Study of potential toxic effects on rainbow trout hepatocytes of surface water treated with chlorine or alternative disinfectants

This study evaluates the effects of disinfection on the formation of toxic compounds in lake water treated with sodium hypochlorite, chlorine dioxide and peracetic acid (a disinfectant not previously used in drinking water processes). Chlorine reacts with the natural organic matter or contaminants in surface waters and produces a complex mixture of disinfection by-products (DBPs), some of which have been shown to be carcinogenic, mutagenic and/or teratogenic in animal studies. To define the potential toxicity on aquatic animals, disinfected drinking waters obtained from a pilot plant fed with water coming from Lake Trasimeno (Perugia) were collected, adsorbed by using silica C18 cartridges, and then eluted in sequence with ethylacetate, dichloromethane and methanol. The eluates were concentrated under vacuum and resuspended in dimethylsulfoxide (DMSO). Primary cultures of rainbow trout hepatocytes were exposed to three amounts of water concentrate (equivalent to 0.5, 0.25 and 0.125 l of disinfected water per ml of culture medium) for 24 h at 20°C, after which their viability, glutathione content (GSH), free radical production (ROS) and cytochrome P4501A3 expression were determined. The disinfected water samples were collected during different seasons in order to evaluate a possible correlation between seasonal water variations and formation of toxic compounds. None of the water concentrates showed any cytotoxic effect or variations in GSH content, but significant increases in ROS production were detected in the autumn water concentrates from the treatments with sodium hypochlorite and chlorine dioxide. Cytochrome P4501A3 expression was not modified in the hepatocytes exposed to the water concentrates irrespective to the sampling season.