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Mycotoxins are chemicals produced by fungi. Some fungi that grow on wheat plants or the grains themselves can produce these chemicals. Whilst naturally-occurring, excessive consumption of mycotoxins can have negative health impacts and consequently, the levels of these chemicals in grain is strictly regulated. Extensive monitoring of mycotoxins in wheat used by UK millers is carried out and the results show that the low levels do not pose a threat to consumer health.

T2 and HT2

T2 and HT2 are related mycotoxins also produced by Fusarium fungi. They can be found as natural contaminants in a range of cereals including wheat, barley, oats, maize and rye, but levels in wheat are usually very low.

The European Commission has set ‘indicative’ legal limits for T2/HT2 in cereals intended for human consumption and is currently discussing whether to set maximum limits. Since 2003, the presence of T2/HT2 in wheat used by UK millers has been routinely surveyed and the levels of these mycotoxins remains low in UK wheat samples.  UK Flour Millers will continue to monitor these mycotoxins. 


Ergot (Claviceps purpurea) is a fungal disease that affects wheat, barley, oats, rye, triticale and a wide range of grasses, particularly black-grass. It infects the grass ear at flowering and replaces a few spikelets with hard, black fruiting bodies (sclerotia).

Although ergot has very little effect on crop yields, the ergot alkaloids which are produced may have harmful effects on humans and animals.

Cleaning equipment on farms and in grain stores is effective at removing sclerotia from grain. Flour millers reject grain where ergot can be seen.

UK Flour Millers member companies demonstrate ‘due diligence’ by participating in a monitoring project which tests for ergot alkaloids in samples of milling grain. Results indicate that ergot alkaloid levels in wheat used by UK millers are extremely low.

EU limits for ergot alkaloids in processed cereal products came into effect from January 2022.

Ochratoxin A (OTA)

Ochratoxin A (OTA) is produced by the fungi Aspergillus ochraceus and Penicillium verrucosum. Its presence is normally associated with poor storage conditions rather than developing in the field. Prevention is achieved by drying and cooling grain promptly after harvest and ensuring that it remains in this condition throughout the storage period. Advice to farmers on how to minimise the risk of storage mycotoxins developing is available in the AHDB’s Grain Storage Guide. UK millers only purchase grain from farmers who operate under assurance schemes, in which they are expected to follow this guide.  This ensures the risk of grain containing high levels of OTA entering the food chain is minimised.

All UK flour millers remain vigilant and carry out ‘due diligence’ monitoring procedures (using rapid tests) to check for any potential OTA contamination when grain arrives at a mill.  If levels of OTA exceed the legal maximum, the grain is rejected. UK Flour Millers routinely surveys OTA levels in milling wheat using confirmatory methods as part of the AHDB monitoring project. These results show OTA contamination of wheat used my UK millers to be consistently low.

If consumed at high levels, OTA can have a destructive effect on the kidneys. The European Food Safety Authority (EFSA) therefore decided, in 2006, on a tolerable weekly intake (TWI) for OTA of 120 ng/kg bodyweight.

Owing to negative health effects if consumed in high quantities, legal limits are set for OTA in various foodstuffs as follows:

OTA graph.png
Deoxynivalenol (DON)

Deoxynivalenol (DON), sometimes called ‘vomitoxin’, is produced by several Fusarium species but most commonly in the UK by Fusarium graminearum and Fusarium culmorum, which cause fusarium headblight in wheat. The main risk factors for DON are rain at the time when crops are flowering and at harvest time.

In the UK risk is managed by several processes. Farmers can assess and manage the risk to their crops by following the AHDB’s risk assessment guide. An early warning system (CropMonitor) monitors the level of fusarium infection as the crop develops and is used to assess the potential risk across the UK.

When grain is delivered to UK flour mills, millers test the levels of DON as part of their due diligence procedures. The grain is rejected if the levels exceed the legal or contractual limit. A monitoring project is run by the AHDB which compares levels of DON in wheat each year using confirmatory methods.  The UK is not a high risk region for DON and this is reflected in the results from the mill testing and independent monitoring of grain, which shows that levels very rarely exceed the legal limits.

The EU set legal limits for the presence of DON in grain are as follows:
Unprocessed common wheat and barley    1250 DON (ppb)
Unprocessed durum wheat and oats    1750 DON (ppb)
Flour    750 DON (ppb)
Finished products    500 DON (ppb)
Infant food    200 DON (ppb)

The EU is currently considering changes to the DON maximum levels.

Zearalenone (ZON)

Zearalenone (ZON) is a mycotoxin produced by the fungi Fusarium graminearum, which is responsible for Fusarium head blight in wheat. The presence of elevated levels of ZON in grain is particularly associated with rainfall at harvest. 

Grain delivered to UK mills is tested (using rapid test kits) for ZON as part of millers ‘due diligence’ procedures.  If levels in the grain exceed the legal or contractual maximum, the grain is rejected. Additionally, a monitoring project is run by the AHDB which examines levels in grain as they are delivered throughout the season.  The presence of ZON in UK crops is usually low and this is reflected in the results from the mill testing and independent monitoring of grain.

Legal limits are established for the presence of ZON in grain, as follows:
Unprocessed common wheat and barley    100 ZON (ppb)
Unprocessed durum wheat and oats    100 ZON (ppb)
Flour    75 ZON (ppb)
Finished products    50 ZON (ppb)
Infant food    20 ZON (ppb)

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