Heavy metal contamination of selected rivers in Ghana was studied as part of a bigger project aimed at setting background standard for heavy metals in the Ghanaian environment. Water samples were collected from major mining and eight pristine areas. The samples were acid digested with aqua-regia and analyzed with ICP-MS for As, Cd, Hg, Zn, Cu, Mn, Fe, Cr, Al, V, Co, Ni, and Pb. The average concentrations (mg/L) from the pristine sites ranged from 0.002 ± 0.00(As) to 0.929 ± 0.06 (Fe) and 0.002 ± 0.00 (Pb) to 20.355 ± 5.60 (Fe) from the mining sites. With the exception of Al, Fe, and Mn, the metals level were found to be within the WHO and USEPA guideline limits. Hazard quotients (HQ) for ingestion and dermal contact for pristine and mining samples ranged from 3.00E-04 (Cu) to 0.84 (Cr) and 2.40E-06 (Cu) to 7.44 (As), respectively. The carcinogenic risk (CR) for ingestion and dermal contact ranged from 5.03E-06 to 1.71E-07 (Cr) and 4.22E-08 to 1.44E-09 (Cr), respectively. Arsenic showed a CR value higher than the acceptable limit (1.8E-02) from the mining sites which poses carcinogenic health threat. Multicriteria ranking suggests Birim river (EAM) as the most contaminated. The pattern recognition and multicriteria approach in characterizing the heavy metal contamination (for the first time in the case of Ghana) from the various sites will provide fresh insights into the risk assessment of heavy metals in contaminated surface waters.
Keywords: Health risk; Metal contamination; Mining; Physicochemical; Surface water; Toxicity.