Study the effect of hexavalent chromium on some biochemical, citotoxicological and histopathological aspects of the Orechromis spp. fish

Determination of chromium species in water using diphenylcarbazide with a sequential spectrophotometric discrete robotic analyser

There is an increasing need for fast and reliable analytical methods for the determination of chemical forms of elements in environmental samples. The interest in chromium is driven by the fact that its toxicity depends on its oxidation state. Although chromium (III) is essential for mammals to maintain their metabolism of proteins, fats, and carbohydrates, chromium (VI) is toxic to humans. For chromium speciation, several costly analytical methods coupling separation methods with atomic absorption and emission spectroscopy have been developed. This article presents the online robotic discrete analyser procedure with the 1,5 diphenylcarbazide (DPC) method for the speciation of Cr (III) and Cr (VI). Cr (III) was determined by difference since it does not interfere with the reaction of Cr (VI)-DPC. Chromium (VI) and total chromium were characterised sequentially (after online oxidation of Cr (III) by Cerium (Ce (IV)). The calibration graphs were linear under experimental conditions up to 1 mg/L Cr (VI) and 2 mg/L total Cr with correlation coefficient R2, 0.9997 and 0.9999 respectively. At a signal-to-noise ratio of three, the detection limits were 0.004 mg/L Cr (VI) and 0.015 mg/L total Cr. Good agreement between the real values of certified reference materials and the chromium species content was obtained in this study. The method was precise with a percentage relative standard deviation of less than 2 for hexavalent chromium and total chromium. The t-stat demonstrates that there was no significant difference between the developed robotic discrete analyser method and the ICP-MS method. Except for effluent water, which had recoveries between 65 and 75 % in the assessment of the devised method's selectivity, the overall percentage of recoveries fell between 90 and 110 %, which was generally satisfactory. This method proved to be appropriate for its intended use.

Pollution and risk assessment of heavy metals in water, sediment and fish (Clarias gariepinus) in a fish farm cluster in Niger Delta region, Nigeria

The study determined the following heavy metals: cadmium (Cd), chromium (Cr), copper (Cu), manganese (Mn), lead (Pb) and zinc (Zn) concentrations in surface water and in fish pond (water, sediments and farmed fish (Clarias gariepinus)) from a fish farm cluster with the view of assessing its pollution level and associated human health exposure risk to these heavy metals through fish consumption. Samples were digested with aqua regia and metal concentrations were determined with an atomic absorption spectrophotometer equipped with an air acetylene flame. Mean concentrations of the heavy metals (ppm) in surface and pond water ranged as follows: cadmium (below detection limit (bdl): 0.298); chromium (bdl: 0.257); copper (bdl: 0.067); manganese (bdl: 0.163); lead (bdl: 0.736) and zinc (bdl: 0.078) while in sediment, the ranges (mg/kg dry weight) were as follows: cadmium (1.156-3.329); chromium (9.439-14.373); copper (26.710-121.819); manganese (3.143-37.202); lead (0.340-1.537) and zinc (87.681-371.060). The mean concentrations of the metals in surface water were significantly different (p < 0.05) from those in sediment in all the sampling sites. The mean metal concentrations (mg/kg dry weight) in C. gariepnus were in the following ranges: cadmium (0.733-1.405); chromium (0.593-1.692); copper (175.882-245.321); manganese (bdl: 3.326); lead (0.221-0.263) and zinc (248.191-292.333). Some of the heavy metal concentrations obtained in water, sediment and catfish analyzed were above the permissible limit set by some National (DPR) and International organisations (WHO, FEPA and FAO). The pollution studies showed that lead, cadmium and chromium contaminated the surface water samples. Sediment from all sites showed low to considerable contamination by the heavy metals. The human exposure risk assessment of the metals showed that the total hazard index was less than one which indicates no probable adverse health effect from the consumption of fish from the ponds, although this case is different for Pb since there is no estimation of oral reference dose (RfDo) for lead according to EPA.

Toxic effects of chlorpyrifos on the growth, hematology, and different organs histopathology of Nile tilapia, Oreochromis niloticus

Chlorpyrifos is a widely applied insecticide that permeates on most waterways and affects aquatic organisms. The growth performances, hematological and histological impacts on Nile tilapia, Oreochromis niloticus following a 60 day of exposure to varying concentrations of chlorpyrifos 20 EC (T₁ 08 µgL⁻¹, T₂ 16 µgL⁻¹, and T₃ 32 µgL⁻¹) were compared to a control T_c 0 µgL⁻¹. The 96-hour LC50 of chlorpyrifos 20 EC was calculated as 46.80 μgL⁻¹. The water quality parameters were recorded regularly. The value of dissolved O₂ and NH₃ stayed rather steady, although temperature varied considerably. It was revealed that as chlorpyrifos levels go up, the percentage of weight gain (WG %), specific growth rates (SGR), and survival rate decreases. The control group T_c had the highest percentages of SGR weight (1.16 ± 0.58) and the T₃ group had the lowest percentages of SGR weight (0.25 ± 0.77). The hematological assessment showed significant differences of hemoglobin concentration, white blood cell counts and red blood cell numbers between chlorpyrifos treatment and control group (P < 0.05). Histological alterations in the liver, gills, and muscle tissues reported to be worse for T₃ as compared to others. There were no statistical differences in GSI, HSI values between control and treatment groups. The chlorpyrifos 20 EC was shown to be highly toxic to O. niloticus at sub-lethal dosages.

Effect of triclosan (TCS) on the protein content and associated histological changes on tilapia, Oreochromis mossambicus (Peters, 1852)

Triclosan is a chlorinated phenolic antimicrobial agent having a wide application in commercial and healthcare products. The toxic effects of the emerging pollutant, triclosan (TCS), on behavior, protein content, and associated histological alterations in the muscle tissue of the freshwater fish Oreochromis mossambicus were studied. Healthy fishes were exposed to five different acute concentrations of TCS, viz., 0.131, 0.262, 0.523, 1.046, and 2.092 ppm for a period of 96 h. The 96-h LC₅₀ of TCS for O. mossambicus was determined as 0.715 ppm using probit analysis. The fishes were also chronically exposed to the five different concentrations of TCS based on LC₅₀ to study the toxic effects of long-term exposure. The protein content of the fish muscle gradually decreased with an increase in the concentration of TCS. Further, the histological alterations such as splitting of myotomes, vacuolar degeneration, degenerated myotomes, multifocal degeneration of myocytes, degeneration of myoepithelium, myolysis, melanomacrophage in the dermis, vacuolation in the epidermis, atrophy of myotomes, and necrosis were observed during the acute and chronic exposure of fishes to TCS. The study revealed that TCS can affect the aquatic organisms even at a minimum concentration of 0.715 ppm causing changes in the behavior and biochemical constituents of tilapia.

Molecular mechanism of heavy metals (Lead, Chromium, Arsenic, Mercury, Nickel and Cadmium) - induced hepatotoxicity - A review

Heavy metals pose a serious threat if they go beyond permissible limits in our bodies. Much heavy metal's viz. Lead, Chromium, Arsenic, Mercury, Nickel, and Cadmium pose a serious threat when they go beyond permissible limits and cause hepatotoxicity. They cause the generation of ROS which in turn causes numerous injuries and undesirable changes in the liver. Epidemiological studies have shown an increase in the levels of such heavy metals in the environment posing a serious threat to human health. Epigenetic alterations have been seen in the event of exposure to such heavy metals. Apoptosis, caspase activation as well as ultrastructural changes in the hepatocytes have also been seen due to heavy metals. Inflammation involving TNF-alpha, pro-inflammatory cytokines, MAPK, ERK pathways have been seen in the event of heavy metal hepatotoxicity. All these have shown that these heavy metals pose a serious threat to human health in particular and the environment as a whole.

Multiorgan histopathological changes in the juvenile seabream Sparus aurata as a biomarker for zinc oxide particles toxicity

Zinc oxide nanoparticles are widely used in some domains (cosmetics, pharmaceuticals optical devices, and agricultural field) due to their physical, optical, and antimicrobial properties. However, the release of ZnO-NPs into the environment may affect organisms like fish with potential consequences for human health. Histological approaches of the acute effects of these materials on fish are scarce; thus, the present study aimed to investigate the potential toxic effects of acute exposure to ZnO particles in marine environments, by assessing histological changes in the gills, liver, spleen, and muscle of gilthead seabream (Sparus aurata) juveniles. Thus, fish were exposed for 96 h, via water, to 1 mg L-1 of ionic zinc and zinc oxide particles (1.1, 1.2, and 1.4 μm of size). Histological examination revealed gills as the most affected organ, followed by liver, muscle, and spleen. In the gills, histopathological changes included hyperplasia of epithelial cells, fusion of the secondary lamellae, and lifting of the lamellar epithelium with edema. In the liver, lipid vacuolation of several degrees, necrosis of hepatic and pancreatic tissues, blood congestion in sinusoids and hepatoportal vessels, presence of cellular infiltrate, and melano-macrophages diffusion was found. Muscle showed degeneration, atrophy, thickening and necrosis of muscle fibers with edema between them, and presence of melano-macrophages in the muscle layer. Spleen was the less damaged organ, displaying congested blood, white pulp increase/rupture, and bigger and darker melano-macrophage aggregates in the splenic stroma. These results underline that the size of particles plays a determinant role in their potential pernicious effects. A short-term exposure caused major histopathological changes in relevant organs of S. aurata juveniles, possibly affecting their function.

Genotoxicity induced by hexavalent chromium leading to eryptosis in Ctenopharyngodon idellus

The initiation of eryptosis as a result of genotoxic action of Cr(VI), seen through micronucleus and comet assay in the peripheral erythrocytes of Ctenopharyngodon idellus was evaluated through RT-qPCR. For this, fish was exposed to sublethal concentration of hexavalent chromium (5.30 and 10.63 mg/L), and the blood was sampled on different endpoints (15, 30 and 45 days). Accumulation of chromium in the erythrocytes was also studied, which depicted a significant increase in toxicant concentration and time dependent manner. Both concentrations of hexavalent chromium induced DNA damage, visible in the form of comet tails. The presence of micronuclei in the erythrocytes was accompanied with occurrence of nuclear bud (NBu), lobed nucleus (Lb), notched nucleus (Nt), vacuolated nucleus (Vn), binucleated cell (Bn) as nuclear abnormalities; and acanthocytes (Ac), echinocytes (Ec), notched cells (Nc), microcytes (Mc) and vacuolated cytoplasm (Vc) as cytoplasmic abnormalities. The expression of genes related to intrinsic apoptotic pathway induced by Cr(VI) presented significant (p < 0.05) upregulation in the expression of p53, Bax, Apaf-1, caspase9 and caspase3, and downregulation of Bcl2; inferring the initiation of apoptotic pathway. The ration of Bax and Bcl2 also appended the apoptotic state of the erythrocytes. From the present investigation, it can be concluded that genotoxicity induced by hexavalent chromium lead to eryptosis in C. idellus.

Assessment of DNA integrity through MN bioassay of erythrocytes and histopathological changes in Wallago attu and Cirrhinus mirigala in response to freshwater pollution

The aim of this study was to determine the level of contamination and genotoxic impact through micronucleus assay and histopathology in Wallago attu and Cirrhinus mrigala procured from the polluted site of the River Chenab at industrial and sewage waste disposal. The water sample was found viciously contaminated with heavy metals i.e. Ni, Cr, Mn, Co, Pb, Hg, Zn, Sn, Cu while all other physio-chemical variables crossed the suggested limits of WHO. The heavy metals load induced histopathological alterations were correlated to environmental degradation and the productivity of this biological system. W. attu and C. mrigala harvested from contaminated sites of the river indicated higher intensity of DNA damage through micronucleus induction and nuclear abnormalities with 5.46 ± 0.17, 1.23 ± 0.08 and 4.2 ± 0.11, 0.4 ± 0.04‰ respectively. Muscle sections of W. attu and C. mrigala harvested from the polluted section of river demonstrated the necrosis, degeneration of muscle fibers, intra-fibular edema and release of the blood into the tissues due to the bursting of blocked of the blood vessels. Dermal layers showed degeneration of the collagen bundles those were found loose or collapsed in some regions. Photomicrography also revealed vacuolar degeneration in muscle tissues and atrophy of muscle bundles. Intra fibular edema and splitting of muscle fibers were also seen along with bioaccumulation of toxicants. W. attu showed maximum incidence of alterations with highest histopathological alteration index related to environmental degradation. Control fish samples showed normal muscle tissues with normal equally spaced muscle bundles and myotomes.

Oxidative Effects of Potassium Dichromate on Biochemical, Hematological Characteristics, and Hormonal Levels in Rabbit Doe (Oryctolagus cuniculus)

The present study was conducted to evaluate the toxicity induced by the increasing doses of potassium dichromate in rabbit doe. Twenty-eight adult does of 6 months of age were divided into four groups (A, B, C, and D; n = 7), with comparable average body weight (bw). Group A rabbits received only distilled water daily and served as a control, while groups B, C, and D received, respectively, 10 mg/kg bw, 20 mg/ kg bw, and 40 mg/kg bw of potassium dichromate via gavage for 28 days, after which animals were anesthetized with ether vapor and sacrificed. Blood samples were obtained via cardiac puncture and collected without anticoagulant for biochemical dosages and with anticoagulant (EDTA) for complete blood count. Follicle stimulating hormone (FSH), luteinizing hormone (LH), and estradiol (E2) were dosed in serum and in homogenates of ovary with the help of AccuDiagTM ELISA kits from OMEGA DIAGNOSTICS LTD (Scotland, England) while respecting the immuno-enzymatic method. Activities of superoxide dismutase (SOD), glutathione (GSH), catalase (CAT), and concentration of malondialdehyde (MDA) in liver, kidney, ovary and uterus were measured. Hematology revealed a significant (p < 0.05) decrease in mean values of hemoglobin and platelets while white blood cells and lymphocytes showed a significant (p < 0.05) increase in exposed groups. No significant (p > 0.05) difference was registered in monocytes, red blood cells, hematocrits, and plaquetocrits values with respect to the control. No matter the organ considered, no significant (p > 0.05) change was recorded in weight and volume. Nephrotoxicity analysis registered a significant (p < 0.05) increase in urea and creatinine, unlike renal tissue protein, which decreased significantly (p < 0.05). However, hepatotoxicity registered no significant (p > 0.05) variation in aspartate aminotransferase but total protein, alanine aminotransferase, and total cholesterol increased significantly (p < 0.05), while hepatic tissue protein revealed a significant (p < 0.05) decrease. Analysis on reproductive parameters showed a significant (p < 0.05) decrease in ovarian and uterine tissue proteins, as well as in follicle stimulating hormone, luteinizing hormone, and estradiol. Oxidative stress markers recorded no significant (p > 0.05) difference in glutathione reductase except in ovary where a significant (p < 0.05) decrease was seen when compared with the control, while catalase revealed a significant (p < 0.05) decrease, except in liver where there was no significant (p > 0.05) change. Superoxide dismutase and malondialdehyde recorded a significant (p < 0.05) decrease and increase respectively, with respect to the control. Results obtained from this study showed that the reduction process of chromium in tissues may cause the generation of reactive oxygen species, which are involved in hematoxic, nephrotoxic, hepatotoxic, and reproductive toxicity effects.

Genotoxicity assessment of pesticide profenofos in freshwater fish Channa punctatus (Bloch) using comet assay and random amplified polymorphic DNA (RAPD)

The present study explored the induced genotoxicity (DNA damage) due to organophosphate pesticide profenofos (PFF) after in vivo exposure in freshwater fish Channa punctatus by the use of Comet assay and Random amplified polymorphic DNA (RAPD). The fish specimens were exposed to sub-lethal concentration of 1.16 ppb (50% of LC₅₀) in a semi-static system and the DNA damage was assessed in exposed and control fish. The DNA damage was measured in erythrocytes as the percentage of DNA damage in Comet tails and RAPD technique using oligonucleotide primers of fish specimens exposed to the sublethal concentrations of PFF. The most informative primers in terms of variation in RAPD profile were found to be OPA-01, OPA-03, OPB-02, OPB-01 and OPA-13. Appearance/disappearance of bands and increase/decrease in the band intensity were evident in the RAPD profile of fish specimens exposed to PFF as compared to the control. Findings from the present study suggest that the potential impacts of assessment of the genotoxic impact of pesticide on fish.

Bioaccumulation factors and multivariate analysis of heavy metals of three edible fish species from the Barekese reservoir in Kumasi, Ghana

The Barekese reservoir has seen persistent degradation for decades through anthropogenic activities within its catchment. In spite of this, heavy metal pollution profile of fish species of the reservoir is not well studied. Total concentrations of Hg, Cd, Ni, and Cr were analyzed in muscle tissues of 45 edible fish species comprising (Tilapia zilli, Oreochromis niloticus, and Heterotis niloticus) from the reservoir. The examined fish species showed varying bioaccumulative factors for detected metals. A PCA biplot revealed that Cd showed association with all examined fish species used in the study indicating that Cd in the reservoir is biologically available for uptake by all examined fish species. A dendrogram of cluster analysis also revealed that Cd and Cr are in one cluster indicating their associations and similarities to a common anthropogenic source. The study suggests that anthropogenic activities are possible sources of heavy metal pollution in the Barekese reservoir and, hence, the examined fish species could be used to monitor the levels of Ni, Cr, Hg, and Cd in the reservoir.

Transcriptome analysis reveals the molecular mechanism of hepatic metabolism disorder caused by chromium poisoning in chickens

Chromium (Cr) is one of the most important environmental pollutants which are released into the environment due to their wide usage in numerous industries. The excess of Cr (VI) can induce hepatotoxicity, while the molecular mechanism that is involved in Cr (VI)-induced hepatotoxicity is unclear. We demonstrated the induction of chromium poisoning model in chickens to identify the differentially expressed genes (DEGs), and their functions were analyzed under different physiological and pathological conditions. Histopathological examination and transcriptome data for chromium-poisoned livers and control livers were annotated with Illumina® HiSeq 2000. The histopathological examination in chromium poisoning groups showed diapedesis, hemolysis, degeneration, nucleus pycnosis, and central phlebectasia in the liver. A total of 334 genes were upregulated and 509 genes were downregulated. The most strongly upregulated genes were HKDC1, DDX4, ACACA, FDFT1, CYYR1, PPP1R3C, and SLC16A14, while the most downregulated genes were MYBPC3, CCKAR, PCK1, and CPT1A. A Gene Ontology (GO) term with the highest enrichment of DEGs is small molecule metabolic process. In cell component domain, the term with the highest enrichment is extracellular matrix. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways showed that glucose metabolism, lipid metabolism, and protein metabolism were the most important metabolic pathways in the liver. The current study first time provides important clues and evidence for identifying the differentially expressed genes in livers due to Cr (VI)-induced liver injury in chickens.

Application of fish cell lines for evaluating the chromium induced cytotoxicity, genotoxicity and oxidative stress

In the present study, we hypothesize that cytotoxicity, genotoxicity and oxidative stress play a key role in chromium induced toxicity in SISS, SISK, IEE, IEK, IEG, SICH and ICG cell lines after 24 h exposure. Three fish species namely Lates calcarifer, Etroplus suratensis and Catla catla were exposed to the concentrations of 0, 10, 20, 30, 40 and 50 mg/L of chromium for 96 h under static conditions for conducting acute toxicity tests. LC₅₀ was then calculated. The percentage cell survival was assessed by multiple endpoints such as MTT, NR, AB and CB assays in the seven fish cell lines exposed to different concentrations of chromium and EC₅₀ values of all the four endpoints were calculated. High significances were noted in the correlations between each in vitro cytotoxicity assays and in vivo mortality data. Cell shrinkage, cell detachment, vacuolations and cell swelling at the highest concentration of chromium (50 mg/L) were seen on microscopic examination of cell morphology. Comet assay and Hoechst staining were carried out to assess DNA damage and nuclear fragmentation in the seven fish lines exposed to chromium. The results of antioxidant parameters obtained indicate a significant reduction in the level of catalase, superoxide dismutase, glutathione S-transferase and Glutathione peroxidase, and increased level of lipid peroxidation in all the cell lines exposed to chromium. These results confirm that fish cell lines could be used as an alternative to whole fish for cytotoxicity, genotoxicity and oxidative stress assessment in chromium toxicity studies.

Assessment of genotoxic and mutagenic potential of hexavalent chromium in the freshwater fish Labeo rohita (Hamilton, 1822)

The present study was undertaken to investigate the genotoxicity and mutagenicity of sublethal concentrations of hexavalent chromium (potassium dichromate) in the Indian major carp, Labeo rohita. The 96 h LC50 value of potassium dichromate estimated was 118 mg L(-1) by probit analysis using SPSS (version 16.0) software. Based on 96 h LC50 value, three sublethal test concentrations of potassium dichromate (29.5, 59.0 and 88.5 mg L(-)(1)) were selected and specimens were exposed in vivo to these test concentrations for 96 h. The mutagenic and genotoxic effects of potassium dichromate were evaluated in gill and blood cells using micronucleus (MN) test and comet assay. In general, significant (p < 0.05) effects due to the concentrations and the exposure durations were observed in exposed specimens. The MN induction was highest at 96 h at all the test concentrations in the peripheral blood. A similar trend was observed for the DNA damage, measured in terms of percentage of tail DNA, in erythrocyte and gill cells. The study indicated hazardous effect of the hexavalent chromium to fish and other aquatic organisms and indirectly to human beings.

Effects of heavy metals on antioxidants and expression of HSP70 in different tissues of Milk fish (Chanos chanos) of Kaattuppalli Island, Chennai, India

Distribution of heavy metals and its associated oxidative stress, ultrastructure and expression of HSP 70 were studied in varies tissues of Chanos chanos collected from polluted sites compared with the fish collected from less polluted sites of Kaattuppalli Island. The concentrations of copper, lead, zinc, cadmium, manganese and iron were quantified in gills and liver. The results showed marked differences between the two sites as well as significant variations within the tissues. The decreasing trend of metals in the tissues of fish sampled from both polluted and less polluted sites was in the order of Fe>Mn>Zn>Cu>Pb>Cd. Overall, the highest metal concentrations were found in the fish collected from polluted sites. Similarly increase of antioxidant enzymes biomarkers due to heavy metals was also evident in gills and liver of the fish collected from polluted sites. These tissues were further investigated by scanning and electron microscopy and the results were compared with the reference less polluted sites. The presence of large lipid droplets in liver and increase of mucous cells in gills were some of the most noticeable alterations observed and were related to heavy metal contaminants. It is concluded that scanning, ultrastructural and useful of HSP70 biomarkers for heavy metal induced oxidative stress, and demonstrate that precautions need to be taken in polluted sites of Kaattuppalli Island in order to prevent heavy metal pollution that can occur in the future.

Integrated use of histological and ultrastructural biomarkers in Mugil cephalus for assessing heavy metal pollution in Ennore estuary, Chennai

Bioaccumulation of heavy metals and its associated histological perturbations were studied in various tissues of Mugil cephalus collected from Ennore estuary and compared with the fish collected from off-shore region. The concentration of copper, lead, zinc, cadmium, manganese and iron were quantified in gills, liver and muscle. The results showed marked differences between the two sites as well as significant variations within the tissues. The decreasing trend of metals in the tissues of fish sampled from both Ennore estuary and off-shore was in the order of Fe>Mn>Zn>Cu>Pb>Cd. Overall, the highest metal concentrations were found in the fish collected from Ennore estuary. The accumulation in the gills and liver of M. cephalus was found to be quite high in comparison with the muscle. These tissues were further investigated by light and electron microscopy and the results were compared with the reference site (off-shore region). The presence of large lipid droplets in liver and increase of mucous cells in gills were some of the most noticeable alterations observed and were related to heavy metal contaminants. It is concluded that histopathological and ultrastructural biomarkers provide reliable and discriminatory data to augment heavy metal pollution in Ennore estuary. Therefore, long-term monitoring is necessary to assess the eco-health of the Ennore estuarine environment by choosing bio-indicator species like M. cephalus, which provide accurate, reliable measurements of environmental quality.

Chromium-induced biochemical, genotoxic and histopathologic effects in liver and kidney of goldfish, carassius auratus

Fish constitute an excellent model to understand the mechanistic aspects of metal toxicity vis-à-vis oxidative stress in aquatic ecosystems. Hexavalent chromium (Cr (VI)), due to its redox potential can induce oxidative stress (OS) in fish and impair their health. In the present investigation, we hypothesize that OS plays a key role in chromium induced toxicity in goldfish; leading to the production of reactive oxygen species (ROS) such as O(.)(2), H(2)O(2), OH(.), and subsequent modulation of the activities of antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD), metallothioneins (MT), glutathione proxidase (GPx), genotoxicity and histopathology. To test this hypothesis, antioxidant enzymes, DNA damage and histopathology assays were performed in liver and kidney tissues of goldfish exposed to different concentrations of Cr (VI) (LC(12.5), LC(25) and LC(50)) following 96h static renewal bioassay. The results of this study clearly show that the fish experienced OS as characterized by significant modulation of enzyme activities, induction of DNA damage and microscopic morphological changes in the liver and kidney. In both tissues, CAT activity was decreased whereas SOD activity and hydroperoxide levels were increased. In addition, GPx activity also increased significantly in higher test concentrations, especially in the kidney. MT induction and DNA damage were observed in both tissues in a concentration dependent manner. Microscopic examination of organ morphology indicated degeneration of liver tissue and necrosis of central vein. Necrosis of kidney tubular epithelial cells and tubules was observed at higher Cr (VI) concentrations. Taking together the findings of this study are helpful in organ-specific risk assessment of Cr (VI)-induced oxidative stress, genotoxicity and histopathology in fish.