Guidelines for drinking-water quality: fourth edition incorporating the first and second addenda

Overview

The fourth edition incorporating the first and second addenda, of the World Health Organization’s (WHO) Guidelines for drinking-water quality (GDWQ) builds on over 60 years of guidance by WHO on drinking-water quality, which has formed an authoritative basis for the setting of national regulations and standards for water safety in support of public health.

It is the product of significant revisions to clarify and elaborate on ways of implementing its recommendations of contextual hazard identification and risk management, through the establishment of health-based targets, catchment-to-consumer water safety plans and independent surveillance.

Updates in this latest edition reflect new evidence and further, provides additional explanations to support better understanding and application of the guidance. More details on the updates are included in the GDWQ preface.

What is new?

Guidance has been updated on a number of chemicals: asbestos, bentazone, chromium, iodine, manganese, microcystins,  nickel, silver, tetrachloroethene and trichloroethene. Guidance has also been added for chemicals not previously assessed in the Guidelines: anatoxin-a and analogues, cylindrospermopsins and saxitoxins. The new guidance on organotins has replaced the prior guidance focused on dialkyltins. With these updates, the guideline values for tetrachloroethene and trichloroethene have been revised while new guideline values for cylindrospermopsins, manganese, microcystins, and saxitoxins have been established  .

Updated information on cyanobacteria has been included, introducing an alert level framework for early-warning and to guide short-term management responses. Guidance has also been updated in the sections on adequacy of water supply, climate change, emergencies, food production and processing, and radiological aspects, particularly on managing radionuclides when exceeding WHO screening values and guidance levels.

More details on the updates are included here.

Read individual chapters

1. Introduction
2. A conceptual framework for implementing the Guidelines
3. Health-based targets
4. Water safety plans
5. Surveillance
6. Application of the Guidelines in specific circumstances
7. Microbial aspects
8. Chemical aspects
9. Radiological aspects
10. Acceptability aspects: Taste, odour and appearance
11. Microbial fact sheets
12. Chemical fact sheets
13. Annex 1: Supporting documentation to the Guidelines
14. Annex 2: References cited
15. Annex 3: Chemical summary tables
16. Annex 4: Anaytical methods and achievability
17. Annex 5: Treatment methods and performance More information
18. Annex 6: Supporting information on radionuclides
19. Annex 7: Contributors to the development of the Guidelines for drinking-water - fourth edition incorporating the first and second addenda