Ntigoroku and Agbaire 2025 - Heavy metals in edible oils from Delta State, Nigeria

Ntigoroku and Agbaire measured physicochemical quality parameters, Cd, Cr, Pb, Cu, and screening-level health risk metrics in 20 edible vegetable oil samples purchased from major markets in Delta State, Nigeria. The source is routeable occurrence evidence for olive oil and other cooking oils. Concentrations are reported as ug/g, numerically equivalent to mg/kg oil.

Key numbers

Heavy metals by oil type

Table 2 reports mean +/- SD in ug/g. The source’s WHO comparator row is retained as printed.

The abstract and results text report category ranges:

The authors state that Pb was below the FAO/WHO maximum permissible limit of 0.1 mg/kg in all analyzed oils. Several Cd, Cr, and Cu values exceeded the comparator limits cited in the paper. The source summarizes overall metal load as palm oil > olive oil > soybean oil > sunflower oil, and individual burdens as palm > sunflower > soybean > olive for Cd; palm > sunflower > soybean > olive for Cr; sunflower > olive > palm > soybean for Pb; and palm > olive > soybean > sunflower for Cu.

Physicochemical properties

Table 1 reports mean +/- SD by oil type:

The authors state that physicochemical parameters were within acceptable limits overall, while the results prose also says most acid values exceeded a 0.6 mg KOH/g comparator. Peroxide values were below the 10 meq O2/kg Codex comparator cited by the paper.

Non-carcinogenic risk indices

The source calculates health risk index (HRI/HI) using a daily oil intake of 0.03 kg/day, adult body weight of 70 kg, and child body weight of 15 kg. All reported HI values were below 1.

Adult HI values:

Child HI values:

Carcinogenic risk

Table 5 reports estimated daily intake (EDI) and incremental lifetime cancer risk (ILCR) for Cd, Pb, and Cr. The authors state that cancer risk values were within the US EPA acceptable range of 1e-6 to 1e-4, with Cd and Cr closer to the upper acceptable bound for some oils.

Methods (brief)

The authors purchased 20 edible vegetable oil samples from major markets in Delta State, Nigeria, covering palm oil, soybean oil, olive oil, and sunflower oil. Physicochemical parameters included density, peroxide value, iodine value, acid value, and saponification value using AOAC-style titrimetric methods. For metals, 0.5 g oil was digested with nitric acid and perchloric acid, diluted, filtered, and analyzed by Agilent 55A atomic absorption spectrophotometer. The health-risk calculations used the source’s assumed daily oil intake of 30.4 g/day, body weights of 70 kg for adults and 15 kg for children, and US EPA-style ILCR framing for Cd, Cr, and Pb.

Implications

Certification: This is direct cooking-oil occurrence evidence for Delta State, Nigeria. It supports an oil-category concern for Cd, Cr, and especially Cu in palm/olive/soybean/sunflower oils, while Pb was below the paper’s cited 0.1 mg/kg comparator. Do not pool this source with US-market oil distributions without jurisdiction and market stratification.

Courses: Useful example of how oils can pass acute/non-carcinogenic HI screening while still exceeding concentration comparators for several metals. It also illustrates why oil type and local processing conditions should be preserved in evidence routing.

App: Route sunflower, soybean, and palm oil findings to other cooking oils; route olive oil findings to olive oil and broader cooking-oil context. Preserve the Nigeria market and Delta State sampling context.

Wiki pages this source may touch

• sunflower-oil
• soybean-oil
• olive-oil
• palm-oil
• vegetable-oil
• vegetable-oils
• olive-oil
• cooking-oils-other
• cadmium
• chromium
• lead
• copper

Verification notes

The PDF has author attribution and DOI 10.4314/jasem.v29i10.32; no DOI conflict was observed. The article gives slightly different chromium ranges in the abstract and results prose: palm oil is 0.038-0.169 ug/g in the abstract and 0.038-0.167 ug/g in the results prose, while olive oil is 0.050-0.076 ug/g in the abstract and 0.037-0.076 ug/g in the results prose. This page uses the abstract’s full range table and notes the discrepancies rather than adjudicating the last digit or substituting a prose-only value. The child-HI table reports palm-oil Pb as 0.0023 +/- 0.0066; given the adult table and body-weight scaling, this may be a decimal-place error, but it is preserved as printed. Brand/sample codes are omitted under the brand firewall.

2026-06-02 merge-enhance pass corrected three transcription errors against PDF Table 2 and Table 5: Olive oil Cr mean restored to 0.06 +/- 0.02 ug/g (was 0.05 +/- 0.02); Palm oil Cu SD restored to 1.29 +/- 2.2 ug/g (was 1.29 +/- 0.20, an order-of-magnitude SD compression); Olive oil ILCR(Cr) SD restored to 0.000006 +/- 0.000014 (was 0.000006 +/- 0.0000014, an extra-zero error). PDF page 6 (Table 2) and page 7 (Table 5) verified for all four oil categories on this pass.

2026-06-02 fresh-context audit subagent (Agent tool, general-purpose, agent ID aa96f64c7a143f163) returned REVISE with two findings. One applied: palm-oil Cu range discrepancy added below for parallelism with the existing Cr discrepancies. One rejected as false positive: subagent flagged palm-oil ingredient slug as missing from the taxonomy snapshot, but wiki/ingredients/palm-oil.md exists as a live page; the GPT-drafting snapshot is stale relative to live wiki state, and slug validity for an existing-page merge-enhance is checked against the live wiki/ingredients/ directory per docs/gpt-collaboration/verification-checklist.md. Snapshot refresh is separate work and does not affect this page. Checks 3 (speciation/methods), 4 (Part 12 brand firewall — brand codes EF/G/B/CA correctly omitted, Agilent vendor name permitted under Exception 2), and 5 (Part 2 wiki/HMTc firewall — no threshold proposals, no consumer advisories, no cross-source synthesis) returned clean.

Additional source-internal discrepancy noted: palm-oil Cu range is reported as 1.10-1.65 ug/g in the abstract and 1.01-1.65 ug/g in the results prose on page 5. This page uses the abstract figure for parallelism with the Cr-range handling above.

Page history

The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.