Albishi et al. 2026 — Heavy metal concentrations in biofortified cassava flour from Nigeria
Albishi and colleagues measured Pb, Cd, As (total), and Cr in cassava (Manihot esculenta) flour samples from Nigeria under different natural biofortification treatments, finding that all heavy metal concentrations were well below WHO/FAO maximum permissible limits (Pb: 300 µg/kg DW; Cd and As: 200 µg/kg DW). The control group (unfortified cassava flour) showed Pb at 61.33–68.67 µg/kg DW, Cd at 57.67–63.00 µg/kg DW, As at 9.97–11.13 µg/kg DW, and Cr at 65.00–68.00 µg/kg DW, and biofortification treatments generally reduced heavy metal levels, with the best-performing treatment (F11) achieving Pb 21.33, Cd 27.33, As 6.07, and Cr 55.33 µg/kg DW. The primary focus of the paper is nutritional biofortification rather than contamination surveillance, so the cassava samples were not selected to represent worst-case contamination and the geographic sourcing details are limited.
Key numbers
All concentrations in µg/kg dry weight (DW), n=3 per treatment, mean ± SD (Table 6):
| Sample | Pb (µg/kg DW) | Cd (µg/kg DW) | As (µg/kg DW) | Cr (µg/kg DW) |
|---|---|---|---|---|
| Control A | 68.67 ± 3.21 | 63.00 ± 2.65 | 11.13 ± 0.80 | 68.00 ± 3.00 |
| Control B | 61.33 ± 2.08 | 57.67 ± 1.53 | 9.97 ± 0.15 | 65.00 ± 1.00 |
| F1 (least-fortified) | 58.00 ± 2.00 | 54.33 ± 1.53 | 9.43 ± 0.06 | 64.33 ± 0.58 |
| F10 | 28.33 ± 3.06 | 36.67 ± 1.53 | 6.13 ± 0.72 | 58.33 ± 1.15 |
| F11 (best) | 21.33 ± 1.53 | 27.33 ± 2.52 | 6.07 ± 0.15 | 55.33 ± 1.53 |
WHO/FAO limits cited: Pb 300 µg/kg DW, Cd 200 µg/kg DW, As 200 µg/kg DW.
As speciation: not performed; values are total arsenic (tAs). Cr speciation: not performed; values are total chromium.
Methods (brief)
Analytical method for heavy metals: ICP with HPLC referenced in methods (exact ICP variant not specified in extracted text). Samples are cassava flour specimens (CF) from Nigeria. The study design is a biofortification experiment with 11 treatment groups plus 2 controls; heavy metal measurement is a safety check rather than a contamination survey. LOD/LOQ not reported. Basis: dry weight. The Nigeria geographic context is relevant; cassava is a staple crop in West Africa and this provides a baseline for Nigerian commercial cassava flour heavy metal levels.
Implications
Certification: Cassava is a significant ingredient in gluten-free products and West African food supply chains. The control values (Pb ~62–69, Cd ~58–63, As ~10–11, Cr ~65–68 µg/kg DW) represent background contamination for Nigerian cassava flour and are well below WHO/FAO limits, suggesting this ingredient does not present elevated heavy metal risk in the Nigerian production context sampled here.
Courses: Illustrates that plant-based processing (biofortification, fermentation, or additive treatments) can reduce heavy metal concentrations in flour, with F11 achieving roughly 65–70% reduction in Pb and Cd vs controls.
App: Nigerian cassava flour baseline: Pb ~62–69 µg/kg DW, Cd ~58–63 µg/kg DW, tAs ~10–11 µg/kg DW, Cr ~65–68 µg/kg DW. Small n per treatment (n=3); single-country data point; sourcing details limited.