Previously unidentified sources of perfluoroalkyl and polyfluoroalkyl substances from building materials and industrial fabrics

Raphael M. Janousek a, Stephan Lebertz b and Thomas P. Knepper *a
aHochschule Fresenius, Limburger Str. 2, 65510 Idstein, Germany. E-mail: knepper@hs-fresenius.de; Tel: +49 6126935264
bSGS INSTITUT FRESENIUS GmbH, Im Maisel 14, 65232 Taunusstein, Germany

Received 22nd February 2019 , Accepted 11th June 2019

First published on 20th June 2019


Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are applied during the production of various consumer and industrial goods. As a consequence of their use in building materials and fabrics, unreacted nonpolymeric PFASs might enter the environment by evaporation or urban run-off. Since the PFAS content of building materials and industrial fabrics is hardly investigated, studies have to be performed in order to assess their total PFAS load. Building material samples (n = 23) and fabric samples (n = 28) were collected and their PFAS content was investigated. A total of 29 PFASs were analyzed (chain length in the range of C4–C14). PFASs of diverse chain lengths were detected in 53% of the analyzed samples. The sum of PFASs for awning materials and coating samples were amongst the highest. Furthermore, PFASs were detected in the majority of fabrics for maritime applications, public transport seat covers and fluoropolymer facade materials. To the best of our knowledge, this study was the first to investigate the PFAS concentrations in fabrics for maritime applications, fluoropolymer facade materials and coatings for architectural purposes. Thus, new sources of PFASs were identified that might lead to release of PFASs into the environment.



Environmental significance

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) depict an important group of organic trace pollutants that have been widely studied in environment, wildlife and diverse products. PFASs are ubiquitous in aquatic environments and were also detected in very remote areas. As a consequence of the hazardous environmental properties of some PFASs, such as persistence, bioaccumulation and toxicity, their fate is subject of past and ongoing discussions. Although there is some evidence that PFASs can be found in building materials and industrial used fabrics, there are only a few studies available dealing with this issue. In order to identify new sources of PFAS contaminations it is crucial to analyze these products. This paper provides data of so far not identified sources of PFASs in order to promote further research regarding the PFAS content of building materials and industrial used fabrics.

1 Introduction

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are a class of compounds that contain at least one perfluorinated alkyl moiety. They have been used for numerous applications in various consumer as well as industrial goods for several decades1 (e.g. as surfactants or incorporated into polymers2). Both, the high temperature and chemical stability as well as hydrophobic and oleophobic properties of the perfluoroalkyl chain, render PFASs suitable for a variety of applications.3 As a consequence of their extensive use as processing aids or raw material for polymers, unreacted portions or directly applied nonpolymeric PFASs reach the environment and have been detected in air, surface water, wastewater and soil in a number of studies.4–8 The fate, persistence and toxicity of legacy PFASs have been investigated to a high degree.9–14 As a consequence, the use perfluorooctane sulfonic acid (PFOS) and its salts was restricted (Annex B, Stockholm convention, 2009 (ref. 15)). Industry partially started to phase-out perfluorocarboxylic acids (PFCAs) with a chain length ≥ C8 and perfluorosulfonic acids (PFASs) with a chain length ≥ C6 and introduced replacement chemicals.16 However, some of these substances exhibit similar persistence and also have been detected in the environment.17,18 Their hazard is currently being assessed.

PFASs are frequently detected in consumer and industrial goods.19–21 Thus, investigation of possible sources and elucidation of entrance pathways into the environment or disclosure of exposure routes became necessary. The PFAS content of various industrial goods has already been investigated to a high extent.20,21 However, few studies have been performed for building materials and industrial textiles, fabrics or tarpaulins. PFASs could be used in building materials in order to lower surface tension and thus, improve wetting behaviour or visual appearance of paints or surface treatment applications (e.g. for paints, lacquers, coatings and stains).22,23 Dinglasan-Panlilio et al., detected 6[thin space (1/6-em)]:[thin space (1/6-em)]2, 8[thin space (1/6-em)]:[thin space (1/6-em)]2 and 10[thin space (1/6-em)]:[thin space (1/6-em)]2 fluorotelomer alcohol (FTOH; with decreasing percentages) in Zonyl® FSN-100 and FSE,24 which can be used in paints, adhesives or coatings. In 2012, Herzke et al. detected PFASs in two of three investigated paint samples.25 Other than surface treatment agents, PFASs can also be used in components for structural builds, e.g. derived timber products or fluorinated polymers. In 2016, Běcanová et al. investigated 46 samples from diverse building materials (e.g. oriented strand board (OSB) wood, insulating material or facade materials) on their level of perfluoroalkyl acids (PFAAs). The researchers detected PFASs in OSB wood samples and other derived timber products with the highest average concentration (4.87 μg kg−1) compared to other categories.26 They assumed that application of PFASs in derived timber products could be linked to the adhesives that were used within these products. Application of fluoropolymers for structural builds has distinct advantages over conservative building materials. Due to their remarkable UV transparency and a beneficial weight-to-surface ratio, fluoropolymers are used as substitutes for glass in solar panels or greenhouses. Furthermore, modern architecture incorporates fluoropolymers for manifold applications (e.g. the shaping of sidings and sunroofs) because they are light, and they are easy to maintain as they have dirt and water repellent properties. Thus, fluoropolymers have been used in various buildings (e.g. skyscrapers or sports stadiums). To the best of our knowledge, the PFASs content of fluorinated polymers for building purposes has not been investigated. Furthermore, the investigations on industrial textiles mainly focused on products like carpets (e.g. office or car interior) or outdoor clothing. In addition, scattered studies dealt with the PFAS content of upholstering for indoor furniture.20,21,27,28

This study was conducted to determine the PFAS content of previously not explored industrial goods. The concentration of PFASs was investigated in products of two categories (building materials and fabrics for industrial purposes). The PFASs that were investigated in the present study were perfluoro carboxylic acids (C4–C14), perfluoro sulfonic acids (C4–C8, C10 and C12), n[thin space (1/6-em)]:[thin space (1/6-em)]2 fluorotelomer sulfonates (n[thin space (1/6-em)]:[thin space (1/6-em)]2 FTS, n = 4, 6 and 8), n[thin space (1/6-em)]:[thin space (1/6-em)]2 FTOHs (n = 6, 8 and 10), 2H,2H-perfluorodecanoic acid (8[thin space (1/6-em)]:[thin space (1/6-em)]2 FTCA), 2H,2H,3H,3H-perfluoroundecanoic acid (8[thin space (1/6-em)]:[thin space (1/6-em)]3 FTCA), 7H-perfluoroheptanoic acid (7HPFHpA), perfluoro-3,7-dimethyloctanoic acid (PF37DMOA) and perfluorooctane sulfonamide (PFOSA).

2 Material and methods

For the comparability of presented results, the method used in this study is based on DIN CEN/TS 15968:2010-11.

2.1 Standards and reagents

All non-volatile PFASs and isotopically labelled standards were purchased from Wellington Laboratories INC (Canada). The standards for FTOH analysis were purchased from Neochema GmbH (Germany). All standards were certified and were obtained either as single compounds with a concentration of 50 μg L−1 or as mixtures with a concentration of 2 μg L−1. A list of the reference standards used in the present study is shown in the ESI (Table S4). The working solutions for non-volatile PFASs, isotopically labelled standards and FTOHs were prepared in a concentration of 500 ng mL−1. All standards were stored at 4 °C. The standard mixtures were used for calibration and recovery studies.

2.2 Sample collection

Sample selection for building materials (n = 23) and industrial fabrics (n = 28) was based on an extensive literature search, comprising available material safety data sheets and advertisement towards lowering of surface tension, as well as dirt or moisture repellent properties. Furthermore, some products were directly advertised with fluorocarbon or Teflon® coating. If possible, samples were directly purchased. However, some samples could not be purchased in conventional stores, since the investigated product categories are aimed at industrial or specialized use. In these cases, manufacturers or specialized retailers were contacted for samples of products. All samples were collected in between October 2016 and August 2017, stored as indicated by the supplier and analysed as soon as possible (individual dates see Table S11).

2.3 Sample preparation

Depending on the sample type, either extraction via liquid–solid extraction (LSE) or solid phase extraction (SPE) was performed. LSE was performed with methanol (MeOH) and water (for individual results see ESI). MeOH extracts were directly injected for FTOH determination or further enriched for non-volatile PFASs. Solid samples were cut into small pieces prior to extraction. Coatings that were only available in pressurized containers were frozen with liquid nitrogen and center-drilled so that the fuel gas could evaporate during thawing. Contrary to solids, most liquid samples (paints, lacquers, glues, sealants, coatings or stains) were applied on aluminum weighing pans, dried at room temperature, scraped off and further treated as solids. All solids were extracted via LSE. Coating 2 was available as an aqueous solution and directly enriched using SPE. Furthermore, coating 1-A and 1-B, coating 3 and coating 4-A and 4-B were also treated as aqueous samples and directly enriched via SPE.

2.4 Liquid-solid extraction

LSE was performed with both, water and MeOH. Non-volatile PFASs were investigated in aqueous and methanol extracts, whereas only methanol extracts were examined on their FTOH concentrations. After cutting or drying, 1 g of solid samples was weighed into a 50 mL polypropylene (PP) tube and extracted with 20 mL water or MeOH, respectively.
MeOH extracts. Internal standard (IS) was prepared in MeOH at 100 ng mL−1 and 50 μL were spiked to samples prior to extraction. Extractions were performed under constant sonication at 60 °C for 2 h and samples were further processed after cooling to room temperature. The extracts were filtered using a syringe filter (PTFE, 0.2 μm, 13 mm and 25 mm, respectively). In order to avoid false positives, blank samples were also filtered (no artefacts of analyzed PFASs were observed in blank samples). Furthermore, FTOH extracts were treated with extra care (see section 2.6). Extracts for PFAA determination were divided into three fractions (5 mL each) and collected in 15 mL PP centrifuge tubes. Two fractions were spared for quality assurance (see section 2.6) and the third fraction was further processed as it was. The extracts were evaporated to dryness under a constant stream of N2 at 40 °C. Finally, dry residues were reconstituted with 250 μL water/MeOH (v/v; 1/1), vortexed and analyzed using HPLC-MS/MS. Extraction for FTOH determination was carried out as described above and two aliquots of 500 μL were withdrawn from the 20 mL extracts. One aliquot was directly analysed using HPLC-MS/MS and the other one was spared for quality assurance (see section 2.6).
Water extracts. Extraction with water was performed under constant sonication at 60 °C for 2 h. Aqueous extracts were centrifuged (2000 rpm) and enriched with SPE (see section 2.5).

It was expected that MeOH provides better extraction yields. This was later on confirmed (see Fig. S9). Thus, mainly MeOH extracts were evaluated (see section 3), while water extracts were partially used to compliment the results.

2.5 Solid phase extraction

Aqueous products and water extracts were enriched using SPE (Phenomenex Strata-X-AW, 60 mg, 3 mL). Cartridges were conditioned using 2 mL 0.1% NH3 in MeOH, 2 mL MeOH and 2 mL ultrapure water. The pH values of all samples were adjusted to 6–8. Aqueous products were spiked with 5 ng IS (50 μL of 100 ng mL−1). Cartridges were loaded with 60 mL of aqueous products (coating 1-A and 1-B, coating 2, coating 3 and coating 4-A and 4-B) or complete water extracts, respectively. Samples were eluted into 15 mL PP centrifuge tubes using 0.1% NH3 in MeOH (2 × 1 mL), evaporated to dryness under a constant stream of nitrogen gas at 40 °C and reconstituted in 200 μL water/MeOH (1/1; v/v), vortexed and analysed using HPLC-MS/MS.

2.6 Quality control

Blanks. Blank samples were prepared with every extraction batch. Empty 50 mL PP tubes were extracted with MeOH or water and treated as normal samples. Further sample preparation was conducted according to section 2.4 and 2.5. Blank levels were only observed for perfluorohexane sulfonic acid (PFHxS) and perfluoro octanoic acid (PFOA) being significantly below the reporting level (factor 39–105 lower).
Evaluation of matrix effects. Aliquots that were spared for quality assurance (60 mL of aqueous products, 2 × 5 mL of methanol extracts for PFAA determination and 500 μL methanol extracts for FTOH determination) were spiked with known amounts of PFASs and analysed for the determination of matrix effects.
Aqueous products. Prior to SPE, aqueous samples were spiked at 0.01 μg L−1 (60 μL of 10 ng mL−1 in MeOH) and 0.1 ng L−1 (60 μL of 100 ng mL−1 in MeOH). Aqueous samples were further processed as stated in section 2.5.
Methanol extracts. One of the three fractions from MeOH extracts was spiked with PFAAs at 2 ng g−1 dry sample (50 μL of 10 ng mL−1 in MeOH) and one fraction was spiked at 8 ng g−1 dry sample (200 μL of 10 ng mL−1 in MeOH). Afterwards, these fractions were processed as stated in section 2.4. Finally, another 500 μL aliquot of MeOH extracts for the FTOH determination was partitioned and spiked at 2 ng mL−1 (10 μL, 100 ng mL−1 FTOH solution in MeOH; corresponding to the method limit of quantification) or 10 ng mL−1 (10 μL, 500 ng mL−1), respectively. In order to avoid false positive results for FTOHs (detection as [M + Ac] with one MRM transition only), these samples were treated with extra care. FTOH data was exclusively reported whenever separation from matrix interferences was observed and good recovery rates were obtained. Fig. S1–S6 display generic chromatograms for positive findings, negative findings as well as signals that were considered as not evaluable of both, solely extracted samples and recovery experiments. All non-volatile PFAAs were calculated against isotopically labelled internal standards. An assignment of the analytes to the isotopically labelled standards used here is shown in the ESI, Table S5. Depending on observed matrix effects, quantification limits were individually adjusted for each analyte and sample, respectively (see ESI, Table S10). Adjustment of quantification limits for individual analytes was based on DIN 32645. Table S12–S14 show individual recoveries for matrix effect experiments. Recoveries of FTOHs in samples with reported concentrations thereof ranged from 40–210%, whereas PFAA recoveries for samples with reported concentrations ranged from 44–173% except for three cases. PFHxA recoveries of coating sample 1-A and 2 were 7 and 10%, respectively. Furthermore, the calculated recovery for PFDoDA in awning 1 was 256%. Thus, relatively high matrix effects were observed for these samples, which might have resulted in under or overestimations of PFHxA or PFDoDA in these samples and reported concentrations should be treated with care.
Matrix effects for generic sample matrices – performed in triplicate. In addition to single determinations of matric effects, three representative samples (awning 2, awning 4 and foil 2) were extracted in triplicate and spiked post extraction. MeOH extracts were prepared from awning 2, awning 4 and foil 3, whereas water extracts were prepared form awning 4 and foil 2. Sample preparation was carried out as described in section 2.4. Table S15 shows recovery and RSD levels of these samples. Furthermore, triplicates of these samples were spiked prior to extraction (see ‘Method recoveries for generic sample matrices – performed in triplicate’). Comparison of observed results shows that the ranges of recovery levels for the determination of matrix effects are similar to observed method recovery levels. Hence, increased or decreased method recoveries almost entirely result from strong matrix effects.
Trueness and repeatability.
Spiking experiments of empty tubes. Spiking experiments were conducted with empty PP vials. Blank samples were prepared without spiking and with spiking at a known concentration for both, MeOH and water. Table S17 shows obtained concentrations for empty tubes and tubes with spiking, as well as recoveries for the spiking experiment.
Method recoveries for generic sample matrices – performed in triplicate. Triplicates of four representative samples (awning 2, awning 4, foil 2 and coating 3) were prepared without spiking and with spiking at 8 μg kg−1 prior to sample preparation. MeOH extracts were prepared from awning 2, awning 4 and foil 3, whereas water extracts were prepared form awning 4 and foil 2. Sample preparation was carried out as described in section 2.4. Coating 3 was diluted and directly measured and spiking was performed prior to dilution. Recoveries and RSD values were calculated for all experiments (see Table S15–S16). As already stated in section ‘Matrix effects for generic sample matrices – performed in triplicate’, increased or decreased recoveries mainly resulted from matrix effects. Method recoveries for all PFAAs in these four samples ranged from 5.2–177.2%. Consideration of PFASs that were actually detected in investigated samples showed recoveries between 28.0 and 177.2%. Low recoveries were obtained for PFTrDA (28.0–39.6%) over all generic matrices and thus, reported concentrations of PFTrDA might be underestimations. However, PFTrDA was only reported in one sample. The highest recovery (177.2%) was observed for PFDA in awning sample 2, which means that reported PFDA concentrations in awning samples could be slightly overestimated and should be treated with care.
Comparison of MeOH and water extracts. Extraction efficiency of MeOH and water extracts was compared in regard of detected chain lengths of PFAAs. Fig. S9 shows relative extraction efficiencies and ∑PFAAs. Extraction efficiencies of short chain PFAAs are comparable for all samples except coating 1-A, whereas the ∑PFAAs of this samples was the highest sum that was observed. In average, extraction efficiency of long chain PFASs with water yielded 63% of the amount that was extracted with MeOH.

2.7 HPLC-MS/MS

Quantitative data was recorded with three different UPLC-MS/MS systems. All mass analysers that were used in the present study were triple quadrupole mass spectrometers (QqQ-MS). Two UPLC-MS/MS systems consisted of an Agilent 1290 infinity HPLC (CTC PAL autosampler) either coupled with a Triple Quad 5500 or Triple Quad 6500 (AB Sciex LLC, Framingham, MA, USA, software MultiQuant version 3.0.3, AB SCIEX). The third UPLC-MS/MS system was a Waters Acquity UPLC with a Acquity UPLC Autosampler and a Aquity UPLC Binary Solvent Pump, coupled to a QqQ-MS (Waters Xevo TQ MS, software MassLynx version 4.1, Waters). Ionization was performed with an electrospray ionization (ESI) source in negative mode (−4.5 kV). Separation was carried out on a Waters AQUITY UPLC BEH T3 reversed phase (RP) column with 1.7 μm particle size and dimensions of 2.1 × 100 mm at 25 °C column oven temperature and a flow rate of 300 μL min−1. Solvents, HPLC gradient and mobile phase, as well as the instruments and MRM transitions used in this study are available in the ESI (see Tables S1–S3 and S5).

3 Results and discussion

The PFAS content of 51 building material and fabric samples was investigated in order to estimate their possible contribution to environmental PFAS concentrations. Twenty-nine PFCAs, PFSAs and precursors with diverse chain lengths (C4–C14) were analysed, 11 of which (PFSAs (C4–C7 and C12), 4[thin space (1/6-em)]:[thin space (1/6-em)]2 FTS, 7H-dodecafluoroheptanoic acid (7HPFHpA), perfluoro-3,7-dimethyloctanoic acid (PF37DMOA), 8[thin space (1/6-em)]:[thin space (1/6-em)]2 FTCA, 8[thin space (1/6-em)]:[thin space (1/6-em)]3 FTCA and PFOSA) were not detected in any sample and will not be discussed. Table 1 shows the number of analysed samples per category, number of findings and detected substance classes. In total, PFASs were detected in 39% of investigated building material samples and in 60% of fabric samples. Fig. 1 and 3 show the sum of PFAAs and FTOHs, respectively, with the PFAS composition for individual samples while Fig. 2 and 4 show the detection frequencies of PFASs. The sum of concentrations of the 26 detected PFAAs, ionic precursors and non-volatile precursors (∑PFAA) ranged from 2 to 885 μg kg−1. Detected concentrations of non-volatile PFASs were all below 0.1% (w/w). FTOHs were detected in a concentration range of 40 μg kg−1 to 4020 μg kg−1 for solid samples and 4.0 g L−1 to 4.3 g L−1 for liquid samples (sum of three FTOHs (∑FTOH)). PFOA had the highest detection frequency over all samples (29%), followed by 8[thin space (1/6-em)]:[thin space (1/6-em)]2 FTOH (25%). Consideration of individual sample types showed that perfluorobutanoic acid (PFBA) was the most frequently detected PFAA in building material samples (26%) while PFOA was most frequently detected in fabric samples (39%; see Fig. 4). 8[thin space (1/6-em)]:[thin space (1/6-em)]2 FTOH was the most frequently detected FTOH in fabric samples (36%); whereas, 6[thin space (1/6-em)]:[thin space (1/6-em)]2 FTOH, 8[thin space (1/6-em)]:[thin space (1/6-em)]2 FTOH and 10[thin space (1/6-em)]:[thin space (1/6-em)]2 FTOH were detected in the same number of building materials (13%). While detection frequencies of fabric samples showed strong trends toward C8 chemistry, the data for building materials indicated a predominant use of short-chain PFAAs (see Fig. 4). However, chain-length trends could possibly result from different production or formulation dates. Tests for correlation of the concentrations between different PFASs did not reveal significant trends (see ESI, Fig. S1 and S2). Due to the varying nature and application fields of investigated samples as well as the tremendous differences in detected PFASs and their concentrations, categories will be discussed in individual sections (see 3.1 (building materials) and 3.2 (fabrics)). The individual concentrations of building materials and fabrics are available in the ESI (Tables S6, S7, S8 and S9).
Table 1 Overview of investigated sample per category for the sample groups building materials and fabrics with the number of positive findings and detected substance classes; ntotal describes the number of samples of this category and npositive describes the number of samples with detection of PFASsa
Sample type (n) Category Findings ntotal(npositive) Detected substance class
a “—” no PFASs detected.
Building materials (23) Coating 4(3) PFCAs (C4–C14), 6[thin space (1/6-em)]:[thin space (1/6-em)]2 FTS, FTOHs (6[thin space (1/6-em)]:[thin space (1/6-em)]2, 8[thin space (1/6-em)]:[thin space (1/6-em)]2, 10[thin space (1/6-em)]:[thin space (1/6-em)]2)
Paint 3(0)
Stain 1(1) PFBA
Lacquer 2(0)
OSB 1(1) PFBA
Sealant 2(1) FTOHs (8[thin space (1/6-em)]:[thin space (1/6-em)]2, 10[thin space (1/6-em)]:[thin space (1/6-em)]2)
Wood glue 1(0)
Foil (ETFE/PTFE for facades or glass-substituents) 4(3) PFCAs (C4–C14), 6[thin space (1/6-em)]:[thin space (1/6-em)]2 FTS, FTOHs (6[thin space (1/6-em)]:[thin space (1/6-em)]2, 8[thin space (1/6-em)]:[thin space (1/6-em)]2, 10[thin space (1/6-em)]:[thin space (1/6-em)]2)
Foil (PE for packaging of building materials) 2(0)
Foil (roofing material) 2(0)
Foil (ETFE for solar panel cover) 1(0)
Fabric/Textiles (21) Awning 5(4) PFCAs (C4–C10, C12, C14), FTOHs (6[thin space (1/6-em)]:[thin space (1/6-em)]2, 8[thin space (1/6-em)]:[thin space (1/6-em)]2, 10[thin space (1/6-em)]:[thin space (1/6-em)]2)
Seat cover (public transport) 7(6) PFCAs (C8, C10, C12), PFOS, 8[thin space (1/6-em)]:[thin space (1/6-em)]2 FTS, 8[thin space (1/6-em)]:[thin space (1/6-em)]2 FTOH
Maritime application 5(5) PFCAs (C7, C8) FTOHs (6[thin space (1/6-em)]:[thin space (1/6-em)]2, 8[thin space (1/6-em)]:[thin space (1/6-em)]2, 10[thin space (1/6-em)]:[thin space (1/6-em)]2)
Seat cover (car) 3(0)
Seat cover (furniture) 1(1) PFCA (C4–C6), 6[thin space (1/6-em)]:[thin space (1/6-em)]2 FTOH
Fabric/Tarpaulins (7) Truck trailer cover 3(1) 6[thin space (1/6-em)]:[thin space (1/6-em)]2 FTOH
Tent material 4(0)



image file: c9em00091g-f1.tif
Fig. 1 ∑PFAA (in μg kg−1, respectively μg L−1) for investigated products ((a) fabrics; (b) building materials). Only samples with positive findings shown. Product category and numbering of samples indicated below bars. If not indicated otherwise, results from MeOH extracts are shown. Sample 1-A (top) and 1-B (bottom) show the results of the top and bottom formulation of coating sample 1.

image file: c9em00091g-f2.tif
Fig. 2 Detection frequencies of individual PFAAs in fabric samples (a) and building materials (b) in percent. Sorted by substance class and chain length. Only samples with positive findings shown.

image file: c9em00091g-f3.tif
Fig. 3 ∑FTOH (in μg kg−1, g L−1 or μg L−1 respectively) for investigated products ((a) fabrics; (b) building materials). Only samples with positive findings shown. Product category and numbering of samples indicated below bars.

image file: c9em00091g-f4.tif
Fig. 4 Detection frequencies of individual FTOHs in fabric samples (a) and building materials (b) in percent. Sorted by chain length. Only samples with positive findings shown.

3.1 PFAS content of building material samples

Within the group building materials, the highest diversity of PFAAs and the highest sum of PFASs was observed in coatings. Similarly, the highest ∑FTOH was detected in one of the four investigated coating samples (coating 2). Relatively high FTOH concentrations were also detected in the other three coating samples. The detection frequencies increased with decreasing chain length. However, since the formulation dates are unknown, it is not clear if manufacturers generally tend to shift towards short-chain PFASs. Only one of the investigated coating samples was directly advertised to be PFOA and PFOS free, which indicates a general awareness by the examined industrial sector. Samples were summarized in logical groups and are discussed in the proceeding text.

Coating samples 1 and 4 consisted of a top and a bottom coating (1-A (top), 1-B (bottom), 4-A (top) and 4-B (bottom)). PFAAs were detected in every coating except coating sample 4 (both, top and bottom coating). No MeOH extract of coating 3 was generated. No PFASs were detected in coating 4-A and 4-B (top and bottom coating). The concentrations and chain lengths of PFAAs strongly varied in the investigated coatings.

Interestingly, the PFAA compositions and chain length distribution also strongly varied between coating 1-A and 1-B (top and bottom coating of one product). The producer could have used different additives for bottom and top coating, however, the intended purpose is not clear. The PFAA concentration of 1-A was approximately tenfold higher than the concentration in coating 1-B or other coating samples. Furthermore, only PFCAs with a chain length of C4–C7 were detected in coating 1-A whereas coating 1-B has PFCAs with a chain length of C4–C14. One similarity between the investigated coating samples is the relatively high portion of PFHxA. Coating sample 2 was advertised as a fluorocarbon impregnation for natural and artificial stones and the producer claimed that the product does not contain PFOA or PFOS. This was confirmed since only PFCAs with a chain length of C4–C6 were detected. FTOHs were also detected in three coating samples (1-A, 2 and 3) with concentrations of up to 4.3 g L−1 (∑FTOH, coating 2). Coating 2 and 3 had to be considerably diluted (1[thin space (1/6-em)]:[thin space (1/6-em)]1000, 1[thin space (1/6-em)]:[thin space (1/6-em)]10[thin space (1/6-em)]000 or 1[thin space (1/6-em)]:[thin space (1/6-em)]100[thin space (1/6-em)]000) in order to determine FTOH concentrations. Both, the retention time and the peak shape of the diluted solutions matched those of the FTOH standards. Furthermore, comparison with detected PFAAs showed comparable chain-length pattern, hence, support detected FTOH species and observed concentrations. However, high dilution could have caused a slight offset in measured concentration transfer to a higher error when multiplied according to the dilution factor. Thus, observed FTOH concentrations for coating 2 and 3 should be considered as approximate values. In general, we assume that application of PFASs in such products – albeit not necessarily the ones investigated in this study – is carried out intentionally in order to achieve water, dirt and oil repelling properties as this was stated in the corresponding advertisements.

No PFASs were detected in lacquer samples. Chromatograms of paint samples pointed towards moderate concentrations of 6[thin space (1/6-em)]:[thin space (1/6-em)]2 or 8[thin space (1/6-em)]:[thin space (1/6-em)]2 FTOH in the three investigated paint samples. Unfortunately, strong interferences (matrix) hampered accurate data evaluation. Thus, FTOHs were not evaluated for paint samples. PFBA was detected in the investigated stain sample. However, PFBA was only detected in the MeOH extract of the stain sample. This is a peculiar observation, since PFBA is very mobile and easily soluble in water.

One OSB sample was also investigated. PFBA was the only PFAA that was detected in the aqueous extract. Furthermore, no PFAAs were detected in the MeOH extract of this sample. No FTOHs were detected in the investigated OSB sample. Běcanová et al. reported only short chain and C8 PFCAs (C5–C8) in derived timber products; whereas, they did not investigate the PFBA content.26 However, the concentrations observed by the researchers were comparable to the PFBA concentration in the OSB sample that was investigated during this study.26 PFASs in derived timber products could possibly come from adhesives.29,30 Although it is mentioned in literature that wood glue could contain PFASs, no PFASs were detected in the investigated wood glue sample (see Table 1). However, there is only one sample, and it is not representative of a group.

The investigated foil samples can be divided into four general categories (see Table 1). Investigated roofing materials consisted of ethylene propylene diene monomer rubbers (EPDM). None of the PFASs analysed was detected in roofing materials. No PFASs were detected in polyethylene (PE) foil samples for packaging purposes. The water resistance of these polymers is not dependent on additional treatments (e.g. fluorocarbon coatings) and the application of PFASs (both, for processing as well as treatment for water repellent properties) might be redundant. The last two categories are the cover for solar panels and the materials for architectural purposes. They consisted of fluoropolymers polytetrafluoroethylene (PTFE) or ethylene tetrafluoroethylene copolymer (ETFE). No PFASs were detected in the investigated solar panel cover (ETFE). PFAAs were detected in three of the four investigated foils for architectural purposes. Concentration and PFAS composition strongly varied (see Fig. 3; ∑PFAA in the range of 3.0–32.5 μg kg−1). PFBA and perfluoropentanoic acid (PFPeA) were detected in foil 1, whereas PFOS was detected in foil 2 and PFOA was detected in foil 3. The concentration of PFBA was approximately ten-fold higher compared to other PFASs that were detected in foil samples. No FTOHs were detected in the investigated foil samples for architectural purposes. PFAAs are presumably applied as processing aids during production of fluoropolymers and remain in the finished product.31,32

No PFAAs were detected in the investigated sealant samples. FTOHs were detected in one of the two investigated sealants (8[thin space (1/6-em)]:[thin space (1/6-em)]2 FTOH and 10[thin space (1/6-em)]:[thin space (1/6-em)]2 FTOH; ∑FTOH = 540 μg kg−1). This product was advertised as a “water-stop” sealant. It is not known if PFASs were intentionally applied during production or resulted as impurities from storage or transport, however, literature suggests that PFASs might be used in sealant products.30

3.2 PFAS content of fabric samples

The highest diversity of PFAAs was observed in awning materials (see Fig. 3). Two of the four awning samples with positive findings (awning 1 and 2) revealed the same PFAA finger print pattern. This can be easily explained, since both samples came from the same producer. Furthermore, the ∑PFAA for these two samples was approximately tenfold higher compared to other samples. The largest portion of detected PFAAs in awning 1 and 2 showed chain lengths ≥ C8, whereas other awnings as well as the investigated furniture cover revealed higher shares of PFAS with lengths < C8. As expected, PFOA had the highest detection frequency in fabric samples. The different product categories are further discussed in the proceeding text.

Investigated awning materials can be divided into two groups. The first group consisted of tarpaulins used as party tents (n = 4). No PFASs were detected in this group. In contrast, PFASs were detected in every sample of the second group (awning materials for marquees; n = 5). PFAAs were detected in all samples but one (awning 5) whereas PFBA, PFHxA and PFOA were detected in all of them. FTOHs were also detected in all awning samples but one. Awning 1 and 2 revealed the highest ∑PFAA over all fabric samples (approximately tenfold higher compared to other awning samples). The concentration of PFCAs with a chain length ≤ C7 were detected in comparable concentrations among all awnings. The main share of PFASs contributing to the ∑PFAA for awning 1 and 2 decreased from PFCAs with a chain length ≥ C8. On the other hand, no PFAAs with a chain length > C8 were detected in awning 3 and 4. Comparable findings were observed for FTOHs where 8[thin space (1/6-em)]:[thin space (1/6-em)]2 FTOH and 10[thin space (1/6-em)]:[thin space (1/6-em)]2 FTOH are the main contributors in awning 1 and 2. Interestingly, awning 4, which was advertised to having a dirt-, water- and mold-repelling finish unlike the other marquee samples, was found to have the lowest ∑PFAA, the least PFAA diversity and the lowest FTOH concentration. Perhaps, other PFASs than the ones investigated in the present study were used. However, the determination of adsorbable organic fluorine and non-target measurements were not conducted in order to test this hypothesis. It should be stated that the chain length profiles of PFAAs matched the profile of the detected FTOHs. General advertisement suggests that PFASs were added intentionally to improve weatherability.

Only one sample for textile furniture covers was investigated, and the results revealed a ∑PFAA of 9.8 μg kg−1 resulting from short chain PFAAs only. Accordingly, only 6[thin space (1/6-em)]:[thin space (1/6-em)]2 FTOH was detected with a concentration of 690 μg kg−1. Furthermore, some of the investigated samples from the category textiles for maritime applications can be used for upholstering of boat furniture.

PFASs were detected in six out of seven investigated seat covers for public transport. Only long chain PFASs (C8–C12) were detected in these samples. PFOA was detected in every sample but one. PFOS and PFDoDA were each detected in one sample. Although PFAS concentrations in seat covers for public transport were relatively high (∑PFAA = 2.0–49.0 μg kg−1), FTOHs were only detected in one of the samples with a comparably low concentration (40 μg kg−1 8[thin space (1/6-em)]:[thin space (1/6-em)]2 FTOH in public transport seat cover 6). However, public transport seat cover samples 1, 2, 4 and 5 showed high concentrations of 8[thin space (1/6-em)]:[thin space (1/6-em)]2 FTS (9.5–26.0 μg kg−1), possibly as a precursor. Thus, observed chain length-profiles of detected precursors matched detected PFCAs. On the contrary, no PFASs were detected in investigated textiles for passenger car seats. It should be noted that investigated passenger seat covers were purchased from a single original equipment manufacturer (OEM), hence, it is not evident if textiles will or already have experienced a potential final treatment or impregnation.

PFASs were detected in all of the investigated textile samples for maritime applications. Samples included textiles that can be used for bimini tops, console housings, seat covers, sail covers, weather protection for wooden boats and complete covers. Two samples (maritime application 1 and 2) contained low concentrations of PFHxA or PFHxA and PFOA, respectively (∑PFAA = 2.4–7.4 μg kg−1). Furthermore, FTOHs with ∑FTOH ranging from 50 to 910 μg kg−1 were detected in maritime application samples 1, 3, 4 and 5. Two textiles were advertised with water repelling properties, two with water resisting properties and one was explicit described to be treated with a fluorocarbon coating. Therefore, we assume that PFASs were added intentionally.

Overall, PFASs were only detected in one sample from the product group truck trailer covers. 6[thin space (1/6-em)]:[thin space (1/6-em)]2 FTOH was detected with a concentration of 260 μg kg−1 (truck trailer cover 1). The investigated truck trailer covers were all made from polyvinyl chloride (PVC), which generally provides good water and weather resistance. Moreover, two of the investigated party tent materials were also made from PVC and no PFASs were detected either.

3.3 Release of PFASs

Complementary to methanol extraction, sample preparation was also performed with water as the extraction solvent (see ESI) resulting in slightly lower ∑PFAA. Therefore, obtained results indicate a possible release of PFAAs into the environment, resulting from weathering and run-off. Thus, this study shows strong evidence that investigated materials contribute to the overall pollution with PFASs, and therefore, might cause a threat for human health and the environment. It is known that PFASs can enter the environment via run-off or directly evaporate into the atmosphere and are then further transformed into non-volatile PFAS.33 Some of the investigated products are not directly exposed to all weather conditions and therefore might only contribute to environmental PFAS levels after their disposal. The application of investigated materials in indoor environments could lead to a discharge of volatile portions into room-air or direct contact (dermal uptake; e.g. public transport seat covers).

Analysis of the worst case scenarios indicate a maximum release of up to 0.014 mg PFOA resulting from one public transport seat cover with an estimated area of 0.47 m2, which was calculated from the PFAA content of public transport seat cover 5. Similar calculations for a likely PFAS contribution were made for a football stadium, whose outer shell is built from ETFE cushions (approximate surface area of 64[thin space (1/6-em)]000 m2).34 Worst case calculations (complete extraction of PFASs in detected concentrations (foil 1) for the outer surface area of a football arena) show a possible release of up to 4 g PFASs from the complete shell. Furthermore, fluoropolymers can also be used as glass-substituents in greenhouses, skyscrapers and public swimming pools or for the covering of solar panels. Furthermore, we want to express concerns related to coatings for architectural purposes, which are predominantly used in urban environments (e.g. walls in cities like Hamburg, Cologne, London and San Francisco). One of the investigated coatings, which is assumed to be directly linked to impregnations in these cities, showed the highest ∑PFAA of all examined materials (885 μg kg−1). Furthermore, highest FTOH concentrations were detected in coating samples. Positive advertisement and widespread use of such impregnations could lead to further applications in a global scale, thus, entail a relevant pollution source of PFASs. Only one coating sample did not show any PFASs, which seems suspicious since use and advertisement closely resemble other investigated products.

4 Conclusions

In this study, we investigated the PFAS content of 51 industrial goods that can be applied in building industry, transportation and for general upholstering. The application fields of these products comprise both, indoor and outdoor environments. PFASs were detected in a majority of the investigated samples. Volatile PFASs showed individual concentrations up to approximately 4.3 g L−1 (6[thin space (1/6-em)]:[thin space (1/6-em)]2 FTOH), while non-volatile PFASs were partially detected in concentrations above 100 μg kg−1 (PFOA). Under consideration of application areas, assessment of data suggests the possibility of direct PFAS discharge into the environment for most of the investigated building materials and fabrics (e.g. coatings, fluoropolymer siding, maritime applications or marquees). While detected concentrations of analysed legacy PFASs show alarming levels in some cases, the use of novel PFASs that have already been reported in the environment18 or PFASs that were not monitored cannot be ruled out. This study shows that PFASs can be detected in materials that were previously not investigated. Thus, further studies need to be performed in order to (1) increase the knowledge of possible sources for PFASs, (2) deduce entrance pathways into the environment and (3) conduct life-cycle assessments. Moreover, new studies should include sum parameters or non-target approaches, in order to gain information regarding possible sources of the so-called “dark matter”, as described by Kotthoff et al.,35 which is derived from the discrepancy of target analysis and adsorbable organic fluorine36 determination.

Funding

We thank the German Environmental Agency (UBA) for the financial support of the research project: “Potenzielle SVHC in Umwelt und Erzeugnissen: Messungen zum Vorkommen potentiell besonders besorgniserregender Stoffe in Umwelt und Erzeugnissen” (FKZ: 3716644300).

Conflicts of interest

There are no conflicts to declare.

Acknowledgements

We appreciate the sample contributions by vendors and retail stores that supplied materials free of charge.

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Footnote

Electronic supplementary information (ESI) available. See DOI: 10.1039/c9em00091g

This journal is © The Royal Society of Chemistry 2019