Landfill leachate ingestion induces protein oxidation and DNA-protein crosslinks in mouse viscera

Alterations in viscera histoarchitecture and organosomatic index as biomarkers of toxicity induced by Aba-Eku and Olusosun solid waste landfill leachates in Rattus norvegicus

Solid waste disposal generates leachate, a mixture of deleterious chemical, physical and microbial contaminants, which poses risk to human and wildlife health. Leachate toxicity on relative organ weight and histopathology of important viscera in mammalian body is scarce. Leachate induced toxic effects on organosomatic indices and histopathology of vital mammalian organs were investigated. Wister rats were orally exposed to 1 - 25 % of raw and simulated leachates from Aba-Eku and Olusosun landfills for 30 days. At post-exposure, organosomatic index and histoarchitectural assessment of major viscera (heart, spleen, thymus and lungs) were conducted. The physico-chemical and organic compositions of the leachates were analysed using standard protocol. The tested leachates decreased weekly and terminal body weights, and altered organosomatic index of examined viscera in rats. The histoarchitecture of the investigated viscera revealed pathologies that ranged from mild to severe degeneration, cellular infiltration, haemorrhage, congestion, necrosis, disorganization of tissues and vacuolations. Others include increased histiocytes within the bronchial associated lymphoid, lymphoid depletions, haemosiderin deposits and apoptosis were observed in the examined viscera. Physico-chemical analysis of the leachates showed different concentrations of toxic metals, PAHs and PCBs that were higher than national and international permissible limits allowed in wastewaters. The physico-chemical compositions of the leachates are capable of eliciting the observed alterations in organosomatic indices and histopathological lesions in mammalian viscera. Xenobiotic components of the leachates possibly generated free radicals and/or directly disrupted the organ architectures. These findings suggest health risk to wildlife and human population exposed to emissions from waste landfills.

A comprehensive overview on solid waste leachate effects on terrestrial organisms

Leachate is a highly complex waste with high toxicological potential that poses a significant threat to the terrestrial environment. Determining leachate physicochemical parameters and identifying xenobiotics alone is, however, not enough to determine the real environmental impacts. In this context, the use of terrestrial model organisms has been highlighted as a tool in ecotoxicological leachate assessments and as a guiding principle in risk assessments. In this context, this review aimed to present the most current state of knowledge concerning leachate toxicity and the bioassays employed in this evaluation concerning terrestrial plants and animals. To this end, a literature search on leachate effects on terrestrial organisms was carried out using ten search terms, in 32 different combinations, at the Web of Science and Scopus databases. A total of 74 eligible articles were selected. The retrieved studies analyzed 42 different plant and animal species and employed nine endpoints, namely phytotoxicity, genotoxicity, bioaccumulation, antioxidant system, cytotoxicity, reproduction, physiological changes, behavior and lethality. A frequent association of toxic leachate effects with metals was observed, mainly Pb, Cd, Cr, Mg, Zn and Cr, which can cause antioxidant system alterations and cyto- and genotoxicity. These elements have also been associated to reproductive effects in earthworms and mice. Specifically concerning plants, most of the retrieved studies employed Allium cepa in toxicity assays, reporting phytotoxic effects frequently associated to metals and soil parameter changes. Animal studies, on the other hand, mostly employed mice and evaluated genotoxicity and antioxidant system effects. Even with the description of toxic leachate effects in both plants and animals, a lack of knowledge is still noted concerning reproductive, physiological, cytotoxic, and behavioral effects in terrestrial species. We, thus, suggest that further studies be carried out on other animals, advancing our understanding on potential environmental leachate effects, also allowing for human health risk assessments.

Neurobehavioral deficits, histoarchitectural alterations, parvalbumin neuronal damage and glial activation in the brain of male Wistar rat exposed to Landfill leachate

Concerns about inappropriate disposal of waste into unsanitary municipal solid waste landfills around the world have been on the increase, and this poses a public health challenge due to leachate production. The neurotoxic effect of Gwagwalada landfill leachate (GLL) was investigated in male adult Wistar rats. Rats were exposed to a 10% concentration of GLL for 21 days. The control group received tap water for the same period of the experiment. Our results showed that neurobehavior, absolute body and brain weights and brain histomorphology as well as parvalbumin interneurons were severely altered, with consequent astrogliosis and microgliosis after 21 days of administrating GLL. Specifically, there was severe loss and shrinkage of Purkinje cells, with their nucleus, and severe diffused vacuolations of the white matter tract of GLL-exposed rat brains. There was severe cell loss in the granular layer of the cerebellum resulting in a reduced thickness of the layer. Also, there was severe loss of dendritic arborization of the Purkinje cells in GLL-exposed rat brains, and damage as well as reduced populations of parvalbumin-containing fast-spiking GABAergic interneurons in various regions of the brain. In conclusion, data from the present study demonstrated the detrimental effects of Gwagwalada landfill leachate on the brain which may be implicated in neuropsychological conditions.

2,2-Dichloroacetamide exposure induces behavior and memory disorders in mice: Detrimental effects of long-term dietary restriction on neurotoxicity

2, 2-dichloroacetamide (DCAcAm), a nitrogen-containing disinfection byproduct (DBPs), is commonly found in potable water. This study aimed to compare the neurotoxicity of DCAcAm in C57/BL6 mice at both environmentally relevant and higher doses through oral exposure over a 28-day period. Furthermore, the potential effects of dietary restriction (DR) on the cerebral toxicity induced by 20 ppb DCAcAm were examined. The findings indicated that DCAcAm exposure and DR treatment resulted in reduced memory retention and cognitive adaptability in mice. Additionally, higher doses of DCAcAm exposure induced severe brain inflammation and oxidative stress. Metabolic profiling revealed disruptions in fatty acid, energy, and amino acid metabolism in the brain. Remarkably, the negative impacts of 20 ppb DCAcAm on the mice brain were worsened by DR treatment. Analysis of 16S rRNA sequencing revealed notable changes in the composition and structure of intestinal microorganisms after exposure to DCAcAm. This study discovered that DCAcAm has both direct effects on the brain and indirect effects through the microbial-brain-intestinal axis, which collectively result in neurotoxicity and dietary restriction exacerbates these effects. This study provides emerging views on the assessment of the toxicity of nitrogen containing DBPs.

Interaction of heavy metals in Drosophila melanogaster larvae: Fourier transform infrared spectroscopy and single-cell electrophoresis study

The present study evaluates the Murraya Koenigii (CuLE) and Tinospora Crispa (TiSE) antimutagenic effect and the impact of industrial soil and solid waste leachate on Drosophila larvae. Larvae were exposed to leachate prepared at different pH (7, 4.93, 2.88) and treated with TiSE and CuLE at different concentration (4 g/L and 6 g/L) mixed with standard Drosophila medium. Emphasis was given to the binding interaction of heavy metals with proteins in Drosophila. The change in structure and molecular composition in Drosophila by leachate containing heavy metals induced toxicity has been studied by using Fourier transform infrared (FTIR) spectroscopy. Results from the study demonstrated that CuLE/TiSE administration restored the level of oxidative stress as evidenced by an enhanced antioxidant system and a decrease in lipid peroxidation and protein oxidation. The amide I and amide II bands spectral shifting revealed the binding interaction. The shift in the peak of PO2- asymmetric stretching might be due to compositional changes in nucleic acids. Single-cell electrophoresis was performed to detect the DNA damage which also proved to be ameliorated by administration of CuLE/TiSE. The result concludes that CuLE/TiSE may have great potential in the protection of Drosophila larvae from leachate induced oxidative stress through antioxidant and antimutagenic mechanisms this might help to cope with environmental toxicants.Communicated by Ramaswamy H. Sarma.

A comprehensive assessment of leachate contamination at a non-operational open dumpsite: mycoflora screening, metal soil pollution indices, and ecotoxicological risks

The final disposal of municipal solid waste (MSW) in dumpsites is still a reality worldwide, especially in low- and middle-income countries, leading to leachate-contaminated zones. Therefore, the aim of this study was to carry out soil and leachate physicochemical, microbiological, and toxicological characterizations from a non-operational dumpsite. The L-01 pond samples presented the highest physicochemical parameters, especially chloride (Cl; 4101 ± 44.8 mg L^-1), electrical conductivity (EC; 10,452 ± 0.1 mS cm^-1), and chemical oxygen demand (COD; 760 ± 6.6 mg L^-1) indicating the presence of leachate, explained by its close proximity to the landfill cell. Pond L-03 presented higher parameters compared to pond L-02, except for N-ammoniacal and phosphorus levels, explained by the local geological configuration, configured as a slope from the landfill cell towards L-03. Seven filamentous and/or yeast fungi genera were identified, including the opportunistic pathogenic fungi Candida krusei (4 CFU) in an outcrop sample. Regarding soil samples, Br, Se, and I were present at high concentrations leading to high soil contamination (CF ≤ 6). Pond L-02 presented the highest CF for Br (18.14 ± 18.41 mg kg^-1) and I (10.63 ± 3.66 mg kg^-1), while pond L-03 presented the highest CF for Se (7.60 ± 1.33 mg kg^-1). The most severe lethal effect for Artemia salina was observed for L-03 samples (LC₅₀: 79.91%), while only samples from L-01 were toxic to Danio rerio (LC₅₀: 32.99%). The highest lethality for Eisenia andrei was observed for L-02 samples (LC₅₀: 50.30%). The applied risk characterization indicates high risk of all proposed scenarios for both aquatic (RQ 375-909) and terrestrial environments (RQ > 1.4 × 10⁵). These findings indicate that the investigated dumpsite is contaminated by both leachate and metals, high risks to living organisms and adjacent water resources, also potentially affecting human health.

Mitochondrial dysfunctions elicited by solid waste leachates provide insights into mechanisms of leachates induced cell death and pathophysiological disorders

Emissions (mainly leachates and landfill gases) from solid waste facilities are laden with mixtures of dangerous xenobiotics implicated with significant increase in various pathophysiological disorders including cancer, and eventual mortality of exposed wildlife and humans. However, the molecular mechanisms of solid waste leachates induce pathophysiological disorders and cell death are still largely unknown. Although, evolving evidence implicated generation of reactive oxygen species and oxidative stress as the possible mechanism. Recent scientific reports are linking reactive oxygen species and mitochondrial dysfunctions as the player mechanism in pathophysiological disorder and apoptosis induced by xenobiotics in solid waste leachates. This systematic review presents an explicit discussion of recent scientific findings on the structural and functional alterations in mitochondria induced by solid waste leachates as the molecular mechanisms plausibly responsible for the pathophysiological disorders, cancer and cell death reported in landfill toxicology and epidemiological studies. This review aims to increase scientific understanding on solid waste leachate induced mitochondria dysfunctions as the key player in molecular mechanisms of solid waste induced toxicity. The findings in this review were mainly from using primary cells, cell lines, Drosophila and fish. Whether the findings will similarly be observed in mammalian test systems in vivo and particularly in exposed humans, remained to be investigated. Improvement in technological advancements, enforcement of legislation and regulations, and creation of sophisticated health surveillance against exposure to solid waste leachates, will expectedly mitigate human exposure to solid waste emissions and contamination of the environment.

Evaluation of genotoxic and oxidative stress potential of Ajakanga Landfill Leachate in rats

Genotoxicity and oxidative stress potential of Ajakanga Landfill Leachate (ALL) were investigated in this study. Forty-two male albino rats of the Wistar strain (100 g and 150 g) were divided equally into six groups. Group A (control) animals were given distilled water as drinking water for forty-five days; while groups B-F animals were exposed to 12.5%, 25%, 50%, 75% and 100% leachate respectively via drinking water for forty-five days. The effect of the leachate was assessed on markers of oxidative stress in the liver, kidney and testes of rats; markers of liver function (Alanine aminotransferase (ALT) and Aspartate aminotransferase (AST) were determined in the serum and the genotoxic effect of the leachate was investigated using micronucleus assay. Physicochemical and heavy metal analysis were also carried out on the leachate sample. Exposure to ALL resulted in increase in the activities of ALT and AST. A significant increase in malondialdehyde level as well as alterations in antioxidant status was observed in the liver, kidney and testes of the rats compared with control. There was also significant increase in micronuclei formation in the bone marrow of rats exposed to the leachate. Physicochemical and heavy metal analysis of the leachate revealed the presence of some heavy metals at high concentrations as well as other toxic constituents and the total number of active bacteria in the leachate sample were also high. In conclusion, ALL induced oxidative stress and genotoxicity in rats. This suggests that the leachate may be toxic to humans if exposure occurs.

Metal Bioaccumulation, Cytogenetic and Clinico-Biochemical Alterations in Rattus norvegicus Exposed In Situ to a Municipal Solid Waste Landfill in Lagos, Nigeria

This study aimed at determining in animal model the health effects of in situ exposure to landfill chemicals. We evaluated metal concentrations in tissues and cytogenetic and clinico-biochemical effects in Wistar rats (Rattus norvegicus) exposed in situ at Olusosun landfill in Lagos, Nigeria. Male rats (n = 30/point) were exposed at three different points to ambient air and underground water (via drinking) at the landfill for 4-, 8-, 12-, 16-, 20- and 24-week periods. Rats concurrently sited at a residential area, 17.3 km from the landfill site served as control. There was significantly (p < 0.05) time-dependent: accumulation of lead, cadmium, chromium, copper and zinc in the liver and kidney and increase in body weight gain, in exposed rats compared to control. There was significant induction of micronuclei and cytotoxicity (reduced PCE/NCE ratios) in exposed rats. Haematological parameters (RBC, PCV, Hb and WBC) and serum biomarkers of hepato-renal damage [aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH) activities; creatinine and urea levels] revealed significant increases. There was significant increase in hepatic levels of reduced glutathione, malondialdehyde, catalase activities, and decrease in superoxide dismutase, at all periods. Chromium and copper concentrations in the liver and kidney revealed significant positive correlations with either one or more of AST, ALT, LDH and urea. Significant metal concentrations in the underground water and tissues suggest that heavy metals are responsible for the observed alterations, and this may have been via oxidative stress. These findings suggest potential health risk due to occupational and residential exposure to landfill pollutants.

Landfill soil leachates from Nigeria and India induced DNA damage and alterations in genes associated with apoptosis in Jurkat cell

Landfill soil leachates, containing myriad of xenobiotics, increase genotoxic and cytotoxic stress-induced cell death. However, the underlying mechanism involved in the elimination of the damaged cells is yet to be fully elucidated. This study investigated the apoptotic processes induced in lymphoma (Jurkat) cells by landfill soil leachates from Olusosun (OSL, Nigeria) and Nagpur (NPL, India). Jurkat was incubated with sub-lethal concentrations of OSL and NPL for 24 h and analyzed for DNA fragmentation and apoptosis using agarose gel electrophoresis and Hoechst 33258-PI staining, respectively. Complementary DNA expression profiling of some pro-apoptotic and anti-apoptotic genes regulating apoptosis was also analyzed using real-time PCR (RT-PCR) method. Agarose gel electrophoresis revealed DNA fragmentations in OSL and NPL-treated cells. Hoecsht-33258 - Propidium Iodide (PI) based apoptotic analysis confirmed apoptotic cell death in exposed Jurkat. RT-PCR analysis revealed different fold changes in the pro- and anti-apoptotic genes in OSL and NPL-treated Jurkat. There was significant increase in fold change of the up-regulated genes; apoptosis inducing factor mitochondrion-associated 2 (AIFM2), Fas-associated death domain (FADD), Caspase-2, Caspase-6, BH3 interacting domain death agonist (BID), tumor suppressor (p53), and BCL2 associated agonist of cell death (BAD) and down-regulation of apoptosis inhibitor 5 (API5). Results suggest that OSL and NPL elicited genotoxic stress-related apoptosis in Jurkat. The dysregulation in the expression of genes involved in apoptotic processes in wildlife and human exposed to landfill emissions may increase aetiology of various pathological diseases including cancer.

Long-term landfill leachate exposure modulates antioxidant responses and causes cyto-genotoxic effects in Eisenia andrei earthworms

It is estimated that approximately 0.4% of the total leachate produced in a landfill is destined for treatment plants, while the rest can reach the soil and groundwater. In this context, this study aimed to perform leachate toxicity evaluations through immune system cytotoxic assessments, genotoxic (comet assay) appraisals and antioxidant system (superoxide dismutase - SOD; catalase - CAT, glutathione-S-transferase - GST; reduced glutathione - GSH and metallothionein - MT) evaluations in Eisenia andrei earthworms exposed to a Brazilian leachate for 77 days. The leachate sample contained high organic matter (COD - 10,630 mg L^-1) and ammoniacal nitrogen (2398 mg L^-1), as well as several metals, including Ca, Cr, Fe, Mg, Ni and Zn. Leachate exposure resulted in SOD activity alterations and increased CAT activity and MT levels. Decreased GST activity and GSH levels were also observed. Antioxidant system alterations due to leachate exposure led to increased malondialdehyde levels as a result of lipid peroxidation after the 77 day-exposure. An inflammatory process was also observed in exposed earthworms, evidenced by increased amoebocyte density, and DNA damage was also noted. This study demonstrates for the first time that sublethal effect assessments in leachate-exposed earthworms comprise an important tool for solid waste management.

Standardized experimental model for cement dust exposure; tissue heavy metal bioaccumulation and pulmonary pathological changes in rats

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Exposure model is a reliable method of studying pulmonary toxicity of aerosolized xenobiotics.

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Deposition of particles beyond the conducting zone and tissue bioaccumulation accompany exposure to cement dust (ECD).

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Histoarchitectural alteration, body-organ weight discordance are indicators of acute ECD.

A controlled experimental model of exposure to aerosols particularly for cement dust was recently invented in a study from the laboratory that found high serum levels of heavy metals, decrease gastrointestinal motility, and altered hematological variables in cement dust exposed rats. However, reproducibility was not considered. This work aims at standardizing the model and investigating preliminary toxicological indicators. Thirty male rats used in this study were divided into 3 groups (n = 10). Group 1; control, while groups 2 and 3 were exposed to cement dust for 14 days and 28 days respectively. We assessed clinical signs of toxicity, tissue heavy metal concentration, histopathological, and body weight (BW) changes. We observed poor movement coordination, abnormal posture, cephalic fur loss. Evidence of ischemia and fibrotic pneumoconiosis were grossly observed in the lungs of the exposed groups. There was a significant increase in tissue level of heavy metals with pulmonary and gastric heavy metal content showing a trendy relationship during the period of the exposure as the value of Lead, Chromium, Cadmium, Iron, Calcium, and Nickel increased by nearly similar percentages in both tissues. Organs weights increased; the 14-day exposed (198 ± 31; 168 ± 22) and 28-day exposed (198 ± 22; 187 ± 26) groups had significantly reduced body weight at the first and second weeks of exposure compared to the control group (265 ± 26; 357 ± 40) respectively. Exposure to cement dust induced low bone density in the exposed rats (p < 0.05). Histopathological alterations include necrosis, inflammatory cellular infiltration, and alveolar hyperplasia suggestive of the proliferative response of pulmonary tissue to the dust. The operation of the standardized apparatus mimics a typical occupational exposure and the findings show that cement dust induces systemic toxicity via respiratory perturbation and body/organ weight discordance mediated by heavy metal bioaccumulation.

Wild black rats (Rattus rattus Linnaeus, 1758) as zoomonitor of genotoxicity and systemic toxicity induced by hazardous emissions from Abule Egba unsanitary landfill, Lagos, Nigeria

Wild black rats (Rattus rattus) inhabiting Abule Egba landfill (AEL) were used as zoomonitor to assess health risk associated with exposure to hazardous chemicals from landfills. Twenty five R. rattus (16♂ and 9♀) captured within AEL and 15 (9♂ and 6♀) (control) caught from Iyano Ipaja (10 km away from AEL) were examined for bone marrow micronucleated polychromatic erythrocytes (MNPCE) and polychromatic erythrocytes/normochromatic erythrocytes (PCE/NCE) ratio, abnormal sperm morphology, alterations in hematological indices and erythrocyte morphology, and histopathology of the viscera using standard protocols. There was significant (p < 0.05) increase in MNPCE but decrease PCE/NCE ratio in bone marrow cells of exposed rats than the reference site. MNPCE was insignificantly higher in male than females. Cauda epididymal sperms from exposed rats showed significant high frequency of teratozoospermia. Erythrocyte count, hemoglobin concentrations, percentage hematocrits, mean corpuscular hemoglobin concentrations, leucocyte count, and lymphocytes decreased while mean corpuscular volume, neutrophils, and mean corpuscular hemoglobin increased in the exposed rats compared to the control. Also, abnormal erythrocyte morphology: acanthocytes, codocytes (target cells), schizocytes, and tear drops significantly increased in the exposed rats. Marginal sexual dimorphism was observed between males and females in the incidence of hematological indices. Histopathological lesions including interstitial edema, hemorrhage, lymphoid depletion, cellular infiltrations, proliferation of the alveolar pneumocytes, necrosis, tissue degeneration, and reduced germinal epithelium were observed in the testes, liver, lungs, heart, kidney, and spleen from the exposed rats compared to the control. Some physicochemicals and metals analyzed in leachates from the landfill are capable of inducing genome instability and systemic toxicity in the exposed rats. Rattus rattus exposed to hazardous chemicals from AEL harbored somatic and germ cell mutations, and tissue damage compared to the control rats. We suggest that R. rattus are useful sentinel for genotoxicity and system toxicity assessment of landfill-polluted sites.Graphical abstract.

Recent advances in municipal landfill leachate: A review focusing on its characteristics, treatment, and toxicity assessment

Nowadays, sanitary landfilling is the most common approach to eliminate municipal solid waste, but a major drawback is the generation of heavily polluted leachates. These leachates must be appropriately treated before being discharged into the environment. Generally, the leachate characteristics such as COD, BOD/COD ratio, and landfill age are necessary determinants for selection of suitable treatment technologies. Rapid, sensitive and cost-effective bioassays are required to evaluate the toxicity of leachate before and after the treatment. This review summarizes extensive studies on leachate treatment methods and leachate toxicity assessment. It is found that individual biological or physical-chemical treatment is unable to meet strict effluent guidelines, whereas a combination of biological and physical-chemical treatments can achieve satisfactory removal efficiencies of both COD and ammonia nitrogen. In order to assess the toxic effects of leachate on different trophic organisms, we need to develop an appropriate matrix of bioassays based on their sensitivity to various toxicants and a multispecies approach using organisms representing different trophic levels. In this regard, a reduction in toxicity of the treated leachate will contribute to assessing the effectiveness of a specific remediation strategy.

Characterization of leachates from waste landfill sites in a religious camp along Lagos-Ibadan expressway, Nigeria and its hepatotoxicity in rats

Landfill sites near human settlements are known to have adverse health effects. Here, we investigated the effect of different concentrations of leachates from the Redemption Camp landfill (RCLL, 10%, 30%, 50%) on the liver of adult female rats after 21 days of exposure in their drinking water. The physicochemical and metal analyses showed that biochemical oxygen and chemical oxygen demand, zinc and magnesium levels were significantly high, whereas copper level was low in RCLL when compared to water samples from residential areas close to the landfill site, and were higher than the acceptable limits (p < 0.05). The predominant bacteria isolates recovered from the leachate and drinking water samples were Escherichia coli, Salmonella spp and Shigella spp. At the end of the 21-day exposure, RCLL increased the weight of the liver. Malondialdehyde concentrations were increased and glutathione levels were decreased significantly in the liver of treated animals at all concentrations of leachates tested. Furthermore, the activities of serum alanine amino transferase, aspartate amino transferase, gamma glutamyl transferase and cholesterol concentrations were increased whereas bilirubin and albumin levels were decreased dose-dependently. Histological examination of the liver was characterized by accumulation of inflammatory cells around hepatocytes, and extended sinusoids. The histo-pathological alterations and oxidative damage observed in the liver of treated rats and occurrence of pathogenic species and metals in the RCLL may suggest possible impaired hepatic health in subjects with occupational or environmental exposure.

Investigating landfill leachate toxicity in vitro: A review of cell models and endpoints

Landfill leachate is a complex mixture characterized by high toxicity and able to contaminate soils and waters surrounding the dumpsite, especially in developing countries where engineered landfills are still rare. Leachate pollution can severely damage natural ecosystems and harm human health. Traditionally, the hazard assessment of leachate is based on physicochemical characterization but the toxicity is not considered. In the last few decades, different bioassays have been used to assess the toxicity of this complex matrix, including human-related in vitro models. This article reviews the cell bioassays successfully used for the risk assessment of leachate and to evaluate the efficiency of toxicity removal of several processes for detoxification of this wastewater. Articles from 2003 to 2018 are covered, focusing mainly on studies that used human cell lines, highlighting the usefulness and adequacy of in vitro models for assessing the hazard involved with exposure to leachate, particularly as an integrative supporting tool for chemical-based risk assessment. Leachate is generally toxic, mutagenic, genotoxic and estrogenic in vitro, and these effects can be measured in the cells exposed to already low concentrations, confirming the serious hazard of this wastewater for human health.

Impairment of Mitochondrial-Nuclear Cross Talk in Lymphocytes Exposed to Landfill Leachate

Landfill leachate, a complex mixture of different solid waste compounds, is widely known to possess toxic properties. However, the fundamental molecular mechanisms engaged with landfill leachate exposure inducing cellular and sub-cellular ramifications are not well explicated. Therefore, we aim to examine the potential of leachate to impair mitochondrial machinery and its associated mechanisms in human peripheral blood lymphocytes. On assessment, the significant increase in the dichlorofluorescein (DCF) fluorescence, accumulation of 8-Oxo-2'-deoxyguanosine (8-oxo-dG), and levels of nuclear factor erythroid 2-related factor 2 (Nrf-2) strongly indicated the ability of the leachate to induce a pro-oxidant state inside the cell. The decrease in the mitochondrial membrane potential and alterations in the mitochondrial genome observed in leachate-exposed cells further suggested the disturbances in mitochondrial machinery. Moreover, these mitochondrial-associated redox imbalances were accompanied by the increased level of NF-κβ, pro-inflammatory cytokines, and DNA damage. In addition, the higher DNA fragmentation, release of nucleosomes, levels of polyadenosine diphosphate ADP-ribose polymerase (PARP), and activity of caspase-3 suggested the involvement of mitochondrial mediated apoptosis in leachate exposed cells. These observations were accompanied by the low proliferative index of the exposed cells. Conclusively, our results clearly indicate the ability of landfill leachate to disturb mitochondrial redox homeostasis, which might be a probable source for the immunotoxic consequences leading to plausible patho-physiological conditions in humans susceptible to such environmental exposures.

Bioassays for toxicological risk assessment of landfill leachate: A review

Landfilling is the most common solid waste management practice. However, there exist a potential environmental risk to the surface and ground waters due to the possible leaching of contaminants from the landfill leachates. Current municipal solid waste landfill regulatory approaches consider physicochemical characterization of the leachate and do not assess their potential toxicity. However, assessment of toxic effects of the leachates using rapid, sensitive and cost-effective biological assays is more useful in assessing the risks as they measure the overall toxicity of the chemicals in the leachate. Nevertheless, more research is needed to develop an appropriate matrix of bioassays based on their sensitivity to various toxicants in order to evaluate leachate toxicity. There is a need for a multispecies approach using organisms representing different trophic levels so as to understand the potential impacts of leachate on different trophic organisms. The article reviews different bioassays available for assessing the hazard posed by landfill leachates. From the review it appears that there is a need for a multispecies approach to evaluate leachate toxicity.

Leachate composition and toxicity assessment: an integrated approach correlating physicochemical parameters and toxicity of leachates from MSW landfill in Delhi

Landfills are considered the most widely practiced method for disposal of municipal solid waste (MSW) and 95% of the total MSW collected worldwide is disposed of in landfills. Leachate produced from MSW landfills may contain a number of pollutants and pose a potential environmental risk for surface as well as ground water. In the present study, chemical analysis and toxicity assessment of landfill leachate have been carried out. Leachate samples were collected from Ghazipur landfill site, New Delhi. Leachates were characterized by measuring the concentration of heavy metals (Pb, Cu, Cr and Ni), 5-day biochemical oxygen demand (BOD₅), chemical oxygen demand (COD), pH, electrical conductivity and SO₄²-. For toxicity testing of leachate, Triticum aestivum (wheat) was selected and testing was done in a time- and dose-dependent manner using the crude leachate. Median lethal concentration after 24 and 48 h of exposure was observed. The main objective of this study was to evaluate toxicity of MSW landfill leachate and establish a possible correlation between the measured physicochemical parameters and resultant toxicity. Statistical analysis showed that toxicity was dependent on the concentration of heavy metals (Pb, Cu), conductivity, and organic matter (COD and BOD5).

Chemical characterization of simulated landfill soil leachates from Nigeria and India and their cytotoxicity and DNA damage inductions on three human cell lines

Landfill soils are sources of emerging carcinogens, teratogens and mutagens in the environment. There is inadequate information on its possible health risk and cytogenotoxicity. This study evaluated chemical characterization of four simulated landfill leachates with their cytotoxicity and DNA damage in human cells. Hepatocarcinoma (HepG2), lymphoma (Jurkat) and osteosarcoma (HOS) cells, incubated with 6.25, 12.5, 25, 50, 75 and 100% of Aba Eku (AEL), Olusosun (OSL), Awotan (AWL) and Nagpur (NPL) simulated leachates for 24 h, were assessed for cell viability using MTT assay and morphological alterations. DNA damage was also assessed after 24 h treatment of cells with sub-lethal concentrations of the leachates using comet assay. Metals and organic compounds in the soil leachates were determined using inductively coupled plasma-mass spectrometry (ICP-MS) and gas chromatography-mass spectroscopy (GC-MS) respectively. The leachates induced significant cytotoxicity in the treated cells with evidence of apoptosis; shrunken morphologies, detachment from the substratum and cytoplasmic vacuolations. Similarly, there was significant DNA damage induced in the treated cells, with increased Olive tail moment, tail length and % tail DNA. Jurkat was the most sensitive (Jurkat > HepG2 > HOS) to the cytotoxic and genotoxic effects of the leachates. All the analyzed metals except Cd, Fe, Zn and Mn were found at levels lower than standard allowable limits. 32, 17, 23 and 23 different PAHs and PCBs were detected in AEL, AWL, OSL and NPL respectively, at varying retention peak times. These toxic constituents induced the observed cytogenotoxicity in the cells and may suggest possible public health risk.

In vivo micronucleus test in the assessment of cytogenotoxicity of landfill leachates in three animal models from various ecological habitats

The in vivo micronucleus (MN) test, a standard test for the genotoxicity screening of xenobiotics, was used to evaluate the cytotoxic and genotoxic activities of landfill leachates in Clarias gariepinus, Coturnix coturnix japonica and Rattus norvegicus. These organisms were exposed to various sub-lethal concentrations (1-50%) of Olusosun and Aba Eku landfill leachates. At post exposure, peripheral erythrocytes from catfish and quail, and bone marrow cells of quail and rat were subjected to MN analysis following standard protocols. The leachates induced significant increase in MN formation and total nuclear abnormalities (NAs) in the peripheral erythrocytes of catfish and quail. NAs occurred in the order; BN > BL > LB > NT in the catfish and BN > BudN > TLN > TN in quail. There was significant increase in MN formation in the bone marrow cells of quail, and micronucleated polychromatic erythrocytes and micronucleated normochromatic erythrocytes formation in the bone marrow of rats. The concentration dependent significant (p < 0.05) decrease in the PCE/NCE ratio in the bone marrow of the leachate treated rats suggest alterations in the bone marrow cell proliferation, leading to the suppression of immature erythrocytes (PCE). MN induction showed positive corrections with leachate concentrations in the test organisms; and it increased with exposure duration in the catfish. Indiscriminate disposal of solid waste generates leachates containing multiple xenobiotics that are capable of increasing genomic instability among vertebrates inhabiting various ecological habitats.

Evaluation of phytotoxicity of municipal landfill leachate before and after biological treatment

In the present study, leachate toxicity of a municipal solid waste landfill located in the Sinos River Valley region (southern Brazil) was evaluated using plant bioassays. Leachate toxicity was assessed by analysis of seed germination and root elongation of lettuce (Lactuca sativa L.) and rocket plant Eruca sativa Mill.) and root elongation of onions Allium cepa L.). Bioassays were performed by exposing the seeds of L. sativa and E. sativa and the roots of A. cepa to raw leachate, treated leachate (biological treatment) and negative control (tap water). The levels of metals detected in both samples of leachate were low, and raw leachate showed high values for ammoniacal nitrogen and total Kjeldahl nitrogen. There is a reduction in the values of several physicochemical parameters, which demonstrates the efficiency of the treatment. Both L. sativa and A. cepa showed a phytotoxic response to landfill leachate, showing reduced root elongation. However, the responses of these two plant species were different. Root elongation was significantly lower in A. cepa exposed to treated leachate, when compared to negative control, but did not show any difference when compared to raw leachate. In L. sativa, seeds exposed to the raw leachate showed significant reduction in root elongation, when compared to treated leachate and negative control. Seed germination showed no difference across the treatments. The results of the study show that plant species respond differently and that municipal solid waste landfill leachate show phytotoxicity, even after biological treatment.

Antioxidant response and histopathological changes in brain tissue of pigeon exposed to avermectin

Avermectins (AVMs) are the active components of some insecticidal and nematicidal products used in agriculture and veterinary medicine for the prevention of parasitic diseases. Residues of AVM drugs or their metabolites in livestock feces have toxic effects on non-target aquatic and terrestrial organisms. In this study, oxidative stress responses and pathological changes on pigeon brain tissues and serum after subchronic exposure to AVM for 30, 60 and 90 days were investigated. The decrease in antioxidant enzyme (superoxide dismutase, SOD and glutathione peroxidase, GSH-Px) activities and increase in methane dicarboxylic aldehyde content in a dose-time-dependent manner in the brain and serum of pigeon were observed. The protein carbonyl content, an indicator of protein oxidation, and DNA-protein crosslink coefficient were significantly augmented with dose-time-dependent properties. The microscopic structures of the cerebrum, cerebellum and optic lobe altered obviously, the severity of which increased with the concentration of AVM and exposure time. The results imply that AVM could induce oxidative damage to the brain tissue and serum of pigeon. The information presented in this study is helpful to understand the mechanism of AVM-induced oxidative stress in birds.

Environmental and human risk assessment of landfill leachate: an integrated approach with the use of cytotoxic and genotoxic stress indices in mussel and human cells

The present study investigates leachate hazardous effects on marine biota and human cells, with the use of a battery of assays, both under in vivo and in vitro conditions. According to the results, mussels exposed for 4 days to 0.01 and 0.1% (v/v) of leachate showed increased levels of DNA damage and micronuclei (MN) frequencies in their hemocytes. Similarly, enhanced levels of DNA damage were also observed in hemocytes treated in vitro with relevant concentrations of leachate, followed by a significant enhancement of both superoxide anions (O₂(-)) and lipid peroxidation products (malondialdehyde/MDA). On the other hand, human lymphocyte cultures treated with such a low concentrations of leachate (0.1, 0.2 and 1%, v/v), showed increased frequencies of MN formation and large MN size ratio, as well as decreased cell proliferation, as indicated by the use of the cytokinesis block micronucleus (CBMN) assay and Cytokinesis Block Proliferation Index (CBPI) respectively. These findings showed the clear-cut genotoxic and cytotoxic effects of leachate on both cellular types, as well as its potential aneugenic activity in human lymphocytes.

Investigation of landfill leachate toxic potency: an integrated approach with the use of stress indices in tissues of mussels

The present study investigates the harmful impacts of landfill leachate release and/or disposal into the marine environment, as well as its ability to induce lethal and pre-pathological alterations in marine organisms, such as the mussel Mytilus galloprovincialis. In specific, mortality test (96 h), performed first in order to estimate leachate lethal endpoints, showed increased levels of mussel mortality after exposure to leachate higher than 0.5%, v/v (96 h LC(50)=0.526%, v/v), while the exposure to 0.01 and 0.1% (v/v) of leachate showed negligible levels of mortality (96 h LC(10)=0.167%, v/v). Furthermore, the estimation of lysosomal membrane integrity in hemocytes of exposed mussels (Neutral Red Retention Time assay) showed increased levels of lysosomal destabilization in cells of mussels exposed to sub-lethal concentrations of leachate (0.01, 0.1 and 0.5%, v/v) for 4 days. In order to exclude parameters, such as mussel mortality and cell death, which could interfere with the obtained results, leachate at final concentrations of 0.01 and 0.1% (v/v) were finally used for the estimation of a battery of stress indices in target tissues of mussels, such as hemolymph, gills and digestive gland. According to the results, leachate-exposed mussels showed a significant inhibition of acetylcholinesterase activity, increased levels of nuclear abnormalities, as well as increased levels of metallothionein, superoxide anion and lipid peroxides (in terms of malondialdehyde equivalents) in each tissue tested. The results of the present study clearly indicate leachate-induced lethal effects as well as the ability of leachate to induce disturbances on different levels of organism function before mortality occurs.

Effect of landfill leachate on oxidative stress of brain structures and liver from rodents: modulation by photoelectrooxidation process

The decomposition of solid waste in landfill is responsible for the formation of leachate, a dark liquid with an unpleasant odor; studies investigating its toxicity on mammals are rare. Oxidative stress has been considered as an important biochemical mechanism of the toxicity of several xenobiotics. The aim of this study was to evaluate the effects of landfill leachate on oxidative parameters in striatum, hippocampus and liver homogenates of mice and rats. In order to propose a clean technology for the treatment of leachate, we also investigated the effects of landfill leachate submitted to photoelectrooxidation process (PEO). The homogenates of cerebral structures and liver of Swiss albino mice and Wistar rats were incubated with different concentrations of non-PEO landfill leachate and PEO-treated landfill leachate. After the incubation, the levels of free radicals, determined by 2',7'-dichlorofluorescein diacetate probe, and the lipoperoxidation, quantified by the thiobarbituric acid reactive substances, were evaluated. There was an increase on the levels of free radicals in striatum of both mice and rats when exposed to non-PEO leachate. Moreover, PEO-treated leachate increased the lipoperoxidation in striatum homogenates from rodents. However, both leachates did not alter any of the parameters evaluated in the hippocampus. In the liver, the incubation with leachates induced an augment on levels of free radicals only in samples of mice. In addition, PEO-treated leachate increased the lipoperoxidation indexes in the liver of mice and rats. These results suggest that the landfill leachate can induce an oxidative stress state in the liver and the striatum of rodents. Additionally, the PEO process was unable to efficiently alter the toxic compounds of landfill leachate.

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.