Heavy metals

Heavy metals are toxic elements, chiefly lead, arsenic, cadmium and mercury, that plants can absorb from soil and water and carry into finished products.

Hemp is efficient at drawing up elements from the soil, a trait that has been used to clean contaminated land, so metal content depends heavily on where and how the crop was grown. Extraction can concentrate whatever the plant contained. Processing equipment and packaging are additional, less common sources.

On a certificate of analysis, the heavy metals section lists each element with a measured value in parts per million or parts per billion, the method's reporting limit, and an action limit with a pass or fail indication. A pass means each element was below the limit chosen for that product type, and limits differ between ingested and topical products. The test is usually done by inductively coupled plasma mass spectrometry. Because pets are smaller and may consume products regularly, the same section is worth reading on an animal product.