What constitutes a perfectly satisfactory water supply to some consumers leaves others, even in developing countries, considering themselves unserved. In much of rural Africa, a hand pump 500 meters from the household is a luxury, but most residents in urban Latin America would not consider themselves served by a water supply unless they had a house connection. In Asia, urban planners would consider a community served if there were sufficient standposts on the street corner; however, if the water only flows for a few hours per week, producing lengthy nighttime queues, the residents may regard this situation as a lack of service and opt to buy water expensively from itinerant vendors. As these examples illustrate, water supply is not a single, well-defined intervention, such as immunization, but can be provided at various levels of service with varying benefits and differing costs.
Levels of Service and Their Costs
Many public health workers unfamiliar with the water sector assume that the most important characteristic of a water supply is its improved quality. However, most of the benefit is attributable to improved convenience of access to water in quantity. Moreover, global statistics are not available on the coverage and costs of provision of water in terms of its quality. The Global Water Supply and Sanitation Assessment 2000 Report (WHO and UNICEF 2000), the most recent compilation of global statistics on water supply, changed the way that such data are compiled, from the previous unreliable estimates by provider agencies to consumers' responses in population-based surveys. The change required a departure from the old definition of reasonable access to safe water, because most consumers cannot tell whether their water supply is safe. They can, however, state the type of technology involved, and that fact was used to define a new indicator of improved water supply. In the main, improved water supplies could be expected to provide water of better quality and with greater convenience than traditional not improved sources. The report treated the following technologies as improved: household connection, public standpipe, borehole, protected (lined) dug well, protected spring, and rainwater collection. Unprotected wells and springs, vendors, and tanker-trucks were considered unimproved. Bottled water was also considered unimproved because of concerns about the quantity of water supplied, not because of concerns over the water quality.
Reasonable access was defined as the availability of at least 20 liters per capita per day from a source within 1 kilometer of the user's dwelling. Within the broad category of those with reasonable access to an improved water supply, two significantly different levels of service can be distinguished:
public or community sources.
In most settings, these subcategories correspond to very different levels of water consumption, different amounts of time spent collecting water, and as discussed in later sections, different health benefits.
The Global Water Supply and Sanitation Assessment 2000 Report also gives median construction costs per person served for the various technologies in the three main regions of the developing world. These costs are shown in figure 41.1. However, local conditions, such as the size of the community to be served and the presence of suitable aquifers, can cause tremendous variations in the unit cost of water supply.
Median Construction Cost of Water Supply Facilities for Africa, Asia, and Latin America and the Caribbean
For a community of given size, there are no significant returns to scale in the number of house connections made. Most of the investment in major works must be made before house connections can be offered, so that the marginal cost of each connection is only a fraction of the total. For those and other reasons, water supply is a natural monopoly requiring "lumpy" investments, which makes the unit costs difficult to calculate.
The cost of house connections may be representative in Latin America and the Caribbean, where they are often provided in rural areas. In Asia and Africa, however, the reported costs of house connections relate almost exclusively to urban areas because such connections are only rarely provided in smaller communities. The smaller size of rural communities means that piped systems in general—and house connections in particular—will tend to be more expensive per capita there than in urban areas. An overall unit cost figure of US$150, just above the highest of the three continental medians, is therefore taken for house connections in the cost-effectiveness calculations.
For public water points corresponding to improved water supply, hydrogeological and other constraints mean that the cheapest technology is not feasible in every community. A cost figure of US$40 per capita is about the middle of the range offered by different technologies (standpost, borehole, and dug well) providing this level of service for each continent (figure 41.1) and, therefore, seems reasonable for this level of service, although it can be expected to vary between US$15 and US$65 or more, depending on local conditions. The range of costs reported by individual countries for the Global Water Supply and Sanitation Assessment 2000 Report varied by more than an order of magnitude.
In calculating the cost-effectiveness of investment in water supplies, one must amortize these capital costs over an appropriate lifetime. Most major components of an urban water supply system have a potential lifetime of 50 years or more, but a prudent utility would aim to amortize them within about 20 years. A reasonable basis for calculation, for both urban and rural supplies, is to allow an amount of 5 percent of the capital cost as an annual straight-line amortization of the construction cost of the water supply.
Construction costs do not represent the full cost of water supplies. The Global Water Supply and Sanitation Assessment 2000 Report also gives median reported production costs per cubic meter for urban (house connection) water supplies as US$0.20 for Asia and US$0.30 for Africa and Latin America and the Caribbean. If we assume a mean daily water consumption of 100 liters per capita by those with household connections, those figures give annual per capita operation and maintenance costs of US$7.30 and US$10.95, respectively, or 8 to 10 percent of the capital cost of construction. In this chapter, a generic figure of US$10 is used for the annual per capita operation and maintenance cost.
Reliable figures for the annual maintenance costs for rural water supplies are harder to find, particularly because much of the maintenance is carried out by the volunteer labor of villagers. Arlosoroff and others (1987), after reviewing a wide range of rural water supply projects in various countries, concluded that with a centralized maintenance system, the annual per capita cost of maintenance of a hand pump–based supply can range from US$0.50 to US$2.00, while well-planned, community-level maintenance can bring that figure down as low as US$0.05 per capita per year. A nominal annual figure of US$1.00 per capita is therefore used in this chapter. A similar figure can be applied to urban public standposts, for which volunteer labor is less forthcoming but transport costs are lower. This maintenance cost represents 2.5 percent of the construction cost arrived at above.
The Time-Saving Benefit
Benefits to health are not normally foremost in the minds of those provided with new water supplies. An exhaustive study of the economics of rural water supply by the World Bank concluded that "the most obvious benefit is that water is made available closer to where rural households need it. . . . It is not clear that rural populations think much about the relationship between water and health" (Churchill and others 1987, 21–22).
The Value of Time
The saving in time and drudgery of carrying water home from the source is substantial, and several reasons exist to attribute a money value to it. The most powerful argument for the money value of poor women's time is that households often pay others to deliver their water, or pay to collect from nearby rather than from more distant sources that are free of charge. Thompson and others (2001) found that, of urban East African households lacking a piped supply, the proportion paying for water had increased from 53 percent to 80 percent over 30 years. In a survey of 12 sites in 10 countries, Zaroff and Okun (1984) found that households were spending a median of over 20 percent of their income on the purchase of water from vendors. The prices charged by vendors are typically more than 10 times—and can be up to 50 times—the normal tariff charged by the formal water supply utility.
Cairncross and Kinnear (1992) found that vendor prices increased with the time required to collect the water, showing that households pay more as the alternative of collecting water themselves becomes more burdensome. If the amount paid to the vendor for bringing the water is divided by the time saved from collecting it, the implicit value that people ascribe to their time can be calculated. Whittington, Mu, and Roche (1990), working in rural Kenya, showed in this way that the implicit value of the time saved was roughly US$0.38 per hour, very close to the average imputed wage rate for such households of US$0.35 per hour.
Because the poorest urban households typically spend more than 90 percent of their household budget on food, the money they spend on water is sacrificed from their food budget (Cairncross and Kinnear 1992). The provision of water more cheaply thus offers a substantial nutritional benefit to the poorest.
Assessing the Time Saved
The cost of water collection in rural areas is usually in time and effort rather than in money paid to vendors. The saving in time and drudgery underlies many social benefits. Given the relevance of the time-saving benefit to water supply policy and the fact that the benefit is usually uppermost in the mind of the consumer, it is remarkable how few data have been collected on the amounts of time spent collecting water.
Working in 334 study sites in Kenya, Tanzania, and Uganda, Thompson and others (2001) found a mean distance from rural unpiped households to their water sources of 622 meters. In urban areas, the distance was only 204 meters, but queuing at the tap meant that a water collection journey took almost as long.
Feachem and others (1978) found in 10 villages of the densely populated lowlands of Lesotho that the installation of a water supply had saved the average adult woman 30 minutes per day. In one-third of the villages, the saving per woman was more than an hour a day. Lesotho has many springs, so that time saving is likely to be on the low side compared with Africa as a whole.
These time-saving benefits are confirmed by the Multi-Indicator Cluster Surveys of the United Nations Children's Fund (UNICEF). A recent analysis of the responses in 23 African countries has produced a more representative account of water collection journey times in that continent (G. Keast, UNICEF, personal communication 2003). Nearly half the households interviewed (44 percent) required a journey of more than 30 minutes to collect water, implying that the women in such households spent an hour or more each day in water collection. At almost any reasonable level of service, most of that time would be saved by an improved water supply.
In Asia, an Indian national survey for UNICEF found that women spent an average of 2.2 hours per day collecting water from rural wells (Mukherjee 1990). A study in Sri Lanka, which is generally considered to be well provided with water sources, found that 10 percent of women had to travel more than 1 kilometer to their nearest source (Mertens and others 1990).
Valuation of the Time-Saving Benefit
Putting a precise figure on the money value of the time of poor people is a tricky task, even for the most self-confident economist. In 1987, Churchill and others took US$0.125 per hour as an illustrative but not unrealistic figure. To take the same figure today could hardly be described as extravagant. Assuming this valuation of an hour of time—and that a water supply bestows a mean saving of only 15 minutes per person per day—yields a conservative estimate of the value of the time-saving benefit of US$11.40 per year. The data presented earlier indicate that, at least in Africa, the true figure is nearer to double that amount, enough to justify the full construction cost of a dug well or borehole supply in a single year. In Latin America and the Caribbean, costs are higher, and time savings may be less, but rural incomes are also higher—and so, therefore, is the value of people's time. Little doubt exists that, in all three regions of the developing world, the value of time saved is sufficient on its own to justify both the investment costs (at any reasonable rate of amortization) and the operation and maintenance costs of water supplies.
Even in settings where water vending is not common, contingent valuation surveys have widely demonstrated a willingness to pay for water supplies, particularly at the level of service of house connections (World Bank Water Demand Research Team 1993). In general, such measured willingness to pay has exceeded the cost of providing the supplies, and payment to vendors often exceeds it by many times.
Whether the consumers actually pay for the full value of the time-saving benefit, it is what makes water supplies popular and largely it is what motivates politicians to invest in them. More than half the total annual investment in water supply in the developing countries of Africa, Asia, and Latin America and the Caribbean is from domestic sources (WHO and UNICEF 2000). Most of the investment is from the public sector. In general, investments in water supply—whether by the governments of developing countries or by external support agencies—do not come from health sector budgets and are not compared with other health interventions when investment decisions are made, even though health benefits do arise from water supply improvements.
Water supply is thus a health-related intervention that comes without cost to the budgets of the health sector. Although it undoubtedly offers health benefits, it has a sufficient economic and political rationale in other social benefits associated with time saving. The health benefits are a positive externality to this rationale. However, this fact does not mean that the authorities responsible for public health should ignore the water sector. The function of the health sector is one of regulation, advocacy, and provision of supplementary inputs, as appropriate, to ensure that potential health benefits of water supply are realized to the optimal extent.
For example, the regulatory role of the health sector in quality surveillance of drinking water is well known and widely accepted. Substantial and largely unexploited additional potential is present in this role if quality is interpreted in the wider sense of quality of service rendered by the water supply utility, in terms not only of water quality but also of quantity, continuity, coverage, control of sanitary hazards, and cost. Those other aspects, as will be argued in the following sections, are no less important for health.
Where a regulatory role is not available to the health sector or agencies concerned with public health, advocacy can be no less cost-effective. For example, connection charges are a major barrier to house connections for low-income groups. In many cities of the developing world, the individual connection charge is about a month's basic wage. Advocacy of lower connection charges, with the amount recovered from the monthly water tariffs, can therefore help achieve an increase in the number of people who have house connections and who can benefit from the corresponding health gain at no cost to the public purse. Finally, the health sector can provide important complementary services, such as hygiene promotion and promotion of low-cost sanitation to increase coverage; because of the nature of such services, the water sector, with its focus on technology, is ill-equipped to offer them.
The unit costs of such regulation and advocacy are minimal. One example is the case of UNICEF's participation over the past 30 years in India's rural water supply program. UNICEF's investment has represented no more than 1 percent of the total, but its influence has played a central part in the evolution of the technical and institutional model of the program that supplies water to 1 in 10 members of the human race.
An example of the effectiveness of such measures is provided by the interventions of the Mexican Ministry of Health in June 1991. Fostered by fear of the devastating effects of cholera, these measures included the chlorination of water supplied for human consumption and the prohibition of sewage irrigation of fruit and vegetables. As a result, the incidence of diarrhea in children under five years of age fell from 4.5 to 2.2 episodes per child-year, and the corresponding mortality rate fell from 101.6 to 62.9 per 100,000 children (Gutiérrez and others 1996).
The current rate of annual investment per capita in water supply and sanitation, including both national investment and external aid funds, is reportedly US$2.25 in Asia, US$7.53 in Africa, and US$8.87 in Latin America and the Caribbean (WHO and UNICEF 2000). One percent of the water sector's investment would, therefore, be US$0.02 to US$0.10 per capita. If each ministry of health in the developing world were to invest such a sum in public health advocacy and regulation related to water supply, the sector's performance, at least where low-income groups are concerned, could be transformed. It is hard to put a figure on the health effects of such investment, but the Mexican example suggests that they would be substantial. For the sake of cost-effectiveness estimation, such spending is arbitrarily assumed to have the effect of ensuring improved water supplies for an additional 10 percent of the population to which it refers.
Direct Health Effects
The full list of water-related infections is large and varied, but most are only marginally affected by water supply improvements. The first effort to simplify the relationship between water supplies and health in developing countries was made by David Bradley (White, Bradley, and White 1972), who developed a classification of disease transmission routes in terms of whether they were
waterborne, in the strict sense in which the pathogen is ingested in drinking water
water-washed—that is, favored by inadequate hygiene conditions and practices and susceptible to control by improvements in hygiene
water-based, referring to transmission by means of an aquatic invertebrate host
water-related insect vector routes, involving an insect vector that breeds in or near to water.
Whereas the prevention of waterborne disease transmission requires improvements in water quality, water-washed transmission is interrupted by improvements in the availability—and hence the quantity—of water used for hygiene and the purposes to which it is put. Water supply may affect water-based transmission (for example, if it reduces the need for people to enter schistosomiasis-infected water bodies) or water-related insect vectors of disease (for example, if a more reliable supply averts the need for the water-storage vessels in which dengue vectors breed), though that will depend on the precise life cycle of the parasite involved and the preferred breeding sites and behavior of the vector.
Classification and Burden of Water-related Diseases
Before Bradley's classification can be applied to diseases (rather than transmission routes), it requires a small adjustment (Cairncross and Feachem 1993) to allow for the fact that practically all potentially waterborne infections that are transmitted by the feco-oral route can potentially be transmitted by other means (contamination of fingers, food, fomites, field crops, other fluids, flies, and so on) all of which are water-washed routes. In addition to the feco-oral infections, a number of infections of the skin and eyes can be considered water washed but not waterborne. The final classification is shown in table 41.1.
The Bradley Classification of Water-related Infections.
The classification can now be used to assess how the disease burden prevented by water supply is distributed among disease groups. Bradley himself did this, a time long before the disability-adjusted life year (DALY) had been invented as a unit of benefit measurement (White, Bradley, and White 1972, 191). He used official statistics on the number of cases of each disease diagnosed and treated by health services in East Africa and combined them with notional percentages by which morbidity and mortality caused by each condition could be expected to fall if water supply were "excellent."
Those notional reductions were based on subjective assessments of the literature available at the time and were described by their author as "little more than guesses," but it is hard to prove many of them seriously at fault, even today. A selection is presented in table 41.2.
Percentage Reductions in Disease Rates Assumed by Bradley.
The result of these calculations was that the feco-oral disease group accounted for 91 percent of the deaths preventable by water supply, 50 percent of inpatient bed nights, and 33 percent of outpatient consultations. Rosen and Vincent (2001) have made a similar calculation for the whole of Africa in 1990 and found that the feco-oral group accounted for 85 percent of the preventable DALYs. When measured in terms of deaths or DALYs, feco-oral infections account for the vast majority of the impact, because of the high mortality caused by diarrheal diseases among young children. Most deaths from diarrheal diseases are of children younger than age five, and most of those are among children younger than two. A child death averted is worth 30 DALYs. Varley, Tarvid, and Chao (1998) have calculated that for diarrhea morbidity reduction to have the same effect in DALYs as averting one such death, it would have to prevent 115,000 child-days of diarrhea. After the diarrheal diseases, the next most important category in terms of DALYs (12 percent of the total) is the water-based group, primarily schistosomiasis. The purely water-washed diseases, mainly skin infections, represent a more conspicuous portion only when compared in terms of the burden placed on health services by inpatients or outpatients.
How representative is this African breakdown of the developing world as a whole? Diarrheal disease among poor communities is cosmopolitan. A global review of studies of the incidence of diarrhea morbidity could find no clear geographic or climatic trend (Bern and others 1992), so the burden of disease is no doubt similar around the developing world. The second most important disease group is represented by schistosomiasis, which is absent from much of Asia and Latin America. The relative importance of feco-oral disease is, therefore, likely to be still greater in the poor communities of Asia and the Western Hemisphere than it is in Africa.
Epidemiological Questions and Problems
The predominant contribution of feco-oral diseases to the burden of disease attributable to water supply raises an important question, because this group can be transmitted by both waterborne and water-washed routes. It is important for the water engineer to know whether scarce funding should be spent on improved water treatment and measures to protect water quality or instead on providing a limitless supply of water at a high level of access and convenience and encouraging its use for improved hygiene practices. We need to know, that is, whether the feco-oral infections endemic in poor communities are mainly waterborne or mainly water washed.
Moreover, the fact that some diarrheal diseases are still prevalent in communities with a high level of water supply service indicates that water supply alone cannot completely prevent these diseases. A further question then, is this: by how much do water supply improvements reduce diarrheal diseases?
Numerous studies have sought to answer these questions, but they are hard to answer rigorously, for several reasons. First, it is almost impossible, ethically and politically, to randomize the intervention. Where the intervention is an improvement in the level of access to water, it cannot be blinded; no placebo exists for a standpost. Where quasi-experimental studies have been used—opportunistically exploiting an intervention allocated by political or technical means—significant confounding has frequently been found (Briscoe, Feachem, and Rahaman 1985).
Confounding has been especially intractable in studies in which the allocation of facilities has been on a household basis, so that the exposure groups are self-selected—for instance, studies in which individual households that have chosen to install a private tap are compared with others that have chosen not to do so. The former households are likely to be wealthier, better educated, and more conscious of hygiene than their neighbors, so it would not be surprising if they were also more likely do many other things that protect their families from feco-oral disease. The more sophisticated studies have used multivariate models to control for confounding, but where relative risks are low and the exposure groups are self-selected, even those models do not guarantee that confounding is eliminated (Cairncross 1990).
A further difficulty arises from the fact that cases of feco-oral disease in a given community cannot be considered independent events, because such diseases are infectious. The sample size, it can be argued, is the number of such villages rather than the number of individuals enrolled in the study. Yet a number of important studies in the literature compare a single intervention area with only one control area.
Other epidemiological weaknesses exist in the data. Blum and Feachem (1983) reviewed 50 studies of the health effect of water supply and sanitation projects and noted that every one contained one or more of these basic errors of methodology. A further weakness in the evidence for the effect of water supply on diarrheal disease burden is that most of it relates to diarrheal disease morbidity, and significant assumptions are needed to extrapolate such evidence to an effect on diarrheal mortality.
Effect on Diarrheal Disease
Esrey and Habicht (1985) and Esrey and others (1991) reviewed the same literature from a different perspective. Though conscious of the methodological shortcomings of most studies, they sought to assess the overall reductions in diarrheal disease that water supply could be expected to cause. They applied a number of criteria of epidemiological rigor and took the median reduction in morbidity reported from each type of intervention. Their conclusions are summarized in table 41.3.
Median Reductions in Diarrhea Morbidity Reported from Different Water Supply and Sanitation Interventions.
For more than a decade, this review has remained the most authoritative on the subject. However, the small reductions in disease that it reports for water supply conceal an important heterogeneity. Though these overall results are frequently quoted, the following remark by Esrey and others (1991, 613) has usually been overlooked:
In the studies reporting a health benefit, the water supply was piped into or near the home, whereas in those studies reporting no benefit, the improved water supplies were protected wells, tubewells, and standpipes.
In the studies in the two reviews by Esrey and Habicht (1985) and Esrey and others (1991) in which the water supply was provided in the home, the median reduction in diarrheal disease is 49 percent (from 12 studies), and the reduction from the two better studies is 63 percent. Those reductions are several times greater than the overall median impacts in table 41.3. The 63 percent figure will be used in the burden of disease calculations that follow. In the two better studies, the members of the comparison group were using not an unimproved water supply, but a protected water source away from the home. The reductions they found are, therefore, in addition to those resulting from a public standpost level of service.
Some subsequent studies have confirmed this pattern. For example, Bukenya and Nwokolo (1991) showed in Papua New Guinea that use of a household tap was associated with 56 percent less diarrhea than use of public standposts providing water of good quality.
Conditions for Health Effect
Providing a public water point appears to have little effect on health, even where the water provided is of good quality and replaces a traditional source that was heavily contaminated with fecal material. By contrast, moving the same tap from the street corner to the yard produces a substantial reduction in diarrheal morbidity. How is this pattern to be understood?
The first step to an explanation is an understanding that most endemic diarrheal disease is transmitted by water-washed routes and is not waterborne. Although waterborne epidemics of diarrheal diseases such as cholera and typhoid have been notorious in the history of public health, the endemic pattern of transmission seems to be different, particularly in poor communities. Five types of evidence support this view:
Negative health impact studies. As mentioned earlier, Esrey and Habicht (1985) and Esrey and others (1991) cite a number of studies of the health impact of water supplies in which water quality improvements have failed to have a significant effect on diarrheal disease incidence.
Food microbiology. Studies of the microbiology of foods in developing countries—particularly the weaning foods fed to children in the age group most susceptible to diarrheal disease—have shown such food to be far more heavily contaminated with fecal bacteria than is drinking water (Lanata 2003), even when the water has been stored in open pots.
Seasonality of diarrhea. In countries with a seasonal variation in temperature, bacterial diarrheas peak in the warmer season, whereas viral diarrheas peak in the winter. This pattern suggests that the bacterial pathogens show environmental regrowth at some stage in their transmission route, which means that they must have a nutritional substrate. Water is, thus, a less likely vehicle than food.
Fly-control studies. Trials in rural Asia and Africa have shown that fly control can reduce diarrheal disease incidence by 23 percent (Chavasse and others 1999).
Hand-washing studies. A recent systematic review of the effect of hand washing with soap has shown that this simple measure is associated with a reduction of 43 percent in diarrheal disease and 48 percent in diarrheas with the more life-threatening etiologies (Curtis and Cairncross 2003).
Those five types of evidence suggest that domestic hygiene—particularly food and hand hygiene—is the principal determinant of endemic diarrheal disease rates and not drinking water quality.
The second step is an understanding of how the level of service and convenience of a water supply influence such hygiene practices in the home. Taking the amount of water used per capita as an indicator of hygiene changes, other things being equal, one finds that providing a source of water closer to the home—and therefore more convenient to use—has very little effect on water consumption unless the old source was more than 1 kilometer (30 minutes' roundtrip journey) away from the user's dwelling (Feachem and others 1978).
However, water consumption doubles or triples when house connections are provided (White, Bradley, and White 1972), and reason exists to believe that much of the additional consumption is used for hygiene purposes. For example, Curtis and others (1995) found that provision of a yard tap nearly doubled the odds of a mother washing her hands after cleaning her child's anus and more than doubled the odds that she would wash any fecally soiled linen immediately.
In conclusion, water supplies are likely to have an effect on diarrheal disease when they lead to hygiene behavior change—that is, when the old source of water was more than 30 minutes' roundtrip away or when house connections are provided.
By a happy coincidence, then, the health benefits of water supply are most likely to be realized in exactly those cases in which the time-saving benefit is greatest—when the old source of water is farthest away, and when the new one is on the plot of the individual household. Though water supplies offering house connections are more expensive, the additional time savings offered by this level of service mean that people are willing to pay more for them. Moreover, collecting revenue from households with private connections is far simpler than collecting it from public taps because the sanction of disconnection can be used against households that default on payment of the tariff.
Calculating the burden of disease associated with inadequate water supply requires a figure for the reduction associated with the levels of service for which coverage statistics are available. The following burden of disease calculations are based on a reduction of 17 percent from an improved public water supply (table 41.3) and of a further 63 percent from house connections.
The effect of water supply improvements (and of hygiene practices such as hand washing) on diarrhea mortality can be expected to be at least as great as—and probably greater than—their effect on morbidity for several reasons. A theoretical argument for this improvement pattern is given by Esrey, Feachem, and Hughes (1985) in terms of infectious doses. Esrey and others (1991) also reported a median reduction of 65 percent in diarrhea mortality attributable to water supply, sanitation, or both in three studies, compared with 22 percent from 49 studies of morbidity. The effect of hand washing on life-threatening diarrheas—shigellosis, typhoid, cholera, and hospitalized cases—is greater than that on diarrhea morbidity as a whole (Curtis and Cairncross 2003). Finally, the two known direct studies in the literature of the effect of house connections on diarrhea mortality ("Serviço Especial da Saúde Pública," an unpublished study in Palmares, Pernambuco, Brazil, cited by Wagner and Lanoix 1959; Victora and others 1988) found reductions of 65 percent (relative to a public standpost) and 80 percent (relative to various communal sources, some polluted), respectively.
Effect on Other Disease Categories
Water supplies have a beneficial effect on a number of disease groups other than diarrhea, although the corresponding burden of disease is far less. The median reductions in morbidity from other water-related conditions, reported by Esrey and others (1990), are shown in table 41.4.
Median Reductions in Morbidity Associated with Improved Water Supply and Sanitation: Conditions Other Than Diarrhea, Related Most Closely to Water Supply.
To be effective in controlling schistosomiasis, the water supply must be so convenient as to discourage water contact for laundry and bathing. It is unlikely that this level of convenience can be achieved without house connections.
Evidence suggests that water availability and hygiene can produce substantial reductions in trachoma (Emerson and others 2000). Because the reductions come from hygiene improvements such as hand and face washing, they are also likely to be greatest with house connections. Dracunculiasis is affected by water quality, but the simplest improved water supply is adequate to prevent transmission.
Conflicting evidence exists about whether water supply or improved water-washed hygiene affects the transmission of intestinal helminths. On one hand, Henry (1981) found in an intervention study in St. Lucia that piped water supplies were associated with a 30 percent reduction in ascariasis among children under age three over a two-year period. On the other hand, Han and others (1988) showed in Burma that an intervention to promote hand washing with soap had no effect on prevalence or intensity of infection with Ascaris spp. However, the potential contribution of water supply to reducing the burden of disease through its effect on these other infections is relatively minor when compared with its effect on diarrheal disease.
In the modern world the problem of the reliable water supply is extremely important because the water resources are widely exploited and water is used in different fields of human activities. In fact, the life of human beings is impossible without water but nowadays water is used not only simply to provide people with the essential substance they consume to survive but it is also widely used in agriculture and different industries. As a result, the water, being widely used, is naturally deteriorating in quality and decreasing in quantity because the water used in agriculture and industries is often impossible to recycle or filter to make it drinkable. In such a situation, the problem of scarcity of water as the vitally important product seems to be quite real. In this respect, it is necessary to underline that the US undertake various steps to improve the current situation and one of the strategic directions in the development of the federal and state policy is the effective treatment of wastewater. Despite the exiting differences in the water supply and water quality in different states, the high level of standards is equally important in all of the states.
First of all, it should be said that the water quality is extremely important to human health. It is not a secret that the current problem of the water pollution is a serious threat to the health of the entire nation since if the existing standards were lower the national health would be under a threat. The reason is quite obvious since nowadays it is practically impossible to consume water without any artificial treatment being applied (Anon 1998). What is meant here is the fact that nowadays water cannot be used in its original form as it is taken from the nature. In stark contrast, water needs to undergo various stages of special treatment that make it really pure and prepared for the consumption by people without any harm to their health.
Nowadays, due to the development of modern technologies, water undergoes various treatment that make the water purer and closer to its natural and practically ideal consistency. However, the latter is quite difficult to achieve because of the current environmental situation since the development of industries and water pollution undermine the natural potential of the effective water treatment so that the wastewater needs to be specifically treated to avoid the further pollution of natural water (Anon 1998). At this point, it should be said that various states may have different standards concerning the quality of water but, nonetheless, these standards should guarantee the safety of water consumed by people. This means that all states need to supply water which is really safe to human health and is close to its natural consistency without any pollutants.
By the way, it should be said that the water supply is another serious problem since it is getting to be more and more difficult to provide a permanent and ample supply of water to the population. In fact, in the result of the pollution and the increasing costs of its treatment the supply of water may vary depending on states (Bartram 2005). For instance, the states with larger natural resources of water and lower level of pollution could supply more water to consumers compared to the states where the water is naturally scarce and the situation is deteriorated by the high level of the pollution of water.
As a result, the states which are in a disadvantageous position in relation to the water supply need to invest more in the effective treatment of the wastewater and the reliable supply it to consumers. At the same time, these states face a serious problem of the lack of water. In such a situation, the water supply is really a great challenge since it is necessary to provide population with water of possibly higher quality regardless the resources of water and its initial quality. However, the state with larger water resources also need to pay a particular attention to the quality of water since it is the major condition of the supply of water to consumers.
Thus, taking into consideration all above mentioned, it is possible to conclude that nowadays states are in different positions since some states have larger resources of water and have better environmental situation, while others have scarce resources of water and the level of pollution is dangerously high. Nevertheless, regardless all these factors, the states need to provide population with the sufficient amount of water which should be of a high quality in order to guarantee the national health since the low quality of water or its insufficient supply threatens to the health of people and may provoke infectious diseases. This is why the quality of water and high standards remain the major factors that unite all the states in relation to the water supply.
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Posted in Essay Examples Tags: Environmental Issues, Health