WORLD Health Organisation’s Guidelines for safe drinking water are intended to be appropriate for national, regional and local circumstances.

That is to say, they are meant to suit the environmental, social, economic and cultural circumstances of each country, region or locality. The priorities are to be set accordingly.

According to WHO, the quality of drinking-water must be scrutinised through a combination of three strategies - protection of water sources, maintenance of treatment processes, and management of the distribution and handling of the water.

The Guidelines outline ‘a preventive management framework for safe drinking water’.

This framework comprises five key components: (1) health-based targets based on an evaluation of health concerns (2) system assessment to determine whether the drinking-water supply as a whole can deliver water that meets the health-based targets (3) monitoring of the control measures in the drinking- water supply, which are of particular importance in securing drinking-water safety (4) management plans, documenting the system-assessment and monitoring plans, and describing actions to be taken in normal operations and incident conditions, including upgrade and improvement, documentation and communication (5) and a system of independent surveillance that verifies the above are operating properly.

In support of the framework for safe drinkingwater, the Guidelines provide a range of supporting information, including microbial aspects, chemical aspects, radiological aspects and acceptability aspects.

The detection of microbial and chemical constituents of drinking-water that can cause adverse human health effects, is often slow, complex and costly. Reliance on water quality determination alone is insufficient to protect public health because it is neither physically nor economically feasible to test for all drinking-water quality parameters. Hence,monitoring efforts and resources should be carefully planned and directed at significant/key characteristics.

The control of microbial and chemical quality of drinking-water requires the development of management plans by water suppliers. Termed as ‘Water Safety Plans’, (WSPs) ensure that pathogens and chemicals do not pose any substantial risk to public health and that the water is fit for consumption. The WSP comprises system-assessment and design, operational-monitoring and management plans, including documentation and communication.

Even in the absence of formalized WSPs, many drinking-water suppliers provide adequately safe drinking water. However, there are benefits in developing and implementing a WSP for these supplies.

The benefits include the systematic and detailed assessment and prioritizations of hazards and the operational monitoring of barriers or control measures.

WSPs also provide for an organized and structured system to minimise the chance of failure through lapse of management. They also provide for contingency plans to respond to system failures or unforeseen hazardous events.

Health-based targets are an essential component of the drinking-water safety framework. They should be established by a high-level authority responsible for health in consultation with others, including water suppliers and affected communities.

They should take account of the overall public health situation and the contribution of drinking-water quality to disease. They must also take account of the importance of ensuring access to water to those who have no access to safe drinking water.

There are four principal types of health-based targets - Health outcome targets, Water quality targets (WQTs), Performance targets and Specified technology targets.

Health Outcome Targets apply in circumstances where waterborne diseases contribute to measurable health risks. Examples are the high microbial hazards in developing countries and chemical hazards with clearly defined health effects.

Water Quality Targets are established for individual drinking-water constituents that represent a health risk from long-term exposure and where fluctuations in concentration are small or occur over long periods.

Performance Targets are employed for constituents where short-term exposure represents a public health risk. They are typically expressed in terms of required reduction of the substance of concern or effectiveness in preventing contamination.

Specified Technology Targets are established by national regulatory agencies for specific actions for smaller municipal, community and household drinking-water supplies. Such targets may identify specific permissible devices or processes for given situations and/or for generic drinking-water system types.

Health-based targets underpin development of WSPs and assist in identifying the level and type of inspection and analytical verifications that are appropriate.

Most countries apply several types of targets for different types of supply and different contaminants. In order to ensure that they are relevant and supportive, representative scenarios should be developed.

These should also be supported by general guidance addressing the identification of national, regional or local priorities and progressive implementation, thereby helping to ensure that best use is made of available resources.

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