2100 The American Journal of Clinical Nutrition 31: NOVEMBER 1978, pp. 2100-2113. Printed in U.S.A.

The role of water supply in improving health inpoor countries (with special reference toBangla Desh)1

John Briscoe,2’3 Ph.D.

The literature on water supply and healthis strikingly heterogeneous in design, inmethod, and in conclusions (1) and “offerslittle in explaining water’s health impact be-yond confirming the existence of a generalassociation between improved quality andincreased quantity of domestic water and areduced incidence of enteric disease” (2).

Several excellent recent reviews examinethe relevant literature (1-5). This review ad-dresses itself to the role of improved water

supplies in easing the burden of infection inpoor countries. Since the relationship be-tween health and water is so markedly af-fected by the cultural, socioeconomic, andecological characteristics of an area, it is rec-ognized that universal conclusions are impos-sible and general ones are of limited practicalvalue. The approach taken in this paper,

therefore, is to examine in detail a limited set

of studies that have been conducted in thesame environment, a rural area of BanglaDesh. The analysis is illustrative rather thancomprehensive. Through examination ofthese studies, general methodological prob-lems will become apparent, the difficubties in

drawing a consensus from a set of studies ofessentially the same population will becomeclear, and the ways in which imperfect infor-mation may yet be useful in formulating pol-icy will be illustrated.

Research on water supply and health

Some methodological issues in studies of theeffect of water supply on health

Both inferential and deductive reasoninghave been used in analyzing the relationshipsbetween water supply and health. A largenumber of diseases are believed to be con-tracted through the ingestion of pathogenic

organisms that are present in the water. It is

assumed that the provision of a “pure” watersupply will drastically reduce their incidence.Diarrheas, accounting for about 30% of themortality in the Indian subcontinent, are usu-

ally assumed to be the most important ofthese diseases, yet understanding of this mostimportant syndrome is rudimentary (2).

Although interesting epidemiobogicalmodels of typhoid and cholera have beendeveloped by Cvjetanovic and his colleaguesat the World Health Organization (6, 7), it isquestionable whether adequate primary epi-demiobogical data exist for the construction

of realistic models for even these much-stud-ied diseases. In general, the epidemiobogicalunderstanding of enteric diseases is so poorthat realistic a priori models cannot be con-structed. Investigators therefore usually usestatistical inferential methods to analyze therelationships between water supply and dis-ease.

The large amount of literature on the em-pirical relationships between water supplyand health consists of both cross-sectionaland longitudinal studies. The former, such as

those of the World Health Organization Diar-rheal Diseases Advisory Team (8), have beenplagued by the existence of high multicollin-earity of “independent” variables. For ex-ample, income and nutritional status are usu-ally highly correlated with quality of watersupply. That one may show a correlationbetween water supply quality and health mayimply either that the communities or individ-uals with better health status are more healthybecause of the quality of their water supply,or that a more healthy community has taken

‘From the Epidemiology Division, Cholera Research

Laboratory, Dacca, Bangla Desh.2 Sanitary Engineer.

3Present address: Division of Applied Sciences, Har-vard University, Cambridge, Massachusetts 02138.

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ROLE OF WATER SUPPLY IN IMPROVING HEALTH IN POOR COUNTRIES 2101

steps to improve the quality of its water sup-ply. It is somewhat surprising and unfortu-nate, given the frequency with which the

multicollinearity question has arisen, that noanalysis of cross-sectional data using multi-variate techniques has been attempted.

The bongitudinab studies are generally pro-spective; water supply improvements aremade in an “experimental” community, whilethe health of this and a “similar” controlcommunity are monitored. The assumptionthat the two communities are similar in allimportant respects has proved to be a major

problem. Frequently, adequate preinterven-tion monitoring has not taken place and dif-ferentiab changes in the “experiment” and“control” communities occur during thestudy which have unmeasurable effects on

health in the two communities. Particularlyserious is the fact that the communities areoften exposed to quite different probabilitiesof infection due to the occurrence of an epi-

demic in only one of the communities. Con-verseby, the carefully conducted INCAP threevillage longitudinab study (9) failed to yielddefinitive conclusions, perhaps because theinterventions failed, for a variety of reasons,to substantially alter either water use or def-ecation patterns.

Studies of water supply and diarrhea! diseases

in rural Bang!a Desh

Under the auspices of the Cholera Re-search Laboratory, four studies have been

conducted on the effect of the provision ofhand-pump tubewells on the incidence ofcholera and other diarrheal diseases inMatlab Thana, a rural area in the deep waterflooding plain of the Meghna River (10).

One study upheld the traditional belief that“barge-scale installation of adequate tube-wells would be of cardinal importance for theprevention of cholera in rural areas in whichit is not possible to provide for piped watersupplies” (11) in the case of classical cholera,but not for the Eb Tor biotype. The otherthree studies (12-14) found no difference inattack rates between tubewell users and non-users for both Vibrio cholerae biotypes. Allfour of the investigators suggested that thehand-pump tubewell program was not meet-ing its stated objective, namely, reducing theincidence of cholera. The studies raise an-

other important policy issue by examiningthe hypothesis that those who use tanks tomeet their needs for water have bower choleraattack rates than those who draw their waterfrom other surface sources. The findings ofthe two studies which address this issue areapparentby contradictory.

Beyond the field ofwater per se, the studieshave implications for the understanding oftransmission of disease in general. These

counterintuitive results have suggested tosome that the widely accepted model of chol-era as primarily a waterborne disease may beincorrect, at least in the tropical countries.Moreover, counterintuitive and apparentlycontradictory results undoubtedly confusethose who are attempting to devise appropri-ate water improvement programs in ruralBangla Desh.

Surface water sources (ditches, tanks, ca-nabs, and rivers) are easily accessible to mostMatbab families and all use them for all pur-

poses other than drinking. Despite the factthat these sources are frequently contami-nated with fecab organisms, the water “qual-

ity” (color, turbidity, temperature, smell, andtaste) is generally perceived as satisfactory.The only protected water sources availableare hand-pumped shallow tubewells, about20% of which are privately owned. Althoughabout 30% of the families report tubewellwater as their source of drinking water, tube-webls are virtually never used for any otherpurposes. Tubewell water is not attractive for

a variety of reasons, including being less ac-cessible than surface water sources, requiringconsiderable effort to pump, and in this areabeing generally poor in quality. Although itoften looks clear when fresh, it turns turbidand forms brown scum and precipitates onovernight storage. “It causes discoloration of

teeth, rice, curry, clothes and tea and tastesof iron” (13).

Sommer and Woodward (10) examined theeffect of use of protected drinking watersources (i.e., hand-pump tubewell) on choleraattack rates. They considered the answersgiven by villagers to questionnaires on wateruse to be unreliable, and therefore comparedcholera attack rates between families livingwithin 50 feet of a functioning tubewell andthose who lived further away during 2 suc-cessive years in Meheran, a Hindu fishing

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2102 BRISCOE

village of about 1,800 inhabitants. The firstepidemic (1968-1969) was caused by the clas-sical/Inaba strain. In the immediate vicinityof tubewells, there was a bower rate of infec-tion (1 of 27 or 3.7%) than farther away (19

of 75 or 25.3%). During an epidemic thefollowing year (1969-1970), now caused bythe El Tor/Ogawa strain, there was no dif-

ference in the rates of infection of these twogroups (16 of 53 or 26.9%, and 37 of 149 or26.4%, respectively). The authors suggested

that the difference in the 2-year results “mightreflect the inherently different patterns oftransmission of the classical and El Tor bio-

types. Infection with the El Tor strain resultsin both a longer period of vibno sheddingand a lower incidence of clinically apparentdisease than infection with the classical van-ety. In addition, the El Tor vibrio is hardierthan the classical and remains viable in watermuch longer” (8).

Khan et al. (13) examined the relationshipof reported water use patterns to choleraattack rates for a random sampbe of over2,000 families in Matbab Thana during theperiod from 1966 to 1970. During this period,

cholera was of the classical/Inaba type. Con-nected tank users were excbuded. Table 1,which shows these data, suggests that thosewho used tank water for drinking, washing,

or bathing had attack rates from cholera thatwere lower than those for families using other

sources. In particular there was no significantdifference between attack rates of families

drinking canal, river, or tubewell water,whereas the attack rate for tank water drink-ers was significantly bower than that for usersof any other source. Extending the period ofanalysis to 10 years and thus including bothclassical and El Tor chobera, Khan foundsimilar differential attack rates.

Levine et al. (14) observed the water cob-

bection practices of 88 families in two cholera-prone villages in 1975. Hospitalization ratesfor cholera and diarrhea! diseases from 1963to 1969 were computed for all families. Theattack rates for those families who collectedtubewel! water at beast five times more oftenthan water from any other source for thestated purpose of drinking were comparedwith the attack rates for other famibies (Table

2). They concluded that “tubewell users hadas much or more cholera and other diarrhealdiseases than nonusers,” and “in affectedbaris, annual rates for canal and tank userswere almost equal (cholera = 1 1.9 versus10.4, and hospitalized noncholera diarrhea

= 4.0 versus 3.8 per 1,000 annual, respec-tively” (14). Tubewell water was found to befree of coliforms whereas canal water hadcoliform counts of over l,800/ml. Since “con-nections exist between tanks and canab, par-ticularly during the monsoon” (14), tank wa-ter was also, presumably, highly contami-

nated.Curlin et al. (12) have recently reported the

preliminary results of the 1st year of a 2-yearproject to study the impact of the hand-pump

TABLE 1

The effect of water source on cholera attack rates in

Matlab Thana, Bangladesh”

- -1 of families with cholera

1965-1970

Significant differ ence at S’S level?

Canal.

River Tank Tubewell

Drinking

Canal

River

Tank

Tubewell

6.9 (27/389)

5.6 (19/342)

1.9 (18/962)

5.2 (27/5 15)

No

Yes

No

No

Yes

No

Yes

Yes

Yes

No

No

Yes

Washing

Canal

River

Tank

8.9 (35/395)4.1 (6/145)

3.0 (50/1663)

No

Yes

No

No

Yes

No

Bathing

Canal

River

Tank

7.0 (32/459)

5.4(17/317)

2.9 (42/1430)

No

Yes

No

Yes

Yes

Yes

“From Reference 13.

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ROLE OF WATER SUPPLY IN IMPROVING HEALTH IN POOR COUNTRIES 2103

TABLE 2

Tubewell use and diarrheal disease”

Cases Person.yearsAnnual rate!

000Rate ratio Rate ratio (90% CL)’

P (2.tailed ex�

act)

Cholera

Tubewell users

Tubewell nonusers

Noncholera diarrhea

Tubewell users

Tubewell nonusers

53

13

28

5

3725

1545

3725

1545

14.2

8.4

7.5

3.2

1.7

2.3

1.0;2.8

l.0;5.2

0.08

0.07

“From References 14. CL, confiden ce limits.

TABLE 3One-year disease rates (per 1000 per year)”

- -Dnnking

water source

Reported diar.

rhea rates

(in field)

Confirmedchol.

era rates

(at hospital)

Confirmed

shigellosis rates

(at hospital)

Tubewell 789 4.32 0.93

Other757b 1�b l.50c

sources

“ From Reference 12. ii Rates are significantly dif-

ferent at 1% probability level. C Rates are not signifi-

cantly different at 1% probability level.

tubewell on diarrheal illness rates in 12 vil-lages of Matlab Thana. Families were visitedweekly and diarrhea! episodes recorded, and

each month families were questioned on thesources of water for drinking, bathing, cook-ing, washing utensils, and use after defecation(Table 3). The authors “failed to detect aconsistent pattern relating drinking tubewellwater and diarrhea rates” (12).

These studies were executed in the beliefthat the findings would provide policy makerswith guidelines for future water improvementprograms, but serve to confuse rather than toilluminate. Several hypotheses can be offeredto explain the surprising and contradictory

findings. The epidemiobogicab and practicalimplications of the studies are critically de-pendent on which set of hypotheses appearsto be most plausible. Some of these hy-

potheses have been suggested by the investi-gators themselves, others have appeared inthe literature as possible explanations of thefindings. A few have not been presented pre-viousby, but appear to me to resobve some ofthe confusions arising from this set of studies.

Hypothesis 1: the use of tubewe!l water fordrinking does not protect individuals against

cholera

Hypotheses concerning the effect of pro-tected drinking water supplies on attack rates

from chobera arise from the knowledge thatthe vibnos must be ingested and that the bulkof this ingestion comes through the swallow-

ing of polluted water. To test the hypothesisthat those who drink bacteriobogically purewater will have lower cholera attack rates

than those who drink polluted water, thevariable which needs to be measured is actualwater ingestion by the individual in terms of

its source, quality, and quantity. Since thesedata are extremely difficult to collect, a vari-ety of surrogates has been used in these stud-ies. Thus, despite the fact that each of theMatlab studies has been interpreted as reject-ing the hypothesis that the use of tubewellwater for drinking protects individualsagainst cholera, it cannot be tested on thebasis ofthe available data, since none of thesestudies have collected data on actual water

consumption by individuals.Sommer and Woodward (10) stated that

villagers’ responses were unreliable and as-sumed that distance to a protected source wasa proxy for the use of drinking water fromthat source; Khan et ab. (13) used question-naire response data directly; Levine et al. (14)observed water collection patterns at the vil-lage tubewel!s; and Curlin et al. (12) checkedquestionnaire responses by testing drinkingwater containers in the home for iron (since

the iron content of Matlab tubewell water ishigh). As will become evident, this failure tomeasure actual consumption of water by in-dividuabs may be a serious deficiency in thesestudies. This limitation is clearest in the studyof Sommer and Woodward (10). They as-sumed that villagers who lived within 50 feet

of a tubewell would be much higher users oftubewelb water than those who lived furtheraway. However, Levine et al. (14) observedthat families close to tubewells did not takewater from this source any more frequently

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2104 BRISCOE

than those further from the tubewell. Al-

though the data of Curlin et al. (12) showthat there is a relationship between proximityand use by the family, this relationship ismuch less pronounced than that assumed bySommer and Woodward (10). This assump-tion is compared with actual questionnaire

data from the study village in Table 4. Thereis virtually no misreporting of tubewell wateruse, since every family which claimed todrink tubewell water had a container of tube-well water in their house (12). Thus, the

Sommer and Woodward analysis appears tobe completely invalidated by their choice ofan inappropriate water consumption surro-gate. The other three studies do not obviouslysuffer from the same deficiency in the surro-

gate measure. They provide convincing evi-dence that those families who say that theyuse tubewell water for drinking, who carry

tubewell water to their homes, and who havetubewell water in a container in their homes,do not have significantly lower attack ratesthan those families who do not use tubeweblwater. These studies do not, however, refute

the hypothesis that those individuals whodrink primarily tubewell water have lowercholera attack rates than those who drinkprimarily from surface sources. The differ-ence is subtle but, as will become apparent,possibly extremely important.

Hypothesis 2: cholera in rural Bangla Desh isnot primarily a waterborne disease

The Matlab studies have stimulated a pro-

vocative response from Feachem, who hasstated that “cholera is more likely to bespread by indirect fecal-oral contacts, for ex-ample with contaminated food, than by wa-ter” (15) and who considers the paper byLevine et al. to be “another piece of evidenceto support the concept that much fecal-oral

disease transmission in the rural tropics is

nonwaterborne” (16).

TABLE 4Relationship between tubewell use and distance from

the well

Distanc fromtubewell

Usage of tubewell water for drinking

Sommer and Woodwards as-

sumption1974 Census data

feet %

<50 Very high use 100>50 Very low use 89.7

For cholera in Bangla Desh, however, a

large body of epidemiologicab evidence cor-roborates the classical findings ofJohn Snow,leaving little doubt that water is the primaryvehicle of transmission while person-to-per-

son contact is of secondary importance. Mar-tin et al. (17) found that classical choleraclustered in geographically compact com-munities, each of which was affected for arelatively short time. “Family outbreaks wereseen in only 6.9% of families where adultmales were the first cases . . . multiple cases

occurred in 21.3% offamilies in which womenand children were the first cases.” The pos-tubate that this discrepancy in secondary casedevelopment was due to the closer contact ofwomen and children with food and water

supplies is not supported by the timing ofthese secondary cases. The authors suggestthat this differential was due to the fact thatthe more mobile male was exposed to sourcesof infection which were not shared by otherfamily members. The relative unimportance

of person-to-person spread in Bangla Desh issuggested by other data as well. Mosley (18)noted that repeated bacteriological examina-

tions of hospital attendants of cholera pa-tients and of neighborhood contacts not shar-

ing common water suppby have rarely re-vealed infection, “suggesting that person-to-person contact is very rare.” Extensive mon-itoring for the presence of V. cholerae in theenvironment of index cases in the 1976 to1977 cholera season in Matbab Thana bySpira et al. (personal communication) sup-ported previous findings that V. cholerae areseldom detected in food (19) and fomites (20)under natural conditions, Spira et a!. wereseldom able to isolate V. cholerae from thehands of those who lived in the community

of the index case, but consistently detectedvibrios in the majority of tanks and canals inthe vicinity. Moreover, exceptionally high at-

tack rates in groups whose occupations bringthem into close association with surface watersources, indicate the primary robe of water inchobera transmission in Bengal. Boatmen andpeople who reside on boats have been espe-cially afflicted (1 1) while boatmen and fish-ermen have frequently been the source ofinfection for others using surface waters (21,22).

Thus, while contaminated foods, in addi-

tion to contaminated water, have been impli-

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ROLE OF WATER SUPPLY IN IMPROVING HEALTH IN POOR COUNTRIES 2105

cated in explosive cholera epidemics in the

typical protracted cholera epidemics ofBangla Desh, “this pattern has been relatedprimarily to transmission by water. Usuallya large body of water, such as a river, tank orcanal, exposes a community to a relativelybow dose, which only occasionally reaches asusceptible person to produce a frank case”(20).

Hypothesis 3: the small amount of protection

afforded by drinking bacterio!ogically safewater is overwhelmed by the exposure to

polluted surface water through bathing, food

preparation, and utensil washing

In rural Bengal, in generab, during bathingand washing a handful of water is repeatedlytaken into the mouth and “the nose andmouth are irrigated and rinsed, a procedureaccompanied by vigorous hawking and spit-ting” (23). In addition, in Matlab the high-iron content in the tubewell water ensuresthat it is virtually never used for cooking orutensil washing. The investigators of each ofthe tubewell studies in Matlab have suggestedthat use of nontubewell water for purposesother than drinking may explain why familieswho used tubewell water did not have bower

cholera attack rates than those families who

did not use tubewells. This explanation doesnot appear to be entirely satisfactory. The

water use habits of rural Bengabis are suchthat all members of a community would beexposed to cholera if the surface sources con-tamed cholera vibrios. The issue, however, isnot whether it is possible for those who drinktubewell water to contract cholera from sur-

face water sources, but whether cholera at-tack rates among tubewell drinkers are sub-stantially lower than attack rates among pop-ulations who do not drink tubewell water.

To examine this issue further, consider thefollowing simple model:

Probability of acquiring cholera

= � (Probability of ingesting i vibrio

x Probability of contracting cholera

given the ingestion of i vibrio)

Although we know little about the behaviorof vibrios in water, it seems unlikely thatthere would be systematically different vibriocounts, per unit of volume, in the water usedfor bathing and in the water that is drawnfrom the same surface source for drinking.Whereas, again, there are no data on this

factor, it seems reasonable to assume that the

quantities of water that people consciouslydrink are likely to be substantially larger than

those that are ingested during other uses ofwater. We would thus expect people who

drink tubewell water to ingest a given number

of vibrios (e.g., “i” vibrios) far bess frequentlythan people who drink surface water. Al-though something is known of the secondfactor in the above equation for a small group

of U.S. prison volunteers (24), nothing isknown about the susceptibility of any popu-

lation, including rural Bangladeshis, to var-ious doses of cholera vibrios under field con-ditions. What is important, however, is notthe absolute bevel ofthis dose, but the relativebevels of this dose in the tubewell-using and

surface water-drinking populations. There isunlikely to be any systematic difference. Thissimple model would suggest that the findingthat people who drink primarily tubewellwater do not have substantially lower cholera

attack rates than those who drink surfacewater is not plausible. That this model is not

radically different from the implicit models

of cholera epidemiologists is evident from theresults of informal interviews with a smallsampbe of foreign cholera experts living inDacca. These people all drank boiled water

but generally brushed their teeth, bathed, andwashed their dishes in unboibed water. Al-

though they agreed that if there were choleravibrios in the water supply it might be possi-

ble for them to contract cholera, they believedthat the probability of contracting cholerawould be substantially reduced as a result oftheir drinking exclusively boiled water.

Hypothesis 4: infamilies who are tubewellusers there may be individuals who do not

drink tubewell water and these individualsmay be those who are most susceptible to

cholera

The hypothesis that the tubewell programin Matlab would affect cholera rates in the

population was founded on the two assump-tions that cholera is primarily a waterbornedisease in this environment, and that individ-uals who drink bactenobogicably pure waterare much less likely to contract cholera thanthose who drink contaminated water. Theseassumptions have been examined above andseem to hold in the Matlab environment.Why, then, do tubewell-using families not

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2106 BRISCOE

have lower attack rates from cholera? Mc-Cormack et al. (22) have published data onthe age-specific attack rates from classicalcholera in Matbab in 1963 to 1964, 1964 to1965, and 1965 to 1966. The age structure forBangba Desh as a whole in 1961, as presentedby Mosley and Hossain (25), is assumed tohold for Matlab in these years. Yen (26) hasdocumented an outbreak of cholera in Tai-

wan which occurred 16 years after the pre-vious outbreak, and found that the carrier to

case ratio in chibdren was such much higherthan in adults. In Bangba Desh, an endemiccholera area, the opposite is found-the car-

rier to case ratio is higher for adults than it isfor children in both urban (27) and ruralsettings (22, 28). By pooling the availabbe

Bangla Desh data, we find the carrier to caserate to be 1.22 for children under 10 and 2.07for individuals over 10. From these dataTable 5 is derived. Cholera in Matbab, then,is strikingly a pediatric disease and, over-whebmingby, an infection of young children.

These age-distributed characteristics of chol-era make the drinking habits of those overthe age of 10 essentially irrelevant in theMatlab investigations. If the drinking habitsof children under the age of 10 are such thatthey consume most of their water from non-tubewell sources, even when there is tubewellwater in the house and this water is used for

drinking by other family members, then wewould not expect the presence of this tubewellwater to have a discernible effect on theincidence of cholera disease and infection inthis community.

In fact, experienced field workers suggestthat children in tubewell-using families maydrink primarily surface water. Since no fam-ilies use tubewell water for cooking, there isalways at least one container of surface waterin the house. In middle-cbass Matbab families,

TABLE 5

Age-specific patterns of cholera in Matlab Thana

Average at-

tack rate (3 ‘S of to- ‘S of to- ‘S of totalAge group seasons

data)Cases/

l000!year

tal pop-

ulation

al chol-

eracases

choleracar-

riers

0-4 lO.0 19 48 63.05-9 6.2 17 26 35.0

10-14 2.9 10 7 0.715-29 2.9 21 15 1.530-49 0.6 20 3 0.3Over 50 0.0 12 0 0.0

“children below the age of about one year aresaid never to be given plain cold water todrink as its temperature is considered too

chilling for them . . . (and) . . . some peoplesay that (tubewell water) temperature is toocold and causes them to catch cold and losetheir voices” (29). Indeed, children are Un-likely to be instructed or supervised concern-ing the choice of a container from which toextract drinking water. Children may preferthe nontubewell water for drinking, since “thesurface water is warm . . . (and) of muchbetter quality in both a chemical and aestheticsense” (12). Moreover, and finally, childrenmay drink water from outside of the home.

Two ways of investigating the issue furtherremain. First, if it is true that children under

the age of 10 do not drink tubewell watereven when it is in the house but that peopleover the age of 10 do drink this water, thenwe would expect no differential attack rates

for those under the age of 10 but wouldexpect to find differential attack rates forthose over 10 years old. It is clear that a bargesample, even greater than the population ob-served by Khan et ab. (13) is needed beforemeaningful conclusions can be drawn fromsuch an analysis. This would certainly be a

useful exercise, but the work involved wouldbe considerable. Second, to study, at thehousehold level, the water consumption prac-tices of different age groups in both tubewellusing and nontubewell using families wouldbe helpful. This would appear to be a highlyworthwhile study which would give a goodindication of whether the hypothesis ad-vanced in this section provides an expbana-tion for the counterintuitive results of theMatlab studies.

Hypothesis 5: those who use water from“disconnected” tanksfor their surface waterrequirements are likely to have lower cholera

attack rates than those who use canal or riverwaterfor drinking, cooking, bathing, and

utensil washing

There is an apparent contradiction in thefindings of Khan et al. (13) and Levine et al.(14) on the difference in attack rates between

tank water users and canal water users. Theformer results, based on data for the wholeof Matlab Thana, indicate that those who usetanks which are disconnected from canals

and rivers during the cholera season have

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ROLE OF WATER SUPPLY IN IMPROVING HEALTH IN POOR COUNTRIES 2107

much lower cholera attack rates than those

who use canal water. However, Levine et ab.found no such differential. They comparedcholera rates among users of all tanks whichappear to be mostly “connected” tanks and

canal water users in two villages which, inaddition, had unusually high attack rates.Since these findings have potentially impor-tant policy implications, I will examine this

apparent “contradiction” further. Extensivemonitoring of water sources in villages thathad cases of cholera during the 1976 to 1977season by Spira and his colleagues (personalcommunication) showed that there is little, ifany, difference in the mean vibrio countsamong tank, river, and canal water in thesevillages. These data and those of Levine et al.

suggest that once cholera is introduced into

a community it would be unlikely for anydifference in attack rates between tank usersand canal users to be found.

The spread of cholera has historically beenwidely associated with communication andtransportation routes (1 1). In Bangla Desh,

the association between rivers and canals hasbeen documented many times and unusuallyhigh cholera attack rates in boatmen and

fishermen have been recorded (20). We thusexpect communities that are located on busycanals to have higher attack rates than those

that are more isolated.Two factors may account for the finding

that disconnected tank users have lower chol-era attack rates (13). On the one hand, com-munities that are not located on canals andrivers may be expected to have a higher

proportion of disconnected tanks. Since thesecommunities are likely to have lower cholerarates for the same reason, namely their dis-

tance from canals, the apparent relationshipbetween the use of disconnected tanks andlow attack rates may be, in part, a spuriousrelationship. On the other hand, the proba-bility of introduction of cholera into a com-munity that is located on a canal may beproportional to the percentage of the popu-lation who use the canal and/or connected

tanks to meet their water requirements. Thefindings of Khan et ab. (17) and Levine et al.(18), then, are not necessarily contradictory.They can be reconciled, in part, by makingtwo assumptions:

1) Given its location relative to a canal, ifthe proportion of the community using dis-

connected tanks increases, the likelihood of

that community having cases of cholera willdecrease.

2) Once cholera has entered a community,those who use disconnected tanks are likelyto have the same attack rates as those who

use canal, river and “connected” tank water.

Issues in domestic water supply policy

The policy implications ofstudies on water

supply and cholera in rural Bangla Desh

The Cholera Research Laboratory investi-

gators have suggested that the present 40million dollar program for increasing thenumber of tubewells in rural Bangba Desh

may not be justified for the stated purpose of

controlling cholera and other waterborne dis-

eases. On the basis of the cholera data alone,however, the implications of the analysis pre-

sented above are quite different.The unusually high population density

(2,322 persons per square mile in MatlabThana compared with 1,286 persons persquare mile in Bangla Desh as a whole) (30)implies an unusually high density of housing.The deep flooding to which the Matlab area

is subjected (World Bank data show that only15% of the population of Bangla Desh live incomparably flooded areas) necessitates ab-normally large flood-protection mounds for

these houses. Since tanks are excavated toobtain earth for both the mounds and thehouses themselves, the areal density of tanksin Matlab is almost certainly extraordinarilyhigh. These demographic and hydrologic fac-

tors further lead to an exceptionally densenetwork of rivers and canals. The averageMatbab villager, then, in terms of access to

surface water sources, is atypical for the restof the country. While the government has

experienced difficulties in its tubewell pro-gram in other thanas (approximately 14%require deep tubewells, 2% have chlorideproblems, and 1% are unsuitable for either

deep or shallow tubewells in at beast someareas), in only 6% have problems similar tothose of Matlab been experienced with high-iron content of the groundwater (31). The

combination of these factors means that inMatlab tubewell water is bess attractive thanit is in most other parts of Bangba Desh, whilethere is an uncharacteristically high availa-bility of water from tanks, canals, and rivers.

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If the hypothesis that young Matlab chil-

dren are drinking a large amount of surfacewater which is in the house for cooking pur-poses is correct, then we would expect quite

different results from a similar study of wateruse and cholera in an area where the ground-water quality is good and where this water isused for drinking and cooking. Although dataon water use habits in other parts of BanglaDesh are few, informal interviews with Bang-ladeshis from different parts of the country

suggest that in most areas groundwatersources are used for both cooking and drink-ing water. Data from the Teknaf DysenteryProject in the extreme southeastern tip of the

country show that, despite the availability ofsurface water in a few tanks, drinking wateris obtained exclusively from groundwatersources (85% from ringwells), and that invirtually all families cooking water and drink-ing water are drawn from the same source(M. Rahaman, personal communication). Inthis area we would expect groundwater usersto have substantially lower attack rates thanthose who use surface water sources fordrinking and cooking. If the hypothesis be-hind these speculations is correct, in areaswhere tubewell or other groundwater is usedfor drinking, but not for cooking, health ed-

ucation programs should be initiated to stressthe importance of encouraging young chil-dren to drink from the drinking water sourceand not the cooking water pot.

The interpretation of the data on differen-tial attack rates among disconnected tankusers and other surface water users has inter-esting policy implications. It would appearthat the probability of introducing cholerainto a village would be substantially reducedif a higher proportion of villagers used dis-connected tanks for most of their water re-quirements. This could be achieved by a con-struction program that would convert con-nected tanks into disconnected tanks. It couldalso be achieved by educating people to use

disconnected tanks and by enhancing the at-tractiveness of these tanks through furtherexcavation and by improving the quality ofthe ghats. Although land is scarce, the possi-

bility of constructing new disconnected tanksshould also be considered. Tank developmentprograms should explicitly take into accountthe integral relationship between health andpoverty and, particubarly, health and nutri-

tion. The use of ponds for other importantpurposes, such as irrigation, fish, fertilizer,

and fuel production (32, 33) may be compet-itive with their use for domestic water supply.Pond fertilization, for instance, may increasefish productivity but adversely affect water

quality, while the maximum demands on theponds for both irrigation and domestic water

supply are likely to occur during the dryseason. Problems arising from unequal distri-bution and divided and disputed ownershipof tanks must also be explicitly addressed ifthese resources are to be efficientby and eq-uitably utilized.

The use of classical waterborne diseases, such

as cholera, as modelsfor water-related

diseases

The approach taken by John Snow in his

investigations of the Broad Street pump chol-era epidemic of 1854, an approach that has

been modified and elaborated in many sub-sequent studies of common-source epidemic

outbreaks, has enormous appeal. The scien-tific method, in which a model of diseasecommunication is postulated and the validityof the modeb tested by the acquisition of fielddata, is elegant, and the results have clear andimmediate policy implications. For most en-demic diarrhea! diseases, however, under-standing of transmission is rebativeby poor.Microbiobogists are unable to isolate causa-tive organisms for most diarrheas and epide-miobogists have yet to satisfactorily describethe relationships of most diarrheal diseases toenvironmental conditions. The clarity of the

cholera-type model has made this the domi-nant form for conceptualization of the reba-tionships between the environment and wa-ter-related diseases. “Waterborne” is widely

considered to be synonymous with “water-related” and the provision of a pure watersupply is generally accepted as the foremostpriority in domestic water planning.

The traditional classification of water-re-

lated diseases as bacterial, protozoab, hel-minthic, and viral provides few insights intothe modes of transmission of these diseasesand few clear policy guidelines. The mostimportant recent advance in understandingthe relationships between water and healthhas been the development of a scheme byBradley (5), in which diseases are classified

according to the specific nature of their rela-

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ROLE OF WATER SUPPLY IN IMPROVING HEALTH IN POOR COUNTRIES 2109

tionships to water. Waterborne diseases, suchas cholera and infectious hepatitis, are con-tracted through the drinking of contaminatedwater which acts as the passive carrier for thepathogenic organism. These diseases arecombated through water quality improve-ments and by the prevention of the casual

ingestion of water from contaminatedsources. Water-washed diseases, such as shig-

ellosis and scabies, are prevalent where hy-gienic practices are poor. The incidence ofthese diseases declines when water becomesmore available and increased quantities ofwater, irrespective of quality, are used for

hygienic purposes. The pathogens transmit-ting water-based diseases, such as schistoso-miasis and guinea worm, are dependent onaquatic organisms for completion of their lifecycles. Water improvement strategies forcombating these diseases include improvingthe quality of the water, controlling the vec-tor, and reducing the contact of the popula-tion with infected water sources. Diseasessuch as sleeping sickness and malaria are

transmitted by water-related insect vectorswhich either breed or bite near water. Controb

strategies include improved surface and wastewater management and reduction in timespent in the vicinity of breeding sites.

When the important water-related diseases

of an area are classified according to thisscheme, a series of policy directions are im-mediately evident. In Bangla Desh, the an-cestral home of cholera, water improvementprograms have been exclusively focused onthe provision of a pure source of drinkingwater. The most important diseases in young

infants and children, the diarrheas in general,are, however, usually transmitted by person-

to-person contact (10) and their prevalence islikely to be affected more by water quantitythan by water quality (2). The diarrheas are,therefore, properly classed as water-washeddiseases (5). In rural Bangla Desh the highestseasonab prevabence of diarrheas is not coin-cidental with the cholera season in the post-monsoon months, but occurs, as in otherareas of the world (35), during the season ofbow water availability. Superficial water-washed diseases are also important. In Noa-khali district “scabies is a major cause of

death from overwhelming infection and fromnephritis subsequent to bess serious infectionwith streptococcal organisms” (34). Water-

based and water-bred diseases are relatively

unimportant at present, although indicationsare that malaria may soon be a major healthproblem once again. The strategies for reduc-ing the threat of cholera and other primarilywaterborne diseases discussed earlier should

not be ignored, but should be considered inconjunction with the logical primary waterimprovement objective, which is the provi-

sion of adequate quantities of water withinthe home, particularly during the season oflower water availability.

The use of “intermediate variables” in

research and planning

Water improvement programs are expectedto improve health by facilitating differentpatterns of water use and by altering thequality and quantity of water used by mdi-viduals. In the cholera studies we have seenhow serious problems of interpretation arisefrom the use of intermediate variables suchas distance from tubewells rather than theactual water use patterns of individuals. Indesigning water improvement programs, aprimary aim is to improve health by alteringwater use patterns. Since the planning and

execution of these programs are the respon-sibility of bureaucrats and engineers, the suc-

cess of such programs tends to be measuredin terms of the proportion of allocated re-sources that have been spent and the achieve-ment of physical targets such as the installa-

tion of tubewells. Little attention is paid tothe behavioral changes induced by the pro-gram.

The result of such centralized, technocraticplanning is that the association between theprovision and use of water supply and sani-

tation facilities is often weak. This is partic-ularly marked for rural areas. Changes arerequired in both research and planning meth-odologies. Microlevel behavioral researchmust be undertaken to expand the presentrudimentary understanding of factors whichaffect the choices of water sources for differ-ent purposes and the quantity of water used.As Navarro (36) has shown, the health plan-ning process reflects the distribution of polit-ical power within a country. In Bangla Desh,as in many other poor countries, rural pre-ventive health programs have been accordedlow priority by the Western-trained urban

elite. Where rural water improvement pro-

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grams are undertaken, villagers are seen as“ignorant beneficiaries” of the benevolenceof the central government. They, therefore,simply need to be educated to change theirhabits and therefore are seldom consulted onwhat they perceive to be their water supply

problems. Until the power structure is alteredand the masses become involved in the healthplanning process, it is unlikely that the cur-

rent poor correlation between investment andhealth (1) will change.

The spec�fIcation of waler supply standards

As has been the case with the importationof technology, poor countries have frequentlyadopted the quality standards of Westerncountries. This has been particularly markedin engineering and medical practice. Watersupply quality standards, and health stan-dards in general, however, reflect the society’simplicit valuation of human life, the oppor-

tunity cost of capital and the cost of watertreatment (37). Given the existing distribu-tion of resources, poor countries should, cet-

ens paribus, set bower quality standards thanrich countries, since the opportunity cost of

capital in poor countries is higher. Althougheconomies of scale may imply lower per cap-ita treatment costs in urban areas and thus

justify somewhat higher water supply stan-dards in these areas, the high public expend-itures on the water supply of certain groupsand the much smaller per capita expendituresfor the majority suggests that the lives of theelite are being valued much more highly thanthe lives of other members of society. This isnot surprising but it is not generally under-stood that this is implicit in the frequentmaintenance of “international” standards forthe few, while the many receive little or noattention. Bradley (1) arguing for similarchanges has stated: “(The engineer) must de-sign less orthodox low cost systems. Theseincrease the risk of water-borne disease andhe must choose between some people catch-ing typhoid from one of his systems, or leav-ing a lot of others to go on catching typhoidfrom unimproved wells... . The problem isstrictly analogous to the struggle over com-

munity medicine in the education of doctors.The physician’s view was limited to his pa-tients, he felt no responsibility for the sick (orheabthy) who did not come to see him.”

Summary and conclusions

Awareness of a rebationship between wateruse and health is not new. Frontinus, theWater Commissioner of Rome, understoodthat health was affected by the quality andquantity of water consumed and that differ-ent water sources were appropriate for differ-ent purposes (38). Our knowledge has ad-vanced, in some ways, so little, and we arestill able to make only general statementssuch as “other things being equal, a safe andadequate water supply is generally associatedwith a healthier population” (39). The state

of the art should make us cautious of under-taking mubtimillion dollar research projectsin the hope that these will provide definitive

answers to all ofthe important questions. Theliterature on the subject of water and healthis both extensive and confusing. What ap-pears to be necessary is some serious thinking,perhaps along the lines of the analysis of thecholera studies above, on the reasons for themany apparent contradictions in the findingsof already published studies. These differ-

ences are frequently brushed aside too lightlywith the assertion that we should not expectsimilar results in different study areas. Wemust explain why the effect of improved wa-ter supplies on cholera is different in thePhilippines and Bangba Desh, and why the

effects of water supply are different for shig-ellosis and cholera in Bangba Desh.

In water supply policy the fundamentalneed appears to be a reorienting and restruc-

turing of the decision-making process. Thecontinuation of traditional water use habitswhen the people of poor countries are pre-sented with alternative sources of pure wateris generally ascribed to the “ignorance of theuneducated masses.” The prescription thenbecomes education of the ignorant and the

identification of communication barriers. Inthis paper it has been suggested that the faubtlies not so much with the recipients of theseprograms as with the process of decision-making on water improvement programs.

Addendum

This addendum reports new actual obser-vations of the water consumption practices ofyoung children in Matbab families who re-ported using tubewell water for drinking,

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ROLE OF WATER SUPPLY IN IMPROVING HEALTH IN POOR COUNTRIES 2111

which are relevant to the explanation of the

“failure” of tubewell water to reduce theincidence of cholera.

Ten families were chosen on the basis ofthe following criteria: 1) The villages chosenwere to be easily accessible to the MatlabHospital but were not to be part ofthe MatbabBazaar area; 2) The families were to have atleast two young children; 3) The families wereto have reported using tubewell water in the1974 census; 4) The families were to be cho-sen such that the socioeconomic and educa-

tional status ranged from well-off and edu-cated to poor and uneducated; and 5) BothHindu and Muslim families were to be rep-

resented.During the month of April 1977, two

trained female field workers were employedfor this briefstudy. Each family was observedfor a full day, with one observer stationed inthe house from 6 AM until 2 PM and theother observing from 1 PM until the childrenwent to bed (at about 8 PM). One child ofage 4 or 5 was chosen in each family and

every interaction of that child with water wasobserved and the time and nature of the

interaction was recorded. All interactions ofother young children with water was recordedwhere these could be observed. Particular

attention was paid to the source of the waterin the various containers, the place in whichthe water was stored, whether the water wastaken from a container inside or outside ofthe dwelling, whether the water was given tothe child by an adult, and whether waterappeared to be ingested during the interac-

tion. Although the families were informedthat the activities of the children were to be

observed, the mothers were not aware thatthe specific purpose was to observe water usepatterns.

In nine families the tubewell water fordrinking was stored in containers inside thehouse, while the surface water for cookingand washing of hands and feet was storedoutside of the house. In the 10th family threecontainers of canal water and two of tubewellwater were inside the house, while one con-

tainer of canal water was placed outside ofthe house. Thirty-six children between theages of 6 months and 10 years were observedto ingest water a total of 105 times. Despite

the fact that in nearly 50% of the cases the

water was drawn by the children themselves,

on every single occasion the water was drawneither directly from a tubewell or from a

container of tubewell water.In collecting these data a 4- or 5-year-old

child was followed throughout the day; theactivities of the other children were recordedwhen possible. The mobility of children un-der the age of 5 proved to be limited and it is

believed that most of the activities of allchildren in this age group were recorded. Theolder children were less accessible for obser-vation since they played further from the

home and, in some cases, went to school. Itseems certain that a significant proportion of

water that was ingested by these children was

not observed. Despite the fact that the sampleis very small, it is striking that young childrendo drink tubewell water when this is storedin the drinking water vessels within theirhomes. This is true when the children with-draw the water from the containers them-selves and when the water is drawn for thechild by an adult. Although this preliminarystudy was conducted in April and not in the“cholera season” (November to January), itseems unlikely that these patterns would varygreatly.

We are thus left with no satisfactory expla-nation of the results of the tubewell studies inMatbab. A large body ofepidemiological datapoints to water as the primary vehicle oftransmission in rural Bangla Desh and itappears that in those families who use tube-well water, the vast majority of the wateringested by the most susceptible group-young children-comes from this safe source.Tubewell water in Matlab does not becomepolluted between the pump and the mouth(Spira, personal communication). Thus, chil-dren who ingest, almost exclusively, water ofgood bacteriological quality apparently havethe same cholera attack rates as those chil-dren who drink highly polluted water. The

question, why, remains.

The author thanks his colleagues Drs. Moslemuddin

Khan, George Curlin and Bill Spira for permission touse their data and for their helpful comments.

Glossary of Terms

Ghat: A structure providing access to a surface water

source in Bangla Desh, varying in quality from a muddy

embankment to a concrete structure.

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Ring well: An uncovered shallow dug well, lined with

concrete or sun-dried or fire-burned clay rings. Wells are

typically 2 to 3 feet in diameter and water is drawn by

bucket and rope.

Tank: An artificial reservoir, usually excavated to

obtain earth to build flood protection mounds and

houses. Tanks are also frequently used for fish produc-

tion and domestic water supply.

Thana: The smallest administrative unit in Bangla

Desh.

Tubewell: A small diameter cased well fitted with a

cast-iron suction hand pump. The lift of these pumps is

limited to about 25 feet, although the water is typically

drawn from aquifers 50 to 250 feet away.

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