In 1999 the United Nations acknowledged that the development gap between rich and poor countries was widening: about three-fifths of the world's population lacked access to basic sanitation; and one-third did not have access to safe drinking water. Industrial development affects public health both favorably and unfavorably. Improved housing and social conditions and reductions in infectious diseases like gastroenteritis or pneumonia are often accompanied by increases in degenerative, noninfectious diseases like cancer and heart disease. In rapidly developing countries, such as Mexico, the People's Republic of China, and the Philippines, new public health problems often emerge before the old ones have been solved, and it is important to assess which problems pose the greatest risks to health, and which solutions are most cost-effective. Large funding organizations like the United Nations, the World Bank, and regional development banks now recognize that to solve priority health problems requires improvements in behaviors, attitudes, skills, services, products, and infrastructure that together yield lasting benefits long after external support is withdrawn.
In this global context, providing both safe drinking water and wastewater sanitation have long been recognized as priorities for the improvement of human health, especially in the prevention of infant and child mortality from diarrheas and dysenteries (e.g., Amoebiasis, caused by a protozoan; or E. coli diarrhea, caused by a bacterium). An estimated 4 billion cases of diarrheal disease occur worldwide every year, killing an estimated 3
|Major Water-Related Diseases and Sanitation Solutions|
|Disease||Infection route||Range||Cases1||Deaths per year||
br />Sanitation Solution
|Major Water-borne Diseases|
|1. Amoebic dysentry||Protozoa (e.g. Giardiaor Cryptosporidium) follow the fecaloral route; i.e., feces contaminate water and/or food that is ingested.||Worldwide||500 million per year||included in 3. below||Unsanitary excreta disposal, poor personal and
domestic hygiene, unsafe drinking water.
br /> Low-cost sanitation such as latrines, pour-flush toilets, and septic tanks. Education to promote basic hygiene (e.g., washing food, handwashing before eating and preparing meals). Provide safe drinking water sources.
|2. Bacillary dysentry||Bacteria by fecal-oral route||Worldwide||included in 3.||included in 3.|
|3. Diarrheal disease (incl. Amoebic and Bacillary dysentry)||Various bacteria, viruses, and protozoa by fecal-oral route.||Worldwide||4 billion in 1998||3-4 million|
|4. Cholera||Bacteria by fecal-oral route.||S. America, Africa, Asia||384,000 per year||20,000|
|5. Hepatitis A||Virus by fecal-oral route.||Worldwide||600,000 to 3 million per year||2,400-12,000|
|6. Paratyphoid & Typhoid||Bacteria by fecal-oral route.||Asia (80%), Africa, Latin America (20%)||16 million in 1996||600,000|
|7. Polio||Virus by fecal-oral route.||India (66%), Near East, Asia, Africa (34%)||82,000 in 1996||9,000|
|Major Water-based Diseases|
|8. Ascariasis||Eggs in human fecesarvae develop in soiloil on foodood eaten by humans and worm infects small intestine.||Africa, Asia, Latin America||250 million in 1996||60,000||Unsanitary excreta disposal, poor personal and domestic
br /> Low-cost sanitation. Education to promote basic hygiene, especially in children.
|9. Clonorchiasis||Worms in snailsnails eaten by fishaw/undercooked fish eaten by humans.||Southeast Asia||28 million in 1994||None reported||Unsanitary excreta disposal, poor personal and domestic
br /> Low-cost sanitation. Education to promote basic hygiene.
|10. Dracunculiasis (Guinea worm)||Human host has blister, immersion in water causes larvae to release, larvae eaten by crustacean, in turn eaten by humans.||Sudan (78%), sub-Saharan Africa||153,000 per year||None reported||Unsafe drinking water supply.
br /> Provide safe drinking water supply.
|11. Necatoriasis (Hookworm)||Eggs in feces hatch to larvae in soil and on grass, pass into humans through skin to infect small intestine.||Tropical and subtropical Africa and Asia||900 million in 1990||60,000 per year||Unsanitary excreta disposal, poor personal and domestic
br /> Low-cost sanitation such as
|12. Paragonimiasis||Worms in human lungs lay eggs, coughed up and swallowedggs excreted in feces and break in freshwater. Larvae find snail host then move into crab or crayfishumans eat raw seafoodorms move from stomach to lungs.||Far East, Latin America||5 million in 1994||None reported||latrines, pour-flush toilets, and septic tanks. Education to promote basic hygiene.|
|13. Schistosomiasis (Bilharzia)||Eggs passed out in feces to water, releasing parasitesass into snail host to replicateass into waterass through human skin and become worms.||Africa, Near East, Western Pacific, Southeast Asia||200 million in 1996||20,000||Unsanitary excreta disposal, unsafe bathing water.
br /> Provide safe water. Low-cost sanitation such as latrines, pour-flush toilets, and septic tanks.
Table 1 continued
|Major Water-Related Diseases and Sanitation Solutions|
|Disease||Infection route||Range||Cases1||Deaths per year||ProblemSanitation Solution|
|*cases given as number per year (incidence) or as number of cases in existence at a given time/in a given year (prevalence)|
|SOURCES: Hinrichsen et al., 1998; World Health Organization at http://www.who.ch/|
|Major Water-related Vector Diseases|
|14. Dengue||Virus passes to mosquito from infected person or animaleplicates and passes again into human by mosquito bite.||Tropical areas, Asia, Central and South America||50-100 million per year||24,000||Poor water management: poor operation of water
sources, drainage and storage. Poor solid waste management.
br /> Combination of improved water management (drainage, preventing stagnant water bodies), physical barriers to hosts (bednets, screens at night), biological methods (introduce natural enemies of hosts), and chemical (pesticides). Best methods emphasize sanitation to reduce dependence on chemicals like DDT.
|15. Filariasis (includes Elephantiasis)||Worm larvae pass to mosquito and replicateass into humans by bite.||Africa, Eastern Mediterranean, Asia, South America||120 million in 1996||None reported|
|16. Malaria||Protozoa in mosquito gut pass to humans by bite.||Africa, Southeast Asia, India, South America||300-500 million per year (clinical)||2 million|
|17. Onchocerciasis (river blindness)||Worm embryos eaten by black flies and become larvaeass to humans by bite.||sub-Saharan Africa, Latin America||18 million in 1996||None reported but 270,000 cases of blindness per year|
|18. Rift valley fever (RVF)||Virus passes to mosquito/other blood-sucking insects from infected person or animaleplicates and passes again into human by bite.||sub-Saharan Africa||No data||No data|
|19. Trachoma||Virus infects eye and infection is contagious.||Worldwide||150 million||None reported but 5.9 million cases of blindness or severe complications per year||Lack of face washing, bathing and safe water.
br /> Provide safe water. Personal hygiene and education.
|20. Flea, mite (e.g. Scabies), lice, and tick-borne diseases||Contagious skin infections caused by contact with fleas, mites, lice and ticks.||Worldwide||No data||No data|
to 4 million people per year, most of them children (see Table 1). While it can be readily argued that a safe water supply plus wastewater sanitation is the most cost-effective public health goal for any given population, in practice, many social, cultural, technical, and economic factors govern whether the design and implementation of these systems will provide the long-term benefits sought.
To measure development and health progress, public health agencies use indicators such as access to water supply, access to sanitation, the under-five-year-old child mortality rate (U5MR), and per capita income. In 2000, the UN reported that the U5MR varied from 4 per 1,000 live births for developed countries like Sweden, Japan, and Norway, to 280,292, and 316 per 1,000 for Niger, Angola, and Sierra Leone, respectively. Figure 1 shows the relationship between the U5MR and access to safe water. Figure 2 shows the relationship between the U5MR and access to sanitation. These figures clearly show that improved water supply and/or sanitation can reduce child mortality (see Table 2).
WATER AND HEALTH
The uncontrolled pollution of water supplies by chemical and pathogens is one of the most serious threats to public health and the natural environment in developing countries. Standing water is a
medium for vector-borne diseases, and caused by poor water management, especially poor drainage. Table 1 shows the main water-related diseases from pathogens (viruses, bacteria, and protozoa), their relative geographical extent, numbers of cases, mortality rate, and sanitation solutions. Although the focus for remediation varies by disease and local conditions, all solutions include attention to four basic factors: 1) basic infrastructure (water supply and waste disposal); 2) personal and domestic hygiene; 3) better housing; and 4) primary health care and health promotion. Where basic infrastructure is lacking, pathogens are the priority contaminants, although the comparative risks posed by chemical pollutants should also be considered, especially in industrial areas and areas using pesticides. In dealing with pathogens in these areas, it is important to consider the life cycle of pathogens, pathogen infection routes, and pathogen susceptibility to treatment.
Chemical pollution of water from agricultural and/or industrial practices may include organic substances such as polychlorinated biphenyls (PCBs), chlorinated pesticides and herbicides, polyaromatic hydrocarbons (PAHs), solvents and disinfection by-products (DBPs), as well as inorganic substances like metals and nitrates. The risks posed by such chemicals to human health depend on three parameters: their concentrations in the water; their specific toxicity for both cancer effects and noncancer effects (e.g., birth defects, reproductive effects, neurotoxicity); and dose rate (the amount of substance entering the body over time). Pollutants in water can enter the body by ingestion of the water in drinks and food, by bathing and skin contact with the water, and by inhalation of the water vapor while showering.
Sanitation solutions for chemical agents combine prevention and cure tactics. Prevention includes minimizing the sources of pollution by substituting nontoxic substances and using cleaner, more efficient technologies. Cure consists of treating water to appropriate quality standards according to use (domestic, industrial, or agricultural). Water supply and wastewater treatment systems in developing countries must be affordable, cost-effective, and able to be maintained by local people.
The monitoring and enforcement of appropriate water quality standards is a vital part of sanitation. Diverse chemical and microbial standards seek to regulate important known risk agents, and acceptable levels must be monitored. In the United States, the Primary ("legally enforceable") Drinking Water Standards cover 60 organic chemicals, 20 inorganics, and 8 microbes/indicator organisms. The World Health Organization's Guidelines for Drinking-Water Quality includes over 60 organic chemicals (31 of them pesticides), 19 inorganics, 17 disinfectants and their by-products, and pathogens. However, although water quality laws exist in many developing countries, their enforcement is either weak or nonexistent, most often due to a lack of resources and political will.
The 1980s were designated the International Drinking Water Supply and Sanitation Decade by the United Nations. Despite the efforts of this campaign, however, in many countries more than half the rural populations are without adequate water supply access and sanitation. Many of the failures can be explained by weaknesses in the design and implementation of projects, as evidenced by many abandoned water and wastewater treatment plants. Such weaknesses often stem from a lack of maintenance caused by failures in equipment or training. A widespread lack of community participation in projects also helps explain failures. In most developing countries, the public sector provides facilities to central urban areas but
|World Sanitation Status|
|Country||W (%)||S (%)||U5MR||P||Country||W (%)||S (%)||U5MR||P||Country||W (%)||S (%)||U5MR||P|
|SOURCE: UNICEF 2000, multiple data compilation|
|Bahrain||94||97||133||20||Haiti||37||25||36||130||Papua New Guinea||41||83||45||112|
|Bhutan||58||70||41||116||Iraq||81||75||37||125||St. Kitts and Nevis||100||100||90||37|
|Botswana||90||55||77||48||Jordan||97||99||93||36||Sao Tome and Principe||82||35||61||77|
|Burundi||52||51||17||176||Korea, Dem. People's Rep.||100||99||104||30||Sierra Leone||34||11||1||316|
|Cambodia||30||19||24||163||Korea, Rep. of||93||100||175||5||Somalia||31||43||8||211|
|Cape Verde||65||27||65||73||Lao People's Dem. Rep.||44||18||41||116||Sri Lanka||57||63||137||19|
|Central African Rep.||38||27||18||173||Lebanon||94||63||94||35||Sudan||73||51||43||115|
|Congo, Dem. Rep.||42||18||9||207||Malaysia||78||94||153||10||Tonga||95||95||120||23|
|Dominica||96||80||133||20||Micronesia||22||39||117||24||United Arab Emirates||97||92||153||10|
|Dominican Rep.||79||85||75||51||Rep. of Moldova||55||50||94||35||United States||100||100||160||8|
|Equatorial Guinea||95||54||20||171||Myanmar||60||43||44||113||Viet Nam||45||29||85||42|
|W percentage of population with access to safe drinking water 1990-98|
|S percentage of population with access to adequate sanitation 1990-98|
|U5MR world ranking of under-five-year-old mortality (1998 data)|
|P 1998 under-five-year-old mortality: probability of dying between birth and 5 years old expressed per 1,000 live births|
leaves rural and marginal urban areas underserved. A 1990 evaluation of water-decade achievements in rural Bangladesh revealed that even when safe water supply and sanitary latrines were provided, people did not always use them, while only a third of the household water supplies had adequate usage. This demonstrates the need for joint improvements in education and economic conditions to accompany investments in infrastructure.
A useful reference for the visualization of health-risk sources, diseases, and solutions is the water-wastewater cycle (see Figure 3). The cycle ideally consists of water supply parts and sanitation counterparts, with each stage (or lack of it) affecting others. It should be remembered that this engineered cycle operates within the natural constraints of a dynamic hydrological cycle that supplies water to plants and animals as well as
people. Human beings have coevolved with other species in these ecosystems, while at the same time becoming super-modifiers of them. Logically, the health of people is influenced by the condition of these ecosystems.
Holistic environmental sanitation has four main water-related aspects: water supply, rainwater drainage, solid waste disposal, and excreta disposal.
Water Supply. The major problem for poor people in most countries is access to safe water in adequate quantity, with reasonable convenience, and at an affordable cost. Solutions include local grants to install household gutters and rainwater capture tanks; local wells designed to resist pollution; and small networks of water points served by a local well, borehole, or spring. The supply problems of major cities require integrated approaches that combine demand management, leak repair, backflow prevention, wastewater reuse, and the efficient, sustainable exploitation of sources.
Rainwater Drainage. Without adequate control of rainwater to mitigate floods and soil erosion, other sanitation measures can be nullified. People safe from floods and mudslides are more willing to invest in sanitation for their homes; and those in poor tropical urban areas attach a high priority to rainwater drainage. While local communities can build local drainage, downstream obstructions can cause the backing-up of channels and rivers, requiring a watershed-wide strategy.
Solid Waste Disposal. The interdependence of sanitation aspects is illustrated by the need for adequate solid waste removal to prevent the blockage of rainwater drains. Collection of refuse in hot climates must be frequent since piles attract flies and rats, and it should rely more on local labor-intensive methods rather than on expensive trucks. For the operation to be successful requires close cooperation between the users and providers of the service, and financing must come either from municipal recurrent funds and/or user fees.
Excreta Disposal. Large sewerage infrastructure projects tend to be too expensive for the vast majority of urban and rural people in developing countries, and it may be impossible to build a sewage network infrastructure in congested, narrow streets. On-site options include latrines, pourflush toilets, and septic tanks. There should be evaluated at each location according to needs and priorities. As water use grows in villages and towns, wastewater from washing and bathing (sullage) can be cost-effectively handled by a separate drainage system coupled to on-site excreta disposal.
TOWARD LASTING SANITATION
Sanitation, including water supply, is a major part of the United Nation's 1992 Agenda 21, a "Blueprint for Sustainable Development." The paradigm of sustainable development focuses on how to satisfy the basic needs of the present human population, and also secure resources to satisfy the needs of future generations. Growing population pressure, persistent poverty, and ecological degradation call for new integrated solutions to sanitation problems that strengthen both socio-economic and technical elements, including the following:
- Financial, political, and societal will to invest in public health and the environment.
- Human resources and public awareness through education and training.
- Information resourcesn health, water cycle, and ecological monitoringor informed planning and actions.
- Regulatory frameworks, enforcement, and compliance.
- Basic sanitation infrastructure suited to local priorities and conditions.
- A market for public health and environmental support goods and services that provide economically viable, effective, and lasting sanitation strategies.
These elements are interdependent. For example, adequate training improves monitoring and the operation and maintenance of infrastructure; and effective, enforced regulations stimulate a market and long-term investment. In India, state water boards were established to prevent pollution under the 1974 Water Act, closely modeled on systems in Great Britain. However, despite good scientists and engineers on staff, the chronic shortage of funds means controls have a limited effect on sanitation.
Above all, the support and involvement of the local community are essential if sanitation is to work. Ideally, many social sectors should be involved, to varying degrees, in community-driven ("bottom-up") sanitation projects. Sanitation users, water and public health regulators and administrators, health professionals, sanitation engineers, ecologists, researchers and scientists, financing agencies and donors, nongovernmental organizations, and suppliers of health and sanitation products and services can all contribute to a successful project. These new approaches reflect the trend away from professionally centered, curative methods and towards multi-stakeholder preventive strategies. To face these challenges, public health professionals and institutions need to play an expanding role as facilitators and promoters of this trend, building new partnerships in developing and developed countries. Protecting public health and ecological integrity are ethical and practical imperatives to be viewed as opportunities for people from diverse cultures, social groups, and disciplines to work more closely together.
TIMOTHY J. DOWNS
I. H. SUFFET
(SEE ALSO: Chlorination; Drinking Water; E. Coli; International Development of Public Health; Rural Public Health, Sanitation; Sewage System; Wastewater Treatment; Waterborne Diseases; Water Quality; Water Treatment)
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