Quality, lab testing & contamination — the knowledge hub
Cannabis is an agricultural product — it can carry pesticides, heavy metals, mold spores and, for extracts, residual solvents. A Certificate of Analysis (COA) from an accredited lab is the only reliable way to objectively demonstrate purity and potency. This hub explains how a COA is structured, which limits apply in Switzerland and internationally, which contaminants are most common, and how to recognise quality sensorially.
The analysis of contaminants in detail
Cannabis sativa is considered a pronounced bioaccumulator. The plant has the property of intensively absorbing pollutants, heavy metals, and pesticides from the substrate and accumulating them in the plant tissue. For laboratory analysis, this means that highly sophisticated methods such as mass spectrometry must be used to detect even the smallest traces of lead, cadmium, or persistent plant protection products. Without these precise measurements, the health risk for consumers remains invisible, as contamination is not reliably perceptible either visually or by smell. Reliable analyses thus ensure the purity of the final product.
Another critical field of quality control concerns microbiology. Insufficient drying or incorrect storage can cause moulds such as Aspergillus as well as hazardous mycotoxins to spread on the flowers. These biological contaminants pose a serious risk, particularly for patients with compromised immune systems. Professional laboratories therefore systematically test samples for colony-forming units and specific toxins. Compliance with strict microbiological limit values protects consumers from respiratory infections and chronic exposure to toxic fungal metabolites.
- Detection of heavy metals such as lead and arsenic using ICP-MS
- Screening for pesticide residues using LC-MS methods
- Determination of microbiological contamination such as yeasts and moulds
- Analysis of residual solvents in extracted products
Swiss regulation and regulatory oversight
In Switzerland, the quality control of cannabis is subject to clear legal requirements. A product is only not considered a narcotic within the meaning of the Narcotics Act (BetmG) if the total THC content is below one percent. This value is calculated from the sum of free THC and the precursor THCA, multiplied by the legally defined conversion factor. Federal authorities such as the BAG and the BLV are responsible for monitoring these limit values and general product safety, conducting random checks to ensure compliance with the legal framework in the market.
Since the amendment of the law in August 2022, medical cannabis can be prescribed by doctors in Switzerland without an exceptional permit from the BAG. These medical products are subject to the strict quality standards of the Pharmacopoeia and the guidelines of Swissmedic. In parallel, scientific pilot trials in various Swiss cities enable the controlled dispensing of recreational cannabis. These projects, which are under strict regulatory supervision, use comprehensive laboratory analyses to guarantee consistent quality and absolute freedom from contaminants for the participants. This generates valuable data for future regulated dispensing.
- Statutory limit of under one percent total THC according to the BetmG
- Oversight and coordination by the BAG, BLV and Swissmedic
- Facilitated access to medical cannabis since August 2022
- Strict quality requirements and laboratory testing in the ongoing pilot trials
Interpretation of Certificates of Analysis for Consumers
Understanding a Certificate of Analysis is essential for assessing product quality. Consumers should check whether the document was issued by an ISO/IEC 17025 accredited laboratory. A key aspect is the distinction between the limit of detection and the limit of quantification. Values lying below these limits are often declared as non-detectable in the certificate. A comprehensive certificate not only lists the cannabinoid content but also documents the absence of contaminants in detail to ensure maximum transparency.
In addition to the absence of contaminants, the certificate provides information on the specific cannabinoid profile. The exact determination of CBD, THC, and other accompanying substances enables precise dosing and assessment of the effects. Swiss providers who have their batches seamlessly analysed and make the certificates publicly accessible demonstrate a high degree of professionalism. The match between the batch number on the product and the number on the Certificate of Analysis is the decisive proof that the laboratory results are indeed valid for the product in question.
- Verification of laboratory accreditation according to the ISO/IEC 17025 standard
- Matching the batch number on the product and the certificate
- Differentiation between limits of detection and limits of quantification
- Verification of the complete cannabinoid profile for active ingredient determination
FAQ
How is the legally relevant total THC value calculated in Switzerland?
In Switzerland, the total THC content is decisive for legal classification. Since THC is predominantly present as an acid in the raw plant, the value is determined mathematically. The formula is: total THC equals free THC plus the product of THCA and the factor 0.877. If this total value is below 1.0 percent, the product does not fall under the Narcotics Act. If the value exceeds this limit, the product is considered an illegal narcotic, which can lead to legal consequences during inspections.
What quality differences exist between medical cannabis and over-the-counter CBD?
As medicinal products, medical cannabis is subject to the strict guidelines of Good Manufacturing Practice and is regulated by Swissmedic. Every batch must meet precisely defined pharmaceutical standards. Over-the-counter CBD products, on the other hand, are classified as food, cosmetics, or utility articles depending on their intended use. They are subject to the supervision of the BLV or cantonal laboratories. While seamless quality controls are mandatory for medical products, the frequency of inspections for CBD products varies depending on the manufacturer's self-regulation and cantonal enforcement.
What should be done if contamination of the product is suspected?
If contaminated products are suspected, consumption should be stopped immediately. Typical warning signs include an unusual smell, atypical burning behaviour or immediate respiratory discomfort. In the event of acute health problems or symptoms of poisoning, Tox Info Suisse provides medical advice around the clock via the emergency number 145. In addition, it is recommended to store the product safely for any subsequent laboratory tests and to report the incident to the responsible cantonal laboratory or the point of sale in order to protect other consumers.