PLENNY LEARN · CONTAMINANT TESTING
Read beyond the potency panel
Heavy metals in cannabis are evaluated with a separate laboratory test, not the THC percentage. To read the result, match the batch, find the named elements, check the units and reporting limits, and identify the specification used for the pass or fail decision.
By Plenny · Updated September 19, 2026 · 4 minute read
Which heavy metals are tested in cannabis?
Look for individual entries such as lead (Pb), cadmium (Cd), arsenic (As) and mercury (Hg). These four appear in California’s heavy metals testing requirements. Arsenic is technically a metalloid, but it is included in this testing category.
California’s July 2026 regulations, section 15723, require results in micrograms per gram and a pass/fail outcome. This is an example of one regulated program, not a rule that automatically applies to every hemp or cannabis report.
Each named element has its own result. Do not add different metals together to decide whether a panel passed.
A number needs a unit, such as µg/g. A bare decimal cannot be interpreted reliably.
The specification depends on the applicable program and product category.
How do heavy metals get into cannabis?
Cannabis can take up elements from its growing environment. NIST’s toxic-elements study describes hemp’s ability to accumulate elements from soil and the need for accurate measurements in plant materials and finished products.
That explains why testing matters. It does not prove that every plant is contaminated or that a particular growing method guarantees a clean result. A COA provides measurements for the submitted sample; it does not, by itself, identify where an element came from.
What do ppm, ppb and µg/g mean?
When the concentration is expressed as mass per mass, these units describe the same relationship at different scales:
1 ppm = 1 mg/kg = 1 µg/g
1 ppm = 1,000 ppb
The EPA’s unit-conversion explanation describes why milligrams per kilogram equal parts per million. One microgram per gram is the same mass fraction. Do not apply this conversion blindly to a result expressed per milliliter or to a different reporting basis.
Example: is 0.20 µg/g the same as 200 ppb?
Yes, for mass-based reporting:
0.20 µg/g = 0.20 ppm = 200 ppb
This is a fictional conversion example, not a safety limit or a real batch result. The larger-looking number in ppb does not mean the concentration increased.
What do ND, a number and pass actually mean?
Open each example before comparing two reports. Always use the laboratory’s own legend for qualifiers.
The result says ND. Does that prove zero metal?
No. ND generally means not detected under the method’s reporting convention. It does not establish absolute absence. Find the detection or reporting threshold and check how the lab defines the abbreviation.
The result is a number below the listed action limit.
You can compare the values only after checking that they use the same units and that the limit applies to the named element and product. Read the laboratory’s official outcome and any notes instead of replacing its decision with your own calculation.
The page says pass, but only lists THC and CBD.
A potency result does not provide a heavy metals result. Locate the actual contaminant panel or ask for the complete report. A missing panel is missing evidence; it is not the same as either a contaminant failure or a verified pass.
Is there one safe heavy metals limit for all cannabis?
No single number covers every element and product. California’s example distinguishes inhalable from non-inhalable goods. Health Canada’s production guidance also explains why intended use and route of exposure matter when selecting contaminant limits.
Use the current specification applicable to the actual product and testing program. A pass is a decision against that specification, not a promise of zero metal or an individualized medical assessment.
Keep the panels separate. A heavy metals pass does not establish that pesticides, microbes, mycotoxins or residual solvents passed. California’s testing overview lists these as distinct testing categories.
A five-point heavy metals COA checklist
If something is unclear, ask: “Which specification was used for this result, and can the laboratory confirm this report number and batch?” Use the laboratory’s independently verified contact details.
Common questions
Can a THC percentage tell me whether heavy metals were tested?
No. Potency and elemental contamination are different measurements. Find the named heavy metals results rather than inferring them from the cannabinoid panel.
Can I compare two ND results from different labs?
Only with their definitions and thresholds in view. Two reports can use ND while having different detection or reporting limits. The abbreviation alone does not show that the tests had equal sensitivity.
Does a result for one batch cover another batch of the same strain?
Do not assume that it does. Match the specific batch identifiers. A shared strain name is not a substitute for the report’s sample and batch information.
Keep learning
Sources and scope
Sources checked September 19, 2026. Regulatory examples are identified by jurisdiction and are not universal hemp requirements. This guide explains report terminology; it does not certify a product or supply a personal exposure assessment.
Chris Garcia, Owner and CEO
September 19, 2026
How this page is prepared: Plenny uses linked research and other relevant sources for educational explanations, and product details and batch COAs where relevant. General strain, flavor, and effect descriptions are not guarantees.
Commercial transparency: Plenny sells products discussed on this website. Educational pages are not medical or legal advice, and content is not medically reviewed unless a named licensed reviewer is shown.