properties. Among environmental samples, water has been extensively investigated, especially drinking water, where the occurrence of genotoxic contaminats and chlorine by-products has intensively been studied with bacterial tests, because drinking water has a potential to impact human health.3,33,34
Since the presence of potentially genotoxic components in drinking water is expected to be very low, very sensitive test methods should be used or water samples should be concentrated. We should be aware however, that the method used for sample concentration can have an important bearing on study results. The concentration of the water samples allows efficient detection of trace amounts of organic genotoxic components trough their concentration on proper absorbents and components otherwise untestable can be proven by the bioassays.35 In our study the concentration of water samples was performed on XAD4 columns containing copolymer of styrene divinil benzene in order to be able to detect possible presence of pesticides or herbicides.21
The results of the bacterial reversion assay with three nonconcentrated and 50 x concentrated drinking water samples are presented in Table 2. According to the EPA and GenPharmTox guidelines, a mutagenic potential of a test item, tested with Ames test, is confirmed if the mutant frequency is 2.0 or higher.22,24 A dose effect relationship could underline this conclusion. A possible mutagenic potential is assumed if the quotient ranges between 1.7 to 1.9 in combination with dose effect relationship. No mutagenic potential is assumed if all quotients range between 1.0 (and lower) to 1.6. A nonexistent dose effect relationship could underline