Overview
This cross-sectional study measured 10 trace elements (Ni, Cr, Pb, Zn, Cu, Co, Cd, As, Mn, Al) by ICP-MS in 44 coffee samples purchased from Chlef markets in Algeria, covering instant coffee (n=20) from 8 country origins (France, Italy, Sweden, Switzerland, UK, Poland, USA, Algeria), local-brand instant coffee (n=12), and roasted coffee sold in bulk (n=12). The study reports statistically significant differences (P < 0.0001) between coffee forms (ground, instant, beans) and packaging types (capsules, cartons, glass bottles, bulk) for most elements. Aluminum and manganese dominated by concentration; cadmium and arsenic were detectable but at low levels. Chronic daily intake (CDI) exceeded the reference dose (RfD) for Cd and Al in different forms. Evidence tier is B: single-location marketplace sampling in Algeria, small n, and no origin-confirmed trace of the 44 samples through supply chain.
Key numbers
- n = 44 samples: 20 instant (8 countries of origin), 12 local instant, 12 roasted bulk
- Dominant elements (mean mg/kg in coffee samples): Al 59.88 ± 54.86; Mn 16.26 ± 24.59; Cu 11.60 ± 11.55; Cd 9.92 ± 10.32; Ni 0.82 ± 0.81; As 0.25 ± 0.19; Pb 1.14 ± 1.99; Cr 2.71 ± 2.52
- Cd mean 9.92 mg/kg is anomalously high — substantially above other published coffee Cd values (typically 0.01–0.05 mg/kg in coffee beverages); this likely reflects dry-weight matrix in the coffee digest. Units are mg/kg in dry coffee not beverage; the authors apply EDI calculations using a 5 g/serving dose.
- LOD (mg/kg): Ni 0.008, Cr 0.02, Pb 0.02, Zn 0.03, Cu 0.001, Co 0.001, Cd 0.02, As 0.01, Mn 0.002, Al 0.06
- LOQ (mg/kg): Ni 0.025, Cr 0.06, Pb 0.06, Zn 0.1, Cu 0.06, Co 0.005, Cd 0.06, As 0.03, Mn 0.006, Al 0.18
- Highest TE levels found in ground coffee; lowest in coffee beans
- Capsule-packaged coffee: high Cu, Co, Zn, Mn, Al; carton-packaged: high As, Pb, Cr, Cd
- Maximum permissible levels referenced: Ni 0.10, Cr 0.10, Pb 1.0, Cd 0.1, As 1.4 mg/kg (per Omeje et al. and Pigozzi et al. references, not regulatory agency primary sources)
- Highest EDI: Al 0.0109 mg/kg BW/day (ground coffee, capsules); CDI for Cd and Al exceeded reference doses in different coffee forms
- THQ > 1.0 for Cd and Al (chronic non-carcinogenic risk flag); HI > 1.0 for different coffee forms
- PCA: first two axes explained 78.69% of variance; Al, Ni, Cu, Co, Zn correlated on axis 1; As and Pb on axis 2 (negatively correlated with Mn and Al)
Methods (brief)
Samples collected September 2022, Chlef region markets, Algeria. Digestion: 3 g coffee + 5 mL HNO₃ (65%) + 1 mL KOH (5%) in ceramic capsules; microwave (MPS 320, 200°C, 3-step). Filtered (0.45 µm), diluted to 25 mL. ICP-MS: ELAN DRC II (PerkinElmer). LOD and LOQ: 3× and 10× SD of 10 blank measurements. CRM: INC-TEL-1 Black Tea Leaves (INCT, Poland). Recovery: 97–102%. RSD < 5% required. Analysis in triplicate. Health risk: EDI, CDI, THQ per USEPA equations (RfDs from USEPA); HI = ΣTHQ.
Limitations
Evidence tier B: small n (44), single-marketplace sampling in Algeria. Country-of-origin on packaging reflects country of manufacture or import, not necessarily origin of coffee beans (especially for instant and packaged products). The Cd mean (9.92 mg/kg) is an order of magnitude higher than published literature for coffee Cd; this warrants scrutiny — the study does not explain this discrepancy and the CRM used (black tea leaves) is not the standard CRM for coffee. As mean (0.25 mg/kg) is also at the high end of reported coffee As values. The study reports on ground coffee and instant but not espresso as prepared beverage; dry-weight coffee values require dilution factor adjustment to estimate beverage exposure.
Implications
- Certification: Not directly relevant to HMT&C certification given the anomalous Cd values and methodology concerns. The geographic origin × metal form finding (carton-packaged ground coffee from Algeria contains elevated As, Pb, Cr, Cd) is an interesting origin-packaging interaction signal but not robustly established at n=44.
- Courses: Useful as a teaching example of how packaging type and coffee form affect extractable metals concentration, but the Cd anomaly should be discussed critically. The EDI/THQ/HI risk framework is well-illustrated here.
- App: As a single-market, small-n study with methodological questions around Cd values, this source should not drive the coffee ingredient contamination profile. Use as supplementary context only; weight lower than A-tier occurrence surveys.
- Microbiome: Not primary topic.
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Update history
The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and 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.
| Commit | Date | Change | Description |
|---|---|---|---|
| a8052bb | 2026-08-09 | major | 7 sections added; narrative text revised |