Analysis of heavy metals from water, sediment, and tissues of Labeo angra (Hamilton, 1822), from an Ox-box lake- an wetland site from Assam, India

Transfer of chromium from environment to fish in East Kolkata wetlands - evaluation by structural equation modeling

Chromium (Cr) is a significant pollutant in the effluents from leather industries and domestic city sewage. Cr was determined in water, sediment, and different tissues (gill, muscle, intestine, liver, and kidney) of Nile tilapia, Oreochromis niloticus harvested from wastewater-fed aquaculture (WFA) situated at Bamonghata, Bantala, Chowbaga and Chingrighata of East Kolkata Wetlands (EKW), a Ramsar site in West Bengal, India. The results showed that Cr concentration in surface water ranged between 0.05 to 0.15 mg/L, while Cr was detected at high concentration (100-300 mg/kg) in the sediment soil of the first three WFAs and in moderate concentration (50-110 mg/kg) in Chingrighata WFA. Average Cr concentrations in the tissues were ranked in the following sequence: kidney>liver>intestine>gill>muscle. However, the extent of accumulation of Cr in different tissues varied between the WFAs. We used Structural Equation Modeling (SEM) to determine the route of Cr transfer. The fitness of the model was evaluated by the performance measures. Cr accumulation pathways varied between the sites depending upon the level of Cr in water or sediment. Except for Bamonghata WFA, sediment was found as the principal source of accumulation of Cr in different tissues of O. niloticus. Cr refluxed from sediment into overlying water and accumulated in fish either through the food chain or through direct accumulation from water. In Bamonghata WFA, the role of sediment in the transfer of Cr could not be established due to the high water depth or biological non-availability of Cr in the sediment. It is concluded from this study that fish reared in the WFAs of EKW are still not hazardous in respect to Cr but require proper management to avoid the influx of Cr-containing effluents into the WFAs.

Heavy metal bioaccumulation triggers oxystress, genotoxicity and immunomodulation in head kidney macrophages of Channa punctatus Bloch

Studies on heavy metal induced toxicity have been conducted in many water bodies across the globe and such effects have been evaluated in various fish species. The present study was designed to determine the load of some heavy metals in select sites in Southern Assam, India, along with estimating their concentration in tissues of Channa punctatus Bloch. inhabiting those niches. The effect of heavy metals in oxystress generation, genotoxicity and subsequent immune response in fish was also evaluated. In all of these sites, the concentration of Hg, Cd, Pb and Cr were above the permissible ranges while their concentrations were several folds higher in the piscine tissues due to bioaccumulation and possible biomagnification. Kidney showed the highest metal pollution index followed by liver and gills. Generation of ROS was significantly elevated and that in turn triggered oxystress, as is evident from enhanced lipid peroxidation, protein carbonylation and respiratory burst activity. These were in association with the compromised antioxidant enzyme levels with concomitant damage to DNA as evident from Comet parameters. The innate immune potential was significantly impaired as evident from the compromised cell adhesion, phagocytosis, intracellular killing activity in head kidney macrophages (HKM) along with decreased release of nitric oxide (NO) and myeloperoxidase (MPO). Immunosuppression was further validated at protein levels where compromised release of cytokines viz. TNF-α, IL-1β, IL-6, IL-10 and IL-12 and cell signaling molecules iNOS and NF-κβ were noted. Thus the present study indicates genotoxicity along with a compromise in immune status of Channa punctatus Bloch. living in a habitat laden with heavy metals.

Metal pollution in freshwater fish: A key indicator of contamination and carcinogenic risk to public health

Metals are micropollutants that cannot be degraded by microorganisms and are infiltrated into various environmental media, including both freshwater and marine water. Metals from polluted water are absorbed by many aquatic species, especially fish. Fish is a staple food in the diets of many regions in the world; hence, both the type and concentration of metals accumulated and transferred from contaminated water sources to fish must be determined and assessed. In this study, the heavy metal concentration was determined and assessed in fish collected from freshwater sources via published literature and Estimated of Daily Intake (EDI), Target hazard quotient (THQ), and Carcinogenic Risk (CR) analyses, aiming to examine the metal pollution in freshwater fish. The fish was used as a bioindicator, and Geographic information system (GIS)was sued to map the polluted regions. The results confirmed that Pb was detected in fish sampled at 28 locations, Cr at 24 locations, Cu and Zn at 30 locations, with values Pb detected ranging from 0.0016 mg kg^-1 to 44.3 mg kg^-1, Cr detected ranging from 0.07 mg kg^-1 to 27 mg kg^-1, Cu detected ranging from 0.031 mg kg^-1 to 35.54 mg kg-¹, and Zn detected ranging from 0.242 mg kg^-1 to 103.2 mg kg^-1. The strongest positive associations were discovered between Cu-Zn (r = 0.74, p < 0.05) and Cr-Zn (r = 0.57, p < 0.05). Spatial distribution maps depicting the consumption of fish as food and its corresponding Pb and Cr intake revealed a higher incidence of both carcinogenic and non-carcinogenic health concerns attributed to Pb and Cr in the region with populations consuming the fish.

Lead and cadmium exposure network in children in a periurban area in India: susceptibility and health risk

To investigate the complex Pb-Cd exposure network in school-going children, a thorough investigation of the probable exposure means (diet, water, and school micro-environments such as paint dust and school courtyard soil) and exposure route (ingestion, inhalation and dermal) was carried out in a periurban area spanning three districts in southern Assam, India. Multivariate statistical analysis was carried out to understand the complex data matrices, and the health risk assessments (carcinogenic and non-carcinogenic) based on US EPA Risk Assessment models were also made. We found the median values to be 0.9-4.0 mg Pb/kg and 0.21-6.2 mg Cd/kg in various food items. Groundwater also had Pb (0.13-0.48 mg/L) and Cd (0.11-0.29 mg/L). Pb levels in paint dust were within the permissible limits, but 50% of the samples had higher than permissible levels of Cd. Approximately 23% of the school courtyard soil had Pb above the global background levels, but all the samples had 4-27 times elevated levels of Cd in them. School micro-environment contributed significantly to the metal load in children due to their typical hand-to-mouth behavior and dietary intake (food and water) via ingestion was the most prominent route of exposure in children. The evaluation of the estimated chronic daily intake and the hazard quotient indicated hazardous exposure over a lifetime to both Pb and Cd, but only Cd posed a prominent cancer risk. It could be concluded that chronic insidious effects of metals would be a noteworthy toxicological threat to children when exposed early on.

Eichhornia crassipes mediated copper phytoremediation and its success using catfish bioassay

Copper (Cu) pollution in aquaculture ponds poses substantial ecological threats. Most phytoremediation studies deal with the efforts of removing Cu from water, but seldom, such endeavors are validated by suitable bioassays. The present study undertook a two-pronged effort to remediate Cu by phytoextraction with an aquatic macrophyte, Eichhornia crassipes, and establish the efficacy of such endeavors by Clarias batrachus bioassay. For phytoextraction trials, E. crassipes was exposed to Cu concentration 0, 5, 10, 15 and 20 mg L^-1 in Hoagland solution for 21 days. The highest uptake of 2168 μg g^-1 dw was at 10 mg L^-1 Cu exposure, and efficient root to leaf translocation was seen for 5-10 mg Cu L^-1. For these doses, there was 55-57% decline in Cu from test waters. We evaluated morphological, physiological and biochemical response of plants towards Cu stress to gauge its phytomediation capacity. For bioassays, fish were reared for 7 days in phytoremediated Cu doses of 5 and 10 mg L^-1. The accumulation of Cu followed the pattern: kidney > liver > gill > muscle. Fish muscle accumulated 21.8-27.0 μg Cu g^-1 dw after 7 d, however, for E. crassipes remediated doses, muscle accumulated 8.2-10.9 μg Cu g^-1 dw, which was within the safe levels of Cu in edible tissues. Metal doses declined protein contents and augmented malondialdehyde, superoxide dismutase, catalase and peroxidase concentrations in tissues. Although their concentrations in remediated groups failed to reach the levels of control fish, significant recovery in these parameters were observed. The results pointed towards the efficacy of Cu phytoextration by E. crassipes.