Mutagenic activity in drinking water.

Drinking water samples concentrated by freeze drying were found to be mutagenic in a mammalian tissue culture assay using Chinese hamster embryonic lung cells (V79). The mutagenicity could be enhanced by the promoter 12-O-tetradecanoyl-phorbol-13-acetate. The water itself was also shown to contain promoting chemicals. The mutation frequency of cells pretreated with low levels of benzo(a)pyrene was increased following subsequent exposure to the concentrated water sample. Approaches to estimate the risk involved in exposure to present drinking water are proposed.