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Per- and polyfluoroalkyl substances (PFASs) in indoor air and dust from homes and various microenvironments in China: Implications for human exposure Yiming Yao, Yangyang Zhao, Hongwen Sun, Shuai Chang, Lingyan Zhu, Alfredo Carlos Alder, and Kurunthachalam Kannan Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.7b04971 • Publication Date (Web): 08 Feb 2018 Downloaded from http://pubs.acs.org on February 15, 2018

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Environmental Science & Technology

1

Per- and polyfluoroalkyl substances (PFASs)

2

in indoor air and dust from homes and

3

various

4

Implications for human exposure

microenvironments

in

China:

5 6 7 8 9 10 11 12 13 14 15 16

Yiming Yao,a,1 Yangyang Zhao,a,1 Hongwen Sun,*,a Shuai Chang,a Lingyan Zhu,a Alfredo C. Alder,a,b Kurunthachalam Kannanc a MOE Key Laboratory of Pollution Processes and Environmental Criteria, College of Environmental Science and Engineering, Nankai University, Tianjin 300071, China. 38 Tongyan Road, Jinnan District, Tianjin 300350, China TEL: 86-22-23509241, Email: [email protected] b Eawag, Swiss Federal Institute of Environmental Science and Technology, 8600 Dübendorf, Switzerland c Wadsworth Center, New York State Department of Health, and Department of Environmental Health Sciences, School of Public Health, State University of New York at Albany, Albany, NY 12201, USA 1 Equally contribution

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ABSTRACT

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A newly developed solid-phase extraction cartridge composed of mixed sorbents

19

was optimized for collection of both neutral and ionizable per- and polyfluoroalkyl

20

substances (PFASs) in indoor air. Eighty-one indoor air samples and 29 indoor dust

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samples were collected from rooms of homes and hotels, textile shops, and cinemas in

22

Tianjin, China. Fluorotelomer alcohols (FTOHs) were the predominant PFASs found

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in air (250-82,300 pg/m3) and hotel dust (24.8-678 ng/g). Polyfluoroalkyl phosphoric

24

acid diesters were found at lower levels of n.d.-125 pg/m3 in air and 0.32-183 ng/g in

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dust. Perfluoroalkyl carboxylic acids (PFCAs) were dominant ionizable PFASs in air

26

samples (121-20,600 pg/m3) with C4-C7 PFCAs contributing to 54%±17% of the

27

profiles, suggesting an ongoing shift to short-chain PFASs. Long-chain PFCAs (C>7)

28

were strongly correlated and the intermediate metabolite of FTOHs, fluorotelomer

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unsaturated carboxylic acids, occurred in all the air samples at concentrations up to 1

ACS Paragon Plus Environment


30

413 pg/m3, suggesting the transformation of precursors such as FTOHs in indoor

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environment. Daily intake of ΣPFASs via air inhalation and dust ingestion was

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estimated at 1.04-14.1 ng/kg bw/d and 0.10-8.17 ng/kg bw/d, respectively,

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demonstrating that inhalation of air with fine suspended particles was a more

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important direct exposure pathway than dust ingestion for PFASs to adults.

35

ABSTRACT ART

36

37 38

2


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1. INTRODUCTION

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Per- and polyfluoroalkyl substances (PFASs) are a family of synthetic

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compounds extensively applied in industrial processes and commercial products as

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protective coatings for fabrics and metals, and as additives in fire-fighting foams, due

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to their surface activity, and thermal and chemical stability.1,

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perfluoroalkane sulfonic acids (PFSAs, n ≥ 6) and perfluoroalkyl carboxylic acids

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(PFCAs, n ≥ 7) are persistent and bioaccumulative and have been ubiquitously

46

detected in food,

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associated with hepatotoxicity, reproductive toxicity, developmental toxicity, and

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immunotoxicity.9, 10

3, 4

2

Long-chain

drinking water,5, 6 and human specimens.7, 8 PFASs exposure is

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The phase-out of C8 PFASs has been implemented in most developed

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countries,11, 12 where shifting to shorter-chain PFASs and other alternatives has led to

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their increasing levels in environmental matrices and progressive human exposure

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risk.13 Meanwhile, the production and application of legacy long-chain perfluoroalkyl

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acids (PFAAs) and their precursor fluorotelomer alcohols (FTOHs) rehabilitated in

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mainland China.2 In China, perfluorooctanoic acid (PFOA) was found dominant in

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both indoor and outdoor dust around a fluorochemical industrial park.14 Dominating

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air emission of long-chain PFASs was found at a textile manufacturing although

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short-chain PFASs were claimed to be used.15 Moreover, the product profiles of

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short-chain substitutes may vary between countries. The emission profiles of PFASs

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in China may be unique and more complicated due to a co-occurrence of PFASs with

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different chain lengths in final consumer products. Therefore, exposure to PFASs in

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residential places is of primary interest. Besides, the occurrence of PFASs in public

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places where PFAS-containing products are stored, sold or used may also raise

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concerns for occupational exposure risk and is yet to be clarified in China.

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In addition to ingestion through diet and drinking water,16-18 indoor air inhalation

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and dust ingestion are major pathways of human exposure to PFASs.19 As for PFAAs, 3



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which are most concerned PFASs due to their persistence and toxicity, apart from

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direct uptake of from the environment,20 inhalation of volatile precursors including

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FTOHs and perfluorooctane sulfonamidoethanols/sulfonamides (FOSE/FOSAs) and

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subsequent internal biotransformation also contributes to human exposure to PFAAs

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(called as indirect uptake). FTOHs and polyfluoroalkyl phosphoric acid diesters

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(diPAPs) of newly concern have been shown to be metabolized in human and rodents

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to produce PFCAs,21-24 whereas biotransformation of FOSE/FOSAs in vivo can yield

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perfluorooctane sulfonic acid (PFOS).25, 26 Till now, the direct uptake of PFAAs in

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indoor dust has been well documented, however, a direct exposure to PFAAs via air

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inhalation has been less emphasized on. The ionizable PFASs (i.e. PFAAs) can be

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enriched in fine particles (< 5 µm)27 that may as well undergo pulmonary uptake.

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Even so, limited studies have simultaneously investigated the occurrence of both

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neutral and ionizable PFASs in indoor air,28, 29 whereas ionizable PFASs have been

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frequently detected in indoor dust.20, 30, 31 This knowledge gap presents considerable

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uncertainty in exposure and risk assessment of human exposure to PFAAs. Therefore,

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simultaneous investigation on both neutral and ionizable PFASs in air and paired dust

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samples is indispensable for a comprehensive and accurate exposure assessment in

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indoor environment.

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A suitable sampling technique is crucial for simultaneous and accurate collection

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and measurement of both neutral and ionizable PFASs in air. Both passive (XAD-4

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impregnated polyurethane foam (PUF) disks in steel housings)32 and active samplers

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(glass column containing XAD-2 resin sandwiched between two PUF plugs) have

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been used for air monitoring of PFASs.33 However, sampling using these two types of

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samplers either requires much space or takes a long sampling time, which are primary

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drawbacks when sampling indoor air. Besides, these two techniques require tedious

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pre-sampling and extraction processes, which might incur contamination of target

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chemicals. Apart from these two types of samplers, solid-phase extraction (SPE)

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cartridge is portable, flexible, and feasible for indoor air collection. A low-volume

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SPE sampler (Isolute ENV+ SPE cartridges) was initially developed for volatile 4


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neutral PFASs,34 but its use for the collection of ionizable PFASs was not validated.35

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Therefore, it is necessary to develop a new type of SPE sampler that would enrich

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both neutral and ionizable PFASs including diPAPs in ambient air from indoor

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environments.

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In the present study, a new type of SPE sampler composed of two kinds of

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sorbents was initially developed to enable simultaneous collection of the totality of

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neutral PFASs, ionizable PFASs, and diPAPs in indoor air. Sampling campaign was

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conducted in different kinds of rooms of residential and hotel buildings, and

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microenvironments of public places (cinemas/outdoor equipment/textile shops);

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paired indoor dust samples of some sites were also collected and analyzed. The aims

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of this study were to determine the occurrence and composition profiles of PFASs in

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different indoor environments, to elucidate potential influencing factors on indoor

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profiles of PFASs based on different room setups, as well as to evaluate human

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exposure to PFASs via air inhalation and dust ingestion. Our results may provide

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further information on exposure pathways and clarify exposure risks in various

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microenvironments in China.

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2. MATERIALS AND METHODS

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2.1. Sample Collection.

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Airborne PFASs were collected on a SPE cartridge, which was initially

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developed and optimized for the target analytes (Table S1 in supporting

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information(SI)). The SPE cartridge (6 mL) consisted of two layers of absorbents: the

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upper layer of HC-C18 (250 mg) for trapping mainly neutral PFASs and the bottom

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layer of WAX (250 mg) for trapping ionizable PFASs. A diaphragm vacuum pump

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(Jinteng, GM-0.33A) was used for pumping air consecutively through the HC-C18

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and WAX layers of absorbents. The validation of the sampling device including

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extraction efficiency, breakthrough, and micro-chamber spiking tests was given in the

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SI. 5



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Indoor air sampling was performed in Tianjin, China, in the summer (June-September)

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of 2015 in standard rooms of 13 hotels, living rooms of 19 homes, and

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microenvironments of 13 public places. Nine living rooms of the homes were

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resampled in the winter (December) for comparison of PFAS concentrations between

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the two seasons. The public places included 5 outdoor equipment shops (OS) that sell

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outdoor wear, 3 curtain shops (CurS), 2 carpet shops (CarS), and 3 cinemas, where the

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goods sold or decorations used were thought to be potential sources of PFASs. The

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details of indoor air sampling are given in Table S2. Prior to assembly, the SPE

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cartridges were sequentially conditioned with methanol and ethyl acetate and wrapped

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in aluminum foil sealed in polyethylene plastic (PP) bags. For sampling, two

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cartridges were connected to the pump in parallel to reduce the loading pressure and

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to increase sampling efficiency. Indoor air about 1 m above the floor was collected at

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an initial sampling rate of 4.5 L/min for 8-12 h to reach a volume of 2.16-3.24 m3. In

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some cases, sampling time was extended for convenience that gave a sampling

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volume up to 8.33 m3. At some public places, due to logical constraints, sampling

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time was less than 8 h but that volume was sufficient for the quantification of PFASs

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(Table S2). After sampling, the cartridges were detached on site, wrapped and sealed

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in aluminum foil and PP bags, transported to the laboratory, and kept at -20 °C before

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extraction.

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In summer, a total of 11 hotel and 18 home dust samples were collected within

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the period of air sampling. The dust samples from hotels were collected from dust

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bags in vacuum cleaners and those from homes were collected using a pre-cleaned

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disposable bristle brush from multiple sites on surfaces of furniture and floor. The

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sampled areas were all kept from cleaning at least for one week. All dust samples

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were directly swept into PP tubes, sealed in PP bags, and kept at -20 °C until analysis.

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Neutral PFASs were analyzed using GC-MS, while ionizable PFASs were

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analyzed using HPLC-MS/MS. Details of chemical information, sample pretreatment,

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and instrumental analysis are provided in SI. 6


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2.2. Calculation of Daily Intake.

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Direct and indirect exposure pathways to PFASs via indoor air inhalation and

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dust ingestion were estimated for toddlers (1-2 years) and adults (>20 years) using the

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following equations: 36

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Eair = (Cair × Vair × Fuptake × Ymeta) / (mbw × 1000)

(1)

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Edust = (Cdust × Qdust × Fuptake × Ymeta) / (mbw × 1000)

(2)

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where Eair (ng/kg bw/d) and Edust (ng/kg bw/d) are the estimated daily intakes of

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PFASs through indoor air and dust samples, respectively; Cair (pg/m3) is PFAS

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concentration in air samples; Cdust (ng/g) is PFAS concentration in dust samples; Vair

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(m3/d) is daily inhalation volume; Qdust (mg/d) is dust ingestion rate; Fuptake is uptake

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fraction (unitless); For estimation of indirect exposure, Ymeta was introduced as a

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factor to account for metabolic yield (mass basis, unitless) of PFAAs from precursors

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and mbw is body weight (kg).

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For direct exposure assessment, two scenarios were considered: an average-case

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scenario with measured median PFAS concentrations and a worst-case scenario with

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95th percentile concentrations. Daily inhalation volume was kept constant between the

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two scenarios (Vair, 8.0 m3/d and 15.7 m3/d for toddlers and adults, respectively);

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median dust ingestion rates were used for average-case scenario (Qdust, 60 mg/d and

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30 mg/d for toddlers and adults, respectively) and high rates for the worst-case

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scenario (200 mg/d and 100 mg/d for toddlers and adults, respectively).35, 37-39 Due to

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the lack of adequate pharmacokinetic data, pulmonary and gastrointestinal uptake

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fractions (Fuptake unitless) in both scenarios were assumed to be 100% for all PFASs,

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which was usually adopted in other studies.20,

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recommended in Korean Exposure Factors Handbook were 11.7 kg and 62.8 kg for

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toddlers and adults, respectively. These values adopted for Korean population were

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more appropriate for the Chinese population than those from the western countries.43

40-42

7


The mean body weights


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For

indirect

exposure,

metabolic

yield

(Ymeta)

Page 8 of 31

values 44, 45

that

represent

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biotransformation of 8:2 FTOH to PFOA were proposed.22,

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0.0027 (mass basis) was used for human studies, and this value was fitted in the

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average-case exposure scenario.42 For the worst-case exposure scenario, instead of

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assuming a 100% transformation yield, a value of 0.05 (Ymeta) was used as a

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conservative estimation, which was so far the highest yield of those used in previous

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studies.46 As for 8:2 diPAP, a value of 0.1, which was obtained from an in vivo rodent

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study, was used for Ymeta in average-case exposure scenario,47 whereas that for the

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worst-case scenario was 1.

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2.3. Quality Control and Quality Assurance.

A Ymeta value of

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Procedure blanks consisting of SPE cartridges fortified with internal standards

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were extracted with each batch of samples to evaluate potential analytical

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interferences or possible carryover of the target chemicals between samples. During

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analysis, a calibration standard and an instrumental blank were injected between each

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batch of 20 samples to check instrumental performance. Quantification was

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performed using an eight-point calibration curve (200-50,000 pg/mL) spiked with 5

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ng of each internal standard as same as those in air and dust samples. The regression

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coefficients (R2) of the standard calibration curves were ≥ 0.99 for all target analytes.

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For samples with PFAS signals above the highest point of the calibration curve, the

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extracts were re-analyzed after dilution. Method detection limits (MDLs) were set at

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three times the standard deviation (SD) of values found in procedural blanks, if the

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analyte was present in the blank; otherwise limits of quantification (LOQ) was

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derived from the peak values with a signal-to-noise ratio (S/N) of 10. The MDL

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values for each analyte are given in Table S3. Most of the target analytes were not

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found in procedural and instrumental blanks. PFOA was detected in procedural blanks

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but correction to concentrations in samples was not made because the background

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level was far below the concentrations found in samples in this study (Table S3).

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Recoveries of PFASs spiked into home and hotel dust ranged from 90% to 110%, with 8


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the exception of FTOHs in hotel dust, which were between 60% and 65% (Table S4).

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For cartridge validation, extraction efficiency for neutral and ionizable PFASs

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successively was achieved with ethyl acetate and 0.5% NH4OH/MeOH solution at

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79-123% (Table S5) and no significant breakthrough was observed (Table S6-1). In

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the micro-chamber test at the spiking level of 5 ng, the recoveries of neutral and

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ionizable PFASs were 45-87% and 68-102%, respectively (Table S6-2).

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2.4. Statistical analysis.

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Non-detected analytes were assigned with a value of zero and incorporated into

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statistical analysis. Concentrations below the MDLs were taken as left-censored data

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and the dataset was treated with robust regression on order statistics for median

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calculation. Spearman rank correlation analysis and Mann-Whitney Test were

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conducted using IBM SPSS Statistics 22. Prior to analysis, concentrations were

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natural log-transformed. Pearson’s correlation was only conducted for ventilation test.

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The hierarchical cluster analysis and heatmap were conducted and created using R

218

3.4.3 with agglomeration method of Ward.D (Euclidean). All other illustrations

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presented on this manuscript were created using OriginLab OriginPro 2016.

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3. RESULTS AND DISCUSSION

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3.1. PFASs in Air Samples

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Hotel and Residential Buildings. For neutral PFASs, FTOHs were more frequently

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detected than FOSE/FOSAs in hotels (100% vs. 68%) and homes (100% vs. 27%), at

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similar median levels of 3,330 and 3,210 pg/m3, respectively (Fig. 1A and Table 1).

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8:2 FTOH was the dominant FTOH homologue. The highest concentration of

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ΣFTOHs was 62,100 pg/m3 found in a hotel room. In comparison, the concentrations

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of ΣFOSE/FOSAs were 1 to 3 orders of magnitude lower and the highest

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concentration found was 2,460 pg/m3 in a hotel room. DiPAPs were present in 53%

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and 77% of the hotel and home samples, with much lower median levels at 1.08 9



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pg/m3 and 1.17 pg/m3, respectively.

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PFCAs and PFSAs were ionizable and found occurring in most samples (Table

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S7). Detection of ionizable PFASs was also reported in the literature in indoor air and

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the atmosphere using low-volume or passive air samplers.28,

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partially be due to that the finest suspended particles (< 5 µm) was sampled together

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with air. Due to their particular affinity to glass fiber filters, it is not likely to

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differentiate ionizable PFASs between gas and particle phases with them.49 Moreover,

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to account for this total levels in the bulk air is important for health risk assessment.50

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The medians of ΣPFCAs (C4-C12) in hotels and homes were 563 pg/m3 and 691

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pg/m3, respectively (Fig. 1A). In most cases, PFOA was the dominant long-chain

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PFCA (39.0-378 pg/m3), while in some homes, perfluorononanoic acid (PFNA) was

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dominating at concentrations of 182-380 pg/m3. The concentrations of short-chain

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PFCAs (C4-C7) were significantly higher in homes than in hotels (p

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