Change to mycotoxin risk assessment

Tests conducted on wheat samples by merchants and at mill intakes revealed the risk assessment was failing to identify loads exceeding the legal limits for mycotoxins. From February 2009, millers demanded that mycotoxin test results be supplied with every load of grain.

According to mycotoxins expert Dr Simon Edwards, Harper Adams University College, the risk assessment did not work well last season for two main reasons. First, the wet, delayed harvest had a major impact on mycotoxin levels and these conditions had not been experienced when the data used in the risk assessment was collected. Secondly, growers may have completed risk assessments incorrectly.

“Merchants and millers reported a high proportion of loads scored as ‘low risk’ in a high risk season,” says Dr Edwards.

False negatives

Evaluation of the risk assessment using harvest 2008 samples and comparison of risk scores with the actual mycotoxin content of grain samples showed too many false negatives – samples with a low or moderate risk score but exceeding mycotoxin legal limits.

“I’ve done retrospective risk assessments on samples that came in under the survey – the risk assessment didn’t work, even if you filled it in properly,” says Dr Edwards.

Changes have been made to the risk assessment to account for high rainfall pre-harvest. An additional risk level has been added for rainfall at flowering and risk scores for northern England and Scotland have been reduced, even when high rainfall occurs.

The new system has been tested using harvest 2008 samples. No false negatives (low risk but high mycotoxin content) were produced, but 36 per cent of samples produced false positives (high risk but low mycotoxin).

These results indicate the new system is more risk averse but the indication from industry stakeholders is that this is the preferred position, says Dr Edwards.

“We hope industry will revert to using the risk assessment. This will reduce the amount of testing required,” he says.

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