Heavy metals represent a major health risk to consumers. The FDA imposes strict limitations on the amounts of heavy metals that are allowed in our food and pharmaceuticals. Now the California Bureau of Cannabis Control has followed suit. Here’s how heavy metals end up in cannabis and how they affect human health.

How Do Heavy Metals Get into Cannabis?

Heavy metals are metallic elements that have a relatively high density. They’re a natural component of the Earth’s crust and can be found readily in soil. However, human activities such as mining and industrial agriculture can create pollution that leads to a concentration of heavy metals in surrounding soils.

When consumable plants like fruits, vegetables, and cannabis are grown in heavy metal-laden soil, the final product can be contaminated with unhealthy levels of heavy metals. Contaminated water, inorganic fertilizers, and low-grade pesticides are also possible sources of heavy metal contamination for cannabis.

Cannabis, in particular, is adept at absorbing heavy metals from the soil. That’s because cannabis is a bioaccumulator or phytoremediator. This means cannabis is highly effective at absorbing and retaining chemicals and elements like heavy metals from its environment.

Heavy Metals in Cannabis Pose a Health Risk

Bioaccumulation of heavy metals can be a useful feature for farmers looking to decontaminate their soil, but it’s bad news for cannabis producers. When cannabis absorbs and stores environmental contaminants like heavy metals in its stems, stalks, leaves, and flower, it poses a health risk to cannabis consumers.

Some heavy metals are more dangerous than others. The U.S. FDA highly regulates these heavy metal elemental impurities which “pose toxicological risks to patients without providing any therapeutic benefit.” Mercury, cadmium, lead, and arsenic are especially toxic, even in very small amounts.

Mercury exposure occurs through the skin or when mercury is consumed. Even small amounts can lead to loss of coordination, muscle weakness, loss of memory, and trouble speaking, hearing, and seeing.

Acute cadmium exposure can cause flu-like symptoms including chills, fever, and muscle pain, as well as damage to the lungs if inhaled. Chronic exposure causes kidney, bone, and lung disease.

Lead is toxic when inhaled or swallowed and no amount of lead exposure is considered safe. This heavy metal interferes with enzyme function. As a result, major organs such as the kidneys, heart, and brain will eventually fail with high enough exposure to lead.

Arsenic also affects nearly every major organ system in the body by inducing cell death. Acute arsenic poisoning results in vomiting and abdominal pain and chronic exposure can lead to heart disease and cancer.


Heavy metal exposure represents a major threat to public health. Unfortunately, the cannabis plant is particularly skilled at absorbing these toxic elements from the surrounding environment. That’s why the California Bureau of Cannabis Control requires all cannabis products to be tested for heavy metal contamination. At Encore Labs, we are equipped to run cannabis heavy metals testing to ensure your product is safe & compliant with the California cannabis testing lab regulations.