Combinatorial effects increase risks in food production

Currently, more than 90 different transgenic plants (events), or their harvest, have already been approved for import into the EU as food and feed. The European Food Safety Authority (EFSA) has in each case carried out a risk assessment as part of the individual approval procedure, including determining potential effects of the import and consumption of food and feed derived from genetically engineered plants on human, animal and environmental health. The aim of this procedure is to ensure that only those genetically engineered plants are approved which are safe for humans, animals and the environment, and which will not cause any consequential damage.

The cultivation of transgenic plants has led to an increase in herbicide-resistant weeds and the adaptation of pests. The answer of the biotech industry to these developments is to rearm transgenic plants by combining several genetic engineering traits in one plant (so-called ‘stacked events’). This has led to a veritable arms race in the fields, with individual varieties currently producing up to six insecticides and containing resistance to several herbicides. Stacked events now account for the clear majority of approvals, including in the EU. This also poses new challenges for the risk assessment of the food and feed produced from these plants, as interactions between multiple Bt toxins or pesticides are much more difficult to assess than the risks associated with individual active substances. The combinatorial effect of the individual insecticides and herbicides can also be mutually amplified under certain circumstances, whereby the possible health effects can exceed the sum of the individual substances. The effects can also be triggered indirectly if, for example, the composition of the microorganisms in the gut (microbiome) changes as a result of consuming these products. This is shown in numerous studies, especially for the broad-spectrum herbicide glyphosate. Amongst others, this could promote chronic inflammatory processes, e. g. in the gastrointestinal tract. Interactions can occur with the Bt toxins, amongst others, which are known to be capable of causing immune responses. So far, neither EFSA nor the industry have investigated any of these effects more closely. For example, the EU does not request empirical studies on the overall toxicity of ‘stacked events’, which typically contain mixtures of residues from spraying with various herbicides in combination with Bt-toxins produced by the plants. Mixtures of transgenic plants in food and feed are also not subjected to any additional risk assessment. Consequently, possible (negative) combinatorial effects of the various events in food and feed are being disregarded in the authorisation procedures.

Uncertainties with regard to the health risks of food and feed have increased since the introduction of genetic engineering – this is due to insufficient examination of combinatorial effects. The increasing number of approvals means that new cocktails of herbicide residues and insect toxins are also being imported with the plants. As a result, risks can accumulate unnoticed in the food chain, and thus lead to an increase in health problems when the corresponding products are consumed. Many metabolic or immune diseases in humans and animals have multiple and complex causes. It cannot be ruled out that the consumption of products from genetically engineered plants may play a part in this. More detailed, in-depth investigations are therefore essential. The introduction of plants from new genetic engineering also raises the question of how possible combinatorial effects can be assessed when consuming these plants.

Further information:
RAGES report

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