Total Per- and Polyfluoroalkyl Substances (PFAS) Concentration and Composition in Pesticides

Abstract

Per- and polyfluoroalkyl substances (PFAS) have been increasingly reported in pesticide formulations, raising concerns regarding their contribution to agricultural PFAS contamination. However, uncertainties remain regarding PFAS composition, unidentified PFAS, and the environmental relevance of PFAS in currently used pesticides. This study characterizes PFAS in six commercial pesticides using target and nontarget analysis, evaluates sample preparation methods, and assesses environmental implications of pesticide applications. Solvent dilution and EPA 1633 were selected based on favorable internal standard and matrix spike (MS) recoveries. The total oxidizable precursors (TOP) assay was applied to all formulations. No PFAS were detected before and after TOP in two formulations. Four PFAS were detected in the remaining formulations at concentrations of 40 ng/L-pesticides (6:2 FTS, malathion)─39,123 ng/L-pesticides (6:2 FTS; spiromesifen). Increased perfluoroalkyl carboxylates after TOP suggested unknown PFAS in spiromesifen, imidacloprid, and malathion. Nontarget analysis tentatively identified two additional PFAS (CAS Nos. 376-27-2 and 2681-00-7) in imidacloprid. Total organic fluorine (TOF) analysis achieved 84% MS recovery; but sample concentrations were below detection by a combustion ion chromatography (CIC), suggesting larger sample volumes are needed. Simulated results based on PFAS concentration fluxes indicated currently used pesticides are unlikely to be a major source of groundwater or soil contamination.