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Current Organic Chemistry, 2014, 18, 2182-2199
The Occurrence of Bisphenol A, Phthalates, Parabens and Other Environmental Phenolic Compounds in House Dust: A Review Wan-Li Maa, b, Bikram Subedib and Kurunthachalam Kannana,b,c * a
International Joint Research Center for Persistent Toxic Substances, State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150090, China; bWadsworth 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; cBiochemistry Department, Faculty of Science and Experimental Biochemistry Unit, King Fahd Medical Research Center, King Abdulaziz University, Jeddah, Saudi Arabia Abstract: Dust from indoor environments can contain significant amounts environmental contaminants and is an important source of human exposure to several toxicants. In this article, studies on the occurrence of several emerging environmental contaminants, namely bisphenol A (BPA), tetrabromobisphenol A (TBBPA), phthalates, parabens, and other environmental phenolic compounds in indoor dust from various countries, were reviewed. Issues associated with sampling of dust and the uncertainties introduced in the analytical procedures were also summarized. Finally, exposure to environmental phenolic compounds through dust ingestion was evaluated, and the contribution of indoor dust to the total daily exposure of toxicants was estimated. Overall, the reported concentrations of target chemicals in dust were found, in decreasing order, as phthalates (overall mean: 949 ± 669 μg/g, range: 0.9-10,900 μg/g) >>> nonylphenol (8.9 ± 6.8 μg/g, 2.6-29.2 μg/g) > BPA (3.6 ± 4.5 μg/g, 0.35-16.6 μg/g) > parabens (1.53 ± 0.52 μg/g, 0.03-125 μg/g) > pentachlorophenol (1.39 ± 2.31 μg/g, 0.050- 5.76 μg/g) > triclosan (0.65 ± 0.23 μg/g, 0.38-0.93 μg/g) > TBBPA (0.18 ± 0.14 μg/g, 0.049-0.505 μg/g). Despite the elevated levels of the target phenolic compounds reported in indoor dust, exposure of humans through dust ingestion was minor. Nevertheless, dust can be a significant source of exposure to phenolic compounds for infants and toddlers. Elevated levels of phenolic compounds were found in dust collected from certain microenvironments such as offices and laboratories.
Keywords: BPA, environmental phenolic compounds, house dust, human exposure, phthalates. 1. INTRODUCTION People spend most of their time (approximately 90%) indoors. In the last few decades, the quality of indoor environments (indoor air and indoor dust) has received considerable attention among regulatory and public health agencies because of its significance in terms of public health. The quality of air that we breathe in our homes, schools, and offices is directly related to our health [1, 2]. Exposure to contaminants in indoor environments has been shown to elicit a variety of adverse health effects [3]. Poor indoor air quality can result from contaminants such as volatile organic compounds (VOCs) and industrial chemicals released by outgassing of building materials [4]. Further, the use of a wide range of chemicals in consumer products contributes to the contamination of the indoor environments. For example, introduction of several new chemicals in commerce and in consumer products contributes to the occurrence of these chemicals in indoor dust [5]. Indoor air and indoor dust are the most frequently used matrixes for the assessment of the quality of indoor environments [6-8]. For VOCs, measurements in indoor air provide a direct estimate of exposure levels [3]. However, episodic measurements of contaminants in indoor air cannot integrate exposures for a long period of time. Further, non-volatile chemicals tend to adsorb to dust particles [2]. Thus, indoor dust is a sink and a repository for many indoor environmental contaminants, and the contaminants in indoor dust can be considered as a marker of indoor exposure [3]. Indoor dust integrates contamination that occurs over a long period of time
in the indoor environment, and thus, levels of contaminants in indoor dust are useful for retrospective exposure assessment [2]. The composition, methods of sampling and analysis for organic and inorganic contaminants (e.g., polybrominated diphenyl ethers [PBDEs], polychlorinated biphenyls [PCBs], polycyclic aromatic hydrocarbons [PAHs], pesticides, heavy metals) in dust, and human exposures through dust ingestion have been previously reviewed [24, 6, 9, 10]. Two reviews have documented the occurrence of emerging environmental chemicals such as bisphenol A (BPA), phthalates, and phenolic contaminants in house dust [3, 4]. Many novel compounds that are widely used in building materials and consumer products are known to possess hormonally active properties [3, 11]. Some contaminants, such as BPA, are reported as endocrine disrupting chemicals (EDCs) [12-14]. Recent studies have shown the significance of house dust as a source of human exposure to EDCs [15-19]. The aim of this review is to provide a comprehensive summary of the available literature on the occurrence and human exposure of BPA, tetrabromobisphenol A (TBBPA), phthalates, parabens, and other environmental phenolic compounds such as nonylphenol, octylphenol, chlorophenols, bromophenols, triclosan (TCS), and benzophenone in indoor dust. Due to the wide range of physicochemical properties of the target compounds, each chemical class is described separately in this review. The structure, chemical formula, and select physicochemical properties of the target compounds are listed in Table 1. 2. INTRODUCTION OF TARGET COMPOUNDS 2.1. Bisphenol A
*Address correspondence to this author at the Wadsworth Center, Empire State Plaza, P.O. Box 509, Albany, NY 12201-0509, USA; Tel: 1-518-474-0015; Fax: 1-518-473-2895; E-mail:
[email protected] /14 $58.00+.00
BPA (4,4´-dihydroxy-2,2-diphenylpropane) is an industrial chemical synthesized by condensation of two phenol groups and © 2014 Bentham Science Publishers
The Occurrence of Bisphenol A, Phthalates, Parabens and Other Environmental Phenolic
Current Organic Chemistry, 2014, Vol. 18, No. 17 2183
Table 1. Structures and physicochemical properties of target compounds in this review. Formula
CAS
Molecular Weight
Water Solubilitya
Log Koa b
Log Kow c
BPA
C15H 16O2
80-05-7
228.29
172.7
12.747
3.64
bis(2-ethylhexyl) phthalate
DEHP
C24H 38O4
117-81-7
390.56
1.132E-03
12.557
8.39
di-methyl phthalate
DMP
C10H 10O4
131-11-3
194.18
2014
6.694
1.66
di-ethyl phthalate
DEP
C12H 14O4
84-66-2
222.24
287.2
7.023
2.65
di-propyl phthalate
DPP
C14H 18O4
131-16-8
250.29
37.99
8.053
3.63
di-n-butyl phthalate
DBP
C16H 22O4
84-74-2
278.34
2.351
8.631
4.61
di-n-hexyl phthalate
DNHP
C20H 30O4
84-75-3
334.45
0.012
9.799
6.57
di-n-octyl phthalate
DNOP
C24H 38O4
117-84-0
390.56
4.236E-04
12.079
8.54
di-iso-butyl phthalate
DiBP
C16H 22O4
84-69-5
278.34
5.061
8.412
4.46
di-iso-nonyl phthalate
DiNP
C26H 42O4
2855312-0
418.61
2.317E-05
13.585
9.37
di-iso-decyl phthalate
DiDP
C28H 46O4
2676140-0
446.66
2.239E-06
14.703
10.36
benzyl-butyl phthalate
BBP
C19H 20O4
85-68-7
312.36
0.9489
9.018
4.84
di-cyclo-hexyl phthalate
DCHP
C20H 26O4
84-61-7
330.42
0.04098
11.588
6.20
Chemicals
Abbreviation
bisphenol A
Molecular Structure
2184 Current Organic Chemistry, 2014, Vol. 18, No. 17
Ma et al.
Table 1. Contd……. Formula
CAS
Molecular Weight
Water Solubilitya
Log Koa b
Log Kow c
TBBPA
C15H 12Br 4O2
79-94-7
543.87
0.001
18.225
7.20
methyl paraben
MeP
C8H8O 3
99-76-3
152.15
5981
8.791
1.96
ethyl paraben
EtP
C9H10O3
120-47-8
166.17
1894
9.178
2.49
propyl paraben
PrP
C10H 12O3
94-13-3
180.08
529.3
9.624
2.98
butyl paraben
BuP
C11H 14O3
94-26-8
194.23
159
10.032
3.47
benzyl paraben
BzP
C14H 12O3
94-18-8
228.24
107.8
11.483
3.70
heptyl paraben
HeP
C14H 20O3
1085-127
236.30
8.0
10.922
4.94
4-hydroxybenzoic acid
4-HB
C7H6O 3
99-96-7
138.12
14500
10.915
1.39
triclosan
TCS
C12H 7Cl 3O2
3380-345
289.54
4.621
11.450
4.66
4-octylphenol
4-OP
C14H 22O
1806-264
206.32
3.114
9.235
5.50
4-nonylphenol
4-NP
C15H 24O
104-40-5
220.35
1.57
8.617
5.99
2,4-dichlorophenol
-
C6H4 Cl2O
120-83-2
163.00
614.2
7.108
2.80
3,4-dichlorophenol
-
C6H4 Cl2O
95-77-2
163.00
361.2
8.230
2.80
2,4,5-trichlorophenol
-
C6H3 Cl3O
95-95-4
197.45
114.1
7.899
3.45
2,4,6-trichlorophenol
-
C6H3 Cl3O
88-06-2
197.45
121
7.66
3.45
Chemicals
Abbreviation
tetrabromobisphenol A
Molecular Structure
The Occurrence of Bisphenol A, Phthalates, Parabens and Other Environmental Phenolic
Current Organic Chemistry, 2014, Vol. 18, No. 17 2185 Table 1. Contd……. Formula
CAS
Molecular Weight
Water Solubilitya
Log Koa b
Log Kow c
-
C6H3 Cl3O
609-19-8
197.45
64.49
9.041
3.45
2,3,4,5-tetrachlorophenol
-
C6H2 Cl4O
4901-51-3
231.89
28.69
9.371
4.09
2,3,4,6-tetrachlorophenol
-
C6H2 Cl4O
58-90-2
231.89
17.9
7.892
4.09
2,3,5,6-tetrachlorophenol
-
C6H2 Cl4O
935-95-5
231.89
54.9
9.041
4.09
pentachlorophenol
PCP
C6Cl 5OH
87-86-5
266.34
3.09
11.119
4.74
2,4,6-tribromophenol
-
C6H3 Br3O
118-79-6
330.80
9.127
9.968
4.18
4-hydroxybenzophenone
4-OH-BP
C13H 10O2
1137-42-4
198.22
405.8
11.153
2.67
2,4dihydroxybenzophenone
2,4-2OH-BP
C13H 10O3
131-56-6
214.22
413.4
11.925
2.96
2-hydroxy-4methoxybenzophenone
BP-3
C14H 12O3
131-57-7
228.24
68.56
10.002
3.52
2,2'-dihydroxy-4methoxybenzophenone
2,2'-2OH-4MEO-BP
C14H 12O4
131-53-3
224.24
52.73
10.914
3.82
2,2',4,4'tetrahydroxybenzophenone
2,2',4,4'-4OHBP
C13H 10O5
131-55-5
246.22
398.5
16.611
2.78
Chemicals
Abbreviation
3,4,5-trichlorophenol
Molecular Structure
a
Water solubility (mg/L, 25 oC) estimated from Log Kow using the US Environmental Protection Agency’s EPISuite™, [WSKOWWIN v1.41]; Log octanol-air partition coefficient (25 oC) estimated using the US Environmental Protection Agency’s EPISuite™, [KOAWIN v1.10]; c Log octanol-water partition coefficient (25 oC) estimated using the US Environmental Protection Agency’s EPISuite™, [KOWWIN v1.67]. b
one acetone molecule [20]. BPA is used primarily as an intermediary in the production of polycarbonate plastics and epoxy resins [21, 22], which are widely used in consumer products, including feeding bottles, adhesives, protective coatings, powder paints, automotive lenses, protective window glazing, dental fillings, compact disks, optical lenses, and thermal receipt papers [23-25]. BPA is a weak estrogen receptor agonist. Emerging evidence suggests that BPA can influence multiple endocrine pathways [20, 26, 27].
2.2. Phthalates Phthalates (phthalic acid esters) are dialkyl or aryl alkyl esters of 1,2 benzene dicarboxylate [28] and have a broad range of applications in industry and commerce [29]. Phthalates are used mainly as plasticizers and stabilizers in food processing and medical applications, personal care products, building materials, household furnishings, nutritional supplements, toys, and insecticides [29-32].
2186 Current Organic Chemistry, 2014, Vol. 18, No. 17
Phthalates can enter the environment through manufacturing processes and leaching from consumer products [24]. Epidemiological studies have found associations between exposure to phthalates and reproductive toxicity, asthma/allergies, and hepatotoxicity [33-35]. Kolarik et al. (2008) reported a significant association between wheezing among preschool children and urinary concentration of di-2-ethylhexyl phthalate (DEHP) [34]. The health risks of phthalates are still unclear and debatable [13], but there is unequivocal evidence that humans are exposed to high levels of phthalates on a daily basis, and urinary concentrations can range from several tens to hundreds of nanograms per milliliter [36]. 2.3. Tetrabromobisphenol A TBBPA is a phenolic and hydrophobic compound, which is used primarily as a reactive flame retardant in epoxy and polycarbonate resins [37]. The industrial production process involves bromination of BPA in the presence of a solvent, such as methanol, 50% hydrobromic acid, or aqueous alkyl monoethers [38]. TBBPA is the most widely used brominated flame retardant in epoxy resin printed circuit boards and acrylonitrile-butadiene-styrene plastics [39]. TBBPA has a low acute toxicity in humans but is toxic to aquatic organisms [40]. Rodent exposure study indicated that TBBPA was both a thyroid hormone and an estrogen agonist [38]. 2.4. Parabens Parabens are esters of para-hydroxybenzoic acid and are widely used singly, or in combination of several homologues, as broad spectrum antimicrobial preservatives in foods, cosmetics, and pharmaceutical products [41, 42]. Six commonly known parabens are methyl-paraben (MeP), ethyl-paraben (EtP), propyl-paraben (PrP), butyl-paraben (BuP), heptyl-paraben (HeP) and benzylparaben (BzP). Laboratory animal studies have shown that parabens can elicit estrogenic activity [43-47]. 2.5. Other Phenolic Compounds Other target phenolic compounds considered in this review are triclosan (TCS), 4-octylphenol (OP), 4-nonylphenol (NP), chlorophenols (di-, tri-, tetra- and penta- or PCP), tribromophenol, benzotriazoles (BTRs), benzothiazoles (BTHs), and benzophenones. These phenolic compounds are widely used in building materials and consumer products, including household cleaners and detergents (e.g., alkylphenols, benzotriazoles), paints, paper coatings, corrosion inhibitors (e.g., benzothiazoles), biocides (e.g., TCS), and wood preservatives [4, 48]. These phenolic compounds have been found at high levels in indoor dust and in samples of human serum and urine [48-51]. 3. HOUSE DUST SAMPLING METHODS Indoor dust, in general, consists of inorganic and organic matter, and the relative proportions of these components vary considerably. Indoor dust varies greatly in composition depending on the season, ventilation, building characteristics, and the materials used in the building. The “true” concentration of contaminants in indoor dust is difficult to obtain due to the heterogeneous and complex nature of the matrix. To achieve homogeneity and comparability of results between studies, it is important to collect a representative fraction of dust, and the concentration can be dependent on the sampling method. Further, standard methods for the collection of indoor dust are not available, and the optimal method can depend on the surface to be sampled and the goal of the study [9]. A comprehensive description as well as the advantages and disadvantages
Ma et al.
of different dust sampling methods and strategies can be found in earlier reviews [3, 4, 52]. In general, indoor dust can be collected by passive and active sampling methods. Passive sampling is performed using beakers or non-electrostatic plates that are placed in a stationary position and that allow the dust to accumulate on the surface. This method requires a long time to obtain a sufficient quantity of dust, thus, this method is rarely used [3, 4]. Active sampling of dust includes the use of vacuum cleaners, surface wiping, press sampling, or sweeping/brushing [3]. The advantage of the active sampling method is its cost effectiveness and that this method can integrate contamination in several rooms/areas over a specific period of time [53]. Two metrics have been used in the determination of contaminant levels in dust. The first is the loading of contaminants on a surface in units of micrograms per square centimeter of the surface per unit time, and the second is the “concentration of contaminants in the collected dust” in units of micrograms per gram [52]. The former is usually used for the passive sampling method and the latter for the active sampling method. An overview of the sampling methods used in the analysis of the select target compounds of this review is presented (See details in Table S1 of Supporting Information). Except for some Asian countries, where house dust samples were collected by sweeping the floors and furniture surfaces with a brush [16, 54], the most common method of dust sampling was through use of a vacuum cleaner in several other countries. Collection of dust by a vacuum cleaner can permit compositing of samples from several rooms in a house and can eliminate the need for an inhome visit by the investigator, thereby minimizing the invasiveness of home sampling [2]. In addition to household vacuum cleaners, some commercial vacuum cleaners were also used in dust sampling [39, 55-58]. For example, a high-volume small-surface sampler (HVS3), which is a modified vacuum cleaner for the collection of particles greater than 5 m using various cyclones, has been recommended by the American Society for Testing and Materials (ASTM) [59]. To avoid contamination from vacuum cleaners during sampling, prior to each use, the vacuum’s hose and nozzle assemblies are cleaned. For phthalates, phthalate-free materials were used during sampling [60], and sampling on plastic surfaces and textiles was avoided [61]. House dust was collected primarily by study participants, residents, and volunteers with conventional vacuum cleaners, whereas trained field staff were involved in sampling when commercial vacuum cleaners were used [18]. In most of the studies discussed in this review, the vacuum cleaners were fitted with cellulose filters, paper bags, and nylon socks to collect the dust [62-64]. In some studies, filters were cleaned in a Soxhlet apparatus with a hexane-dichloromethane mixture prior to sampling [65]. In addition, the vacuum cleaner bags were changed after each sample collection [66]. The sampling procedure used in some studies involved the collection of “fresh settled dust” and “old dust” concurrently. In general, ‘‘old dust’’ is expected to contain high levels of contaminants [67]. Fan et al. (2010) compared two sampling methods for the determination of parabens and triclosan in dust: “fresh” or “active” dust (FD) collected using a Pullman Holt vacuum sampler and “old dust” (HD) from a household vacuum cleaner. They found that the concentrations of chemicals in HD samples were higher than those in FD samples [68]. Depending on the study objectives, specific protocols can be established for dust sampling, which include height, area, and time of sampling. For sampling at different heights, dust was collected from
The Occurrence of Bisphenol A, Phthalates, Parabens and Other Environmental Phenolic
Current Organic Chemistry, 2014, Vol. 18, No. 17 2187
Table 2. Summary of treatment and analysis methods for phenolic compounds in house dust.
Compounds
Pretreatment
BPA
m, 425 m, 500 m,
Extraction Method
sieved to 63 m, 150 sonicate/ultrasonicate, solid-liquid
2 mm
TBBPA
Parabens
Other phenols
distilled water, Florisil SPE cartridge, Oasis MCX
acetone, ethyl acetate methanol, diethyl ether, hexane, acetone, toluene, dichloromethane,
ized liquid (fluid), solid phase micro
ethyl acetate, cyclohexane car-
extraction
boxen/polymethylsilyl adsorbent
sieved to 63 m, 150
sonicate/ultrasonicate, liquid-liquid,
hexane, acetone, toluene, dichloro-
m, 500 m
Soxhlet, pressurized liquid (fluid)
methane,
300 m, 500 m, 2 mm
sieved to 60 m, 75 m,
sonicate, solid-liquid, the matrix
80 m, 100 m, 150 m,
solid phase dispersion, pressurized
2 mm
liquid
sieved to 150 m, 2 mm
acetonitrile, ethyl acetate, ultrapure and/or Milli-Q water, methanol
sonicate, solid-liquid, accelerated
methanol, water, dichloromethane,
solvent
diethyl ether, hexane, acetone
the tops of bookshelves, cupboards, desks, and/or casings of windows and doors, at least 0.8 m above the floor, in a previous study [63]. There is no consensus on the sampling area and length needed to be vacuumed and as such there are wide variations in the literature. In regard to the sampling area, D'Hollander et al. (2010) established a standard protocol for houses (20 or 24 m2), offices (10 m2), living rooms (8 m2), bedrooms (8 m2), kitchens (4 m2), and work areas (4 m2) [69]. However, Geens et al. (2009) reported that house dust was collected from the living room (8 m2), bedroom (4 m2), and kitchen (4 m2) [64]. Dust samples were also collected from airconditioner filters or from the inside of electronic devices [66, 70]. In regard to the sampling time, Abdallah et al. (2008) established a protocol for 1 m2 area of carpet wit h2 min and 4 m2 concrete floors with 4 min [39]. However, Nilsson et al. (2005) suggested that dust sampling should be performed until the amount of dust collected was sufficient for analysis [71]. 4. HOUSE DUST TREATMENT AND ANALYSIS The treatment, extraction, and purification (clean-up) methods applied in the analysis of each class of target compounds in dust are presented in Table S2-S6 (SI), and a brief summary of the methods is presented in Table 2. Usually, a fine fraction of the indoor dust is used for chemical analysis (with an aerodynamic diameter
