Stacking traits in GM plants has been found to cause unexpected effects, including synergistic effects, which are not investigated in regulatory authorisations. These changes could affect the safety of the GMO.

1. Comment on new study by Claire Robinson of GMWatch
2. Plain English summary of the new study
3. Effect of stacking insecticidal cry and herbicide tolerance epsps transgenes on transgenic maize proteome – study abstract

1. Comment on new study by Claire Robinson of GMWatch

An important new paper has been published that challenges regulators' lax approaches to assessing the risks of GM stacked trait crops.

In Europe, EFSA's approach to regulating stacked trait GMOs is arguably the most stringent in the world, as it requires a full risk assessment even if the single GMO parent varieties have already been approved. The new paper compares EFSA's approach favourably with that of Brazil's regulator, which does not require a full risk assessment if the parent varieties have been approved.

However, in Europe, the stacked trait GM maize SmartStax was approved for food and feed in November 2013 without an investigation of potential combinatorial and synergistic effects between the insecticidal toxins and the residues from herbicide spraying.

Also, EFSA does not require animal feeding studies with the complete stacked trait crop – only with the single-trait GM parent varieties. Testbiotech has reported on how industry and EFSA have systematically undermined the risk assessment of SmartStax maize.

Contrary to EFSA's view, experts from EU Member States such as Austria, Belgium and Germany have advocated the need to carry out feeding studies to test for synergistic effects.

Austrian experts describe it thus: “The safety of all newly expressed proteins in animal models applied simultaneously and combined was not assessed in the dossier. Insecticidal Cry proteins produced by GM plants as well as transproteins conferring tolerance to herbicides constitute a sum of new plant constituents possibly interacting within the organism. So far, there is absolutely no scientific knowledge about such those in the respective new combinations and possibly resulting additive and/or synergistic effects.”

Now a new study has found that stacking herbicide and insecticide transgenes in a stacked trait variety commonly available in Brazilian markets (not SmartStax) induces synergistic effects in the protein profile of the stacked trait GM plant. Also, metabolic pathways that might affect the safety of this stacked GM maize event were changed in the stacked trait crop when compared to the single-trait parent crops.

All this does not in itself prove that the GMO is dangerous. It does, however, show that the safety of stacked trait GMOs cannot be assumed from data on the single trait GMOs that went into a stacked variety. It also shows that each stacked GMO must undergo its own safety assessment and testing, including animal feeding trials. Otherwise new toxins, allergens, or altered nutritional value in the new stacked trait GMO could be missed.