Nevertheless, the metabolite MNBA (4-methylsulfonyl-2-nitrobenzoic acid) is detected with the parent mesotrione in crops,and two degradation products, MNBA and AMBA (2-amino-4-methylsulfonylbenzoic acid), are found together with the parentcompound in soil and water [1]. Toxic effects of these mesotri-one metabolites has been found by Bonnet et al. [6] in two microorganisms. Crouzet et al. [11] tested the effects of mesotrioneover soil microbial community, at doses far exceeding the recom-mended rates, mesotrione had impacts on these non-target soilmicroorganisms. Kreutz et al. [23] evaluated the LC50of this com-pound in the neotropical fish Rhamdia quelen. No work testing thepotential sub-lethal effects of mesotrione through a biomarkersapproach was performed in any species of fish.