Medium-Chain Chlorinated Paraffins Trigger Thyroid Hormone Synthesis and Interfere with Mitochondrial Function in the Thyroid Gland.

Medium-chain chlorinated paraffins (MCCPs, C14-C17) are frequently detected in diverse environmental media. It has been proposed to be listed in Annex A of the Convention on Persistent Organic Pollutants in 2023. Although MCCPs are a crucial health concern, their toxicity remains unclear. This study investigated the toxic effects of MCCPs (0.1-50 mg/kg body weight/day) on the thyroid gland of female Sprague-Dawley rats and characterized the potential toxic pathways via transcriptomics and metabolomics approaches. MCCPs exposure caused histopathological changes to the endoplasmic reticula and mitochondria in thyroid follicular cells at a dose of 50 mg/kg bw/d and increased serum thyrotropin-releasing hormone, thyroid-stimulating hormones, and thyroxine when exposed to a higher dose of MCCPs. Transcriptomic analysis indicated the excessive expression of key genes related to thyroid hormone synthesis induced by MCCPs. Integrating the dual-omics analysis revealed mitochondrial dysfunction of the thyroid by mediating fatty acid oxidation, Kreb's cycle, and oxidative phosphorylation. Significant metabolic toxicity on the thyroid might be linked to the characteristics of the chlorine content of MCCPs. This study revealed the toxicity of MCCPs to the thyroid gland via triggering thyroid hormone synthesis and interfering with mitochondrial function, which can provide new insights into the modes of action and mechanism-based risk assessment of MCCPs.

Enhanced effects of slowly co-released TGF-ß3 and BMP-2 from biomimetic calcium phosphate-coated silk fibroin scaffolds in the repair of osteochondral defects.

Bioactive agents have demonstrated regenerative potential for cell-free bone tissue engineering. Nevertheless, certain challenges persist, including ineffective delivery methods and confined therapeutic potency. Here, we demonstrated that the biomimetic calcium phosphate coating system (BioCaP) could effectively uptake and slowly release the incorporated bioactive agents compared to the surface absorption system via osteoclast-mediated degradation of BioCaP coatings. The release kinetics were determined as a function of time. The release rate was stable without remarkable burst release during the first 1 day, followed by a sustained release from day 7 to day 19. Then, we developed the bi-functional BioCaP-coated silk fibroin scaffolds enabling the effective co-delivery of TGF-ß3 and BMP-2 (SFI-T/SFI-B) and the corresponding slow release of TGF-ß3 and BMP-2 exhibited superior potential in promoting chondrogenesis and osteogenesis without impairing cell vitality in vitro. The SFI-T/SFI-B scaffolds could improve cartilage and bone regeneration in 5 × 4 mm rabbit osteochondral (OC) defect. These findings indicate that the biomimetic calcium-phosphate coated silk fibroin scaffolds with slowly co-released TGF-ß3 and BMP-2 effectively promote the repair of OC defects, hence facilitating the future clinical translation of controlled drug delivery in tissue engineering.

Effects of exercise on depression and anxiety in postmenopausal women: a pairwise and network meta-analysis of randomized controlled trials.

BACKGROUND: Exercise has been identified as a promising non-pharmacological therapy for the management of depression, but there is still controversy over which type is most effective. We aimed to compare and rank the types of exercise that improve depression in postmenopausal women by quantifying information from randomized controlled trials (RCTs). METHODS: The PubMed, Web of Science, SPORTDiscus, CNKI, The Cochrane Library, PsycINFO, EMBASE, and CINAHL Plus databases were searched to identify articles published from inception to 1 March 2024 reporting RCTs that examined the effectiveness of exercise on depression in postmenopausal women. The risk of bias was assessed using the revised Cochrane risk-of-bias tool for RCTs. The quality of the evidence for each comparison was graded using the online confidence in network meta-analysis tool (CINeMA). Standardized mean differences (SMDs) were calculated using the mean and standard deviation of pre-to-post intervention changes and then pooled using a random effects model in a pairwise meta-analysis using Review Manager 5.4. Then, a frequentist network meta-analysis was conducted using a random effects model was conducted to evaluate the efficacy of different exercise types using the network package of Stata 15. RESULTS: This study included 26 studies involving 2,170 participants. The pairwise meta-analysis revealed that exercise had a significant positive effect on depression in postmenopausal women (SMD = -0.71, 95% confidence interval [CI] = -0.94 to -0.48; I2 = 78%). The network meta-analysis revealed that mind-body exercise (SMD = -0.97, 95% CI = -1.28 to -0.67), aerobic exercise (SMD = -0.58, 95% CI = -0.88 to -0.27) and multicomponent exercise (SMD = -0.57, 95% CI = -1.15 to -0.002) significantly reduced depression compared to the control intervention. Mind-body exercise had the highest probability of being the most effective intervention. Exercise interventions also showed positive effects on anxiety. Most studies were judged to have some concerns regarding their risk of bias, and the confidence in evidence was often very low according to CINeMA. CONCLUSION: For postmenopausal women, there is very low to moderate quality evidence that exercise interventions are an effective antidepressant therapy, with mind-body exercise most likely being the optimal type. TRIAL REGISTRATION: This meta-analysis was prospectively registered with PROSPERO (registration number: CRD42024505425).

Residual levels and health risk assessment of trace metals in Chinese resident diet.

Large-scale metal contamination across the food web is an intractable problem due to increasing pollutant emissions, atmospheric transport, and dry and wet deposition of elements. The present study focus on several trace metals that are rarely studied but have special toxicity, including tin (Sn), antimony (Sb), gold (Au), hafnium (Hf), palladium (Pd), platinum (Pt), ruthenium (Ru), tellurium (Te) and iridium (Ir). We investigated trace metals residues and distribution characteristics, and further evaluated the potential health risks from major daily food intakes in 33 cities in China. Sn, Sb, Ir, Hf, and Au were frequently detected in food samples with the concentrations ranged from ND (not detected) to 24.78 µg/kg ww (wet weight). Eggs exhibited the highest residual level of all detected metals (13.70 ± 14.70 µg/kg ww in sum), while the lowest concentrations were observed in vegetables (0.53 ± 0.17 µg/kg ww in sum). Sn accounting for more than 50% of the total trace metals concentration in both terrestrial and aquatic animal origin foods. In terrestrial plant origin foods, Sn and Ir were the most abundant elements. Hf and Au were the most abundant elements in egg samples. In addition, Sb and Ir showed a clear trophic dilution effect in terrestrial environments, while in aquatic ecosystems, Sn, Hf, and Au exhibited obvious trophic amplification effects. The calculated average estimated daily intake (EDI) via food consumption in five regions of China was 0.09 µg/(kg·day), implying the health risk of aforementioned elements was acceptable.

Spotlights on ubiquitin-specific protease 12 (USP12) in diseases: from multifaceted roles to pathophysiological mechanisms.

Ubiquitination is one of the most significant post-translational modifications that regulate almost all physiological processes like cell proliferation, autophagy, apoptosis, and cell cycle progression. Contrary to ubiquitination, deubiquitination removes ubiquitin from targeted protein to maintain its stability and thus regulate cellular homeostasis. Ubiquitin-Specific Protease 12 (USP12) belongs to the biggest family of deubiquitinases named ubiquitin-specific proteases and has been reported to be correlated with various pathophysiological processes. In this review, we initially introduce the structure and biological functions of USP12 briefly and summarize multiple substrates of USP12 as well as the underlying mechanisms. Moreover, we discuss the influence of USP12 on tumorigenesis, tumor immune microenvironment (TME), disease, and related signaling pathways. This study also provides updated information on the roles and functions of USP12 in different types of cancers and other diseases, including prostate cancer, breast cancer, lung cancer, liver cancer, cardiac hypertrophy, multiple myeloma, and Huntington's disease. Generally, this review sums up the research advances of USP12 and discusses its potential clinical application value which deserves more exploration in the future.

Release Mechanism of Short- and Medium-Chain Chlorinated Paraffins from PVC Materials under Thermal Treatment.

Chlorinated paraffins (CPs) as plasticizers are massively added to polyvinyl chloride (PVC) products, during whose life cycle CPs can be continuously released especially under thermal stress. In this study, a PVC cable sheath was adopted as a representative kind of PVC material to investigate the release behaviors of short- and medium-chain CPs (SCCPs and MCCPs) under thermal treatment. Release percentages of CPs with increasing temperature followed a Gaussian-like curve. At the unmolten stage of 80 °C, heating for 10 min caused 0.051% of added SCCPs and 0.029% of added MCCPs to be released. At the molten stage of 270 °C, accumulative release rates of SCCPs and MCCPs within 10 min were up to 30 and 14%, respectively. The developed emission model indicated that material-gas partitioning and internal diffusion simultaneously governed the release of CPs. During thermal treatment, the release of CPs could be remarkably affected by the thermal expansion of the PVC material and the formation of breakage and micropores. Congener group profiles of released CPs indicated a slight fractionation effect for SCCPs during the release process. Furthermore, the release risk of CPs from the whole life cycle of PVC products was preliminarily evaluated.

Relationships between physical activity, body image, BMI, depression and anxiety in Chinese college students during the COVID-19 pandemic.

BACKGROUND: Both depression and anxiety are worldwide burden that is not being abated with our current knowledge and treatment of the condition. Numerous clinical trials have supported that physical activity (PA) can reduce the depression and anxiety in adolescents, but little is known about its mechanism of action. Therefore, the study objectives were to explore the potential relationship between physical activity and depression and anxiety from the perspective of body image and body mass index (BMI), and to provide an important reference for future self-esteem education and health promotion intervention. METHODS: The participants in this study were 251 Chinese college students between 17 and 22 years old. Participants completed the International Physical Activity Questionnaire-Short Form (IPAQ-SF), the Body Image Questionnaire (BIQ), the Self-rating Depression Scale (SDS) and the Self-rating Anxiety Scale (SAS). A descriptive and correlational approach was used, using the PROCESS macro for Statistical Package for the Social Sciences (SPSS). RESULTS: (1) Physical activity was significantly negatively correlated with both depression and anxiety (t = -0.216, p < 0.001; t = -0.184, p < 0.01). (2) Body image had a significant moderating effect on the relationship between physical activity and anxiety among college students, but there was no moderating effect between depression and physical activity. BMI has no moderating effect on the two interrelationships. CONCLUSION: There is only body image that moderates the relationship between anxiety and physical activity.

Dense Conductive Metal-Organic Frameworks as Robust Electrocatalysts for Biosensing.

Due to the fascinating properties such as high porosity, large surface areas, and tunable chemical components, metal-organic frameworks (MOFs) have emerged in many fields including catalysis, energy storage, and gas separation. However, the intrinsic electrical insulation of MOFs severely restricts their application in electrochemistry. Here, we synthesize a series of 2D conductive MOFs (cMOFs) through tuning the structure with atomic precision using simple hydrothermal methods. Various electroactive probes are used to reveal the structure-property relationships in 2D cMOFs. Then, we demonstrate the first exploration and implementation of 2D cMOFs toward the construction of electrochemical biosensors. In particular, the biosensor based on Cu3(tetrahydroxy-1,4-quinone)2 [Cu3(THQ)2] displays a remarkably improved electrocatalytic performance at a much lower potential. The mechanism study reveals the essential role of charge-transfer interactions between the dense catalytic sites of Cu3(THQ)2 and analytes. Furthermore, the Cu3(THQ)2-based biosensor demonstrates robust anti-interference capability, good stability, fast response speed, and an ultralow detection limit for paraoxon. These promising results indicate the great potential of cMOFs in biomedical, food safety, and environmental sensing applications.

A cleanup method of serum extracts with molecular sieves as SPE sorbents for the analysis of polybrominated diphenyl ethers.

Based on the size- and shape-selective sorption, 13X molecular sieves were developed as solid-phase extraction adsorbents to cleanup serum extract for the determination of polybrominated diphenyl ethers. The important parameters affecting the cleanup efficiency were investigated including the amount of sorbents, the type, and volume of solvents. Under the optimized conditions, the capacity for removing impurities was evaluated via gel permeation chromatography and gas chromatography with mass spectrometry. The results demonstrated that up to 99% of lipids in corn oil (13 mg) can be removed after cleanup, and endogenous compounds in serum can also be effectively eliminated. The cleanup efficiency is not only superior to hydrophile-lipophile balance column, but also close to acid silica gel and multifunction impurity sorbents. Generally, the developed cleanup method exhibited higher recovery for polybrominated diphenyl ethers with more than four bromines, especially for nona- and deca-brominated diphenyl ethers (99.1-117.8%). The cleanup method can be coupled with gas chromatography and tandem mass spectrometry for polybrominated diphenyl ethers analysis in human serum. The method detection limits were 0.01-0.27 ng/mL and average recovery was 50.9-113.3%, except 2,3',4',6-tetrabrominated, 2,3',4,4',6-pentabrominated, and 2,3,3',4,4',5',6-heptabrominated diphenyl ethers. 2,2',4,5'-Tetrabrominated diphenyl ethers had the highest detection frequency (95%) in human serum, whereas decabrominated diphenyl ethers had the maximum mean concentration (0.50 ng/mL).

Risk factors for midcourse correction during treatment of first series of aligners with Invisalign.

INTRODUCTION: This study aimed to analyze risk factors for midcourse correction (MC) during the first series of aligners in treatments with Invisalign (Align Technology, Santa Clara, Calif). METHODS: Three hundred and fourteen patients treated with Invisalign were divided into MC and non-midcourse correction groups according to whether they completed the first series of aligners. Differences between these groups were compared with independent sample t tests, chi-square tests, and Wilcoxon rank sum tests. A multivariate logistic regression analysis was performed to identify independent risk factors, including gender, age, extraction treatment, interproximal reduction, correction steps (steps in first series treatment), overbite, overjet, the curve of Spee, Angle classification, and crowding. RESULTS: The percentage of females (86.3%), Angle Class I malocclusion (62.4%), and nonextraction (56.1%) was relatively higher in all 314 patients. More than half of the patients (73.6%) completed the first series of aligners. Differences between the groups in the number of patients with extraction, correction steps, and the curve of Spee were significant (P <0.05). The proportions of MC were 41.3% and 14.8% in extraction and nonextraction patients, respectively. More initially planned correction steps were seen in the MC group (53.4 ± 15.6 steps). Extraction (adjusted odds ratio, 0.375; P = 0.001) and correction steps (adjusted odds ratio, 1.06; P <0.001) were independent risk factors for MC. CONCLUSIONS: Extraction and the number of initially planned correction steps are independent risk factors for MC. In patients with complex dentofacial abnormalities, such as extraction, MC may be needed to achieve predicted changes.

FT-ICR mass spectrometry for molecular characterization of water-insoluble organic compounds in winter atmospheric fine particulate matters.

Water-insoluble organic compounds (WIOCs) are an important fraction of atmospheric fine particulate matters (PM2.5), which could affect the climate system and threaten human health potentially. In this study, molecular characterization of WIOCs in PM2.5 were investigated by 15 T Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) with atmospheric pressure photoionization (APPI) source in positive ion mode. A total of 2573 and 1875 molecular formulas were identified in WIOCs extracted by dichloromethane, which were collected in hazy and normal days, respectively. The identified molecular formulas were further classified into four major subgroups, including CH, CHN, CHO and CHNO compounds. CHO compounds predominated in WIOCs, accounting for more than 60% in both samples. CHNO compounds (26.6%) and CH compounds (16.1%) were the second highest subgroups in WIOCs from the hazy days and normal days, respectively. The relative abundance and number of nitro-substituted aromatic compounds were significantly higher in hazy days than in normal days. The molecular composition of WIOCs was more complex in hazy days while more aromatic compounds were identified in normal days.

Nitrogen-Doped Graphdiyne as a Robust Electrochemical Biosensing Platform for Ultrasensitive Detection of Environmental Pollutants.

Owing to its unique chemical structure, natural pores, high structure defects, good surface hydrophilicity and biocompatibility, and favorable electrical conductivity, nitrogen-doped graphdiyne (NGDY) has been attracting attention in the application of electrochemical sensing. Taking advantage of these fascinating electrochemical properties, for the first time, two types of electrochemical enzymatic biosensors were fabricated for the respective detection of organophosphorus pesticides (OPs) and phenols based on the immobilization of acetylcholinesterase or tyrosinase with NGDY. Results revealed that the sensitivities of the NGDY-based enzymatic biosensors were almost twice higher than that of the matching biosensor in the absence of NGDY, proving that NGDY plays a vital role in immobilizing the enzymes and improving the performance of the fabricated biosensors. The effects of nitrogen doping on improving the biosensing performance were studied in depth. Graphitic N atoms can enhance the electrical conductivity, while imine N and pyridinic N can help to adsorb and accumulate the substance molecules to the electrode surface, all of which contribute to the significantly improved performance. Furthermore, these two types of biosensors also demonstrated excellent reproducibility, high stability, and good recovery rate in real environmental samples, which showed a valuable way for the rapid detection of OPs and phenols in the environment. With these excellent performances, it is strongly anticipated that NGDY has tremendous potential to be applied to many other biomedical and environmental fields.

Extreme Exposure Levels of PCDD/Fs Inhaled from Biomass Burning Activity for Cooking in Typical Rural Households.

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), emitted during biomass combustion, are carcinogenic chemicals. The association between indoor biomass burning and PCDD/Fs inhalation exposure levels is still poorly understood. This study first reports direct measurement of personal exposure to PCDD/Fs in real-world households with wood combustion. In homes where biomass burning is used for cooking, toxic equivalent quantity (TEQ) PCDD/Fs concentrations were found to be 545 ± 251 fg I-TEQ/m3 in kitchens, with levels of 4.5-, 6.9-, and 13.3-fold higher than those in living rooms (122 ± 92 fg I-TEQ/m3), bedrooms (79 ± 27 fg I-TEQ/m3), and ambient air (41 ± 15 fg I-TEQ/m3), respectively. PCDD/Fs exposure levels in populations using biomass fuels for cooking (353 ± 110 fg I-TEQ/m3) were 4.3-fold higher than those in the control groups (82 ± 32 fg I-TEQ/m3). Additionally, the average cancer risks for biomass cooking person were approximately 3.1-fold higher than those in factory workers. Overall, residents of household that use biomass fuels for cooking have the highest known risk of PCDD/Fs exposure. These results highlight that aiming to mitigate the PCDD/Fs exposure risk in the general population, the focus of dioxin emission source control measures should shift from industrial sectors to residential biomass combustion.

Inhibition Effect and Mechanism of Thiourea on Electrophilic Chlorination of Aromatics in Combustion Flue Gas.

Thiourea can effectively inhibit the formation of highly toxic chlorinated aromatics in postcombustion zone. However, the inhibition mechanism was still not adequately understood. In this study, naphthalene was adopted as a model aromatic compound to investigate the inhibition effect and mechanism of thiourea on the formation of chlorinated aromatics via electrophilic chlorination over Cu and Fe chlorides. Thiourea addition resulted in the reductions of 77.6-99.8% and 36.4-98.1% in the yield of polychlorinated naphthalenes from naphthalene chlorination mediated by CuCl2 and FeCl3 at 150-300 °C, respectively. The inhibition efficiency of chlorination presented a decreasing tendency with increasing reaction temperature and O2 content in flue gas. X-ray diffraction analysis revealed that the thiourea-induced reduction of highly active Cu (II) and Fe (III) chlorides to less active Cu (I) and Fe (II) chlorides was a primary mechanism for inhibiting aromatic chlorination. [thiourea-Cu]+ complex generated during the reduction process could be transformed into CuS and Cu2S, and isomeric reaction product NH4SCN could react with Cu2+ to produce Cu(SCN)2 and then also form Cu sulfides, suggesting sulfidization of Cu chloride was another important inhibition mechanism. Chlorination inhibition induced by the volatile decomposition products of thiourea might only play a minor role.

The dose effect of dansyl chloride on the derivative products of bisphenols and its application for the determination of bisphenols in human serum by high-performance liquid chromatography-tandem mass spectrometry.

Human exposure to bisphenols has rarely been reported. The most important challenges in this regard are the sensitivity and accuracy of the analytical methods employed. Dansyl chloride derivatization prior to high-performance liquid chromatography-tandem mass spectrometry has been prevalently employed to improve sensitivity. However, the dose effect of the derivatization reagent on the reaction products is not well understood, especially for reactants with two or more active groups. This study investigated the mass ratio of dansyl chloride to bisphenols and found the mass ratio played a vital role in changing the composition of derivatives; further, the optimal ratio for obtaining di-substituted derivatives was confirmed. Under optimal conditions, solid-phase extraction followed by dansyl chloride derivatization coupled with high-performance liquid chromatography-tandem mass spectrometry was used to detect eight bisphenols in human serum samples. The method detection limits of the eight bisphenols were 0.025-0.28 ng/mL, and the recoveries were 72.9-121.7% by spiking bisphenols (2, 5, and 20 ng/mL) into bovine serum. The detection frequencies of bisphenol A and bisphenol F in 73 serum samples obtained from children from Guangzhou were 41.1% and 71.2%, respectively, while the detection frequencies of other bisphenols were below 20%. The concentrations of bisphenol A and bisphenol F were < 0.28-8.0 ng/mL and < 0.028-7.6 ng/mL, respectively.

Robust Single-Molecule Enzyme Nanocapsules for Biosensing with Significantly Improved Biosensor Stability.

The present study demonstrates the use of highly stable single-molecule enzyme nanocapsules (SMENs) instead of traditional native enzyme as biorecognition element in enzyme-based biosensors. The main purpose of this study is to resolve the major obstacle and challenge in the biosensor field, i.e., the poor stability of enzyme-based biosensors, including thermal stability, organic solvent tolerance, long-term operational stability, etc. Highly active and robust SMENs of glucose oxidase (GOx, as a model enzyme) were synthesized (nGOx) using an in situ polymerization strategy in an aqueous environment. The particle-size distribution, transmission electron microscopic (TEM) images, and UV-vis spectral characterization revealed the formation of a thin polymer layer around each enzyme molecule. The polymer shell effectively stabilized the GOx enzyme core while enabling rapid substrate transportation, resulting in a new class of biocatalytic nanocapsules. Multiple covalent attachments between a thin polymer layer and an enzyme molecule strengthened the encapsulated GOx molecule. Encapsulation created a favorable microenvironment to avoid any structural dissociation at high temperature and helped to retain essential water during the organic solvent operation. The present work reports a study implementing nGOx SMENs as highly stable nano(bio)sensors for point-of-care diagnostic applications. Prepared nGOx SMENs manifested significantly improved thermal stability (even at 65 °C) and organic solvent tolerance without any compromise in biocatalytic activity. For example, the native GOx-based biosensor lost its catalytic activity for glucose after 4 h of incubation at high temperature (65 °C), while the nGOx/N-CNTs-Chi/GCE nano(bio)sensor maintained ∼56% of its original catalytic activity for glucose oxidation. The proposed SMENs-based nano(bio)sensors with robust stability in variable working environment could promote the development and applications of biosensors in point-of care diagnostics, biomedical detection, wearable devices, implantable equipment, and biofuel cells.

Sources and health risks of PM2.5-bound polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in a North China rural area.

Polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) are typical persistent organic pollutants (POPs), which have high toxicity, bioaccumulation and long-distance transfer capability. Daily variation, sources of PCBs and OCPs in PM2.5 are rarely explored in polluted rural area. Here, the sources and health risks of the PCBs and OCPs were evaluated for 48 PM2.5 samples collected in winter 2017 in Wangdu, a heavy polluted rural area in the North China Plain. The average diurnal and nocturnal concentrations of Σ18PCBs and Σ15OCPs were 1.74-24.37 and 1.77-100.49, 11.67-408.81 and 16.89-865.60 pg/m3, respectively. Hexa-CBs and penta-CBs accounted for higher proportions (29.0% and 33.6%) of clean and polluted samples, respectively. Hexachlorobenzene (HCB) was the dominant contributor to OCPs with an average concentration of 116.17 pg/m3. Hexachlorocyclohexane (ΣHCHs) and dichlorodiphenyltrichloroethane (ΣDDTs) were the other two main classes in OCPs with the average concentrations of 4.33 and 15.89 pg/m3, respectively. ß-HCH and p,p'-DDE were the main degradation products of HCHs and DDTs, respectively. The principal component analysis and characteristic ratio method indicated both waste incineration and industrial activities were the main sources of PCBs, contributing 76.8% and 12.7%, respectively. The loadings of OCPs were attributed to their application characteristics and the characteristic ratio method reflected a current or past use of OCPs. Health risk assessment showed that the respiratory exposure quantity of doxin-like PCBs (DL-PCBs) and the lifetime cancer risk from airborne OCPs exposure was negligible, while the other exposure modes may pose a risk to human bodies.

Electrophilic Chlorination of Naphthalene in Combustion Flue Gas.

Naphthalene chlorination is an important formation mechanism of polychlorinated naphthalenes (PCNs) in combustion flue gas. In this study, a total of 21 metal chlorides and oxides were screened for their activities in the electrophilic chlorination of naphthalene. Copper(II) chloride exhibited the highest activity at 200-350 °C, followed by copper(I) chloride. Copper(II) chloride primarily acted as a strong chlorinating agent to facilitate chlorine substitution on naphthalene. Iron (II and III) chlorides were only highly active at 200-250 °C. At 250 °C, the average naphthalene chlorination efficiency over CuCl2·2H2O was 7.5-fold, 30.2-fold and 34.7-fold higher than those over CuCl, FeCl3·6H2O and FeCl2·4H2O, respectively. The other metal chlorides were less active. Under heated conditions, copper(II) and iron(III) chlorides were transformed to copper(I) and iron(II) chlorides via dechlorination, and then transformed to oxychlorides and oxides, thereby forming dechlorination-oxychlorination cycles of copper and iron species, respectively. The results obtained suggest that electrophilic chlorination of naphthalene in combustion flue gas is primarily driven by dechlorination-oxychlorination cycles of copper and iron species, and the reaction produces a selective chlorination pattern at 1 and 4 positions of naphthalene.

Release and Transformation of BTBPE During the Thermal Treatment of Flame Retardant ABS Plastics.

Thermal scenarios inevitably occur during the lifecycle of engineering plastics laden with brominated flame retardants (BFRs). However, little information on the fate of embedded BFRs during the thermal processes is available. In this study, we measured the release and transformation of a typical BFR, 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), during the thermal treatment of acrylonitrile butadiene styrene (ABS) plastics. The possible thermal scenarios were simulated by varying the heating temperature and atmosphere. The maximum release rate of BTBPE was observed at 350 °C. A release kinetic model was developed to explore the mechanism of BTBPE release while heating ABS. Material-phase diffusion was found to be the rate-determining step during release. According to the developed release model, it was estimated that 0.04-0.17% of embedded BTBPE could be released to air during the industrial processing of ABS plastics. When the heating temperature was ≥350 °C, approximately 15-56% of embedded BTBPE decomposed to bromophenols (BPs) and 1,3,5-tribromo-2-(vinyloxy) benzene (TBVOB), and the decomposition followed a first-order kinetics at 350 °C. Polybrominated dibenzo- p-dioxins and dibenzofurans (PBDD/Fs) were also significantly formed at ≥350 °C from BPs and TBVOB via a precursor mechanism. A higher temperature (≥450 °C) was favorable for the formation of PBDFs.

Quantification of Cl-PAHs and their parent compounds in fish by improved ASE method and stable isotope dilution GC-MS.

This study aimed at developing a simple and accurate method for determination of emerging chlorinated polycyclic aromatic hydrocarbons (Cl-PAHs) in fish by stable isotope dilution gas chromatography tandem mass spectrometry. Fish samples were extracted by improved accelerated solvent extraction (ASE) method. Matrix effects were observed, and matrix-matched calibration was verified with good intra-day and inter day precisions (lower than 16.1% and 15.1% respectively). Method detection limits were 0.10-5.62 ng g-1 (dry weight) with satisfactory linearity, and recoveries ranged from 50% to 150%, with relative standard deviation values less than 18.5% at different concentration levels. This improved ASE method was proved to be suitable for analyzing Cl-PAHs in fish samples, with good analytical selectivity, linearity, recovery and precision. Furthermore, the composition analysis revealed that chlorinated compounds of phenanthrene, pyrene and acenaphthene were dominated in Cl-PAHs contaminants. The correlationship between the pollution of Cl-PAHs and their corresponding parent structures in fish samples was also analyzed in detail.