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An Illusory Consensus behind GMO Health Assessment

Date Added to website 9th August 2015

An Illusory Consensus behind GMO Health Assessment

Sheldon Krimsky

Science, Technology, & Human Values 1-32 DOI: 10.1177/0162243915598381


Prominent scientists and policymakers assert with confidence that there is no scientific controversy over the health effects of genetically modified organisms (GMOs)—that genetically modified crops currently in com- mercial use and those yet to be commercialized are inherently safe for human consumption and do not have to be tested. Those who disagree are cast as ‘‘GMO deniers.’’ This article examines scientific reviews and papers on GMOs, compares the findings of professional societies, and discusses the treatment of scientists who have reported adverse effects in animal feeding experiments. This article concludes by exploring the role that politics and corporate interests have had in distorting an honest inquiry into the health effects of GMO crops.


I began this article with the testimonials from respected scientists that there is literally no scientific controversy over the health effects of GMOs. My investigation into the scientific literature tells another story. I found twenty-six animal feeding studies that have shown adverse effects or animal health uncertainties (Table 2). The eight review articles were mixed in their assessment of the health effects of GMOs (Table 1). The analysis of how two respected scientists were treated so poorly by the scientific community over their peer-reviewed work raises questions about likely political and ideological influences in the science. I could find no comparable case in the history of science where someone’s published and peer-reviewed work was retracted because it was not definitive. Comparable works that found GMOs equivalent to their non-GMO parental strain were not retracted for the same reason since they too were not definitive. It has been argued that the weight of evidence is favorable to the hypothesis that the current family of commercialized GMOs is safe to humans and animals because there is a prepon- derance of articles establishing that point. In risk assessment, the number of studies that reveal a risk can be more significant than a larger number of studies that do not. Imagine a hundred flights to test a new aircraft. Ninety-five prove safe. Five flights produce electrical problems, failed landing gear, and a wing collapse. Does one just negate the five flights and go with the weight of evidence? Those five flights are very significant, perhaps because the aircraft was pushed beyond standard flight operations but within its design limits.

When there is a controversy about the risk of a consumer product, instead of denying the existence of certain studies, the negative results should be replicated to see if they hold up to rigorous testing. This point was made by the 300 scientists who signed a joint statement that was published in Environmental Sciences Europe. The statement ‘‘does not assert that GMOs are unsafe or safe. Rather the statement concludes that the scarcity and contradictory nature of the scientific evidence published to date prevents conclusive claims of safety, or lack of safety, of GMOs’’ (Hilbeck et al. 2015, 1). David Schubert, professor at the Salk Institute, summarized the state of affairs of the GMO controversy as follows: ‘‘To me, the only reasonable solution is to require that all GM plant products be tested for long-term toxicity and carcinogenicity before being brought to market’’ (2002, 969). Until the twenty-six studies, or at least the best of them, are replicated and shown to be false positives, we have an obligation to treat these studies with respect and concern. My results have broad implications for the study of scientific and medical controversies, whether climate change, endocrine disruptors, statins, or mercury preservatives in vaccines. STS scholarship is best accomplished when it approaches a controversial issue systemically and includes a deep analysis of the primary science, a review of the function of professional societies, an analysis of the peer review process of journals, a study of the political climate and its impact on science and on federal regulatory agencies which set policy, the media’s role in shaping public understanding or misunderstanding, and the role that financial interests play in scientific risk analysis. All of these factors are brought into play in the GMO debate, about which I have argued that the putative consensus about the inherent safety of transgenic crops is premature.