**3. Manganese**

Manganese in groundwater has been considered as a technical problem causing blackish flushes in tap water after oxidation of the Mn2+ to Mn oxides in the distribution networks. Manganese inhaled from air has neurological effects known from metallurgical industries [18]. Recently, however, reports have come to indicate that chronic exposure of children to manga‐ nese in drinking water may affect their intellectual capacity [19]. So far, there are three reports that are comparable, from Quebec in Canada [19], from Mexico [20] and from Brazil [21], and that give concern regarding the neurotoxicity of manganese in drinking water. A summary of the findings regarding toxicity is published from a conference [22]. Manganese is an essential element and the major intake is via food. Elevated intake via drinking water by women may be positive for foetal survival [23] but foetal growth may be impaired [24]. The intake of man‐ ganese via drinking water is smaller but seems unregulated. This is mirrored in hair in which the concentration increases with that in drinking water but not with the intake via food. The Mn2+ seems to be taken up by the divalent metal transporter 1 (DMS-1) and be affected by, for instance, iron status [25]. A hypothesis, as humans have not developed a regulation, could be that moderately reduced groundwater from larger depth has, in the history of mankind, not been a common way to get drinking water but rather from surface water and springs.
