Spotting adulterated hash: the signs, and what analysis says

Hash is the resin of cannabis or hemp: the trichome heads separated from the plant, then most often pressed. Adulterated hash is therefore neither a grade nor a category: it is an altered resin, one that contains, alongside the trichomes, material that has no business being there. Three situations can be distinguished, and confusing them muddles the reading.

The inert filler. It adds mass without changing anything else, and targets the weight sold. It lodges all the more easily when the starting material is already loaded with plant debris: our article on Moroccan hash and dry sifting in the Rif describes that mechanism of successive sieve passes.

The active adulterant. A psychoactive molecule is added to weakly dosed material to give it an effect. Since 2019, several European countries have observed resins and herbal material very low in delta-9-THC to which synthetic cannabinoids have been added, a family with no chemical kinship to it.

Contamination. It is not a deliberate addition but a consequence of manufacturing and storage conditions: moulds, bacteria, foreign bodies.

The European network of drug checking services, TEDI, published a joint survey in 2022: 1 142 samples sold as cannabis, in herbal, resin or e-liquid form, analysed by nine services spread across eight countries. 270 of them contained MDMB-4en-PINACA, a synthetic cannabinoid. All the cannabis samples concerned were below 1 % THC, and three serious incidents leading to hospitalisation were reported.

In France, the SINTES scheme run by the Observatoire francais des drogues et des tendances addictives has products collected from users analysed. Its Point no. 10, on the 2023 data, records 731 collections, of which 63 % matched the product they were assumed to be. Among the non-conforming ones, 42 % contained another psychoactive product, and adulteration was confirmed for 20 % of them, that is 47 cases against 21 the previous year. On cannabis, the OFDT recorded three adulterations of herbal material with synthetic cannabinoids in 2023: ADB-BUTINACA, MDMB-4en-PINACA, MDMB-BUTINACA. And of five collections presented as CBD, all contained ADB-BUTINACA.

The same report gives the contents recorded on the 29 resins analysed in 2023: a median of 30.0 % delta-9-THC, a central half of the values between 24.8 % and 33.4 %, a maximum of 47.0 %. The OFDT's overview gives the long-run trend: an average content that moved from 12.3 % in 2011 to 29 % in 2023, for 87 tonnes seized in 2023.

Finally, a study published in Forensic Science International in 2019 covered 90 resins bought on the street in the Community of Madrid. Its authors recorded foreign elements in 64.7 % of the bars and 30.2 % of the balls, and found 25 % of the samples to be deliberately adulterated. On the microbiology side, 93 % of the balls carried Escherichia coli against 29.4 % of the bars, and 10 % of the whole set carried Aspergillus. The authors conclude that 88.3 % are not fit for human consumption.

The most frequently cited clues, and their real worth.

The TEDI survey puts it another way: those 270 samples circulated as ordinary cannabis, and it was analysis, not appearance, that revealed the added molecule.

A second point makes visual examination moot, and it is structural. A clandestine market has no specification, no batch number and no traceability: by construction it escapes any verification, and two pieces of identical appearance may come from unrelated production. That is the fundamental difference with a product sold together with its batch analysis, where the constraint bears on the measurement and not on the appearance.

The word filtered describes a separation step, not an analytical result. Filtered hash is a resin whose trichomes have been sorted, dry on stacked sieves or in iced water on calibrated mesh. The operation removes plant debris. It does not remove a molecule added afterwards, says nothing about heavy metals or about pesticides coming from the plant, and is verifiable by nobody on the finished product. Outside a controlled channel, "filtered" is a sales argument; on a product page backed by a certificate, it is process information to be read alongside the measured contents.

White hash refers to a very pale resin, from light beige to cream. The shade comes from the starting material and from the process: a sift low in plant debris is pale, a resin that has been heated or pressed darkens. No source consulted links paleness to the absence of an adulterant. Commercial logic in fact runs the other way, with colour names serving to add value to a street product: our article on jaune mousseux shows how a name becomes an argument.

There remains the question of varieties. People commonly speak of varieties of Moroccan hash, but the names in circulation, special or double zero, are sifting grades, not botanical varieties. The variety, in the regulatory sense, concerns the plant: in 2024, 116 hemp varieties appear in the European common catalogue, the only list that opens the right to cultivation below the THC threshold.

A certificate of analysis does not bear on a product in general, but on an identified batch, produced on a given date. Four lines are worth checking before the rest: the laboratory and its accreditation, the batch number matching the one on the pouch, the cannabinoids quantified with their method, and the date of the report. The our laboratory page sets out the four blocks: cannabinoids, terpenes, heavy metals, pesticides.

Accreditation is the central piece. In France, the Cofrac accredits testing laboratories under the standard NF EN ISO/IEC 17025, and each accreditation holds for a defined scope, the list of tests actually covered. A laboratory accredited for other tests tells you nothing about the one you care about: the scope counts as much as the accreditation.

The French framework rests on two texts. The order of 30 December 2021 authorises only the varieties of Cannabis sativa L. listed in the common catalogue or the French catalogue, with a delta-9-THC content that is not higher than 0.30 %, a threshold it also applies to hemp extracts and to the products that contain them. The Conseil d'Etat, by its decision of 29 December 2022 (no. 444887), annulled the ban on selling raw flowers and leaves to consumers.

Phytogrammes sells only analysed hemp resins, below 0.3 % delta-9-THC on the finished product: that is the perimeter of the CBD resins and hash category, and the reason every product page links to its batch report. These products are reserved for adults and are not intended to be swallowed. Questions about batches and documents are gathered in the frequently asked questions.

• OFDT, SINTES Point no. 10 (2023 data, adulterations and contents)
• OFDT, cannabis: overview of current knowledge
• Oomen et al., cannabis adulteration with MDMB-4en-PINACA, International Journal of Drug Policy, 2022
• Perez-Moreno et al., Madrid resins, Forensic Science International, 2019
• Legifrance, order of 30 December 2021 (article 1, I and III)
• Conseil d'Etat, decision of 29 December 2022, no. 444887
• Cofrac, testing under the standard NF EN ISO/IEC 17025 and accreditation scopes
• European Commission, hemp: common catalogue and THC threshold