title: World Health Organization discontinues its drinking-water guideline for manganese.
abstract: BACKGROUND
  The World Health Organization (WHO) released the fourth edition of Guidelines for Drinking-Water Quality in July 2011. In this edition, the 400-µg/L drinking-water guideline for manganese (Mn) was discontinued with the assertion that because "this health-based value is well above concentrations of manganese normally found in drinking water, it is not considered necessary to derive a formal guideline value."
  
  
  OBJECTIVE
  In this commentary, we review the WHO guideline for Mn in drinking water--from its introduction in 1958 through its discontinuation in 2011.
  
  
  METHODS
  For the primary references, we used the WHO publications that documented the Mn guidelines. We used peer-reviewed journal articles, government reports, published conference proceedings, and theses to identify countries with drinking water or potential drinking-water supplies exceeding 400 µg/L Mn and peer-reviewed journal articles to summarize the health effects of Mn.
  
  
  CONCLUSIONS
  Drinking water or potential drinking-water supplies with Mn concentrations > 400 µg/L are found in a substantial number of countries worldwide. The drinking water of many tens of millions of people has Mn concentrations > 400 µg/L. Recent research on the health effects of Mn suggests that the earlier WHO guideline of 400 µg/L may have been too high to adequately protect public health.
  
  
  CONCLUSIONS
  The toxic effects and geographic distribution of Mn in drinking-water supplies justify a reevaluation by the WHO of its decision to discontinue its drinking-water guideline for Mn.
authors.affiliation: Department of Chemistry and Biochemistry, Norwich University, Northfield, Vermont, USA.
authors.forename: Seth H
authors.initials: SH
authors.lastname: Frisbie
authors.forename: Erika J
authors.initials: EJ
authors.lastname: Mitchell
authors.forename: Hannah
authors.initials: H
authors.lastname: Dustin
authors.forename: Donald M
authors.initials: DM
authors.lastname: Maynard
authors.forename: Bibudhendra
authors.initials: B
authors.lastname: Sarkar
mesh_terms: D060766:Drinking Water / Q000592:standards*; D017408:Guidelines as Topic / Q000592:standards*; D049673:History, 20th Century; D049674:History, 21st Century; D008345:Manganese / Q000032:analysis* / Q000633:toxicity*; D014944:World Health Organization / Q000266:history*
chemical_list: D060766:Drinking Water; D008345:Manganese