Excreta Disposal
In much the same way as with water supply, care is needed to ensure that different people who talk about sanitation are referring to the same thing. When the WHO-UNICEF Joint Monitoring Program was compiling the Global Water Supply and Sanitation Assessment 2000 Report (WHO and UNICEF 2000), a major effort was needed to persuade some of the Latin American partners that a pit latrine, considered a status symbol in much of rural Africa, was an acceptable form of excreta disposal. In some countries, even engineered sewerage systems are considered unacceptable if not connected to a functioning wastewater treatment plant.
Levels of Service, Technologies, and Their Costs
A wide range of technologies is used, particularly for settings in which low-cost solutions are required, and this variation has led some to inquire whether the different types of latrine might confer differing health benefits. In the early 1980s, the World Bank established a Technology Advisory Group for low-cost sanitation, and this question was among those it was asked to investigate. Using field studies and a thorough literature review, the group concluded that all types of systems can be operated hygienically, and that
The greatest determinants of the efficacy of alternative facilities are, first, whether they are used by everyone all the time, and second, whether they are adequately maintained. . . . Pit latrines would, from the viewpoint of health rather than convenience, approximate the same rating as a waterborne sewerage system. (Feachem and others 1983, 49-50)
The group therefore judged it most appropriate not to distinguish between sanitation technologies and to consider all of them as providing adequate access to sanitation as long as they were private or shared (but not public) and hygienically separated human excreta from human contact. This definition was followed in the Global Water Supply and Sanitation Assessment 2000 Report, which accepted only sewerage, septic tanks with soakaways, pour-flush latrines, and pit latrines as improved technologies. Service or bucket latrines and latrines with an open pit were not accepted. The effect of technology type on health benefit is discussed further in the sections that follow.
Public latrines, however, do not provide an adequate solution to the excreta disposal needs of a community. Quite apart from the notorious and widespread inadequacies in their maintenance, they are not usually accessible at night or by the elderly, by those with disabilities, or—if there is an entry charge—by young children. Thus, some promiscuous defecation continues to be practiced, particularly by children, in communities where public latrines are the only level of service available.
Figure 41.2 shows the regional median construction costs per capita of the various sanitation technologies found by the Global Water Supply and Sanitation Assessment 2000 Report. Although the simple, on-site systems tend to be cheaper than systems such as sewerage and septic tanks, the difference is less than might be expected. For example, a World Bank survey in several developing countries found the mean cost of conventional sewerage to be 10 times that for on-site systems such as improved pit latrines and pour-flush toilets (Kalbermatten, Julius, and Gunnerson 1982). It is likely that the off-site costs of sewered systems and the cost of the additional water needed for them to function have not been fully included in national reports to the Global Water Supply and Sanitation Assessment 2000 Report. For the purposes of calculating cost-effectiveness, a construction cost of US$60 per capita seems adequate for basic sanitation facilities (a household pit latrine, ventilation-improved latrine, or a pour-flush toilet) in any region of the developing world. Taking a relatively short lifetime of five years for a latrine and straight-line amortization gives an annual cost of US$12 per capita per year. In such a short lifetime, very little maintenance is normally required, other than occasional cleaning; the cost of maintenance is, therefore, considered to be included in the amortized annual cost.
[Figure
41.2]
That said, it should be borne in mind that substantially cheaper solutions are often feasible, such as the "15 taka latrine" (costing only US$0.27 per household) developed in Bangladesh, which includes a pour-flush pan made of tin sheet and an odor-and insect-proof seal made of flexible plastic pipe.
Social Benefits
Like water supply, sanitation offers a number of social benefits in addition to direct health gains, which tend to feature more prominently in the minds of the users. This outcome is illustrated by the responses given by a sample of householders in rural Benin when asked to rate the importance they ascribed to the various benefits of latrines on a scale of 1 to 4 (table 41.5). Health-related benefits (shown bold in table 41.5) were rarely mentioned spontaneously and generally rated among the less important benefits.
[Table .]
With sanitation as with water supply, strong gender differences exist in the perception of the social benefits of sanitation. For male heads of household in Benin as in other countries around the world, enhanced social status figures highly among the benefits of latrine ownership, whereas for women, security, convenience, and aesthetic factors count for more. Women who lack sanitation often risk sexual harassment on the way to and from their defecation site. In some cultural settings, women are constrained to go out for defecation and urination only during the hours of darkness, effectively becoming prisoners of daylight. Though no systematic study has been made of the health implications of such practices, they are likely to include an increased prevalence of urinary tract infections. The emancipation that a latrine bestows on such women cannot lightly be dismissed.
Willingness to Pay
The governments of developing countries cannot afford to provide heavily subsidized sanitation to all—or even to the majority—of their populations. The 2.6 billion people in Africa, Asia, and Latin America who do have adequate sanitation—53 percent of the population of those regions—have paid most of the cost themselves. Even those of the urban poor who do not have sanitation have expressed a willingness to pay for its full cost—or at least the local cost (excluding major interceptor sewers and treatment works, if required)—in a number of surveys, as long as credit is available on reasonable terms to smooth the cash flow (Altaf 1994). With regard to the rural poor, the success of well-conceived sanitation promotion programs in achieving coverage close to 100 percent, without a substantial subsidy, in some of the poorest rural communities in the world (Allan 2003) shows that people are willing to pay for sanitation if a suitable product is offered to them on suitable terms.
Why then do 2.4 billion people still lack sanitation? Several factors constrain the expression of the existing demand.
The constraint most frequently mentioned by unserved householders is cost, but this factor is usually more a perceived constraint than an objective one, for several reasons. First, many households are unaware of the true cost of latrines in their area, or the lower-cost models are not offered because local suppliers and artisans do not know about them or are attracted by the greater margins to be made on the more expensive technologies. Second, the high cost of capital to the poor rules out their borrowing the cost of a latrine, which to them would be a substantial investment. Third, they may be wary of investing in a property that belongs to their landlord, lest it be used as an excuse for a rent increase or even eviction. They may also feel, with some reason, that it is for the landlord to make the investment, rather than themselves, and they may be waiting for the landlord to do so. This belief has a similar effect to the common misapprehension of citizens, often encouraged by politicians, that the local government is responsible for sanitation and will eventually come to their aid; in either case, the outcome is inaction.
Other constraints include lack of ready access to necessary techniques and skills or to specific building materials and components. Where the skills exist locally, residents may lack confidence in the quality of work and value for money offered by the local artisans, or they may not know how to contact the right artisans. In many urban areas, local building regulations make low-cost sanitation technologies illegal.
Those constraints are compounded by the fragmentation of governmental responsibility for sanitation. Often it is devolved to local governments with little capacity to implement sanitation improvements. At the national level, one ministry may be responsible for sewerage and another for low-cost technologies; one may be responsible for construction, another for promotion, and a third for enforcing building codes and planning regulations.
Policy Implications
There are important externalities to households' investment in sanitation. Households are protected from their own feces by their sanitation facilities, but so, too, are their neighbors, and this factor is probably more important in epidemiological terms. If households are not fully aware of the health benefit—or if much of it accrues to others—a case exists for public intervention to increase coverage because these externalities exist.
This public intervention need not be in the form of subsidy. Strong arguments can be marshaled against a subsidy for low-cost sanitation (Cairncross 2003a). Subsidy limits the number of facilities that are built to the size of the subsidy budget; it encourages the design and marketing of unaffordable sanitation systems; it frequently leads to capture by the better-off, who install expensive toilets while the poor go without; and it distorts the market, diverting the efforts of latrine builders who would otherwise be seeking to meet the needs of low-income groups.
The intervention can be by regulation. National and local governments have substantial regulatory powers that can be used to increase sanitation coverage without significantly increasing costs or public expenditure. For example, more than 90 percent of households in the town of Bobo Dioulasso, Burkina Faso, have their own latrine (Traore and others 1994) as a direct result of the local administration's practice in the past of withdrawing rights of land tenure from owners who did not build a latrine on their plot within a specified time. Another regulatory intervention is to enforce the obligation of landlords to provide sanitation for their tenants.
An alternative strategy is to provide support to the marketing of sanitation. This strategy can be undertaken in a number of ways that are not feasible for the existing producers, mainly artisan builders and small component manufacturing workshops. Those interventions would aim principally at overcoming the constraints to the expression of effective demand for sanitation and could include the following:
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advertising and other forms of promotion
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facilitation of building regulation approval
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brokerage to put potential purchasers in touch with providers
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quality assurance and guarantee schemes
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training in low-cost construction techniques and in marketing
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centralized production of essential components
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provision of pit emptying and desludging services.
Promotion of improved hygiene practices, including appropriate use and maintenance of the sanitation facilities, is another possible intervention by the public sector. All of those measures will help increase sanitation coverage and health benefits and are appropriate interventions for the health sector. The costs of several of them are recoverable (after an initial launch period) as fees, so that public intervention need not require public expenditure.
Costs of Promotion
The costs of promotion and administration found in two government-run rural sanitation programs documented by the World Bank were US$16.80 (Zimbabwe) and $20.00 (the Philippines) per latrine, respectively (Cairncross 1992). Because these costs are largely fixed, the cost per unit falls as the number of units built increases. Unit costs will therefore be high in relatively unsuccessful programs. Successful programs, on the other hand, often engender the construction of more latrines than they can account for, which also gives an upward bias to the promotional costs per unit built. For example, for every latrine built by Lesotho's rural sanitation program in the late 1980s, four others were built independently but as a result of its promotional activities.
More recently, successful sanitation programs managed by nongovernmental organizations (NGOs) have documented slightly lower unit costs for promotion. For example, the Zimbabwean NGO AHEAD (Applied Health Education and Development), working through district-level health staff and a network of community health clubs, achieved the construction of 3,400 latrines in Makoni district within two years at a total promotional cost of US$45,660, or US$13.43 per unit, equivalent to US$2.24 per household member served (Waterkeyn 2003). In Bangladesh, WaterAid and its partner, a local NGO named VERC (Village Education Resource Centre), have developed an approach that has successfully achieved 100 percent sanitation coverage and the elimination of open defecation in more than 100 villages in six districts at a cost of US$8 per household, or US$1.50 per capita (Allan 2003). Both programs also promoted domestic hygiene practices in addition to the construction and use of latrines. In Bangladesh, all (and in Zimbabwe, most) of the costs of latrine construction were paid by the population themselves.
The programs in Bangladesh and Zimbabwe were particularly successful and well managed. The promotion cost is taken as US$2.50 per capita for cost-effectiveness calculations, which is slightly above the higher of the two, to allow for the imperfections of sanitation programs in the real world.
Direct Health Benefits
Evidence supports the claim that improved excreta disposal helps prevent a number of diseases, including diarrhea, intestinal worm parasites, and trachoma. Of these, the effect that accounts for the largest burden of DALYs is that on diarrheal disease.
Diarrheal Disease
The effect of sanitation on diarrhea morbidity has already been mentioned. Table 41.3 shows the results of Esrey and others' (1991) review, attributing a median reduction in incidence of 36 percent to sanitation. Although this figure is the median of the five "better" studies, it must be interpreted with great care because almost all the known studies on the health effects of sanitation are observational studies that use self-selected exposure groups. Confounding by a sense of hygiene is likely to be a significant problem in any such study. From Brazil to Bangladesh, the owners of latrines have been observed to behave more hygienically than their neighbors in practices such as hand washing that are not affected by the presence of a latrine (Hoque and others 1995—see table 41.6; Strina and others 2003). It is thus impossible to prove, except by an intervention study, that any health benefit associated with latrine ownership is due to the latrine and not to the hygiene habits of latrine owners.
[Table .]
The overall reduction in diarrhea from sanitation quoted by Esrey and others (1991) likely disguises considerable heterogeneity in terms of the context rather than the type of sanitation technology. For example, sanitation is likely to have a greater effect on diarrheal disease in high-density urban areas, where open defecation leads to gross fecal pollution of the neighborhood, and less effect in rural communities, where all but the youngest children use communal defecation sites some distance away from their homes.
For example, Moraes and others (2003), working in urban favelas in northeast Brazil, found that diarrhea incidence among children in households with a toilet was half that in households that did not have one. This comparison is likely to be affected by confounding because the households with toilets were a self-selected group. Comparison between communities is less likely to be affected by confounding, but Moraes and others found a greater reduction. The mean incidence of diarrhea in young children in communities with sewers was only one-third of that in the communities that, for administrative and technical reasons, did not have sanitary drainage.
Thus, although the quality of the studies reviewed by Esrey and others (1991) was in general poor and the range of reductions wide, little doubt exists that excreta disposal can be associated with significant reductions in diarrhea morbidity. Studies showing that proximity to open or overflowing sewers (Moraes and others 2003), failure to dispose hygienically of children's stools (Traore and others 1994), or the presence of excreta on the ground in the household compound (Bukenya and Nwokolo 1991) is a risk factor for fecal-oral infections provide supporting evidence for the likely effect of sanitation infrastructure, particularly in urban settings, on diarrheal disease transmission.
In conclusion, there are some reasons, such as the likelihood of confounding, to believe that Esrey and others' (1991) median reduction is an overestimate, but reasons exist also to believe that the reductions measured were not as great as they might have been had the provision of sanitation been accompanied by hygiene promotion to ensure that the facilities were fully and appropriately used (especially by young children) and maintained. A systematic review of the effect of sanitation on diarrheal disease is urgently required. Meanwhile, and on balance, Esrey and others' median reduction of 36 percent in diarrhea incidence is the most authoritative estimate available.
Interaction with Water Supply
The results of Esrey and others' (1991) review suggest that the effect of water supply and sanitation combined is no greater than that of either on its own. However, that conclusion is based on only two studies, and the percentage reductions found in the individual studies of each type of intervention exhibit a wide range. Reflection on how in practice each of the two interventions interrupts the transmission of fecal-oral pathogens would suggest that their effects would be largely independent: whereas water supply helps prevent contamination of drinking water, hands, and food, excreta disposal helps prevent contamination of the household yard and surroundings, including children's play areas. Esrey and others (1990) reported three other studies in which sanitation and water supply had a greater effect together than individually, but the reductions in diarrhea incidence in those studies could not be calculated.
For the purpose of burden of disease calculations, therefore, the effects of water supply and sanitation improvements on diarrhea are considered here to be independent and additive, which has the advantage of simplicity.
Effect on Other Disease Categories
The first evidence for the health benefits of excreta disposal related not to its effect on diarrheal disease but on intestinal helminths.
A prolonged series of in-depth studies from 1920 to 1930 by researchers of the Rockefeller Foundation established beyond doubt that promiscuous defecation, especially in the household surroundings and particularly by children, played a major role in the transmission of Ascaris spp., Trichuris spp., and hookworms in a range of settings from Panama to China and the southeastern United States. By implication, the use of sanitary toilets should interrupt transmission by that route.
However, more recent attempts to measure the reductions in parasite prevalence or intensity attributable to improved sanitation have often suffered from the same shortcomings as the studies of their impact on diarrheal disease; many have been cross-sectional studies and, therefore, subject to confounding.
Esrey and others (1991), in reviewing this literature, found that water supply and sanitation reduced the prevalence of ascariasis by a median of 28 percent (range 0 to 83 percent) and of hookworm infection by 4 percent (0 to 100 percent). Those reductions are likely caused by the sanitation rather than by the water-supply improvements. Indeed, three of the nine positive studies of ascariasis and three of the five positive studies of hookworm involved sanitation alone. It is also likely that the effect of excreta disposal on Trichuris infection is similar to that on ascariasis (Henry 1981).
Much emphasis has been placed in recent years on chemotherapy as a control intervention for intestinal helminths, particularly the chemotherapy of schoolchildren. However, that option is not always sustainable because the children are quickly reinfected by the eggs and larvae that remain in the environment. Sanitation, particularly school sanitation, has been adopted by the major international donor agencies as an integral component of the FRESH (Focusing Resources on Effective School Health) framework to ensure its sustainability.
A study in Bangladesh (Mascie-Taylor and others 1999) suggested that chemotherapy was more cost-effective (though less effective) as a helminth control intervention than a health education program that included the promotion of sanitation. However, the health education program was excessively labor intensive and, therefore, expensive; it involved the constant deployment of six health educators and a supervisor in each study area of only 550 households, resulting in a cost of Tk 1600 (US$30) per household, compared with Tk 330 (US$6) per year for chemotherapy. That cost compares with the total cost of US$8 per family for WaterAid's successful "100 percent sanitation" approach in rural Bangladesh (Allan 2003). Whereas the promotion of sanitation is a one-time cost, the cost of chemotherapy is a recurrent annual expenditure. Allowing for such a sanitation promotion initiative once every five years—and using the chemotherapy costing of Mascie-Taylor and others (1999)—sanitation promotion is more cost-effective against helminths in Bangladesh than is chemotherapy. If the cost were apportioned between the effect on diarrheal disease and the effect on helminths, sanitation would be far more cost-effective than chemotherapy.
Sanitation can also help prevent trachoma. More than 70 percent of the incidence of this infection has been shown to be caused by flies, mainly of the species Musca sorbens, which breeds preferentially in scattered human feces. Pit latrines have been shown to reduce the population of these flies by depriving them of their breeding sites (Emerson and others 2004).
