Criticizing the Séralini study on the grounds that it does not meet the criteria for a carcinogenicity study is equivalent to criticizing a cat for not being a dog.
According to Dr Hayes’ retraction statement, retraction was justified because “The low number of animals, and the strain selected, rendered the conclusions unreliable.”[1]
Other critics of the study, including the European Food Safety Authority (EFSA),[2] have voiced the same views.
However, these arguments are specious and derive from the false premise that Séralini and colleagues conducted a carcinogenicity study – which they did not. The authors clearly stated in the title of the paper and in the introduction that this was a long-term (chronic) toxicity study, not a carcinogenicity study.
Indeed, the authors affirmed the need to follow up the tumour observations in a separate, dedicated carcinogenicity study, which would include a larger sample size, in their “Answers to Critics”,[3] published in FCT prior to the retraction decision.
Carcinogenicity studies have a different design from chronic toxicity studies. They require larger groups of animals,[4] typically 50 per sex per group. This is in order to achieve statistical significance – a higher degree of certainty or conclusiveness – in their results, and also to prevent a “false negative” conclusion: that is, failing to find a rare toxic effect because too few animals are used.
Chronic toxicity studies such as Séralini’s require fewer animals. For example, the OECD chronic toxicity protocol no. 452 recommends 20 animals per sex per group but only requires 10 per sex per group to be analyzed for blood and urine chemistry.[5] This is the same number of animals that Séralini used in total and the same number that Monsanto analyzed for blood and urine chemistry in its 90-day study on the same GM maize.[6]
The Sprague-Dawley strain of rat used by Séralini and colleagues is routinely used for chronic toxicity and long-term carcinogenicity studies performed by both industry and academic scientists.[7]
Criticizing the Séralini study on the grounds that it does not meet the criteria for a carcinogenicity study is equivalent to criticizing a cat for not being a dog. It is an irrelevance that diverts attention from the importance of the toxicological findings.
[1] Hayes AW (2013). Food and Chemical Toxicology editor-in-chief, A. Wallace Hayes, publishes response to Letters to the Editors. 10 Dec. http://www.elsevier.com/about/press-releases/rese...
[2] European Food Safety Authority (EFSA) (2012). Review of the Séralini et al. (2012) publication on a 2-year rodent feeding study with glyphosate formulations and GM maize NK603 as published online on 19 September 2012 in Food and Chemical Toxicology. EFSA Journal 10(10): 2910.
[3] Séralini GE et al. (2013). Answers to critics: Why there is a long term toxicity due to NK603 Roundup-tolerant genetically modified maize and to a Roundup herbicide. Food and Chemical Toxicology 53: 461-468.
[4] Organisation for Economic Cooperation and Development (OECD) (2009). OECD guideline no. 451 for the testing of chemicals: Carcinogenicity studies: Adopted 7 September 2009.
[5] Organisation for Economic Cooperation and Development (OECD) (2009). OECD guideline no. 452 for the testing of chemicals: Chronic toxicity studies: Adopted 7 September 2009.
[6] Hammond B et al (2004). Results of a 13 week safety assurance study with rats fed grain from glyphosate tolerant corn. Food Chem Toxicol 42(6): 1003-1014.
[7] Meyer H and Hilbeck A (2013). Rat feeding studies with genetically modified maize – a comparative evaluation of applied methods and risk assessment standards. Environmental Sciences Europe 25(33). Online publication prior to print.
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