no longer available. Therefore, EPA analyzed 

the NEEAR culturable enterococci data using the same statistical approaches employed in the 

1980s studies (Cabelli, 1983; Dufour, 1984).

In the 1986 criteria, quantitative relationships between the rates of swimming-associated illness 

and FIB densities were determined using regression analysis. Linear relationships were estimated 

from data grouped in two ways: (1) pairing the GM indicator density for a summer bathing 

season at each beach with the corresponding swimming-associated GI rate for the same summer 
24

(fresh water beaches), and (2) by sampling days with similar indicator densities from each study 

location (marine beaches). The second approach, grouping by sampling days with similar 

indicator densities, was not possible with the 1980s fresh water data because the variation of 

bacterial indicator densities in fresh water samples was not large enough to allow such groupings 

(U.S. EPA, 1986). For the 2012 RWQC, EPA evaluated both approaches (seasonal and days of 

similar water quality) with the NEEAR culture-based enterococci data to estimate the illness 

associated with the recommended levels of water quality.

EPA applied the 1986 fresh water analysis described above to the NEEAR culture-based 

enterococci data. This analysis summarized each NEEAR beach as a seasonal GM of water 

quality and its average seasonal illness rate estimate, using the entire body of culturable 

enterococci data from the NEEAR study. Consistent with the 1986 fresh water analysis, this 

approach did not account for covariates. These data points generally fell within the predicted 

range of the published epidemiological regressions (Cabelli, 1983; Dufour, 1984) after 

conversion to comparable GI case definitions (U.S. EPA, 2011). However, this analysis proved 

to be insufficient to estimate NEEAR study illness rates, because it generated only seven data 

points—one for each of the NEEAR beaches. 

EPA then extended the seasonal analysis of the NEEAR culture-based enterococci data using the 

1986 marine water analytical approach as described above. For this analysis, EPA aggregated 

data by days of similar water quality (bins) for each beach (Cabelli, 1983; U.S. EPA 1986). The 

NEEAR data were sorted by the observed GM for each beach day and the data for each beach 

were then grouped according to natural breaks in these data. Bins of beach days were established 

from these data to balance, to the extent feasible, the existence of natural breaks of days with 

similar culturable enterococci GM and the number of study participants represented in each bin 

(Table 3, Figures 3 and 4 - Illness rates in the 1986 criteria are presented as NGI equivalents for 

comparative purposes). This analysis resulted in a total of 27 data points as compared to the 

seven data points for the seasonal analysis. The raw data underlying these analyses are presented 

in Appendix B.

EPA compared the binned fresh water and marine culture-based NEEAR indicator and health 

data to the corresponding regressions in the 1986 criteria. Results indicated that the vast majority

of these data points fall within the 95th percentile prediction intervals derived from the 1986 

regression models (Figure 35). It should be noted that the NEEAR marine culture-based data 

cluster at the lower end of the water quality and illness distribution, described by the 1986 

criteria marine regression. Moreover, the NEEAR marine and fresh water culture-based data 

exhibited a similar correspondence between water quality and illness as observed in the 

freshwater studies (Figures 3 and 4). 

 

5 The prediction intervals can be used to assess whether these NEEAR data fall within an expected range based on 

the 1986 criteria data.
25

Table 3. NEEAR culture-based enterococci and illness rate data for each of the seven 

beaches.

a) b)

Figure 3. NEEAR study culture data aggregated by similar water quality and 1986 criteria 

data for (a) fresh water beaches and (b) marine water beaches.

EPA used these analyses to 1) provide a linkage to illness estimates associated with the 1986 

criteria and the historically accepted level of water quality for protecting the primary contact 

recreation use, and to 2) estimate the potential levels of illness associated with the water quality 

levels recommended in the 2012 RWQC for marine and fresh waters. Based on this analysis and 

results illustrating the consistency between the culturable NEEAR epidemiological data to the 

Log 10 Enterococci density / 100mL

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

NGI rate / 1000 swimmners

0

20

40

60

80

100

120

140

160

180

1986 freshwater data

1986 freshwater regrression

1986 95% prediction interval

NEEAR freshwater data

Log 10 Enterococci density / 100mL

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

NGI rate / 1000 swimmers

-40

-20

0

20

40

60

80

100

120

140

160

180

1986 marine data

1986 marine regression

1986 95% Prediction Interval

NEEAR marine data
26

1986 fresh water studies, the corresponding mean estimate of illness associated with the 2012 

RWQC recommendations is approximately 27 to 36 cases of NGI per 1,000 primary contact 

recreators for both marine and fresh water (Figures 3 and 4). See section 3.2.2 for discussion of 

illness rate conversion. 

Figure 4. NEEAR marine and fresh water culture-based enterococci and illness rate data 

aggregated by days of similar water quality.

Approach 5

Based on public comments received on the draft RWQC document, EPA conducted an additional 

analysis to determine if similar results to those found in Approach 2 would occur at lower (i.e. 

below 35 cfu per 100 mL) enterococci densities. To achieve this, EPA extended the published 

approaches by developing and conducting cut-point analyses, similar to those described by Wade 

et al. (2003, 2008, 2010) and Colford et al. (2012), at multiple enterococci densities. 

In this approach, EPA considered the daily GM culture-based enterococci data from the seven 

NEEAR study sites by conducting cut-point analyses at multiple enterococci densities, ranging 

from 5 cfu per 100 mL to 35 cfu per 100 mL, in five cfu increments and an NGI health end point. 

Points above 35 cfu per 100 mL are not recommended because these values would be less 

protective than the 1986 criteria values. 

Adjusted risk estimates were developed for each of the individual cut-points, comparing 

swimmers in the NEEAR study exposed above and below the selected enterococci cut-points. 

Figure 5 presents odds ratios (and the corresponding 95% confidence intervals [CI]) for the 

probabilities of GI illness for swimming in water with enterococci GM levels above each of the 

cut-points compared to swimming in waters with enterococci GM levels below that cut-point. 

These odds ratios were computed as the adjusted risk of NGI among swimmers above the cutpoint divided by the adjusted risk of NGI among swimmers below the cut-point. The adjusted 

odds ratios account for important covariates from the NEEAR epidemiological model and were 

calculated at the means of the covariate values (this approach is called the marginal average 

effects approach). The adjusted risk of NGI for non-swimmers was 56 cases per 1,000 primary

Log10 Enterococci density / 100mL

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

N

GI rate / 10

0

0

s

wim

m

ers

-20

-10

0

10

20

30

40

50

60

70

80

27 NGI (6 HCGI/1000)

36 NGI (8 HCGI/1000)

30 cfu/100mL

NEEAR marine data

NEEAR fresh data
27

contact recreators; the adjusted risk of NGI for swimmers was approximately 75-90 cases per 

1,000 primary contact recreators depending on the level of water quality evaluated.

Figure 5. Adjusted odds ratios of GI illness for swimming above specific cut-points in 

NEEAR marine and fresh water study sites.

The odds ratios for swimming-associated GI illness are statistically significant (that is, p ≤ 0.05) 

at enterococci densities of 30 cfu per 100 mL and 35 cfu per 100 mL. None of the other 

individual cut-points exhibited odds ratios that were statistically significant (lower 95% CI 

values are less than one in all other cases). These results indicate that the illness rates for 

swimming in waters with GMs in the narrow range of 30 to 35 cfu per 100 mL were significantly

greater than the illness rates for swimming in waters with GMs below those levels. Similar 

illness rate changes are not seen outside this range.

Culturable Enterococcus conclusion

Taken together, the set of approaches described above provide lines of evidence to support the 

recommendation of a GM criterion value of 30 or 35 cfu per 100 mL. These approaches also 

provide evidence that the recommended RWQC are similarly protective of the designated use of 

primary contact recreation in both marine and fresh water. EPA is presenting two sets of criteria 

(consisting of a GM and related STV) associated with two different illness rates. EPA 

recommends that states make a risk management decision to choose one or the other set.

Derivation of an equivalent E. coli value

Using the results from the culturable enterococci analyses described above, EPA derived criteria 

values for culturable E. coli that are comparable to the two recommended enterococci GM 

culture-based values. First, using the preceding approaches, 35 cfu per 100 mL culturable 

enterococci corresponds to 36 NGI per 1,000 primary contact recreators. From the 1986 fresh 

water relationship between swimming-associated illness (see equation below) and water quality, 

Cut Point (enterococci cfu/100mL) 

0 5 10 15 20 25 30 35

O

d

d

s

R

atio

c

o

m

p

arin

g

s

wim

m

ers

a

b

o

v

e

c

ut p

oint to

s

wim

m

ers

b

elo

w

c

ut p

oint

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

1.6

1.7

White symbols P<0.05

Black symbols P > 0.05
28

36 NGI per 1,000 primary contact recreators (8 HCGI per 1,000 primary contact recreators) 

corresponds to an E. coli density of 126 cfu per 100 mL. 

Swimming-associated HCGI illness = − 11.74 + 9.397 (mean log10 E. coli per 100 mL)

Similarly, EPA derived an E. coli density comparable to 30 cfu enterococci per 100 mL by

solving the above equation at an illness rate of 7 HCGI per 1,000 primary contact recreators 

(translated from approximately 32 NGI per 1,000 primary contact recreators which was the 

estimated midpoint of the illness range derived in Approach 4) to yield an estimated E. coli

density of 99 cfu per 100 mL. EPA rounded this estimated density to 100 E. coli cfu per 100 mL. 

EPA believes this rounding was appropriate, given the uncertainty surrounding the predicted 

illness range of the recommended 2012 RWQC enterococci culture-based value. This 

recommended criterion value (100 E. coli cfu per 100 mL) is consistent with the threshold 

suggested by Wiedenmann et al. (2006) based on an E.U. RCT epidemiological study using 

completely different data and statistical methods (as summarized in section 3.2.3). 

Derivation of an equivalent qPCR value

EPA derived values for enterococci measured using EPA’s Enterococcus spp. qPCR Method 

1611 (U.S. EPA, 2012b) in a manner similar to the derivation for E. coli at 32 NGI per 1,000 

primary contact recreators described above. The qPCR values were computed from the combined 

NEEAR epidemiological regression model (Figure 6) (see Appendix A; U.S. EPA, 2011). This 

model was preferred over separate models for marine and fresh waters because EPA’s analysis 

indicated that there was little evidence for differences in illness rate estimates obtained from 

separate models from marine and fresh water beaches and because the beach-specific separate 

models showed no statistical improvement over a single combined model (U.S. EPA, 2011). The 

statistically significant relationship between swimming-associated illness in terms of NGI per 

1,000 primary contact recreators and water quality developed from the combined marine and 

fresh water data is defined as follows: 

Swimming-associated NGI = -27.31 + 23.73 (mean log10 qPCR cce per 100 mL)

Based on the regression model, the following equation was used to derive the qPCR value:

qPCR Value =

where: 

qPCR = qPCR value in units of cce per 100 mL

NGI = NGI rate6in illnesses per 1,000 primary contact recreators

 

6

See U.S. EPA (2011) for translation information of HCGI illness rate into the NEEAR illness rate.

23.73

27.31

10

NGI 
29

Figure 6. Swimming-associated NGI and daily average Enterococcus spp. measured by 

qPCR (cce per 100 mL). All subjects, marine and fresh water beaches combined.

Thus, qPCR-based GM values of 301 and 466 cce enterococci per 100 mL correspond to 

approximately 32 and 36 cases of NGI per 1,000 primary contact recreators, respectively. EPA 

rounded 301 to 300 cce per 100 mL, and 466 to 470 cce per 100 mL to obtain a comparable 

Enterococcus spp. measured by qPCR density to the enterococci measured by culture-based 

value described above. 

3.3 Scope of Protected Population

EPA’s 1986 criteria recommendations are supported by epidemiological studies that were 

conducted in the late 1970s and early 1980s. Those studies enrolled participants according to the 

following criteria: “Whenever possible, family units were sought because information on 

multiple individuals could be obtained from one person, usually an adult member of a family. 

During this initial contact, the following information was obtained on each participant: sex, age, 

race and ethnicity” (Dufour, 1984). This enrollment strategy ensured that children were highly 

represented in those epidemiological studies. Thus, the illness rates corresponding to the 1986 

criteria recommendations are based on the epidemiological relationship for the general 

population that is inclusive of children. EPA used a similar epidemiological approach for 

deriving illness rates for the 2012 RWQC. 

As in the previous EPA epidemiological studies, children were well represented in EPA’s 

NEEAR study population. The proportions of individuals in the under five-year and five to tenyear age categories that were enrolled in the epidemiological studies were greater than in the 

U.S. demographic. According to the U.S. Census data for 2009, children younger than ten years 
30

of age make up approximately 14 percent of the U.S. population (Census, 2010). At West Beach, 

the proportion of children aged ten years and under made up 20 percent of the study sample. A 

similar over-representation of children compared to the U.S. population is true for studies at the 

other beaches, including Huntington (20 percent of the study sample), Washington Park (22 

percent), Silver Beach (22 percent), Edgewater (17 percent), Fairhope (30 percent), and Goddard 

(20 percent). 

EPA conducted statistical analyses of the data from each of EPA’s epidemiological studies at 

fresh water, marine, and tropical beaches to evaluate whether children at these sites were at an 

increased risk of illness following exposure to recreational waters. The results for children were 

compared to adults and other age groups. The age groups used for comparison included the 

following: ten years and under, 11 to 55 years, and over 55 years of age. Other age groups for 

children were not separately analyzed due to small sample sizes. Data for children (i.e., ten years 

and under) were specifically analyzed to evaluate whether they exhibit different illness rates 

compared to the general population.

In the NEEAR marine epidemiological studies, the association between water quality as 

measured by qPCR and illness in children was not different from that observed for the general 

population, despite a higher proportion of children age five to ten years (75 percent) immersed 

their bodies or head in the water compared with adults over age 55 years (26 percent) (Wade et 

al., 2010). Elevated GI illness rates were, however, observed among swimmers of all age groups 

compared with non-swimmers on days that exceeded the enterococci GM value of 35 cfu per 100 

mL (Wade et al., 2010). In the NEEAR fresh water epidemiological studies, the association 

between GI illness and water quality, as measured by EPA’s Enterococcus spp. qPCR Method 

1611 (U.S. EPA, 2012b), was stronger among children (age ten years and under) compared with 

the NEEAR general population, which also included children. The reason for the stronger 

association in children compared to the general population is not known. However, there are 

several possible explanations. Relative to body size, children breathe more air and ingest more 

food and water than adults (U.S. EPA, 2003). Children also exhibit behaviors that increase their 

exposure to environmental contaminants, including increased head and body immersion in 

recreational waters (U.S. EPA, 2010a; Wade et al., 2006, 2008) and hand-to-mouth contact (Xue 

et al., 2007). The immature immune systems of children can also leave them particularly 

vulnerable to the effects of environmental agents (Pond, 2005). Children also stay in the water 

longer than adults (Wade et al., 2006, 2008) and often times ingest more water (Dufour et al., 

2006). 

In data from the NEEAR fresh water study sites, there was considerable overlap in the CIs 

associated with the estimated mean illness responses between children and the general 

population. The CIs for the children’s curve were wider than the CIs for the general population. 

When health effects were compared with water quality, as measured by culturable enterococci, 

differences between children (age ten years and under) and the general population were not 

observed (Wade et al., 2008). As indicated previously, swimmers exposed to water qualities 

above densities of 33 enterococci cfu per 100 mL had an elevated risk of developing GI illness 

compared with non-swimmers and swimmers exposed to water having densities less than 33 

enterococci cfu per 100 mL. Both cohorts, including children (age ten years and under) and the 
31

general population, demonstrated similar responses to water having more than 33 enterococci cfu 

per 100 mL. 

The epidemiological studies conducted by EPA in tropical regions (Boquerón Beach, Puerto 

Rico) and temperate marine water that were impacted by urban runoff (Surfside Beach, South 

Carolina) showed no evidence of increased illness in children or the general population 

associated with increasing levels of FIB in the recreational waters (U.S. EPA, 2010a). 

EPA considered developing criteria based specifically on the results for children. The collective 

results of the NEEAR study, however, provide inconclusive evidence that children (age ten years 

and under) exhibited a significantly different illness response given the range of water qualities 

measured in these studies.

Participants over the age of 55 years were studied, but in numbers that were too low to be 

evaluated separately. For example, in the fresh water studies, this subgroup represented seven 

percent of the study population. This small sample size did not allow EPA to make any

conclusions about risk in the subpopulation over 55 years old. Additionally, EPA’s NEEAR 

study were not designed to evaluate the effects on groups with compromised immune systems or 

other vulnerable subpopulations.

EPA considered all the demographic data and results presented above and concluded that the 

robustness of the estimates for the general population data provide a significant advantage over 

the more uncertain and smaller sample set that consisted only of children. Importantly, the 

general population data are weighted to include children in a robust manner. Thus, the general 

population data provide an appropriate basis for deriving EPA’s recommended values for the 

2012 RWQC. 

This RWQC document includes information regarding several additional ways to protect 

children at beaches through use of a lower value in beach notification programs (i.e., BAV), 

rapid indicator methods, and predictive modeling. The BAVs are values that correspond to the 

75th percentile of a water quality distribution based on these criteria, and can be used by states to 

make precautionary beach management decisions before there is an excursion of the applicable 

WQS (see section 5.1). Rapid indicator detection methods, such as qPCR can allow beach 

managers to make real-time decisions to protect families and their children, in contrast to 

traditional culture methods, which provide estimates of water quality a day or two after the actual 

exposure. The qPCR method can be performed in 2–6 hours and has been shown to be successful 

when implementing same-day beach management decisions (Griffith and Weisberg, 2011). 

Predictive models can also be used for rapid notification of potential water quality problems. 

These models have been demonstrated to be useful tools for implementing beach notification 

programs in the Great Lakes (Francy, 2009; Frick et al., 2008; Ge and Frick, 2009). Because 

children may be more exposed and/or more sensitive to pathogens in recreational waters, it is 

imperative that effective risk communication and health outreach be done to effectively mitigate 

exposure to contaminated waters. Alerting families with children to the level of water quality on 

a given beach day, in real time, will allow for better protection of children.
32

3.4 Waterbody Type

EPA’s 2012 RWQC recommendations are scientifically defensible for all surface waters of the 

U.S. designated by a state for primary contact recreation. Historically, the scientific evidence 

used to generate criteria recommendations has been based on data collected mostly from coastal, 

temperate and Great Lakes fresh waters. The stakeholder community asked EPA to consider 

whether EPA’s criteria recommendations could be used to develop state WQS for other types of 

waters. 

In response, EPA conducted a review of the available information comparing coastal (including 

Great Lakes and marine) and non-coastal (including flowing and non-flowing inland waters, 

such as streams, rivers, impoundments, and lakes) waters to evaluate whether EPA should 

include recommendations in the 2012 RWQC for all waterbody types (U.S. EPA, 2010f). 

Additionally, EPA considered the WERF Inland Water Workshop report (WERF, 2009) and 

subsequent meeting report publication (Dorevitch et al., 2010). These publications concluded 

that the inclusion of non-coastal waters in the 2012 criteria will result in public health protection, 

by preventing illnesses associated with exposure to non-coastal waters. Specifically, these 

studies found the distinction of non-coastal waters versus coastal waters is of less importance

than more fundamental variables, such as the source of fecal contamination, scale of the body of 

water, and the effects of sediment, which translate into differences in the densities, transport, and 

fate of indicators and pathogens (Dorevitch et al., 2010). Further, epidemiological studies in noncoastal waters also support the inclusion of all waterbody types into the criteria. Outbreaks from 

recreational exposure to non-coastal waters indicate a need for public health protection in such 

settings. Historical use of culturable Enterococcus spp. and E. coli, paired by the recommended 

1986 criteria, have been used to prevent the occurrence of outbreaks of severe illness as well as 

the sporadic cases of illness that occur among swimmers. The next two subsections describe the 

data that EPA considered in determining which waterbody types are covered by the 2012 

RWQC. For additional information see the WERF Inland Water Workshop report (WERF, 

2009).

Waterbody type and sources of fecal contamination. 

EPA’s literature review identified the source of fecal pollution as a factor when considering the 

potential differences between EPA epidemiological study sites and non-coastal waters (U.S. 

EPA, 2010f). More information specifically concerning the source of fecal contamination is 

found in section 3.5. Sources of fecal contamination are discussed in this section only insofar as 

they potentially impact FIB in coastal versus non-coastal settings.

All surface waters may potentially receive FIB from point sources, diffuse sources (which may

consist of point source and non-point source pollution), direct deposition, and resuspension of 

FIB contained in sediments. FIB loadings in WWTP-impacted coastal and non-coastal waters are 

generally similar. WWTP discharges, which are known sources of human-derived pathogens and 

indicators from fecal pollution, are relatively steady. Differences exist in FIB loadings between 

waters that are WWTP-impacted and waters impacted by sources other than treated sewage 

effluent. Due to differences in the physical and biological characteristics, FIB survival compared 

to pathogen survival may differ between coastal and non-coastal waters. Some of the potential 
33

differences between coastal and non-coastal waters that may impact survival include extent of 

shading, hydrodynamics, potential for sedimentation, and microbial ecology. 

Epidemiological studies in non-coastal waters. 

EPA also evaluated the available epidemiological evidence in non-coastal waters. Only a handful 

of studies have been conducted in small lakes and even fewer in inland flowing waters. Among 

those, one of the epidemiological sites for earlier EPA studies (Dufour, 1984) was a small inland 

lake in Oklahoma, which helped provide the basis for the 1986 criteria.

Ferley et al. (1989) conducted a retrospective study in the French Ardèche basin to determine the 

relationship between swimming-related morbidity and the bacteriological quality of the 

recreational water. Tourists (n = 5,737) in eight holiday camps were questioned about the

occurrence of illness and their bathing habits during the week preceding the interviews. GI 

illness was higher in swimmers than in non-swimmers. Fecal streptococci were best correlated to 

GI illness. Direct linear regression models and fecal coliforms did not predict risk as well. The 

concentration of fecal streptococci above which bathers exhibited higher illness rates than nonbathers was 20 fecal streptococci cfu per 100 mL. 

A series of RCT epidemiological studies was conducted in Germany to establish the association 

of illness with recreational use of designated fresh recreational waters (four lakes and one river) 

(Wiedenmann et al., 2006). All study sites were in compliance with the European standards for 

total coliform and fecal coliform for at least the three previous bathing seasons. Sources of fecal 

contamination at the study sites included treated and untreated municipal sewage, non-point 

source agricultural runoff, and fecal contamination from water fowl. Based on the water quality

measured as levels of E. coli, enterococci, somatic coliphages, or Clostridium perfringens and 

observed health effects, the authors recommended guideline values for each of these fecal 

indicator organisms. Their recommended guideline values for enterococci and E. coli are very

similar to the 2012 RWQC recommendations. 

Epibathe evaluated the health effects of swimming in E.U. fresh and Mediterranean marine 

waters (European Commission-Epibathe, 2009). Four riverine recreational sites were examined 

in Hungary in 2007, which were in compliance with the European standards specified in the E.U. 

bathing Water Directive (EP/CEU, 1976). For these fresh water studies, E. coli provided the best 

indicator-illness relationship between GI symptoms and water quality. These data support the use 

of E. coli as an effective fecal indicator for use in inland waters. 

A PC study was recently conducted at a small inland lake in Ohio (Marion et al., 2010). The 

study was undertaken to examine the illness rates among inland recreational water users. It also 

evaluated the effectiveness of E. coli as an effective predictor of an increased GI illness rate 

among recreators. Human health data were collected during the 2009 swimming season at East 

Fork Lake, Ohio and adverse health outcomes were reported eight to nine days post-exposure. 

The authors concluded that E. coli was significantly associated with an elevated GI illness rate 

among swimmers compared to non-swimmers. The predicted illness rate increased among 

swimmers with increasing densities of E. coli. 
34

Based on the information summarized above, EPA has determined that the 2012 RWQC 

recommendations are scientifically defensible and protective of the primary contact recreation 

use in both coastal and non-coastal waterbodies. Although some differences may exist between 

coastal and non-coastal waters, those differences were not significant enough to justify the 

development of different WQC recommendations for non-coastal waters. States wishing to 

address site-specific conditions or local waterbody characteristics in their WQS should refer to 

section 6 of this document for suggestions on approaches. 

3.5 Sources of Fecal Contamination

In §on 303(i)(2)(A) of the CWA, EPA was required to promulgate criteria that are as protective 

of human health as EPA’s 1986 criteria where states had failed to do so for their coastal and 

Great Lakes waters. When EPA promulgated WQS for those states based on the 1986 criteria in 

2004, EPA evaluated the scientific understanding of the human health risks associated with 

nonhuman sources of fecal contamination and concluded that although “[the] EPA’s scientific 

understanding of pathogens and pathogen indicators has evolved since 1986, data characterizing 

the public health risk associated with nonhuman sources is still too limited for the [EPA] to 

promulgate [WQS for states based on] another approach.” Thus, the federally promulgated 

criteria values in the 2004 BEACH Act Rule applied regardless of origin, unless a sanitary

survey shows that the sources of the indicator bacteria are nonhuman and an epidemiological 

study shows that the indicator densities are not indicative of a human health risk. In addition, in 

evaluating whether state standards were as protective of human health as EPA’s 1986 criteria, 

EPA concluded that state WQS with exemptions for nonhuman sources were not as protective of 

human health as EPA’s 1986 criteria (see 69 FR at 67228).

EPA has continued to examine the potential for illness from exposure to nonhuman fecal 

contamination compared to the potential for illness from exposure to human fecal contamination. 

One of the key topics discussed at the Experts Scientific Workshop on Critical Research Needs 

for the Development of New or Revised Recreational Water Quality Criteria (U.S. EPA, 2007a) 

was different sources of FIB, including human sources, and a variety of nonhuman sources (such 

as agricultural animals). EPA further investigated sources of fecal contamination in Review of 

Published Studies to Characterize Relative Risks from Different Sources of Fecal Contamination 

in Recreational Waters (U.S. EPA, 2009b) and Review of Zoonotic Pathogens in Ambient Waters 

(U.S. EPA, 2009a). EPA recognizes the public health importance of waterborne pathogens that 

can affect both human and other species (zoonotic). However, the state of the science has only 

recently allowed for the characterization of the potential health impacts from recreational 

exposures to zoonotic pathogens relative to the risks associated with human sources of fecal 

contamination. Overall, the aforementioned reviews indicate that both human and animal feces in 

recreational waters do pose potential risks to human health, especially in immunocompromised 

persons and vulnerable individuals. EPA has conducted analyses to characterize the potential 

differences in magnitude of illness arising from different fecal sources. These analyses indicate 

that the human health risk associated with exposure to waters impacted by animal sources can 

vary substantially. In some cases these risks can be similar to exposure to human fecal 

contamination, and in other cases, the risk is substantially lower. The criteria recommendations 

do not address pollutants in sand, except to the degree that sand may serve as a source of FIB in 

recreational waters. 
35

3.5.1 Zoonotic Potential

Zoonotic diseases are those that are communicable from animals to humans. Fecal contamination 

from nonhuman sources can transmit pathogens that can cause GI illnesses, such as those 

reported in EPA’s NEEAR and other epidemiological studies. 

Livestock and wildlife carry both human pathogens and FIB, and can transmit these microbes to 

surface waters and other bodies of water (CDC, 1993, 1996, 1998, 2000, 2002, 2004, 2006, 

2008; USDA, 2000). Additionally, many documented outbreaks of potential zoonotic pathogens, 

such as Salmonella, Giardia, Cryptosporidium, and enterohemorrhagic E. coli O157:H7 could be 

of either human or animal origin, although providing proper source attribution for these 

outbreaks can be quite difficult. U.S. Centers for Disease Control and Prevention (CDC) reports 

have documented instances of E. coli O157:H7 infection resulting from exposure to surface 

waters, but the source of the contamination is not specified (CDC, 2000, 2002). Other studies 

have linked recreational water exposure to outbreaks caused by potentially zoonotic pathogens, 

but the sources of fecal contamination in these waters were not identified (Roy et al., 2004; U.S. 

EPA, 2009a; Valderrama et al., 2009). Although formal surveillance information is not 

comprehensive, Craun et al. (2005) estimated that 18 percent of the 259 recreational water 

outbreaks reported to the CDC from 1970 to 2000 were associated with animals.

One study documenting a 1999 outbreak of E. coli O157:H7 at a lake in Vancouver, Washington 

suggested that duck feces were the source of the pathogen causing the outbreak (Samadpour et 

al., 2002). More than 100 samples of water, soil, sand, sediment, and animal feces were collected 

in and around the lake and tested. E. coli O157:H7 was detected in both water and duck fecal 

samples. Genetic analyses of the E. coli isolates demonstrated similar results in the water, duck 

feces, and patient stool samples. Duck feces could not be confirmed as the primary source of the 

zoonotic pathogens, however, because the ducks could have been infected by the same source of 

contamination that was present in the lake. Other notable outbreaks are discussed in EPA’s 

Review of Published Studies to Characterize Relative Risks from Difference Sources of Fecal 

Contamination in Recreational Water (U.S. EPA, 2009b).

3.5.2 Differential Health Risks from Human versus Nonhuman Sources

EPA’s research indicates that the source of contamination appears to be an important factor for 

understanding the human health risk associated with recreational waters and that the potential 

human health risks from human versus nonhuman fecal sources can vary (Schoen and Ashbolt, 

2010; Soller et al., 2010b). 

Researchers have documented human health impacts in numerous epidemiological studies in 

marine and fresh water primarily impacted by human sources of fecal contamination (see 

sections 3.2 and 3.4 for a discussion of these studies). The cause of many of the illnesses, 

particularly those resulting from exposure to WWTP effluent, is thought to be viral (Soller et al., 

2010a; U.S. EPA, 1986; WERF, 2011). These human viruses are generally unlikely to occur in 

animal feces although pigs and birds may periodically carry zoonotic viruses.
36

Nonhuman sources of fecal contamination and the associated potential human health risks can 

vary from site-to-site depending on factors such as: the nature of the nonhuman source(s), the 

fecal load from the nonhuman source(s), and the fate and transport characteristics of the fecal 

contamination from deposition to the point of exposure. Nonhuman fecal sources can 

contaminate recreational bodies of water via direct fecal loading into the body of water, and 

indirect contamination can occur via runoff from the land. The fate and transport characteristics 

of the zoonotic pathogens and FIB present under these conditions can be different (such as, 

differences in attachment to particulates or differences in susceptibility to environmental 

parameters affecting survival) (U.S. EPA, 2011l). For more information on pathogenic risks from 

nonhuman sources, see Review of Zoonotic Pathogens in Ambient Waters (U.S. EPA, 2009a). 

However, only a few epidemiological studies have been conducted in waters impacted by

nonhuman sources of fecal contamination. The results of these studies are less clear than those 

conducted in waters impacted by human sources, particularly as related to conventionally

enumerated FIB in those types of waters. For example, Calderon et al. (1991) found a lack of a 

statistical association between swimmers’ illness risk and FIB levels in a rural fresh waterbody 

impacted by animal fecal contamination; however, other researchers have commented that this 

lack of statistical association may have been due to the small study size and not a lack of 

potential human health risks (McBride, 1993). Another epidemiological study conducted at a 

nonhuman, nonpoint source impacted beach at Mission Bay, California documented an increase 

in diarrhea and skin rash in swimmers versus non-swimmers, but the incidence of illness was not 

associated with any of the traditional FIB levels tested (Colford et al., 2007). On the other hand, 

McBride et al. (1998) conducted an analysis of the impact on human sources versus animal 

sources on New Zealand beach sites and concluded that the illness risks posed by animal versus 

human fecal material were not substantially different. These studies collectively suggest that 

waterbodies with substantial animal inputs may potentially result in human health risks that vary

based upon the relative proportion of the human and nonhuman fecal input and the nature of the 

nonhuman source of infective agent(s). 

Microbial risk assessment approaches are available to assist in characterizing potential human 

health risks from nonhuman sources of fecal contamination (Roser et al., 2006; Soller et al., 

2010b; Schoen and Ashbolt, 2010; Till and McBride, 2004). For example, New Zealand, where 

roughly 80 percent of the total reported illnesses are zoonotic and potentially waterborne, 

recently updated its recreational fresh water guidelines based on a risk analysis of 

campylobacteriosis (accounting for over half of the reported total notifiable disease burden in 

that country) and using E. coli as a pathogen indicator (Till and McBride, 2004). Since those 

waters were highly impacted by fecal contamination, in this case from agricultural sources, a 

predictable relationship between the pathogen and the FIB could be developed. The correlation 

between the occurrence of Campylobacter and E. coli is unlikely to hold in all waters, but this 

relationship was demonstrated in parts of New Zealand, particularly in waters with high levels of 

Campylobacter and E. coli. 

The risk presented by fecal contamination from nonhuman sources has been shown in some 

cases, to be potentially less than the risk presented by fecal contamination from human sources 

(Schoen and Ashbolt, 2010; Soller et al., 2010a, b; WERF, 2011). EPA’s research also indicates 

that some nonhuman fecal sources (cattle in particular) may pose risks comparable to those risks 
37

from human sources (Soller et al., 2010a, b; U.S. EPA, 2010g). Human pathogens are present in 

animal fecal matter, and there is, therefore, a potential risk from recreational exposure to human 

pathogens in animal-impacted waters that must be accounted for in the 2012 RWQC. For waters 

dominated by nonhuman sources and in the absence of site-specific criteria, EPA recommends 

that the national criteria be used to develop WQS for all waters including those impacted by 

point and nonpoint sources.

Because there have been few epidemiological studies, with mixed findings, in waters impacted 

by nonhuman sources and QMRA shows that risks from some animals may be comparable to 

humans, EPA is not developing separate national criteria for nonhuman sources. However, since 

some studies have site-specifically shown less risk in waters impacted by nonhuman sources, 

states interested in addressing the potential human health risk differences from different sources 

of fecal contamination on a site-specific basis should refer to section 6.2.2 of this document for 

suggestions on approaches. 

Naturally occurring environmental sources of traditional FIB, another nonhuman source, may

exist, particularly under tropical conditions. Results of the EPA epidemiological beach study at 

Boquerón, Puerto Rico did not refine EPA’s understanding of risk enough to justify a different 

criteria recommendation for tropical waters. In addition to the epidemiological study at 

Boquerón, Puerto Rico, EPA conducted a literature search and reported the results in the Review 

of Fecal Indicator Organism Behavior in Ambient Waters and Alternative Indicators for 

Tropical Regions (U.S. EPA, 2009c). The literature indicates that FIB, fecal coliforms, 

enterococci, and E. coli are endemic to tropical, subtropical, and temperate regions. Studies 

conducted in the tropics and subtropics show proliferation of E. coli, enterococci, and/or fecal 

coliforms (Boehm, 2007; Byappanahalli, 2012; U.S. EPA, 2009c). Changing environmental 

conditions in tidally-influenced sediments help support proliferation and elevated FIB in water 

(U.S. EPA, 2009c). 

Overall, EPA believes that the state of the science is not developed sufficiently to distinguish 

environmental sources from other sources of FIB on a national basis. In some circumstances, the 

presence of FIB in water is not necessarily an indication of recent fecal contamination or 

potential health risk. Therefore, EPA has concluded that states adopting the 2012 RWQC would 

result in WQS protective of the designated use of primary contact recreation. States wishing to 

consider alternative indicators should refer to section 6.2 for information on how to develop 

alternative criteria. 

3.6 Expression of Criteria

EPA identified a number of opportunities to improve clarity and to enhance implementation of 

the 2012 RWQC, which are discussed in the sections below.

3.6.1 EPA’s 1986 Ambient Water Quality Criteria for Bacteria 

In 1986, EPA recommended criteria for enterococci and E. coli that contain two components: a 

GM and an SSM. EPA derived the 1986 criteria values from beach water quality datasets that 

were collected as part of EPA’s epidemiological studies conducted during the late 1970s and 
38

early 1980s. The GM values were computed as described in section 3.2.1. The SSM values were 

derived from upper percentiles of the water quality distribution around the GM criteria values. 

Together, the 1986 criteria GM and SSM described a water quality distribution that would be 

protective of primary contact recreation, based on the epidemiological studies conducted during 

that period. Thus, the GM and SSM values in the 1986 criteria corresponded to the same illness 

rate because they are both derived from the same water quality distribution. 

The 1986 criteria contained four different SSM values corresponding to the 75th, 82nd, 90th, and 

95th percentiles of the expected water quality sampling distribution at the GM criteria value. EPA 

recommended using different SSM values on the basis of the use intensity of the recreational 

water. However, treating the SSM as a never to be exceeded value for such an evaluation would 

impart a level of protection much more stringent than intended by the 1986 criteria GM value. 

For example, a marine beach that is in compliance with the 1986 GM criteria for enterococci 

(GM = 35 cfu per 100 mL) would be expected to have 25% of the sample values above 104 cfu 

per 100 mL (the 75th percentile of the expected water quality sample distribution) because of 

expected variability in individual water quality measurements. Expecting that beach to never 

exceed 104 cfu per 100 mL would require an actual GM much lower, associated with a lower 

illness rate, than the recommended GM criterion value.

3.6.2 The 2012 RWQC

In the 2012 RWQC, EPA is recommending the criteria magnitude be expressed as a GM value 

corresponding to the 50th percentile and a STV corresponding to the 90th percentile of the same 

water quality distribution, and thus associated with the same level of public health protection. 

EPA’s criteria recommendations are both for a GM and STV (rather than just a GM or just an 

STV) because used together they would indicate whether the water quality is protective of the 

designated use of primary contact recreation.. Using the GM alone would not reflect spikes in 

water quality because the GM alone is not sensitive to them. 

EPA is recommending that the GM of a waterbody be calculated in the same way as 

recommended in the 1986 criteria by taking the log10 of sample values,7averaging those values, 

and then raising that average to the power of 10. The STV is also derived in a manner similar to 

how the 1986 criteria SSM was derived by estimating the percentile of the expected water 

quality distribution around the GM criteria value. 

EPA believes that the STV, used in conjunction with the GM, can help ensure the FIB densities 

in recreational waters correspond to a water quality level protective the designated use of 

primary contact recreation by constraining the number of high water quality values. The 

distribution of FIB in water is highly variable and can generally be represented as a log10 normal 

distribution (Bartram and Rees, 2000; Kay et al., 2004; Wyer et al., 1999). EPA derived the STV 

from the observed pooled variance of the FIB data reported in EPA’s epidemiological studies. 

The computed pooled variances represent a wide range of weather and hydrological conditions 

because monitoring was conducted over the full course of the set of epidemiological studies. 

EPA stratified the epidemiological data by beach and water depth (14 subgroups) because FIB 

 

7

For data points reported below detectable limits, the GM calculation should be based on the assumption that those 

observations were present at the detection limit.
39

distributions are known to differ systematically for these factors (Wade et al., 2008), and the 

pooled variance was then calculated. For EPA’s Enterococcus spp. qPCR Method 1611, the 

pooled variance resulted in a log standard deviation (the standard deviation of the base 10 

logarithms of the data) of 0.49. From the NEEAR study sites, the pooled variance estimates for 

culturable enterococci are 0.44 (the pooled variance for culturable E. coli was reported 

previously (U.S. EPA, 1986) as 0.40). 

For the STV, EPA selected the estimated 90th percentile of the water quality distribution to take 

into account the expected variability in water quality measurements, while limiting the number 

samples allowed to exceed the STV, before deciding water quality is impaired. In addition, the 

approach encourages monitoring because once an exceedance is observed, at least ten more 

samples need to be below the STV before water quality is considered unimpaired.

Further, EPA is no longer utilizing the concept of “use intensity” as a basis for recommending 

multiple SSM criteria. EPA’s recommends instead that states adopt both the GM and STV into 

their WQS for all primary contact recreation waters.

EPA now specifically recommends a duration period over which the GM of samples should be 

calculated and over which the STV should be compared against a recommended limit on the 

frequency of excursions. EPA is recommending that states use a duration for the GM and STV of 

30 days. The duration and frequency of excursion should be explicitly included in the state's 

WQS as it is a component of the WQS. 

EPA understands that a longer duration would typically allow for more samples to be collected 

and that including more samples in calculation of the GM and STV improves the accuracy of the 

characterization of water quality. However, because the designated use protected by this criterion 

is primary contact recreation, EPA believes that a shorter duration (i.e., 30 days), used in a static 

or rolling manner, coupled with limited excursions above the STV, allows for the detection of 

transient fluctuations in water quality in a timely manner. In the development of their monitoring 

program, EPA recommends that states consider the number of samples evaluated in order to 

minimize the possibility of incorrect use attainment decisions (see section 3.6.4).

3.6.3 Criteria Magnitude, Duration, and Frequency for CWA Purposes

EPA recommends that RWQC consist of a magnitude, duration and frequency. Magnitude is the 

numeric expression of the maximum amount of the pollutant that may be present in a waterbody 

that supports the designated use. Duration is the period of time over which the magnitude is 

calculated. Frequency of excursion describes the maximum number of times the pollutant may be 

present above the magnitude over the specified time period (duration). A criterion is set in a 

WQS such that the combination of magnitude, duration and frequency protect the designated use 

(such as primary contact recreation).
40

EPA’s 2012 RWQC recommendations to protect primary contact recreation consist of a 

magnitude, duration and frequency of exceedance.

 Magnitude: GM and the STV (regardless of the sample size). 

 Duration and Frequency: The waterbody GM should not be greater than the selected 

GM magnitude in any 30-day interval. There should not be greater than a ten percent 

excursion frequency of the selected STV magnitude in the same 30-day interval. 

3.6.4 Application of State WQS based on EPA’s 2012 RWQC for NPDES Permitting, 

303(d) Listing, TMDL Development, and Beach Notification Programs

WQC in state WQS are used: to derive water quality-based effluent limits (WQBELs) for 

National Pollutant Discharge Elimination System (NPDES) permits; to identify impaired and 

threatened waters for waterbody assessments; to develop waste load allocations and load 

allocations for TMDLs; and for beach notification programs under §406 of the CWA. 

NPDES permitting purposes

The NPDES regulation at 40 CFR 122.44(d) requires the development of WQBELs as necessary

to attain WQS. Under §122.45(d), permit limits for continuous dischargers must include both 

short- and long-term WQBELs unless there is a specific finding of “impracticability”. EPA 

recommends that permitting authorities use an effluent limit derivation approach that considers 

both the GM and STV in the limit calculations, and which results in short- and long-term effluent 

limits that derive from and comply with all applicable criteria expressions. Once established, 

pathogen indicator-based limits for continuous dischargers are applied and enforced in a manner 

consistent with all other water quality parameters. 

For non-continuous or episodic discharges, 40 CFR 122.45(e) requires WQBELs to reflect the 

frequency of discharge; total mass; maximum discharge rate; and prohibition or limitation of 

specified pollutants by mass, concentration, or other measure. Wet weather-related events 

influence episodic discharges such as combined sewer overflows (CSOs). The 1994 CSO 

Control Policy (reflected in §402(q) of the CWA) describes various approaches for addressing 

CSO discharges in NPDES permits and should be consulted when establishing WQBELs for 

intermittent dischargers. The CSO Policy also recommends WQS review and revision, as 

appropriate, to reflect the site-specific wet weather impacts of CSOs. In conjunction with an 

approved long-term CSO control plan, a WQS review could involve a use attainability analysis 

(40 CFR 131.10(g)) and subsequent modification of a designated use. 

Detailed approaches for deriving WQBELs to meet WQS based on EPA’s final 2012 RWQC 

will be further explained in upcoming TSM.

Identification of Impaired and Threatened Waters

Under §303(d) of the CWA and EPA’s implementing regulation (40 CFR 130.7), states, 

territories, and authorized tribes (hereafter referred to as states) are required to develop lists of 

impaired and threatened waters that require TMDLs. Impaired waters are those waters for which 

effluent limitations and other pollution control requirements are not stringent enough to 

implement any WQS applicable to the waterbody. EPA recommends that states consider as 
41

threatened those waters that are currently attaining WQS, but which are expected not to meet 

WQS by the next listing cycle (every two years). Consistent with EPA recommendation, many

states consolidate their §303(d) and §305(b) reporting requirement into one “integrated” report. 

For making these water quality attainment determinations, a state that adopts WQS consistent 

with the 2012 RWQC would evaluate all readily available data and information to determine 

whether a waterbody meets the WQS (i.e., whether the waterbody is in attainment). Both the GM 

and the STV would be part of the WQS and therefore both targets would be used to determine 

whether a waterbody meets the WQS for primary contact recreation. The waterbody condition 

would need to be evaluated based on all existing and readily available data and information for 

the specified duration. EPA’s regulation defines “all existing and readily available water quality 

related data and information” at 40 CFR 130.7(b)(5). EPA expects that water quality attainment 

determinations would include water quality monitoring data collected as part of a beach 

notification program, as well as information regarding beach closures and advisories. 

Beach Notification Programs

WQC in state WQS are the applicable targets for EPA grant funded state beach notification 

programs under §406 of the CWA. The BAV is not a component of EPA’s recommended 

criteria, but a tool that states may choose to use, without adopting it into their WQS as a “do not 

exceed value” for beach notification purposes (i.e., advisories). While the GM and STV would 

be the applicable WQS, a BAV could be used at the state’s discretion as a more conservative, 

precautionary tool for beach management decisions. Similarly, states could also choose to use 

the STV as a “do not exceed value” for the purposes of their beach notification program, without 

adopting it as a “do not exceed value” in their WQS.

3.6.5 Practical Considerations for Implementing State WQS based on the 2012 RWQC

The number of samples, to be collected by a state in determining if WQS have been exceeded, is 

not an approvable element of a WQS package (Florida Public Interest Research Group vs. EPA,

2007). Therefore states should not include a minimum sample size as part of their criteria 

submission. When identifying sampling frequency as part of a state’s monitoring plan, a state 

may consider that, typically, a larger dataset will more accurately characterize the water quality 

in a waterbody, which may result in more meaningful attainment determinations. Therefore, EPA 

is recommending that states conduct at least weekly sampling to evaluate the GM and STV over 

a 30-day period and encourages more frequent sampling at more densely populated beaches.

4.0 Recreational Water Quality Criteria

EPA evaluated the available information and the results of the analyses presented above (section 

3.2.4) and determined that the primary contact recreation designated use would be protected if 

one of the following criteria sets consisting of a GM and an STV were adopted into a state’s 

WQS and approved by EPA (see Table 4). 
42

Table 4. Recommended 2012 RWQC.

Criteria 

Elements

Estimated Illness Rate (NGI): 

36 per 1,000 primary contact 

recreators

OR

Estimated Illness Rate (NGI): 

32 per 1,000 primary contact 

recreators

Magnitude Magnitude

Indicator 

GM

(cfu/100 mL)a

STV

(cfu/100 mL)

a

GM

(cfu/100 mL)a

STV

(cfu/100 mL)a

Enterococci 

– marine 

and fresh 35 130 30 110

OR

E. coli

– fresh 126 410 100 320

Duration and Frequency: The waterbody GM should not be greater than the selected GM 

magnitude in any 30-day interval. There should not be greater than a ten percent excursion 

frequency of the selected STV magnitude in the same 30-day interval. 

a

EPA recommends using EPA Method 1600 (U.S. EPA, 2002a) to measure culturable enterococci, or another 

equivalent method that measures culturable enterococci and using EPA Method 1603 (U.S. EPA, 2002b) to measure 

culturable E. coli, or any other equivalent method that measures culturable E. coli.

EPA believes both criteria sets outlined above are protective of the designated use of primary

contact recreation. EPA recommends that states make a risk management decision regarding 

illness rate to determine which set of criteria values (both a GM and related STV) to adopt into 

their WQS and that this risk management decision should be applied statewide. In order to 

ensure downstream protection of estuarine and marine swimming waters, upstream inland waters 

should have WQS based on the same illness rate as those downstream waters. Note that either 

enterococci or E. coli can be selected for fresh waters, as adopting one of the indicators is 

sufficient and only enterococci can be selected for marine waters. Adopting criteria based on one 

illness rate for some waters and criteria based on the other illness rate for remaining waters is not 

recommended. The criteria that correspond to an illness rate of 36 NGI per 1,000 primary contact 

recreators correlate to water quality levels associated with the 1986 criteria. Accordingly, the 

illness rate has a history of acceptance by the public. The criteria that correspond to an illness 

rate of 32 NGI per 1,000 primary contact recreators would encourage an incremental 

improvement in water quality.

5.0 Supplemental Elements for Enhanced Protection of Recreational Waters

In addition to the RWQC values described above, EPA is providing supplemental elements for 

states’ consideration and possible use. These elements include the BAV and values for 

Enterococcus spp. as measured by qPCR. The BAV can be used as a precautionary tool for 

making beach notification decisions, and use enterococci measured using EPA’s Enterococcus

spp. qPCR Method 1611 (U.S. EPA, 2012b) qPCR is anticipated to provide increased public 

health protection by facilitating timely notification to swimmers from elevated levels of FIB. 

Details for these supplemental elements are described below.
43

5.1 Beach Action Value (BAV)

EPA suggests that states use a BAV as a conservative, precautionary tool for making beach 

notification decisions. The BAV is not a component of EPA’s recommended criteria, but a tool 

that states may choose to use, without adopting it into their WQS as a “do not exceed” value for 

beach notification purposes (such as advisories). The BAV was developed from the same water 

quality distribution (section 3.6.2) as the criteria values in section 4.0 and corresponds to the 

estimated 75th percentile of the enterococci and E. coli water quality distributions. 

For states that choose to use a BAV (see Table 5), any single sample above the BAV could 

trigger a beach notification until another sample below the BAV is collected. While the GM and 

STV would be the applicable WQS, a BAV could be used at the state’s discretion as a more 

conservative, precautionary tool for beach management decisions. This applies to all states, 

including those with grants under §406 of the CWA. 

EPA suggests that the state’s chosen criterion illness rate be used to determine the corresponding 

BAV. For states that do not use a BAV, EPA suggests using the criteria STV values (provided in 

Table 4) as “do not exceed” values for beach notification or retaining their current beach 

notification values in their WQS. Additionally, if a state is not sampling during or immediately 

after a rain event, the state should consider advising the public of the potential additional risk of 

primary contact recreation when sources such as urban runoff or CSOs may be impairing water 

quality.

Table 5. Beach Action Values (BAVs).

Indicator

Estimated Illness Rate 

(NGI): 36 per 1,000 

primary contact 

recreators

OR

Estimated Illness Rate 

(NGI): 32 per 1,000 

primary contact 

recreators

BAV

(Units per 100 mL)

BAV

(Units per 100 mL)

Enterococci – culturable 

(fresh and marine)a70 cfu 60 cfu

E. coli – culturable 

(fresh)b235 cfu 190 cfu

Enterococcus spp. –

qPCR (fresh and marine)c 1,000 cce 640 cce

a Enterococci measured using EPA Method 1600 (U.S. EPA, 2002a), or another equivalent method that measures 

culturable enterococci.

b

E. coli measured using EPA Method 1603 (U.S. EPA, 2002b), or any other equivalent method that measures 

culturable E. coli.

c EPA Enterococcus spp. Method 1611 for qPCR (U.S. EPA, 2012b). See section 5.2.

5.2 Rapid Method: Enterococcus spp. as measured by qPCR (EPA Method 1611)

EPA has developed a qPCR method to detect and quantify enterococci more rapidly than the 

culture method for ambient waters. Introduction of EPA Enterococcus spp. qPCR Method 1611 
44

is anticipated to provide increased public health protection by facilitating timely notification8to 

swimmers from elevated levels of FIB. Importantly, enterococci as measured by EPA 

Enterococcus spp. qPCR Method 1611 have shown a stronger relationship to GI illness in the 

recent EPA NEEAR epidemiological study compared to other methods tested (Wade et al., 2008; 

U.S. EPA, 2010a, 2012b).

While EPA Enterococcus spp. qPCR Method 1611 (U.S. EPA, 2012b) offers some advantages, 

EPA has limited experience with its performance across a broad range of environmental 

conditions. States should be aware of the potential for qPCR interference (see section 3.1.1) in 

various waterbodies, which may vary on a site-specific basis. Thus, EPA encourages a sitespecific analysis of the method’s performance prior to use in a beach notification program or 

adoption of WQS based on the method. A “site” may be a beach, a waterbody, a particular 

watershed, or a larger area (such as a state) that is shown to have uniform water quality 

characteristics throughout. Considerations for determining how a qPCR-based WQS could be 

developed will be provided in additional TSM. EPA’s Enterococcus spp. qPCR Method 1611 

(U.S. EPA, 2012b) is not currently suggested for NPDES permitting or effluent-related 

monitoring purposes because this method may not reflect the efficacy of WWTP disinfection 

since it detects and enumerates both live and dead enterococci.

A state may adopt a WQS based on EPA’s Enterococcus spp. qPCR Method 1611 (U.S. EPA, 

2012b) if it would be scientifically defensible and protect the designated use. As noted above, 

prior to adoption EPA recommends a site-specific evaluation of the method’s performance. For 

states interested in adopting a value for enterococci using EPA’s Enterococcus spp. qPCR 

Method 1611 into their WQS, EPA is providing GM and STV values for use in marine and fresh 

waters based on its epidemiological study data as shown in Table 6. The state’s chosen criterion 

illness rate would determine the suggested corresponding qPCR values to be used by the state. 

States may also choose a qPCR-based BAV for beach notification purposes (see Table 5). 

This document includes only supplementary information about a WQS for Enterococcus spp. 

measured by EPA’s Enterococcus spp. qPCR Method 1611 (U.S. EPA, 2012b) because of the 

concerns discussed in section 3.1.1 of this document.

 

8

See section 5.2.1 for a discussion on the use of predictive models as an additional approach for achieving timely 

notification.
45

Table 6. Values for qPCR in marine and fresh waters.

Element

Estimated Illness Rate 

(NGI): 36/1,000 primary 

contact recreators

OR

Estimated Illness Rate 

(NGI): 32/1,000 primary 

contact recreators

Magnitude Magnitude

GM

(cce per

100 mL)

STV

(cce per

100 mL)

GM 

(cce per 

100 mL)

STV 

(cce per

100 mL)

qPCRa470 2,000 300 1,280

Duration and Frequency: The waterbody GM should not be greater than the selected 

GM magnitude in any 30-day interval. There should not be greater than a 10 percent 

excursion frequency of the selected STV magnitude in the same 30-day interval.

a

EPA Enterococcus spp. Method 1611 for qPCR (U.S. EPA, 2012b).

6.0 Tools to Support States and Tribes in Evaluating and Managing Recreational Waters 

and for Considering Alternative Water Quality Criteria 

EPA’s implementing regulations for §303 of the CWA provide that “states must adopt those 

WQC that protect the designated use. Such criteria must be based on sound scientific rationale 

and must contain sufficient parameters or constituents to protect the designated use” (40 CFR 

§131.11(a)). EPA’s regulation stated in 40 CFR §131.11(b)(1) provides that “In establishing 

criteria, states should (i) Establish numerical values based on (i) 304(a) Guidance; or (ii) 304(a) 

Guidance modified to reflect site-specific conditions; or (iii) Other scientifically defensible 

methods.” WQS can be established for waterbodies or a portion of a waterbody and therefore 

they could be established for a specific site. A “site” may be a beach, a waterbody, a particular 

watershed, or a larger area (such as a state) that is shown to have uniform water quality 

characteristics throughout. When EPA reviews state WQS for approval or disapproval under the 

CWA, EPA must ensure that the WQC in the standard (regardless of whether they are “sitespecific”) are scientifically defensible and protective of the designated use. 

The tools discussed in this section fall into two main categories: (1) tools that states can use to 

further evaluate and manage their waterbodies (see section 6.1); and (2) tools that can be used by 

states in the development of WQC that differ from EPA’s recommended criteria (“alternative 

criteria”) (see section 6.2). Alternative criteria could be developed on a site-specific basis, or 

they could be developed using different indicators and analytical methods. State WQS including 

alternative criteria would need to be scientifically defensible and protective of the use. Because 

some alternative criteria for primary contact recreation could be based in part on assumptions 

regarding the current state of a watershed such as current land uses, they should be revisited no 

less frequently than triennially to ensure the site-specific criteria remain protective of the primary

contact recreation use. This section does not provide details on how to implement these tools. 

Rather, detailed information on these tools will be provided in upcoming TSM. 

The tools discussed below (and the corresponding subsections) include: (1) sanitary surveys 

(section 6.1.1); (2) predictive models (section 6.1.2); (3) epidemiological studies (section 6.2.1); 

(4) QMRA (section 6.2.2); and (5) approaches for developing criteria using alternative fecal 

indicators and/or methods (section 6.2.3).
46

6.1 Tools for Evaluating and Managing Recreational Waters

EPA recognizes that advancements have been made since the publication of the 1986 criteria in 

the area of managing recreational waters. This section discusses tools that states can use to 

further evaluate and manage their waterbodies, which can aid in identifying days of poor water 

quality on a site-specific basis. Specifically, this section discusses the use of sanitary surveys as a 

tool for identifying sources of fecal contamination and the use of predictive models for timely

beach notification. EPA encourages the use of sanitary surveys by beach managers to better 

understand and potentially control sources of fecal contamination and pathogens. EPA also 

encourages the use of predictive models to supplement a sound beach notification program. 

Predictive modeling has the potential to identify days of poor water quality in time to inform the 

public of the potential risks. Together, the tools for evaluating and managing waters in this 

section could be used by a state or locality to assess and communicate the risks associated with 

fecally contaminated recreational waters. These tools would not be part of the adopted WQS and 

do not result in different numerical criteria values.

6.1.1 Sanitary Survey 

Water quality managers often use sanitary surveys to evaluate waters for fecal contamination 

potential and to prioritize clean-up and remediation efforts. Sanitary surveys involve collecting 

information about the surrounding watershed for the purpose of cataloging physical conditions 

that may influence water quality in a watershed or at a beach. A sanitary survey is a detailed 

process that compiles information on pollution sources (such as streams or stormwater outfalls), 

physical features on or near a site, land use in adjacent areas and in the watershed that drains to 

the site, and other information that could regularly influence water quality. Additional 

observations may include the presence or absence of sanitary facilities or the nature of existing 

management activities (such as beach cleaning). Molecular source tracking tools may also be 

useful in verifying the results of the sanitary survey by confirming the presumed sources of fecal 

contamination in the watershed.

A sanitary survey collects information that relates to the specific conditions at a site at a 

particular time. Sanitary surveys are a snapshot of the conditions in a waterbody, which can 

change due to factors including those listed above. Sanitary surveys help state and local water 

quality managers and public health officials identify sources of fecal contamination, assess the 

magnitude of the contamination, and designate priority locations for water testing. Observations 

taken daily or at the time of water quality sampling can not only assist managers in evaluating 

water quality conditions (such as, turbid water conditions, rainfall, source flow), but sanitary

survey data and measured FIB densities can be used to develop models to predict water quality. 

Other information such as molecular source tracking and watershed information may be needed 

to effectively delineate sources within the watershed.

Information on EPA’s sanitary survey approach is available at: 

http://water.epa.gov/type/oceb/beaches/sanitarysurvey_index.cfm. EPA plans to include 

additional information on developing and using sanitary surveys in TSM. 
47

6.1.2 Predictive Models

EPA recognizes that, at some locations and under some conditions, use of culturable or 

molecular enumeration methods, such as qPCR, are not feasible or are unlikely to provide timely 

information for making a same-day beach notification decision (i.e., in locations where water 

samples cannot be transported to laboratories for analysis in a timely manner). This section 

describes predictive modeling, an approach that may supplement water quality monitoring results 

to allow for timely beach notification decisions. Typically, states would use site-specific 

predictive models, such as statistical models, rainfall threshold levels, or notification protocols 

(U.S. EPA, 2010h, 2010i), to supplement monitoring using culture-based methods. 

Predictive models are currently used in areas such as the Great Lakes and have proven to be an 

effective means of implementing beach notification programs. These models draw on existing 

culture-based monitoring data, are inexpensive to use, and allow for rapid water quality

management decisions (U.S. EPA, 2010h, 2010i). 

Predictive modeling tools fall into the following categories: statistical regression models, 

rainfall-based notifications, decision trees or notification protocols, deterministic models, and 

combinations of tools. There are various considerations for developing and selecting predictive 

models, and each has its own set of challenges (Boehm et al., 2007). To be effective, these 

models should reflect site-specific conditions (i.e., inter-seasonal variations). Development of 

predictive models typically requires monitoring data for establishing and maintaining statistical 

relevance. 

EPA conducted research and published a two-volume report to advance the use of predictive 

models (U.S. EPA, 2010h, 2010i). Volume I summarizes the basic concepts for developing 

predictive tools for coastal and non-coastal waters (U.S. EPA, 2010h). Volume II provides the 

results of EPA’s research on the development of statistical models at research sites. It also 

presents Virtual Beach, a software package designed to build statistical multivariate linear 

regression predictive models (U.S. EPA, 2010i). EPA is expanding the Virtual Beach tool to 

include other statistical approaches. Beyond these Virtual Beach improvements, other efforts, 

such as linking watershed and statistical models, Cyterski's temporal synchronization approach 

to incorporate time lags, and process-based transformations are being pursued to improve 

predictive modeling efforts. More information on developing and using predictive models for 

water quality management purposes will be provided in upcoming TSM.

6.2 Tools for Developing Alternative Criteria

States could adopt site-specific alternative criteria to reflect local environmental conditions and

human exposure patterns. An alternative WQS may involve the adoption of different numerical 

value(s) that are based on: (1) an alternative health relationship derived using epidemiology with 

or without QMRA; (2) QMRA results to determine water quality values associated with a 

specific illness rate; or (3) a different indicator/method combination. EPA recommends that these 

alternative criteria reflect the same risk management decision regarding illness rate, as discussed 

in section 4.0. Such alternative criteria may be adopted into a state WQS provided that the 
48

resulting site-specific WQS are scientifically defensible, protective of the use, and reviewed and 

approved by EPA under CWA §303(c). 

6.2.1 Epidemiological Studies

Recreational water epidemiological studies describe the risks associated with exposure to fecal 

contamination as measured by FIB. Epidemiological studies with or without QMRA could be 

used to develop an alternative health relationship for a waterbody. This alternative health 

relationship could be used to develop site-specific alternative criteria. 

EPA’s NEEAR epidemiological study were conducted in water primarily impacted human fecal 

contamination, with the exception of one site that was impacted by urban runoff (U.S. EPA, 

2010a; Wade et al., 2006, 2008, 2010). Statistically significant associations between water 

quality, as determined using EPA’s Enterococcus spp. qPCR Method 1611 (U.S. EPA, 2012b), 

and reported GI illness were observed in the temperate marine water and fresh water WWTPimpacted beaches. Other agencies have also conducted recreational water epidemiological 

studies. For example, epidemiological studies of recreational water exposures have been 

conducted recently in Southern California (Colford et al., 2012), Southern Florida (Fleming, 

2006; Sinigalliano, 2010), and Ohio (Marion et al., 2010). 

Several factors can influence the potential epidemiological relationship between indicator density

and relative human health risk. Some of the potentially important factors include the source of 

fecal contamination, age of the fecal contamination, solar radiation, water salinity, turbidity, 

dissolved organic matter, water temperature, and nutrient content. Additionally, numerous 

factors also affect the occurrence and distribution of FIB and pathogens, including but not 

limited to: predation of bacteria by other organisms; differential interactions between microbes 

and sediment, including the release and resuspension of bacteria from sediments in the water 

column; and differential environmental effects on indicator organisms versus pathogens (U.S. 

EPA, 2010a; WERF, 2009).

States or local agencies may choose to conduct epidemiological studies in their waterbodies and 

use the results from those studies to derive alternative criteria, site-specifically. To derive 

scientifically defensible alternative WQC for adoption into state standards, ideally the 

epidemiological studies should be rigorous, comparable to those used to support the 2012 

RWQC, and peer-reviewed. However, smaller scale epidemiological studies may also provide a 

scientifically defensible foundation for alternative criteria. Additionally, QMRA (see section 

6.2.2) has been identified as potentially useful for developing alternative criteria by enhancing 

the interpretation and application of new or existing epidemiological data (Boehm et al., 2009; 

Dorevitch et al., 2011). QMRA can supplement new or existing epidemiological results by

characterizing various exposure scenarios, interpreting potential etiological drivers for the 

observed epidemiological results, and accounting for differences in risks posed by various types 

of FIB sources. 

Epidemiological studies are resource intensive and logistically difficult, although the results can 

provide the data necessary for a scientifically defensible basis to allow the adoption of WQS 

based on fecal indicator/methods that are not part of EPA’s national §304(a) recommendations. 

Such studies may also support the development and adoption of alternative criteria based on 
49

different health endpoints, such as respiratory illnesses, than EPA has used in its current 

recommendations (i.e., GI illnesses). When the studies demonstrate a statistically significant 

correlation between levels of water quality measured using particular FIB(s) and adverse health 

outcomes, they may be scientifically defensible and, as such, could be used to develop and adopt 

alternative criteria. 

The epidemiological information underlying the recommended 2012 RWQC used a PC study

design. If a state wishes to develop alternative criteria using their own epidemiological studies, 

EPA advises that the studies also be of the PC design to facilitate the interpretation of the 

alternative health relationship and potential resulting alternative criteria. EPA will provide 

additional information on the use of epidemiological studies in development of alternative 

criteria in upcoming TSM. 

6.2.2 Quantitative Microbial Risk Assessment

QMRA is a formal process, analogous to chemical risk assessment, of estimating human health 

risks due to exposures to selected infectious pathogens (Haas et al., 1999; NRC, 1983). To the 

greatest possible extent, the QMRA process should include the evaluation and consideration of 

quantitative information; however, qualitative information is also used when appropriate (WHO, 

1999). In general, QMRA can be initiated for a variety of reasons, including but not limited to, 

the following: 

 To assess the potential for human risk associated with exposure to a known pathogen; 

 To determine critical points for control, such as watershed protection measures;

 to evaluate specific treatment processes to reduce, remove, or inactivate various 

pathogens; 

 To predict the consequences of various management options for reducing risk; 

 to determine appropriate criteria (regulatory) levels that will protect individuals and/or 

populations to a specified risk level or range;

 To identify and prioritize research needs; and

 To assist in interpretation of epidemiological investigations. 

QMRA methodologies have been applied to evaluate and manage pathogen risks for a range of 

scenarios, including those from food, sludge/biosolids, drinking water, recycled water, and 

recreational waters. Moreover, chemical risk assessment in general has been used extensively by

EPA for decades to establish human health criteria for a wide range of pollutants in water and 

other media, and QMRA specifically has been used to inform EPA’s policy making for 

microbiological pollutants in drinking water and biosolids, and by other U.S. and international 

governmental agencies (such as, U.S. Department of Agriculture, U.S. Food and Drug 

Administration, and WHO) to protect public health from exposure to microbial pollutants in food 

and water. 

Although EPA believes the 2012 RWQC are appropriate for waterbodies impacted by all 

sources, QMRA can be used to develop alternative site-specific criteria, where sources are 

characterized predominantly as nonhuman or nonfecal (U.S. EPA, 2009b). EPA’s research 

indicates that understanding the predominant source of fecal contamination could help 
50

characterize the human health risks associated with recreational water exposure. Various 

epidemiological investigations, including EPA’s have documented human health effects in 

waters impacted by human fecal contamination. QMRA studies have demonstrated that the 

potential human health risks from human and nonhuman fecal sources could be different due to 

the nature of the source, the type and number of pathogens from any given source, as well as 

variations in the co-occurrence of pathogens and fecal indicators associated with different 

sources (Roser et al., 2006; Schoen and Ashbolt, 2010; Soller et al., 2010b; Till and McBride, 

2004; WERF, 2011). Additional information and case studies of QMRA for recreational waters 

will be provided in upcoming TSM. 

Further, research demonstrates that swimming-associated illnesses are caused by different 

pathogens, which depend on the source of fecal contamination. For example, in human-impacted 

recreational waters, human enteric viruses appear to cause a large proportion of illnesses (Soller 

et al., 2010a). In recreational waters impacted by gulls and agricultural animals such as cattle, 

pigs, and chickens, bacteria and protozoa are the etiologic agents of concern (Roser et al., 2006; 

Schoen and Ashbolt, 2010; Soller et al., 2010b). The relative level of predicted human illness in 

recreational waters impacted by nonhuman sources can also vary depending on whether the 

contamination is direct or via runoff due to a storm event (U.S. EPA, 2010g). EPA is developing 

TSM for QMRA to assist states in developing site-specific criteria to account for local scale, 

nonhuman sources that are protective of the designated use of primary contact recreation. 

To derive site-specific criteria that are considered scientifically defensible and protective of the 

designated use, QMRA studies should be well documented, follow accepted practices, and rely 

on scientifically defensible data. A sanitary characterization can provide detailed information on 

the source(s) of fecal contamination in a waterbody to determine whether the predominant source 

is human or nonhuman. EPA developed a QMRA-specific sanitary survey application, which 

could be included in a sanitary characterization, to capture information directly applicable to a 

QMRA. This sanitary characterization process will be described in upcoming QMRA TSM.

EPA’s QMRA framework can also be useful for informing human health relationships with 

alternative FIBs (MFE, 2003; Viau et al., 2011) and may help to clarify epidemiological results 

in scenarios where waterbodies are impacted by nonhuman sources or the epidemiological results 

are inconclusive (see section 6.2.1). 

6.2.3 Alternative Indicators or Methods

EPA anticipates that scientific advancements will provide new technologies for enumerating 

fecal pathogens or FIB. New technologies may provide alternative ways to address 

methodological considerations, such as rapidity, sensitivity, specificity, and method 

performance. As new or alternative indicator and/or enumeration method combinations are 

developed, states may want to consider using them to develop alternative criteria for adoption in 

WQS. 

Previously, EPA has used the evaluation of multiple indicators and enumeration methods to 

describe a common level of water quality. For example, the derivation of the 1986 criteria values 

was fundamentally based on the comparison of multiple indicators: fecal coliform, enterococci, 
51

and E. coli. In those specific cases, comparisons were made among membrane filtration methods 

specific to each target organism. Another example of this occurred when EPA approved the use 

of the IDEXX-based methods for the detection of enterococci and E. coli. In this comparison, 

results from a membrane-filtration method were compared to another method that relied on 

substrate-utilization and MPN enumeration. Rapid methods, such as E. coli enumerated by 

qPCR, have already been evaluated against culturable methods and demonstrated utility on a 

site-specific basis (Lavender and Kinzelman, 2009).

Some examples of new enumeration methods for FIB include: immunomagnetic 

separation/adenosine triphosphate (IMS/ATP), propidium monoazide (PMA) qPCR, reverse 

transcriptase (RT) qPCR, covalently linked immunomagnetic separation/adenosine triphosphate 

(COV-IMS-ATP), and transcription mediated amplification (TMA-RNA). New methods and 

additional improvements to currently available methods, platforms and chemistries may also be 

developed in the future.

Examples of possible alternative indicators include, but are not limited to: Bacteroidales, 

Clostridium perfringens, human enteric viruses, and coliphages. These possible alternative 

indicator organisms could be used with new methodologies or methodologies similar to those 

recommended by the 2012 RWQC. For example, in one case, Bacteroidales measured by qPCR 

were highly correlated with Enterococcus spp. and E. coli when either culture-based methods or 

qPCR methods were used (WERF, 2011). The pathogens norovirus GI and GII have also been 

shown to be predictors of the presence of other pathogens such as adenovirus measured by qPCR 

(WERF, 2011). 

If a state adopts WQS using alternative indicator/method combinations, EPA will review those 

standards, including any technical information submitted to determine whether such standards 

are scientifically defensible and protective of the primary contact recreation use. To facilitate 

consideration of such standards, states may gather water quality data over one or more 

recreational seasons for the indicator/method recommended in the 2012 RWQC and the proposed 

alternative indicator/method combination. A robust relationship need not be established between 

EPA’s recommendation and alternative indicator(s) for the whole range of indicator densities 

(U.S. EPA, 2010e). It is, however, important that a consistent and predictable relationship exist 

between the enumeration methods and an established indicator/health relationship in the range of 

the recommended criteria. EPA will provide information on demonstrating the relationship 

between two indicator/method combinations in upcoming TSM. 
52

References

ASTM International (formerly known as American Society for Testing and Materials (ASTM)). 

2012. Standard Practice for Determining Microbial Colony Counts from Waters Analyzed by 

Plating Methods. Designation: D5465 – 93 (Reapproved 2012).

Bartram, J., Rees, G., editors. 2000. Monitoring bathing waters. Lopdon: E & F N Spon. 

http://www.who.int/water_sanitation_health/bathing/monbathwat.pdf

Boehm, A.B. 2007. Enterococci concentrations in diverse coastal environments exhibit extreme 

variability. Environ. Sci. Technol., 41: 8227-8232.

Boehm, A.B., Whitman, R.L., Nevers, M.B., Hou, D. Weisberg, S.B. 2007. Nowcasting 

Recreational Water Quality, in Statistical Framework for Recreational Water Quality Criteria and 

Monitoring (ed L. J. Wymer), John Wiley and Sons, Ltd, Chichester, UK.

Boehm, A.B., Ashbolt, N., Colford, J., Dunbar, L., Fleming, L., Gold, M., Hansel, J., Hunter, 

P.R., Ichida, A., McGee, C., Soller, J.A., Weisberg, S.B. 2009. A Sea Change Ahead for 

Recreational Water Quality Criteria. Journal of Water and Health 7(1): 9-20.

Byappanahalli, M.N., Roll, B.M., Fujioka, R.S. 2012. Evidence for Occurrence, Persistence, and 

Growth Potential of Escherichia coli and Enterococci in Hawaii’s Soil Environments. Microbes 

and Environments, 27(2): 164-170.

Cabelli, V.J., Dufour, A.P., McCabe, L.J., Levin, M.A. 1982. Swimming Associated 

Gastroenteritis and Water Quality. American Journal of Epidemiology 115: 606-616.

Cabelli, V.J. 1983. Health Effects Criteria for Marine Recreational Waters, Technical Report. 

U.S. Environmental Protection Agency, Health Effects Research Laboratory: Research Triangle 

Park, NC. EPA 600/1-80-031.

Calderon, R.L., Mood, E.W., Dufour, A.P. 1991. Health effects of swimmers and nonpoint 

sources of contaminated water. International Journal of Environmental Health Research 1: 21-31.

Census 2010. Table 1. Annual Estimates of the Resident Population by Sex and Five-Year Age 

Groups for the United States: April 1, 2000 to July 1, 2009 (NC-EST2009-01) Source: U.S. 

Census Bureau, Population Division. Release Date: June 2010.

CDC 1993. Moore, A.C., Herwaldt, B.L., Craun, G.F., Calderon, R.L., Highsmith, A.K., 

Jurankek, D.D. Surveillance for Waterborne Disease Outbreaks - United States, 1991-1992. 

Morbidity and Mortality Weekly Report 42: 1-22.

CDC 1996. Kramer, M.H., Herwaldt, B.L., Craun, G.F., Calderon, R.L., Juranek, D.D. 

Surveillance for Waterborne-Disease Outbreaks - United States, 1993-1994. Morbidity and 

Mortality Weekly Report 45: 1-33.
53

CDC 1998. Levy, D.A., Bens, M.S., Craun, G.F., Calderon, R.L., aHerwaldt, B.L. Surveillance 

for Waterborne-Disease Outbreaks - United States, 1995-1996. Morbidity and Mortality Weekly 

Report 47: 1-33.

CDC 2000. Barwick, R.S., Levy, D.A., Craun, G.F., Beach, M.J., Calderon, R.L. Surveillance 

for Waterborne Disease Outbreaks - United States, 1997-1998. Morbidity and Mortality Weekly 

Report 49: 1-35.

CDC 2002. Lee, S.H., Levy, D.A., Craun, G.F., Beach, M.J., Calderon, R.L. Surveillance for 

Waterborne-Disease Outbreaks - United States, 1999-2000. Morbidity and Mortality Weekly 

Report 51: 1-48.

CDC 2004. Yoder, J.S., Blackburn, B.G., Craun, G.F., Hill, V., Levy, D.A., Chen, N., Lee, S.H., 

Calderon, R.L., Beach, M.J. Surveillance for Waterborne-Disease Outbreaks Associated with 

Recreational Water - United States, 2001-2002. Morbidity and Mortality Weekly Report 53: 1-

22.

CDC 2006. Dziuban, E.J., Liang, J.L., Craun, G.F., Hill, V., Yu, P.A., Painter, J., Moore, M.R., 

Calderon, R.L., Roy, S.L., Beach, M.J. Surveillance for Waterborne Disease and Outbreaks 

Associated with Recreational Water - United States, 2003-2004. Morbidity and Mortality

Weekly Report 55: 1-30.

CDC 2008. Yoder, J.S., Hlavsa, M.C., Craun, G.F., Hill, V., Roberts, V., Yu, P.A., Hicks, L.A., 

Alexander, N.T., Calderon, R.L., Roy, S.L., Beach, M.J. Surveillance for Waterborne Disease 

and Outbreaks Associated with Recreational Water Use and Other Aquatic Facility-Associated 

Health Events - United States, 2005-2006. Morbidity and Mortality Weekly Report 57: 1-38.

57: 1-38.

Cheung, W.H.S., Chang, K.C.K., Hung, R.P.S., Kleevens, J.W.L. 1990. Health Effects of Beach 

Water Pollution in Hong Kong. Epidemiology and Infection 105(1): 139-162.

Colford, J.M., Jr., Rees, J.R., Wade, T.J., Khalakdina, A., Hilton, J.F., Ergas, I.J., Burns, S., 

Benker, A., Ma, C., Bowen, C., Mills, D.C., Vugia, D.J., Juranek, D.D., Levy, D.A. 2002. 

Participant Blinding and Gastrointestinal Illness in a Randomized, Controlled Trial of an InHome Drinking Water Intervention. Emerging Infectious Diseases 8(1): 29-36.

Colford, J.M., Jr., Wade, T.J., Schift, K.C., Wright, C., Griffith, J.F., Sandhu, S.K., Weisberg, 

S.B. 2005. Recreational Water Contact and Illness in Mission Bay, California. Southern 

California Coastal Water Research Project, Technical Report 449.

Colford, J.M., Jr., Wade, T.J., Schiff, K.C., Wright, C.C., Griffith, J.F., Sandhu, S.K., Burns, S., 

Sobsey, M., Lovelace, G., and Weisberg, S.B., 2007. Water Quality Indicators and the Risk of 

Illness at Beaches with Nonpoint Sources of Fecal Contamination. Epidemiology 18(1): 27-35.

Colford, J., Schiff, K.C., Griffith, J.F., Yau, V., Arnold, B.F., Wright, C.C., Gruber, J.S., Wade, 

T.J., Burns, S., Hayes, J., McGee, C., Gold, M., Cao, Y., Noble, R.T., Haugland, R., Weisberg, 
54

S.B. 2012. Using rapid indicators for Enterococcus to assess the risk of illness after exposure to 

urban runoff contaminated marine water. Water Research, 46: 2176-2186.

Corbett, S.J., Rubin, G.L., Curry, G.K., Kleinbaum, D.G. and the Sydney Beach Users Study

Advisory Group 1993. The Health Effects of Swimming at Sydney Beaches. American Journal 

of Public Health 83(12): 1701-1706.

Craig, D.L., Fallowfield, H.J., Cromar, N.J. 2003. Effectiveness of guideline faecal indicator 

organism values in estimation of exposure risk at recreational coastal sites. Water Science and 

Technology 47(3): 191-198.

Craun, G.F., Calderon, R.L., Craun, M.F. 2005. Outbreaks associated with recreational water in 

the United States. International Journal of environmental Health Research. 15(4): 243-262.

Davies, C.M., Long, J.A.H., Donald, M., Ashbolt, N.J. 1995. Survival of fecal microorganisms 

in marine and fresh water sediments. Applied and Environmental Microbiology, 61(5): 1888-

1896.

Dorevitch, S., Ashbolt, N.J., Ferguson, C.M., Fujioka, R., McGee, C.D., Soller, J.A., Whitman, 

R.L. 2010. Meeting Report: Knowledge and Gaps in Developing Microbial Criteria for Inland 

Recreational Waters. Environmental Health Perspectives 118(6): 871-876.

Dorevitch, S., Doi, M., Hsu, F.C., Lin, K.T., Roberts, J.D., Liu, L.C., Gladding, R., Vannoy, E., 

Li, H., Javor, M., Scheff, P.A. 2011. A comparison of rapid and conventional measures of 

indicator bacteria as predictors of waterborne protozoan pathogen presence and density. Journal 

of Environmental Monitoring Aug 8.

Dufour, A.P. 1984. Health Effects Criteria for Fresh Recreational Waters. EPA 600/1-84-004.

Dufour, A.P., Evans, O., Behymer, T., and Cantu, R. 2006. Water ingestion during swimming 

activities in a pool: a pilot study. J Water Health 4(4): 425-430.

Dufour, A.P., Schaub, S. 2007. The Evolution of Water Quality Criteria in the United States 

1922-2003, in Statistical Framework for Recreational Water Quality Criteria and Monitoring (ed 

L. J. Wymer), John Wiley and Sons, Ltd, Chichester, UK.

EP/CEU (European Parliament/Council of the European Union) 1976. Directive 76/100/EEC of 

the European Parliament and of the Council of 8 December 1975 concerning the quality of 

bathing water. Available at: http://eurlex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:31976L0160:EN:NOT

EP/CEU 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
55

European Commission-Epibathe, 2009. EpiBathe Report.

Ferley, J.P., Zmirou, D., Balducci, F., Baleux, B., Fera, P., Larbaigt, G., Jacq, E., Moissonnier, 

B., Blineau, A., and Boudot, J. 1989. Epidemiological Significance of Microbiological Pollution 

Criteria for River Recreational Waters. International Journal of Epidemiology 18(1): 198-205.

FL PIRG vs. EPA 2007. Florida Public Interest Research Group Citizen Lobby, Inc., et al. v. 

U.S. EPA, et al., No. 4:02-cv-00408-WS-WCS (N.D. Fla. Feb 15, 2007) (Order Granting EPA's 

Motion for Summary Judgment based on EPA's July 6, 2005 Determination on Referral 

Regarding Florida Administrative Code Chapter 62-303, Identification of Impaired Surface 

Waters).

Fleisher, J.M., Jones, F., Kay, D., Stanwell-Smith, R., Wyer, M., Morano, R. 1993. Water and 

non-water-related risk factors for gastroenteritis among bathers exposed to sewage-contaminated 

marine waters. International Journal of Epidemiology 22(4): 698-708.

Fleisher, J.M., Kay, D., Wyer, M.D., Godfree, A.F. 1998. Estimates of the Severity of Illnesses 

Associated with Bathing in Marine Recreational Waters Contaminated with Domestic Sewage. 

International Journal of Epidemiology 27(4): 722-726.

Fleming, L.E., Solo-Gabriele, H.M., Fleisher, J.M., Goodwin, K., Backer, L., Elmir, S., Wang, J. 

2006. The Pilot Epidemiologic Assessment of Microbial Indicators for Monitoring Recreational 

Water Quality in Marine Sub/Tropical Environments.

Fleming, L.E., Solo-Gabriele, H., Fleisher, J.M., Elmir, S., Sinigalliano, C., Plano, L., and Wang, 

J. 2008. Final Report on the Pilot Epidemiologic Assessment of Microbial Indicators for 

Monitoring Recreational Water Quality in Marine Sub/Tropical Environments. The NSF NIEHS 

Oceans and Human Health Center, University of Miami.

Francy, D.S. 2009. Use of predictive models and rapid methods to Nowcast bacteria levels at 

coastal beaches. Aquatic Ecosystem Health and Management 12(2): 177-182.

Frick, W.E., Z. Ge, Zepp, R.G. 2008. Nowcasting and Forecasting Concentrations of Biological 

Contaminants at Beaches: A Feasibility and Case Study. Environmental Science and Technology

42(13): 4818-4824.

Ge, Z. Frick, W.E. 2009. Time-Frequency Analysis of Beach Bacteria Variations and its 

Implication for Recreational Water Quality Modeling. Environmental Science and Technology

43(4): 1128-1133.

Griffith, J.F., Weisberg, S.B. 2011. Challenges in Implementing New Technology for Beach 

Water Quality Monitoring: Lessons from a California Demonstration Project. Marine 

Technology Society Journal 45: 65-73.

Haas, C.N., Rose, J., Gerba, C.P. 1999. Quantitative Microbial Risk Assessment. John Wiley and 

Sons, Ltd, New York, NY.
56

Haile, R.W., Witte, J.S., Gold, M., Cressey, R., McGee, C., Millikan, R.C., Glasser, A., Harawa, 

N, Ervin, C., Harmon, P., Harper, J., Dermand, J., Alamillo, J., Barrett, K., Nides, M., Wang, 

G.Y. 1999. The Health Effects of Swimming in Ocean Water Contaminated by Storm Drain 

Runoff. Epidemiology 10(4): 355-363.

Harrington J, Wilcox D, Giles P, Ashbolt N, Evans J, Kirton C. 1993. The health of Sydney

surfers: an epidemiological study. Water Science Technology 27(3-4): 175-182.

Haugland, R.A., Siefring, S.C., Wymer, L.J., Brenner, K.P., Durfour, A. 2005. Comparison of 

Enterococcus measurements in fresh water at two recreational beaches by quantitative 

polymerase chain reaction and membrane filter culture analysis. Water Research 39: 559-568.

Haugland, R.A., Siefring, S., Lavender, J., Varma, M. 2012. Influences of sample interference 

and interference controls on quantification of enterococci fecal indicator bacteria in surface water 

by the qPCR method. Water Research

http://dx.doi.org/10.1016/j.watres.2012.08.017.

Kay, D., Fleisher, J.M., Salmon, R.L., Jones, F., Wyer, M.D., Godfree, A.F., ZelenauchJacquotte, Z., Shore, R. 1994. Predicting Likelihood of Gastroenteritis from Sea Bathing: Results 

from Randomised Exposure. Lancet 344(8927): 905-909.

Kay, D., Bartram, J., Prüss, A., Ashbolt, N., D. Wyer, M.D., Fleisher, J.M., Fewtrell, L., Rogers, 

A., Rees, G. 2004. Derivation of numerical values for the World Health Organization guidelines 

for recreational waters, Water Research38(5): 1296-1304.

Kinzelman, J.L., Bushon, R.N., Dorevitch, S., Noble, R.T. 2011. Comparative evaluation of 

molecular and culture methods for fecal indicator bacteria for use in inland recreational waters. 

WERF PATH7R09.

Lavender, J. S., Kinzelman, J.L. 2009. A cross comparison of qPCR to agar-based or defined 

substrate test methods for the determination of Escherichia coli and enterococci in municipal 

water quality monitoring programs. Water Research 43: 4967-4979.

Marion, J.W., Lee, J., Lemeshow, S., Buckley, T.J. 2010. Association of Gastrointestinal Illness 

and Recreational Water Exposure at an Inland U.S. Beach. Water Research 44(16): 4796-4804.

McBride, G.B., Salmond, C.E., Bandaranayake, D.R., Turner, S.J., Lewis, G.D., Till, D.G. 1998. 

Health effects of marine bathing in New Zealand. International Journal of Environmental Health 

Research 8(3): 173-189.

MFE (Ministry for the Environment, New Zealand) 2003. Microbiological Water Quality

Guidelines for Marine and Fresh water Recreational Areas. Available 

at:http://www.mfe.govt.nz/publications/water/microbiological-quality-jun03/microbiologicalquality-jun03.pdf
57

MNHW (Minister of National Health and Welfare) 1992. Guidelines for Canadian Drinking 

Water Quality. Fifth Edition. Canadian Government Publishing Center: Ottawa, Canada.

NRC (National Research Council) 1983. Risk Assessment in the Federal Government: Managing 

the Process. National Research Council of the National Academies. National Academy Press: 

Washington, DC.

Noble, R.T., Lee, I.M., Schiff, K.C. 2004. Inactivation of indicator micro-organisms from

various sources of faecal contamination in seawater and fresh water. Journal of Applied

Microbiology 96: 464-472.

Noble, R.T., Blackwood, A.D., Griffith, J.F., McGee, C.D., and Weisberg, S.B., 2010. 

Comparison of Rapid Quantitative PCR-Based and Conventional Culture-Based Methods for 

Enumeration of Enterococcus spp. and Escherichia coli in Recreational Waters. Applied and 

Environmental Microbiology 76(22): 7437-7443.

Payment, P., Richardson, L., Siemiatycki, J., Dewar, R., Edrawrdes, M., Franco, E. 1991. A 

Randomized Trial to Evaluate the Risk of Gastrointestinal Disease due to Consumption of 

Drinking Water Meeting Current Microbiological Standards. American Journal of Public Health 

81(6): 703-708.

Payment, P., Siemiatycki, J., Richardson, L., Renaud, G., Franco, E., Prévost, M. 1997. A 

Prospective Epidemiological Study of Gastrointestinal Health Effects Due to the Consumption of 

Drinking Water. International Journal of Environmental Health Research 7: 5-31. 

Pond, K. 2005. Water Recreation and Disease Report: Plausibility of Associated Infections: 

Acute Effects, Sequelae and Mortality. World Health Organization: Geneva, Switzerland.

Prieto, M.D., Lopez, B., Juanes, J.A., Revilla, J.A., Llorca, J., Delgado-Rodriguez, M., 2001. 

Recreating in coastal waters: health risks associated with bathing in sea water. Journal of 

Epidemiology and Community Health 5: 442-447.

Prüss, A. 1998. Review of Epidemiological Studies on Health Effects from Exposure to 

Recreational Water. International Journal of Epidemiology 27(1): 1-9.

Roser, D. and N. Ashbolt. 2006. Microbial exposure assessment of an urban recreational lake: a 

case study of the application of new risk-based guidelines. Water Science and Technology. 

54:245-252.

Roy, S.L., DeLong, S.M., Stenzel, S.A., Shiferaw, B., Roberts, J.M., Khalakdina, A., Marcus, R., 

Segler, S.D., Shah, D.D., Thomas, S., Vugia, D.L., Zansky, S.M., Dietz, V., Beach, M.J., the 

Emerging Infections Program FoodNet Working Group 2004. Risk Factors for Sporadic 

Cryptosporidiosis Among Immunocompetent Persons in the United States from 1999 to 2001. 

Journal of Clinical Microbiology 42(7): 2944-51.

Samadpour, M., Stewart, J., Steingart, K., Addy, C., Louderback, J., McGinn, M., Ellington, J., 
58

Newman, T. 2002. Laboratory investigation of an E. coli O157:H7 outbreak associated with 

swimming in Battle Ground Lake, Vancouver, Washington. Journal of Environmental Health 

64(10): 16-26.

Schoen, M.E., Ashbolt, N.J. 2010. Assessing Pathogen Risk to Swimmers at Non-Sewage 

Impacted Recreational Beaches. Environmental Science and Technology 44(7): 2286-2291.

Seyfried, P.L., Tobin, R.S., Brown, N.E., and Ness, P.F., 1985. A Prospective Study of 

Swimming-Related Illness I. Swimming-Associated Health Risk. American Journal of Public 

Health 75(9):1068-1070.

Sinclair, R.G., Jones, E.L., Gerba, C.P. 2009. Viruses in recreational water-borne disease 

outbreaks: a review. J Appl Microbiol 107(6): 1769-1780.

Sinigalliano, C.D., Fleisher, J.M., Gidley, M.L., Solo-Gabriele, H.M., Shibata, T., Plano, L.R., 

Elmir, S.M., Wanless, D., Bartkowiak, J., Boiteau, R., Withum, K., Abdelzaher, A.M., He, G., 

Ortega, C., Zhu, X., Wright, M.E., Kish, J., Hollenbeck, J., Scott, T., Backer, L.C., and Fleming, 

L.E., 2010. Traditional and Molecular Analyses for Fecal Indicator Bacteria in Non-Point Source 

Subtropical Recreational Marine Waters. Water Research 44(13): 3763-3772.

Soller, J.A., Bartrand, T., Ashbolt, N.J., Ravenscroft, J., Wade, T.J. 2010a. Estimating the 

Primary Etiologic Agents in Recreational Fresh waters Impacted by Human Sources of Faecal 

Contamination. Water Research 44(16): 4736-4747.

Soller, J.A., Schoen, M.E., Bartrand, T., Ravenscroft, J., Wade, T.J. 2010b. Estimated Human 

Health Risks from Exposure to Recreational Waters Impacted by Human and Non-Human 

Sources of Faecal Contamination. Water Research 44(16): 4674-4691.

Solo-Gabriele, H.M., Wolfert, M.A., Desmarais, T.R., Carol, J.P. 2000. Sources of Escherichia 

coli in a coastal subtropical environment. Applied and Environmental Microbiology 66(1): 230-

237.

Stevenson, A.H. 1953. Studies of Bathing Water Quality and Health. American Journal of Public 

Health 43: 429-538.

Till, D., McBride, G. 2004. Potential public health risk of Campylobacter and other zoonotic 

waterborne infections in New Zealand. Chapter 12 in Waterborne Zoonoses: Identification, 

causes and control. Cotruvo, J.A., Dufour, A., Rees, G., Bartram, J., Carr, R., Cliver, D.O., 

Craun, G.F., Fayer, R., Gannon, V.P.J., ed. 2004. World Health Organization (WHO). IWA 

Publishing: London, UK.

USDA 2000. Waterborne Pathogens in Agricultural Watersheds. United States Department of 

Agriculture, Natural Resources Conservation Service, Watershed Science Institute. 

U.S. EPA 1976. Quality Criteria for Water. U.S. Environmental Protection Agency: Washington, 

DC.
59

U.S. EPA 1978. Microbiological Methods for Monitoring the Environment: Water and Wastes.

U.S. Environmental Protection Agency, Office of Research and Development: Cincinnati, OH. 

EPA 600-8-78-017.

U.S. EPA 1986. EPA’s Ambient Water Quality Criteria for Bacteria – 1986. U.S. Environmental 

Protection Agency: Washington, DC. EPA440/5-84-002.

U.S. EPA. 1994. Water quality standards handbook: 2nd ed. EPA-823-B-94-005a,b. National 

Technical Information Service, Springfield, VA. 

U.S. EPA 2002a. Method 1600: Enterococci in Water by Membrane Filtration Using membraneEnterococcus Indoxyl-β-D-Glucoside Agar (mEI). Available at: 

http://www.epa.gov/microbes/1600sp02.pdf

U.S. EPA 2002b. Method 1603: Escherichia coli (E. coli) in Water by Membrane Filtration 

Using Modified Membrane-Thermotolerant Escherichia coli Agar (Modified mTEC). Available 

at: http://www.epa.gov/microbes/1603sp02.pdf

U.S. EPA 2003. America’s Children and the Environment: Measures of Contaminants, Body 

Burdens and Illnesses, 2nd Edition. Available at:

http://yosemite1.epa.gov/ee/epa/eerm.nsf/vwGA/F042C8CE39DE432285256CD7006B8001

U.S. EPA 2004. Water Quality Standards for Coastal and Great Lakes Recreation Waters Rule 

(BEACH Act). 69 FR 67217. November 16, 2004.

U.S. EPA 2007a. Report of the Expert Scientific Workshop on Critical Research Needs for the 

Development of New or Revised Recreational Water Quality Criteria (Airlie Workshop). EPA823-R-07-006.

U.S. EPA 2007b. Critical Path Science Plan. EPA-823-R-08-002.

U.S. EPA 2009a. Review of Zoonotic Pathogens in Ambient Waters. EPA 822-R-09-002. 

Available at:

http://water.epa.gov/scitech/swguidance/waterquality/standards/criteria/health/recreation/upload/

2009_07_16_criteria_recreation_zoonoticpathogensreview.pdf

U.S. EPA 2009b. Review of Published Studies to Characterize Relative Risks from Different 

Sources of Fecal Contamination in Recreational Water, U.S. Environmental Protection Agency, 

Office of Science and Technology: Washington, DC. EPA 822-R-09-001.

U.S. EPA 2009c. Fecal Indicator Organism Behavior in Ambient Waters and Alternative 

Indicators for Tropical Regions, U.S. Environmental Protection Agency, Office of Science and 

Technology: Washington, DC.

U.S. EPA 2010a. Report on 2009 National Epidemiologic and Environmental Assessment of 
60

Recreational Water Epidemiology Studies (NEEAR 2010 - Surfside & Boquerón). EPA-600-R10-168. Available at: http://www.epa.gov/neear/files/Report2009v5_508comp.pdf

U.S. EPA 2010b. Comparison and Evaluation of Epidemiological Study Designs of Health 

Effects Associated with Recreational Water Use.

U.S. EPA 2010c. A Study of the Various Parameters that Affect the Performance of the New 

Rapid U.S. Environmental Protection Agency Quantitative Polymerase Chain Reaction (qPCR) 

Method for Enterococcus Detection and Comparison with Other Methods and Pathogens in 

Treated Wastewater Mixed with Ambient Water. EPA 600-R-10-149. 

U.S. EPA 2010d. Evaluation of the Suitability of Individual Combinations of Indicators and 

Methods for Different Clean Water Act Programs. EPA 823-R-10-004.

U.S. EPA 2010e. Effects of Holding Time, Storage, and the Preservation of Samples on Sample 

Integrity for the Detection of Fecal Indicator Bacteria by Quantitative Polymerase Chain 

Reaction. EPA/600/R-10/150. Available at: 

http://water.epa.gov/scitech/swguidance/standards/criteria/health/recreation/upload/P16-FinalReport.pdf

U.S. EPA 2010f. Applicability of Great Lakes NEEAR Dataset to Inland Recreational Water 

Criteria; Summary of Key Studies. EPA-823-R1-0002. 

U.S. EPA 2010g. Quantitative Microbial Risk Assessment to Estimate Illness in Fresh water 

Impacted by Agricultural Animal Sources of Fecal Contamination. EPA 822-R-10-005. 

Available at: 

http://water.epa.gov/scitech/swguidance/standards/criteria/health/recreation/upload/P4-QMRA508.pdf

U.S. EPA 2010h. Predictive Tools for Beach monitoring Volume I: Review and Technical 

Protocol. EPA-823-R-10-003. Available at:

http://water.epa.gov/scitech/swguidance/standards/criteria/health/recreation/upload/P26-ReportVolume-I-Final_508.pdf

U.S. EPA 2010i. Predictive Modeling at Beaches Volume II: Predictive Tools for Beach 

monitoring. EPA-600-R-10-176. Available at:

http://water.epa.gov/scitech/swguidance/standards/criteria/health/recreation/upload/P23-25-

Report-Volume-II-Final_508.pdf

U.S. EPA 2010j. Evaluation of Multiple Indicator Combinations to Develop Quantifiable 

Relationships. EPA-822-R-10-004. Available at: 

http://water.epa.gov/scitech/swguidance/standards/criteria/health/recreation/upload/P15-Reportto-EPA-12-28-10.pdf

U.S. EPA 2011. Translation of 1986 Criteria Risk to Equivalent Risk Levels for Use with New 

Health Data Developed Using Rapid Methods for Measuring Water Quality. In Preparation.
61

U.S. EPA 2012a. Water Quality Standards Handbook: Second Edition. EPA-823-B-12-002; 

March 2012. Retrieved November 13, 2012 from 

http://water.epa.gov/scitech/swguidance/standards/handbook/index.cfm

U.S. EPA 2012b. Method 1611: Enterococci in Water by TaqMan® Quantitative Polymerase 

Chain Reaction (qPCR) Assay. EPA-821-R-12-008.

Valderrama, A.L., Hlavsa, M.C., Cronquist, A., Cosgrove, S., Johnston, S. P., Roberts, J.M., 

Stock, M.L., Xiao, L., Xavier, K., Beach, M.J. 2009. Multiple Risk Factors Associated with a 

Large Statewide Increase in Cryptosporidiosis. Epidemiological Infections 137(12): 1781-8.

Viau, E.J.; Lee, D.; Boehm, A.B. 2011. Swimmer Risk of Gastrointestinal Illness from Exposure 

to Tropical Coastal Waters Impacted by Terrestrial Dry-Weather Runoff. Environmental Science 

and Technology 45: 7158-7165. 

Von Schirnding, Y.E.R., Kfir, R., Cabelli, V., Franklin, L., Joubert, G. 1992. Morbidity among 

bathers exposed to polluted seawater. South African Medical Journal 81:543-546.

Wade, T.J., Pai, N., Eisenberg, J.N.S., Colford, J.M., Jr. 2003. Do U.S. Environmental Protection 

Agency Water Quality Guidelines for Recreational Waters Prevent Gastrointestinal Illness? A 

Systematic Review and Meta-Analysis. Environmental Health Perspectives 111(8): 1102-1109.

Wade, T.J., Calderon, R.L., Sams, E., Beach, M., Brenner, K.P., Williams, A.H., Dufour, A.P., 

2006. Rapidly Measured Indicators of Recreational Water Quality Are Predictive of SwimmingAssociated Gastrointestinal Illness. Environmental Health Perspectives 114(1): 24-28.

Wade, T.J., Calderon, R.L., Brenner, K.P., Sams, E., Beach, M., Haugland, R., Wymer, L., 

Dufour, A.P. 2008. High Sensitivity of Children to Swimming-Associated Gastrointestinal 

Illness – Results Using a Rapid Assay of Recreational Water Quality. Epidemiology 19(3): 375-

383. 

Wade, T.J., Sams, E., Brenner, K.P., Haugland, R., Chern, E., Beach, M., Wymer, L., Rankin, 

C.C., Love, D., Li, Q., Noble, R., Dufour, A.P. 2010. Rapidly Measured Indicators or 

Recreational Water Quality and Swimming-Associated Illness at Marine Beaches: A Prospective 

Cohort Study. Environmental Health 9: 66.

WERF 2009. Report on the Expert Scientific Workshop on Critical Research and Science Needs 

for the Development of Recreational Water Quality Criteria for Inland Waters. PATH4W09.

WERF 2011. Final Report: Quantification of Pathogens and Sources of Microbial Indicators for 

QMRA in Recreational waters. PATH2R08.

WHO 1999. Principles and Guidelines for the Conduct of Microbiological Risk Assessment, 

CAC/GL-30. World Health Organization: Geneva, Switzerland. Available at: 

http://www.who.int/foodsafety/publications/micro/cac1999/en/
62

WHO 2003. Guidelines for Safe Recreational Water Environments: Volume 1 Coastal and Fresh 

Waters. Available at: http://www.who.int/water_sanitation_health/bathing/srwe1/en/

Wiedenmann, A., Krüger, P., Dietz, K., López-Pila, J.M., Szewzyk, R., Botzenhart, K. 2006. A 

Randomized Controlled Trial Assessing Infectious Disease Risks from Bathing in Fresh 

Recreational Waters in Relation to the Concentration of Escherichia coli, Intestinal Enterococci, 

Clostridium perfringens, and Somatic Coliphages. Environmental Health Perspectives 114(2): 

228-236.

Wyer M.D., Kay, D., Fleisher, J.M., Salmon, R.L., Jones, F., Godfree, A.F., Jackson, G., Rogers. 

A. 1999. An experimental health-related classification for marine waters. Water Research 33: 

715–22.

Xue, J., Zartarian, V., Moya, J., Freeman, N., Beamer, P., Black, K., Tulve, N., Shalat, S. 2007. 

Meta-Analysis of Children’s Hand-to-Mouth Frequency Data for Estimating Nondietary

Ingestion Exposure. Risk Analysis 27(2): 411-420.

Zmirou, N., Pena, L., Ledrans, M., Leterte, A. 2003. Risks Associated with the Microbiological 

Quality of Bodies of Fresh and Marine Water Used for Recreational Purposes: Summary

Estimates Based on Published Epidemiological Studies. Archives of Environmental Health