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.
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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
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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.
11
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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 epidemiological-
microbiological 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
m
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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 ofKlebsiella 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 ofE. coli, the characterization of
a highly chlorine resistant, male specific coliphage from sewage, and the microbial
colonization of the external ear canal.
IV
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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).
v
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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
Elealth 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
vii
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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
vm
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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
A1 Total and Fecal Coliform Standards for Primary Contact Recreational
Waters as of 1978 55
(continued)
IX
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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
Klebsiella 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
A15 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)
x
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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
All 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
All 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)
XI
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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 Nonswimmers 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 1977 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)
xn
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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 (PM80 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.
xm
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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 cost-
benefit 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,
1
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Recommended health effects criterion tor marine recreation waters.
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./Leromonas 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."
2
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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 program 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)(1) of Public Law 92-500.
3
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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 Alf, 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
¦fWhen a table number is preceded by "A," the table is to be found in the Appendix.
5
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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 Engi-
neering (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 coliform 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.
6
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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) out-
put 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 dysen-
tery), 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,
7
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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:lg
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 sewage-
contaminated 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.
8
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ment. The removal of suspended solids during treatment decreases the number of
multisalmonellae-containing particles. When the human rD50 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 mlS. sonnei. The same antibiogram and colicin type
as the isolates from seven swimmers, also was recovered from these waters. A case-
control 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 swimming-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
9
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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
10
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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 rD50 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 rD50 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 spatially 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
11
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TABLE 1, METHODS DEVELOPMENT IN SUPPORT OF THE USEPA
EPIDEMIOLOGICAL PROGRAM
Indicator
Method I
Indicator
Method Ref
Conforms
£ coli
mC
mTEC
(35) P. aeruginosa
136} A. hydrophila
(37) V. pamhaemofyticus
(381 Salmonella
(39) Enteropathogenic
mPA (43)
mA (44)
mVP (45)
HVS (48)
—* (ATt\
Klebsiella
Enferococci
C perfringpns
mK
mE
mCP
(47)
£ coli
Bifidobacteria
Coliphage
C, albicans
(40)
(41) Coprostanoi
(42!
(48)
: L^fi^uirc xiUH.-n li.i- ilu- mc:h>>
-------
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
GUIDELINE
WATER QUALITY INDICATOR DENSITY •
Fi§ure 1. Graphic representation of the desired recreational water quality criteria. It
is assumed that only an extremely small risk of "serious" illness will be
accepted
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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.
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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-
15
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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
16
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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.
17
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TABLE 2. SEQUENCE OF EVENTS TOR EPIDEMIOLOGICAL-
MICROBIOLOGICAL TRIALS
D»y of
D *y
wmk
number
Activity
Function
Saturday
1
Beach interview.
(a) Obtain name, address, phone.
water sampling
etc
(b) Reject pre-trial midweek
swimmers
(c) Query on beach activity
Ml Assay of water samples
Sunday
2
Same as Saturday
As above
Monday
3
Reminder letter
(a) Provide name of physician
(b> Reminder to note illness
MoriiJsy
10
Phone or mail
(a) Obtain illness information
interview
(bl Reject post-trial midweek
swimmers
Ic) Obtain remainder of demogra-
phic information.
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 proce-
dures were chosen because they provide more precise estimates than MPN determina-
tions 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
18
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(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).
19
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TABLE 3. SUCCESS OF FOLLOW-UP PHONE INTERVIEWS AND THE NUMBER OF USABLE RESPONSES BY BEACH AND YEAR
FOR STUDIES CONDUCTED UNDER THE EPA PROGRAM
% Follow-up During
Number of Usable
Study Year1
Responses During Year
Location
Beaches
1
2
3
1
2
3
New York City, NY
Coney Island
82,3
78.3
78.3
641
3146
6491
Rockaway
86.8
82.9
681
4923
Lake Pontchartrairi, LA
Levee
Fontainebleau
77.2
77.9s
3432
2768
551
Boston Harbor, MA
Revere
Nahant
81.2
81.2
1824
2229
Alexandria, Egypt
Maamoura3
88.6
84.8
84.4
819
1492
1786
4
91.2
88.3
1696
2173
Ibrahemia3
81.2
87.8
90.4
823
1117
2050
4
87.5
87.2
1159
1820
Mandara3
82.9
1163
Sporting3
90.7
90.6
1257
2025
4
84.9
88,5
1243
2457
1 Coney Island. Rockaway. 1973-197S. Levee. I97"M978. Fomainebk'au, 1978- Revere. Nahani, 1978; Maamoura. Jbrahemia, 1976-1978; Munara. 1976; Sporting. 1977-1978.
: Fomainebleau included vuth Levee
5 Alexandria residents.
J Cairo visitors.
-------
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 suit-
ability of the test beaches. In 1972, the reliability of information obtained from the
interviewees concerning their bathing activities was examined using the method de-
scribed 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 1973, 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.
21
-------
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 exam-
ined 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.
22
-------
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.
TABLE 4. CORRELATION COEFFICIENTS FOR TOTAL
GASTROINTESTINAL SYMPTOMS AND THE "HIGHLY
CREDIBLE" PORTION AGAINST THE MEAN INDICATOR
DENSITIES FOR 1973-1975 TRIALS CONDUCTED AT NEW
YORK CITY BEACHES
Correlation Coefficients frl for
Number of
Highly Credible GI'
Gastrointestinal (GI)J
Points (Nl
Indicator
Surom3
Oust*
Surom
Oust
Surmm
Clust
Enterococci
75
.96
.84
.81
8
9
£. coh
52
.56
.56
.51
8
9
Klebsiella
32
.61
.35
.47
8
11
Enterobact.-Citrobact.
.26
.64
.23
.54
8
13
Total coliforms
.19
65
.12
.48
8
11
C. perfringens5
.19
.01
38
- ,38
5
8
P. aeruginosa
.19
.59
.25
.35
8
11
Fecal coliforms
-.01
.51
.01
,36
8
12
A hydrophtla
- .09
60
- .08
.27
7
11
V. parohaemoiyVcus5
- .20
.42
.19
.05
5
7
Staphylococci"'
23
60
.71
.03
5
10
A- ! : ' - • -!¦¦¦ J - a vmijf -JcDm! C\
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 regres-
sion 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 symptoms
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.
23
-------
HCSI Ytm
A 1973
* 1974
A 1975
-TOTAL GI SYMPTOMS
HIGHLY CREDIBLE G! SYMPTOMS
TRIALS GROUPED BY SUMMER AND BEACH
r = .75
TRIALS CLUSTERED BY INDICATOR DENSITY
9
i mill ^ 1 J_ii.it
MEAN ENTEROCOCCUS
DENSITY/100 ml
MEAN £. coti
DENSITY 100 ml
Figure 2. Swimming-associated (swimmer minus nonswimmer) gastrointestinal symptom rates
against the mean enterococcus and /V. 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 dose-
response 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
24
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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.
1 I I IHI
101 102
MEAN ENTEROCOCCUS DENSITY'100 mi
Figyre 3. Data from Figure 2a shown as percentages on a scale more akin to thai
used in dose-response representations.
25
-------
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 fromE. 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
200-300/100 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.
W
O
w
cc
LL1
<
O UJ
2 c
*1
< Q
s;
§1
0
02
UJ
<
6
z
1
1
S
m
O
>
cc
O
60
50
40
30
20
10
0
a ALEXANDRIA RESIDENTS
1976
" a ALEXANDRIA RESIDENTS
1977
- * ALEXANDRIA RESIDENTS
1978
° CAIRO VISITORS
1977
r - 88
- CAIRO VISITORS
1978
_
© _ —-y(f~
X9 e
_
/ /
/ /
/ /
/ /
/ A
/ /
/
i /
a r= 68
_ ¦—
7 *
1 III 1 i KlaT 11/
A
I. 1. .1 1 1.1.1 . .. I ! 1 1 1 111
10°
10' 10z 103
MEAN ENTEROCOCCUS DENSITY/100 ml
10"
Figure 4, Swimming-associated rates for vomiting or diarrhea against the mean en-
terococcus density in the water (Egyptian study). The correlation coeffi-
cients (r) are those for the linear relationship. The dotted lines are the
author's interpretation of the overall relationship from those seen for the
individual years. Data given in Table A38. Appendix A.
26
-------
m
S
m
a ALEXANDRIA RESIDENTS
• ALEXANDRIA RESIDENTS
+ ALEXANDRIA RESIDENTS
• CAIRO VISITORS
• CAIRO VISITORS
10' ioJ to3
MEAN £ colt DENSITY.'100 ml
Figure 8, Swimming-associated rates for vomiting or diarrhea against the mean £.
cofidensity in the water (Egyptian study). Sea Figure 4 caption for explana-
tions
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 A3 5. 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
27
-------
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 nonswirnmers. 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).
W
NONSWIMMER RATES
AGE VISITORS
<1 2.2
5-10
10-25 1.8
25 1.2
RESIDENTS
3.5
A =
-------
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 swimming-
associated, 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 nD50 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
29
-------
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 ofE. 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
30
-------
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.
31
-------
[This page is intentionally blank.]
-------
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
33
-------
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 fori?, 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 andE. coli densities when examined by trials clustered by
indicator density or by summer are presented in Figure 7. The input data for the analyses
34
-------
TABLE 5. CORRELATION COEFFICIENTS FOR ENTEROCOCCUS AND £ coli DENSITIES AGAINST THE GASTROINTESTINAL
SYMPTOM RATES FOR UNITED STATES AND EGYPTIAN STUDIES
Correlation Coefficients (r) for trial clustered by:
Indicator Densities2
Summers*
Symptom
Studies
Years
Enterococcus
E coli
Enterococcus
fc coli
Gastrointestinal
New York City
1973-74
.90
.94
.95
,96
New York City
1973-75
.81
.51
.84
,56
I, Point-Boston Harbor1
1977-78
.84
.16
.86
,02
All U.S.
1973-78
.82
.25
.86
.20
Highly Credible Gl
New York City
1973-74
.98
.96
96
.97
New York City
1973-75
96
.56
75
,52
L. Point.-Boston Harbor
1977-78
.62
.57
.74
,54
All U.S.
1973-78
.75
.54
.72
,52
Alex.. Egypt (Resid.)4
.89
.76
Alex., Egypt (Visit.)5
.88
.87
1 Lake Pontchartrain and Boston Harbor studies analyzed together.
2 Trials clustered by similar indicator densities
3 Trials grouped by summers.
4 Alexandria residents at Alexandria beaches
5 Cairo visitors to Alexandria beaches
-------
<
z
i=
CO
90
80
Si.
HCGi
STUDY
YEAR
~o
A
NEW YORK CITY
€
A
mw YORK CITY
1974
" m
A
NEW YORK CITY
1975
e
A
LAKE PONTCHARTRAIN
1977
¦ Q
A
LAKE PONTCHARTRAIN
1978
0
BOSTON HARBOR
1978
r = ,82 / b
<0 co
uxun )
MEAN ENTEROCOCCUS
DENSITY 100 ml
MEAN £ co//
DENSITY 100 ml
Figure 7. Swimming-associ atari rates for Gl symptoms against the mean enrerococ-
cus and E, coti densities in the water. Data from all U,S- studies. Values for
the points given in Tables 6-9. Definition of highly credible Gl symptoms
given in text, as is the rationale for clustering the trials. See Figure 2 for the
meanings of a. b, c, and d. The actual trials clustered are shown in Tables
A8 through A3', A44. A46, A47 and A50 in Appendix A
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 Gl 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
36
-------
TABLE 6. SUMMARY OF THE MEAN ENTEROCOCCUS DENSITY—GASTROINTESTINAL SYMPTOM RATE RELATIONSHIPS
OBTAINED FROM CLUSTERED TRIALS FOR ALL THE U.S. STUDIES (INPUTS TO THE REGRESSION ANALYSIS,
FiGURE 7a, TABLE 10)
Enterococcus
Symptom Rates in Cases Per 1000
Density per
N
Total Gastrointestinal
Highly Credible Gl
Study
Beach
Year
100 ml
Swim Nonswim
Swim
Nonswim
A1
Swim
Nonswim
A
NYC2
Rock5
19738
21.8
484
197
81
46
35
30.4
15.2
15.2
C. Is.6
91.2
474
167
72
24
48*
46.4
18.0
28.4'
1974
3.6
1391
711
27
23
4
7.6
4.2
3.4
7.0
951
1009
38
34
4
10.5
6.9
3.6
13.5
625
419
42
17
25*
16.0
2.4
13.6
31.5
831
440
43
23
20
18.1
—
18.1*
1975
5.7
2232
935
63
55
8
18.8
19.3
-0.5
20.3
1896
678
59
37
22*
14.8
7.4
7.4
154
579
191
60
31
29
34.5
—
34.5*
Lake Pont.3
Levee
1977
44
874
451
86
51
35*
32.0
11.1
20.9*
224
720
456
108
50
58**
31.9
8.8
23.1*
495
895
464
108
54
54**
35.8
8.6
27.2**
Levee
1978
11.1
1230
415
75
34
• 41**
36.6
14.5
22.1*
Font.7
14.4
248
303
81
63
18
44.3
23.1
21.2
Levee
142
801
322
112
50
62**
42.4
15.5
26.9*
Boston H.4
Revere
1978
4,3
697
529
83
• 66
17
23
11
12
Nahant
7.3
1130.
1099-
71
67
4
33
28
5
Revere
12.0
222
376
108
74
34*
41
13
28*
1 Difference (swimmer rate minus ncmswimmer rate).
2 New York City, NY.
3 Lake Pontchamain, LA.
4 Boston Harbor.
5 Rockaways.
6 Coney Island.
1 Fontainebleau,
8 Study population too small to cluster trials by similar indicator densities.
*p<0.05; "p<0.01
-------
TABLE 7. SUMMARY OF THE MEAN ENTEROCOCCUS DENSITY—GASTROINTESTINAL SYMPTOM RATE RELATIONSHIPS
OBTAINED FROM TRIALS GROUPED BY BEACH AND YEAR FOR ALL U.S. STUDIES (INPUTS TO THE
REGRESSION ANALYSIS, FIGURE 7b).
Enterococcus
Symptom Rates in Cases Per 1000 Study
Density per
N
Total Gastrointestinal
Highly Credible Gl
Study
Beach
Year
100 mi
Swim
Nonswim
Swim
Nonswim
A1
Swim
Nonswim
~
NYC2
Rock5
1973
21.8
484
197
81
46
35
30.4
15.2
15.2 •
C. Is.®
91.2
474
167
72
24
48*
46.4
18.0
28.4
Rock.
1974
3.5
2767
2156
39
35
4
12.0
12.0
0.0
C. Is.
16.4
1961
1185
42
26
16*
16.0
9.3
6.7
C. !s.(1)
1975
17,9
1534
590
70
54
16,
21.2
12.6
8.6
(2)
27,7
1744
623
57
42
15
21.8
22.5
-0.7
(3)
6.7
1131
475
50
44
6
13.7
8,5
5.2
(4)
14.2
298
96
60
31
29
23.5
10.4
13.1
Lake Pont.3
Levee8
1977
44
874
451
86
51
35*
32.0
11.1
20.9*
224
720
456
108
50
58**
31,9
8.8
23.1*
495
895
464
108
54
54#*
35.8
8.6
27.2**
Levee8
1978
11.1
1230
415
75
34
41##
36.6
14.5
22.1*
142
801
322
112
50
62**
42.4
15.5
26.9*
Font.7
14.4
248
303
81
63
18
44.3
23.1
21.2
Boston H.4
Revere
1978
6.3
919
905
89
• 70
19
27.0
12.0
15.0
Nahant
7.3
1130
1099
70
64
6
33.0
28.0
5.0
1-7 See Table 6 for abbreviations.
8 Data from Levee Beach were only clustered by trials with similar indicator densities for reasons explained in text.
•p
-------
TABLE 8. SUMMARY OF THE MEAN £ coli DENSITY—GASTROINTESTINAL SYMPTOM RATE RELATIONSHIP OBTAINED
FROM CLUSTERED TRIALS FOR ALL THE U.S. STUDIES (INPUTS TO THE REGRESSION ANALYSIS FIGURE 7c)
E. cali
Symptom Rates in Cases Per 1000
Density per
N
Total Gastrointestinal
Highly Credible Gi
Study
Beach
Year
100 m!
Swim Nonswim
Swim
Nonswim
A1
Swim
Nonswim
~
NYC2
Rock.5
19738
24.8
484
197
81
46
35
30.4
15.2
15.2
C. Is.6
174.0
474
167
72
24
48*
46.4
18.0
28.4
1974
2.2
2514
1641
25
34
-9
8.0
3.7
4I3
13.3
1304
1045
38
29
9
14.1
5.7
8.4*
30.5
600
425
65
33
32*
23.3
2.4
20.9
1975
46,8
1945
1099
55
51
4
13.4
17.8
-4.4
142
775
194
76
41
3S
24.5
10.3
14.2
278
1049
330
55
24
31*
21.0
3.0
18.0*
514
937
271
68
55
13
24.5
7.4
17.1
Lake Pont.3
Levee
1977
44
372
222
132
45
87**
32.3
9.0
23.3
161
910
306
120
65
55**
52.7
22.8
29.9*
497
574
307
85
45
40#
32.8
13.0
19.8
3091
419
204
88
83
5
31.0
4.9
26.1
Font.7
1978
9.0
248
303
81
63
18
44.3
23.1
21.2
Levee
32.6
1123
382
78
44
34*
38.3
20.9
17.4
93.7
918
355
103
36
67**
39.2
8.5
30.7
Boston H.4
1978
5.5
541
874
72
63
9
39
29
10
7.0
477
410
86
68
18
23
10
13
17.5
589
225
70
67
3
27
27
0
29.5
442
495
93
71
22
32
14
18
1-8 See Table 6 for abbreviations.
. *p<0.05; "pCO.OI
-------
TABLE 9. SUMMARY OF THE MEAN E coli DENSITY—GASTROINTESTINAL SYMPTOM RATE RELATIONSHIP OBTAINED
FROM TRIALS GROUPED BY BEACH AND YEAR FOR ALL U.S. STUDIES (INPUTS TO THE REGRESSION
ANALYSIS, FIGURE 7d)
E. coli
Symptom Rates in Cases Per 1000
Density per
14
Total Gastrointestinal
Highly Credible Gl
Study
Beach
Year
100 ml
Swim
Nonswim
Swim
Nonswim
A1
Swim
Nonswim
~
NYC2
Rock.5
1973
24.8
484
197
81
46
35
30.4
15.2
15.2
C. is.6
174.0
474
167
72
24
48*
46.4
18.0
28.4
Rock.
1974
2.4
2767
2156
39
35
4
12.0
12.0
0
C. Is.
15.3
1961
1185
42
26
16*
16.0
9.3
6.7
C. is.(1)
1975
52.4
1534
590
70
54
16
21.2
12.6
8.6
(2)
98.6
1744
623
57
42
15
21.8
22.5
-0.7
(3)
61.3
1131
475
50
44
6
13.7
8.5
5.2
(4)
157
. 298
96
60
31
29
23.5
10.4
13.1
Lake Pont.3
Levee8
1977
44
372
222
132
45
87**
32.3
9.0
23.3
161
910
306
120
65
55**
52.7
22.8
29.9*
497
574
307
85
45
40*
32.9
13.0
19.8
3091
419
204
88
83
5
31.0
4.9
26.1
Font.7
1978
9.0
248
303
81
63
18
44.3
23.1
21.2
IjayggS
32,6
1123
382
78
44
34*
38.3
20.9
17.4
93.7
918
355
103
36
g-J**
39.2
8.5
30.7*
Boston H.4
Revere
1978
18.0
919
905
89
70
19
27.0
12.0
15.0
Nahant
.11.5
1130
1099
70
64
6
33.0
28.0
5.0
1-8
See Table 7 for abbreviations and notations.
*p<0.05; **p<0.01
-------
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 densi-
ties 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 credibil-
ity 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
relationshps obtained are generalizatons 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 over-
all 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
W
Z
O
<0
cc ec
gui
70
60
H ©
£
o 2
gg
o >-
<
ii
s
£ 50 -
REGRESSION LINE
(Y ON X)
95% G.L. AROUND LINE
TOTAL Gl SYMPTOMS
40 —
—! 30 —
20
10 —
HIGHLY CREDIBLE
Gl SYMPTOMS
Figure
MEAN ENTEROCOCCUS DENSITY/100 ml
8. Regression lines for swimming-associated Gl symptom rates (Y) against
the mean enterococcus densities in water (X). Lines drawn from averages
of slopes and intercepts from Figures 7a and 7b. Confidence limits are
those for the regression lines shown in Figure 7a. Representation predicts
the illness rates from the indicator densities and presents the 95% confi-
dence limits of the former.
41
-------
TABLE 10. REGRESSION FORMULAE AND CORRELATION COEFFICIENTS FOR SWIMMING-ASSOCIATED Gl SYMPTOMS
AGAINST ENTEROCOCCUS DENSITIES AND AGAINST E. coli DENSITIES IN THE BATHING WATERS (ALL
U.S. STUDIES)
Indicator
Analysis
by
N
Gastrointestinal Symptoms
' HCGI Symptoms1
Slope
Intercept
r
P
Slope
Intercept
r
P
Enterococcus
Trials
18
24.19
-5.09
.82
<.001
12.17
0.20
.75
<.001
Summers
16
27.37
-9.52
.86
<.001
11.53
-1.36
.72
<.005
Average
25.78
-7.31
11.85
-0.58
£ coli
Trials
20
7.37
15.73
.25
6.30
5.88
.54
Summers
17
6.63
17.72
.20
7.30
2.79
.52
1 Highly credible gastrointestinal symptoms.
-------
w
2
O
w
m
Ss
|i
Si
<£
81
82
< <
a 2
S P
li
CO
<
O
70
60
50
40
30
20
10
r = 0.82 /
/
/
- 95% C.L. AROUND LINE /
REGRESSION LINE
(X ON Y)
TOTAL Gl SYMPTOMS /
tog x = .Q277Y + 0.604 >V //
/ / //
HIGHLY CREDIBLE
Gl SYMPTOMS
log m=.0456Y + 0.677
J L
10° 101 102
MEAN ENTEROCOCCUS DENSITY/100 ml
103
Figure 9. Health effects criteria for marine recreational waters developed by the
USEPA epidemiological-microbiological program. Criteria areX on Y re-
gression lines of the mean enterococcus density in the water against the
swimming-associated rate of gastrointestinal symptoms. Lines drawn in
the same manner as those shown in Figure 8. The 95% confidence limits
around the lines are those for data given in Table 6.
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 Gl symptoms. The lines for total Gl 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 re-
gression lines for highly credible but not total Gl symptoms. In any event, these results
emphasize the conclusion ihat 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 dis-
charging population), an environmental (sanitary) survey, and judgment with regard to
their limitations in time and space. In fact,' the correlations obtained are remarkably
43
-------
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 G1 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 swim-
ming 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 11) and graphic (Figure 10) representations of the ratios of the rates for
TABLE 11. RATIO OF SWIMMER TO NONSWIMMER GASTROINTESTINAL
SYMPTOM RATES BY ENTEROCOCCUS DENSITY1
Enterococcus
Swim/Nonswim GI Symptom Rate
Density/100 ml
Total Gastrointestinal
Highly Credible GI
3.6
1.17
1.81
4.3
1.26
2.09
5.7
1.15
0.97
7.0
1.12
1.52
7.3
1.06
1.18
11.1
2.21
2.52
12.0
1.46
3.15
13.5
2.47
6.67z
14.4
1.29
1.92
20.3
1.59
2.00
21.8
1.76
2.00
31.5
1.87
I3
44.0
1.69
2.89
91.2
3.00
2.58
142.0
2,24
2.74
154.0
1.94
I3
224.0
2.16
3.63
495.0
2.00
4.13
1 Data taken from Table 6.
2 Due lo unusually tow nonswimmer rate.
3 Indeterminate because of no cases among nonswimmers.
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 nonswim-
mers, and they are projected to be equal (a ratio of "1") at an enterococcus density of
about 11100 ml. This suggests that the etiologic agent(s) for the observed GI symptoma-
tology 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.
44
-------
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 re-
gression 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 die 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 be-
nign gastroenteritis with a short incubation period (Figure 12), acute onset, short dura-
m
m
W H
yj
a
5^
w
UJ
go
1 < 1
i2
go
u. 0
A 6.5
O TOTAL GI
A HIGHLY CREDIBLE GI
t
$3 A
^cT
> 1111 m
j i i 11 mi
i nun
10° 101 I 102
MEAN ENTEROCOCCUS DENSITY/100 ml
103
Figure 10. Ratios of swimmer to nonswimmer rates of gastrointestinal symptoms
against the mean enterococcus density in the water. Data from Table 6.
One value not used in the calculations.
45
-------
TABLE 12. RELATIONSHIP OF SWIMMING-ASSOCIATED ( A ) TO
BACKGROUND (NONSWIM) RATES FOR GASTROINTESTINAL
SYMPTOMS
Rates Per 1000 Persons
Enterococcus
Total Gl
Highly Credible Gl
Density1
Nonswim
A
Nonswim
A
3.6-7.0
23
4
4.2
3.4
34
4
6.9
3.6
55
8
19.3
-0.5
66
17
23.0
11.0
67
4
28.0
5.0
11.1-21.8
17
25
2.4
13.6
34
41
13.0
28.0
37
22
14.5
22.1
46
35
14.8
7.4
63
18
15.2
15.2
74
34
•23.1
22.1
91.5-154
24
48
15.5
26.9
31
29
18.0
28.0
50
62
2
34.5
1 Values ordered according to the nonswimming rate within a density cluster. Only clusters of 3 or more reasonably close values
used.
2 Nonswimming rate "0."
M
2
O
<0
cc
ui
Q.
s
DC
a
UI
m
2
1
2
>
§ 5
0 cc
co o
CO LL
<£
a
z
2
1
5
to
60
50
40
30
20
10
0
TOTAL Gl U.S. STUDIES
VOMITING OR DIARRHEA
CAIRO VISITORS
HIGHLY CREDIBLE GI^Sj
U.S. STUDIES^-""
/
/
/
J' VOMITING OR DIARRHEA
, , ff/ , ALEXANDRIA RESIDENTS
I I H III I I II l I ktflU 1—r tiiliii l I t » 1 111.
101 10* 103
ENTEROCOCCUS DENSITY/100 ml
104
Figure 11. Comparison of the illness-indicator relationship obtained from the U.S.
studies with those for the Cairo visitors and Alexandria residents in the
Egyptian studies. Those for the U.S. populations taken from Figure 7 and
those for the Egyptian study from Figure 4.
46
-------
30
• SWIMMERS
O NONSWIMMERS
2 3 4 S 6 7
DAY OF ONSET FOR Gl SYMPTOMS
8
Figure 12. Day of onset of Gl symptoms as obtained from the 1975 New York City
trials.
tion (Table 13) and rare, if any, sequelae, (it) It is widely distributed; most individuals
are immune, and, in general, children have the highest attack rates. (Hi) 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 Gl symptom rates. The
obvious one is that these are "healthier" individuals. The second assumes that the ex-
tent 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 be a good immunity to the etiological agents. The ra-
tionale for the Egyptian observations is that the susceptible individuals become ill within
a day or so of the time they start swimming.
47
-------
TABLE 13. DURATION OF GASTROINTESTINAL SYMPTOMATOLOGY:
NEW YORK CITY, 1975 TRIALS
Duration of Symptoms in Days for
Swimmers
Nonswimmers
Number
Average
Number
Average
Symptom
Reporting
Duration
Reporting
Duration
Tdtaf
Vomiting
30
2.8
10
2.6
Diarrhea
73
2.6
26
2.7
Stomachache
101
2.7
36
2.4
Nausea
64
2,7
18
2.8
Disabling
Vomiting
17
3.7
5
2.6
Diarrhea
22
3.0
11
3.2
Stomachache
36
3.5
12
3.0
Nausea
24
2.6
8
3.2
48
-------
SECTION? .
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 generaliza-
tions 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 im-
portant, 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 con-
sidered 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 condi-
tions 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 probabil-
ity 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 relation-
ships 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 earner 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 administra-
tive action prohibiting such discharges into recreational waters.
ILLNESS MATES 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 prob-
ably 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 Jess than
predicted. The absence of recreational water-associated salmonellosis probably repre-
sents a case in point.
49
-------
FECAL INDICATORS VERSUS PATHOGENS
The use of fecal indicators such as coliforms or portions of the coliforra 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 prac-
tices were and are sound both on theoretical and practical grounds since it is recognized
that (i) there are a 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 her-
culean 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 inter-
pret 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 num-
bers 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 ame-
nable 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 in-
volved 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 ef-
fluent 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 re-
lates 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 ques-
tions should be continued.
I
50
-------
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Haven. Unpublished Report.
2. Scott, W. J. 1951. Sanitary Study of Shore Bathing Waters. Bull. Hyg. 33:353.
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: •
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32. Prescott, S. C., C. A. Winslow, and M. McCrady. 1945, Water Bacteriology, 6th Ed. Wiley,
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33. American Public Health Association, Standard Methods for the Examination of Water and
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pendix I. London: Her Majesty's Stationary Office, 1969, 4th Ed.
35. Dufour, A. P., and V, J. Cabelli, 1975, Membrane Filter Procedure for Enumerating the Com-
ponent Genera of the Coliform Group in Seawater. Appl. Microbiol. 29:826,
36. Dufour, A. P., E. R. Strickland, and V. J. Cabelli. A Procedure for Enumerating
Thermotolerant E. coli in Surface Waters. Proc. 9th National Shellfish Sanitation Workshop.
June, 1975.
37. Dufour, A. P., and L. B. Lupo. A Membrane Filter Method for Enumerating Klebsiella Spe-
cies. Abst. Ann. Meet. Am. Soc. Microbiol. 1977. p. 262.
38. Levin, M. A., J. R. Fischer, and V. J. Cabelli. 1975. Membrane Filter Technique for Enu-
meration of Enterococci in Marine Waters. Appl. Microbiol, 30:66.
39. Bisson, J. W., and V. J. Cabelli. 1979. Membrane Filter Enumeration Method for Clostridium
perfringens. Appl. and Environ. Microbiol. 37:55.
40. Resnick, G., and M, A. Levin. Enumeration of Bifidobacterium in Aquatic and Fecal Sam-
ples. Abstr. Ann. Meet. Am. Soc. Microbiol, 1977. p. 261.
52
-------
REFERENCES (Continued)
41. McBride, G. A Bacteriphage Simulant for Enteric Virus Behavior in Water Systems. M. S.
Thesis, Univeristy of Rhode Island, Kingston. 1979.
42. Buck, J. D., and P. M, Bubucis. 1978. Membrane Filter Procedure for Enumeration of
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 Enu-
meration of Vibrio parahaemolyticus. Appl. Environ. Microbiol. 32:679.
46. Levin, M, A., J. 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 the Enumeration of
Enteropathogenic Escherichia coli. J, Clin. Microbiol. In press.
48. Wun, C. W., R. W. Walker, and W. Litsky. 1976. The Use ofXAD-2 Resin for the Analysis
of Coprostanol in Water. Water Res. 10:995.
49. Cabelli, V. J. Evaluation of Recreational Water Quality, the EPA Approach. In: Biological
Indicators of Water Quality, Eds. S. James and L. Evison, Wiley, London. 1979. p. 14-1.
50. Dufour, A. P. E. coli: The Fecal Coliform. In: Bacterial Indicators/ Health Hazards Associated
with Water, Eds. A. W. Hoadley and B. J. Dutka. ASTM, Philadelphia, 1976. p. 48.
51. Miescier, J, J. The Occurrence and Variability of Bacterial Indicator Organisms in Raw and
Treated Sewage, M. S. Thesis, Univ. of Rhode Island, Kingston. 1977.
52. Vlassoff, L. T. Klebsiella. In: Bacterial Indicators/Health Hazards Associated with Water. Ed,
A. W. Hoadley and B. J. Dutka. ASTM, Philadelphia, 1977. p. 275.
53. Seidler, R. J,, J. E. Morrow, and S, T. Bagley. 1977. Klebsielleae in Drinking Water Emanat-
ing from Redwood Tanks. Appl. Environ. Microbiol. 33:893.
54. Cabelli, V. J., and L. J. McCabe. 1974. Recreational Water Quality Criteria. News of Envi-
ronmental Research in Cincinnati.
55. McCabe, L. J. Epidemiological Consideration in the Application of Indicator Bacteria in North
America. In: Bacterial Indicators/Health Hazards Associated with Water. Ed. A, W. Hoadley
and B. J. Dutka, ASTM, Philadelphia, 1977. p. 15.
56. Verber, J. L, 1972. Shellfish-Borne Disease Outbreaks. Internal report. Northeast Technical
Service Unit, U.S. Food and Drug Admin., Davisville, Rhode Island.
57. American Public Health Association, Standard Methods for the Examination of Water and
Wastewater, 13th Ed. Amer. Public Health Assoc., Washington, DC, 1971.
58. Cabelli, V. J., M. A. Levin, A. P. Dufour, and L. J. McCabe. The Development of Criteria
for Recreational Waters. In: International Symposium on Discharge of Sewage for Sea
Outfalls. Ed. H. Gameson, Pergamon, London, England. 1974. p. -63.
59. Haberman, P. W, Study of Sanitary Criteria for Criteria for Salt Water Beaches: Pretest of
Illness Inquiry System and Site Selection, Part 1 1972 (Jan. 1973), Part 2 (Jan. 1974). Epide-
miological Study of Health Effects Among Swimmers at New York Recreational Beaches Part
1, 1974 (Feb. 1975); Phase III 1975 (April 1976). Reports to United States Environmental
Protection Agency on Grant Nos. 802240 and 803254.
60. Cabelli, V. J., A. P. Dufour, M. A. Levin, L. J. McCabe, and P. W. Haberman. 1979. Rela-
tionship of Microbial Indicators to Health Effects at Marine Bathing Beaches. Am. J. Public
Health. 69:690.
61. Cabelli, V. J., A. P. Dufour, M. A. Levin, and P. W. Haberman. The Impact of Pollution on
Marine Bathing Beaches: An Epidemiological Study. In: Middle Atlantic Continental Shelf
and the New York Bight. Limnology and Oceanography, Special Symp. Vol. 2. Ed. G. Gross,
1976. p. 424.
53
-------
SEFEBSKCSS (Cucfinutd)
m. Euues, V K, A c: tadflBaa,x*M. H. Diem. Sp^emtftogUtri-Aficrcfcsfogitwl Sh»8y of
Health Aiwng Svimrun » Lsfee Pontfbarmdn ui Me,' Oltaos: fell
-'>3*? D-*oe»i!_ *-7. 5979. A3«BR^s.RfJ^iiI0B«iMS«fi£PEb&£jfe§!fc.. AJtsa-
-------
APPENDIX
TABLE A1. TOTAL AND FECAL COLIFORM STANDARDS FOR PRIMARY CONTACT RECREATIONAL WATERS AS OF 1978
Year
Water
Total Collform Limit per 100 mi
Fecal Conform Limit per 100 ml
State®
Rev'*
Type®
Average
Percentile One Sample
Average
Percentile
One Sample
Alabama1,2,3
77
77
SW
sw
LMd 100
LM 200
Alaska
79
ALL
Mean 20
90%s40
Arizona
73
FVV
EPA
EPA
Arkansas
77
FW
EPA
EPA
California
78
SW
Ave 1000
o
o
o
*—
VI
o
CO
EPA *
EPA
76
FW
Med® 240
<10,000
Med 50
90%<400
Colorado
75
FW
EPA
EPA
Connecticut4,5,6
76
SW
Med 700
90%<2300
EPA*
90%s=5009
76
FW
Med 1000
80%±s2400
EPA'
96%=s5OO0
Delaware
75
ALL
EPA
District of Columbia
Pro'1
ALL
EPA
EPA
Florida
74
ALL
LM 1000
80s1000 <2400
EPA
EPA
<800
Georgia1,2
77
77
SW
FW
LM 10Q2B
LM 200
Hawaii
74
ALL
Med 1000
90%<2400
EPA
EPA
Idaho
Pro
FW
LM 50
90%<200
<500
Illinois
75
FW
EPA
EPA
<400a''
Indiana7
78
FW
EPA
Iowa8
77
FW
EPA
EPA
Kansas
78
FW
EPA
EPA
Kentucky9,10
76
FW
Ave 1000
80%<1Q00 <2400
EPA11
EPA11
Louisiana
77
ALL
EPA
EPA
-------
Table A1. (continued)
State®
Year Water
Revb Type®
Total Coliform Limit per 100 ml
Average Percentile One Sample
Fecal Coliform Limit per 100 ml
Average Percentile One Sample
Maine
77 SW
Med 70 90%<230
Med. 1000 90%<200
77 FW
NTE 2009
-------
Table A1. (continued)
u»
-4
State®
• Year Water
Revb Typec
Total Coliform Limit per 100 ml
Average Percentile One Sample
Fecal Coliform Limit per 100 ml
Average Percentile One Sample
Tennessee1,23,24
77 FW
EPA <1000
Texas6
76 ALL
EPA EPA
Utah
78 FW
LM 1000
EPA
Vermont
78 FW
NTE 500
NTE 200
Virginia
77 ALL
EPA EPA
Washington
77 SW
MED 14 90%<4325
77 FW
LM 100 90%^20016
West Virginia
77 FW
Ave 1000 80%<1000 <2400
EPA EPA
Wisconsin28
78 FW
EPA EPA
Wyoming
78 FW
EPA - EPA
Puerto Rico
76 ALL
EPA 80%"400
Virgin Islands
73 ALL
LM 70
Trust Territory
73 ALL
EPA EPA
American Samoa
73 ALL
Ave 100 90%=£200
Guam9
76 ALL
Ave 200 EPA
* Does not include all (he caveats, special requirements, limitations, etc.
' Year of latest revision.
seawater (estaurine and coastal); FW - freshwater.
Log mean.
CSW
d
e Median.
' Geometric mean not to exceed 200/100 ml.
8 Guideline.
. Proposed.
} In one month.
J Not to exceed.
Waters in vicinity of STP outfall not suitable.
2 Desipated as "coastal" and "all other recreational waters."
3 If standard exceeded, waters considered acceptable if a second sanitary
survey and evaluation indicates no significant public health risk.
4 For listed rivers, disinfection of STP effluents required; and standards only
apply between months of May through September.
5 " Col i form bacteria ... are related to the probability of contamination-
by undisinfected sewage. High results may be due to soil bacteria or
bacteria from the feces of warm-blooded animals' which are not of
sanitary significance."
6 Sanitary surveys required.
7 Applies only from April through October.
8 Applies April I - October 31.
9 Unless naturally occurring.
10 If TC exceeded, then FC is used.
" Only applicable from May through October,
12 Waters exceeding standard acceptable only if sanitary survey shows
no significant public health risk.
13 Except as provided in Regulation 2,1.
14 Standards relate only to intrastate waters.
15 Except when affected by storma-ster runoff.
16 Varies with body of water, standard as given used in most cases,
EPA guideline used in a few.
17 Applies only when disinfection is practiced.
18 For "International Boundary Waters" under Great Lakes Water
Quality agreement of 1972, log mean TC 1000/100 ml and FC
200/100 ml.
19 Applicable only during May through September.
20 Not applicable during or immediately following periods of rainfall.
Where there are no lifeguards and/or bathhouse facilities, log mean
of 1000/100 ml and 90% £2000/100 ml apply.
n icterial pollution or other conditions deleterious to waters used
for. . , bathing ... or otherwise injurious to public health
shall not be allowed."
23 <1/100 ml set as !/t00 ml in calculating log mean.
24 Individual samples cannot be collected within 12 hours of each other.
35 Standard given is for Class A (Excellent) waters which", . .shall
•meet or exceed the standards for all or substantially all uses
..." Class AA (Extraordinary) fresh water standard is a median TC
of 50/100, 90% £100/100 ml. Class B (Good) for fresh water is
median FC of 200/100 ml, 90% S400/100 ml; for sea waters, the
standard is the same as that for Class A fresh waters.
36 If water quality and sanitary surveys show 200/100 ml exceeded
occasionally due to "natural causes," log mean of 300/100 ml
in lakes and reservoirs and 500/100 ml in free flowing FW streams
becomes the limit.
27 Limits may be exceeded if due to "uncontrollable non-point sources.
28 Sanitary survey to assure protection is chief criterion; bacterial limits
are guidelines.
21
-------
TABLE A2. DEMOGRAPHIC CHARACTERISTICS OF THE FOUR
SUBPOPULATIONS FOR 1974 NEW YORK CITY TRIALS
! ' !|
Percent of Respondents by Category
BA Beach
RU Beach
Demographic
Swim
Nonswim
Swim
Nonswim
Group
(N = 1961)
{N = 1185)
(N=2767)
CN=4156)
Sex
Male
44.0
33.5
46.9
27.1
Female
56.0
66.5
53.1
62,9
Age Group
0-9
24.9
10.1
26,7
26.4
10-19
36.1
12.7
21.3
11.7
20-39
14.4
65,2
43.1
47,7
2:40
24.6
12,0
8.9
14,4
Ethnic Group
Hispanic-American
47.8
33.5
52.6
53.1
White
36.8
37.4
' 30.1
29.6
Black
15.4
29.1
17.3
17.3
Persons/rooms ratio1
£0.9
26.2
21.8
21.3
29.5
1.0-1.3
32.7
40.8
40.6
39.2
3:1.4
41,1
37.4
38.1
31.3
'N umber of persons in household divided by number of rooms in household, as an indicator of socioeconomic status (SES), 0.9 or
less persons/rooms indicates higher SES; 1,0-1.3, middle SES; and 1.4 or more, lower SES.
BA — barely acceptable; RU — relatively unpolluted.
TABLE A3. MEAN INDICATOR DENSITIES AT THE CONEY ISLAND AND
ROCKAWAY BEACHES DURING 1973 AND 1974 TRIALS
Indicator
Log10 Mean Recovery/100 ml
1973 1974
Coney Island Rockaway Coney Island Rockaway
Total conforms
983*
39.8
1213*
43.2
Fecal coliforms
165*
21.5
565*
28.4
Escherichia coli
174*
24.8
15.3*
2.4
Klebsiella
122*
13.7
59.2*
3.5
Enterbacter-Citrobacter
530*
11.1
434
6.6
Fecal Streptococci
91.2
21.8
16,4*
3,5
Pseudomonas aeruginosa
30.4
6.5
45.8*
3.1
Aeromonas hydrophila
25.3
26.5
9.6
4.9
Vibrio parahaemolyticus
ND
ND
54,5
32.8
~Significantly different from density at Rockaways at 95 percent confidence level.
58
-------
TABLE A4. SWIMMING ASSOCIATED SYMPTOM RATES FOR NEW YORK
CITY BEACHES IN 1973, 1974
Swimming Assoc. (swim -
nonswim) Sympt. Rates1
Rockaway, NYC
Coney Island, NYC
1973
1974
1973
1974
Symptom
(484-197)2
(2767-2156)*
(474-167)2
(1961-1185)2
Vomiting
0
0
21*
4
Nausea
15
-2
26*
-1
Diarrhea
18
0
28*
8**
Stomachache
41**
0
,39**
Sore throat
47»#
-3
18
-2
Bad cough
20 -
1
6
5
Chest cold
-3
-1
-2
-2
Nose
21
5
8
3
Ear
-3
6
-1
6*
Eye
28
3
24
3
Skin {exclusive of sunburn)
64**
7
113**
g»#
Fever (100°F)
15
6*
6
4
Headache
6
-6
10
2
Backache
-8
-6
2
-1
Home due to symptom
-10
4
6
9*
In bed due to symptom
-6
1
-3
4
Medical help due to
symptom
0
2
5
3
1 Rates in cases per 1000 persons.
2 () = swim, nonswim,
*P< .1; "p< .05.
TABLE A5, SWIMMING ASSOCIATED RATES FOR SYMPTOM GROUPS AT
THE NEW YORK CITY BEACHES (1973-74)
Swimming Associated Rate (Per 1000 Persons)
Rockaway, NYC
Coney Island, NYC
Symptom Groups1
1973
1974
1973
1974
Gastrointestinal
35
5
48*
16*
Highly Credible G!
15
0.0
28
6.7
Respiratory
63*
4
27
8
"Other"
5
9
33
6
Disabling
4
4
17
9
Skin
642
7
1132
9*
1 See text for symptoms included in each group.
2 Partly due to jellyfish stiings,
*p<,05; "p<,01 for differences between swimmer and nonswimmer rates.
59
-------
TABLE A6. COMPARISON OF Salmonella AMD TOTAL COLIFORM
DENSITIES (PER 100 ML) AT CONEY ISLAND AND
ROCKAWAY BEACHES (ARRANGED IN DESCENDING ORDER
OF COLIFORM VALUES)
Coney Island
Rockaway
Total
Total
Date
Coliforms1
Salmonella2
Date
Coliforms1
Salmonella2
11 Aug,
14500
0.020
18 Aug.
350
<0,018
12 Aug.
3300
0.045
22 July
205
<0.(018
19 Aug.
18503
0.020
29 July
185
0.040
18 Aug.
1550
0.020
19 Aug.
90
<0.018
22 July
900
0.040
12 Aug.
703
0.020
29 July
435
0.020
14 July
30
<0.018
28 July
360
0.020
14 July
145 •
0.020
1 m€ estimate of total colifonns from low-tide samples collected concurrently with those for the Salmonella assays.
2 Obtained from examination of 55.5 liters by S-HVS method (46).
3 Estimate obtained by MPN method.
60
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TABLE A7. ANALYSIS OF GASTROINTESTINAL (Gl) AND HIGHLY CREDIBLE GASTROINTESTINAL (HCGI) SYMPTOM RATES
BY DEMOGRAPHIC GROUPING
Gl Symptom Rates Per 100 Persons
Barely Acceptable Beach
Relatively Unpolluted Beach
.
Gl
HCGI8
Gl
HCGI.
Demographic Group
Swim
Nonswim
Swim
Nonswim
Swim
Nonswim
Swim Nonswim
Total sample
Children1
42®
26
16
9.3
39
35
12
12
576,7
14
246
<4.5
23e
55
9.26
28
Hispanic-American
45"
17
216,7
7.6
24
12
5.6
3.0
High-Middle persons/rooms2
426
16
14®
5.2
41
34
15
10
Ratio
.. .
Adults3
37
29
13
11
42
32
12
9.5
Non-Hispanic-Americans4
38
35
10
11
43
39
13
13
Lowest persons/rooms Ratio5
42
45
21
17
37
35
9,1
13
1 sIO yts. old;
1 a 1.0 persons/rooms ratio;
3 >10 yrs. old;
4 white and black;
5 <1.0 persons/rooms ratio;
6 significantly different (P-O.OS) than nonswimming control;
7 significantly higher (P-.05) than RU swimmers;
8 All instances of vomiting, diantrea with fever or a "disabling" response, and nausea and stomachache with fever.
-------
TABLE A8. MEAN AND RANGE OF NEW YORK CITY TRIALS CLUSTERED
ACCORDING TO ENTEROCOCCUS DENSITIES
Year
Beach and Date1
Enterococcus Density/100 ml
Mean Range
19732
R7/14, R7/22, R7/28, R7/29, R8/11
R8/12, R8/18, R8/19
21,8
1.2-59
C7/14, C7/22, C7/28, C7/29, C8/11
C8/12, C8/18, C8/19
91.2
6-186
1974
R7/28, R8/18, R8/31
3.6
2-5
R7/20, R7/21, C8/31
7.0
7
C7/20, C7/28
13.5
10-17
C7/21, C8/18
31.5
30-33
1975
A7/6, A7/5, A7/11, A7/19, A7/20
A7/27, B7/6, B7/19, B7/26, C6/19
C7/20, C7/27, D7/19, D7/20
5.7
2-11
A8/2, B7/5, B7/27, B8/2, C7/5
C7/6, C7/26, C8/2, D8/2, D8/3
20.3
14-38
A8/3, B7/20, B8/3, C8/3
154
86-298
1 R — Rockaway; C — Coney Island; D — 34th-38th Streets, Coney Island:
A — 18th-24th Streets. Coney Island; B — 8th-10th Streets, Coney Island;
C — 2nd-4th Streets, Brighton, Coney Island.
3 1973 trials clustered by beach.
TABLE A9. MEAN AND RANGE OF NEW YORK CITY TRIALS CLUSTERED
ACCORDING TO E. coti DENSITIES
Year
Beach and Date1
E co// Density/100 ml
Mean Range
1973
R7/14, R7/22, R7/28, R7/29, R8/11
R8/12, R8/18, R8/19
24.8
3-34
C7/14, C7/22, C7/28, C7/29, C8/11
C8/12, C8/18, C8/19
174
50-708
1974
R6/22, R7/21, R7/28, R8/18, R8/31
C8/31
2.2
1-4
R7/20, C7/21, C7/28, C8/18
13.3
9-19
C6/22, C7/20
30.52
26-35
1976
A7/5, A7/6, A7/26, A7/27, B7/5, B7/6
B7/26, C7/5, C7/6, C7/26
46.8
22-89
A7/19, A7/20, A8/3, C7/19, C7/20, D8/2
142
115-169
A8/2, B7/20, B7/27, C8/2, C8/3
D7/19, D7/20, D8/3
278
208-356
B7/19, B8/2, B8/3, C7/27
514
441-659
' R — Rockaway; C — Coney Island; D — 34th-38th Streets, Coney Island;
A— 18th-24th Streets, Coney Island; B — Sth-lQth Streets, Coney Island;
C — 2nd-4tb Streets, Brighton, Coney Island.
'Arithmetic mean
! ' I
62
-------
TABLE A10. MEAN AND RANGE OF NEW YORK CITY TRIALS CLUSTERED
ACCORDING TO FECAL COLIFORM DENSITIES
Year
Beach and Date1
Fecal Coliform Density/100 m!
Mean Range
1973
R7/14, R7/22, R7/28, R7/29, R8/11
R8/12, R8/18, R8/19
21.5
6.2-34
C7/14, C7/22, C7/28, C7/29, C8/11
C8/12, C8/18, C8/19
165
49-431
1974
R7/28, R8/18
182
17-19
R6/22, R7/20, R7/21
38
29-50
C7/20, C7/28
2522
231-273
C7/21, C8/18
. 614s
528-701
C6/22
2449
2449
1975
A7/5, A7/6, B7/6, C7/5, C7/6
42
28-68
A7/19, A7/26, A7/27, B7/5, B7/26
C7/19, C7/20, €7/26, C8/2
169
107-228
A7/20, A8/3, B7/27, D7/19, D8/2
324
273-372
A8/2, B7/19, B7/20, B8/2, C7/27, D7/20
552
478-634
B8/3, C8/3
13122
800-1824
1 R — Rockaway; C — Coney Island; D — 34th~38th Streets, Coney Island;
A — I8th-24th Streets, Coney Island; B — 8th-IOth Streets, Coney Island;
C — 2nd-4th Sheets, Brighton, Coney Wand.
Arithmetic mean
TABLE A11. MEAN AND RANGE OF NEW YORK CITY TRIALS CLUSTERED
ACCORDING TO TOTAL COLIFORM DENSITIES
Year
Beach and Date1
Total Coliform Density/100 ml
Mean Range
1973
R7/14, R7/22, R7/28, R7/29, R8/11
R8/12, R8/18, R8/19
39.8
14-68
C7/14, C7/22, C7/28, CI 12% C8/11
C8/12, €8/18, C8/19
983
256-5015
1974
R7/28, R8/18
28.02
26-30
R6/22, R7/20, R7/21
62.7
49-80
C7/20, C7/21, C7/28
866
765-933
C6/22, C8/18
23792
1820-2938
1975
A7/6, C7/5, C7/6
109
92.9-141
A7/5, A7/26, A7/27, B7/5, B7/6, B7/26
212
179-296
A7/19, A8/2, A8/3, B7/20, 87/27
C7/19, C7/20, €7/26, C8/2, D8/2
576
391-765
A7/20, B8/2, C7/27, D7/19, D8/3
1071
1007-1167
B7/19, B8/3, €8/3, D7/20
2221
1332-3450
1 R — Rockaway; C — Coney Island; D — 34th-38th Streets, Coney Island;
A — 18th-24th Streets, Coney Island; B — 8th-10th Streets, Coney Island;
C — 2nd-4th Streets, Brighton, Coney Island.
Arithmetic mean
63
-------
TABLE A12. MEAN AND RANGE OF NEW YORK CITY TRIALS CLUSTERED
ACCORDING TO Klebsiella DENSITIES
Year
Beach and Date1
Klebsiella Density/100 mi
Mean Range
1973
R7/14, R7/22, R7/28, R7/29, R8/11
R8/12, R8/18, R8/19
13.7
1.2-15.3
C7/14, C7/22, C7/28, C7/29, C8/11
C8/12, C8/18, C8/19
122
49-1006
1974
R6/22, R7/20, R7/21, R7/28, R8/18, R8/31
C7/27, C8/31
C7/20, C7/21
C6/22, C8/18
4.0
163
453
3363
2-11
11-21
38-52
199-473
1975
A7/5, A7/6, B7/26, C7/5, C7/16
C7/19, C7/26
21.8
8.9-36
A7/26, A7/27, B7/5, B7/6, B7/27
C7/27
57.6
49-67
A7/19, A8/3, B7/20, C8/2
130
100-159
A8/2, B7/19, C7/20, D8/2
203
182-214
A7/20, B8/2, B8/3, C8/3, D7/19
D7/20, D8/3
378
235-17802
' R — Rockaway; C — Coney bland! D — 34th-38th Streess, Coney Island;
A — I8th-24th Streets, Coney Island; B — 8th-l0th Streets, Coney Island;
C — 2nd-4th Streets, Brighton, Coney Island.
1 All but one trial in range 23S-389.
*3
Arithmetic mean
64
-------
TABLE A13. MEAN AND RANGE OF NEW YORK CITY TRIALS CLUSTERED
ACCORDING TO Enterobacter-Citrobacter DENSITIES
Year
Beach and Date1
Entero-Citro. Density/100 ml
Mean Range
1973
R7/14, R7/22, R7/28, R7/29, R8/11
R8/12, R8/18, R8/19
11.1
1-24
C7/14, C7/22, C7/28, C7/29, C8/11
C8/12, C8/18, C8/19
530
333-3612
1974
R7/28, R8/18
2.0
2
R7/21, R8/31
7.52
6-9
R6/22, R7/20
20.02
19-21
C7/20, C7/21, C7/28
316
281-364
C8/18, C8/31
4852
459-511
C6/22
935
935
1975
A7/6, B7/5, B7/6, C7/5, C7/6
35.5
60-92
A7/5, A7/26, A7/27, A8/3, B7/26
B7/27, C7/19, C8/2, D7/19
224
152-318
A7/19, A7/20, A8/2, B7/20, C7/20,
C7/26
376
338-407
B8/2, C7/27, D8/2, D8/3
606
476-735
B7/19, B8/3, C8/3, D7/20
1269
941-1979
' R — Rockaway; C — Coney Island; D — 34th-38th Streets, Coney Island;
A — 18th-24th Streets, Coney Island; B — 8th-10th Streets, Coney Island;
C — 2nd-4th Streets, Brighton, Coney Island.
^Arithmetic mean
65
-------
TABLE A14. MEAN AND RANGE OF NEW YORK CITY TRIALS CLUSTERED
ACCORDING TO P. aeruginosa DENSITIES
Year
Beach and Date1
P. aeruginosa Density/100 ml
Mean Range
1973
R7/14, R7/22, R7/28, R7/29, R8/11
R8/12, R8/18, R8/19
6.5
0.3-11
C7/14, C7/22, G7/28, C7/29, C8/11
C8/12, C8/18, C8/19
30.4
8-45
1974
R7/20, R8/18, R8/31
2.0
0-4
R7/21, R7/28
6.0
6
C7/20, C8/18, C8/31 .
22.0
16-24
C7/28
60.0
60
C7/21
377
377
1975
A7/19, A7/26, A7/27, B7/6, B7/26, C7/19
8.0
5.4-13.5
A7/6, B7/19, B7/27, C7/6, C7/26
19.5
16.2-24.6
A8/2, C7/20, C8/2, D8/2
34.2
30.2-37.2
A7/20, A8/3, C7/27, D8/3
60.7
50.1-77.7
B7/20, B8/2, B8/3, €8/3
173
100-6612
1 R — Rockaway; C — Coney Island; D — 34th-38th Streets, Coney Island;
A — 18th-24th Streets, Coney Island; B — 8th-10th Streets, Coney Island;
C — 2nd-4th Streets, Brighton, Coney Island.
1 AH but one trial in range lbO-126.
TABLE A15. MEAN AND RANGE OF NEW YORK CITY TRIALS CLUSTERED
ACCORDING TO A. hydrophila DENSITIES
Year
Beach and Date1
A. hydrophila Density/100 mi
Mean Range
1973
R7/14, R7/22, R7/28, R7/29, R8/11
R8/12, R8/18, R8/19
26.5
1-39
C7/14, C7/22, C7/28, C7/29, C8/11
C8/12, C8/18, C8/19
25.3
1-244
1974
R7/20, R7/21, R7/28
1.7
1-3
C7/20, C7/28, C8/31
5.0
5
R8/18, C7/21
8.5s
7-10
R6/22, R8/31, C6/22, C8/18
25.8
20-33
1975
B7/5, C7/5
2.4s
2.0-2.9
A7/5, B7/6, B7/26, B7/27, C7/6, C7/27
40.9
18-75
A7/6, A8/2, C7/19, C7/20, C7/26
C8/2, C8/3
140
104-163
A7/26, A7/27, A8/3, B7/19
B8-2, B8/3
412
221-723
A7/19, A7/20, B7/20
1182
899-1740
1 R — Rockaway; C — Coney Island; D — 34th-38th Streets, Coney Island;
A— 18-24th Streets, Coney Island; B — 8th-10th Streets, Coney Island;
C — 2nd-4th Streets, Brighton, Coney Island.
Arithmetic mean
66
-------
TABLE A16. MEAN AND RANGE OF NEW YORK CITY TRIALS CLUSTERED
ACCORDING TO C. perfrmgens DENSITIES
Year
Beach and Date1
C. perfrmgens Density/100 ml
Mean Range
1974
R7/21, R7/28, R8/31, C7/21
3.8
2-5
R8/18, C7/28, C8/18
10.3
10-11
R7/20, C7/20, C8/31
32.7
24-47
R6/22
351.
351
1975
Aim, B7/27, C7/27
9.3
7.1-11
A7/26, B7/6, C7/5
18.2
16-21
A7/6, A7/27, A8/3, B7/9, B7/26
28.7
25-33
C7/6, C7/26, C8/3
B7/19, B7/20, B8/3
68.6
48-91
1 R — Rockaway; C — Coney Island; D — 34th-38th Streets, Coney Island;
A — I8th-24th Streets, Coney Island; B — 8th-1 Oth Streets, Coney Island;
C — 2nd-4th Streets, Brighton, Coney Island.
TABLE A17. MEAN AND RANGE OF NEW YORK CITY TRIALS CLUSTERED
ACCORDING TO Staphylococcus DENSITIES
Staphylococcus Density/100 ml
Year
Beach and Date1
Mean
Range
1974
R8/31
32
32
R8/18, C6/22, C8/31
112
98-137
R6/22, R7/28, C7/28
189
177-210
R7/20, C7/20, C8/18
344
303-398
R7/21, C7/21
742z
558-926
1975
A7/5, A7/6, C7/5
11.7
5.5-32
A7/19, A7/27, B7/5, B7/27, C7/6, C7/19
76.7
46-123
B7/6, B7/19, B7/26, C7/20, C7/27
197
155-245
A7/20, A7/26, A8/3, C8/2, C8/3
655
537-776
A8/2, B7/20, B8/2, B8/3, C7/26
1572
955-4070
1 R — Rockaway; C — Coney Island; D — 34th-38th Streets, Coney Island;
A ~ 18th-24th Streets, Coney Island; B — Sth-lOth Streets, Coney Island;
C — 2nd-4th Streets, Brighton, Coney Island.
aArithmstic mean
67
-------
i
TABLE A18. MEAN AND RANGE OF NEW YORK CITY TRIALS CLUSTERED
ACCORDING TO V. parahaemolyticus DENSITIES
Year
Beach and Date1
V. parahaemolyticus Density/100
ml
Mean Range
1974
R7/21, C7/21
9.5Z
5-14
R7/28, R8/18, C7/28, C8/18
36.6
28-61
R8/31, C8/31
3092
249-368
1975
A7/5, A7/6, A7/27, B7/5, B7/6
3,8
1.5-10.6
B7/27, C7/5, C7/6, C7/27
A7/19, A7/26, B7/19, B7/26, 07/19
35.5
23-68
C7/26, C8/2, C8/3
A8/2, B7/20, B8/2, C7/20
121
82-189
A7/20, A8/3, B8/3
444
431-463
l R — Rockaway; C — Coney Island; D — 34th-38th Streets, Coney Island;
A — 18th-24th Streets, Coney Island; B — 8sh-10th Streets, Coney Island;
C—. 2nd-4th Streets, Brighton, Coney Island.
"Arithmetic mean
68
-------
TABLE A19. GASTROINTESTINAL (Gl) AND HIGHLY CREDIBLE Gt (HCGI) SYMPTOM RATES FOR NEW YORK CITY TRIALS
CLUSTERED BY ENTEROCOCCUS DENSITIES
Year
Enterococcus
Density/100 ml
Swim1
N
Nonswim2
Swim
Rate/GI Symptoms
Nonswim
Per 1000 Persons
A3
Rate/HCGI Symptoms
Swim Nonswim A
Per 1000 Persons
1973
21,8
484
197
81
46
35
30
15
15
91.2
474
167
72
24
48*
46
18
28
1974
3.6
1441
711
27
23
4
7.6
4.2
3.4
7.0
951
1009
38
34
4
10.5
6.9
3.6
13.5
625
419
42
17
25*
16.0
2.4
13.6
31.5
831
440
43
23
20
18.1
—
18.1*
1975
5.7
2232
935
63
55
8
18.8
19.3
-0.5
20.3
1896
678
59
37
22*
14.8
7.4
7.4
154
579
191
60
31
29
34.5
—
34.5*
1 Swimmer.
2 Nonswimmer.
3 Swimming-Associated (swimmer-nonswinraier).
*p
-------
TABLE A20. GASTROINTESTINAL (Gl) AND HIGHLY CREDIBLE Gl (HCGI) SYMPTOM RATES FOR NEW YORK CITY TRIALS
CLUSTERED BY E. coli DENSITIES
Year
E. coli
Density/100 ml
Swim1
N
Nonswim2
Swim
Rate/GI Symptcms
Nonswim
Per 1000 Persons
A3
Rats/HCG! Symptoms
Swim Nonswim
Per 1000 Persons
A
1973
24.8
484
197
81
46
35
*30
15
15
174
474
167
72
24
48*
46
18
28
1974
2.5
2514
1641
25
34
-9
8.0
3.7
4.3
13.8
1304
1045
38
29
9
14.1
5.7
8.4*
30.5
600
425
65
33
32*
23.3
2.4
20.9*
1975
46.8
1945
1099
55
51
4
13.4
17.8
-4.4
142
775
194
76
41
35
24.5
10.3
14.2
278
1049
330
55
24
31*
21.0
3.0
18.0*
514
937
271
68
55
13
24.5
7.4
17.1
1 Swimmer.
2 Nonswiramer.
3 Swimming-Associated (swiimner-iKmswinuner),
~p<.05;
-------
TABLE A21. GASTROINTESTINAL (Gil AND HIGHLY CREDIBLE Gl (HCGI) SYMPTOM RATES FOR NEW YORK CITY TRIALS
CLUSTERED BY FECAL COLIFORM DENSITIES
Rate/Gl Symptoms
Rate/HCGI Symptoms
Fecal ColSform
N
Swim
Nonswim
A3
Swim
Nonswim
A t
Year
Density/100 ml
Swim1
Nonswim2
Per 1000 Persons
Per 1000 Persons
1973
21,6
484
197
81
46
35
30
15
15
165
474
167
72
24
48*
46
18
28
1974
18.0
958
472
35
34
1
10.4
6.4
4.0
39.0
1133
1246
48
43
5
"10.7
6.4
4.3
252
625
419
42
17
25*
16.0
2.4
13.6
614
831
440
. 43
23
20
18.1
—
18.1*
2449
236
184
72
49
23
21.2
5.4
15.8
1975
41.6
1131
472
69
57
12
16
23
-7.0
169
1457
680
55
44
11
13
13
0
324
724
223
54
27
27
22
4.5
17.5
552
1123
333
62
48
14
24
6.0
18.0
1312
292
. 96
72
31
41
34.5
—
34.5
1 Swimmer.
1 Nonswimmer.
J Swimming-Associated (swimmer-nonswimmer).
•pC05;
-------
TABLE A22. GASTROINTESTINAL (Gl) AND HIGHLY CREDIBLE Gi (HCGI) SYMPTOM RATES FOR NEW YORK CITY TRIALS
CLUSTERED BY TOTAL COLIFORM DENSITIES
Rate/GI Symptoms
Rate/HCGI Symptoms
Total Coiiforin
N
Swim
Nonswim
A3
Swim
Nonswim
A
Year
Density/100 ml
Swim1
Nonswim2
Per 1000 Persons
Per 1000 Persons
1973
39.8
487
197
81
46
35
30
15
15
983
474
167
72
24
48*
46
18
28
1974
28.0
958
472
35
34
1
10.4
6.4
4.0
62.7
1133
1246
48
43
5
10.6
6.4
4.2
866
1086
719
44
22
22*
16.6
1.4
15.2**
2380
606
324
51
31
20
19.8
3.1
16.7
1975
109
717
318
56
54
2
12.6
T2.6
0.0
212
1074
597
58
50
8
13.0
20.1
-7.1
576
1618
478
62
34
28»*
22.2
8.4
13.8
1071
694
229
69
57
12
20.2
8.7
11.5
2221
604
182
63
33
30
28.1
5.5
22.6
1 Swimmer.
2 Nonswimmer,
3 Swimming-Associated (swimmer-nonswimmer),
•p<05: "p<01.
-------
i ABLE A23. GASTROINTESTINAL (Gl) AND HIGHLY CREDIBLE Gl (HCGI) SYMPTOM RATES FOR NEW YORK CITY TRIALS
CLUSTERED BY Klebsiella DENSITIES
Rate/GI Symptoms
Rata/HCGI Symptoms
KhbsMla
N
Swim
Nonswim
A*
Swim
Nonswim
A
Ymr
D*fi*tty/100 ml
Swim1
Nonswim*
Pw 1000 Persons
Par 1000 Parsons
1973
13.7
484
197
81
46
35
30
15
15
122
474
167
72
24
48
46
18
28
1974
3.7
2767
2156
39
35
4
11.9
11.6
0.3
18.0
463
289
17
21
-4
2.2
3.4
-1.2
45.0
825
541
53
26
27
20.5
—
20.5
336
606
324
51
31
20
19.8
3.1
16.7
1975
22.0
1475
607
62
51
11
11.5
21.4
-9.9
. 58.0
1182
668
55
49
6
16.9
12.0
4.9
130
566
148
64
20
44
24.7
—
24.7
203
633
136
65
44
21
30.0
22.1
7.9
378
841
245
65
37 •
28
23.8
4.1
19.7
' Ncanriaacr.
' SwiMMt-AoodMad finii—i ¦iwimwuii)
•p<05; ••p<01.
-------
TABLE A24. GASTROINTESTINAL (GI) AND HIGHLY CREDIBLE Gl (HCGi) SYMPTOM RATES FOR NEW YORK CITY TRIALS
CLUSTERED BY Enterobacter-Citrobacter DENSITIES
Rate/GI Symptoms
Rate/HCGl Symptoms
Entero.-Citro,
N
Swim
Nonswim
A3
Swim
Nonswim
A
Year
Density/100 ml
Swim1
Nonswim2
Per 1000 Persons
Per 1000 Persons
1973
11.1
484
197
81
46
35
30
15
15
530
474
167
72
24
48**
-46
18
28*
1974
2.0
958
472
35
34
1
10,4
6.4
4.0
7.5
970
710
27
17
10
8.2
2.8
5.4
20.0
596
775
54
53
1
8.4
7.7
0.7
316
1086
719
44
22
22
16.6
1.4
15.2
485
572
251
31
20
11
12.2
—
12.2
935
236
184
72
45
27
21,2
5.4
15.8
1975
35.5
1136
' 560
59
48
11
14.1
16.1
-2.0
224
1652
616
56
46
10
12.1
14.6
-2.5
376
725
276
59
40
19
29.0
14.5
14.5
606
590
170
80
59
21
27.1
5.9
21.2
1269
604
182
63
33
30
28.1
5.5
22.6
1 Swimmer.
5 Nonswimmer.
3 Swimming-Associated (swimmer-nonswiminer).
»p<05; **p<.01.
-------
TABLE A2S. GASTROINTESTINAL (Gl) AND HIGHLY CREDIBLE Gl (HCGI) SYMPTOM RATES FOR NEW YORK CITY TRIALS
CLUSTERED BY P. aeruginosa DENSITIES
Rsta/GI Symptoms
Rata/HCGI Symptoms
P. aeruginosa
N
Swim
Nonswfm
A*
Swim
Nonswim
~
Year
Density/100 ml
Swim1
Nonswim*
Par 1000 Parsons
Pi
ir 1000 Parsons
1973
6.5
484
197
81
46
35
30
15
15
30.4
474
167
72
24
48"
46
18
28
1974
2.0
1277
879
30
28
2
9.4
8.0
1.4
6.0
873
730
37
29
8
10.4
4.1
6.3
22.0
936
492
43
20
23
17.1
—
17.1
60.0
261
178
15
11
4
3.8
5.6
-1.8
377.0
461
300
48.
30
18
17.4
—
17.4
1975
8.0
1097
480
58
60
-2
13.7
20.8
-7.1
19.5
1111
448
43
38
5
18.9
11.1
7.8
34.2
543
116
76
35
41
23.9
17.5
6.7
60.7
389
182
72
55
17
20.6
5.5
15.5
173
736
192
68
37
31
32.6
—
32.6
' NHHfnMMV,
' Swmmif-AHocMtad (l«i»»ntt-t>«u»»niper).
•p<-06; ••p<01.
-------
TABLE A26. GASTROINTESTINAL (Gl) AND HIGHLY CREDIBLE Gl (HCGI) SYMPTOM RATES FOR NEW YORK CITY TRIALS
CLUSTERED BY A. hydrophila DENSITIES
Year
A, hydrophila
Density/100 ml
Swim1
N
Nonswim2
Rate/GI Symptoms
Swim Nonswim A3
Per 1000 Persons
Rate/HCGi Symptoms
Swim Nonswim
Per 1000 Persons
A
1973
26,5
484
197
81
46
35
30
15
15
25.3
474
167
72
24
48**
46
18
28*
1974
1.7
1085
1157
39
34
5
11.1
6.9
4.2
5.0
827
530
36
21
15
12.1
1.9
10.2
8.5
1083
513
42
31
11
12.9
3.9
9.0
25.8
1423
911
40
36
4
10.5
2.2
8.3
1975
2.4
471
251
66
40-
26
8.5
8.0
0.5
40.9
1280
580
63
53
10
14.8
20.7
-5.9
140
1076
365
69
38
31
21.4-
13.7
7.7
412
1210
403
53
52
1
21.5
7.4
14.1
1182
322
109
71
28
43
34.2
—
34.2
1 Swimmer.
3 Nonswimmci.
3 Swimming-Associated (svrimmer-nonswimmer).
*p<.05; "p<.01.
-------
TABLE A27. GASTROINTESTINAL (GI) AND HIGHLY CREDIBLE GI (HCGi) SYMPTOM RATES FOR NEW YORK CITY TRIALS
CLUSTERED BY C. perfringens DENSITIES
Rate/GI Symptoms
Rate/HCGI Symptoms
•
C, perfringens
N
Swim
Nonswlm
A3
Swim
Nonswim
A
Year
Density/100 ml
Swim1
Nonswim2
Per 1000 Persons
Per 1000 Persons
1974
3.8
1767
1269
33
24
9
10.2
2.4
7.8
10.3
1253
531
34
19
15
'12.8
6.0
6.8
32.7
778
779
46
36
10
15.4
6.4
9.0
351.
384
348
57
66
-9
2.6
5.7
-3.1
1975
9.3
617
267
75
45
30
19.4
11.2
8.2
18.2
699
312
64
67
-3
14.3
25.6
11.3
28.7
1178
713
48
41
7
17.8
11.2
6.6
68.6
607
172
61
41
20
31.3
5.8
25.5
1 Swimmer.
2 Nonswimmer.
3 Swimming-Associated (swimmer-nonswimmer).
~p<.05; "p<01.
-------
TABLE A28. GASTROINTESTINAL (GI) AND HIGHLY CREDIBLE Gl (HCGI) SYMPTOM RATES FOR NEW YORK CITY TRIALS
CLUSTERED BY Staphylococcus DENSITIES
Rate/GI Symptoms
Rate/HCGI Symptoms
Staphylococcus
N
Swim
Nonswim
A3
Swim
Nonswim
A
Year
Density/100 ml
Swim1
Nonswim2
Per 1000 Persons
Per 1000 Persons
1974
32.0
433
239
9.2
—
9.2
* 2.3
—
2.3
112
1060
508
43
39
4
12.3
5.9
6.4.
189
1081
785
33
43
-10
4.6
3.8
0.8
344
946
808
49
30
19
20.1
6.2
13.9
719
998
949
44
24
20
15.0
2.1
12.9
1975
11.7
631
251
76
52
24
17.4
19.9
-2.5
76.9
1175
544
57
39
18
12.8
3.7
9.1
197
947
399
66
1 65
1
23.2
30.1
-6.9
DOO
AAA,
OOU
pn
oo
31
*1-1
£./
16.7
4.5
1 O
1 £.*£.
1572
946
290
58
41
17
25.4
6:9
18.5
1 Swimmer.
2 Nonswimmcr.
3 Swimming-Associated (swimmer-nonswimmer).
•p<05; **p<01.
-------
TABLE A29. GASTROINTESTINAL (Gl) AND HIGHLY CREDIBLE GI (HCGI) SYMPTOM RATES FOR NEW YORK CITY TRIALS
CLUSTERED BY V. parahemolyticus DENSITIES
Rate/Gl Symptoms
Rate/HCGI Symptoms
V. parahaemolytiem
N
Swim
Nonswim
A3
Swim
Nonswim
~
Year
Density/100 ml
Swim1
Nonswim2
Per 1000 Persons
Per 1000 Persons
1974
8.4
998
771
44
27
17
15
2.6
12.4
36.2
1589
800
33
24
9
11.3
5.0
6.3
303
635
350
13
11
2
1.6
—
1.6
1975
3.8
1907
939
64
50
14
16.3
13.8
2.5
35.5
1369
468
57
41
16
16.1
15.0
1.1
121
674
169
65
47
18
31.2
12.5
18.7
444
390
132
64
38
26
23.1
—
23.1
1 Swimmer.
2 Nonswimmer.
3 Swimming-Associated (swimmer-nonswimmer).
~p<05; "p<01.
-------
TABLE A30. MEAN AND RANGE OF INDICATOR DENSITIES FOR ALL TRIALS CONDUCTED DURING A GIVEN YEAR (SUMMER),
NEW YORK CITY BEACHES
Indicator Density Per 100 ml
Enterococci
Escherichia cott
Fecal Coliforms
Total Collfbrms
Year
Beach
Mean
Range
Mean
Range
Mean
Range
Mean
Range
1973
Rockaways
21.8
5-30
24.8
12-34
21.5
10-31
39.8
22-68
Coney Island
91.2
23-186
174
40-709
165
49-431
983
256-5015
1974
Rockaways
3.5
2-7
2.4
1-9
28.4
17-50
43.2
26-80
Coney Island
16.4
7-33
15.3
4-35
565
231-2449
1213
765-2938
19751
Coney Island(C)
17.9
6-199
52.4
22-506
184
37-585
426
93-1920
Coney Island(B)
27.7
6-298
98.6
60-659
359
68-1824
633
179-3450
Coney Island(A)
6.7
2-88
61.3
23-318
130
28-478
844
141-1167
Coney Island(D)
14.2
8-26
157
137-292
405
326-565
1050
765-1332
Indicator Density Per 100 ml
Klebsiella sp.
En tar.
•Citro.
P. aeruginosa
A. hydropN/a
Mean
Range
Mean
Range
Mean
Range
Mean
Range
1973
Rockaways
13.7
1-15
11.1
1-24
6.5
1-11
26.5
2-39
Coney Island
122
49-260
530
123-3612
30.4
8-45
25.3
1-244
1974
Rockaways
3.5
2-5
6.6
2-21
3.1
0-6
4.9
1-33
Coney Island
59.2
11-473
434
93-281
45.8
16-377
9.6
5-27
1975'
Coney Island(C)
56.4
9-288
288
63-140
26.6
9-126
63.2
2-163
Coney Island(B)
126
30-1780
348
89-197
47.7
10-661
124
3-899
Coney lsland(A)
75
16-288
204
60-377
16.7
5.4-66
216
18-1740
Coney Island(D)
279
209-389
545
94-318
51.9
35-78
ND
ND
1 Coney Maid Beaches: (Q 2ad-4* Streets. Bngfcam: (B) tth-IOlh Succts; (A) llth-24th Streets; ID) Mth-Jfch Streets.
-------
TABLE A30. (Continued)
Indicator Density Per 100 ml
C. perfringens
V. parahaemolyticus
Staphylococci
Year
Beach
Mean
Range
Mean
Range
Mean
Range
1973
Rockaways
ND
ND
V ND
ND
'ND
ND
Coney Island
ND
ND
ND
ND
ND
ND
1974
Rockaways
12.5
2-351
32.8
5-249
178
32-558
Coney Island
18.3
50-66
54.5
14-368
243
98-926
19751
;Coney island(C)
17.5
7.1-32
16.1
3.0-100
209
32-955
Coney Island(B)
21.6
10-91
34.2
1.5-463
378
96-4370
Coney Island(A)
22.6
12-33
41.5
3.3-438
128
5.5-219
-Coney Island(D)
ND
ND
ND
ND
ND
ND
1 Coney Island Beaches: (C) 2nd-4th Streets, Brighton; (B) 8th-10th Streets; (A) !8th-24th Streets; (D) 34th-38th Streets.
-------
TABLE A31. GASTROINTESTINAL
-------
TABLE A32. SYMPTOM RATES FOR TRIALS CONDUCTED AT THREE ALEXANDRIA BEACHES IN 1976
Symptom Rates
*er 1000 Individuals By Beach and Swimming Status
Maamoura1
Ibrahemia2
Mandara3
Swim
Nonswim
A
Swim
Nonswim
A
Swim
Nonswim
A
Symptom
(560)4
(259)
(511)
(312)
{766)
(397)
Fever
3,2
<3.9
3.2
7.8
3.2
4.6
5.2
2.5
2.7
Diarrhea or Vomit
16.1
11.5
4.6
.15.6
3.2
12.4
31.3
17.6
13.7
Upper Respiratory Tract
24.1
7.7
16.4
45.0
3.2
41.8**
22.2
15.1
7.1
Ear
7.1
3.9
3.2
11.7
<3.2
11.7
10.4
2.5
7.9
Eye
21.4
<3.9
21.4*
23.0
3.2
19.8*
20.8
<2.5
20.8**
Skin
23.2
3.9
19.3
27.4
<3.2
27.4
18.2
7.6
10.6
' Moderate;1 high; and 3 very high pollution levels according to E. coli and enterococcus densities and proximity to known sewage sources.
4 Number in parenthesis ( ) are numbers of usable responses (N).
•pC05; **p<01.
-------
TABLE A33. SYMPTOM RATES FOR ALEXANDRIA RESIDENTS AND CAIRO VISITORS AT THE ALEXANDRIA BEACHES IN 1977
Symptom Rates, per 10OO Individuals by Beach and Swimming Status
Symptom
Study Pop.
Swim
Maamoura1
Nonswim
A
Swim
Ibrahemia2
Nonswim
A
Swim
Sporting3
Nonswim
A
Fever
Visit.4
12.9®
9.4°
3.5
10.4e
2.69
7.8
16.7'
5.0k
11.7
Resid.
3.3b
<1.7d
>1.6
6.5f
4.0h
2.5
. 13.0)
3.141
9.9
Diarrhea or Vomit
Visit.
21.5
22.6
-1.1
25.9
13.0
12.9
51.2
12.4
38.8**
Resid.
12.2
8.5
3.7
16.2
2.0
14.2
29.6
5.2
24.4**
Upper Resp. Tract
Visit.
18.9
9.4
9.5
23.3
10.4
12.9
33.3
17.4
15.9
Resid,
19.9
12.6
6.3
14.5
6.0
8.5
13.3
3.4
9.9
Ear
Visit
3.4
<1.9
>1.5
2.6
<2.6
>0.0
4.8
<2.5
>1.3
Resid.
2.2
<1.7
>0.5
8.1
<2.0
>6.1
10.4
1.7
8.7
Eye
Visit.
2.6
1.9
0.7
5.2
<2.6
>2.6
4.8
<2.5
>2.3
Resid.
8.8
<1.8
>7.0
14.5
2.0
12.5
5.9
<1.7
>4.7
Skin
Visit.
17.2
7.5
9.7
25.9
7.8
18.1
25,5
7.4
17.6
Resid.
19.9
5.1
14.8
24.2
6.0
18.2*
32.6
5.2
27.4
' Moderate; 2 high and 3 very high pollution levels according to E, coli and enterococcus densitfes and proximity to known sewage sources.
* Rates given are for first weekly follow-np interview; subsequent follow-ups not used because of lower nonswimmer rates, possibly because most nonswimmers may have returned home to Cairo,
N = alI6S, b905, c53l, d587, e773, f619, S386, h498, %40, J675, k403,'582,
*p<.05; **p<01.
-------
TABLE A34. SYMPTOM RATES FOR ALEXANDRIA RESIDENTS AND CAIRO VISITORS AT THE ALEXANDRIA BEACHES IN 1978
Symptom Rates, per 10OO Individuals by Beach and Swimming Status
IMaamoura1
Ibrahemia2 .
Sporting3
Symptom
Study Fop.
Swim
Nonswim
A
Swim
Wonswim
A
Swim
Nonswim
A
Fever
Visit.4
4.4a
2.7C
1.7
17.2e
0.79
16.5**
18.9'
2.4*
15.9**
Resid.
6.0b
<1.6d
>4.4
10.9f
5.2h
5.7
12.0*
3.91
8.1
Diarrhea or Vomit
Visit.
17.5
18.1
-0.6
48.3
7.5
40.8**.
44,8
7.2
37.6**
Resid.
10.3
6.5
3.8
21.1
13.0
8.1
19.2
7.8
11.4**
Upper Resp Tract
Visit.
43.0
14.3
34.7**
20.7
6.2
14.5*
28.5
11.5
17.0**
Resid.
14.5
6.5
8.0
22.7
9.1
13.6*
16.0
13.0
3,0
Ear
Visit.
<2.2
0.5
<1.7
3.4
1.4
2.0
2.2
1.0
1,0
Resid.
1.7
<1.6
1.7
2.3
2.6
-0.3
3.2
<1.3
3.2
Eye
Visit.
4.4
0.5
3.9
10.3
1.4
8.9
4.2
1.4
1.7
Resid.
4.3
3.2
1.1
4.7
1.3
3.4
8.0
1.3
6.7
Skin
Visit.
30.6
1.6
29.0**
20.7
3.4
17.3**
36.7
7.7
29.0**
Resid.
12.8
3.2
9.6
13.3
6.5
6.8*
12.8
6.5
6.3
' Moderate;1 high and } very high pollution levels according to E. coli and enterocoecus densities.
4 Total rates Tor first two weekly follow-ups with individuals who swam 1-2 days/week; subsequent follow-ups, of lower nonswimmer rates, possibly because most of nonswlmmers may have returned home, to Cairo,
N = 11458, bl 169, c] 820, d617, e290, fS280, 81461, ll7?0, '491, J1253, k2089, *772. Beach totals will not agree with those given in Table 3 because data from individuals who swam more than 2 days/ week are not
included in first two weekly follow-ups used,
*p<0,05; **p<0,01.
-------
TABLE A35. SWIMMING-ASSOCIATED SYMPTOM RATES FOR
ALEXANDRIA, EGYPT STUDY
Study1
Swimming-Assoc. Rate (Per 1000 Persons2)
Symptom
Pop.
Year
Maamoura
Ibrahemia
Mand. or Sport.
Fever
Resid.
1976
3.2
4.6
2.7
1977
3,3
2.5
9.9
1978
6.0
5.7
8.1
Visit.
1977
3.5
7.8
11.7
1978
1.7
16.5**
15.9**
Ave.
3.5
7.4
9.7
Diarrhea or
Resid.
1976
4.6
12.4
13.7
Vomit
1977 "
3.7
14.2*
24.4**
1978
3.8
.8.1
11.4*
Visit.
1977
-1.1
12.9
38.8**
1978
-0.6
40.8**
37.6**
Ave.
2.1
17.7
25.2
Upper Resp.
Resid.
1976
16.4
41.8** .
7.1
Tract
1977
6.3
8.5
9,9
1978
8.0
13.6**
3.0
Visit.
1977
9.5
12.9
15.9
1978
34.7**
14.5*
17.0s*
Ave.
15.0
18.3
10.6
Ear
Resid.
1976
3.2
11,7
7.9
1977
2.2
8.1
8.7
1978
1.7
-0.3
3.2
Visit.
1977
3.4
2.6
4.8
1978
<1.7
2.0
1.0
Ave.
2.4
4.8
5.1
Eye
Resid.
1976
21.4*
19.8*
20.8**
1977
8.8
12.5
5.9
1978
1.1
3.4
6.7
Visit.
1977
0.7
5.2
4.8
1978
3.9
18.9
1.7
Ave.
7.2
10.0
8.0
Skin
Resid.
1976
19.3
27.4**
10.6
1977
14.8**
18.2*
27.4**
1978
9.6
6.8
6.3
Visit.
1977
9.7
18,1
17.6
1978
29.0**
17.3**
29.0**
Ave.
16.5
17.6
18.3
1 Study populations: Resid.—Alexandria residents; Visit.—Cairo visitors at Alexandria Beaches,
2 Study beaches: Maamoura (enterococcus density, 10'-102/100 ml); Ibrahemia (enterococcus density, loMo3; Mandaim or
Sporting (enterococcus density 103-104).
•p<.05: **p<.01 • for swimmer versus nonswimmer rates.
86
-------
TABLE A36. COMPARISON OF NONSWIMMING SYMPTOM RATES FOR
1ST AND 2ND FOLLOW-UP INQUIRIES WITH CAIRO
VISITORS DURING 1978 TRIALS
Symptom Rates/1000 Nonswimmers by Beach
and Follow-up
Maamoura
Ibrahemia
Sporting
Symptom1
1st 2nd
1st 2nd
1st 2nd
Fever
3.4 2.1
1.6 <1.2
2.2 2.5
Diarrhea or Vomit
, 30.9 6.3
11.0 4.9
13.3 2.5
Upfjer Resp. Tract
12.6 15.8
12.0 2.4
17.8 6.7
Skin
3.4 <1.1
3.1 3.6
6.7 8,4
1 Ear and eye symptoms not included because of small number of cases.
TABLE A37. SYMPTOM RATES PER 1000 PERSON-DAYS FOR CAIRO
VISITORS BY THE NUMBER OF SWIMMING DAYS PER
WEEK (1978)
Swimming-Associated Rate
Beach
Symptom
per 1000 Person-Days1
1-2
3-4
5-7
Maamoura
N2
4.58
470
1017
Diarrhea or Vomiting
_3
2.7
5.5
Upper Respiratory
22.5
3.8
5.3
Fever
1.1
1.0
.69
Ear
_3
.45
1.38
Skin
19.3
6.2
5.3
Ibrahemia
N
290
464
1100
Diarrhea or Vomiting
27.2
9,6
3.8
Upper Respiratory
9,7
4.4
3.1
Fever
11.0
1.7
1.4
Ear
1.4
1.5
1.7
Skin
11.5
6.4
2.9
Sporting
N
491
622
1439
Diarrhea or Vomiting
25.1
5.8
3.9
Upper Respiratory
11.3
5,9
3.9
Fever
10.6
1.6
1.8
Ear
.72
_3
1.3
Skin
19.3
5.6
2.7
1 For individuals who swam indicated number of days per week. The person-day rates were obtained by calculating the overall rates
obtained from the first two follow-up inquiries for nonswimmers and swimmers in the three use categories, subtracting the former
from the latter, and dividing the resulitng values (swimming-associated rates) by the average number of swimming days in each
category, 1.5, 3,5, and 6.
2N umber of responses for the two follow-ups in each category. The numbers for the nonswimmers at the three beaches were 1820,
1461, and 2089, The totals will not agree with those in Table 3 for the reasons stated in Table A34.
^Negative values, nonswimming rate higher than swimming rate.1
87
-------
TABLE A38. SYMPTOM RATES FOR VOMITING AND DIARRHEA AND MEAN INDICATOR DENSITIES FOR ALEXANDRIA, EGYPT
STUDY (INPUTS TO FIGURES 4 AND 5]
Year Beach
Mean Density/
100 ml
Entero-
coccus E. coti
Alexandria Residents
Cairo Visitors1
Swim
N
Nonswim
Symptom Rate/
1000 Persons
Swim Nonswim A
Swim
N
Nonswim
Swim
Symptom Rate/
1000 Persons
Nonswim
A
1976 Maamoura
103
14.6
560
259
16.1
11.5
4.6
ND2
ND
Ibrahemia
286
184
511
312
15.6
3.2
12.4
ND
ND
Maridara
5760
1620
766
397
31.3
17.6
13.7
ND
ND
1977 Maamoura
72.8
35.3
905
587
12.2
8.5
3.7
1165
531
21.5
22.6
-1.1
Ibrahemia
211
415
619
498
16.2
2.0
14.2*
773
386
25.9
13.0
12.9
Sporting
6780
6300
675
582
29.6
5.2
24.4**
840
403
51.2
12.4
38.8**
1978 Maamoura
214
53.1
1169
617
10.3
6.5
3.8
458
1820
17.5
18.1
-0.6
Ibrahemia
954
668
1280
770
21.1
13.0
8.1
290
1461
48.3
7.5
40.8**
Sporting
9160
10400
1253
772
19.2
7.8
11.4*
491
. 2089
44,8
7.2
37.6**
1 Data from Istfoliow-up interview, 1977; data from 1st and 2nd follow-up interviews !978.
1 No data,
*p
-------
TABLE A39. SYMPTOM RATES FOR SWIMMERS AND NONSWIMMERS
DURING 1977 LAKE PONTCHARTRAIN TRIALS
1
Symptom Bate/1000 Persons For
Swim
Nonswim
A
Symptom
{N = 2647)
(N = 1131)
Gastrointestinal:
Vomiting
22##
9
13
Diarrhea
58**
22
36
Stomachache
59**
39
20
Nausea
34
25
9
Respiratory:
Sore throat
68
61
7
Bad cough
48
42
6
Chest cold
32
28
4
"Other"
Fever (more than 100° F.)
30
31
-1
Headache (more than few hours) 1
44
. 39
5
Backache
16
16
0
Eye, Ear, Nose:
Runny or stuffed nose
58
58
0
Earache or runny ears
30**
10
20
Red, itchy or watery eyes
(more than 1 day), styes
21
18
3
Nonspecific:
Skin rash, itchy skin, welts
24*
13
11
Sneezing, wheezing, tight chest,
breathlessness (5 or more min.)
20
21
-1
Severity:
Home because of symptoms
68
63
5
In bed because of symptoms
52
45
7
Sought medical help
28
26
2
~p<.05; **p<,0l.
TABLE A40. SYMPTOM CATEGORY RATES FOR SWIMMERS AND
NONSWIMMERS DURING 1977 LAKE PONTCHARTRAIN
TRIALS
Rate Per 1000 Persons For
Symptom Group
Swim
Nonswim
A
Gastrointestinal (1 or more)
101**
59
42
Respiratory (1 or more)
99
90
9
"Other" (1 or more)
73
65
8
Eye, Ear, Nose (1 or more)
92
76
16
Non-specific (1 or more)
48
37
11
Severity (1 or more)
85
69
16
Highly credible Gt1
40*#
15
25
•All instances of {I) vomiting or (2) diarrhea with fever or a severe response, or (3) nausea and stomachache with fever.
~~Significantly (p<.01) higher than nonswitnmers.
89
-------
TABLE A41. GASTROINTESTINAL SYMPTOM RATES BY AGE FOR 1377
LAKE PONTCHARTRAIN TRIALS
• !" 'i . i * . !
Symptom Rate/1000 Persons For individuals
Under Age 10
Age 10 and Older
Symptom
Swim
Nonswim
~
Swim
Nonswim A
Stomachache
74
28
46**
52
39 13
Diarrhea
85
22
63**
49
22 27**
Nausea
34
33
-1
33
23 10
Vomiting
36
22
14
18
6 12**
Combined Gl
123
50
73**
94
61 33**
Highly Credible Gl
61
28
33*
33
12 21**
•p<0.05; "p<0.01.
TABLE A42. INDICATOR DENSITIES IN THE BAYOU ST. JOHN AS
COMPARED TO THE ROPED-OFF AREA AT LEVEE BEACH
ON LAKE PONTCHARTRAi^ (1977)
Mean Indicator Density Per 100 ml
Enteroccocci
Escherichia coli
Daily
Roped
Roped
Rainfall
Trial
Bayou
Area
Ratio
Bayou
Area
Ratio
(inches)
1
446
136
3.3
764
64
11.9
.15
3
273
228
1.2
89.6
32.5
2.8
.00
4
114
314
.36
147.0
32.9
4.5
.18
5
850
632
1.3
92.3
241.0
.38
.87
6
699
169
4.1
80.0
155.0
.52
.03
7
40.3
34.2
1.2
2650.0
4336.0
.61
,44
8
39.6
17.3
2.3
518.0
597.0
.87
.43
9
311.0
11.1
28.0
4632.0
3930.0
1.2
.84
10
211.0
17.3
12.2
1173.0
858.0
1.4
.88
11
45.2
33.5
1.3
3359.0
5676.0
.59
1.21
12
56.0
63.0
.89
289.0
650.0
.44
1.10
13
9.7
9.9
1.0
3481.0
1657.0
2.1
1.08
15
76.6
10.9
7.0
2942.0
531.0
5.5
3.18
16
126.0
62.1
2.0
625.0
351.0
1,8
.8
90
-------
TABLE A43. ANALYSIS OF 1977 LAKE PONTCHARTRAIN DATA BY RAINFALL (DRY VERSUS WET PERIODS)
Characteristic
Relatively Dry Period
Relatively Wet Period
Trial Numbers
1,3,4,5,6
7, 8, 9,19,11,12,13,15,16
Period
7/9 — 7/24
7/30—8/28
Rainfall1
.128 in/day
.433 in/day
Indicator Densities/100 ml2
Enterococcus
£ co/i
Enterococcus
£ coli
Roped-off Area
253
76.1
22.7
2074
Bayou
362
149.0
66.3
2219
Total
301
107.0
38.8
2145
Gl Symptom Rates
Swim
Nonswim
A
Swim Nonswim
A
Total
123.23
56.84
66.4***
86.6s 60.76
25.9
Highly Credible
46.8
17.0
29.7**
32.2 . 9.8
22,4**
1 Total rainfall for the interval starting 6 days before the first trial and ending with the trial date divided by the number of days in the interval.
? Geometric mean for all samples collected on the trial dates.
3 N—1282;4 N-528; 5 N-993; 4 N-51I.
**p<.01; «"p<001.
-------
TABLE A44. GASTROINTESTINAL SYMPTOM RATES FOR 1977 LAKE PONTCHARTRAIN TRIALS CLUSTERED BY INDICATOR
DENSITIES
Indicator
Density/100 ml
Mean Range
Swim
N
Nonswim
Gastrointestinal Symptoms
Swim Nonswim A
Highly Credible Symptoms
Swim Nonswim £
Enteroccocci
441
9.7-88
874
451
85.8
51.0
34.8*
32.0
11.1
20.9*
2242
190-249
720
456
108.0
50.4
579#*
31.9
8.8
23.1*
4953
344-711
€95
464
108.0
53.9
54.1**
35.8
8.6
27.2**
£ coli
44"
33-54
372
222
132
45.0
87.0**
32.3
9.0
23.3
161s
112-221
910
306
119.8
65.4
54.5**
52.7
22.8
29.9*
4976
433-556
574
307
85.4
45.6
39.8*
32.9
13.0
19.8
3091'
1033-4267
419
204
88.3
83.3
4.3
31.0
4.9
oe i
C.VI
Trials clustered-1 7, 8, 9. 11, 12, 13, 15, 16; 2 1, 3, 4. 10; 3 5, 6;4 3, 4; 5 1, 5, 6; 6 8, 12, 15, 16; 7 7, 9, 10, II, 13.
*p
-------
TABLE A45. GASTROINTESTINAL SYMPTOM FOR THE FOUR, 1977 LAKE
PONTCHARTRAIN TRIALS WITH THE HIGHEST £. coti AND
ENTEROCOCCUS DENSITIES
Rate for Symptoms Per 1000 Persons
Density Per 100 ml
Total Gastrointestinal
Highly Credible Gi
Trials
E. coli
Errterococcus
Swim Nonswim A
Swim Nonswim
7
3390
37.0
9
4267
59.0
11
4366
39.0
13
2401
9.7
Ave.
3606
36.2
86.7 62.5 24.2
30.0 6.9 24.2
5
149
711
6
112
344
3
54
249
1
221
246
Ave.
134
388
116.2 65,8 50.4**
48.4 18.4 30.0**
"p<0.01.
93
-------
TABLE A46. CLUSTERING OF TRIALS FOR THE CALCULATION OF GASTROINTESTINAL SYMPTOM RATES FOR 1978 TRIALS
AT LEVEE BEACH, LAKE PONTCHARTRAIN
Indication Density/100 ml
.
Enterococcus
£ coli
Clustering for
Trial
Date
Rainfall
Bayou
Roped Area1
Bayou
Roped Area
Enterococcus E. coli
1
6/10
.45
42
45
400
367
Eliminated2
2
6/11
.72
34
3
198
214
¦
Eliminated
3
6/17
.05
127
17
79
32
H3
H
4
6/18
.02
122
17
142
105
H
H
5
6/24
.01
292
239
117
89
H
H
6
6/25
.02
25
18
70
57
L4
H
7
7/11
.00
67
67
37
64
H
L
8
7/2
.14
18
29
45
83
L
L
9
7/8
.02
17
14
32
52
L
L
10
7/9
.00
9
37
25
15
L
L
11
7/15
.09
3
5
27
8
L
L
12
7/16
1.47
442
717
286
67
Eliminated
2 Trial eliminated from analysis; see text for basis,
3 Trial assigned to high indicator density cluster.
4 Trial assigned to low indicator density cluster.
-------
TABLE A47. GASTROINTESTINAL SYMPTOM RATES AND CORRESPONDING MEAN INDICATOR DENSITIES FOR 1978 TRIALS
AT LAKE PONTCHARTRAIN
Rate for 1000 Persons for
Density/100 ml
N
Gastrointestinal Symptoms
Highly Credible Gl Symptoms
Indicator
IMean
Range
Swim
Nonswim
Swim
Nonswim
A
Swim
Nonswim
~
Enterococcus
11.1
3-30
1230
415
75
34
41 *#
36.6
14.5
22.1*
14.41
3-325
248
303
82
63
18
44.3
23.1
21.3
142
67-303
801
322
112
50
62**
42.4
15.5
26.9*
£ coli
9.01
1-23
248
303
81
63
18
44.3
23.1
21.3
32.6
17-87
1123
383
78
44
33*
38.3
20.9
17.4
93.7
53-177
918
355
103
36
67**
39.2
8.5
30.7*
1 Fomaiuebleau Beach.
*p<0.05; *'p<0.01
TABLE A48. SYMPTOM RATES FOR REVERE AND NAHANT BEACHES
DURING 1S78 BOSTON HARBOR STUDY
Rate Per 1000 Persons At
Revere Beach1
Nahant Beach2
Symptom Group
Swim
Nonswim
A
Swim
Nonswim
A
Gastrointestinal
89.0
70.0
19.0
69.6
63.7
5.9
Respiratory
82.7
72.3
10.4
98.2
102.8
-4.6
Other
83.8
68.5
14.3
82.3
102.8
-20.5
Ear, Eyes, Nose
95.8
99.0
-3.2
87.7
109.2
-21.4
Highly Credible Gl
27.0
12.0
15.0
33.0
28.0
5.0
Severe Gl
34.8
29.8
5.0
26.5
28,2
-1.7
1 N—919 swimmers; 905 nonswimmers.
1 N—1150 swimmers; 1099 nonswimmers.
-------
TABLE A49. GASTROINTESTINAL SYMPTOM RATES AND CORRESPONDING INDICATOR DENSITIES FOR REVERE AND
NAHANT BEACHES FOR 1978 BOSTON HARBOR STUDY
Indicator Density/100 ml
Rate for GI1 Symptoms
Rate for HCGI2 Symptoms
Enterococci
E.coH
Per 1000 Persons
Per 1000 Persons
Beach
Mean
Range
Mean
Range
Swim3 Nonswim4
A
Swim
Nonswim
k
Revere5
6.3
2-12
18.0
5-31
89 70
19
27
10
15
Nahant6
7.3
6-9
11.5
4-22
70 64
6
33
28
5
1 Gastrointestinal; 5 highly credible gastrointestinal; 3 swimmers; 4 nonswimmeiy, 5 data from four trials (days); N for swimmers 919, for nonswimmers 905; 6 data from four trials (days); N for swimmers 1150, for
nonswimmers 1099,
TABLE A50. GASTROINTESTINAL SYMPTOM RATES AND CORRESPONDING INDICATOR DENSITIES FOR CLUSTERED
TRIALS DURING 1978 BOSTON HARBOR STUDY
Indicator
Density/100 ml
Mean Range
Beach
Swim
N
Nonswim
Gastrointestinal Symptoms
Per 1000 Persons
Swim Nonswim A
Highly Credible Symptoms
Per 1000 Persons
Swim Nonswim A
Enteroccocci
4.31
2-6
Revere
697
529
83
66
17
23
11
12
7.32
6-3
fc|—a
iNdnSiu
1130
10S9
71
67
4
33
28
5
12.03
12
Revere
222
376
108
74
34*
41
13
28*
£ colt
5.54
4-7
Nahant
541
874
72
63
9
39
29
10
7.0s
5-9
Revere
477
410
86
68
18
23
9.8
13
17.5®
13-22
Nahant
589
225
70
67
3
27
27
0
29.57
28-31
Revere
442
495
93
71
22
32
14
17
Trials clustered—1 1, 3, 4;2 1, 2; 3 2;11 1, 2; 5 1, 3; 6 3, 4; 7 2, 4.
*P<0.05.
-------
TABLE A51. 95% CONFIDENCE LIMITS FOR SWIMMING-ASSOCIATED
GASTROINTESTINAL SYMPTOM RATES PREDICTED FROM
THE OBSERVED MEAN ENTEROCOCCUS DENSITIES
(TRIALS CLUSTERED BY INDICATOR DENSITIES)
Enterococcus
Density Per
100 ml
Total GI Symptoms
Predict.2 95% Conf. Lim.
Rate Lower Upper
HCGI
Predict.
Rate
Symptoms
95% Conf. Lim.
Lower Upper
3.6
8.4
-0.8
17.6
6.9
1.0
12.8
4.3
10.2
1.6
18.9
7.8
2.3
13.4
5.7
13.2
5.3
21.0
9.3
4.3
14.4
7.0
15.4
8.0
22.7
10.4
5.7
15.1
7.3
15.8
8.6
23.0
10.7
6.0
15.3
11.1
20.2
13.9
26.4
'12.9
8.9
16,9
12.0
21.0
14.9
27.1
13,3
9.0
17.2
13.5
22.3
16.3
28.2
13.9
10.1
17.7
14.4
22.9
17.1
28.8
14.3
10.5
18.0
20.3
26.5
21.1
32.0
16.1 "
12.6
19.6
21.8
27.3
21.8
32.7
16.5
13.0
20.0
31.5
31.2
25.7
36.7
18.4
14.9
22.0
44.0
34.7
28.8
40.5
20.2
16.5
24.0
91.2
42.3
35.0
49.7
24.1
19.4
28.8
142.0
47.0
38.4
55.5
26.4
21.0
31.9
154.0
47.8
39.0
56.3
26.9
21.2
32.5
224.0
51.8
41.8
61.7
28,9
22.5
35.3
495.0
60.1
47.5
72.7
33.1
25.0
41.2
' Highly credible gastrointestinal.
1 Rates predicted from Y on X regression lines.
97
-------
TABLE A52. 95% CONFIDENCE LIMITS 'f^OR MtAN ENTEROCOCCUS
DENSITIES PREDICTED FROM THE OBSERVED
SWIMMING-ASSOCIATED Gi SYMPTOM RATES
Total GI
Enterococcus Density/100 ml
HCGI1
Enterococcus Density/100 ml
Per 1000
95% Conf. Lim.
Per 1000
95% Conf. Lim.
Persons
Predict.2
Lower
Upper
Persons
Predict.
Lower
Upper
4
5,1
2.5
10.4
—0.5
3.8
1.4
10.3
8
6.6
3.4
12.5
3.4
5.7
2.5
13.3
17
11.7
7.1
19.5
3.6
5,9
2.5
13.5
18
12.5
7.6
20.5
5.0
6.8
3.1
14.8
20
14.2
8.9
' 22.9
7.4
8.8
4.4
17.5
22
16.2
10.3
25.5
12.0
14.4
8.2
25.1
25
19.7.
12.7
30.4
13.6
17.0
10.1
28.8
29
29.0
16.6
39.0
15.2
20.2
12.2
33.5
34
35,2
22.6
54.8
18.1
27.6
16.8
45.2
35
37.5
23.9
58.9
20.9
37.2
22.0
62.9
41
55.4
33.1
92.6
21.2
38.4'
22.6
65.3
48
87.1
46.8
162.0
22.1
42.3
24.4
73,2
54
128,0
61.9
266.0
23.1
47.1
26.6
83.4
58
166.0
74.0
373.0
26.9
70.6
35.6
140.0
62
215.0
88.4
524.0
27.2
72,9
36.3
146.0
28.0
79.5
38.5
164.0
28.4
82.9
39.6
174,0
34.5
159.0
59.5
426.0
1 Highly credible GI symptom,
! Predicted from X on Y regression lines.
*U.a60VEflNMEffFPRINTINQOFFICE 1S83- 659-095/0730
98
------- |