Tallow amine polyethoxylate, commonly referred to as POEA (polyoxyethylene alkyl amine), is a nonionic surfactant contained in many glyphosate-based formulations that improves uptake and efficacy of the active ingredient, thereby reducing the amount needed for effective weed control. Four regulatory-guideline environmental fate studies were initiated in 2012 to obtain data for potential use in ecological risk assessments for formulations containing POEA and include: hydrolysis, aerobic aquatic degradation, adsorption/desorption, and aerobic soil degradation. 14C-Labeled POEA was synthesized for use in the studies to aid in analysis of the surfactant, to assess mineralization to CO2, and to allow for mass balance determinations. POEA was found to be chemically stable under abiotic hydrolysis conditions. POEA dissipated rapidly from the water column of natural water-sediment systems under aerobic conditions through a combination of metabolism and adsorption to sediment, with a DT50 of 2-3 hours. The rate of dissipation of POEA from the water column is consistent with rates reported in other water-sediment studies. Results from the adsorption/desorption study showed that POEA was strongly sorbed to soils and that sorption primarily correlated with increasing organic carbon. Based on the calculated adsorption coefficients, POEA is considered hardly mobile in soil according to the FAO mobility classification. Dissipation in both soil and sediment involved a combination of metabolism and binding. The DT50s for POEA in the aerobic soil study ranged from 20 to 166 days with rates slowing as the percent organic carbon of the soils increased. Dissipation of POEA in the aerobic aquatic sediments was relatively slow and approximately 17-18% of the applied dose was still extractable at the end of the 100-day study in both systems. Based on results of the studies, along with predicted environmental concentrations and available toxicity data, acute and chronic risk to organisms in the water column and in the sediment/soil are considered to be low due to rapid dissipation/degradation of POEA and limited bioavailability.

Environmental fate studies with 14C-POEA

254th National Meeting (2017)

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