How many times have you gazed into a glass of water unimpressed with the utter simplicity of this liquid? Yet what tremendous power and versatility this innocent substance belies as it dazzles us throughout nature with a multitude of ever-changing forms, shapes, colors, and smells.

There are few things that equate with life as water does. Water creates life, and water maintains life. We exist as living beings only because there is water. It is as simple as that. There are plenty of reasons for the Bible, the Koran, and epic poems to praise the virtues of water and its seemingly magical properties. Many ancient oracles urged respect for this life-giving force and counseled that its prudent use would enable the resource to satisfy the needs of entire populations.

The strategic importance of water has been recognized since the dawn of time, serving as the canvas upon which have been drawn many of history's greatest triumphs and tragedies. In 1492, the mighty Atlantic carried Columbus to the discovery of previously unimagined lands and civilizations. The conquest of South America was greatly facilitated by formidable rivers that provided highways into the interior. Brazil owes most of its western border to the fact that emerald-seeking Portuguese explorers could travel far inland by means of a network of westward-running waterways. Ponce de León, in 1513, went to Florida in search of the fountain that would rejuvenate him and restore his battle-weary soul. Throughout history, disputes over access to and use of water have spawned regional and international conflicts, even wars. Most of the colonization of the Americas took place along waterways, and today many of the Region's largest and most important cities owe their prosperity to their proximity to rivers and oceans. Water fuels their industries and sustains economic development. In much the same way, life's most precious fluid fuels and sustains the human body by providing the medium in which all cellular activity takes place and by maintaining a stable temperature for these processes. The prodigious, around-the-clock performance of water enables the body to renew and regenerate itself continuously by carrying away old, worn-out substances and replacing them with fresh building materials.

To carry out this work, each of us will require about 23,000 gallons of water during our lifetime, or roughly 350 gallons every year. This is only for drinking. Our other water needs-for bathing, cleaning, cooking, and leisure, for example-call for even larger quantities. Therefore, say water experts, an adequate water supply is one capable of delivering 50 gallons of fresh water a day to each person in the community it serves.

How Much Water Do We Have?

Perhaps the most serious water problem we face today is its availability. Between 1900 and 1990, the world's demand for water increased sixfold, while the population only doubled during that same period. These demands include a variety of uses-from municipal, agricultural, and industrial to recreational and navigational-and the increase largely reflects the evolving sophistication of technology in the production of goods and services designed to improve our lives.

Yet even as the demand for water grows, the amount available to us through nature remains the same. In its continuous circular journey between the sky and earth, the rainwater captured from a river, lake, or stream for human activity actually is quite small: of the approximately 7 million cubic miles of freshwater in the world, only about 2,800 cubic miles is readily available to us in any given year. Although this translates into roughly 620 gallons a day for each person alive today, the figure is somewhat misleading: the world's irrigation needs alone account for two-thirds of this amount, followed by industrial use, which leaves only a very small fraction for our personal use.

Another issue of concern to health and environmental experts is the unequal geographical distribution of water among the world's continents, countries, and regions. Most of these resources are located in humid tropical areas and temperate zones. About 25 percent of the world's freshwater resources are found in Latin America and the Caribbean, where only 8 percent of the population lives. By contrast, Africa possesses 13 percent of the world's population but only 9 percent of its water. In the most arid deserts, the lack of rain forces people to make an impossible choice: divert the water to irrigate crops and increase food supply, while looking for additional, highly expensive sources for domestic and industrial use. For the residents of these areas, the search for water is a daily struggle for survival itself.

Water and Health

We are in contact with water throughout our lives and thus exposed to whatever it contains. The consequences to health of drinking or coming in physical contact with water contaminated by human, chemical, or industrial wastes can be enormous. The principal diseases caused by water include those that are waterborne, such as cholera, typhoid fever, amebic dysentery, and other diarrheal diseases. Others are water-washed diseases, which are caused by poor personal hygiene and skin or eye contact with contaminated water, and include scabies, trachoma, and lice-transmitted diseases. There also are water-based diseases such as dracunculiasis, schistosomiasis, and other helminths, which are caused by parasites found in organisms living in water, and water-related diseases caused by insects that breed in water and carry dengue, malaria, yellow fever, and other diseases.

Some of these diseases, such as ma-laria, which infects 300 million people a year globally and kills over 1 million of these, are leading public health problems in developing countries. According to the World Health Organization, "no single type of intervention has greater overall impact upon national development and public health than does the provision of safe drinking water and proper disposal of human excreta," adding that improved water and sanitation can reduce sickness and death from some of the most serious of these diseases by 20-80 percent.

Visible Results

As an environmental engineer, I have been surrounded by water, literally and figuratively, almost all my life. Many times I've stared out over vast expanses of water and remembered Samuel Coleridge's The Rime of the Ancient Mariner, written 200 years ago and still true today: "Water, water everywhere/nor any drop to drink." I have worked on drinking water projects for São Paulo, Brazil, the world's third largest metropolis, and small cities in the Amazonian interior such as Rio Branco. I've seen firsthand how water can transform people's lives and am convinced there are few public health interventions with such power to impact upon the hopes and aspirations of so many.

In the case of São Paulo, for example, a new system built during the early 1970s tripled the amount of clean drinking water available to 11 million Paulistas. An epidemiological study showed that as a consequence of the new system, the infant mortality rate fell from 93 per 1,000 live births in 1974 to 54 per 1,000 in 1981.

Public health authorities in Salvador da Bahia, Brazil's third largest city, have similar reasons to be optimistic. In 1992 they launched a project to improve the quality of the water supply and wastewater collection in Baixo Camarajipe, a poor community on the city's outskirts. The prevalence of intestinal infestations among children 7-14 years old fell from 90.5 percent in 1992 to 55 percent in 1997, while the prevalence of diarrheal diseases in children ages 0-5 dropped by some 30 percent between 1993 and 1998.

Perhaps the most dramatic example to illustrate the relationship between safe water and disease avoidance is the cholera epidemic that hit Latin America with a fury in 1991. Announcing itself in fishing villages along Peru's Pacific coast, the disease spread rapidly and left the sick to die within hours. Public health officials, unprepared for a pathogen not seen in the Americas for nearly a century, quickly dusted off the medical textbooks of their grandfathers' generation only to confirm what they already suspected: the cholera bacteria would thrive wherever water supplies were not disinfected and waste disposal systems did not meet minimum hygienic standards.

Three interactive elements could, however, turn the tide, and eventually, they did: better use and care of public and household water and sanitation facilities, increased availability of safe drinking water and sanitary means for excreta disposal, and a greater commitment by individuals, local governments, and community groups to provide sustainable improvements to water and sanitation infrastructure. At the same time, people quickly realized that the water they used could potentially kill them and came to accept the importance of chlorinating and boiling water, frequent hand-washing, safe food handling and preparation, and proper waste disposal. As a result of this large-scale knowledge transfer, behavior change, and awareness of personal and collective responsibility, the cholera situation in Latin America has greatly improved: in 1991, the disease's incidence was 96.5 per 100,000 inhabitants and by 1997, it had fallen to 3.9 per 100,000.

Attitudes and Knowledge

Yet in the year 2000, cholera is still with us, along with many other water diseases, despite our knowledge of applications leading to their irrevocable eradication. If governments have been lax in investing in long-term solutions, we as individuals are also guilty of indifference, misunderstanding, and undervaluing the link between water and health. Since ancient times, human instinct has been to react first to this naturally occurring pale blue odorless liquid based on its appearance and smell, with much less concern for its chemical and biological contents. I remember visiting villages in the Amazon where people flatly would reject muddy water. In order to render it drinkable, they would add pumice stones to the water pot. Once the sediment trickled to the bottom and the water took on a relatively clear appearance, it was deemed safe. This age-old custom served its observers well until the spreading cholera epidemic found a new habitat, and many people became sick and died.

At the peak of its eminence, nearly 2,000 years ago, the Roman Empire included almost all of the Western world then known to humankind. One of the hallmarks of this civilization was its well-maintained water and sanitation system and the enlightened views of its citizenry regarding health. Around A.D. 100, Frontinus, who was Rome's municipal water commissioner, commented on lessons learned from earlier times when he wrote in a government report: "I cannot understand why the prudent superior Augustus decided to conduct the waters from Alsietina, since they always were horrible and unhealthy, [and] therefore the population never came to use them." The basis for his observation could well have come from Hippocrates, who, some 500 years earlier, in his Airs, Waters, and Places, had ascribed the origins of disease to environmental causes and encouraged physicians to consider the quality of community water supplies relative to the existence-or absence-of health and disease.

Even as the body of evidence grew to support a link between water and health, public acceptance of measures to improve water quality waxed and waned. For example, water treatment as we know it today started in 1829 when the Chelsea Water Works in London installed a slow sand filter to process water from the Thames River. It was not a very prodigious start, and for several decades there was little public enthusiasm for this "new" invention. Yet it was also during the mid-1800s that typhoid fever and cholera epidemics raged throughout Europe at the same time the Americas waged war against cholera, yellow fever, and malaria.

In 1854, a cholera outbreak in London's Saint James parish killed 142 people during its first week. Dr. John Snow discovered that the majority of those who died had lived within 250 yards of a water pump at the intersection of Cambridge and Broad Streets. In reporting his findings to the Board of Guardians, the local officials responsible for public health and safety issues, he further noted that his colleague, the Reverend Henry Whitehead, had traced the disease's origin to conta-minated wastewater that had seeped into the well. The following day, the pump's handle was removed, "and the plague was stayed," according to Dr. Edwin Lankester, who later became the affected area's first public health officer.

Dr. Louis Pasteur added another dimension to Snow's work by shedding new light on the microorganisms causing typhoid fever in 1880 and cholera in 1883. Subsequent cholera outbreaks in Hamburg and Altona in 1892 benefited from the increasingly indisputable evidence that treating water supplies protected populations large and small from disease.

Water and Equity

In many ways, the cholera crisis of 1991 served as a definitive catalyst to mobilize governments and people to care more about water. Communities began to learn and observe basic safety measures and became more vigilant about the quality of their water. As a result, the affected countries have gained a greater awareness that most, if not all, of the more than 1.3 million cholera cases and some 11,000 deaths could have been prevented, and why.

With the link between safe water, a healthy population, and socioeconomic progress clearer than ever before, the question today for governments is how to reduce long-standing inequities in access to safe drinking water. According to a 1995 study conducted by the Pan American Health Organi-zation (PAHO), 18.22 percent of the total population of the Americas lacked access to safe water, with 40.58 percent living in rural areas and 13.28 percent in urban areas. The future work of governments, principally through ministries of health in conjunction with other public and private sector groups and the international community, will lie in forging effective partnerships to bridge these gaps.

In 1984, WHO published the first edition of its comprehensive Guidelines for Drinking-Water Quality that today is widely used in setting national standards to ensure water safety. The landmark publication established values for a large number of water constituents and contaminants, covering their microbiological, biological, chemical, radiological, and organoleptic aspects (i.e., qualities relating to taste, color, odor, and feel). In the book's second edition (1996), these values have been reviewed and updated wherever necessary to reflect new scientific discoveries.

One of the most cost-effective measures now gaining acceptance in the Region is a joint effort of various health ministries and national water authorities to place hypochlorite generators in community centers easily accessed by rural and marginal urban populations. Health posts are one of these places. During a visit here, a mother not only can receive medical attention, but learn how to disinfect the water her family drinks and take home a bottle of hypochlorite solution as a "remedy for the water." All Central American and many of the Andean countries have made impressive gains utilizing this community-based strategy. In El Salvador, for example, the public health sector recently launched "El Salvador 100 Percent," with the goal of ensuring that all public drinking water is bacteriologically safe. Similarly, PAHO and the U.S. Centers for Disease Control and Prevention have collaborated for a number of years on projects to disinfect water in remote rural villages in the highlands of Bolivia, as well as in neighboring countries.

Who Pays?

At a recent conference in Miami, Florida, PAHO's Director Dr. George A. O. Alleyne told water experts that in developing equitable policies for the provision of safe water, "it is inevitable that the economics of water use will enter into the discussion, as well as the need to consider water as an economic good in the sense that it has a value for which consumers will pay. Particularly in developing countries, there is a disproportionate benefit to the rich in that they enjoy the use of subsidized water, especially in the urban areas. Our own experience is that the marginalized urban poor who are often not connected to public systems pay inordinately high prices for the water they consume. The cost to the rural poor is high both in money terms, as well as in terms of the time and energy consumed in ferrying water for domestic use long distances."

These pivotal concerns are guiding the current debate in the Americas over how best to achieve equity in the provision of safe water at an affordable cost, on a sustainable basis, to 100 percent of the population. For governments, the challenge is to see water as both a social and an economic good. For you and me, our most valuable contribution will be to protect and use our water sources rationally and understand and practice the basic measures that will yield optimum health for us, our families, and our communities.

Freshwater is a scarce, valuable, and finite resource. The responsibility for its continued availability and ability to satisfy our needs belongs to all of us.

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Horst Otterstetter is a public health engineer, university professor, and environmental health consultant. From 1993 to 1999 he served as Director of PAHO's Division of Health and Environment in Washington, D.C.