CANCER RISKS ASSOCIATED WITH ARSENIC, CADMIUM, CHROMIUM AND LEAD EXPOSURE IN FLUORSPAR MINING BELT ELGEYO-MARAKWET COUNTY, KENYA

Abstract

The elevated levels of heavy metals due to the mining activities in Fluorspar mining belt are a cause of environmental and health concern. The study was aimed at determining the concentrations of Arsenic (As), Cadmium (Cd), Chromium (Cr) and Lead (Pb) in soils, water and food (milk, maize, millet and beans) in the study area. The study area covered Fluorspar mining belt in Kimwarer sub-catchment zoned into upper, middle and lower Kimwarer.Samples were prepared and digested then analyzed for Cd, Cr and Pb using Atomic Absorption Spectrophotometer (AAS). Arsenic was analyzed using AAS coupled with hydride vapour generator. The exposure of the selected metals was determined by daily Estimated Daily Intake (EDI) of heavy metals in water, food and also by determining the concentrations of the metals in human hair. Cancer risks were determined from Incremental Lifetime Cancer Risk (ILCR) while target hazard quotient (THQ) estimated non-carcinogenic risks using USEPA probabilistic models. Cancer prevalence was obtained from a cross sectional survey. The results showed metal mean concentration of water were all above the WHO recommended levels of (<0.05mg/l) in dry and wet season. All the soil samples were above the levels of what is considered as unpolluted soils.Themetal mean concentrations in food were above the CODEX Alimentarium Commission recommended levels of As (0.14ppm), Cd (0.1mg/l), Cr (1ppm) and Pb (6ppm). The EDI results of selected metals within acute, intermediate and chronic Minimal Risk Levels (MRL) as recommended by Agency for Toxic Substances and Disease Registry were 20%, 9.17% and 5.83% respectively. The female had a higher percentage (98.7%) of EDI above recommended MRLs compared to their male counterparts who had 95% of EDI results. The concentration of As and Pb in hair had a positive significant (P>0.01) correlation to cancer while Cr had a negative significant difference with cancer prevalence in the study area. The values of THQ for the individual heavy metals and the hazard indices (HI) due to the combined non-cancer effects of all the metals considered in the study were HI>1. The sum totals of ILCR were all above WHO acceptable levels of 1 x 10-6 to 1 x 10-4 for all the metals. The prevalence of cancer cases in the study area was 39 cases in a sample population of about 355 people.In conclusion, the study established that there was a significant spatial and temporal variation in the selected metal concentration in the study area between the wet and dry seasons. The THQ and ILCR showed potential health riskfor humans due to the intake of water, milk, maize, beans and millet especially in the villages closest to the mine (MK and LK)due to As Cd Cr and Pb. The study recommended a concerted effort from the stakeholders to create awareness of the dangers of the heavy metals and find ways of mitigating the effects and enforcing the safe environmental practices, regulations and laws.