Monsanto's safety testing of GM maize does not include neurobehavioural assessments. Apparently, these are "not considered appropriate for test articles like corn grain that has no history of producing neurotoxicological effects".. Presumably this reasoning would apply to most food crops.
However, the vast majority of GM crops are designed to accumulate glyphosate herbicide, and questions are emerging on the neurotoxicity of this chemical.
Parkinson's disease is one of the most common neurodegerative disorders. It's characterised by progressive nerve cell loss due to natural self-destruct mechanisms gone wrong in the cells.
A Chinese team, lead author Ya-xing Gui, noted that, while Parkinson's is certainly multifactorial, five pieces of independent evidence point to glyphosate as one of its causative factors. Gui therefore set about elucidating the mechanism of glyphosate's involvement.
His study used cultured embryological cells which had been induced to differentiate into neurone-like cells. Exposure of this nerve-cell model to glyphosate promoted programmed cell death which is how healthy cells clear themselves from tissues once their role there is complete. The herbicide also promoted a process of cell degradation which , in limited form, is thought to be a protective measure for adapting to stress, but in the case of Parkinson's disease, goes to the extreme of terminal self-digestion.
True to toxicological ideals, the lethal effects of glyphosate on the nerve cells were both time- and dose-dependent.
It's interesting to note that Gui's discovery of a link between Parkinson's and glyphosate pre-dates Nancy Swanson's analysis of deteriorating health in the US . Swanson's investigations revealed an uncomfortably close parallel between the rise in glyphosate usage and the year-on-year rise in deaths from Parkinson's disease.
Why has it taken so long for such proofs of harm from an agricultural chemical to emerge?
Could it be something to do the 'adjusting' the science to avoid finding the evidence of harm? For example:
- experimental exposures may be kept too brief (routinely not more than 90 days and often much less) for degenerative changes to become measurable
- as described in the first paragraph, excuses can easily be contrived to avoid measuring neurological effects
- the use of toxin-contaminated control populations and test materials will naturally veil the presence of warning responses [see 2]
 HOW MUCH DISEASE IS ROUNDUP CAUSING? - December 2014
 NO SCIENCE AT ALL - March 2015
- C. Healy, et al., 2008, Results of a 13-week safety assurance study with rats fed grain from corn rootworm-protected, glyphosate-tolerant MON 88017 corn
- Ya-xing Gui, et al., 2012, glyphsoate induced cell death through apoptotic and autophagic mechanisms, Neurotoxicology and Teratology 34
- Nancy L. Swanson, et al., 2014, Genetically engineered crops, glyphosate and the deterioration of health in the United states of America
Image credit: Michelle Tribe on Flickr