Update on long-term toxicity of agricultural GMOs tolerant to roundup

Agricultural genetically modified organisms (GMOs) are plants obtained by gene transfer or more recently by gene-editing. Their major common phenotypic trait for which 99% have been modified is that these are designed to be grown with pesticides, which may bioaccumulate in the plants and/or the consumer, and/or express insecticides in their cells. Examples of both types are Roundup-tolerant soy and corn and Bt insecticidal plants. Recently, Steinberg et al. concluded that there were no adverse effects in rats from consumption of a GM corn tolerant to Roundup, called NK603, and that no other long-term studies are justified. This contradicts several of our in vivo studies on the short- and long-term toxicological effects of either the same GMO, other GMOs, or the pesticide Roundup itself. Our results were attributed in particular to the long-term in vivo effects of Roundup residues, which also present toxic and endocrine-disrupting effects in vitro. These effects were clearly linked to the formulants of the pesticide, such as petroleum residues and heavy metals, and not to glyphosate alone. In fact, the treated rats in Steinberg et al.’s experiment showed many adverse effects, some of which, including increased mortality in males fed GM corn + Roundup, were statistically significant. Other adverse effects affected both treated and control groups. The latter trend may be due to contamination of the feed of the control animals by many carcinogenic pollutants, including pesticides, but also by Roundup residues and Roundup-tolerant GMOs. For instance, glyphosate contained in Roundup was found to be 300–1400 times more elevated in their control feed than in our treated group. In conclusion, Steinberg et al.’s study is invalidated by the contaminated feed, biased interpretations, and major undeclared conflicts of interest.