The World Health Organization (WHO) has released the first addendum to the third edition of the Guidelines for Drinking-water Quality. This addendum adds important information to, and replaces parts of, the third edition of the guidelines.
The addendum includes new and expanded information on the management of emergencies and unforeseen events. For example, it includes more guidance on identifying local actions in response to microbial and chemical water quality problems, such as the issuance of advisories to boil and/or avoid drinking water under certain conditions.
New fact sheets for some chemicals not previously considered in the guidelines appear for the first time: 1,4-dioxane, methyl tertiary-butyl ether (MTBE) and petroleum products, including a new guideline value for 1,4-dioxane. Updated fact sheets are included for chloral hydrate (trichloroacetaldehyde), dichloroacetic acid, 1,1-dichloroethene, formaldehyde, mercury, nickel, permethrin, trichloroethene and trihalomethanes (THMs). For most of these, the guideline values have been changed.
The addendum also includes additions concerning chlorination by-products and the development of standards for volatile substances.
The Guidelines are used by developing and developed countries worldwide as the basis of regulation and standard setting to ensure the safety of drinking water. They recognize the priority that should be given to ensuring microbial safety and provide health-based guideline values for a large number of chemical hazards. The third edition of the guidelines, published in 2004, particularly takes account of developments in risk assessment and risk management and introduced the “Framework for Safe Drinking Water,” including “Water Safety Plans.” The guidelines are kept up to date through a process of rolling revisions.