Cytotoxicity and genotoxicity of sewage treatment plant effluents in rainbow trout cells (RTG-2)

Transcriptome analysis and cytochrome P450 monooxygenase reveal the molecular mechanism of Bisphenol A degradation by Pseudomonas putida strain YC-AE1

BACKGROUND

Bisphenol A (BPA) is a rapid spreading organic pollutant that widely used in many industries especially as a plasticizer in polycarbonate plastic and epoxy resins. BPA reported as a prominent endocrine disruptor compound that possesses estrogenic activity and fulminant toxicity. Pseudomonas putida YC-AE1 was isolated in our previous study and exerted a strong degradation capacity toward BPA at high concentrations; however, the molecular degradation mechanism is still enigmatic.

RESULTS

We employed RNA sequencing to analyze the differentially expressed genes (DEGs) in the YC-AE1 strain upon BPA induction. Out of 1229 differentially expressed genes, 725 genes were positively regulated, and 504 genes were down-regulated. The pathways of microbial metabolism in diverse environments were significantly enriched among DEGs based on KEGG enrichment analysis. qRT-PCR confirm the involvement of BPA degradation relevant genes in accordance with RNA Seq data. The degradation pathway of BPA in YC-AE1 was proposed with specific enzymes and encoded genes. The role of cytochrome P450 (CYP450) in BPA degradation was further verified. Sever decrease in BPA degradation was recorded by YC-AE1 in the presence of CYP450 inhibitor. Subsequently, CYP450bisdB deficient YC-AE1 strain △ bisdB lost its ability toward BPA transformation comparing with the wild type. Furthermore, Transformation of E. coli with pET-32a-bisdAB empowers it to degrade 66 mg l^-1 of BPA after 24 h. Altogether, the results showed the role of CYP450 in biodegradation of BPA by YC-AE1.

CONCLUSION

In this study we propose the molecular basis and the potential role of YC-AE1cytochrome P450 monooxygenase in BPA catabolism.

A sensitive electrochemical sensor for environmental toxicity monitoring based on tungsten disulfide nanosheets/hydroxylated carbon nanotubes nanocomposite

There has been growing concern about the toxic effects of pollutants in the aquatic environment. In this study, a novel cell-based electrochemical sensor was developed to detect the toxicity of contaminants in water samples. A screen-printed carbon electrode, which was low-cost, energy-efficient, and disposable, was modified with tungsten disulfide nanosheets/hydroxylated multi-walled carbon nanotubes (WS₂/MWCNTs-OH) to improve electrocatalytic performance and sensitivity. The surface morphology, structure, and electrochemical property of WS₂/MWCNTs-OH composite film were characterized by emission scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, X-ray diffraction, Raman spectroscopy, and electrochemical impedance spectroscopy. Grass carp kidney cell line was utilized as the sensor biorecognition element to determine the electrochemical signals and evaluate cell viability. The sensor was used to detect the toxicity of one typical contaminant (2,4,6-trichlorophenol) and two emerging contaminants (bisphenol AF and polystyrene nanoplastics). The 48 h half inhibitory concentration (IC₅₀) values were 169.96 μM, 21.88 μM, and 123.01 μg mL^-1, respectively, which were lower than those of conventional MTT assay, indicating the higher sensitivity of the proposed sensor. Furthermore, the practical application of the sensor was evaluated in chemical wastewater samples. This study provides an up-and-coming tool for environmental toxicity monitoring.

Genotoxic risk assessment and mechanism of DNA damage induced by phthalates and their metabolites in human peripheral blood mononuclear cells

The human genome is persistently exposed to damage caused by xenobiotics, therefore the assessment of genotoxicity of substances having a direct contact with humans is of importance. Phthalates are commonly used in industrial applications. Widespread exposure to phthalates has been evidenced by their presence in human body fluids. We have assessed the genotoxic potential of selected phthalates and mechanism of their action in human peripheral blood mononuclear cells (PBMCs). Studied cells were incubated with di-n-butyl phthalate (DBP), butylbenzyl phthalate (BBP) and their metabolites: mono-n-butylphthalate (MBP), mono-benzylphthalate (MBzP) in the concentrations range of 0.1-10 µg/mL for 24 h. Analyzed compounds induced DNA single and double strand-breaks (DBP and BBP ≥ 0.5 µg/mL, MBP and MBzP ≥ 1 µg/mL) and more strongly oxidized purines than pyrimidines. None of the compounds examined was capable of creating adducts with DNA. All studied phthalates caused an increase of total ROS level, while hydroxyl radical was generated mostly by DBP and BBP. PBMCs exposed to DBP and BBP could not completely repair DNA strand-breaks during 120 min of postincubation, in opposite to damage caused by their metabolites, MBP and MBzP. We have concluded that parent phthalates: DBP and BBP caused more pronounced DNA damage compared to their metabolites.

Insights into the mechanism of groove binding between 4-octylphenol and calf thymus DNA

4-Octylphenol is an endocrine disruptor, belonging to environmental estrogens. It can be enriched in the human body through the food chain and may harm human health. Herein, we used a variety of spectroscopic techniques, molecular docking, and gel electrophoresis to study the interaction of 4-octylphenol and ctDNA. It was found that the mechanism of ctDNA quenching the endogenous fluorescence of 4-octylphenol was static quenching, and formed a complex. The negative enthalpy change (ΔH°), entropy change (ΔS°) and Gibbs free energy (ΔG°) have shown that 4-octylphenol and ctDNA spontaneously bind together under the action of hydrogen bonds and van der Waal's force. Viscosity, melting temperature and iodide quenching experiments showed that 4-octylphenol acted on the groove of ctDNA. Insignificant change in circular dichromism spectra further confirmed this binding mode. The binding sites and groups for 4-octylphenol and ctDNA interaction were identified by molecular docking. Gel electrophoresis found that 4-octylphenol at high concentrations caused DNA cleavage. Above findings may lay a theoretical foundation for understanding the toxicity mechanism of 4-octylphenol.

Discrepant dose responses of bisphenol A on oxidative stress and DNA methylation in grass carp ovary cells

Bisphenol A (BPA), is a common contaminant in diverse environmental compartments and its endocrine disruptive effect on living organisms has been widely reported. Further works are still required to facilitate the research on cytotoxicity and genotoxicity. In the present study, grass carp ovary (GCO) cells were used to investigate cellular oxidative stress and genomic DNA methylation under BPA exposure. Results showed that BPA exposure for 48 h arrested cell proliferation and viability. The oxidative stress was distinctly enhanced with increased reactive oxygen species (ROS), malondialdehyde level, and oxidation of reduced glutathione (GSH) in 30 μM BPA group. Furthermore, the global 5-methylcytosine (5 mC) level was elevated and showed inverted U-shaped responses to the BPA doses. Besides, one-carbon metabolism and de novo GSH synthesis were disrupted at 30 μM BPA. Current data suggested that low dose of BPA exposure could exhibit hormesis in recycling circular biosynthesis of GSH and scavenging ROS to create a relatively reductive intracellular environment, and up-regulate transcripts of methyltransferases that increased the 5 mC level in GCO cells. While high dose of BPA distinctly induced oxidative stress, elevated de novo GSH synthesis, and then attenuated transmethylation activity and decreased 5 mC level. Current study highlighted the discrepant dose responses of BPA in fish ovary cells that facilitated the understanding of pleiotropic consequences in organisms.

Repeated exposure to the irrigative wastewater in Shijiazhuang induced precancerous lesion associated with cytochrome P450

In the present study, the carcinogenic effects of the wastewater sample collected from the Dongming Canal in Shijiazhuang city were first detected by the rat medium-term liver bioassay. The experiment contained five groups: a negative control group, a DEN-alone group, 25% wastewater, 50% wastewater, and 100% wastewater. The body weight of rats decreased significantly as the dose increased. Morphologically, we also found that the damage of the hepatic lobule was more serious and the proliferation of liver cells was more obvious as the dose increased. In addition, we observed a significantly increased liver organ coefficient in rat. With the increase in dose, the damage of the hepatocytes was more serious, which was manifested in significantly elevated of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and gammaglutamyl transfer peptide enzyme (γ-GT). And, the irrigative wastewater significantly increased GST-p in the liver of rats at both the transcriptional and translational levels dose-dependently, eventually causing precancerous lesions in the liver tissues. CYP1A1 and CYP1B1 expressions in the rat liver cells at the level of transcription and translation were also significantly increased dose-dependently. Our data clearly demonstrated that the irrigative wastewater had a carcinogenetic effect that was associated with CYP1A1 and CYP1B1. The risk of carcinogenic potential to human health might be due to joint action and accumulative effects over a long period of exposure. We can also concluded that the medium-term liver bioassay could be used as an effective method for evaluating the carcinogenicity of complex water mixtures such as irrigative wastewater.

Global Transcriptional Analysis of Nontransformed Human Intestinal Epithelial Cells (FHs 74 Int) after Exposure to Selected Drinking Water Disinfection By-Products

BACKGROUND

Drinking water disinfection inadvertently leads to the formation of numerous disinfection by-products (DBPs), some of which are cytotoxic, mutagenic, genotoxic, teratogenic, and potential carcinogens both in vitro and in vivo.

OBJECTIVES

We investigated alterations to global gene expression (GE) in nontransformed human small intestine epithelial cells (FHs 74 Int) after exposure to six brominated and two chlorinated DBPs: bromoacetic acid (BAA), bromoacetonitrile (BAN), 2,6-dibromo-p-benzoquinone (DBBQ), bromoacetamide (BAM), tribromoacetaldehyde (TBAL), bromate (BrO3-), trichloroacetic acid (TCAA), and trichloroacetaldehyde (TCAL).

METHODS

Using whole-genome cDNA microarray technology (Illumina), we examined GE in nontransformed human cells after 4h exposure to DBPs at predetermined equipotent concentrations, identified significant changes in gene expression (p≤0.01), and investigated the relevance of these genes to specific toxicity pathways via gene and pathway enrichment analysis.

RESULTS

Genes related to activation of oxidative stress-responsive pathways exhibited fewer alterations than expected based on prior work, whereas all DBPs induced notable effects on transcription of genes related to immunity and inflammation.

DISCUSSION

Our results suggest that alterations to genes associated with immune and inflammatory pathways play an important role in the potential adverse health effects of exposure to DBPs. The interrelationship between these pathways and the production of reactive oxygen species (ROS) may explain the common occurrence of oxidative stress in other studies exploring DBP toxicity. Finally, transcriptional changes and shared induction of toxicity pathways observed for all DBPs caution of additive effects of mixtures and suggest further assessment of adverse health effects of mixtures is warranted. https://doi.org/10.1289/EHP4945.

The evaluation of the potential ecotoxicity of pyroligneous acid obtained from fast pyrolysis

Pyroligneous acid (PA) is a by-product of bio-oil, which is obtained by pyrolysis of the wood. This product has been tested for use in several areas, such as agriculture, as a promising green herbicide; however, there are few scientific data regarding its environmental impacts. For this study, an ecotoxicity testing battery, composed of Daphnia magna acute toxicity test, Allium cepa test and in vitro Comet assay with the rainbow trout gonad-2 cell fish line (RTG-2) were used to evaluate the acute toxicity and genotoxicity of PA obtained from fast pyrolysis of eucalyptus wood fines. The PA presented acute toxicity to D. magna (microcrustacea) with EC₅₀ of 26.12 mg/L, and inhibited the seed germination (EC₅₀ 5.556 g/L) and root development (EC₅₀ 3.436 g/L) of A. cepa (higher plant). No signs of genotoxicity (chromosomal aberrations and micronuclei in A. cepa and primary DNA lesions in RTG-2 cells) were detected to this product. The acute toxicity and absence of genotoxicity may relate to the molecules found in the PA, being the phenolic fraction the key chemical candidate responsible for the toxicity observed. In addition, daphnids seem to be more sensitivity to the toxicity of PA than higher plants based on their EC₅₀ values. This first ecotoxicological evaluation of PA from fast pyrolysis pointed out the need of determining environmental exposure limits to promote the safer agriculture use of this product, avoiding impacts to living organisms.

Cumulative effects of municipal effluent and parasite infection in yellow perch: A field study using high-throughput RNA-sequencing

Multiple metabolic, immune and reproductive effects have been reported in fish residing in effluent-impacted sites. Natural stressors such as parasites also have been shown to impact the responses of organisms to chronic exposure to municipal effluent in the St. Lawrence River (Quebec, Canada). In order to comprehensively evaluate the cumulative impacts of anthropogenic and natural stressors on the health of yellow perch, differential mRNA transcription profiles were examined in juvenile females collected from effluent-impacted and upstream sites with low or high infection levels of the larval trematode Apophallus brevis. Transcriptomics was used to identify biological pathways associated with environmental exposure. In total, 3463 isoforms were differentially transcribed between sites. Patterns reflecting the combined effects of stressors were numerically dominant, with a majority of downregulated transcripts (68%). The differentially expressed transcripts were associated with 27 molecular and cellular functions ranging from cellular development to xenobiotic metabolism and were involved in the development and function of 13 organ systems including hematological, hepatic, nervous, reproductive and endocrine systems. Based on RNA-seq results, sixteen genes were measured by qPCR. Significant differences were observed for six genes in fish exposed to both stressors combined, whereas parasites and effluent individually impacted the transcription of one gene. Lysozyme activity, lipid peroxidation, retinol-binding protein and glucose-6-phosphate dehydrogenase were selected as potential biomarkers of effects to study specific pathways of interest. Lipid peroxidation in perch liver was different between sites, parasite loads, and for combined stressors. Overall, results indicated that juvenile yellow perch responded strongly to combined parasite and effluent exposure, suggesting cumulative effects on immune responses, inflammation and lipid metabolism mediated by retinoid receptors. The present study highlight the importance of using a comprehensive approach combining transcriptomics and endpoints measured at higher levels of biological organization to better understand cumulative risks of contaminants and pathogens in aquatic ecosystems.

Cytotoxic and genotoxic effect of oxyfluorfen on hemocytes of Biomphalaria glabrata

Chemicals released from anthropogenic activities such as industry and agriculture often end up in aquatic ecosystems. These substances can cause serious damage to these ecosystems, thus threatening the conservation of biodiversity. Among these substances are pesticides, such as oxyfluorfen, a herbicide used for the control of grasses and weeds. Considering its widespread use, it is important to investigate the possible toxicity of this compound to aquatic organisms, especially invertebrates. Hence, the use of biological systems able to detect such effects is of great importance. The mollusk Biomphalaria glabrata has been shown to be useful as an environmental indicator to assess the potential ecological effects of physical and chemical stressors in freshwater environments. The present study sought to detect mutagenic changes in hemocytes of B. glabrata exposed to oxyfluorfen. To perform these tests, this study used ten animals per group, exposed acutely (48 h) and chronically (15 days) to oxyfluorfen. The herbicide concentrations were 0.125, 0.25, and 0.5 mg/L. The results showed that oxyfluorfen induced significant frequencies of micronuclei, binucleated cells, and apoptosis in hemocytes of mollusks when compared to the control group. Unlike chronic exposure, acute exposure was dose-dependent. The present study's results demonstrate the cytotoxic and genotoxic effects of oxyfluorfen on hemocytes of B. glabrata.

Assessing the concentration of phthalate esters (PAEs) and bisphenol A (BPA) and the genotoxic potential of treated wastewater (final effluent) in Saudi Arabia

Plasticizers such as phthalate esters (PAEs) and bisphenol A (BPA) are highly persistent organic pollutants that tend to bio-accumulate in humans through the soil-plant-animal food chain. Some studies have reported the potential carcinogenic and teratogenic effects in addition to their estrogenic activities. Water resources are scarce in Saudi Arabia, and several wastewater treatment plants (WTPs) have been constructed for agricultural and industrial use. This study was designed to: (1) measure the concentrations of BPA and six PAEs, dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), butyl benzyl phthalate (BBP), bis (2-ethylhexyl) phthalate (DEHP) and dioctyl phthalate (DOP), in secondary- and tertiary-treated wastewater collected from five WTPs in three Saudi cities for four to five weeks and (2) test their potential genotoxicity. Three genotoxicological parameters were used: % tail DNA (%T), tail moment (TM) and percentage micronuclei (%MN). Both DBP and DEHP were detected in all treated wastewater samples. DMP, DEP, BBP, DOP, and BPA were found in 83.3, 84.2, 79, 73.7 and 97.4% of the samples, respectively. The levels of DMP (p<0.001), DOP (p<0.001) and BPA (p=0.001) were higher in tertiary- treated wastewater than secondary-treated wastewater, perhaps due to the influence of the molecular weight and polarity of the chemicals. Both weekly sampling frequency and WTP locations significantly affected the variability in our data. Treated wastewater from Wadi Al-Araj was able to induce DNA damage (%T and TM) in human lymphoblastoid TK6 cells that was statistically higher than wastewater from all other WTPs and in untreated TK6 cells (negative control). %MN in samples from both Wadi Al-Araj and Manfouah did not differ statistically but was significantly higher than in the untreated TK6 cells. This study also showed that the samples of tertiary-treated wastewater had a higher genotoxicological potential to induce DNA damage than the samples of secondary-treated wastewater. BPA and some PAEs in the treated wastewater might have the potential to induce genetic damage, despite their low levels. Genotoxicity, however, may also have been due to the presence of other contaminants. Our preliminary findings should be of concern to Saudi agriculture because long-term irrigation with treated wastewater could lead to the accumulation of PAEs and BPA in the soil and ultimately reach the human and animal food chain. WTPs need to remove pollutants more efficiently. Until then, a cautious use of treated wastewater for irrigation is recommended to avoid serious health impacts on local populations.

Long-term water quality data explain interpopulation variation in responsiveness to stress in sticklebacks at both wastewater effluent-contaminated and uncontaminated sites

The magnitude of the corticosteroid response to a standardized stressor varied in proportion to the concentration of effluent in three-spined sticklebacks (Gasterosteus aculeatus L.) captured downstream of 10 wastewater-treatment plants (WWTPs). However, at 9 sites with no upstream WWTP input interpopulation variation in the reactivity of the stress axis occurred across a similar range to that seen for fish at impacted sites, suggesting that the factor(s) responsible for modulating stress responsiveness in sticklebacks is not unique to sites receiving WWTP effluent. Physicochemical data from a long-term monitoring program were employed to investigate whether variation in water quality contributed to between-site variation in stress axis reactivity. Between-site variation in 14 water quality determinands explained between 30% and 60% of the variation in stress reactivity and fish size for sticklebacks at both WWTP-contaminated and uncontaminated sites. At uncontaminated sites the mean mass and length of sticklebacks increased with total oxidized nitrogen (N) concentration (as an indicator of anthropogenic input), whereas at WWTP-contaminated sites fish size decreased with increasing effluent concentration, suggesting that factors adversely affecting growth were present predominantly at WWTP-contaminated sites. In contrast, at both contaminated and uncontaminated sites the magnitude of the corticosteroid response to a standardized stressor increased with anthropogenic input (effluent concentration or total oxidized N, respectively), indicating that a factor or factors modulating the reactivity of the stress axis may be present at both WWTP-contaminated and uncontaminated sites. Environ Toxicol Chem 2016;35:3014-3022. © 2016 SETAC.

Landfill leachate sludge use as soil additive prior and after electrocoagulation treatment: A cytological assessment using CHO-k1 cells

Electrocoagulation has recently attracted attention as a potential technique for treating toxic effluents due to its versatility and environmental compatibility, generating a residue chemically suitable to be used as a soil additive. In the present study, landfill leachate sludge hazardous effects were investigated prior and after electrocoagulation process using in vitro assays with the mammalian cells CHO-k1. An integrated strategy for risk assessment was used to correctly estimate the possible adverse landfill leachate sludge effects on human health and ecosystem. Electrocoagulation process proved to be an effective treatment due to possibility to improve effluent adverse characteristics and produce sludge with potential to be used as soil additive. Despite low cytoxicity, the residue presented genotoxic and mutagenic effects, indicating a capacity to induce genetic damages, probably due to induction of polyploidization process in cells. The observed effects demand an improvement of waste management methods for reduce negative risks of landfill leachate sludge application.

Lagos lagoon sediment organic extracts and polycyclic aromatic hydrocarbons induce embryotoxic, teratogenic and genotoxic effects in Danio rerio (zebrafish) embryos

An expansion of anthropogenic activity around Lagos lagoon, Nigeria, has raised concerns over increasing contaminants entering the lagoon's ecosystem. The embryotoxicity, teratogenicity and genotoxicity of sediment organic extracts from four sampling zones around Lagos lagoon, Ilaje, Iddo, Atlas Cove and Apapa, as well as the dominant polycyclic aromatic hydrocarbons (PAHs) identified in water measured during the wet season (naphthalene, phenanthrene, pyrene, benzo[a]pyrene and a mixture of these), were assessed with Danio rerio embryos. Embryos were exposed to varying concentrations of toxicants from 0-72 h post-fertilization (hpf). Embryotoxicity at 72 hpf showed a dose-dependent increase in mortality upon exposure to extracts from all zones, except Atlas Cove. Similarly, higher levels of teratogenic effects, such as increased oedema, and haemorrhage and developmental abnormalities resulted from exposure to extracts from Ilaje, Iddo and Apapa zones. Treatment with single PAHs revealed that significant levels of detrimental effects were obtained only for phenanthrene. The modified comet assay revealed that the oxidative damage to DNA was generally low (<12 %) overall for all sediment extracts, but was significantly elevated with Ilaje and Iddo sediment extracts when compared with solvent controls. Oxidative damage was observed with the single PAHs, phenanthrene and benzo[a]pyrene, as well as with the PAH mixture. This study highlights that Lagos lagoon sediment extracts have teratogenic, embryotoxic and genotoxic properties, which are likely due to the high molecular weight PAHs present in the extracts, some of which are known or are suspected human carcinogens.

Sewage sludge hazardous assessment: chemical evaluation and cytological effects in CHO-k1 cells

Application of sewage sludge in agricultural lands is a growing practice in several countries due to its numerous benefits to soil and crops, where chemical and pathogen levels are determined by corresponding legislation. However, the presence of contaminants in residues must always be controlled before application due to their dangerous effects over the ecosystem and potential risks to human health. The main objective of this study was to integrate biological and chemical analysis in order to help elucidating the residue potential toxic, cytotoxic, and mutagenic effects. We evaluate samples of sewage sludge before and after the sanitizing treatment with lime in cytokinesis-block assay using CHO-k1 culture cells. The sanitizing treatment promoted a decrease in pathogen levels, which is the main purpose of this process. Even with chemical levels below the established by environmental agencies, results showed sewage sludge ability to enhance genotoxic and mutagenic effects, proving that residue should be handled with caution in order to minimize its environmental and human risk.

Genotoxicity Evaluation of Irrigative Wastewater from Shijiazhuang City in China

In the present study, the wastewater sample collected from the Dongming discharging river in Shijiazhuang city was analysed using both chemical analysis and biological assays including the Salmonella mutagenicity test, micronucleus test and single-cell gel electrophoresis. Chemical analysis of the sample was performed using gas chromatography mass spectrometry and inductively coupled plasma mass spectrometry. The Salmonella mutagenicity test was performed on Salmonella typhimurium TA97, TA98, TA100 and TA102 strains with and without S9 mixture. The mice received the wastewater in natura through drinking water at concentrations of 25%, 50%, and 100%. One group of mice was exposed for 2 consecutive days, and the other group of mice was exposed for 15 consecutive days. To establish the levels of primary DNA damage, single-cell gel electrophoresis was performed on treated mouse liver cell. The concentrations of chromium and lead in the sample exceeded the national standard (GB20922-2007) by 0.78 and 0.43-fold, respectively. More than 30 organic compounds were detected, and some of the detected compounds were mutagens, carcinogens and environmental endocrine disrupters. A positive response for Salmonella typhimurium TA98 strain was observed. Mouse exposure via drinking water containing 50% and 100% of wastewater for 15 consecutive days caused a significant increase of MN frequencies in a dose-response manner. Mouse exposure via drinking water containing 50% and 100% of wastewater for 15 consecutive days caused a significant increase of the Olive tail moments in a dose-response manner. All the results indicated that the sample from the Dongming discharging river in Shijiazhuang city exhibited genotoxicity and might pose harmful effects on the local residents.

Cytotoxicity assays to evaluate tannery effluents treated by photoelectrooxidation

The advanced oxidation process (AOP) is used to increase the treatment efficiency of effluents however, it is necessary to compare the toxicity of treated and untreated effluents to evaluate if the decontamination process does not cause any biological harm. Cultured cells have been previously used to assess the genotoxic and cytotoxic potential of various compounds. Hence, the aim of this work was to assess the applicability of cytotoxicity assays to evaluate the toxicity related to the AOP treatment. Samples of an industrial effluent were collected after their treatment by a conventional method. Cytotoxicity of standard and AOP treated effluents was assessed in CRIB and HEp-2 cell line using the MTT and neutral red assays. We observed decrease at cell viability in the both assays (50% MTT and 13% NRU) when cells were exposed to the AOP treatment in the highest concentration. Thus, cytotoxic assays in cultured cells can be explored as an useful method to evaluate toxicity as well as to optimize effluents treatment process.

Cytotoxic and genotoxic responses of the RTgill-W1 fish cells in combination with the yeast oestrogen screen to determine the sediment quality of Lagos lagoon, Nigeria

Economic advancements in developing countries have seen an increase in urbanisation and industrialisation with a rise in the levels of discharge of effluents and municipal waste into aquatic ecosystems. Unfortunately, aquatic environmental regulations in these countries are often rudimentary and the development of environmental monitoring programmes will help identify ecological risks. As an example, the current study assesses the pollution status of 11 sampling sites in Lagos lagoon, Nigeria. The organic solvent sediment extracts were assessed for cytotoxicity and genotoxicity in rainbow trout gill-W1 cells. The induction of oestrogenic activities using the yeast oestrogen screen was also determined. The sediments were analysed for polycyclic aromatic hydrocarbons (PAHs) and other contaminants (polychlorinated biphenyls, organochlorine and organophosphate pesticides). Only sediments from three sites were cytotoxic at both 25 and 12.5mg eQsed/ml using the Alamar Blue cell viability assay. The alkaline Comet assay showed that all sites caused significant DNA damage at 7 mg eQsed/ml; the extent of the damage was site specific. The measure of oxidative damage to DNA via the formamidopyrimidine DNA-glycosylase-modified Comet assay revealed similar results. Toxicity to yeast cells was observed in extracts from six sites; of the remaining sites, only two exhibited oestrogenic activity. There was no strong consistent relationship between sediment PAH concentrations and the cell toxicity endpoints. The dynamic nature of Lagos lagoon with its tides and freshwater inputs are suggested as factors that make it difficult to link the sources of pollution observed at each site with PAH levels and toxic endpoints. The study has demonstrated that the Comet assay is a sensitive endpoint to identify sediments that possess genotoxic contaminants, and this in vitro bioassay has the potential to be incorporated into an environmental monitoring framework for Lagos lagoon.

Genotoxicity Study with Special Reference to Comet Test in the Blood Cells of Workers Exposed to Sewage Water

Awareness among sewage workers to occupational exposure is growing slowly in many developing countries. Lead (Pb) and cadmium (Cd) are present in sewage water and workers are exposed to these metals as a result of unprotected handling. These heavy metals exposures are responsible for DNA damage and lowering blood total iron (Fe) concentration. Zinc (Zn) is an element for promoting metallothionine expression and binds the free Cd. The total suspended solids (TSS), total dissolved solids (TDS), Pb, and Cd were estimated in sewage water. The whole blood Zn and Fe concentration and Pd and Cd were also estimated. Genotoxicity as indicated by DNA damage was studied by comet assay. It was observed that there were significant differences (P<0.001) of Pb and Cd concentration in blood for the sewage workers when compared with control population. DNA damage was also observed to be significantly (P<0.001) higher in the exposed groups but their blood Fe concentration was significantly lower, which may be the reason for their tendency for retention of blood Cd and make them more susceptible. This study also indicated that aged workers had higher blood Zn concentrations as compared to the younger (working < 20 years) workers. This may indicate a possible adaptive response. The present study proposes that younger (working < 20 years) group is more susceptible as compared to aged group (working > 20 years).

Effects of Tapinanthus globiferus and Zanthoxylum zanthoxyloides extracts on human leukocytes in vitro

Objective:

This study aimed at investigating the genotoxicity and cytotoxicity effect of Tapinanthus globiferus and Zanthoxylum zanthoxyloides to human leukocytes. In addition, the reductive potential and the chemical composition of the two plant extracts were also determined.

Materials and Methods:

Human leukocytes were obtained from healthy volunteer donors. The genotoxicity and cytotoxicity of T. globiferus and Z. zanthoxyloides were assessed using the comet assay and trypan blue exclusion, respectively. The antioxidant activity of the plant extracts was evaluated by the reducing power assay. Furthermore, high-performance liquid chromatography-diode array detector was used to characterize and quantify the constituents of these plants.

Results:

T. globiferus (10-150 µg/mL) was neither genotoxic nor cytotoxic at the concentrations tested, suggesting that it can be consumed safely at relatively high concentrations. However, Z. zanthoxyloides showed cytoxicity and genotoxicity to human leukocytes at the highest concentration tested (150 µg/mL). In addition, the total reducing power of T. globiferus was found higher than Z. zanthoxyloides in potassium ferricyanide reduction. Both plants extract contained flavonoids (rutin and quercetin) and phenolic acids (chlorogenic and caffeic).

Conclusion:

The results obtained support the fact that some caution should be paid regarding the dosage and the frequency of use of Z. zanthoxyloides extract.

Haloactamides versus halomethanes formation and toxicity in chloraminated drinking water

In this study we quantified the concentrations of nine haloacetamides (HAcAms) and nine halomethanes (HMs) in the final waters of five drinking water treatment plants (DWTPs) that use either chlorination or chloramination for disinfection and evaluated the toxicity of dichloroacetamide (DCAcAm) and dichloromethane (DCM) in normal rat kidney (NRK) cells using four in vitro toxicity assays. All the DWTPs final waters contained primarily di-HAcAms, followed by tri- and mono-HAcAms, and DCAcAm was the most abundant species of the 9 HAcAms, regardless of chlorination or chloramination being applied. In the final waters of DWTPs using chlorination, tri-HMs (trihalomethanes, THMs) accounted for the majority of HMs, whereas chloramination resulted in more di-HMs (especially DCM) than THMs. All four in vitro toxicity assays indicated that the NRK cell chronic cytotoxicity and acute genotoxicity of DCAcAm were substantially higher than that of DCM. In view of observed occurrence concentrations and quantified toxicity levels, the findings of this study suggest that DCAcAm represents a higher toxicity risk than DCM in chloraminated drinking waters.

Cytotoxic and genotoxic effects of water and sediment samples from gypsum mining area in channel catfish ovary (CCO) cells

Man-made activities such as mining generate certain amounts of metal contaminated wastes which can reach aquatic environment and cause the serious effects on different organisms and ecosystem. Chemical analysis of the environmental samples is the most direct approach to reveal their pollution status but it cannot always provide information on biological effects to different organisms, including fish. This study was aimed to investigate the in vitro cytotoxicity and genotoxicity of water and sediment samples from gypsum mining area using the channel catfish ovary (CCO) cell line. Results obtained by the WST-1 assay and alkaline comet assay revealed that exposure of CCO cells to the same concentrations of contaminated water and sediment samples caused significant decrease in cell viability and increased DNA damages. Chemical analysis of water and sediment samples showed that increased concentrations of strontium, aluminum and iron were mainly responsible for the observed cytotoxic and genotoxic effects in CCO cells. The study suggested that fish CCO cells could be useful biological test-system for water and sediment cytotoxicity and genotoxicity assessments.