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Notice to Readers: World Water Day --- March 22, 2007

In 1992, the United Nations (UN) Conference on Environment and Development designated March 22 as World Water Day. The objective of World Water Day is to promote activities related to the conservation and development of water resources, such as the publication and distribution of related documents and the organization of conferences and seminars (1). The theme for World Water Day 2007 is Coping with Water Scarcity.

Approximately 1.1 billion persons lack access to an improved water source,* and 2.4 billion persons lack access to adequate sanitation. As a result of infectious diseases related to unsafe water and inadequate sanitation, an estimated 3 million people in developing regions of the world die each year, primarily children aged <5 years (2). One of the UN's millennium development goals is, by 2015, to decrease by half the proportion of persons without sustainable access to safe drinking water and basic sanitation. According to a recent assessment, some regions, including sub-Saharan Africa, will not meet their targets if current trends continue (3).

Diarrhea accounts for approximately 4 billion episodes of illness and 1.8 million deaths every year, disproportionately affecting young children (4). Likewise, developing regions are disproportionately affected by illnesses and deaths from waterborne pathogens. The World Health Organization (WHO) estimates that 94% of diarrheal disease episodes are preventable through environmental modifications, including interventions to increase the availability of clean water and to improve sanitation and hygiene (5).

Families without access to improved water sources or who might be using unsafe water can improve the quality of their drinking water through simple, inexpensive technologies to treat and safely store drinking water in their homes. Studies have documented a reduced risk for diarrhea in families who treat their household drinking water through solar disinfection or by chlorination, filtration, combined chlorination, and flocculation (6). Additional information on household water treatment is available from CDC at and from WHO at

In the United States, improved water quality has dramatically enhanced the health of the population. However, new challenges have developed, including the emergence of chlorine-resistant pathogens, chemical contamination of water sources, aging infrastructure, increased recreational water contamination, exposure to water from cooling towers and other nontraditional water sources, and increasing water reuse. These challenges are reflected in increasing numbers of disease outbreaks associated with 1) small or individual water systems, 2) recreational water, 3) building distribution systems, and 4) other water sources (e.g., cooling towers). An estimated 4 million to 33 million cases of gastrointestinal illness associated with public drinking water systems in the United States occur annually (7). However, these estimates are imprecise and do not include illnesses in the 45 million persons served by small or individual water systems, the >60 million persons who swim each year, other water exposures, or illnesses other than gastrointestinal illness.

Water-related activities throughout CDC address the relationship between water and public health from various perspectives, including the public health effects from contaminated drinking water and recreational water, global issues regarding safe water, waterborne disease outbreak surveillance and investigations, support for local and state health departments delivering water-related programs, and terrorism related to waterborne pathogens.


  1. United Nations Educational, Scientific, and Cultural Organization. 22 March---World Day for Water: coping with water scarcity. Available at
  2. Hutton G, Haller L. Evaluation of the costs and benefits of water and sanitation improvements at the global level. Geneva, Switzerland: World Health Organization; 2004. Available at
  3. World Health Organization, UNICEF. Meeting the MDG drinking water and sanitation target: the urban and rural challenge of the decade. 2006. Available at
  4. Kosek M, Bern C, Guerrant RL. The global burden of diarrhoeal disease, as estimated from studies published between 1992 and 2000. Bull World Health Organ 2003;81:197--204.
  5. Pruss A, Corvalan C. Preventing disease through healthy environments: towards an estimate of the environmental burden of disease. Geneva, Switzerland: World Health Organization; 2006. Available at
  6. Clasen T, Roberts I, Rabie T, Schmidt W, Cairncross S. Interventions to improve water quality for preventing diarrhoea. 2006. Cochrane Database Syst Rev 3:CD004794.
  7. CDC. 2006 national estimate of waterborne disease associated with public drinking water. Available at

* Water that is supplied through a household connection, public standpipe, borehole well, protected dug well, protected spring, or rain water collection.

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Date last reviewed: 3/15/2007


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