DRINKING WATER SUPPLY AND ENVIRONMENTAL SANITATION FOR HEALTH

Dr Dennis B. Warner
Chief, Water, Sanitation and Health
World Health Organization
1211 Geneva 27, Switzerland

1 Introduction

 

For a large percentage of the world's population, drinking water supplies and sanitation services are neither safe nor adequate. Currently, over 1000 million people do not have access to an adequate supply of safe water for household consumption and nearly 3000 million lack a sanitary means of excreta disposal.

The provision of safe water and the management of wastewater have had a central role in reducing the incidence of many waterborne or water-related communicable diseases. One of the major achievements of the past 150 years is the extent to which diseases associated with water have become of minor significance in the mortality and morbidity statistics of most developed countries and of some developing countries (especially for richer groups living in major cities). The diseases associated with contaminated water, however, remain serious public health problems for most of the world's population. At the same time, water shortages in many countries are now imposing serious constraints on municipal and community development, as well as on the expansion of food production and the growth of industry. Countries with relatively low per capita levels of available freshwater are finding it difficult to meet the increasing demands for fresh water from expanding populations and the growing demands from agriculture and industry.

The main concerns in the relationship between water, sanitation and health are the effects of contaminated domestic environments on diseases associated with poor quality water and with unsanitary disposal of wastewater and human faeces.

2 The Impact of Water Upon Human Health

 

An adequate supply of safe drinking-water is universally recognized as a basic human need. Yet more than 1000 million people do not have ready access to an adequate and safe water supply, and a variety of physical, chemical and biological agents render many water sources less than wholesome for human consumption. Health hazards resulting from waterborne epidemics are usually due to poor management of water resources, although adverse natural conditions can also be causative.

The direct effects of improved water and sanitation services on health are most clearly seen in the case of water-related diseases, which arise from the ingestion of pathogens from contaminated water or food, and from exposure to insects or other vectors associated with water. Esrey et al. (1991) calculated that access to safe drinking water and basic sanitation services for populations currently at risk would result in:

· 200 million/year fewer diarrhoeal episodes

· 2.1 million/year fewer deaths caused by diarrhoea

· 76 000 fewer dracunculiasis cases

· 150 million fewer schistosomiasis cases

· 75 million fewer trachoma cases.

Safe water supplies for all populations can only be guaranteed when access, equity and sustainability are assured. Access can be defined as the number of people who have the capability to draw sufficient quantities of safe drinking water for meeting basic personal consumption and hygiene needs. Equity refers to the fair allocation of water between countries, between rich and poor populations and between rural and urban areas. Sustainability, a newer concept, refers to the capability of maintaining a service within available resources.

Water supply access and equity

The number of people without access to safe water dropped from around 1600 million in 1990 to around 1100 million in 1994. Currently, more than 800 million of the unserved live in rural areas. At the same time, the number of urban unserved is actually rising sharply in developing countries due to rapid urbanization, much of which is occurring in peri-urban and slum areas. Table 1 shows water supply coverage in the developing countries at the end of 1994.

Table 1. Water Supply Coverage: Urban and Rural Areas, 1994

Note: statistics are for developing countries only.

Source: WHO/UNICEF/WSSCC, 1996

Although per capita water availability is being reduced continuously due to increasing population density urban water utilities have been able to achieve at least partial coverage. The future outlook is rather bleak, however, with a water crisis predicted for many countries for the first half of the next century. Large-scale agricultural and industrial use will make it more difficult, and certainly much more costly, to supply urban areas with drinking-water in an increasingly competitive water market.

Global figures mask regional variations. Although the number of people without a safe water supply dropped by around 470 million during 1990–1994, the number unserved in Africa and in Latin America and the Caribbean has actually increased; almost all of the coverage gains have been in Asia and the Pacific.

In poorer areas, millions of people have access only to standpipes, which often receive intermittent supplies and at which they must queue for long periods, or handpumps which are poorly maintained. The health consequences resulting from the inequity of these poor services are sometimes considerable, as evidenced by the infant mortality rates which may vary between two and ten times in magnitude between those served with good water supplies and those which are not. The poor, in particular, are at high risk from epidemic diarrhoeal diseases, such as cholera.

Unaccounted for water (UFW) is a major water supply problem. In many large cities in the developing world UFW may exceed 50% of the total water produced. Most of this water is lost through leaking pipes, from overflowing service reservoirs or during distribution. Those who suffer most from this inefficiency are populations living in impoverished, outlying urban areas. They often must buy water of doubtful quality from private vendors at prices that may be 10 to 20 times higher than average piped water rates. But if measures to ensure the sustainability and organization of facilities were implemented, the extension of coverage to the fringe and poor areas of large cities would be possible. This would bring about considerable improvements in health. At the same time, the need to expand treatment and distribution facilities would be minimized, in effect releasing resources for other development activities.

Sustainability of water supply servicesof water supply services

Water supply sustainability involves ensuring the continuous availability of sufficient quantities of water of sufficient quality and within adequate institutional frameworks. It also involves applying sound management practices, appropriate technologies, and full-cost accounting, and effectively maintaining facilities and equipment. In rural areas, sustainability also involves the need to strengthen the ability of communities or local governments to operate and maintain water supply systems and, where possible, build or improve facilities. In developing countries, however, the management of water supply and sanitation systems is often poor, resulting in interruptions in the provision of services and sometimes in the complete collapse of water supply systems. When the latter happens, users often resort to traditional water sources which may be contaminated.

Measures to ensure the sustainability and optimization of water supply services should deal not only with the visible effects of poor performance, such as leakage, intermittent water supplies or collapse of a handpump, but also with the causes of poor performance, including planning aspects, financial issues, operation, maintenance, information systems, human resources development, administrative issues, gender aspects and community management.

3 The Role of Sanitation in Protecting Health

 

In its broadest sense, environmental sanitation refers to measures taken to control or change the physical environment in order to prevent the transmission of diseases to human beings. Thus, environmental sanitation here means interventions intended to improve access to safe and sufficient water supply, to encourage the sanitary disposal of human excreta and household wastes, and to change human behaviours through hygiene education. The primary purpose of these interventions is to prevent or limit the transmission of diseases arising from poor environmental sanitation. Annex 1 provides estimates of illness and death resulting from diseases related to poor environmental sanitation.

In developed countries nearly all human excreta is collected safely via sewerage systems, septic systems or other sanitation systems. However, considerable amounts of sewage are nevertheless discharged into the environment in these countries.

In developing countries the sanitation coverage picture is very different. A small proportion of the total population, very roughly 10% and mainly urban, has access to sewerage systems and a slightly larger proportion, very roughly 20%, has some type of on-site sanitation facility. But the vast majority (about 65%) of people in developing countries do not have appropriate sanitation systems.

Sanitation coverage also varies enormously by region. Table 2 shows the variability in rural and urban sanitation coverage for developing countries in the four regions of the world.

Table 2. Sanitation Coverage: Urban and Rural Areas, 1994

Note: statistics are for developing countries only.

Source: WHO/UNICEF/WSSCC, 1996

Of the unserved in developing countries (2900 million), 80% live in rural areas. Most of the faeces of the unserved are recycled for use in agriculture or deposited on land without prior destruction of pathogens, most of which eventually enter surface and groundwaters, sometimes surviving for considerable lengths of time. Not surprisingly, infectious diseases such as diarrhoeal diseases, schistosomiasis and hepatitis are endemic, and sometimes epidemic in unserved areas.

The health threat from human excreta

On average, human beings produce 1150 g of urine and 200 g of faeces per day. Thus, globally, about 500 million kg per day of human faeces are generated in urban areas and about 600 million kg in rural areas, producing a total of over one million tons per day. Most of this biodegradable organic material is disposed of with very little or no treatment, thereby polluting the environment with organisms that are highly dangerous to human health. Pathogens enter the human body via contaminated drinking-water and contaminated food, via hands contaminated with faecal matter, and, in the case of some helminthic worm infections, directly through the skin. Ingestion of faecal pathogens can cause diarrhoeal disease, cholera, intestinal worm infections and typhoid fever. Urinating into bodies of water perpetuates urinary schistosomiasis. If a dangerous pathogen, such as Vibrio cholerae, is introduced into a community with poor sanitation, poor water supply and poor food safety, epidemic cholera may ensue, as in South America in the early 1990s.

The most effective way to break these cycles of disease is by improving sanitation coverage, treating wastewaters discharged by sewer systems, and educating the populations at risk.

On-site sanitation

Of the 20% of people in developing countries who have on-site sanitation, such as a septic system or latrine (such as pit, pour-flush or composting), a number are still at risk. This is because some on-site sanitation systems do not completely protect human health. For example, an on-site sanitation system may protect the health of an individual household, but its design may be such that pathogens are released into local water bodies. Pit latrines, for instance, often leach into groundwater, contaminating it with pathogens. This problem is certainly increasing in those urban areas where crucial groundwater resources lie beneath crowded communities not connected to sewerage systems. Additionally, in rural areas, the contents of pit latrines are deposited on fields to dry and decompose causing, and pathogens to wash into nearby water bodies.

Sewerage

Most cities in developed countries are fully sewered, collecting virtually all wastewater and removing it away from city centres. But some of this wastewater is discharged without treatment. In developing countries, cities are typically only partially sewered: the proportion of the population served may range from a small percentage to 100% in a very few cases. The treatment of wastewater also varies considerably. In most cases sewerage systems in developing countries rarely connect to effective treatment facilities. Data on these issues are not readily available. As for rural communities in developing countries, sewerage is uncommon.

Trends in sanitation coverage

Based upon current trends, the total unserved population is expected to increase to 3300 million by the year 2000. Various factors complicate the task of improving sanitation in developing countries. For instance, recent urbanization has been very rapid, often consisting of the mushrooming of informal settlements at the periphery of principal settlements. Informal urban settlements are usually densely populated, suffer from poor-quality housing, and frequently lie outside the remit of the municipal waste management authority. The application of conventional waste treatment methods is obviously difficult in such conditions and innovative approaches are called for.

The state of existing sewerage systems presents further problems. Many of the sewerage networks in developing countries, especially Africa, were constructed a century or more ago. Most of these systems have not been maintained adequately and are now in dire need of rehabilitation. Additionally, increases in population density and per capita water consumption have caused the systems to become overloaded. Sanitation planning for the future must therefore take into consideration not only the financial requirements of new systems for those as yet unserved, but also the resources needed to rehabilitate systems representing past infrastructural investments. This underscores the importance of continuous operation and maintenance to avoid later costly repairs and reconstruction works.

                        4 Conclusions

Two major conclusions can be derived from the previous discussion. The first is that human health is very much impacted by unsafe drinking water and poor environmental sanitation. Diseases related to polluted drinking water, unsanitary food preparation, improper excreta disposal and unclean household environments constitute a major burden on the health of peoples in the developing world and are the leading causes of ill-health in children. Diarrhoea and dysentery alone strike young children several billion times per year and annually kill over 2 million before their fifth birthday. Environmental sanitation interventions, however, can reduce the incidence of certain illnesses by 20% to 80% by inhibiting disease generation, interrupting disease transmission and reducing disease exposure. Sustainable health, especially for children, is not possible without good environmental sanitation.

The second conclusion is that development interventions in the form of water supply, sanitation and hygiene education are not meeting the needs of the developing countries. There are currently 1.1 billion people without safe drinking water and 2.9 billion people lacking a sanitary means of excreta disposal. Countries with the highest rates of infant and child mortality and the lowest figures for income and life expectancy tend to have poor environmental sanitation services. Since water and sanitation facilities are normally provided by institutions outside of the health sector, these services do not achieve optimal health benefits. Recent developmental work, however, has shown that the incorporation of hygiene education, participatory methods, communication techniques and concepts of behaviour change into environmental sanitation programmes can greatly strengthen their effectiveness in improving health conditions.

References

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Annex 1. Estimates of Morbidity and Mortality of Diseases Related to Poor Environmental Sanitation

Source: WHO, 1997a