Lack of adverse effects in subchronic and chronic toxicity/carcinogenicity studies on the glyphosate-resistant genetically modified maize NK603 in Wistar Han RCC rats

Abstract

In 2012, a controversial study on the long-term toxicity of a Roundup herbicide and the glyphosate-tolerant genetically modified (GM) maize NK603 was published. The EC-funded G-TwYST research consortium tested the potential subchronic and chronic toxicity as well as the carcinogenicity of the glyphosate-resistant genetically modified maize NK603 by performing two 90-day feeding trials, one with GM maize inclusion rates of 11 and 33% and one with inclusion rates of up to 50%, as well as a 2-year feeding trial with inclusion rates of 11 and 33% in male and female Wistar Han RCC rats by taking into account OECD Guidelines for the testing of chemicals and EFSA recommendations on the safety testing of whole-food/feed in laboratory animals. In all three trials, the NK603 maize, untreated and treated once with Roundup during its cultivation, and the conventional counterpart were tested. Differences between each test group and the control group were evaluated. Equivalence was assessed by comparing the observed difference to differences between non-GM reference groups in previous studies. In case of significant differences, whether the effects were dose-related and/or accompanied by changes in related parameters including histopathological findings was evaluated. It is concluded that no adverse effects related to the feeding of the NK603 maize cultivated with or without Roundup for up to 2 years were observed. Based on the outcome of the subchronic and combined chronic toxicity/carcinogenicity studies, recommendations on the scientific justification and added value of long-term feeding trials in the GM plant risk assessment process are presented.

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

“…µg/kg, corresponding to 300-1400 times more of glyphosate and thus the other Roundup residues than the levels we found to be toxic in our study [16]. This is explained in Steinberg et al 's paper (in [2] discussion, 1st column, 2nd paragraph), as well as in another publication from the same group, specifically on the contamination of their feed [23,24]. This increases the background level of serious diseases in the controls, preventing any specific observable effect of the GMO treatment on animals.…”

“…However, as tumours were developing at higher rates in the treatment groups, we were required to report this as an indicator for other serious effects that must be followed up. Steinberg et al [2] also benefited from far more funding than our pioneering study.…”

“…Almost 7 years after our research showed Roundup and Roundup-tolerant GM corn to be toxic, we welcomed the intention of a detailed study inspired by half of our work, which is quoted in the first few words of the summary of Steinberg et al [2]. "Half of our work", because the testing of long-term effects of Roundup alone at environmental levels (0.1 ppb) on a diet without pesticides was not accomplished nor tested in Steinberg et al 's work, in contrast with ours, as indicated by these authors.…”

“…The Wistar Han rat is considered less sensitive than the Sprague-Dawley strain, without real proof. Steinberg et al [2] also used a larger number of animals, as is suited for a carcinogenicity study. In contrast, we followed a long-term toxicity protocol.…”

“…In the summer of 2019, the authorization for the consumption of a genetically modified (GM) corn, NK603, engineered for tolerance to Roundup as well as many similar GMOs, was renewed in the European Union. The Seralini Environ Sci Eur (2020) 32:18 scientific basis for the European Food Safety Authority (EFSA) review lies especially on a new paper by Steinberg et al [2], which concludes that there are no long-term effects from consumption of this corn.…”