Time to re-evaluate the guideline value for manganese in drinking water?
OBJECTIVE
We reviewed the scientific background for the current health-based World Health Organization (WHO) guideline value for manganese in drinking water.


METHODS
The initial starting point was the background document for the development of the WHO's guideline value for manganese in drinking water as well as other regulations and recommendations on manganese intake levels. Data referred to in these documents were traced back to the original research papers. In addition, we searched for scientific reports on manganese exposure and health effects.


RESULTS
The current health-based guideline value for manganese in drinking water is based partly on debatable assumptions, where information from previous reports has been used without revisiting original scientific articles. Presently, preparation of common infant formulas with water containing manganese concentrations equivalent to the WHO guideline value will result in exceeding the maximum manganese concentration for infant formula. However, there are uncertainties about how this maximum value was derived. Concurrently, there is increasing evidence of negative neurologic effects in children from excessive manganese exposure.


CONCLUSIONS
The increasing number of studies reporting associations between neurologic symptoms and manganese exposure in infants and children, in combination with the questionable scientific background data used in setting the manganese guideline value for drinking water, certainly warrant a re-evaluation of the guideline value. Further research is needed to understand the causal relationship between manganese exposure and children's health, and to enable an improved risk assessment.
Ljung
Karin
K
Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
Vahter
Marie
M
D000328:Adult; D002648:Child; D002675:Child, Preschool; D004326:Drinking; D005618:Fresh Water / Q000737:chemistry; D017408:Guidelines as Topic; D006801:Humans; D007223:Infant; D041943:Infant Formula / Q000737:chemistry; D007231:Infant, Newborn; D008345:Manganese / Q000032:analysis / Q000633:toxicity*; D009422:Nervous System Diseases / Q000209:etiology*; D014881:Water Supply / Q000592:standards*; D014944:World Health Organization
D008345:Manganese