Heavy Metals Accumulation in Tissues of Wild and Farmed Barramundi from the Northern Bay of Bengal Coast, and Its Estimated Human Health Risks.

Globally, both natural water bodies and aquaculture systems are being severely contaminated by heavy metals due to rising anthropogenic activities. Fish living in aquatic environments can easily accumulate metals in their bodies, which can then be transferred to consumers and put them at risk. In this study, metal concentrations (Pb, Cd, Cr, As, Mn, Cu, Zn) in different organs (gill, liver, and muscle) of farmed and wild Barramundi (Lates calcarifer) fish from the northern Bay of Bengal were evaluated to quantify and compare contamination levels and related human health risk. Heavy metal concentrations were higher in liver tissues of farmed Barramundi than in wild Barramundi, with the following relative mean values in the liver, gills, and muscle: Zn > Cu > Pb > Mn > Cd > Cr > As; Zn > Cr > Cu > Pb > Mn > Cd > As; Zn > Pb > Cu > Cr > Mn > Cd > As; Zn > Pb > Cu > Cr > Mn > Cd > As; and Zn > Pb > Cu > Cr > Mn > Cd > As, respectively. The differences in heavy metal accumulation observed between farmed and wild fish were probably related to the differences in their environmental conditions and dietary element concentrations. However, ANOVA indicated that the variation of metals in wild and Barramundi was not statically significant. Pb concentrations in the liver tissue of farmed Barramundi exceeded the national and international threshold limits, whereas concentrations of other metals were within the limit. Among the examined organs in both fish species (wild and farmed), muscle had the lowest concentration compared to others, and liver was the target organ for Pb, Cu, and Cd accumulations. Metals such as Zn and Mn exhibited higher concentration in the gills. However, all the studied heavy metals were below the maximum permissible limits of national and international standards, but the mean concentrations of Pb and Cd values in the liver of farmed Barramundi exceeded all international and national guidelines. Based on the contamination factors (CF) and pollution indices (PLI and MPI), the degree of contamination in the fish organs was as follows: gills > liver > muscle. The major accumulation tissues for both farmed and wild fish were found to be the gills (MPI = 0.970) and the liver (MPI = 0.692). Based on the estimated daily intake (EDI), the fish samples examined in this study are safe for human consumption as within the recommended daily allowance (RDA) range established by various authorities. According to the Target Hazard Quotient (THQ) and Carcinogenic Risk (CR) calculations, though the Barramundi fishes depicted no potential hazard to humans, farmed fish posed a higher health risk than wild fish.

Concentration, source identification, and potential human health risk assessment of heavy metals in chicken meat and egg in Bangladesh.

Chicken meat and hen egg are very popular foodstuffs around the world and highly consumed as curry, fast food, processed food, etc. assuming a promising source of protein. In the present study, the concentrations of Pb, Cd, Cr, As, Hg, Mn, Fe, and Zn in nationally representative samples of chicken meat and hen egg were determined and found in the range of 0.03-2.73, 0.01-0.015, 0.025-0.67, 0.04-0.06, 0.01-0.015, 0.15-0.63, 2.50-38.6, and 1.02-19.4 mg/kg-fw, respectively. The results demonstrated that only Pb exceeded the maximum allowable concentration (MAC) for dietary food. Multivariate statistical analyses depicted that anthropogenic activities were the major source of heavy metals in the investigated foodstuffs. Human health risks associated with the dietary intake of these metals through the consumption of chicken meat and hen egg were evaluated in terms of estimated daily intake (EDI), non-carcinogenic risk of individual heavy metal by target hazard quotient (THQ), total target hazard quotient (TTHQ) for combined metals, and carcinogenic risk (CR) for lifetime exposure. The calculated values of EDI, THQ, TTHQ, and CR were below their respective permissible benchmarks indicating the safe consumption of the investigated foodstuffs with respect to heavy metal contamination.

Accumulation of Trace Metals in Indigenous Fish Species from the Old Brahmaputra River in Bangladesh and Human Health Risk Implications.

In this study, accumulation of the top six most toxic trace metals (Arsenic (As), Cadmium (Cd), Chromium (Cr), Mercury (Hg), Nickel (Ni) and Lead (Pb)) were assessed in six indigenous fish species (Barilius barila, Salmostoma acinaces, Gudusia chapra, Labeo bata, Corica soborna, and Sperata aor) collected from the Old Brahmaputra River in Bangladesh. Human health risk associated with these fish consumption was also evaluated. Metals were analyzed in whole body of fish by an atomic absorption spectrometer (AAS). Mean concentrations of metals (µg/g, wet weight) were in the range of As (< 0.02-0.278), Cd (< 0.002-0.005), Cr (0.239-0.761), Hg (0.008-0.057), Ni (< 0.02-0.044), and Pb (< 0.01-0.038). The metal contents varied significantly among the fishes regarding their feeding habits and living habitats. Concentrations of As, Cr, Hg, and Pb were significantly higher in omnivorous species, whereas the benthopelagic species showed significantly higher accumulation of As (p < 0.05). The target hazard quotient (THQ) for noncarcinogenic risk and target cancer risk (TR) for carcinogenic risk were calculated to estimate the probabilities of experiencing these adverse health effects for the fish consumers. Metal-specific THQ values were all below 1 indicating no potential human health risk. Nonetheless, the hazard index (HI) values to estimate the effects from exposure to all metals collectively elucidated chronic noncarcinogenic health risk particularly from G. chapra consumption. The TR values revealed that there was carcinogenic risk from exposure to As through consumption of the fish. This study finally suggests a systematic and continuous monitoring of trace metal contamination in fishes from the river to ensure the fitness of this food item regarding the safety for human health.

Electrode surface modification of graphene-MnO2 supercapacitors using molecular dynamics simulations.

In this study, molecular dynamics (MD) simulations have been performed to explore the variation of ion density and electric potential due to electrode surface modification. Two different surface morphologies, having planer and slit pore with different conditions of surface charge, have been studied for graphene-MnO2 surface using LAMMPS. For different pore widths, the concentration of ions in the double layer is observed to be very low when the surface of the graphene-MnO2 electrode is charged. With a view to identify the optimal pore size for the simulation domain considered, three different widths for the nano-slit type pores and the corresponding ion-ion interactions are examined. Though this effect is negligible for pores with 9.23 and 3.55 Å widths, a considerable increase in the ionic concentration within the 7.10 Å pores is observed when the electrode is kept neutral. The edge region of these nano-slit pores leads to effective energy storage by promoting ion separation and a significantly higher charge accumulation is found to occur on the edges compared to the basal planes. For the simulation domain of the present study, partition coefficient is maximum for a pore size of 7.10 Å, indicating that the ions' penetration and movement into nano-slit pores are most favorable for this optimum pore size for MnO2-graphene electrodes with aqueous NaCl electrolyte. Graphical Abstract The importance of understanding the commercial feasibility of supercapacitor material has made qualitatively predicting the optimized electrode structure one of the main targets of energy related researches. While great progress has been made in recent years, a coherent theoretical picture of the optimized electrode structure remains elusive. This article discusses the most favorable design of supercapacitor electrode for ion-electrode interaction.