Widespread Occurrence of Non-Extractable Fluorine in Artificial Turfs from Stockholm, Sweden

Per- and polyfluoroalkyl substances (PFAS) are frequently used in the production of rubber and plastic, but little is known about the identity, concentration, or prevalence of PFAS in these products. In this study, a representative sample of plastic- and rubber-containing artificial turf (AT) fields from Stockholm, Sweden, was subjected to total fluorine (TF), extractable organic fluorine (EOF), and target PFAS analysis. TF was observed in all 51 AT samples (ranges of 16–313, 12–310, and 24–661 μg of F/g in backing, filling, and blades, respectively), while EOF and target PFAS occurred in <42% of all samples (<200 and <1 ng of F/g, respectively). A subset of samples extracted with water confirmed the absence of fluoride. Moreover, application of the total oxidizable precursor assay revealed negligible perfluoroalkyl acid (PFAA) formation across all three sample types, indicating that the fluorinated substances in AT are not low-molecular weight PFAA precursors. Collectively, these results point toward polymeric organofluorine (e.g., fluoroelastomer, polytetrafluoroethylene, and polyvinylidene fluoride), consistent with patent literature. The combination of poor extractability and recalcitrance toward advanced oxidation suggests that the fluorine in AT does not pose an imminent risk to users. However, concerns surrounding the production and end of life of AT, as well as the contribution of filling and blades to environmental microplastic contamination, remain.

increased to 100% B at 5 min, held constant for 3 min and equilibrated at 10% B for another 2 min. The electrospray ionisation source was operated in negative mode where the source and desolvation temperature were held at 150 °C and 350 °C, respectively, while the capillary voltage was set to 1 kV.
Instrumental parameters were based on the method used in a previous study. 1 The monitored ion transitions for all PFAS can be found in Table S2. Quantification was performed using isotope dilution with an 8-point calibration curve (linear, 1/x weighting). Exactly matched, isotopically-labelled standards were used when available, otherwise a structurally similar isotopically-labelled standard was used (see Table S 3). The Limit of Detection (LOD) for individual PFAS was defined as three times the standard deviation of the blank for those PFAS appearing in blanks; for all others, the LOD was estimated as the concentration producing a signal-to-noise ratio above three, based on analysis of the lowest calibration standard. The LODs ranged from 3.4-197.9 pg/g (Table S 3).

Total Oxidizable Precursor Assay Procedure
Approximately 40 mg of each sample were weighed in a 50 mL falcon tube to which were added 30 mL of MilliQ water, 0.48 g of potassium persulfate and 0.456 mL of NaOH (10 M). The tubes were placed in a temperature-controlled oven at 85⁰C for 6 hours. After cooling samples were amended with 50 μl of a 200 pg/μl solution of isotopically labelled standards and their pH was adjusted between 5-9 using HCl (33%). Solid phase extraction (SPE) was carried out using Oasis WAX SPE cartridges (150 mg, 6 mL, Waters). Cartridges were conditioned with 4 mL each of 0.1% NH4OH in methanol, methanol and water after which samples were loaded and extracted under vacuum, followed by a rinse with 4 mL of MilliQ water. After drying, samples were eluted into new 13 mL tubes with 4 mL each of 0.1% NH4OH in methanol and methanol. Samples were dried to approximately 1 mL and 50 μl of a 200 pg/μl solution of isotopically labelled standards were added. An aliquot of 250 μL of sample was combined with 250 μL of 4 mM NH₄OAc in water for LC-MS/MS analysis.

Inventory Calculations
The total quantity of fluorine from all artificial turfs (ATs) in Stockholm was estimated using the measured TF concentrations in backing, blades, and fill. Weight-based TF concentrations (i.e. µg F/g) in backing were first converted to area-based concentrations (i.e. µg F/cm 2 ) using a weight-to-surfacearea conversion factor (1g/cm 2 ) which was approximately the same for all backing samples. The resulting concentrations were multiplied by the area of the field to obtain the mass of TF per field from backing. For fill, weight-based concentrations (i.e. µg F/g) were multiplied by the estimated quantity of fill added to a field per year (which is estimated between 2 and 3 metric tons, we therefore used 2500 kg for these calculations), only one application of fill for each field was considered in the estimation calculation. 2 For blades, weight-based concentrations (i.e. µg F/g) were converted to field area-based concentrations (µg F/cm 2 ) using a conversion factor (0.01g/blade) and the density of the blades on the turf (~10 blades/cm 2 ); thereafter, concentrations were multiplied by the area of the field to obtain the total quantity of fluorine from all of the blades in a single field. Finally, the amount of fluorine in backing, fill and blades of a given field were summed together to obtain the total amount of fluorine for that field. As an example calculation, Gröndals BP, which has a surface area of 4230 m 2 , was found to have TF concentrations of 31984 ng F/g in backing: ( ö ) = 31 984 • 1 2 • 4 230 2 = 1.35 The TF concentration in filling was 136018 ng F/g: The total amount of Fluorine for Gröndals is therefore estimated as: Details of the TF measured for the other fields can be found in Table S5.
The sum of the total fluorine found in the sampled fields is 57.387 kg. The lowest amount of fluorine was found in Kungsholmens Gym BP at 0.315 kg, while the highest was found at Kälvesta BP at 17.439 kg. These values were used as upper and lower bounds estimates for the ATs not sampled and were multiplied by 86 (the remaining fields in Stockholm that were not sampled). The sum total of these estimates plus the measured values provided a total estimate of the quantity of fluorine in ATs in Stockholm, resulting in a range spanning from 84.45 kg to 1557.16 kg.

Extraction of Fluoride in Water
Contributions from fluoride towards TF measurements were ruled out based on the negligible concentrations of fluorine in water extracts from a subset of three samples of backing, blades, and filling containing high TF (backing from Hammarby IP, filling from Rågsveds BP and blades from Stadhagens IP). They were extracted twice with MilliQ water (7 and 6 mL) using an ultrasonic bath. The combined extracts were concentrated under nitrogen in a heated bath (60 °C) to ca 200 µL, which were then analysed by CIC. Results showed an average of less than 760 ng F/g, much lower than the TF values for these samples, while the same samples spiked with 5000 ng Fshowed recovery of fluoride in water extract of 65% (see Table S 3). However, we cannot rule out contributions from other inorganic fluorine species which may occur in the turf and were not extractable in water. Overall, these results point towards a polymeric organofluorine consistent with patent literature. into an ice-skating rink. In Hammarby IP and Knutby BP, sand was listed as the filling, but an unknown filling material was observed in addition to sand. The backing differed between fields as well, with some being thicker than others. In general, the new fields had thinner backing than the old fields but no inventory information was supplied regarding the nature of the backing material.

Field
Year of Installation      Figure S 1 -Overview of experimental approach. A stratified random sampling design was applied using two strata. In the first stratum, 2 fields for each filling type were selected while in the second stratum, 2 fields installed pre-2010 and 2 fields installed after 2017 were selected for filling types EPDM and TPE. For each location, samples of backing, blades and filling were collected. All samples were subjected to TF, EOF and targeted PFAS analyses. Smaller subsamples were selected for Fand TOPA analyses.