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In a paper published in PLoS One and entitled ‘Laboratory rodent diets contain toxic levels of environmental contaminants: Implications for regulatory tests’, Mesnage et al. (2015) analysed commercial laboratory rodent diets for environmental contaminants and genetically modified organisms (GMOs). In samples from 13 different commercial rodent diets, the authors of the study report the presence of pesticides, heavy metals, polychlorinated dibenzo-p-dioxins and dibenzofurans, and GMOs.
There are several limitations with the methodological approach used by the authors, including insufficient information about the test material and methodology used, incomplete reporting of the data, and inappropriate interpretation of legislation and results. The vast majority of pesticides were absent (below the limit of detection), and where detected, the levels of pesticides, heavy metals and dioxins were only just above the limit of detection in the feed samples but below regulatory levels for feed and foodstuffs.
Only in a limited number of feed diets did the authors report levels of lead that exceeded the maximum levels specified by legislation for foodstuffs. The application of the ADI concept to claim the existence of a health risk in rodents or to demonstrate background levels of diseases or disorders in rodents has no scientific justification.
In an interview with Dr Samsel, the farmwars.info website reports on the presence of glyphosate in three different rodent diets. The information reported on the website is not supported by sufficient detail or a reference to permit a full scientific review. In conclusion, no new scientific elements were provided that would impact on the validity of regulatory feeding tests in the EU.