Lithium and other trace elements of relevance in fish from two African lakes compared with fish from European rivers and health risks for human consumers involved

During a screening of trace elements in fish from Lake Turkana and Lake Naivasha, Kenya, high levels of cadmium and zinc have been reported, presenting risks for human consumers in the area. Besides of the geological... [ view full abstract ]

During a screening of trace elements in fish from Lake Turkana and Lake Naivasha, Kenya, high levels of cadmium and zinc have been reported, presenting risks for human consumers in the area. Besides of the geological background, the pollution of water bodies is probably due to anthropogenic sources, including fertilizing of farmland. In addition, lithium was detected in high levels in one migratory fish species (Hydrocynus forskhalii) from Lake Turkana; Lithium has been neglected as a possible source of contamination in fish, as there are practically no reports on levels of this element in freshwater fish available. For this study, we have included a non migratory fish species (Tilapia zillii) from Lake Turkana comparing it to the migratory species and included samples of Oreochromis leucostictus from Lake Naivasha. In addition, samples from two fish species with different nutritional behaviors from the Danube River in Central Europe were included. The results show, that, amongst others, the levels of lithium in fish seem to correlate with the intensity of land use around the water bodies or more precisely, the usage of mineral fertilizers; highest levels, presenting a high risk for fish consumers, were found in O. leucostictus from Lake Naivasha, which is heavily influenced by intense land use. Second highest levels were present in H. forskhalii from Lake Turkana, which is exposed to heavily influenced waters only seasonally during migration into the highly influenced delta of the Omo river. Due to the high content of carbonate in the lake - in contrast to Lake Naivasha -, lithium from the Omo river might precipitate in the mixing zone. Therefore, lithium concentration in the waterbody and sediment in the middle area of the west bank of the lake and the non migratory T. zillii was below LOD, indicating no pollution with this element. Also in all fish samples from Danube River lithium concentrations were below LOD.