Water for people.pdf - WHO Thailand Digital Repository

B A S I C N E E D S A N D T H E R I G H T T O H E A LT H / 1 0 3amoebiasis and a number of other protozoal and viral infections),typhoid and paratyphoid fevers, acute hepatitis A, acute hepatitis Eand F, fluorosis, arsenicosis, legionellosis, methaemoglobinaemia,schistosomiasis, trachoma, intestinal helminth infections (includingascariasis, trichuriasis and hookworm infection), dracunculiasis,scabies, dengue, the filariases (including lymphatic filariasis andonchocerciasis), malaria, Japanese encephalitis, West Nile virusinfection, yellow fever and impetigo.Yet there are also indications of water quality, quantity and/orhygiene links to conditions as diverse as ischemic heart disease ormalignant bladder tumours. Unintentional drowning is a major causeof death in the category of accidents and injuries, and that samecategory also includes the permanent skeletal damage caused towomen from carrying heavy loads of water over long distances dayafter day.The burden of disease conceptAn extensive debate took place in the 1980s on the issuessurrounding the economic impact of ill-health, the ways in whichthe health sector should let economics influence decision-makingand the use of its limited resources for interventions, and thetransfer of hidden costs to the health sector resulting fromdevelopment projects with adverse health impacts. This healtheconomicsdebate led to the development of a number of newindicators linking the costs of interventions to health outcomes interms of quality of life and well-being, while striving for greaterequity. The 1993 World Development Report, with the themeInvesting in Health (World Bank, 1993) formally introduced a newindicator of population health, the Disability-Adjusted Life Year(DALY).The DALY is a summary measure of population health. One DALYrepresents a lost year of healthy life and is used to estimate thegap between the current health of a population and an idealsituation where everyone in that population would live into old agein full health. For each disease DALYs are calculated, on apopulation scale, as the sum of years lost due to prematuremortality (YLL) and the healthy years lost due to disability (YLD) forincident cases of the ill-health condition (WHO, 2002e).Within the context of the health sector, DALYs are used to estimatethe burden caused by specific diseases, injuries and risk factors.Burden of disease estimates are used as a decision-making criterion tochoose between the deployment of such disparate interventions as, forexample, a measles vaccination campaign and indoor residual sprayingfor malaria control. Now that the effect of interventions can beexpressed in fully comparable units it has become possible to establishthe relative cost-effectiveness of each intervention. The WHO reportson the status of world health every year with global burden of diseaseestimates as the main statistics.The mortality and burden of disease estimates for the year 2001for some water-associated infectious diseases and for drowning arepresented in table 5.1. The causes of death have been estimatedbased on data from national vital registration systems that captureabout 17 million deaths annually. In addition, information from sampleregistration systems, population laboratories and epidemiologicalanalyses of specific conditions has been used to improve theestimates. These figures illustrate how the extended debilitatingnature of some diseases reflects in the burden they cause (e.g.lymphatic filariasis); they also indicate where major reductions indisease burden can be achieved beyond a strict reduction in mortality.Water and health: an intricate relationshipThe definition of health as contained in the 1948 Constitution ofWHO has withstood the ravages of time: ‘Health is a complete stateof physical, mental and social well-being, and not merely theabsence of disease and infirmity.’ Certainly, having one’s basicneeds in terms of water met and being able to rely on a sustainablelivelihood are crucial elements of social well-being, and contributesubstantially to physical and mental well-being as well. From hereon, however, the issue becomes more complex. Water and healthare intricately linked. A workable public health perspective of allwater issues requires a clear definition of the nature and magnitudeof the links between the two.There are basically two types of links, which facilitate theelucidation of cause-effect relationships between water managementissues and impacts on health: water as the conveyance medium ofpathogens (disease-causing organisms), and water providing thehabitat for vectors and intermediate hosts of pathogens (for speciesthat produce or maintain pathogens). Water plays a conveyance rolefor micro-organisms, chemical pollutants and sources of radiologicalrisks. The importance of this role for health relates mainly to drinkingwater, but also indirectly to water applied to food crops andlivestock, and through aerosols generated by air conditioningsystems. This role alters to a health-promoting mechanism whenwater is used for purposes of hygiene: from this perspective,quantity is a more important determining factor than quality.Aquatic ecosystems serve as breeding habitats for insect vectorsof diseases and for snails that serve as intermediate hosts in thetransmission cycle of certain parasitic diseases. These ecosystemscan be permanent, with wetland areas as the most obviousexample, or seasonal, linked to local weather patterns.Lack of adequate sanitation is the most critical determinant ofcontamination of drinking water with micro-organisms. Pollutionfrom urban and industrial waste and runoff of agrochemicals is byand large responsible for chemical contamination, although naturallyoccurring anorganic pollutants (fluor and arsenic) may alsocontribute substantially. Wastewater use in agricultural production