Water distribution system, a new source of mutagens in drinking waters

Three water supply systems from uncontaminated ground water, a lake receiving paper mill wastes and the Ohio river receiving industrial waste waters and sewage, were analysed for chemical constituents and for mutagens, by the Ames Salmonella test, modified by preparing minimal glucose agar with the test water. It is shown that treatment processes cause a reduction in the mutagenicity of raw waters but a consistent and significant increase was observed upon passage of the water through distribution pipes.