Mutagenicity of drinking water obtained by different treatment procedures from two northern Italian lakes

Raw water and drinking water samples collected from four treatment plants supplied by two north Italian lakes were studied for their mutagenic activity. The samples were concentrated on XAD‐2 columns and the adsorbates were tested at increasing doses with the Ames test, using Salmonella typhimurium TA98 and TA100 strains, with and without metabolic activation. Raw water from both lakes was found to contain direct‐acting mutagens detectable with TA98 strain. The analysis of water from the four treatment systems showed that new mutagens detectable with strain TA100 (−S9) were produced when pre chlorination or post chlorination with NaCIO was performed, as previously found by other authors. When chlorine dioxide and/or ozone were used, TA98 mutagenicity was reduced and no new mutagens were produced. The results showed the applicability of the Ames test to evaluate drinking water treatment processes and to produce additional data useful in the detection of potential health hazards associated with drinking water production.