Abstract
BackgroundThe need to evaluate the human health safety of fishery resources remain urgent in the mist of the ever-increasing fear of heavy metal toxicity from the consumption of Ghana’s fisheries resource, as a consequence of pollution from several anthropogenic activities including artisanal gold mining. Nevertheless, the bigeye grunt (Brachydeuterus auritus) and Bagrid catfish (Chrysichthys nigrodigitatus) remain commercially valuable fish species in West Africa and continue to attract high patronage.MethodForty-five specimens each of C. nigrodigitatus and B. auritus collected from the Weija Dam and the Tema Fishing Habour in Ghana, between June and September 2016, were analysed for seven heavy metals using Atomic Absorption Spectrometry.ResultLead and Cadmium were below detection in all samples while Cu was not detected in B. auritus. Levels of the remaining metals (mg kg-1) were below FAO/WHO maximum permissible limits in fish and occurred in the rank order Se (3.5) > Zn (2.34) > Cu (0.59) > As (0.37) > Hg (0.19) in C. nigrodigitatus and Se (2.97) > Zn (2.28) > Hg (0.31) > As (0.21) in B. auritus. Only As in C. nigrodigitatus recorded Estimated Weekly Intake (EWI) greater than FAO/WHO Provisional Tolerable Weekly Intake (PTWI). Also, As in C. nigrodigitatus and Hg in B. auritus had Targeted Hazard Quotient (THQ) greater than 1 for individuals consuming the fishes on daily basis and therefore, raising concerns. However, for both species of fish, cancer risk of As was 1 in 10,000,000,000 and modified Health Benefits values of Se (HBVSe) were positive indicating the health risks that might accompany Hg exposure would be negated. Since toxicity depends on the concentration and quantity of a pollutant consumed, safe maximum consumption rate of C. nigrodigitatus based on As concentrations was 0.21 mg per day and that of B. auritus was 0.058 mg per day for Hg. With an average of 0.227 kg fish per meal of an adult human, these translated into not more than 24 C. nigrodigitatus and nine (9) B. auritus meals in a month but because fish is consumed at 0.0685 kg per person per day in Ghana, these values respectively translates to 93 and 30 safe days of consumption per month.ConclusionAt the rate of 0.0685 kg fish per person per day that fish is consumed in Ghana, the consumption of the two species of fish in Ghana would essentially be of little or no consequence to consumers.
Highlights
Heavy metal contamination is a serious environmental concern because of the direct toxic effect of metals on organisms and, the indirect effects of the consumption of metal contaminated food
Comparison of metal concentrations between the species indicated Se and As were significantly higher in the sampled muscles of C. nigrodigitatus than B. auritus while Hg was significantly higher in B. auritus (Mann–Whitney U test, p < 0.05) (Table 1)
As skeletal muscle constitutes the most significant component of fish meat, the health risk assessments in this current study were based on the metal contents of the skeletal muscle tissues only and caution must be exercised in the use of the figures. This current study established that the rank order of heavy metals in C. nigrodigitatus and B. auritus was similar with the concentrations of the essential metals generally higher than the toxic ones
Summary
Heavy metal contamination is a serious environmental concern because of the direct toxic effect of metals on organisms and, the indirect effects of the consumption of metal contaminated food. The pollution and degradation of land and water bodies from artisanal gold mining, for instance, are so wide spread in Ghana that efforts to combat the menace have recently been boosted nationwide [10, 11]. While most of these activities and contaminations occur in the terrestrial environment, the metals are transferred to rivers and the sea through fluvial processes, predisposing both fresh and marine water fisheries to the risk of heavy metal accumulation [12, 13]. The bigeye grunt (Brachydeuterus auritus) and Bagrid catfish (Chrysichthys nigrodigitatus) remain commercially valuable fish species in West Africa and continue to attract high patronage
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