-
Visit the National Academies Press online, the authoritative
source for all books from the National Academy of Sciences, the
National Academy of Engineering, the Institute of Medicine, and the
National Research Council: • Download hundreds of free books in PDF
• Read thousands of books online for free • Explore our innovative
research tools – try the “Research Dashboard” now! • Sign up to be
notified when new books are published • Purchase printed books and
selected PDF files
Thank you for downloading this PDF. If you have comments,
questions or just want more information about the books published
by the National Academies Press, you may contact our customer
service department toll-free at 888-624-8373, visit us online, or
send an email to [email protected]. This book plus thousands more
are available at http://www.nap.edu. Copyright © National Academy
of Sciences. All rights reserved. Unless otherwise indicated, all
materials in this PDF File are copyrighted by the National Academy
of Sciences. Distribution, posting, or copying is strictly
prohibited without written permission of the National Academies
Press. Request reprint permission for this book.
ISBN: 0-309-55400-4, 948 pages, 6 x 9, (1977)
This PDF is available from the National Academies Press
at:http://www.nap.edu/catalog/1780.html
http://www.nap.edu/catalog/1780.html
We ship printed books within 1 business day; personal PDFs are
available immediately.
Drinking Water and Health, Volume 1
Safe Drinking Water Committee, National Research Council
http://www.nap.edu/catalog/1780.htmlhttp://www.nap.eduhttp://www.nas.edu/nashttp://www.nae.eduhttp://www.iom.eduhttp://www.nationalacademies.org/nrc/http://lab.nap.edu/nap-cgi/dashboard.cgi?isbn=0309068371&act=dashboardhttp://www.nap.edu/agent.htmlhttp://www.nap.edumailto:[email protected]://www.nap.eduhttp://www.nap.edu/v3/makepage.phtml?val1=reprinthttp://www.nap.edu/catalog/1780.html
-
Drinking Water andHealth
Safe Drinking Water CommitteeAdvisory Center on Toxicology
Assembly of Life SciencesNational Research Council
NATIONAL ACADEMY OF SCIENCESWashington, D.C. 1977
i
Abou
t thi
s PD
F fil
e: T
his
new
dig
ital r
epre
sent
atio
n of
the
orig
inal
wor
k ha
s be
en re
com
pose
d fro
m X
ML
files
cre
ated
from
the
orig
inal
pap
er b
ook,
not
from
the
orig
inal
type
setti
ng fi
les.
Pag
e br
eaks
are
true
to th
e or
igin
al; l
ine
leng
ths,
wor
d br
eaks
, hea
ding
sty
les,
and
oth
er ty
pese
tting
-spe
cific
form
attin
g, h
owev
er, c
anno
t be
reta
ined
,an
d so
me
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted.
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion.
Copyright © National Academy of Sciences. All rights
reserved.
Drinking Water and Health, Volume
1http://www.nap.edu/catalog/1780.html
http://www.nap.edu/catalog/1780.html
-
NOTICE: The project that is the subject of this report was
approved by the Governing Board of theNational Research Council,
whose members are drawn from the Councils of the National Academyof
Sciences, the National Academy of Engineering, and the Institute of
Medicine. The members ofthe Committee responsible for the report
were chosen for their special competences and with regardfor
appropriate balance.
This report has been reviewed by a group other than the authors
according to proceduresapproved by a Report Review Committee
consisting of members of the National Academy of Sci-ences, The
National Academy of Engineering and the Institute of Medicine.At
the request of and funded by the U.S. Enviornmental Protection
Agency Contract no. 68-01-3139
Library of Congress Catalog Card Number: 77-089284International
Standard Book Number: 0-309-02619-9Available fromPrinting and
Publishing OfficeNational Academy of Sciences2101 Constitution
Ave.Washington, D.C. 20418
Printed in the United States of AmericaFirst Printing, November
1977Second Printing, July 1980Third Printing, September 1982Fourth
Printing, July 1983Fifth Printing, October 1984Sixth Printing,
September 1985Seventh Printing, January 1987Eighth Printing, May
1988
ii
Abou
t thi
s PD
F fil
e: T
his
new
dig
ital r
epre
sent
atio
n of
the
orig
inal
wor
k ha
s be
en re
com
pose
d fro
m X
ML
files
cre
ated
from
the
orig
inal
pap
er b
ook,
not
from
the
orig
inal
type
setti
ng fi
les.
Pag
e br
eaks
are
true
to th
e or
igin
al; l
ine
leng
ths,
wor
d br
eaks
, hea
ding
sty
les,
and
oth
er ty
pese
tting
-spe
cific
form
attin
g, h
owev
er, c
anno
t be
reta
ined
,an
d so
me
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted.
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion.
Copyright © National Academy of Sciences. All rights
reserved.
Drinking Water and Health, Volume
1http://www.nap.edu/catalog/1780.html
http://www.nap.edu/catalog/1780.html
-
Contents
Preface v
Historical Note 1
I Approach to the Study 9
II Chemical Containmants: Safety and Risk Assessment 19
III Microbiology of Drinking Water 63
IV Solid Particles in Suspension 135
V Inorganic Solutes 205
VI Organic Solutes 489
VII Radioactivity in Drinking Water 857
Appendixes
A Legislation and Terms of Reference of the Study 905
B List of Participants 911
C Executive Summary 917
CONTENTS iii
Abou
t thi
s PD
F fil
e: T
his
new
dig
ital r
epre
sent
atio
n of
the
orig
inal
wor
k ha
s be
en re
com
pose
d fro
m X
ML
files
cre
ated
from
the
orig
inal
pap
er b
ook,
not
from
the
orig
inal
type
setti
ng fi
les.
Pag
e br
eaks
are
true
to th
e or
igin
al; l
ine
leng
ths,
wor
d br
eaks
, hea
ding
sty
les,
and
oth
er ty
pese
tting
-spe
cific
form
attin
g, h
owev
er, c
anno
t be
reta
ined
,an
d so
me
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted.
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion.
Copyright © National Academy of Sciences. All rights
reserved.
Drinking Water and Health, Volume
1http://www.nap.edu/catalog/1780.html
http://www.nap.edu/catalog/1780.html
-
CONTENTS iv
Abou
t thi
s PD
F fil
e: T
his
new
dig
ital r
epre
sent
atio
n of
the
orig
inal
wor
k ha
s be
en re
com
pose
d fro
m X
ML
files
cre
ated
from
the
orig
inal
pap
er b
ook,
not
from
the
orig
inal
type
setti
ng fi
les.
Pag
e br
eaks
are
true
to th
e or
igin
al; l
ine
leng
ths,
wor
d br
eaks
, hea
ding
sty
les,
and
oth
er ty
pese
tting
-spe
cific
form
attin
g, h
owev
er, c
anno
t be
reta
ined
,an
d so
me
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted.
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion.
Copyright © National Academy of Sciences. All rights
reserved.
Drinking Water and Health, Volume
1http://www.nap.edu/catalog/1780.html
http://www.nap.edu/catalog/1780.html
-
Preface
This volume presents the findings of a study of the potentially
harmfuleffects that impurities in water may have on the health of
those who drink it. Thestudy was conducted by the Committee on Safe
Drinking Water of the NationalResearch Council, supported by a
contract between the Environmental ProtectionAgency and the
National Academy of Sciences.
Several factors combined to place an unusually heavy burden on
all thosewho participated in this effort. At the outset, the
purpose, scope, and duration ofthe study were defined in the Safe
Drinking Water Act of 1974 in such a way asto require the
Administrator of the Environmental Protection Agency not only
toarrange for the study to be performed, but to make prompt use of
the findings asthe scientific basis for revision or ratification of
the Interim Primary DrinkingWater Regulations that were promulgated
under the Act. These requirements, ofnecessity, imposed a severe
restriction on the time available to the participants. Itwas also
apparent that the application of modern methods of analysis had
greatlyexpanded and diversified our knowledge of the occurrence of
trace impurities inwater and was continuing to do so much more
rapidly than the rate ofaccumulation of information about their
toxicity. This necessitated a careful andlaborious scrutiny of a
large and diverse segment of the scientific literature.Furthermore,
the central effort of the study, namely, assessment of the
long-termbiological effects of ingesting the variety of different
materials that are present intrace amounts in drinking water, made
severe demands on our ability to apply the
PREFACE v
Abou
t thi
s PD
F fil
e: T
his
new
dig
ital r
epre
sent
atio
n of
the
orig
inal
wor
k ha
s be
en re
com
pose
d fro
m X
ML
files
cre
ated
from
the
orig
inal
pap
er b
ook,
not
from
the
orig
inal
type
setti
ng fi
les.
Pag
e br
eaks
are
true
to th
e or
igin
al; l
ine
leng
ths,
wor
d br
eaks
, hea
ding
sty
les,
and
oth
er ty
pese
tting
-spe
cific
form
attin
g, h
owev
er, c
anno
t be
reta
ined
,an
d so
me
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted.
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion.
Copyright © National Academy of Sciences. All rights
reserved.
Drinking Water and Health, Volume
1http://www.nap.edu/catalog/1780.html
http://www.nap.edu/catalog/1780.html
-
contemporary knowledge of toxicology and epidemiology to
quantitativeestimation of the risks to public health in terms that
would be useful in framingregulations. In recognition of these
limitations, it was concluded that the intent ofCongress and the
possibilities inherent in the body of scientific knowledge onwhich
we could draw could best be reconciled in terms of the
interpretation of thescope of the study given in Appendix A.
To carry out the work of the study, the principal subdivisions
of the subjectmatter were assigned to subcommittees, each of which
was chaired by a memberof the Safe Drinking Water Committee, which,
in turn, was responsible for thegeneral direction of the study (see
Appendix B). We are most grateful to all thosemembers of the
scientific community who served on these committees, meetingas
frequently as the task required, and whose written contributions
form the basisfor this report.
It is a pleasure also to express, on behalf of the entire study
group, a specialnote of thanks to the staff: Dr. Riley D.
Housewright, Mr. J. P. T. Pearman, Dr.Robert Golden, Mrs. Susan
Chen, and Mr. Ralph C. Wands, whose informed andtireless efforts
ably supported the committees, not only in the planning andconduct
of the study, but also by procuring the various bibliographic
andconsulting services that proved to be required. In this
connection we are gratefulto the International Agency for Research
on Cancer for helping to assess thepotential carcinogenicity of
organic compounds found in drinking water; and toMs. Libbey Smith,
Ms. Judith L. Mullaney, Ms. Florence Carleton, Dr. PenelopeCrisp,
and Dr. Lana Skirboll, all of whom assisted in an extensive search
of thescientific literature.
We acknowledge with gratitude the assistance of all those
outsideconsultants who supplied information for our consideration,
and the help of manymembers of the staff of the Environmental
Protection Agency, especially Dr.Edgar A. Jeffrey and his
successor, Dr. Joseph Cotruvo, and Dr. Robert Tardiffand Mr. Lee
McCabe, who helped to place at our disposal the
informationavailable within that agency.
Organization of meetings and the labor of preparing manuscripts
was madeeasier by the dedicated secretarial services of Mrs.
Delores Banks, Ms. HelenHarvin, Mrs. Merle Morgan, and Ms. Carol
Fisher.
Last, but not least, we thank the members of the public who took
the troubleto submit suggestions for our consideration and
expressed to us their views andconcerns at our public meetings.
GERARD A. ROHLICH, CHAIRMANSAFE DRINKING WATER COMMITTEE
PREFACE vi
Abou
t thi
s PD
F fil
e: T
his
new
dig
ital r
epre
sent
atio
n of
the
orig
inal
wor
k ha
s be
en re
com
pose
d fro
m X
ML
files
cre
ated
from
the
orig
inal
pap
er b
ook,
not
from
the
orig
inal
type
setti
ng fi
les.
Pag
e br
eaks
are
true
to th
e or
igin
al; l
ine
leng
ths,
wor
d br
eaks
, hea
ding
sty
les,
and
oth
er ty
pese
tting
-spe
cific
form
attin
g, h
owev
er, c
anno
t be
reta
ined
,an
d so
me
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted.
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion.
Copyright © National Academy of Sciences. All rights
reserved.
Drinking Water and Health, Volume
1http://www.nap.edu/catalog/1780.html
http://www.nap.edu/catalog/1780.html
-
vii
Abou
t thi
s PD
F fil
e: T
his
new
dig
ital r
epre
sent
atio
n of
the
orig
inal
wor
k ha
s be
en re
com
pose
d fro
m X
ML
files
cre
ated
from
the
orig
inal
pap
er b
ook,
not
from
the
orig
inal
type
setti
ng fi
les.
Pag
e br
eaks
are
true
to th
e or
igin
al; l
ine
leng
ths,
wor
d br
eaks
, hea
ding
sty
les,
and
oth
er ty
pese
tting
-spe
cific
form
attin
g, h
owev
er, c
anno
t be
reta
ined
,an
d so
me
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted.
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion. Drinking Water and
Health
Copyright © National Academy of Sciences. All rights
reserved.
Drinking Water and Health, Volume
1http://www.nap.edu/catalog/1780.html
http://www.nap.edu/catalog/1780.html
-
viii
Abou
t thi
s PD
F fil
e: T
his
new
dig
ital r
epre
sent
atio
n of
the
orig
inal
wor
k ha
s be
en re
com
pose
d fro
m X
ML
files
cre
ated
from
the
orig
inal
pap
er b
ook,
not
from
the
orig
inal
type
setti
ng fi
les.
Pag
e br
eaks
are
true
to th
e or
igin
al; l
ine
leng
ths,
wor
d br
eaks
, hea
ding
sty
les,
and
oth
er ty
pese
tting
-spe
cific
form
attin
g, h
owev
er, c
anno
t be
reta
ined
,an
d so
me
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted.
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion.
Copyright © National Academy of Sciences. All rights
reserved.
Drinking Water and Health, Volume
1http://www.nap.edu/catalog/1780.html
http://www.nap.edu/catalog/1780.html
-
Historical Note
As noted by Baker (1949), the quest for pure water began in
prehistorictimes. Recorded knowledge of water treatment is found in
Sanskrit medical loreand in Egyptian inscriptions. Pictures of
apparatus to clarify liquids (both waterand wine) have been found
on Egyptian walls dating back to the fifteenth centuryB.C. Boiling
of water, the use of wick siphons, filtration through porous
vessels,and even filtration with sand and gravel, as means to
purify water, are methodsthat have been prescribed for thousands of
years. In his writings on publichygiene, Hippocrates (460-354 B.C.)
directed attention principally to theimportance of water in the
maintenance of health, but he also prescribed that rainwater should
be boiled and strained. The cloth bag that he recommended
forstraining became known in later times as "Hippocrates'
sleeve."
Public water supplies, already developed in ancient times,
assumed addedimportance with the progressive increase in
urbanization. But though they wereclearly beneficial in
distributing water of uniform quality, large numbers ofpeople ran
the risk of suffering adverse effects when the water was unsafe
todrink.
The first clear proof that public water supplies could be a
source of infectionfor humans was based on careful epidemiological
studies of cholera in the city ofLondon by Dr. John Snow in 1854
(Snow, 1855). Although Snow's study of thecontaminated Broad Street
pump is the most famous, his definitive workconcerned the spread of
cholera through water supplied by the Southwark andVauxhall Company
and the
HISTORICAL NOTE 1
Abou
t thi
s PD
F fil
e: T
his
new
dig
ital r
epre
sent
atio
n of
the
orig
inal
wor
k ha
s be
en re
com
pose
d fro
m X
ML
files
cre
ated
from
the
orig
inal
pap
er b
ook,
not
from
the
orig
inal
type
setti
ng fi
les.
Pag
e br
eaks
are
true
to th
e or
igin
al; l
ine
leng
ths,
wor
d br
eaks
, hea
ding
sty
les,
and
oth
er ty
pese
tting
-spe
cific
form
attin
g, h
owev
er, c
anno
t be
reta
ined
,an
d so
me
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted.
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion.
Copyright © National Academy of Sciences. All rights
reserved.
Drinking Water and Health, Volume
1http://www.nap.edu/catalog/1780.html
http://www.nap.edu/catalog/1780.html
-
Lambeth Company. The former obtained its water from the Thames
at Battersea,in the middle of London in an area almost certainly
polluted with sewage,whereas the Lambeth Company obtained its water
considerably upstream on theThames, above the major sources of
pollution. In one particular area served bythese two companies,
containing about 300,000 residents, the pipes of bothcompanies were
laid in the streets, and houses were connected to one or the
othersources of supply. Snow's examination of the statistics of
cholera deaths gavestriking results. Those houses served by the
Lambeth Company had a lowincidence of cholera, lower than the
average for the population of London as awhole, whereas those
served by the Southwark and Vauxhall Company had a veryhigh
incidence. As the socioeconomic conditions, climate, soil, and all
otherfactors were identical for the populations served by the two
companies, Snowconcluded that the water supply was transmitting the
cholera agent. Snow'sstudy, a classic in the field of epidemiology,
is even more impressive when it isrealized that at the time he was
working, the germ theory of disease had not yetbeen
established.
During the seventeenth to the early nineteenth centuries, a
number ofimprovements in water supply were made, most of them
related to improvementsin filtration to remove the turbidity of
waters. During this same period, the germtheory of disease became
firmly established as a result of research by LouisPasteur, Robert
Koch, and others, and in 1884 Koch isolated the causal agent
ofcholera, Vibrio cholera.
Importance of Water FiltrationIn 1892, a study of cholera by
Koch in the German cities of Hamburg and
Altona provided some of the best evidence of the importance of
water filtrationfor protection against this disease (Koch, 1894).
The cities of Hamburg andAltona both received their drinking water
from the Elbe River, but Altona usedfiltration, since its water was
taken from the Elbe below the city of Hamburg andhence was more
grossly contaminated. Hamburg and Altona are contiguouscities, and
in some places the border between the two follows a contorted
course.Koch traced the incidence of cholera in the 1892 epidemic
through these twocities, with special attention directed to the
contiguous areas. In such areas it wasassumed that climate, soil,
and other factors would be identical, the principalvariable being
the source of water. The results of this study were
dear-cut:Altona, even with an inferior water source, had a markedly
lower incidence ofcholera than Hamburg. Since by this time it was
well established that cholera wascaused by intestinal bacteria
excreted in
HISTORICAL NOTE 2
Abou
t thi
s PD
F fil
e: T
his
new
dig
ital r
epre
sent
atio
n of
the
orig
inal
wor
k ha
s be
en re
com
pose
d fro
m X
ML
files
cre
ated
from
the
orig
inal
pap
er b
ook,
not
from
the
orig
inal
type
setti
ng fi
les.
Pag
e br
eaks
are
true
to th
e or
igin
al; l
ine
leng
ths,
wor
d br
eaks
, hea
ding
sty
les,
and
oth
er ty
pese
tting
-spe
cific
form
attin
g, h
owev
er, c
anno
t be
reta
ined
,an
d so
me
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted.
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion.
Copyright © National Academy of Sciences. All rights
reserved.
Drinking Water and Health, Volume
1http://www.nap.edu/catalog/1780.html
http://www.nap.edu/catalog/1780.html
-
large numbers in the feces, it was concluded that the role of
filtration was toremove the contaminating bacteria from the
water.
In the United States, cholera was not a problem after the
mid-nineteenthcentury; the waterborne disease of particular concern
was typhoid fever. InEngland, William Budd had shown by the
mid-nineteenth century that typhoidfever was a contagious disease,
and the causal agent was isolated and identifiedby Eberth in 1880
and Gaffky in 1884 (Wilson and Miles, 1957). Although thecausal
agent, now called Salmonella typhi, is transmitted in a variety of
ways, oneof the most significant is by drinking water.
Experiments on water filtration were carried out in the United
States duringthe late 1880's and early 1890's, notably by the
Massachusetts State Board ofHealth experiment station established
in 1887 at the city of Lawrence. At thisstation the treatment of
water as well as sewage was considered by aninterdisciplinary group
that included engineers, chemists, and biologists. A leaderin this
work was W. T. Sedgwick, a professor at the Massachusetts Institute
ofTechnology (MIT), and MIT's influence on water-supply research
remainedstrong throughout the first quarter of the twentieth
century. Much of the historyof this work has been reviewed by
Whipple (1921) and in the two editions ofHazen's book (1907, 1914);
the technical aspects are discussed and clearlyillustrated by
Johnson (1913). One important technological advance that madewater
filtration adaptable even to rather turbid sources of water was the
use ofchemical-coagulation filtration processes, patented about
1884 by the brothers J.W. and I. S. Hyatt.
While the Lawerence experiments were going on, an epidemic of
typhoidswept through the city, hitting especially hard at those
parts that were using theMerrimac River as its water supply. As a
result, the city of Lawrence built a sandfilter, and its use led a
marked reduction in the typhoid fever incidence. Asreported by
Hazen (1907), the death rate from typhoid fever in Lawrence
dropped79% when the 5-yr periods before and after the introduction
of the filter werecompared. Of additional interest was a reduction
in the general death rate (allcauses) of 10%, from 22.4 to 19.9 per
1,000 living.
Another major series of filtration experiments were made in
1895-1897 atLouisville, Ky., where the source of water was the
muddy and polluted OhioRiver. These experiments were successful,
and from an engineering point of viewwere of importance because
they showed that it was possible to treat sourcewaters of a rather
poor quality (the Merrimac River at Lawrence may have beenpolluted,
but at least it was a clear water, making filtration rather
easier.) Thesuccess of the Louisville experiments and the other
studies led to rapidestablishment of filters as a
HISTORICAL NOTE 3
Abou
t thi
s PD
F fil
e: T
his
new
dig
ital r
epre
sent
atio
n of
the
orig
inal
wor
k ha
s be
en re
com
pose
d fro
m X
ML
files
cre
ated
from
the
orig
inal
pap
er b
ook,
not
from
the
orig
inal
type
setti
ng fi
les.
Pag
e br
eaks
are
true
to th
e or
igin
al; l
ine
leng
ths,
wor
d br
eaks
, hea
ding
sty
les,
and
oth
er ty
pese
tting
-spe
cific
form
attin
g, h
owev
er, c
anno
t be
reta
ined
,an
d so
me
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted.
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion.
Copyright © National Academy of Sciences. All rights
reserved.
Drinking Water and Health, Volume
1http://www.nap.edu/catalog/1780.html
http://www.nap.edu/catalog/1780.html
-
means of water purification; by 1907 Hazen could list 33 cities
in the UnitedStates, some of comparatively large size, which were
using mechanical filters,and 13 cities that were using slow sand
filters. As discussed by Hazen, filtrationled to an elimination of
turbidity and color from the water, and to a removal ofabout 99% of
the bacteria present. At that time these conditions were
consideredas a standard by which the quality of a treated water
should be judged. As Hazenstates: "There is no final reason for
such standards. They have been adopted byconsent because they
represent a purification that is reasonably satisfactory andthat
can be reached at a cost which is not burdensome to those who have
to payfor it . . .. There is no evidence that the germs
(characteristic of sewage pollution)so left in the water are in any
way injurious. Certainly if injurious influence isexercised it is
too small to be determined or measured by any methods now at
ourdisposal." This last statement is of considerable importance
when considered inthe light of the important advance in water
purification practice yet to come,chlorination.
An excellent overview of the relationship between water quality
and typhoidfever incidence was published at about this time by
Fuertes (1897). He gatheredtyphoid fever statistics for a large
number of cities in North America and Europeand grouped the data by
type of source water and water treatment.
Chlorination, The Most Significant Advance in WaterTreatment
Although a reading of Hazen's 1907 book might lead one to
conclude thatexcellent water quality had been well established by
filtration, the most importanttechnological advance in water
treatment was yet to come. The introduction ofchlorination after
1908 provided a cheap, reproducible method of ensuring
thebacteriological quality of water. Chlorination has come down to
us today as oneof the major factors ensuring safety of our drinking
water.
Calcium hypochlorite was manufactured industrially for use as a
bleachingpowder and was used in paper mills and textile industries.
It was a cheapchemical, and hence readily adaptable to use on the
large scale necessary fordrinking water. The first practical
demonstration in the United States of its use inwater supply was at
the filter plant of the Chicago Stock Yards, where it wasintroduced
by Johnson in the fall of 1908 (Johnson, 1913).
The use of chlorination in an urban water supply was introduced
in JerseyCity, N.J., in the latter part of 1908. The circumstances
surrounding the JerseyCity case are of some interest from a
historical point of view and will be brieflyreviewed. Jersey City
received its water from a
HISTORICAL NOTE 4
Abou
t thi
s PD
F fil
e: T
his
new
dig
ital r
epre
sent
atio
n of
the
orig
inal
wor
k ha
s be
en re
com
pose
d fro
m X
ML
files
cre
ated
from
the
orig
inal
pap
er b
ook,
not
from
the
orig
inal
type
setti
ng fi
les.
Pag
e br
eaks
are
true
to th
e or
igin
al; l
ine
leng
ths,
wor
d br
eaks
, hea
ding
sty
les,
and
oth
er ty
pese
tting
-spe
cific
form
attin
g, h
owev
er, c
anno
t be
reta
ined
,an
d so
me
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted.
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion.
Copyright © National Academy of Sciences. All rights
reserved.
Drinking Water and Health, Volume
1http://www.nap.edu/catalog/1780.html
http://www.nap.edu/catalog/1780.html
-
private company that used a large reservoir at Boonton, an
impoundment of theRockaway River. The water was supplied to the
city unfiltered, although somesettling took place in the reservoir.
Several years before 1908 the city raised thecontention that the
water being supplied was not at all times pure and wholesomefor
drinking, as was required by the terms of its contract with the
privatecompany. At certain times of the year, the water in the
reservoir became pollutedas a result of sewage influx from
communities on the river above the reservoir.Rather than undergo
the expense of a filtration plant, or attempt to control thesewage
influx from the various communities, the private company chose
tointroduce a chlorination system. The results were dramatic. A
marked drop intotal bacterial count was obtained, and at a cost far
lower than any otherprocedure. After many months of operation,
further testimony before the courtwas held, to determine whether
the company was meeting its contract, and thecourt decided that the
evidence was favorable to the company. As stated by thecourt
examiner: ''I do therefore find and report that this device
[chlorination] iscapable of rendering the water delivered to Jersey
City pure and wholesome forthe purposes for which it is intended
and is effective in removing from the waterthose dangerous germs
which were deemed by the decree to possibly exist thereinat certain
times.''
The dramatic effect that chlorination had on water-supply
problems is wellillustrated by comparing the first and second
editions of Hazen's book (1907 and1914). In the first edition,
barely any mention of disinfection is made (merely aremark about
ozone being too expensive), but in the second edition Hazen
waxesenthusiastic about the advantages of chlorination. As he says,
chlorination couldbe used "at a cost so low that it could be used
in any public waterworks plantwhere it was required or advantageous
. . .. When the advantages to be obtainedby this simple and
inexpensive treatment became realized, as a result of thepublicity
given by the Jersey City experience, the use of the process
extendedwith unprecedented rapidity, until at the present (1914)
the greater part of thewater supplied in cities in the United
States is treated in this way or by somesubstitute and equivalent
method."
Interestingly from the point of view of the present report, the
introduction ofchlorination also changed markedly the established
ideas about water-qualitystandards: "The use of methods of
disinfection has changed these standardsradically. By their use it
has been found possible to remove most of the remainingbacteria so
that the water supplied can be as easily and certainly held within
one-tenth of one percent of those in the raw water, as it formerly
could be held withinone percent . . . . Even today the limit has
not been reached. It may be admittedthat the
HISTORICAL NOTE 5
Abou
t thi
s PD
F fil
e: T
his
new
dig
ital r
epre
sent
atio
n of
the
orig
inal
wor
k ha
s be
en re
com
pose
d fro
m X
ML
files
cre
ated
from
the
orig
inal
pap
er b
ook,
not
from
the
orig
inal
type
setti
ng fi
les.
Pag
e br
eaks
are
true
to th
e or
igin
al; l
ine
leng
ths,
wor
d br
eaks
, hea
ding
sty
les,
and
oth
er ty
pese
tting
-spe
cific
form
attin
g, h
owev
er, c
anno
t be
reta
ined
,an
d so
me
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted.
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion.
Copyright © National Academy of Sciences. All rights
reserved.
Drinking Water and Health, Volume
1http://www.nap.edu/catalog/1780.html
http://www.nap.edu/catalog/1780.html
-
time will come when a still higher degree of bacterial
efficiency will be required.Present conditions do not seem to
demand it, but we must expect that in sometime in the future
conditions will arise which will make it necessary. Whenadditional
purification is required it can be furnished." (Hazen, 1914).
The importance of Hazen's book is that Hazen was a major
consultingengineer for a wide variety of water works, and was very
influential inrecommending treatment methods. Chlorination was
introduced at about the timethat adequate methods of
bacteriological examination of water had developed,permitting an
objective evaluation of the efficiency of treatment. This
evaluationwas not based on the incidence of typhoid fever directly,
but was based on anindirect evaluation using bacterial or coliform
counts.
Soon after chlorination was introduced, it was possible to
obtain firmepidemiological evidence that cities chlorinating water
had lowered incidences oftyphoid fever (G. C. Whipple, 1921).
Filtration was introduced in 1906 andchlorination in 1908, and both
led to marked reductions in the incidence oftyphoid fever. Another
dramatic example derives from observations at Wheeling,W.Va., in
1917-1918 (Gainey and Lord, 1952). The incidence of typhoid fever
inWheeling was 155-200 per 100,000 during these years. Chlorination
wasintroduced in the latter part of 1918, with the result that
during the first 3 monthsof 1919 only seven cases were recorded.
For 3 weeks during April 1919chlorination was discontinued, with
the result that the number of cases increasedto 21, or a 300%
increase. Chlorination was continued thereafter, and only 11cases
were recorded for the last 6 months of the year. Other examples of
this sortcould be cited (Gainey and Lord, 1952).
SummaryWe thus see that by the beginning of World War I the
essential features of
water purification techniques were known, and their worth had
been wellestablished. Since that time there have been many
refinements made at anengineering level, but no changes in the
basic concepts. It is clear that the primemotivation for the
development and introduction of purification methods has beento
protect the public health, with special concern for controlling the
spread oftyphoid fever. An ancillary consideration has been
esthetics, showing concern forthe appearance, taste, and odor of
the water.
One point worth emphasizing is that the availability of adequate
treatmentmethods has influenced the standards for drinking water.
This point was impliedin the books by Hazen (1907 and 1914), but is
most
HISTORICAL NOTE 6
Abou
t thi
s PD
F fil
e: T
his
new
dig
ital r
epre
sent
atio
n of
the
orig
inal
wor
k ha
s be
en re
com
pose
d fro
m X
ML
files
cre
ated
from
the
orig
inal
pap
er b
ook,
not
from
the
orig
inal
type
setti
ng fi
les.
Pag
e br
eaks
are
true
to th
e or
igin
al; l
ine
leng
ths,
wor
d br
eaks
, hea
ding
sty
les,
and
oth
er ty
pese
tting
-spe
cific
form
attin
g, h
owev
er, c
anno
t be
reta
ined
,an
d so
me
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted.
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion.
Copyright © National Academy of Sciences. All rights
reserved.
Drinking Water and Health, Volume
1http://www.nap.edu/catalog/1780.html
http://www.nap.edu/catalog/1780.html
-
clearly seen in the preamble to the 1925 Federal Standards,
which superseded thebrief 1914 Standards (see Standard Methods, 7th
edition, 1933, p. 136, for thecomplete 1925 Standards). The
following quote is relevant:
The first step toward the establishment of standards which will
insure the safetyof water supplies conforming to them is to agree
upon some criterion of safety.This is necessary because "safety" in
water supplies, as they are actuallyproduced, is relative and
quantitative, not absolute. Thus, to state that a watersupply is
'safe' does not necessarily signify that absolutely no risk is
everincurred in drinking it. What is usually meant, and all that
can be asserted fromany evidence at hand, is that the danger, if
any, is so small that it cannot bediscovered by available means of
observation. Nevertheless, while it isimpossible to demonstrate the
absolute safety of a water supply, it is wellestablished that the
water supplies of many of our large cities are safe in thesense
stated above, since the large populations using them continuously
have, inrecent years, suffered only a minimal incidence of typhoid
fever and otherpotentially waterborne infections. Whether or not
these water supplies have hadany part whatsoever in the conveyance
of such infections during the periodreferred to is a question that
cannot be answered with full certainty; but the totalincidence of
the diseases has been so low that even though the water supplies
becharged with responsibility for the maximum Share Which may
reasonably besuggested, the risk of infection through them is still
very small compared to theordinary hazards of everyday life.
At present other considerations make it necessary [for us] to be
lessconfident than was the 1925 Committee on Standards. Typhoid
fever and choleraare dramatic diseases whose causal agents are
transmitted by the water route.Typhoid fever statistics have
provided some of the best evidence of the efficacyof treatment
systems, but it should be kept in mind that other diseases, not
soeasily diagnosed, might also be kept under control at the same
time. The so-calledMills-Reincke theorem held that, for every death
from waterborne typhoid, therewere several deaths from other
diseases for which the causal agents weretransmitted by water
(Shipple, 1921). At present, the incidence of typhoid fever inthe
United States is so low that no useful information on the
effectiveness ofrecent changes in water-purification practices can
be obtained from anexamination of the statistics. During the years
1946-1970, there were 53outbreaks of waterborne infectious disease
due to typhoid, but there were 297outbreaks due to other bacterial
or vital agents, including 178 outbreaks ofgastroenteritis of
undetermined etiology (Craun and McCabe, 1973). Of theoutbreaks, 71
percent resulted from contamination of private water systems,
butmost of the illness (83%) was associated with community water
systems. Duringthe period 1946-1960 there were 70 outbreaks of
waterborne disease incommunities served by public utilities (Weibel
et al., 1964), of which only 6 weretyphoid fever. When data
HISTORICAL NOTE 7
Abou
t thi
s PD
F fil
e: T
his
new
dig
ital r
epre
sent
atio
n of
the
orig
inal
wor
k ha
s be
en re
com
pose
d fro
m X
ML
files
cre
ated
from
the
orig
inal
pap
er b
ook,
not
from
the
orig
inal
type
setti
ng fi
les.
Pag
e br
eaks
are
true
to th
e or
igin
al; l
ine
leng
ths,
wor
d br
eaks
, hea
ding
sty
les,
and
oth
er ty
pese
tting
-spe
cific
form
attin
g, h
owev
er, c
anno
t be
reta
ined
,an
d so
me
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted.
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion.
Copyright © National Academy of Sciences. All rights
reserved.
Drinking Water and Health, Volume
1http://www.nap.edu/catalog/1780.html
http://www.nap.edu/catalog/1780.html
-
during this period for the number of outbreaks are examined, the
incidence oftyphoid is even lower—103 cases out of a total of
19,928 (for a percentage of0.5%). Even considering that typhoid is
more likely to be fatal than infectioushepatitis or gastroenteritis
of unknown etiology, the Mills-Reincke theorem doesseem to have
considerable merit. Thus, the rationale that has been used
indevising standards for microbiological contaminants (see
quotation above fromthe 1925 Standards) does not necessarily hold
up on careful examination. Thecoliform standards may have ensured
freedom from typhoid fever, but we do nothave the same assuredness
that they have guaranteed freedom from otherinfections. Even
granted that most of the outbreaks reported have occurredbecause of
breakdowns in the proper functioning of water systems, the
resultsshow that intestinal infections other than typhoid are
common and, because oftheir often ill-defined nature, may be
improperly diagnosed. Finally, only"outbreaks" find their way into
public health statistics, whereas sporadic, randomcases of
gastroenteritis generally go unreported. The epidemiological
significanceof the present microbiological standards warrants
continuing investigation tobring about further refinements in
meeting the goal of maximum protection ofpublic health.
REFERENCESBaker, M.N. 1949. The Quest for Pure Water. Am. Water
Works Assoc., New York.Craun, G.F., and L. J. McCabe. 1973. Review
of the causes of waterborne-disease outbreaks . J. Am.
Water Works Assoc. 65:74.Fumes, J.H. 1897. Water and public
health. John Wiley, New York.Gainey, P.L., and T.H. Lord. 1952.
Microbiology of water and sewage. Prentice-Hall, Inc., New
York.Hazen, A. 1907. Clean water and how to get it, 1st ed. John
Wiley, New York.Hazen, A. 1914. Clean water and how to get it, 2d
ed. John Wiley, New York.Johnson, G.A. 1913. The purification of
public water supplies. U.S. Geol. Surv. Water-Supply Paper
315.Koch, R. 1894. Professor Koch on the Bacteriological
Diagnosis of Cholera, Water-filtration and
Cholera, and the Cholera in Germany during the Winter of
1892-93. Translated by G.Duncan David Douglas, publisher,
Edinburough.
Snow, J. 1855. A reprint of two papers by John Snow, M.D., 1936.
The Commonwealth Fund, NewYork.
Weibel, S.R., F.R. Dixon, R.B. Weidner, and L.J. McCabe. 1964.
Waterborne-disease outbreaks,1946-60. J. Am. Water Works Assoc.
56:947-958.
Whipple, G.C. 1921. Fifty years of water purification. In M.P.
Ravenel, ed. A Half Century of PublicHealth, pp. 161-180. American
Public Health Association, New York. (Reprinted 1970 bythe Arno
Press and the New York Times.)
HISTORICAL NOTE 8
Abou
t thi
s PD
F fil
e: T
his
new
dig
ital r
epre
sent
atio
n of
the
orig
inal
wor
k ha
s be
en re
com
pose
d fro
m X
ML
files
cre
ated
from
the
orig
inal
pap
er b
ook,
not
from
the
orig
inal
type
setti
ng fi
les.
Pag
e br
eaks
are
true
to th
e or
igin
al; l
ine
leng
ths,
wor
d br
eaks
, hea
ding
sty
les,
and
oth
er ty
pese
tting
-spe
cific
form
attin
g, h
owev
er, c
anno
t be
reta
ined
,an
d so
me
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted.
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion.
Copyright © National Academy of Sciences. All rights
reserved.
Drinking Water and Health, Volume
1http://www.nap.edu/catalog/1780.html
http://www.nap.edu/catalog/1780.html
-
I
Approach to the Study
INTRODUCTION
In this chapter the general approach, principles, and criteria
adopted in thestudy are discussed in outline. Considerations that
entered into evaluations of theeffects on health of the various
contaminants of drinking water are described,together with the
reasons for selecting the subjects that were studied. Thefindings
of the study are not summarized comprehensively in this section;
eachsucceeding chapter includes a summary of the relevant
conclusions andrecommendations. A short summary of the principal
conclusions of the study isgiven in Appendix C.
The study was undertaken by the NAS-NRC to meet the needs
expressed inthe Safe Drinking Water Act (PL 93-523), which requires
the EnvironmentalProtection Agency to promulgate national drinking
water standards and, for thefirst time, regulations for enforcing
them. The Act also directs the Administratorof the Environmental
Protection Agency to arrange with the National Academyof Sciences,
or other appropriate organization, to study the adverse effects
onhealth attributable to contaminants in drinking water. Although
the high qualityof drinking water in the United States is
recognized throughout the world, the lawis an expression by the
Congress of the concern of many citizens aboutmaintaining the
quality of public water supplies in this country.
The reader should not equate the size of this report or that of
any of itschapters with the Committee's assessment of the magnitude
of the challenge topublic health that may be due to the presence of
particular
APPROACH TO THE STUDY 9
Abou
t thi
s PD
F fil
e: T
his
new
dig
ital r
epre
sent
atio
n of
the
orig
inal
wor
k ha
s be
en re
com
pose
d fro
m X
ML
files
cre
ated
from
the
orig
inal
pap
er b
ook,
not
from
the
orig
inal
type
setti
ng fi
les.
Pag
e br
eaks
are
true
to th
e or
igin
al; l
ine
leng
ths,
wor
d br
eaks
, hea
ding
sty
les,
and
oth
er ty
pese
tting
-spe
cific
form
attin
g, h
owev
er, c
anno
t be
reta
ined
,an
d so
me
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted.
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion.
Copyright © National Academy of Sciences. All rights
reserved.
Drinking Water and Health, Volume
1http://www.nap.edu/catalog/1780.html
http://www.nap.edu/catalog/1780.html
-
constituents in drinking water in the United States. Several
factors havecontributed to the length of this report: The Safe
Drinking Water Act defined thescope of the study in encyclopedic
terms and consequently the length of some ofthe chapters reflects
the large number of topics and substances that it wasnecessary to
consider. Other chapters deal with subjects that are complex
andabout which there are uncertainties, conflicting opinions, and
inconclusive orincomplete data. The relevant studies, assumptions,
methodologies, healtheffects, and research recommendations for each
group of constituents requireddetailed consideration from several
points of view before balanced judgmentscould be achieved. In some
cases brevity had to be sacrificed to reach thisobjective within a
reasonable time.
The primary purpose of the study was to assess the significance
of theadverse effects that the constituents of drinking water may
have on public health.The economic or technological feasibility of
controlling the concentration ofthese constituents was outside the
scope of the study.
The health effects associated with some methods of disinfection
were noted,but the relative effectiveness and potential hazards
associated with the variousmethods of water disinfection were not
evaluated.
Application of analytical methods of great sensitivity has, in
recent years,expanded our knowledge of the occurrence and diversity
of impurities in drinkingwater. However, information about the
biological results of chronic ingestion, atlow dose rates, of most
of these substances is acquired slowly because thebioassays that
are usually required may take two or more years to
complete.Although new approaches to the problem of estimating
chronic adverse healtheffects may, in the future, ease this
difficulty, the current knowledge on whichthis study is based is
insufficient to assess all the contaminants of drinking water.The
results reported here must therefore be considered as a
contribution to aneffort that should be continued.
Besides the known constituents of drinking water, some were
alsoconsidered that it would be plausible to expect to be present,
even though theyhave not yet been detected in water. (Certain
pesticides used in large quantitiesfall into this category.)
In our review of water constituents, we have attempted to take
into accountnot only their identities, concentrations, and
toxicities, but also to consider otherquestions, such as:
1. What reason is there for concern about the material? What
risks areassociated with its presence in water?
2. How does the material get into water?3. What sources are
there other than water?
APPROACH TO THE STUDY 10
Abou
t thi
s PD
F fil
e: T
his
new
dig
ital r
epre
sent
atio
n of
the
orig
inal
wor
k ha
s be
en re
com
pose
d fro
m X
ML
files
cre
ated
from
the
orig
inal
pap
er b
ook,
not
from
the
orig
inal
type
setti
ng fi
les.
Pag
e br
eaks
are
true
to th
e or
igin
al; l
ine
leng
ths,
wor
d br
eaks
, hea
ding
sty
les,
and
oth
er ty
pese
tting
-spe
cific
form
attin
g, h
owev
er, c
anno
t be
reta
ined
,an
d so
me
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted.
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion.
Copyright © National Academy of Sciences. All rights
reserved.
Drinking Water and Health, Volume
1http://www.nap.edu/catalog/1780.html
http://www.nap.edu/catalog/1780.html
-
4. What contaminants need to be controlled?5. Are there special
places or persons at higher than average risk?6. Are there
essential nutritional requirements for this material?7. In view of
the data at hand, can one say that this is a material that
causes temporary ill effects? Permanent ill-effects?
Reversibleeffects?
8. In view of these effects—and their reversibility (or lack of
it)—is itpossible to set "no-observed-adverse-health-effects"
levels?
9. For materials with special health benefits, what
concentrations willmaximize these benefits, while keeping the
health risk associatedwith them at an acceptably low level?
10. What additional information is required to resolve the
outstandingproblems?
Many of the constituents of drinking water are natural
materials, and enterwater from the rocks and the soil and the air.
Some are the natural waste productsof men or animals. Others are
artificial or synthetic materials, made and used forspecial
purposes, that inadvertently find their way into water. Yet others
occurnaturally, but have become more widely distributed in
populated areas as a resultof industrial and agricultural
activity.
WATER CONSUMPTION
In this study, a quantity of 2 liters per day has been taken to
be the averageamount of water consumed per person. This is also the
amount used by EPA tocalculate the current interim standards. Daily
consumption of water is a functionof temperature, humidity,
physical activity, and other factors that vary widely.The average
per capita water (liquid) consumption per day as calculated from
asurvey of nine different literature sources was 1.63 liters (NAS,
1974; McNalland Schlegal, 1968; Wolf, 1958; Guyton, 1968; Evans,
1941; Bourne and Kidder,1953; Walker et al., 1957; Randall, 1973;
Pike and Brown, 1975). However, thelarger volume of 2 liters/day
was adopted as representing the intake of themajority of water
consumers. We estimate that most of those who consume morethan 2
liters per day still are afforded adequate protection, because the
margin ofsafety estimated for the contaminants is sufficient to
offset excess waterconsumption. Nevertheless, consideration should
be given to establishing somestandards on a regional or
occupational basis, to take extremes of waterconsumption into
account.
APPROACH TO THE STUDY 11
Abou
t thi
s PD
F fil
e: T
his
new
dig
ital r
epre
sent
atio
n of
the
orig
inal
wor
k ha
s be
en re
com
pose
d fro
m X
ML
files
cre
ated
from
the
orig
inal
pap
er b
ook,
not
from
the
orig
inal
type
setti
ng fi
les.
Pag
e br
eaks
are
true
to th
e or
igin
al; l
ine
leng
ths,
wor
d br
eaks
, hea
ding
sty
les,
and
oth
er ty
pese
tting
-spe
cific
form
attin
g, h
owev
er, c
anno
t be
reta
ined
,an
d so
me
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted.
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion.
Copyright © National Academy of Sciences. All rights
reserved.
Drinking Water and Health, Volume
1http://www.nap.edu/catalog/1780.html
http://www.nap.edu/catalog/1780.html
-
RISK AND SAFETY
The hazards of ingesting chemical pollutants in drinking water
have beenassessed in two general ways: with laboratory toxicity
studies andepidemiological studies. The aim of studies of both
types is to provideinformation about the risk to man. Risk
constitutes only half of the equation; theother half is benefit to
the exposed population. It is not possible to guarantee arisk-free
society. The scientific methods and criteria we have used for
evaluatinglong-term effects and risks in man are described in
Chapter II, "ChemicalContaminants: Safety and Risk Assessment" and
in the chapters concerning eachgroup of contaminants.
Most of the experimental results on which the current knowledge
of toxicityrests are based on observed effects on man and animals
of doses and dose ratesthat are much larger than those that
correspond to the usual concentrations ofharmful materials in
drinking water. There is, consequently, great uncertainty
inestimating the magnitude of the risk to health that ingestion of
contaminants inwater may produce. An additional problem is to take
into account the combinedeffects of two or more contaminants.
The theoretical and experimental bases for extrapolating
estimations of riskto low levels of dose have been reviewed, and
some principles are proposed toguide the conduct of this and
similar studies.
MICROBIOLOGICAL CONTAMINANTS
Outbreaks of waterborne disease are reported to the National
Center forDisease Control (CDC) by state health departments. In
addition, EPA obtainsinformation about additional outbreaks from
state water-supply agencies. BothCDC and EPA are aware that data on
waterborne outbreaks have limitations andmust be interpreted with
caution. The data collected represent only a small part of alarger
public health problem. The number and kind of reported outbreaks
and ofsome etiologies may depend upon the interest or capabilities
of a particular statehealth department or individual. They do not
reflect the actual number ofoutbreaks, cases, or etiologies of
disease associated with drinking water.
Many small outbreaks are not reported to state health
departments. There isno law or regulation requiring state
authorities to report all gastroenteritis cases toCDC. In 1975, CDC
reported 24 waterborne disease outbreaks involving 10,879cases. No
etiologic agent was found for the two largest outbreaks
(Sewickley,Pa., 5,000 cases and Sellersburg,
APPROACH TO THE STUDY 12
Abou
t thi
s PD
F fil
e: T
his
new
dig
ital r
epre
sent
atio
n of
the
orig
inal
wor
k ha
s be
en re
com
pose
d fro
m X
ML
files
cre
ated
from
the
orig
inal
pap
er b
ook,
not
from
the
orig
inal
type
setti
ng fi
les.
Pag
e br
eaks
are
true
to th
e or
igin
al; l
ine
leng
ths,
wor
d br
eaks
, hea
ding
sty
les,
and
oth
er ty
pese
tting
-spe
cific
form
attin
g, h
owev
er, c
anno
t be
reta
ined
,an
d so
me
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted.
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion.
Copyright © National Academy of Sciences. All rights
reserved.
Drinking Water and Health, Volume
1http://www.nap.edu/catalog/1780.html
http://www.nap.edu/catalog/1780.html
-
Ind., 1,400 cases). In fact, no etiologic agent was identified
in 17 of the 24outbreaks. These 17 outbreaks accounted for 9,760
cases, or 89%, of the totalreported in 1975.
Conclusions in the microbiology chapter, based on
epidemiological data, aresubject to the limitations of the
reporting system and to our limited ability toidentify etiologic
agents in outbreaks known to be associated with drinkingwater.
The microbiological contaminants selected for consideration in
this reportare those for which there is epidemiological or clinical
evidence of transmissionby drinking water. They include a variety
of bacteria, viruses, and protozoa.Methods of detecting these
contaminants of drinking water were reviewed, andthe quantitative
relationships between dose levels and infectivity were
examined.Because current drinking water standards place major
emphasis on detection ofmicrobiological contaminants, attention was
devoted to the validity and healthsignificance of microbiological
standards.
PARTICULATE CONTAMINANTS
Finely divided solid particles of mineral and organic
composition arecommonly found suspended in some drinking water,
particularly those suppliesthat do not practice coagulation and
filtration. To discover whether or not thelong-term ingestion of
these materials in water is likely to produce adverseeffects on
human health, their occurrence, composition, and properties
werereviewed.
This review indicated that many kinds of particulate matter may
indirectly,through adsorption, facilitate the transport of toxic
substances and pathogenicorganisms and affect the efficiency of
disinfection. Particles of organiccomposition also may indirectly
give rise to chlorinated compounds by reactionwith chlorine in
water treatment.
Only in the case of particles derived from asbestos minerals,
however, arethere grounds for suspecting that direct effects on
human health could beinvolved. Fibrous particles of asbestos
minerals are known to be associated withincreased incidence of
cancer, including gastrointestinal cancer, among workerswho inhale
asbestos-laden air. Experiments on the inhalation of asbestos
mineralfibers by animals have also demonstrated a carcinogenic
effect. The particulatematter in drinking water often includes
similar particles.
Although epidemiological studies have not indicated an increase
with time incancer death rates that can be ascribed to fibrous
contamination of the drinkingwater, these negative findings do not
exclude the
APPROACH TO THE STUDY 13
Abou
t thi
s PD
F fil
e: T
his
new
dig
ital r
epre
sent
atio
n of
the
orig
inal
wor
k ha
s be
en re
com
pose
d fro
m X
ML
files
cre
ated
from
the
orig
inal
pap
er b
ook,
not
from
the
orig
inal
type
setti
ng fi
les.
Pag
e br
eaks
are
true
to th
e or
igin
al; l
ine
leng
ths,
wor
d br
eaks
, hea
ding
sty
les,
and
oth
er ty
pese
tting
-spe
cific
form
attin
g, h
owev
er, c
anno
t be
reta
ined
,an
d so
me
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted.
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion.
Copyright © National Academy of Sciences. All rights
reserved.
Drinking Water and Health, Volume
1http://www.nap.edu/catalog/1780.html
http://www.nap.edu/catalog/1780.html
-
possibility that such an increase may be detected in the future,
because manycancers have long induction periods.
For these and other reasons, detailed elsewhere, it is believed
to beimportant that research on the analysis of fibrous mineral
particles in water, andon the toxicity of these materials when
ingested, should be strongly pursued.
INORGANIC SOLUTES
The Interim Primary Drinking Water Regulations list maximum
allowableconcentrations for six metallic elements—barium, cadmium,
chromium, lead,mercury, and silver. Ten additional metals were
reviewed in this study—beryllium, cobalt, copper, magnesium,
manganese, molybdenum, nickel, tin,vanadium, and zinc. Sodium,
which is also a metal, was considered separately,because the
problems it poses are quite distinct from those associated with
theother metallic substances. In addition, the effects on health of
several otherinorganic constituents of drinking water were studied.
These include arsenic,selenium, fluoride, nitrate, and sulfate. The
relationship between water hardnessand health also received
attention.
The sources of inorganic ions in groundwater, surface water,
water-treatment chemicals, and from the storage and distribution
system are consideredalong with the health effects resulting from
the total intake from food, air, andwater.
ORGANIC SOLUTES
Of the 298 volatile organic compounds so far identified in
drinking water, 74were selected for detailed study along with 55
pesticides. A compound wasselected for consideration if any of the
following criteria applied:
1. Experimental evidence of toxicity in man or animals,
includingcarcinogenicity, mutagenicity, and teratogenicity.
2. Identified in drinking water at relatively high
concentration.3. Molecular structure closely related to that of
another compound of
known toxicity.4. Pesticide in heavy use; potential contaminant
of drinking water
supplies.5. Listed in the Safe Drinking Water Act or National
Interim Primary
Drinking Water Regulations.
APPROACH TO THE STUDY 14
Abou
t thi
s PD
F fil
e: T
his
new
dig
ital r
epre
sent
atio
n of
the
orig
inal
wor
k ha
s be
en re
com
pose
d fro
m X
ML
files
cre
ated
from
the
orig
inal
pap
er b
ook,
not
from
the
orig
inal
type
setti
ng fi
les.
Pag
e br
eaks
are
true
to th
e or
igin
al; l
ine
leng
ths,
wor
d br
eaks
, hea
ding
sty
les,
and
oth
er ty
pese
tting
-spe
cific
form
attin
g, h
owev
er, c
anno
t be
reta
ined
,an
d so
me
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted.
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion.
Copyright © National Academy of Sciences. All rights
reserved.
Drinking Water and Health, Volume
1http://www.nap.edu/catalog/1780.html
http://www.nap.edu/catalog/1780.html
-
The evaluation of toxicity was based on a critical review of the
scientificliterature. The available data were of variable quality
and quantity and, in someinstances, inadequate for proper
assessment of toxicity. In those cases wheresufficient data were
available, professional judgment was used to determinewhich
compounds are carcinogenic, mutagenic, teratogenic,
andnoncarcinogenic.
The limitations that are inherent in the extrapolation of
high-dose animalbioassay data to low-dose human exposure and the
difficulty of makingpredictions for species that may have different
metabolic rates and pathways forhandling carcinogens, or different
target-organ responses, are well known. Suchrisk assessment and
extrapolation procedures are further compromised by thelimited
information that is available concerning the mechanisms by which
theseagents act (such as initiators, promoters, and modifiers) and
the almost total lackof data regarding the potential synergistic
and antagonistic interactions of theseagents with each other and
with other environmental agents. The risk of ingestingknown or
suspected carcinogens was estimated by the methods described
inChapter II. These methods are based on an assumption that there
is no thresholdin the dose-response relationship. The risk-estimate
approach may provide uniqueadvantages for other areas of
toxicologic evaluation.
The more traditional approach of combining the maximum
no-observed-adverse-effect level with an uncertainty (safety)
factor to calculate an acceptabledaily intake (ADI) was used for
agents that were not considered to be known orsuspected carcinogens
and for which there was adequate toxicity data fromprolonged
ingestion studies in man or animals. Several alternative terms
otherthan ADI were considered, but it was concluded that the
introduction of newterms might lead to confusion and that the use
of a widely recognized andgenerally acceptable term would be
preferable for this report. Although the ADIhas been used
previously as an internationally established standard for
thetoxicological evaluation of food additives and contaminants, the
concept isapplicable to other cases of exposure by ingestion. The
ADI is an empiricallyderived value that reflects a particular
combination of knowledge and uncertaintyconcerning the relative
safety of a chemical. The uncertainty factors used tocalculate ADI
values in this report represent the level of confidence that can
bejustified on the basis of the animal and human toxicity data. ADI
values were notcalculated for agents where the data were considered
to be inadequate.
Since the calculation of the ADI values is based on the total
amount of
APPROACH TO THE STUDY 15
Abou
t thi
s PD
F fil
e: T
his
new
dig
ital r
epre
sent
atio
n of
the
orig
inal
wor
k ha
s be
en re
com
pose
d fro
m X
ML
files
cre
ated
from
the
orig
inal
pap
er b
ook,
not
from
the
orig
inal
type
setti
ng fi
les.
Pag
e br
eaks
are
true
to th
e or
igin
al; l
ine
leng
ths,
wor
d br
eaks
, hea
ding
sty
les,
and
oth
er ty
pese
tting
-spe
cific
form
attin
g, h
owev
er, c
anno
t be
reta
ined
,an
d so
me
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted.
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion.
Copyright © National Academy of Sciences. All rights
reserved.
Drinking Water and Health, Volume
1http://www.nap.edu/catalog/1780.html
http://www.nap.edu/catalog/1780.html
-
a chemical ingested, the ADI values calculated in tiffs report
do not represent thesafe level for drinking water.
Little or no data are available on the toxicity of many organic
compoundsidentified in drinking water. There is a need to determine
which of thesecompounds should be subjected to extensive toxicity
testing. Some of the criteriaused for developing the order in which
compounds should be tested are:
1. The relative concentrations of the compounds and the number
ofpeople likely to be exposed.
2. The number of supplies in which they occur.3. Positive
responses in in vitro mutagen screening systems.4. Positive
responses in in vitro prescreening systems for potential
carcinogens (mammalian cell transformations).5. Similarity of
the chemical structure of the test compound with that of
other compounds having defined toxic properties (i.e.,
structure-activity relationships).
6. Relationships of dose from water to total body burden.
RADIOACTIVE CONTAMINANTS
Because the presence of ionizing radiation is one of the
standard features ofthe earth's surface, the adverse effects on
health that may be ascribed toradioactive contaminants of drinking
water were assessed in relation to theaverage background radiation
dose, from all sources, of 100 mrem per year.
Previous estimations of the biological effects of the background
radiation onhuman health were reviewed in the light of more recent
scientific knowledge andused to calculate the magnitude of three
kinds of adverse health effects thatradiation can produce; namely,
developmental and teratogenic effects on thefetus, genetic disease,
and somatic (principally carcinogenic) effects.
When these estimates are related to the concentrations of
radionuclides thatare commonly found in drinking water, it is seen
that consumption of 2 liters ofwater per day contributes such a
small fraction to the total radiation backgroundthat the incidence
of developmental, teratogenic, and genetic disorders is
notincreased enough for the change to be detectable.
Where somatic effects are concerned, it is estimated that the
radionuclides indrinking water typically account for less than 1%
of the incidence of cancers thatmay be attributed to the natural
background of
APPROACH TO THE STUDY 16
Abou
t thi
s PD
F fil
e: T
his
new
dig
ital r
epre
sent
atio
n of
the
orig
inal
wor
k ha
s be
en re
com
pose
d fro
m X
ML
files
cre
ated
from
the
orig
inal
pap
er b
ook,
not
from
the
orig
inal
type
setti
ng fi
les.
Pag
e br
eaks
are
true
to th
e or
igin
al; l
ine
leng
ths,
wor
d br
eaks
, hea
ding
sty
les,
and
oth
er ty
pese
tting
-spe
cific
form
attin
g, h
owev
er, c
anno
t be
reta
ined
,an
d so
me
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted.
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion.
Copyright © National Academy of Sciences. All rights
reserved.
Drinking Water and Health, Volume
1http://www.nap.edu/catalog/1780.html
http://www.nap.edu/catalog/1780.html
-
radiation. Only certain bone-seeking radionuclides (chiefly
radium), in a fewregions, reach concentrations in drinking water
that are high enough to cause asignificant increase in the
incidence of bone cancer.
SUSCEPTIBLE SUBGROUPS AND OTHER CONSIDERATIONS
Groups that are more susceptible than the normal population are
consideredin the chapters on various classes of contaminants.
This report is concerned only with water used for drinking.
Although allcontaminants may cause problems when present in water
used in health carefacilities, the health hazards associated with
such diverse uses of water as inhumidifiers, kidney dialysis units,
laundries, heating and cooling equipment, ormany special uses that
require further treatment of tap water, have not beenconsidered.
References and summaries of the scientific literature in this field
havebeen published by DeRoos et al. (1974).
REFERENCESBourne, G.H., and G.W. Kidder, eds. 1953. Biochemistry
and Physiology of Nutrition, vol. 1.
Academic Press, New York.DeRoos, R.L., V.R. Oviatt, A.G.
DuChene, and N.J. Vick. 1974. Water use in biomedical research
and health care facilities—A presentation of article summaries.
National Institutes ofHealth, Department of Health, Education, and
Welfare, Contract no. NIH-ORS-72-2111.
Evans, C.L. ed. Starling's Principles of Human Physiology, 8th
ed. Lea and Febiger, Philadelphia.Federal Register, Wednesday,
December 24, 1975, vol. 40, no. 248.Guyton, A.C. 1968. Textbook of
Medical Physiology, 3d ed. W.B. Saunders Co., Philadelphia.McNall,
P.E., and J.C. Schlegel. 1968. Practical thermal environmental
limits for young adult males
working in hot, humid environments. ASHRAE Transactions
74:225-235.National Academy of Sciences-National Research Council.
1974. Recommended Dietary
Allowances, 8th ed. Washington, D.C.Pike, R.L., and M. Brown.
1975. Minerals and Water in Nutrition—An Integrated Approach, 2d
Ed.
John Wiley, New York.Randall, H.T. 1973. Water, electrolytes and
acid base balance. In R.S. Goodhart and M.E. Shils, eds.
Modem Nutrition in Health and Disease. Lea and Febiger,
Philadelphia.Walker, B.S., W.C. Boyd, and I. Asimov. 1957.
Biochemistry and Human Metabolism, 2d ed.
Williams & Wilkins Co., Baltimore.Wolf, A.V. 1958. Body
water. Sci. Am. 99:125.
APPROACH TO THE STUDY 17
Abou
t thi
s PD
F fil
e: T
his
new
dig
ital r
epre
sent
atio
n of
the
orig
inal
wor
k ha
s be
en re
com
pose
d fro
m X
ML
files
cre
ated
from
the
orig
inal
pap
er b
ook,
not
from
the
orig
inal
type
setti
ng fi
les.
Pag
e br
eaks
are
true
to th
e or
igin
al; l
ine
leng
ths,
wor
d br
eaks
, hea
ding
sty
les,
and
oth
er ty
pese
tting
-spe
cific
form
attin
g, h
owev
er, c
anno
t be
reta
ined
,an
d so
me
typo
grap
hic
erro
rs m
ay h
ave
been
acc
iden
tally
inse
rted.
Ple
ase
use
the
prin
t ver
sion
of t
his
publ
icat
ion
as th
e au
thor
itativ
e ve
rsio
n fo
r attr
ibut
ion.
Copyright © National Academy of Sciences. All rights
reserved.
Drinking Water and Health, Volume
1http://www.nap.edu/catalog/1780.html
http://www.nap.edu/catalog/1780.html
-
APPROACH TO THE STUDY 18
Abou
t thi
s PD
F fil
e: T
his
new
dig
ital r
epre
sent
atio
n of
the
orig
inal
wor
k ha
s be
en re
com
pose
d fro
m X
ML
files
cre
ated
from
the
orig
inal
pap
er b
ook,
not
from
the
orig
inal
type
setti
ng fi
les.
Pag
e br
eaks
are
true
to th
e or
igin
al; l
ine
leng
ths,
wor
d br
eaks
, hea
ding
sty
les,
and
oth
er ty
pese
tting
-spe
ci