Investigating toxic metal levels in popular edible fishes from the South Durban basin: implications for public health and food security

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 mu g g(-1)) followed by Bronze seabream (31.07 mu g g(-1)). Al levels ranged from 5.6 mu g g(-1) in Atlantic mackerel to 35.04 mu g g(-1) in Horse mackerel tissue while Cu and Cr concentrations were highest in the tissues of Horse mackerel (6.83 and 1.81 mu g g(-1), respectively) followed by Santer seabream (3.15; 1.09 mu g g(-1)) and Bronze seabream (3.09; 1.30 mu g g(-1)), respectively. The highest tissue concentration of Mn was detected in Bronze seabream (8.23 mu g g(-1)) followed by Catface rockcod (6.05 mu g g(-1) ) and Slinger seabream (5.21 mu g g(-1)) while Pb concentrations ranged from a high of 8.44 mu g g(-1) in Horse mackerel to 1.09 mu g g(-1) 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.