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Is Ongoing Sulfluramid Use in South America a Significant Source of Perfluorooctanesulfonate (PFOS)? Production Inventories, Environmental Fate, and Local Occurrence John Löfstedt Gilljam,† Juliana Leonel,*,‡ Ian T. Cousins,† and Jonathan P. Benskin*,† †
Department of Environmental Science and Analytical Chemistry (ACES), Stockholm University, Stockholm SE-106 91, Sweden Oceanography DepartmentIGEO, Federal University of Bahia, Salvador 41170110, Brazil
‡
S Supporting Information *
ABSTRACT: Despite international phase-out initiatives, production and use of perfluorooctanesulfonate (PFOS) and related substances continues in some countries. In Brazil, the PFOS-precursor N-ethyl perfluorooctane sulfonamide (EtFOSA) is used in Sulfluramid, a pesticide for controlling leaf-cutting ants. New data on production, environmental fate, and occurrence of Brazilian Sulfluramid are reported herein. From 2003 to 2013, Brazilian Sulfluramid manufacturing increased from 30 to 60 tonnes yr−1 EtFOSA. During this time 10) for each analyte, and its corresponding internal standard area measured in individual samples. This approach accounts for procedural losses and matrix effects on a sample-to-sample basis. Sample specific method detection limits (MDLs) were set to 3/10 of the MQLs, which in all cases produced peaks with S/N > 3. Both MDLs and MQLs are provided in Tables S9 and S10, respectively. In general, MDLs were on the order of tens to hundreds of pg L−1 depending on the target and sample. Targets above the MDL were quantified using a 9-point calibration curve and linear regression with 1/x weighting. Values in between the MDL and the MQL are reported as flagged concentrations. BTS samples were analyzed together with transport, field, method blanks, and QC samples. Transport (n = 2) and field (n = 1) blanks consisted of 500 mL HPLC-grade water from Brazil. Method blanks consisted of either 3 mL (n = 3) or 500 mL (n = 4) of MQ-water and Instant Ocean (4% salinity). QC samples consisted of (a) a high-level matrix spike prepared by fortifying 500 mL Stockholm archipelago water with 20 ng of
distribution of a chemical in a closed environment (see Supporting Information, SI, for full description). Since application of EtFOSA occurs to soil to control leaf-cutter ants, emissions are assumed to occur exclusively to soil. While the emission rate is often arbitrary in evaluative modeling, here we have chosen a realistic emission rate (0.35 tonnes yr −1 or 0.04 kg h−1) in our modeling. The Brazilian State of Bahia is about 5.7 times larger (at 567 295 km2) than the EQC model environment (100 000 km2) and consumed 2 tonnes of EtFOSA in 2013. We have scaled the emissions of EtFOSA to the area of the EQC model environment by dividing 2 tonnes yr −1 by 5.7. The Level III model requires inputs of various chemical properties, namely; molecular weight (g mol−1), solubility in water (g m−3), vapor pressure (Pa), log KOW and first-order degradation half-lives (h) in air, water, soils, and sediments. All physical-chemical properties of EtFOSA were taken from Wang et al.29 (see Table S1). Degradation half-lives of EtFOSA were taken from the literature and/or estimated using the US EPA Estimation Programs Interface (EPI) Suite (EpiSuite).30 The model outputs are only sensitive to the estimated degradation half-life in soil as the chemical does not significantly partition to other media. Avendano and Liu11 estimated the apparent soil half-life of EtFOSA to be 13.9 ± 2.1 days in soil biodegradation experiments. In the model, we use a range for the soil half-life of EtFOSA of 13.9 days (334 h) (from ref 11) to 360 days (8640 h) (estimated with EPiSuite). Although EtFOSA can be degraded by other environmental transformation processes within soil, biodegradation is expected to be the dominant degradation process. For PFOS, the vapor pressure is assumed to be negligibly low (10−10 Pa) as PFOS is completely dissociated, and the solubility in water is 570 g m−3.31,32 Log KOW is assumed to be 2.89 (to provide a model estimated [KOC = 0.41 KOW] log KOC of 2.5 in line with measurements33). The half-lives in air, water, soil and sediment are assumed be extremely large (1011 h) as no degradation of PFOS has been observed under environmental conditions.34 See Table S1 for a summary of PFOS properties. Three separate model simulations were performed; (i) EtFOSA was emitted to soil at a steady 0.04 kg h−1 using chemical inputs from Table S1 and an assumed degradation half-life in soil of 13.9 days, (ii) EtFOSA was emitted to soil at a steady 0.04 kg h−1 using chemical inputs from Table S1 and an assumed degradation half-life in soil of 360 days, and (iii) for comparative purposes, PFOS was emitted to soil at a steady 0.04 kg h−1 using chemical inputs from Table S1. Sampling campaign. Seven 0.5 L surface water grab samples were collected in polypropylene bottles in February, 2015 at sites around Todos os Santos Bay (BTS) in Bahia state (Figure 1). Bahia is among the top 4 consumers of EtFOSA in Brazil (2 tonnes in 2013 alone). Major urban centers around BTS include the city of Salvador (population 2.9 million) on the Eastern Cape and the city of Camaçari (population 280 000) to the northeast. BTS has seen heavy industrialization since the 1960s and receives both domestic and industrial discharges. There are three major catchment areas and numerous small rivers entering the BTS region, with a total area of 61 000 km2. The largest by over an order of magnitude is Rio Paraguaçu, entering BTS from the northwest. Sampling was designed to create a snapshot of PFAS profiles among diverse regions of BTS. Additional water was collected from Stockholm, Sweden (February−March, 2015) for reference C
DOI: 10.1021/acs.est.5b04544 Environ. Sci. Technol. XXXX, XXX, XXX−XXX
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Environmental Science & Technology
2015). Remaining countries imported ≤1 tonne EtFOSA (2004−2015) from Brazil. While for most countries a constant or increasing trend in imports existed, Venezuela imports decreased and were negligible from 2013 to 2015. It is unclear whether this indicates a reduction in Sulfluramid use or a shift to another supplier (e.g., China). Production of EtFOSA in China was estimated at ∼4−8 tonnes yr−1 in 2008,16 with
