DSpace at VNU: Occurrence of perchlorate in indoor dust from the United States and eleven other countries: Implications for human exposure

Environment International 75 (2015) 166–171

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Environment International
journal homepage: www.elsevier.com/locate/envint

Occurrence of perchlorate in indoor dust from the United States and
eleven other countries: Implications for human exposure
Yanjian Wan a,b,1, Qian Wu a,1, Khalid O. Abualnaja c, Alexandros G. Asimakopoulos a, Adrian Covaci d,
Bondi Gevao e, Boris Johnson-Restrepo f, Taha A. Kumosani g, Govindan Malarvannan d, Hyo-Bang Moon h,
Haruhiko Nakata i, Ravindra K. Sinha j, Tu Binh Minh k, Kurunthachalam Kannan a,c,⁎
a
Wadsworth Center, New York State Department of Health, and Department of Environmental Health Sciences, School of Public Health, State University of New York at Albany, Empire State Plaza,
P.O. Box 509, Albany, New York 12201-0509, United States
b
CDC of Changjiang River Administration and Navigational Affairs, General Hospital of the Yangtze River Shipping, Wuhan 430019, China
c
Biochemistry Department, Faculty of Science, Experimental Biochemistry Unit, King Fahd Medical Research Center and Bioactive Natural Products Research Group, King Abdulaziz University, Jeddah 21589, Saudi Arabia
d
Toxicological Center, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Antwerp, Belgium
e
Environmental Management Program, Environment and Life Sciences Center, Kuwait Institute for Scientific Research, P.O. Box 24885, Safat 13109, Kuwait
f
Environmental and Chemistry Group, Sede San Pablo, University of Cartagena, Cartagena, Bolívar 130015, Colombia
g
Biochemistry Department, Faculty of Science, Experimental Biochemistry Unit, King Fahd Medical Research Center and Production of Bioproducts for Industrial Applications Research Group,
King Abdulaziz University, Jeddah, Saudi Arabia
h
Department of Marine Sciences and Convergent Technology, College of Science and Technology, Hanyang University, Ansan, South Korea
i

Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555, Japan
j
Department of Zoology, Patna University, Patna 800 005, India
k
Faculty of Chemistry, Hanoi University of Science, Vietnam National University Hanoi, 19 Le Thanh Tong, Hoan Kiem, Hanoi, Viet Nam

a r t i c l e

i n f o

Article history:
Received 17 September 2014
Accepted 11 November 2014
Available online xxxx
Keywords:
Perchlorate
Indoor dust
Human exposure
Global survey

a b s t r a c t
Perchlorate is a widespread environmental contaminant and potent thyroid hormone disrupting compound.
Despite this, very little is known with regard to the occurrence of this compound in indoor dust and the exposure
of humans to perchlorate through dust ingestion. In this study, 366 indoor dust samples were collected from 12
countries, the USA, Colombia, Greece, Romania, Japan, Korea, Pakistan, Kuwait, Saudi Arabia, India, Vietnam, and
China, during 2010–2014. Dust samples were extracted by 1% (v/v) methylamine in water. Analyte separation
was achieved by an ion exchange (AS-21) column and analysis was performed by high performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS). The overall concentrations of perchlorate in dust were
in the range of 0.02–104 μg/g (geometric mean: 0.41 μg/g). The indoor dust samples from China contained the
highest concentrations (geometric mean: 5.38 μg/g). No remarkable differences in perchlorate concentrations
in dust were found among various microenvironments (i.e., car, home, office, and laboratory). The estimated

median daily intake (EDI) of perchlorate for toddlers through dust ingestion in the USA, Colombia, Greece,
Romania, Japan, Korea, Pakistan, Kuwait, Saudi Arabia, India, Vietnam, and China was 1.89, 0.37, 1.71, 0.74,
4.90, 7.20, 0.60, 0.80, 1.55, 0.70, 2.15, and 21.3 ng/kg body weight (bw)/day, respectively. Although high concentrations of perchlorate were measured in some dust samples, the contribution of dust to total perchlorate intake
was b 5% of the total perchlorate intake in humans. This is the first multinational survey on the occurrence of
perchlorate in indoor dust.
© 2014 Elsevier Ltd. All rights reserved.

1. Introduction
Perchlorate is both a naturally occurring (Rao et al., 2010; Urbansky
et al., 2001) and man-made chemical, widely used as an oxidant in rocket fuel, missiles, flares, fireworks, and automobile air bag inflators
⁎ Corresponding author at: Wadsworth Center, Empire State Plaza, P.O. Box 509, Albany,
NY 12201-0509, United States.
E-mail address: (K. Kannan).
1
Co-first author contributed to this study equally.

/>0160-4120/© 2014 Elsevier Ltd. All rights reserved.

(Motzer, 2001). Anthropogenic sources are thought to be the major
sources of perchlorate in the environment. Perchlorate has been reported
to occur in human bodily fluids, such as saliva, breast milk, serum, and
urine (Blount et al., 2009; Eguchi et al., 2014; Oldi and Kannan, 2009).
Perchlorate has the ability to inhibit the uptake of iodide at 30 times
greater affinity than iodine itself by the sodium/iodide symporter
(NIS) (Tonacchera et al., 2004), which results in the disruption of thyroid hormone production in animals and humans (Blount et al., 2006;
Chen et al., 2014; Dohán et al., 2007; Gilbert and Sui, 2008; Wu et al.,
2010; York et al., 2003). A decreased thyroid hormone level has been


Y. Wan et al. / Environment International 75 (2015) 166–171

shown to adversely affect neurodevelopment in mammals, human
fetuses, infants, toddlers, and children (Charatcharoenwitthaya et al.,
2014; Mendez and Eftim, 2012; Wu et al., 2012; York et al., 2003).
Perchlorate is also recognized as a persistent and pervasive contaminant (Fisher et al., 2000; Motzer, 2001). It can accumulate in leafy vegetables and reach humans through the food chain (Lee et al., 2012;
Sanchez et al., 2006; Voogt and Jackson, 2010). The United States Environmental Protection Agency (USEPA) has proposed an oral reference
dose (RfD) of 0.7 μg perchlorate/kg body weight (bw)/day (Greer
et al., 2002; Zewdie et al., 2010).
Assessing sources of human exposure to perchlorate is a subject of
considerable interest among various environmental and public health
agencies throughout the world. Thus far, perchlorate has been reported
to occur in drinking water (Blount et al., 2010; Kannan et al., 2009; Wu
et al., 2010), foodstuffs (Lee et al., 2012; Wang et al., 2009), and outdoor
dust particles (Gan et al., 2014). The current estimates of exposure to
perchlorate, extrapolated from blood or urine biomonitoring studies in
the USA and China, suggested values that exceed the RfD in many
cases, especially for infants and toddlers (Zhang et al., 2010). Because
perchlorate is a water-soluble contaminant present in fertilizers, it
was believed that agricultural produce was the major source of
human exposure to this chemical. However, perchlorate is also used in
many products in the indoor environment, including bleach, matches,
and pharmaceutics (Zewdie et al., 2010). Despite this, no earlier studies
have reported the occurrence of perchlorate in indoor dust.
Indoor dust can be a significant source of human exposure to contaminants such as polybrominated diphenyl ethers (PBDEs) (Rudel
et al., 2003; Lorber, 2008; Wu et al., 2007) and ingestion of indoor
dust has been shown to be an important exposure pathway to environmental chemicals, especially for infants and toddlers (Johnson-Restrepo
and Kannan, 2009; Guo and Kannan, 2011; Liao et al., 2012). Determination of perchlorate levels in indoor dust and the assessment of human
exposure doses through the ingestion of dust are imperative to the
assessment of risks and for the development of strategies to mitigate
exposures. In this study, we conducted a multinational survey of perchlorate levels in 366 indoor dust samples collected from 12 countries

(two American, two European, and eight Asian countries). Perchlorate
exposures via dust ingestion for various age groups (infants, toddlers,
children, teenagers, and adults) were calculated on the basis of the measured concentrations. This is the first study to report the occurrence of
perchlorate in indoor dust from several countries.
2. Materials and methods
2.1. Chemicals
Ammonium perchlorate (N99.9%) and methylamine (40 wt.% solution in water) were purchased from Sigma-Aldrich (St. Louis, MO,
USA). Isotope-labeled sodium perchlorate (Cl18O−
4 , N 90%) was purchased from Cambridge Isotope Laboratories (Andover, MA, USA).
Milli-Q water was obtained from an ultrapure water system (Barnstead
International, Dubuque, IA, USA). All other reagents used in the study
were analytical grade.
2.2. Sample collection
From 2010 to 2014, 366 dust samples were collected from single or
multiple cities in 12 countries, including Athens, Greece (2014, n = 30);
Iasi, Romania (2012, n = 23); Albany, New York, USA (2014, n = 30);
Cartagena, Colombia (2014, n = 39); Kumamoto, Nagasaki, Fukuoka,
Saitama, and Saga, Japan (2012, n = 22); Ansan and Anyang, Korea
(2012, n = 40); Faisalabad, Pakistan (2011–2012, n = 24); Kuwait
City (2013, n = 34); Jeddah, Saudi Arabia (2014, n = 31); Patna, India
(2014, n = 30); Hanoi, Thai Binh, and Hungyen, Vietnam (2014, n =
33); and Beijing, Guangzhou, and Shanghai, China (2010–2011, n = 30).

167

Bedrooms and living rooms of homes and apartments (all countries),
offices (Korea, Vietnam, and Japan), laboratories (Korea and Vietnam),
and cars (Kuwait) were selected for sampling. Floor dust samples
were obtained from vacuum cleaner bags in each of the sampling
sites, with the exception of samples from China and India, which were

obtained by sweeping the floor. All samples were sieved through a
150 μm sieve, homogenized, packed in clean aluminum foil, and stored
at 4 °C until analysis.
2.3. Sample preparation
Dust samples were extracted and analyzed by following the method
described elsewhere, with some modifications (Gan et al., 2014). Briefly,
50 mg of sample was accurately weighed and transferred into a 15 mL
polypropylene (PP) conical tube. Samples were then spiked with 5 ng
of 18O-perchlorate, as an internal standard. The dust samples were
extracted with 5.0 mL of 1% methylamine in water by shaking in an
orbital shaker (Eberbach Corp., Ann Arbor, MI, USA) for 30 min. The
mixture was centrifuged at 4,500 ×g for 5 min (Eppendorf Centrifuge
5804, Hamburg, Germany), and the supernatant was transferred into
a new PP tube. The extract was purified by passage through an
Envi-Carb cartridge (250 mg/3 mL; Supelclean, Bellefonte, PA, USA),
preconditioned with 5 mL of water. The purified extract was filtered
through a 0.2 μm regenerated cellulose membrane filter (Phenomenex,
Torrance, CA, USA) prior to analysis by liquid chromatography–tandem
mass spectrometry (LC–MS/MS).
2.4. Instrumental analysis
Samples were analyzed with a Waters 2695 high performance liquid
chromatograph (HPLC) (Waters Corporation, Milford, MA, USA) and
Micromass Quattro tandem mass spectrometer (MS/MS) in the negative electrospray ionization mode with multiple reaction monitoring.
Chromatographic separation was achieved with a 250 mm × 2 mm
IonPac AS-21 anion-exchange column (Dionex, Sunnyvale, CA, USA).
An isocratic mobile phase of 20 mM aqueous methylamine was used
at a flow rate of 300 μL/min. Perchlorate was monitored by the mass
transition of m/z 99 → m/z 83 for 35ClO4 and m/z 101 → m/z 85 for
37
37

ClO4. The ratio of the peak areas of 35ClO−
ClO−
4 to
4 was monitored,
and a ratio of 3.12 ± 25% was considered acceptable. The cone voltage
and the collision energy were 40 V and 22 V, respectively. The perchlorate internal standard (Cl18O−
4 ) was monitored by a mass transition of
m/z 107 → m/z 89. Limit of quantitation (LOQ) for perchlorate in indoor
dust was 0.02 μg/g, which was calculated based on the lowest concentration in the calibration that produced a signal-to-noise ratio of 10;
the average weight of samples taken for analysis and the concentration/dilution factors were included in the calculation of LOQ.
2.5. Quality assurance and quality control
Quantification was performed by two internal calibrations, which
were established at six low concentrations of perchlorate standard solutions ranging from 0.2 to 10 μg/L, and at six high concentrations ranging
from 10 to 500 μg/L. The correlation coefficient of the calibration
(r) curve was 0.999. Calibration standards were injected daily before
and after the injection of a batch of samples. For samples with responses
greater than the linear range, extracts were diluted with water and
reanalyzed. All of the standard solutions were prepared in water,
and the spiked concentration of the internal standard (18O-ClO4) was
1.0 μg/L. The injection of 10 μL of 0.2 μg/L standard yielded a signal-tonoise ratio of 10. Recoveries and the presence of matrix effects for
dust samples were tested in triplicate by spiking the native perchlorate
standard at three different levels (1.0, 10, and 100 μg/L), and the results
are presented in Table S1. The recoveries of perchlorate spiked into each
of the samples ranged from 89% to 101%.


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Y. Wan et al. / Environment International 75 (2015) 166–171

Procedural blanks, spiked blanks, and matrix spike samples were
included in each batch of 30 samples analyzed. Perchlorate was not
detected in procedural blanks. A mid-point calibration standard and
water blank were injected after every 10 samples to monitor for drift
in instrumental response and carry-over from previous injections.
2.6. Calculation of daily exposure doses
Based on the median and 95th percentile concentrations of
perchlorate measured in indoor dust samples, daily intake (EDIing;
ng/kg bw/day) doses of perchlorate through dust ingestion were
estimated as shown in Eq. (1) (Guo and Kannan, 2011; USEPA, 2011):
EDIing ¼ C Â DIR=BW

ð1Þ

where C is the concentration of perchlorate in dust samples (ng/g), DIR
is the dust ingestion rate (g/day), and BW is the body weight (kg). We
assumed an absorption efficiency of 100% for perchlorate from dust to
systemic blood circulation. Details of the parameters used in EDIing calculation are shown in Table S2.
Estimated daily intakes (EDIdermal; ng/kg bw/day) of perchlorate
through dermal absorption of dust were calculated as shown in
Eq. (2) (USEPA, 2011; Gan et al., 2014; Guo and Kannan, 2011):
EDIdermal ¼ ðC Â SAR Â FÞ=BW

ð2Þ

where SAR is the skin adherence rate (g/day), and F is the dermal
absorption factor (Table S2).
2.7. Statistical analysis
Statistical analysis was performed with SPSS 18. Concentrations
below the LOQ were substituted with a value equal to LOQ divided by

the square root of 2 for the calculation of geometric mean (GM).
Measured concentration values were not normally distributed and,
therefore, were log-transformed for the analysis of variance (ANOVA)
or t-test. Differences between groups were compared by a one-way
ANOVA with the Tukey test. All statistical tests were considered significant if the two-tailed p-value was b0.05.

Table 1
Concentrations of perchlorate (μg/g) in indoor dust collected from twelve countries.
Country

n

Sampling
year

Geometric
mean

Median

Mean

Range

Greece
Romania
USA
Colombia
Japan
Korea

Pakistan
Kuwait
Saudi Arabia
India
Vietnam
China
All countries

30
23
30
39
22
40
24
34
31
30
33
30
366

2014
2012
2014
2014
2012
2012
2011–2012
2013

2014
2014
2014
2010–2011
2010–2014

0.42
0.18
0.29
0.09
1.16
1.34
0.10
0.20
0.32
0.24
0.68
5.38
0.41

0.37
0.16
0.41
0.08
0.98
1.44
0.12
0.16
0.31
0.14

0.43
4.25
0.30

0.69
0.29
0.46
0.20
7.48
3.21
0.13
0.37
0.47
1.24
4.61
9.45
2.31

0.08–4.67
0.03–1.83
0.03–1.18
0.02–1.79
0.11–104
0.06–47.0
0.03–0.29
0.04–2.07
0.02–3.11
0.04–19.1
0.05–34.6
0.88–60.7

0.02–104

than those found for homes (Table S4). Perchlorate concentrations in
dust collected from offices in Korea and Vietnam were similar to the
concentrations found for homes (p N 0.05), but lower than the concentrations measured for environmental analytical laboratories (p b 0.05;
Table S4). The higher concentrations of perchlorate in dust samples collected from laboratories may be associated with the use of chemicals
and reagents that contain perchlorate in laboratories (Hseu, 2004).
The ubiquitous occurrence of perchlorate in indoor dust suggests the
existence of sources of this compound in the indoor environment. The
measured concentrations are remarkably high and comparable to
those reported for widely studied compounds, such as polybrominated
diphenyl ethers (PBDEs) and phthalates (Rudel et al., 2003; Guo and
Kannan, 2011). The source of perchlorate in the indoor environment is
not well known and is a subject for future investigation. However, perchlorate and its salts are used in many products, including batteries,
bleach, and leather products, and these may contribute to the sources
in the indoor environments (Zewdie et al., 2010). This is the first report
that shows widespread occurrence of perchlorate in indoor dust.

3.2. Perchlorate exposure through dust ingestion
3. Results and discussion
3.1. Concentrations
Perchlorate was found in all 366 dust samples collected from the
12 countries at concentrations ranging from 0.02 to 104 μg/g (GM:
0.41 μg/g). The GM concentrations of perchlorate in indoor dust samples were found, in the decreasing order, as: China (GM: 5.38 μg/g) N
Korea (1.34) N Japan (1.16) N Vietnam (0.68) N Greece (0.42) N Saudi
Arabia (0.32) N the USA (0.29) N India (0.24) N Kuwait (0.20) N Romania
(0.18) N Pakistan (0.10) N Colombia (0.09) (Table 1). The median concentrations for China, Korea, Japan, Vietnam, the USA, Greece, Saudi
Arabia, Kuwait, Romania, India, Pakistan, and Colombia were 4.25, 1.44,
0.98, 0.43, 0.41, 0.37, 0.31, 0.16, 0.16, 0.14, 0.12 and 0.08 μg/g,
respectively.

The highest GM and median concentrations of perchlorate from
China were significantly higher than the concentrations determined
for any other country studied. The measured perchlorate concentrations
in dust from China were four times higher than the concentrations
found for Korea (second highest), and 60 times higher than the concentrations found for Colombia (lowest) (p b 0.05; Fig. 1, Table 1, and
Table S3). The highest concentration measured in China can be related
to their high volume of production and usage of fireworks (Gan et al.,
2014; Wu et al., 2010).
Among various microenvironments studied, perchlorate concentrations in dust collected from cars in Kuwait were not significantly higher

The significance of indoor dust ingestion as a pathway for human exposure to PBDEs (Rudel et al., 2003) and phthalates (Guo and Kannan,
2011) has been highlighted recently. Sources of human exposure to perchlorate have not been fully characterized, and the contribution of
indoor dust to perchlorate exposure was not known prior to this
study. Humans can be exposed to perchlorate via dust ingestion, dermal
absorption, and inhalation. In comparison with ingestion, exposure
through dermal absorption and inhalation of dust is two to three orders
of magnitude lower (Table S5) (Guo and Kannan, 2011). Therefore, no
further discussions were conducted with regard to exposure calculations based on dermal absorption and inhalation of indoor dust.
Several factors, such as age, time spent in indoor microenvironments
(i.e., home, office/laboratory, and car), and amount of dust ingestion,
can influence exposure doses (Geens et al., 2009). For the EDI of perchlorate through dust ingestion, we categorized the population into
five age groups: infants (b 1 year), toddlers (1–3 years), children
(4–11 years), teenagers (12–21 years), and adults (≥21 years) according to the U.S. Environmental Protection Agency's Exposure Factors
Handbook (USEPA, 2011). The body weights for various age groups in
China were adopted from a previous study (Guo and Kannan, 2011),
and these values were also applied in the calculation of EDI for the populations in other Asian countries. The median and 95th percentile values
of perchlorate concentrations measured in indoor dust in this study
were used in the calculation of EDI for median and high exposure scenarios, respectively.

Y. Wan et al. / Environment International 75 (2015) 166–171

169

Fig. 1. Spatial distribution of perchlorate (median; μg/g) in indoor dust from 12 countries studied.

Infants and toddlers experienced higher doses of perchlorate exposure through dust ingestion than did the other age groups for all
of the countries studied (Table 2). The median daily perchlorate
intakes via indoor dust ingestion in China were up to 0.018 and
0.015 μg/kg bw/day for toddlers and infants, respectively; the intake
values estimated for adults (0.003 μg/kg bw/day) in China were approximately 5–6 times lower than those found for infants and toddlers (Table 2). A similar intake pattern was found for various age
groups in the other countries. Among countries investigated,
Colombia had the lowest exposure dose, approximately 40–60
times lower than the exposure doses estimated for China (Table 2).
The EDI values calculated for toddlers and infants in China through
dust ingestion were one order of magnitude lower than the USEPA's
RfD (0.7 μg/kg bw/day). It should be noted that exposure doses estimated for some dust samples from Korea and Vietnam, which were
collected in laboratories, may overestimate the actual exposure
doses for the general populations in these two countries. A few samples from laboratories in these countries had elevated levels of
perchlorate.

3.3. Perchlorate exposure doses through indoor dust compared with other
sources of exposures
Diet and drinking water are considered significant sources of
human exposure to perchlorate (Huber et al., 2011). A few studies
have extrapolated biomonitoring studies of perchlorate in urine or
blood to assess total daily intake (Valentín-Blasini et al., 2011;
Zhang et al., 2010). Among the 12 countries studied here, the EDI of
perchlorate through diet and water was characterized for the USA.
Based on the total daily perchlorate intake values reported for the

USA (calculated based on urinary concentrations as shown in
Table 3; median, 0.160 and 0.066 μg/kg bw/day for infants and
adults, respectively; data for toddlers are not available) (Huber
et al., 2011; Valentín-Blasini et al., 2011), the percentage of exposure
contributed by indoor dust ingestion (this study, median, 1.76 and
0.15 ng/kg bw/day for infants and adults, respectively) were 1.1% and
0.2% for infants and adults, respectively. Thus, despite high concentrations of perchlorate found in dust samples, the contribution of dust to
daily intake is small.

Table 2
Estimated daily intakes (EDIing, ng/kg bw/day) of perchlorate by ingestion of indoor dust for various age groups in twelve countries.
Country

Greece
Romania
USA
Colombia
Japan
Korea
Pakistan
Kuwait
Saudi Arabia
India
Vietnam
China
All countries

Median

95th percentile

Infants

Toddlers

Children

Teenagers

Adults

Infants

Toddlers

Children

Teenagers

Adults

1.59
0.69
1.76
0.34
5.88
8.64
0.72
0.96
1.86

0.84
2.58
25.5
1.80

1.71
0.74
1.89
0.37
4.90
7.20
0.60
0.80
1.55
0.70
2.15
21.3
1.50

0.82
0.36
0.91
0.18
2.35
3.46
0.29
0.38
0.74
0.34
1.03

10.2
0.72

0.35
0.15
0.38
0.08
1.11
1.63
0.14
0.18
0.35
0.16
0.49
4.81
0.34

0.14
0.06
0.15
0.03
0.47
0.69
0.06
0.08
0.15
0.07
0.20
2.02
0.14

4.45
1.93
2.53
1.36
104
34.1
0.98
3.19
4.07
16.0
46.7
88.2
19.0

4.79
2.07
2.72
1.46
86.8
28.5
0.82
2.66
3.39
13.3
38.9
73.5
15.8

2.31

1.00
1.31
0.71
41.7
13.7
0.39
1.28
1.63
6.41
18.7
35.3
7.58

0.97
0.42
0.55
0.30
19.7
6.44
0.19
0.60
0.77
3.02
8.82
16.6
3.58

0.39
0.17
0.22

0.12
8.27
2.71
0.08
0.25
0.32
1.27
3.71
7.00
1.50


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Y. Wan et al. / Environment International 75 (2015) 166–171

Table 3
Estimated daily intakes (EDI) of perchlorate calculated through dust ingestion pathway in
comparison with several other pathways.
Location Group

EDI
(ng/kg/day)

Route

USA

Median, 160
Median, 66.0

GM, 119
GM, 57.0
Median, 1.76
Median, 1.89
Median, 0.15
Mean, 2220
Mean, 1550
Mean, 1120
Mean, 1050
Mean, 340
Mean, 80.0
Median, 25.5
Median, 21.3
Median, 2.02
Median, 17.0
Median, 110
Median, 40.0
Median, 8.64
Median, 7.20
Median, 0.69

Urine
Valentín-Blasini et al. (2011)
Urine
Blount et al. (2007)
Food & water Huber et al. (2011)

China

Korea

Infants
Adults
Children
Adults
Infants
Toddlers
Adults
Infants
Toddlers
Adults
Hengyang
Nanchang
Overall
Infants
Toddlers
Adults
Ages 1–2
Ages 3–6
Adults
Infants
Toddlers
Adults

New York State Department of Health, where the study was conceived
and performed. Its contents are solely the responsibility of the authors
and do not necessarily represent the official views of the CDC.

Reference

Appendix A. Supplementary data

Indoor dust

Supplementary data to this article can be found online at http://dx.
doi.org/10.1016/j.envint.2014.11.005.

This study

References
Blood

Zhang et al. (2010)

Water

Wu et al. (2010)

Indoor dust

This study

Food

Lee et al. (2012)

Indoor dust

This study

In China, rice and dairy milk have been analyzed for perchlorate (Shi
et al., 2007). Further, a mean EDI of perchlorate in tap water in China
was reported as 0.08 μg/kg bw/day (Table 3) (Huber et al., 2011; Wu
et al., 2010). Thus, the EDI of perchlorate through dust ingestion was
2.5% of that reported for tap water in China. In comparison with the
total EDI of perchlorate (Table 3; median 1.55 and 1.12 μg/kg bw/day
for toddlers and adults, respectively) calculated based on blood concentrations in Nanchang, China, indoor dust ingestion (median 0.022 and
0.002 μg/kg bw/day for toddlers and adults in China, respectively) contributed to 1.4% and 0.2%, respectively, of perchlorate intake for toddlers
and adults (Zhang et al., 2010).
In Korea, the daily perchlorate exposure dose through domestic food
consumption (Lee et al., 2012) (0.17 μg/kg bw/day for toddlers and 0.04
μg/kg bw/day for adults) was similar to the values reported for the USA
(Table 3; GM 0.12 μg/kg bw/day for children and 0.06 μg/kg bw/day for
adults) (Huber et al., 2011). In general, the daily intake of perchlorate
through indoor dust ingestion in Korea was 6.5% (toddlers) and 1.7%
(adults) of the values reported for dietary intakes in Korea.
In summary, high concentrations of perchlorate, on the order of
several micrograms per gram, were detected in indoor dust collected
from several countries. Concentrations of perchlorate in dust samples
from China (GM: 5.38 μg/g) were significantly higher than those
from Korea (1.34 μg/g), Japan (1.16 μg/g), Vietnam (0.68 μg/g),
Greece (0.42 μg/g), Saudi Arabia (0.32 μg/g), the USA (0.29 μg/g),
India (0.24 μg/g), Kuwait (0.20 μg/g), Romania (0.18 μg/g), Pakistan
(0.18 μg/g), and Colombia (0.09 μg/g). Although high concentrations
of perchlorate were measured in some dust samples, the contribution
of dust to total perchlorate intake is minor (b 5% of the total perchlorate
intake). To our knowledge, this is the first study to describe the
widespread occurrence of perchlorate in indoor dust. The sources
of high levels of indoor concentrations of perchlorate need further
investigation.

Acknowledgments
The authors thank Pierina Maza-Anaya, a youth research fellow supported by the Colombian National Science and Technology System, for
helping with dust sample collection from Colombia; Dr. Dilip Kumar
Kedia helped with collection of dust samples from India. This study
was funded by a grant (1U38EH000464-01) from the Centers for Disease Control and Prevention (CDC, Atlanta, GA) to Wadsworth Center,

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