Mexico’s Precaution on GM Corn Safety Is Justified

A Presidential decree has banned the use of genetically modified (GM or genetically engineered) corn for food in Mexico. But the governments of the United States and Canada are using the U.S.-Canada-Mexico trade agreement (USMCA) to challenge Mexico’s actions.

The purpose of Mexico’s restrictions on GM corn is to safeguard the integrity of native corn from GM contamination and to protect human health. The purpose of the U.S. and Canadian challenge is to defend the interests of the biotechnology industry.

The U.S. and Canada want to force Mexico to open its market to all genetically modified foods and seeds. Canada is supporting the U.S. challenge (as a third party in the dispute) even though Canada does not export any corn to Mexico.

Mexico has the right to restrict the use of GM corn. The U.S. argues that Mexico’s actions are not based on scientific principles, but the government has sufficient science to justify its precautionary policies.

Our organization, the Canadian Biotechnology Action Network, is a large network of farmer and environmental groups that has been monitoring the use of genetically modified organisms (GMOs) for over 15 years, and we support Mexico’s restrictions. We were one of two Canadian groups that were given permission to send expert comments on the risks of GM corn to the arbitration panel in this dispute, but in January, Canadian groups were uninvited at the request of the U.S. government, supported by Canada, on the technicality that the dispute is just between the U.S. and Mexico.

We published our analysis anyway, to show that Mexico’s ban is supported by the science. Research continues to find indicators of potential harm to humans from eating GM insect-resistant corn. The science also continues to warn of health impacts from exposure to the herbicide glyphosate which is used in GM corn production.

Most GM corn plants are genetically modified to kill insect pests. The GM plants express a toxin from the soil bacteria Bacillus thuringiensis (Bt) that is known to harm the guts of specific types of insects but not others. Farmers have long used Bt as a spray to kill pests but the Bt toxins in GM crops are different from this natural Bt in structure, function, and biological effects. In fact, peer-reviewed studies across the scientific literature continue to find that Bt toxins in GM plants can harm insects (spiders, wasps, ladybugs, and lacewings, for example) that are not the intended targets.

Just last year, new peer-reviewed studies further found impacts of Bt where there was assumed to be none. For example, a 2023 study conducted by a team of researchers from universities in Brazil and Colombia, funded by the Brazilian government, found Bt had many significant impacts on the health of wasps, even affecting the next generation. University researchers in China and Pakistan also found lower diversity of bacteria in the gut of wolf spiders exposed to Bt. This adds to a laboratory test published in 2023, funded by the French government, that found a particular Bt toxin disrupts normal growth and functioning of gut cells in fruit flies, raising the possibility that Bt toxins could harm the intestinal lining of animals, including humans.

To add to these results, a number of animal feeding trials also find that Bt toxins and GM Bt crops could have toxic effects on mammals. Toxic effects and indications of toxicity have variously been observed in the blood, stomach, small intestine, liver, kidney, spleen, and pancreas, as well as immune responses, though the mechanism is not clear from these studies. Critically, animal feeding studies are not required by the U.S. or Canadian governments in order to demonstrate GM food safety. In fact, there are very few long-term and multigenerational tests on animals in the scientific literature.

But Bt toxicity is not the only safety concern. GM corn production is also tied to the use of glyphosate and other herbicides that are linked to serious health problems including neurological diseases and some cancers. The International Agency for Cancer Research of the World Health Organization classifies glyphosate is a “probable human carcinogen” and, as successful lawsuits against Bayer/Monsanto demonstrate, there is ample evidence that direct exposure to glyphosate-based herbicides can result in non-Hodgkin’s lymphoma in particular. Critically, evidence also points to danger from exposure to residues in food which is the concern highlighted by Mexico in relation to GM corn.

This concern is particularly pressing because Mexicans eat more corn than anyone in the world, largely through minimally processed flour for tortilla. This is an entirely different way of eating GM corn from the diet of corn ingredients in highly processed foods in the U.S. and Canada. Mexico’s unique dietary exposure to GM corn requires Mexico to set its own “acceptable level of protection” from the risks.

In their submission to the trade dispute panel, the U.S. government argues that no adverse health effects on consumers have been found. However, with no monitoring of GM foods, there is no scientific basis for making this statement. There have been no post-market studies on human populations to determine if there have been adverse health effects and, without tracing or labelling of GM foods, such studies are not possible.

The U.S. and Canada essentially argue that if they have decided a genetically modified food is safe, then Mexico should agree.

In early March, Mexico’s formal defense of the GM corn ban will be published as part of the trade dispute process. Soon after, we’ll hear arguments from eight non-governmental groups who have permission to send comments. Those documents should make it clear that Mexico’s corn restrictions are backed by science and are justified in order to defend the future of corn and protect food safety.

Tags: Bacillus thuringiensis, United States, Canada, Mexico, GM, genetically modified corn, bacteria, USMCA