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Abstract

Glyphosate, the main ingredient in Roundup®, is the most widely used herbicide in the world. It is also used in combination with another effective herbicide, 2,4-D, in the formulation called Enlist Duo®. The EPA approved the use of Enlist Duo® on certain crops including those genetically modified to be resistant to both herbicides. The predicted significant increase in the use of these herbicides raised concerns from the general public because both compounds have been classified as possibly or probably carcinogenic. Since herbicides are applied directly to vegetation, the safety of organisms that come in contact with the herbicides is at risk. In this toxicity study, the responses of earthworms exposed to various concentrations of 2,4-D, glyphosate, or both were investigated. Results of direct contact studies show severe effects of 2,4-D on worms, including death. Despite seeing ill effects in direct contact trials, we saw no significant difference in the mortality rates, reproductive health, and weight of the earthworms treated via ingestion of contaminated soil or vegetation. As earthworms constitute a food source for other organisms, bioaccumulation is possible. An HPLC method to detect herbicide uptake in earthworm tissues was also developed. These methods were suitable for analyzing worms obtained from soil and plants treated with 2,4-D, glyphosate, or both. HPLC analysis showed uptake of both 2,4-D and glyphosate but no evidence indicating that the presence of 2,4-D changed the uptake of glyphosate.