Skip to main content Global Regions Select language Select language English العربية 中文 Français Русский Español Português Home Health Topics Countries Newsroom Emergencies Data About WHO Home/ Publications/ Overview/ Guidelines for drinking-water quality: fourth edition incorporating the first and second addenda Guidelines for drinking-water quality: fourth edition incorporating the first and second addenda 21 March 2022 | Guideline Download (5.1 MB) 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 Introduction A conceptual framework for implementing the Guidelines Health-based targets Water safety plans Surveillance Application of the Guidelines in specific circumstances Microbial aspects Chemical aspects Radiological aspects Acceptability aspects: Taste, odour and appearance Microbial fact sheets Chemical fact sheets Annex 1: Supporting documentation to the Guidelines Annex 2: References cited Annex 3: Chemical summary tables Annex 4: Anaytical methods and achievability Annex 5: Treatment methods and performance More information Annex 6: Supporting information on radionuclides Annex 7: Contributors to the development of the Guidelines for drinking-water - fourth edition incorporating the first and second addenda Related links Guidelines for drinking-water quality: small water supplies Corrigenda - 24 May 2023 More information View the list of chemical hazards considered in the WHO Guidelines for Drinking-water Quality Previous editions of the Guidelines for drinking-water quality (including French and Spanish versions of the fourth edition incorporating the first addendum and Russian, Chinese and Japanese versions of the fourth edition) EDITORS World Health Organization NUMBER OF PAGES 614 REFERENCE NUMBERS ISBN: 978-92-4-004506-4 COPYRIGHT Regions Africa Americas Eastern Mediterranean Europe South-East Asia Western Pacific Policies Cybersecurity Ethics Information disclosure Permissions and licensing Preventing sexual exploitation Terms of use About us Careers Frequently asked questions Library Procurement Publications Contact us Newsletters Report misconduct Privacy policy © 2026 WHO