Bioaccumulation and potential human health risks of Cu, Co, Pb and Zn in Guizotia scabra and Urena lobata growing in a copper mining environment

This study investigated the potential bioaccumulation and human health risks of Cu, Co, Pb and Zn in G. scabra and U. lobata growing in a copper mining environment. Roots, leaves and stems were collected from the studied species. Soil samples were also from the spots of each sampled plant. Samples were digested in HCl and HNO3 to obtain a solution. The concentration of Cu, Co, Pb and Zn was determined from the solution using an atomic absorption spectroscopy. The heavy metal content was further processed for soil contamination, accumulation in plants and human health risks. Geoaccumulation indices and enrichment factors show that the study site is significantly polluted with Cu, Co, and Pb except for Zn, all taken up in elevated quantities by the study species. The bioaccumulation index indicated that Zn, Co and Pb accumulate in G. scabra and U. lobata. In addition, the incremental lifetime cancer risk index demonstrated that Pb quantities in both G. scabra and U. lobata exceeded acceptable carcinogenic risk levels across plant organs. The carcinogenic risk levels were at a minimum 17 times higher than the acceptable limits. Non-carcinogenic risk levels of all studied heavy metals, measured by hazard index, were also exceeded by a minimum of 2,021 times. These results indicate that exposure to G. scabra and U. lobata growing in a polluted environment may instigate adverse human health effects, including carcinogenicity.