This study measured 18 metals by ICP-MS/MS in 100 dried cannabis inflorescences: 50 purchased from licensed Canadian retailers and 50 seized from illegal sources by law enforcement. Results were compared against USP 232 concentration limits assuming 10 g/day oral or inhalation exposure. The comparison is the first head-to-head metals dataset for the Canadian legal versus illegal cannabis divide.
Key numbers
All concentrations are µg/g dry weight. USP 232 limits assume 10 g/day consumption (oral/inhalation route). Values are ranges across 50 samples per group. ND below the sample detection limit listed in Table 2. [VERIFY table check]
Lead (Pb): USP 232 limit 0.5 µg/g. Legal: 8% detection, range <0.05 to 0.24 µg/g. Illegal: 32% detection, range <0.05 to 0.32 µg/g. No samples from either group exceeded the limit (Table 2).
Cadmium (Cd): USP 232 limit 0.3 µg/g. Legal: 18% detection, range <0.03 to 0.16 µg/g. Illegal: 50% detection, range <0.03 to 0.28 µg/g. No samples exceeded the limit (Table 2).
Total arsenic (tAs): USP 232 limit 0.2 µg/g. Legal: 18% detection, range <0.02 to 0.16 µg/g. Illegal: 44% detection, range <0.02 to 0.29 µg/g. Two percent of illegal samples exceeded the limit (Table 2).
Total mercury (tHg): USP 232 limit 0.1 µg/g. Legal: 6% detection, range <0.01 to 0.03 µg/g. Illegal: 12% detection, range <0.01 to 0.06 µg/g. No samples exceeded the limit (Table 2).
Total chromium (Cr): USP 232 limit 0.3 µg/g. Legal: 66% detection, range <0.03 to 0.89 µg/g; 6% exceeded the limit. Illegal: 50% detection, range <0.03 to 0.33 µg/g; 4% exceeded the limit (Table 2).
Nickel (Ni): USP 232 limit 0.6 µg/g. Legal: 72% detection, range <0.05 to 4.7 µg/g; 2% exceeded the limit. Illegal: 78% detection, range <0.05 to 0.91 µg/g; 2% exceeded the limit (Table 2).
Copper (Cu): USP 232 limit 3.0 µg/g. Legal: 100% detection, range 3.7 to 64 µg/g; none exceeded the limit at the assumed consumption rate. Illegal: 100% detection, range 2.6 to 24 µg/g; 98% of samples exceeded the limit (Table 2). Note: copper is an essential element and the USP 232 inhalation daily PDE of 30 µg/day, applied at 10 g/day, sets this limit low relative to dietary intakes.
Molybdenum (Mo): USP 232 limit 1.0 µg/g. Legal: 98% detection, range <0.10 to 9.9 µg/g; 74% of legal samples exceeded the limit. Illegal: 100% detection, range 0.15 to 2.5 µg/g; 16% exceeded the limit (Table 2). The authors note molybdenum is an essential micronutrient and its prevalence may reflect soil molybdenum levels rather than contamination.
Barium (Ba): USP 232 limit 30.0 µg/g. Legal: 36% detection, range <3.00 to 40 µg/g; 2% exceeded the limit. Illegal: 38% detection, range <3.00 to 95 µg/g; 2% exceeded (Table 2).
Metals not detected in either group: antimony (Sb), gold (Au), selenium (Se), silver (Ag), thallium (Tl).
Methods (brief)
ICP-MS/MS (Mars 6 microwave acid digestion); 18 metals panel aligned with USP 232. LOD values in Supplementary Tables 1 and 2. CRM recovery data not stated in the main paper text. USP 232 concentration limits applied at an assumed consumption rate of 10 g/day (oral and inhalation routes combined).
Evidence fitness
This study directly measures metal concentrations in dried cannabis inflorescences from both regulated and unregulated Canadian market sources. It supports occurrence profiling for lead, cadmium, total arsenic, total mercury, total chromium, and nickel in dried cannabis flower. The USP 232 limit exceedance percentages are based on a 10 g/day consumption assumption; different daily-dose assumptions change the exceedance rates. Copper and molybdenum exceedances require interpretation in context of their essential-element status and the inhalation PDE basis. Arsenic speciation is not reported; the total arsenic values cannot be used as inorganic arsenic measurements.
Limitations
Sampling year, specific cultivar details, and soil provenance are not reported. The 50/50 split is by design and does not represent the market share of legal versus illegal product. LOD/LOQ values are in supplementary materials not extracted here. CRM and recovery data are not stated. Arsenic is total arsenic only.
Related evidence
- Cannabis flower / dried herb
- Vape cartridges and hardware
- Lead
- Cadmium
- Arsenic
- Mercury
- Chromium
- Nickel
Update history
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