Human health risk assessments of mercury from the ingestion of edible fishes from Birim River, Ghana

A significant source of mercury emissions into the aquatic environment is artisanal and small-scale gold mining (ASGM). The Birim River provides essential ecological services to nearby communities that rely on fish for protein. A total of 49 fish specimens of the species Oreochromis niloticus, Brycinus imberi, and Schilbe uranoscopus were collected from the river in the East Akim Municipality. Fish’s gill and muscle mercury levels were measured using the MA 3000 mercury analyzer. The muscle and gill of S. uranoscopus had the highest median Hg concentrations, at 0.870 mg/kg w.w. and 0.345 mg/kg w.w., respectively. On the contrary, the muscle and gill of O. niloticus had the lowest median Hg levels, measuring 0.138 and 0.066 mg/kg w.w., respectively. All samples had Hg levels lower than the WHO limit, except for the muscles of S. uranoscopus. While the Hg levels in the gills and muscles of B. imberi showed a negative correlation with body weight and length, O. niloticus showed a positive correlation with both body weight and length. No significant correlation was observed between Hg in gills and muscles of S. uranoscopus and weight. The Hazard Quotient of B. imberi and S. uranoscopus exceeded the limit of one. This means that individuals who consume B. imberi and S. uranoscopus from ASGM sites will be at a non-carcinogenic risk. Subsequently, eight meals of B. imberi, four meals of S. uranoscopus, and eighteen meals of O. niloticus are recommended for consumers each month.