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OCR for page 137
v
Health implications of
Distribution System
Deficiencies
Although it is not the purpose of this report to review the optimum engi-
neering design. construction, and operation of distribution systems, it is
important to recognize that waterborne diseases may result from inade-
quate attention to any of those areas.
Outbreaks of acute disease associated with contaminated drinking
water are reported to the Centers for Disease Control (CDC) by state
health departments or to the Health Effects Research Laboratory of the
U.S. Environmental Protection Agency (EPA) by state water supply agen-
cies. These reports are made on a voluntary basis. The data are reviewed
and summarized annually by representatives from CDC and EPA.
In the majority of these reports, the etiologic agent is not identified.
However, the clinical and epidemiological evidence suggests that most of
these outbreaks are caused by infectious agents. In many investigations of
outbreaks of unknown etiology, appropriate laboratory specimens are not
collected; in others, sophisticated laboratory procedures required for
identification of some potential etiologic agents are not performed.
Well-documented cases of acute waterborne disease outbreaks in the
United States have implicated bacteria, viruses, and protozoa. Some of
the bacteria (e.g., Salnzo'`ella and Shigella) and the protozoa (e.g. Giar-
dia lamblia and E''tanzoeba histolytica) can be identified by culture or mi-
croscopic examination of stool specimens, respectively. Identification of
some other pathogenic bacteria (e.g., Campylobacter fetus subspecies je-
juni and Yersi''ia enterocolitica) requires the use of special media or incu-
bation conditions that are not available in all laboratories. Identification
of enterotoxigenic Escherichia cold and viral causes of acute gastroenteritis
137
OCR for page 138
138 DRINKING WATER AND HEALTH
(e.g., Norwalk-like agents and rotaviruses) requires the use of very sophis-
ticated laboratory methodology generally accessible only in a research lab-
oratory.
DEFINITIONS
A waterborne disease outbreak is defined by CDC and EPA as an incident
in which (1) two or more persons experience similar illness after consump-
tion or external use of water intended for drinking and (2) epidemiological
evidence implicates water as the source of illness. A single case of acute
chemical poisoning constitutes an outbreak if laboratory studies indicate
that the water is contaminated by the suspect chemical. With the excep-
tion of acute chemical poisoning' data on single cases of acute disease that
might be waterborne are rarely reported to CDC or EPA and are not tabu-
lated.
Municipal or community systems are public or investor-owned water
supplies that serve large or small communities, subdivisions, or trailer
parks with at least 15 service connections or 25 year-round residents.
Semipublic (noncommunity) water systems are those in institutions, in-
dustries, camps, parks, hotels, or service stations that may be used by the
general public. Individual (private water) systems are those used by single
or several residences or by persons such as backpackers who travel outside
populated areas. These definitions correspond to those used in the Safe
Drinking Water Act (PL 93-523~.
ORIGINS OF WATERBORNE DISEASES
Sources of the contamination responsible for the outbreak include un-
treated surface water, untreated groundwater, treatment deficiencies
(e.g., malfunction of a chlorinator), and deficiencies in the distribution
system (e.g., cross-connections). Several well-known outbreaks have been
caused by deficiencies in the distribution system. Examples include a
large outbreak of amebiasis among guests at two Chicago hotels in 1933
(U.S. Treasury Department, Public Health Service, 1936) and infectious
hepatitis in members of a college football team (Morse et al., 1972~. In
both outbreaks, potable water was contaminated as a result of a defect in
the distribution system.
INTERPRETATION OF DATA
One must be cognizant of the limitations of the data pertaining to these
outbreaks in order to avoid inappropriate interpretation. Since some in
OCR for page 139
Health Implications of Distribution System Deficiencies 139
vestigations were incomplete or were conducted long after the outbreak,
the waterborne transmission hypothesis could not always be proven al-
though it was the most logical explanation.
It is known that the reports of outbreaks received by the CDC and EPA
represent only a fraction of those that occur. but the actual extent of these
outbreaks is unknown. The likelihood of an outbreak coming to the atten-
tion of health authorities varies considerably from one locale to another
depending largely upon consumer awareness. physician interest, and dis-
ease surveillance activities of state and local health and environmental
agencies. The sequence of events leading to the reporting of an outbreak is
summarized in Figure V-l, but this sequence can be interrupted at any
stage.
Large interstate outbreaks and outbreaks of serious illness are most
likely to come to the attention of health authorities. On occasion, initial
investigation of a few cases of illness has led to the identification of a large
outbreak. For example, investigation of 10 culture-proven cases of Shi-
gella infection in a Miami suburb in 1974 led to identification of 1,000
cases of waterborne illness (Weissman et al., 1976~.
The number of reported outbreaks of different etiologies may depend
REPORTING OF AN OUTBREAK
I ngesti on
Illness
Physician Visit
Diagnosis
t
Report to Health Department
1
I nvestigation
i
Report to Centers for Disease Control and/or U.S. Environmental Protection Agency
FIGURE V-1 Sequence of events leading to the reporting of an outbreak.
OCR for page 140
140 DRINKING WATER AND HEALTH
upon the interest of a particular health department or individual. In addi-
tion, a few outbreaks involving very large numbers of persons may vastly
alter the relative proportion of cases attributed to various etiologic agents.
For these reasons, the existing data should not be used as the basis for
drawing firm conclusions about the true incidence of waterborne disease
outbreaks or about the relative incidence of waterborne diseases of various
etiologies. Nevertheless, these data can be useful in determining the caus-
ative agents and water system deficiencies that most frequently result in
outbreaks.
More intensive surveillance and prompter reporting of suspected out-
breaks to public health authorities are needed so that more timely and
thorough epidemiological investigations can be conducted. By utilizing re-
cent advances in diagnostic laboratory techniques, such investigations will
increase knowledge of waterborne pathogens, identify factors responsible
for the outbreaks, and provide a better estimate of the true magnitude of
this route of disease transmission.
OUTBREAKS
From 1971 through 1978, 224 outbreaks of waterborne diseases were re-
ported. Of these, 33 (lS
OCR for page 141
Health Implications of Distribution System Deficiencies 141
ciencies had a chemical etiology. In contrast, no outbreaks of giardiasis
were caused by distribution system deficiencies.
The 33 outbreaks attributed to deficiencies in all systems were reported
by 23 different states. Pennsylvania reported the most (5 outbreaks or
into); however, during this period Pennsylvania also reported 44 (into) of
the 191 outbreaks caused by other deficiencies. This observation is con-
sistent with the fact that Pennsylvania reports the largest number of out-
breaks each year. reflecting that state's great interest in outbreaks of
waterborne disease.
The number of outbreaks due to distribution system deficiencies by year
is depicted in Figure V-2. The number of outbreaks involving municipal
systems has remained fairly constant, while the semipublic system out-
breaks were only reported in 1976-1978.
Sewickley, Pennsylvania
During the last 10 days of August 1975, an outbreak of diarrhea! illness
occurred in residents of Sewickley. A community survey indicated that ap-
proximately 60% of the people who obtained their water from the Sewick-
ley municipal system had been ill. The illness occurred much more fre-
quently in persons using water from this system than in those using well
water or water from another, nearby municipal system.
Examination of the water system revealed that no free residual chlorine
was detectable at several points in the distribution system on at least one
of the days on which transmission occurred. The most likely source of the
water contamination was an open holding reservoir, since the fence re-
stricting access to it had been broken by falling trees the previous winter.
Several soda bottles and golf balls were found in that reservoir, but no
specific source of human excrete was identified. Despite extensive bacte-
rial and viral laboratory studies, no specific etiologic agent was identified.
A heavy growth of algae had been observed where contamination was
thought to have occurred in the reservoir, but it is not known if the algae
played any role in causing the disease (Lippy and Erb, 1976~. Control
measures included covering the reservoir and maintaining adequate chlo-
rination of the system.
Suffolk County, New York
During the last week of March 1976, approximately 37% of the people
who attended one of four functions at a large catering establishment de-
veloped a diarrhea! illness caused by Saln~o,~ella typhinzurium. Although
foodborne transmission was initially suspected, epidemiological investiga-
tion suggested that the illness was transmitted by contaminated drinking
OCR for page 142
142
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OCR for page 146
146 DRINKING WATER AND HEALTH
TABLE V-3 Proportion of Reported Waterborne
Outbreaks and Cases Due to Deficiencies in
Distribution System by Type of System, 1971-1978a
System Outbreaks Cases
Municipal 26/68 (memo) 9,298/33,473 (28%)
Semipublic 6/129 (Woo) 710/14,470(55'o)
Individual 1/27 (4% ) 2/249 ( 1 To )
TOTAL 33/224 ( 15870 ) 10,010/48,192 (21 (Jo )
a From Center for Disease Control. 1978.
water. Further investigation indicated that municipal water used to cool a
refrigerator compressor was discharged through a pipe submerged in a
clogged sink filled with wastewater containing Salmonella typhimurium.
The resulting indirect cross-connection resulted in back-siphonage during
a period of high demand caused by the operation of on-site pumps to pres-
surize the irrigation system for a nearby golf course. Control measures in-
cluded removing the discharge pipe from the sink (Center for Disease
Control, 1976~.
Chattanooga, Tennessee
On March 24, 1976, residents of a three-street area in Chattanooga com-
plained that their water turned white and smelled of insecticide. Epidemi-
ological investigation identified 13 ill individuals. Extremely high concen
TABLE V-4 Nature of Distribution System Deficiency
in Reported Outbreaks Involving Municipal Systems,
1971 -1978a
Deficiency No. Percentb
Indirect cross-connections
Direct cross-connections
Contamination during construction
Leaching of copper from pipes
Contamination of open reservoir
Unknown
TOTAL
13
s
3
1
1 1
26 10
so
9
2
2
4
a From Center for Disease Control, 1978.
bNumbers are rounded off. Thus, total is not exactly LOOM.
OCR for page 147
Health Implications of Distribution System Deficiencies 147
TABLE V-S Etiology of Reported Outbreaks Due to
Deficiencies in Municipal Distribution System or to
Other Deficiencies, 1971-1978a
Outbreaks Due to
Deficiencies in Outbreaks Due to
Distribution System Other Deficiencies
Etiology No. Percent No. Percent
Unknown
Chemical
Bacterial diarrhea
(Shigella sonnet
Salmonella typhimurium)
0
2
3 so
386
8
7 40
5h
2
9
21
Hepatitis 1 4 4 1O
Giardia lamblia O oc 10 24C
TOTAL 26 100 42 100
a From Center for Disease Control, 1978.
bF~sher's tw~tailed exact test, p = 0.00067.
c Fisher's tw~tailed exact test, p = 0.01.
"rations of chlordane were identified in the water of and soil surrounding a
house in which chlordane had been used on March 24 to exterminate ter-
mites. The exact mode in which the municipal water supply in this three-
street area was contaminated was not identified. However, the most likely
explanation is that back-siphonage of chlordane occurred when the con-
centrated chlordane solution was diluted with water from a hose. This
could have taken place during a period of low pressure resulting from the
breakage of several nearby water mains the previous week by a building
contractor. Control measures included replacement of all street pipes in
the affected area and flushing of pipes to each house (Center for Disease
Control, 1976~.
Los Lunas, New Mexico
On the morning of November 17, 1978, 34 students at an elementary
school developed an acute gastrointestinal illness. Epidemiological inves-
tigation indicated that the illness was related to contaminated drinking
water from the semipublic supply at the school. Examination of the water
system indicated a faulty electrical relay switch in the circuit from the
pressure gauge for the storage tanks to the well pump and the fluoridator
pump. This malfunction permitted the fluoridator to pump concentrated
sodium fluoride solution into the storage tanks without simultaneously
OCR for page 148
148 DRINKING WATER AND HEALTH
2
1
o
5
4
A
6 3
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cr
m
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1
CC
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o
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m
2
7
6
5
4
3
2
1
o
Individual
1 1 1 1
1 1
Semipublic
O ~ I I I I ~
Municipal
~~ ~:
In
GAL 1 1
11 I I T
~ I I I
Municioal
1 971 1 972 1 973 1 974 1 975 1 976 1977 1 978
YEAR
FIGURE V-2 Reported waterborne outbreaks due to deficien-
cies in distribution systems, by type of system and year, 1971-
1978.
OCR for page 149
Health Implications of Distribution System Deficiencies 149
pumping an appropriate amount of water into the tanks. In addition, a
toilet in the bathroom near a hallway drinking fountain continued to run
following flushing. The continual flow of water into this building caused
by this toilet defect accounted for the concentration of fluoride (275 ma/
liter) in the school's water being higher than that in the water in an adja-
cent building (93.5 mg/liter). Control measures included repair of the
electrical relay switch and the toilet (Center for Disease Control, 1978~.
Pierce County, Washington
During the first week of May 1978, approximately 70~o of the students
and teachers at a rural elementary school developed an acute gastrointes-
tinal illness. Epidemiological investigation suggested that the illness had
been acquired by drinking water from the semipublic supply at the school.
Serologic studies indicated that the outbreak was caused by a Norwalk-
like agent. Further investigation revealed that a pipe had been installed to
deliver overflow from the air outlet of a pressure tank to a nearby floor
drain. On the day when transmission occurred, turbid foul-smelling water
was noted on the floor around the drain. The overflow was caused by a
jammed baffle at the point of entry of the drain line into the school septic
tank. Control measures included removal of the cross connection and
repair of the jammed baffle (Center for Disease Control, 1978~.
HEALTH EFFECTS OF CHEMICAL CONTAMINANTS IN
DISTRIBUTION SYSTEMS
Chemical contaminants that may be introduced into drinking water from
the distribution system are listed in Table V-6. The adverse health effects
of most of these agents have been reviewed in previous publications of the
Safe Drinking Water Committee. For the convenience of the reader of this
volume, references are provided to the appropriate Drinking Water and
Health volume for each of the agents listed in the table.
SUMMARY AND CONCLUSIONS
Deficiencies in distribution systems were responsible for 15~o of water-
borne disease outbreaks reported from 1971 through 1978.
Municipal water systems were more likely than semipublic or individual
water systems to be associated with outbreaks related to distribution sys-
tem deficiencies; 38~o of the outbreaks and 28~o of the cases involving
OCR for page 150
150 DRINKING WATER AND HEALTH
TABLE V-6 Health Effects of Chemical Contaminants
Associated with the Distribution System
Contaminant Source
References to Discussions
of Health Effects in the
Drinking Water clued Health
Series of ReportsU
Lead
Zinc
C.
orroslon
1 :309-31 1
1 :258-260
3:270-271
4:179-183
Corrosion and 1:299-302
1 :315-316
corrosion
inhibitors
Cadmium Corrosion
Iron
Copper
Nickel
Chromium
Manganese
Phosphates
Vinyl chloride
Asbestos
Inorganic hydrated
silicates
Polynuclear aro
matic hydro
carbons and re
lated substances
Tetrachlorethylene Pipe or tank
Corrosion,
. .
deposition,
and resus
Corrosion
C.
orroslon
1 :238-240
3:92-96
3:271
4:1 70- 1 74
3:309-312
pension
Corrosion 1 :252-253
1 :308-309
3:312-315
1: 287-288
1 :34S-350
1: 242-246
1 :306-307
3:364-369
Deposition and 1:266-270
resuspension 1:31 1-312
3:334-337
3:277-278
Corrosion
inhibitors
Plastic pipe
Asbestos
cement pipe
Asbestos
cement pipe
Pipe or tank
,. .
mung
1: 783-787
1: 160- 1 68
1:189
4:255-264
1: 769-780
lining 3: 134-142
a References are cited as volume and page number(s), from this (volume 4) and the
first three volumes of Dri,~kir7g Water arid Health (National Academy of Sciences,
1977, 1980a,b), e.g., 1:309-311 refers to pages 309-311 in the first volume (Na-
tional Academy of Sciences. 1977).
OCR for page 151
Health Implications of Distribution System Deficiencies 151
municipal systems were caused by such defects. However, these data must
be interpreted with caution since reporting of outbreaks is certainly not
complete. That municipal systems were most frequently involved probably
reflects both the fact that they have more complex distribution systems re-
sulting in greater potential for cross-connections and the fact that out-
breaks involving municipal systems are most likely to be recognized and
reported. The most common defects were indirect cross-connections,
which permitted wastewater or toxic chemicals to gain access to the water
system by back-siphonage through hoses or defects in water pipes during
periods of low pressure. Less frequent defects included direct cross-con-
nections, contamination of the system during construction, leaching of
copper from pipes, and contamination of an open reservoir. Outbreaks of
chemical etiology involving municipal water systems were especially likely
to be caused by distribution system deficiencies.
RECOMMENDATIONS
· Intensify surveillance, investigation, and reporting of outbreaks of
waterborne diseases at the local, state, and federal levels.
· Maintain adequate pressure in distribution systems so that back-si-
phonage cannot occur.
· Develop public education programs that focus on the prevention of
indirect cross-connections.
· Maintain a chlorine residual throughout the system.
REFERENCES
Center for Disease Control. 1976. Water Related Disease Outbreaks-Annual Summary.
Center for Disease Control, Atlanta, Ga.
Center for Disease Control. 1978. Water Related Disease Outbreaks-Annual Summary.
Center for Disease Control. Atlanta, Ga.
Lippy, E.C., and J. Erb. 1976. Gastrointestinal illness at Seuickley, Pa. J. Am. Water
Works Assoc. 68:606-610.
Morse, L.J., J.A. Bryan, J.P. Hurley, J.F. Murphy, T.F. O'Brien, and W.E.C. Wacker.
1972. The Holy Cross College football team hepatitis outbreak. J. Am. Med. Assoc. 219:
706-708.
Weissman, J.B., G.F. Craun, D.N. Lawrence, R.A. Pollard, M.S. Saslau, and E.J. Ganga
rosa. 1976. An epidemic of gastroenteritis traced to a contaminated public hater supply.
Am. J. Epidemiol. 103:391-398.
U.S. Treasury Department, Public Health Service. 1936. Epidemic Amebic Dysentery. The
Chicago Outbreak of 1933. National Institute of Health Bulletin No. 166. U.S. Govern
ment Printing Office, Washington, D.C. 187 pp.
Representative terms from entire chapter:
waterborne diseases
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