Soil-to-Crop Transfer, Bioaccumulation, and Health Risk Assessment of Heavy Metals in Cassava Grown in Illicitly Mined Areas of Noyem and Nyafoman, Eastern Ghana

Background: Illicit mining has become a major source of heavy metal contamination in Ghana, which threatens soil fertility, food safety, and public health. Despite growing concern, data on metal transfer into staple crops such as cassava remain limited. Objectives: This study assessed heavy metal concentrations in soils from illicitly mined sites at Noyem and Nyafoman and examined their transfer into cassava tubers to evaluate ecological and dietary health risks. Methods: Soil and cassava samples were collected from illicitly mined and control sites. Concentrations of Zn, Fe, Cu, Hg, and Cd were analyzed using Atomic Absorption Spectrophotometry (AAS). Soil–plant transfer factors and ecological risk indices were computed, while dietary exposure was evaluated using estimated daily intake (EDI) and risk index (RI) based on FAO/WHO guidelines. Data were analyzed in SPSS v20.0 and summarized through descriptive statistics and correlation analysis. Results: Concentrations of Zn, Fe, Hg, and Cd were significantly higher in mined soils compared to controls. Fe exceeded control limits, while Zn remained below global limit. Mercury occurred at concerning levels, consistent with other Ghanaian mining studies which reported Hg concentrations between 0.68 and 17.03 mg/kg. Cassava tubers from mined soils accumulated Cu and Hg above FAO/WHO permissible limits. A strong positive correlation (r = 1.00) between soil and cassava Cu confirmed cassava’s capacity to bioaccumulate Cu and its potential as a bioindicator crop. Zn, Hg, and Cd showed weak or negative correlations, likely due to low bioavailability influenced by soil pH and organic matter. Dietary risk analysis revealed potential long-term Cu exposure risk, while Zn intake exceeded safe limits for children (RI > 1), indicating heightened vulnerability in mining-affected communities. Conclusion: Illicit mining at Noyem and Nyafoman area has resulted in substantial heavy metal contamination of soils and cassava, posing both environmental and public health risks. The findings underscore the need for stricter regulation of small-scale mining, periodic soil and crop monitoring, and sustainable remediation interventions to safeguard food security, child health, and agricultural sustainability in Ghana’s mining areas.