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Heavy metals

Cannabis products require testing for heavy metals, which are generally considered toxic and carcinogenic. Cannabis plants can draw them up from soil, and while trace amounts of some heavy metals, such as copper, selenium, and zinc, are needed for healthy functioning in the body, high amounts of them can cause poisoning.

“Cannabis and hemp are powerful bioaccumulators because they draw heavy metals and other toxins out of soil and into their roots.”

What are heavy metals?

Heavy metals are a class of metals and metalloids with a heavy atomic weight and a density at least five times greater than water. Examples of heavy metals include: arsenic, cadmium, copper, chromium, iron, lead, mercury, nickel, palladium, platinum, silver, and zinc. 

Cannabis testing regulations in a majority of states only require testing for arsenic, cadmium, lead, and mercury, though every state is different in limiting the amount of each chemical in cannabis products, and some states require testing for additional heavy metals. Heavy metals naturally occur in the Earth’s crust, in water, and even in air. In addition to natural sources, many human activities contribute to heavy metal pollution of the environment, including driving cars, mining, agriculture, industrial discharge, and much more.

In very small doses, some heavy metals—such as copper, selenium, and zinc—are needed in the body for healthy functioning, but high amounts of those same metals can cause poisoning. Generally speaking, heavy metals are considered toxic and most are carcinogenic, even at very low doses. Heavy metal toxicity has been linked to organ damage and is considered a significant public health hazard by numerous government agencies. 

Heavy metals can get into our bodies through numerous ways, including drinking water contamination (as in Flint, Michigan), food sources (mercury in fish), and household contamination (lead in paint). Once heavy metals enter the body, they will bioaccumulate and remain until they can be metabolized, which will not likely happen in cases of prolonged heavy metal exposure, such as with contaminated drinking water. 

Cannabis is a powerful bioaccumulator, and cannabis and hemp plants can draw numerous types of toxins from soil, including heavy metals. Hemp’s potential as a potent bioaccumulator is wonderful in environmental clean up, as it can be used to clean up industrial pollution, but it is a double-edged sword: Since cannabis can draw numerous toxins from the soil into the plant itself, it is critical that cannabis plants are grown in a medium free of heavy metals and other toxins. Cannabis and hemp products must be tested for heavy metals, pesticides, and other toxins before consumption.