Article pubs.acs.org/est
Feasibility Study of Feces for Noninvasive Biomonitoring of Brominated Flame Retardants in Toddlers Leena M. O. Sahlström,*,† Ulla Sellström,† Cynthia A. de Wit,† Sanna Lignell,‡ and Per Ola Darnerud‡ †
Department of Applied Environmental Science (ITM), Stockholm University, SE-106 91 Stockholm, Sweden Science Department, National Food Agency, Box 622, SE-751 26 Uppsala, Sweden
‡
S Supporting Information *
ABSTRACT: This study investigated the feasibility of using feces as a noninvasive matrix to estimate serum concentrations of brominated flame retardants (BFRs) in toddlers for biomonitoring purposes. Tri- to decabrominated diphenyl ethers (tridecaBDEs), isomer-specific hexabromocyclododecanes, and 16 emerging BFRs were determined in feces from 22 toddlers (11−15 months of age), and results were compared to previously analyzed matched serum samples. BDE-47, -153, -196, -197, -203, -206, -207, -208, and -209 were detected in the feces creating a matched data set (feces−serum, n = 21). Tetra-octaBDE concentrations were significantly higher (Student’s paired comparisons t test, α = 0.05) in serum versus feces with BDE-153 having the highest mean difference between the sample matrices. BDE-209 was found in significantly higher concentrations in feces compared to serum. Significant correlations (Pearson’s, α = 0.05) between congener-specific concentrations in feces and serum were found for all BDEs except BDE-197 and -203. The feces−serum associations found can be used to estimate serum concentrations of tetra-decaBDEs from feces concentrations and enable a noninvasive sampling method for biomonitoring BDEs in toddlers.
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INTRODUCTION Brominated flame retardants (BFRs) are used in, e.g., textiles, carpets, housings of electronic devices and building materials to slow down the spread of fire. These chemicals are persistent, and due to extensive use, they have become ubiquitous in the environment.1 Polybrominated diphenyl ethers (PBDEs), a group of BFRs that have been used for decades, have been detected in, e.g., biota, indoor air and dust, and humans.2,3 Penta- and OctaBDE technical mixtures, containing BDE-47, -99, -100, -153, -154 and BDE-153, -154, -183, -196, -197, -203, -206, -207, -208, respectively,4 were recently banned,5 and the DecaBDE mixture, containing primarily BDE-209, but some BDE-206, -207, and -208,4 has been phased out6 in several countries. Hexabromocyclododecane (HBCD), a BFR used in building insulation and textiles is currently being phased out.7 These actions have resulted in the application of a number of other BFRs to replace the banned or phased-out ones.8 Most of the non-PBDE flame retardants we include in this study (Table 1) fit into the definition of emerging BFRs (EBFRs) recently suggested by Bergman et al.9 PBDEs and HBCD have been shown to disturb thyroid hormone homeostasis and neurobehavioral development in children after pre- and postnatal exposure.10−12 EBFR toxicology in laboratory mammals or humans is not yet as widely studied. The European Food Safety Authority (EFSA) has compiled existing data on EBFR toxicology.13 These data, usually based on single studies, show that a few have effects on genetic material in in vitro tests (DBE-DBCH, Firemaster 550 technical product containing EH-TBB and BEH-TEBP), act as endocrine disruptors in in vitro tests, acute or subchronic rat © 2014 American Chemical Society
Table 1. Names and Abbreviations of the EBFRs Included in This Study compound name
abbreviation
2-ethylhexyl-2,3,4,5-tetrabromobenzoate bis(2-ethylhexyl) tetrabromophthalate bis(2,4,6-tribromophenoxy) ethane decabromodiphenyl ethane α-tetrabromoethylcyclohexane β-tetrabromoethylcyclohexane 2,3,5,6-tetrabromo-p-xylene 2-bromoallyl 2,4,6-tribromophenyl ether 1,2,3,4,5-pentabromobenzene tetrabromo-o-chlorotoluene pentabromotoluene pentabromoethylbenzene 2,3-dibromopropyl 2,4,6-tribromophenyl ether hexabromobenzene hexachlorocyclopentenyl-dibromocyclooctane octabromotrimethylphenylindane
EH-TBB BEH-TEBP BTBPE DBDPE α-DBE-DBCH β-DBE-DBCH TBX BATE PBBz TBCT PBT PBEB TBP-DBPE HBBz DBHCTD OBTMPI
studies (DBDPE, DBE-DBCH, PBT), or induce porphyria in rats (HBBz).13 Firemaster 550 has also shown endocrine disruptive effects in laboratory rats.14 For most other EBFRs, no data were available.13 Received: Revised: Accepted: Published: 606
September 25, 2014 December 5, 2014 December 10, 2014 December 10, 2014 dx.doi.org/10.1021/es504708c | Environ. Sci. Technol. 2015, 49, 606−615
Environmental Science & Technology
Article
Humans are exposed to BFRs via several different routes,15 where diet and ingestion of indoor dust are considered to be most important for the general population.16−18 PBDE levels in cord blood of newborn babies are similar to those of their mothers due to placental transfer;19−22 infant levels then increase due to ingestion from breastfeeding, and their concentrations are still elevated compared to formula-fed children at 4 years of age.23 Dust ingestion is also considered an important pathway for PBDE exposure in children,24 in particular for BDE-209.25 Due to children’s higher hand-tomouth activity the importance of dust ingestion is probably greater for them compared to adults.24 There were also strong indications that breastfeeding and dust ingestion were the major exposure routes for the tetra-hexaBDEs and octadecaBDEs, respectively, in the toddler cohort included in the present study.26 BFRs have been detected in human blood globally in many studies.2,27−29 Only a few studies have reported BFR concentrations in serum of toddlers or young children, but when included, the concentrations are higher than in adults.25,26,30,31 Thus, toddlers and children may be at higher risk from BFRs due to their higher internal exposure to these compounds compared to adults. However, the lack of adequate biomonitoring data for this population hinders proper exposure and risk assessment.32 The limited amount of data available on BFR levels in serum of young children is partly due to difficulties in obtaining samples, in getting sufficient amounts of blood for reliable chemical analyses, but also for ethical reasons as parent’s informed consent is required. Pooling of samples from several children or the use of noninvasive sample matrices such as urine have been applied to overcome some of these difficulties33 but are not sufficient if biomonitoring and exposure assessments are to be carried out on an individual basis. Since risk assessment is based on serum concentrations, the noninvasive matrix used should reflect serum concentrations. Urine is not adequate as a sample matrix as persistent hydrophobic chemicals such as BFRs are not sufficiently watersoluble for this to be a major excretion route, and thus, concentrations are too low for detection.34 For adults, a variety of organic environmental pollutants have been analyzed in other noninvasive matrices besides urine, including hair, saliva, and breast milk as reviewed by Esteban and Castano.35 Hair is subject to external contamination and thus may not be representative of actual body burden, and saliva is not applicable for persistent hydrophobic chemicals for the same reasons as urine. Either these matrices are also not available or sample amounts are too small for use in young children. Surprisingly few studies have explored feces as a noninvasive matrix for biomonitoring. Several studies in adults of dietary absorption, body concentrations, and fecal elimination of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs), polychlorinated biphenyls (PCBs), and hexachlorobenzene (HCB) have shown that digestive absorption of hydrophobic organic chemicals (HOCs) is dependent on dietary intake, whereas fecal excretion is independent of dietary intake but dependent on body burden.36−41 This was postulated to be due to a two-stage process, called the “fat-flush” theory, whereby dietary lipids are first absorbed from the small intestine lumen into gut tissue, leading to subsequent reduction in gut tissue HOC concentrations. This change in chemical gradient then facilitates diffusion of HOCs from the small intestine lumen into the tissue and further distribution to the body’s fat
reservoirs.39−41 When the lumen contents later reach the large intestine, the process is reversed and excretion of lipids from the body into the feces leads to a concentration gradient favoring diffusion of HOCs from the tissues into the feces. Thus, concentrations of HOCs in feces represent HOC concentrations that have accumulated over time in the body fat reservoirs and not those in the diet.39−41 Strong correlations were also seen between feces and blood concentrations of PCDD/Fs, PCBs, and HCB in several of these studies, further strengthening the hypothesis that feces concentrations reflect body burdens.37−39 Several studies of nursing infants have also compared PCDD/F, PCB, and HCB42,43 and PCBs, tetra-hexaBDEs, and pesticide44 concentrations in feces to those in breast-milk to determine uptake and fecal excretion rates. Tri-heptaBDEs have been reported in feces from an infant and a toddler from Australia comparing BDE levels between the two feces samples and a pooled blood sample from Australian children 0−4 years of age.45 No other BFRs have been reported in human feces. If BFR concentrations correlate between serum and feces in toddlers as has been seen for adults, feces could be feasible for use as a noninvasive sample matrix to estimate BFR concentrations in serum of toddlers for biomonitoring purposes. The objective of this study was therefore to determine BFR concentrations in feces samples, compare these to concentrations in previously published matched serum samples from the same toddlers,26 and study possible associations between the concentrations in the two matrices. Significant correlations were studied to build simple linear regression models for estimating serum concentrations in human toddlers. This is the first feasibility study for using feces as a noninvasive method to determine BFR body burden in human toddlers and, to our knowledge, the first time octa-decaBDEs, HBCD, and some emerging BFRs are reported in human feces. The 16 EBFRs included in this study are listed in Table 1.
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METHODS Study Population and Sampling. The toddlers (n = 22) participating in this study were recruited via their mothers (60 first-time mothers who delivered one healthy child in Uppsala University Hospital) in 2009−2010 and who were included in the POPUP study (Persistent Organic Pollutants in Uppsala Primiparas).46 The mothers were contacted and asked to participate in a follow-up study when their children were 10−15 months of age. A visit was planned for blood sampling of mothers and toddlers, and they were asked to save one diaper with feces in their freezer before the visit. The diapers were collected, and blood sampling was performed in the participants’ homes as described in Sahlström et al.26 1−17 weeks (median 5 weeks) after contact. The diapers were stored in a freezer at −25 °C until sample preparation and analysis. Empty diapers were also collected to control for the possible presence of BFRs in the diaper material. The sampling was organized by the Swedish National Food Agency in Uppsala, Sweden. This study was approved by the Regional Ethics Committee in Uppsala, Sweden (Permit 2004:M-177). Chemical Analyses. The feces were carefully removed from the diapers using a stainless steel spoon and/or spatula. Undigested pieces of, e.g., peas and corn were removed from the feces with a pair of tweezers before the samples were homogenized. Between 2.8 and 16 g of fresh weight of feces was accurately weighed into glass test tubes for analysis. Sample 607
dx.doi.org/10.1021/es504708c | Environ. Sci. Technol. 2015, 49, 606−615
Environmental Science & Technology
Article
Table 2. BFR Concentrations (ng/g lipid) in Toddler Feces (n = 22) lipid content (%) BDE-28 BDE-47 BDE-99 BDE-100 BDE-153 BDE-196 BDE-197 BDE-203 BDE-206 BDE-207 BDE-208 BDE-209 DBDPE α-HBCD β-HBCD γ-HBCD Σ-HBCDc BTBPE EH-TBBd BEH-TEBPd α-DBE-DBCH β-DBE-DBCH TBX BATE PBBz TBCT PBT PBEB TBP-DBPE HBBz DBHCTD OBTMBI
DF %a
GMb
(95% CI)
median
min
max
− 0 100 0 0 77 73 91 86 100 100 100 100 100 100 61 74 − 13 0 50 23 32 0 41 64 4.5 45 14 4.5 4.5 23 23
9.4 − 0.39 − − 0.18 0.049 0.16 0.71 0.6 0.75 0.21 22 5.6 0.37 0.14 0.33 0.96 0.092 − 7.4 0.039 0.033
(8.5−10) − (0.30−0.51)
10 − 0.41 − − 0.23 0.055 0.18 0.86 0.44 0.62 0.18 18 4.7 0.30 0.11 0.18 0.71 0.074 − 9.5 0.024 0.022 − 0.0072 0.014 − 0.014 0.0092 − − 0.16 0.010
6.1
