Levels and human health risk assessment of heavy metals in surface soil of public parks in Southern Ghana

This study evaluates the extent to which humans may be exposed to health risk from heavy metals in surface soils of public parks in Southern Ghana during outdoor activities. The study investigated surface soils of 56 public parks from seven metropolitan cities in Southern Ghana. Heavy metals (Cd, Cr, Cu, Hg, Mn, Ni, Pb, and Zn) were determined using microwave-assisted HNO3-HF acid digestion and atomic absorption spectroscopy with flame, graphite furnace, and cold vapor options. All parks studied registered the presence of heavy metals with mean concentrations following the order: Mn > Zn > Cr > Pb > Cu > Ni > Cd > Hg. Whereas the mean concentrations of Zn (221.92 mg/kg) and Cr (107.01 mg/kg) respectively exceeded the Canadian (200 mg/kg; 64 mg/kg) and the EU (100-200 mg/kg; 50-100 mg/kg) standards, the ranges of Cu (14.27-138.85 mg/kg) and Pb (6.46-628.31 mg/kg) also exceeded their EU range of 50-100 mg/kg. The results indicated that there was no immediate risk to Ni and Hg on the public parks studied; however, Pb, Cd, Zn, Cu, and Cr may pose some adverse effects as they exceed their respective guideline limits in soil. The ranges of non-carcinogenic risk for adults and children were 0.0186-0.0787 and 0.0197-0.0850 respectively while the corresponding ranges for carcinogenic risks were 3.75 x 10(-7)-1.28 x 10(-6) and 4.17 x 10(-7)-1.31 x 10(-6). Even though risk assessment suggested low and acceptable health risk levels to patrons, there is the need for close monitoring since Pb, Cd, Zn, Cu, and Cr have shown tendency of accumulating beyond acceptable limit.