Biotransfer of heavy metals along the soil-plant-edible insect-human food chain in Africa

Abstract

Although mining is Zambia's major economic activity, it is implicated in environmental contamination, particularly with heavy metals. This study investigated the accumulation and transfer of heavy metals along the soil-plant-edible insect-human food chain. Our results revealed the presence of eight heavy metals (Arsenic, Cadmium, Chromium, Cop-per, Iron, Nickel, Lead, and Zinc) with a 28–60 % increase in soil concentrations at the proximity of the mining facilities. There was a higher accumulation of Cd, Cu, Ni, Fe, Pb, and Zn than As and Cr in plant species near the mine.Among the insect species studied, C. forda accumulated nickel significantly higher (70–81 %), I. obscura had higher cadmium (2–84 %) and lead (10–79 %), while I. rubra and M. falciger accumulated higher iron (41–96 %) and zinc (1–67 %), respectively, than other insect species. The quantity of I. obscura consumed (248 g person−1 day−1 ) was significantly higher (9–37 %) than other insect species. It was noted that the consumption of insects increased the daily intake of heavy metals, enhanced the target hazard quotient, and increased the associated health risks by up to 9 folds compared to the WHO permissible limits meaning that the daily intake of metals consumed depends on the daily quan- tity of insects consumed. Our findings suggest that the accumulation of heavy metals along the soil-plant-edible insect-human food chain could pose severe human and environmental health risks along the mining gradients. The potential consequences of heavy metal mobility in the consumer trophic levels and the ecotoxicological consequences are particularly concerning. Furthermore, physiological and biological studies are needed to investigate the abovementioned effects