Per- and polyfluoroalkyl substances and fluorinated alternatives in urine and serum by on-line solid phase extraction–liquid chromatography–tandem mass spectrometry

Highlights

• First mass-spectrometry method to quantify GenX, ADONA, and PFAS in urine or serum.

• Serum is preferred to assess background exposure to long-chain PFAS for biomonitoring.

• Biomonitoring of urine is preferred to assess background exposure to short-chain PFAS.

Abstract

Per- and polyfluoroalkyl substances (PFAS), man-made chemicals with variable length carbon chains containing the perfluoroalkyl moiety (C_nF_2n+1–), are used in many commercial applications. Since 1999–2000, several long-chain PFAS, including perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA), have been detected at trace levels in the blood of most participants of the National Health and Nutrition Examination Survey (NHANES)—representative samples of the U.S. general population—while short-chain PFAS have not. Lower detection frequencies and concentration ranges may reflect lower exposure to short-chain PFAS than to PFOS or PFOA or that, in humans, short-chain PFAS efficiently eliminate in urine. We developed on-line solid phase extraction–HPLC–isotope dilution–MS/MS methods for the quantification in 50 μL of urine or serum of 15 C₃-C₁₁ PFAS (C₃ only in urine), and three fluorinated alternatives used as PFOA or PFOS replacements: GenX (ammonium salt of 2,3,3,3,-tetrafluoro-2-(1,1,2,2,3,3,3-heptafluoropropoxy)-propanoate, also known as HFPO-DA), ADONA (ammonium salt of 4,8-dioxa-3H-perfluorononanoate), and 9Cl-PF3ONS (9-chlorohexadecafluoro-3-oxanonane-1-sulfonate), main component of F53-B. Limit of detection for all analytes was 0.1 ng/mL. To validate the method, we analyzed 50 commercial urine/serum paired samples collected in 2016 from U.S. volunteers with no known exposure to the chemicals. In serum, detection frequency and concentration patterns agreed well with those from NHANES. By contrast, except for perfluorobutanoate, we did not detect long-chain or short-chain PFAS in urine. Also, we did not detect fluorinated alternatives in either urine or serum. Together, these results suggest limited exposure to both short-chain PFAS and select fluorinated alternatives in this convenience population.

Introduction

Some per- and polyfluoroalkyl substances (PFAS), including perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA), persist in humans and the environment and have been detected worldwide in wildlife and the ecosystem (Dewitt, 2015; ATSDR, 2015). Exposure to PFOS and PFOA in the general population is also widespread, although demographic, geographic, and temporal differences exist (Dewitt, 2015; CDC, 2017; Lee et al., 2017; Schoeters et al., 2017; Fromme et al., 2017; De Felip et al., 2015; Kato et al., 2011a; Eriksson et al., 2017; Stubleski et al., 2016; Bartolome et al., 2017). PFOS was used in a wide variety of industrial and consumer products including protective coatings for carpets and apparel, paper coatings, insecticide formulations, and surfactants (Dewitt, 2015; ATSDR, 2015). PFOA has been used primarily to produce its salts, which are used in the production of fluoropolymers and fluoroelastomers. These polymers are used in many industrial and consumer products, including soil, stain, grease, and water resistant coatings on textiles and carpet; uses in the automotive, mechanical, aerospace, chemical, electrical, medical, and building/construction industries; personal care products; and non-stick coatings on cookware (Dewitt, 2015; ATSDR, 2015).

In animals, exposure to PFOS and PFOA is associated with adverse health effects, albeit at serum concentrations higher than the concentrations observed in the general population (Dewitt, 2015; ATSDR, 2015). In 2002, 3 M, the main worldwide manufacturer of PFOS, voluntarily discontinued the production of PFOS precursors and related compounds in the United States. In 2006, the U.S. EPA invited eight major companies in the PFAS industry to join in a global stewardship program with the goal to eliminate emissions of PFOA and its related products by 2015 (US EPA, 2006). As a result of the above changes in manufacturing practices, PFAS with shorter alkyl chains, and fluorinated alternatives, including perfluoroalkyl ether carboxylic acids (PFECAs) and perfluoroalkyl ether sulfonic acids (PFESAs) have entered the market (Gordon, 2011; Wang et al., 2013a) and the environment (Xiao, 2017).

Two PFECAs, GenX (ammonium salt of 2,3,3,3,-tetrafluoro-2-(1,1,2,2,3,3,3-heptafluoropropoxy)-propanoate [also known as HFPO-DA]) and ADONA (ammonium salt of 4,8-dioxa-3H-perfluorononanoate [DONA]) (Table 1), introduced as replacements for long-chain PFAS (Gordon, 2011; Wang et al., 2013a), have shorter elimination half-lives in animals than PFOA (hours versus days) (Gannon et al., 2016; Hundley et al., 2006). However, previous research suggested toxicity of HFPO-DA and ADONA in experimental animals, with a similar mode of toxicity as that of PFOA (Wang et al., 2013a). Furthermore, these fluorinated alternatives cannot be metabolized in biota and may have a similar high affinity to proteins, resulting in a potential for bioaccumulation (Wang et al., 2013a). Last, the detection of GenX in surface waters and drinking water (Heydebreck et al., 2015; Sun et al., 2016; Gebbink et al., 2017) has raised concerns about the potential health implications from human exposure to PFECAs through contaminated drinking water.

A chlorinated PFESA (2-[(6-chloro-1,1,2,2,3,3,4,4,5,5,6,6-dodecafluorohexyl)oxy]-1,1,2,2-tetrafluoroethanesulfonic acid potassium salt, F-53B (CAS No. 73606−19−6) (Wang et al., 2013a)) has been used in chrome plating industry in China for decades (Wang et al., 2013b), and recently detected at relatively high concentrations in the environment and biota in China (Liu et al., 2017; Shi et al., 2015; Wang et al., 2016). In vitro, in vivo, and in silico studies suggest that F-53B can disrupt the thyroid endocrine system at environmentally relevant concentrations (Deng et al., 2017). Documented uses of F-53B outside China are not known, but the persistence and transport potential of F-53B raise some concerns about a future global contamination problem (Wang et al., 2016).

PFAS with five or fewer carbon chains could be possible degradation products generated in the environment or during waste water treatment processes (Lee et al., 2009) and do not seem to bioaccumulate or be toxic (Lieder et al., 2009; Olsen et al., 2009). For example, perfluorobutane sulfonate (PFBS) appears to be much more efficiently eliminated than perfluorohexane sulfonate (PFHxS) or PFOS (Olsen et al., 2009). Nonetheless, the potential impact of these short-chain PFAS on human health and the environment is still unclear (Olsen et al., 2009; Newsted et al., 2008). Short-chain PFAS have been used as replacements of traditional long-chain PFAS. We have measured select short-chain PFAS in U.S. National Health and Nutrition Examination Survey (NHANES) participants’ sera since 1999; yet, we infrequently detected these short-chain PFAS, and when we did, concentrations were rather low compared to other PFAS (CDC, 2017). The low detection frequencies and concentration ranges (Kato et al., 2011a; Olsen et al., 2012) may reflect limited human exposure to short-chain PFAS or the fact that, in humans, these PFAS have relatively short half-lives and are efficiently eliminated in urine. Therefore, urine, not serum, may be the preferred matrix for biomonitoring of short-chain PFAS.

Information on urinary concentrations of PFAS in humans is critical to understand exposure to alternative PFAS. A few methods for the quantification of select PFAS in human urine exist (Li et al., 2013; Perez et al., 2012; Zhang et al., 2013; Kim et al., 2014; Fu et al., 2016; Worley et al., 2017; Zhang et al., 2015), but no methods for the concurrent quantification of select PFAS, PFECAs, and PFESAs for population-based biomonitoring programs such as NHANES. Therefore, we developed an on-line solid phase extraction–high performance liquid chromatography–isotope dilution–tandem mass spectrometry (on-line SPE-HPLC-MS/MS) method for the selective analysis of urine for both short- and long-chain PFAS, two PFECAs, and one PFESA. We also updated our current on-line SPE-HPLC-MS/MS serum method so it could include PFAS alternatives. We analyzed 50 urine–serum paired samples to validate the performance of these methods.