Exposure of agricultural products to metallic trace elements in the limestone mining area of Scan Mine in the Canton of Tokpli (Togo): Case of grains of zea mays (corn), leaves and stems of corchorus olitorius (Ademe) and tubers of manihot esculenta (Cassava)

The pollution of environmental components by metallic trace elements around many mining sites is known around the world. This metallic pollution constitutes a serious public health problem and the bioaccumulation of these metallic trace elements by food plants is a major concern. This study highlighted the level of pollution by metallic elements in edible products of three plant species (zea mays, corchorus olitorius and manihot esculenta) regularly grown in the Tokpli limestone mining area. The analysis of metallic trace elements in soil and plant samples is respectively carried out by inductively coupled plasma microwave atomic emission spectrometer (ICP-AES 4200) and inductively coupled plasma atomic emission spectroscope (the Optima 80,000 ICP). The contents of various metallic trace elements were analyzed in the grains of zea mays, the leaves and stems of corchorus olitorius and tubers of manihot esculenta. The results show a high accumulation of most of these elements in edible products and in soils. These metallic elements in the soil would come from mining activity, the degradation of soils and other ecosystems, and the misuse of chemical fertilizers and pesticides. Their presence in edible products would be linked to the process of bioaccumulation by root and/or aerial ways.The pollution factors are of metallic trace elements (Hg, Fe, Pb, Al, Se…) in edible products such as zea mays (Hg: 2806.29; Fe: 1667.62; Pb: 1622.99), corchorus olitorius (Hg: 3463.24; Al: 2715.78; Fe: 1882.98) and manihot esculenta (Fe: 964.51; Hg: 670.13; Se: 539.26) plants grown around the Tokpli mining area are much higher than the thresholds recommended by the World Health Organization (WHO). Consumption of these products could expose consumers to chronic poisoning.