Heavy metals in CBD: what limit for flower or hash?

Commission Regulation (EU) 2023/915 of 25 April 2023 replaced Regulation (EC) No 1881/2006 and sets maximum levels for contaminants in foodstuffs. Section 3, "Metals and other elements", deals with lead (3.1), cadmium (3.2), mercury (3.3), arsenic (3.4) and inorganic tin (3.5).

The only mention of hemp is in section 2.6, on Δ⁹-THC equivalents: 3.0 mg/kg for hemp seeds and processed seeds, 7.5 mg/kg for hemp seed oil. Flower and resin have no line at all, for THC or for metals. This is consistent with French practice, where CBD flower or hash is not sold as food. For these products the applicable value is the French 0.30% Δ⁹-THC threshold, explained in our article on the legal THC level.

With no dedicated line, a laboratory compares its results with the nearest category. The analyst makes that choice, no law imposes it, and the certificate should say which category was used.

For lead, the limits run from 0.20 mg/kg for cereals to 3.0 mg/kg for supplements, a factor of fifteen. A maximum level reflects the quantities consumed, and people eat far more cereals than supplements. It should not be read as a toxicity threshold.

Arsenic is a special case. Inorganic arsenic has a cap only for the products in points 3.4.1 to 3.4.4, namely rice and rice products, infant foods and fruit juices. Total arsenic is capped only in salt, at 0.50 mg/kg (3.4.5). Food supplements have no arsenic line, so a resin certificate claiming arsenic compliance "with the European regulation" cites a line that does not exist.

Health reference values are set by EFSA and expressed per kilo of body weight. In 2009 the agency fixed a tolerable weekly intake of 2.5 µg/kg for cadmium, with the kidney as the target organ. Such values are used to estimate a population's dietary exposure and cannot be applied to judge a single batch.

People smoke or vaporise CBD flower and hash, so the substance enters through the lungs and bypasses the digestive tract. Europe has no rule for that route in hemp. California wrote one for cannabis: its heavy metal testing regulation, 4 CCR § 15723, sets different action levels for inhaled and non-inhaled products.

Since one microgram per gram is one milligram per kilo, the columns can be read side by side. The Californian limit for an inhaled product sits six times below the EU "supplements" line for lead and five times below it for cadmium. At 1.2 mg/kg of lead, a batch passes the European reference and fails the Californian one.

Californian law has no force in France. Of the grids we were able to read, though, it is the only one designed for a cannabis product that is breathed in. When a laboratory applies it, you read the certificate against stricter limits.

Hemp draws elements out of its substrate and stores them, which is why it is used to clean polluted soils. One research team grew hemp in hydroponics at four cadmium inputs: 0, 2.5, 10 and 25 mg/L. The results appeared in 2023 in Frontiers in Plant Science and are open access.

With 2.5 mg/L in the solution, the roots held about 150 times more cadmium than the leaves. The flowers took some up as well: 8.7 and 7.6 mg/kg in the two experiments at 2.5 mg/L, then 66.2 and 25.5 mg/kg at 10 mg/L. According to the authors, hemp can accumulate cadmium in its flowers, and testing consumer products can matter.

The study has two limits. Its inputs were set high on purpose, and hydroponics differs from a field, so the figures cannot be extrapolated to a commercial batch. What it shows is a pathway: cadmium can reach the flower, so the flower itself needs testing as well as the soil. The product pages in the CBD flowers category state the growing method; that is context and no substitute for a measurement.

In ICP-MS (inductively coupled plasma mass spectrometry), the sample goes through an argon plasma and the elements are then sorted by mass. The NF EN 15763 standard describes how arsenic, cadmium, mercury and lead are determined this way in foodstuffs after pressure digestion. Digestion, where the plant material is dissolved in hot acid before injection, matters as much as the measurement.

Regulation (EC) No 333/2007 governs sampling and analysis in official controls. As the Commission's page on sampling notes, it first covered lead, cadmium, mercury, inorganic tin, 3-MCPD and benzo(a)pyrene. It was later extended to inorganic arsenic and nickel.

The limit of quantification (LOQ) is the lowest level a method can quantify with the required precision. Because it depends on the method and matrix together, it varies from one laboratory to the next. In section 2.6, Regulation 2023/915 itself follows a cautious convention and counts any value below the LOQ as zero when calculating levels. A certificate showing "< LOQ" is telling you "below the quantifiable level of this laboratory", and it never means "absent".

Run four checks, in this order.

1. Compare batch numbers: the one on the certificate must match the one on the pouch. A document with no batch number proves nothing about your product.
2. Look for the method, which should be ICP-MS for metals, with the standard followed. Metal results given without a method cannot be compared with anything.
3. Find the limit of quantification, element by element, in mg/kg. If it is missing, a "not detected" has no scale.
4. Check that the comparison category is named (food supplements, spices, Californian grid), since it decides the verdict.

You can also check accreditation. ISO/IEC 17025 accreditation, described on the Cofrac page, is granted test by test, so a laboratory accredited for cannabinoids may not be accredited for metals. Our guide to the scope of accreditation shows where to find this, and the article on pesticides applies the same method to the other block of contaminants.

On Phytogrammes, the product pages for resins and flowers give a batch reference and a reference cannabinoid profile. They show no metal results, and as of 18 October 2026 no laboratory certificate is published on them. For a line-by-line reading of a full certificate, see our guide how to read a certificate of analysis. The laboratory page describes the measurement methods.