Alatise et al. 2025 - metals in edible fruit nuts from Nigerian markets

Alatise, Aluko, and Okoye measured natural radionuclides and heavy metals in six edible fruit-nut categories from Lagos and Ogun State markets. The source is routeable to nuts and seeds because it reports market-sourced edible nut matrices and includes Pb, Cd, Cr, Ni, Co, Cu, Zn, As, and Hg in the analytical scope. The authors report Ni and Cr as the metals with the most cross-sample variation, with the highest concentrations in tiger nuts and kola nuts; they conclude that observed levels do not pose a significant health risk at the consumption levels considered.

Key numbers

• Matrices were peanuts (PN), cashew nuts (CN), walnuts (WN), date nuts (DN), tiger nuts (TN), and kola nuts (KN) sourced from major Lagos and Ogun State markets. One composite per nut type; n = 6 nut types.
• Heavy-metal analytes were Pb, Cd, Cr, Ni, Co, Cu, Zn, As, and Hg by flame atomic absorption spectrometry; values are reported in mg/kg on a dry-weight basis (samples sun-dried to constant weight, then pulverized, then microwave-digested).
• Pb (0.04 mg/kg), Cd (0.08 mg/kg), Co (0.20 mg/kg), and Hg (0.04 mg/kg) were reported as constant across all six nut types — consistent with values at or below the AAS method detection limit rather than measured variation.
• Cr (Table 3, dry-weight mg/kg): DN 0.43, PN 0.72, CN 0.72, KN 1.76, WN 2.23, TN 2.63 (mean 1.42).
• Ni (Table 3, dry-weight mg/kg): DN 0.04, PN 1.45, WN 2.00, KN 2.55, CN 2.84, TN 3.39 (mean 2.05).
• Cu (Table 3, dry-weight mg/kg): CN 0.43, DN 0.48, TN 0.72, PN 1.07, KN 2.05, WN 2.40 (mean 1.19).
• Zn (Table 3, dry-weight mg/kg): DN 0.04, TN 0.49, PN 1.04, KN 1.52, WN 1.73, CN 2.32 (mean 1.19).
• As (Table 3, dry-weight mg/kg, total As by flame AAS — no speciation): four samples at the apparent detection limit of 0.04; CN 0.11, TN 0.09 (mean 0.06).
• Radionuclide results (40K, 226Ra, 232Th in Bq/kg) are background context only; they are outside the HMI heavy-metal routing scope.

Methods (brief)

For heavy metals: 0.5 g of pulverised, sun-dried nut sample was digested with 7 mL concentrated HNO3 (65%) and 1 mL H2O2 (30%) in PTFE Teflon bombs using a SINEO JUPITA-A microwave digester (30 min), made up to 20 mL with double-distilled water, and assayed on a Varian AA 240FS flame atomic absorption spectrometer (acetylene-air flame). No As or Hg speciation; values reported as total As and total Hg. Analyses performed at the Ghana Atomic Energy Commission (NNRI Chemistry Department AAS Laboratory). Method detection limits are not explicitly reported in the paper but appear implicit from the constant 0.04, 0.08, 0.20, and 0.04 mg/kg values across all samples for Pb, Cd, Co, and Hg. For radionuclides: sodium-iodide gamma-ray spectrometry on Marinelli-beaker-sealed pulverised samples after 30 d secular equilibrium.

Implications

Occurrence data: contributes Nigerian-market nuts-and-seeds occurrence values for Cr, Ni, Cu, Zn, and total As, with Pb/Cd/Hg/Co below the apparent AAS detection floor. Direct routing applies to cashew nuts, peanuts, and walnuts (matched ingredients/products); date nuts, tiger nuts, and kola nuts have no current ingredient or product slug, so their data sits unrouted pending taxonomy expansion (see Verification notes). The constant-value pattern for Pb/Cd/Hg/Co should be treated as left-censored rather than as quantitative occurrence; downstream synthesis should use these as ≤LOD entries, not as detected concentrations.

Wiki pages this source may touch

• Cashews
• Peanuts
• Nuts and Seeds, Other
• cashew-nuts
• Peanuts
• Walnuts
• Nickel
• Chromium
• Lead
• Cadmium
• Arsenic, Total
• Mercury, Total

Verification notes

• Pb, Cd, Co, and Hg are reported as identical constants across all six nut types (0.04, 0.08, 0.20, 0.04 mg/kg). The paper does not state method detection limits, but the constant-value pattern is consistent with reporting at-or-below LOD as the LOD itself, not as measured concentrations. Synthesis should treat these as left-censored (<=LOD) values.
• Three nut types in the dataset — date nuts, tiger nuts, and kola nuts — have no current ingredient or product slug in the wiki taxonomy. Their per-nut Cr/Ni/Cu/Zn/As values are documented in Key numbers above but are not routed to dedicated ingredient/product pages; they currently flow only through the broad products/nuts-seeds-other channel. Taxonomy expansion is a Karen judgment call (n=1 paper, so below the 5-paper page-creation threshold).
• Values are on a dry-weight basis (samples sun-dried to constant weight, then pulverized, then microwave-digested). The paper does not provide a moisture content or fresh-weight conversion.
• Heavy-metal analyses were performed at the Ghana Atomic Energy Commission, not in Nigeria; the samples are Nigerian-market but the laboratory work is Ghanaian. Jurisdictional tagging remains NG (market of origin), not GH.

Page history

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