ITP & TBPP

TBPP isomers in 4 commercial flame retardant mixtures: FM 550, FM 600, ... 59 assessment under the 2016 amendment to the Toxic Substances Control ...
6 downloads 0 Views 3MB Size
Subscriber access provided by READING UNIV

Article

Characterization of Individual Isopropylated and Tert-butylated Triarylphosphate (ITP & TBPP) Isomers in Several Commercial Flame Retardant Mixtures and House Dust Standard Reference Material SRM 2585 Allison Phillips, Stephanie Hammel, Alex Konstantinov, and Heather M Stapleton Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.7b04179 • Publication Date (Web): 27 Oct 2017 Downloaded from http://pubs.acs.org on October 27, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Environmental Science & Technology is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 25

Environmental Science & Technology

1

Characterization of Individual Isopropylated and Tert-butylated

2

Triarylphosphate (ITP & TBPP) Isomers in Several Commercial

3

Flame Retardant Mixtures and House Dust Standard Reference

4

Material SRM 2585

5 6

Allison L. Phillips†, Stephanie C. Hammel†, Alex Konstantinov‡, and Heather M. Stapleton†*

7 8



9



Nicholas School of the Environment, Duke University, Durham, NC, USA

Wellington Laboratories, Inc., Guelph, Ontario, Canada

10 11 12

*

13

[email protected]; Address: 9 Circuit Drive, Box 90328, Durham, NC 27708-0328

Corresponding Author: Heather M. Stapleton; Phone: (919) 613-8717; Email:

14 15 16 17 18 19

ACS Paragon Plus Environment

1

Environmental Science & Technology

Page 2 of 25

20

Abstract

21

Since the phase-out of pentaBDE in the early 2000s, replacement flame retardant mixtures

22

including Firemaster® 550 (FM 550), Firemaster® 600 (FM 600), and organophosphate aryl

23

ester technical mixtures, have been increasingly used to treat polyurethane foam in residential

24

upholstered furniture. These mixtures contain isomers of isopropylated and tert-butylated

25

triarylphosphate esters (ITPs and TBPPs), which have similar or greater neuro- and

26

developmental toxicity compared to BDE 47 in high throughput assays. Additionally, human

27

exposure to ITPs and TBPPs has been demonstrated to be widespread in several recent studies;

28

however, the relative composition of these mixtures has remained largely uncharacterized. Using

29

available authentic standards, the present study quantified the contribution of individual ITP and

30

TBPP isomers in 4 commercial flame retardant mixtures: FM 550, FM 600, an ITP mixture, and

31

a TBPP mixture. Findings suggest similarities between FM 550 and the ITP mixture, with 2-

32

isopropylphenyl diphenyl phosphate (2IPPDPP), 2,4-diisopropylphenyl diphenyl phosphate

33

(24DIPPDPP), and bis(2-isopropylphenyl) phenyl phosphate (B2IPPPP) being the most

34

prevalent ITP isomers in both mixtures. FM 600 differed from FM 550 in that it contained TBPP

35

isomers instead of ITP isomers. These analytes were also detected and quantified in a house dust

36

Standard Reference Material, SRM 2585, demonstrating their environmental relevance.

37 38 39 40 41

ACS Paragon Plus Environment

2

Page 3 of 25

Environmental Science & Technology

42

Introduction

43

In the early to mid- 2000s, the use of polybrominated diphenyl ethers (PBDEs) was globally

44

phased-out due to concerns about their persistence, bioaccumulation and potential toxicity

45

(PBT). One PBDE commercial mixture, PentaBDE, was primarily used in furniture as a flame

46

retardant to meet residential flammability standards; however, new flame retardant chemicals

47

and mixtures have since entered the market. Recent studies by our group demonstrate that many

48

of these new flame retardant mixtures contain alkylated organophosphate aryl esters, and in

49

particular, several types of isopropyl- and tert-butyl-triphenyl phosphates (ITP and TBPP,

50

respectively; Figure 1).1,2 In addition to being used as flame retardants, both ITPs and TBPPs are

51

used in hydraulic fluids and as plasticizers in a variety of materials.3,4 In our previous research,

52

we identified ITPs in a common commercial flame retardant mixture, Firemaster® 550 (FM

53

550), a mixture of organophosphate and brominated flame retardants, and an ITP mixture.5

54

Similarly, we identified TBPPs in Firemaster® 600 (FM 600) and in a mixture with TPHP that

55

we refer to as the TBPP mixture.2 Despite their documented neuro- and developmental toxicity,

56

there is currently very little information regarding human exposure to ITPs and TBPPs and

57

limited documentation of the presence of these isomers in environmental samples.6,7 This

58

pressing lack of data has been recognized by the U.S. Environmental Protection Agency (EPA),

59

which recently prioritized ITPs as one of five Fast-Tracked PBT Chemicals for further

60

assessment under the 2016 amendment to the Toxic Substances Control Act (TSCA).8 Previous

61

research conducted by our laboratory has demonstrated that exposure to ITP chemicals is very

62

common in the US population, and that exposure ranges considerably among individuals, likely

63

based on differential exposure to flame retardant and plasticizer-treated consumer products. For

64

instance, Hammel et al. detected ITPs on silicone wristbands worn by human participants with

ACS Paragon Plus Environment

3

Environmental Science & Technology

Page 4 of 25

65

100% frequency (n=40).9 Furthermore, out of 5 organophosphate flame retardant (PFR)

66

metabolites measured in urine in this study, mono-isopropylphenyl phenyl phosphate (mono-

67

ipPPP), a confirmed metabolite of ITPs, had the highest geometric mean concentration (2.6

68

ng/mL). Another recent study detected mono-ipPPP in 98% of all tested urine samples (n=48),

69

and found that on average, levels of urinary mono-ipPPP were 1.2 times higher in children than

70

in their mothers.10 Other recent studies have used commercial flame retardant mixtures

71

containing ITPs and TBPPs to assess toxicological endpoints, and yet the composition of these

72

mixtures has not been well described. For example, FM 550 has been shown to be endocrine

73

disrupting and potentially obesogenic in rats, and exposure in fathead minnows resulted in

74

significant DNA damage.11,12 The ITP and TBPP commercial mixtures have been found to

75

disrupt C. elegans larval development, zebrafish embryonic development, and zebrafish behavior

76

at concentrations in the low µM range.6,13 The TBPP mixture has also been shown to elevate

77

estradiol serum levels, alter reproductive cycles, and elicit cholesteryl lipidosis in adrenocortical

78

and ovarian interstitial cells of exposed female rats.14 However, because there have been no

79

studies that identify the composition and ITP/TBPP isomer profile of these commercial mixtures,

80

it is difficult to attribute toxicological findings to a specific component(s) of the mixture. Such

81

information will give context to toxicological studies using these mixtures, and give direction to

82

future exposure studies. Moreover, there is considerable confusion in the flame retardant

83

literature regarding the naming and acronyms associated with these compounds, and these

84

mixtures also have a myriad of technical/brand names associated with them from multiple

85

manufacturers (Table I). For the purposes of this study and to avoid future confusion, individual

86

ITP and TBPP isomer acronyms are used according to their practical abbreviations (PRABs).15

87

Individual standards for these isomers have become available in the past year, and the present

ACS Paragon Plus Environment

4

Page 5 of 25

Environmental Science & Technology

88

study attempts to alleviate confusion regarding these compounds. Here we characterize the ITP

89

and TBPP isomer profiles present in FM 550 and FM 600, and two other types of

90

organophosphate commercial mixtures that are currently available on the market.

91 92

Experimental

93

Materials

94

Individual, authentic standards of 2-isopropylphenyl diphenyl phosphate (2IPPDPP), 3-

95

isopropylphenyl diphenyl phosphate (3IPPDPP), 4-isopropylphenyl diphenyl phosphate

96

(4IPPDPP), 2,4-diisopropylphenyl diphenyl phosphate (24DIPPDPP), bis(2-isopropylphenyl)

97

phenyl phosphate (B2IPPPP), bis(3-isopropylphenyl) phenyl phosphate (B3IPPPP), bis(4-

98

isopropylphenyl) phenyl phosphate (B4IPPPP), bis(2,4-diisopropylphenyl) phenyl phosphate

99

(B24DIPPPP), tris(3-isopropylphenyl) phosphate (T3IPPP), tris(4-isopropylphenyl) phosphate

100

(T4IPPP), 4-tert-butylphenyl diphenyl phosphate (4tBPDPP), bis(2-tert-butylphenyl) phenyl

101

phosphate (B2tBPPP), bis(4-tert-butylphenyl) phenyl phosphate (B4tBPPP), 13C-TPHP,

102

d15TPHP,

103

Laboratories (Guelph, Ontario, Canada). TPHP (99% pure) and tris(4-tert-butylphenyl)

104

phosphate (T4tBPP) were purchased from Sigma-Aldrich (St. Louis, Missouri). HPLC grade

105

isooctane was purchased from Honeywell Burdick & Jackson (Muskegon, Michigan). FM 550

106

was provided by Chemtura (lot #77000DI8P), the commercial mixture containing only ITPs was

107

purchased from Jinan Great Chemical Industry Co. (no lot information provided by

108

manufacturer), and the TBPP mixture was produced by Ubichem and obtained from the National

109

Toxicology Program (lot #M062011NS) for research purposes as part of a materials transfer

110

agreement. The commercial FM 600 mixture itself was not available for analysis; for this reason,

13

C-EH-TBB, and 13C-BEH-TEBP were purchased from or provided by Wellington

ACS Paragon Plus Environment

5

Environmental Science & Technology

111

a block of FM 600-treated polyurethane foam was obtained from a North Carolina foam

112

manufacturer for analysis.

Page 6 of 25

113 114

Commercial Mixture Preparation

115

Each flame retardant mixture preparation was weighed using a Mettler Toledo A21 Comparator

116

microbalance and dissolved in isooctane to make three low (~1 µg/ml) and three high (~5 µg/ml)

117

concentration solutions. FM 600-treated foam was weighed (100 mg) and extracted in triplicate

118

using dichloromethane according to previously published methods.16 For the analysis here, the

119

concentration of FM 600 in the foam was assumed to be 4% by weight, similar to measurements

120

made previously in polyurethane foam.16 Prior to analysis, each solution was spiked with the

121

appropriate internal standards.

122 123

SRM 2585 Analysis

124

Approximately 300 mg of SRM 2585 (National Institute of Standards & Technology,

125

Gaithersburg, MD) was spiked with 13C-TPHP and extracted three times in DCM with

126

sonication. SRM extracts (n=4) were cleaned using Supelclean™ ENVI-Florisil® SPE cartridges

127

(6 mL; 1.0g; Supelco, Bellefonte, Pennsylvania) using previously published methods.17 ITP and

128

TBPP isomers were eluted using 10 mL of ethyl acetate. Eluents were concentrated under

129

nitrogen and solvent-exchanged to hexane prior to analysis.

130 131

Component Quantification

132

EH-TBB and BEH-TEBP were quantified with previously described GC/ENCI-MS methods

133

using 13C-EH-TBB and 13C-BEH-TEBP as internal standards.5 TPHP and individual ITP and

ACS Paragon Plus Environment

6

Page 7 of 25

Environmental Science & Technology

134

TBPP isomers were quantified with previously described GC/EI-MS methods using 13C-TPHP as

135

an internal standard.16 Briefly, quantification of TPHP, ITP, and TBPP isomers was performed

136

using an Agilent (Wilmington, DE) gas chromatograph (model 7890A) mass spectrometer

137

(model 5975C) operating in electron impact (EI) mode. Pressurized temperature vaporization

138

(PTV) injection was employed in the inlet and a 0.25 mm (I.D.) x 30 m fused silica capillary

139

column coated with 5% phenyl methylpolysiloxane (J&W Scientific, 0.25 µm film thickness)

140

was used in the GC to resolve the analytes. Helium was used as the carrier gas in the GC with a

141

constant flow rate of 1.3 mL/min. The inlet was set to a temperature of 80˚C for 0.3 minutes and

142

then ramped to 300˚C at a rate of 600˚C/min to efficiently transfer samples to the head of the GC

143

column. The GC oven was held at 80˚C for 2 minutes, then ramped to 250˚C at 20˚C/min, then

144

ramped to 260˚C at 1.5˚C/min, then ramped to 300˚C at 25˚C/min and held at 300˚C for 20

145

minutes. The transfer line temperature was held at 300˚C, and the ion source was maintained at

146

200˚C. Table II outlines the m/z ions and retention times used for quantification of ITP and

147

TBPP isomers.

148 149

QA/QC

150

Laboratory blanks were included in both the commercial mixture preparation (n=3) and the SRM

151

2585 analysis (n=6). All samples were blank corrected using the average blank level, and method

152

detection limits (MDLs) were calculated using 3 times the standard deviation of the average lab

153

blanks, and were normalized to the amount of dust extracted for the SRM 2585 analysis. MDLs

154

are reported in Table S-1 for each isomer. Linear calibration curves were constructed using a five

155

point calibration for the quantification of each isomer, with r2 values ranging from 0.9985 to

156

0.9999. To evaluate the recoveries of ITP and TBPP isomers in house dust, a matrix spike

ACS Paragon Plus Environment

7

Environmental Science & Technology

157

experiment was performed using a low and high dose of isomers. Samples of SRM 2585 were

158

spiked with either a low dose (50 ng) or a high dose (500 ng) of all ITP and TBPP isomers, and

159

extracted, in triplicate, according to the methods detailed above. 13C TPHP was added prior to

160

GC/MS analysis to quantify recovery of each analyte. Recoveries ranged from 72.4 ±1.0% to

161

109.9 ± 10.7% (see Table S-2) for the various isomers.

Page 8 of 25

162 163

Results & Discussion

164

Firemaster® 550 and ITP Mixture

165

The percent composition of each ITP isomer present in the FM 550 and ITP mixture,

166

respectively, is shown in Table III and is presented on a percent w/w basis. The FM 550 mixture

167

consisted of approximately 44% of the brominated components, with the remaining mass

168

comprised of TPHP and the ITPs. Like the FM 550 mixture, the ITP mixture consisted of very

169

similar ITP isomers, particularly TPHP, 2IPPDPP, and B2IPPPP, which were the dominant

170

compounds in the mixture. Notably, the contribution of the individual organophosphate

171

components in the ITP mixture is roughly twice that of their contribution in FM 550, suggesting

172

a common ITP formulation and/or synthesis (Figure 2). T4IPPP was not detected in either of the

173

mixtures. Our analyses accounted for 97.8 ± 1.5% of FM 550 and 97.0 ± 5.3% of the ITP

174

mixture.

175 176

Firemaster® 600 and TBPP Mixture

177

The percent composition of each TBPP isomer present in the FM 600 and TBPP mixture is

178

shown in Table IV and is presented on a percent w/w basis. In the case of the FM 600 analysis,

179

we used foam as a standard which could be a limitation affecting the accuracy of our characterization.

ACS Paragon Plus Environment

8

Page 9 of 25

Environmental Science & Technology

16

180

We assumed that the foam was treated with 4% FM 600 by weight.

Using that assumption, the

181

foam treated with FM 600 contained approximately 40% of the brominated compounds, with the

182

remaining mass being comprised of TPHP and TBPP isomers. The organophosphate

183

formulation of FM 600 was dominated by B4tBPPP and T4tBPP isomers, with relatively little

184

TPHP or 4tBPDPP present in the mixture. In contrast, the TBPP mixture was comprised of

185

higher percentages of TPHP and 4tBPDPP (Figure 3). In total, we could account for 95.3 ±

186

5.2% of the FM 660 mixture and 79.5 ± 1.1% of the TBPP mixture. 2tBPDPP and B2tBPPP

187

were not detected in either FM 600 or the TBPP mixture, but chromatographic peaks for

188

3tBPDPP and B3tBPPP were observed for both mixtures (Figure S1). These peaks were

189

presumed to be the meta-isomers based on their mass spectra (m/z = 382 for 3tBPDPP and m/z =

190

438 for B3tBPPP), retention times between ortho- and para-substituted isomers, and lack of

191

matching with the ortho- and para-substituted isomers. Standards of meta-TBPP isomers are not

192

commercially available so quantification of 3tBPDPP and B3tBPPP was not possible.

193 194

Concentrations in SRM 2585

195

Levels of ITP and TBPP isomers in house dust standard reference material 2585 are shown in

196

Table V. Deuterated TPHP was used as a recovery standard and percent recovery of 13C-TPHP

197

was 95.7 ± 6.2%. Measured concentrations of TPHP were 1002.13 ± 52.88 ng/g, similar to those

198

reported previously.17,18 2IPPDPP, 4IPPDPP, 4tBPDPP, and B4BPDPP were the most prevalent

199

ITP and TBPP isomers in SRM 2585, all of which had concentrations >200 ng/g. In contrast,

200

T3IPPP, T4IPPP, 2tBPDPP, and B2tBPPP were not detected in SRM 2585 above MDL levels

201

(0.67, 1.07, 0.61, and 0.98 ng/g respectively.) While individual isomer levels are lower than that

202

of other organophosphate flame retardants, ΣITP and ΣTBPP levels (1098.28 and 762.09 ng/g,

ACS Paragon Plus Environment

9

Environmental Science & Technology

Page 10 of 25

203

respectively) approach, and in some cases, exceed levels that have been reported for TPHP,

204

TCEP, and TCPP previously.18,19 These concentrations suggest the potential for chronic human

205

exposure to ITP and TBPP isomers via inadvertent dust ingestion and hand-to-mouth contact. In

206

addition, the fact that SRM 2585 was prepared from dust collected in 1993 and 1994 suggests

207

ITP and TBPP use has been ongoing before PentaBDE was phased out. Interestingly, it has been

208

reported that the ITP isomers were originally developed as tricresyl phosphate replacements due

209

to the erratic supply and increasing cost of cresols in the 1970s. Similarly, TBPP isomers were

210

introduced in the 1970s for use in hydraulic applications.4 However, to the authors’ knowledge,

211

this is the first demonstration of their presence in SRM 2585.

212 213

Implications

214

There is growing evidence that the organophosphate components in these mixtures may elicit

215

adverse health effects and human exposure to them has been demonstrated to be widespread in

216

recent years.9,20–22 A recent epidemiological study found a signfiicnat association between the

217

urinary metabolite of ITPs and decreases in successful pregnancy outcomes.23 Identification of

218

the predominant ITP and TBPP isomers in commonly used commercial flame retardant mixtures

219

will aid in hazard characterization and the ongoing, prioritized, risk assessment of these

220

compounds by the U.S. EPA. With the exception of FM 600, all of these mixtures contain ≥ 20%

221

TPHP, a compound with known toxicological activity.24–26 Interestingly, FM 600 has very low

222

TPHP content, potentially due to distillation or other treatment following isomerization. The four

223

mixtures in this study are complex, containing many different components, each with potentially

224

unique health hazards and physicochemical properties. These findings should be taken into

225

account when designing and interpreting toxicological studies. Furthermore, it should be

ACS Paragon Plus Environment

10

Page 11 of 25

Environmental Science & Technology

226

recognized that there are many different manufacturers of these mixtures, and mixture

227

formulations may differ among manufacturers and across lots. It is possible that the minor

228

components of the ITP mixture (