Posted: November 2014
Long-Term Toxicity of a Roundup Herbicide and a Roundup-Tolerant
Genetically Modified Maize
A long-term study claiming to show toxic effects on rats of the herbicide
Roundup and genetically modified (GM) Roundup-tolerant maize (corn) was
originally published in 2012 (Seralini et al. 2012). It roused significant
controversy. The journal retracted the article — although it had been
peer-reviewed and elicited no “red flags” during the review process. The
authors stood by their findings. In 2014, this study was re-published in a
different journal (Seralini et al. 2014).
While some of the results of this study are striking, especially the
report of toxic effects of small amounts of the herbicide Roundup
(glyphosate) in the rats’ drinking water, we also believe that the
interpretation of the findings is difficult especially because of the
small number of rats used in the study (10 rats per test group). (Other
studies on feeding toxicity share some of this study’s shortcomings; see
Meyer and Hilbeck 2013; and
Nonetheless we feel that in the interest of open communication, and
because the study was carried out by qualified scientists and was
peer-reviewed, we should include it among the studies on the unintended
effects of genetic manipulation.
Meyer, H. and A. Hilbeck (2013). “Rat Feeding Studies with Genetically
Modified Maize — A Comparative Evaluation of Applied Methods and Risk
Assessment Standards,” Environmental Sciences Europe vol. 25,
no. 33. Available online:
Séralini, G. E., E. Claire, R. Mesnage et al. (2012). “Long Term Toxicity
of a Roundup Herbicide and a Roundup-Tolerant Genetically Modified Maize,”
Food and Chemical Toxicology vol. 50, pp. 4221–31.
Séralini, G. E., E. Claire, R. Mesnage et al. (2014). “Republished Study:
Long Term Toxicity of a Roundup Herbicide and a Roundup-Tolerant
Genetically Modified Maize,” Environmental Sciences Europe vol. 26.
Séralini, G. E., R. Mesnage, N. Defarge et al. (2013). “Answers to
Critics: Why There Is a Long Term Toxicity Due to a Roundup-Tolerant
Genetically Modified Maize and to a Roundup Herbicide,” Food and Chemical
Toxicology vol. 53, pp. 476–83.
Information on the retraction of Seralini et al. 2012 at:
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