In this survey,five cyclic D3–D7 and 11 linear L4–L14 siloxanes were determined in 310 indoor dust samples collected from 12 countries.. Dust samples collected from Greece contained the h
Trang 1A survey of cyclic and linear siloxanes in indoor dust and their
implications for human exposures in twelve countries
Tri Manh Trana,b, Khalid O Abualnajac, Alexandros G Asimakopoulosa, Adrian Covacid, Bondi Gevaoe,
Haruhiko Nakatai, Ravindra K Sinhaj, Kurunthachalam Kannana,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, NY 12201-0509, United States
b
Faculty of Chemistry, Hanoi University of Science, Vietnam National University, Hanoi, 19 Le Thanh Tong, Hoan Kiem, Hanoi, Viet Nam
c
Biochemistry Department, Faculty of Science, Experimental Biochemistry Unit, King Fahd Medical Research Center and Bioactive Natural Products Research Group, King Abdulaziz University, Jeddah, 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
a b s t r a c t
a r t i c l e i n f o
Article history:
Received 10 December 2014
Received in revised form 19 February 2015
Accepted 23 February 2015
Available online xxxx
Keywords:
Siloxanes
Dust
Exposure
D5
Silicone
Siloxanes are used widely in a variety of consumer products, including cosmetics, personal care products, medical and electrical devices, cookware, and building materials Nevertheless, little is known on the occurrence of silox-anes in indoor dust In this survey,five cyclic (D3–D7) and 11 linear (L4–L14) siloxanes were determined in 310 indoor dust samples collected from 12 countries Dust samples collected from Greece contained the highest concentrations of total cyclic siloxanes (TCSi), ranging from 118 to 25,100 ng/g (median: 1380), and total linear siloxanes (TLSi), ranging from 129 to 4990 ng/g (median: 772) The median total siloxane (TSi) concentrations in dust samples from 12 countries were in the following decreasing order: Greece (2970 ng/g), Kuwait (2400), South Korea (1810), Japan (1500), the USA (1220), China (1070), Romania (538), Colombia (230), Vietnam (206), Saudi Arabia (132), India (116), and Pakistan (68.3) TLSi concentrations as high as 42,800 ng/g (Kuwait) and TCSi concentrations as high as 25,000 ng/g (Greece) were found in indoor dust samples Among the 16 siloxanes determined, decamethylcyclopentasiloxane (D5) was found at the highest concentration in dust samples from all countries, except for Japan and South Korea, with a predominance of L11; Kuwait, with L10; and Pakistan and Romania, with L12 The composition profiles of 16 siloxanes in dust samples varied by country TCSi accounted for a major proportion of TSi concentrations in dust collected from Colombia (90%), India (80%) and Saudi Arabia (70%), whereas TLSi predominated in samples collected from Japan (89%), Kuwait (85%), and South Korea (78%) Based on the measured median TSi concentrations in indoor dust, we es-timated human exposure doses through indoor dust ingestion for various age groups The exposure doses ranged from 0.27 to 11.9 ng/kg-bw/d for toddlers and 0.06 to 2.48 ng/kg-bw/d for adults
© 2015 Elsevier Ltd All rights reserved
1 Introduction
Organosilicons are compounds that contain carbon–silicon bonds
Among the various types of organosilicon compounds in commerce,
methyl siloxanes are widely used in industrial and consumer products
Methyl siloxanes, depending on the structure, can be divided into cyclic and linear siloxanes The most widely used methyl siloxanes include polydimethyl siloxane (PDMS) and volatile methyl silox-anes (VMSs) The total worldwide production of siloxsilox-anes in 2002 was 2 million tons, of which 34% were used in North America, 33% in Western Europe, 28% in Asia, and 5% in the rest of the world (Brooke
et al., 2009a,b,c)
Siloxanes are used in products due to their low surface tension, high thermal stability, and smooth texture The concentrations of siloxanes
⁎ Corresponding author at: Wadsworth Center, Empire State Plaza, P.O Box 509, Albany,
NY 12201-0509, USA.
E-mail address: kkannan@wadsworth.org (K Kannan).
http://dx.doi.org/10.1016/j.envint.2015.02.011
Contents lists available atScienceDirect Environment International
j o u r n a l h o m e p a g e :w w w e l s e v i e r c o m / l o c a t e / e n v i n t
Trang 2on the order of several percentages by weight (as high as 7.3% for linear
siloxanes and 8.2% for cyclic siloxanes) have been reported in personal
care and household products (Horii and Kannan, 2008; Wang et al.,
2009) Remarkable concentrations of octamethylcyclotetrasiloxane
(D4; 72.9μg/g), D5 (1110 μg/g), and total linear siloxanes (L4–L14;
1.02 mg/g) were reported in shampoos and hair conditioners in China
(Lu et al., 2011) Siloxanes were also found in siliconized rubber
prod-ucts (Kawamura et al., 2001), electrical devices, healthcare products,
cosmetics, cookware, sealants, and household cleaning products
(Watts et al., 1995; Environment Canada, 2011)
The occurrence of siloxanes in environmental media was
report-ed in several earlier studies The mean concentration of total
silox-anes (5 cyclic and 15 linear) in sludge samples from wastewater
treatment plants in South Korea was 45.7μg/g (Lee et al., 2014)
Influent wastewater and sewage sludge collected from Greece
contained 17 siloxanes at mean concentrations of 20μg/L and
75 mg/kg, respectively (Bletsou et al., 2013) Cyclic and linear siloxanes
were found in sediment and wastewater collected from China (Zhang
et al., 2011), Spain (Sanchís et al., 2013), and Canada (Wang et al.,
2013) Indoor and outdoor air samples collected from Chicago
contained a median concentration of 2200 and 280 ng/m3,
respec-tively, for the sum of D4, D5, and dodecamethylcyclohexasiloxane
(D6) (Yucuis et al., 2013) Linear and cyclic siloxanes were reported
in indoor air from Italy and the UK at concentrations ranging from 18
to 240 ng/m3and 78 to 350 ng/m3, respectively (Pieri et al., 2013)
Owing to their widespread use in consumer products, there is a
great potential for the occurrence of elevated concentrations of
si-loxanes in indoor dust Thus far, only one study, from China, reported
the concentrations of total siloxanes as high as 21,000 ng/g in indoor
dust (Lu et al., 2010)
Several studies have reported toxicity, especially reproductive and
endocrine effects, of siloxanes in laboratory animals (Burns-Naas
et al., 1998; Burn-Naas et al., 2002; McKim et al., 2001; He et al.,
2003; Meeks et al., 2007; Quinn et al., 2007a,b; Siddiqui et al.,
2007) A risk assessment conducted in Canada indicated that D5
met the criteria for persistence (Environment Canada, 2011) The
en-vironmental distribution, fate, and toxicity of siloxanes have been
under scrutiny by several environmental and public health agencies
in various countries in recent years There is a lack of information
with regard to the sources of human exposure to siloxanes In this
study, we surveyed the composition and distribution offive cyclic
and 11 linear siloxanes in indoor dust collected from 12 countries
Human exposure to siloxanes through dust ingestion was estimated
for infants, toddlers, children, teenagers, and adults based on the
measured median TSi concentrations in dust
2 Materials and methods
2.1 Standards
Hexamethylcyclotrisiloxane (D3), D4, D5, and D6, with a
pu-rity of N95%, were obtained from Tokyo Chemical Industry
(Wellesley Hills, MA) Decamethyltetrasiloxane (L4) (97%) and
dodecamethylpentasiloxane (L5) (97%) were purchased from
Sigma-Aldrich (St Louis, MO) PDMS 200 fluid (viscosity of
5cSt) that contained octadecamethylcycloheptasiloxane (D7), linear
tetradecamethylhexasiloxane (L6), and other linear polydimethyl
silox-anes (L7, L8, L9, L10, and L11) were purchased from Sigma-Aldrich
Tetrakis-(trimethylsiloxy)-silane (M4Q) of 97% purity was from
Sigma-Aldrich Decamethylcyclopentasiloxane-[2, 4, 6, 8, 10-13C5] 99%
atom13C (13C-D5) of 98% purity was from Bristlecone Biosciences, Inc
(Brea, CA) M4Q and13C-D5 were used as internal standards All
standards were dissolved in hexane The composition of PDMS was
determined in an earlier study (Horii and Kannan, 2008), and this
mixture, with known composition and content, was used in the
de-termination of concentrations of linear siloxanes
2.2 Sample collection Indoor dust samples were collected from 12 countries, including China (n = 18), Colombia (n = 28), Greece (n = 28), India (n = 28), Japan (n = 13), Kuwait (n = 28), Pakistan (n = 28), Romania (n = 23), Saudi Arabia (n = 28), South Korea (n = 28), the USA (n = 22), and Vietnam (n = 38) during 2010–2014 The details of the sampling locations are shown inTable 1 Floor dust samples were collected by a vacuum cleaner or by sweeping thefloor with a (non-siliconized) brush directly Dust samples from offices, labora-tories, and cars were available for certain countries Samples were stored in polyethylene bags or glass jars at 4 °C in the dark until analysis
2.3 Sample preparation Prior to the analysis, all dust samples were sieved through a
150μm sieve and homogenized One hundred nanograms of M4Q and13C-D5 were spiked as internal standards onto 150–200 milligrams
of dust samples The spiked dust samples were equilibrated for
30 min at room temperature The extraction procedure was similar
to that described earlier (Horii and Kannan, 2008; Lu et al., 2010), with slight modifications The dust samples were extracted by shak-ing in an orbital shaker (Eberbach Corporation, Ann Arbor, MI) with
5 mL mixture of dichloromethane (DCM) and hexane (3:1, v:v) for
5 min Samples were then centrifuged at 2000 g for 5 min (Eppendorf Centrifuge 5804, Hamburg, Germany), and the supernatant was transferred to a 12 mL glass tube The extraction was repeated twice, with 3 mL of DCM: hexane mixture (3:1) for the second time and 3 mL hexane for the third time The extracts were concentrated
to 1 mL under a gentle stream of nitrogen and thenfiltered through
a regenerated cellulose membrane filter (Phenomenex Inc., Torrance, CA, pore size: 0.2μm), and transferred into a gas chroma-tography (GC) vial
2.4 Instrumental analysis Analysis was performed on an Agilent Technologies 6890 GC interfaced with a 5973 mass spectrometer (MS) Separation of silox-anes was achieved by an HP-5MS capillary column (Agilent, Santa Clara, CA; 30 m × 0.25 mm i.d × 0.25μm film thickness) Samples were injected into the splitless mode, and the injection volume was
2μL The oven temperature was programmed from 40 °C (held for 2.0 min) to 220 °C at 20 °C/min, increased to 280 °C at 5 °C/min (held for 10 min) and then held for 5.0 min at 300 °C Injector and detector temperatures were 200 °C and 300 °C, respectively Ion frag-ment m/z 207 was monitored for D3, m/z 281 for D4, D7, and L5, m/z
355 for D5, and m/z 341 for D6 Ion fragment m/z 147 was used for the confirmation of L6 and L7 Ion fragment m/z 207 was monitored for the confirmation of L4 and m/z 221 for the other siloxanes Ion fragment m/z 281 was monitored for M4Q and m/z 360 for13C-D5 (Horii and Kannan, 2008; Badjagbo et al., 2009; Zhang et al., 2011; Bletsou et al., 2013)
2.5 Quality assurance and quality control Contamination of siloxanes from materials and laboratory products has been examined in our laboratory (Horii and Kannan, 2008; Lu
et al., 2010; Bletsou et al., 2013), and considerable efforts to reduce background levels of siloxane contamination were made (Lu et al.,
2011) All glassware were baked at 450 °C for 20 h and placed in an oven at 100 °C until use The GC vials were capped with aluminum foil (instead of Teflon® or rubber/silicon), and the solvents were dispensed directly from new glass bottles (i.e., a solvent-bottle that was kept open for more than a day was not used) Prior to instrumental analysis, hexane was injected into the GC–MS until the background levels of
Trang 3siloxanes became stable Hexane also was injected before every sample
as a check for background contamination and carry-over (Bletsou et al.,
2013) We analyzed dust samples collected from the same homes with
vacuum cleaners and sweeping thefloors (n = 3) and found no
differ-ence in siloxane levels between the two methods of sampling (coef
fi-cient of variation was below ±5%)
The calibration curve was linear over a concentration that ranged
from 0.5 to 500 ng/mL for individual siloxanes, for which the correlation
coefficient (r) was greater than 0.995 D3, D4, D5, and D6 were found at
respective concentration ranges of 5.5–20 ng (mean: 6.5), 9–46 ng
(mean: 13.5), 11–39.7 ng (mean: 16.0), and 6–30 ng (mean: 8.5) in
pro-cedural blanks analyzed with each batch of 12–14 samples Other
silox-anes were not found in procedural blanks All of the reported
concentrations of siloxanes in dust samples were subtracted from the
mean values found in procedural blanks
One hundred nanograms of13C-D5 and M4Q were spiked into
every sample and passed through the entire analytical procedure
The average recoveries of13C-D5 and M4Q (for all procedural blanks
and samples) ranged from 75.3 to 118% (RSD: 9.3%) and 77.5 to 115%
(RSD: 12.6%), respectively The mean recoveries of target
com-pounds in spiked dust samples (i.e., matrix spikes) were 67.2–121%
(RSD: 9.7%) The limits of quantification (LOQs) were determined
based on the lowest point in the calibration standard with a
signal-to-noise ratio of 10; an average sample weight of 200 mg, and the
di-lution factors were included in the calculation of LOQ LOQs were
2.0 ng/g for D3, D5, and D7; 3.0 ng/g for D4 and L4 to L9; 4.0 ng/g
for D6, L10, and L11; and 6.0 ng/g for L12 to L14 For concentrations
below the LOQ, a value of one-half the LOQ was assigned for
statisti-cal analysis Data analysis was conducted using Microsoft Excel
(Microsoft Office 2010) and Graph Pad Prism V 5.0 Statistical
signif-icance was set at pb 0.05
3 Results and discussion 3.1 Concentrations of total siloxanes in indoor dust Five cyclic (D3–D7) and 11 linear siloxanes (L4–L14) were found in
310 indoor dust samples collected from 12 countries during 2010–2014 (Table S1) Total siloxanes (TSi) refer to the sum offive cyclic and 11 linear siloxanes (Table 2andFig 1) The concentrations of TSi in indoor dust samples varied between countries, although the overall differences were not statistically significant (p N 0.05) Indoor dust samples
collect-ed from Greece containcollect-ed the highest concentrations of TSi (mcollect-edian:
2970 ng/g), followed by samples from Kuwait (median: 2400), South Korea (1810), Japan (1500), the USA (1220), China (1070), Romania (538), Colombia (230), Vietnam (206), and Saudi Arabia (132) A TSi concentration as high as 42,800 ng/g was found in dust samples
collect-ed from Kuwait The lowest concentrations of TSi were found in dust samples collected from India (median: 116 ng/g) and Pakistan (median: 68.3 ng/g) The median concentration of TSi found in indoor dust from Greece (highest) was 25 times higher than the concentrations found for India (second lowest) and 43 times higher than the concentrations found for Pakistan (lowest) The country-specific differences in the centrations of siloxanes in indoor dust can be attributed to the con-sumption and usage patterns of siloxanes between countries Further, the difference also reflects the usage pattern of personal care products among various countries Personal care products, especially skin care products, are the major sources of siloxanes in the indoor environments (Horii and Kannan, 2008)
The TSi concentrations measured in indoor dust samples from homes, laboratories, and offices in South Korea, the USA, and Vietnam were compared (Fig 2); the dust samples collected from homes contained the highest TSi concentrations The median concentrations
Table 1
Details of indoor dust samples collected from various countries.
China (n = 18) Shanghai Homes, laboratories 2010–2011
Greece (n = 28) Athens, Erateini, Komotini Homes 2014
Japan (n = 13) Kumamoto, Nagasaki, Fukuoka, Saitama, Saga Homes, offices 2012
Pakistan (n = 28) Faisalabad Homes, cars, offices 2011–2012
Saudi Arabia (n = 28) Jeddah Homes, cars, air conditioners 2013 South Korea (n = 28) Ansan, Anyang Homes, laboratories, offices 2012 USA (n = 22) Albany Homes, laboratories, offices 2014 Vietnam (n = 38) Hanoi, Hatinh, Hungyen, Thaibinh Homes, laboratories, offices 2014
Table 2
Concentrations of total cyclic siloxanes (TCSi), total linear siloxanes (TLSi), and total siloxanes (TSi) in indoor dust collected from 12 countries (ng/g).
Mean Median Range Mean Median Range Mean Median Range China (n = 18) 458 362 95.3–1350 627 471 21.5–2350 1090 1070 117–2670 Colombia (n = 28) 304 193 81–1700 198 21.5 n.d.–1080 502 230 102–2730 Greece (n = 28) 4100 1380 118–25,100 1490 772 129–4990 5590 2970 384–30,100 India (n = 28) 90.4 87.3 n.d.–244 112 21.5 n.d.–562 202 116 n.d.–657 Japan (n = 13) 296 156 42.9–757 3950 1300 248–29,000 4240 1500 321–29,400 Kuwait (n = 28) 847 354 50.3–10,400 3940 2060 246–42,400 4780 2400 476–42,800 Pakistan (n = 28) 118 30.3 n.d.–1870 2570 21.5 n.d.–25,800 2690 68.3 n.d.–25,900 Romania (n = 23) 317 192 31.7–1800 1700 235 n.d.–12,000 2020 538 88.7–12,200 Saudi Arabia (n = 28) 194 68.7 12–2930 262 29.6 n.d.–2160 456 132 33.5–3040 South Korea (n = 28) 430 326 54–1700 2190 1190 131–9010 2620 1810 335–9340 USA (n = 22) 587 296 69–3660 882 623 36.8–4110 1470 1220 114–4950 Vietnam (n = 38) 111 94.3 n.d.–336 179 97.7 n.d.–733 291 206 n.d.–943 TCSi, TLSi, and TSi: Total concentrations of five cyclic siloxanes (D3–D7), eleven linear siloxanes (L4–L14), and sixteen siloxanes (sum of cyclic and linear) in indoor dust, respectively n.d.:
Trang 4of TSi in dust from the US homes (1450 ng/g) were 1.5 to 3.5 times
higher than the concentrations found in laboratories (1050 ng/g) and
offices (423 ng/g) Higher concentrations of siloxanes in dust from
homes than in offices and laboratories from the USA and Korea further
suggest that personal care products and household products are the
major sources of siloxanes in the indoor environment There existed a
considerable difference in mean and median concentrations of TSi in
dust samples collected from Pakistan (mean: 2690 ng/g; median:
68.3 ng/g) This difference can be explained by elevated concentrations
of TLSi (median: 4670 ng/g) found in car dust samples (n = 7), which
accounted for 99% of the TSi concentrations (median: 4710 ng/g) Dust
from homes in Pakistan contained significantly lower TSi concentrations
(median: 60.5 ng/g)
3.2 Composition profiles of cyclic and linear siloxanes in dust
The detection frequencies and concentrations of individual siloxanes
determined in indoor dust are shown in Table S1 Among thefive cyclic
siloxanes analyzed, D5 was found at 100% frequency in dust from all
countries, except for samples collected from India (79%), Pakistan
(50%), Saudi Arabia (75%), and Vietnam (82%) Overall, D5 was also the
predominant siloxane found in indoor dust The highest D5 concentration
was found in samples from Greece, ranging from 60 to 24,600 ng/g
(median: 1200), followed by the USA (range: 6.34 to 1740 ng/g and
me-dian: 159 ng/g) The lowest concentration of D5 was found in dust
sam-ples from Pakistan (range: LOQ to 371 ng/g; medianb LOQ), followed
by Vietnam (median: 16.6 ng/g), and India (median: 22.1 ng/g) D3, D4, and D6 also were found in indoor dust samples collected from all coun-tries with detection frequencies and concentrations lower than those of D5 The highest concentrations of D6 were found in dust samples from China (median: 131 ng/g) and D3 was found in dust samples from Kuwait (median: 29.4 ng/g) D4 was found at the highest concentration
in samples from Greece (median: 65.8 ng/g) Personal care products, especially deodorants and antiperspirants, contained D5 concentrations
as high as 14.3% by weight (Horii and Kannan, 2008).Horii and Kannan (2008)also reported the predominance of D5 in hair care products and cosmetics from the USA
Among linear siloxanes, L8, L9, and L10 were found at higher detec-tion frequencies than the other linear siloxanes analyzed L8, L9, and L10 were found at 100% in indoor dust samples from Greece, Japan, Kuwait, and South Korea L10 was measured at the highest concentrations, rang-ing from 83.9 to 22,100 ng/g (median: 537), followed by L9 (20.8 to 15,300 ng/g with a median value of 287) in dust samples from Kuwait L11 and L12 were found in all samples from Japan at the highest concen-trations, which ranged from 45.5 to 7940 ng/g (median: 389) for L11 and from 33.9 to 7720 ng/g (median: 337) for L12 L4, L5, L13, and L14 were less frequently detected in dust samples Some dust samples contained elevated concentrations of L12, L13, and L14, which were found at concentrations as high as 8060, 2600, and 580 ng/g,
respective-ly, in car dust samples from Pakistan (Table S1) These results suggested country-specific differences in the profiles of siloxanes in indoor dust samples Similar to that for cyclic siloxanes, a major source of linear siloxanes in the indoor environment is personal care products
Horii and Kannan (2008)reported TLSi concentrations in personal care and household products in the USA atb0.059 to 73,000 μg/g (mean: 1690), and that sanitary products (e.g., furniture polish, dish cleaners) contained elevated concentrations of linear siloxanes (b0.059 to 53,000 μg/g with a mean of 8840)
The distribution percentage of TCSi and TLSi in TSi concentrations in indoor dust from various countries is shown inFig 3 TCSi concentra-tions in dust samples collected from Colombia, India, and Saudi Arabia accounted for 90, 80 and 70%, respectively, of the TSi concentrations TLSi predominated in dust samples collected from Japan (89%), Kuwait (85%), South Korea (78%), and the USA (68%) TCSi and TLSi contributed almost equally to TSi concentrations in dust samples from China, Greece, Pakistan, Romania, and Vietnam
3.3 Human exposure to siloxanes through indoor dust ingestion
A few studies have reported exposure of humans to siloxanes through dermal absorption from the use of personal care products in the USA and China (Horii and Kannan, 2008; Jovanovic et al., 2008; Lu et al.,
Fig 1 Median concentrations (ng/g) of total siloxanes (sum of 5 cyclic plus 11 linear
siloxanes) in homes dust collected from 12 countries Values in parentheses (next to
country) refer to the number of samples.
Fig 2 Comparison of total siloxane concentrations in indoor dust from homes,
laborato-ries, and offices in South Korea, USA, and Vietnam.
Fig 3 Distribution profiles of total cyclic siloxanes (TCSi; D3–D7) and total linear siloxanes (TLSi; L4–L14) in indoor dust collected from twelve countries Values in parentheses
Trang 52011) and inhalation of indoor air in the UK (Pieri et al., 2013) The
re-ported daily intake of TSi through indoor dust ingestion in China for
tod-dlers and adults was 32.8 and 15.9 ng/d, respectively (Lu et al., 2010)
Human exposure to siloxanes through dust ingestion was estimated
based on the measured median TSi concentrations in indoor dust,
aver-age body weights reported for various aver-age groups, and the dust
inges-tion rates (Lu et al., 2010; Guo and Kannan, 2011; Liao et al., 2012)
The average body weights (bw) reported in the U.S Environmental
Pro-tection Agency (EPA) exposure factor handbook were: infants (6–12
months): 8 kg, toddlers (1–6 yrs): 15 kg, children (6–11 yrs): 32 kg,
teenagers (11–16 yrs): 57 kg, and adults (≥19 yrs): 72 kg (U.S EPA,
2008) The mean dust ingestion rates were 30 mg/d for infants and
60 mg/d for toddlers, children, teenagers, and adults (U.S EPA, 2008)
Based on the median TSi concentrations (Table 2), the calculated
ex-posure doses of TSi for infants and toddlers from 12 countries were in
the ranges of 0.26 to 11.9 ng/kg-bw/d (Table 3) Infants and toddlers
from Greece had the highest exposure to TSi, with the exposure doses
at 11.1 and 11.9 ng/kg-bw/d, respectively Among siloxanes, D5
expo-sure was the highest for infants and toddlers from Greece and the
re-spective doses were 4.50 and 4.80 ng/kg-bw/d Infants and toddlers in
Pakistan had the lowest exposure to TSi through indoor dust ingestion
(0.26 and 0.27 ng/kg-bw/d, respectively) For adults, indoor dust
inges-tion contributed to exposure doses to TSi that ranged from 0.06 for
Pakistani adults to 2.48 ng/kg-bw/d for Greek adults Overall, these
re-sults suggest that TSi exposure through indoor dust ingestion decreases
with increased age However, it should be noted that the exposure doses
calculated for children are a crude estimate as the dust concentrations
for some countries include the office environment A dermal intake
value for TSi from the use of personal care products by an adult
woman in the USA was estimated at 307 mg/d (Horii and Kannan,
2008) The siloxane exposure doses calculated from dust ingestion
were 3 to 5 orders of magnitude lower than the exposure doses from
dermal intake through the use of personal care products Furthermore,
it has been shown that 0.12–0.3% and 0.05% of the dermally applied
dose of D4 and D5, respectively, were absorbed into the systemic
circu-lation (Reddy et al., 2007) A no-observed adverse effect level (NOAEL)
of 19 mg/kg/d was reported for D5 based on a 90-day inhalation
expo-sure study in rats (Brooke et al., 2009a,b,c), and the exposure doses
es-timated from indoor dust ingestion were several orders of magnitude
lower than the NOAEL
In summary, this is thefirst survey of siloxanes in indoor dust
collected from 12 countries D5, L8, L9, and L10 were found frequently
in indoor dust samples at concentrations as high as 42,800 ng/g Dust
samples collected from Greece, Kuwait, and Japan contained the highest
siloxane concentrations The profiles of siloxanes in dust varied by the
country of origin Dust samples collected in homes contained higher
TSi concentrations than those from offices and laboratories Based on
the median concentrations of siloxanes found in indoor dust, and the
dust ingestion rates, the human exposure doses to TSi were calculated
to range from 0.27 to 11.9 ng/kg-bw/d for toddlers and 0.06 to 2.48 ng/kg-bw/d for adults This study has several limitations; samples were collected from select cities and the sample size is small for each country The number of samples from various microenvironments is in-adequate to discern distribution of siloxanes The exposure assessment
of siloxanes through dust ingestion involves several assumptions, which may under- or over-estimate actual exposures Further studies are needed to assess the significance of indoor dust as a source of siloxane exposure in humans
Acknowledgments The authors thank Pierina Maza-Anaya, a youth research fellow sup-ported by the Colombian National Science and Technology System, for helping with the collection of dust samples from Colombia; Dr Dilip Kumar Kedia helped with the 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, New York State Department of Health Its contents are solely the responsibility of the authors and do not necessarily represent the of-ficial views of the CDC
Appendix A Supplementary data Supplementary data to this article can be found online athttp://dx doi.org/10.1016/j.envint.2015.02.011
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Table 3
Estimated human exposure doses (ng/kg-bw/d) to total siloxanes through indoor dust
in-gestion by infants, toddlers, children, teenagers, and adults in various countries (based on
median concentrations).
Countries Infants Toddlers Children Teenagers Adults
China 4.01 4.28 2.01 1.13 0.89
Colombia 0.86 0.92 0.43 0.24 0.19
Greece 11.1 11.9 5.57 3.13 2.48
India 0.44 0.46 0.22 0.12 0.10
Japan 5.63 6.0 2.81 1.58 1.25
Kuwait 9.0 9.6 4.5 2.53 2.0
Pakistan 0.26 0.27 0.13 0.07 0.06
Romania 2.02 2.15 1.01 0.57 0.45
Saudi Arabia 0.5 0.53 0.25 0.14 0.11
South Korea 6.79 7.24 3.39 1.91 1.51
USA 4.58 4.88 2.29 1.28 1.02
Vietnam 0.77 0.82 0.39 0.22 0.17
Trang 6Lu, Y., Yuan, T., Wang, W., Kannan, K., 2011 Concentration and assessment of exposure to
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