Potential human risk of dissolved heavy metals in gold mine waters of Gauteng Province, South Africa

This paper evaluates the potential health risks from dissolved heavy metals in water sources around a gold mining area in the Gauteng Province of South Africa. In this study, 29 samples of water were collected around a gold mining area and were analyzed for Arsenic (As), Lead (Pb), Mercury (Hg), Cadmium (Cd), Chromium (Cr), Copper (Cu), Zinc (Zn), Cobalt (Co) and Nickel (Ni) using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Measured concentrations of these heavy metals were then used to calculate the hazard quotient (HQ) and hazard index (HI) leading to the determination of carcinogenic and non-carcinogenic effects of these heavy metals. The average concentrations of the heavy metals decreased in the order of Ni>Cu> Zn>As> Cr>Co>Pb.  In mg.L-1 the average concentrations were as follows: Ni (0.39); Cu (0.38); Zn (0.33); As (0.19); Cr (0.14); Co (0.08); Pb (0.01). Hg and Cd were not detectable. For the non-carcinogenic risk assessment, calculated values of HQ showed an HI value of 3.38×10-1, a value less than 1, which is potentially safe according to United States Environmental Protection Agency (USEPA) and South Africa guidelines. When the carcinogenic risk assessment was carried out, the results showed that the total cancer risk due to the heavy metals was 2.94 × 10-6 mainly due to dermal contact. The USEPA considers a cancer risk in the range of 1 × 10-6 to 1 × 10-4 acceptable for regulatory purposes. From the findings presented, it can be concluded that dissolved heavy metal levels in the mine waters were within permissible limits. Key words: Health risk assessment, heavy metals, hazard index, target hazard quotient, average daily intake, cancer risk.