Genotoxicity of surface water treated with different disinfectants using in situ plant tests

Abstract

Disinfection of surface drinking water, in particular water chlorination, results in many by-products with potential genotoxic and/or carcinogenic activity. In the present study, we evaluated the genotoxicity of surface water after treatment with different disinfectants by means of in situ plant genotoxicity assays (micronucleus and chromosomal aberration tests) which can detect both clastogenic and aneugenic effects. The study was carried out at a pilot plant using lake water after sedimentation and filtration. This water supplied four stainless steel basins: three basins were disinfected with sodium hypochlorite, chlorine dioxide, and peracetic acid and the fourth basin containing untreated lake water was used as a control. Plants were exposed in situ in the basins. The study was carried out using water collected in different seasons over a period of about 1 year in order to assess the treatments in different physical and chemical lake water conditions. The micronucleus test in root cells of Vicia faba (Vicia faba/MCN test) revealed genotoxicity in many samples of disinfected water. The micronucleus test in Tradescantia pollen cells and the chromosome aberration test in root cells of Allium cepa showed genotoxic effects only in some disinfected samples, but also revealed genotoxicity in raw water. The results of the study indicated that the Vicia faba/ MCN test was the most sensitive plant assay for disinfected water and that peracetic acid disinfection produced similar or lower genotoxicity than sodium hypochlorite or chlorine dioxide treatment. INTRODUCTIONDrinking water disinfection may produce toxic compounds, particularly if the water is obtained from surface sources. Water chlorination results in mutagenic/carcinogenic by-products derived from the reaction of chlorine with organic compounds (humic and fulvic acids) naturally present in water [Rook, 1974; WHO, 1996]. For this reason it is very important to test alternative disinfectants to chlorine in order to reduce these potential health risks. Among the new disinfectants, peracetic acid (CH 3 -CO-OOH, PAA) deserves to be studied for its application in drinking water disinfection, since it is a potent antimicrobial agent and has many applications in hospitals, laboratories, and factories [Baldry et al., 1991[Baldry et al., , 1995Lefevre et al., 1992]. More recently, PAA has been found to be an effective biocidal compound for wastewater disinfection, and previous research showed that disinfection of lake and river drinking water with PAA gave rise to a very low level of genotoxicity and produced only carboxylic acids [Monarca et al., 2002a], which are not recognized as mutagenic.Drinking water has been intensively examined for gene mutations, primarily by assaying extracts of water in bacterial tests, and several studies on different disinfectants have been carried out [Koivusalo et al., 1994;Loper et al., 1980;Monarca 1985Monarca , 1998Monarca , 2002aRomero et al., 1992;Tuomisto et al., 1990;Wilcox and Williamson, 1986;Wilcox et al., 1988]. Plant genot...

Modulating effects of humic acids on genotoxicity induced by water disinfectants in Cyprinus carpio

“…The observed genotoxic effects of NaClO + HA and of ClO 2 + HA are in accordance with results obtained from previous studies [18] on MN-carp erythrocytes after in situ exposures to similar concentrations of the disinfectants. The present results are also in agreement with those obtained from in situ plant genotoxicity tests, where clear clastogenic/aneugenic effects of NaClO-and ClO 2 -disinfected surface waters were reported in different monitoring seasons [22]. Mutagenic activity induced by chlorinated humic acid compounds was also shown in bacteria [52,1,2].…”

“…The micronucleus test and the Comet assay performed in fish erythrocytes indicated the induction of genotoxic effects by the chlorinated disinfectants. Supported by literature data on the mutagenic effects induced as a result of humic acid chlorination, our positive results were discussed taking into account the formation of genotoxic intermediate compounds, such as adsorbable organic halogens (AOX), which were also found in the treated lake waters [22]. However, some confounding factors had been identified, such as temperature and/or other seasonal/environmental variables.…”

“…Thus, the concern for effects on human health from drinkingwater contaminated with genotoxic compounds is the reason for intensive studies, where the widest spectrum of biological systems and exposure conditions are needed. Indeed, results obtained from different organisms used as bio-indicators have indicated several genotoxic and mutagenic effects of disinfected waters, including drinking-water, after direct exposure of vertebrates [14][15][16][17][18], invertebrates [19,20] and plants [21,22].…”

“…The micronucleus (MN) test performed in proliferating cell systems of such exposed organisms is a very common and recommended approach for the detection of genotoxicity of treated waters [14][15][16][17][18][19][20][21][22]; the use of fish as a suitable bio-indicator has been proposed because of its high sensitivity for the detection of both clastogenic and aneugenic activity (reviewed in [27,28]). The application of the MN assay to circulating erythrocytes of fish has been considered a promising tool for the screening of drinking-water.…”

“…Fish were exposed to the disinfectants dissolved in water, with or without humic acids. In view of the possible relevance of the results in relation to drinking-water consumption, we tested the disinfectants at low concentrations: the highest concentration employed (0.2 ppm) corresponds to the maximum free disinfectant residue adopted in surface water disinfection experiments [18,22]. The humic acids concentration (0.1 ppm) was chosen to obtain a 1:0.32 molar-ratio C:Cl for the highest NaClO concentration and a 1:0.08 molar-ratio for the lowest concentration (0.05 ppm), so as to achieve almost complete reaction of chlorine with organic carbon, according to carcinogenicity/mutagenicity studies [4,52,53].…”