Distribution and Risk Assessment of Heavy Metals in Surface Water from Pristine Environments and Major Mining Areas in Ghana

Abstract

BACKGROUND Ghana, like many countries in Africa, has a history of heavy metal pollution largely emanating from industrial effluent discharges and anthropogenic deposits on prevailing winds of pollutants from industrial activities. One of the biggest contributors to pollution in the Ghanaian environment is mineral mining. OBJECTIVES The aim of this study was to determine the distribution and health risks of heavy metals in surface water from both pristine environments and major mining areas in Ghana. METHODS A total of 32 composite samples were collected between September and October, 2014 to assess concentrations of heavy metals and pollution levels, as well as cancer and non-cancer risks to human health from exposure to heavy metals from four major mining regions and four rain forest reserves in the Western, Ashanti, Brong Ahafo and Eastern regions of Ghana. Samples were analyzed using atomic absorption spectrometry. RESULTS The mean concentrations (mg/L) of heavy metals at the pristine sites ranged from 1.747 for iron (Fe) to 0.001 for mercury (Hg) and 0.453 for Fe to 0.002 for Hg at the mining sites. All the metals were found to be below World Health Organization (WHO) and United States Environmental Protection Agency (USEPA) recommended limits except for Hg, which was at the USEPA guideline limit. However, the concentrations of the metals from the mining sites were found to be slightly higher than those from the pristine sites. CONCLUSIONS The concentrations of heavy metals in the Nyam, Subri, Bonsa and Birim Rivers from the mining sites and the Atiwa Range, Oda, Ankasa and Bosomkese Rivers from the pristine sites were found to be either below or within the USEPA and WHO's recommended limits for surface water. The health risk assessment values for the hazard quotient for ingestion of water (HQing), dermal contact (HQderm) and chronic daily intake (CDI) indicated no adverse effects as a result of ingestion or dermal contact from the rivers. However, arsenic (As) in both the pristine and mining sites and chromium (Cr) in the pristine sites pose a carcinogenic threat to the local residents.