Mycotoxins are secondary metabolites produced by some fungi. The ones cannabis labs usually test for are the aflatoxins (B1, B2, G1, G2), made mainly by Aspergillus flavus and A. parasiticus, and ochratoxin A, made by some Aspergillus and Penicillium species. They are heat-stable chemicals, so killing the mould, by heat or irradiation, doesn't destroy toxin already made.
In practice
Testing is by LC-MS/MS, reported in µg/kg (ppb). A typical panel lists each aflatoxin plus a total and ochratoxin A, with action limits in the low tens of µg/kg (limits vary; check local rules). Risk rises with warm, humid drying and storage above safe water activity, and with damp, compressed material. The best prevention is upstream: good airflow, controlled drying, cure to a stable moisture and store cool.
µg/kg = ppb (parts per billion). 20 µg/kg = 0.02 µg/g.
Don't confuse with
- Microbial count (TYMC): counts live mould; mycotoxins are its chemical residue.
- Botrytis bud rot: Botrytis cinerea is the common grey mould, not a major aflatoxin producer.
- Endotoxins: bacterial cell-wall compounds, a separate category.
Cannabis irradiation is treating harvested flower with ionising radiation, gamma, electron beam or X-ray, to cut microbial counts; permission and labelling rules vary.LC-MS couples liquid chromatography with mass spectrometry, identifying compounds by mass as well as retention time; it is used for pesticides, mycotoxins and detailed cannabinoid profiling.A 0-1 measure of how freely available the water in a material is; for dried cannabis flower the accepted range is about 0.55-0.65 aw.Pest and disease prevention by changing how the crop is grown, such as humidity, airflow, spacing, watering and cultivar choice, so pests and pathogens struggle to establish.Microbial testing counts or detects bacteria and fungi in a cannabis sample, including total aerobic count (TAMC), total yeast and mould count (TYMC) and specific pathogens.Botrytis cinerea, the fungus behind bud rot or grey mould, which rots dense colas from the inside in cool, humid conditions late in flower.A water activity test measures how much of a sample's water is free to support microbial growth, reported as aw from 0 to 1, with cured flower targeted around 0.55-0.65.A COA (certificate of analysis) is a lab's signed report of what it measured in a specific sample, such as cannabinoids, terpenes, moisture and contaminants, with methods and limits.The LOD (limit of detection) is the lowest amount of a compound a method can reliably tell apart from zero, but not necessarily measure accurately.
