Daina Mudimbu1, Dr. Maideyi Lydia Meck1, Prof. Theophilus Davies2, Prof Dexter Tagwireyi3, Ms Daina Mudimbu1
1. Department of Chemistry and Earth Sciences, University of Zimbabwe, Nigeria
2. Department of Geosciences, University of Lagos, Nigeria
3. Department of Pharmacy and Pharmaceutical Science, Faculty of Medicine and Health Sciences, University of Zimbabwe
Geochemical elements released through natural as well as mining operations into agroecosystems pose a serious threat to the health of communities that reside in mining towns even well after the cessation of mining activities. This study tests the hypothesis that geologic materials in mineralized areas contaminate water and vegetables and are associated with the distribution of non-communicable diseases observed in populations residing in the mining district of Kadoma, Zimbabwe. A plausible explanation for the etiology and prevalence of these diseases, hinges on the dispersion of potentially harmful geochemical elements in the soils, sediments and water and their bioaccumulation in the vegetables consumed by the local communities. Elements such as arsenic, cadmium, chromium, copper, lead, mercury, manganese, nickel and zinc that are associated with precious and base metal mineralisation, are amongst potentially harmful elements (PHEs) that have been linked to variety of human health challenges. The Kadoma District hosts some of the most economically viable gold and base metal deposits in Zimbabwe that have been mined for over a century. Historical medical data for the Kadoma district revealed an incidence rate of 6 to 12 times more prevalence of chronic renal failure, heart failure, mental illnesses and still births compared to other nonmined districts in the country. Soil, stream sediment (n = 94) and vegetable (n = 25) samples collected over 4 seasons during the period 2015 to 2017 in the farming and residential areas around the Kadoma District were analysed for PHEs concentrations using Inductively Coupled Plasma-Mass Spectrometer (ICP-MS). The results were used to compute contamination indices and bioaccumulation factors to assess the intensity of pollution by PHE and the health risk to the locals. In some localities soil and stream sediment had levels of arsenic, chromium and nickel well above the maximum permissible levels (MPL) for residential use. All vegetables assessed were found to have arsenic and lead levels above the FAO/WHO Codex maximum permissible levels (MPL). Leafy vegetables were found to accumulate more PHEs than root vegetables. Tomatoes were found to have an average concentration of lead and cadmium of the order of 1400 and 1.8 times above the MPL. The study concluded that there was potential human health risks due to ingestion of vegetables having As, Cd and Pb levels above safe limits (MPLs). It illustrated the importance of geochemical surveys in better informing public policy and governance in water food and health.