Professor Gilles-Eric Séralini and his research team at the University of Caen, France carried out their chronic toxicity study to investigate the long-term effects on rats of feeding the Monsanto genetically modified (GM) maize NK603 and low levels of the Roundup herbicide it is engineered to tolerate. The study lasted two years, around two-thirds of the rats’ natural lifespan.
The study was the first and only investigation of the long-term effects of this variety of GM maize (called NK603), grown with and without the pesticide Roundup, which the maize is engineered to tolerate during cultivation. Roundup was also tested alone in drinking water. Doses of Roundup started within the range of levels permitted by regulatory authorities in drinking water and as residues in GM feed.
The study was carried out using two hundred rats fed a standard balanced diet. They were divided into ten groups, each containing ten males and ten females.
The effect of NK603 maize alone was tested on three groups of rats. Each group had a different proportion of NK603 in their feed, starting at 11%, then 22%, and finally 33% of the total diet.
The effect of NK603 maize, which had been sprayed with Roundup in the field at the same proportions of 11%, 22% and 33% of their total diet, was tested on three groups.
Roundup alone, administered via drinking water at three different concentrations, was tested on three groups. Doses were as follows:
• The lowest dose corresponded to contamination found in some tap water
• The mid dose corresponded to the maximum level permitted in the US in GM feed
• The highest dose was half the strength of Roundup when diluted for use in agriculture.
The control group of ten male and ten female rats was fed a diet containing 33% of non-GM maize and plain drinking water.
The researchers took blood and urine samples for analysis monthly for the first three months and then every three months. At the end of the trial they studied 30 organs from each rat.