DNA damage exerted by mixtures of commercial formulations of glyphosate and imazethapyr herbicides in Rhinella arenarum (Anura, Bufonidae) tadpoles.

Glyphosate (GLY) and imazethapyr (IMZT) are two herbicides commonly used worldwide, either alone or in mixtures. They represent key pesticides in modern agricultural management. The toxicity that results when employed as mixtures has not been characterized so far. Acute toxicity of the 48% GLY-based herbicide (GBH) Credit and the 10.59% IMZT-based herbicide (IBH) Pivot H alone and their binary combinations was analyzed in Rhinella arenarum tadpoles exposed in a semi-static renewal test. Lethal effects were determined using mortality as the end-point, whereas sublethal effects were determined employing the single-cell gel electrophoresis (SCGE) bioassay. Based on mortality experiments, results revealed LC50 values of 78.18 mg/L GBH and 0.99 mg/L IBH for Credit and Pivot H, respectively. An increase in the genetic damage index (GDI) was found after exposure to Credit or Pivot H at 5 and 10% of LC50 values. The combinations of 5% Credit-5% Pivot H LC50 and 10% Credit-10% Pivot H LC50 concentrations significantly enhanced the GDI in comparison with tadpoles exposed only to Credit or Pivot H. Thus, the effect of interaction between GBH and IBH inducing DNA damage in R. arenarum blood cells can be considered to be synergistic.