What are heavy metals?


Heavy metals are common environmental contaminants resulting from human industrial activities such as mining operations, industrial waste, automotive emissions, coal fired power plants and farm/house hold water run-off. They affect the water and soil, and become concentrated in plants, animals, pesticides and the sediments used to make fertilizers. They can also be present in low quality glass or plastic packaging materials that can leach into the final cannabis product upon contact. The inputs used by cultivators that can be contaminated with heavy metals include fertilizers, growing media, air, water and even the plant itself.


The four heavy metals tested in the cannabis industry:



Lead is one of the most widespread heavy metal contaminant in soils. It is highly toxic to living organisms. Lead has no biological function but can cause morphological, physiological, and biochemical dysfunctions in plants. Lead affects plants primarily through their root systems.



Arsenic is an environmental toxin that is found naturally in all soils. The main environmental exposure to arsenic for humans is through contaminated drinking water.  Arsenic is non-essential and generally toxic to plants. Roots are usually the first tissue to be exposed to arsenic.



Plants can be exposed to mercury either by direct administration as antifungal agents, mainly to crop plants through seed treatment or foliar spray, or by accident. The availability of soil mercury to plants is low, and there is a tendency for mercury to accumulate in roots, indicating that the roots serve as a barrier to mercury uptake



Cadmium is a heavy metal that is of great concern in the environment, because of its toxicity to animals and humans. Concentrations of cadmium can accumulate in plants that are not toxic to them, yet are toxic to the animals eating the plants. Heavy metals enter soils through addition of sludge, composts, or fertilizers.