Breast-milk levels of polybrominated diphenyl ether flame retardants in relation to women's age and pre-pregnant body mass index

Has Regulatory Action Reduced Human Exposure to Flame Retardants?

Flame retardant (FR) exposure has been linked to several environmental and human health effects. Because of this, the production and use of several FRs are regulated globally. We reviewed the available records of polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecanes (HBCDDs) in human breast milk from literature to evaluate the efficacy of regulation to reduce the exposure of FRs to humans. Two-hundred and seven studies were used for analyses to determine the spatial and temporal trends of FR exposure. North America consistently had the highest concentrations of PBDEs, while Asia and Oceania dominated HBCDD exposure. BDE-49 and -99 indicated decreasing temporal trends in most regions. BDE-153, with a longer half-life than the aforementioned isomers, typically exhibited a plateau in breast milk levels. No conclusive trend could be established for HBCDD, and insufficient information was available to determine a temporal trend for BDE-209. Breakpoint analyses indicated a significant decrease in BDE-47 and -99 in Europe around the time that regulation has been implemented, suggesting a positive effect of regulation on FR exposure. However, very few studies have been conducted globally (specifically in North America) after 2013, during the time when the most recent regulations have been implemented. This meta-analysis provides insight into global trends in human exposure to PBDEs and HBCDD, but the remaining uncertainty highlights the need for ongoing evaluation and monitoring, even after a compound group is regulated.

Analysis of Polybrominated Diphenyl Ethers and Lipid Composition in Human Breast Milk and Their Correlation with Infant Neurodevelopment

Breastfeeding is recommended over formula feeding, but human breast milk (HBM) composition varies and can be affected by food additives. Whether flame-retardant polybrominated diphenyl ethers (PBDEs) found in HBM interact with lipid components of HBM to impede infant neurodevelopment is a critical public health issue. Using lipidomic analysis, we examined the association of PBDEs in HBM and HBM lipid components with infant neurodevelopment. HBM samples (n = 100) were collected at the beginning stage of breastfeeding and analyzed for 30 PBDE congeners as well as a group of lipid components by using high-resolution gas chromatography, mass spectrometry, and liquid chromatography time-of-flight mass spectrometry. Infants were examined at 8 to 12 months of age by using the Bayley-III to assess neurodevelopment. A total of seven PBDEs, 35 lipids, and 27 fatty acids in HBM showed significant associations with Bayley-III scores. Multivariate analysis confirmed that these candidate PBDEs and lipid components were significant predictors of infant neurodevelopment. Eicosapentaenoic acid and docosapentaenoic acid in HBM showed no association with infant neurodevelopment in the general Taiwanese population. While certain PBDEs may play a role, our findings indicate that the lipid components of HBM are directly important for infant neurodevelopment.

Women with high plasma levels of PBDE-47 are at increased risk of preterm birth

OBJECTIVES

Nearly 100% of North American women have detectable levels of flame retardants such as polybrominated diphenyl ethers (PBDEs) in their plasma. These molecules have structural homology to thyroid hormones and may function as endocrine disruptors. Thyroid dysfunction has previously been associated with increased risk for preterm birth. Therefore, we conducted a multi-center, case-cohort study to evaluate if high plasma concentrations of a common PBDE congener in the first trimester increases the risk of preterm birth and its subtypes.

METHODS

Pregnant women were recruited at the onset of initiation of prenatal care at Kaiser-Permanente Southern California (KPSC)-West Los Angeles and KPSC-San Diego medical centers. Plasma samples from women whose pregnancies ended preterm and random subset of those delivering at term were assayed for PBDE-47 and thyroid-stimulating hormone (TSH) by immunoassay. Quartile cutoffs were calculated for the patients at term and used to determine if women with exposures in the 4th quartile are at increased risk for preterm birth using logistic regression.

RESULTS

We found that high concentrations of PBDE-47 in the first trimester significantly increased the odds of both indicated (adjusted odds ratio, adjOR=2.35, 95% confidence interval [CI]: 1.31, 4.21) and spontaneous (adjOR=1.76, 95% CI: 1.02, 3.03) preterm birth. Regardless of pregnancy outcome, TSH concentrations did not differ between women with high and low concentrations of PBDE-47.

CONCLUSIONS

These results suggest that high plasma concentrations of PBDE-47 in the first trimester, increases the risk of indicated and spontaneous preterm birth.

Polybrominated diphenyl ethers in mothers' breast milk and associated health risk to nursing infants in Uganda

The aim of this study was to investigate levels of polybrominated diphenyl ethers (PBDEs) in breast milk samples from healthy primiparous mothers who had lived in Kampala capital city (urban area) and Nakaseke district (a rural area) for the last five years. Fifty samples were collected between March and June 2018 and were extracted by dispersive solid-phase extraction (SPE). Clean-up was performed on an SPE column and analysis was done using gas chromatography-mass spectrometry. Total (∑) PBDEs (BDE 28, 47, 49, 66, 77, 99, 100,138,153, 154, 183 and 209) ranged from 0.59 to 8.11 ng/g lipid weight (lw). The levels of PBDEs in samples from Kampala capital city were significantly higher than those from Nakaseke (p < 0.01, Mann-Whitney U test). The most dominant congeners were BDE-209 and -47 (contributed 37.1% and 20.2%, respectively to ∑PBDEs), suggesting recent exposure of mothers to deca-and penta-BDE formulations. Fish and egg consumption, plastics/e-waste recycling and paint fumes were associated with higher levels of BDE-47, -153 and -99, respectively, implying that diet and occupation were possible sources of the pollutants. Estimated dietary intakes (ng kg^-1 body weight day^-1) for BDE-47, -99 and -153 were below the US EPA reference doses for neurodevelopmental toxicity, suggesting minimal health risks to nursing infants who feed on the milk. Generally, the risk quotients for BDE-47, -99 and -153 were <1 in majority (96%) samples, indicating that the breast milk of mothers in Uganda was fit for human consumption.

Isoliquiritigenin as an antioxidant phytochemical ameliorates the developmental anomalies of zebrafish induced by 2,2',4,4'-tetrabromodiphenyl ether

2,2',4,4'-Tetrabromodiphenyl ether (BDE47) is the most abundant PBDE congeners in biological samples. It has strong tendencies to bioaccumulate and potentially endangers development of mammals through oxidative stress. Isoliquiritigenin (ISL), an emerging natural chalcone-type flavonoid, possesses various biological and pharmacological properties, including antioxidant, anti-allergic, anti-inflammatory, anti-tumor and estrogenic activities. The purpose of the study is to explore the antioxidant effect of ISL on the amelioration of developmental anomalies induced by BDE47. Zebrafish (Danio rerio) embryos were exposed to BDE47 (1 and 10 μM) and/or ISL (4 μM) for 4 to 120 hours post fertilization (hpf), and the morphology, development, behavior, oxidative stress status and related genes expression were assessed. The results showed that BDE47 contributed to dose-dependent growth retardation and deformities, including delayed hatching, spinal curvature, reduced body length, increased death rate, aberrant behaviors and impaired dark-adapted vision, which were significantly mitigated by ISL. Besides, ISL ameliorated excessive ROS accumulation, and exaggerated the expressions of apoptosis-related genes p53, Bcl-2, caspase 3 and caspase 9 induced by BDE47, suggesting that ISL protected zebrafish from the developmental toxicity of BDE47 by inactivation of programmed apoptosis and activation of antioxidant signaling pathways. Taken together, developing ISL as a dietary supplement might be a promising preventive strategy for the amelioration of developmental toxicity induced by environmental pollutants.

Levels of PCDD/Fs, PBDEs, and PBDD/Fs in Breast Milk from Southern Taiwan

This study investigates the congener-specific concentrations of polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs), polybrominated dibenzo-p-dioxins/furans (PBDD/Fs), and polybrominated diphenyl ethers (PBDEs) in 25 breast milk samples from southern Taiwan. Most investigated congeners in Taiwanese breast milk are detectable except for PBDD/Fs. The geometric means of PCDD/Fs and PBDEs in the breast milk are 2.44 pg WHO₂₀₀₅-TEQ/g lipid and 2810 pg/g lipid. Several PCDD/F and PBDE congeners were highly correlated to each other like 1,2,3,7,8-PeCDD and 2,3,4,7,8-PeCDF (r = 0.919, p < 0.001). The longest duration of menstruation could be predicted by BDE-153 (β = 0.252) and 1,2,3,4,6,7,8-HpCDF (β = 0.345) with adjustment of confounders using a multiple stepwise linear regression model (r = 0.963, p < 0.001).

Distribution of polybrominated diphenyl ethers in breast milk, cord blood and placentas: a systematic review

Polybrominated diphenyl ethers (PBDEs) have been extensively used as flame retardants in consumer products. PBDEs rapidly bioaccumulate in the environment, food, wild animals and humans. In this review, we investigated the harmful effects of PBDEs on humans, especially in early life, and summarised the levels of PBDEs in human biological samples (breast milk, cord blood and placentas). In addition, we described the spatiotemporal distribution of PBDEs in this review. PBDE levels in breast milk, cord blood and placentas were generally higher in North America than in other regions, such as Asia, Europe, Oceania and Africa. However, high levels of PBDEs in human biological samples were detected at e-waste recycling sites in South China, East China and South Korea. This finding suggests that newborns living in e-waste regions are exposed to high levels of PBDEs during prenatal and postnatal periods. The time trends of PBDE concentration differed according to the region. Few studies have investigated PBDE levels in humans from 1967 to 2000, but they increased rapidly after 2000. PBDE concentration peaked at approximately 2006 globally. Compared with other PBDE congeners, BDE-47, BDE-153 and BDE-209 were the major components, but the detection rate of BDE-209 was lower than those of others. Future studies should focus on determining the BDE-209 concentration, which requires the implementation of different analytical approaches. Additionally, the levels of PBDEs in human samples and the environment should be monitored, especially in e-waste recycling regions. Graphical abstract The figures described the spatial distribution of the lowest (Fig. a1) and highest concentration of ∑PBDE (Fig. a2) in different countries by 2006 and described the spatial distribution of the lowest (Fig. b1) and highest concentration of ∑PBDE (Fig. b2) in different countries from 2007 to 2015. All the figures indicated that the levels of PBDEs in North America were substantially higher than those in many regions of Europe, Asia, Oceania, or Africa. Comparing Fig. a1-b1 or Fig. a2-b2, increasing trends were observed in some countries, especially in some regions in China, Korea and Canada.

Distribution of persistent organic pollutants in serum, omental, and parietal adipose tissue of French women with deep infiltrating endometriosis and circulating versus stored ratio as new marker of exposure

Several studies have assessed the potential role of environmental chemicals in the onset, growth, and/or physiopathology of endometriosis. However, their contour in terms of considered exposure markers remains limited. The present study aimed to characterize the internal exposure levels of 78 persistent organic pollutants (POPs, including dioxins, polychlorobiphenyls, brominated flame retardants and organochlorine pesticides) in a set of 113 adult French women (45 controls, 68 cases), and to characterize the distribution of these POPs within three biological compartments (omental adipose tissue, parietal adipose tissue, and serum). For all targeted substances, the correlation between the concentrations measured in omental versus parietal adipose tissue was found strongly significant (p<0.0001). An equivalence of the measures performed in parietal and omental adipose tissue was moreover observed with median levels of 6.4 vs. 7.4pg/gl.w. for WHO-TEQ₂₀₀₅ PCDD/F, 4.5 vs. 4.7pg/gl.w. for WHO-TEQ₂₀₀₅ dl-PCB, 137.1 vs. 147.9ng/gl.w. for sum of 6 ndl-PCB, and 2.1 vs. 2.0ng/gl.w. for sum of 7 i-PBDE, respectively. The same observation was made for individual targeted OCs compounds. Significant correlations were also observed between these concentrations determined in adipose tissue and those measured in serum for dioxins (WHO-TEQ₂₀₀₅ PCDD/F=6.1pg/gl.w), PCBs (WHO-TEQ₂₀₀₅ dl-PCB=3.6pg/gl.w., sum of 6 ndl-PCB=81.1ng/gl.w.), and brominated flame-retardants (sum of 7 i-PBDE=0.9ng/gl.w.). The circulating versus stored ratio of some exposure markers (Sum PCDDs, 1,2,3,6,7,8-HxCDF, slightly versus highly chlorinated PCBs ratio, PBDE 99 and PBB 153) was found statistically different for control and case individuals. These extended exposure data from deep infiltrating endometriosis patients are the first ones available for France and give a new insight about the equilibrium of chemicals between storage and circulating compartments that should be further considered as new marker of exposure in the context of exposure-health relationship studies.

Country-specific chemical signatures of persistent organic pollutants (POPs) in breast milk of French, Danish and Finnish women

The present study compares concentrations and chemical profiles of an extended range of persistent organic pollutants (dioxins, polychlorobiphenyls, brominated flame retardants and organochlorine pesticides) in breast milk samples from French (n = 96), Danish (n = 438) and Finnish (n = 22) women. Median exposure levels observed in French women (WHO-TEQ₂₀₀₅ PCDD/F = 6.1 pg/g l.w., WHO-TEQ₂₀₀₅ dl-PCB = 4.3 pg/g l.w., sum of 6 ndl-PCB = 85.2 ng/g l.w., sum of 7 i-PBDE = 1.5 ng/g l.w.) appeared overall lower than in Danish and Finnish women for all examined POPs, except for α-HBCD (2-fold higher level at 0.6 ng/g l.w.). Furthermore, the observed exposure levels of dioxins and PCBs were higher in Danish women (WHO-TEQ₂₀₀₅ PCDD/F = 13.2 pg/g l.w., WHO-TEQ₂₀₀₅ dl-PCB = 6.6 pg/g l.w., sum of 6 ndl-PCB = 162.8 ng/g l.w.) compared to Finnish women (WHO-TEQ₂₀₀₅ PCDD/F = 9.0 pg/g l.w., WHO-TEQ₂₀₀₅ dl-PCB = 4.6 pg/g l.w., sum of 6 ndl-PCB = 104.0 ng/g l.w.), whereas the concentrations of PBDEs were similar for Danish and Finnish women (sum of 7 i-PBDE = 4.9 and 5.2 ng/g l.w. respectively). The organochlorine (OC) pesticide contamination profile, determined in a subset of French samples, was dominated by p,p'-DDE (56.6%), followed by β-HCH (14.2%), HCB (9.7%) and dieldrin (5.2%), while other compounds were only minor contributors (<5%). The three countries appeared to be discriminated by the observed contamination patterns of the PCDD/F versus PCB, and the 1,2,3,6,7,8-HxCDD versus 1,2,3,4,7,8-HxCDD ratios, in addition to the relative contributions of specific congeners to the contamination profile (PCBs #118 and #156, PBDEs #28, #47, #99 and #153). In conclusion, unique chemical signatures were observed for each country on the basis of some POP congeners. Future biomonitoring studies will need to consider the high variability of individual exposure profiles in relation to multiple exposure sources but also physiological and metabolic differences.

Aberrant 5'-CpG Methylation of Cord Blood TNFα Associated with Maternal Exposure to Polybrominated Diphenyl Ethers

Growing evidence suggests that maternal exposures to endocrine disrupting chemicals during pregnancy may lead to poor pregnancy outcomes and increased fetal susceptibility to adult diseases. Polybrominated diphenyl ethers (PBDEs), which are ubiquitously used flame-retardants, could leach into the environment; and become persistent organic pollutants via bioaccumulation. In the United States, blood PBDE levels in adults range from 30–100 ng/g- lipid but the alarming health concern revolves around children who have reported blood PBDE levels 3 to 9-fold higher than adults. PBDEs disrupt endocrine, immune, reproductive and nervous systems. However, the mechanism underlying its adverse health effect is not fully understood. Epigenetics is a possible biological mechanism underlying maternal exposure-child health outcomes by regulating gene expression without changes in the DNA sequence. We sought to examine the relationship between maternal exposure to environmental PBDEs and promoter methylation of a proinflammatory gene, tumor necrosis factor alpha (TNFα). We measured the maternal blood PBDE levels and cord blood TNFα promoter methylation levels on 46 paired samples of maternal and cord blood from the Boston Birth Cohort (BBC). We showed that decreased cord blood TNFα methylation associated with high maternal PBDE47 exposure. CpG site-specific methylation showed significantly hypomethylation in the girl whose mother has a high blood PBDE47 level. Consistently, decreased TNFα methylation associated with an increase in TNFα protein level in cord blood. In conclusion, our finding provided evidence that in utero exposure to PBDEs may epigenetically reprogram the offspring’s immunological response through promoter methylation of a proinflammatory gene.

Spatial and temporal trends of the Stockholm Convention POPs in mothers' milk -- a global review

Persistent organic pollutants (POPs) have been of environmental and health concern for more than half a century and have their own intergovernmental regulation through the Stockholm Convention, from 2001. One major concern is the nursing child's exposure to POPs, a concern that has led to a very large number of scientific studies on POPs in mothers' milk. The present review is a report on the assessment on worldwide spatial distributions of POPs and of their temporal trends. The data presented herein is a compilation based on scientific publications between 1995 and 2011. It is evident that the concentrations in mothers' milk depend on the use of pesticides and industrial chemicals defined as POPs. Polychlorinated biphenyls (PCBs) and "dioxins" are higher in the more industrialized areas, Europe and Northern America, whereas pesticides are higher in Africa and Asia and polybrominated diphenyl ethers (PBDEs) are reported in higher concentrations in the USA. POPs are consequently distributed to women in all parts of the world and are thus delivered to the nursing child. The review points out several major problems in the reporting of data, which are crucial to enable high quality comparisons. Even though the data set is large, the comparability is hampered by differences in reporting. In conclusion, much more detailed instructions are needed for reporting POPs in mothers' milk. Temporal trend data for POPs in mothers' milk is scarce and is of interest when studying longer time series. The only two countries with long temporal trend studies are Japan and Sweden. In most cases, the trends show decreasing concentrations of POPs in mothers' milk. However, hexabromocyclododecane is showing increasing temporal concentration trends in both Japan and Sweden.

PBDEs and PBBs in human serum and breast milk from cohabiting UK couples

Concentrations of PBDEs and PBBs were measured in matched blood and breast milk samples from 10 UK couples collected in 2011-12. These data are the first measurements in human serum from the UK since the 2004 EU ban on all uses of the penta-and octa-BDE formulations and the 2008 ban on the use of the deca-BDE formulation in some applications. Serum ∑PBDE tri-hepta concentrations ranging from 1.0 to 16 ng g(-1) lipid weight, with median 4.0 ng g(-1) lw were measured. Breast milk ∑PBDE tri-hepta concentrations ranged from 1.3 to 21 ng g(-1) lw, with median 5.7 ng g(-1) lw. Couples had similar serum congener concentrations unless one of them frequently stayed away from home for work (different diet and dust exposures) or one had occupational exposure to foams and furnishings or electronics. BB-153 were measured above LOD in 40% of sera and 100% of breast milks samples, with median concentrations of 0.04 and 0.06, and maximums of 0.91 and 0.79 ng g(-1) lw respectively. Concentrations in this study indicated a modest decrease from pre-ban levels reported for the UK. BDE-209 was detected above the limit of detection (LOD) in 15% of sera and 83% of breast milks, with ranges <1.2-20 and <0.2-1.0 ng g(-1) lw respectively. Average daily infant intakes were estimated at 17, 5, 5 and 3 ng kg(-1) bw for BDE-47,-99,-153 and -209 respectively, all well below relevant US-EPA threshold reference dose values (RfDs).

Polybrominated biphenyl ethers in breast milk and infant formula from Shanghai, China: temporal trends, daily intake, and risk assessment

To investigate the temporal trend of polybrominated diphenyl ethers (PBDEs) in breast milk and assess the risks to breast- and formula-fed infants, breast milk and infant formula samples were collected from Shanghai, China. The PBDE concentrations decreased from 14.8 to 4.85 pmol/g lipid weight during 2006-2012, with a rate of decrease by half approximately every four years. Although there were no significant correlations between the total PBDEs in breast milk and age, parity, and pre-pregnant BMI of mothers, there were significant differences between primiparous and multiparous mothers for tri- to hepta-BDEs. PBDEs in breast milk were much higher than those in infant formula (equivalent to 91.9 vs. 5.25 pg/mL). Among the different brand infant formulas, there were no significant differences in their PBDE concentrations. The estimated daily intake of PBDEs by breast- and formula-fed infants suggested that breast-fed infants are exposed to much more PBDEs than formula-fed ones (12.9 vs. 0.72 ng/kg-bw/day). However, the hazard quotient values were much smaller than one, indicating that the ingested PBDEs did not exert obvious adverse effects on both breast- and formula-fed infants considering non-carcinogenic effect endpoint. This is the first report on temporal trend of PBDEs in breast milk from China.

Polybrominated diphenyl ethers (PBDEs) in breast milk of Korea in 2011: current contamination, time course variation, influencing factors and health risks

Breast milk is a valuable biological specimen to assess maternal and infant exposure to polybrominated diphenyl ethers (PBDEs). In this study, 208 breast milk samples were collected from 89 participants during lactation period, at <7, 15, 30, and 90 days postpartum, in four cities in Korea, and were determined for 19 PBDE congeners. The total PBDE concentrations (ΣPBDE) ranged from 0.23 to 68.4 (mean: 2.73) ng/g lipid weight, and were within the ranges reported for European and Asian countries. Within a month of lactation after delivery, no significant changes were found in the PBDE concentrations. The predominance of BDE 153 rather than BDE 47 was found in the most samples that BDE 153 was detected, and was likely to be associated with stepwise debromination of BDE 209. No associations were found between PBDE concentrations in breast milk and demographic parameters, except for ΣPBDE with maternal age and delivery mode. Certain types of diet such as corn, seafood and nut correlated significantly with PBDE levels in breast milk. The estimated daily intakes of ΣPBDE for breast-feeding infants were lower than the guidelines proposed by the US EPA, indicating limited health risk from PBDEs through breast feeding.

Proposed mechanistic description of dose-dependent BDE-47 urinary elimination in mice using a physiologically based pharmacokinetic model

Polybrominated diphenyl ethers (PBDEs) have been used in a wide variety of consumer applications as additive flame retardants. In North America, scientists have noted continuing increases in the levels of PBDE congeners measured in human serum. Some recent studies have found that PBDEs are associated with adverse health effects in humans, in experimental animals, and wildlife. This laboratory previously demonstrated that urinary elimination of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) is saturable at high doses in mice; however, this dose-dependent urinary elimination has not been observed in adult rats or immature mice. Thus, the primary objective of this study was to examine the mechanism of urinary elimination of BDE-47 in adult mice using a physiologically based pharmacokinetic (PBPK) model. To support this objective, additional laboratory data were collected to evaluate the predictions of the PBPK model using novel information from adult multi-drug resistance 1a/b knockout mice. Using the PBPK model, the roles of mouse major urinary protein (a blood protein carrier) and P-glycoprotein (an apical membrane transporter in proximal tubule cells in the kidneys, brain, intestines, and liver) were investigated in BDE-47 elimination. The resulting model and new data supported the major role of m-MUP in excretion of BDE-47 in the urine of adult mice, and a lesser role of P-gp as a transporter of BDE-47 in mice. This work expands the knowledge of BDE-47 kinetics between species and provides information for determining the relevancy of these data for human risk assessment purposes.

Using whole mount in situ hybridization to examine thyroid hormone deiodinase expression in embryonic and larval zebrafish: a tool for examining OH-BDE toxicity to early life stages

Polybrominated diphenyl ethers (PBDEs) and their oxidative metabolites (hydroxylated PBDEs; OH-BDEs) are known endocrine disrupting contaminants that have been shown to disrupt thyroid hormone regulation both in mammals and in fish. The purpose of this study was to determine the precise organ and tissue locations that express genes critical to thyroid hormone regulation in developing zebrafish (Danio rerio), and to determine the effects of an OH-BDE on their expression. While RT-PCR can provide quantitative data on gene expression, it lacks spatial sensitivity to examine localized gene expression; and, isolation of organs from zebrafish embryos is technically difficult, if not impossible. For this reason, the present study used whole mount in situ hybridization to simultaneously localize and quantify gene expression in vivo. While PBDEs and OH-BDEs have been shown to inhibit the activity and expression of deiodionases, a family of enzymes that regulate thyroid hormone concentrations intracellularly, it is unclear whether or not they can affect regional expression of the different isoforms during early development. In this study we investigated deiodinase 1 (Dio1), deiodinase 2 (Dio2), and deiodinase 3 (Dio3) mRNA expression at the following life stages (2, 8, and 1k-cells; 50%-epiboly, 6 and 18-somites, 22, 24, 48, 72 hpf and/or 10 dpf) in zebrafish and found life stage specific expression of these genes that were highly localized. To demonstrate the use of this technique for investigating potential endocrine disrupting effects, zebrafish embryos were exposed to 1, 10 and 100nM 6-OH-BDE-47. Significant increases in mean intensity of Dio1 and Dio3 expression in the periventricular zone of brain and pronephric duct, respectively (quantified by measuring intensity of coloration using ImageJ analysis software) were observed, suggesting localized response at the HPT axis with the possibility of impacting neurodevelopment. Our results demonstrate effects of OH-BDEs on thyroid regulating gene expression and provide more insight into potential sites of injury during early life stages.

Lactation exposure to BDE-153 damages learning and memory, disrupts spontaneous behavior and induces hippocampus neuron death in adult rats

OBJECTIVE

To study the effects of 2,2',4,4',5,5'-hexa-brominated diphenyl ether (BDE-153) exposure during lactation on the learning and memory abilities, spontaneous behavior and brain cells of adult rats and to elicit basic information on PBDE's developmental neurotoxicity.

METHODS

Newborn male rat pups were randomly categorized into the following groups (15 pups per group), according to their weights and litters: a control group, and 1mg/kg, 5mg/kg and 10mg/kg BDE-153 groups. At postnatal day 10 (PND10), the pups in the BDE-153 groups were intraperitoneally injected once with BDE-153 plant oil solutions at 0.1ml/10g body weight, and the controls were injected with plant oil. Throughout the entire experiment, physiological measures were recorded, such as food and water consumption, body weight and clinical symptoms. At 1 month and 2 months after treatment, the learning and memory abilities of the rats were tested by the Morris water maze test, the step-down test, and the step-through test; spontaneous behavior was tested by the open-field test. After all tests were accomplished, rats were weighed and sacrificed, and the brain tissue was immediately isolated and divided into two parts. Sections were fabricated from one part, and changes in the morphology and ultrastructure in CA3 region of hippocampus were observed under an optical microscope and transmission electron microscope, along with the detection of apoptotic cells with the terminal-deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) method. The tissue of the second part was digested into single-cell suspension liquid, and the cell apoptosis was assayed with flow cytometry and the lactate dehydrogenase (LDH) leakage was detected with spectrophotometry.

RESULTS

There was no obvious change in food and water consumption, body weight and the ratio of brain to body weight, or any overt clinical symptoms in the BDE-153-treated rats. Compared to the control group, rats' latency time in the test session (LT2) in the step-down test was significantly increased in the 10mg/kg BDE-153 group at 2 months after treatment (P<0.05), and the BDE-153-treated rats' swimming times and distances in the target quadrant were significantly decreased at 1 month and 2 months after treatment (P<0.05 or P<0.01). These parameters were also significantly increased in the opposite quadrant at 1 month after treatment (P<0.05 or P<0.01). The spontaneous behavior was significantly reduced in the treated groups compared to the controls (P<0.05 or P<0.01). The severity of neurobehavioral dysfunction was dependent on the exposure dose of BDE-153, and worsened with age. Under an optical microscope, the treated rats' neurons in the CA3 region of the hippocampus were observed to be reduced and disarranged, and the cell junctions were loosened and the intercellular spaces were enlarged. Under a transmission electron microscope, the cell nucleus was observed to shrink; the chromatin was condensed and gathered near the nuclear membrane, the Nissl bodies and other organelles in the perikaryon were reduced, and the vacuole was observed to degenerate and even disappear. Moreover, compared to the controls, the cell apoptosis rates were significantly increased in the 5 and 10mg/kg BDE-153 groups (P<0.05), and the LDH activity was significantly increased in the 10mg/kg BDE-153 groups (P<0.01).

CONCLUSION

Lactation exposure to BDE-153 damaged adult rats' learning and memory abilities, disrupted their spontaneous behavior (hypoactivity) and induced hippocampus neuron apoptosis.

Polybrominated diphenyl ethers, polychlorinated biphenyls, and organochlorine pesticides in adipose tissues of Korean women

Studies on residue levels and accumulation profiles of persistent organic pollutants (POPs) in human adipose tissues of Korean populations are scarce. In this study, concentrations and accumulation features of polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), and polybrominated diphenyl ethers (PBDEs) were measured in adipose tissues of Korean women age 40-68 years. The highest concentrations were found for PCBs and DDTs, which were 1-2 orders of magnitude greater than the concentrations of hexachlorocyclohexanes, chlordanes, and PBDEs. The concentrations of PCBs and OCPs were lower than those reported for other countries. However, PBDE concentrations were greater than those reported for other countries, suggesting that ongoing exposure to PBDEs is a concern in Korea. The profiles of PBDEs were characterized by the predominance of BDE 209, followed by nona- and octa-BDEs, which are consistent with the consumption patterns of products containing PBDEs in Korea. The concentrations of PCBs and some OCPs were significantly correlated with each other, whereas PBDEs showed low or moderate correlations with other POPs, suggesting differences in exposure routes and biotransformation potentials of the compounds studied. The concentrations of organochlorines and PBDEs were not correlated with subjects' age and body mass index. The results of this study provide baseline information on POPs in adipose tissues of the general population in Korea.

Neurodevelopment of infants with prenatal exposure to polybrominated diphenyl ethers

The study aimed to examine the impact of prenatal exposure to polybrominated diphenyl ethers (PBDEs) on infant neurodevelopment. PBDEs levels in 36 cord blood samples were analyzed with a high-resolution-gas-chromatograph/high-resolution-mass-spectrometer and infant neurodevelopment was assessed using the Bayley Scales of Infant and Toddler Development, Third Edition. The mean and median of Σ(11)PBDEs were 6.63 and 4.63 ng/g lipid, respectively. As compared to the lower PBDEs group (Σ(11)PBDEs < 4.63 ng/g lipid), the higher PBDEs group (Σ(11)PBDEs > 4.63 ng/g lipid) had a significantly higher actual odds ratio (OR = 1.13, p < 0.05) of the cognition score as well as a lower odds ratio (OR = 0.904, p < 0.01) of the adaptive behavior score, suggesting that prenatal PBDEs exposure may potentially affect infant neurodevelopment.

Levels of breast milk PBDEs from southern Taiwan and their potential impact on neurodevelopment

In vivo studies have demonstrated that prenatal or neonatal exposure to polybrominated diphenyl ethers (PBDEs) causes developmental neurotoxicity. However, there is a lack of human data. Our hypothesis was that PBDEs would result in lower infant neurodevelopment scores. This is a post hoc analysis of previous studies. Fourteen PBDEs in 70 breast milk were analyzed using a high-resolution gas chromatograph/high-resolution mass spectrometer. Infant neurodevelopment at the age of 8-12 mo was determined using the Bayley Scales of Infants and Toddlers Development, third edition (Bayley-III). The median of Σ14 PBDEs (the sum of 14 PBDE congeners) was 2.92 ng/g lipid. The Σ14 PBDE concentrations were not correlated with Bayley-III scores on cognitive, language, motor, social-emotional, or adaptive behavior scales. A significantly inverse association between brominated diphenyl ether (BDE)-209 and the cognitive scale was found after multivariate stepwise linear regression analyses (B = -0.007, adjusted R = -0.224, p = 0.032). In contrast, the language scale was positively correlated with BDE-196 (B = 0.096, adjusted R = 0.315, p = 0.002). Our results are consistent with most in vivo studies, suggesting that prenatal or postnatal exposure to BDE-209 potentially delays the neurological development.

Cord blood levels of thyroid hormones and IGF-1 weakly correlate with breast milk levels of PBDEs in Taiwan

In vivo studies indicate that prenatal or neonatal exposure of rodents to polybrominated diphenyl ethers (PBDEs) disrupts thyroid hormone balance, but few studies have reported an association of PBDEs and insulin-like growth factor 1 (IGF-1). The goal was to examine whether PBDEs exposure affects the levels of thyroid hormones and IGF-1 in cord blood. Study participants were healthy pregnant women recruited from the general population in central Taiwan between 2000 and 2001 and in southern Taiwan from 2007 to 2009. One-hundred-forty-nine breast milk samples (n=149), which were collected within one month after delivery, were analyzed using a high resolution gas chromatograph equipped with a high resolution mass spectrometer. The average and median levels of breast milk Σ(14)PBDEs were 5.34 and 3.38 ng/g lipid in 2000-2001 and 5.22 and 3.13 ng/g lipid in 2007-2009, respectively. In general, levels of PBDE congeners were very low in this study population and not significantly different between the years 2000-2001 and 2007-2009. Breast milk Σ(14)PBDEs were not significantly correlated with thyroid hormones and IGF-1 in cord blood. After examining multiple stepwise linear regression models with adjustment for maternal age, pre-pregnancy body mass index (BMI), parity, gestational age, and region (namely, central and southern Taiwan), we found that log of T4 in cord blood was significantly but slightly correlated with higher BDE-154 (B=0.113, p=0.017) in breast milk. The log of FT4 concentration was significantly related to a decrease in the log of BDE-99 level (B=-0.137, p=0.043) and an increase in the log of BDE-154 level (B=0.158, p=0.008). Meanwhile, the log of IGF-1 level was also significantly linked to an increase in the log of BDE-196 level (B=0.532, p=0.028) and decrease in the log of BDE-85 level (B=-0.235, p=0.018). Few epidemiological studies report an association between PBDEs exposure and IGF-1. Based on our findings, further in vivo and epidemiological studies are encouraged and needed to explore associations between PBDEs exposure and levels of thyroid hormones and IGF-1.

Negative associations between PBDE levels and thyroid hormones in cord blood

Polybrominated diphenyl ethers (PBDEs) causing thyroidal effects have been demonstrated in in vivo and in vitro studies. PBDEs with structural similarities to thyroid hormones have increased recently, but the health effects for thyroid hormones have not been well studied. The study aimed to determine PBDE levels in cord blood and further to explore associations between prenatal PBDE exposures and thyroid hormones in cord blood. Fifty-four cord blood samples were collected after delivery. Cord-blood levels of BDE-15, 28, 47, 99, 100, 153, 154, and 183 were analyzed using a high resolution gas chromatograph with a high resolution mass spectrometer. Thyroid hormones were determined by an automated chemiluminescence analyzer. The mean, median, and standard deviation of ΣPBDEs were 4.72, 3.49, and 6.36 ng/g lipid, respectively. To adjust for confounding by maternal age, pre-pregnant BMI and gestational age, stepwise multiple linear regression was used after log(2) transformation of the exposure variables. A doubling of BDE-154 was associated with 0.043 ng/mL lower triiodothyronine (T3) values (adjusted r=-0.245, p=0.043). Likewise a doubling of BDE-153 was associated with 0.143 ng/mL lower free T3 (FT3) values and a doubling of BDE-183 with 0.084 ng/mL lower FT3 values (adjusted r=-0.487, p=0.023). In contrast, the T4 (thyroxine)/T3 ratio increased by 4.93 (adjusted r=0.277, p=0.017) when doubling BDE-100 exposure. No significant associations with BDE-47 or any other of the PBDEs was found. Our findings of an inverse relationship between BDE-153, BDE-154 or BDE-184 and thyroid hormones confirm the results of animal experiments but are in contrast to most epidemiological studies.

Impact of non-occupational exposure to polybrominated diphenyl ethers on menstruation characteristics of reproductive-age females

Polybrominated diphenyl ethers (PBDEs) have documented effects on thyroid functions and rodent behavior in vivo. Epidemiological studies, however, have revealed only limited information about associations between PBDE exposure and menstruation characteristics. Our goal was to examine whether high breast milk PBDE levels in reproductive-age females lead to interference with menstruation characteristics. We analyzed 15 PBDE congeners in 46 breast milk samples. Fifteen PBDE congeners (BDE-15, 28, 47, 49, 99, 100, 153, 154, 183, 196, 197, 203, 207, 208, and 209) were analyzed using a gas chromatograph equipped with a high resolution mass spectrometer. The mean sum of PBDEs (SigmaPBDEs) in breast milk was 3.42 ng/g lipid. Women's age at menarche was not correlated with breast milk PBDE levels. Increased BDE-208 and 209 levels were significantly associated with the prolonged length of average and the longest menstrual cycle independent of age, pre-pregnant BMI, and parity. Higher concentrations of SigmaPBDEs and the higher brominated PBDEs from BDE-183 to 209, except 197, were significantly linked to women whose menstruation periods were still coming irregularly at the sampling time. Age-adjusted odds ratios (ORs) of BDE-153, 183, 207, 208, and SigmaPBDEs were significantly higher in women with length of average menstrual cycle >32 days, compared to the control. Women whose menstruation periods still came irregularly when they were 18 years old had higher age-adjusted ORs of BDE-207, 208, 209, and SigmaPBDEs than those whose periods came regularly at the same age. Although SigmaPBDEs and certain higher brominated PBDEs appear to have potential to prolong length of average menstrual cycle and delay the age when menstruation periods begin coming regularly, these findings are not conclusive because our sample size is small and more scientific evidence is needed.