organicconsumers.org/articles/article_27540.cfm Monsanto has invoked “historical norms” to dismiss findings of increased tumours and mortality rates in rats fed GM maize NK603, as well as in rats exposed to levels of Roundup claimed by regulators to be safe, in a 2-year study by Professor Gilles-Eric Seralini’s research team in France. Monsanto says that the increased mortality rates and tumour incidence “fall within historical norms for this strain of laboratory rats, which is known for a high incidence of tumours”. By “historical norms” and “within this historical range”, Monsanto means historical control data – data from various other studies that they find in the scientific literature or elsewhere. However, the use of historical control data is an unscientific strategy used by industry and some regulators to dismiss statistically significant findings of toxicity in treated (exposed) groups of laboratory animals in toxicological studies intended to evaluate safety of pesticides, chemicals, and GMOs. The only scientifically valid control for such experiments is the concurrent control, not historical control data. This is because scientific experiments are designed to reduce variables to a minimum. The concurrent control group achieves this because it consists of animals treated identically to the experimental group, except that they are not exposed to the substance under study. Thus, the only variable is exposure to the substance(s) being tested – in the case of Seralini’s experiments, NK603 maize and Roundup. With this experimental design, any differences seen in the treated animals are very likely to be due to the substance being tested, rather than due to irrelevant factors, as is the case with historical control data. Historical control data consists of a wide range of data gathered from diverse experiments performed under widely differing conditions. As a result, factors totally irrelevant to the study are responsible for the majority of differences in historical control data. Such factors may include environmental conditions; different diet for the animals; different pesticide residue exposures; different genetic background of the animals; even different years in which the experiments were performed, which is known to affect results for reasons that are poorly understood. In contrast, using the concurrent controls reduces such variables to a minimum and enables researchers to reach evidence-based conclusions about the effects of the substance being tested.
Posted on: Wed, 22 May 2013 20:03:28 +0000
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