Contamination of the ocean by heavy metals may have ecosystem-wide implications because they are toxic even if present in trace levels, and the relative ease of their bioaccumulation by marine organisms may affect human health, primarily through consumption of contaminated fish. We evaluated metal concentrations in six different popular edible fish species and estimated the potential health risks from consumption of contaminated fish. There was no correlation between fish length and average metal accumulation although the fish species tended to accumulate significantly more Al and Zn (P < 0.05) than any of the other metals. Significantly higher Mn concentrations were found in fish gills compared to other body parts in all fish species. Bronze seabream, Catface rockcod, and Slinger seabream had significantly higher mean Cr concentration in the liver than in either the tissues or gills. The highest concentration of Zn in fleshy tissue was in Horse mackerel (56.71 μg g) followed by Bronze seabream (31.07 μg g). Al levels ranged from 5.6 μg g in Atlantic mackerel to 35.04 μg g in Horse mackerel tissue while Cu and Cr concentrations were highest in the tissues of Horse mackerel (6.83 and 1.81 μg g, respectively) followed by Santer seabream (3.15; 1.09 μg g) and Bronze seabream (3.09; 1.30 μg g), respectively. The highest tissue concentration of Mn was detected in Bronze seabream (8.23 μg g) followed by Catface rockcod (6.05 μg g) and Slinger seabream (5.21 μg g) while Pb concentrations ranged from a high of 8.44 μg g in Horse mackerel to 1.09 μg g in Catface rockcod. However, the estimated potential health risks from fish consumption as determined by the target hazard quotient (THQ) and hazard index (HI) were significantly lower than 1, implying that metals were not present in sufficiently high quantities to be of any health and/or food and security concern in the studied fishes.

While fish is considered a healthy component of the human diet, consumption of fish with high levels of trace metals in their flesh constitutes a public health risk as trace metals have been proven to be toxic. We investigated the concentrations of toxic elements in seawater and also in different body parts of the fish Trachurus capensis caught near Durban, South Africa, using inductively coupled plasma-atomic emission spectrometry (ICP-AES). The highest metal concentration in fish body parts was observed for Pb, followed by Zn. Significantly higher levels of Mn were observed in fish gills as compared to the tissue (muscle) and fish frame. With respect to bioaccumulation, significantly higher Pb levels were observed in fish tissues compared to As, Cr, and Mn. In the frame, significantly higher Pb levels were observed compared to all other metals except Ba. There were no significant differences in the concentrations of different metals in fish gills. Overall, the toxic metal concentrations in the muscle of cape horse mackerel were below levels of concern for human consumption as defined by the FAO and WHO.

The bioaccumulation of heavy metals (HMs) in marine fish is a growing global concern due to potential health risks. The study analysed HM in the muscle tissue, gills, and gut of cape horse mackerel and slinger seabream caught in the polluted Durban Basin and pristine Cape Vidal from April 2018 to February 2019. Results revealed interspecific, spatial, and organ-specific variability in HM levels. In the Durban basin, slinger seabream had bioaccumulation (in mg/kg) of As (2.3± 0.2), Cr (2.6±0.2), Ni (2.0±0.1), and Pb (4.1±0.3) while cape horse mackerel had Ni (1.6±0.2), Pb (4.7±0.6), and Zn (52±3.01) exceeding WHO regulatory limits. Metal pollution index (MPI) values were also higher in Durban Basin (>5.13) than Cape Vidal (<3.32) for both species muscles. Liver and gills of slinger seabream and gut of cape horse mackerel exhibited higher HM accumulation patterns proportionate to the environmental concentrations, indicating the bioindicative potential of HM pollution by the two species. Risk assessment indicated that both fish species had target hazard quotient (THQ) > 1 for Cr, and target cancer risk (TR) < 10-4 for Pb, implying significant non-carcinogenic and carcinogenic health risks associated with fish consumption from the Durban Basin. The study recommends daily consumption limits of 16 g/day for slinger seabream and 14 g/day for cape horse mackerel to ensure health safety. The findings contribute to the understanding of HM pollution in the Durban basin and provide important information for decision-makers and policymakers in developing effective strategies to mitigate and manage HM contamination in fish populations.

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