Unexpectedly High Concentrations of a Newly Identified

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Unexpectedly High Concentrations of a Newly Identified Organophosphate Ester, Tris(2,4-di-tert-butylphenyl) Phosphate, in Indoor Dust from Canada Runzeng Liu, and Scott Andrew Mabury Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.8b03061 • Publication Date (Web): 03 Aug 2018 Downloaded from http://pubs.acs.org on August 6, 2018

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Environmental Science & Technology

Submitted to Environmental Science & Technology Unexpectedly High Concentrations of a Newly Identified Organophosphate Ester, Tris(2,4-di-tert-butylphenyl) Phosphate, in Indoor Dust from Canada

Runzeng Liu* and Scott A. Mabury Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, M5S 3H6, Ontario Canada

*Corresponding author Dr. Runzeng Liu Department of Chemistry, University of Toronto E-mail: [email protected] +1 (416) 946-7736

1

ACS Paragon Plus Environment


1

Abstract

2

Organophosphate esters (OPEs) represent a group of additives with significant

3

production and application to various household and industrial products. Given their

4

potential adverse effects on human health, accurate analysis of novel OPEs in indoor

5

dust is crucial. In this study, the novel tris(2,4-di-tert-butylphenyl) phosphate

6

(AO168=O) and six well-known OPEs were investigated. The seven target OPEs

7

were detected in 100% of the office and home dust samples, with ∑OPEs (sum of the

8

OPE concentrations) from 2.92 to 124 µg/g (geometric mean, GM: 12.3 µg/g).

9

Surprisingly, the novel AO168=O (0.10–11.1 µg/g, GM: 1.97 µg/g) was among the

10

highest concentration congeners, contributing 1.36–65.5% to ∑OPEs (mean: 20.7%).

11

AO168=O was the dominant congener in the home dust samples, indicating it is an

12

important OPE congener overlooked previously. AO168=O was also detected in

13

Standard Reference Material 2585 (indoor dust) at an elevated concentration of 10.9

14

µg/g, and significantly higher than the concentrations of the other target OPEs

15

(0.38–2.17 µg/g). Despite the high concentrations measured in this study, no industrial

16

production or application could be identified for AO168=O. The precursor of

17

AO168=O, tris(2,4-di-tert-butylphenyl) phosphite, was detected in 50% of the dust

18

samples, with a GM concentration of 1.48 ng/g. The present study demonstrates that

19

human OPE exposure in indoor environments is greater than was previously reported.

20

This is the first report of the occurrence of AO168=O, its precursor, and its hydrolysis

21

products in the environment.

2


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22

Introduction

23

Organophosphate esters (OPEs) are produced in massive quantities and widely

24

applied in various household and industrial products.1,

25

polybrominated diphenyl ethers, the production and application volume of their

26

replacements, the OPEs, has increased rapidly in recent years.3 The global

27

consumption of OPEs was reported to be 500,000 in 2011, which increased to

28

680,000 tons in 2016.4 Besides being used as flame retardants, OPEs are also used as

29

plasticizers and anti-foaming agents in many products including furniture, textiles,

30

cables, building materials, insulation materials, paints, floor polishes, hydraulic fluids,

31

and electronics.1 In most cases, OPEs are used as additives and are not chemically

32

bonded to the original materials.1 Therefore, OPEs can be slowly released into the

33

environment by abrasion and volatilization. As a result, many OPE analogues,

34

including aryl, alkyl, and halogenated alkyl phosphates, have been detected in various

35

environmental matrices including air, water, sediment, soil, and indoor dust.5-8 The

36

detection of OPEs has also been reported in animals such as fish and birds, and even

37

in human sera.6, 9, 10

38

Exposure to OPEs can potentially cause toxicity such as endocrine disrupting effects.

39

For example, tris(2-chloroethyl) phosphate (TCEP) was reported to alter sex hormone

40

balance in H295R cells and zebrafish through mechanisms such as alterations to

41

steroidogenesis and estrogen metabolism.11 Tris(1,3-dichloro-2-propyl) phosphate

42

(TDClPP) can be transferred to the offspring of adult zebrafish exposed to the

43

compound, leading to thyroid endocrine disruption and developmental neurotoxicity.12 3


2

After the phase-out of


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44

Triphenyl phosphate (TPHP) has also been shown to reduce fecundity in zebrafish by

45

significantly increasing plasma estradiol levels and inhibiting androgen levels.13

46

In recent years, more and more new OPE analogues are being identified in both

47

commercial products and environmental matrices. For instance, novel OPE analogues

48

such as isopropylated and tert-butylated triarylphosphate were recently identified in

49

commercial flame retardant mixtures.14 They were also detected in house dust

50

Standard

51

2,2-Bis(chloromethyl)-propane-1,3-diyltetrakis(2-chloroethyl)bisphosphate (known as

52

V6) was detected in both house and car dust, and had a strong positive relationship

53

with TCEP.15 These results improve our understanding of environmental

54

contamination by OPEs. Tris(2,4-di-tert-butylphenyl) phosphate (AO168=O or

55

T2,4DtBPP) has been reported in plastic combustion products at very high

56

concentrations of part-per-million (ppm) level and suggested its use as a possible

57

tracer for plastic combustion.16 These results also indicate that plastic combustion is

58

likely a source of AO168=O to the surrounding environment. It should be noted that

59

AO168=O was not reported to be used as a flame retardant or plasticizer. It was

60

widely detected as an oxidation product from a phosphite antioxidant used in polymer

61

products.17 Despite these results, no reports are available on the occurrence of

62

AO168=O and related chemicals in the environment.

63

There is mounting evidence for the importance of indoor dust ingestion as a pathway

64

for human exposure to multiple contaminants.18,

65

environments can significantly impact human health, as people spend more than 90%

Reference

Material

(SRM)

19

4


2585.14

Contaminants in indoor

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66

of their time indoors.20 A recent study demonstrated that OPE concentrations in indoor

67

dust were significantly related to serum free thyroxin (T4), prolactin, and decreased

68

semen quality in men.21 Given their adverse effects on human health, accurate

69

analysis of OPEs (especially of previously unreported congeners) in indoor dust is

70

important. In the present investigation, indoor dust samples were collected from

71

several offices and homes located in Toronto to explore the occurrence of the novel

72

congener AO168=O as well as other more frequently identified OPEs with the goal of

73

improving understanding of human exposure to OPEs in indoor environments. The

74

potential sources and relevant transformation products of AO168=O are also

75

discussed.

76 77

Materials and Methods

78

Materials

79

The analyte names, abbreviations, structures, and other relevant data are shown in

80

Figure 1 and the supporting information (Table S1). Tris(2,4-di-tert-butylphenyl)

81

phosphite (AO168) and AO168=O were obtained from Toronto Research Chemicals

82

(Toronto, Canada), bis(2,4-di-tert-butylphenyl) phosphate (B2,4DtBPP) was obtained

83

from Advanced BioChemicals (Lawrenceville, USA), and native standards of the

84

other OPE analytes were supplied by Tokyo Chemical Industry (Tokyo, Japan).

85

Isotope-labeled triphenyl phosphate-d15 (TPHP-d15) was obtained from Cambridge

86

Isotope Laboratories (Andover, USA). The purities of all target analytes were > 95%.

87

Stock solutions at concentrations of 1000 µg/mL were individually prepared in 5



88

acetonitrile (ACN), except for AO168 and B2,4DtBPP, which were prepared in

89

acetone. Intermediate solutions were prepared weekly from the stock solutions by

90

methanol (MeOH) dilution. HPLC-grade ACN and MeOH were obtained from Sigma

91

Aldrich (Oakville, Canada). Formic acid (FA) was supplied by Caledon (Georgetown,

92

Canada). Ultrapure water (H2O, 18.2 MΩ×cm) was generated by Purelab flex (Veolia

93

Water Technologies, Mississauga, Canada). SRM 2585 organic contaminants in house

94

dust was obtained from National Institute of Standard and Technology (Gaithersburg,

95

USA).

96 97

Sample Collection

98

Dust samples were collected from houses (n= 30, 1–2 samples per house) and offices

99

(n = 54, 1 sample per office) located in Toronto between December 2017 and

100

February 2018. Dust samples were collected using a vacuum cleaner (Bissell, Grand

101

Rapids, USA) with cotton pads (4 × 4 inch, VWR, Mississauga, Canada) inserted on

102

the tube extender. Before use, the cotton pads were pre-cleaned with MeOH. Dust

103

samples were obtained from the surfaces of upholstery, furniture, and windowsills.

104

Field blanks were prepared by collecting Na2SO4 using the same vacuum cleaner and

105

the same procedure that were used to collect the indoor dust. All dust samples were

106

wrapped in aluminum foil, sealed in polypropylene bags, and stored at −20°C until

107

analysis.

108 109

Sample Preparation and Instrumental Analysis 6


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The dust was pretreated as follows. First, 0.1 g of sample spiked with 100 ng of

111

TPHP-d15 was placed in a glass tube and extracted by 3 mL of ACN in an

112

ultrasonication bath for 30 min. After centrifugation, the supernatant was transferred

113

to another glass tube. The extraction, centrifugation, and transfer steps were

114

performed three times on each replicate. Next, the combined extract was dried under a

115

gentle stream of nitrogen, and then solvent exchanged into 1 mL of MeOH. This final

116

sample was further centrifuged at 3000 rpm for 5 min to remove any suspended

117

particles, following which a 2 µL aliquot was injected into the instrument.

118

The quantification of target molecules was performed on a Waters ultrahigh

119

performance liquid chromatograph coupled to a Xevo triple-quadrupole mass

120

spectrometer (Milford, USA). Electrospray ionization (ESI) was operated in both

121

positive and negative modes. The cone and desolvation gas flow were set to 120 and

122

800 L/h, respectively. The source temperature was set to 120°C and the desolvation

123

temperature was set to 400°C. The details of the multiple-reaction monitoring (MRM)

124

parameters are presented in Table S2. A Waters ACQUITY BEH C18 analytical

125

column (2.1 × 100 mm, 1.7 µm) was used for analyte separation, with a flow rate of

126

0.3 mL/min. The column temperature was set to 60°C. The flow gradient was started

127

at a composition of 40:60 (MeOH/H2O, v/v, 0.1% FA additive in each phase). This

128

composition was held for 3 min, linearly ramped to 100% MeOH over 7 min, and

129

then held there for another 5 min. Finally, the column was immediately returned to the

130

initial composition of 40:60 and allowed to re-equilibrate for 2 min, for a total

131

analysis time of 17 min. 7



132 133

Quality Assurance/Quality Control

134

As shown in Table S3, recoveries of the target OPEs in spiked dust (1.00 µg/g for

135

each target) were 77–91%; relative standard deviations (RSD, n = 3) were less than 12%

136

for all samples. The extraction efficiencies of the target OPEs in real dust samples

137

were determined by performing a fourth extraction on 5 randomly selected samples

138

and quantifying the extracts. The extraction efficiencies were found to be sufficient:

139

only TCEP and TPHP were detected in the fourth extractions, and the amount

140

extracted contributed 0.99). The concentrations of the targets were corrected using the internal

153

standard, TPHP-d15. When analyte concentrations fell outside the dynamic range, 8


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154

MeOH dilution was carried out to bring the concentration within the dynamic range.

155 156

Statistical Analysis

157

Geometric mean (GM), mean, concentration range, and quantification frequency are

158

used to describe the detection results of OPEs in dust samples. Statistical analyses

159

were carried out using SPSS V19.0 for Windows Release (SPSS Inc.). The level of

160

significance was set to p < 0.05. Pearson’s test (2-tailed) was used to assess

161

correlations among the OPE residue levels. Nonquantifiable analyte concentrations

162

with S/N less than 10 were set to the MQL divided by the square root of 2. Analytes

163

with low quantification frequency (< 50%) excluded in the statistical analysis. All the

164

data

165

Kolmogorov-Smirnov test, combined with visual inspection of frequency diagrams,

166

revealed concentrations in all data sets to be normally distributed after

167

log-transformation. The significance of the concentration difference between office

168

and home dust samples was checked using a 2-tailed t test. The total concentration of

169

OPEs (∑OPEs) is defined as the sum of the concentrations of all the target OPEs

170

analyzed in this study. The composition profile of the detected OPEs is expressed as

171

the percent contribution of individual congeners to ∑OPEs.

were

log-transformed

during

the

correlation

analysis.

Results

from

172 173

Results and Discussions

174

Newly Identified Congener AO168=O and Other OPEs in Indoor Dust

175

All target OPEs were detected in 100% of the investigated indoor dust samples (Table 9



176

1), with ∑OPEs varying from 2.92 to 124 µg/g (GM: 12.3 µg/g, mean: 19.7 µg/g).

177

These results indicate the prevalent use of OPEs in indoor environments. The

178

chlorinated OPE congener TCEP tended to dominate the samples, with concentrations

179

ranging from 0.17 to 113 µg/g (GM: 2.09 µg/g, mean: 5.80 µg/g). As illustrated in

180

Figure 2, TCEP accounted for 1.09–91.6% of ∑OPEs (mean: 23.9%). The other

181

chlorinated OPE congener, TDClPP, was also detected at high concentrations of

182

0.15–10.5 µg/g (GM: 1.63 µg/g, mean: 2.54 µg/g) and contributed 1.08–65.6% to

183

∑OPEs (mean: 16.1%). The primary analogue among the non-chlorinated OPEs was

184

TPHP, which had concentrations of 0.48–46.6 µg/g (GM: 2.17 µg/g, mean: 4.25 µg/g)

185

and contributed 0.84–80.7% to ∑OPEs (mean: 20.1%). 2-Ethylhexyl diphenyl

186

phosphate (EHDPP) was detected with concentrations ranging from 0.13–47.2 µg/g

187

(GM: 1.22 µg/g, mean: 3.26 µg/g) and contributed 14.4% to ∑OPEs on average. An

188

unknown peak was found in all dust samples when analyzing EHDPP using MRM

189

method (Figure S1). In order to check if the peak belongs to a potential isomer of

190

EHDPP, the dust samples were injected into Thermo Q-Exactive hybrid

191

quadrupole-orbitrap mass spectrometer. The parent ion for the peak is 363.3103+

192

([M+H]+), suggested as C20H42O5 (error: -1.38 ppm), which is not an EHDPP isomer

193

(parent ion: 363.1725+). The other non-chlorinated OPEs, including tricresyl

194

phosphate (TMPP, GM: 0.23 µg/g, mean: 0.79 µg/g) and tris(2-ethylhexyl) phosphate

195

(TEHP, GM: 0.13 µg/g, mean: 0.23 µg/g), were detected at relatively lower

196

concentrations, accounting for an average of merely 3.30% and 1.58% of ∑OPEs,

197

respectively. Generally, the composition profiles of OPEs in this study were similar to 10


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198

previous studies that TCEP, TDClPP, and TPHP were the primary congeners.22, 23

199

Besides, the concentrations of OPEs detected in the present study were also

200

comparable to previously reported concentrations in indoor dust collected from the

201

United States and Canada (Table S4), which also ranged from high part-per-billion

202

(ppb) to ppm levels.22, 24, 25

203

Somewhat surprising, the novel congener AO168=O was also detected in all the

204

indoor dust samples. The concentrations of AO168=O were in the range of 0.10–11.1

205

µg/g (GM: 1.97 µg/g, mean: 2.80 µg/g), and contributed 1.36–65.5% to ∑OPEs (mean:

206

20.7%). The concentrations of AO168=O detected in this study were much higher

207

than those of the other non-chlorinated OPEs (except TPHP), indicating that

208

AO168=O is an important OPE congener in the indoor environment, and one that

209

appears to have been overlooked. As a novel alkylated-TPHP, AO168=O showed

210

significantly higher concentrations than TMPP (p < 0.01), the alkylated-TPHP that

211

receives the most attention in the scientific community. Furthermore, the

212

concentrations of AO168=O reported here are much higher than previously reported

213

tris(4-tert-butylphenyl) phosphate concentrations (0.96–57.7 ng/g) in indoor dust

214

samples (n = 23) that were also collected in Toronto.22 The concentrations of

215

AO168=O are also much higher than 4-tert-butylphenyl diphenyl phosphate (GM:

216

511 ng/g) and bis(4-tert-butylphenyl) phenyl phosphate (GM: 70.2 ng/g) in home dust

217

samples (n = 188) collected in United States.26 To the best of our knowledge, this is

218

the first report on the occurrence of AO168=O in indoor dust.

219 11



220

Multivariate Analysis

221

To further elucidate the potential sources of both the well-known OPEs and the novel

222

congener AO168=O in indoor environments, the dust samples were classified as

223

either office dust (n = 54) or home dust (n = 30). The composition profiles of OPEs in

224

the office dust and indoor dust samples are shown in Figure 2. TCEP was the primary

225

congener in the office dust samples, accounting for 1.10–91.6% (mean: 30.9%) of

226

∑OPEs, followed by TPHP (mean: 18.3%), AO168=O (mean: 15.4%), TDClPP (mean:

227

15.1%), and EHDPP (mean: 14.9%), with all other congeners contributing little to

228

∑OPEs. In the home dust samples, surprisingly, the newly identified AO168=O

229

dominated the composition profiles, contributing 2.45–65.5% (mean: 30.0%) to

230

∑OPEs. ∑OPEs was significantly higher in the office dust samples (GM: 18.8 µg/g,

231

mean: 24.5 µg/g) than in the home dust samples (GM: 8.10 µg/g, mean: 10.9 µg/g; p
0.05), which might imply that

246

AO168=O has different sources than the well-known OPEs typically found in indoor

247

environments.

248 249

Potential Sources of AO168=O

250

AO168=O is not on Canada’s Domestic Substance List (DSL) or the U.S. EPA’s High

251

Production Volume (HPV) list, indicating its low production and application volume

252

in North America. As AO168=O had concentrations comparable to those of TPHP in

253

indoor dust samples, and was the dominant congener in the home dust samples, it is

254

highly unlikely that AO168=O is a byproduct of the well-known OPEs measured here.

255

A more likely explanation is that AO168=O is a transformation product of a specific

256

precursor. AO168 (also known as Irgafos 168), which is on the U.S. EPA’s HPV list,

257

is one of the most widely used organic phosphite antioxidants in various polymeric

258

materials.17 The phosphite antioxidants can decompose peroxides, providing

259

protection to various man-made materials such as adhesives, plastics, and coatings. In

260

this oxidation resistance process, the organic phosphite antioxidants are oxidized to

261

the corresponding organophosphates.28 The global production volume of phosphite

262

antioxidants was 123,000 tons in 2006, with an annual growth rate of 7%.29 Previous

263

studies have shown that AO168 was ubiquitously detected in commercial products 13



264

such as plastic materials with concentrations up to 256 µg/g.30 Given the ability of

265

AO168 to migrate out of plastics,31 its reported occurrence in commercial products

266

implies its potential release into the surrounding environment. The present study

267

demonstrates the occurrence of AO168 in indoor dust for the first time. AO168 was

268

positively identified in 50% of the investigated dust samples with concentrations

269

varying from < MQL to 75.5 ng/g (GM: 1.48 ng/g, mean: 5.06 ng/g). No significant

270

correlation between AO168=O and AO168 was found (Table S5), possibly due to the

271

low detection of AO168.

272

In the present study, the concentrations of AO168 detected in the indoor dust samples

273

were much lower than the concentrations of its oxidation product AO168=O

274

(AO168=O/AO168 = 1331, based on GM concentrations), in line with previous

275

findings in plastic trash.30 There are three possible explanations for this finding: first,

276

AO168 is mainly used as processing stabilizer and most of it is consumed during the

277

polymer thermal production process to provide protection, especially when the

278

processing temperature is very high (200 oC);32, 33 second, as the polymeric materials

279

age, the amount of AO168 in the polymeric materials will decrease as the amount of

280

the oxidation product AO168=O will increase;34 third, after being discharged into the

281

surrounding environment, AO168 can be also biotically or abiotically transformed to

282

form the phosphate product.32 The reported transformation rate from AO168 to

283

AO168=O varied significantly in previous studies. Complete oxidation of AO168

284

dissolved in tetrahydrofuran was reported in 24 hours,35 while the oxidation of AO168

285

in isopropanol was much lower, completing in one week.36 As for the AO168 added in 14


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286

polypropylene films, only 4% of it was oxidized to AO168=O during the 45 days of

287

storage in the dark.34 The varied transformation rate from AO168 to AO168=O are

288

possibly affected by differential experimental conditions.

289 290

SRM 2585

291

SRM 2585 was prepared from a composite of dust collected in vacuum cleaner bags

292

from homes, motels, hotels, and cleaning services in Maryland, Montana, New Jersey,

293

North Carolina, Ohio, and Wisconsin during the years 1993–1994. The composite

294

dust material was processed and passed through a sieve to retain only particles ≤ 100

295

µm. As shown in Table 3, all seven OPEs were detected in SRM 2585, with ∑OPEs of

296

17.2 ± 0.94 µg/g (mean ± standard deviation, n = 3). The concentrations of the

297

well-known OPEs detected in this study are comparable to those detected in a

298

previous study,37 which demonstrates the good performance of our analytical method.

299

Surprisingly, the concentration of AO168=O (10.9 ± 0.66 µg/g) in SRM 2585 was

300

significantly higher than that of any of the previously-identified OPEs (0.38–2.17

301

µg/g; p < 0.05). AO168=O was the dominant OPE congener in SRM 2585, accounting

302

for 63.3% of ∑OPEs. A previous study reported the occurrence of eight isopropylated

303

TPHPs and three tert-butylated TPHPs in SRM 2585 with concentrations in the range

304

of 16.3–475 ng/g,14 which are much lower than the concentrations of the newly

305

detected AO168=O reported here. These results further support the importance of

306

detecting AO168=O in indoor dust. Furthermore, the detection of AO168=O in SRM

307

2585 at a high concentration demonstrates that AO168 has been in use in the U.S. for 15



308

over 20 years. This is in line with a previous study that reported the detection of

309

AO168 in polypropylene resin in 1991.38

310 311

Relevant Transformation Products of AO168=O

312

In addition to oxidation, the phosphite esters are prone to hydrolysis in humid air,

313

liberating free phenols.39 Previous studies have reported the occurrence of

314

2,4-di-tert-butylphenol (2,4DtBP), a known hydrolysis product of AO168 and

315

AO168=O, along with its precursors, in various plastic pipes, packaging, and drinking

316

water.40-42 2,4DtBP has been demonstrated to have endocrine effects using in vitro

317

assays.43,

318

concentrations ranged from < MQL to 1162 ng/g (GM: 22.8 ng/g, mean: 72.6 ng/g). It

319

should be noted that although 2,4DtBP is on the HPV list of the U.S. EPA, its main

320

reported use is in the manufacture of other products such as AO168.45 The low

321

concentrations and quantification frequency of 2,4DtBP in the indoor dust samples

322

support the above 2,4DtBP usage information. B2,4DtBPP was detected in most of

323

the dust samples (94%) with concentrations from < MQL to 214 ng/g (GM: 32.6 ng/g,

324

mean: 52.4 ng/g). A strong positive relationship was found between B2,4DtBPP and

325

AO168=O (p < 0.01, Table S5). B2,4DtBPP has been identified from single-use

326

bioprocess containers as being highly detrimental to cell growth.46 Compared to the

327

AO168=O concentrations reported here, the concentrations of B2,4DtBPP and

328

2,4DtBP were very low, as hydrolysis is not a common transformation pathway in

329

indoor environments.47

44

The present study detected 2,4DtBP in 42% of the dust samples. Its

16


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330 331

Environmental Implications

332

In the present study, the novel congener AO168=O was positively identified in all the

333

indoor dust samples collected from Toronto, Canada. To the best of our knowledge,

334

this is the first report of the occurrences of this novel OPE congener, its precursor

335

(AO168), and its relevant transformation products in the environment. The current

336

study demonstrates that people are exposed to more OPEs through indoor dust than

337

had previously been thought. In particular, the concentrations of the newly detected

338

AO168=O were comparable to or even higher than those of other, well-known OPEs.

339

The detection of AO168=O shows that organic phosphite antioxidants, which are a

340

family of additives widely used in polymers to retard oxidation reactions, is a very

341

significant source of OPEs in the indoor environment. The widespread application of

342

these phosphite antioxidants provides a previously-unknown indirect source of OPEs

343

to the environment, contributing to environmental contamination by OPEs.

344

Furthermore, several other organic phosphite antioxidants, such as tris(nonylphenyl)

345

phosphite, have also been reported as having high production and use volumes.48 The

346

estimated daily intakes of ∑OPEs for adults via ingestion of office and home dust

347

were 2.62 and 4.20 ng/kg bw/day, respectively, based on GM concentrations. Much

348

higher EDIs (GM: 62.3 ng/kg bw/day) were found for toddlers via ingestion of home

349

dust. To avoid underestimating human exposure to OPEs, further studies are

350

warranted both to determine whether other OPE analogues are present in the

351

environment and to evaluate the potential toxicity of these novel OPEs and their 17



352

relevant transformation products; particularly in dust samples, due to human exposure

353

to dust being unavoidable.

354 355

Supporting Information

356

The Supporting Information is available free of charge on the ACS Publications

357

website.

358

(Table S1) Information on target analytes; (Table S2) Optimized multiple-reaction

359

monitoring parameters; (Table S3) Validation and performance data of the developed

360

method; (Table S4) Comparison of OPE concentrations in indoor dust collected from

361

North America; (Table S5) Pearson’s correlation matrix for the concentrations of

362

AO168 and related transformation products in indoor dust; (Table S6) Estimated daily

363

intakes (EDI, ng/kg bw/day) of OPEs. (Figure S1) MRM chromatograms of EHDPP

364

and the detected unknown peak.

365

Notes

366

The authors declare no competing financial interest.

367 368

Acknowledgements

369

This work was funded by a Natural Sciences and Engineering Research Council of

370

Canada grant to S.A.M.

371

18


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Page 19 of 31


372

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Page 25 of 31


Figure 1. Names, structures, and transformation pathways of AO168 and related target analytes.

25



Figure 2. Composition profiles of individual OPE in each dust sample (the x-axis represents the sample number).

26


Page 26 of 31

Page 27 of 31


Figure 3. Concentration differences between the OPEs in the office and home dust samples. The black diamonds show the 1st and 99th percentiles; the vertical black lines show the range from the 5th to the 95th percentile; the boxes show the range from the 25th to the 75th percentile; and the horizontal line within the boxes shows the 50th percentile. “＊” indicates significance at the 0.05 level, and “＊＊” indicates significance at the 0.01 level.

27



Page 28 of 31

Table 1. Descriptive Statistics of the Measured Concentrations (µg/g) of OPEs and Relevant Compounds (ng/g) in Indoor Dust Samples. Quantification Compounds

GM

Mean

Median

Range frequency (%)

Organophosphate Esters (µg/g) TCEP

2.09

5.80

2.13

0.17 – 113

100

TDClPP

1.63

2.54

1.70

0.15 – 10.5

100

TEHP

0.13

0.23

0.15

0.003 – 1.12

100

EHDPP

1.22

3.26

0.98

0.13 – 47.2

100

TPHP

2.17

4.25

2.14

0.48 – 46.6

100

TMPP

0.23

0.79

0.30

0.008 – 21.1

100

AO168=O

1.97

2.80

2.17

0.10 – 11.1

100

∑OPEs

12.3

19.7

15.4

2.92 – 124

100

Relevant Compounds (ng/g) AO168

1.48

5.06

0.74

< MQL – 75.5

50

B2,4DtBPP

32.6

52.4

41.7

< MQL – 214

94

2,4DtBP

22.8

72.6

8.49a

< MQL – 1162

42

a

: Concentration corresponding to MQL divided by the square root of 2.

28


Page 29 of 31


Table 2. Pearson’s Correlation Matrix for the Detected OPE Concentrations in Indoor Dust. TCEP

TDClPP

TEHP

EHDPP

TPHP

TDClPP

0.300**

TEHP

-0.016

0.482**

EHDPP

0.240*

0.448**

0.310**

TPHP

0.303**

0.340**

0.410**

0.403**

TMPP

0.470**

0.415**

0.210

0.582**

0.394**

0.232

0.606**

0.186

0.341**

AO168=O -0.031

** Correlation is significant at the 0.01 level (2-tailed). *Correlation is significant at the 0.05 level (2-tailed).

29


TMPPP

0.049


Page 30 of 31

Table 3. Descriptive Statistics of the Measured OPE Concentrations (µg/g) in SRM 2585 (n = 3). Compounds

Mean Concentration

Standard Deviation

RSD

Proportions

(µg/g)

(µg/g)

(%)

(%)

TCEP

1.15

0.06

5.3

6.64

TDClPP

2.17

0.27

13

12.6

TPHP

1.13

0.01

1.0

6.57

TMPP

0.47

0.04

9.1

2.74

TEHP

0.38

0.03

7.6

2.18

EHDPP

1.03

0.01

1.3

5.94

AO168=O

10.9

0.66

6.1

63.3

∑OPEs

17.2

0.94

5.5

100

30


Page 31 of 31


TOC ART

31


Unexpectedly High Concentrations of a Newly Identified

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