Genetically modified (GM) crops are the subject of heated debate. It was in the late 1980s that scientists first proposed the use of transgenic methods - involving the introduction of desirable genes into food crops - in order to improve yields, shelf-lives and resistances to pesticides and herbicides. Since then, the scientific community has made major advancements which have improved our understanding of genetics and, in the wake of this ever-improving knowledge, concerns have been raised about the health implications of genetically modified crops. Critics worry that the safety and quality of crops may be compromised and may pose threats to the health of animal and human consumers (Newman, 2013).

Should we as South Africans be worried? On March 19 the South African GMO authorities approved the importing of Dow Chemical’s genetically engineered (GE) soybean. This went almost unreported in our commercial media, but it stirred outrage amongst civil society organisations both here and in North and Latin America. Like many GM crops, this variety is engineered to resist substantial applications of toxic herbicides and pesticides. Of particular concern is the fact that Dow’s soybean variety belongs to a new generation of GM crops tolerant of even more toxic chemicals (ACBio, 2013).

Recently, particularly in the US, GM crop-fields have become over-run with herbicide-tolerant ‘super-weeds’. As a result of this apparent herbicide and transgenic crop failure, new GM varieties (such as Dow’s new soybean variety) tolerant of even more toxic herbicides are being introduced. In July 2012, Dow Chemical applied to South African authorities for approval of the import of its 2,4D herbicide-tolerant soybean. The development of this new variety is deeply disturbing (ACBio, 2012).

2,4-D was one of the principal ingredients in the infamous chemical defoliant ‘Agent-Orange’ used widely during the Vietnam war. The company responsible for producing ‘Agent Orange’ for the US Department of Defence’s chemical warfare program in the 1960s was none other than Dow Chemical - the very same company that will now supply soy seeds to South Africa. One only need look at the devastating ecological and health impacts of ‘Agent Orange’ in Vietnam as a warning against the introduction of crops dependent upon 2,4D-herbicides. Thousands of children are still being born with birth defects and contaminated soil continues to poison food chains in Vietnam. Dr Marcia Ishii-Eiteman, a Senior Scientist with Pesticide Action Network North America states (ACBio, 2013) that an increasing number of medical studies are linking 2,4-D and related herbicides to decreased sperm counts in farmers, birth defects, liver and nerve damage, hormonal disruption and increased rates of Parkinson’s Disease and cancer. Indeed, the World Health Organisation (WHO) has classified 2,4-D as potentially carcinogenic.

Because 2,4-D is prone to drift beyond the agricultural area of application, its biodiversity impacts can be extensive.  In the U.S. it has been reported by the Environmental Protection Agency (EPA) and National Marine Fisheries Service (NMFS) that several endangered species are being affected by the herbicides. These include the California red-legged frog, the Alameda whipsnake, and Pacific salmon (ACBio, 2013).

Given that 2,4-D is banned completely in Norway, Sweden and Denmark (ACB, 2012), it is deeply concerning that South Africa will begin to import a soybean variety that is tolerant of and dependent upon this toxic chemical with potentially grave consequences for our human and environmental health. No wonder civil society organisations around the world are worried that the approval in South Africa has set a dangerous precedent.

Having watched this disastrous situation unfold over the last few months, I felt an impassioned obligation to find out more about GM crops and their implications for human - and ecosystem - health. In the light of concerns raised by reputable organisations such as the USA’s EPA and NMFS and the WHO, it is astonishing that there is an almost complete void of recent literature on GMO’s in the world’s most esteemed science journals: Proceedings of the National Academy of Sciences (PNAS), Nature, and Science. What is evident is that the sparse GMO literature is plagued by bad science, intimidation, emotional attacks and economic interests.

An examination of the recent articles in the PNAS, Nature and Science databases turned up just one single paper on the possible negative implications of GM crops for the environment. Rosi-Marshall et al (2007) focus their research on the environmental impacts of transgenic corn genetically modified to express insecticidal toxins from the bacterium Bacillus thuringiensis (Bt). The authors found that streams running through these crop-fields also contained Bt-Corn debris and, as a result, endeavored to determine possible implications of contamination of food resources for stream insects. Laboratory experiments revealed that caddis-flies (moth-like stream-dwelling insects in the order Trichoptera) that were fed on a diet of BT-corn grew half as fast and died at more than double the rate of those fed on non-BT-corn.

Two weeks after the article was published in PNAS, a flood of fervent attacks and criticism rippled through the scientific community. The research was labeled as ‘bad science’ and following several scathing letters to the editor, the article was removed from the PNAS database. A particular point of concern was a sentence in the abstract of the Rosi-Marshall et al (2007) paper, namely that “widespread planting of Bt-crops has unexpected ecosystem-scale consequences”. This was argued to be tenuous on the grounds that it is not scientifically sound to extrapolate from laboratory experiments to complex ecosystems (Parrott, 2008).

Parrott (2008) criticises the methods that Rosi-Marshall et al (2007) employed. The authors of the original study made no mention of the exact amount of BT-corn that the insects consumed. Critics argue that the authors should have administered fixed amounts using a routine toxicity assessment method known as dose-response studies. I believe it is unfair to dismiss the entire worth of the study on the grounds that the authors failed to use this established method. Even though we do not know for certain at what point BT-corn becomes dangerous for caddis-flies, it is noteworthy that the study appears to reveal a level of susceptibility to the toxin.

Critics also faulted the fact that Rosi-Marshall et al (2007) failed to adequately control their experiments in order to isolate the direct impact of the toxin. They argue that the insects should have been administered isogenic lines - strains of corn that have identical genes except for the Bt-genes (Parrott, 2008). Because the authors simply fed the test-group of caddis-flies with Bt-corn and the control-group with non- Bt-plants, it is not possible to determine whether the observed growth and mortality effects were due to the toxin itself or to some other difference between the plant-foods (Parrott et al, 2008). However, Rosi-Marshall et al (2007) do defend their choice of non-isogenic lines by explaining in their Methods section that isogenic corn varieties differ in nutritional content. As a result, in order to standardise the experiments, they chose to match non-Bt plants and Bt plants based on nutritional value for their control - and test- experiments.

The Rosi-Marshall et al (2007) study is just one of the many pieces of research highlighting the potential hazards associated with GM crops that have been dismissed. Even more concerning is the possibility that this kind of rejection might be related to the economics of research funding. One comprehensive literature review of the published scientific journal articles on health risk studies on GM crops has found that the majority of these studies are undertaken by the very same biotechnology companies that are responsible for developing the crops (Domingo and Bordonaba, 2011). It is possible that critics of studies that allude to health hazards of GM crops are driven by financial ties to the biotechnology industry. In such a commercially-influenced research environment, it is no wonder there is a void of information on the safety of GM foods. However scientifically flawed the Rosi-Marshall et al (2007) paper may be, it is studies like these that lay the ground for furthering our understanding of GM crop safety. Not one of the articles that lambast the caddis-fly study called for further research into the tentative findings of the authors. To entirely reject these research findings disregards the fundamentals of scientific study which requires constant testing and refining of hypotheses.

The world is in trouble if scientists become too intimidated to ask questions. It is worrying that the South African decision to endorse the importation of GM-crops that are reliant on toxic chemicals could well be based on a debate skewed by commercial power. The South African scientific community needs to ensure that it sustains a robust independence from commercial interests. We as ordinary South Africans should insist upon effective GM-labeling of foodstuffs, and we should use our purchasing power to ensure that commercial interests do not trump our well-being.



ACBio. 2013. South African government blasted over approval of ‘agent orange’ GM soya. African Center for Biosafety. [online] 19 March. Available at: <> [Accessed 7 April 2013]


ACBio.2013. The new generation of GM herbicide crops. [online] The African Center for  Biosafety. Available at: < > [Accessed 7 April 2013].


Domingo, J. L. and Bordonaba, J.G. 2011. A literature review on the safety assessment of genetically modified plants. Environ Int. 37: 734-742.

Rosi-Marshall EJ, Tank, JL, Royer, TV, Whiles, MR, Evans-White, M, Chambers, C, Griffiths, A, Pokelsek, J, Stephen, ML. 2007. Toxins in transgenic crop byproducts may affect headwater stream ecosystems. Proceedings of the National Academy of Sciences of the United States of America 104:16204–16208


Newman, S. 2013. The state of the science. Council for Responsible Genetics, [online] 10 February. Available at < > [Accessed 7 April 2013]


Parrott, W. 2008. Study of Bt impact on caddisflies overstates its conclusions: Response to Rosi-Marshall et al. Proceedings of the National Academy of Sciences of the United States of America, 105(7), E10.