Drinking water quality: an in vitro approach for the assessment of cytotoxic and genotoxic load in water sampled along distribution system

Endocrine disrupting chemicals in Italian drinking water systems: Insights from a three-year investigation combining chemical and effect-based tools

Drinking water quality can be compromised by endocrine-disrupting chemicals (EDCs). Three phenolic compounds [bisphenol A (BPA), nonylphenol (NP), and 4-octylphenol (OP)] and three hormones [17β-estradiol (E2), estrone (E1), and 17α-ethinylestradiol (EE2)] were analyzed as EDCs potentially occurring in source and drinking water from three full-scale drinking water treatment plants (DWTPs) in the Romagna area (Italy) by a combined approach of HPLC-MS/MS target analysis and effect-based tests for estrogenicity and genotoxicity. The EDC removal efficiency was evaluated at different steps along the treatment process in the most advanced DWTP. NP prevailed in all samples, followed by BPA. Sporadic contamination by OP and E1/E2 appeared only in the source waters; EE2 was never detected. No estrogenic or genotoxic activity was found, except for two samples showing estrogenicity well below the effect-based trigger value suggested for drinking water safety (0.9 ng/L EEQ). BPA and NP levels were largely below the threshold value; however, increases were observed after the intermediate steps of the treatment chain. The good quality of the water relied on the last step, i.e. the activated carbon filtration. DWTPs may represent an extra source of EDCs and monitoring chemical occurrence at all steps of the process is advisable to improve efficiency.

Using Pgst-4::GFP-transformed Caenorhabditis elegans for drinking water quality monitoring

Biological effect-based monitoring is essential for predicting or alerting to a possible deterioration in drinking water quality. In the present study, a reporter gene assay based on oxidative stress-mediated Pgst-4::GFP induction in the Caenorhabditis elegans strain VP596 (VP596 assay) was assessed for its applicability in evaluating drinking water safety and quality. This assay was used to measure the oxidative stress response in VP596 worms exposed to six ubiquitous components (As³⁺, Al³⁺, F^-, NO₃^--N, CHCl₃, and residual chlorine) in drinking water, eight mixtures of these six components designed through orthogonal design, ninety-six unconcentrated water samples from source to tap water in two supply systems, and organic extracts (OEs) of twenty-five selected water samples. Pgst-4::GFP fluorescence was not induced by Al³⁺, F^-, NO₃^--N, and CHCl₃, and was significantly enhanced by As³⁺ and residual chlorine only at concentrations higher than their respective drinking water guideline levels. Pgst-4::GFP induction was not detected in any of the six-component mixtures. Induction of Pgst-4::GFP was observed in 9.4% (3/32) of the source water samples but not in the drinking water samples. However, a notable induction effect was revealed in the three OEs of drinking water, with a relative enrichment factor of 200. These results suggest that the VP596 assay has limited utility for screening drinking water safety by testing unconcentrated water samples; however, it offers a supplemental in vivo tool for prioritizing water samples for an enhanced quality assessment, monitoring pollutant removal performance by drinking water treatment plants, and evaluating water quality in water supplies.

Contaminants of emerging concern in drinking water: Quality assessment by combining chemical and biological analysis

Drinking water quality is a priority issue of the environmental policy agenda, however regulation on Contaminants of Emerging Concern (CECs) is limited. A proposal to revise the Drinking Water Directive has recently been approved (EU Council 2020), which updates the quality standards and introduces the watch list mechanism, including for the first time endocrine disruptors and pharmaceuticals. The purpose of this study was to evaluate the occurrence of selected CECs in surface water at the entrance of drinking water treatment plants (DWTPs) and in treated water, ready for distribution in the network. Samples were collected at three different DWTPs (Italy) and CECs assessed by LC-MS/MS were the following: bisphenol A (BPA), nonylphenol (NP), octylphenol, perfluorooctanesulfonic and perfluorooctanoic acids (PFOS and PFOA), atenolol, caffeine (CFF), carbamazepine (CBZ), estrone, 17-β-estradiol, 17-α-ethinyl estradiol, diclofenac, and ibuprofen. In addition, biological analyses were performed to ascertain cumulative estrogenic and/or genotoxic potential of the samples. CFF, NP, PFOA, BPA, and CBZ were the most frequently detected contaminants, found in treated water in the following ranges: CFF 12.47-66.33 ng/L, NP 7.90-53.62 ng/L, PFOA <LOQ-12.66, ng/L, BPA <LOQ-6.27 ng/L, and CBZ <LOQ-1.20 ng/L. While treatments were generally efficacious in reducing BPA, CFF and CBZ, they were sometimes ineffective for NP and PFOA. According to the low concentrations and/or regulation limit for each single contaminant, the water analyzed met the criteria of good quality. No estrogenic or genotoxic activities were induced by the water assessed, with the exception of one sample. It has been suggested that drinking water may not represent a significant source of human exposure to CECs, however co-occurrence of different compounds may lead to additive/synergistic interactions causing unexpected effects on human health and the environment, and deserve implementation of strategies for detection and removal.

Algicidal Efficiency and Genotoxic Effects of Phanerochaete chrysosporium against Microcystis aeruginosa

Eutrophication has become a severe environmental problem. This study evaluated the algicidal efficiency and genotoxic effects of Microcystis aeruginosa co-cultured with Phanerochaete chrysosporium for 48 h under the optimum conditions of 250 mg/L of P. chrysosporium at 25 °C with dissolved oxygen content of 7.0 mg/L. The results showed that the activity of algal dehydrogenase, superoxide dismutase, and peroxidase were all decreased and the malondialdehyde content increased after co-culturing. Fourier transform infrared spectroscopy and scanning electron microscopy observations showed that the functional group and structure of algal cells were significantly changed. Compared with those of control tadpoles, blood cells of Fejervarya multistriata tadpoles had increased micronucleus frequency (from 1.05 ± 0.09 to 1.99 ± 0.05) and abnormal nuclei (from 2.45 ± 0.06 to 5.83 ± 0.07). The tail length of M. aeruginosa co-cultured with P. chrysosporium increased from 1.12 ± 0.21 to 21.68 ± 0.34, and the comet length increased from 6.45 ± 0.09 to 36.45 ± 0.67 within 48 h. Micronucleus assay and Comet assay results demonstrated that P. chrysosporium might effectively remove algae and reduce genotoxic effects and may be safe for aquatic ecosystems.

Surrogates for the removal by ozonation of the cytotoxicity and DNA double-strand break effects of wastewater on mammalian cells

Effluents from wastewater treatment plants (WWTPs) may contain various pollutants with potential toxic effects. Ozonation is widely applied to purify wastewater, which may influence the toxicity and water quality indices simultaneously. The main goal of this study was to reveal influence of ozonation on toxicity of WWTP effluents and to find the surrogates for toxicity changes. Cytotoxicity and DNA double-strand break (DSB) effect of WWTP effluents were measured based on Chinese hamster ovary (CHO) cells. Changes of water quality parameters and molecular weight distribution of WWTP effluents were also measured. The organic extracts in WWTP effluents were shown to decrease the cell viability. Besides, an increased level of DNA DSBs was found in cells when exposed to the organic extracts. Ozonation significantly eliminated cytotoxicity and DNA DSB-based genotoxicity of WWTP effluents, with removal rates of 53-66% and 51-76% for cytotoxicity and genotoxicity, respectively, with 10 mg/L ozone dose. Although the DOC contents in WWTP effluents were hardly removed by ozonation, the chromophores and fluorophores were significantly eliminated. Organic matter in WWTP effluents mainly consists of fractions with molecular weight (MW) < 500 Da. Ozonation generally decreased the fluorescence intensity and UV₂₅₄ values of all the MW fractions, but increased the DOC contents of the 100-500 Da fraction. During ozonation, the removal rates of UV₂₅₄ and SUVA₂₅₄ were significantly correlated to the removal rates of both cytotoxicity and genotoxicity. UV₂₅₄ might be an ideal surrogate for cytotoxicity and genotoxicity reduction during wastewater ozonation.

Chlorinated effluent organic matter causes higher toxicity than chlorinated natural organic matter by inducing more intracellular reactive oxygen species

During unplanned indirect potable reuse, treated wastewater that contains effluent organic matter (EOM) enters the drinking water source, resulting in different toxicity from natural organic matter (NOM) in surface water during chlorination. This study found that, during chlorination, EOM formed more total organic halogen (TOX) and highly toxic nitrogenous disinfection byproducts (DBPs) like dichloroacetonitrile and trichloronitromethane than NOM did. Oxidative stress including both reactive oxygen species (ROS) and reactive nitrogen species (RNS) in Chinese hamster ovary (CHO) cells substantially increased when exposed to chlorinated EOM and chlorinated NOM. The excessive ROS damaged biological macromolecules including DNA, RNA to form 8-hydroxy-(deoxy)guanosine and proteins to form protein carbonyls. Impaired macromolecule further triggered cell cycle arrest at the S and G₂ phases, led to cell apoptosis and eventual necrosis. Cytotoxicity and genotoxicity of chlorinated EOM were both higher than those of chlorinated NOM. Adding the blocker L-buthionine-sulfoximine of intracellular antioxidant glutathione demonstrating that oxidative stress might be responsible for toxicity. ROS was further identified to be the main cause of toxicity induction. These findings highlight the risk from chlorinated EOM in the case of unplanned indirect potable reuse, because it showed higher level of cytotoxicity and genotoxicity than chlorinated NOM via inducing more ROS in mammalian cells.

Genotoxicity effects of Phanerochaete chrysosporium against harmful algal bloom species by micronucleus test and comet assay

Algal blooms and toxins have become serious ecological problems. White-rot fungi have been demonstrated to be a feasible means of control, but the genotoxicity mechanisms involved have not been reported. In this study, Cryptomonas obovata FACHB-1301, Oscillatoria sp. FACHB-1083, and Scenedesmus quadricauda FACHB-507 were co-cultured with Phanerochaete chrysosporium under optimal conditions of 250 mg-l at 25 °C with DO 7.0 mg-l for 1, 3, 5 and 7 d. Compared to the control groups, the values for tadpoles exposed to algae treated with Phanerochaete chrysosporium were only increased from 1.95 ± 0.09, 2.78 ± 0.08 and 2.37 ± 0.13 to 2.45 ± 0.07, 3.56 ± 0.08 and 2.54 ± 0.10, and the frequency of nuclear anomalies reached 6.45 ± 0.06, 11.14 ± 0.05 and 7.85 ± 0.10 to 7.68 ± 0.08, 13.12 ± 0.06 and 8.57 ± 0.12 in the experimental groups after 7 d. What's more, the tail lengths were only increased to 36.77 ± 0.54, 41.58 ± 0.78 and 35.38 ± 0.66, and the comet length reached 55.67 ± 0.68, 68.56 ± 0.85 and 51.43 ± 0.82. The results demonstrated that Phanerochaete chrysosporium effectively decreased genotoxicity effects in Fejervarya multistriat tadpoles. These results could provide new ideas for inhibiting water blooms, and lay a theoretical foundation for promoting the deepening of water eutrophication.

Isotopic Labeling Studies Reveal the Patulin Detoxification Pathway by the Biocontrol Yeast Rhodotorula kratochvilovae LS11

Patulin (1) is a mycotoxin contaminant in fruit and vegetable products worldwide. Biocontrol agents, such as the yeast Rhodotorula kratochvilovae strain LS11, can reduce patulin (1) contamination in food. R. kratochvilovae LS11 converts patulin (1) into desoxypatulinic acid (DPA) (5), which is less cytotoxic than the mycotoxin (1) to in vitro human lymphocytes. In the present study, we report our investigations into the pathway of degradation of patulin (1) to DPA (5) by R. kratochvilovae. Isotopic labeling experiments revealed that 5 derives from patulin (1) through the hydrolysis of the γ-lactone ring and subsequent enzymatic modifications. The ability of patulin (1) and DPA (5) to cause genetic damage was also investigated by the cytokinesis-block micronucleus cytome assay on in vitro human lymphocytes. Patulin (1) was demonstrated to cause much higher chromosomal damage than DPA (5).

Multiple-endpoints gene alteration-based (MEGA) assay: A toxicogenomics approach for water quality assessment of wastewater effluents

Wastewater effluents contain a significant number of toxic contaminants, which, even at low concentrations, display a wide variety of toxic actions. In this study, we developed a multiple-endpoints gene alteration-based (MEGA) assay, a real-time PCR-based transcriptomic analysis, to assess the water quality of wastewater effluents for human health risk assessment and management. Twenty-one genes from the human hepatoblastoma cell line (HepG2), covering the basic health-relevant stress responses such as response to xenobiotics, genotoxicity, and cytotoxicity, were selected and incorporated into the MEGA assay. The genes related to the p53-mediated DNA damage response and cytochrome P450 were selected as markers for genotoxicity and response to xenobiotics, respectively. Additionally, the genes that were dose-dependently regulated by exposure to the wastewater effluents were chosen as markers for cytotoxicity. The alterations in the expression of an individual gene, induced by exposure to the wastewater effluents, were evaluated by real-time PCR and the results were validated by genotoxicity (e.g., comet assay) and cell-based cytotoxicity tests. In summary, the MEGA assay is a real-time PCR-based assay that targets cellular responses to contaminants present in wastewater effluents at the transcriptional level; it is rapid, cost-effective, and high-throughput and can thus complement any chemical analysis for water quality assessment and management.

Monitoring the Genotoxic and Cytotoxic Potential and the Presence of Pesticides and Hydrocarbons in Water of the Sinos River Basin, Southern Brazil

The Sinos River is one of the most polluted rivers in Brazil. The purpose of this work was to monitor the presence of some pesticides and hydrocarbons as well as the genotoxic and cytotoxic potential on HEp-2 cells from water samples collected at seven sites in the Sinos River Basin (SRB), southern Brazil. Nine samples were taken from the three main rivers in the SRB and used as a solution to dilute the HEp-2 cell culture medium after microfiltration. Twenty-four pesticides and 19 hydrocarbons were measured. Cytotoxicity was assessed by methyl thiazolyl tetrazolium (MTT) and neutral red (NR) assays, in which cells were exposed to different concentrations of the water samples for 24 h. Genotoxicity of the microfiltrated raw water samples was assessed by comet assay after 6 and 24 h of exposure. Among the chemicals analyzed, only the 2,4-D, dichloromethane, tetrachloroethene, chloroform, bromodichloromethane, styrene, and toluene were detected, but they were all lower than the limit established by Brazilian regulations. Twenty samples from a total of 60 had a cytotoxic effect in the MTT assay and 30 in the NR assay. The comet assay indicated the presence of genotoxic substances in the water at the seven locations monitored. Temporal and spatial variation was observed in the cytotoxicity and genotoxicity assays. Results indicated that the water in all stretches of the SRB is contaminated and it can cause harmful effects to humans and to the aquatic biota. This HEp-2 cell-line approach can be an additional tool for environmental monitoring.

Cytogenotoxicity screening of source water, wastewater and treated water of drinking water treatment plants using two in vivo test systems: Allium cepa root based and Nile tilapia erythrocyte based tests

Biological effect directed in vivo tests with model organisms are useful in assessing potential health risks associated with chemical contaminations in surface waters. This study examined the applicability of two in vivo test systems viz. plant, Allium cepa root based tests and fish, Oreochromis niloticus erythrocyte based tests for screening cytogenotoxic potential of raw source water, water treatment waste (effluents) and treated water of drinking water treatment plants (DWTPs) using two DWTPs associated with a major river in Sri Lanka. Measured physico-chemical parameters of the raw water, effluents and treated water samples complied with the respective Sri Lankan standards. In the in vivo tests, raw water induced statistically significant root growth retardation, mitodepression and chromosomal abnormalities in the root meristem of the plant and micronuclei/nuclear buds evolution and genetic damage (as reflected by comet scores) in the erythrocytes of the fish compared to the aged tap water controls signifying greater genotoxicity of the source water especially in the dry period. The effluents provoked relatively high cytogenotoxic effects on both test systems but the toxicity in most cases was considerably reduced to the raw water level with the effluent dilution (1:8). In vivo tests indicated reduction of cytogenotoxic potential in the tested drinking water samples. The results support the potential applications of practically feasible in vivo biological test systems such as A. cepa root based tests and the fish erythrocyte based tests as complementary tools for screening cytogenotoxicity potential of the source water and water treatment waste reaching downstream of aquatic ecosystems and for evaluating cytogenotoxicity eliminating efficacy of the DWTPs in different seasons in view of human and ecological safety.

Effects of chlorinated drinking water on the xenobiotic metabolism in Cyprinus carpio treated with samples from two Italian municipal networks

Drinking water (DW) disinfection represents a milestone of the past century, thanks to its efficacy in the reduction of risks of epidemic forms by water micro-organisms. Nevertheless, such process generates disinfection by-products (DBPs), some of which are genotoxic both in animals and in humans and carcinogenic in animals. At present, chlorination is one of the most employed strategies but the toxicological effects of several classes of DBPs are unknown. In this investigation, a multidisciplinary approach foreseeing the chemical analysis of chlorinated DW samples and the study of its effects on mixed function oxidases (MFOs) belonging to the superfamily of cytochrome P450-linked monooxygenases of Cyprinus carpio hepatopancreas, was employed. The experimental samples derived from aquifers of two Italian towns (plant 1, river water and plant 2, spring water) were obtained immediately after the disinfection (A) and along the network (R1). Animals treated with plant 1 DW-processed fractions showed a general CYP-associated MFO induction. By contrast, in plant 2, a complex modulation pattern was achieved, with a general up-regulation for the point A and a marked MFO inactivation in the R1 group, particularly for the testosterone metabolism. Together, the toxicity and co-carcinogenicity (i.e. unremitting over-generation of free radicals and increased bioactivation capability) of DW linked to the recorded metabolic manipulation, suggests that a prolonged exposure to chlorine-derived disinfectants may produce adverse health effects.

Evaluation of a drinking water treatment process involving directly recycling filter backwash water using physico-chemical analysis and toxicity assay

Recycling the filter backwash water of a drinking water treatment plant (DWTP) was considered as a feasible method to enhance the efficiencies of pollutant removal and water conservation.

Combining physico-chemical analysis with a Daphnia magna bioassay to evaluate a recycling technology for drinking water treatment plant waste residuals

Recycling water treatment plant (WTP) waste residuals is considered to be a feasible method to enhance the efficiency of pollutant removal. This study also evaluated the safety and water quality of a pilot-DWTP waste residuals recycling technology by combining physical-chemistry analysis with a Daphnia magna assay. The water samples taken from each treatment step were extracted and concentrated by XAD-2 resin and were then analyzed for immobilization and enzyme activity with D. magna. The measured parameters, such as the dissolve organic carbon (DOC), UV254 and THM formation potential (THMFPs) of the recycling process, did not obviously increase over 15 days of continuous operation and were even lower than typical values from a conventional process. The extract concentration ranged from 0 to 2 Leq/ml as measured on the 7th and 15th days and the immobilization of D. magna exposed to water treated by the recycling process was nearly equivalent to that of the conventional process. Both the superoxide dismutase (SOD) and the catalase (CAT) activity assay indicated that a lower dose of water extract (0.5, 1, 1.5 Leq/ml) could stimulate the enzyme activity of D. magna, whereas a higher dose (2 Leq/ml at the sampling point C3, R3, R4 ) inhibits the activity. Moreover, the SOD and CAT activity of D. magna with DOC and UV254 showed a strong concentration-effect relationship, where the concentration range of DOC and UV254 were 4.1-16.2 mg/L and 0.071-4.382 cm(-1), respectively. The results showed that there was no statistically significant difference (p>0.05) between the conventional and recycling treatment processes and the toxicity of water samples in the recycling process did not increase during the 15-day continuous recycling trial.

Evaluation of genotoxic effects caused by extracts of chlorinated drinking water using a combination of three different bioassays

Potential genotoxic effects of chlorinated drinking water now are of a great concern. In this study, raw water, finished water, and tap water from a water plant in Wuhan, China were collected in two different sampling times of the year (January and July). Genotoxic effects of water extracts were evaluated using a combination of three different bioassays: SOS/umu test, HGPRT gene mutation assay, and micronucleus assay, which were separately used to detect DNA damage, gene mutation, and chromosome aberration. The results of three different bioassays showed that all water samples in January and July induced at least one types of genotoxic effects, of which the DNA-damage effects were all detectable. The levels of DNA-damage effects and gene-mutation effects of finished water and tap water in January were higher than those in July. Chlorination could increase the DNA-damage effects of drinking water in January and the gene-mutation effects of drinking water in both January and July, but did not increase the chromosome-aberration effects of drinking water in both January and July. Our results highlighted the importance of using a combination of different bioassays to evaluate the genotoxicity of water samples in different seasons.

Genotoxic potency of mercuric chloride in gill cells of marine gastropod Planaxis sulcatus using comet assay

In vivo and in vitro exposures were used to investigate the genotoxicity of mercuric chloride (HgCl2) to the marine snail, Planaxis sulcatus. The comet assay protocol was validated on gill cells exposed in vitro to hydrogen peroxide (H2O2, 0-50 μM). Snails were exposed in vivo for 96 h to HgCl2 (10, 20, 50, and 100 μg/l). Our results showed significant concentration-dependent increase in the tail DNA (TDNA) and olive tail moment (OTM) in exposed snails for all doses compared with controls. In vitro exposure to HgCl2 (10-100 μg/l) resulted in significantly higher values for TDNA at all concentrations. Our results showed that DNA damage increased in the gill cell with increasing exposure time. This study demonstrates the usefulness of comet assay for detection of DNA damage after exposure to HgCl2 and the sensitivity of marine snail P. sulcatus as a good candidate species for metal pollution.

Evaluation of genotoxicity and cytotoxicity of water samples from the Sinos River Basin, southern Brazil

<p>Some water bodies in the Sinos River Basin (SRB) have been suffering the effects of pollution by residential, industrial and agroindustrial wastewater. The presence of cytotoxic and genotoxic compounds could compromise the water quality and the balance of these ecosystems. In this context, the research aimed to evaluate the genotoxicity and cytotoxicity of the water at four sites along the SRB (in the cities of Santo Antônio da Patrulha, Parobé, Campo Bom and Esteio), using bioassays in fish and cell culture. Samples of surface water were collected and evaluated <italic>in vitro</italic> using the <italic>Astyanax jacuhiensis</italic> fish species (micronucleus test and comet assay) and the Vero lineage of cells (comet assay and cytotoxicity tests, neutral red - NR and tetrazolium MTT). The micronucleus test in fish showed no significant differences between the sampling sites, and neither did the comet assay and the MTT and NR tests in Vero cells. The comet assay showed an increase in genetic damage in the fish exposed to water samples collected in the middle and lower sections of the basin (Parobé, Campo Bom and Esteio) when compared to the upper section of the basin (Santo Antônio da Patrulha). The results indicate contamination by genotoxic substances starting in the middle section of the SRB.</p>

Mutagenicity of drinking water sampled from the Yangtze River and Hanshui River (Wuhan section) and correlations with water quality parameters

A total of 54 water samples were collected during three different hydrologic periods (level period, wet period, and dry period) from Plant A and Plant B (a source for Yangtze River and Hanshui River water, respectively), and several water parameters, such as chemical oxygen demand (COD), turbidity, and total organic carbon (TOC), were simultaneously analyzed. The mutagenicity of the water samples was evaluated using the Ames test with Salmonella typhimurium strains TA98 and TA100. According to the results, the organic compounds in the water were largely frame-shift mutagens, as positive results were found for most of the tests using TA98. All of the finished water samples exhibited stronger mutagenicity than the relative raw and distribution water samples, with water samples collected from Plant B presenting stronger mutagenic strength than those from Plant A. The finished water samples from Plant A displayed a seasonal-dependent variation. Water parameters including COD (r = 0.599, P = 0.009), TOC (r = 0.681, P = 0.02), UV₂₅₄ (r = 0.711, P = 0.001), and total nitrogen (r = 0.570, P = 0.014) exhibited good correlations with mutagenicity (TA98), at 2.0 L/plate, which bolsters the argument of the importance of using mutagenicity as a new parameter to assess the quality of drinking water.

Comet Assay on Daphnia magna in eco-genotoxicity testing

Detection of potentially hazardous compounds in water bodies is a priority in environmental risk assessment. For the evaluation and monitoring of water quality, a series of methodologies may be applied. Among them, the worldwide used toxicity tests with organisms of the genus Daphnia is one of the most powerful. In recent years, some attempts were made to utilize Daphnia magna in genotoxicity testing as many of the new environmental contaminants are described as DNA-damaging agents in aquatic organisms. The aim of this research was to develop a highly standardized protocol of the Comet Assay adapted for D. magna, especially regarding the isolation of cells derived from the same tissue (haemolymph) from newborn organisms exposed in vivo. Several methods for haemolymph extraction and different Comet Assay parameters were compared. Electrophoretic conditions were adapted in order to obtain minimum DNA migration in cells derived from untreated organisms and, at the same time, maximum sensitivity in specimens treated with known genotoxicants (CdCl2 and H2O2). Additional tests were performed to investigate if life-history traits of the cladoceran (such as the age of adult organisms that provide newborns, the clutch size of origin, the number of generations reared in standard conditions) and the water composition as well, might influence the response of the assay. This study confirms the potential application of the Comet Assay in D. magna for assessing genotoxic loads in aqueous solution. The newly developed protocol could integrate the acute toxicity bioassay, thus expanding the possibility of using this model species in freshwater monitoring (waters, sediment and soil elutriates) and is in line with the spirit of the EU Water Framework Directive in reducing the number of bioassays that involve medium-sized species.

Toxicity assessment of chlorinated wastewater effluents by using transcriptome-based bioassays and Fourier transform mass spectrometry (FT-MS) analysis

Effects of chlorination on the toxicity of wastewater effluents treated by activated sludge (AS) and submerged membrane bioreactor (S-MBRB) systems to HepG2 human hepatoblastoma cells were investigated. In addition to the cytotoxicity and genotoxicity assays, the DNA microarray-based transcriptome analysis was performed to evaluate the change in types of biological impacts on HepG2 cells of the effluents by chlorination. Effluent organic matter (EfOM) and disinfection by-products (DBPs) were also characterized by using Fourier transform mass spectrometry (FT-MS). Although no significant induction of genotoxicity was observed by chlorination for both effluents, the chlorination elevated the cytotoxicity of AS effluent but reduced that of S-MBRB effluent. The FT-MS analyses revealed that more DBPs including nitrogenated DBPs (N-DBPs) were formed in the AS effluent than in the S-MBRB effluent by chlorination, supporting the increased cytotoxicity of AS effluent. The lower O/C ratio of S-MBRB EfOM suggests that a large number of organic molecules were detoxified by chlorination, which consequently decreased the cytotoxicity of S-MBRB effluent. Integration of all the results highlights that both cytotoxicity and biological impacts of chlorinated wastewater effluents were clearly dependent on the EfOM characteristics such as DBPs and O/C ratio, namely, on types of treatment systems.

Signal transduction disturbance related to hepatocarcinogenesis in mouse by prolonged exposure to Nanjing drinking water

Toxicogenomic approaches were used to investigate the potential hepatocarcinogenic effects on mice by oral exposure to Nanjing drinking water (NJDW). Changes in the hepatic transcriptome of 3 weeks male mice (Mus musculus) were monitored and dissected after oral exposure to NJDW for 90 days. No preneoplastic and neoplastic lesions were observed in the hepatic tissue by the end of NJDW exposure. However, total of 746 genes were changed transcriptionally. Thirty-one percent of differentially expressed genes (DEGs) were associated with the functional categories of cell cycle regulation, adhesion, growth, apoptosis, and signal transduction, which are closely implicated in tumorigenesis and progression. Interrogation of Kyoto Encyclopedia of Genes and Genomes revealed that 43 DEGs were mapped to several crucial signaling pathways implicated in the pathogenesis of hepatocellular carcinoma (HCC). In signal transduction network constructed via Genes2Networks software, Egfr, Akt1, Atf2, Ctnnb1, Hras, Mapk1, Smad2, and Ccnd1 were hubs. Direct gene-disease relationships obtained from Comparative Toxicogenomics Database and scientific literatures revealed that the hubs have direct mechanism or biomarker relationships with hepatocellular preneoplastic lesions or hepatocarcinogenesis. Therefore, prolonged intake of NJDW without employing any indoor water treatment strategy might predispose mouse to HCC. Furthermore, Egfr, Akt1, Ctnnb1, Hras, Mapk1, Smad2, and Ccnd1 were identified as promising biomarkers of the potential combined hepatocarcinogenicity.

Bioanalytical assessment of the formation of disinfection byproducts in a drinking water treatment plant

Disinfection of drinking water is the most successful measure to reduce water-borne diseases and protect health. However, disinfection byproducts (DBPs) formed from the reaction of disinfectants such as chlorine and monochloramine with organic matter may cause bladder cancer and other adverse health effects. In this study the formation of DBPs through a full-scale water treatment plant serving a metropolitan area in Australia was assessed using in vitro bioanalytical tools, as well as through quantification of halogen-specific adsorbable organic halogens (AOXs), characterization of organic matter, and analytical quantification of selected regulated and emerging DBPs. The water treatment train consisted of coagulation, sand filtration, chlorination, addition of lime and fluoride, storage, and chloramination. Nonspecific toxicity peaked midway through the treatment train after the chlorination and storage steps. The dissolved organic matter concentration decreased after the coagulation step and then essentially remained constant during the treatment train. Concentrations of AOXs increased upon initial chlorination and continued to increase through the plant, probably due to increased chlorine contact time. Most of the quantified DBPs followed a trend similar to that of AOXs, with maximum concentrations observed in the final treated water after chloramination. The mostly chlorinated and brominated DBPs formed during treatment also caused reactive toxicity to increase after chlorination. Both genotoxicity with and without metabolic activation and the induction of the oxidative stress response pathway showed the same pattern as the nonspecific toxicity, with a maximum activity midway through the treatment train. Although measured effects cannot be directly translated to adverse health outcomes, this study demonstrates the applicability of bioanalytical tools to investigate DBP formation in a drinking water treatment plant, despite bioassays and sample preparation not yet being optimized for volatile DBPs. As such, the bioassays are useful as monitoring tools as they provide sensitive responses even at low DBP levels.

Reproductive toxicity in male mice exposed to Nanjing City tap water

End points of reproductive toxicity were investigated in male mice (Mus musculus, ICR) fed Nanjing City tap water for 90 days. There was no significant alteration in body weights between treatment and control mice. In treated mice, flow cytometry analysis of testicular tissue indicated that the relative percentage of the elongated spermatid (HC) decreased significantly (P < 0.05). Also slight increases in the relative percentage of round spermatids (1C) and primary spermatocytes (4C) were noted. The ratios of 4C:2C (diploid germ cells) and 1C:2C increased, and testicular histopathology indicated an expansion of interstitial space and a decreased number and size of Leydig cells in treated mice. The current study suggests that Nanjing City tap water is toxic to the reproductive system of mice and additional study to evaluate its effects on other species, including human beings, would be warranted.

Evaluation of contaminant removal of reverse osmosis and advanced oxidation in full-scale operation by combining passive sampling with chemical analysis and bioanalytical tools

Advanced water treatment of secondary treated effluent requires stringent quality control to achieve a water quality suitable for augmenting drinking water supplies. The removal of micropollutants such as pesticides, industrial chemicals, endocrine disrupting chemicals (EDC), pharmaceuticals, and personal care products (PPCP) is paramount. As the concentrations of individual contaminants are typically low, frequent analytical screening is both laborious and costly. We propose and validate an approach for continuous monitoring by applying passive sampling with Empore disks in vessels that were designed to slow down the water flow, and thus uptake kinetics, and ensure that the uptake is only marginally dependent on the chemicals' physicochemical properties over a relatively narrow molecular size range. This design not only assured integrative sampling over 27 days for a broad range of chemicals but also permitted the use of a suite of bioanalytical tools as sum parameters, representative of mixtures of chemicals with a common mode of toxic action. Bioassays proved to be more sensitive than chemical analysis to assess the removal of organic micropollutants by reverse osmosis, followed by UV/H₂O₂ treatment, as many individual compounds fell below the quantification limit of chemical analysis, yet still contributed to the observed mixture toxicity. Nonetheless in several cases, the responses in the bioassays were also below their quantification limits and therefore only three bioassays were evaluated here, representing nonspecific toxicity and two specific end points for estrogenicity and photosynthesis inhibition. Chemical analytical techniques were able to quantify 32 pesticides, 62 PCPPs, and 12 EDCs in reverse osmosis concentrate. However, these chemicals could explain only 1% of the nonspecific toxicity in the Microtox assay in the reverse osmosis concentrate and 0.0025% in the treated water. Likewise only 1% of the estrogenic effect in the E-SCREEN could be explained by the quantified EDCs after reverse osmosis. In comparison, >50% of the estrogenic effect can typically be explained in sewage. Herbicidal activity could be fully explained by chemical analysis as the sampling period coincided with an illegal discharge and two herbicides dominated the mixture effect. The mass balance of the reverse osmosis process matched theoretical expectations for both chemical analysis and bioanalytical tools. Overall the investigated treatment train removed >97% estrogenicity, >99% herbicidal activity, and >96% baseline toxicity, confirming the suitability of the treatment train for polishing water for indirect potable reuse. The product water was indistinguishable from local tap water in all three bioassays. This study demonstrates the suitability and robustness of passive sampling linked with bioanalytical tools for semicontinuous monitoring of advanced water treatment with respect to micropollutant removal.

A combined approach to investigate the toxicity of an industrial landfill's leachate: chemical analyses, risk assessment and in vitro assays

Solid wastes constitute an important and emerging problem. Landfills are still one of the most common ways to manage waste disposal. The risk assessment of pollutants from landfills is becoming a major environmental issue in Europe, due to the large number of sites and to the importance of groundwater protection. Furthermore, there is lack of knowledge for the environmental, ecotoxicological and toxicological characteristics of most contaminants contained into landfill leacheates. Understanding leachate composition and creating an integrated strategy for risk assessment are currently needed to correctly face the landfill issues and to make projections on the long-term impacts of a landfill, with particular attention to the estimation of possible adverse effects on human health and ecosystem. In the present study, we propose an integrated strategy to evaluate the toxicity of the leachate using chemical analyses, risk assessment guidelines and in vitro assays using the hepatoma HepG2 cells as a model. The approach was applied on a real case study: an industrial waste landfill in northern Italy for which data on the presence of leachate contaminants are available from the last 11 years. Results from our ecological risk models suggest important toxic effects on freshwater fish and small rodents, mainly due to ammonia and inorganic constituents. Our results from in vitro data show an inhibition of cell proliferation by leachate at low doses and cytotoxic effect at high doses after 48 h of exposure.

Genotoxicity of lavender oil, linalyl acetate, and linalool on human lymphocytes in vitro

The potential genotoxicity of lavender essential oil and its major components, linalool, and linalyl acetate, was evaluated in vitro by the micronucleus test on peripheral human lymphocytes. In the range of non-toxic concentrations (0.5-100 μg/ml), linalyl acetate increased the frequency of micronuclei significantly and in concentration-dependent manner; lavender oil did so only at the highest concentration tested, whereas linalool was devoid of genotoxicity. None of the tested substances led to an increase in nucleoplasmic bridges or nuclear buds frequency. These findings suggest that the mutagenic activity of lavender oil can be related to the presence of linalyl acetate, which seems to have a profile of an aneugenic agent.

Genotoxic analysis in aquatic environment under influence of cyanobacteria, metal and radioactivity

The micronucleus (MN) and nuclear abnormality (NA) tests were employed to evaluate the genotoxic potential of the Lucrecia dam (RN, Brazil) located in a semi-arid region and influenced by crop irrigation and irregular rainfall. The analyses of these water samples demonstrated the presence of several cyanobacteria as well as metals and radioactivity. The Nile Tilapia (Oreochromis niloticus) was used for micronucleus and nuclear abnormality assays and analysis of metal concentrations in gills and liver samples. Genotoxic assays in source water fish showed a significant increase in the frequency of nuclear damage (MN and NA) in relation to the negative control group. In conclusion, the results obtained with water surface and biological samples from the Lucrecia dam suggest that this important water resource contains a number of chemical and microbiological pollutants with genotoxic potential and that these substances may be compromising the species inhabiting this ecosystem. Particular care must be taken to prevent further degradation of this water supply. Capsule: A battery of assay was successfully applied to assess the water quality of Lucrecia dam from a Northeastern region of Brazil.