Heavy Metals of Concern in Cannabis
How It Enters the Plant: Contaminated soil, legacy pollution from leaded gasoline, low-grade fertilizers, hydroponic solutions, and processing equipment.
Affected Body Systems: Central nervous system, kidneys, and hematologic system.
Key Notes: Lead is a potent neurotoxin with no safe exposure threshold, especially dangerous for developing
How It Enters the Plant: Contaminated soil, legacy pollution from leaded gasoline, low-grade fertilizers, hydroponic solutions, and processing equipment.
Affected Body Systems: Central nervous system, kidneys, and hematologic system.
Key Notes: Lead is a potent neurotoxin with no safe exposure threshold, especially dangerous for developing brains. Its accumulation in cannabis plant tissues, particularly in flowers and leaves, poses a high-risk exposure for consumers.
How It Enters the Plant: Through contaminated soil, fertilizers, irrigation runoff, and uptake via plant roots.
Affected Body Systems: Kidneys, bones, and respiratory system. Cadmium is also a Group 1 carcinogen (IARC).
Key Notes: Cannabis readily absorbs and retains cadmium, with higher levels found in cannabis users’ blood and urine compa
How It Enters the Plant: Through contaminated soil, fertilizers, irrigation runoff, and uptake via plant roots.
Affected Body Systems: Kidneys, bones, and respiratory system. Cadmium is also a Group 1 carcinogen (IARC).
Key Notes: Cannabis readily absorbs and retains cadmium, with higher levels found in cannabis users’ blood and urine compared to non-users, even when accounting for tobacco exposure. Cadmium bioaccumulates, particularly in kidneys, and persists in the body for decades.
How It Enters the Plant: Through arsenic-rich soils, contaminated water, and pesticide residues.
Affected Body Systems: Skin, lungs, bladder (carcinogenicity); cardiovascular and neurological systems.
Key Notes: Arsenic exists in inorganic and organic forms, with inorganic arsenic (iAs) being the most toxic. However, most state cannabis reg
How It Enters the Plant: Through arsenic-rich soils, contaminated water, and pesticide residues.
Affected Body Systems: Skin, lungs, bladder (carcinogenicity); cardiovascular and neurological systems.
Key Notes: Arsenic exists in inorganic and organic forms, with inorganic arsenic (iAs) being the most toxic. However, most state cannabis regulations test for total arsenic, not its more harmful inorganic form.
How It Enters the Plant: Atmospheric deposition, hydroponic water systems, proximity to gold mining or coal plants.
Affected Body Systems: Central nervous system, kidneys, and developing fetal systems.
Key Notes: Mercury can exist in elemental, inorganic, and organic forms (methylmercury), all of which are toxic. Volatile forms may enter ca
How It Enters the Plant: Atmospheric deposition, hydroponic water systems, proximity to gold mining or coal plants.
Affected Body Systems: Central nervous system, kidneys, and developing fetal systems.
Key Notes: Mercury can exist in elemental, inorganic, and organic forms (methylmercury), all of which are toxic. Volatile forms may enter cannabis plants through environmental exposure and are particularly concerning when inhaled.
How It Enters the Plant: Via industrially contaminated soils and certain fertilizers.
Affected Body Systems: Respiratory tract (particularly from inhaled Cr(VI)), kidneys, and skin.
Key Notes: Chromium exists in multiple oxidation states; hexavalent chromium (Cr(VI)) is a known carcinogen, while trivalent Cr(III) is less toxic. Most state regulations do not distinguish between Cr species.
How It Enters the Plant: From industrial waste, natural ultramafic soils, fertilizers, and nutrient solutions.
Affected Body Systems: Respiratory tract, skin (dermatitis), and potentially carcinogenic to humans.
Key Notes: Nickel is efficiently taken up by cannabis roots and leaves. Despite its prevalence, it is not universally tested for i
How It Enters the Plant: From industrial waste, natural ultramafic soils, fertilizers, and nutrient solutions.
Affected Body Systems: Respiratory tract, skin (dermatitis), and potentially carcinogenic to humans.
Key Notes: Nickel is efficiently taken up by cannabis roots and leaves. Despite its prevalence, it is not universally tested for in-state regulations. Its presence in the plant is concerning due to its known allergenic and toxic effects.
