We, authors of the paper published in FCT more than one year ago on the effects of
Roundup and a Roundup-tolerant GMO (Séralini et al., 2012), and having answered to
critics in the same journal (Séralini et al., 2013), do not accept as scientifically sound
the debate on the fact that these papers are inconclusive because of the rat strain or
the number of rats used. We maintain our conclusions. We already published some
answers to the same critics in your Journal, which have not been answered (Séralini et
al., 2013).
Rat strain
The same strain is used by the US national toxicology program to study the carcinogenicity
and the chronic toxicity of chemicals (King-Herbert et al., 2010). Sprague Dawley rats are
used routinely in such studies for toxicological and tumour-inducing effects, including those
90-day studies by Monsanto as basis for the approval of NK603 maize and other GM crops
(Sprague Dawley rats did not came from Harlan but from Charles-River) (Hammond et al.,
2004; Hammond et al., 2006a; Hammond et al., 2006b).
A brief, quick and still preliminary literature search of peer-reviewed journals revealed that
Sprague Dawley rats were used in 36-month studies by (Voss et al., 2005) or in 24-month
studies by (Hack et al., 1995), (Minardi et al., 2002), (Klimisch et al., 1997), (Gamez et al.,
2007).Some of these studies have been published in Food and Chemical Toxicology.
Number of rats, OECD guidelines
OECD guidelines (408 for 90 day study, 452 chronic toxicity and 453 combined
carcinogenicity/chronic toxicity study) always asked for 20 animals per group (both in 1981
and 2009 guidelines) although the measurement of biochemical parameters can be
performed on 10 rats, as indicated. We did not perform a carcinogenesis study, which would
not have been adapted at first, but a long-term chronic full study, 10 rats are sufficient for that
at a biochemical level according to norms and we have measured such a number of
parameters! The disturbance of sexual hormones or other parameters are sufficient in
themselves in our case to interpret a serious effect after one year. The OPLS-DA statistical
method we published is one of the best adapted. For tumours and deaths, the chronology
and number of tumours per animal have to be taken into account. Any sign should be
regarded as important for a real risk study. Monsanto itself measured only 10 rats of the
same strain per group on 20 to conclude that the same GM maize was safe after 3 months
(Hammond et al., 2004).
The statistical analysis should not be done with historical data first, the comparison is
falsified, thus 50 rats per group is useless
The use of historical data falsifies health risk assessments because the diet is contaminated
by dibenzo-p-dioxins and dibenzofurans (Schecter et al., 1996), mercury (Weiss et al., 2005),
cadmium and chromium among other heavy metals in a range of doses that altered mouse
liver and lung gene expression and confounds genomic analyses (Kozul et al., 2008). They
also contained pesticides or plasticizers released by cages or from water sources
(Howdeshell et al., 2003). Historical data also come from rats potentially fed on GMOs, some
1
animal pellets in the world do indicate that. All that corresponds to the contamination levels
for which we have detected some effects in our treated rats versus appropriate controls.
2-year historical data mammary fibroadenoma rate from Charles River SD females ranged
from 13 to 62% (Giknis, 2004). We obtain a lot less in our controls, the real comparators, a
lot more in treated rats. This makes our results significant, like for deaths.
Double standards
A factual comparative analysis of the rat feeding trial by the Séralini’s group and the
Monsanto trials clearly reveals that if the Séralini experiments are considered to be
insufficient to demonstrate harm, logically, it must be the same for those carried out by
Monsanto to prove safety. Basically, all previous studies finding adverse effects of GE crops
have been treated by regulators with the attitude: only those studies showing adverse effects
receive a rigorous evaluation of their experimental and statistical methods, while those that
claim proof of safety are taken at face value. All studies that reported no adverse effects
were accepted as proof of safety regardless of these manifest (but deemed irrelevant)
deficiencies of their methods.
The review by (Snell et al., 2012) illustrates this issue. In the abstract, the authors state
"Results from all the 24 studies [reviewed] do not suggest any health hazards [...]" – taking all
those studies at face value. Yet in their review, the authors find numerous weaknesses of
similar or greater severity [than those] raised for the Séralini group's paper. For example, of
the 24 studies they evaluated 16 (67% of all studies) did not mention using the isogenic line
as control (interpreted as having not used them), many did not describe the methods in any
detail, and according to the reviewers had other deficiencies too.
FCT should retract the Hammond et al. paper on Roundup tolerant maize for all these
reasons, published for Monsanto’s authorization, or consider that each of these papers is
part of the scientific debate.
References
Gamez, R., Noa, M., Mas, R., Mendoza, N., Pardo, B., Menendez, R., Perez, Y., Gonzalez,
R.M., Gutierrez, A., Marrero, G., Goicochea, E., Garcia, H., Curveco, D., 2007. Long-term
carcinogenicity of D-003, a mixture of high molecular weight acids from sugarcane wax, in
Sprague Dawley rats: a 24 months study. Food Chem Toxicol 45, 2352-2358.
Giknis, M.L.A.a.C., C.B., 2004. Charles River Laboratories. Compilation of spontaneous
neoplastic lesions and survival in Crl:CD (SD) rats from control groups.
Hack, R., Ebert, E., Leist, K.H., 1995. Chronic toxicity and carcinogenicity studies with the
insecticide endosulfan in rats and mice. Food Chem Toxicol 33, 941-950.
Hammond, B., Dudek, R., Lemen, J., Nemeth, M., 2004. Results of a 13 week safety
assurance study with rats fed grain from glyphosate tolerant corn. Food Chem Toxicol 42,
1003-1014.
2
Hammond, B., Lemen, J., Dudek, R., Ward, D., Jiang, C., Nemeth, M., Burns, J., 2006a.
Results of a 90-day safety assurance study with rats fed grain from corn rootworm-protected
corn. Food Chem Toxicol 44, 147-160.
Hammond, B.G., Dudek, R., Lemen, J.K., Nemeth, M.A., 2006b. Results of a 90-day safety
assurance study with rats fed grain from corn borer-protected corn. Food Chem Toxicol 44,
1092-1099.
Howdeshell, K.L., Peterman, P.H., Judy, B.M., Taylor, J.A., Orazio, C.E., Ruhlen, R.L., Vom
Saal, F.S., Welshons, W.V., 2003. Bisphenol A is released from used polycarbonate animal
cages into water at room temperature. Environ Health Perspect 111, 1180-1187.
King-Herbert, A.P., Sills, R.C., Bucher, J.R., 2010. Commentary: update on animal models
for NTP studies. Toxicol Pathol 38, 180-181.
Klimisch, H.J., Deckardt, K., Gembardt, C., Hildebrand, B., Kuttler, K., Roe, F.J., 1997. Longterm inhalation toxicity of N-vinylpyrrolidone-2 vapours. Studies in rats. Food Chem Toxicol
35, 1041-1060.
Kozul, C.D., Nomikos, A.P., Hampton, T.H., Warnke, L.A., Gosse, J.A., Davey, J.C., Thorpe,
J.E., Jackson, B.P., Ihnat, M.A., Hamilton, J.W., 2008. Laboratory diet profoundly alters gene
expression and confounds genomic analysis in mouse liver and lung. Chem Biol Interact 173,
129-140.
Minardi, F., Belpoggi, F., Soffritti, M., Ciliberti, A., Lauriola, M., Cattin, E., Maltoni, C., 2002.
Results of long-term carcinogenicity bioassay on vinyl acetate monomer in Sprague-Dawley
rats. Ann N Y Acad Sci 982, 106-122.
Séralini, G.E., Clair, E., Mesnage, R. Gress, S., Defarge, N. Malatesta, M. Hennequin, D.
Spiroux de Vendômois, J. (2012) Long term toxicity of a Roundup herbicide and a Rounduptolerant genetically modified maize. Food and Chem. Tox. 50:4221-4231
Séralini, G.E., Mesnage, R., Defarge, N., Gress, S., Hennequin, D., Clair, E., Malatesta, M.,
Spiroux de Vendômois, J. (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
Chem. Tox. 53:461-468
Schecter, A.J., Olson, J., Papke, O., 1996. Exposure of laboratory animals to polychlorinated
dibenzodioxins and polychlorinated dibenzofurans from commerical rodent chow.
Chemosphere 32, 501-508.
Snell, C., Bernheim, A., Berge, J.B., Kuntz, M., Pascal, G., Paris, A., Ricroch, A.E., 2012.
Assessment of the health impact of GM plant diets in long-term and multigenerational animal
feeding trials: a literature review. Food Chem Toxicol 50, 1134-1148.
Voss, C., Zerban, H., Bannasch, P., Berger, M.R., 2005. Lifelong exposure to di-(2ethylhexyl)-phthalate induces tumors in liver and testes of Sprague-Dawley rats. Toxicology
206, 359-371.
Weiss, B., Stern, S., Cernichiari, E., Gelein, R., 2005. Methylmercury contamination of
laboratory animal diets. Environ Health Perspect 113, 1120-1122.
3