NON-CANCER HUMAN HEALTH RISK ASSESSMENT FROM EXPOSURE TO HEAVY METALS IN SURFACE AND GROUNDWATER IN IGUN IJESHA, SOUTHWEST NIGERIA

Non-cancer hazard index for inhabitants exposed to heavy metals in surface and groundwater of the abandoned metal mine in Igun-Ijesha area were evaluated. A total of thirty-eight water samples were collected from surface and ground water sources in the study area between September 2012 and February 2013 and the concentrations of heavy metals were determined using Atomic Absorption Spectrophotometer. Non-cancer risk assessments from possible exposure to heavy metals were evaluated using the United States Environmental Protection Agency’s human health risk assessment guidelines. Simple random sampling was used to administer questionnaires to investigate demographic characteristics and public health status of residents. Data obtained were subjected to descriptive statistics and ANOVA using SPSS for Windows version 16. Results indicated elevated levels of Cadmium (Cd), Chromium (Cr), Copper (Cu), lead (Pb), Manganese (Mn), Nickel (Ni) and Zinc (Zn) ranging from 0.01-1.20, 0.05-0.52, 0.80-34.80, 0.09-4.30, 0.09-8.30, 0.05-3.94, 0.05-19.60 and 1.80-29.90 mg L^-1 respectively which exceeded national recommended limits with few exceptions. Hazard Quotients (HQ) and Hazard Index (HI) of heavy metals were calculated and results greater than 1 indicate non-carcinogenic adverse health effects of the observed metals. A daily intake of water by the local residents could pose a potential health threat from long-term heavy-metal exposure. The risk assessment provided by this study can be beneficially used and applied for risk communication to avoid negative public health impact. Similarly, Water Safety quality assurance strategic plan should be developed to safeguard source, water and public health within the mining community.