Polybrominated diphenyl ethers and bromophenols in paired serum, hair, and urine samples of e-waste dismantlers: Insights into hair as an indicator of endogenous exposure

Polybrominated diphenyl ether flame retardants inhibit growth factor-induced activation of EGFR by binding to its extracellular domain

For many years, polybrominated diphenyl ethers (PBDEs) were used as flame retardants in a large number of consumer products. Even though international law meanwhile prohibits the production and usage of PBDEs, these persistent and bioaccumulative chemicals still leak into the environment, and are frequently detected in wildlife and humans. Population-based studies reveal positive correlations between human PBDE exposure and various adverse health effects, emphasizing that a better understanding of the mode of action of these polybrominated chemicals is urgently needed. Therefore, we investigated the effect of two widespread PBDEs, namely BDE-47 and BDE-99, on epidermal growth factor receptor (EGFR) activity in human cells. Recent studies showed that the EGFR is not only orchestrating cellular functions, but also serves as a cell-surface receptor for dioxins, phenolic benzotriazoles and related organic pollutants. Results from in silico docking analyses, AlphaLISA-based receptor binding studies and SDS-PAGE/Western blot analyses revealed that BDE-47 and BDE-99 inhibit the growth factor-triggered activation of EGFR by binding to its extracellular domain. In keratinocytes, PBDEs also inhibit amphiregulin-induced and EGFR-mediated DNA synthesis as well as the EGFR-triggered trans-repression of the aryl hydrocarbon receptor signaling pathway. Our data identify EGFR as a cell-surface receptor for PBDEs and shed light on a novel mode of action of these ubiquitous and persistent chemicals. This finding may contribute to an improved hazard assessment of PBDEs and structurally related flame retardants.

Comprehensive analysis, comprehensive understanding: The benefit of widening the scope to uncover the complexity of human chemical exposome and tailor personalized risk assessment

While biomonitoring approaches are frequently employed for assessing chemical exposure, many of them are constrained to a limited number of target chemicals, running counter to our current understanding of interactions within chemical mixtures and the growing evidence of multiple exposures within human populations. Although authors agree on the need for more comprehensive methodologies, literature provides insufficient evidence of the multifaceted nature of exposure and of the benefit of widening the analytical scope to improve exposure assessment. Moreover, although multiple exposures are generally admitted, very few are known on the scale of the human chemical exposome. Here, we illustrate how increasing the number of chemicals possibly captured improves the information on exposure. Through a literature review centered on studies utilizing hair analysis to assess exposure to anthropogenic organic pollutants, we provide here the first demonstration of how expanding the number of compounds analyzed in biomonitoring methods enhances our understanding of the chemical exposome. The results not only underscore the prevalence of multiple exposures but also reveal distinct exposure patterns within various demographic groups. Utilizing extrapolated biomonitoring data, we introduce a novel approach to estimate the number of chemicals to which humans can be simultaneously exposed. This biomonitoring-based approach is the first one relying on data derived from human samples rather than indirect metrics such as sales figures or registered chemicals. Eventually, we draw upon results from studies conducted in our team to illustrate local specificities in exposure among different populations, emphasizing the complexity of risk assessment while implemented in prevention strategies.

Study on association between human plasma polybrominated diphenyl ethers (PBDEs) and thyroid homeostasis and carcinoma

Polybrominated diphenyl ethers (PBDEs), a category of persistent organic pollutants (POPs), are ubiquitous in the environment and have been reported to have endocrine-disrupting and tumor-promoting activities. However, the evidence for the correlation between plasma PBDEs levels, thyroid homeostasis and thyroid carcinoma in humans remains limited. Herein, we analyzed eight PBDE congeners in 53 patients undergoing thyroid surgery. BDE-209 was identified as the most abundant PBDE congener in plasma (median, 11.36 ng/g lipid). BDE-100 concentration was positively associated with free triiodothyronine (FT3), indicating a potential interference with thyroid function. Point-biserial correlation analysis revealed positive associations between certain plasma PBDE congeners (BDE-28, BDE-47, BDE-99, BDE-100, and BDE-154) and aggressive pathological parameters. There was no significant correlation between PBDEs and BRAF or RAS mutations in PTC patients, indicating that PBDEs may not directly promote the initiation and progression of thyroid cancer through these genetic mutations. It implies the complexity of the relationship between PBDEs exposure and thyroid cancer development. Although not statistically significant, Bayesian kernel-machine regression (BKMR) analysis of single-exposure effects model found that BDE-47 and BDE-99 were positively associated with the risk of malignant neoplasms. The present study not only contributes to the growing evidence regarding the impact of PBDEs on thyroid function but also provides new insights into the association between exposure to certain PBDE congeners and the aggressive pathological parameters of thyroid cancer. Large-scale prospective studies are still needed to support our findings.

Update of the risk assessment of brominated phenols and their derivatives in food

The European Commission asked EFSA to update its 2012 risk assessment on brominated phenols and their derivatives in food, focusing on five bromophenols and one derivative: 2,4,6-tribromophenol (2,4,6-TBP), 2,4-dibromophenol (2,4-DBP), 4-bromophenol (4-BP), 2,6-dibromophenol (2,6-DBP), tetrabrominated bisphenol S (TBBPS), tetrabromobisphenol S bismethyl ether (TBBPS-BME). Based on the overall evidence, the CONTAM Panel considered in vivo genotoxicity of 2,4,6-TBP to be unlikely. Effects in liver and kidney were considered as the critical effects of 2,4,6-tribromophenol (2,4,6-TBP) in studies in rats. A BMDL10 of 353 mg/kg body weight (bw) per day for kidney papillary necrosis in male rats was identified and was selected as the reference point for the risk characterisation. The derivation of a health-based guidance value was not considered appropriate due to major limitations in the toxicological database. Instead, the margin of exposure (MOE) approach was applied to assess possible health concerns. Around 78,200 analytical results for 2,4,6-TBP in food were used to estimate dietary exposure for the European population. Considering the resulting MOE values, all far above an MOE of 6000 that does not raise a health concern, and accounting for the uncertainties affecting the exposure and hazard assessments, the CONTAM Panel concluded with at least 95% probability that the current dietary exposure to 2,4,6-TBP does not raise a health concern. Due to lack of occurrence data, no risk assessment could be performed for breastfed or formula-fed infants. No risk characterisation could be performed for any of the other brominated phenols and derivatives included in the assessment, due to lack of data both on the toxicity and occurrence.

In-situ acetylation followed by liquid-liquid extraction and gas chromatography - mass spectrometry for the determination of bromophenols in urine

A novel and simple method combining in-situ acetylation, liquid-liquid extraction and gas chromatography-mass spectrometry (GC-MS) has been developed for the quantification of 10 bromophenols in urine, used as biomarkers of exposure to polybrominated diphenyl ethers. The analytical process involves an enzymatic hydrolysis of the bromophenol glucuronide fraction followed by an aqueous derivatization of the phenol group with acetic anhydride. A subsequent liquid-liquid extraction of the sample with hexane allows the injection of the organic layer, using a programmed temperature vaporizer, into a gas chromatograph coupled to a single quadrupole mass spectrometer. Quantification is performed by the standard addition method. Limits of detection are in the pg mL-1 range. Trueness, assessed in terms of percentages of recovery, varies between 100 % and 118 % in synthetic urine and between 79 % and 117 % in human urine. Precision, assessed at two different levels, 0.25 ng mL-1 and 2.5 ng mL-1, shows values of relative standard deviation below 14 % both in intra- and inter-day studies for both matrices. The method has been applied to the analysis of seven urine samples, measuring concentrations higher than the LOQ in three of them. These levels are in agreement with others found in literature, but they have been obtained by applying a much simpler and faster protocol. In addition, the replacement of silylating reagents by acetic anhydride, to derivatize the phenol moiety, provides a greener alternative to other GC-MS procedures published up to date.

A meta-analysis highlighting the increasing relevance of the hair matrix in exposure assessment to organic pollutants

Owing to a wide range of advantages, such as stability, non-invasiveness, and ease of sampling, hair has been used progressively for comprehensive biomonitoring of organic pollutants for the last three decades. This has led to the development of new analytical and multi-class analysis methods for the assessment of a broad range of organic pollutants in various population groups, ranging from small-scale studies to advanced studies with a large number of participants based on different exposure settings. This meta-analysis summarizes the existing literature on the assessment of organic pollutants in hair in terms of residue levels, the correlation of hair residue levels with those of other biological matrices and socio-demographic factors, the reliability of hair versus other biomatrices for exposure assessment, the use of segmental hair analysis for chronic exposure evaluation and the effect of external contamination on hair residue levels. Significantly high concentrations of organic pollutants such as pesticides, flame retardants, polychlorinated biphenyls and polycyclic aromatic hydrocarbon were reported in human hair samples from different regions and under different exposure settings. Similarly, high concentrations of pesticides (from agricultural activities), flame retardants (E-waste dismantling activities), dioxins and furans were observed in various occupational settings. Moreover, significant correlations (p < 0.05) for hair and blood concentrations were observed in majority of studies featuring pesticides and flame retardants. While among sociodemographic factors, gender and age significantly affected the hair concentrations in females and children in general exposure settings, whereas adult workers in occupational settings. Furthermore, the assessment of the hair burden of persistent organic pollutants in domestic and wild animals showed high concentrations for pesticides such as HCHs and DDTs whereas the laboratory-based studies using animals demonstrated strong correlations between exposure dose, exposure duration, and measured organic pollutant levels, mainly for chlorpyrifos, diazinon, terbuthylazine, aldrin, dieldrin and pyrethroid metabolites. Considering the critical analysis of the results obtained from literature review, hair is regarded as a reliable matrix for organic pollutant assessment; however, some limitations, as discussed in this review, need to be overcome to reinforce the status of hair as a suitable matrix for exposure assessment.

Polybrominated diphenyl ethers in dust, hair and urine: Exposure, excretion

Polybrominated diphenyl ethers (PBDEs) have been detected in various environmental media and human tissues. PBDEs concentrations in dust from college buildings and homes and in paired hair and urine samples from students were determined. This is of great significance to explore the accumulation and excretion patterns of PBDEs in the human body. The median PBDEs concentrations in the dust (College: 84.59 ng/g; Home: 170.32 ng/g) and hair (undergraduate: 6.16 ng/g; Home: 3.25 ng/g) samples were generally lower than were found in the majority of previous studies. The PBDEs concentrations in the hair and urine samples were subjected to principal component analysis, and the results combined with the PBDEs detection rates confirmed that hair is a useful non-invasive sampling medium for assessing PBDEs exposure and the risks posed. Body mass indices (BMIs) were used to divide students who had not been exposed to large amounts of PBDEs into groups. Body fat percentage is an important factor affecting the accumulation of PBDE in the human body. Environmental factors were found to affect the PBDEs concentrations in the hair and urine samples less for normal-weight students (BMI≤24) than overweight students (BMI>24). Short-term environmental changes to more readily affect the PBDEs concentrations in the tissues of the normal-weight than overweight students. PBDEs with seven or more bromine substituents were found not to be readily excreted in urine. Performing molecular docking simulations of the binding of isomers BDE-99 and BDE-100 to megalin. The binding energy was higher for BDE-100 and megalin than for BDE-99 and megalin, meaning BDE-99 would be more readily excreted than BDE-100.

BDE-47 induces metabolic dysfunction-associated steatotic liver disease (MASLD) through CD36-mediated increased fatty acid uptake and PPARα-induced abnormal fatty acid oxidation in BALB/c mice

The widespread existence of 2,2',4,4'-tetra-bromodiphenyl ether (BDE-47) in the environment has aroused great concern. BDE-47 induces the occurrence of metabolic dysfunction-associated steatotic liver disease (MASLD), but the mechanism has not been fully elucidated. Here, we further investigate the underlying mechanism using BALB/c mice. After BDE-47 exposure, the livers of mice enlarged, the serum levels of ALT, ALP, TG and TC enhanced, and hepatic steatosis occurred. Transcriptome sequencing identifies 2250 differentially expressed genes (DEGs). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis reveals that down-regulated DEGs are mainly enriched in pathways associated with lipid metabolism, particularly in fatty acid (FA) degradation. And up-regulated DEGs are mainly enriched in pathways related to lipid and FA transport. The expression levels of AhR, Pparγ and Cd36 involved in FA uptake are up-regulated, and those of PPARα and target genes including Cpt1 and Cyp4a1 related to β and ω-oxidation are inhibited. These results reveal BDE-47 could lead to metabolic dysfunction-associated steatotic liver disease (MASLD) by promoting FA uptake via upregulating Cd36 and hindering oxidative utilization by downregulating PPARα.

Distribution of phthalate metabolites, benzophenone-type ultraviolet filters, parabens, triclosan and triclocarban in paired human hair, nail and urine samples

In this study, the distribution of nineteen ingredients of personal care product (PCPs), including seven metabolites of phthalates (mPAEs), five benzophenone-type ultraviolet filters (BPs), and seven antimicrobial agents (AAs), were investigated in paired human hair, nail and urine samples. The median concentrations of ΣmPAEs, ΣBPs and ΣAAs were 135, 2.76 and 179 ng/g in hair, 37.3, 2.95 and 297 ng/g in nails, and 345, 4.03 and 50.1 ng/mL in urine, respectively. Mono-methyl phthalate (49%), 2,4-dihydroxybenzophenone (45%) and triclosan (71%) were the most abundant mPAE, BP and AA in hair samples, respectively, and had similar abundance in nail samples. In contrast, mono-n-butyl phthalate (45%), 4-hydroxy benzophenone (29%) and methyl paraben (54%) were the predominant mPAE, BP and AA in urine samples, respectively. Significant differences in the concentrations of some target compounds were observed between male and female but inconsistent across different matrices. Moreover, most compounds with significant correlations had quite different correlation coefficients in each matrix. No significant correlations were found between hair, nail and urine samples for most of the target analytes. These results suggest these analytes have matrix-specific distribution, and it is necessary to use multiple matrices to comprehensively assess the risk of ingredients of PCPs to human health.