Chime et al. 2025 — Toxic trace metals in food spices from Enugu, Nigeria
This study measured total arsenic (As), cadmium (Cd), and lead (Pb) in seven spice/herb samples (six commercial brands labeled A–F, plus one fresh scent leaf) purchased from a single market in Enugu, Nigeria, using AAS. The most alarming finding is cadmium: all seven samples exceeded the FAO/WHO permissible limit of 0.02 µg/g by a substantial margin, with values ranging from 2.58 to 6.45 µg/g — between 129 and 322 times the limit. Arsenic exceeded the 0.5 µg/g safe limit in three samples (C: 1.68, E: 1.26, D: 0.315 µg/g), and lead exceeded the 2.0 µg/g threshold in two samples (A: 2.16, B: 2.19 µg/g). The authors attribute contamination to roadside sun-drying, polluted irrigation sources, and atmospheric deposition.
Key numbers
Concentrations in µg/g (= mg/kg), n = 7 total samples:
| Sample | As (µg/g) | Cd (µg/g) | Pb (µg/g) |
|---|---|---|---|
| A | 0.165 | 6.45 | 2.16 |
| B | 0.300 | 4.71 | 2.19 |
| C | 1.680 | 3.675 | 1.71 |
| D | 0.315 | 2.835 | 1.305 |
| E | 1.260 | 2.835 | 1.26 |
| F | 0.075 | 3.21 | 1.53 |
| Scent leaf | 0.180 | 2.58 | 1.71 |
| Permissible limit | 0.1–0.5 | 0.02 | 2.00 |
All Cd values exceed the permissible limit by 129–322x. Method: Agilent FS240AA AAS, APHA 1998, aqua regia acid digestion. No LOD/LOQ values explicitly reported for the samples; no speciation of As (total As reported, not iAs/organic split).
Methods (brief)
Samples were labelled A–F (brand identities not disclosed) plus one scent leaf grown locally and washed. Digestion used aqua regia (HNO3 + HClO4 + H2SO4 mixture) heated at 60°C to clear digest. Analysis by AAS with calibration curves from single-element stock solutions. Study limitations: very small n (7), single market, no certified reference material reported, no LOD/LOQ stated, brand/matrix identity not disclosed, and As is reported as total As without iAs/organic speciation.
Implications
Certification: The cadmium results in this study are extraordinary — 129–322x over FAO/WHO limits — and should be treated as evidence of a severely contaminated informal-market supply chain rather than a representative distribution for certified supply chains. The study reinforces that spice sourcing geography and post-harvest handling are critical Cd drivers. For HMT&C purposes, spice Cd monitoring is warranted; these values should not anchor threshold math but do support the need for testing requirements.
Courses: Excellent case study for contamination-pathway modules: roadside drying, atmospheric deposition, and informal market monitoring failure. Pair with better-controlled A-tier spice studies for a balanced picture.
App: Flags spices as a Cd- and As-relevant ingredient category, consistent with other literature. The extremely high values here are likely outliers from informal market conditions rather than typical commercial-grade supply.