USA and South America: Mycotoxins found in maize cargoes


Published: 8 November 2012

We have recently been alerted by the London based consultancy firm CWA to an increased risk of problems with mycotoxins (poisons) found in maize cargoes of the 2012 harvest coming from the USA and South America.

CWA have recent experience of 3 different vessels which carried 2012 harvest maize from Argentina to Egypt, where unsafe levels of mycotoxins were found in the cargo. Although these toxins were only found in a few areas in the stow, due to their nature as a carcinogen (cancer-causing), the presence of the toxins will be considered to have contaminated the whole hold. All or parts of these shipments were correctly rejected by the Egyptian authorities.

Mycotoxins are toxins produced by some species of mold. These mycotoxins are some of the most toxic substances in existence. There are many different types, e.g. aflatoxins, fumonisins, ochratoxins and zearalenone. However, they are all produced by fungi growing on cereal grains. The toxins themselves are tasteless, odorless and cannot be seen by eye.

In normal seasons mycotoxin contamination is associated with wet conditions at harvest time when there is a delay in harvesting and drying the crop. It is at this time that the fungal spores, naturally present on all grains, are able to germinate and infect the kernel. The mycotoxins are a natural byproduct associated with the growth of the fungi.

However, this season in the USA and Argentina we are aware that there is another and greater risk of contamination of grains such as maize with mycotoxins. The crops in both of these countries were subjected to serious and widespread drought early in the season. When growing plants, such as cereals, experience drought conditions their natural resistance to fungal infection is weakened. The result is that the fungal spores present on the immature grains in the field are able to infect the developing grain and thereby contaminate them with toxins long before harvest.

This situation has been recognized this season by plant scientists in both North and South America. They are expecting widespread contamination in the cereal crops harvested in 2012 in these areas.

Problems with 2012 Argentinean maize cargoes have already been experienced by CWA. The expected problems with the 2012 North American harvest have been formally recognized by the United States Department of Agriculture. It has long been a established procedure that grain contaminated with the mycotoxin known as aflatoxin cannot be permitted to be blended with sound grain so as to dilute the level of aflatoxin present. This is because although there are established permitted maximum levels of aflatoxin allowed in food and feed grain for the purposes of trade it is acknowledged that there is in fact no truly safe acceptable level that has been proved to be harmless.

However on 19 October 2012 it was reported that six states in the USA have applied for and received government waivers to allow maize contaminated with more than the permitted level of aflatoxin in animal feed to be blended with sound cargo so as to reduce the overall content. This is an exceptional measure and demonstrates the extent of the problem with the current USA harvest.

Most countries have established maximum permitted tolerances for mycotoxins imports of maize and other cereals. Unfortunately, the toxins are very hard to test for. The GAFTA 124 standard, which is universally applied to cargoes of maize, is not rigorous enough to always be able to assist with detecting the toxins. This is because mycotoxins are not always uniformly present in a shipment. As such, shippers are likely to argue that they could not have known about the existence of the toxins, as they have carried out the usual sampling and testing. Nevertheless, this season's problems with mycotoxins, aflatoxin in particular, are now well known and it is possible that such a defence could be questioned.

There is an EU sampling protocol (Commission Regulation (EC) 401/2006) designed for detecting the presence of mycotoxins in grain cargoes. The sampling is more detailed and in-depth, which will of course take more time and be more costly. However with the recent occurrences of mycotoxins found in cargoes of maize, with further occurrences expected in the near future, shippers might consider applying the EU protocol on all maize cargoes shipped from drought affected areas.

Members should therefore ensure that all 2012 season maize cargoes being shipped from South and North America have undergone appropriate testing prior to it being shipped.

CWA are able to supply more information and guidance on the issues associated with mycotoxins in grain cargoes.

CWA International Ltd, London
David Walker
Food Department