Metals such as mercury, cadmium, chromium, barium, aluminum are widely dispersed in the environment, and contaminate environmental compartments, like water, agricultural soils to varying degrees. Cannabis has been found to readily accumulate metals from contaminated soils. Metals can be recovered by acid leaching after cannabis harvesting.
The American Herbal Products Association (AHPA 2013) has proposed the following levels as maximum quantitative limits for orally consumed herbal products:
- Arsenic (As): 10.0 μg/day
- Cadmium (Cd): 4.1 μg/day
- Lead (Pb): 6.0 μg/day
- Mercury (as Me-Hg): 2.0 μg/day
Moreover, there are other mostly heavy metals tested:
- Nickel (Ni),
- Baryum (Ba),
- Strontium (Sr),
- Aluminum (Al).
Testing method consist of total acid leaching, followed by ICP-MS.