Overview
Tefera and Teklewold measured cadmium (Cd), chromium (Cr), Cu, lead (Pb), and Zn in 144 samples of four spice species (ajwain, Nigella sativa, coriander, and fenugreek) from Central Gondar Zone, Ethiopia. Pb and Cd were not detected in any of the 144 samples. The highest concentrations among detected metals were Cr in ajwain (24.85 +/- 1.673 mg/kg), Cu in ajwain (32.267 +/- 7.355 mg/kg), and Zn in fenugreek (54.13 +/- 6.122 mg/kg). THQ values for Cu, Zn, and 75% of Cr samples were less than 1; about 66.7% of Hazard Index (HI) values were less than 1, indicating the majority of samples posed no non-carcinogenic health risk from these metals.
Species disambiguation: “Black cumin” throughout this paper is Nigella sativa L. (family Ranunculaceae), explicitly identified in Table 1 by botanical name and family. This is distinct from Cuminum cyminum L. (family Apiaceae, true cumin). This source page is filed under herbs-and-spices rather than cumin.
Key numbers
Concentrations by species (mean +/- SD, mg/kg dry weight, FAAS). Pb and Cd were not detected in all 144 samples.
Positive correlations among Cr, Cu, and Zn in fenugreek and among Zn with Cr and Cu in Nigella sativa were observed. Negative correlation between Cr and Cu/Zn in ajwain and coriander.
THQ and HI:
- THQ <1 for Cu, Zn, and 75% of Cr across all spices
- HI <1 in 66.7% of samples
- RfD values used: Cr 0.003, Cu 0.04, Zn 0.3 mg/kg/day
Methods (brief)
Sampling: 144 composite samples from 3 districts x 3 markets x 4 samples per market per species; washed with tap water then deionized water. Digestion: HNO3/HClO4 mixtures at 240 degrees C (species-specific ratios and times); reagent blank run simultaneously. Analysis: FAAS; LOD values for Cd 0.0004, Cr 0.036, Cu 0.064, Pb 0.22, Zn 0.012 mg/L (Table 2). Recovery: 92.62-107.13% (Table 3). Health risk: EDI, THQ, and HI computed per USEPA formulas; IR from WHO average spice consumption; BW = 60 kg. Basis: dry weight of spice seeds.
Implications
Certification: Non-detection of Pb and Cd in all 144 samples from Ethiopia is a consistent pattern across Nigella sativa studies (also Tura et al. 2023, also Imperl et al. 2023). These non-detections are relevant to Nigella sativa risk assessment but do not transfer to Cuminum cyminum (true cumin) or other Apiaceae seed spices.
Courses: The Cr data for ajwain are noteworthy (24.85 mg/kg, approaching the WHO guidance of 30 mg/kg for Cr in spices), illustrating that Cr can be a relevant metal for Apiaceae seed spices even when Pb and Cd are absent.
App: No cumin data. File under herbs-and-spices for Nigella sativa and Ethiopian spice context.
Related evidence
Update history
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