Guidelines for Drinking-water Quality FOURTH EDITION
Author: WHOThis edition of the Guidelines for drinking-water quality integrates the third edition, which was published in 2004, with both the first addendum to the third edition, published in 2006, and the second addendum to the third edition, published in 2008. It supersedes previous editions of the Guidelines and previous International Standards. This edition of the Guidelines further develops concepts, approaches and information introduced in previous editions, including the comprehensive preventive risk management approach for ensuring drinking-water quality that was introduced in the third edition. It considers: drinking-water safety, including minimum procedures and specific guideline values and how these are intended to be used; approaches used in deriving the Guidelines, including guideline values; microbial hazards, which continue to be the primary concern in both developing and developed countries. Experience has shown the value of a systematic approach to securing microbial safety. This edition builds on the preventive principles introduced in the third edition on ensuring the microbial safety of drinkingwater through a multiple-barrier approach, highlighting the importance of source water protection; climate change, which results in changing water temperature and rainfall patterns, severe and prolonged drought or increased flooding, and its implications for water quality and water scarcity, recognizing the importance of managing these impacts as part of water management strategies; chemical contaminants in drinking-water, including information on chemicals not considered previously, such as pesticides used for vector control in drinkingwater; revisions of existing chemical fact sheets, taking account of new scientific information; and, in some cases, reduced coverage in the Guidelines where new information suggests a lesser priority; those key chemicals responsible for large-scale health effects through drinkingwater exposure, including arsenic, fluoride, lead, nitrate, selenium and uranium, providing guidance on identifying local priorities and on management; the important roles of many different stakeholders in ensuring drinking-water safety. This edition furthers the discussion introduced in the third edition of the roles and responsibilities of key stakeholders in ensuring drinking-water safety; guidance in situations other than traditional community supplies or managed utilities, such as rainwater harvesting and other non-piped supplies or dual piped systems.