Cytotoxic and genotoxic potential of surface water from the Pitimbu river, northeastern/RN Brazil

Genotoxicity of surface waters in Brazil

Brazil has abundant surface water resources, huge aquatic biodiversity and is home to 213 million people. Genotoxicity assays are sensitive tools to detect the effects of contaminants in surface waters and wastewaters, as well as to determine potential risks of contaminated waters to aquatic organisms and human health. This work aimed to survey the articles published in 2000-2021 that evaluated the genotoxicity of surface waters within Brazilian territory to unveil the profile and trends of this topic over time. In our searches, we considered articles focused on assessing aquatic biota, articles that conducted experiments with caged organisms or standardized tests in the aquatic sites, as well as articles that transported water or sediment samples from aquatic sites to the laboratory, where exposures were performed with organisms or standardized tests. We retrieved geographical information on the aquatic sites evaluated, the genotoxicity assays used, the percentage of genotoxicity detected, and, when possible, the causative agent of aquatic pollution. A total of 248 articles were identified. There was a trend of increase in the number of publications and annual diversity of hydrographic regions evaluated over time. Most articles focused on rivers from large metropolises. A very low number of articles were conducted on coastal and marine ecosystems. Water genotoxicity was detected in most articles, regardless of methodological approach, even in little-studied hydrographic regions. The micronucleus test and the alkaline comet assay were widely applied with blood samples, mainly derived from fish. Allium and Salmonella tests were the most frequently used standard protocols. Despite most articles did not confirm polluting sources and genotoxic agents, the detection of genotoxicity provides useful information for the management of water pollution. We discuss key points to be assessed to reach a more complete picture of the genotoxicity of surface waters in Brazil.

Evaluating Potential Ecological Risks of Heavy Metals of Textile Effluents and Soil Samples in Vicinity of Textile Industries

The present study pertains to assessing the heavy metal (Cd, Cr, Co, Cu, Pb, and Zn) contents of untreated and treated effluents of two textile industries and agricultural soil samples in the vicinity of these industries located in Ludhiana, Punjab (India). The genotoxicity of the effluents samples was estimated using Allium cepa root chromosomal aberration assay. The exposure of Allium cepa roots to untreated effluents from both industries resulted in the reduction of mitotic index (MI) and increase in chromosomal aberrations in the root tip meristematic cells when compared to those that were exposed to the treated effluents indicating the significant genotoxic potential of untreated effluents. Risk characterization of soil sample was carried out by calculating the potential ecological and human health risks of heavy metals. The hazard index was observed to be less than 1, indicating there was no potential health risk of heavy metals in soil samples. Furthermore, bioaccumulation potential studies on plant species grown in the vicinity of these industries have shown that bioaccumulation factor (BAF) varied as Ricinus communis L. > Chenopodium album L. > Cannabis sativa L. with Co and Pb having maximum and minimum values, respectively.

Evaluation of bacterial contamination and mutagenic potential of treated wastewater from Al-Samra wastewater treatment plant in Jordan

Jordan is one of the lowest countries in the world in terms of water resources. The reuse of treated wastewater is an important alternative to supply agricultural demands for water. In Jordan, Kherbet Al-Samra wastewater treatment plant (KSWWTP) is the largest and its effluent is mainly used for irrigation purposes. In this study, bacterial contamination and mutagenic potential were evaluated in six sites, beginning with KSWWTP and ending with King Tallal Dam. The results showed high contamination with many pathogenic bacteria and coliforms. The isolated pathogenic bacteria were Salmonella sp., Shigella sp., Bacillus cereus and Staphylococcus aureus. The isolated opportunistic pathogenic bacteria were Acinetobacter lwoffii, Elizabethkingia meningosepticum, Pseudomonas fluorescens and Bacillus licheniformis. These bacteria were found in all sampling sites without a specific prevalence pattern. Differences in temperature between seasons affect total coliform and other bacterial count. All water samples showed positive mutagenic activity and high bacterial pollution. Improving the disinfection efficiency in the wastewater treatment plant is important to minimize potential toxicity and exposure of public health to pathogenic bacteria, reduce water resources' contamination and environmental pollution. Increasing effluent sampling frequency from KSWWTP is required to monitor bacterial contamination and toxicity/mutagenicity level for water safety and public health risk assessments.

Evaluation of Cytotoxicity and Mutagenicity of Wastewater from Istanbul: Data from Hospitals and Advanced Wastewater Treatment Plant

Wastewater (WW) carry considerable amount of chemicals that could have mutagenic or cytotoxic effect from hospital discharges to aquatic environment. Our objective was to determinate the possible mutagenic and toxic effects of hospital originated WWs and effectiveness of the wastewater treatment plants (WTP) functions. In the study the mutagenic and cytotoxic potential of three hospitals and influent/effluent of a treatment plant WW collected in Istanbul and was examined using AMES, XTT, and lactate dehydrogenase (LDH) assays. Mutagenic effects were detected at both hospital discharges and advanced biological wastewater plant. We observed no cytotoxic effect in fibroblasts for LDH and XTT assays whereas high cytotoxicity for all samples was found in hepatocytes by XTT assay. According to the results even if advanced technology is used for treatment of WW, mutagenic and cytotoxic effects still remain, and the present technologies need to be further improved.

Treated Textile Effluents: Cytotoxic and Genotoxic Effects in the Natural Aquatic Environment

Textile effluent treatment methods use biological and chemical treatments to reduce the toxicity and to comply with standard effluent discharge limits. However, trace amounts of pollutants can affect the biological organisms in the receiving environment. The present study used Allium cepa bio assay to assess the cytotoxic and genotoxic effects of treated textile effluents discharged to the natural environment. The results of the bioassay indicated that treated textile effluents can induce alterations in the mitotic index. Also nuclear buds, bi nuclei, condensed nuclei, were recorded in the bioassay and the severity of them decreased towards downstream of the effluent discharge point. Therefore, it can be concluded that even the discharged effluents comply with the standard limits, there is a possibility of causing cytotoxic and genotoxic effects in the organisms living in the natural environment.

Hydrophobic organic compounds in drinking water reservoirs: Toxic effects of chlorination and protective effects of dietary antioxidants against disinfection by-products

This study investigated formation and genotoxicities of disinfection by-products (DBPs) during chlorination of hydrophobic organic compounds (HOCs) extracted from six drinking water reservoirs around the Pearl River Delta region, China. Chemical analyses firstly showed that after chlorination aromatic HOCs (including polycyclic aromatic hydrocarbons, PAHs) decreased but DBPs (including chlorinated PAHs) increased, while genotoxicity assays revealed that the chlorination increased DNA damage in human Caco-2 cells. Although the link between DBPs and the genotoxicity was weak (insignificant correlations, p ≥ 0.05), we observed that chlorination of HOCs from more contaminated reservoirs in general resulted in higher genotoxicity. Secondly, remedial effects of catalase and dietary antioxidants (i.e. vitamin C and epigallocatechin gallate) in protecting cells against DBPs genotoxicity were detected. After 1 h treatment by the antioxidants, the DNA damage in Caco-2 cells (due to previous exposure to DBPs) significantly decreased (p < 0.05) in 7 out of a total of 18 treatments (38.9%). This is the first study demonstrating that catalase, vitamin C and epigallocatechin gallate protected human cells in vitro against DNA damage upon exposure to chlorinated genotoxic DBPs.

Toxicity of chlorinated and ozonated wastewater effluents probed by genetically modified bioluminescent bacteria and cyanobacteria Spirulina sp

Chlorination and ozonation of various waters may be associated with the formation of toxic disinfection byproducts (DBPs) and cause health risks to humans. Monitoring the toxicity of chlorinated and ozonated water and identification of different toxicity mechanisms are therefore required. This study is one of its kind to examine the toxic effects of chlorinated and ozonated wastewater effluents on three genetically modified bioluminescent bacteria, in comparison to the naturally isolated cyanobacteria, Spirulina strains as test systems. Three different secondary wastewater effluents were collected from treatment plants, chlorinated using sodium hypochlorite (at 1 and 10 mg L^-1 of chlorine) or treated using 3-4 mg L^-1 of ozone at different contact times. As compared to cyanobacterial Spirulina sp., the genetically modified bacteria enhancing bioluminescence at the presence of stress agents demonstrated greater sensitivity to the toxicity induction and have also provided mechanism-specific responses associated with genotoxicity, cytotoxicity and reactive oxygen species (ROS) generation in wastewater effluents. Effects of effluent chlorination time and chlorine concentration revealed by means of bioluminescent bacteria suggest the formation of genotoxic and cytotoxic DBPs followed with their possible disappearance at longer times. Ozonation could degrade genotoxic compounds in some effluents, but the cytotoxic potential of wastewater effluents may certainly increase with ozonation time. No induction of ROS-related toxicity was detected in either chlorinated or ozonated wastewater effluents. UV absorbance- and fluorescence emission-based spectroscopic characteristics may be variously correlated with changes in genotoxicity in ozonated effluents, however, no associations were obtained in chlorinated wastewater effluents. The bacterial response to the developed mechanism-specific toxicity differs among wastewater effluents, reflecting variability in effluent compositions.

Assessment of phytoremediation potencial of Allium cepa L. in raw sewage treatment

Whereas the effects of the substances found in domestic sewage on live organisms is important to evaluate the use of plants to remove pollutants from the environment. The objective of this study was to assess the phytoremediation activity of Allium cepa L. (onion) roots exposed to raw sewage, as well as the acute toxic activity of this effluent for the bioindicators A. cepa, through a cytotoxicity test, and Artemia salina L., through a mortality/immobility test. The physicochemical assessments of the sewage were conducted in two scenarios: immediately after collection and after being in contact with onion roots (phytoremediation) for 24 hours. The physicochemical data indicate there was a reduction in nitrogen and phosphorus levels and in biochemical oxygen demand in sewage treated. The results from the cytotoxicity test with A. cepa indicated a reduction in the mitotic cell divisions of the onions treated with the raw sewage. The mortality/immobility test with A. salina indicated that the concentrations with 50 and 100% of raw sewage induced the mortality of the nauplii. Thus, the data suggest new studies that seek greater efficiency, efficacy and viability of onion phytoremediation.

Phytotoxicity, cytotoxicity and genotoxicity evaluation of organic and inorganic pollutants rich tannery wastewater from a Common Effluent Treatment Plant (CETP) in Unnao district, India using Vigna radiata and Allium cepa

The leather industry is a major source of environmental pollution in India. The wastewater generated by leather industries contains very high pollution parameters due to the presence of a complex mixture of organic and inorganic pollutants even after the treatment at a Common Effluent Treatment Plant (CETP) and disturbs the ecological flora and fauna. The nature, characteristics and toxicity of CETP treated wastewater is yet to be fully elucidated. Thus, this study aims to characterize and evaluate the toxicity of CETP treated tannery wastewater collected from the Unnao district of Uttar Pradesh, India. In addition to measuring the physico-chemical parameters, the residual organic pollutants was identified by GC-MS analysis and phytotoxicity, cytotoxicity and genotoxicity of the treated wastewater was evaluated using Vigna radiata L. and Allium cepa L. Results showed that the treated wastewater contained very high pollution parameters (TDS 3850 mg/L, BOD 680 mg/L, COD-1300 mg/L). GC-MS analysis revealed the presence of various types of residual organic pollutants including benzoic acid, 3-[4^,-(T-butyl) Phenyl] furan-2-5-dione, benzeneacetamide, resorcinol, dibutyl phthalate, and benzene-1,2,4-triol. Further, toxicological studies showed the phytotoxic nature of the wastewater as it inhibited seed germination in V. radiata L. and root growth of A. cepa. Genotoxicity was evidenced in the root tip cell of A. cepa where chromosomal aberrations (stickiness, chromosome loss, C-mitosis, and vagrant chromosome) and nuclear abnormalities like micronucleated and binucleated cells were observed. Thus, results suggested that it is not safe to discharge these wastewater into the environment.

Toxicological aspects of trihalomethanes: a systematic review

Chlorine is considered the most used chemical agent for water disinfection worldwide. However, water chlorination can lead to by-product generation which can be toxic to humans. The present study aimed to perform a systematic review on the toxicity of trihalomethanes (THMs) through bioindicators of cytotoxicity, genotoxicity, and mutagenicity. The results showed that studies on the effects of THMs on DNA are a current research concern for evaluating the toxicity of the pure compounds and real samples involving several types including water for recreational use, reused water, and drinking water. THMs deleterious effects have been assessed using several biosystems, where the Ames test along with experimental animal models were the most cited. A wide range of THM concentrations have been tested. Nevertheless, DNA damage was demonstrated, highlighting the potential human health risk. Among the studied THMs, chloroform presented a different action mechanism when compared with brominated THMs, with the former being cytotoxic while brominated THMs (bromodichloromethane, bromoform, and dibromochloromethane) were cytotoxic, genotoxic, and mutagenic. The described evidence in this research highlights the relevance of this topic as a human health issue. Nevertheless, research aimed to represent THMs current exposure conditions in a more accurate way would be needed to understand the real impact on human health.

Genotoxicity assessment of raw and treated water samples using Allium cepa assay: evidence from Perak River, Malaysia

Allium cepa assay was carried out in this study to evaluate genotoxic effects of raw and treated water samples from Perak River in Perak state, Malaysia. Samples were collected from three surface water treatment plants along the river, namely WTPP, WTPS, and WTPK. Initially, triplicates of equal size Allium cepa (onions) bulbs, 25-30 mm in diameter and average weight of 20 g, were set up in distilled water for 24 h at 20 ± 2 °C and protected from direct sunlight, to let the roots to grow. After germination of roots (0.5-1.0 cm in length), bulbs were transferred to collected water samples each for a 96-h period of exposure. The root physical deformations were observed. Genotoxicity quantification was based on mitotic index and genotoxicity level. Statistical analysis using cross-correlation function for replicates from treated water showed that root length has inverse correlation with mitotic indices (r = - 0.969) and frequencies of cell aberrations (r = - 0.976) at lag 1. Mitotic indices and cell aberrations of replicates from raw water have shown positive correlation at lag 1 (r = 0.946). Genotoxicity levels obtained were 23.4 ± 1.98 (WTPP), 26.68 ± 0.34 (WTPS), and 30.4 ± 1.13 (WTPK) for treated water and 17.8 ± 0.18 (WTPP), 37.15 ± 0.17 (WTPS), and 47.2 ± 0.48 (WTPK) for raw water. The observed cell aberrations were adherence, chromosome delay, C-metaphase, chromosome loss, chromosome bridge, chromosome breaks, binucleated cell, mini cell, and lobulated nuclei. The morphogenetic deformations obtained were likely due to genotoxic substances presence in collected water samples. Thus, water treatment in Malaysia does not remove genotoxic compounds.

Direct and Indirect Anthropogenic Contamination in Water Sources: Evaluation of Chromosomal Stability and Cytotoxicity Using the Allium cepa Test

Increasing industrialization and urbanization has deteriorated water quality around the world. Nowadays, evaluation of the effects of chemical compounds using bioassays is a critical step in the hazard identification assessment. Thus, this work aimed to determine the genetic damage caused by different types of anthropogenic contamination in a river´s water in Brazil. Two points (P1 and P2) and two periods (referred as direct and indirect anthropogenic contamination) were evaluated in Allium cepa roots. MI was increased (p < 0.05) in both points in the indirect anthropogenic contamination and decreased in the indirect anthropogenic contamination periods. Moreover, parameters as DNA instability (CA and MN) were observed in both periods indicating substances in the water with mutagenic, genotoxic, and cytotoxic potential. Interestingly, a 20-fold increase in CA frequencies were observed in P1 and P2 in the second collection period (direct anthropogenic contamination) (p < 0.05). In conclusion, our data indicated that anthropogenic activities in the area contributed to contaminate this water source. Moreover, direct anthropogenic contamination maximized the damage, posing a possible hazard to population health.

Genotoxicity evaluation of two metallic-insecticides using Allium cepa and Tradescantia pallida: A new alternative against leaf-cutting ants

In order to combat leaf-cutting ants, the pesticide sulfluramid used to be the most widely utilized active ingredient. However, its use was banned in 2009 by the Stockholm Convention, although some countries were allowed to continue using it. As an effective alternative to its replacement, researchers developed a metallic-insecticide system, which is a natural product linked to metal complexes. Thus, the aim of this study was to evaluate the ability of these new metallic-insecticides in change the genetic material of non-target organisms. The tests were performed utilizing chromosomal aberrations and micronucleus tests in the Allium cepa test system and the Trad-MCN test in Tradescantia pallida. To better understand the results, one of the components of the formula, 5-methyl-phenanthroline, was also analyzed according to the same parameters. To A. cepa, the results showed that one of the metallic insecticides induced cytotoxicity and genotoxicity at different concentrations, while the other metallic-insecticide showed chromosomal instability only at the highest concentration. The analysis of 5-methyl-phenanthroline revealed that it can be related with the positive results, since genotoxic effects were induced. In the Trad-MCN test, none of the metallic-insecticides showed genotoxic activity, although one of them induced more micronucleus formation.

Evaluation of the Phytotoxic and Genotoxic Potential of Pulp and Paper Mill Effluent Using Vigna radiata and Allium cepa

Pulp and paper mill effluent induced phytotoxicity and genotoxicity in mung bean (Vigna radiata L.) and root tip cells of onion (Allium cepa L.) were investigated. Physicochemical characteristics such as electrical conductivity (EC), biological oxygen demand (BOD5), chemical oxygen demand (COD), and total phenols of the pulp and paper mill effluent were beyond the permissible limit specified for the discharge of effluent in inland water bodies. Compared to control plants, seedling exposed to 100% effluent concentration showed a reduction in root and shoot length and biomass by 65%, 67%, and 84%, respectively, after 5 days of treatment. A. cepa root tip cells exposed to effluent concentrations ranging from 25 to 100% v/v showed a significant decrease in mitotic index (MI) from 32 to 11% with respect to control root tip cells (69%) indicating effluent induced cytotoxicity. Further, the effluent induced DNA damage as evidenced by the presence of various chromosomal aberrations like stickiness, chromosome loss, anaphase bridge, c-mitosis, tripolar anaphase, vagrant chromosome, and telophase bridge and micronucleated and binucleated cell in A. cepa. Findings of the present study indicate that pulp and paper mill effluents may act as genotoxic and phytotoxic agents in plant model system.

Cytotoxic and genotoxic assessment of surface water from São Paulo State, Brazil, during the rainy and dry seasons

The aim of this study was to determine if the cytotoxic and genotoxic responses of Allium cepa are effective biomarkers of harmful effects caused by polluted river water and if changes in the responses reflect seasonality in the harmful effects. Samples were collected in the dry season (August 2011 and 2012) and rainy season (February 2012 and 2013) at sampling points on the Jaguari River and the Ribeirão Lavapés, in Brazil. Allium cepa bulbs were exposed to the samples, to positive controls (15 µg/L methyl methanesulfonate), and to negative controls (tap water). Three root tips from each bulb were then stained using the Feulgen reaction, then the micronucleus frequency, the mitotic index, and mitotic anomalies were measured. The total number of anomalies (stickiness, c-mitosis, multipolarity, chromosome bridges, and unidentified anomalies) in the rainy season (8.61 ± 3.65) and dry season (7.07 ± 2.96) were significantly different (U = 11.31, p = 0.04). Toxicity, indicated by the formation of micronuclei and the mitotic index, was higher in the February 2012 samples than in the August 2012 samples. The mean manganese concentration (0.13 mg/L) in the rainy season samples was higher than the maximum concentration permitted by the Brazilian National Environmental Council (<0.1 mg/L) and the manganese concentrations positively correlated with chromosomal aberration induction (p = 0.01, r = 0.69). In conclusion, the rainy season samples were more toxic than the dry season samples. This was probably related to rain water carrying compounds with potentially negative impacts into the rivers. These findings highlight the importance of biomonitoring studies and of treating wastewater in urban areas.

Mutagenic potential of fine wastes from dimension stone industry

The industrial treatment of dimension stones, such as marbles and granites, includes a stage of plate polishing, in which resins and abrasives are used, producing a fine grained waste with high moisture content. These wastes pass through decantation tanks in order to separate the solid and liquid phases. Until now, there is no knowledge about the mutagenic effects that this effluent can cause to organisms exposed to it. Thus, this study evaluated the mutagenic potential of dimension stone polishing wastes in onion root cells and fish erythrocytes. The onion seeds were germinated in Petri dishes with filter paper moistened in the liquid phase of the effluent. After germination, the onion roots were prepared for analysis of chromosomal aberrations in meristematic cells. The fishes were exposed during 72h to the solid phase of the effluent diluted in pure groundwater. Blood samples were used for counting of micronucleus and nuclear abnormalities. The onion seeds had similar germination and mitotic index in all treatments. However, it was observed in the seeds exposed to the polishing waste, numbers significantly higher of micronucleus, nuclear buds and other chromosomal aberrations when compared with the negative control. The fishes exposed to the waste showed numbers significantly higher of micronucleus when compared with the negative control. The fishes from all treatments showed significant increase in nuclear abnormalities when compared to the negative control. We concluded that the analysed wastes have mutagenic potential at the studied conditions; this effect can be related to the high content of phenolic compounds identified in the samples.

Water quality of urban streams: the Allium cepa seeds/seedlings test as a tool for surface water monitoring

The present study investigates the genotoxic, mutagenic, and cytotoxic potential of surface waters in urban streams using Allium cepa and analyzes the applicability of this assay for environmental monitoring. Water samples were collected from three streams located in the urban area of a municipality in the south of Brazil. For each stream, two samples were collected, one upstream and one downstream of the pollution discharge site. Physicochemical evaluation indicated that all samples had various degrees of environmental impact, but substantial impact was seen for the downstream samples of the Preto and Pedras streams. All samples increased the frequency of chromosome aberrations (P < 0.05). The sample from Pedras downstream site also caused a decrease in mitotic index (P < 0.08) and increase in micronuclei (P < 0.08) frequency, indicating potential cytotoxicity and mutagenicity. The Pedras stream receives mixed industrial and urban wastewater, while the Lajeado and Preto streams receive wastewater predominantly domestic in nature, which may partially explain the difference in toxicity among the samples. Moreover, the Allium cepa seeds/seedlings were shown to be extremely sensitive in detecting the genotoxicity of environmental water samples and can be applied as the first tool for environmental health hazard identification and prediction.

The impact of gypsum mine water: a case study on morphology and DNA integrity in the freshwater invertebrate, Gammarus balcanicus

The aim of our study was to investigate how exposure to heavy metal-rich waters from gypsum mining affects the morphology and levels of primary DNA damage in Gammarus balcanicus. Chemical analysis revealed increased concentrations of metals in water and sediment collected at a site impacted by gypsum mine wastewaters. The specimens also showed elevated total tissue metal levels when compared with the organisms collected at the reference site. The most prominent increase was observed for strontium, followed by iron, nickel, vanadium, aluminium, and manganese. The major pathway of entry for these toxic substances was through the degraded exoskeleton as a consequence of excessive strontium input (unbalanced calcium/strontium ratio) and altered permeability. Disturbed exoskeleton integrity was observed only in individuals collected downstream of the gypsum mine, which was confirmed by electron microscopy. Levels of primary DNA damage were evaluated using the alkaline comet assay in the haemolymph of the specimens.

Allium cepa L. as a bioindicator to measure cytotoxicity of surface water of the Quatorze River, located in Francisco Beltrão, Paraná, Brazil

Due to an increase in water consumption in the industrial sector and within the Brazilian population, surface water that receives wastewater from industries, domestic sewage, agricultural industries, and sewage treatment stations can pollute water bodies when not properly treated. The water quality has been linked to catchment characteristics and intensity of agricultural activities. Thus, the aim of this study was to monitor the cytotoxic potential of the water of the Quatorze River, located in the town of Francisco Beltrão, Paraná, Brazil, along its route in the rural area, using the root meristematic cells of Allium cepa L. as a bioindicator. The results showed that the water at points 2, 3, and 4 were not cytotoxic because the rates of A. cepa cell division were unaltered. Point 1 had presented a mitotic index that was statistically larger than the negative control, indicating that this water contained substances with mitogenic capacity, as demonstrated by elevated values in chemical oxygen demand (COD) and biochemical oxygen demand (BOD). However, the mitotic index values decreased along the route of the river (point 1 to point 4), possibly indicating a mechanism of self-purification, despite having received other sources of pollution. Thus, the results of this study show that the water of the Quatorze River should undergo periodic environmental monitoring at different times of the year, including cytotoxicity analysis, to evaluate the principal sources of contamination to maintain the quality of the river water and, consequently, to maintain human health and equilibrium of the entire ecosystem.

The efficiency of combined CaO/electrochemical treatment in removal of acid mine drainage induced toxicity and genotoxicity

Acid mine drainage (AMD) is a by-product of the mining industry that has a detrimental effect on aquatic plant and animal life due to high load of heavy metals and sulfates. In the present study, the toxic and genotoxic potential of AMD prior to and following combination of neutralization/electrocoagulation processes was evaluated using several bioassays and selected parameters. Regardless of pH correction of AMD prior to Daphnia bioassay, high acute toxicity was observed in Daphnia magna. The mine leachate also induced strong phyto-, cyto- and genotoxicity to Allium cepa roots. Short term exposure to AMD inhibited duckweed growth and chlorophyll a content and simultaneously promoted lipid peroxidation and DNA damage despite duckweed capability to upregulate antioxidative defense mechanisms. The results show that observed (geno)toxicity could be related to oxidative stress most probably induced by toxic metal action. However, influence of low pH as a contributing factor in the phytotoxicity of AMD cannot be excluded. The application of combined treatment eliminated genotoxicity and was highly efficient in reducing toxicity of AMD. Thus, the method seems to be suitable for treatment of AMD waters enabling their safe discharge to an aquatic environment.

Mutagenicity and genotoxicity assessment of industrial wastewaters

The genotoxicity of industrial wastewaters from Jajmau (Kanpur), was carried out by Ames Salmonella/microsome test, DNA repair-defective mutants, and Allium cepa anaphase-telophase test. Test samples showed maximum response with TA98 strain with and without metabolic activation. Amberlite resins concentrated wastewater samples were found to be more mutagenic as compared to those of liquid-liquid extracts (hexane and dichloromethane extracts). The damage in the DNA repair defective mutants in the presence of Amberlite resins concentrated water samples were found to be higher to that of liquid-liquid-extracted water samples at the dose level of 20 μl/ml culture. Among all the mutants, polA exhibited maximum decline with test samples. Mitotic index (MI) of root tip meristematic cells of A. cepa treated with 5, 10, 25, 50, and 100 % (v/v) wastewaters were significantly lower than the control. Complementary to the lower levels of MI, the wastewaters showed higher chromosomal aberration levels in all cases investigated.

Evaluation of germination, root growth and cytological effects of wastewater of sugar factory (Afyonkarahisar) using Hordeum vulgare bioassays

In this study, the effect of Afyonkarahisar Sugar Factory's discharge water on germination percentage, root growth and mitotic divisions of the root tip cells of Hordeum vulgare L. were investigated. Six concentrations of wastewater and ranging from 10(0), 10( -1), 10( -2), 10( -3), 10( -4), 10( -5), were applied for 6, 12, 18 and 24 h, respectively. It was observed that the treatments reduced the germination percentages of H. vulgare grains and inhibited the root growth as well as reduced mitotic index compared to the control group at all concentrations. It was also observed that the increase of the concentrations of wastewater decreased the cell division, and several mitotic anomalies such as c-mitosis, lagging chromosomes, multipolar anaphases and chromosome bridges increased.

Oxidative stress-mediated genotoxicity of wastewaters collected from two different stations in northern India

Oxidative stress-mediated genotoxicity of wastewaters taken from two different cities, Saharanpur (SWW) and Aligarh (AWW), were compared with a battery of short-term assays namely the Allium cepa genotoxicity test, the plasmid-nicking assay, and the Ames fluctuation test. Both test-water samples - when used undiluted - increased the frequency of chromosomal abnormalities and/or micronuclei and alterations in the mitotic index of root cells of Allium cepa. Bridges and fragmentation of the chromosome were the predominant effects of the Saharanpur water sample while the Aligarh sample induced mainly chromosome fragmentation. Single- and double-strand breaks were also observed in plasmid DNA treated with these test wastewaters. The plasmid-nicking assay performed on SWW resulted in linearization of plasmid DNA when 18μl was tested (in a total reaction volume of 20μl). However, with the same amount of AWW, all three forms of plasmid, viz. supercoiled, open circular and linear were observed. Supplementation with specific scavengers of reactive oxygen species (ROS) caused a significant decline in mutagenicity of test-water samples in all the tests, pointing at oxidative stress as the mediator of the observed genotoxicity. The role of heavy metals in the AWW-induced oxidative stress and that of phenolics in SWW cannot be ruled out.

Genotoxicity testing and biomarker studies on surface waters: an overview of the techniques and their efficacies

Rapid industrialization, use of modern agriculture practices, and fast urbanization vis-a-vis indiscriminate use of xenobiotics have led to the serious problems of water pollution in India and abroad. The complexicity of the pollutants in environmental samples demands a multitude of genotoxicity testing with increasing simplicity, sensitivity, and affordability. Moreover, various pollutants mutually affect their own toxic behavior, which complicates the problem of risk assessment. An overview, highlighting the genotoxicity testing system, such as Ames plate incorporation test, Ames fluctuation test, E. coli survival assay, Allium cepa toxicity/genotoxicity test, comet assay, and plasmid nicking assay, is presented in this article, and a comparison has been made to estimate the efficacy of these genotoxicity bioassays performed on some surface waters. Some work on toxicity biomarkers vis-a-vis studies on surface waters has also been included in the present review.

Assessment of genotoxic potency of sulfate-rich surface waters on medicinal leech and human leukocytes using different versions of the Comet assay

The aim of the present study was to investigate how exposure to sulfate-rich surface waters affects the level of primary DNA damage in hemocytes of leech Hirudo medicinalis. Samples of surface water were collected at two sites near a gypsum factory (Knin, Croatia) and two reference sites. In the laboratory, samples were subjected to detailed chemical analysis and used in toxicity testing. For that purpose, previously acclimatized individuals of H. medicinalis were sub-chronically exposed (for 28 days) to tested water samples. Levels of primary DNA damage were evaluated using the alkaline Comet assay in hemocytes collected on days 7, 14, 21 and 28 of exposure and compared with their baseline values. Genotoxic potency of the water sample with the highest sulfate concentration was further evaluated using the alkaline, neutral and hOGG1-modified Comet assay on human peripheral blood leukocytes exposed ex vivo for 30 min. The purpose was to explore which mechanisms are responsible for DNA damage. Chemical analysis revealed that sulfate concentrations in two water samples collected in Mali Kukar Lake (1630 mg/L SO₄) and Kosovčica River (823.3 mg/L SO₄) exceeded the WHO and US EPA defined limits for sulfate in drinking water. Increased levels of metals were found only in the water sample collected in Mali Kukar Lake. However, of the 65 elements analyzed, only nickel and titanium exceed the value legally accepted in Croatia for drinking water. The levels of DNA damage, estimated by the alkaline Comet assay in hemocytes of medicinal leech, increased with the duration of exposure to two sulfate-rich water samples. Since hemocytes responded sensitively to treatment, they could be used for biomonitoring purposes. As observed on treated human peripheral blood leukocytes, all versions of the Comet assay were effective in detecting DNA damage, which was measured in samples with sulfate concentrations equal to or higher than the legally accepted levels for drinking water. Based on the obtained results, it can be assumed that genotoxicity was a consequence both of direct (single- and double-strand DNA breaks) and indirect effects (oxidative damage) caused by the combined effects of all contaminants present in the tested water samples. Our results indicate the need for in situ monitoring and purification of gypsum mine water prior to its release in the natural environment.

Standardization of bulb and root sample sizes for the Allium cepa test

Although the Allium cepa test has been widely used to identify potentially cytotoxic and genotoxic pollutants in aquatic environments, variable non-standardized choices have been made regarding the number of plant bulbs and roots analyzed. We propose numbers for bulbs and roots per bulb when comparing the frequencies of micronuclei, mitotic anomalies and mitotic index with this test. Roots that had been treated with aqueous solutions, such as water samples collected in August 2007 from the Paraíba do Sul River at the Brazilian cities of Tremembé and Aparecida; negative and positive controls were used for bioassays. The presence of pollutants in the river water had been presumed based on our previous cytological data and an official report by the São Paulo State Environmental Agency (Brazil) on presence of fecal contaminants (Tremembé and Aparecida) and elevated dissolved aluminium (Aparecida) in the water under study. The sampling of ten bulbs and five roots per bulb was found adequate for comparative studies to evaluate with the A. cepa test the potential damage inflicted by pollutants in aquatic environments. Furthermore, even one bulb and one root per bulb was sufficient in discerning this damage, thereby shortening the time required to attain a statistically confident comparative evaluation. However, to allow for the use of statistical programs based on the evaluation of average values, and to avoid criticism based on genetic variability, we propose that three bulbs and three roots per bulb be considered as standard sample sizes for the A. cepa test.

Use of native species Crenicichla menezesi (Ariidae) as a model for in situ evaluation of genotoxicity in surface water

The aim of this work was to analyze the genotoxicity in surface water from the Pitimbú River (Natal, Brazil) using a neotropical species Crenicichla menezesi as bioindicator for in situ evaluation. The genotoxicity was analyzed using the micronucleus (MN) and comet assays in erythrocytes. The animals were collected from five sites of the river. A significant increase of MN frequency and comet class L1 to L4 were observed only in specimens collected from three sampling sites (SS3, SS4 and SS5) located into urban areas. These same sites also presented high metals concentration. Correlation of DNA damage and concentrations of Cu (Spearman r=0.8080), Cr (Spearman r=0.9772), and Ni (Spearman r=0.9909) were observed. These data indicate the presence of genotoxic agents. Moreover the C. menezesi species showed to be a good indicator for prompt analyses since this species presents sedentary and carnivore habits.

Evaluation of the cytotoxic and genotoxic potential of water from the River Paraíba do Sul, in Brazil, with the Allium cepa L. test

This work investigated the cytotoxic and genotoxic potential of water from the River Paraíba do Sul (Brazil) using Allium cepa roots. An anatomo-morphological parameter (root length), mitotic indices, and frequency of micronuclei were analysed. Eight bulbs were chosen at random for treatment for 24 to 120 hours with the River water collected in the years of 2005 and 2006 from sites in the cities of Tremembé and Aparecida (São Paulo state, Brazil). Daily measurements of the length of the roots grown from each bulb were carried out throughout the experiment. Mitotic index (MI) and frequency of micronuclei (MN) were determined for 2000 cells per root, using 3-5 root tips from other bulbs (7-10). Only in the roots treated with samples of the River water collected in 2005 in Tremembé city was there a decrease in the root length growth compared to the respective control. However, a reduction in MI values was verified for both sites analysed for that year. Considering the data involving root length growth and especially MI values, a cytotoxic potential is suggested for the water of the River Paraíba do Sul at Tremembé and Aparecida, in the year of 2005. On the other hand, since in this year the MN frequency was not affected with the river water treatments, genotoxicity is not assumed for the river water sampled at the aforementioned places.

Genotoxicity assessment in aquatic environment impacted by the presence of heavy metals

The aim of this study was to access the genotoxic potential of Extremoz Lake waters in Northeastern Brazilian coast, using the Allium cepa system, piscine micronucleus test and comet assay. In addition, heavy metal levels were quantified by atomic absorption flame spectrometry. The results of the A. cepa system showed significant changes in the frequency of chromosome aberrations and in the mitotic index compared to negative control. No significant changes were observed in micronuclei frequency in the erythrocytes of Oreochromis niloticus. The comet assay showed a statistically significant alteration in the level of DNA breaks of O. niloticus. Chemical analysis detected an increase in heavy metal levels in different sampling periods. These results point out a state of deterioration of water quality at Extremoz Lake, caused by heavy metal contamination and genotoxic activity. It is recommended to establish a monitoring program for the presence of genotoxic agents in this water lake.