Emissions of Phthalates from Indoor Flat Materials in Chinese

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Emissions of Phthalates from Indoor Flat Materials in Chinese Residences Shanshan Shi, Jianping Cao, Yinping Zhang, and Bin Zhao Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.8b03580 • Publication Date (Web): 29 Oct 2018 Downloaded from http://pubs.acs.org on October 29, 2018

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Environmental Science & Technology

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Emissions of Phthalates from Indoor Flat Materials in Chinese

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Residences Shanshan Shi1,3,‡, Jianping Cao2,4,‡, Yinping Zhang5,6, Bin Zhao5,6,*

3

4

1School

of Architecture and Urban Planning, Nanjing University, 210093 Nanjing, China

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2School

of Environmental Science and Engineering, Sun Yat-sen University, 510006 Guangzhou,

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China

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3Nicholas

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States

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4Department

School of the Environment, Duke University, 27708 Durham, North Carolina, United

of Civil and Environmental Engineering, Virginia Tech, 24061 Blacksburg,

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Virginia, United States

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5Department

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China

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6Beijing

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100084 Beijing, China

of Building Science, School of Architecture, Tsinghua University, 100084 Beijing,

Key Laboratory of Indoor Air Quality Evaluation and Control, Tsinghua University,

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1 Environment ACS Paragon Plus


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Abstract

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Phthalates are ubiquitous pollutants in residential environments. Indoor airborne phthalate

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concentrations in Chinese residences are comparable to, or even higher than, those of western

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countries. However, the major sources of phthalates in Chinese residences are not well known. In

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this study, we measured the phthalates emission features of 23 flat materials used in Chinese

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residences in the laboratory environment, including the mass fraction (wt) and the concentration

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in the air adjacent to the material surface (y0). The measured wt of seven phthalates ranged from

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below the limit of quantitation (LOQ) to 17%, and y0 ranged from LOQ to 2 μg/m3. To evaluate

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the potential contributions of the studied materials to phthalates in residential air, concentrations

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of di-2-ethylhexyl phthalate (DEHP, a typical indoor phthalate) in air due to the emissions from

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selected materials in typical Chinese residential exposure scenarios were modeled and compared

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with measured concentrations from the literatures. The modeled gas-phase, particle-phase, and

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airborne concentrations of DEHP in residential air due to emissions from the selected materials

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were 2-65 times lower than the mean value of measured concentrations. To formulate

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appropriate control strategies, further efforts are needed to identify the dominant sources of

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phthalates in Chinese residences.

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TOC Art Furniture Wall paper

Window sticker

Phthalates

Natural Ventilation

Table mat

Flooring Carpet

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Chinese residence


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Introduction

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Phthalates are common additives (as plasticizers) in consumer products that are widely used in

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residences. Because phthalates are usually not chemically bound to the material matrix, they can

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be emitted from the source materials to the indoor air, and subsequently become ubiquitous

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indoors.1, 2 Chronic exposure to phthalates may result in detrimental health outcomes for humans,

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including asthma,3 endocrine disruption,4 and reproductive problems.5 Considering the fact that

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indoor phthalates concentrations are much higher than their ambient levels6-8, indoor sources are

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the major contributors to indoor phthalates. Therefore, the emission features of phthalates from

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indoor materials must be studied to better understand the indoor concentration levels, human

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exposures and the resulting health risks.

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Blanchard et al.9 and Wang et al.8 compared the indoor phthalate concentrations of different

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countries from previous literatures. The comparisons implied that indoor phthalate

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concentrations in China are comparable to, or even higher than, those in western countries. For

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example, the measured median concentrations of gas-phase diethyl phthalate (DEP), diisobutyl

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phthalate (DiBP), and di-2-ethylhexyl phthalate (DEHP) for the studied private homes in Albany,

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USA, in Tran et al.’s study10 were 390, 19.6, and 17.4 ng/m3, respectively. Bu et al.11 measured

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the gas-phase concentrations of several phthalates in residential apartments at least one year after

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the latest renovation in Chongqing, China. According to their results, the median values of the

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measured gas-phase concentrations in bedroom air were 160, 320, and 260 ng/m3 for DEP,

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DiBP, and DEHP, respectively. Regarding to the particle-phase concentrations of phthalates, the

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median values in 30 French residences of DEHP and DiBP in Blanchard et al.’s study9 were 41.5

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and 30.2 ng/m3, respectively. In this field study, half of the selected dwellings were built before

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1990 and 8 out of the 30 were retrofitted within 5 years. Meanwhile, in Wang et al.’s study8 in


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Xi’an, China, the measured median concentrations of indoor particle-phase DEHP and DiBP in

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buildings constructed within 5 years were 560 and 720 ng/m3, respectively. Thus, it is urgent to

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identify the indoor sources of phthalates in Chinese residences.

63 64

The mass fraction of phthalates within the material (wt, %) determines the maximum amount of

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phthalates that can be emitted into indoor environments. On the other hand, previous studies

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demonstrated that the gas-phase mass transfer at the surface of the material limited the emissions

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of phthalates from polymeric materials.12 The emission rate (Ss, μg/h) can be described as

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follows:

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S s  hm As  y0  Cs 

(1)

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where hm is the mass transfer coefficient at the emission surface (m/h), As is the surface area of

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the material (m2), y0 is the phthalate concentration in the air adjacent to the material surface

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(μg/m3), and Cs is the background gas-phase concentration of phthalate (μg/m3). Therefore, wt

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and y0 are the key parameters governing the emissions of phthalates from the source materials. In

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the past two decades, emissions of phthalates from polyvinyl chloride (PVC) floorings have been

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frequently studied,13-16 and these studies have found that y0 can be treated as constant after a

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sufficiently long period (e.g., after one year for DEHP according to Clausen et al.14). However,

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PVC flooring is more widely used in western countries than in China. In 2010, PVC flooring

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occupied 17.1 % and 11.0 % of the total flooring sales by volume in the United States and

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Western Europe, respectively. Meanwhile, PVC flooring only occupied 4.8 % of sales in the

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Chinese flooring market.17 Chinese residents prefer laminate flooring and various wood

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floorings, including solid wood flooring and multi-player wood flooring. However, whether or

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not these commonly used flooring materials in China make a contribution to indoor phthalates

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keeps unknown. In addition, the phthalate emission features of other commonly utilized flat

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materials in Chinese residences have also not been studied. 5 Environment ACS Paragon Plus


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The objective of this study was to experimentally investigate the phthalate emission features of

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23 flat materials available in the Chinese housing decoration market. wt within the selected flat

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materials were measured using the extraction method, and y0 of the selected materials were

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measured using the solid-phase micro-extraction (SPME) sealed-chamber method recently

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developed by Cao et al.18 To evaluate the potential contribution of the selected flat materials to

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phthalates in residential air, airborne concentrations of DEHP due to the emission from the

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studied materials were modeled with the measured emission features.

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Materials and Methods

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Selection of flat materials in Chinese residences

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The emissions of phthalates from the following flat materials were analyzed: a plastic table mat,

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two PVC wallpapers, a PVC carpet, two PVC floorings, a toddler play mat, two dados (a kind of

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wall material usually installed on the lower part of the facade wall), and a window sticker.

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Additionally, several flooring materials together with the corresponding supporting materials,

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which are commonly used in Chinese residences, were also measured. The types of flooring

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materials included solid wood flooring, multi-layer solid wood parquet flooring, and laminate

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flooring. The measured supporting materials were a moisture-proof mat and a poly mat. The

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products have the highest sale volume on a Chinese shopping website (http://www.JD.com) or

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from the local housing decoration market were purchased and chosen as the selected flat

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materials in this study. All the material samples were newly purchased, except for one laminate

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flooring sample, which has been used for eight years. All the material samples were examined to

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determine both the wt and y0 of phthalates. It should be noted that the SPME-based method

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cannot quantify the y0 values for the samples of flooring materials and the supporting materials

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(because y0 is below the quantitation limit of the SPME-based method) even though the wt 6 Environment ACS Paragon Plus

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values were quantified by the extraction method for some of them. For these cases, the y0 values

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were predicted based on the relationship between wt and y0 from the literature (see details

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below).

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Chemicals

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Seven phthalates were selected as the target pollutants; their physicochemical features are listed

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in Table 1. Among them, di-n-octyl phthalate (DOP) is the phthalate with the largest yield in

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China19, and the others were frequently detected in Chinese residences in existing studies 7, 8, 11, 20.

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All standards used in this study were purchased from Sigma-Aldrich Co. LLC. A certified

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reference material of DiBP was used for calibration of DiBP. A standard mixture of the other six

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phthalates (2000 µg/mL of each phthalate in methanol), including dimethyl phthalate (DMP),

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DEP, di-n-butyl phthalate (DBP), butyl benzyl phthalate (BBzP), DEHP, and DOP, was used for

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their calibration. Dichloromethane (CH2Cl2, MREDA Tech. Inc., HPLC Grade) was used as the

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solvent. SPMEs (with polydimethylsiloxane as the coating material) were purchased from

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Sigma-Aldrich Co. LLC (Supelco Analytical, No. 57302).

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Table 1. Physicochemical features of the selected phthalates Name

Abbr.

Chemical formula

Dimethyl phthalate

DMP

C10H10O4

Molecular weight (g/mol) 194.2

Diethyl phthalate

DEP

C12H14O4

Diisobutyl phthalate

DiBP

Di-n-butyl phthalate

CAS No.

log Koaa

131-11-3

7.01

222.2

84-66-2

7.55

C16H22O4

278.3

84-69-5

8.54

DBP

C16H22O4

278.4

84-74-2

8.54

Butyl benzyl phthalate

BBzP

C19H20O4

312.4

85-68-7

8.78

Di(2-ethylhexyl) phthalate

DEHP

C24H38O4

390.6

117-81-7

10.5

DOP

C24H38O4

390.6

117-84-0

10.5

Di-n-octyl phthalate

127

aOctanol/air

128 129

Extraction of phthalates from flat materials

partition coefficients (Koa) at 25 ºC. Obtained from Cousins and Mackay.21



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Phthalates in flat materials were extracted using a Soxhlet apparatus.22 Extractions were

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immediately started after the delivery of the materials. A small piece (approximately 0.2-0.4 g)

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from each material was cut from a random location and weighed. Samples were extracted with

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60 mL of CH2Cl2 at 70 °C for 12 h (overnight). The extracts were concentrated to 10 mL using a

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rotary evaporator. Then, 100 µL of the concentrated extracts were transferred into 5 mL

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volumetric flask and diluted to 5 mL with CH2Cl2. Finally, 100 µL of the diluted extracts were

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transferred from the 5 mL volumetric flask into 2 mL Agilent sample vials equipped with 250 µL

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micro-volume inserts using a 100 µL syringe. The vials were stored at -4 °C in a laboratory

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refrigerator and analyzed within one week. The wt of each material sample was measured for

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three times.

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Measurement of phthalate concentration in the air adjacent to the material surface based on

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the solid-phase micro-extraction method

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We followed the SPME sealed-chamber method developed by Cao et al.18to measure y0 values

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for phthalates emitted from flat materials. A detailed principle of the method and structure of the

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measurement system can be found in Cao et al.18 Experiments were immediately conducted after

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the delivery of the materials. Two circular samples (diameter: 22.0 cm) were cut from randomly

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selected locations of each material, which were then placed on the top and bottom of a circular

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ring made of stainless steel (thickness: 2.0 cm; inner diameter: 20.0 cm; outer diameter: 22.0

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cm). Two flat plates made of stainless steel (thickness: 5 mm; diameter: 22.0 cm) were placed on

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the other side of each surface material. The gravity of the flat plate on the top helped to seal the

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airtight cavity (thickness: 2.0 cm; diameter: 20.0 cm) formed between the two flat materials and

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the circular ring. In addition, several small holes (diameter: 1.0 mm) were drilled in the middle

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of the side of the circular ring so that the SPME could be inserted into the chamber to quantify 8 Environment ACS Paragon Plus

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the y0 values. Gas-phase phthalates in the airtight cavity were sorbed by the coating of SPME,

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and the sorption amount was linearly related with y0 and the sampling time.18 According to the

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analysis of a previous study, the sampling time for DEP, DMP, DiBP, and DBP was set as 15

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min, and it was set as 6 h for BBzP, DEHP, and DOP.23 The temperature of the whole

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experimental system was set as 25 ºC during the measurement. For each material sample, the

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measurement of y0 was repeated three times.

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Instrumental analysis

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All samples (extracts in vials and SPME samples) were analyzed using a gas

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chromatography-mass spectrometry system (GC-MS, Agilent Technologies 7820A Gas

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Chromatograph (GC) system equipped with a 5975C Mass Spectrometer (MS)). A fused silica

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capillary column (HP-5MS, 30 m × 0.25 mm × 0.25 µm) was used for GC separation using high

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purity helium with a flow rate of 1.2 mL/min as the carrier gas. The GC oven temperature was

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maintained at 100 °C for 2 min, increased to 300 °C at 10 °C/min, and finally maintained at 300

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°C for 1 min (23 min in total). Temperatures of the GC injection port and MS ion source were set

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at 280 °C and 250 °C, respectively. For extracts in vials, the injection volume was 1.0 µL. For

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SPME samples, the coating of the SPME fiber was manually inserted into the GC injection port

171

for 5 min (i.e., thermally desorbed for 5 min at 280 °C). The GC was operated in splitless mode,

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and the MS was operated in selected ion monitoring mode. The target compounds were

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quantified using the selected molecular ions, namely m/z = 163 for DMP and m/z = 149 for the

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other six phthalates.

175 176

Quality assurance and control



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A nine-point calibration was prepared based on 1 μL injections of mixture solutions of the seven

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phthalates with concentrations of 0.05, 0.1, 0.2, 0.5, 1.0, 2.0, 5.0, 10, and 20 µg/mL. The mixture

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solutions were analyzed using the GC-MS system according to the procedure described in the

180

previous section. A linear function between the GC-MS peak area and the concentration of each

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phthalate (for solvent extracts) or the injected amount of each phthalate (for SPME samples) was

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obtained. The calibration curve was valid only when R2 of the linear fitting was larger than 0.99.

183 184

For solvent extracts, the limit of quantitation (LOQ) was 0.05 μg/mL because the calibration line

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was no longer linear below this level. If the phthalate concentration in the extract was greater

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than 20 µg/mL, then the extract was diluted and re-analyzed. No phthalate was detected in the

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lab blanks (Soxhlet extraction but without flat materials in the extraction flask).

188 189

For SPME samples, when the measured amount of phthalates was greater than 20 ng

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(corresponding to 5 μg/mL × 1 μL), the sampling time of SPME samples was reduced by half;

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conversely, the sampling time was doubled if the measured amount was less than 0.05 ng

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(corresponding to 5 μg/mL × 1 μL). It should be noted that the sampling time should be less than

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tlinear according to the principle of the SPME-based method,18, 23 where tlinear is the longest time

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that ensures the uptake rate of phthalates by SPME keeping constant (after tlinear, the uptake rate

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decreases as the sampling time increases). According to our measurements, tlinear was about 20

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hour for BBzP, DEHP, and DOP, and about 2 hours for the other four phthalates. If the measured

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amount was still less than 0.05 ng when the sampling time reached tlinear, y0 cannot be quantified

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with the SPME based method, and the relationship between wt and y0 from the literature was

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used to estimate y0 values (see details below). Before measurements, each SPME sample was


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conditioned (thermally desorbed) by heating in the GC injection port at 280 °C for 5 min. After

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conditioning, the amount of each phthalate remaining in the SPME coating was undetected.

202 203

Relationship between mass fraction and the concentration in the air adjacent to the material

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surface

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Eichler et al. studied the equilibrium relationship between the phthalates in PVC products and

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the corresponding y0.24 According to this analysis, the theoretical correlation between the volume

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fraction (φ, %) of phthalates within the source material and y0 obeys Henry’s law, which can be

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represented as the following equation:

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y0  c

(2)

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where c is a compound-specific constant related to the activity coefficient. In this study, c was

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set as 3.7 according to Eichler et al.’s study. The φ of phthalates within the source material can

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be derived from the wt as follows:

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i 

V ph ,i Vm

wti /  ph ,i





n j i

wt j

 ph , j

1   j 1 wt j n



(3)

m

214

where subscript “ph” represents phthalate, subscript “m” represents source material, V represents

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the volume (m3), and ρ represents the density (g/cm3). The measured density of the selected

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materials was utilized as ρm here, and ρph of each phthalate specie was obtained from CAMEO

217

Chemicals (https://cameochemicals.noaa.gov).

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Potential contribution of the selected flat materials to indoor phthalates

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To evaluate the potential contribution of the selected flat materials to indoor phthalates, indoor

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airborne concentrations of phthalate due to the emissions from the selected materials were

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calculated for several typical Chinese residential scenarios. Then, the calculated concentrations



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were compared to measured ones in Chinese residences obtained from the literatures. DEHP was

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selected as the target compound for comparison as it is a ubiquitous phthalate congener in

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Chinese residences.

226 227

We previously developed a model to predict indoor phase-specific concentrations of

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semi-volatile organic compounds (SVOCs) 25 that considers the kinetic partition process between

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gas-phase SVOCs and airborne particles. According to this model, the mass balance of gas- and

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particle-phase DEHP at the steady state can be described as follows:26, 27

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 Csp  n Cs  hmp Ap N p  Cs   K pC p 

 S   s V  0 

232

 Csp  n Csp  hmp Ap N p  Cs   K pC p 

   D p Csp  0 

(4) (5)

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where αn is the air exchange rate (h-1), hmp is the mass transfer coefficient at the surface of

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airborne particles (m/h), Ap is the surface area of an individual particle (m2), Np is the indoor

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particle number concentration (m-3), Csp is the indoor particle-phase DEHP concentration

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(μg/m3), Kp is the particle-gas partition coefficient of DEHP (m3/μg), Cp is the indoor particle

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mass concentration (μg/m3), V is the volume of the indoor environment (m3), and Dp is the

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indoor particle deposition rate (h-1). Detailed information of the model can be found in the

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original study.25 Because the atmospheric DEHP concentrations are much lower than the

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concentration levels in residences in China6-8, the influence of atmospheric DEHP was not taken

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into account. The emission of DEHP from indoor flat materials can be described with eq. (1).

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Therefore, gas- and particle-phase concentrations of DEHP can be calculated with the following

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equations by solving eqs. (1) and (4)-(5):


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 As  hmp Ap N p y0    n  Dp   K C  V p p   Cs  h A N A As   mp p p  s   hmp Ap N p   n  hm V   n  D p   K C   n  hm V      p p A hm s y0 hmp Ap N p V Csp  hmp Ap N p  As  As    hmp Ap N p   n  hm V   n  D p   K C   n  hm V      p p hm

244

245

(6)

(7)

246

A naturally ventilated apartment was set up to represent a typical residential exposure scenario in

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China. αn was set as 2 h-1 to represent a long-term average scenario for the naturally ventilated

248

apartments according to our previous studies.28,

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temperature (ta, °C), which was set as 25°C as a typical indoor scenario. The empirical equation

250

proposed by Cao et al.18 was utilized to determine the vapor pressure of DEHP (PL, Pa) at 25°C.

251

Then, Kp of DEHP at 25°C was calculated to be 0.034 m3/μg based on its relationship with PL.30,

252

31

253

empirical equation.32 The corresponding hm can be subsequently calculated with ta and va,33

254

which was 1.24 m/h for the modeled scenario. PM10 (particles with aerodynamic diameters

255

smaller than 10 μm) was set to represent indoor airborne particles. For the modeled scenario, Cp

256

of PM10 was set as 150 μg/m3, which is the national standard of indoor PM10 in China.34 To

257

account for the influence of particle diameter on particle related parameters (i.e. hmp, Ap, Dp),

258

PM10 was divided into 8 diameter bins: < 0.10, 0.10-0.22, 0.22-0.36, 0.36-0.56, 0.56-1.14,

259

1.14-2.26, 2.26-5.66, and 5.66-10.0 μm. For each particle-related parameter, the value within

260

each diameter bin was firstly determined and then the integrated value of PM10 was obtained by

261

averaging the size-resolved ones weighted by a typical mass distribution of PM10 in residential

262

environment.35 The determinations of αn, Kp, hm and size resolved particle related parameters are

263

introduced in detail in Section S1 of the SI.

29

Kp is strongly dependent on indoor air

Indoor air speed (va, m/s) within the residence with αn as 2 h-1 was estimated via Liu et al.’s

264



265

It is noteworthy that indoor environmental factors, including indoor air temperature (ta,), air

266

exchange rate (αn) and indoor particle concentration (Cp), have significant impacts on both mass

267

transfer and source emission of phthalates.32, 33, 36 Therefore, sensitivity analysis was conducted

268

to investigate the influences of ta, αn, and Cp on the calculated indoor DEHP concentrations in air

269

due to the emission from the selected flat materials, which are introduced in detail in Section S2

270

of the SI.

271 272

Results and Discussion

273

Mass fraction of phthalates within the materials

274

Mass fractions of the target phthalates within the selected flat materials (wt, %) are listed in

275

Table 2. Six of the seven targeted phthalates were found in the selected flat materials. In general,

276

the detection rates of phthalates were not high among the selected flat materials. DEHP had the

277

highest detection rate (39.1 %), followed by DOP (17.4 %), DEP (8.7 %), and DiBP/DBP/BBzP

278

(4.3 %). DMP was not detected in any of the selected flat materials.

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Table 2. The mass fraction of the target phthalates within the flat materials (wt, %) Material/Compound

DMP

DEP

DiBP

/a

281 282 283 284 285

DnBP

BBP

DEHP 17±0.8b

DOP

Plastic table mat / / / / / Wallpaper I / / / / / / / / / / / / 2±0.7 / Wallpaper Ⅱ Carpet / / / / / 3±0.4 2±0.2 PVC flooring I / / / 0.07±0.01 / 4±0.6 / / / / / / 14±0.7 0.09±0.01 PVC flooring Ⅱ Toddler play mat / / / / / 0.01±0.002 / Dado A / / / / / / / Dado B / / / / / / / Window sticker / / / / / 7±0.3 / Moisture proof mat / / / / / / / Poly mat / / / / / / / c / / LOQ-0.08 / / LOQ-0.1 / Solid wood flooring Ⅰ / / / / / / / Solid wood flooring Ⅱ / LOQ-0.06 / / / / / Solid wood flooring Ⅲ / / / / / / LOQ-0.2 Solid wood flooring Ⅳ / / / / / / / Multi-ply solid wood parquet flooring Ⅰ / / / / / LOQ-0.1 / Multi-ply solid wood parquet flooring Ⅱ / / / / / / / Laminate flooring Ⅰ / / / / / / / Laminate flooring Ⅱ / / / / / / / Laminate flooring Ⅲ / LOQ-0.09 / / LOQ-0.1 / LOQ-0.2 Laminate flooring Ⅳ / / / / / / / Laminate flooring Ⅴ a / means all the wt of a material from the triplicate measurements are below the limit of quantitation b If all the wt of a material from the triplicate measurements are over the limit of quantitation, the measured wt is represented by mean±standard deviation c If some of the wt of a material from the triplicate measurements are over the limit of quantitation, the measured wt is represented by min-max and LOQ means blow the limit of quantitation



286

The plastic table mat had the largest wt of the target phthalate species, which was 17%. The wt of

287

the target phthalate species in the carpet, PVC flooring B and window sticker was also larger

288

than 5%. For the rest flat materials, the wt of the target phthalate species were smaller than 5%.

289

For materials with all the wt of the triplicate measurements over the limit of quantitation (LOQ),

290

the relative standard deviations of wt were all less than 30%, giving confidence in the accuracy

291

of our measurements of wt. The selected flooring materials and the supporting materials

292

corresponded to very small wt values of the target phthalate species (i.e., LOQ-0.2%). Among

293

the selected flat materials, wallpaper I, dados I and II, moisture-proof mat, poly mat, solid wood

294

flooring II, multi-layer solid wood parquet flooring I, and laminate floorings I, II, III, and V were

295

found to be free of the target phthalates. None of the target phthalates were detected in the used

296

laminate flooring sample. Afshari et al.1 summarized the wt of DEHP and DBP in some indoor

297

materials, including PVC flooring and wallpaper. In their study, the wt of DEHP within the PVC

298

flooring materials ranged from 17% to 18.5%, while that of wallpaper was 18%. These surveyed

299

wt values of DEHP were much larger than the majority of the measured ones in the present

300

study. As the health hazards of phthalates have become well recognized, more governments and

301

agencies have issued regulations to limit the amount of phthalates in consumer products.37, 38 As

302

a result, newly produced materials tested in this study may have a smaller wt of phthalates

303

compared to those of the surveyed materials. PVC flooring I and the window sticker selected in

304

this study are heterogeneous materials that are made up with layers of different materials.

305

However, the wt of phthalates from the extraction method was obtained by dividing the amount

306

of phthalates within the material by the total weight of the material. In this case, the measured wt

307

may deviate from the actual value.

308 309

Equilibrium concentration in the air directly adjacent to the material surface


Page 16 of 27

Page 17 of 27


310

The measured equilibrium concentrations in the air adjacent to the material surface (y0) are listed

311

in Table 3. For plastic table mat, wallpaper II, carpet, PVC flooring I and II, window sticker, and

312

solid wood flooring I, y0 was represented as the average value and the standard deviation from

313

the triplicate measurements. For solid wood flooring IV, multi-layer solid wood parquet flooring

314

II, and laminate flooring IV, y0 was calculated from the maximum measured wt from the

315

triplicate experiments using eqs. (2)-(3) to show the most unfavorable situation. For materials

316

with all the measured wt from the triplicate experiments smaller than 0.1 %, the corresponding y0

317

could not be quantitatively determined.

318 319

Table 3. The equilibrium concentration in the air adjacent to the product surface (y0, μg/m3) Material/Compound Plastic table

DMP

mata

DEP

DiBP

DBP

BBzP

DEHP

DOP

/d

/

/

/

/

2±0.07

/

Wallpaper I

/

/

/

/

/

/

/

Wallpaper IIa

/

/

/

/

/

0.2±0.01

/

Carpeta

/

/

/

/

/

0.07±0.06

0.1±0.03

PVC flooring

Ia

/

/

/

/

/

1±0.05

/

PVC flooring

IIa

/

/

/

/

/

2±0.01

/

Toddler play mat Dado I Dado II

/

/

/

/

/

/

/

/

/

/

/

/

/

/

/

/

/

/

/

/

/

Window stickera

/

/

/

/

/

2±0.3

/

Moisture-proof mat Poly mat

/

/

/

/

/

/

/

/

/

/

/

/

/

/

/

/

/

/

/

0.009

/

/

/

/

/

/

/

/

/

/

/

/

/

/

/

/

/

/

/

/

/

0.002

/

/

/

/

/

/

/

Multi-layer solid wood parquet flooring IIb

/

/

/

/

/

0.008

/

Laminate flooring I

/

/

/

/

/

/

/

Laminate flooring II Laminate flooring III

/

/

/

/

/

/

/

/

/

/

/

/

/

/

/

/

/

/

0.05

/

0.003

/

/

/

/

/

/

/

Solid wood flooring

Ib

Solid wood flooring II Solid wood flooring III IVb

Solid wood flooring Multi-layer solid wood parquet flooring I

Laminate flooring

IVb

Laminate flooring V (Used)



Page 18 of 27

Vinyl flooring Ic,12

-e

-

-

-

-

1.13

-

Vinyl flooring IIc,16

-

-

-

-

-

2.3

-

Vinyl flooring

IIIc,16

-

-

-

-

-

2.37

-

Vinyl flooring

IVc,16

-

-

-

-

-

0.02

-

Vinyl flooring

Vc,16

-

-

-

-

-

1.54

-

320 321 322 323 324 325

a Measured

326

For DEHP, the plastic table mat, PVC flooring II, and window sticker had the largest y0 (i.e., 2

327

μg/m3) and multi-layer solid wood parquet flooring II had the smallest y0 (i.e., 0.008 μg/m3). For

328

DOP, the carpet had the largest y0 (i.e., 0.1 μg/m3) and solid wood flooring IV had the smallest y0

329

(i.e., 0.002 μg/m3). For BBzP, laminate flooring IV was found to have an y0 of 0.05 μg/m3.

330

Previous studies have examined the y0 of DEHP within vinyl flooring materials,12, 16 the results

331

of which are also summarized in Table 3. For the selected flooring materials in this study, the

332

determined y0 of DEHP was 0.009 and 0.008 μg/m3 for solid wood flooring I and multi-layer

333

solid wood parquet flooring II, which were two orders smaller than most of the vinyl flooring

334

materials measured in previous studies.

y0 according to the solid-phase micro-extraction sealed-chamber method y0 from the measured mass fraction c Summarized y from the literature 0 d/ means below the limit of quantitation e- means not reported b Calculated

335 336

Potential contribution of the selected flat materials to indoor phthalates

337

The measured materials were classified into three categories according to their emission

338

strengths (i.e. y0) and applied surface areas. Category 1 refers to materials with small y0 but large

339

applied surface areas, represented by wallpaper II; category 2 refers to materials with large y0 but

340

small applied surface areas, represented by window sticker; category 3 refers to materials with

341

large y0 and relatively large applied surface areas, represented by PVC flooring II. Then, DEHP

342

concentrations in indoor air due to the emissions of the representative material were calculated

343

for each category to estimate the potential contribution of the selected materials to indoor DEHP.


Page 19 of 27


344

y0 was set as the measured value of the representative material. The applied area of the source

345

material was represented by the loading factor of the source material (i.e., As/V). As/V was set as

346

1.0 m2/m3 for wallpaper II as it’s an experience value of inner wall surface area. For window

347

sticker and PVC flooring II, As/V was set as 0.1 and 0.4 m2/m3, respectively.39 The calculated

348

airborne DEHP concentrations due to the emissions from the representative materials are shown

349

in Figure 1. Several studies have reported indoor gas- and particle-phase concentrations of DEHP

350

in Chinese residences, as summarized in Table 4.

351

Indoor concentration of DEHP at steady state (μg/m3)

0.50 Gas-phase Particle-phase 0.40

Airborne

0.30

0.20

0.10

0.00 Wallpaper II y0=0.2, As/V=1.0

352

Window sticker y0=2.0, As/V=0.1

PVC flooring II y0=2.0, As/V=0.4

353 354 355

Figure 1. DEHP concentrations in residential air due to the emissions from the selected flat materials

356

Table 4. DEHP concentrations in the air of Chinese residences from the literature

357

References

Gas-phase (µg/m3)a

Particle-phase (µg/m3)a

Pei et al., 20137 Wang et al., 20148 Bu et al., 201611 Tao et al., 201340

1.12 0.47 0.38

1.32 1.04

Airborne (µg/m3)a

1.19

a Mean value from the reference



358 359

For wallpaper II, representing materials with small emission strength but large applied area, the

360

modeled gas-phase, particle-phase, and airborne concentrations of indoor DEHP due to its

361

emissions were 0.017, 0.087, and 0.10 μg/m3, respectively, which are 11-65 times smaller than

362

the average measured values from the literatures. With regard to window sticker, although it has

363

a strong emission strength, the modeled indoor gas-phase, particle-phase and airborne

364

concentrations of DEHP, i.e., 0.018, 0.095, and 0.11 μg/m3, respectively, due to its emission

365

were also 10-61 times smaller than the average values from the field measurements. Therefore,

366

these two categories of materials may not be the major contribution to indoor DEHP in Chinese

367

residences. For PVC flooring II, it had the highest modeled concentrations of indoor gas-phase,

368

particle-phase and airborne DEHP, which were 0.071, 0.37 and 0.44 μg/m3. These modeled

369

concentrations were about 6-37% of the average measured ones from the literatures. Although

370

PVC flooring has the same emission strength (i.e., y0) comparing to window sticker, the larger

371

applied surface area of PVC flooring II make it a possible important contributor to indoor DEHP.

372

However, it has been stated that PVC flooring materials are not commonly used as residential

373

flooring material in China. Hence, to sum up, the flat materials selected in this study might not

374

be the major contributors to indoor DEHP for most Chinese residences. It is noteworthy that y0

375

of phthalates increased significantly with increasing temperature.13 The measurements of Pei et

376

al.7 and Tao et al.40 were conducted in normal residences in transient seasons. The indoor

377

temperatures during the measurements by Wang et al.8 and Bu et al.11 ranged from 14.6 to 21.5

378

ºC and 3.1 to 18.8 ºC, respectively. The indoor temperature air of the modeled scenario was set

379

as 25 ºC, which was higher than the air temperatures of the majority of the measured scenarios.

380

Because evaluated indoor temperature would increase y08 , the modeled DEHP concentrations

381

due to the selected flat materials in the measured scenarios of these literatures may be further


Page 20 of 27

Page 21 of 27


382

lower than the measured results. In addition, results of sensitivity analysis (see details in Section

383

S2 of the SI) also support the above conclusion, i.e., the materials measured in this study might

384

not be the major contributors of indoor SVOCs for most Chinese residences.

385 386

Limitations and further study

387

There were several limitations in the present study. First, the selected flat materials may not

388

represent the overall source materials of phthalates in Chinese residences. Besides, personal care

389

products, plastic shoes, and shower curtains are also potential sources of indoor phthalates in

390

residences41, but they were not considered in this study. Second, the extraction method may not

391

be suitable to measure the wt of phthalates within heterogeneous materials, which were

392

composed of multiple layers. Third, the model utilized to estimate DEHP concentrations in

393

indoor air due to the emissions from the selected flat materials was a simplified model based on

394

several assumptions. The kinetic partitions between gas-phase DEHP and indoor sorption

395

surfaces, and settled dust were not considered. The modeled residence was assumed to be

396

well-mixed and reached a steady state. This was supported by the measured data of existing

397

studies for the case where stable and persistent sources of phthalates (such as the flat materials

398

measured in this study) have stayed in the room for a sufficient amount of time.14, 42 Quantitative

399

analysis of the errors caused by these assumptions is worthwhile, but may require the

400

employment of computational fluid dynamics (CFD) modeling, which was out of the scope of

401

this study. A previous study reported that the relative difference between SVOC phase-specific

402

concentrations at a steady state with time-averaged input parameters and time-averaged

403

phase-specific concentrations resulting from the non-steady state model with periodic input

404

parameters can be nearly 20 %.26 Finally, as an assumption in Eq. (5), all particles were assumed

405

to have the same residence time and particle-air partition coefficient of DEHP. However, 21 Environment ACS Paragon Plus


406

assuming the same residence time for indoor particles may not be the real case (i.e., residence

407

time varies among individual particles), and this assumption may result in an error of up to 30 %

408

to the modeled SVOC concentrations.43 Besides, the particle-air partition coefficient of DEHP is

409

dependent on the particle type.44

410 411

The emissions of phthalates from more materials and consumer products containing phthalates

412

with a large consumption volume in Chinese residences still need to be examined. Moreover, the

413

contributions of different sources to Chinese residential phthalates need to be quantitatively

414

studied in controlled experiments. By understanding the major sources of phthalates in Chinese

415

residences, optimal control strategies can be subsequently formulated to reduce indoor airborne

416

phthalates and mitigate the related health risks.

417 418

Associated Content

419

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

420

Publications website. This includes input parameters of the typical exposure scenarios for

421

Chinese residences (Section S1), and sensitivity analysis for room temperature, air exchange

422

rate, and particle concentration (Section S2, Figure S1, Tables S1 and S2).

423 424

Author Information

425

Corresponding Author

426

*E-mail:

427

ORCID

428

Shanshan Shi: 0000-0002-8848-4219

[email protected]; Phone: +86-10-6277-9995; Fax: +86-10-62773461.


Page 22 of 27

Page 23 of 27


429

Jianping Cao: 0000-0002-8633-388X

430

Yinping Zhang: 0000-0001-9175-7890

431

Bin Zhao: 0000-0003-1325-6091

432

Author Contributions

433

‡Authors

434

Notes

435

The authors declare no competing financial interest.

S.S. and J.C. contributed equally.

436 437

Acknowledgments

438

This study was supported by the National Key Project of the Ministry of Science and

439

Technology, China, on “Green Buildings and Building Industrialization” through Grant No.

440

2016YFC0700500, by funding from the National Natural Science Foundation of China through

441

Grant Nos. 51708278 and 51521005, and by funding from the Natural Science Foundation of

442

Jiangsu Province of China through Grant No. BK20170643.

443



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Emissions of Phthalates from Indoor Flat Materials in Chinese

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