Identification and quantification of per- and polyfluorinated alkyl substances (PFAS) migrating from food contact materials (FCM).

Per- and polyfluorinated alkyl substances (PFAS) can be added to food contact materials (FCM) to increase their water and/or grease repellent properties. Some well-known PFAS are perfluoroalkyl carboxylic acids (PFCA), perfluoroalkyl sulfonic acids (PFSA), and polyfluorinated telomer alcohols (FTOH). Due to the strength of the carbon-fluorine bond, PFAS are chemically very stable and highly resistant to biological degradation, posing a risk to human health and the environment. To examine the presence of PFAS in paper-based FCM, various samples were collected, including popcorn bags, muffin cups, and pizza boxes with high total organic fluorine (TOF) content from the Danish and Spanish markets. The FCM composition was characterised by FTIR. Quantification of some well-known PFAS such as PFCA, PFSA, and FTOH was performed in food simulants using LC-MS/MS, and in addition a non-targeted screening approach was performed by LC-Orbitrap-HRMS. Among analysed samples, the highest concentrations of PFAS were found in a muffin cup made of cellulose (PFCA âˆ¼ 1.41 µg kg-1 food, FTOH âˆ¼ 11.5 µg kg-1 food), and the results were used to estimate dietary exposures to PFAS migrated from this FCM. Compared to measured TOF value in this sample, the fluorine from all quantified PFAS accounted for only 0.6%. Thus, a more powerful analytical approach was used to further investigate PFAS occurrence in this sample. Using non-targeted screening, an additional twenty compounds were identified, among them five with confidence level 1 and ten with confidence level 2. Many of them were either fluorotelomer carboxylic acids or sulfonic acids or ether-containing compounds.

Examination of Taurine Chloramine and Taurine on LPS-Induced Acute Pulmonary Inflammatory in Mice.

The novel coronavirus disease (COVID-19), which is prevalent in the world, develops severe pneumonia, of which 30% have fatal acute respiratory distress and acute lung injury. At present, there is no established treatment method for ARDS, and it is desired to develop a therapeutic drug as soon as possible. While TauCl has been reported to have anti-inflammatory effects on culture cells, little information is available concerning in vivo experiments. In the present study, we evaluated the anti-inflammatory effect of taurine chloramine (TauCl), a taurine derivative, against LPS-induced pneumonia in mouse. The mice were pretreated with TauCl intraperitoneally before intratracheal administration of LPS. Additionally, we evaluated the effect of taurine treatment by maintaining the mice on drinking water containing 0.5% taurine. Two days after LPS injection, body weight was decreased by 9.5 %, while lung weight was increased due to the infiltration of inflammatory cells; TauCl attenuated the gain in lung weight. LPS-induced acute pneumonia caused an increase in cytokine/chemokine mRNA expression, including that of IL-1ß, -6, -17, TNF-α, and MCP-1. However, TauCl treatment attenuated IL-6 expression, but not that of the others although the induction of plasma IL-6 tended to be reduced by TauCl treatment. Importantly, a similar effect against LPS-induced acute lung inflammation was confirmed by taurine pretreatment. These findings suggest that TauCl treatment partially prevents IL-6 production induced by acute pneumonia in vivo.

Bioavailability of Tauropine After Oral Ingestion in Mouse.

In the present study, we investigated the pharmacokinetics of oral ingested tauropine which is a natural taurine derivative found in marine invertebrates, such as abalone, and in mouse. To measure tauropine in the blood, it was derivatized with phenyl isothiocyanate (PITC), and PITC-tauropine was separated by reverse-phase high-performance liquid chromatography (HPLC) and detected by ultraviolet absorbance. Tauropine was detectable in the blood obtained from mice intraperitoneally injected with tauropine. However, it was not detectable in blood obtained from orally treated mice. In conclusion, oral ingested tauropine may be poorly absorbed by the gastrointestinal tract and transported into the blood.

Is the use of paper food contact materials treated with per- and polyfluorinated alkyl substances safe for high-temperature applications? - Migration study in real food and food simulants.

Migration of per- and polyfluorinated alkyl substances (PFAS) from paper food contact materials (FCMs) can pose a consumer risk. However, risk assessment procedures typically do not consider PFAS contribution from FCMs. Moreover, migration studies are often limited to one subclass of PFAS or simplified by using food simulants (FS). To assess the risk comprehensively, migration of three PFAS subclasses (perfluorinated carboxylic acids/ sulfonic acids (PFCAs/PFSAs), polyfluoroalkyl phosphate esters (PAPs), and fluorotelomer alcohols (FTOHs)) from six FCMs were investigated to FS (50% and 20% ethanol) and food (oatmeal porridge, muffins, and tomato soup) under high-temperature conditions. Migration of PFCAs and FTOHs to all food samples was observed. Migration of PFCAs and FTOHs to 50% ethanol was significantly higher than migration to real food whilst FTOHs did not migrate into 20% ethanol. Estimated dietary PFAS exposure for children (1.06 - 5.67 ng/kgbw/day) exceeded EFSA's proposed safety threshold (0.63 ng/kgbw/day), risking consumer health.

Formation and mitigation of acrylamide in oven baked vegetable fries.

Investigation into oven baked sweet potato and carrot fries at various temperatures and times demonstrated the in situ formation of acrylamide in an exponential manner. High levels of acrylamide were found in these food items: up to 327 µg/kg for sweet potato baked at 190 °C for 14 min, and 99 µg/kg for carrot baked at 190 °C for 13 min. Risk assessment via Margin of Exposures estimation showed that consumption of these fries might pose adverse health effects to consumers from toddlers to adults, especially when the fries were prepared at high temperatures above 175 °C and for a long time. Raw ingredient blanching and immersion in acetic acid prior to preparation have been proven to greatly reduce acrylamide formation, up to 99%. It is recommendable to apply these techniques either at industrial or domestic cooking scales to ensure minimal health risk from dietary exposure to acrylamide.

Quantification of furan and 5 alkylfurans with complete separation of 2-ethylfuran and 2,5-dimethylfuran isomers in cereals, coffee and Infant products by GC-MS.

Alkylfurans have been found concurrently to furan in thermally processed food and might add to the overall exposure, thereby increase the health concern. The analytical methods developed for these compounds are based on gas chromatography separation coupled to mass spectrometry. Two of those alkylfurans, 2,5-dimethylfuran and 2-ethylfuran, are isomers, for which accurate quantification require either complete chromatographic separation or tandem mass spectrometry (MS/MS) selectivity. A new chromatographic method is reported using the Supelco Equity-1 column, demonstrating complete baseline separation of these two isomers, with a shorter runtime when using single mass spectrometry. Full validation was performed successfully for furan, 2- and 3-methylfuran, 2-ethylfuran, 2,5-dimethylfuran and 2-pentylfuran on different food matrices with recovery rates in the range of 80-110 %, repeatability below 14%, intermediate reproducibility below 22% as well as expanded uncertainty under 50%.

Effect of calcium peroxide pretreatment on the remediation of sulfonamide antibiotics (SMs) by Chlorella sp.

This study investigated the effect of CaO2 pretreatment on sulfonamide antibiotics (SMs) remediation by Chlorella sp. Results showed that a CaO2 dose ranging from 0.05 to 0.1 g/g biomass was the best and led to higher SMs removal efficacy 5-10% higher than the control. The contributions made by cometabolism and CaO2 in SMs remediation were very similar. Bioassimilation could remove 24% of sulfadiazine (SDZ) and sulfamethazine (SMZ), and accounted for 38% of sulfamethoxazole (SMX) remediation. Pretreatment by CaO2 wielded a positive effect on microalgae. The extracellular polymeric substances (EPS) level of the CaO2 pretreatment microalgae was three times higher when subjected to non-pretreatment. For the long-term, pretreatment microalgae removed SMs 10-20% more than the non-pretreatment microalgae. Protein fractions of EPS in continuous operation produced up to 90 mg/L for cometabolism. For bioassimilation, SMX intensity of the pretreatment samples was 160-fold less than the non-treatment one. It indicated the CaO2 pretreatment has enhanced the biochemical function of the intracellular environment of microalgae. Peroxidase enzyme involved positively in the cometabolism and degradation of SMs to several metabolites including ring cleavage, hydroxylation and pterin-related conjugation.

Some characters of bacterial cellulases in goats' rumen elucidated by metagenomic DNA analysis and the role of fibronectin 3 module for endoglucanase function.

OBJECTIVE: Fibronectin 3 (FN3) and immunoglobulin like modules (Ig) are usually collocated beside modular cellulase catalytic domains. However, very few researches have investigated the role of these modules. In a previous study, we have sequenced and analyzed bacterial metagenomic DNA in Vietnamese goats' rumen and found that cellulase-producing bacteria and cellulase families were dominant. In this study, the properties of modular cellulases and the role of a FN3 in unique endoglucanase belonging to glycosyl hydorlase (GH) family 5 were determined. METHODS: Based on Pfam analysis, the cellulases sequences containing FN3, Ig modules were extracted from 297 complete open reading frames (ORFs). The alkaline, thermostability, tertiary structure of deduced enzymes were predicted by AcalPred, TBI software, Phyre2 and Swiss models. Then, whole and truncated forms of a selected gene were expressed in Escherichia coli and purified by His-tag affinity column for assessment of FN3 ability to enhance enzyme activity, solubility and conformation. RESULTS: From 297 complete ORFs coding for cellulases, 148 sequences containing FN3, Ig were identified. Mostly FN3 appeared in 90.9% beta-glucosidases belonging to glycosyl hydrolase family 3 (GH3) and situated downstream of catalytic domains. The Ig was found upstream of 100% endoglucanase GH9. Rarely FN3 was seen to be situated downstream of X domain and upstream of catalytic domain endoglucanase GH5. Whole enzyme (called XFN3GH5 based on modular structure) and truncate forms FN3, XFN3, FN3GH5, GH5 were cloned in pET22b (+) and pET22SUMO to be expressed in single and fusion forms with a small ubiquitin-related modifier partner (S). The FN3, SFN3 increased GH5 solubility in FN3GH5, SFN3GH5. The SFN3 partly served for GH5 conformation in SFN3GH5, increased modules interaction and enzyme-soluble substrate affinity to enhance SXFN3GH5, SFN3GH5 activities in mixtures. Both SFN3 and SXFN3 did not anchor enzyme on filter paper but exfoliate and separate cellulose chains on filter paper for enzyme hydrolysis. CONCLUSION: Based on these findings, the presence of FN3 module in certain cellulases was confirmed and it assisted for enzyme conformation and activity in both soluble and insoluble substrate.

Occurrence of MCPD and glycidyl fatty acid esters in standard and specialised infant formula in Denmark.

Standard infant formula and specialised infant formula for medical purposes in Denmark (n = 42) were assessed for the levels of 2-MCPDEs, 3-MCPDEs, and GEs. Similar concentrations of GEs were observed in both standard and specialised powder infant formula at around 11.5 µg/kg. For 2-MCPDEs and 3-MCPDEs, significantly higher concentrations were observed in specialised products (18.0 and 49.8 µg/kg, respectively) in comparison with the standard ones (11.8 and 31.0 µg/kg, respectively). The concentration profiles also revealed discrepancies in MCPDEs and GEs concentrations not only between different manufacturers but also in terms of infant formula variety. For instance, the hypoallergenic powder formula showed twice as much MCPDEs as the normal formula variety. Exposure estimation using average contaminant concentrations in each variety suggested no potential risk of 3-MCPDEs and GEs intake for Danish infants via infant formula consumption. However, special attention is required for a few specific products where risks might occur in terms of 3-MCPDEs and/or GEs consumption.

Micropollutants cometabolism of microalgae for wastewater remediation: Effect of carbon sources to cometabolism and degradation products.

This study investigated the impacts of selective sole carbon source-induced micropollutants (MPs) cometabolism of Chlorella sp. by: (i) extracellular polymeric substances (EPS), superoxide dismutase and peroxidase enzyme production; (ii) MPs removal efficiency and cometabolism rate; (iii) MPs' potential degradation products identification; and (iv) degradation pathways and validation using the Eawag database to differentiate the cometabolism of Chlorella sp. with other microbes. Adding the sole carbon sources in the presence of MPs increased EPS and enzyme concentrations from 2 to 100-fold in comparison with only sole carbon sources. This confirmed that MPs cometabolism had occurred. The removal efficiencies of tetracycline, sulfamethoxazole, and bisphenol A ranged from 16-99%, 32-92%, and 58-99%, respectively. By increasing EPS and enzyme activity, the MPs concentrations accumulated in microalgae cells also fell 400-fold. The cometabolism process resulted in several degradation products of MPs. This study drew an insightful understanding of cometabolism for MPs remediation in wastewater. Based on the results, proper carbon sources for microalgae can be selected for practical applications to remediate MPs in wastewater while simultaneously recovering biomass for several industries and gaining revenue.

In Vivo and In Vitro Study of N-Methyltaurine on Pharmacokinetics and Antimuscle Atrophic Effects in Mice.

Various types of seaweed are potential functional foods as they contain multiple bioactive compounds. N-Methyltaurine (NMT) is a taurine derivative metabolite found in a type of red algae. The functional actions of NMT in mammalian animals have not been investigated, but the parent compound, taurine, possesses a variety of cellular actions. To explore the beneficial role of NMT in animals, the present study analyzed the effect of NMT against glucocorticoid-induced skeletal muscle atrophy. Glucocorticoids are one of the major causes of pathological muscle atrophy. Initially, we assessed the bioavailability of ingested NMT by determining its concentration in mouse blood. The bioavailability of orally administered NMT was found to be 96.1% that of intravenously administered NMT. Mice maintained on water containing 0.5% NMT for several days lead to the distribution of the taurine derivative to various tissues, including skeletal muscles. Like taurine, the delivery of NMT to skeletal muscles or myoblast cells is cytoprotective. The treatment with NMT prevents dexamethasone-induced atrophy of myotubes derived from C2C12 cells. Similarly, the addition of 0.5% NMT to drinking water attenuates dexamethasone-mediated reduction in muscle mass of the treated mice. The present study supports the hypothesis that orally administered NMT partially reverses skeletal muscle atrophy.

Acetaminophen micropollutant: Historical and current occurrences, toxicity, removal strategies and transformation pathways in different environments.

Acetaminophen (ACT) is commonly used as a counter painkiller and nowadays, it is increasingly present in the natural water environment. Although its concentrations are usually at the ppt to ppm levels, ACT can transform into various intermediates depending on the environmental conditions. Due to the complexity of the ACT degradation products and the intermediates, it poses a major challenge for monitoring, detection and to propose adequate treatment technologies. The main objectives of this review study were to assess (i) the occurrences and toxicities, (2) the removal technologies and (3) the transformation pathways and intermediates of ACT in four environmental compartments namely wastewater, surface water, ground water, and soil/sediments. Based on the review, it was observed that the ACT concentrations in wastewater can reach up to several hundreds of ppb. Amongst the different countries, China and the USA showed the highest ACT concentration in wastewater (≤300 µg/L), with a very high detection frequency (81-100%). Concerning surface water, the ACT concentrations were found to be at the ppt level. Some regions in France, Spain, Germany, Korea, USA, and UK comply with the recommended ACT concentration for drinking water (71 ng/L). Notably, ACT can transform and degrade into various metabolites such as aromatic derivatives or organic acids. Some of them (e.g., hydroquinone and benzoquinone) are toxic to human and other life forms. Thus, in water and wastewater treatment plants, tertiary treatment systems such as advanced oxidation, membrane separation, and hybrid processes should be used to remove the toxic metabolites of ACT.

An Update on Anti-CD137 Antibodies in Immunotherapies for Cancer.

The selective expression of CD137 on cells of the immune system (e.g., T and DC cells) and oncogenic cells in several types of cancer leads this molecule to be an attractive target to discover cancer immunotherapy. Therefore, specific antibodies against CD137 are being studied and developed aiming to activate and enhance anti-cancer immune responses as well as suppress oncogenic cells. Accumulating evidence suggests that anti-CD137 antibodies can be used separately to prevent tumor in some cases, while in other cases, these antibodies need to be co-administered with other antibodies or drugs/vaccines/regents for a better performance. Thus, in this work, we aim to update and discuss current knowledge about anti-cancer effects of anti-CD137 antibodies as mono- and combined-immunotherapies.

First insight into human extrahepatic metabolism of flame retardants: Biotransformation of EH-TBB and Firemaster-550 components by human skin subcellular fractions.

2-ethylhexyl-2,3,4,5-tetrabromobenzoate (EH-TBB) and a mixture of EH-TBB, Bis(2-ethylhexyl)tetrabromphthalate (BEH-TEBP) and Triphenyl phosphate (TPhP), prepared in a ratio similar to the Firemaster-550™ (FM550) flame retardant formulation, were exposed to human skin subcellular fractions (S9) to evaluate their dermal in vitro metabolism for the first time. After 60 min of incubation, tetrabromobenzoic acid (TBBA) and diphenyl phosphate (DPhP) were identified as the major metabolites of EH-TBB and TPhP, respectively using UPLC-Q-Exactive Orbitrap™-MS analysis. Dermal biotransformation of EH-TBB and TPhP was catalyzed by skin carboxylesterases rather than CYP450 enzymes, while no stable metabolites could be identified for BEH-TEBP. Metabolite formation rates of EH-TBB as individual compound and as a component of FM550 fitted the Michaelis-Menten model, while no steady state could be reached for TPhP under experimental conditions. Estimated maximum metabolic rate (Vmax) for TBBA formation upon exposure to FM550 was lower than Vmax for EH-TBB (1.08 and 15.2 pmol min-1 mg protein-1, respectively). This indicates dermal metabolism would contribute less to the clearance of EH-TBB body burden than hepatic metabolism (Vmax = 644 pmol min-1 mg protein-1). Implications for human exposure include EH-TBB accumulation in skin tissue and human exposure to dermal metabolic products, which may have different toxicokinetic and toxicodynamic parameters than parent flame retardants.

A single run, rapid polarity switching method for determination of 30 pharmaceuticals and personal care products in waste water using Q-Exactive Orbitrap high resolution accurate mass spectrometry.

The analytical capability of the UPLC-Q Exactive™ Orbitrap MS was exploited for simultaneous determination of 30 acidic and basic PPCPs in a single run, using rapid polarity switching of the electrospray ionisation source. Full scan MS mode at resolution of 35,000 FWHM, Automatic gain control (AGC) target of 1E6 ions at injection time of 50 ms provided the optimum parameters for high sensitivity, together with sufficient data points per peak (≥15) for improved reproducibility. In addition to chromatographic retention times, method selectivity was achieved via applying high resolution accurate mass with low mass tolerance filter (<5 ppm) for identification of each target compound. Six-point linear calibration curves (R2 > 0.95) were established for all target analytes over a concentration range of 1-1500 ng/ml. Good results were obtained for method accuracy (% recovery = 76-104%), inter- and intra-day precision (relative standard deviation <15%) at 3 concentration levels. Instrumental detection and quantification limits ranged from (0.02-1.21 ng/ml) and (0.07-4.05 ng/ml), respectively. While optimised MS/MS analysis through parallel reaction monitoring (PRM) mode provided slightly higher sensitivity, Full scan MS mode allowed for higher mass resolution (selectivity), more data points per peak (reproducibility) and more importantly, the potential for post-acquisition screening of non-target compounds. Following solid phase extraction (SPE) of target analytes, the method was successfully applied to provide first data on PPCPs occurrence in effluent and surface water samples (n = 10) from Egypt. Moreover, screening for non-target compounds revealed the presence of bisphenol A, which was further confirmed via matching with an authentic standard. Overall, this study provides first insight into the high analytical capabilities of the Q-Exactive™ Orbitrap platform for both targeted/non-targeted analysis of PPCPs in environmental matrices.

An update on physical health and economic consequences of overweight and obesity.

Overweight and obesity (OW and OB) have been on the increase globally and posed health risks to the world's population of all ages, including pre-born babies, children, adolescents, adults and elderly people, via their comorbid conditions. Excellent examples of comorbidities associated with obesity include cancer, cardiovascular diseases (CVD) and type 2 diabetes mellitus (T2DM). In this article, we aimed to review and update scientific evidence regarding the relationships between obesity and its common physical health consequences, including CVD, T2DM, hypertension, ischemic stroke, cancer, dyslipidemia and reproductive disorders. In addition, the economic burden of OW and OB will be discussed. Abundant evidence is found to support the associations between obesity and other diseases. In general, the odd ratios, risk ratios or hazard ratios are often higher in OW and OB people than in the normal-weight ones. However, the molecular mechanism of how OW and OB induce the development of other diseases has not been fully understood. Figures also showed that obesity and its-related disorders exert enormous pressure on the economy which is projected to increase. This review highlights the fact that obesity can lead to numerous lethal health problems; therefore, it requires a lot of economic resources to fight against this epidemic.

Metagenomic insights into lignocellulose-degrading genes through Illumina-based de novo sequencing of the microbiome in Vietnamese native goats' rumen.

The scarcity of enzymes having an optimal activity in lignocellulose deconstruction is an obstacle for industrial-scale conversion of cellulosic biomass into biofuels. With the aim of mining novel lignocellulolytic enzymes, a ~9 Gb metagenome of bacteria in Vietnamese native goats' rumen was sequenced by Illumina platform. From the data, 821 ORFs encoding carbohydrate esterases (CEs) and polysaccharide lyases (PLs) serving for lignocellulose pre-treatment, 816 ORFs encoding 11 glycoside hydrolase families (GHs) of cellulases, and 2252 ORFs encoding 22 GHs of hemicellulases, were mined. The carbohydrate binding module (CBM) was also abundant with 763 ORFs, of which 480 ORFs are located with lignocellulolytic enzymes. The enzyme modularity analysis showed that CBMs are usually present in endoglucanase, endo 1,3-beta-D-glucosidase, and endoxylanase, whereas fibronectin 3-like module (FN3) mainly represents in GH3 and immunoglobulin-like domain (Ig) was located in GH9 only. Every domain located in each ORF was analyzed in detail to contribute enzymes' modularity which is valuable for modelling, to study the structure, and for recombinant production. With the aim of confirming the annotated results, a mined ORF encoding CBM63 was highly expressed in E. coli in soluble form. The purified recombinant CBM63 exhibited no cellulase activity, but enhanced a commercial cellulase activity in the destruction of a paper filter.

Metagenomic analysis of bacterial community structure and diversity of lignocellulolytic bacteria in Vietnamese native goat rumen.

OBJECTIVE: In a previous study, analysis of Illumina sequenced metagenomic DNA data of bacteria in Vietnamese goats' rumen showed a high diversity of putative lignocellulolytic genes. In this study, taxonomy speculation of microbial community and lignocellulolytic bacteria population in the rumen was conducted to elucidate a role of bacterial structure for effective degradation of plant materials. METHODS: The metagenomic data had been subjected into Basic Local Alignment Search Tool (BLASTX) algorithm and the National Center for Biotechnology Information non-redundant sequence database. Here the BLASTX hits were further processed by the Metagenome Analyzer program to statistically analyze the abundance of taxa. RESULTS: Microbial community in the rumen is defined by dominance of Bacteroidetes compared to Firmicutes. The ratio of Firmicutes versus Bacteroidetes was 0.36:1. An abundance of Synergistetes was uniquely identified in the goat microbiome may be formed by host genotype. With regard to bacterial lignocellulose degraders, the ratio of lignocellulolytic genes affiliated with Firmicutes compared to the genes linked to Bacteroidetes was 0.11:1, in which the genes encoding putative hemicellulases, carbohydrate esterases, polysaccharide lyases originated from Bacteroidetes were 14 to 20 times higher than from Firmicutes. Firmicutes seem to possess more cellulose hydrolysis capacity showing a Firmicutes/Bacteroidetes ratio of 0.35:1. Analysis of lignocellulolytic potential degraders shows that four species belonged to Bacteroidetes phylum, while two species belonged to Firmicutes phylum harbouring at least 12 different catalytic domains for all lignocellulose pretreatment, cellulose, as well as hemicellulose saccharification. CONCLUSION: Based on these findings, we speculate that increasing the members of Bacteroidetes to keep a low ratio of Firmicutes versus Bacteroidetes in goat rumen has resulted most likely in an increased lignocellulose digestion.

Biotransformation of the Flame Retardant 1,2-Dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH) in Vitro by Human Liver Microsomes.

The technical mixture of 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH or DBE-DBCH) and the pure ß-TBECH isomer were subjected to in vitro biotransformation by human liver microsomes (HLM). After 60 min of incubation, 5 potential metabolites of TBECH were identified in microsomal assays of both the TBECH mixture and ß-TBECH using ultraperformance liquid chromatography-Q-Exactive Orbitrap mass spectrometry. These include mono- and dihydroxylated TBECH and mono- and dihydroxylated TriBECH as well as an α-oxidation metabolite bromo-(1,2-dibromocyclohexyl)-acetic acid. Our results indicate potential hepatic biotransformation of TBECH via cyctochrome P450-catalyzed hydroxylation, debromination, and α-oxidation. Kinetic studies revealed that the formation of monohydroxy-TBECH, dihydroxy-TBECH, and monohydroxy-TriBECH were best fitted to a Michaelis-Menten enzyme kinetic model. Respective estimated Vmax values (maximum metabolic rate) for these metabolites were 11.8 ± 4, 0.6 ± 0.1, and 10.1 ± 0.8 pmol min-1 mg protein-1 in TBECH mixture and 4992 ± 1340, 14.1 ± 4.9, and 66.1 ± 7.3 pmol min-1 mg protein-1 in ß-TBECH. This indicates monohydroxy-TBECH as the major metabolite of TBECH by in vitro HLM-based assay. The estimated in vitro intrinsic clearance (Clint) of TBECH mixture was slower (P < 0.05) than that of pure ß-TBECH. While the formation of monohydroxy-TBECH may reduce the bioaccumulation potential and provide a useful biomarker for monitoring TBECH exposure, further studies are required to fully understand the levels and toxicological implications of the identified metabolites.

Progressive risk assessment of polychlorinated biphenyls through a Total Diet Study in the Korean population.

Human exposure to polychlorinated biphenyls (PCBs) from foods was investigated through a Total Diet Study (TDS) for the first time in Korea. A representative food list was developed from food intake data. Non-selected foods were also included in the TDS through the mapping process to anticipate practical risk assessment. For better representativeness, data (2008-2011) from the Korea National Health and Nutrition Examination Survey (KNHANES) were combined with the TDS data set. And also, we estimated the dietary exposure to PCBs from various food items using a 'best-fit' mapping process and assessed the differences in PCB exposures by sex and age. In this study, we examined total PCBs (62 congeners) including dioxin-like PCBs (DL-PCBs) and indicator PCBs, which are congeners that are mainly detected in various environmental matrices. The average dietary exposure (3.94 ng/kg body weight/day) that was estimated through food intake was 19.7% of the World Health Organization (WHO) recommendation.