Concentrations and human health risk assessment of selected heavy metals in soils and food crops around Osukuru phosphate mine, Tororo District, Uganda

Abstract

This study investigated the concentrations of heavy metals, particularly chromium (Cr), cadmium (Cd); lead (Pb), copper (Cu), and iron (Fe) in the soil and crops. The accumulation of heavy metals in the crop system, the probable daily intake of heavy metals, and the assessment of potential health threats associated with the uptake of metals by the residents around the Osukuru phosphate mine in Tororo, Uganda. The concentrations were assessed with the assistance of an Atomic Absorption Spectrometer (AAS). The crops studied were amaranthus (Amaranthus hybridus) leaves, pumpkin (Cucurbita pepo) leaves, maize (Zea mays) grains, and cowpeas (Vigna unguiculata) leaves. A total of 200 samples were collected from five villages of Osukuru Sub County. The findings of this study showed that elemental concentrations of heavy metals in the soil were within the standard recognized limit for agriculture as documented by World Health Organization (WHO) and European Union (EU). While more noticeable levels of these elements were detected in crop samples, especially amaranthus. Chromium composition was lower than the detection level in all samples. The transfer factor results showed elemental intake by the crops in the sequence; Fe > Cu > Cd > Pb. The probable daily intakes of the elements were below the daily threshold values endorsed by WHO/FAO. The health threat index showed high values for Pb and Cd from maize but low values of Cu and Fe in all samples and therefore these crops may not be very safe for human intake.

Keywords

• Concentration of heavy metals
• Transfer factor
• Predicted daily intake
• Health threat index
• Danger index
• Phosphate mining