8 Water Quality and Hygiene
Box 8.1:
Summary of primary threats to drinking water quality8
The WHO Quality Guidelines identify the following as the general order of priority for water quality: a) Ensure an adequate supply of microbiologically safe water and maintain acceptability to discourage consumers from using potentially less microbiologically safe water; b) Manage key chemical contaminants known to cause adverse health effects; and c) Address other chemical contaminants. Microbial agents (Pathogens) These include harmful bacteria, viruses, protozoa and other biological organisms. The greatest microbial risks are associated with the ingestion of water contaminated with human or animal faeces. The overwhelming number of health concerns linked to water use relate to microbial agents. They can cause diseases after relatively brief periods of exposure. Chemical agents These agents normally cause adverse health effects after a long period of exposure, with the exception of massive accidental contamination of water supply. Many chemical agents, such as iron and manganese, can cause water to become undrinkable due to unacceptable, taste, odour and appearance. Natural chemical agents known to cause widespread health concerns are fluoride and arsenic and, when present in excess, uranium and selenium. Nitrates, which may arise from excessive application of fertilizers in agriculture or from the leaching of organic waste or wastewater into surface water and groundwater, are also hazardous to human health. The use of lead pipes, fittings or solder, particularly in areas with aggressive or acidic waters, can lead to high lead levels in water, causing adverse health effects. Radiological aspects It is also important to consider naturally occurring radionuclides in drinking water. However, the contribution of drinking water towards overall exposure to radionuclides is normally very small.
8.2 Formulating short and medium term targets to eliminate pollutants Since they necessitate the removal of all substances that threaten a person’s health, the requirements of General Comment No. 15 on water quality may seem unattainable in many developing countries. However, General Comment No. 15 also specifies that the obligations are to be realised progressively to the maximum extent possible with the available resources and that the ‘core obligation’ relating to water quality is to ensure that water is sufficient and safe enough to prevent disease.9 This can be achieved by prioritising the removal of harmful microbial contamination and a small number of chemical contaminants of primary concern to health, as listed in Box 8.1.10 The WHO Quality Guidelines indicate how the most significant risks to human health may be controlled. Short-term and medium- term targets can be set in a manner that builds the foundations for long-term progress.11 These targets can undergo periodic upgrading, involving periodic review to ensure that the norms
8
9 10
11
100
WHO Quality Guidelines, see note 3, pp. 3-7 and 34. See also A. Dufour et. al, Assessing Microbial Safety of Drinking Water: Improving Approaches and Methods (Geneva: WHO, 2003) and T. Thompson et al, Chemical Safety of Drinking-water: Assessing Priorities for Risk Management (Geneva: WHO, 2003). General Comment 15, paras. 17, 18, 37 (a). It should be noted that other human rights also have implications for water quality. The rights to food and an adequate standard of living require that water used for agriculture does not cause health risks. Information on this is provided in a document by the WHO, Guidelines on the Use of Waste-water in Agriculture. WHO Quality Guidelines, see note 3, p. 32. See also the application of this general principle in the Grootboom decision of the South African Constitutional Court, in Chapter 9: Accessibility, Box 9.3.
part iii • policies for implementation