Environmental Protection
              Agency
              "
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          Bacteriological  Ambient Water Quality Criteria
             for  Marine  and  Fresh Recreational  Waters
               U.S. Environmental Protection Agency
Office of Research and Development
Microbiology and Toxicology  Div.
Cincinnati, Ohio
Office of Water Regulations
  and Standards
Criteria and Standards Div.
Washington, D.C.

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                              :ONTENTS
Foreword	.«	• • •	   iii



Acknowledgements 	    ^v








Introduct ion 	• • «	     1



Study De s i g n	•	<     ^



Data Base for Marine and  Fresh Water 	     4



Basis of Criteria for Marine and  Fresh Water  	     6



Recommendation on Bacterial Criteria Monitoring	     7



Development of Recommended Criteria Based on  E.  coli



  and enterococci	'• • •     8



Limitations and Extrapolations of Criteria  	       10



Relationship With the Criteria Contained  In Quality



  Criteria for Water  	•••	.•     10



Tables	     12-15



National Criteria		     16








References 	•»	•• •     •*•'

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                            DISCLAIMER



     This report has been reviewed by the Criteria and Standards



Division., Office of Water Regulations and Standards,  U.S. Environ-



mental" Protection Agency, and approved for publication.  Mention



of trade names or commercial products does not constitute endorse-




ment or recommendation for use.
                       AVAILABILITY NOTICE





     This document  is  available  to  the  public  through  the National



Technical Information  Service  (NTIS), 5285  Port  Royal  Road,



Springfield, VA   22161.   NTIS  Access  Number is PB 86-158045.
                                 ii

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                                                   L  95-217)


                                     „

have
                    by

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                     AC KN1 OW LE DGEM E NTS
Alfred P. Dufour
(research-author)
Health Effects Research
  Laboratory
Cincinnati, OH

Theadore H. Ericksen
(review)
HERL
Cincinnati, OH

Richard  K.  Ballentine
(author)
OWRS  - Washington,  D.C.
Victor J. Cabelli
(research)
Health Effects Research
  Laboratory
West Kingston, RI

Miriam Goldberg
(statistical assistance]
OWRS
Washington,  D.C.

William  E.  Fox
(coordinator)
OWRS - Washington,  D.C.
                              iv

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              BACTERIOLOGICAL AMBIENT iVATER QUALITY CRITERIA  FOR
                    MARINE AND FRESH RECREATIONAL WATERS


 Introduction

      Federal water quality criteria reccmmendations w=re  first proposed
 in  1968  by the  National  Technical  Advisory Committee  (NTAC)  of the
 Department of the  Interior (1).  The microbiological  criterion suggested
 by  the NTAC for bathing  waters was based on a  series  of studies conducted
 during  the late 1940's and early 1950's, by the United States Public
 Health Service,  the results of.which were "sumnarized  by Stevenson in 1953
 (2).   Ihe  studies  were conducted at bathing beaches located  on Lake Michi-
 gan at Chicago,  Illinois;  on the Ohio River at Dayton, Kentucky; and on
 Long  Island Sound  at Mamaroneck  and New ftochelle,  New York.  All of the
 studies  followed a similar design.   Two beaches with  different water
 quality  were selected at each location except at the  Dayton  location
 where a  beach with high  quality  water could not be  found.  A large public
 swimming pool was  used as  a substitute.  Each location was chosen because,
 in  addition to  beaches having  suitable water quality, there  was a large
 residential population nearby that used the beaches.  Cooperating families
 used  a calendar system which allowed them  to record their swimming activity
 and illnesses on a daily basis for the entire summer. Gastrointestinal,
 respiratory,  and other symptoms  such as skin irritations were recorded.
 The water  quality  was measured on  a routine basis  using total coliform
 bacteria as the  indicator  organism.

      The results of the  Lake Michigan beach study  indicated  that there
 was no excess illnesses  of any type  in swimmers at  beaches that had
 median coliform densities  of 91  and 180 per 100 ml  over a swimming season
 when  compared to the  number of illnesses in the total study  population.
 The water  quality  similarity at  the  two Chicago beaches was  unexpected
 since previous experience  had  indicated that there  was a difference in
 water quality at the  beaches.  A second method of analysis compared the
 illness  observed in the  week following three days of  high coliform density
 with  that observed following swimming on three days of low coliform
 density.  The analyses showed  that there was a significantly greater
 illness  rate  in  individuals who  swam on the three days when  the geometric
mean  coliform density was  2300/100 ml when compared to the illness in
 swimmers who  swam  on  the three days  when the geometric mean  coliform
 density  was  43 per 100 ml.   A difference was not observed when the geo-
metric mean coliform  density per 100 ml on high and low days was 732 and
 32  respectively.  Data fron the  Ohio River study indicated that swimmers
 who swam in water  with a median  coliform density of 2300 coliforms per
 100 ml had  an excess  of  gastrointestinal illness when compared to an
 expected rate calculated from  the  total study population.  No other
 associations  between  swimming  and  illness  were observed.  The results of
 two marine  bathing beach studies showed no association between illness
 and swimming  in  water containing 398 and 815 coliforms per 100 ml.

      The coliform  water  quality  index used during the USPHS  epideralologi-
 cal studies was  translated into  a  fecal coliform index in the mid-'60s
 by  using the  ratio of fecal  coliforms to coliforms at the location on the
 Chio  River  where the  original  study had been conducted in 1949.  The NTAC
 commit'tee suggested  that the change  was necessary  because fecal coliforms

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were more fecal specific and  less  subject to variation than total  .oil-
forms which were greatly influenced  by storm water runoff.  About  18% of
the coliforms were found to be fecal conforms and this Proportion was
used to determine that the equivalent of  2300 conforms per 100 ml , the
density at which a statistically significant swHtming-assccia ted gastro-
intestinal illness was observed, was about  400 fecal colifoms per 100
ml.  The OTAC suggested that  a detectable risk was undesirable and,
therefore, one-half of the density at which a health risk occurred, 200
fecll coliforms per 100 ml, was proposed.   The NTAC also suggested that
tS  use of tte 4er should not cause a detectable health effect more    -
than W% o£ the tine.  Thus,  the reconverted criterion for recreational
waters was as  follows:

          "Fecal coliforms should be used as the  indicator organism
     for evaluating the microbiological  suitability of recreation
     waters.   As determined by mul tiple-tube  fermentation or ™2m-
     brane filter procedures and based on a minimun of not less than
     five ssamples taken over not more than a 30-day period, the
     fecal coliform content of primary contact recreation 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."

     This criterion was recotmended again  in 1976 by tte USEPA (3),  even


                              SA22- - -
 the poor quality of the data base,  the derivation of the
 and the indicator system used,,

 «.                     £
 lumped togiether.
                         suggested other weaknesses in the USPHS study
                              «>» u»      "^'061"


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variability in the pollution levels at the beaches increased  the probabi-
lity of a given individual's exposure to different levels of  pollution
during the incubation period of the illness.

     The deficiencies in the study, design and in the data used to  _
establish the 200 fecal coliforms per 100 ml criterion were noted  oy
the National Academy of Science - National Academy of Engineers Cormattee
in their 1972 report which stated that they could not recotmend a
recreational water quality criterion because of the paucity of epideni-
ological information available (7).

     The fecal coliform indicator used to measure water quality under the
current system has also been faulted because of the non-fecal sources of
at least one member of the fecal coliform group.  For example, the^o-
tolerXt Slbsiella species have many sources.  They have been ^served
in pu^ and paper nillef fluents (8,9), textile processing plant effluents
(10),  cotton mill wastewaters  (11), and. sugar beet wastes  (12), in the
absence of  fecal  contamination.

     The Ehvirormental Protection  Agency,  in  1972,  initiated  a series of
studies at marine and fresh water bathing  beaches which  were  designed to
correct the Reived deficiencies of the  Public  Haalth  Service studies.
XS Joal of the EPA studies was  to determine  if swinging in  sewage-
SntaTinatid  wtter  carries a health risk for bathers;  and, if so, to what
tvne of  illness.   If a quantitative relationship  between water quality
and health risk was obtained,  two  additional goals were  to determine
which bacterial  indicator  is best  correlated to swuraing-associated
health effects and if  the  relationship is strong  enough  to provide  a
criterion.

 Study Design

      The marine studies were conducted at bathing beaches in New York
 Citv
    y
          arne s
          York, Boston,  Massachusetts, and at lake Pontchartrain,  near
          s? Louisiana.   Two beaches ware selected at each site, one that
       d very little or  no contamination and the other whose water quali-
       barSy acceptable with respect to local recreational water  quality
       HQ   Tn the New York City and Boston Harbor studies, the "barely
accple" SacSs ^re^o/tamLaterf with pol lut ion f ran multiple point-
SurXs, usually treated effluents that had been disinfected.

     The freshwater studies were conducted on Lake Erie J*5ie'
Pennsylvania and on Kfeystore Lake outside of Tulsa, ^f^'
acceptable" beaches at both sites were contaminated by effluents
charged from single point-sources.

     The eoideniolcgical surveys were carried out on weekend days and


-------
study has teen described elsewhere (13,14).   Specific steps taken to
correct the; deficiencies of earlier studies  were  noted earlier.

     In tte initial  phases of the overall study,
-------
earlier USPHS  studies.  The only .evidence,,that sewage-contaminated water
carried a  risk for gastroenteritis  in those studies was observed at the
Ohio  River beach where swimmers had an excess of gastrointestinal illness
when  the" median coliform density in the water was 2300 per 100 ml.  This
was counter  to the results found at freshwater beaches in 'Chicago and at
marine beaches on Long Island Sound where swimmers had no more gastro-
intestinal illness than nonswiirmers even when days of "high" and "low"
colifom densities were selected.  Therefore, other than the occasional
association of an outbreak of disease with swimming (17), the data frcm
•labelLi (15)'and Dufour (16) are the only available'evidence linking
sewage contaminated water with a health risk for bathers.

      Although  the association of illness in swimmers using bathing water
contaminated by treated sewage is an important aspect of the process for
developing recreational water quality criteria, it is the establishment
of a  quantitative relationship between the two variables that provides a
useful relationship for regulating water quality.  A part of this process
is the development of suitable methods for measuring the quality of the
water.

      A comprehensive discussion of microbial water quality indicators is
beyond the scope of this document, even as the basis for the selection of
those examined in the epidemiological studies.  The reader is referred
for this to the reports of the studies (15,16) and to reviews on the
subject (18,19).  The exanination of a number of potential indicators,
including the ones most commonly used in the United States (total colifdrms
and fecal coliforms), was included  in the studies.  Furthermore, the
selection of the best indicator was based on the strength of the relation-
ship between the rate of gastroenteritis and the indicator density, as
measured with  the Pearson Correlation Coefficient.  This coefficient
varies between minus one and plus one.  A value of one indicates a
perfect relationship, that is, all of the paired points lie directly on
the 1ine which defines the relationship.  A value of zero means that
there is no linear relationship.  A positive value indicates that the
relationship is direct, one variable increases as the other increases.
A negative value indicates the relationship is inverse, one variable
decreases as the other increases.  The correlation coefficients for
gastroenteritis rates as related to the various indicators of water
quality from both marine and fresh bathing water are shown in Table 2.

     The data  frcm the three years of the New York City study were ana-
lyzed in two ways.  The first was by grouping trial days with similar
indicator densities from a given swimming season and the second was by
looking at each entire summer.  The results from both analyses are shown
in Table 2.  For either type of analysis, enterococci shoved the strong-
est relationship to gastroenteritis.  E. coli was a very poor second and
all of the other indicators, including total coliforms and fecal coli-
forms, showed very weak correlations to gastroenteritis.  Enterococci and
E. coli were used in subsequent studies including the freshwater trials.
Fecal coliforms also were included  in subsequent studies because of their
status as an accepted basis for a criterion.

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                                 — D "~
        freshwater studies were analyzed only by sunmer.   The correla-
Baals of Criter*- «~
                                 Fresh Recreational Waters
     CabeUi (15) defined a recreational water quality criterion as a



risks for swinmers.
     The Quantitative relationships  between the  rates of  swimming-associ-

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     £s - -1-"             --
              95%
water =""*--- p coli-
confirmed as £• 	.        successfully -~---  t LaboratoL
 SS: sast-r8^. -. - --ss.
 -^£SS.«&^.^a.T-



-------
                                  — 8  —
improves the likelihood of correct decisions on  whether  to close
or leave open a beach.

     Waters, with more casual and intermittent swimming use need  fewer
samples because of the reduced population at risk.   Such sampling may
IT£ be used in establishing trends in the bacterial water quality  so
that the necessary improvements in the sanitary quality  can  be  identified
before disease risks becone acute.

     Thp following compliance protocol is one recomended by SPA for
monitoring recreational bathing waters.  It is based on  the  assumption
   t tte currently accepted risk level based on the CCW recommendation
    been d Smined  to be appropriate and that the mo"it°rinJ.^^S'1
i e   bacterial enumeration techniques are  imprecise, and environmental
cc^it^s  such as  rainfall, wind and 'temperature will vary temporally
and soatially.  The  variable nature of the  environment,  which affects
£ne dte-Sff a^d transport of bacterial indicators, and the  inherent
imprecision of bacterial enumeration methods, suggests an approach that
   eTSXS elects into account.  Nbrcompl iance with the  criterion
   signaled when the maximun acceptable  geometric mean  is exceeded or
   n^1ndS!dual  sample exceeds a confidence Innit, chosen accordingly
or to a level of swiimung use.  The mean log  standard deviation for £.
                 .
.with the proposed monitoring protocol and upper percentile values
      It is recormended that sampling frequency be related to the intensity
    use of the water body.  In areas where weekend use is substantial,
              s^ollecSX during the peak use periods are reasonable.   In
              used areas perhaps bi-weekly or monthly samples nay be
          to decide bacterial water quality,

                                         £




  (25).
  nevelocment of Recotnended Criteria Based on B.  coli/Enterccocci
       Currently EPA is not recomnending  a change  in the  stringency of  its

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                                   - 9 -
      EPA's evaluation of the bacteriological data  indicated  that using  the
 fecal colifonn indicator group at the maximum geometric mean of 200 per
 100 ml, recommended in Qiality Criteria for Water  wold cause  an estimated
 8 illness per 1,000 swimners at fresh water beaches  and 19 illness per
 1,000 swimmers at marine beaches.  These relationships are only approximate
 and are based on applying ratios of the geometric  means of the various
 indicators from the EPA studies to the 200 per 100 ml  fecal  coliform
 criterion.  However,  these are EPA's best estimates  of the accepted
 illness rates for areas which apply the EPA fecal•coliform criterion.

      The E_.  coli and  enterocccci criteria presented  in Table 4 were deve-
 loped using  these currently accepted illness rates.  The eouations deve-
 loped by Dufour(16) and Cabelli(lS)  were used to calculate the geometric
 mean indicator densities corresponding to the accepted gastrointestinal
 illness rates.   These densities are for steady state dry weather conditions.
 The beach is in nonconpliance   with,the criteria  if the geometric mean
 of several bacterial  density samples exceeds the Value listed  in Table  4.

      Nonconpliance is also signalled by an unacceptably high value for
 any single bacterial  sample.   The maximum acceptable bacterial density
 for a single sample is set higher than that for the  geometric mean, in
 order to  avoid  unnecessary beach closings based on single sanples.  In
 deciding  whether  a beach should be  left open,  it is  the long term geometric
 mean bacterial density that is of interest.   Because of day-to-day fluctu-
 ations around this mean,  a decision based on a single sample (or even
 several sanples) may  be erroneous,  i.e.,  the sanple  may exceed the recom-
 mended mean  criteria  even though the long-term geometric mean  is protective,
 or may fall  below the maximum even  if this mean is in the nonprotective
 range.

      To set  the single  sample maximum,  it is necessary to specify the
 desired chance that the beach will  be left open when the protection is
 adequate.    This chance,"or confidence level,  was based on Agency judgment.
 For  the simple decision rule  considered  here,  a smaller confidence level
corresponds  to a more stringent  (i.e.  lower)  single  sanple maximum.
 Conversely, a greater confidence level  corresponds to less stringent
 (i.e. higher) maximum values.  This  technique  reduces the chances of
 single sanples inappropriately indicating violations of the reconnended
criteria.

      By using a control chart analogy (26) and  the actual log standard
deviations fron the EPA studies,  single  sample maximum densities for
various confidence levels were calculated.   EPA then assigned qualitative
use  intensities to those confidence  levels.  A low confidence level (75%)
was assigned  to designated  beach areas  because a high degree of caution
should be used to evaluate water  quality for heavily used areas.  Less
 intensively used areas would  allow less  restrictive single sample limits.
Thus, 95% confidence might be appropriate  for swiramable water in remote
areas.   Table 4 sutimarizes the  results of these calculations.  These
single sample maximum levels  should be recalculated for individual areas
if significant differences  in  log standard deviations occur.

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standard deviation of log
                            sities^ Du             historically accepted
maximun has been
indicates how the conflde
                                               be applied to multiple
                                  4aP?hflimit for the measured geometric
                       lations of Criteria
Tl-imit-*fions and Extra
                      of —rality
 health effects
 CabellidS).  Briefly, the major
 observed relationship may not be
 contributing the fecal
 are present in a c.
 which is approximately constant
 and therefore, the          r
                                               based

                                             of the criteria are that the
                                              size of the population
                                                z  if epidSuic conditions
                                               pathogen to indicator ratio,
                                                    Ti becomes unpredictable
                                                    r these circunstances,,
                                        importance of sanitary surveys and

                     ^
           presence of these  i^icators
 of  warm blooded  animal
  application of these
                                                   ^idemiological studies
                                               be no^-hunan and that the
 subsequent revisions
                                                       rv-ii-ftria for Water •
               with the Criterion contained in Quali
               .     criterion
  and shellfish harves ting watery      ^^ing m this criterion is


                                                  . «S«h into the

    Criteria  and   cux.             etandard
    office of Water  Regulations and Standard
    Envirormental  Protection Agency
    401 M St., S.W.
    Washington, DC  20640

-------
the
 application of the enterococci and E.  coli indicators  for
 quality of shellfish harvesting watersT-lhe Food and  iS
 is also reviewing the results of these studies.   A changeto     nw
 indicators may be forthcoming if the studies show a correlation between
 gastrointestinal  disease and  the consumption of  raw shellfish  fW^ters
 with defined densities of the new indicators. However,  these  s^Siel
 have not  sufficiently progressed to justify  any  change 'at tSstSe      -
 Thus, the recommendations in  QCW for shellfish waters must remain unchanged,

      The  QCW recomendations  for swinging  waters were based on fecal
 conforms.   Data  subnitted  to EPA during the  public ccrrnent period showed
 that^witnin  sane  beaches, a correlation could be shown between E.  coli
 densities and  fecal coliform  densities.  Such a  site-specific correlation
 £££ 5U1Sri™9,beCaUSZ -  ^ is part of  the e«al^oliform grJu^.     '
 However,  the EPA  tests  show that  no general correlation exists acrosS
different beaches.  Therefore, EPA believes that the newly recotmended
 i££!,tor8 are S^rri°r t0 the fecal c°lifo^ group.  Therefore, EPA
 strongly recomtends that states begin the transition process to the  new
indicators,  ttule either E. coli or enterococci may be used for fresh
waters, only enterococci is recotmended for marine waters.

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Table 1.  Itelationship Between Significant Swiirming-Associated
          Gastroenteritis and the Degree of Pollution at Marine
          and Fresh Nater Bathing Beaches
                                  Beach Water Quality
No. Trials

xt>. Trials  with
Excess Illness in
Swiiraners 1

% Trials with
Excess Swiitsner
Illness
                     Barely Acceptable    Relatively Unpolluted

                                                     8
                              17
41
 iDifference between swininer and nonswimer  illness rates during  a
  trial period statistically significant at  p <0.05 level
                                   -  12 -

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Marine''
enterococci
  . coU.
                        /Citr
                             cbacter:



   Fresh
               en
     teroccjcci
.52
.32
.26
.19
 .19
 .19
^.01
-.09
-.20
 -.23
   .74
   .80
  -.08
.96
.56
.61
 .64
 .65
 .01
 .59
  .51
  .60
  .42
  .60
                                            - 13  -

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                     EPA Criteria for Bathing  (Full
                   Body Contact) Recreational  Waters


Freshwater

     p*«*>rt on a statistically sufficient nunber of samples (generally not

S                                     £55                      1
other of the followir^U).         ' 126 ^ 100 ml; or

                   rufprrr-'orci       33 per 100 ml;
m sa-sle should excel?™^ cenjfdence Unit 
-------
 .References

  1.   National Technical Advisory Cprmittee.  1968.  Water Quality Crite-
      ria... Federal Water Poll. Control Adm., Dept. of the Interior,
      Washington, DC.            '   '            u                 .           •

  2.   Stevenson, A. H.  1953.  Studies of Bathing Water Quality and Health.
      Am.  J.  Public Hlth. Assoc.  43:529.

  3.   U.S.  Environmental Protection Agency.  1976.  Quality'criteria for
      Water,   rj/s.  Environmental Protection Agency, Washington, DC.

  4.   Henderson, J. M.  1968.  Enteric Disease Criteria for Recreational
      Vvaters.   J.  San. Eng.  Div.  94:1253.

  5.   Moore,  B.   1975.  The  Case Against Microbial Standards for Bathing
      Beaches.   In:  International Symposium'on Discharge of Sewage From
      Sea Cutfalls.  Ed. A.  L.  H. Gameson.  Pergamon Press, London,  p. 103.

  6.   Cabelli, V.  J.,  M. A.  Levin, A.  P.  Dufour,  and L. J. McCabe.   1975.
      The Development of Criteria for  Recreational Waters.  In:  Interna-
      tional  Symposium on Discharge of Sewage Fran Sea Outfalls.   Ed. A.
      L. H.   Gameson.   Perganon Press, London, p. 63.

  7.   Committee  on  Water Quality Criteria.  1972.   National Academy of
      Sciences-National Academy of Engineering.  Water Quality Criteria.
      U.S. Environmental Protection Agency,  EPA-R3-73-033, Washington, DC.

  8.   Huntley, B.  E.,  A. C.  Jones, and V. J. .Cabelli.  1976.   Klebsiella
      Densities  in  Waters Receiving Wood  Pulp Effluents.   J.  Water Poll.
      Control Fed.   48:1766.

  9.   Caplenas,  N.  R.,  M.  S.  Kanarek,  and A. P.  Dufour.  1981.   Source and
      Extent of  Klebsiella pneumoniae  in  the Paper Industry.   Appl. En-
     viron.  Microbiol.  42:779.

10.   Dufour, A. P., and V.  J.  Cabelli.  1976.  Characteristics of Kleb-
      siella Fran Textile  Finishing Plant Effluents.   J.  Water Poll.
     Control Fed.   48:872.

11.   Campbell,  L.  M.,  G.  Michaels, R.  D. Klein, and I. L. Roth.   1976.
      Isolation of  Klebsiella pneumoniae  From Lake Water.   Can. J*  Micro-
     biol.  22:1762.

12.  Nunez, W.  J., and A. R. Colmer.   1968.  Differentiation of  Aerobacter-
     Klebsiella Isolated  from  Sugar Cane.   Appl.  Microbiol.   16:875.

13.  Cabelli, V. J., A.  P.  Dufour,  M.  A. Levin, L.  J.  McCabe,  and  P. W.
     Haberman.  1979.   Relationship of Microbial  Indicators  to Health
     Effects at Marine Bathing Beaches.   An. J. Public Hlth.  69:690.

14.  Cabelli, V. J., A. P. Dufour.  L.  J. McCabe,  and M.  A.  Levin.   1982.
     Swimming-Associated  Gastroenteritis and Water Quality.   Am. J.
     Epidemiol.   115:606.

15.  Cabelli, V. J.   1983.   Health Effects  Criteria for Marine Recreation-
     al Waters.  U.S.  Environmental Protection Agency, EPA-600/1-80-031,
     Cincinnati, QH.
                                   - 17-

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16.  Dufour, A. P.  1984.   Health Effects Criteria for  Fresh Recreational
     Waters.  U.S. Environmental Protection Agency,  Cincinnati, OH.
     EPA 600/1-84-004

17.  Cabelli, V. J.  1983.  Water-borne Viral Infections.   In:  Viruses
     and Disinfection of Water and Wastewater.  Eds. M. Butler, A.  R.
     Medlen, and R. Morris.  University of Surrey, Surrey,  England.

1R.  Cabelli, V. J.  1976.  Indicators of Recreational Water Quality.
     In:  Bacterial Indicators/Health Hazards Associated with Water.
     Eds. A. W. Hoadley and 8. J. Dutka.- .ASTM, Philadelphia, PA.

19.  Cabelli, V. J.  1982.  Microbial Indicator Systems for Assessing
     Water Quality.  Antonie van Leeuwenhoek.  48:613.

20.  Cabelli, V. J.  1981.  Epidemiology of Enteric Viral Infections.
     In:  Viruses and Wastewater Treatment.  Eds. M. Goddard, and M.
     Butler.  Pergamon Press, New York.  p. 291.

21.  Dufour, A. P.   1976.  E. coli;  The Fecal Coliform.  In:  Bacterial
     Indicators/Health HazaFds Associated with Water.  Eds. A. W. Hoadley,
     and; B. J. Dutka.  ASTM, Philadelphia, PA.  p.  48.

22.  Fattal, B., R. J. Vasl, E. Katzenelson, and  H. I. Shuval.   1983.
     Survival  of Bacterial Indicator Organisms and  Enteric Viruses in the
     Mediterranean Coastal Waters Off Tel-Aviv.   Water Res.  17:397.

23.  Levin, M. A., J. R.  Fischer, and V. J.  Cabelli.   1975.  Membrane
     Filter Technique for Enumeration of Enterococci  in Marine Waters.
     Appl.  Microbiol.  30:66.

24.  Dufour, A. P.,  E. R. Strickland,  and V. J.  Cabelli.   1981.  _Membrane
     Filter Method for Enumerating  Escherichia coli.   Appl.   Environ.
     Microbiol.   41:1152.

25.  American Public Health Association.  1975.   Standard  Methods  for the
     Examination of Water and Wastewater.  14th Ed.  Washington, DC.

 26.  ASTM.   1951.  Manual on Quality Control of Materials.  Special Tech-
     nical Publication 15-C, American Society for Testing and Materials,
     Philadelphia, PA.
                                   - 18 -

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