Estimations of daily mineral intakes from drinking water.

Duplicate samples of all tap water drank over 24 h, including that used for beverage preparation, were collected from 109 adult subjects. There were more than ten-fold variations in daily water intakes. The mineral concentrations in the 24-h samples from households on the same public water supply showed considerable variation, the differences sometimes being greater than those found in water samples from different sources. These findings raise considerable doubt about the accuracy of accepted methods for the estimation of mineral intakes from drinking water. Although the mineral concentrations in water samples were generally very low some subjects received 10 per cent or more of their recommended dietary intake of Cu and Zn from this source. The implications of the findings are discussed.