This study measured 12 elements by ICP-MS in 34 seized cannabis samples from Ghana, combining police seizures (2017-2020) and farm-collected samples from two regions. The study aimed to use multivariate metal profiles to distinguish farm origins. The matrix is mixed flower and leaf material, not pure inflorescence. Lead and arsenic concentrations span a wide range, reflecting heterogeneous soil contamination across sampling sites.
Key numbers
Concentrations are in ppm (= µg/g) for major elements and ppb (= ng/g) for trace toxic metals. Ranges are across all 34 samples. [VERIFY table check]
Toxic trace metals (from Figures 1-4 and text):
| Metal | Range (all samples) |
|---|---|
| lead (Pb) | 11 to 854 ppb (ng/g) |
| total arsenic (tAs) | up to 242 ppb (ng/g) |
| cadmium (Cd) | up to 181 ppb (ng/g) |
| total mercury (tHg) | not detectable |
Converting to µg/g for direct comparison with other studies: lead 0.011 to 0.854 µg/g; arsenic up to 0.242 µg/g; cadmium up to 0.181 µg/g. The 854 ppb lead maximum represents a heavily contaminated outlier sample; the lower end of 11 ppb (0.011 µg/g) is consistent with cleaner growing conditions.
Essential/major elements (ppm = µg/g, ranges):
| Element | Range |
|---|---|
| K | 20,772 to 60,537 ppm |
| Ca | 10,699 to 45,652 ppm |
| Mg | 2,830 to 12,939 ppm |
| Fe | 131 to 3,335 ppm |
| Mn | 73 to 2,363 ppm |
| Zn | 20 to 197 ppm |
| Cu | 6 to 73 ppm |
| Na | below detection to 643 ppm |
Soil lead at sampling sites: 2.0 to 5.0 ppm; soil arsenic 1.2 to 13 ppb; cadmium and mercury not detectable in soils. The wide cannabis lead range relative to soil lead indicates plant hyperaccumulation from even low soil concentrations at contaminated sites.
Methods (brief)
ICP-MS (Agilent 7700); acid microwave digestion; dry-weight basis. No formal LOD/LOQ table reported; general ICP-MS detection limit noted as approximately 0.1 ppb. No CRM reported.
Evidence fitness
This study provides occurrence data for lead, arsenic, and cadmium in Ghanaian illicit cannabis (mixed flower plus leaves). The wide lead range (11 to 854 ppb) reflects heterogeneous soil contamination across farming sites and indicates that growing location is the dominant driver of lead variation. Total arsenic up to 0.242 µg/g and cadmium up to 0.181 µg/g fall below the stricter regulatory action limits for cannabis in North American programs. Mercury was not detectable in any sample. Matrix is mixed flower and leaves, not pure inflorescence; flower-specific concentrations cannot be isolated. No CRM recovery was reported, which limits quantitative confidence. Arsenic is total arsenic only. This dataset is not representative of regulated North American or European markets.
Limitations
Mixed matrix (flower plus leaves); flower-specific values not separable. No CRM reported; quantitative confidence limited. Sampling represents illicit cannabis from two Ghanaian regions only. Total arsenic only, no speciation.
Related evidence
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