The occurrence of polybrominated diphenyl ether (PBDE) contamination in soil, water/sediment, and air

Cuproptosis is involved in decabromodiphenyl ether-induced ovarian dysfunction and the protective effect of melatonin

Decabromodiphenyl ether (BDE-209) has been universally detected in environmental media and animals, but its damage to ovarian function and mechanism is still unclear, and melatonin has been shown to improve mammalian ovarian function. This study aimed to investigate the toxic effects of BDE-209 on the ovary and tried to improve ovarian function with melatonin. Herein, BDE-209 was administered orally to female SD rats for 60 days. Enzyme-linked immunosorbent assay, HE staining, transcriptome analysis, qPCR and immunohistochemical staining were used to explore and verify the potential mechanism. We found that BDE-209 exposure had effects on the ovary, as shown by abnormal changes in the estrous cycle, hormone levels and ovarian reserve function in rats, while increasing the proportion of collagen fibres in ovarian tissue. In terms of mechanism, cuproptosis, a form of cell death, was identified to play a crucial role in BDE-209-induced ovarian dysfunction, with the phenotype manifested as copper salt accumulation in ovary, downregulation of glutathione pathway metabolism and copper transfer molecule (ATP7A/B), and upregulation of FDX1, lipoic acid pathway (LIAS, LIPT1), pyruvate dehydrogenase complex components (DLAT, PDHB, PDHA1), and copper transfer molecule (SLC31A1). Furthermore, possible interventions were explored. Notably, a supplement with melatonin has a repair effect on the damage to ovarian function by reversing the gene expression of cuproptosis-involved molecules. Overall, this study revealed that cuproptosis is involved in BDE-209-induced ovarian damage and the beneficial effect of melatonin on ovarian copper damage, providing evidence for the prevention and control of female reproductive damage induced by BDE-209.

Halogenated aromatic pollutants in routine animal-derived food of south China: Occurrence, sources, and dietary intake risks

Halogenated aromatic pollutants (HAPs) including polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs), polychlorinated biphenyls (PCBs), polybrominated dibenzo-p-dioxins/furans (PBDD/Fs), and polybrominated diphenyl ethers (PBDEs) exhibit diverse toxicities and bio-accumulation in animals, thereby imposing risks on human via animal-derived food (ADF) consumption. Here we examined these HAPs in routine ADFs from South China and observed that PBDEs and PCBs showed statistically higher concentrations than PCDD/Fs and PBDD/Fs. PCDD/Fs and PCBs in these ADFs were mainly from the polluted feed and habitat of animals, except PCDD/Fs in egg, which additionally underwent selective biotransformation/progeny transfer after the maternal intake of PCDD/F-polluted stuff. PBDEs and PBDD/Fs were mostly derived from the extensive use of deca-BDE and their polluted environments. Significant interspecific differences were mainly observed for DL-PCBs and partly for PBDD/Fs and PBDEs, which might be caused by their distinct transferability/biodegradability in animals and the different living habit and habitat of animals. The dietary intake doses (DIDs) of these HAPs via ADF consumption were all highest for toddlers, then teenagers and adults. Milk, egg, and fish contributed most to the DIDs and risks for toddlers and teenagers, which results of several cities exceeded the recommended thresholds and illustrated noteworthy risks. Pork, fish, and egg were the top three risk contributors for adults, which carcinogenic and non-carcinogenic risks were both acceptable. Notably, PBDD/Fs showed the lowest concentrations but highest contributions to the total risks of these HAPs, thereby meriting continuous attention.

Uptake and translocation of brominated flame retardants in tomato plants (Solanum lycopersicum L.): Results from a standard soil-based biotest

The uptake and translocation of four polybrominated diphenyl ethers (PBDEs) and four novel brominated flame retardants (NBFRs) in tomato plants (Solanum lycopersicum L.) were investigated via the RHIZOtest, a standard soil-based biotest, optimized for organic compounds. Tomato plants were exposed to soil samples spiked with 0 (i.e. control), 5.00 or 50.00 ng g-1dw of each compound. Compared of those of the control, exposure to increasing spiking concentrations resulted in average reductions of 13% and 26% (w/w) in tomato plant biomass. Higher concentrations of NBFRs were analyzed both in roots, ranging from 0.23 to 8.01 ng g-1dw for PBDEs and from 1.25 to 18.51 ng g-1dw for NBFRs, and in shoots, ranging from 0.09 to 5.58 ng g-1dw and from 0.47 to 7.78 ng g-1dw for PBDEs and NBFRs, respectively. This corresponded to an average soil uptake of 5% for PBDEs and 9% for NBFRs at the lower soil-spiking level, and 3% for PBDEs and 6% for NBFRs at the higher soil spiking level. Consequently, among both initial spiking levels, the soil-root concentration factor (RCF) values were lower on average for PBDEs (0.13 ± 0.05 g dw soil g-1dw roots) than for NBFRs (0.33 ± 0.16 g dw soil g-1dw roots). Conversely, nondifferent values of the root-shoot transfer factor (TF) were calculated for both PBDEs (0.54 ± 0.13 g dw roots g-1dw shoots) and NBFRs (0.49 ± 0.24 g dw roots g-1dw shoots). The differences and similarities reported in the RCF and TF between and within the two groups of compounds can be explained by their properties. The calculated RCF and TF values of the PBDEs exhibited a decreasing trend as the number of bromine atoms increased. Additionally, a robust negative linear correlation was observed between RCF values and the respective logKow values for the PBDEs, at both soil-spiking levels. The root uptake of NBFRs exhibited a negative correlation with their hydrophobicity; however, this was not observed in the context of root-to-shoot transfer. The presence of a second aromatic ring appears to be the key factor influencing the observed variations in NBFRs, with biphenyl NBFRs (BTBPE and DBDPE) characterized by lower uptake and reduced translocation potential than monophenyl PBEB and HBB. Understanding the transfer of these compounds to crops, especially near plastic recycling waste sites, is crucial for understanding the risks of their potential inclusion in the human food chain.

Exposure to Polybrominated Diphenyl Ethers and Risk of All-Cause and Cause-Specific Mortality

Importance

Polybrominated diphenyl ethers (PBDEs) are an important group of persistent organic pollutants with endocrine-disrupting properties. However, prospective cohort studies regarding the association of PBDE exposure with long-term health outcomes, particularly mortality, are lacking.

Objective

To examine the association of environmental exposure to PBDEs with risk of all-cause and cause-specific mortality.

Design, Setting, and Participants

This nationally representative cohort study used data from the National Health and Nutrition Examination Survey 2003 to 2004 and linked mortality information through December 31, 2019. Adults aged 20 years or older with available data on PBDE measurements and mortality were included. Statistical analysis was performed from February 2022 to April 2023.

Exposures

PBDE analytes in serum samples were measured using solid phase extraction and isotope dilution gas chromatography high-resolution mass spectrometry.

Main Outcomes and Measures

All-cause mortality, cancer mortality, and cardiovascular mortality.

Results

This study included 1100 participants (mean [SE] age, 42.9 [0.6] years; proportion [SE] female, 51.8% [1.6%]; proportion [SE] Hispanic, 12.9% [2.7%]; proportion [SE] non-Hispanic Black, 10.5% [1.6%]; proportion [SE] non-Hispanic White, 70.8% [3.7%]; proportion [SE] other race and ethnicity, 5.8% [1.1%]). During 16 162 person-years of follow-up (median [IQR] follow-up, 15.8 [15.2-16.3] years; maximum follow-up, 17 years), 199 deaths occurred. Participants with higher serum PBDE levels were at higher risk for death. After adjustment for age, sex, and race and ethnicity, lifestyle and socioeconomic factors, and body mass index, participants with the highest tertile of serum PBDE levels had an approximately 300% increased risk of cancer mortality (HR, 4.09 [95% CI, 1.71-9.79]) compared with those with the lowest tertile of serum PBDE levels. No significant association of PBDE exposure with all-cause mortality (HR, 1.43 [95% CI, 0.98-2.07]) or cardiovascular mortality (HR, 0.92 [95% CI, 0.41-2.08]) was observed.

Conclusions and Relevance

In this nationally representative cohort study, PBDE exposure was significantly associated with an increased risk of cancer mortality. Further studies are needed to replicate the findings and determine the underlying mechanisms.

Distribution and adsorption-desorption of organophosphate esters from land to sea in the sediments of the Beibu Gulf, South China Sea: Impact of seagoing river input

Organophosphate esters (OPEs) have been a class of emerging environmental contaminants. However, studies on their environmental behavior, specifically their adsorption-desorption behavior between sediment and seawater in estuarine and coastal areas, remain limited. To address this gap, our study focused on investigating the levels and behavior of 11 OPEs in sediment samples collected from the Beibu Gulf, South China Sea, encompassing estuaries and coastal regions. The total concentrations of 11 OPEs (Σ11OPEs) in the sediments exhibit a significant decrease in summer, both in seagoing rivers (4.67 ± 2.74 ng/g dw) and the coastal zone (5.11 ± 3.71 ng/g dw), compared to winter levels in seagoing rivers (8.26 ± 4.70 ng/g dw) and the coastal zone (7.71 ± 3.83 ng/g dw). Chlorinated OPEs dominated the sediments, constituting 63 %-76 % of the total. Particularly, port and mariculture areas showed the highest levels of OPEs. Through load estimation analysis, it was revealed that the sedimentary OPEs in Qinzhou Bay (221 ± 128 kg) had the highest load, with input from the Qin River identified as a significant source. Chlorinated OPEs showed a trend of desorption from sediments to the water column with increasing salinity, emphasizing the crucial role of land-based OPEs input through suspended particulate matter in rivers as a pathway to the ocean. The impact of strong flow in estuarine environments was highlighted, as it can scour sediments, generate suspended sediments, and release OPEs into the water bodies. Additionally, the results of the ecological risk assessment indicated that most of the OPEs posed low-risk levels. However, attention is warranted for the contamination levels of some chlorinated OPEs, emphasizing the need for ongoing monitoring and assessment.

The impact of brominated flame retardants (BFRs) on pulmonary function in US adults: a cross-sectional study based on NHANES (2007-2012)

Brominated flame retardants (BFRs) are a group of chemicals widely used in various applications to prevent or slow down the spread of fire. However, they have adverse effects on human health. There is a relative scarcity of population-based studies regarding BFRs, particularly their impact on the respiratory system. This study aimed to investigate the influence of BFRs on pulmonary function using data from the National Health and Nutrition Examination Survey. The study found that elevated serum concentrations of certain BFRs were associated with pulmonary ventilatory dysfunction. Adjusted analyses revealed positive correlations between PBDE47, PBDE183, and PBDE209 concentrations and ventilatory dysfunction. The analysis of mixed BFRs showed a positive relationship with pulmonary ventilation dysfunction, with PBDE47 making the most significant contribution. Our study demonstrates that both individual and combined BFRs exposure can lead to impaired pulmonary ventilation function. These findings provide evidence of the adverse effects of BFRs on lung function, emphasizing the importance of further investigating the potential health consequences of these compounds. Further large-scale longitudinal studies are needed to investigate this relationship in the future.

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.

Disclosing phototransformation mechanisms of decabromodiphenyl ether (BDE-209) in different media by simulated sunlight: Implication by compound-specific stable isotope analysis

As one of the typical brominated flame retardants, decabromodiphenyl ether (BDE-209) has been widely detected in environment. However, scarce information was available on BDE-209 phototransformation mechanisms in various media. In this study, compound-specific stable isotope analysis was first applied to investigate BDE-209 phototransformation in n-hexane, MeOH:H2O (v:v, 8:2), and simulated seawater by simulated sunlight. BDE-209 transformation followed pseudo-first-order kinetic, with degradation rate in the following of n-hexane (2.66 × 10-3 min-1) > simulated seawater (1.83 × 10-3 min-1) > MeOH:H2O (1.41 × 10-3 min-1). Pronounced carbon isotope fractionation was first observed for BDE-209 phototransformation, with carbon isotope enrichment factors (εC) of -1.01 ± 0.14‰, -1.77 ± 0.26‰, -2.94 ± 0.38‰ in n-hexane, MeOH:H2O and simulated seawater, respectively. Combination analysis of products and stable carbon isotope, debromination with cleavage of C-Br bonds as rate-limiting step was the main mechanism for BDE-209 phototransformation in n-hexane, debromination and hydroxylation with cleavage of C-Br bonds as rate-limiting steps in MeOH:H2O, and debromination, hydroxylation and chlorination in simulated seawater. This present study confirmed that stable carbon isotope analysis was a robust method to discovery the underlying phototransformation mechanisms of BDE-209 in various solutions.

20 years of polybrominated diphenyl ethers on toxicity assessments

Polybrominated diphenyl ethers (PBDEs) serve as brominated flame retardants which continue to receive considerable attention because of their persistence, bioaccumulation, and potential toxicity. Although PBDEs have been restricted and phased out, large amounts of commercial products containing PBDEs are still in use and discarded annually. Consequently, PBDEs added to products can be released into our surrounding environments, particularly in aquatic systems, thus posing great risks to human health. Many studies and reviews have described the possible toxic effects of PBDEs, while few studies have comprehensively summarized and analyzed the global trends of their toxicity assessment. Therefore, this study utilizes bibliometrics to evaluate the worldwide scientific output of PBDE toxicity and analyze the hotspots and future trends of this field. Firstly, the basic information including the most contributing countries/institutions, journals, co-citations, influential authors, and keywords involved in PBDE toxicity assessment will be visualized. Subsequently, the potential toxicity of PBDE exposure to diverse systems, such as endocrine, reproductive, neural, and gastrointestinal tract systems, and related toxic mechanisms will be discussed. Finally, we conclude this review by outlining the current challenges and future perspectives in environmentally relevant PBDE exposure, potential carriers for PBDE transport, the fate of PBDEs in the environment and human bodies, advanced stem cell-derived organoid models for toxicity assessment, and promising omics technologies for obtaining toxic mechanisms. This review is expected to offer systematical insights into PBDE toxicity assessments and facilitate the development of PBDE-based research.

Poly(ionic liquid)s threaded into covalent organic framework for synergistic capture of polybrominated diphenyl ethers

The efficient enrichment of trace polybrominated diphenyl ethers (PBDEs) in environmental waters remains challenging for environmental monitoring and analysis. Herein, a covalent organic frameworks-poly(ionic liquid)s hybrid material (COF-γ-PIL) is synthesized by threading poly(1-vinyl-3-methylimidazolium bis ((trifluoromethyl) sulfonyl) imide) into a vinyl-decorated COF via photopolymerization. The resultant hybrid retains the crystallinity and porosity of COF, thus offering adequate adsorption sites for the targets. PIL threaded in COF facilitates the synergistic capture of target molecules within the hybrid through multiple interactions, including Van der Waals forces, weak hydrogen bonding, and hydrophobic interactions. As a proof of concept, COF-γ-PIL was utilized as the fiber coating for SPME of PBDEs in waters prior to their analysis via GC-MS. Excellent analytical results were achieved, with wide linearity (0.01-100 ng L-1), low limits of detection (0.0021-0.014 ng L-1), and satisfactory recoveries (78.6%-103.6%). The outstanding extraction performance can be ascribed to the extraordinary flexibility of the active fraction on linear polymers threaded in COF, which facilitates collaborative capture for target molecules, as revealed by density functional theory (DFT) calculations. This work uncovers the microscopic mechanism for PBDEs capturing and provides new insights into the design of functionalized COF hybrids.

A review of polybrominated diphenyl ethers and novel brominated flame retardants in Chinese aquatic environment: Source, occurrence, distribution, and ecological risk assessment

Due to the widespread commercial production and use of brominated flame retardants (BFRs) in China, their potential impact on human health development should not be underestimated. This review searched the literature on Polybrominated diphenyl ethers and Novel brominated flame retardant (PBDEs and NBFRs) (broad BFRs) in the aquatic environment (including surface water and sediment) in China over the last decade. It was found that PBDEs and NBFRs entered the aquatic environment through four main pathways, atmospheric deposition, surface runoff, sewage effluent and microplastic decomposition. The distribution of PBDEs and NBFRs in the aquatic environment was highly correlated with the local economic structure and population density. In addition, a preliminary risk assessment of existing PBDEs and PBDEs in sediments showed that areas with high-risk quotient values were always located in coastal areas with e-waste dismantling sites, which was mainly attributed to the historical legacy of electronic waste. This research provides help for the human health development and regional risk planning management posed by PBDEs and NBFRs.

Determination of 25 polybrominated diphenyl ethers in Chinese mitten crab ecosystems by gas chromatography-mass spectrometry

A sensitive and reliable method for determining 25 polybrominated diphenyl ethers (PBDEs) in Chinese mitten crabs and their ecosystems ranging from the growing environment to edible feed by gas chromatography coupled to triple quadrupole mass spectrometry with advanced electron ionization (GC-AEI-MS/MS) was developed and validated. Accelerated solvent extraction (ASE) and liquid-liquid extraction were used to extract solid and water samples, respectively. On the basis of a traditional acid-base silica column, deactivated silica was added and n-hexane elution was used to increase the effect of separation and purification. Two oven temperature programs were applied to achieve good separation of low brominated congeners and increase the sensitivity of high brominated congeners. The method provided good linearity (>0.9996). The recoveries of four matrices were in the range of 82-115% and the method quantification limits (MQLs) in crabs, feed, sediment and water ranged from 0.36-6 pg per g wet weight, 0.69-22.29 pg per g dry weight, 1.02-25.26 pg per g dry weight, and 2.43-40.14 pg L-1, respectively. The proposed method was used for ten samples from two aquatic sites and PBDEs were detected in Chinese mitten crabs, commercial feed and sediment, with the highest in crabs. This analytical technique can be used to monitor the content and the accumulation behavior of PBDEs in Chinese mitten crab ecosystems or other aquaculture systems.

Comparative Assessment of the Toxicity of Brominated and Halogen-Free Flame Retardants to Zebrafish in Terms of Tail Coiling Activity, Biomarkers, and Locomotor Activity

BDE-47, a flame retardant that is frequently detected in environmental compartments and human tissues, has been associated with various toxic effects. In turn, information about the effects of aluminum diethyl-phosphinate (ALPI), a halogen-free flame retardant from a newer generation, is limited. This study aims to assess and compare the toxicity of BDE-47 and ALPI to zebrafish by analyzing the tail coiling, locomotor, acetylcholinesterase activities, and oxidative stress biomarkers. At 3000 µg/L BDE-47, the coiling frequency increased at 26-27 h post-fertilization (hpf), but the burst activity (%) and mean burst duration (s) did not change significantly. Here, we considered that the increased coiling frequency is a slight neurotoxic effect because locomotor activity was impaired at 144 hpf and 300 µg/L BDE-47. Moreover, we hypothesized that oxidative stress could be involved in the BDE-47 toxicity mechanisms. In contrast, only at 30,000 µg/L did ALPI increase the catalase activity, while the motor behavior during different developmental stages remained unaffected. On the basis of these findings, BDE-47 is more toxic than ALPI.

The influence of various microplastics on PBDEs contaminated soil remediation by nZVI and sulfide-nZVI: Impedance, electron-accepting/-donating capacity and aging

The microplastics (MPs) existed in the environment widely has resulted in novel thinking about in-situ remediation techniques, such as nano-zero-valent iron (nZVI) and sulfided nZVI (S-nZVI), which were often compromised by various environmental factors. In this study, three common MPs such as polyvinyl chloride (PVC), polystyrene (PS), and polypropylene (PP) in soil were found to inhibit the degradation rate of decabromodiphenyl ether (BDE209) by nZVI and S-nZVI to different degrees due to MPs inhibiting of electron transfer which is the main way to degrade BDE209. The inhibition strength was related to its impedance (Z) and electron-accepting (EAC)/-donating capacity (EDC). Based on the explanation of the inhibition mechanism, the reason for different aging degrees of nZVI and S-nZVI in different MPs was illustrated, especially in PVC systems. Furthermore, the aging of reacted MPs, functionalization and fragmentation in particular, indicated that they were involved in the degradation process. Moreover, this work provided new insights into the field application of nZVI-based materials for removing persistent organic pollutants (POPs).

Efficient removal of polybrominated diphenyl ethers from soil washing effluent by dummy molecular imprinted adsorbents: Selectivity and mechanisms

Surfactant enhanced elution is an effective method for removing hydrophobic organic pollutants from soils. The key to the development of leaching technology is selective removal of targeted pollutants in soil washing effluent and recycling of surfactant solutions. In this study, a molecular imprinting technique was applied to selectively sorb polybrominated diphenyl ethers (PBDEs) in soil washing effluent. The novel molecular imprinted polymers (MIPs) using different template molecules were synthesized by precipitation polymerization. Adsorption behaviors and mechanisms of MIPs were studied through experiments and theoretical calculations. The results show that 4-bromo-4'-hydroxybiphenyl and toluene can be effective imprinting molecule for MIPs synthesis. The maximal adsorption capacity of selected dummy molecular imprinted polymer (D₁-MIP) was 1032.36 µmol/g, and that of part molecular imprinted polymer (P-MIP) was 981.13 µmol/g. Their imprinting factors in 5 PBDEs adsorption ranged from 2.13 to 5.88, the recovery percentage of Triton X-100 can reach 99.09%, confirming the feasibility of reusing surfactant. Various PBDEs could be removed by MIPs, and Quantitative Structure Property Relationship analysis revealed that PBDEs' molecular volume, planarity, polarity, and hydrophobicity have major influences on their adsorption performance. DFT calculation revealed that Van der Waals force and hydrogen bonding played important roles during selective adsorption. These results can provide effective theoretical guidance for surfactant enhanced soil elution in practical engineering applications.

Integration of solid-phase microextraction and surface-enhanced Raman spectroscopy for in-vivo screening of polybrominated diphenyl ether

The monitoring of polybrominated diphenyl ethers (PBDEs) is of great significance owing to their high persistence, bioaccumulation, and toxicity to humans and animals. In this study, a sensitive and reproducible probe that integrates solid-phase microextraction and surface-enhanced Raman spectroscopy (SPME-SERS) was developed for screening PBDEs in multiphase specimens, including live fish, water, and electrical products. A roughed Cu fiber with an Ag layer was fabricated with dual functions. BDE-15 was readily extracted and detected on the SPME-SERS probe consisting of propanethiol-modified Ag nanoplates on a Cu wire. A clear linear relationship (R² = 0.988) was established between the SERS intensity at 782 cm^-1 and the logarithmic concentrations (from 100 ppb to 100 ppm), with a detection limit of 15 ppb. This proposed method enables continuous in vivo monitoring in fish without complicated pretreatments. The results obtained by this SPME-SERS approach were validated by high-performance liquid chromatography and showed good agreement. This "extracting and detecting" SPME-SERS method provides a potential tool to monitor the occurrence, formation, and migration of PBDEs.

Discovery of diphenyl ether-degrading Streptomyces strains by direct screening based on ether bond-cleaving activity

Diphenyl ethers (DEs), which are widely used in the agricultural and chemical industries, have become hazardous contaminants in the environment. Although several DE-degrading bacteria have been reported, discovering new types of such microorganisms could enhance understanding of the degradation mechanism in the environment. In this study, we used a direct screening method based on detection of ether bond-cleaving activity to screen for microorganisms that degrade 4,4'-dihydroxydiphenyl ether (DHDE) as a model DE. Microorganisms isolated from soil samples were incubated with DHDE, and strains producing hydroquinone via ether bond cleavage were selected using hydroquinone-sensitive Rhodanine reagent. This screening procedure resulted in the isolation of 3 bacteria and 2 fungi that transform DHDE. Interestingly, all of the isolated bacteria belonged to one genus, Streptomyces. To our knowledge, these are the first microorganisms of the genus Streptomyces shown to degrade a DE. Streptomyces sp. TUS-ST3 exhibited high and stable DHDE-degrading activity. HPLC, LC-MS, and GC-MS analyses revealed that strain TUS-ST3 converts DHDE to its hydroxylated analogue and generates hydroquinone as an ether bond-cleavage product. Strain TUS-ST3 also transformed DEs other than DHDE. In addition, glucose-grown TUS-ST3 cells began to transform DHDE after incubation with this compound for 12 h, and produced 75 μM hydroquinone in 72 h. These activities of streptomycetes may play an important role in DE degradation in the environment. We also report the whole genome sequence of strain TUS-ST3.

Polybrominated diphenyl ethers (PBDEs) in household dust: A systematic review on spatio-temporal distribution, sources, and health risk assessment

Much attention has been paid on polybrominated diphenyl ethers (PBDEs) in household dust due to their ubiquitous occurrences in the environment. Based on the data from 59 articles sampled from 2005 to 2020, we investigated the spatio-temporal distribution, sources, and health risk of 8 PBDE homologues in household dusts worldwide. BDE-209 is the predominant PBDE in household dusts, followed by BDE-99 and BDE-47. The total concentrations of PBDEs (∑₈PBDEs) are found to be high in household dusts sampled from 2005 to 2008 and show a significant decline trend from 2009 to 2016 (p < 0.05) and a little upward tendency from 2017 to 2020. The concentrations of PBDEs in household dusts vary greatly in different countries of the world. The use of penta-BDE is the main source of three to five bromo-biphenyl ether monomers contributing 17.4% of ∑₈PBDEs, while BDE-209 and BDE-183 are derived from the use of household appliances contributing 82.6% of ∑₈PBDEs. Ingestion is the main exposure route for adults and toddlers, followed by dermal contact. The values of hazard index (HI) exposed to PBDEs in household dusts are all less than 1 for both adults and toddlers, indicating a low non-cancer risk. The incremental lifetime cancer risks (ILCRs) of BDE-209 are less than 10^-6 for both adults and toddlers, suggesting a negligible risk. However, the total carcinogenic risk of toddlers is higher than that of adults, indicating that much attention should be paid to toddlers exposed to BDE-209 in household dust.

Spatiotemporal transitions of organophosphate esters (OPEs) and brominated flame retardants (BFRs) in sediments from the Pearl River Delta, China

Recent regulations on the use of brominated flame retardants (BFRs, especially polybrominated diphenyl ethers, PBDEs) have led a sharp increase in the use of organophosphate esters (OPEs), which have become the subject of widespread environmental concern. To gain insights into their environmental transitions, we investigated the spatiotemporal trends and sources of 25 OPEs and 23 BFRs (21 PBDEs and two alternative BFRs) in sediments from the Pearl River Delta (PRD), the second economic/industrial region of China. Among them, PBDEs showed higher mean concentrations than OPEs and alt-BFRs in PRD sediments, a continual increase in most PRD areas, and positive correlations with most local socioeconomic parameters. The source analysis results indicated that all of these changes resulted from the substantial use/stock of PBDEs (especially deca-BDE) in this region, and BDE-209 displayed debromination in most sediments. OPEs demonstrated obvious increases in sediments from all major PRD rivers, especially those located in less-developed regions. This distribution might be related to the large-scale industry relocation from the central PRD area to its vicinities. Unexpectedly, decabromodiphenyl ethane (DBDPE), an important deca-BDE substitute, presented considerable declines in the PRD sediments while several novel OPEs showed considerably high proportions, especially aryl-substituted OPEs, which merit further screening analysis.

Occurrence and ecological risk assessment of 2,2',4,4'-tetrabromodiphenyl ether and decabromodiphenyl ether in surface waters across China

Polybrominated diphenyl ethers (PBDEs) are efficient brominated flame retardants and are released into various environmental media via usage, recycling and disposal. This study investigated the concentrations and ecological risks of two typical PBDEs, 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) and decabromodiphenyl ether (BDE-209), in surface waters across China from 2011 to 2018. The results showed that the concentration of BDE-209 (8.25 ng L^-1) was higher than that of BDE-47 (1.02 ng L^-1), and the concentrations of BDE-47 and BDE-209 in the lakes (2.56 ng L^-1 and 22.19 ng L^-1, respectively) were higher than those in the rivers (0.58 ng L^-1 and 7.05 ng L^-1, respectively). In addition, the concentration of BDE-209 in the wet season (2.61 ng L^-1) was lower than that in the dry season (10.83 ng L^-1), whereas the concentration of BDE-47 in the wet season (0.24 ng L^-1) was a little lower than that in the dry season (0.99 ng L^-1). BDE-47 and BDE-209 concentrations showed a gradual decrease in surface waters across China during the eight-year period. Based on the species sensitivity distribution (SSD) models, the 5% hazardous concentration (HC₅) and predicted no-effect concentration (PNEC) values were derived using the acute and chronic toxicity data of BDE-47 and BDE-209. Results showed that the PNEC values based on the acute and chronic toxicity data were 2.08 μg L^-1 and 0.52 μg L^-1 for BDE-47, respectively and 370 μg L^-1 and 0.34 μg L^-1 for BDE-209, respectively. The risk quotient (RQ) values of BDE-47 in surface waters across China were far smaller than 0.1 (low ecological risk). Similarly, the RQ values of BDE-209 were also smaller than 0.1, except for those at Baiyangdian Lake and Chaohu Lake, where the probability of 0.1 ≤ RQ < 1.0 (medium ecological risk) was approximately 10% based on 10,000 Monte Carlo simulations.

PBDEs disrupt homeostasis maintenance and regeneration of planarians due to DNA damage, proliferation and apoptosis anomaly

Polybrominated diphenyl ethers (PBDEs) are widely used as brominated flame retardants in the manufacturing industry, belonging to persistent organic pollutants in the environment. Planarians are the freshwater worms, with strong regenerative ability and extreme sensitivity to environmental toxicants. This study aimed to evaluate the potential acute comprehensive effects of PBDE-47/-209 on freshwater planarians. Methods to detect the effects include: detection of oxidative stress, observation of morphology and histology, detection of DNA fragmentation, and detection of cell proliferation and apoptosis. In the PBDE-47 treatment group, planarians showed increased oxidative stress intensity, severe tissue damage, increased DNA fragmentation level, and increased cell proliferation and apoptosis. In the PBDE-209 treatment group, planarians showed decreased oxidative stress intensity, slight tissue damage, almost unchanged DNA fragmentation level and apoptosis, proliferation increased only on the first day after treatment. In conclusion, both PBDE-47 and PBDE-209 are dangerous environmental hazardous material that can disrupt planarians homeostasis, while the toxicity of PBDE-47 is sever than PBDE-209 that PBDE-47 can lead to the death of planarians.

Variation in the formation characteristics of PBDD/F, brominated PAH, and PBDE congeners along the secondary copper smelting processes

Simultaneous determination of 58 congeners of polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs), brominated polycyclic aromatic hydrocarbons (Br-PAHs), and polybrominated diphenyl ethers (PBDEs) from multiple stages of industrial-scale secondary copper smelting plants was conducted with the aim of understanding their variations and control. In addition to the historical manufacture of PBDEs as brominated flame retardants, this study confirmed that PBDEs can be unintentionally produced and released from the secondary copper industry. The average mass emission factors of PBDD/Fs, PBDEs, and Br-PAHs from different sources were 10.0, 5.21 × 10³, and 7.24 × 10³ μg t^-1, respectively. Therefore, the emission of brominated persistent organic pollutants (POPs) in the secondary copper industry should be of concern. The concentration of brominated POPs increased from the gas cooling stage to stack outlet due to the possible "memory effect" and the regenerated POPs were mainly low-brominated homologs. A comparison of brominated POPs with corresponding chlorinated analogs in the same process indicated that the formation pathway of Br-PAHs was consistent with that of chlorinated PAHs. However, unlike chlorinated dioxins and furans, PBDD/Fs can also be formed from PBDEs as precursors, leading to obvious increases in highly brominated furans. Therefore, inhibiting the unintentional formation of PBDEs is important for controlling brominated POPs emissions.

Physiologically based pharmacokinetic (PBPK) modeling of BDE-209 following oral exposure in Chinese population

The wide usage of decabromodiphenyl ether (BDE-209) as additive brominated flame retardant has caused its widespread occurrence in the environment and high exposure risk in humans. Estimating its internal exposure dose and reconstruction of external exposure dose using physiologically based pharmacokinetic (PBPK) modelling approach is a key step in the risk assessment of BDE-209. However, the PBPK model for BDE-209 is currently unavailable. This study has established two oral permeability-limited PBPK models of BDE-209 without enterohepatic recirculation (EHR) (model 1) and with EHR (model 2) for Chinese population. Using the in vitro experiments, the average binding of BDE-209 to human plasma protein (99.64% ± 2.97%) was obtained. Moreover, blood sample analysis and systematic literature review were performed to obtain internal and external exposure data of BDE-209 used for model calibration and validation. The predictions of both models were within 2-fold of the observed, and a longer half-life of serum BDE-209 was observed in model 2 than model 1. Based on the models, a human biomonitoring guidance value (HBM-GV) of 93.61 μg/g lw was derived for BDE-209, and there is no health risk found for Chinese population currently. This study provides new quantitative assessment tools for health risk assessment of BDE-209.

Transcriptomics-based analysis of co-exposure of cadmium (Cd) and 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) indicates mitochondrial dysfunction induces NLRP3 inflammasome and inflammatory cell death in renal tubular epithelial cells

Environmental pollution often releases multiple contaminants resulting in as yet largely uncharacterized additive toxicities. Cadmium (Cd) is a widespread pollutant that induces nephrotoxicity in animal models and humans. However, the combined effect of Cd in causing nephrotoxicity with 2,2',4,4'-tetrabromodiphenyl ether (BDE-47), a typical congener of polybrominated diphenyl ethers (PBDEs), has not been evaluated and mechanisms are not completely clear. Here, we applied transcriptome sequencing analysis to investigate the combined toxicity of Cd and BDE-47 in the renal tubular epithelial cell lines HKCs. Cd or BDE-47 exposure decreased cell viability in a dose-dependent manner, and exhibited cell swelling and rounding similar to necrosis, which was exacerbated by co-exposure. Transcriptomic analysis revealed 2191, 1331 and 3787 differentially-expressed genes following treatment with Cd, BDE-47 and co-exposure, respectively. Interestingly, functional annotation and enrichment analyses showed involvement of pathways for oxidative stress, NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome and inflammatory cell death for all three treatments. Examination of indices of mitochondrial function and oxidative stress in HKC cells showed that the levels of reactive oxygen species (ROS), malondialdehyde (MDA) and intracellular calcium ion concentration [Ca²⁺]i were elevated, while superoxide dismutase (SOD) and mitochondrial membrane potential (MMP) were decreased. The ratio of apoptotic and necrotic cells and intracellular lactate dehydrogenase (LDH) release were increased by Cd or BDE-47 exposure, and was aggravated by co-exposure, and was attenuated by ROS scavenger N-Acetyl-L-cysteine (NAC). NLRP3 inflammasome and pyroptosis pathway-related genes of NLRP3, adaptor molecule apoptosis-associated speck-like protein (ASC), caspase-1, interleukin-18 (IL-18) and IL-1β were elevated, while gasdermin D (GSDMD) was down-regulated, and protein levels of NLRP3, cleaved caspase-1 and cleaved GSDMD were increased, most of which were relieved by NAC. Our data demonstrate that exposure to Cd and BDE-47 induces mitochondrial dysfunction and triggers NLRP3 inflammasome and GSDMD-dependent pyroptosis leading to nephrotoxicity, and co-exposure exacerbates this effect, which could be attenuated by inhibiting ROS. This study provides a further mechanistic understanding of kidney damage, and co-exposure impact is worthy of concern and should be considered to improve the accuracy of environmental health assessment.

Combination of Soxhlet extraction and catalytic hydrodebromination for remediation of tetrabromobisphenol A contaminated soil

As a widely used brominated flame retardants (BFRs), tetrabromobisphenol A (TBBPA) has been detected in various environmental matrices and is known to cause negative effects on both the environment and human health. In this study, a combined method was developed for the abatement of TBBPA contaminated soil based on successive steps of solvent extraction (SE) and catalytic hydrodebromination (HDB) over Pd/C. The results showed that TBBPA could be efficiently extracted from the TBBPA contaminated soil with polar solvents. Subsequently, TBBPA could be completely hydrodebrominated over Pd/C in ethanol, via multistep ultimately yielding bisphenol A. Moreover, NaOH, NH₃H₂O, and Et₃N were more favorable to promote the HDB of 4-TBBPA over Pd/C, and 100% bromide atom removal ratio of TBBPA was achieved within 40 min when [NaOH]₀/[organic-Br]₀ was more than 1.10 in ethanol. However, the catalytic activity of Pd/C decreased with the repeated use in ethanol. To study the mechanism for this phenomenon, fresh and used catalysts were analyzed by characterization techniques including scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), and energy dispersive X-ray spectrometer (EDS). It was found that the deactivation of Pd/C catalyst caused by the gradual accumulation of NaBr could be recovered by washing with water. On the basis of these studies, an effective and practical system for the combined method of SE and catalytic HDB over Pd/C was developed to dispose BFRs contaminated soils.

Photodegradation of Decabrominated Diphenyl Ether in Soil Suspensions: Kinetics, Mechanisms and Intermediates

Pollution by polybrominated diphenyl ethers (PBDEs) is a major concern due to their bioaccumulation, persistence, and carcinogenicity. This study aimed to investigate the decabrominated diphenyl ether (BDE-209) photodegradation in soil suspensions. The results indicate BDE-209 can degrade in soil suspensions and its degradation follows pseudo-first-order kinetics. The light sources and intensity effects were studied and the photodegradation rates were 500 W Mercury Lamp > 300 W Mercury Lamp > 500 W Xenon Lamp > 300 W Xenon Lamp, which indicates UV light is the main reason for BDE-209 degradation. Soil particle inhibits BDE-209 photodegradation due to the light-shielding effect. BDE-209 photodegradation rates increased from 0.055 to 0.071 h−1 with pH value increasing from 3.5 to 9.5. This may be because the products are more easily produced in higher pH soil suspensions. The presence of humic acid (HA) may inhibit BDE-209 photodegradation by photo-shielding. Fe3+ and Cu2+ have an adverse effect on BDE-209 photodegradation due to the photo competition. The •OH and 1O2 were detected in soil solutions. Analysis of the photoproducts of BDE-209 by gas chromatography mass spectrometry (GC-MS) and liquid chromatography time of flight mass spectrometry (LC-TOF-MS) showed that BDE-209 was mainly debrominated to the lower-brominated BDEs and the reactive oxygen radicals may not lead to BDE-209 degradation.

New Evidence of Rubber-Derived Quinones in Water, Air, and Soil

p-Phenylenediamines (PPDs) have been extensively used in the rubber industry and found to be pervasive in various environmental compartments for decades, while their transformation products and associated ecological and human health risks remain largely unknown. Herein, we developed and implemented a mass spectrometry-based platform combined with self-synthesized standards for the investigation of rubber-derived quinones formed from PPD antioxidants. Our results demonstrated that five quinones are ubiquitously present in urban runoff, roadside soils, and air particles. All of the identified sources are closely related to mankind's activities. Among the identified quinones, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone has been recently found to be highly toxic, causing acute mortality of coho salmon in the Pacific Northwest. Ultrahigh-performance liquid chromatography coupled with triple quadrupole mass spectrometry was then applied for quantification of the five quinones and their corresponding PPD antioxidants. The results revealed interesting distinct distribution and concentration patterns of PPD-derived quinones in different environmental matrices. Daily intake rates of these quinones in a compact city of Hong Kong were estimated to be varied from 1.08 ng/(kg·day) for adults to 7.30 ng/(kg·day) for children, which were higher than the exposure levels of their parent compounds. Considering the prevalence of the use of rubber products, the outcome of this study strongly suggests for additional toxicological studies to investigate potential ecological and human health risks of the newly discovered quinones.

Melatonin relieves 2,2,4,4-tetrabromodiphenyl ether (BDE-47)-induced apoptosis and mitochondrial dysfunction through the AMPK-Sirt1-PGC-1α axis in fish kidney cells (CIK)

Polybrominated diphenyl ethers (PBDEs) exist in aquatic environments with nephrotoxicity to non-target aquatic species. Melatonin (MT) exhibits an inhibitory effect of oxidative stress and apoptosis in various diseases. 2, 2', 4, 4'-tetrabromodiphenyl ether (BDE-47) is the main homolog of PBDE samples. Therefore, we investigated the toxic mechanism of BDE-47 and the alleviation effect of MT, the ctenopharyngodon idellus kidney (CIK) cells were treated with BDE-47 (100 μM) and/or MT (60 μM) for 24 h. Firstly, BDE-47 exposure could inhibit oxidative stress-related antioxidant enzymes (T-AOC, SOD, CAT and GPx) and increase the content of malondialdehyde (MDA) to cause oxidative stress. Secondly, BDE-47 enhanced mitochondrial division and inhibited fusion to induce mitochondrial membrane potential in CIK cells. BDE-47 enhanced the mRNA and protein levels of mitochondrial-pathway apoptosis related genes (Cas 3, Cyt-c, and BAX). Thirdly, BDE-47 treatment decreased the expression levels of mitochondrial-related regulatory factors AMPK-Sirt1-PGC-1α signal pathway. Intriguingly, BDE-47-induced oxidative stress, mitochondrial pathway apoptosis and mitochondrial dynamics disorder could be alleviated by MT treatment. Overall, we concluded that MT could relieve BDE-47-induced oxidative stress, mitochondrial dysfunction and apoptosis through the AMPK-Sirt1-PGC-1α axis. These results enrich the mechanisms of BDE-47 poisoning and reveal that MT treatment may be a potential strategy for solving BDE-47 poisoning.

Degradation of Decabromodiphenyl Ether in an Aerobic Clay Slurry Microcosm Using a Novel Immobilization Technique

A novel chitosan immobilization technique that entraps photocatalyst and microbes was developed and applied to decompose decabromodiphenyl ether (BDE-209) in a clay slurry microcosm. The optimized conditions for immobilization were obtained by mixing 1.2% (w/v) chitosan dissolved in 1% (v/v) acetic acid with nano-TiO2 particles and the BDE-209-degrading bacterial mixed culture. This aqueous mixture was injected into 1% (w/v) water solution containing sodium tripolyphosphate to form spherical immobilized beads. The surface of the immobilized beads was reinforced by 0.25% (v/v) glutaraldehyde cross-linking. These beads had enough mechanical strength during BDE-209 degradation to maintain their shape in the system at a stirring rate of 200-rpm, while undergoing continuous 365 nm UVA irradiation. This novel TiO2-Yi-Li immobilized chitosan beads system allowed a successful simultaneous integration of photolysis, photocatalysis and biodegradation to remove BDE-209. The remaining percentage of BDE-209 was 41% after 70 days of degradation using this system. The dominant bacteria in the BDE-209-degrading bacterial mixed culture during remediation were Chitinophaga spp., Methyloversatilis spp., Terrimonas spp. and Pseudomonas spp. These bacteria tolerated the long-term UVA irradiation and high-level free radicals present, while utilizing BDE-209 as their primary carbon resource. This new method has great potential for the treatment of a range of pollutants.

Occurrence, potential sources and risks of organophosphate esters in the high-elevation region, Tibet, China

Organophosphate esters (OPEs) are widely used flame retardants that are frequently released into the environment, causing potential harm to humans and ecosystems. Tibet is located on the Tibetan Plateau, known as the "roof of the world", but the occurrence of OPEs in Tibet remains unclear. This is the first report of the occurrence, potential sources and risks of 12 OPEs in water, soil, sediment and snow from Xainza, a typical town at high-elevation in Tibet (average elevation = 4700 m). Ten OPEs were observed, with ∑OPE concentrations of 46.45-1744.73 ng/L in surface water, 29.74-73.85 ng/g in soil, and 13.30-32.23 ng/g in sediment. Moreover, the mean ∑OPE concentration in snow was 413.90 ng/L. Tris (2-chloroethyl) phosphate (TCEP) and tris (2-chloroisopropyl) phosphate (TCPP) were the main OPEs in surface water and snow, while 2-ethylhexyl diphenyl phosphate (EHDPP) was dominant in soil and sediment. Local human activities and long-distance atmospheric transport may be the main sources of OPEs in Xainza. The assessment of ecological risk indicated that EHDPP in soil poses potential risk. The occurrence of OPEs in Xainza showed that more attention should be paid to persistent organic pollutants in high-elevation regions.

Environmental contamination and human exposure of polychlorinated biphenyls (PCBs) in China: A review

Polychlorinated biphenyls (PCBs), together with 11 other organic compounds, were initially listed as persistent organic pollutants (POPs) by the Stockholm Convention because of their potential threat to ecosystems and humans. In China, many monitoring studies have been undertaken to reveal the level of PCBs in environment since 2005 due to the introduced stricter environmental regulations. However, there are still significant gaps in understanding the overall spatial and temporal distributions of PCBs in China. This review systematically discusses the occurrence and distribution of PCBs in environmental matrices, organisms, and humans in China. Results showed that PCB contamination in northern and southern China was not significantly different, but the PCB levels in East China were commonly higher than those in West China, which might have been due to the widespread consumption of PCBs and intensive human activities in East China. Serious PCB contamination was found in e-waste disassembling areas (e.g., Taizhou of Zhejiang Province and Qingyuan and Guiyu of Guangdong Province). Higher PCB concentrations were also chronicled in megalopolises and industrial clusters. The unintentionally produced PCBs (UP-PCBs) formed during industrial thermal processes may play an increasingly significant role in PCB pollution in China. Low PCB levels were recorded in rural and underdeveloped districts, particularly in remote and high-altitude localities such as the Tibetan Plateau and the South China Sea. However, these data are limited. Human exposure to PCBs is closely related to the characteristics of environmental pollution. This review also discusses existing issues and future research prospects on PCBs in China. For instance, the accumulation characteristics and migration regularities of PCBs in food webs should be further studied. More investigations should be undertaken to assess the quantitative relationship between external and internal exposure to PCBs. For example, bioaccessibility and bioavailability studies should be supplemented to evaluate human health risks more accurately.

Contaminant concentrations and risks associated with the Pacific oyster in the highly urbanized San Diego Bay

Contaminant concentrations in filter-feeding shellfish may indicate the health of coastal waters and consumption risks. Widespread expansion of the Pacific oyster (Crassostrea gigas) and its popularity as food make it a useful sentinel. We surveyed intertidal Pacific oysters in San Diego Bay, California for contaminants during summer 2018 and winter 2019. We compared contaminants in Pacific oyster to California mussel from California's State Mussel Watch Program (1993-2003) and human consumption thresholds. Contaminants such as neonicotinoid and chlorinated pesticides, selenium, and several metals were higher in Pacific oysters in summer, while PBDEs, benzylbutyl phthalate, and plastics were higher in winter. Contaminant levels were generally lower in Pacific oyster than mussel except for copper and zinc. Bay-wide PCB concentrations in oysters exceeded thresholds but individual samples (locations) also met or surpassed chlordane, PCB and PAH thresholds. Monitoring and risk assessments that consider species' biology, season, location, effects of multiple contaminants, and human consumption patterns will contribute to more effective consumption guidelines.

Analysis of brominated flame retardants in the aquatic environment: a review

The most common and consequently analysed brominated flame retardants (BFRs) are polybrominated biphenyls (PBBs), polybrominated diphenyl ethers (PBDEs), tetrabromobisphenol A (TBBPA), tetrabromobisphenol S (TBBPS), and hexabromocyclododecane (HBCD). As these persistent organic pollutants are widespread in the environment and have a number of harmful effects on human health, the production and use of most has been banned for several years. The aquatic environment is polluted by these compounds through their deposition from the atmosphere, sewage sludge, wastewater treatment plants, and landfills, and higher levels are found in areas with developed industry and agriculture and near landfills. Each compound also seems to show preference for specific compartments of the aquatic environment, i.e. water, sediment, or aquatic organisms, according to their physicochemical properties. The aim of this review was to take a closer look at the analysis of BFRs, as without reliable analysis we would not be able to determine their levels and distribution across the aquatic compartments and assess human exposure and health risks. Particularly worrying are the health risks associated with PBDEs in fish, whose levels generally exceed the permitted values.

Health risk assessment and development of human health ambient water quality criteria for PBDEs in China

Polybrominated diphenyl ethers (PBDEs) are not only a class of highly efficient brominated flame retardants (BFRs) but also a class of typical persistent organic pollutants (POPs) that are persistent and widely distributed in various environmental media. This study examined the concentrations of PBDEs in five environmental media (water, soil, air, dust, and food) and two human body media (human milk and blood) in China from 2010 to 2020. In addition, this study conducted multi-pathway exposure health risk assessments of populations of different ages in urban, rural, key regions, and industrial factories using the Monte-Carlo simulation. Finally, the human health ambient water quality criteria (AWQC) of eight PBDEs were derived using Chinese exposure parameters and bioaccumulation factors (BAFs). The results showed that the eastern and southeastern coastal regions of China were heavily polluted by PBDEs, and the variation trends of the ΣPBDEs concentrations in the different exposure media were not consistent. PBDEs did not pose a risk to urban and rural residents in ordinary regions, but the hazard indexes (HIs) for residents in key regions and occupational workers exceeded the safety threshold. Dust exposure was the primary exposure pathway for urban and rural residents in ordinary regions, but for residents in key regions and occupational workers, dietary exposure was the primary exposure pathway. BDE-209 was found to be the most serious individual PBDE congener in China. The following human health AWQC values of the PBDEs were derived: drinking water exposure: 0.233-65.2 μg·L^-1; and drinking water and aquatic products exposure: 8.51 × 10^-4-1.10 μg·L^-1.

Effects of single and combined exposure to BDE-47 and PFOA on distribution, bioaccumulation, and toxicity in blue mussel (Mytilus galloprovincialis)

The contamination of 2,2',4,4'-Tetrabrmodiphenyl ether (BDE-47) and perfluorooctanoic acid (PFOA) has drawn a worldwide attention over the risks in ecological and food safety. In this work, blue mussel (Mytilus galloprpvincialis) was employed to investigate the combined effects of BDE-47 (10 ng mL-1) and PFOA (100 ng mL-1) on tissue distribution, accumulation, elimination, and toxicity. Results suggested that BDE-47 and PFOA accumulated mostly in digestive gland, followed by gills and gonad, and M. galloprovincialis displayed higher accumulation capacity to BDE-47 than PFOA. Co-exposure treatment reduced the accumulation of BDE-47, and enhanced the accumulation of PFOA. Furthermore, biochemical and histopathological tests revealed that the aggravated toxicity in co-exposure groups was mainly attributed to the oxidative stress and damage of tissue structure. This work could be helpful to get a better understanding of the combined behaviors and cumulative risks of BDE-47 and PFOA in marine ecosystem.

Microplastics habituated with biofilm change decabrominated diphenyl ether degradation products and thyroid endocrine toxicity

Microplastics (MPs) are rapidly colonized by microbial biofilms in a natural aquatic environment, and the nature of the microbial community and type of MP can result in different degradation products of organic pollutants. Here, we quantified the degradation products of a ubiquitously detected pollutant, decabrominated diphenyl ether (BDE-209), under both light-only and biota conditions and in the absence or presence of three kinds of MPs, styrofoam polystyrene, hard polyamide, and polypropylene film. The results showed that the BDE-209 concentration increased by 0.7-2.8 fold in the presence of MPs, probably due to the "sustained release" desorption effect. Under light-only conditions, the penta- and hexa-BDE concentrations in the presence of styrofoam or hard MPs were significantly reduced, which can be deemed a beneficial effect. However, when biota were present, the debromination products increased with the addition of MPs, particularly in the presence of styrofoam MPs. These products caused a 1.7-fold upregulation in triiodothyronine content and a 5.9-fold upregulation of thyroid stimulating hormone β expression in zebrafish larvae. The increase in debromination products could be attributed to the distinct high abundance of the bacteria Chloroflexi, Proteobacteria, and Basidiomycotina on styrofoam MPs that can participate in pollutant degradation. Collectively, our results indicate that MPs can alter the degradation pathways of BDE-209 and increase the toxicity to the endocrine system and the thyroid in aquatic organisms.

Spatio-temporal variations and input patterns on the legacy and novel brominated flame retardants (BFRs) in coastal rivers of North China

Decabromodiphenyl ether (BDE209) has been subject to restrictions since 2018 in developed countries but is still manufacturing in China. Decabromodiphenyl ethane (DBDPE) is widely used as a replacement for BDE209. To better understand the behaviors and fates of these legacy and novel brominated flame retardants (BFRs), water samples were collected from the estuaries of 36 rivers that drain into the Bohai Sea (BS) and North Yellow Sea (NYS) in 2017 and 2018. The results showed that BDE209 was still the predominant compound with a median concentration of 2470 pg L^-1, whereas DBDPE had a median concentration of 129 pg L^-1. Spatially, relatively high concentrations were observed in the rivers near Laizhou Bay (LB), which is the manufacturing hub of BFRs. BDE209 concentrations were significantly higher in dry season than in wet season, which indicates a dominant process of dilution by precipitation during the wet season. DBDPE concentration showed no significant seasonal difference. This implies that wet deposition was the major additional source of DBDPE during the wet season, and the concentration increased further during the autumn as a result of a time-lag effect. The BFR concentrations in urban rivers were lower than those reported by a study undertaken in August 2013. An increase in the BFR concentrations in rural rivers since 2013 suggested increases in the use and non-point source emissions of BFRs in some remote aquatic environments. The estimated annual inputs of BDE209 and DBDPE into the BS were ∼95.9 kg yr^-1 and ∼26.8 kg yr^-1, respectively, whereas those into the NYS were ∼24.1 kg yr^-1 and ∼8.38 kg yr^-1. The results revealed an ecological risk of BDE209 in winter especially in the Xiaoqing River, thus suggesting the impact of BDE209 on the aquatic environment and human health.

Effects of ferric ion on the photo-treatment of nonionic surfactant Brij35 washing waste containing 2,2',4,4'-terabromodiphenyl ether

The effects of ferric iron on the photo-treatment of simulated BDE-47 (2,2',4,4'- terabromodiphenyl ether)-Brij35 (Polyoxyethylene lauryl ether) washing waste were studied to evaluate the influences of ferric iron on BDE-47 removal and Brij35 recovery. The results show that Fe³⁺ accelerated BDE-47 degradation at lower concentrations (<0.5 mM) but attenuated it at higher concentrations (0.5-5 mM) and that Brij35 loss was increased with increasing Fe³⁺. These results likely are caused by changes in the rate of •OH production due to the ferric ion, association of Fe³⁺ and electron transfer from Brij35, and light attenuation at high concentration. The BDE-47 and Brij35 had different degradation rates at different pH values and at different dissolved oxygen concentrations. The BDE-47 products were identified by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS). The results indicated that BDE-47 transformed into mainly lower-brominated products, a few bromodibenzofurans, some rearrangement products, and some hydroxylated polybrominated diphenyl ethers. A series of Brij35 oxidization products were detected by ultra-performance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS), including hydroxylation products, carboxylation products, and some hydrophilic chain-breaking products. Brij35 was mainly oxidized by Fe³⁺ and/or reactive oxygen species (ROS) with the final products of CO₂ and H₂O. The iron ions apparently cycled from ferric to ferrous ions in the micelles such that the Fe³⁺-Brij35 complex dominated the main redox reaction, leading to both BDE-47 and Brij35 degradation. It appears that in any applied soil washing system, the ferric ions in the washing waste need to be removed because of the adverse effects on BDE-47 removal and eluate reuse.

A potential threat to the coral reef environments: Polybrominated diphenyl ethers and phthalate esters in the corals and their ambient environment (Persian Gulf, Iran)

Pollution of the surrounding habitat poses one of the biggest threats to the coral health and even survival. This study focuses on the occurrence, distribution, bioaccumulation and bioconcentration of polybrominated diphenyl ethers (PBDEs) and phthalate esters (PAEs) in corals, their zooxanthellae and mucus, as well as in their ambient environment in Larak coral reef (Persian Gulf) for the first time. The highest concentrations of the pollutants were recorded in mucus, followed by zooxanthellae, tissue and skeleton. Soft corals with higher lipid content contained more PBDEs and PAEs. Pollutants were both efficiently bioconcentrated from water and bioaccumulated from the ambient sediment, albeit bioconcentration played the most prominent role. Elevated PBDEs and especially PAEs concentrations were detected in the skeletons of the bleached corals if compared to the skeleton samples of the non-bleached individuals.

Sheathed in-situ room-temperature growth covalent organic framework solid-phase microextraction fiber for detecting ultratrace polybrominated diphenyl ethers from environmental samples

The extraction performance of solid-phase microextraction (SPME) fiber is significantly influenced by coating materials and fabricating process. It is urgently needed for fabricating robust SPME fiber with facile preparation methods. Herein, a novel polyimide (PI) @ covalent organic framework (COF) synthesized by 1,3,5-Tris (4-aminophenyl) benzene (TPB) and 2,5-dimethoxyterephthalaldehyde (DMTP) fiber, named PI@TPB-DMTP fiber, was successfully fabricated with facile method at room temperature. Firstly, a COF crystals TPB-DMTP was in situ grown on stainless steel fiber, where the COF crystals was synthesized by the Schiff-base reaction between TPB and DMTP. Subsequently, the COF coating was covered with an ultrathin layer of PI through a simple dip-coating method to improve the fiber stability. By coupled PI@TPB-DMTP SPME fiber with gas chromatography-negative chemical ion-mass spectrometry (GC-NCI-MS), a sensitive analytical method was established for the determination of ultratrace polybrominated diphenyl ethers (PBDEs) in water sample. To achieve the best efficiency and sensitivity for the analysis of PBDEs, six potential influencing factors in extraction step and desorption step were optimized. Under optimized conditions, the established method showed high enhancement factors of 1470-3555, wide linear range of 0.05-100 ng L^-1, low detection limits of 0.0083-0.0190 ng L^-1, good repeatability for intra-day in the range of 3.71%-7.62% and inter-day in the range of 5.12%-8.81%, good reproducibility in the range of 6.83%-9.21%. The satisfactory recovery was ranged from 79.2% to 117.3% in determining real water samples. The excellent experimental performance was mainly attributed to the large specific surface area of TPB-DMTP, as well as the high permeability of porous PI film. The results demonstrated that the COF-based fiber showed great potential for analysis of PBDEs in complex environmental samples.

Assessment of polybrominated diphenyl ethers and emerging brominated flame retardants in Pheretima (a Traditional Chinese Medicine): Occurrence, residue profiles, and potential health risks

China produces and consumes large quantities of brominated flame retardants (BFRs) as well as several other unregulated electronic waste recycling activities, causing high BFR concentrations in the natural environment. Thus, Traditional Chinese Medicines (TCMs) may be contaminated by legacy BFRs (e.g. polybrominated diphenyl ethers (PBDEs)) and emerging BFRs (eBFRs, such as decabromodiphenyl ethane (DBDPE)) during growth, processing, packaging, and transportation. Pheretima, which is a typical animal drug recorded in Chinese Pharmacopoeia, was used as an example to evaluate human exposure to BFRs through TCM intake. This study is the first to determine 25 PBDEs and 5 eBFRs in Pheretima and estimate the daily BFR intake via Pheretima-containing TCMs. Twenty-seven Shanghai Pheretima and fifty-one Guang Pheretima samples were collected between March and June 2019 in southeast China. High BFR detection frequencies were found in Pheretima, of which BDE-209 and DBDPE were the most predominant analytes. The total PBDE contents ranged from 73 pg/g to 8,725 pg/g, while that of the eBFRs varied between 115 pg/g and 2,824 pg/g. The profiles and abundances were found to be species- and origin-dependent. However, the traditional processing of Pheretima may reduce BFR residues. Based on the usual clinical doses of Pheretima and the available chronic oral reference doses of BDE-47, 99, 153, and 209, the mean (95th percentile) of the total hazard quotient was estimated to be 9.1 × 10^-5 (2.7 × 10^-4). Therefore, there is little risk related to BFR exposure for patients taking formulated Pheretima-containing TCMs. However, it is necessary to establish routine monitoring programs for the co-existence of pollutants in TCMs to perform a systematic and comprehensive risk assessment.

Roles of endoplasmic reticulum stress in 2,2',4,4'-tetrabromodiphenylether-induced thyroid cell apoptosis and autophagy

Polybrominated diphenyl ethers are known to be toxic and impair thyroid function. However, the underlying molecular mechanisms are not well understood. We constructed a female Sprague-Dawley rat model to evaluate the role of endoplasmic reticulum stress, apoptosis and autophagy in 2,2',4,4'-tetrabromodiphenylether (PBDE-47) induced thyroid toxicity. In the brain development spurt period (postnatal day 10), rats were treated with PBDE-47 (0, 1, 5, 10 mg/kg bw, i.g). Two addition groups were administered with 4-Phenylbutyric acid, an endoplasmic reticulum stress modulator, to reverse PBDE-47-induced thyroid toxicity. Our results demonstrated that PBDE-47 significantly decreased serum thyroid stimulating hormone levels, induced histologic changes in thyroid tissues, increased the percentage of cell apoptosis and expression levels of C/EBP-homologous protein, caspase 3, glucose-regulated protein 78, inositol-requiring enzyme 1, and autophagy-related proteins Beclin1 and 1A/1B-light chain 3. Besides of decreased serum thyroid stimulating hormone levels, all these changes were reversed by 4-Phenylbutyric acid. Taken together, these data indicate that, PBDE-47 damages the thyroid tissues by triggering endoplasmic reticulum stress, apoptosis and autophagy.

A review of 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane in the environment and assessment of its persistence, bioaccumulation and toxicity

Following the ban of many historically-used flame retardants (FRs), numerous replacement chemicals have been produced and used in products, with some being identified as environmental contaminants. One of these replacement flame retardants is 1,2-dibromo-4-(1,2-dibromoethyl)-cyclohexane (DBE-DBCH; formerly abbreviated as TBECH), which to date has not been identified for risk assessment and potential regulation. DBE-DBCH technical mixtures consist largely of α- and β-diastereomers with trace amounts of γ- and δ-DBE-DBCH. The α- and β-isomers are known contaminants in various environmental media. While current global use and production volumes of DBE-DBCH are unknown, recent studies identified that DBE-DBCH concentrations were among the highest of the measured bromine-based FRs in indoor and urban air in Europe. Yet our mass balance fugacity model and modeling of the physical-chemical properties of DBE-DBCH estimated only 1% partitioning to air with a half-life of 2.2 d atmospherically. In contrast, our modeling characterized DBE-DBCH adsorbing strongly to suspended particulates in the water column (~12%), settling onto sediment (2.5%) with minimal volatilization, but with most partitioning and adsorbing strongly to soil (~85%) with negligible volatilization and slow biodegradation. Our modeling further predicted that organisms would be exposed to DBE-DBCH through partitioning from the dissolved aquatic phase, soil, and by diet, and given its estimated logKow (5.24) and a half-life of 1.7 d in fish, DBE-DBCH is expected to bioaccumulate into lipophilic tissues. Low concentrations of DBE-DBCH are commonly measured in biota and humans, possibly because evidence suggests rapid metabolism. Yet toxicological effects are evident at low exposure concentrations: DBE-DBCH is a proven endocrine disruptor of sex and thyroid hormone pathways, with in vivo toxic effects on reproductive, metabolic, and other endpoints. The objectives of this review are to identify the current state of knowledge concerning DBE-DBCH through an evaluation of its persistence, potential for bioaccumulation, and characterization of its toxicity, while identifying areas for future research.

Chemical Exposure: European Citizens' Perspectives, Trust, and Concerns on Human Biomonitoring Initiatives, Information Needs, and Scientific Results

Over the last few decades, citizen awareness and perception of chemical products has been a topic of interest, particularly concerning national and international policy decision makers, expert/scientific platforms, and the European Union itself. To date, few qualitative studies on human biomonitoring have analysed communication materials, made recommendations in terms of biomonitoring surveillance, or asked for feedback in terms of specific biomonitoring methods. This paper provides in-depth insight on citizens' perceptions of knowledge of biomonitoring, impact of chemical exposure on daily life, and claims on how results of research should be used. Four semi-structured focus groups were held in Austria, Portugal, Ireland, and the United Kingdom (UK). The cross-sectional observational qualitative design of this study allows for better understanding of public concern regarding chemicals, application, and use of human biomonitoring. The main findings of this study include citizens' clear articulation on pathways of exposure, the demand on stakeholders for transparent decision-making, and sensitivity in communication of results to the public. Validated and trustful communication is perceived as key to empowering citizens to take action. The results can be used to facilitate decision-making and policy development, and feeds into the awareness needs of similar and future projects in human biomonitoring. Furthermore, it also brings to light ideas and concepts of citizens' in shaping collaborative knowledge between citizens', experts, scientists, and policy makers on equal terms.

Long-Term Investigation of the Temporal Trends and Gas/Particle Partitioning of Short- and Medium-Chain Chlorinated Paraffins in Ambient Air of King George Island, Antarctica

The presence of anthropogenically emitted chlorinated paraffins (CPs) has been reported in the pristine regions, providing evidence of their long-range transport. This study comprehensively analyzed the short-chain chlorinated paraffins (SCCPs) and medium-chain chlorinated paraffins (MCCPs) in both gas and particle phases at King George Island, West Antarctica (the Chinese Great Wall Station), from 2014 to 2018. The atmospheric levels of CPs ranged between 71.4 and 4230 pg/m³, with an increasing temporal trend during the sampling time. Three different models (J-P model, H-B model, and L-M-Y model) were built to estimate the progress of gas/particle partitioning of CPs at the measurement site. Furthermore, we compared the measured data of the gas/particle partitioning with the data estimated using three different models. We found that the steady-state model (L-M-Y model) was more suitable for investigating the gas/particle partitioning of CPs instead of equilibrium state models (J-P model and H-B model). The result indicated that steady-state approximation rather than the equilibrium state represents the most predominant contribution to the transport of CPs to the Antarctic region. The steady-state further made it conducive to sustaining the levels of CPs for a more extended period in the atmosphere of West Antarctica.

Impaired sperm quantity and motility in adult rats following gestational and lactational exposure to environmentally relevant levels of PBDE-47: A potential role of thyroid hormones disruption

Polybrominated diphenyl ethers (PBDEs) are flame retardants and the congener 2, 2', 4, 4'-tetrabromodiphenyl ether (PBDE-47) is capable of inducing thyroid endocrine disruption and developmental toxicity. However, little is known about whether developmental PBDE-47 exposure-elicited alterations in semen quality is associated with thyroid hormones (THs) perturbation. In this research, we sought to explore the impacts of gestational and lactational PBDE-47 exposure on adult sperm quantity and motility, and its link with THs levels. For this purpose, female Sprague-Dawley rats were administered environmentally relevant PBDE-47 levels (0.1, 1.0, 10 mg/kg/day) by oral gavage from prepregnancy through lactation cessation to achieve early-life exposure of offspring and to mimic the actual exposure. Sperm quantity and motility together with serum THs levels from male offspring were determined on postnatal day 88. In utero and lactational exposure to PBDE-47 boosted the weight gain while reduced the relative testis weight in adult male offspring. These were accompanied with the reductions in sperm counts (total and living sperm counts), the percentage of progressive sperm motility, sperm velocities (curvilinear velocity, straight-line velocity and average path velocity), motion path (beat cross frequency, linearity and wobble) and linear motile sperm parameters (count, motility and concentration). Further studies identified that the levels of serum triiodothyronine (T₃) were increased by PBDE-47 exposure and negatively associated with those differential semen parameters on quantity and motility. Collectively, our results indicate that exposure to low-level PBDE-47 during early-life development impairs semen quality in adult rats, which could be mediated partially by abnormal T₃ levels.

Content and health risk assessment of heavy metals and polybrominated diphenyl ethers in fish from Songhua Lake (Jilin City), China

Levels of heavy metals and polybrominated diphenyl ethers (PBDEs) were determined in fishes sampled in Jilin Songhua Lake, China. Concentrations and congener profiles of these contaminants varied by fish type. The highest concentrations of Zn, Cu, Mn, and Cd were found in three omnivorous fish (Carassius carassius, Hypomesus olidus, and Hemiculter leucisculus). The highest concentrations of Ni, Cr, and Hg were found in Silurus asotus and Hemibarbus maculatus which are two kinds of carnivorous fish. The minimum total concentration of the seven PBDEs of fish was 0.093 ng/g wet weight (ww) in Ctenopharyngodon idellus, while the maximum, 0.342 ng/g ww, was detected in Aristichthys nobilis. Of all the congeners, BDE 28 and 47 were dominant. The estimated daily intake (EDI) of these metals and PBDEs via consuming the fishes was estimated to be 1.159-10.121 μg/kg bw/day and 0.046-0.597 ng/kg bw/day, respectively. The total hazard quotients (THQs) of both types of pollutants were far below 1, indicating that the health risks of these pollutants were low for the people who consumed the fish species from the Songhua Lake.

Chemical identity and cardiovascular toxicity of hydrophobic organic components in PM2.5

Numerous experimental and epidemiological studies have demonstrated that exposure to PM_2.5 may result in pathogenesis of several major cardiovascular diseases (CVDs), which can be attributed to the combined adverse effects induced by the complicated components of PM_2.5. Organic materials, which are major components of PM_2.5, contain thousands of chemicals, and most of them are environmental hazards. However, the contamination profile and contribution to overall toxicity of PM_2.5-bound organic components (OCs) have not been thoroughly evaluated yet. Herein, we aim to provide an overview of the literature on PM_2.5-bound hydrophobic OCs, with an emphasis on the chemical identity and reported impairments on the cardiovascular system, including the potential exposure routes and mechanisms. We first provide an update on the worldwide mass concentration and composition data of PM_2.5, and then, review the contamination profile of PM_2.5-bound hydrophobic OCs, including constitution, concentration, distribution, formation, source, and identification. In particular, the link between exposure to PM_2.5-bound hydrophobic OCs and CVDs and its possible underlying mechanisms are discussed to evaluate the possible risks of PM_2.5-bound hydrophobic OCs on the cardiovascular system and to provide suggestions for future studies.

Facile synthesis of tubular magnetic fluorinated covalent organic frameworks for efficient enrichment of ultratrace polybrominated diphenyl ethers from environmental samples

Polybrominated diphenyl ethers (PBDEs), known as the most widely used brominated flame retardant, have received great public concern due to its hidden environment and health problems. Development of highly selective and sensitive analytical approaches for enrichment and detection of ultratrace PBDEs are in high demand. Conventional sample pretreatment techniques usually require tedious procedures, long time, and excessive consumption of solvent and sample, thus hindering ultrasensitive detection of PBDEs. To address this issue, we first reported a simple room-temperature approach for synthesis of tubular magnetic fluorinated covalent organic frameworks (MCNT@TAPB-TFTA). The introduction of fluorine atoms played multiple roles in improving the frameworks' hydrophobicity and the adsorption capabilities for PBDEs. Combined with atmospheric pressure gas chromatography-tandem mass spectrometry (APGC-MS/MS), several crucial parameters of magnetic solid-phase extraction (MSPE) including adsorbent dosage, adsorption time, pH, ion strength, the eluent, elution time and elution frequencies were examined in detail. The optimal method exhibited wide linear ranges (0.01-500 ng/L), low limit of detections (LODs, 0.0045-0.018 ng/L), good correlation coefficients (r ≥ 0.9977), and high enrichment factors (EFs, 1425-1886 folds) for eight PBDEs. Furthermore, this proposed method could be successfully applied to sensitive determination of ultratrace PBDEs in environmental samples, demonstrating the promising potential of the MCNT@TPAB-TFTA as an adsorbent in sample pretreatment.

Modeling gas/particle partitioning of polybrominated diphenyl ethers (PBDEs) in the atmosphere: A review

Gas/particle (G/P) partitioning of semi-volatile organic compounds (SVOCs) such as polybrominated diphenyl ethers (PBDEs), is an important atmospheric process due to its significance in governing atmospheric fate, wet/dry deposition, and long-range atmospheric transport. In this article, eight models published to predict the G/P partitioning of PBDEs are reviewed. These eight models are used to calculate the G/P partitioning quotient and particulate phase fraction of selected PBDE congeners. A comparison of the predicted results from the eight models with monitoring data published by several research groups worldwide leads to the following conclusions: 1) when the values of the logarithm of the octanol-air partition coefficient (logK_OA) fall below 11.4 (the first threshold value, logK_OA1), all 8 models perform well in predicting the G/P partitioning of PBDEs in the atmosphere, and 2) when logK_OA is >11.4, and especially above 12.5 (the second threshold value, logK_OA2), the Li-Ma-Yang model, a steady-state model developed based on wet and dry deposition of the particles (Li et al., Atmos. Chem. Phys. 2015; 15:1669-1681), shows the best performance with highest conformity to the measurements for selected PBDEs (94.4 ± 1.6% data points within ±1 log unit). Overall, the Li-Ma-Yang model appears to capture the most important factors that affect the partitioning of PBDEs between gaseous and particular phases in the atmosphere.