External Exposure to Short- and Medium-Chain Chlorinated Paraffins

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External Exposure to Short- and Medium-chain Chlorinated Paraffins for the General Population in Beijing, China Wei Gao, Dandan Cao, Yingjun Wang, Jing Wu, Ying Wang, Yawei Wang, and Guibin Jiang Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.7b04657 • Publication Date (Web): 30 Nov 2017 Downloaded from http://pubs.acs.org on December 3, 2017

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Environmental Science & Technology

External Exposure to Short- and Medium-chain Chlorinated

1 2

Paraffins for the General Population in Beijing, China

3

Wei Gao1, 3, Dandan Cao1, Yingjun Wang1, 3, Jing Wu1, 3, Ying Wang1, Yawei Wang1, 2,

4

3

5

1

6

Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing

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100085, China

8

2

Institute of Environment and Health, Jianghan University, Wuhan 430056, China

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3

University of Chinese Academy of Sciences, Beijing 100049, China

,* and Guibin Jiang1 State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research

10 11 12 13

*Corresponding author

14

Dr. Yawei Wang

15

State Key Laboratory of Environmental Chemistry and Ecotoxicology

16

Research Center for Eco-Environmental Sciences

17

Chinese Academy of Sciences

18

P.O. Box 2871, Beijing 100085, China

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Tel: +8610-6284-9124

20

Fax: +8610-6284-9339

21

E-mail: [email protected]

22

1

ACS Paragon Plus Environment


23

Abstract

24

Chlorinated paraffins (CPs) are a class of compounds that are currently produced

25

and used in large amounts in commercial products worldwide. In this study, food,

26

indoor air, indoor dust and drinking water samples were collected to evaluate the

27

external exposure levels of CPs and possible pathway for the general population in

28

Beijing, China. Short chain CPs (SCCPs) and medium chain CPs (MCCPs) in 199

29

samples were analyzed using a gas chromatography tandem time-of-flight

30

high-resolution mass spectrometry (GC - TOF - HR -MS) method. High levels of CPs

31

were observed in the indoor environment from residential houses, offices and student

32

dormitories. The geometric mean concentrations (GM) of ∑SCCPs and ∑MCCPs in

33

indoor dust were 92 µg g-1 and 82 µg g-1, respectively, while in indoor air, the

34

concentrations were 80 ng m-3 and 3.4 ng m-3, respectively. The GM of ∑SCCPs and

35

∑MCCPs in the diet were 83 ng g-1 dry weight (dw) and 56 ng g-1 dw, respectively.

36

The most important external exposure routes to CPs to the general populations in

37

Beijing were food intake and indoor dust ingestion. Indoor dust and indoor air posed

38

higher risks for toddlers and infants than for adults.

39 40 41 42 43

2


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Table of Contents Figure

3



46 47

Introduction Chlorinated paraffins (CPs) are a class of compounds currently produced and

48

used in large amounts in commercial products and can be divided into three categories:

49

short chain chlorinated paraffins (SCCPs, C10-C13), medium chain chlorinated

50

paraffins (MCCP, C14-C17), and long chain chlorinated paraffins (LCCP, C≥18).1,2 CPs

51

have been used as industrial additives for several decades.1 The current SCCPs

52

production worldwide was estimated to be at least 16,5000 t/year, while the total CPs

53

production volume was much higher as CPs products are mixtures of different chain

54

length CPs.3 China began to produce CP products in the 1950s3,4 and is the largest

55

producer in the world at present according to the data provided by the Chinese Chlor

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Alkali Association. Researchers have paid special attention to SCCPs because of their

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long-distance transport potential,5,6 persistence,7 bioaccumulation potential,8 and

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possible carcinogenic effects.9 In 2006, SCCPs were proposed to be included in the

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Stockholm Convention (SC) on Persistent Organic Pollutants (POPs).10 In 2016, at its

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twelfth meeting, the POPs Review Committee ultimately considered that SCCPs

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fulfilled the criteria of POPs and the eighth Conference of Parties decided to list

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SCCPs in Annex A as new POPs in SC in May, 2017.11,12 Although SCCPs have been

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listed in the SC, the exemptions for SCCPs applications in the document allowed

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SCCPs existence in the environment for a relatively long period. Moreover, MCCPs

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might have equally significant adverse environmental and human health effects

66

because their persistence and bioaccumulation properties were similar to SCCPs.13

67

However, compared to SCCPs, data on MCCPs levels in environment and even for 4


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human exposure are relative scarce as a result of lack of enough attention. Risk

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quotients of MCCPs should also be considered in future studies to address data gaps

70

relevant to the exposure of the general population to CPs.

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CPs have been found in various environmental matrices at high levels in China,

72

including soil, air, biota, food, water, and even in human milk since China is the

73

largest CP producing country.14-22 Our previous studies found high concentrations of

74

SCCPs in the outdoor and indoor atmosphere in Beijing, China.15,17 Harada et al.

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found that concentrations of SCCPs in the diet increased by two orders of magnitude

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from the 1990s to 2009 in Beijing, China.23 In addition, a recent work found relatively

77

high levels of SCCPs and MCCPs in human milk from urban areas in 28 Chinese

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provinces.24 All these studies implied that the general population in China may be

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facing high external exposure to CPs in the living environment. However, the possible

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routes and sources of CPs have not been well evaluated.

81

In this study, congener group distributions and levels of SCCPs and MCCPs

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were studied simultaneously in indoor dust and indoor air from residential houses and

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workplaces, duplicate food samples from participants and fast-food outlets, and

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drinking water by a GC--TOF-HRMS method. The purpose of this study was to study

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the congener profiles and the concentrations of SCCPs and MCCPs in diet, water, dust

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and air and investigate the possible external exposure doses through different

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pathways for the general population in Beijing, China were identified. To our

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knowledge, this is the first work to comprehensively evaluate the external exposure of

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CPs to general populations and it can supply important data for the possible risks 5



90

assessments, especially for MCCPs, since the relative data is very scarce.

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Materials and Methods

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Sample collection

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Samples collection campaign was carried out in 2016. Drinking water (two tap

94

water and two pure water) samples were collected from our office. Duplicate diet

95

samples consisted of two parts: one part was collected from fast food outlets (n=15)

96

and the other part was collected with the help of 6 participants who provided duplicate

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portions of what they consumed for their three meals per day (n=18). The dining

98

places of these participants mainly are two dining halls. One belongs to a university

99

servicing for approximately 20,000 people, and the other is in an institute servicing

100

for approximately 2,000 people. These two dining halls are open to the public,

101

therefore, the diet provided by the participants represented diets consumed by a large

102

group of people. The first part was used to evaluate the CPs exposure level for people

103

who eat take-away food, which is more and more popular in China. The second part

104

was used to evaluate the CPs intake levels of people who eat in the dining rooms and

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those who eat homemade food. The food samples were freeze-dried and triturated.

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The detailed information (food species) of the duplicate food samples is provided in

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Tables S1 and S2. Three different brands of milk powder (n=6 samples) were

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purchased in supermarkets.

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Indoor air samples (n=39) and indoor dust samples (n=115) were collected in

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residential homes, workplaces, and dormitories. Summer and winter samples were

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both collected to study the potential seasonal differences. Passive air sampler 6


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polyurethane foam (PUF) disks were used to collect indoor air samples. Briefly, PUF

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disks were housed in stainless steel domed chambers. Passive air samplers were

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deployed for approximately 60 days in summer (July 2014 to September 2014) and

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winter (December 2014 to early March 2015) at 16 sites in offices and residential

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buildings in Beijing. Field blanks were prepared by installing pre-washed PUF disks

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in the sampler for 5 minutes and then wrapping the PUF disks in aluminum foil and

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placing them in zipped plastic bags until analysis. PUF disks were handled using

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solvent-rinsed tongs. Sampling chambers were pre-cleaned and solvent-rinsed with 95%

120

ethyl alcohol prior to installation of the passive sampling media. PUF disks were

121

extracted by ASE 350 with a 1:1 (volume ratio) mixture of dichloromethane and

122

hexanes prior to use.

123

Indoor dust samples were collected using a household vacuum cleaner (D-530) by

124

placing a nylon bag over the intake nozzle of the aspirator to avoid possible

125

contaminants from the equipment. After sampling, the nylon bag was scraped off and

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the dust was then carefully wrapped in aluminum foil. A 100-mesh sieve was

127

employed to sieve out fragments and flocs. The samples were stored in a refrigerator

128

at -20 °C until analysis.

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Quality assurance/quality control

130

All the glassware used in this study were carefully washed with deionized water,

131

then baked in a muffle furnace at 450 °C overnight. Before use, they were rinsed three

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times with dichloromethane. The column packings (neutral silica gel, anhydrous

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sodium sulfate and Florisil) were all baked in a muffle furnace and rinsed with 7



134

dichloromethane and n-hexane before purification. Each batch of 5-9 samples was

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followed by three procedural blanks. Field blanks were prepared when indoor dust

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and indoor air samples were collected. For indoor air field blanks, a pre-cleaned PUF

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disk was placed in the chamber for five minutes, then scraped off and the collected

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material was wrapped in aluminum foil. Field blanks for indoor dust were prepared by

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sucking pre-baked anhydrous sodium sulfate with the vacuum cleaner in the same

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manner as collecting dust samples. Field blanks showed no difference from the

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procedural blanks. For indoor air and indoor dust samples, procedural blanks

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contained less than 5% of the CPs content in samples. Therefore, these samples were

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not blank-corrected. However, diet, drinking water and milk powder samples with low

144

concentrations were blank-corrected. For diet and milk powder samples, the

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laboratory blanks contained 0.4 to 5.2 ng g-1 of SCCPs (which were equivalent to less

146

than 1% to up to 20% of SCCPs in samples), while for water samples, the procedural

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blanks contained 42 to 48 ng L-1 of SCCPs (which were equivalent to about 30% of

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SCCPs in water samples). MCCPs in the procedural blanks were under instrument

149

detection limit (IDL). The method detection limit (MDLs) which is defined as three

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times the standard deviation of the procedural blanks from all of the batches. The

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MDL of different environment matrices are provided in Table S3. The recoveries of

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13

153

95%).

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Daily exposure calculation

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C10-labeled 1,5,5,6,6,10-hexachlorodecane were in the range of 53%-129% (mean:

Estimated daily intake (EDI) of SCCPs and MCCPs for the general population 8


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via diet, indoor dust, indoor air and drinking water was calculated using the following

157

equations.

EDIdiet =

Cdiet × Mdiet 1 Wt

158

EDItoddler diet =

159

EDIwater =

160

EDIair =

× ×

%&×'%& !

&×'& !

!

2

3

4

EDIindoor dust = EDIingestion + EDIdermal adsorption 1 23 × 41 23× ∑61

1 23 × 789 × 98× 9:× ∑61 23

5

161

=

162

where Cdiet is the concentration of CPs in the diet, Mdiet is the mass of the diet sample,

163

and Wt is the weight of a person. Mmilk is the recommended milk powder daily intake

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(Mmilk = 80 g day-1), Cmilk is the CPs concentration in milk powder, Mtoddler is the total

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food intake of toddlers,26,27 Vwater is the volume of water ingestion (0.3 L d-1for

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toddlers and 1.2 L d-1 for adults),28 Vair is the volume of air inhalation (8 m3 d-1 for

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toddlers and 15.7 m3 d-1 for adults),28 Rindoor dust is the ingestion rate of indoor dust in a

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certain kind of indoor environment (60 mg d-1 for toddlers and 30 mg d-1 for adults),28

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Tindoor is the time spent in a certain kind of indoor environment, Wt is the weight of a

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person, BSA is the body surface area (0.53 m2 for toddlers and 2.05 m2 for adults),28

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AS is the soil adhered to skin (0.022 g m-2),28 and AF is the fraction of CPs adsorbed

172

in the skin (0.14).29

MOE =

!

+

!

NOAEL 6 EDI

173

Margin of exposure (MOE) is applied to evaluate the potential risks of CPs to human

174

health. MOE is the standard used by the European Food Safety Authority (EFSA) for 9



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chemical risks assessment. It is defined as the ratio of the no-observed-adverse-effect

176

level (NOAEL) to its estimated daily intake (EDI) amount for a person.

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Data analysis

178

All the statistical analysis was performed using SPSS version 20.0 software.

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One-way analysis of variance (ANOVA) was used to test statistical significance.

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Correlation was tested applying Spearman’s rank coefficients.

181

Results

182

Levels and congener group profiles of SCCPs and MCCPs in indoor dust

183

Both ∑SCCPs and ∑MCCPs were detected in all 115 dust samples with

184

concentrations ranging from 5.35 to 1022 µg g-1 (GM = 92.0 µg g-1) and 2.10 to 725

185

µg g-1 (GM = 82.8 µg g-1), respectively (Table 1). The concentrations of MCCPs and

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SCCPs were at comparable concentrations. However, in a German study, MCCPs

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levels were much higher than SCCPs levels.30 The median value of SCCPs and

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MCCPs determined in the Germany study were 6 and 176 µg g-1, while in this study

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the corresponding value were 98.7 and 89.8 µg g-1.t in German indoor dust may

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reflect the effective restriction of SCCPs in Europe since the 1990s,31 while in China,

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SCCPs have not been restricted until now. ∑SCCPs + MCCPs (sum-CPs) in dust in

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this study were 10 to 100 times higher than the results from Sweden21 and were

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slightly lower than the concentrations in a newly opened shopping mall in China.18 In

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addition, sum-CPs in indoor dust in Beijing were also much higher than other POPs,

195

e.g., HBCD and PBDEs, by 2-3 orders of magnitude in China.32-34 These high

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concentrations were consistent with the high volume of industrial CP production and 10


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usage in China.

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The relative abundance of different SCCP congener groups in indoor dust were

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ranked in the following order: C13 (35%) > C11 (31%) > C12 (23%) > C10 (12%), while

200

different chlorine atom substitution groups were Cl7 (36%)> Cl8 (33%) > Cl9 (17%) >

201

Cl6 (9.7%) > Cl10 (3.1%) > Cl5 (0.2%) (Table 1 and Figure 1). For MCCPs, the

202

congener distribution patterns were C14 (79%) > C15 (16%) > C16 (3.7%) > C17 (1.2%)

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and Cl8 (44%) > Cl7 (28%) > Cl9 (19%) > Cl6 (6.1%) > Cl10 (3.2%) > Cl5 (0.1%),

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respectively (Table 2 and Figure 1). C13-CPs was the most predominant SCCPs

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congener group in the indoor dust, which was also the most abundant in CP52

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mixtures but with a higher proportion (Figure S2). The distribution pattern in indoor

207

dust was a result of CP52 technical mixtures shifting to lower-chain-CPs. C14 was the

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most abundant MCCP formula group both in our results (79%) and in the results from

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the German indoor study (60%).30 Based on the chlorine atom substitutions groups,

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Cl7- and Cl8-CP species were the dominated species in both the composition of SCCPs

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and MCCPs in dust, which were in agreement with the Cl7- and Cl8-CP species of

212

CP52 (72% and 62%).

213

Levels and congener profiles of SCCPs and MCCPs in indoor air

214

∑SCCPs were detected in all 39 samples in the indoor air, with a range of 9.77 -

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966 ng m-3 (GM: 80.1 ng m-3), while ∑MCCPs were detected in 23 out of 39 samples

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ranging from < LOD to 613 ng m-3.

217

levels in the indoor air, which implied that with lower vapor pressure, MCCPs were

218

more lipophilic and not easily volatilized into the atmosphere. The predomination of

MCCP levels were much lower than SCCP

11



219

SCCPs in indoor environment was very different from the results in outdoor air. 33,

220

35-38

221

SCCP and MCCP levels were 5.13 and 4.21 ng m-3)35 or at even higher levels than

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SCCPs (e.g., in the UK, SCCP and MCCP levels were 1.13 and 3.04 ng m-3,

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respectively).33 This phenomenon implies that CPs in indoor environment and outdoor

224

environment has different sources. In addition, the atmospheric levels of total CPs in

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the outdoor environment were lower than our results by at least one order of

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magnitude. This outdoor dilution was consistent with our previous finding in organic

227

film on window surfaces.17 The assumption is that indoors have CPs-containing

228

consumer goods and relatively less ventilation.

MCCPs in the outdoor environment were at a comparable level (e.g., in Pakistan,

229

As a result of the higher volatility of lower-chain CPs,39 the most abundant SCCP

230

congener groups were C10 and C11 which accounted for 61% and 29%, respectively, of

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∑ SCCPs. For MCCPs, the most abundant congener groups were C14 and C15 -CPs,

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accounting for 55% and 34%, respectively. For different chlorine-atom congener

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profiles of SCCPs, Cl6 and Cl7 species were the dominant groups, accounting for 48%

234

and 38% of total SCCPs. For MCCPs, the Cl5 group was notably high, constituting 41%

235

of total MCCPs. Cl6-CPs, Cl7-CPs and Cl8-CPs were evenly distributed, contributing

236

25%, 18 %, and 13%, respectively, to ∑MCCPs. The congener group profiles showed

237

similar trends among different environmental compartments except in the air (Figure

238

1c, 1d) and were consistent with the profile of CP52 products.

239 240

Levels and congener group patterns of CPs in duplicate diet samples, milk powder, and drinking water. 12


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Both ∑SCCPs and ∑MCCPs were detected in all the 33 duplicate diet samples,

242

while only SCCPs were detected at low levels in water samples. For duplicate diet

243

samples, ∑SCCP and ∑MCCP levels were in the range of 24.4-546 ng g-1 dry weight

244

(dw) (GM = 83.2 ng g-1 dw) and 17.3 to 384 ng g-1 dw (GM = 55.5 ng g-1 dw),

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respectively. For milk powder samples, ∑SCCP and ∑MCCP levels were in the range

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of 1.70-17.6 ng g-1 dw (GM = 18.2 ng g-1 dw) and 17 to 384 ng g-1 dw (GM = 8.87 ng

247

g-1 dw), respectively. The SCCP levels were higher than in the diet from Beijing in

248

200923 (the highest SCCP concentration of 28 ng g-1 dw). Based on the diet data,

249

Figure 4 shows the daily dietary CPs intake (calculated using Equation 1) and the

250

contribution from three meals provided by the six participants. The origins of the food

251

supplied by the participants are also provided in the supporting information (Table S2).

252

The result indicated that fried food may result in higher CPs intake levels (e.g.,

253

breakfast from V02 and V05 both contained fried food, and the CP levels were

254

higher), followed by fast food. In addition, homemade food tended to contain fewer

255

CPs (lunch from V02, lunch and supper from V06). The reason might be that

256

homemade food has different materials and cooking procedures. Hence people eating

257

fast food and eating in restaurants have a higher exposure risk of CPs via the diet

258

(Table S2, Figure S3). Larger sample sizes in further studies will be needed to exclude

259

uncertainties caused by the limited sample size in this study.

260

Congener profiles of CPs in the diet were similar to that in the indoor dust.

261

Different carbon chain length groups were relatively evenly distributed as C13 (35%) >

262

C11 (31%) > C12 (23%) > C10 (12%), while different chlorine atom substitution groups 13



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Cl7 (36%) > Cl8 (33%) > Cl9 (17%) > Cl6 (9.7%) > Cl10 (3.1%) > Cl5 (0.21%) (Table 1,

264

Figure 1a, 1b). For MCCPs, C14 dominated in the diet samples, accounting for 73%.

265

Cl8-CPs were the most abundant chlorine atom congener group, while Cl7- and

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Cl9-CPs composed 26% and 21%, respectively. No statistical correlations (for MCCP,

267

R = 0.19, P = 0.28; for SCCP, R= -0.024, P = 0.89) were found between lipid content

268

and CP content (Figure S4). ∑SCCPs in tap water ranged from 20 to 26 ng L-1, which

269

were lower than the river water levels in Japan where the concentration was 41.8 ng

270

L-1.19

271

Discussion

272

CPs differences among different microenvironments and seasons

273

CPs

in

indoor

environment

were

influenced

by

indoor

decorations

274

(microenvironments) which were related to the different building-function types.

275

SCCPs in indoor dust ranked in the following order: residential home (201 µg g-1) >

276

dormitory (113 µg g-1) > office (60µg g-1), while for MCCPs, dormitory (84 µg g-1) >

277

residential home (82 µg g-1) > office (60 µg g-1). Overall, higher levels of CPs were

278

observed in residential homes, indicating certain characteristics of this kind of

279

microenvironment (e.g., decoration and ventilation system).40

280

ANOVA was performed to analyze seasonal differences of CPs levels in indoor

281

dust, and no statistical significance was found for either SCCPs or MCCPs. Generally,

282

SCCP concentrations in winter dust samples were slightly higher than those in

283

summer (Figure 2). The summer-winter trends of SCCPs were consistent with

284

previous findings in the outdoor particles in Beijing 2011.41 The average temperature 14


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at the sampling sites in wintertime was 24.5 ± 1.5 °C, while in the summer the

286

average temperature was 26.0 ± 1.5 °C. Considering that CPs belong to the

287

semi-volatile organic compounds, the experimental results indicated that higher

288

temperature might result in CPs evaporating from dust particles to the air. As shown

289

in Figure 3, CPs concentrations in indoor air during summertime were higher than the

290

CP concentrations in wintertime. This trend was the same as in our previous study41 of

291

CPs in the Beijing outdoor atmosphere. Although summer indoor air CP

292

concentrations were generally higher, no significant differences could be found

293

because a few exceptions existed (sites S01, S03, S08, and S10). In these four sites,

294

the winter CPs concentrations were at higher levels than the summer concentrations.

295

The insignificant seasonal trend indicated the potential existence of indoor sources for

296

CPs, which was consistent with the findings in the study of organic film on window

297

surfaces.17 One common characteristic of these four sites was the low window

298

frequency, which created a unique microenvironment. These exceptions suggested

299

that ventilation and heating supply differences might result in the higher airborne CP

300

concentrations (e.g., higher temperatures accelerate CPs release from CP-containing

301

consumer goods indoors).

302

Exposure dose calculation of MCCPs and SCCPs via different routes.

303

The fast food and food donated by participants were collected for different

304

purposes. We used the samples provided by six participants to reflect the true CP

305

exposure value of a person. The fast food set meals combined with body weight data

306

from national investigation results were applied to reflect the average dietary 15



307

exposure level for the general population. For adults, diet intake was estimated using

308

24 h duplicated food samples. For toddlers (1 to 2 years old), diet intake was assumed

309

to be a combination of milk powder and adult food.26,27 The detailed calculation

310

processes are provided in the Supporting Information. The dietary exposure levels of

311

SCCPs for adults ranged from 316 to 1101 ng d-1 kg·bw-1 (GM: 611 ng d-1 kg·bw-1),

312

which was at a comparable level with results in Beijing in 2009 (GM, 620 ng d-1

313

kg·bw-1).23 The exposure levels in this study were one order of magnitude higher than

314

the exposure levels in Seoul and Tokyo (GM, 54.0 ng d-1 kg·bw-1).23 The dietary

315

exposure levels to MCCPs for adults ranged from 153 to 1307 ng d-1 kg·bw-1, and for

316

toddlers, dietary exposure levels to MCCPs ranged from 164 to 1465 ng d-1 kg·bw-1

317

(GM, 705 ng d-1 kg·bw-1). This study is also the first to report dietary exposure to

318

MCCPs for the general population in China.

319

People spend most of their time in indoor environments. For adults, we assumed

320

that they spend nine hours at the workplaces, 12.5 hours in domestic apartments, and

321

2.5 hours in other indoor environments and outdoors based on an investigation

322

conducted in the north China urban area. Toddlers were assumed to spend all their

323

time in domestic apartments. The exposure amount was calculated based on equations

324

4 and 5. To reflect the average and high ends of exposure risks of CPs, the mean and

325

95th percentile ingestion factor data adapted from the exposure factors handbook27,28

326

were applied for the calculation using equations 4 and 5. The GM of SCCPs and

327

MCCPs in indoor air and dust were used for the estimation. Toddlers and adolescents

328

have a higher inhalation rate per unit weight, and toddlers’ special behavior (higher 16


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frequency of hand-to-mouth habits) resulted in high amounts of dust ingestion.26

330

Daily inhalation exposure levels descended with age and stabilized in adulthood

331

(Figure S6). We further compared intake doses of SCCPs and MCCPs for adults and

332

1- to 2-year-old toddlers for the indoor environment, and Table 2 shows that the

333

calculated exposure level for the indoor environment for toddlers could be higher than

334

the exposure level for adults by one order of magnitude. The only available data on

335

comprehensive indoor environment exposure to CPs in the indoor environment was

336

one study from Sweden.21 In that study, the estimated median exposures to sum-CPs

337

in the indoor environment for adults and toddlers were 0.017and 0.11 µg kg-1 day-1,

338

respectively, which were much lower than the sum-CP exposure in this study (0.30

339

and 2.19 µg kg-1 day-1). A recent study investigating the CPs levels in a shopping mall

340

in northeast China found the estimated average daily exposure dose of sum-CPs for

341

adults and toddlers were 0.39 and 1.12 µg kg-1 day-1 respectively.18 The high estimated

342

indoor exposure level in China was consistent with the high volume of production and

343

usage in China in recent years.3

344

Based on the calculations above, the average daily intakes of ∑SCCPs and ∑

345

MCCPs via the four exposure pathways were estimated. The investigated daily

346

intakes for adults were 1.01 and 0.83 µg d-1 kg-1, and for toddlers were 2.31 and 1.32

347

µg d-1 kg-1, respectively. For adults, the predominant exposure pathway to SCCPs and

348

MCCPs was dietary intake, which accounted for 88% and 93% of average daily

349

intakes, respectively, followed by indoor dust exposure, which accounted for 9.3% of

350

SCCPs and 6.9% of MCCPs (Figure 5). However, for toddlers, dust ingestion was the 17



351

most predominant exposure route and accounted for 59% of SCCPs and 51% of

352

MCCPs, followed by dietary ingestion (38% of SCCPs, 49% of MCCPs). The

353

contribution of dust ingestion and dermal permeation of dust contact to the toddlers

354

could be as high as 70% according to a study in malls in China.18 Moreover, exposure

355

differences (diet contribute highest proportion for adults’ CPs total intake while dust

356

contribute highest proportion for toddlers’ CPs intake) between adults and toddlers

357

have been observed for other POPs (e.g.: HBCD, TBBPA). 42 The combined toxic

358

effects of a variety of contaminants through dust exposure for toddlers posed potential

359

risks for this subgroup.

360

Unlike the Swedish study in which the median exposure to sum-CPs was equally

361

distributed between dust and air,21 inhalation was a less important exposure route for

362

people in this work, especially in the case of MCCPs. For SCCPs, inhalation

363

constituted 3.0% and 3.2% for adults and toddlers, respectively. Drinking water intake

364

was almost negligible compared to the other three exposure routes as the CPs are

365

highly lipophilic compounds.

366

Risk assessment through CPs exposure

367

The difference in exposure levels between adults and toddlers suggested that

368

toddlers were a highly exposed sub-group. Special attention should be paid to this

369

group when we evaluate potential risks through CPs exposure. According to the

370

European risk assessment, NOAEL of SCCPs and MCCPs were 100 mg d-1 kg-1 and

371

25 mg d-1 kg-1 respectively.1 We used the 95th percentile concentrations (to evaluate

372

potential risks and to exclude singular values) to calculate the exposure of CPs for 18


Page 18 of 33

Page 19 of 33


373

adults and toddlers, respectively. The calculated 95th percentile intake doses of SCCPs

374

for adults and toddlers were 2.03 and 5.71 µg d-1 kg-1, respectively, which were higher

375

than the Swedish level (0.06 and 0.5 µg d-1 kg-1), The 95th percentile exposure level of

376

MCCPs for adults and toddlers were 0.95 and 1.79 µg d-1 kg-1, respectively According

377

to equation 6, the MOE values for SCCPs were 4.93× 104 and 1.75× 104, the MOE

378

values for MCCPs were 2.63× 104 and 1.39× 104. A MOE value less than 1000 (a

379

factor of ten for a research period less than one year, a factor of ten for interspecies

380

differences, and a factor of ten for individual differences) 43 is considered to pose

381

health risk potential. The calculated MOE values in this study indicated that the CPs

382

external exposure level did not posed health risks for the general population.

383

This is the first study to comprehensively evaluate different external exposure

384

pathways of SCCPs and MCCPs at the same time. We found high levels of SCCPs in

385

diet, indoor dust, indoor air, and drinking water. Since the possibly carcinogenic to

386

humans of SCCPs and the similar toxicity SCCPs and MCCPs the combined chronic

387

effects of SCCPs and MCCPs on human beings are unknown and need further efforts

388

in the future to disclose since the concentrations of CPs in environment show an

389

increasing trend in recent years.

390

ACKNOWLEDGMENTS

391

We thank the National Natural Science Foundation of China (21477141, 21625702,

392

21337002, and 21407157), the National Basic Research Program of China

393

(2015CB453102), and the Strategic Priority Research Program of the Chinese

394

Academy of Science (XDB14010400) for providing financial support. 19



Page 20 of 33

395

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Pharmacol. 1998, 27, 108-111. DOI: 10.1006/rtph.1997.119

535 536 537

538 539

Figure 1. Congener profiles of indoor dust, indoor air, duplicate diet, drinking water,

540

and CP52 products: (a) percentage of different carbon chain length groups of SCCPs, 26


Page 26 of 33

Page 27 of 33


541

(b) percentage of different chlorine atom substitution of SCCPs, (c) percentage of

542

different carbon chain length groups of MCCPs, and (d) percentage of different

543

chlorine atom substitutions of MCCPs.

544

27



545 546

Figure 2. Summer-winter concentrations of CPs in indoor dust in different building

547

function types (residential home, office, and dormitory are abbreviated as R (n = 14),

548

O (n = 35), and D (n = 5), respectively, in this paper), the red hollow box represents

549

summer concentration, the black striped box represents winter concentration. The

550

shadowed part represents MCCP results, and the unshaded part represents SCCP

551

results.

552

28


Page 28 of 33

Page 29 of 33


553 554

Figure 3. Winter-summer concentrations (ng m-3) of SCCPs and MCCPs in indoor air.

555

The black bars represent winter concentrations, the red bars represent summer

556

concentrations (a) SCCPs (b) MCCPs.

557

29



558 559

Figure 4. CP dietary intake (ng kg-1 bw d-1) calculated from 24 h duplicate food

560

samples. B represents breakfast, L stands for lunch, and S represents supper. (a)

561

SCCPs daily diet intake; (b) MCCPs daily diet intake

562

30


Page 30 of 33

Page 31 of 33


563 564

Figure 5. Estimation of CP intake of adults and children via indoor dust, diet, indoor

565

air, and drinking water.

566

31



Page 32 of 33

567

Table 1. SCCP and MCCP concentrations in indoor dust, indoor air, diet, milk powder，

568

and drinking water samples Mean

Geomean

Median

Min

Max

Detected

Indoor dust (µg g-1,

ΣSCCPs

148

92.0

98.7

5.35

1022

115

n=115)

ΣMCCPs

139

82.8

89.8

2.10

725

115

Indoor air (ng m-3,

ΣSCCPs

181

80.1

71.9

9.77

966

39

n=39)

ΣMCCPs

41.9

3.36

3.47

< LOD

613

23

Diet (ng g-1 dw, n=33)

ΣSCCPs

113

83.2

79.3

24.4

546

33

ΣMCCPs

82.2

55.5

40.5

17.3

384

33

Milk powder (ng g-1

ΣSCCPs

18.3

18.2

18.1

16.2

20.5

6

dw, n=6)

ΣMCCPs

14.2

8.87

17.6

1.70

23.3

6

Drinking water (ng L-1,

ΣSCCPs

23.0

22.9

23.0

20.0

26.0

4

n=4)

32


Page 33 of 33


569

Table 2. Estimation of indoor environmental exposure of adultsa and childrena to SCCPs

570

and MCCPs via inhalation and dust exposureb. The geometric concentrations in this study

571

were used for calculation. Adults (21 to < 31 years) male -1

572

-1

Children (1 to

External Exposure to Short- and Medium-Chain Chlorinated Paraffins

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