Mexico – Measures Concerning Genetically Engineered Corn (MEX-USA-2023-31-01)

By Professor Michael Antoniou, King’s College London, UK
May 28, 2024

Expert testimony before the Panel established pursuant to Chapter 31 (Dispute Settlement) of the Agreement between the United States of America, the United Mexican States and Canada (USMCA)

Read the full report here.

Summary

This report provides an overview of key studies and other evidence on the toxicity of agents contained in genetically modified (GM) corn and other GM crops, including Bt/VIP insecticidal toxins and herbicide residues, in particular glyphosate. There is no intention to claim that all studies that have investigated the safety of GM crops show toxic or other adverse effects.

Nevertheless, this report compiles a large body of evidence from well controlled laboratory animal toxicity studies that show evidence of harm to multiple physiological systems. This shows that it is not possible to generalise about the safety of GM crops and that each individual variety needs to be tested.

Studies are presented that show major compositional differences between GM and non-GM crop varieties, including corn. These studies demonstrate that the GM transformation process can result in unintended compositional changes at both a protein and metabolite level, stemming from the DNA damaging effects of this procedure. Thus claims that GM foods are substantially equivalent to their non-GM counterparts and are therefore safe are not supported by the scientific evidence. These changes may have unknown health consequences for the consumer.

The report summarises findings from well controlled animal feeding studies, including some commissioned by industry to support regulatory authorisations, that show signs of toxicity from the consumption of GM corn and another GM crop (soy). These studies repeatedly show that the main organs and systems affected by the consumption of the GM food are the liver, kidneys, digestive tract, and immune system.

The report progresses to consider the health implications of glyphosate-based herbicide residues that will inevitably be present in GM glyphosate-tolerant corn and other crops. It is beyond the scope of this report to review the vast number of studies undertaken to investigate glyphosate herbicide toxicity. Instead the report summarises work by my own research group and others of particular relevance.

In studies on animals exposed to regulatory-relevant doses of glyphosate and commercial glyphosate-based herbicide formulations, adverse effects were observed in multiple organs and systems, including gut microbiome structure and functional 5 dysbiosis, oxidative stress in the gut and internal organs, non-alcoholic fatty liver disease, increased markers of genotoxicity (DNA damage), and carcinogenicity. It is particularly noteworthy that these toxic effects were more pronounced in animals exposed to the commercial glyphosate-based herbicide formulations than those exposed to glyphosate alone. This demonstrates the high degree of toxicity of the co-formulants present in these formulations, the composition of which is generally kept secret by manufacturers, and the residues of which are never monitored in foodstuffs by regulatory agencies.

In vivo toxicity studies of glyphosate and commercial glyphosate-based herbicide formulations presented in the report consistently demonstrate that the currently held regulatory “no observed adverse effect level” (NOAEL) for glyphosate, and by default, the acceptable daily intake level (ADI), is incorrect and set too high. Indeed, based on the current available evidence, the safe dose of glyphosate, when consumed over the long term, is unknown. The report also summarises key epidemiological studies. One such study has shown statistically significant associations between glyphosate-based herbicide use and non-Hodgkin lymphoma.

In addition, scientists have found links between occupational use of glyphosate-based herbicides and a marker of DNA damage (genotoxicity) called mosaic loss of chromosome Y (mLOY). mLOY has been associated with blood cancers such as lymphoma, myeloma, and leukemia, as well as with Alzheimer’s disease. Furthermore, in a study that analysed the urine of applicators of glyphosate-based herbicides, it was found that markers of oxidative stress were significantly elevated. This included the marker of oxidative stress known as 8-OHdG, which is also an indicator of direct DNA damage.

Furthermore, the report summarises studies that have investigated the toxicity of glyphosate in combination with other pesticides used on corn, all of which were administered to laboratory animals at the acceptable daily intake (ADI) dose. These mixtures of pesticides, including the glyphosate, resulted in numerous negative health outcomes. This shows that the regulatory practice of setting ADI values based on toxicity studies of individual pesticide active ingredients is invalid and puts public health at risk.
It is important to bear in mind that all the GM corn toxicity studies summarised in this report have tested single-Bt trait or single-herbicide-tolerance trait varieties. However, the current reality is that the vast majority of GM corn that will be imported into Mexico from the US will be stacked-trait varieties, engineered to contain multiple Bt/VIP toxins and herbicide tolerances. Without scientific foundation, regulators have assumed that the toxicity of the stacked-trait varieties is no greater than the toxicity of any individual Bt/VIP or the residues arising from an individual herbicide tolerance trait.

In conclusion, this report provides evidence that Mexican citizens will be exposed to multiple types of toxicity from the consumption of imported US GM corn. This combinatorial source of toxicity has not been properly addressed by regulators. The health implications of this regulatory oversight for Mexican citizens are unknown. However, based on the evidence presented in this report, the consumption of imported US GM corn at the high levels typical for Mexican citizens has the potential to result in serious negative health outcomes.

Read the full document here, Expert report on the toxicity of agents contained in genetically engineered corn and the health risks associated to its consumption