# Mycotoxins

> Mycotoxins are toxic compounds made by certain moulds, such as aflatoxins and ochratoxin A from Aspergillus and Penicillium species; cannabis labs test for them at parts-per-billion levels.

- Canonical: https://genetixbay.com/knowledge/glossary/mycotoxins.html
- Also written: mycotoxin, aflatoxins, aflatoxin, ochratoxin A, aflatoxin B1, mycotoxin panel
- Glossary category: Lab testing · Evidence: Established
- Status: Draft: awaiting expert review · Updated: 2026-10-31
- Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay cannabis glossary"

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](https://genetixbay.com/knowledge/glossary/irradiation.md), doesn't destroy toxin already made.

## In practice

Testing is by [LC-MS/MS](https://genetixbay.com/knowledge/glossary/lc-ms.md), 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](https://genetixbay.com/knowledge/glossary/water-activity.md), and with damp, compressed material. The best [prevention](https://genetixbay.com/knowledge/glossary/cultural-control.md) is upstream: good airflow, controlled drying, cure to a stable moisture and store cool.

## Units and formula

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](https://genetixbay.com/knowledge/glossary/botrytis.md)* is the common grey mould, not a major aflatoxin producer.
- **Endotoxins**: bacterial cell-wall compounds, a separate category.

## Related terms

[Microbial testing](https://genetixbay.com/knowledge/glossary/microbial-testing.md), [LC-MS](https://genetixbay.com/knowledge/glossary/lc-ms.md), [Water activity test](https://genetixbay.com/knowledge/glossary/water-activity-test.md), [COA](https://genetixbay.com/knowledge/glossary/coa.md), [LOD](https://genetixbay.com/knowledge/glossary/lod.md)

## Read more

- [Long-term storage: keeping cured flower potent and aromatic](https://genetixbay.com/knowledge/harvest-cure/long-term-storage.md)
- [Botrytis (bud rot / grey mould) in cannabis](https://genetixbay.com/knowledge/diseases/botrytis-bud-rot.md)