United States

EnvironmentalProtection

Agency

Health Effects

Research Laboratory

Research Triangle Park NC 27711

Research and Development EPA-600 / 1-80-031 Aug 1983

EPA Health Effects

Criteria for Marine

Recreational Waters

Note: This electronic version was prepared from the original document using

optical character recognition software.
EPA-600 / 1-80-031

August 1983

HEALTH EFFECTS

CRITERIA

FOR 

MARINE

RECREATIONAL WATERS

by

Victor J. Cabelli

Marine Field Station

West Kingston, Rhode Island

HEALTH EFFECTS RESEARCH LABORATORY

OFFICE OF RESEARCH AND DEVELOPMENT

U.S. ENVIRONMENTAL PROTECTION AGENCY

RESEARCH TRIANGLE PARK, NORTH CAROLINA 277711
ii

DISCLAIMER

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

Protection Agency policy and approved for publication. Mention of trade names or

commercial products does not constitute endorsement or recommendation for use.
iii

FOREWARD

 The many benefits of our modern, developing, industrial society are accompanied

by certain hazards. Careful assessment of the relative risk of existing and new

man-made environmental hazards is necessary for the establishment of sound

regulatory policy. These regulations serve to enhance the quality of our

environment in order to promote the public health and welfare and the productive

capacity of our Nation's population.

The complexities of environmental problems originate in the deep

interdependent relationships between the various physical and biological segments

of man's natural and social world. Solutions to these environmental problems

require an integrated program of research and development using input from a

number of disciplines. The Health Effects Research Laboratory, Research Triangle

Park, NC and Cincinnati, OH conducts a coordinated environmental health

research program in toxicology, epidemiology and clinical studies using human

volunteer subjects. Wide ranges of pollutants known or suspected to cause health

problems are studied. The research focuses on air pollutants, water pollutants,

toxic substances, hazardous wastes, pesticides and nonionizing radiation. The

laboratory participates in the development and revision of air and water quality

criteria and health assessment documents on pollutants for which regulatory

actions are being considered. Direct support to the regulatory function of the

Agency is provided in the form of expert testimony and preparation of affidavits

as well as expert advice to the Administrator to assure the adequacy of

environmental regulatory decisions involving the protection of the health and

welfare of all U.S. inhabitants.

 This report provides an assessment of the relationship between microbiological

indicators of water quality and illness that may have resulted from swimming. The

data base resulted from a series of in-house and extramural epidemiologicalmicrobiological research projects designed to develop the criterion for marine

waters. The development and periodic reevaluation of such criteria is mandated by

Section 304(a)l of Public Law 92-500: Federal Water Pollution Control Act

Amendments of 1972; Clean Water Act of 1977.

 F. Gordon Hueter, Ph.D.

Director

 Health Effects Research Laboratory
iv

PREFACE

Shortly after they were published by the National Technical Advisory Committee

to the Federal Water Pollution Control Administration in 1968, the microbiological

guidelines for direct contact recreational waters were attacked as being too

restrictive. The basis for the attack was the meager and questionable

epidemiological data from which they were derived, limitations of the microbial

indicator of water quality (fecal coliforms) to be used, and defects in the

methodology available for monitoring environmental waters for its presence. It was

noted that these guidelines were recommended in the face of seemingly conflicting

epidemiological findings from the studies conducted by Stevenson and Moore and

a very limited number of outbreaks of infectious disease clearly shown to be

associated with swimming in sewage polluted waters.

Early in 1969, it was suggested to the author of this report that he “look into the

matter.” During 1969 and early 1970, he and his colleagues developed a design for

a prospective epidemiological-microbiological study differing from that used by

Stevenson in a number of essential ways. A decision was made to look first at

saltwater and later at freshwater beaches, and some beaches in New York City

were identified for the conduct of a study. 

The project was established in 1972 with a target date for completion in

1978-79. Studies were to be conducted at beaches in a number of locations in

addition to New York City. The objective of the program was to produce criteria,

defined as a mathematical relationship of some untoward effect from swimming in

sewage polluted water to the quality of that water as measured by any of a number

of potential microbial or chemical indicators; thus, they were to be amenable to

risk analysis. The objective was achieved, and this report documents the output

from that effort. 

In addition, methods were developed and published for a rather large number of

potential water quality indicators, and information and methodology were

generated and published relative to several other problems in human infectious

disease potentially or actually resultant from pollution of marine and fresh

recreational waters. Included are the discharge of Klebsiella in industrial effluents,

the relationship of Aeromonas hydrophila, Acinetobacter sp., Pseudomonas

aeruginosa, and Vibrio parahaemolyticus densities to nutrient enrichment of

aquatic environments, the potential for individuals to become colonized by

multiantibiotic resistant coliforms via their activities in sewage polluted waters,

the effect of environmental parameters on the survival of human pathogens and

indicator microorganisms in marine and fresh waters, transfer frequencies for

multiple antibiotic resistance into fecal isolates of E. coli, the characterization of

a highly chlorine resistant, male specific coliphage from sewage, and the microbial

colonization of the external ear canal.
v

ABSTRACT

 This report presents health effects quality criteria for marine recreational waters

and a recommendation for a specific criterion among those developed. It is the

mathematical relationship of the swimming-associated rate of gastrointestinal

symptoms among bathers to the quality of the water as determined by the density

of a fecal indicator, enterococci. Thus, it can be used to provide guidelines based

upon acceptable rather than detectable risk and is consistent with risk analysis. 

 The criteria were developed using data collected from an extensive in-house

extramural, microbiological-epidemiological research program conducted by the

U.S. Environmental Protection Agency over the years 1972-1979. Central to this

program was the conduct of prospective epidemiological-microbiological studies

using a design developed at the Marine Field Station of the Health Effects

Research Laboratory. These multi-year studies were conducted at beaches at three

locations in the United States (New York City, NY; Lake Pontchartrain, New

Orleans, LA; and Boston Harbor, MA). An additional study was conducted in

Alexandria, Egypt; however, for the reasons given, only the United States data

were used in the development of the criteria. 

 The two input parameters to the recommended model (criterion), the type of

symptomatology and the specific water quality indicator, were determined from the

analysis of data with a design which considered a number of symptom types and

potential indicators. In addition, swimming was carefully defined as the exposure

of the head to the water, the non-swimming controls were at the beach, and the

trials were conducted over relatively short periods of time (1-2 days).
[This page is intentionally blank.]
vii

CONTENTS

Forward iii

Preface iv

Abstract v

Figures viii

Tables ix

Acknowledgements xiii

1. Introduction 1

2. Recommendations 3

3. Background 5

Existing Guidelines and Standards 5

Data Base in Support of Existing Guidelines and Standards 7

Health Effects Recreational Water Quality Indicators 11

Guidelines Based on Acceptable Risk 12

4. Study Design 15

Perceived Deficiencies in Stevenson Design 15

Design Characteristics 16

Indicator Assays 18

Analysis of theData 18

5. Results of the Studies 21

New York City Study 21

Alexandria, Egypt Study 24

Lake Pontchartrain Study 29

Boston Harbor Study 31

6. Development of Criteria 33

The Etiologic Agent(s) 44

7. Limitations in the Use of the Recommended Criteria 49

Small Point Sources 49

Illness Rates in the Discharging Population 49

Fecal Indicators Versus Pathogens 50

References 51

Appendix 55
viii

FIGURES

Number Page

 1 Graphic Representation of Desired Recreational Water Quality Criteria 13

 2 Swimming-Associated Gastrointestinal Symptom Rates Against the 

 Mean Enterococcus and E. coli Densities in the Bathing Water for

New York City Study (1973-1975) 24

 3 Data from Figure 2a Shown on a Scale More Akin to that Used in

 Dose-Response Representations 25

 4 Swimming-Associated Rates for Vomiting or Diarrhea Against the

 Mean Enterococcus Density in the Water (Egyptian Study) 26

 5 Swimming-Associated Rates for Vomiting or Diarrhea Against the

 Mean E. coli Density in the Water (Egyptian Study) 27

 6 Age-Specific, Swimming-Associated Rates for Vomiting or Diarrhea

 by Beach and Study Population for the 1977 Egyptian Trials 28

 7 Y on X Regression Lines for the Swimming-Associated Rates for GI

 Symptoms Against the Mean Enterococcus and E. coli Densities in the

 Water 36

 8 Swimming-Associated GI Symptom Rates Against the Mean

 Enterococcus Densities in Water and 95% the Confidence Limits

 Around the Lines 41

 9 Health Effects, Quality Criteria for Marine Recreational Waters

 Developed by the EPA Epidemiological-Microbiological Program 43

 10 Ratios of Swimmer to Nonswimmer, Rates of Gastrointestinal Symptoms

 Against Mean Enterococcus Density in the Water 45

 11 Comparison of the Illness-Indicator Relationships from U.S.

 Studies with Those from the Egyptian Studies 46

 12 Day of Onset of GI Symptoms as Obtained from the 1975 New York City

 Trials 47
ix

TABLES

Number Page

 1 Methods Development in Support of the EPA Epidemiological Program 12

 2 Sequence of Events for Epidemiological-Microbiological Trials 18

 3 Success of Follow-up Phone Interviews and the Number of Useable

Responses by Beach and Year 20

 4 Correlation Coefficients for Total Gastrointestinal Symptoms and the

“Highly Credible” Portion Against the Mean Indicator Densities for

New York City Study 23

 5 Correlation Coefficients for Enterococcus and E. coli Densities

Against the Gastrointestinal Symptom Rates for U.S. and Egyptian

Studies 35

 6 Summary of the Mean Enterococcus Density-Gastrointestinal Symptom

Rate Relationships Obtained from Clustered Trials for All U.S.

Studies 37

 7 Summary of the Mean Enterococcus Density-Gastrointestinal Symptom

Rate Relationships Obtained,. from Trials Grouped by Beach and Year

for All U.S. Studies 38

 8 Summary of the Mean E. coli Density-Gastrointestinal Symptom Rate

Relationships Obtained from Clustered Trials for All U.S. Studies 39

 9 Summary of the Mean E. coli Density-Gastrointestinal Symptom Rate

Relationships Obtained from Trials Grouped by Beach and Year for

All U.S. Studies 40

 10 Regression Formulae and Correlation Coefficients for Swimming

Associated GI Symptoms Against Enterococcus Densities in the

Bathing Waters 42

 11 Ratio of Swimmer to Nonswimmer Gastrointestinal Symptom Rates by

Enterococcus Density 44

 12 Relationship of Swimming-Associated to Background (Nonswim)

Rates for Gastrointestinal Symptoms 46

 13 Duration of Gastrointestinal Symptomatology: New York City, 1975

Trials 48

 Al Total and Fecal Coliform Standards for Primary Contact Recreational

Waters as of 1978 55

 

 (continued)
x

TABLES (continued)

Number Page

 A2 Demographic Characteristics of the Four Subpopulations for 1974 New

 York City Trials 59

 A3 Mean Indicator Densities at the Coney Island and Rockaway Beaches

 During 1973 and 1974 Trials 59

 A4 Swimming-Associated Symptom Rates for New York City Beaches in

 1973, 1974 60

 A5 Swimming-Associated Rates for Symptom Groups at the New York

 City Beaches (1973-74) 60

 A6 Comparison of Salmonella and Total Coliform Densities at Coney

 Island and Rockaway Beaches 61

 A7 Analysis of Gastrointestinal and Highly Credible Gastrointestinal

 Symptom Rates by Demographic Group 62

 A8 Mean and Range of New York City Trials Clustered According to

 Enterococcus Densities 63

 A9 Mean and Range of New York City Trials Clustered According to E.

 coli Densities 63

A10 Mean and Range of New York City Trials Clustered According to

 Fecal Coliform Densities 64

A11 Mean and Range of New York City Trials Clustered According to

 Total Coliform Densities 64

A12 Mean and Range of New York City Trials Clustered According to

 Kiebsiella Densities 65

A13 Mean and Range of New York City Trials Clustered According to

 Enterobacter-Citrobacter Densities 66

A14 Mean and Range of New York City Trials Clustered According to P.

 aeruginosa Densities 67

Al5 Mean and Range of New York City Trials Clustered According to A.

 hydrophila Densities 67

A16 Mean and Range of New York City Trials Clustered According to C.

 perfringens Densities 68

A17 Mean and Range of New York City Trials Clustered According to

 Staphylococcus Densities 68

A18 Mean and Range of New York City Trials Clustered According to V.

 parahaemolyticus Densities 69

 

 (continued)
xi

TABLES (continued)

Number Page

A19 Gastrointestinal (GI) and Highly Credible GI Symptom Rates for NYC

Trials Clustered by Enterococcus Densities 70

A20 Gastrointestinal (GI) and Highly Credible GI Symptom Rates for NYC

Trials Clustered by E. coli Densities 71

A21 Gastrointestinal (GI) and Highly Credible GI Symptom Rates for NYC

Trials Clustered by Fecal Coliform Densities 72

A22 Gastrointestinal (GI) and Highly Credible GI Symptom Rates for NYC

Trials Clustered by Total Coliform Densities 73

A23 Gastrointestinal (GI) and Highly Credible GI Symptom Rates for NYC

Trials Clustered by Klebsiella Densities 74

A24 Gastrointestinal (GI) and Highly Credible GI Symptom Rates for NYC

Trials Clustered by Enterobacter-Citrobacter Densities 75

A25 Gastrointestinal (GI) and Highly Credible GI Symptom Rates for NYC

Trials Clustered by P. aeruginosa Densities 76

A26 Gastrointestinal (61) and Highly Credible GI Symptom Rates for NYC

Trials Clustered by A. hydrophila Densities 77

A27 Gastrointestinal (GI) and Highly Credible GI Symptom Rates for NYC

Trials Clustered by C. perfringens Densities 78

A28 Gastrointestinal (GI) and Highly Credible GI Symptom Rates for NYC

Trials Clustered by Staphylococcus Densities 79

A29 Gastrointestinal (GI) and Highly Credible GI Symptom Rates for NYC

Trials Clustered by V. parahaemolyticus Densities 80

A30 Mean and Range of Indicator Densities by Beach and Year for NYC

Trials 81

A31 Gastrointestinal (GI) and Highly Credible GI Symptom Rates by

Beach and Year for NYC Trials 83

A32 Symptom Rates for Trials Conducted at Three Alexandria Beaches in

1976 84

A33 Symptom Rates for Alexandria Residents and Cairo Visitors at the

Alexandria Beaches in 1977 85

A34 Symptom Rates for Alexandria Residents and Cairo Visitors at the

Alexandria Beaches in 1978 86

A35 Swimming-Associated Symptom Rates for Alexandria, Egypt Study 87

A36 Comparison of Nonswimming Symptom Rates for 1st and 2nd

Follow-up Inquiries with Cairo Visitors During 1978 Trials 88

 (continued)
xii

TABLES (continued)

Number Page

A37 Symptom Rates per 1000 Person-days for Cairo Visitors by the

 Number of Swimming Days per Week (1978) 88

A38 Symptom Rates for Vomiting and Diarrhea and Mean Indicator

Densities for Alexandria, Egypt Study 89

A39 Symptom Rates for Swimmers and Nonswimmers During 1977 Lake

Pontchartrain Trials 90

A40 Symptom Category Rates for Swimmers and Nonswirnmers During

1977 Lake Pontchartrain Trials 90

A41 Gastrointestinal Symptom Rates by Age for 1977 Lake Pontchartrain

Trials 91

A42 Indicator Densities in the Bayou St John as Compared to the

Roped-Off Area at Levee Beach on Lake Pontchartrain (1977) 91

A43 Analysis of l977 Lake Pontchartrain Data by Rainfall (Dry Versus

Wet Periods) 92

A44 Gastrointestinal Symptom Rates for 1977 Lake Pontchartrain Trials

Clustered by Indicator Densities 93

A45 Gastrointestinal Symptom for the Four 1977 Lake Pontchattraln Trials

with the Highest E. coli and Enterococcus Densities 94

A46 Clustering of Trials for Calculation of Gastrointestinal Symptom Rates

for 1978 Trials at Levee Beach, Lake Pontchartrain 95

A47 Gastrointestinal Symptom Rates and Corresponding Mean Indicator

Densities for 1978 Trials at Lake Pontchartrain 96

A48 Symptom Rates for Revere and Nahant Beaches During 1978 Boston

Harbor Study 96

A49 Gastrointestinal Symptom Rates and Corresponding Indicator Densities

for Revere and Nahant Beaches for 1978 Boston Harbor Study 97

A50 Gastrointestinal Symptom Rates and Corresponding Indicator Densities

for Clustered Trials During 1978 Boston Harbor Study 97

A51 95% Confidence Limits for Swimming-Associated Gastrointestinal

Symptom Rates Predicted from the Observed Mean Enterococcus

Densities (Trials Clustered by Indicator Densities) 98

A52 95% Confidence Limits for Mean Enterococcus Densities Predicted

from the Observed Swimming-Associated GI Symptom Rates 99

 (continued)
xiii

ACKNOWLEDGMENTS

 The author gratefully acknowledges the contributions of many individuals who

took part in the overall program, especially those of his colleagues, Drs. Alfred P.

Dufour and Morris A. Levin of the Marine Field Station, HERL-Cincinnati, who

worked with him on the in-house portion of the program. Also included are: Mr.

Paul Haberrnan of the Center of Policy Research for his work on the New York

City study (R802240, R803254); Drs. K. E. Hakim, M.K. Wahdan, A. El Molla

and M: Hussein of the High Institute of Public Health, Alexandria University for

their work on the Alexandria study (PM8O 3-542-3); Mrs. Virginia K. Ktsanes, Dr.

John E. Diem and Dr. Anne A. Anderson of Tulane University for their work on

the Lake Pontchartrain study (R805341), and Dr. David W. Drummond of Tufts

University for his work on the Boston study (R806178).

 The author is indebted to Mr. Leland McCabe, HERL-Cincinnati, for his advice

and help and to Mr. McCabe and Dr. R. John Garner, Director, HERL-Cincinnati,

for “keeping the faith” during the execution of this logistically difficult and

arduous long-range program. He owes his thanks to Dr. Harold Wolf for suggesting

the problem in 1969. He especially appreciates the contribution of a most unique

scientific administrator, Dr. John Buckley, for his vision in fostering long-range

anticipatory research programs such as this one, for recommending its initiation in

1972, and for maintaining the administrative impetus for its accomplishment.
1

SECTION 1

INTRODUCTION

 Existing health effects, water quality guidelines (often referred to as criteria) and

standards for primary contact recreational waters, as recommended or promulgated by

federal, state and local agencies, are generally stated as upper limits for fecal indicator

densities. The current EPA guideline's state that, “Based on a minimum of five samples

taken over a 30-day period, the fecal coliform bacterial level should not exceed a log

mean of 200/100 ml, nor shall more than ten percent of the total samples taken during

a 30-day period exceed 400/100 ml.” Without exception, these guidelines suffer from

two major deficiencies. The first is the paucity of epidemiological data which support

some of them and the absence of any such support for others. At best, they relate to a

“detectable risk” of infectious disease; at worst, they are based solely upon

“attainment.” The second, a consequence of the first, is that officials responsible for

making decisions are given a “number,” and this inherently limits the options available

in decision making to compliance or noncompliance. 

 With the availability of a sufficient epidemiological base, a second option is

available. In general terms, it is the promulgation of a criterion as defined herein; that

is, a mathematically expressible relationship (model) of untoward effects among

“users” to the quality of the water used. With reference to recreational waters, it is the

relationship of the incidence or risk of disease among swimmers to the quality of the

water as measured by the density of the infectious agent itself or an appropriate

indicator. As shown herein, the major pollution-associated risk to recreationists is that

of infectious disease consequent to swimming in waters polluted with human and, to

a much lesser extent, lower animal fecal wastes. Therefore, the criterion relates

infectious disease among “swimmers” to some measure of fecal pollution of the water.

This approach then permits a decision as to “acceptable risk” based upon social,

economic, medical, public health, and even political considerations (some form of costbenefit or cost-effectiveness analysis). The acceptable risk of illness or its incidence can

then be extrapolated from the criterion to yield a water quality limit (guideline), and

the guideline can then be fixed in law to provide a standard.

 This report presents such a criterion for marine recreational water quality, documents

its epidemiological base, and discusses its applications and limitations. The

recommended criterion shown in the figure below is the mathematical relationship (X

on Y regression line) of the quality of the bathing water (X), as measured by the

density of a specific fecal indicator (enterococci), to the incidence of

swimming-associated gastroenteritis (“highly credible,” gastrointestinal symptoms, Y).

It is a deterministic model empirically derived from epidemiological and

microbiological data obtained at multiple locations over several years. The

deterministic form appears to lend itself more to cost-benefit types of analyses. The two

input parameters to the model were not chosen arbitrarily. Rather, they were the output

from an experimental design formulated to respond to the questions: Which are the

“important” types of illnesses, and which is the “best indicator? This is detailed in the

body of the report.

 This criterion is directed against potential human health effects consequent to the 

pollution of marine recreational waters with human fecal wastes, notably municipal sewage.

It is a generalization which may not always hold true. Nevertheless, the fact that it has 

been found to be applicable at several locations has some implications concerning

the ecology of the etiological agent(s) and the nature of the infectious process,
2

notably, the ubiquity of the agent in feces, sewage, and its receiving water. A similar

criterion for freshwaters will probably be required, and the establishment of this

criterion does not preclude the possible' need for others, i.e... against the proliferation

of aquatic organisms pathogenic for man (e.g.,Aeromonas hydrophila; Vibrio

parahaemolyticus) which respond to nutrient loading of the water. 

 The criterion may be used to develop guidelines for sewage treatment and outfall

location. Knowledge of the transport and fate of both pathogens and indicator bacteria

would provide a refinement for translating these target area criteria into effluent

guidelines. It is hoped that the criteria will not be used to close swimming areas but

rather to expand the available recreational resource. 

 Finally, when the study design for the EPA program was being developed in

1969-1970, it was thought that swimming in sewage-polluted waters would constitute

a relatively minor route of transmission for gastrointestinal illness and that relatively

high levels of pollution (as indexed by microbial indicator densities) would be required

before gastrointestinal illness could be detected. These assumptions were made on the

basis of existing notions and available information. Both these assumptions were

incorrect. If the nonswimming rates for gastrointestinal symptomatology can be

considered as those for the population at large, then it must be concluded that

swimming in sewage-polluted waters constitutes a significant route of transmission for

the illnesses obtained, at least for individuals of “swimming age.”
3

SECTION 2

RECOMMENDATIONS

1. The health effects criterion for marine recreational waters presented herein should

be considered for use by EPA since it is a relatively reliable generalization which is

amenable to risk analysis, allows a wider choice of options at both the federal and local

levels, and can be defended on the basis of epidemiological data. 

2. A cost-benefit or cost-effectiveness type model should be developed for

determining the acceptable risk or incidence of illness with regard to general and local

factors.

3. Work should be continued toward the development of similar criteria for fresh

recreational waters. 

4. An intensive prograrn should be initiated towards establishing the etiology of the

gastroenteritis observed in these studies and developing methods for quantifying the

agent(s) in environmental waters. This should be followed by a program to compare the

biological decay of the agent(s) to its indicators under conditions best simulating those

in open water. 

5. The most resource responsible use of these criteria is their translation into effluent

guidelines governing the design of sewage treatment facilities, the location of their

outfalls and the decisions to be made relative to the degree of treatment and

disinfection required. This and the preceding recommendation require the reinitiation

of the program towards the development of realistic and facile methods for obtaining

decay coefficients for indicators and pathogens on a case-by-case basis. 

6. Nonspecific gastroenteritis is the major cause of outbreaks of disease from

drinking water and shellfish consumption. The criteria suggest that there are

measurable health effects associated with enterococcus or E. coli water densities as low

as 10/100 ml via a route in which only 10-50 ml of water is ingested. Therefore,

prospective epidemiological studies should be conducted as part of the reevaluation of

existing standards for drinking water and shellfish-growing areas mandated by Sections

104(n)(l), 304 (a)( 1) and 403(c)(l) of Public Law 92-500.
[This page is intentionally blank.]
5

SECTION 3

BACKGROUND

Historically, the development of health effects, water quality guidelines and standards

for recreational waters has followed a pattern characteristic of many such efforts to

control pollution-associated health and ecological effects. The first step is the

development of guidelines and standards dictated largely by attainment with the best

available control technology. These are usually based upon limited epidemiological and

ecological evidence and little, if any, data quantifying the risk in relation to the level

of the pollutant in the environment. The second stage is the modification of these

guidelines and standards on the basis of detectable risk using a limited quantity of data

relating untoward effects to the environmental level of the pollutant. The last step in

the process, the development of guidelines based upon acceptable risk, requires an

epidemiological or ecological data base broad enough to mathematically model the

relationship of some measure of water quality to the risk, degree or rate of untoward

effects. With reference to health effects, water quality guidelines and standards for

recreational waters, we have progressed through the second stage. This report will

describe and substantiate criteria from which guidelines and standards based upon

acceptable risk can be derived by risk analysis. Sewerage systems for the disposal of

domestic wastes from urban areas into nearby fresh and marine waters have been in

existence in the United States since the turn of the century. By that time, it was clearly

established that agents of enteric disease are excreted in large numbers in the feces of

ill individuals and, hence, are potentially present in sewage and its receiving waters.

A swiruming-associated outbreak of typhoid fever was reported in 1921(1). Yet, it was

not until 1951 that Scott (2) proposed microbial guidelines for the quality of

recreational waters; these were based solely upon attainment. It was 1968 (3) before

guidelines related to detectable risks were recommended by the National Technical

Advisory Committee (NTAC.) to the Federal Water Pollution Control Administration

(FWPCA). Criteria permitting the development of guidelines based upon acceptable

risks are now available a decade later.

EXISTING GUIDELINES AND STANDARDS

As of 1972, the two guidelines or standards most commonly used by the various

states and territories in the United States were a total coliform value of 1000/100 ml

of water and a fecal coliform limit of 200/100 ml. The former appears to have

developed from two sources, the anticipated risk of salmonellosis as obtained from

calculations made by Streeter (4) on the incidence of Salmonella species in bathing

waters and attainability as determined by Scott (2) from surveys conducted of

Connecticut bathing waters. The Joint Committee of the American Public Health

Association and the State Sanitary Engineers (5) adopted the Connecticut standard as

did many of the state agencies. The fecal coliform limits will be considered in more

detail since, as can be seen from Table Al†, it is the most prevalent one used by the

various states and it is the guideline currently recommended by the EPA (6). This

guideline will be considered in terms of the data base which supports it, how it was

derived, and the indicator system used.

 The microbial guideline for primary contact recreational waters recommended by the

†When a table number is preceded by “A,” the table is to be found in the Appendix.
6

EPA and adopted by most of the states (Table Al) is essentially that recommended by

NTAC in 1968. Their recommendation was as follows: 

Fecal coliforms should be used as the indicator organism for evaluating the

microbiological suitability of recreational waters. As determined by multiple-tube

fermentation or membrane filter procedures and based on a minimum of not less than

five samples taken over not more than a 30-day period, the fecal coliform content of

primary contact recreational waters shall not exceed a log mean of 200/100 ml, nor

shall more than 10 percent of total samples during any 30-day period exceed 400/100

ml.

Their rationale for specific limits was as follows:

The studies at the Great Lakes (Mich.) and the Inland River (Ohio) showed an

epidemiologically detectable health effect at levels of 2,300-2,400 coliforms per 100

ml. Later work on the stretch of the Ohio River where the study had been conducted

indicated that the fecal coliforms represented. 18 percent of the total coliforms. This

would indicate that detectable* health effects may occur at a fecal coliform level of

about 400/100 ml; a factor of safety would indicate that the water quality should be

better than that which would cause a health effect. . . .The Santee project correlated

the prevalence of virus with fecal coliform concentrations following sewage

treatment. Virus levels following secondary treatment can be expected to be 1

Plaque-Forming-Unit (PFU) per milliliter with a ratio of 1 virus particle per 10,000

fecal coliforms. A bathing water with 400 fecal coliforms per 100 ml could be

expected to have 0.02 virus particles per 100 ml (1 virus particle per 5,000 ml).

The committee pointed out that the Public Health Service's three epidemiological

studies on bathing water quality and health were the only base available for setting

criteria, that these studies were far from definitive, and that they were conducted before

the acceptance of the fecal coliform as a more realistic measure of a health hazard. The

committee concluded that there is an urgent need for research to refine the correlation

of various indicator organisms, including fecal coliforms, to waterborne disease. 

Shortly after its publication, the NTAC guideline was attacked by Henderson (7) as

being too restrictive. He set forth several arguments against the promulgation of

microbiological standards on a nationwide basis; included were the broad confidence

limits on the Most Probable Number (MPN) test (whether for total coliforms or fecal

coliforms), temporal and geographic variability in pathogen to indicator levels, and the

effect of differing sources of pollution (i.e., treatment plant effluents, stormwater

run-off, farm lot wastes, etc.). However, the thrust of his attack was the paucity of

defined epidemiological data in support of the NTAC guideline. To the contrary, he

used the British experience (8); the observations from Santa Monica Bay, California

(9); and the lack of morbidity or mortality data associated with swimming in support

of a much less restrictive microbiological standard for bathing beaches, or even no

standard at all

In 1972, a panel of the National Academy of Sciences, National Academy of Engineering (10) came to the following conclusion: 

No specific recommendation is made concerning the presence or concentrations of

microorganisms in bathing water because of the paucity of valid epidemiological

data.

In explaining their inability to recommend a specific value they noted that many

of the diseases that seem to be causally related to swimming and bathing in

polluted waters are not enteric diseases or are not caused by enteric organisms.

Hence, the presence of fecal coliforrn bacteria or of Salmonella sp. in recreational

waters is less meaningful than in drinking water. Nevertheless, the substance

of the NTAC guideline was adopted by the EPA in 1976 (6); and, by 1978,

the large majority of the states and territories used it as a guideline or a 

standard (Table Al). Because of the seeming contradictions in the conclu-

*Author’s emphasis.
7

sions drawn by different individuals from the same information, it is worthwhile to

critically review that information. 

DATA BASE IN SUPPORT OF EXISTING GUIDELINES

AND STANDARDS

The data base in support of existing microbial guidelines can be sought from three

different sources. These are (i) available morbidity and mortality statistics (including

retrospective epidemiological analyses of case reports and disease outbreaks), (ii) output from predictive models, and (iii) the findings from prospective, controlled,

epidemiological-microbiological studies.

Recreational Waterborne Outbreaks of Disease and Their Retrospective

Analyses

Potentially, all the diseases which are spread by the anal-oral route and whose

etiological agents are shed in the feces of ill individuals or carriers could be contracted

by swimming in sewage-polluted water. This includes (i) bacterial diseases, such as

salmonellosis (including typhoid and paratyphoid levers), shigellosis (bacilliary dysentery), cholera, and gastroenteritis caused by enteropathogenic E. coli, Yersinia

enterocolitica, etc., (ii) viral diseases such as infectious hepatitis, illnesses caused by

enteroviruses (poliovirus, coxsackieviruses A and B, echoviruses, reoviruses and

adenoviruses), and “nonspecific” gastroenteritis caused by the human rotavirus and

parvo-like viruses, and (iii) diseases caused by a variety of protozoan and metazoan

parasites, i.e., amoebic dysentery, giardiasis, ascariasis, etc. 

In actuality, most of the reported outbreaks and cases of infectious disease in the

United States associated with swimming in natural bathing places were nonenteric and

included cases and outbreaks of otitis externa, swimmers' itch, leptospfrosis, granulomas

of the skin, and even very rare cases of tuberculosis and tularemia (11). The existing

guidelines do not prevent these diseases. There have probably been less than 18 reported

outbreaks of enteric disease, encompassing less than 700 cases, associated with

swimming in sewage-polluted waters. Included are: four outbreaks of typhoid fever, three

relatively small ones in the United States (1,12,13) and one of ten cases in Australia

(14); an outbreak of shigellosis on the Mississippi River below Dubuque, Iowa (15); two

very small and questionable outbreaks of enteroviral infections, one caused by Coxsackie

A (16) and the other Coxsackie B (17); and an equally questionable outbreak of

infectious hepatitis (18). The largest reported outbreak by far occurred in 1979; 187

individuals developed gastroenteritis within three days from swimming at two lakes

within a park in Michigan during a three-day period in July (19). 

Thus, it is understandable why workers such as Henderson (7) and Moore (8), after

examining such reports, have questioned the need for water quality guidelines, much less

standards, for recreational waters. There are, however, a number of considerations which

suggest that case and outbreak reports by their very nature markedly understate the

actual incidence of swirming-associated enteric disease. First of all, there are a number

of other modes of transmission for these enteric diseases (i.e. drinking water, food,

person-to-person contact) so that it is difficult to establish an association to a specific

route. Second, much of the swimming occurs at beaches used on a daily basis or on

weekends by urban and suburban populations who return to their homes each evening.

This too adds to the difficulty of establishing a common source association with

swimming at a given beach for “sporadic,” geographically spaced cases of enteric disease.

This is in contrast to drinking water where there is a geographic clustering of cases. It

is of interest in this regard that the reported shigellosis and gastroenteritis outbreaks were

detected under conditions where the population was geographically restricted, campers

at state parks. Third, the levels of pollution at such beaches are relatively constant; thus,
8

one would not expect outbreaks (recognized because of temporal or spacial limits) but

rather sporadic cases. Fourth, as will be pointed out later in this report, the immune

status of the population to some of the potential etiologic agents will also tend to

produce sporadic cases. Finally, the most commonly reported illness associated with

drinking water and shellfish-associated outbreaks, a nonspecific gastroenteritis, is not

a “reportable” disease. The usefulness of information from case and outbreak reports

in developing criteria, guidelines, and standards is also limited because, with few

exceptions and for obvious reasons, data on the quality of the water at the time of

exposure are usually not available. 

Prior to 1974, the only retrospective epidemiologic analysis concerning the risk of

illness associated with swimming in sewage-polluted waters was carried out by Moore

and his associates at some coastal communities along the coast of England and Wales

(8). The basic design was to compare the incidence of swimming in a two-week period

(for the ill individuals, it was the two weeks prior to the onset of illness) between two

groups of individuals. The first was children ill with clinical poliomyelitis, and the

second was a group of demographically paired controls (cohorts). Using this approach,

Moore found no greater association of swimming among children ill with poliomyelitis

than among their cohorts. In addition, he found very few cases of salmonellosis for

which there was even the remotest association with swimming in polluted waters. 

There were a number of problems with the experimental design used: (i) swimming

was not defined rigorously; (ii) the time span between the actual swimming experience

and the query as to its occurrence was protracted in many cases; (iii) it was difficult to

establish a relationship to the quality of the water in which the individuals bathed; (iv)

of necessity with this type of analysis in contrast to that used by Stevenson, there was

a presumption as to which diseases were “important,” poliomyelitis and salmonellosis;

and (v) this type of analysis is rather insensitive except; when conducted during an

outbreak situation. In their report (8) Moore and his associates (the Committee on

Bathing Beach Contamination of the Public Health Laboratory Service) noted some of

these limitations and pointed out that, “A survey of this type could clearly not prove

that poliomyelitis was never caused by bathing, and in any case such a presumptive

finding might be contradicted by future events, but the results of the survey give no

indication that further investigation along those lines is likely to be fruitful except in

the negative sense recorded.” Nevertheless, their findings do not warrant the

conclusions drawn: that there is little, if any, risk of enteric disease from swimmii:1g

in sewage-polluted waters unless aggregate fecal material is found therein and that

aesthetic considerations will limit beach usage long before there is a significant risk of

swimming-associated enteric disease. However, with regard to the two specific diseases

in question, Moore's conclusions were probably correct since, even in the period

subsequent to his report, there have been no outbreaks or cases of poliomyelitis shown

to be associated with the recreational use of water, and there has only been one

outbreak of this disease even remotely associated with any of the waterborne routes

(20). 

There have been some cases of salmonellosis attributed to the recreational use of

polluted waters, but, as Moore predicted, these have been associated with swimming

in heavily polluted waters which were probably aesthetically unattractive. In the

Australian outbreak, there was a broken sewage outfall (14); swimming in a sewagecontaminated drainage ditch (fecal coliform MPN 107

/100 ml) was reported for the

Alabama cases (13); the individuals in the Louisiana outbreak had been swimming

in a river impacted by a broken sewer line (12); and four cases of typhoid fever

detected in the Alexandria, Egypt bathing beach study to be described were all

associated with swimming at a heavily polluted beach immediately impacted with

raw sewage (21). The relatively few cases of swimming-associated salmonellosis

which have been reported in the United States and the findings from

those outbreaks are consistent with the high ID50* for salmonellae (22), the

decrease in Salmonella cases and carriers, and the increase in sewage treat-

*The number of microbial cells required to infect 50 percent of the exposed individuals.
9

ment. The removal of suspended solids during treatment decreases the number of

multisalmonellae-containing particles. When the human ID50 data for salmonellae are

considered, it would seem that such particulates would be required to produce

swimming-associated disease, and the epidemiological setting for the above outbreaks

are consistent with this hypothesis. Moreover, prior to 1979, the only outbreak of enteric

disease unequivocally shown to be associated with swimming in sewage-polluted waters

was a shigellosis outbreak on the Mississippi River below Dubuque, Iowa (15); and the

ID50 for shigellae has been shown in volunteer studies to be several orders of magnitude

less than that for salmonellae (22,23). 

The information provided by the retrospective epidemiological analysis of the

shigellosis outbreak (15) is of such importance in understanding the criteria which will

be described that some detail is warranted (the equally important Michigan outbreak (19)

will be discussed later in another context). Of 45 culture-positive cases studied, 43 (96

percent) of the individuals consulted a physician and 18 (40 percent) were hospitalized.

Twenty-three individuals had a history of swimming in the area within three days of the

onset of symptoms. Thirteen of them were swimming at a park area which, when

sampled periodically during the month following the end of the outbreak, had a mean

fecal coliform density of 17,500/100 ml S. sonnei. The same antibiogram and colicin type

as the isolates from seven swimmers, also was recovered from these waters. A casecontrol analysis and a retrospective, cohort analysis of an additional 262 individuals

revealed a statistically significant association of gastrointestinal illness with swimming

but not with drinking well water or with food consumption. The illness was defined as

diarrhea with fever or cramps occurring within three days. The rate among swimmers at

the park was 12 percent. Of the swimmers, the highest attack rate and the best

correlation to illness was among individuals who took water in their mouths and among

children and adolescents (less than 20 years of age). 

These findings must be used with caution since water quality measurements could be

obtained only after the end of the outbreak and since the source(s) of the Shigella and

indicator organisms in the water could not be unequivocally established. In addition, the

data relate primarily to shigellosis, one of several swirnming-associated diseases.

Nevertheless, the report documents a consequential outbreak of illness clearly associated

with swimming in water polluted with fecal wastes. More important, it would appear that

the health effects occurred in the absence of aesthetic deterioration sufficient to deter

individuals from swimming in the area. The concern with salmonellosis notwithstanding,

this was a shigellosis outbreak, and the incidence of shigellosis in Dubuque had been

steadily increasing over the four years prior to the outbreak. 

Prospective Epidemiological Studies

 

Prior to 1973, the only prospective epidemiological studies dealing with recreational

waterborne disease were those conducted by Stevenson and his associates in the 1950s

(24). Since they were the basis for the NTAC and, hence; EPA guidelines and a point of

departure for the studies to be described in this report, they will be described and

analyzed in some detail. There were three studies. The first was conducted at two

beaches on Lake Michigan in the vicinity of Chicago. The second examined illness rates

among individuals at two locations, a swimming pool in Kentucky and a nearby stretch

of polluted beach on the Ohio River. The third study was conducted at two marine

beaches on Long Island Sound, one in New Rochelle, New York and other in

Mamaroneck, New York. A calendar approach was used in all three studies, and this led

to a number of problems with the experimental design. First of all, swimming was not

defined rigorously enough so that any subsequent illnesses could be attributed exclusively

to contact of the upper body orifices with polluted water as opposed to consumption of

food at the beach, personal contact between beachgoers, aerosols potentially generated

by toilet facilities, etc. Secondly because the trials were conducted over the entire summer, the
10

effects of day-to-day fluctuations in the pollution levels at the beaches were not

eliminated. The consequence of this was that the mean indicator densities and, hence, the

illness rates at the paired beaches in the first and third studies were not significantly

different from each other. A third problem was that measurements were reported only for

one indicator, total coliform bacteria. 

In the first study, symptom rates among the beachgoers at the South Beach were no

different than those at the North Beach. Howeyer, a statistically significant difference

was obtained in the rate of total symptoms among individuals who were at South Beach

during three “high” coliform density days as compared to those there during three “low”

days. This was not true at the North Beach. The mean indicator density during the high

days at the South Beach was 2300 total coliforms/100 ml. In the Ohio River study, the

rate for total symptoms was higher among people at the chlorinated swimming pool than

those at the polluted beach on the Ohio River. However, the age adjusted rate for

gastrointestinal symptoms was higher for the individuals at the river beach than those at

the swimming pool. The mean coliform density in the stretch of the Ohio River was

2700/100 ml. In the third study, conducted at the marine beaches in the vicinity of New

York City, no differences in symptom rates could be obtained even when illness rates

during “high” days and “low” days were compared. 

Aside from those in the experimental design, there are a number of problems with the

analyses of the data and the conclusions drawn thereof. First of all, Stevenson concluded

that swimming per se resulted in a higher rate of illness; because of the experimental

design, it can only be concluded that going to the beach results in a higher illness rate.

Second, the comparison of illness rates for three high days versus three low days during

the Lake Michigan study has been criticized in that the differences were shown for only

one set of high versus low days, and no data are given for all the other possible

combinations. Third, in the first study, the differences were reported for total symptoms,

while in the second they were for gastrointestinal symptomatology; yet, both sets of data

were used identically in the derivation of the NTAC guidelines. Because of the

limitations in the experimental design and analysis, one could conclude the positive

results were spurious and that there was no effect of swimming in sewage-polluted

waters. Alternatively, the limitations in design and analysis notwithstanding, it might be

argued that the findings described a reality obtained with a relatively insensitive

epidemiological instrument. 

There were also problems in the use of these findings in the derivation of the microbial

water quality guidelines as set forth in the NTAC document. As noted earlier, there was

no consistency in the type of symptom used in the derivation. Secondly, the authors of

the NTAC document converted total coliform values into fecal coliform values in order

to state the criteria in terms of “a more fecal specific indicator system.” In fact, the lack

of specificity in the total coliform values would be carried over into the fecal coliform

guidelines in spite of the fact that the relationship between the two indicators was later

determined on the same stretch of the Ohio River. Fourthly, it is now evident that the

so-called fecal coliforms are not as fecal specific as was thought at the time that the

NTAC guidelines were formulated. Finally, the findings from the Stevenson study and

their use in deriving the NTAC and hence EPA guidelines are conceptually deficient in

that they are not amenable to risk analysis. That is, they describe detectable not

acceptable risks. Nevertheless, these were the best guidelines available, and, as noted by

Shuval (25), target area guidelines are needed by engineers as the basis for the design

of sewage treatment facilities. 

Predictive Models

 

Predictive models based on pathogen densities in the water, the infective dose of the

pathogens in question, and the relationship of pathogen to indicator densities have been

equally unproductive in terms of producing the kinds of definitive information needed to

support the existing guidelines. Attempts by Streeter (4) which were similar to those
11

used by Kehr and Butterfield (26,27) for other waterborne routes of transmission,

assumed an ID50 for salmonellae of one, and this is several orders of magnitude less than

those obtained later from human volunteer studies (22). A more recent study by Mechelas

et al. (28) was equally unproductive, not because of the mathematical approach used but

rather because of the poor quality of the input data to the model and the assumptions

made as to which disease agents are important. 

An attempt is made to justify the existing EPA guidelines from information on the

relationship of fecal coliform densities to the frequency of Salmonella isolations in

surface waters (6, 29). As pointed out elsewhere (30), this relationship has not been

confirmed, especially when Salmonella densities rather than isolation frequencies are

examined. Furthermore, it is conceptionally unsound to expect a consistent relationship

between a fecal indicator and a pathogen which is not extremely prevalent in the

population at large. Finally, considering the ID50 for salmonellae, a relationship to the

frequency of its isolation hardly seems appropriate as a justification for a guideline. In

spite of the absence of epidemiological data showing swimming-associated cases of

poliomyelitis, an attempt has been made to justify the guidelines based on some relatively

poor data on poliovirus densities (including those of the vaccine strains) in the water,

their relationship to fecal coliform densities, and the assumption that ID50 of poliomyelitis

is one, if the virion is in the right place at the right time (31). This approach also is

entirely unconvincing for the reasons stated earlier. 

HEALTH EFFECTS RECREATIONAL WATER QUALITY 

INDICATORS

Ideally, recreational water quality indicators are microorganisms or chemicals whose

densities in the water can be quantitatively related to potential health hazards resulting

from recreational use therein. Historically, the concern has been with infectious enteric

diseases, such as cholera and typhoid fever, whose etiological agents are excreted in feces

and are spread by the. contamination of water and food with fecal wastes. 

There are a number of reasons why the pathogens themselves are not used for this

purpose, and most of these are as valid today as they were at the turn of the century when

the indicator concept was developed. First of all, as noted earlier, there is a wide variety

of infectious agents potentially transmitted by the waterborne route, and, since the

density of each will vary both temporally and spacially independent of the others,

measurements would have to be made for each agent. Secondly, facile and reliable

methods for quantifying most of the pathogens are unavailable, even today; in fact, there

are no methods for quantifying what may be the most important (infectious hepatitis) and

most prevalent (rotaviruses and parvo-like viruses) agents of enteric disease. Thirdly, and

most important of all, because of the temporal variability in pathogen densities in feces

and sewage (and hence their receiving waters), monitoring for the pathogens themselves

is more akin to measuring the actual rather than the potential for disease. Thus, it is not

surprising (i) that the indicator concept was developed shortly after fecal transmission

of enteric pathogens was established, (ii) that the first three indicators suggested,

Escherichia coli, Streptococcus faecalis and Clostridium perfringens, were fecal

organisms (32), and (iii) that these, or groups to which they belong, are the three most

commonly used indicators today (33,34). The regrettable fact is that, in each case,

methodological rather than conceptual considerations led to the expansion of the group

measured, i.e., coliforms and fecal coliforms instead of E. coli, fecal streptococci instead

of S. faecalis, and spore-forming, sulfite-reducing anaerobes instead of C. perfringens.

The health effects, water quality indicators which have been considered and the methods

for their enumeration which have been developed under the EPA recreational water

quality criteria program are presented in Table 1. 

The coliform systems require some further discussion because they are the ones most
12

commonly used and because most of the existing criteria are stated in terms of coliform

or fecal coliform densities. 

The total coliform population as commonly enumerated includes four genera in the

family Enterobacteriaceae: Escherichia, Kiebsiella, Citrobacter, and Enterobacter. It

may also include other organisms, notably lactose positive members of the genus

Aeromonas (49). Only E. coli is consistently and exclusively found in feces (50),

although all five genera can be routinely recovered from domestic sewage in rather large

numbers (51). 

Belatedly, the total coliform system is being discarded for many applications because

it is finally recognized that Citrobacter and Enterobacter species are not fecal specific.

However, it is being replaced with the so-called “fecal coliforms,” a group which

includes thermotolerant Kiebsiella as well as E. coli biotypes. There never was any

evidence that the adjective “fecal” was properly applied. In fact, it has been known for

some time that there are substantial extra-fecal sources of Kiebsielia, (50, 52, 53), even

for the thermotolerant biotype. In addition, Kiebsielia is infrequently present in human

feces, and then generally as a minor portion of the coliform population (50). A number

of reasons have been given to justify the use of this coliform system instead of E. coli.

It has been argued that much of the historical data is in terms of fecal coliforms, that the

existing standards for recreational and shellfish waters are stated as fecal coliform

densities, and that Kiebsielia should be enumerated as a fecal indicator because it is an

opportunistic pathogen. First of all, much of the historical data is in terms of total

coliforms not fecal coliforms; secondly, the little epidemiological data in support of

existing recreational or shellfish standards were developed in terms of total coliforms and

extrapolated to fecal coliforms (3); thirdly, Kiebsielia is an opportunistic pathogen of the

respiratory and genito-urinary systems and not the gastrointestinal tract; finally, there are

no data showing that Kiebsiella infections have been obtained via the waterborne route,

much less that they occur at environmental fecal coliform densities of less than 200/100

ml or 14/100 ml, the present EPA guidelines for recreational and shellfish-growing

waters, respectively (6). 

GUIDELINES BASED ON ACCEPTABLE RISK

Another problem with the existing microbial guidelines for direct contact recreational

waters is that they are not amenable to, compatible with, or derived in the context of risk

analysis. That is, the data from which the guidelines were derived and the manner of the

derivation are related to detectable rather than acceptable risk. Therefore, decisions

beyond acceptance or rejection of the specific limits cannot be made on the basis of scien-
13

tific, health, economic or sociological considerations This does not allow for deliberate

decisions by local, state, or federal officials as to the costs to be paid for incremental

decreases in the health risks involved. Finally, it presents a philosophical dilemma to

individuals or groups who recommend guidelines based upon detectable risks. Once more

sensitive epidemiological instruments are developed for measuring the risks involved or

extrapolating them from existing information, they are forced to make the limits more

restrictive in order to be conceptually consistent. In fact, this is precisely the position in

which the EPA finds itself because of the results to be presented. The logical solution is

to proceed to the next stage in the evolution of the guidelines, the use of those developed

on the basis of acceptable risk. 

The microbial water quality criteria for primary contact recreational waters to be

recommended in this report and, hence, the guidelines and standards which can be derived

from them are a radical departure from the guidelines currently recommended by the EPA

and the guidelines and standards currently used by the various states. They differ

conceptually from the existing guidelines (referred to as criteria) in that the usable

information is presented in the form of dose-response type relationships rather than

limiting microbial densities. Because the conceptual basis is different, it becomes

important to define certain terms as they will be used throughout this document. 

A health effects recreational water quality criterion developed for use with indicator

systems is defined as a quantifiable relationship between the density of the indicator in

the water and the potential human health risks involved in the water's recreational use.

It is a set of facts or a relationship upon which a judgment can be made. A water quality

guideline derived from the criterion is a suggested upper limit for the density of the

indicator in the water which is associated with health risks which are considered

unacceptable. The concept of acceptability implies that there are social, cultural,

economic, and political as well as medical inputs to the derivation and that these may vary

in time as well as space. A water quality standard obtained from the criterion is a

guideline fixed by law. The relationship of guidelines to the criteria from which they are derived

is shown graphically in Figure 1. Derivation of the guidelines from the criteria requires a
14

decision as to acceptable risk. This, in turn, is best obtained from some manner of

cost-benefit or cost-effectiveness analysis which should include economic and socio-logic

considerations. Guidelines derived from such criteria differ from those currently in use in

that they are consistent with risk analysis, allow for decision making, and are based on

acceptable rather than detectable risks. This report presents such a criterion for marine

recreational water quality, documents its epidemiological data base, and discusses its

applications and limitations.
15

SECTION 4

STUDY DESIGN

The design of the epidemiological-microbiological program to develop health, effects

recreational water quality criteria was started in January 1969, shortly after the

publication of the NTAC guidelines, and concluded in 1970. From the onset, the

objective was to develop criteria amenable to risk analysis rather than guidelines based

upon detectable risk (54). The experimental work was initiated in 1972 and concluded

in 1978. A prospective approach similar to that used by Stevenson (24) was taken, in

part to avoid prejudgements as to which diseases are spread by the recreational route,

in part because a “nonspecific” gastroenteritis was the most common illness associated

with the drinking water (55) and shellfish (56) routes of transmission, and in part

because of Moore's (8) conclusion that further retrospective studies are unlikely to yield

results other than those obtained in his study. Marine beaches were chosen for the

initial program because Stevenson's study at marine beaches did not produce

demonstrable swimming-associated health effects, yet his freshwater findings were

being applied to such beaches. Furthermore, if swimming-associated health effects were

not obtained, this would tend to confirm the observed differences between fresh and

saltwater beaches. If they were obtained, this would signal the need for a freshwater

program, and the saltwater criteria could be used on an interim basis for freshwater

beaches as well. The freshwater program was initiated in 1976. Finally, there were a

number of heavily used and sewage-impacted marine beaches which could be studied

along the Middle Atlantic and New England coasts. 

PERCEIVED DEFICIENCIES IN STEVENSON DESIGN

 An analysis of Stevenson's (24) study design, relative to the difficulties encountered

and the results obtained, revealed several deficiencies which may have contributed to

the inconclusiveness of his findings. To a large measure, they were due to the necessity

of using the less expensive and time-consuming “calendar approach.” 

Definition of Swimming 

 Neither Stevenson, in defining his bathers as opposed to his nonbathing controls, nor

Moore (8), in his inquiries concerning bathing, appears to have defined swimming such

that individuals actually at risk - those whose upper body orifices were significantly in

contact with the water - were isolated and examined. Thus, if swimming is not defined

precisely, it is possible that differences in pollution-associated illness may be sought

between two populations in both of which most of the individuals never were

appreciably exposed. We considered this to be important from the assumption that less

than 10 percent of the beachgoers would be classified as swimmers when immersion

of the head in the water was used as the criterion for swimming. In fact, we were

wrong. In almost every study, more than 60 percent of the beachgoers were classified

as swimmers. 

Multiple Exposures 

 The day-to-day variability in pollution levels requires that, ideally, the study group

be limited to individuals who have had a single (one-day) swimming experience during

the observation interval associated with a given trial. In both the freshwater (Lake Michi-
16

gan) and saltwater (Westchester) studies, the day-to-day variability as measured by

coliform indicators was considerable; in fact, the range of indicator densities at each pair

of beaches appreciably overlapped each other. Furthermore, in both these studies, the use

of “calendars” to record illness made it necessary to limit the study to seashore residents.

This maximized the probability that multiple exposures would occur. Stevenson, in

comparing the incidence of illness during “high” and “low” pollution days, obviated only

part of this difficulty. 

Nonswimming Controls 

 Stevenson's nonswimming controls were individuals who did not go to the beach.

Thereby, beach-going but not swimming-associated illnesses, such as gastroenteritis from

improperly stored food, increased personal contact, use of communal toilets, etc., could

be erroneously included in calculating the illness rates of the swimming as opposed to

nonswimming populations. This could have affected illness-rate comparisons between

“high” and “low” days as well as between beaches. 

Demographic Considerations

 Stevenson analyzed his data with consideration to age and sex but not to ethnic or

socioeconomic (SES) factors. However, especially in the saltwater study, the test beaches

appear to have been paired with reference to ethnic and SES factors of the resident

populations. Susceptibility to disease, background rate of illness, nature of the swimming

experience, and even the reliability of the respondents' information concerning illness and

the swimming experience could vary by ethnic or social class. 

Tidal Effects

 Hourly variability in the pollution levels due to tide, wind, rainfall, etc., can present a

problem in the interpretation of findings from epidemiological-microbiological trials. In

Stevenson's study this was uncontrolled. Except in those instances where a “captive”

study population is available, such as institutionalized individuals or organized groups,

there is little that can be done to mediate such effects. Individuals at the beach during a

given day can be expected to swim on several occasions during a half tidal cycle. 

Indicators of Pollution

 At the time of Stevenson's study, the state of the art was such that only two

microbiological parameters were measured. Coliform determinations were made in

accordance with confirmed test procedures described in the 13th Edition of “Standard

Methods” (57). Enterococcus levels were also examined. These data were not used in the

analysis because it was subsequently determined that, because of problems in assay

methodology, the density estimates were too unreliable.

DESIGN CHARACTERISTICS

In response to the perceived deficiencies in the Stevenson studies, the calendar

approach was not used (58). Rather, the participants were recruited at the beach and

queried some 7-10 days later by phone or personal interview (mail questionnaires were

tried and found to be unsatisfactory) concerning symptomatology which developed

subsequent to the swimming experience. Other features of design were as follows: 

1. Only individuals whose upper body orifices were exposed to the water were

classified as swimmers, and subjects. were queried on the nature and duration of

swimming activity. The validity of this information was pretested in the New York

City study by observing family groups over a day at the beach and comparing these

observations with information obtained at the day's end from a representative of the

group. The more rigorous definition of swimming allowed for a beach-going
17

but nonswimming control group and thereby eliminated the bias from

nonswimming associated illnesses. 

2. Beach interviews were conducted only on weekends. Exposure was limited to a

single day or at most two successive days on a weekend. This was accomplished

by eliminating individuals who swam in midweeks before and after the weekend

trials from the study. The use of weekends maximized the size of the study

population but limited the illness observation period to 8-10 days. This feature of

the study facilitated the analysis of the data “by days,” thereby obviating the effect

of day-to-day variability in pollution levels. However, it eliminated from

consideration illnesses with incubation periods exceeding nine days, notably

infectious hepatitis (this was examined in the portion of the Egyptian study which

dealt with Cairo visitors to the Alexandria beaches). 

3. The impact of within-day variability in pollution, primarily attributable to tidal

effects, could not be eliminated. However, in the first two years of the New York

City study, an attempt was made to minimize this effect by choosing test and

control beaches which were markedly different in the pollution levels reaching

them. There also was an attempt to select trial dates when minimal tidal effects

coincided with peak beach usage periods (usually 11 A.M. to 5 P.M.). This

problem was potentially even more acute in the Boston Harbor study because of

the greater tidal excursions and the unappealing nature of the intertidal zone.

Because of this, swimmer and even bather densities were very low during low

tides, Therefore, trials were conducted on those weekends when high or mid-tide

corresponded to the hours of peak activity (11 A.M. to 5 P,M,). This forced the

acceptance of lower mean indicator densities for this study. 

4. Demographic effects, which could assert themselves as differences in susceptibility

to infection, in swimming activity and in the reliability of respondent information,

were minimized. This was done by selecting test and control beaches whose

populations were demographically similar and by obtaining age, sex, ethnic, and

SES information that could be used in isolating and identifying the influence of

these factors. 

5. The respondents were asked whether they remained home, remained in bed or

sought medical advice because of the symptoms. This information was used to

indicate disability. 

6. In the pretest year of the New York City study, an attempt was made to validate

the illness information provided by the respondents. This was done by providing

the name of a physician in the reminder letter sent on the Monday following a trial

and by requesting the names of other physicians consulted during the observation

period. This was unsuccessful, and an alternative system was devised for validating

gastrointestinal (GI) symptomology. Highly credible GI symptoms (HCGI) were

defined as (i) vomiting, (2) diarrhea with a fever or disabling enough for the

individual to remain home, remain in bed or seek medical advice, or (ii)

stomachache or nausea accompanied by a fever, The rates for HCGI symptoms

were calculated and compared to those for total GI symptoms in order to determine

if the trends were the same. 

7. The illness questionnaire solicited information on irritations and disturbances of

the skin, upper respiratory tract, eyes, and ears. This was done not only against the

possibility of pollution-associated infectious processes but also against that

possibility of toxic and hypersensitive conditions attributable to chemical pollution

and to pollution-associated changes in marine biota. 

The sequence of events during and subsequent to the beach interview is shown in

Table 2. 

The experimental design as stated was generally followed for all the studies conducted.

The notable exception was the Egyptian study and especially the portion dealing with

health effects among Cairo visitors to the Alexandria beaches.
18

INDICATOR ASSAYS

Water samples were collected in sterile bottles from just below the surface of the

water, at “chest high depth,” and periodically during the time when people were in the

water. They were collected at 2-3 locations along the beach; and, in general, 3-4 samples

were collected between the hours of 11 A.M.-5 P.M., the period of maximum swimming.

The samples were “iced” and returned to the laboratory for assay within six hours of

collection.

Assays of the water samples were performed to determine the densities of a number

of potential microbial indicator systems. These are given in Table 1. Appropriate,

evaluated methods were not available for bifidobacteria, coliphage, Candida albicans,

and enterophathogenic E. coli or for the chemical, coprostanol, by the second year of the

New York City study. Therefore, these indicators could not be included in the study.

Membrane filter procedures were developed and used for most of the indicator systems

examined. The methods are noted and referenced in Table 1. Membrane filter procedures were chosen because they provide more precise estimates than MPN determinations and allow larger samples to be examined than pour or streak plate procedures. A

high volume (55.5 liters), MPN procedure (46) was used for Salmonella, Klebsiella, and

Enterobacter-Citrobacter. Densities were determined by the mC procedure (35), although

a method specifically for Klebsiella (37) was developed subsequent to the completion of

the New York City study. In addition, fecal coliform densities were determined by the

MPN procedure given in Standard Methods for the Examination of Water and

Wastewater (57). Staphylococci were enumerated by a modification of the

Chapman-Stone method for use in a membrane filter procedure (M. Levin, personal

communication).

ANALYSIS OF THE DATA

Since the objective of the program was to relate the swimming-associated rates for

symptoms, classes of symptoms or syndromes to some measure of the quality of the

water, a temporal and spacial control population was provided. This was nonswimmers
19

(head not immersed in water) who were at the beach and, in general, came from the

same family groups as the swimmers. Therefore, in most of the analyses, the swimming

rate for a given symptom or group of symptoms was first compared to the nonswimming

rate. Such differences were then examined relative to the pollution levels at different

beaches or on different days or groups of days at the same beach. During the first two

years of the New York City study, two beaches were used which, according to existing

standards, varied widely with regard to their pollution levels. One was “barely

acceptable” (BA) in that it was immediately adjacent to a beach posted as being unsafe

for swimming; the other was “relatively unpolluted” (RU) according to existing

guidelines and was at a much greater distance than the BA beach from any known

pollution source. The choice of the beaches permitted making a decision as to

“important” symptoms without recourse to a direct comparison with indicator densities.

Chi-square analysis was used for this purpose. The second premise of the program was

that there would be no prejudgment as to which is the “best” indicator. Therefore,

regression analyses of the geometric mean densities of each indicator against the

symptom rates were used to determine which indicator provided the best correlation and,

hence, was the best water quality indicator. 

In the regression analyses, each point was defined by the symptom rate for a single trial

(day), a cluster of trials with similar indicator densities or all the trials conducted over

a given summer at a given location and by the corresponding geometric mean indicator

density for all the samples collected at the beach. Regression analysis was also used to

define the final criteria. 

The studies conducted under the EPA program to develop recreational water quality

criteria, the number of individuals from whom usable information was obtained, and the

success rate for follow-up interview are presented in Table 3. The detailed findings from

individual studies have been or will be presented in individual reports (21, 59-64).
20
21

SECTION 5

RESULTS OF THE STUDIES

NEW YORK CITY STUDY

 This study was conducted in three phases (years) at Coney Island and Rockaway

beaches selected with the assistance of the Bureau of Public Engineering, New York

City Department of Health. The first phase, conducted in 1972 and 1973, was a pretest

of the microbiological and epidemiological methodology and an evaluation of the suitability of the test beaches. In 1972, the reliability of information obtained from the

interviewees concerning their bathing activities was examined using the method described earlier. Their responses were quite accurate regarding entrance into the water

and immersion of the head therein. However, their perceptions as to how long they were

in the water were less reliable, possibly because many of them bathed or swam on

several occasions during the day. In l973, trials were conducted at two beaches: the first,

located between 18th and 22nd Streets on Coney Island, was designated as the BA

beach; and the second, around 67th Street at the Rockaways, was designated as the RU

beach (61). 

The demographic distributions of the populations at the two beaches were similar

(60); about two-thirds of the beachgoers were classified as “swimmers,” and there were

no striking differences between the Coney Island and the Rockaways populations with

regard to the percentage so classified. Swimming was more frequent among males,

Hispanic Americans, and the 0-19 years of age groups (Table A2). The differences in

pollution levels as seen from the densities of a number of potential water quality

indicators were markedly different (Table A3). The success rate for follow-up phone

(not mail) interviews was acceptable (Table 3); however, an alternative to medical

follow-up examination for validation of the respondents' information on symptomatology

was required. The differential (swimming minus nonswimming) rates for the individual

GI symptoms were generally greater at the Coney Island than at the Rockaway beach

(Table A4), and statistically significant differences in the rates for GI symptomatology

were obtained at the Coney Island but not the Rockaway beach (Table A5). The rate for

respiratory symptoms was higher among swimmers than nonswimmers at the

Rockaways, presumably due to the aerosolization of noninfectious material because of

the heavy surf activity at the beach. Assays for Salmonella densities in the water were

omitted from subsequent studies because. of the low densities obtained (Table A6). 

A detailed analysis of the second phase (1974) trials is presented elsewhere (60). The

RU beach was changed from 67th Street to Riis Park at the Rockaways in order to

in-crease the size of the study population. The consequence of this was a somewhat

greater discrepancy between the BA and RU beaches with regard to ethnic and SES

factors (60). With two exceptions, nearly all the 1973 findings were confirmed in 1974.

They were the much lower mean indicator densities (Table A3) and the absence of

differences between swimmers and nonswimmers for the individual respiratory

symptoms or respiratory symptoms taken as a whole (Tables A4 and AS). Of the

nonswimmers at the Coney Island and the Rockaway beaches, only 8.5 percent and 5.4

percent, respectively, did not go swimming because of existing symptoms or illness.

None of the individuals at the BA beach and only 0.1 percent of those at the RU beach

did not go swimming because of GI symptomatology.
22

Because of the larger study population, the rates for GI symptoms could be examined

by demographic groups. However, the increase notwithstanding, data for disabling GI

symptoms by type could not be analyzed statistically because of the small size of the

resultant cells. The disabling GI symptom rate for swimmers was 10/1000 people higher

than that for nonswimmers at the BA beach. At the RU beach, the rate for nonswimmers

was higher than that for swimmers by 2/1000. 

The results from the analysis of GI symptom rates by demographic groups for

swimmers and nonswimmers at both beaches are presented in Table A7. The rates among

children, Hispanic-Americans, and low-middle SES individuals who swam at Coney

Island were significantly and appreciably higher than among those who did not. This was

not so for the residual from each demographic category (adults, blacks plus whites, and

the highest SES group). The GI symptom rate for nonswinmers among the children at the

RU beach was appreciably higher than that for the corresponding group at the BA beach.

The rate for nonswimming children at the RU beach was significantly higher than that

for children who swam. This anomalous finding probably was not due to over-reporting,

since this was also true of the “highly credible” portion. The nonswimming children may

have been more prone to illness, although only 0.1 percent of these children or their

respondents reported that they did not swim because of existing GI symptoms. The

investigators favor the explanation that predominately white or black, higher SES

children did not or were not allowed to swim because they were in the early stages of the

illnesses for which they later reported symptoms (60). 

Secondary transmission of illnesses within a family did not appear to provide an

erroneous picture of the symptom rates associated with swimming (60). The credibility

of the information on gastrointestinal symptomatology was assessed by comparing the

trends of all responses to those considered “highly credible.” The rates for the “highly

credible” symptoms among the four study groups were examined for the total population

and separately for the children, Hispanic-Americans, and the low to middle SES groups.

The trends for the highly credible portion were similar to those for all GI symptoms

(Tables AS and A7). Rates of HCGI symptoms for the three most sensitive groups of

swimmers also were significantly higher than those for their nonswimming controls. 

The finding of a statistically significant, swimming-associated rate of GI

symtomatology at a BA but not at a RU beach showed that such effects could be

determined and suggested that measurable health effects do occur even within existing

guidelines and standards. However, these results did not speak to the overall objective

of the EPA program, the development of criteria amenable to risk analysis as described

earlier. The data from the third phase (1975) of the New York study along with the data

obtained the previous two years were analyzed to further explore this possibility since

a preliminary examination of the data from 1973 and 1974 suggested that criteria could

be developed and that either E. coli or enterococci was the most appropriate indicator

(61). Four beaches on Coney Island were studied in 1975. These were a “posted” area

between 34th and 38th Streets and nonposted beaches between 18th and 24th Streets, 8th

and 10th Streets, and 2nd and 4th Streets, Brighton. 

As noted earlier, the data from the three years of the New York City study were examined by regression analysis in two ways. The first was by clusters of trials with similar

mean indicator densities during a given summer. The second was by summers, that is,

all the trials at a given beach during a given summer. Clustering was necessary in order

to avoid data points with N values of less than 100 persons. This was accomplished with

one exception, a N of 96 for nonswimmers in the analysis of E. coli densities. In a few

instances, however, this was accomplished at the cost of grouping some trials with widely

divergent densities. In almost all cases, this occurred with trials at the upper end of the

density distribution for a given indicator. Where possible, “natural breaks” in the

distribution of mean densities were utilized in clustering the trials. Nevertheless, this was

somewhat arbitrary.
23

In both approaches, the attack rates for GI symptoms or the “highly credible” portion

thereof (HCGI) were regressed against the mean indicator density. The log-linear

regression equation:

Y = a log X + b

was used in which X was the mean indicator density and Y the symptom rate. 

The clustering of the trials for each of the indicators along with geometric mean density

and range for each cluster is shown on Tables A8 through A18. The mean densities along

with the data used in calculating the swimming-associated rates (swim-nonswim) of GI

and HCGI symptoms for each cluster (some single trials were unavoidable) are shown

for each indicator in Tables A19 through A29. The coorelation coefficients are presented

in Table 4.

The mean densities and the ranges for each indicator for all the trials conducted during

a given summer at a given beach are presented in Table A30. The corresponding data on

GI symptom rates are given in Table A31, and the correlation coefficients for the regression of the swimming-associated rates on the mean densities in Table 4.

When the results from both approaches for examining the relationship of the indicator

densities to GI symptoms (and especially the highly credible portion thereof) were

considered, it was apparent that enterococcus densities provided the best correlation.

Nevertheless, as planned; the two best-correlated indicators, enterococci and E. coli, were

used in subsequent studies. It is of equal importance that total coliform and especially

fecal coliform densities were less well correlated with gastrointestinal symptomatology.

The regression lines obtained for swimming-associated GI and HCGI symptorns

against the mean E. coli and enterococcus densities when examined by summers and

clusters of trials with similar indicator densities are presented in Figure 2.
24

Figure 2. Swimming-associated (swimmer minus nonswimmer) gastrointestinal symptom rates

against the mean enterococcus and E. coli densities in the bathing water for New York

City study (1973-1975). Highly credible GI symptoms defined in text. In “a” and “c,”

trials clustered by similar indicator densities to yield points as shown. In “b” and “d,”

trials clustered by summer and beach. The actual trials clustered are given in Tables

8A through A31, Appendix A.

ALEXANDRIA, EGYPT STUDY

Animal infectivity studies conducted with most infectious agents yield sigmoid doseresponse curves. At the inception of the EPA program, the relationship of illness among

swimmers to indicator densities in the bathing waters was also expected to be sigmoid

in nature. However, when the swimming-associated rates for GI symptoms were plotted

in percentages on a scale that was not expanded to show differences (see Figure 3 as an

example), the slopes of the lines were quite shallow relative to those seen in most

dose-response curves. They may have represented the first parts of sigmoid curves, from

which the expectation was accelerated increases in the symptom rates with further

increases in the indicator densities at the beaches. An equally plausible explanation was

that the regression lines obtained were the linear portions of basically sigmoid relationships

(i) in which a measurable response was associated with the ingestion of very low
25

enterococcus or E. coli densities (note the Y axis intercepts in Figure 2) because of the

differential survival of the indicators relative to the etiologic agent(s) over the travel time

between the beaches and the sources of pollution, (ii) in which the shallow slopes of the

regression lines were due to high levels of immunity to the infective agents(s) in the

swimming populations, and (iii) from which the expectation was that the rates for the

specific illness(es) involved would not accelerate with increasing levels of pollution as

seen from the indicator densities. 

Ideally, Figure, 3 should be a log probability plot; practically, it makes no difference

because of the low rates and relatively good “r” values obtained. Furthermore, since this

is an indicator-illness rather than agent-response relationship, a log probability plot may

not be appropriate. 

It was thought that the nature of illness-indicator relationships obtained from studies

conducted at beaches more heavily impacted with more immediate sources of raw sewage

could be used to differentiate between the two possibilities. Therefore, an extensive

search was made for beaches in the United States which not only met the above

requirements but also were used by large numbers of individuals and were not posted as

unsafe. No such beaches were found in the United States; however, several saltwater

beaches which met these requirements were identified in Alexandria, Egypt and could

be studied under the sponsorship of the PL480 program. Most of them were very heavily

used during the summer, and, according to existing information, they varied in their

pollution levels from some which were heavily polluted (even aesthetically undesirable)

to some which were acceptable according to the EPA guidelines. The sources of pollution

to the beaches were a number of short (about 50 meters) outfalls originally designed to

accommodate overloading of the disposal systems due to rainfall. However, they now

discharge sewage daily because the growth of the city created demands for sewage

disposal which exceeded the capacity of the existing system.
26

A preliminary survey of microbiological, demographic and user characteristics

identified three beaches for the study - one very heavily polluted (Mandara), one

moderately polluted (Ibrahemia), and one acceptable, but barely so according to the EPA

guidelines (Maamoura). 

The findings from the first year (pretest) of the study were similar to those obtained

at the New York City beaches. Greater differences in the rates for vomiting and diarrhea

among swimmers relative to nonswimmers were obtained at the heavily and moderately

polluted beaches than at the acceptable one; and gastrointestinal symptomatology alone

seemed to follow pollution as seen from E. coli and enterococcus densities, although the

rates for most symptoms were higher for swimmers than nonswimmers at all three

beaches. Children appeared to be the most susceptible portion of the population.

However, a preliminary examination of the indicator-GI symptomatology relationship

suggested an even shallower response curve than that obtained in the New York City

study, this in spite of the higher pollution levels. Furthermore, there were indications that

the GI symptom rates plateaued at mean E. coli and enterococcus densities of

200-300/l00 ml (see data points for 1976 Alexandria residents in Figures 4 and 5).

Finally, the E. coli and enterococcus densities associated with a “detectable” illness

response (X axis intercepts) were higher than those obtained in the New York City study;

those for enterococci were higher than those for E. coli the indicator with the poorer

survival characteristics in saltwater (65) These findings recommended the second

hypothesis noted earlier in this section. discharge sewage daily because the growth of the

city created demands for sewage disposal which exceeded the capacity of the existing

system.
27

Because of the above findings, the study was not only continued but extended to

examine Cairo tourists at the Alexandria beaches as a population which, with regard to

its immune status, might be more akin to that in the New York City study. In addition, the

follow-up period with the Cairo population was extended to consider infectious hepatitis

which, along with typhoid fever, is much more prevalent in Egypt than in the United

States. This required a somewhat altered experimental design. The “Cairo visitors” were

recruited at the beach shortly after their arrival in Alexandria. Follow-up inquiries were

made in Alexandria and, as required, in Cairo at weekly intervals over a 30-35 day

observation period. Follow-up in Alexandria was facilitated because most of the tourists

remained in Alexandria for 2-4 weeks in rented cabanas at the beach. The altered design

with the Cairo visitors precluded the use of “weekend trials” and, therefore, made the

results more subject to the vagaries of day-to-day variability in pollution levels. However,

the levels were relatively constant since there was little rainfall during the summer and

the sewage impacting these beaches was untreated. 

The pumping schedule at the Mandara outfall was changed in 1977, presumably because

of the 1976 findings; this was reflected in the lower E. coli and enterococcus levels

obtained at this beach in the spring of 1977. Because of this, “Sporting” was substituted

for Mandara as the heavily polluted beach in the 1977 and 1978 trials. 

The swimming and nonswimming rates for the various symptoms among the Alexandria

residents and the Cairo visitors for each of the three years of the study are given in Tables

A32 through A34. The swimming-associated (swimmer minus nonswimmer) rates are

summarized in Table A35. Only data from the first weekly follow-up with the Cairo

visitors were used in the analyses of the 1977 findings in order to maintain comparability

with the data obtained for the Alexandria residents. For the same reason, the symptom

rates given for the Cairo visitors in 1978 are those for individuals who swam
28

1-2 days during the week. Because of the resulting decrease in usable responses and

because of the disparity in the rates of GI and upper respiratory tract symptoms for

nonswirnmers obtained from the first as compared to the second follow-up inquiry

(Table A36), the data for the first two follow-up inquires were used to calculate the

symptom rates for Cairo visitors in the 1978 trials. It can be seen from Table A35 that,

with only three exceptions, the rates for the various symptoms were higher for

swimmers than nonswirnrners. However, only with the gastrointestinal symptoms

(vomiting or diarrhea) and possibly fever did the rates generally increase with the

pollution levels at the three beaches as seen from the E. coli or enterococcus densities

(Table A35). The rates were higher for children than adults (Figure 6).

Another finding that paralleled one obtained in the New York City study was that, with

the exception of GI symptoms (vomiting or diarrhea) at the least polluted beach

(Maamoura) and ear complaints at the other three beaches, the swimming-associated

symptom rates per 1000 person-days decreased with increasing swimming activity. This

can be seen from the analysis of the 1978 data from the Cairo visitors by the number of

swimming days per week (Table A37). 

Only three cases of jaundice were detected among the Cairo visitors, and there was no

association to swimming, much less swimming in polluted waters. Four cases of typhoid
29

fever were found among swimmers at Sporting, the most heavily polluted beach. The

regression lines for the swimming-associated rates for vomiting or diarrhea against the

enterococcus and E. coli mean densities for the Alexandria residents and Cairo visitors

are shown in Figures 4 and 5. The data from which the lines were drawn are given in

Table A38. As expected, the slopes of the lines for the Cairo visitors were greater than

those for the Alexandria residents. Straight lines could be fitted to these illness-indicator

relationships for the data from both the Cairo visitors and the Alexandria residents.

However, examination of the relationships for the individual years suggests that there are

plateaus as shown. 

The plateaus, the differences in the indicator-illness curves for the Cairo visitors as

compared to the Alexandria residents, and the higher GI symptom rates for children as

compared to adults support the premise that the swimming populations were largely

immune to the etiological agent(s). Moreover, from the similarities in the

symptomatology and age distributions of symptoms in the Egyptian and New York City

studies and the differences in the slopes and intercepts on the Y axis of the

indicator-illness curves, we recommend the second explanation for the relationships

obtained in the New York City study. However, these predictions relate only to the

specific agent(s) responsible for the observed GI symptomatology. Swimming-associated

illness rates exceeding those predicted by the illness-indicator relationships obtained

from the New York City and Egyptian studies could occur with etiologic agents to which

there is little immunity in the population . Thus, an attack rate of 13 percent appeared

to be associated with fecal coliform densities of about 17,500/100 ml in the Dubuque

shigellosis outbreak (15). 

In addition to providing insights into the widespread distribution of the swimmingassociated, pollution-associated gastroenteritis, its etiology and the role of immunity, the

results of the Egyptian study suggest the circumstances under which typhoid fever could

become a problem via the recreational route, i.e., near an outfall for untreated sewage.

This finding, along with the available ID50 data for these agents (22), suggests the

importance of the removal of particulates during primary and secondary sewage treatment

in preventing the recreational transmission of this disease and other diseases whose

agents have high infective doses. The absence of swimming-associated infectious

hepatitis in an area where the endemic rate is high would suggest that, by the time they

start to swim, even the Cairo children have been exposed and are immune to infection

with hepatitis A virus. 

LAKE PONTCHARTRAIN STUDY

This study was conducted during the summers of 1977 and 1978 at Levee beach which

is located near the “mouth” of Bayou St. John on Lake Pontchartrain. Individuals swam

both in the mouth of the Bayou and in a nearby roped-off area. In 1978, a second beach

(Fontainebleau) located across the Lake was also included. The setting for the study

differed in a number of important ways from that for the New York City study; there is

very little tidal activity; the water is brackish (about 5 percent) and warmer during the

summer; there is no beach as such but rather a series of steps leading downward from the

grassy bank into the water. Most important of all, the sources of pollution were much less

defined. According to local authorities, there were no discharges of sewage wastes mto

the Lake or Bayou St. John. However, high coliform densities were observed at the beach

following rainfalls during “wet years.” Presumably these were due to stormwater

discharges reaching the beach via canals and bayous which empty into the Lake west of

the beach. 

Because of the ill-defined pollution sources, there was some reluctance to conduct a

study at this location. However, the findings from sampling conducted in 1976 confirmed

the high indicator densities following rainfalls and revealed moderate enterococcus

densities during dry weather. Because of this, because of the desire to test the

illness-indicator relationships under a different set of environmental conditions and
30

because this study could be a vehicle for separating the two indicators which emerged as

the best ones from the New York City study, trials were conducted in the summer of

1977.

When the rates for the individual symptoms were compared for swimmers versus

nonswimmers, statistically significant differences were obtained only for vomiting,

diarrhea, stomachache, earache, and skin complaints (Table A39). When the symptoms

were grouped into categories, significantly higher rates for swimmers were obtained only

for GI and “highly credible” GI symptoms, although there were differences for all the

categories (Table A40). In general the GI symptom rates were higher for children than

adults (Table A41). There were, several striking aspects of the findings which suggested

(i) that the major source of the infective agents was in the Bayou and not stormwater

runoff arriving from west of the beach, (ii) that enterococcus densities were better

correlated with the GI symptom rates, and (iii) that, because of this, the source of the

pathogens was rather remote (in time) from the beach. 

First of all, the mean enterococcus densities in the “mouth” of the Bayou were

generally higher, and at times markedly so, than those at the beach (roped-off area); this

was much less true of E. coli (Table A42). Secondly, in contrast the findings from the

New York City and Egyptian studies wherein the E. coli and enterococcus densities

tended to parallel each other, high E. coli densities were associated with low

enterococcus levels and vice versa. The former occurred during the period 7/30-8/28

when the average daily rainfall exceeded 0.43 inches per day. The overall

swimming-associated GI symptom rates for the trials conducted during this period were

less than those for the trials conducted prior to July 30 when the average daily rainfall

was 0.12 inches per day and the enterococcus densities exceeded those of E. coli (Table

A43). Thirdly, the indicator densities in the roped-off area approached those in the Bayou

only during the rainy period and then only for E. coli (Table A43). Moreover, the lower

enterococcus densities and GI symptom rates during the “wet period” suggested that

stormwater reaching the beach from the west reduced the pathogen and enterococcus

densities at the beach by dilution or exclusion of organisms whose source presumably

was in the Bayou. Fourthly, the trials during which there were high rates of

swimming-associated GI symptoms corresponded better with high enterococcus than high

E. coli densities (Table A44); in fact, when the swimming-associated GI and HCGI

symptom rates for the four lowest E. coli days were compared to those for the four

highest days, the former were higher than the latter.(Table A45). Finally, it has been

reported (65) that enterococci survive better than E. coli, especially in salt water. 

The input data to the criteria model are given in Table A44. The considerable

trial-to-trial variability in the indicator densities required that, even for the regression

analysis by summers, the trials be clustered according to their indicator densities. The

findings from the 1978 trials differed from those obtained in 1977 in a number of ways,

and some of the differences made the interpretation of the illness-indicator density data

even more difficult: 1978 was a somewhat “drier” year than 1977, and, in general, the

densities of both indicators were reduced. Nevertheless, the swimming-associated rate

for GI symptoms was almost the same (39/1000 persons in 1978 as opposed to 42/1000

in 1977). This suggested that rainfall induced stormwater runoff to the beach (and the

resulting elevated indicator densities) was not the source of the infective agents

responsible for the observed symptomatology. 

The rationale derived from the examination of the 1977 information was applied to the

1978 data as follows. It was assumed: (i) that, during a “relatively dry” year, the travel

time down the Bayou was even more protracted, (ii) that because of this, even the

enterococcus densities were reduced relative to the pathogens, and (iii) that these lower

enterococcus densities would be masked at the beach and even at the Bayou by those

carried in with the stormwater. Three trials were associated with especially high E. coli

and enterococcus densities in which the levels at the beach were as high or higher than

those in Bayou (Table A46). Because these were the same three days during which there was
31

a half-inch or more rainfall (Table A46), the data from these three trials were eliminated

from the analysis. Since the premise was that the source of the infective agents was the

Bayou and since the roped-off area was expected to be more heavily impacted by

stormwater, the remaining trials were grouped into high and low. days based upon the

Bayou indicator densities (Table A46), and these were used to calculate the mean indicator

densities to which the symptomatology rates were compared. The mean indicator densities

and associated GI and HCGI symptom rates as used later in the development of the criteria

are given in Table A47. 

The data from Fontainebleau beach, because of the relatively little trial-to-trial

variability in the indicator densities, were used to derive a single relationship. 

The 1978 data differed from the 1977 data in yet another way. In 1978 there were also

statistically significant differences between swimmers and nonswimmers for the

respiratory, other, EEN (ear, eye and nose) as well as disabling GI symptoms. This may

have reflected a change in the pathogens present. 

The Lake Pontchartrain study achieved its major objective. It, along with the third year

of the New York City study, clearly showed enterococci to be superior to E. coli as a

recreational water quality indicator. In addition, there were some important implications

of the results obtained. First, they suggested some conditions under which even the

enterococci may be deficient as a recreational water quality indicator. Second, they

suggested that the etiological agent(s) of the swimming-associated gastroenteritis survives

transport in the aquatic environment extremely well. Third, they provided a reasonably

clear indication that stormwater runoff is less hazardous than wastewater discharges, and,

because the two indicators are not specific for human fecal wastes, they may overstate the

risk under these conditions. 

BOSTON HARBOR STUDY

This study was conducted at two beaches in Boston Harbor in 1978. Its objective was

to expand the data base for the criteria being developed and to confirm the observation that

the measurable swimming-associated health effects were obtained at strikingly low

indicator densities. As in the Lake Ponchartrain study, the sources of pollution to the two

beaches, Revere and Nahant, were not as well defined as those in the New York City or

Alexandria, Egypt studies. At the time it was screened for suitability in 1978, the mean

enterococcus and E. coli densities at Revere beach were about 80/100 ml and exceeded

those at Nahant by about an order of magnitude. 

Four trials were conducted at each beach during June and July of 1978. The rates for the

symptom categories are presented in Table A48. At both the Revere and Nahant beaches,

the highest swimming-associated rates were for the total and HCGI symptoms, although

the differences between the swimmer and nonswimmer rates were not significantly

different. The differential rates were consistently greater at Revere than at Nahant beach,

even though the mean indicator densities at the two beaches were not appreciably different

(Table A49). This observation underscores the fact that the relationships being derived are

generalities which may vary somewhat with a number of factors in the swimming

population (i.e., their immune status, background illness rates, and even in the temporal

and spacial relationship of the beach to its source of pollution). Nevertheless, the swimmer

rates for GI symptoms were consistently higher than those for nonswimmers even at rather

low levels of pollution as seen by the enterococcus or E. coli densities. The mean

enterococcus and E. coli densities at Revere beach were less than those observed the

previous year. These and the corresponding rates for GI and HCGI symptoms calculated

by summer and by clusters of trials are given in Tables A49 and A50. The relationship of

the swimming-associated rates to the indicator densities were more akin to those obtained

at Lake Pontchartrain rather than New York City, i.e., higher rates for given indicator

levels. This suggests differential biological decay of the indicators relative to the pathogens

over more protracted transport times between the sources of pollution and the impacted

beaches.
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33

SECTION 6

DEVELOPMENT OF CRITERIA

In order to reach the objective of the overall program, the development of health

effects criteria for marine recreational waters, four questions needed to be answered.

They were:

1. Does swimming in sea water per se carry with it an increased risk of illness

and, if so, to what type?

Stevenson's findings (24) suggested that it is so for fresh, but not sea, waters Those

from the EPA program indicated this was true of sea water swimming as well. In the

Stevenson study, it was observed most with ear, eye and nose complaints, less so

with upper respiratory symptoms and least with gastrointestinal symptomatology.

 2. Is there an association of the illness rates to pollution from domestic sewage;

and if so, to what type of illness?

Stevenson's results (24) suggested there is such an association for swimming in

freshwater but not in seawater. His results were equivocal as to the type of symptom.

Moore (8) could find no association for poliomyelitis or salmonellosis. The

conclusion from the EPA program is unequivocal; there is an increased risk of

gastroenteritis associated with swimming in waters more as opposed to less polluted

with sewage. Furthermore, the increased risk occurs at beaches which meet and even

exceed the existing EPA guidelines and those of most of the states. Both the Egyptian

and American studies suggest that fever often accompanies the GI symptoms. There

were no indications in any of the American studies that anyone required

hospitalization.

With the Cairo visitors to the Alexandria beaches, no association between

swimming and infectious hepatitis (IH) could be detected, even among individuals

who swam in waters so heavily polluted that they were aesthetically undesirable. The

assumption was that the children of the Cairo visitors, coming from better sanitary

environments and swimming in waters receiving waste loads from a population with

a high endemic rate of IH, would be the most susceptible portion of the swimming

population. However, even these children may have been exposed and rendered

immune to the agents by the age they start swimming (immersion of the head in the

water). A different study population is needed to resolve this question. 

It is of interest that four cases of typhoid fever did occur among swimmers at the

heavily polluted, aesthetically undesirable beach. This was not statistically significant

and may have been a spurious result. However, since the ID50 for salmonellae is high

(22), and that for IH is thought to be fairly low, these results lend credence to the

postulated immunity explanation for the absence of IH among swimmers. There was

no indication of poliomyelitis in any of the studies. Thus, Moore's conclusions (8)

with regard to poliomyelitis and salmonellosis remain as true today as they were then.

3. Which, if any, of the potential indicators of water quality best defines the

association of GI symptomatology to water quality?

The New York City study was designed to answer this question for beaches

impacted with the sewage effluents from large urban areas. The Coney Island beaches

were affected primarily by sewage emerging from the mouth of the Hudson River, and
34

although these were combined effluents subject to the effect of rainfall, treated to various

degrees, and chlorinated only in part, they nevertheless represented a relatively well

defined source. The criterion used to select the “best” indicator was the degree of

association between its levels in the bathing water and the swimming-associated rate for

gastrointestinal symptoms. It was evident from the New York City study that enterococci

and, to a much lesser extent, E. coli were the best indicators of those examined (Table

4). Fecal cohforms were a relatively poor indicator system. 

The marked superiority of enterococci over E. coli as a recreational water quality

indicator was confirmed in the subsequent studies conducted in the United States. Higher

correlation coefficients (r) for the mean indicator densities in the water against the

swimming-associated rates for total or highly credible GI symptoms were obtained with

enterococci than with E. coli (Table 5). However, comparable correlation coefficients

were obtained for the two indicators in the Egyptian studies (Table 5). One explanation

for this difference lies in the nature and proximity of the pollution sources. The sources

of fecal pollution to the Alexandria beaches were untreated, not disinfected, and relatively

close to the beaches. A portion of those to the New York City beaches were both treated

and disinfected, and they were more distant from the beaches. Furthermore, more of the

sewage emerging from the Hudson River and Upper Hudson Bay was treated and/or

disinfected in 1975 than in 1974. This appears to correspond with poorer correlations of

the indicator densities to gastrointestinal symptomatology, especially for E. coli (compare

the 1973-74 to 1973-75 “r” values in Table 5). Insofar as could be determined, there were

no nearby sources of human fecal wastes to either the Lake Pontchartrain or Boston

Harbor beaches.

Implicit to the above explanation is the conclusion that enterococci more closely

resembles the pathogen(s) than does E. coli with regard to its survival characteristics

during sewage treatment, disinfection, and transport in the marine environment.

Furthermore, as the level of sewage treatment and disinfection increases and/or the

transport time becomes more protracted, even the densities of the enterococcus indicator

are not maintained comparable to those of the pathogen. This and other considerations to

be discussed notwithstanding, the mean enterococcus density does provide a meaningful

and useful index of the potential for the observed gastrointestinal symptomatology. 

Four possible indicator Systems were not evaluated in the course of the New York City

studies. As part of the EPA program, new methods have been developed or existing

methods have been modified for each of the four indicators, Candida albicans (42),

bifidobacteria (40), coprostanol (48) and male specific DNA, coliphage (41). Some

preliminary evaluations were made with the first two. The densities of C. albicans were

too low and variable in sewage-polluted waters to be of much value. Bifids were found

to be fecal specific and reasonably human specific; however, their use as the basis for the

criteria is precluded by their exceedingly poor survival during chlorination and transport

in aquatic environments. Nevertheless, the recovery of these bacteria from environmental

water samples indicates an “immediate” source of undisinfected human or, to a lesser

extent, porcine fecal wastes (40). Coprostanol and the f-1 male specific coliphage need

to be evaluated as water quality indicators and as conservative tracers. 

4. Can the relationship of swimming-associated health effects to the quality of the

water, as determined by a microbial or chemical indicator, be quantified

sufficiently to produce health effects quality criteria for marine recreational

waters?

The response to this question will be considered in the next section. 

The Criteria

The regression lines for the rates of swimming-associated GI and HCGI symptoms

against the mean enterococcus and E. coli densities when examined by trials clustered by

indicator density or by summer are presented in Figure 7. The input data for the analyses
35
36

are given in Tables 6-9 and the results of the regression analyses are given in Table 10.

It is obvious that enterococcus densities in the bathing water provide the most meaningful

and useful relationship to the observed GI symptomatology. The formulae for the two

pairs of enterococcus regression lines, the correlation coefficients (r) for the lines, and

the corresponding p values are given in Table 10 along with the equations obtained by

averaging the slopes and intercepts of each pair of lines. The “fits” for quadratic

equations were no better than those for linear equations. These lines are shown in Figure

8 along with the 95 percent confidence limits around the lines. These were obtained from

the data for the clustered trials. The confidence limits of the predicted rates for the

clustered trials are given in Table A51. 

The Y and X regression lines, given in Table 10 for enterococcus and shown with their

confidence limits in Figure 8, predict the illness rates for the indicator densities.

However, as noted earlier in this report, the conceptual framework for the program was

that a decision would be made as to the acceptable risk level and this would be
37
38
39
40
41

a mean indicator density limit to be used as a guideline. This requires the regression of

X on Y. These lines along with their confidence limits, correlation coefficients and

formulae are given in Figure 9. The 95 percent confidence limits for the mean

enterococcus densities predicted for the observed swimming-associated rates are given

in Table A52. The author favors the use of the criteria for HCGI symptoms because of

the greater credibility of its data base and because it is more conducive to economic

analysis. The 95 percent confidence limits for the regression lines as shown (Figure 9)

are rather broad although the slopes are significantly different from zero. This was not

unexpected since the relationships obtained are generalizations which may be altered by

any of a number of temporal and spacial factors relative to the indicator, the pathogen,

the relationship of the pollution sources to the bathing beach, the levels of the specific

illnesses in the overall population, and the immune status of the swimmers. These will

be discussed in the next two sections 

Examination of the illness-indicator relationships by location and by year at a given

location could provide some insight as to possible spatial and temporal effects. The latter

was not attempted because of the small number of points available for analysis by year.

The regression lines for the New York City study were compared to those obtained from
42
43

the combination of the Lake Pontchartrain and the Boston Harbor studies; however, even

for the trials clustered by similar indicator densities (Table 6), each line was defined by

only nine points. Significant differences were obtained between the lines for highly

credible but not total GI symptoms. The lines for total GI symptoms were not

significantly different; however, those for HCGI symptoms were, although the two lines

stay virtually within the 95 percent confidence limits of the total data. This provides

some basis for the generalization obtained from the single regression line. This

generalization may not be totally accurate in all situations. Thus, in the present case, the

sources of pollution to the beaches in the Lake Pontchartrain and Boston Harbor studies

were ill-defined and, presumably, more distant. This and the effect of the immune status

of the swimming population could explain the significant differences between the

regression lines for highly credible but not total GI symptoms. In any event, these results.

emphasize the conclusion that guidelines derived from these criteria cannot be used

without judgment; rather, they must be used in concert with good public health practice

(e.g., taking into consideration changes in the incidence of enteric disease in the

discharging population), an environmental (sanitary) survey, and judgment with regard

to their limitations in time and space. In fact, the correlations obtained are remarkably
44

good when the sources of temporal and geographic variability are considered, and this

has some interesting implications concerning the agent(s) and host population, i.e.,

ubiquity, infectivity, survival, immunity, etc. 

THE ETIOLOGIC AGENT(S)

When the study design for the EPA program was being developed in 1969-1970, it was

thought that swimming in sewage-polluted waters would constitute a relatively minor

route of transmission for GI illness and that relatively high levels of pollution (as indexed

by microbial indicator densities) would be required before GI illness could be detected.

These assumptions were made on the basis of existing notions and available information

(8,24). Both these assumptions were incorrect. If the nonswimming rates for GI

symptomatology can be considered as those for the population at large, then swimming

in sewage-polluted waters constitutes a significant route of transmission for the illnesses

obtained, at least for individuals of “swimming age.” This can be seen from the tabular

(Table II) and graphic (Figure 10) representations of the ratios of the rates for

swimmers divided by those for nonswimmers against the enterococcus densities for the

clustered trials. In fact, at enterococcus densities of 70 and 10/100 ml, respectively, the

rates for total and HCGI symptoms among swimmers were twice those for nonswimmers,

and they are projected to be equal (a ratio of “I”) at an enterococcus density of about

1/100 ml. This suggests that the etiologic agent(s) for the observed GI symptomatology

is present in sewage in large numbers, that it is highly infective and/or that it survives

sewage treatment, disinfection and/or transport better than the indicator.
45

One of the desired outputs from the program was an answer to the question: Does the

swimming-associated illness rate increase with the levels of these specific illnesses in

the population at large? This relationship was not observed for the types of illnesses

obtained in this study (Table 12), probably because of the high level of immunity to the

agent in the population. 

Initially, it was thought that the Egyptian data could be used in the derivation of the

final criteria. By the end of the first year of the Egyptian study, it was obvious that the

data from the Alexandria residents could not be so used, and by the end of the third year,

it was concluded that this was also true of data from the Cairo visitors. The regression

lines for the rates of swimming-associated vomiting and diarrhea from these two groups

along with those for GI and HCGI symptoms from the United States studies against the

corresponding mean enterococcus densities are presented in Figure 11. It can be seen

that, in the United States studies, gastrointestinal illness rates comparable to those

obtained in the Egyptian study were associated with bathing in waters with much lower

enterococcus densities. Part of the dissimilarity is probably due to differences in the

nature (raw vs. treated) and proximity of the pollution sources in the United States and

Egyptian studies. However, disparities in the immune state of the populations to the

etiologic agent(s) probably accounts for most of the differences in the indicator-illness

relationships obtained. 

The importance of immunity in the epidemiology of the swimming-associated

gastroenteritis is also supported by the age distribution of the attack rates. In most of the

studies, children (<10 years of age) were found to have the highest symptom rates. 

The following characteristics of the swimming-associated illness were obtained in or

can be inferred from the findings of the EPA program: (i) The illness is a relatively

benign gastroenteritis with a short incubation period (Figure 12), acute onset, short
46
47

duration (Table 13) and rare, if any, sequelae. (ii) It is widely distributed; most individuals

are immune, and, in general, children have the highest attack rates. (iii) The etiologic

agent is highly infectious, is present in sewage in large numbers, and/or survives sewage

treatment disinfection and transport in the marine environment somewhat better than the

indicators. These considerations suggest the human rotavirus and/or the parvo-like viruses

as. the etiologic agents. 

There are at least three explanations for the observations that individuals who swim

during several days in a given week (from the Egyptian study) or for prolonged periods

during a given day (from the New York City study) have low GI symptom rates. The

obvious one is that these are “healthier” individuals. The second assumes that the extent

of swimming is correlated with age, that is, individuals who swim regularly and

extensively are more experienced and ingest less of the bathing water. However, it is

commonly assumed that children are in the water the longest and also ingest the most

water. The third explanation requires that the illnesses involved have short (< 3 days)

incubation periods and that there may be a good immunity to the etiological agents The

rationale for the Egyptian observations is that the susceptible individuals become ill within

a day or so of the time they start swimming.
48
49

SECTION 7

LIMITATIONS IN THE USE OF THE

RECOMMENDED CRITERIA

The criteria presented in this report (the enterococcus density in the bathing water

against the swimming-associated rates for total and HCGI symptoms) are

generalizations which have been found to apply in a number of situations. Nevertheless,

a number of considerations, including the limitations in the indicator concept itself,

impact on the use of the criteria as well as the guidelines and standards derived

therefrom. More important, these considerations require that the findings from

monitoring programs be interpreted in the light of good public health and

environmental practice. They have been described elsewhere (49, 66) and several of the

more important ones will be considered herein.

SMALL POINT SOURCES

The rationale for the use of guidelines and standards based on fecal indicator

densities for indexing the health hazards in sewage polluted waters is that, under

average conditions of illness in the discharging population, there is a reasonably

constant indicator to pathogen ratio in the sewage and its receiving waters. Thereby,

an acceptable probability of illness caused by the pathogen can be extrapolated to a

given indicator density, which is then recommended as a guideline and promulgated as

a standard. Such relationships appear to hold for waters receiving the discharges from

relatively large municipal sewage treatment facilities. However, as the number of

individuals who contribute to the source of the fecal wastes becomes smaller and

smaller, the indicator-pathogen ratio will vary more and more from the average upon

which the guideline or standard is based. In the extreme case where the fecal wastes

of a single ill individual or carrier are discharged into the water, the number of

pathogens may equal or exceed the number of indicator microorganisms. Routine

examination of such waters for fecal indicators would be of no value. Furthermore, the

routine examination for the pathogens would not be especially useful since the release

of enteric pathogens will be sporadic. The solution is administrative action prohibiting

such discharges into recreational waters.

ILLNESS RATES IN THE DISCHARGING POPULATION

 Most epidemiologists and health officers recognize that, under epidemic conditions,

the actual indicator-pathogen ratio may change sufficiently from that upon which a

guideline was based so that the acceptable risk of illness will be exceeded unless the

guideline is temporarily made more restrictive. The recent swimming-associated

outbreak of shigellosis on the Mississippi River below Dubuque, Iowa (15) appears to

represent an instance where, although the 200/100 ml fecal coliform guideline was

probably exceeded, the outbreak did not occur until there was a large enough number

of ill individuals and carriers in the discharging population. Conversely, if there is a

significant and consistent decrease in the illness rate in the discharging population over

a prolonged period of time, the rate for that specific illness associated with an existing

indicator guideline or standard may be considerably less than predicted. The absence

of recreational water-associated salmonellosis probably represents a case in point.
50

FECAL INDICATORS VERSUS PATHOGENS

The use of fecal indicators such as coliforms or portions of the coliform population, fecal

streptococci, and C. perfringens for indexing the health hazards in drinking and

recreational waters dates back to the late 1800s and early 1900s (32). This occurred shortly

after these organisms were first isolated and associated with the fecal wastes of

warm-blooded animals. Within the context of the limitations being discussed, such

practices were and are sound both on theoretical and practical grounds since it is

recognized that (i) there are large number of pathogenic bacteria and viruses potentially

present in municipal sewage (67,68), each with its own probability of illness associated

with a given dose; (ii) monitoring for each of the pathogens on a routine basis would be

a herculean task; (iii) enumeration methods for some of the more important pathogens are

unavailable and for the rest are difficult; (iv) pathogen density data are difficult to interpret

because the methodology generally is imprecise and inaccurate and because of the meager

dose-response data available; and (v) on theoretical grounds, the intent is not to index the

presence of the pathogen but rather its potential to be there in sufficient numbers to cause

unacceptable health effects. 

By no means should the foregoing be construed as suggesting that recreational water

quality criteria and the derived guidelines are unnecessary. To the contrary, criteria

amenable to risk analysis are absolutely essential. It is evident from the nature of the

illness indicator (Y on X) lines and the heavy usage of estuarine and coastal beaches in

the United States that large numbers of individuals are becoming ill as a consequence of

swimming in sewage-polluted waters. Furthermore, as seen from the Dubuque outbreak

(15), the potential for more serious illness exists. Nevertheless, since the illnesses involved

are relatively benign, there is undoubtedly a rate which is acceptable; however, the

acceptances of the risks involved should be deliberate decisions with consideration of all

the factors involved and with local input.

A temporary consequence of the application of the criteria may be the withdrawal of

certain recreational resources from public use. However, the long range impact should be

pollution abatement. This requires better technology for obtaining the data base needed for

the translation of the target area criteria which have been developed into effluent

guidelines on a case-by-case basis. 

The findings from the EPA program have raised a number of questions. One is the

nature of the etiologic agent for the gastrointestinal symptomatology. A second is the need

for a more human fecal specific and environmentally resistant indicator. This relates to the

difficult question of stormwater runoff and nonpoint sources. The third is need for separate

criteria for fresh waters. Studies in progress which address these questions should be

continued.
51

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23. Dupont, H. L., R. B. Hornick, A. T. Dawlcins, M. J. Snyder, and S. B. Formal. 1969.

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24. Stevenson, A. H. 1953. Studies of Bathing Water Quality and Health. J. Amer. Public

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25. Shuval, H. I. The Case for Microbial Standards for, Bathing Beaches. In: Discharge

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38. Levin, M. A., J. R. Fischer, and V.3. Cabelli. 1975. Membrane Filter Technique for

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41. McBride, G. A Bacteriophage Simulant for Enteric Virus Behavior in Water Systems. M.

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Candida albicans in Natural Waters. Appl. Environ. Microbiol. 35:237. 

43. Levin, M. A., and V.J. Cabelli. 1972. Membrane Filter Technique for Enumeration of

Pseudomonas aeruginosa. Applied Microbiol. 24:864. 

44. Rippey, S. R., and V.J. Cabelli. 1979. Membrane Filter Procedure for Enumeration of

Aeromonas hydrophila. Appl. Environ. Microbiol. 38:108. 

45. Watkins, W. D., C. D. Thomas, and V.J. Cabelli. 1976. Membrane Filter Procedure for

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46. Levin, M. A., 3. R. Fischer, and V.J. Cabelli. 1974. Quantitative Large-Volume Sampling

Technique. Appl. Microbiol. 28:515. 

47. Calderon, R., and M. A. Levin. 1980. Quantitative Method for tne Enumeration of

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48. Wun, C. W., R. W. Walker, and W. Litsky. 1976. The Use of XAD-2 Resin for the

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51. Miescier, J.J. The Occurrence and Variability of Bacterial Indicator Organisms in Raw and

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Emanating from Redwood Tanks. Appi. Environ. Microbiol. 33:893. 

54. Cabelli, V.J., and L. J. McCabe. 1974. Recreational Water Quality Criteria. News of

Environmental Research in Cincinnati. 

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