Polyoxyethylene tallow amine: Environmental fate of an "inert" ingredient

Abstract

The surfactant polyoxyethylene tallow amine (POEA) is a common inert ingredient in formulations of glyphosate—the most widely applied agricultural herbicide in the world, which is also commonly used in urban settings. Little is known about the environmental occurrence, fate, and effects of ancillary additives such as POEA. POEA is not well characterized in the literature, but has been shown to be toxic to numerous aquatic organisms. Characterization of POEA technical mixtures shows that POEA is a complex combination of a central nitrogen atom, different aliphatic moieties, and varying numbers of ethoxylate units. Analysis of several agricultural and household glyphosate formulations confirmed that different POEA technical mixtures are common additives in these formulations and that a POEA technical mixture with an average of 15 ethoxylate units is the most common additive. Experiments to characterize the adsorption of POEA to soils revealed that POEA adsorbs much stronger to soil than glyphosate; the addition of calcium chloride to the system increases the adsorption of POEA; and the adsorption of POEA to soils was highest in low pH conditions. POEA detected on a soil sample from a row crop agricultural field near Lawrence, Kansas shows a change in the distribution of homologs over time with a loss of homologs that contain an alkene moiety. POEA was also detected on row crop agricultural soil samples collected between February and early March from sites in five other states (Iowa, Illinois, Indiana, Missouri, Mississippi). Soil samples collected from a row crop field in Indiana for over a year were analyzed to examine the dissipation of POEA, glyphosate, and aminomethylphosphonic acid (AMPA) and shows that POEA and glyphosate persist on the shallow soil from growing season to growing season but there is some dissipation over time with little migration into deeper soil. Stream bed sediments (agricultural and urban watersheds) from six states (Georgia, Hawaii, Iowa, Mississippi, North Carolina, South Carolina) were analyzed and all were found to have detectable levels of POEA. This is the first indication of the potential widespread contamination of POEA on agricultural soils and stream bed sediments in areas where glyphosate is applied.