December 4, 2013 12:20PM

High‐​profile Paper Linking GMO Corn to Cancer in Rats Retracted

Global Science Report is a feature from the Center for the Study of Science, where we highlight one or two important new items in the scientific literature or the popular media. For broader and more technical perspectives, consult our monthly “Current Wisdom.”


About a year ago, a major paper appeared in a high-profile scientific journal, Food and Chemical Toxicology, claiming a link between genetically modified corn and cancer in rats. The findings were published by a research team led by Gilles-Éric Séralini of the University of Caen in France. It was widely trumpeted by people opposed to genetically modified organisms (GMOs).

Simply put, making a GMO dramatically accelerates the normally slow process of traditional plant breeding, which takes many generations to stabilize some desired new trait in the plant genome, making the philosophical objections to it seem somewhat naïve.

While Séralini’s finding was heralded by anti-GMO activists as an “I told you so,” the paper was promptly, harshly, and widely criticized by geneticists and the general scientific community, many of whom lobbied the journal directly to address the shortcomings in the paper.

The most stinging criticism is going to sound painfully like what we see so often in environmental science, where researchers purposefully design an experiment likely to produce a desired results. Two months ago we documented a similar process that pretty much guaranteed that the chemical currently the darling of green enrages, bisphenyl-A, would “cause” cancer.

In Seralini’s case, the research team used a strain of rats with a known strong proclivity to develop cancer if left to age long enough, which is what they allowed, obeying the maxim that “if you let something get old enough, it will get cancer.”

After an about a year-long investigation into the Séralini results, the editor-in-chief of Food and Chemical Toxicology determined that the findings in the Séralini et al. paper were not methodologically sound enough to support to the conclusions forwarded by the authors. The journal consequently asked the Séralini authors to withdraw the paper. After their refusal to do so, the journal took the unusual step last week of retracting the paper itself, justifying:

The low number of animals had been identified as a cause for concern during the initial review process, but the peer-review decision ultimately weighed that the work still had merit despite this limitation. A more in-depth look at the raw data revealed that no definitive conclusions can be reached with this small sample size regarding the role of either NK603 or glyphosate in regards to overall mortality or tumor incidence. Given the known high incidence of tumors in the Sprague-Dawley rat, normal variability cannot be excluded as the cause of the higher mortality and incidence observed in the treated groups. Ultimately, the results presented (while not incorrect) are inconclusive, and therefore do not reach the threshold of publication for Food and Chemical Toxicology.

Glyphosate is the active ingredient in Roundup, a potent herbicide with little field-demonstrated toxicity in humans. It is used in huge quantities in modern, “no-till”  agriculture, in which the soil surface is never broken with a plow.  Seeds are “drilled” into the ground surrounded by the background vegetative litter, which, left to itself would soon yield a passel of choking weeds. But, by inserting DNA plasmids that render the crop resistant to Roundup’s toxicity, glyphosate becomes a “chemical plow” that kills the competing weeds while leaving the corn or soybeans to prosper. For what its worth, no-till is much more conservative of moisture, making crops less sensitive to long dry spells, and also “sequesters” carbohydrates which would normally oxidize into dreaded atmospheric carbon dioxide.

As a result, farmers pretty much swim in glyphosate. There’s also substantial exposure to suburban homeowners, who use it to spray down weeds that invade small cracks in blacktop and concrete driveways and sidewalks. There’s simply no evidence for increase cancer in these populations, which should have made anyone question Seralini’s finding at the get-go.

Séralini’s group is apparently now contemplating a lawsuit, claiming that the journal’s actions and criticisms were unacceptable. 

We hope this gets beyond “contemplation,” but that’s not likely. The pre-trial discovery process would  be interesting, to say the least.

The whole affair is full of fairly sordid details involving the anti-GMO movement, details which are laid out by the Genetic Literacy Project’s Jon Entine over at his blog. It is worth a read.

Almost surely, this will not be the last you hear about this study. Entine sees it playing out this way:

A court airing of this ugly episode now appears inevitable. Rumors abound that Séralini is already in contact with legal counsel and is set to pursue this issue in court, and perhaps in multiple courts. The disgraced scientist, in an attempt to rehabilitate his reputation, could also turn around and submit the article in its current or revised form to a third-tier journal, including the many pay-for-play publications that cater to activist scientists.

Stay tuned!