Oxidative Stress and Cytotoxicity Induced by Co-Formulants of Glyphosate-Based Herbicides in Human Mononuclear White Blood Cells

The use of genetically modified, glyphosate-resistant crops has led to the widespread application of glyphosate-based herbicides (GBHs), making them one of the most widely used herbicide formulations on the market. To enhance the efficacy of the active ingredient, GBHs used in practice often contain other ingredients marked as inert "adjuvants" or "co-formulants", the toxic properties of which are poorly understood. The objective of this study was to compare the cytotoxic effects of pure glyphosate, three GBHs (Roundup Mega, Fozat 480 and Glyfos) and two co-formulants commonly used in GBHs as assessed via CCK-8 assay, and the extent of their potential oxidative damage as assessed via superoxide dismutase (SOD) assay, in order to reveal the role of adjuvants in the toxicity of the formulations. Our results showed that glyphosate alone did not significantly affect cell viability. In contrast, GBHs and adjuvants induced a pronounced cytotoxic effect from a concentration of 100 μM. SOD activity of cells treated with GBHs or adjuvants was significantly lower compared to cells treated with glyphosate alone. This suggests that the adjuvants in GBHs are responsible for the cytotoxic effects of the formulations through the induction of oxidative stress.