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How much of an effect do pesticide/herbicides used with GMOs have on waterways?

Submitted by: Hileaeyesus Solomon


Expert response from holmquist1x

Friday, 11/05/2018 10:46

Believe it or not, I jump at opportunities to talk about aquatic life, so thank you for your interest. I developed a passion for aquatic animals early on and remain grateful that I have managed to explore my passions in ecotoxicology for over 25 years!

This is a very general question in terms of pesticide/herbicide options that are commercially available and as well as applications. I will focus on glyphosate and dicamba specifically.

Two active ingredients in herbicidal formulations that are applied to herbicide-tolerant GMOs are glyphosate and dicamba. Both active ingredients have low toxicity profiles for aquatic animals (Giesy et al. 2000; USEPA, 1993; USEPA, 2006; EFSA, 2011). The reason for this low toxicity to aquatic animals is that herbicides, like glyphosate and dicamba, are typically developed to target a pathway that are specific to plants and not animals. This has been shown for herbicides across a large number toxicological endpoints in the EPA’s ToxCast program (Judson et al. 2016). Glyphosate inhibits a key enzyme that is unique to plants and some microorganisms and is required to produce essential aromatic amino acids (Giesy et al., 2000). Dicamba is an auxin agonist and targets a pathway found only in plants (USEPA, 2006). Glyphosate and dicamba will not impact aquatic plants under realistic aquatic exposures because levels that reach water from spray-drift or run-off will be below levels that are impactful (USEPA, 1993; EFSA, 2011). Therefore, the use of these two common herbicides for weed control in fields cultivated with GMO crops has been shown to not adversely impact plants and animals in aquatic ecosystems (USEPA, 1993; Giesy et al., 2000; USEPA, 2006).


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