Water sampling
Experimental
Three different parts of Ljubljana drinking water region were selected as sampling sites where tap water samples were taken (samples marked 1, 2, and 3). The regular disinfection process in this area is charcoal filtration. The analysed water samples were the same as those collected for physico-chemical analyses done by the Institute of public health of the Republic of Slovenia (Table 1). Sampling was performed according to the recommended standard method (ISO 5667-5)20 and was done at one occasion in February 2004. Water samples were transported to the laboratory in 500 mL glass flasks and stored at –20 °C for further testing. Prior to the genotoxicity bioassays 0.9% NaCl was added to the samples in order to avoid hypoosmotic shock, which causes cytotoxic effect resulting in false positive genotoxic results later on. The negative control in all biotests performed was sterile 0.9% NaCl solution prepared from MilliQ water. The concentrating of drinking water samples was done on XAD resins according to the guidance of the producer.21 The final concentration factor was 1:1000.
Concentrated water samples, diluted with sterile MilliQ water to final concentration 50 ×, and none concentrated water samples were then tested in triplicates.