Heavy Metal Concentrations and Health Risk Assessment of Cassava Cultivated with Variable Farming Conditions

Abstract

This study assesses the concentrations of heavy metals and associated health risks in sun-dried cassava harvested under four distinct farming conditions in the Niger Delta, Nigeria: normal (control), inorganic fertilizer-treated, herbicide-treated, and crude oil-polluted soils. Using validated digestion protocols and spectrophotometric analysis, levels of Lead (Pb), Cadmium (Cd), Cobalt (Co), Nickel (Ni), and Chromium (Cr) were quantified. Health risk indices such as Estimated Daily Intake (EDI), Target Hazard Quotient (THQ), Hazard Index (HI), Lifetime Cancer Risk (LCR), and Total Lifetime Cancer Risk (TLCR) were calculated for adult and child populations. Results showed that cassava from oil-polluted and chemically treated soils contained higher concentrations of heavy metals, often surpassing FAO/WHO permissible limits. THQ and HI values exceeded the safe threshold (HI > 1.0) in several samples, indicating potential non-carcinogenic health risks. LCR and TLCR values, especially for Cr and Ni, were highest in cassava from fertilizer and oilimpacted soils, exceeding the USEPA safety benchmark (1.0E–04), thus posing longterm carcinogenic risks. The study highlights the significant public health implications of current farming practices in ecologically fragile, oil-producing areas of Nigeria and calls for regulatory oversight, sustainable soil remediation, and community health awareness.