There is more and more scientific criticism over a study that claims that genetically modified maize causes severe diseases in rats, and this controversy shows no signs of abating any time soon. Gilles-Éric Séralini, molecular biologist at the University of Caen, France, is under intense scrutiny to report the full data behind his team’s findings that rats fed for two years with Monsanto’s glyphosate-resistant NK603 maize developed many more tumors and died earlier than control rats.
This study was run in collaboration with the Paris-based Committee for Research and Independent Information on Genetic Engineering (CRIIGEN) and also found that the rats developed tumors when their drinking water was spiked with glyphosate, the herbicide used in the GM maize. The study has had a profound impact in Europe, allowing those opposed to GM foods to voice their frustrations and leading some politicians to call for tighter regulations or outright bans of the maize.
The European Food Safety Authority in Parma, Italy and the German Federal Institute for Risk Assessment in Berlin issued initial assessments asserting that the study’s conclusions aren’t supported by the data presented. The biggest criticism Séralini faces is that his team only used ten rats of each sex in their treatment groups, which is similar to other studies running toxicity tests of GM foods. However, Séralini’s study was almost 2 years, which covered the entire lifespan of the rats. The Organization for Economic Cooperation and Development (OECD) states that at least 20 rats of each sex per group are needed for chemical toxicity studies, and at least 50 for carcinogenicity studies.
The study also used Sprague-Dawley rats, which reviewers noted are prone to develop spontaneous tumors. These kinds of rats are short-lived, and only one -third of males and less than one-half of females live to 104 weeks. Han Wistar rats have a greater survival rate at 104 weeks (70%) and fewer tumors. OECD guidelines state that for two-year experiments, rats should have a survival rate of at least 50% at 104 weeks. If they don’t, each treatment group should include more animals, at least 65 of each sex.
Given the low number of animals, and the spontaneous occurrence of tumors in Sprague-Dawley rats, there is a high probability that the findings are erroneous, states the EFSA report. There have been calls for the study to be retracted, as it could be a dangerous case of failure of the peer-review system.
Séralini states that he didn’t expect to find any differences in tumor incidences, since no other tests on GM foods had suggested a cancer risk. He released a book and film about the work. In an unprecedented move, the ethics committee of the French National Center for Scientific Research (CNRS) decided that the public-relations offensive led by Séralini was inappropriate for a high-quality and objective scientific debate, and reminded researchers working on controversial topics of the need to report their results to the public.
Sérlaini states that he won’t make any data available to the EFSA and the BfR until the EFSA makes public all the data underpinning its 2003 approval of NK603 maize for human consumption and animal feed. Others claim that he is being attacked in an extremely dishonest fashion by lobbies passing themselves off as the scientific community.
Reference: “Rat study sparks GM furore” by Declan Butler, 25 September 2012, Nature.