The first and second editions of the Guidelines for Drinking-water Quality were used by developing and developed countries worldwide as the basis for regulation and standard setting to ensure the safety of drinking-water. They recognized the priority that should be given to ensuring microbial safety and provided guideline values for a large number of chemical hazards.

The third edition of the Guidelines has been comprehensively updated to take account of developments in risk assessment and risk management since the second edition. It describes a “Framework for Drinking-water Safety” and discusses the roles and responsibilities of different stakeholders, including the complementary roles of national regulators, suppliers, communities and independent “surveillance” agencies.

Developments in the third edition of the Guidelines include significantly expanded guidance on ensuring the microbial safety of drinking-water – in particular through comprehensive system-specific “water safety plans”. Information on many chemicals has been revised to account for new scientific information and information on chemicals not previously considered has been included. For the first time, reviews of many waterborne pathogens are provided.

Recognizing the need for different tools and approaches in supporting large and community supplies, in the third edition continues to describe the principal characteristics of the approaches to each. New sections deal with the application of the Guidelines to specific circumstances, such as emergencies and disasters, large buildings, packaged/bottled water, travellers, desalination systems, food production and processing and water safety on ships and in aviation.

The first addendum, which updates the third edition, has been incorporated inthis volume. It includes more guidance on management of emergencies and unforeseen events, additions concerning chlorination by-products and developing standards for volatile substances, and several new fact sheets for chemical substances.

This is a World Health Organization (WHO) Report.