Polyoxyethylene Tallow Amine, a Glyphosate Formulation Adjuvant: Soil Adsorption Characteristics, Degradation Profile, and Occurrence on Selected Soils from Agricultural Fields in Iowa, Illinois, Indiana, Kansas, Mississippi, and Missouri

Abstract

Polyoxyethylene tallow amine (POEA) is an inert ingredient added to formulations of glyphosate, the most widely applied agricultural herbicide. POEA has been shown to have toxic effects to some aquatic organisms making the potential transport of POEA from the application site into the environment an important concern. This study characterized the adsorption of POEA to soils and assessed its occurrence and homologue distribution in agricultural soils from six states. Adsorption experiments of POEA to selected soils showed that POEA adsorbed much stronger than glyphosate; calcium chloride increased the binding of POEA; and the binding of POEA was stronger in low pH conditions. POEA was detected on a soil sample from an agricultural field near Lawrence, Kansas, but with a loss of homologues that contain alkenes. POEA was also detected on soil samples collected between February and early March from corn and soybean fields from ten different sites in five other states (Iowa, Illinois, Indiana, Missouri, Mississippi). This is the first study to characterize the adsorption of POEA to soil, the potential widespread occurrence of POEA on agricultural soils, and the persistence of the POEA homologues on agricultural soils into the following growing season.

Ignoring Adjuvant Toxicity Falsifies the Safety Profile of Commercial Pesticides

“…Furthermore, the finding that POEA is widely found in fields in the United States where glyphosate-based herbicides are applied ( 37 ) raises concerns that this and other classes of pesticide adjuvants may be entering the food and feed chain undetected, with as yet unknown health consequences.…”

Glyphosate, a chelating agent—relevant for ecological risk assessment?

“…The latter are, in general, not identified on product labels and can be claimed confidential business information. The Roundup product line (Monsanto) is the major and best known formulation that, as a surfactant, very often contains polyethoxylated tallow amine (POEA), a complex mixture of di-ethoxylates of unsaturated and saturated tallow amines characterized by their oxide/tallow amine ratio (typically 15% or less of the final formulation) (Tush and Meyer 2016 ). POEA are significantly more toxic to animals, e.g., amphibia, than glyphosate itself (Howe et al 2004 ) and have been shown to be active principles of human cell toxicity (Mesnage et al 2013 ).…”

Use of Adsorbent Biochar from Pequi (Caryocar Brasiliense) Husks for the Removal of Commercial Formulation of Glyphosate from Aqueous Media

“…Based on Langmuir isotherm principles, adsorption occurs in monolayers on the surface, which contains a finite number of identical adsorption sites [44]. It also assumes that the adsorption energies at the surface of the adsorbent are uniform, that there is no adsorbent transmigration in the surface plane and that there is no interaction among adsorbed molecules [12].…”