Food safety journal retracts article on 'cancer effect' of GM corn
Concern cited that the number of rats in study was too small and they were prone to cancer
A food safety journal has decided to retract a paper that seemed to show that genetically modified corn and the herbicide Roundup can cause cancer and premature death in rats.
The editor of the journal, Food and Chemical Toxicology, said in a letter to the paper's main author that the study's results, while not incorrect or fraudulent, were "inconclusive, and therefore do not reach the threshold of publication".
The paper, published 14 months ago, has been cited by opponents of biotech foods and proponents of labelling such foods. But it has been vociferously criticised as flawed, sensationalist and possibly even fraudulent by many scientists, some allied with the biotechnology industry.
The main author of the study, Gilles-Eric Siralini of the University of Caen in France, had done other studies challenging the safety of genetically engineered foods, some of which had also been questioned.
In his letter to Siralini, Wallace Hayes, the editor-in-chief of the journal, said that "unequivocally" he had found "no evidence of fraud or intentional misrepresentation of the data". He said that Siralini had co-operated in providing his raw data to a review panel formed by the journal.
However, Hayes said there was "legitimate cause for concern" that the number of rats in each arm of the study was too small and that the strain of rat used was prone to cancer. That made it difficult to rule out that the results were not explained by "normal variability", he said.
The letter was posted on the website of GMWatch, a British organisation that opposes genetically engineered crops. GMWatch called the journal's action "illicit, unscientific and unethical", saying that inconclusive data was not sufficient grounds for a retraction.
The study followed 200 rats for two years, essentially their entire lives. They were divided into 10 groups, each with 10 males and 10 females.
Some groups were fed different amounts of a Monsanto corn genetically engineered to resist the herbicide Roundup, also known as glyphosate. Some of the corn had been sprayed in the field with Roundup and some not. Some other groups were fed different doses of glyphosate in drinking water.
The rats that ate either the corn or the glyphosate tended to have more tumours and die earlier than the 20 rats in the control group, which were fed nonengineered corn and plain water.
The study passed the peer review process of the journal, which is considered one of the leading publications in toxicology. But many letters to the journal criticised the study, as did European food safety authorities.
Siralini and some other scientists had defended the paper in letters to the journal. They said that the same strain of rats had been used by Monsanto in its 90-day feeding study that led to European approval of the corn. They also said that, even though the rats had a high natural rate of cancer, what mattered was the difference in tumour incidence between the rats fed the corn or herbicide and the controls.