Formulation-Dependent Cytotoxic Effects of Commercial and Analytical-Grade Mancozeb in C6 Glial Cells

Mancozeb (MZ) is a widely used dithiocarbamate fungicide composed of manganese (Mn) and zinc (Zn) complexes. Increasing concern has been raised regarding its occupational and human health relevance, particularly due to its neurotoxic potential associated with Mn-related cellular dysfunction. Despite being marketed exclusively as commercial formulations, most toxicological investigations rely on analytical-grade MZ, thereby neglecting the potential contribution of coformulants to toxicity. In this study, we comparatively evaluated the effects of commercial and analytical-grade MZ in C6 astroglioma cells, focusing on cell viability and intracellular reactive oxygen species (ROS) generation. Cells were initially exposed to increasing concentrations of the commercial formulation (1-500 μM) for 1, 3, 6, and 24 h to characterize time- and concentration-dependent cytotoxicity. Based on this screening, analytical-grade MZ was subsequently evaluated at selected concentrations corresponding to the onset of cytotoxic effects. Comparative analyses were then performed after 6 h of exposure to a shared concentration range (10-50 μM) to assess formulation-specific effects. Both commercial and analytical-grade MZ induced significant reductions in cell viability in a time- and concentration-dependent manner. Although both formulations significantly decreased cell viability starting at 20 μM after 6 h relative to control, a concentration-dependent difference between formulations was observed. At 50 μM, the commercial formulation produced a greater reduction in cell viability (~60%) compared to the analytical-grade MZ (~40%), both relative to controls; this difference between formulations was also supported by the two-way ANOVA. In contrast, intracellular ROS levels increased to a similar extent following exposure to both formulations, with no significant differences observed between them. These findings indicate that the enhanced cytotoxicity induced by commercial MZ is not solely explained by oxidative stress, suggesting the contribution of formulation-specific components. Overall, this study underscores the importance of evaluating complete pesticide formulations to achieve a more realistic assessment of toxicological hazard under occupational and human health exposure scenarios.