Health risk assessment of heavy metals in Cassava cultivated on leachate-contaminated soil during the early transition from landfilling to co-landfilling with incineration

This study aimed to investigate heavy metal contamination in soil and cassava in the area of the Khon Kaen Municipality landfill during the transition period of waste management (December 2015), focusing on non-carcinogenic and carcinogenic health risks from consuming cassava tubers. Soil (0-30 cm) and cassava samples were collected from agricultural areas most affected by leachate leakage. Soil and cassava samples were digested for heavy metal analysis using microwave-assisted acid digestion (USEPA 3052), followed by heavy metal analysis with ICP-AES (USEPA 6010D). The analysis revealed that the concentration of heavy metals in soil did not exceed the WHO/FAO permissible limits, but contamination levels in cassava tubers for Cd, Cr, and Pb exceeded the permissible limits. Cassava demonstrated the ability to accumulate heavy metals in its tubers, with Ni showing the highest bioaccumulation potential (BCF = 5.837). Once accumulated in tubers, heavy metals translocated to leaves (Cd, Cr, Fe, Mn, Pb, Zn) and stems (Cr, Fe, Mn, Pb, Zn), with Mn exhibiting the highest translocation potential (TF tuber to leave = 10.670, TF tuber to stem = 7.094). Health risk assessments showed that both non-carcinogenic and carcinogenic health risks for both children and adults were unacceptable (HI >1, TCR >10-4). These findings highlight that, during the initial phase of waste management improvements, contamination persists in the soil and cassava, posing health risks to consumers. Therefore, enhancing leachate management systems is essential, and the results should serve as a reference for future waste management.