Alternative Flame Retardants in House Dust

Collected from Residential Houses and Kindergartens in Japan

Furukawa M1, Wang Q2, Tokumura M2, Miyake Y2, Amagai T2, Takahashi Y3

1Department of Environmental and Life Science, University of Shizuoka, Shizuoka, Japan, 422-8526

2Graduate School of Integrated Pharmaceutical and Nutritional Science, University of Shizuoka, Shizuoka, Japan,

422-8526

3Faculty of the Contemporary Social Studies, Toyama University of International Studies, Toyama, Japan, 930-1262

Introduction

Hexabromocyclododecane (HBCD), which is one of brominated flame retardants (BFRs), was banned by the

Stockholm Convention. Accordingly, a variety of alternative flame retardants have started to been used. Although

several previous studies reported that novel alternative FRs were detected from indoor environments, information on

them is still not enough. Stapleton et al. reported that a variety of alternative FRs was detected from dust collected

from residential houses [1]. Because most FRs are classified as one of semi-volatile organic compounds (SVOCs),

FRs in dust are likely to be exposed to human via house dust [2]. Especially, the baby tends to take a larger amount

of dust compared with the adult due to baby-specific actions. Therefore, there have been more concerned about a risk

of FRs for the baby than that for the adult.

In public buildings in Japan, some interior products (e.g., curtain and carpet) should be addressed to the risk of fire

according to the regulation about flame retardancy of products under the Fire Defense Law. According to a previous

study, the concentration of FRs in dust collected from hotels in Japan, which is one of public buildings, was at high

level [3]. Given that a kindergarten, in which the baby tends to spend a lot of time, is also public building, the

concentrations of FRs in dust in it are likely to be high. Therefore, it is necessary to comprehensively investigate the

concentrations of alternative FRs in dust in the kindergarten.

In this study, we have determined the concentrations of alternative FRs in dust samples collected from two

kindergartens in Japan, to know the current actual conditions of alternative FRs in house dust at kindergartens. For

compression, dust samples were collected from residential houses in Japan. In this study, phosphorus compounds

were targeted as alternative FRs, and following 15 phosphorus compounds were analyzed: trimethyl phosphate (TMP),

triethyl phosphate (TEP), tripropyl phosphate (TPP), tributyl phosphate (TBP), tris(isobutyl) phosphate (TIBP),

tris(2-ethylhexyl) phosphate (TEHP), tris(2-butoxyethyl) phosphate (TBOEP), triphenyl phosphate (TPhP), cresyl

diphenyl phosphate (CsDPhP), 2-ethylhexyl diphenyl phosphate (EHDPhP), tricresyl phosphate (TCsP), tris(2-

chloroethyl) phosphate (TCEP), tris(2-chloroisopropyl) phosphate (TCPP), tris(1,3-dichloro-2-propyl) phosphate

(TDCPP), and triphenyl phosphine oxide (TPhPO).

Materials and methods

Sampling procedure

Dust samples from two kindergartens in Japan were corrected (KG-1–6) in May–June 2016. House dust samples were

collected from 10 residential houses in Japan (R-1–10) in July–August 2015. The house dust samples were collected

from wooden floors (7 residential houses) and carpet or straw mat (3 residential houses). House dust samples were

Organohalogen Compounds Vol. 79, 651-654 (2017) 651

collected into a paper bag by using a handy cleaner. The paper bag was put into an aluminum shading bag and kept

in –20°C until analysis after the collection.

Analytical procedure

A 0.1 g of house dust sample sieved (250 µm mesh) was extracted by the Soxhlet extraction method with 200 mL

dichloromethane/hexane (1:1, v:v) for 16 h after 2 ng of clean-up spikes (TPhP-d15, TEHP-d51, TCsP-d21, and TCEP-

d12) were added onto it. The extract was concentrated to 20 µL by a rotary-evaporator and nitrogen purge. Then, 100

µL of acetonitrile with 2 ng of syringe spike (TBP-d27) were added to the extract.

The concentrations of 15 phosphorus compounds were determined by a high performance liquid chromatograph

tandem mass spectrometer (LC-MS/MS) in atmospheric pressure chemical ionization (APCI) mode. The injection

volume was 2 µL or 5 µL. Accucore Vanquish C18 (2.1 mm i.d. × 100 mm length, 1.5 µm) was used for the separation.

The flow rate was 0.3 mL min–1. Water (Eluent A) and 80% methanol/acetonitrile (Eluent B) were used as mobile

phases. The gradient program was as follows: isocratic at 10% solvent B for 1.8 min, 10% to 80% solvent B in 2.2

min, isocratic at 80% solvent B for 2.0 min, 80% to 100% solvent B in 1.0 min, isocratic at 100% solvent B for 4.0

min, 100% to 10% solvent B in 0.5 min, and then isocratic at 10% solvent B for 3.5 min. The column temperature

was kept in 50°C. Average recoveries of clean-up spikes (TPhP-d15, TEHP-d51, TCsP-d21 and TCEP-d12) added into

dust samples were 114%, 111%, 120% and 97%, respectively.

Results and discussion

Concentrations of phosphorus compounds in house dust collected from residential houses

Fourteen phosphorus compounds were detected from dust collected from the both of residential houses and

kindergartens targeted in this study. The individual and total concentrations of 14 phosphorus compounds are shown

in Figure 1. The line in the box shows median, and top and bottom of the box indicates the third and first

Figure 1: Concentrations of phosphorus compounds detected from house dust

collected from residential houses and kindergartens in Japan.

0.001

0.01

0.1

1

10

100

1000

10000

0.001

0.01

0.1

1

10

100

1000

10000

TM

P

TE

P

TC

EP

TP

hP

O

TP

P

TC

PP

TD

CP

P

TP

hP

TB

P

CsD

Ph

P

TB

OE

P

EH

DP

hP

TC

sP

TE

HP

To

tal

TM

P

TE

P

TC

EP

TP

hP

O

TP

P

TC

PP

TD

CP

P

TP

hP

TB

P

CsD

Ph

P

TB

OE

P

EH

DP

hP

TC

sP

TE

HP

To

tal

Residential houses Kindergartens

Co

ncen

trati

on

(µ

g g

-1)

Organohalogen Compounds Vol. 79, 651-654 (2017) 652

quartiles. The whiskers of the box show the values of maximum and minimum, respectively. The total concentration

of 14 phosphorus compounds in dust collected from residential houses ranged 4.1–1,600 µg g–1 (median: 48 µg g–1).

CsDPhP, TBOEP, TCEP, TCPP, TDCPP and TPhP were detected from all the dust samples. In contrast, TMP, TEP,

and TPP were rarely detected from the dust, due to their low molecular weights and high volatilities. The highest

median concentration was obtained for TBOEP (concentration range: 1.7–1,600 µg g–1, median: 7.7 µg g–1), followed

by TDCPP (0.11–73 µg g–1, 1.3 µg g–1), TCPP (0.18–16 µg g–1, 0.81 µg g–1), TCEP (0.067–7.5 µg g–1, 0.63 µg g–1)

and TPhP (0.84–13 µg g–1, 0.56 µg g–1). The concentrations of other phosphorus compounds were comparatively low.

It could be concluded that TBOEP was the dominant compound in dust in this study. This tendency was in good

agreement with a previous study, in which the high concentration of TBOEP and low concentrations of the other

phosphorus compounds were reported [3]. As for TBOEP, the concentration in house dust collected from wooden

floors were likely to be high compared to that from the other floors. Mizouchi et al. measured the concentration of

TBOEP in floor wax products used in elementary schools in Japan, which was 40% in weight [4]. This could be come

from the fact that TBOEP is used as plasticizer in wooden floor wax.

Figure 2 shows the composition ratio of phosphorus compounds detected from the house dusts collected from the

residential houses and kindergartens. TBOEP was the dominant phosphorus compound in not only the concentration

but also the composition ratio. As major phosphorus compounds, TDCPP (composition ratio: 0.10–72%, median:

7.2%), TCPP (0.069–33%, 6.5%), TCEP (0.047–11%, 2.4%) and TPhP (0.16–13%, 1.7%). TDCPP, TCEP, and TCPP

are used as flame retardants for cushion (e.g., urethane) and curtain (e.g., polyester). The sum of composition ratios

of them occupied 0.22–79% (R-1–10).

Concentrations of phosphorus compounds in house dust collected from kindergartens

As shown in Figure 1, the total concentration of 14 phosphorus compounds in dust collected from the kindergartens

ranged 1,000–2,900 µg g–1 (median: 2,300 µg g–1). As same as the case for residential houses, the highest median

concentration was obtained for TBOEP (concentration range: 990–2,900 µg g–1, median: 2,100 µg g–1), followed by

TPhP (2.2–8.4 µg g–1, 7.4 µg g–1), TDCPP (2.2–150 µg g–1, 4.6 µg g–1), TCPP (1.1–180 µg g–1, 4.0 µg g–1) and TCEP

(0.66–1.9 µg g–1, 1.2 µg g–1). It can be seen from Figure 2 that the composition ratios of TBOEP in dust

Figure 2: Composition ratios of phosphorus compounds detected from house dusts

collected from residential houses and kindergartens in Japan.

0

0

0

1

1

1

R-1 R-2 R-3 R-4 R-5 R-6 R-7 R-8 R-9 R-10 KG-1KG-2KG-3KG-4KG-5KG-6

Co

mp

osi

tio

n r

ati

o (

%)

TBOEP

TDCPP

TCPP

TPhP

TCEP

CsDPhP

Others

Residential houses

100

80

60

40

20

0

Kindergartens

Organohalogen Compounds Vol. 79, 651-654 (2017) 653

collected from the kindergartens were more than 80%. In this study, the floors in two kindergartens are wooden floor.

Therefore, TBOEP, which is often included in floor wax, could be dominant. Cristale et al. measured the

concentrations of 10 organophosphate FRs in house dust collected from a kindergarten [5]. The previous study did

not include TBOEP in the total concentration, which could be the dominant phosphorus compound. Therefore, the

range of the total concentrations were lower than those of this study.

Comparison of concentrations and composition ratios of phosphorus compounds in house dust collected from

residential houses and kindergartens

To characterize the concentrations and composition ratios of phosphorus compounds in house dust collected from

kindergartens, the comparisons of them with those from residential houses were carried out. Compared with the

median of the total concentration of phosphorus compounds in house dust collected from the residential houses (48

µg g–1), that from the kindergartens (2,300 µg g–1) was 48 times higher. However, the medians of each phosphorus

compound were comparable if TBOEP was excepted from the total concentrations. Therefore, the concentration of

TBOEP in kindergartens was characteristically high.

Further exposure and risk assessments are required to evaluate the risk of phosphorus compounds via dust in indoor

environments (e.g., residential houses and kindergartens). Especially, not only dust ingestion but also dermal exposure

should be taken into account as exposure routes. Furthermore, baby-specific actions (e.g., hand-to-mouth behavior,

crawling, barefoot walk, and stretch out on the floor) should be also taken into account for more realistic risk

assessment for the baby.

Acknowledgements

This study was supported by a Health Labor Sciences Research Grant of the Ministry of Health, Labor and Welfare,

Japan.

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Masunaga S (2017) Environmental Monitoring and Assessment, 189(48), 1-11.

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