Timothy A. Wise
Senior Advisor, IATP

On March 5, Mexico delivered a stunning rebuke to U.S. trade officials who have claimed for years that Mexico’s restrictions on the use of GM corn in tortillas are not grounded in science and violate the countries’ trade agreement. “Mexico’s approach to biotechnology is not based on science,” stated US Agriculture Secretary Tom Vilsack in August when the U.S. government announced it was filing the formal trade dispute under the US-Mexico-Canada agreement (USMCA).

The Mexican government’s formal response was published by the USMCA secretariat, and it offers ample evidence to justify precautionary measures to protect Mexican consumers from potential health impacts of GM corn imported from the U.S. and residues of the pesticide glyphosate.

As the submission lays out in compelling detail, Mexico “demonstrates that the cultivation and consumption of GM corn have different negative effects on health, native corn and the environment.”

The trade dispute is now winding its way through a formal arbitration process expected to deliver a verdict in November. Mexico’s submission in the dispute is its response to the written claim filed by the U.S. in December, 2023, that Mexico’s prohibition of GM corn in tortillas, enacted by presidential decree early last year as a precautionary public health measure, violates the trade agreement.

As Mexico points out in its response, the policies barely affect trade or harm U.S. producers because they affect only 1% of US corn exports; the overwhelming share of those exports go to livestock feed. Mexico also offers voluminous scientific documentation of the potential health risks from GM corn and the herbicide glyphosate for a population that consumes ten times the amount of corn consumed by people in the U.S. That high consumption, in minimally processed ground corn products such as tortillas, dramatically raises the risks, which is partly why Mexico dismisses outright U.S. claims of safety based on U.S. experience with GM foods.

Mexico’s 200-page response, backed by more than 300 references, most from peer-reviewed academic sources, shows that:

  • The science presented by the U.S. in claiming GM safety is woefully out of date, much of it is from industry studies not supported by peer-review. Much of the evidence suffers from overt conflicts of interest with industry involvement. Mexico makes the case that the U.S. regulatory process is too lax to ensure that products are safe for Mexicans to consume at such high levels. As Mexico points out, the US offers not one peer-reviewed study that shows that it is safe to eat such large quantities of GM corn exposed to glyphosate in minimally processed form over a lifetime.
  • Mexico presents the science on public health in 30 detailed pages backed by hundreds of academic references. GM corn, especially Bt corn engineered to kill insect pests, can have adverse impacts on non-target animals, and not just insects. Mammals too have been shown to suffer damage to their digestive systems from a GM trait that kills its targets by attacking their guts. 
  • They also show that Mexican tortillas have been proven to be contaminated with GM corn and glyphosate, the latter in residues from treatments of GM corn engineered to tolerate the herbicide featured in Monsanto’s Roundup, now owned by Bayer. Mexico shows that even low-level exposures can have negative long-term health impacts.

“Far from there being a consensus on the safety of GMOs, scientific evidence points to different negative effects on health, native corn and the environment, derived from the cultivation and consumption of GM corn,” Mexico writes in its defense.

Mexico’s formal response is part of a USMCA dispute-settlement process expected to conclude late this year with a ruling by the three appointed arbitrators. The next step in the process involves submissions by non-governmental groups. Eight Mexican and U.S. NGOs will submit comments supporting different aspects of Mexico’s case. The biotech trade industry group BIO will be the sole commenter supporting the U.S. IATP maintains a resource page with background and updates on the dispute.