Dokubo et al. 2023 — Heavy metals in Nigerian seasoning powders (IJSHR)
This original research study measures ten heavy metals (As, Cr, Ni, Pb, Cd, Fe, Co, Cu, Mn, V) in four brands of commercially sold seasoning powder in Port Harcourt, Nigeria, using Flame Atomic Absorption Spectrophotometry (FAAS), alongside health risk assessment via EDI, Hazard Quotient, Hazard Index, and Cancer Risk computations. The headline findings are that mean Pb (6.35 ± 1.07 mg/kg) and Cd (0.53 ± 0.09 mg/kg) exceeded FAO/WHO maximum permissible limits (MPL) of 5.0 mg/kg and 0.3 mg/kg respectively across the four brands. One brand (SP4) had Pb at 12.61 mg/kg — more than double the MPL. As and Cr were not detected in any sample. The Hazard Index for one brand (SP2) exceeded 1.0 (HI = 1.04), and Cancer Risk values for Pb, Cd, and Ni were above the acceptable range of 1×10⁻⁶ to 1×10⁻⁴ across all brands, indicating potential long-term cancer risk from regular consumption.
Key numbers
Mean concentrations across all 4 brands (mg/kg dry weight):
- Pb: 6.35 ± 1.07 mg/kg (above FAO/WHO MPL of 5.0 mg/kg)
- Cd: 0.53 ± 0.09 mg/kg (above FAO/WHO MPL of 0.3 mg/kg)
- Fe: 16.31 ± 2.56 mg/kg (highest, below MPL)
- Co: — (above WHO MPL of 3.5 mg/kg in SP1, SP3, SP4)
- Ni: — (above WHO MPL of 5.0 mg/kg in SP4 at 8.24 ± 0.01 mg/kg)
- Mn: — (above MPL in SP2 at 10.45 mg/kg and SP4 at 2.78 mg/kg)
- V: 0.16 ± 0.10 mg/kg (lowest, below MPL)
- As: not detected in any sample
- Cr: not detected in any sample
Individual brand values for Pb (mg/kg):
- SP1: 5.94 ± 0.02 (above MPL)
- SP2: < MPL (below 5.0 mg/kg, exact value not extracted)
- SP3: 5.72 ± 0.07 (above MPL)
- SP4: 12.61 ± 0.03 (2.5× above MPL)
Hazard Index: SP2 HI = 1.04 (above safe threshold of 1.0). All others HI < 1.
Cancer Risk: all four brands above the acceptable range of 1×10⁻⁶ to 1×10⁻⁴ for Pb, Cd, and Ni combined.
EDI for Pb: exceeded FAO/WHO tolerable limit of 0.5 µg/kg/day in SP1, SP3, and SP4.
Model parameters: adult body weight 65 kg, seasoning powder ingestion rate 0.01 kg/day, exposure frequency 365 days/year, exposure duration 54 years.
Methods (brief)
FAAS (GBC 908PBMT). Sample preparation: 2 g sample digested in HNO₃ + HCl + H₂SO₄; heated to clear solution; filtered; made up to 50 mL. Health risk: USEPA model (EDI, HQ, HI, CR). Statistical analysis: SPSS v26, values expressed as mean ± SD. Evidence tier B: small sample (n=4 brands), single-city market, FAAS method (lower sensitivity than ICP-MS for some metals, notably As detection failure may reflect LOD limitations not true absence), and journal (IJSHR) is a general health sciences journal with moderate indexing. The As non-detection should be interpreted with caution given FAAS LODs for As are typically in the mg/kg range, which could mask lower-level contamination. The Pb and Cd exceedances, however, are large enough relative to MPLs to be analytically reliable even with FAAS.
Implications
Certification: Seasoning powders are not a current HMT&C product category, but this study establishes that commercially sold bouillon/seasoning powders in Nigerian markets contain Pb and Cd above regulatory limits. If spice-blend or seasoning products are added to HMT&C scope, this is a relevant data point for Africa/West Africa supply chains. The finding is consistent with broader literature on processed spice contamination.
Courses: Useful case study for the processed food contamination module: seasoning powders accumulate heavy metals through multiple ingredient inputs (salt, vegetable extracts, spices, starch, glutamate), making them aggregate-exposure products where contamination from any one ingredient component multiplies through high daily use patterns.
App: Pb and Cd in seasoning powder are above regulatory MPLs in this Nigerian market survey. Bouillon/seasoning ingredients in ingredient lists are a flag for Pb and Cd exposure in the app model, particularly in West African market contexts.