Sulfluramid use in Brazilian agriculture: A source of per- and polyfluoroalkyl substances (PFASs) to the environment.

N-Ethyl perfluorooctane sulfonamide (EtFOSA) is a perfluorooctane sulfonate (PFOS) precursor and the active ingredient in sulfluramid, a pesticide which is used extensively in Brazil for management of leaf cutting ants. Here we investigate the occurrence of EtFOSA, PFOS, and other per- and polyfluoroalkyl substances (PFASs) in soil, eucalyptus leaves, water (ground, riverine, and coastal (estuarine/marine)) and coastal sediment from an agricultural region of Bahia State, Brazil. This area contains a larger number of eucalyptus plantations where sulfluramid is suspected to be applied. Soil, leaves, and coastal water (marine/estuarine) contained ∑PFAS concentrations of up to 5400 pg g-1, 979 pg g-1, and 1020 pg L-1, respectively, with PFAS profiles generally dominated by PFOS and perfluorooctane sulfonamide (FOSA). Coastal sediment contained ∑PFAS concentrations of up to 198 pg g-1, with PFOS, FOSA, and perfluorooctanoic acid (PFOA) being the most frequently observed PFASs. These substances are all potential EtFOSA transformation products, pointing to sulfluramid as a possible source. In riverine water, ∑PFAS concentrations of up to 8930 pg L-1 were observed. PFOS and PFOA were detected in all river water samples. Groundwater also exhibited PFAS contamination (5730 pg L-1 ∑PFASs), likely from sulfluramid use. The observation of other PFASs (e.g. perfluorobutanoic acid) in freshwater suggests that other PFAS sources (in addition to sulfluramid) may be important in this region. Overall, these data support the hypothesis that sulfluramid use contributes to the occurrence of PFASs in the Brazilian environment.

Biodegradation and Uptake of the Pesticide Sulfluramid in a Soil-Carrot Mesocosm.

N-ethyl perfluorooctane sulfonamide (EtFOSA) is the active ingredient of Sulfluramid, a pesticide which is used extensively in South America for control of leaf-cutting ants. Despite being a known precursor to perfluorooctanesulfonate (PFOS), the importance of EtFOSA as a source of environmental PFOS remains unclear. In the present work, uptake, leaching, and biodegradation of EtFOSA and its transformation products were assessed over 81 days in soil-carrot ( Daucus carota ssp sativus) mesocosms for the first time. Experiments performed in the presence of carrot produced PFOS yields of up to 34% using a technical EtFOSA standard and up to 277% using Grão Forte, a commercial Sulfluramid bait formulation containing 0.0024% EtFOSA. Perfluorooctane sulfonamido acetate (FOSAA), perfluorooctane sulfonamide (FOSA), and perfluorooctanoic acid (PFOA) also formed over the course of the experiments, with the latter substance attributed to the presence of perfluorooctanamide impurities. The leachate contained low levels of transformation products and a high FOSA:PFOS ratio, consistent with recent observations in Brazilian surface water. In carrots, the more hydrophilic transformation products (e.g., PFOS) occurred primarily in the leaves, while the more hydrophobic products (e.g., FOSA, FOSAA, and EtFOSA) occurred in the peel and core. Remarkably, isomer-specific analysis revealed that the linear EtFOSA isomer biodegraded significantly faster than branched isomers. These data collectively show that the application of Sulfluramid baits can lead to the occurrence of PFOS in crops and in the surrounding environment, in considerably higher yields than previously thought.