Degree Of Chlorination Research Articles

SYNTHESIS OF AZIDOCELLULOSE NITRATES

A synthesis method of azidocellulose nitrate by chemical interaction between cellulose nitrates or chlorocellulose nitrates with various degree of chlorination with sodium azide in a medium of dimethylsulfoxide and with heating in the temperature range 40–70 °C is proposed. The chemical composition, structure and properties of the obtained compounds are determined on the basis of combination of physico-chemical methods of analysis: IR, 1H NMR and 13C NMR spectroscopy; elemental analysis; gel permeation chromatography; viscometry; thermogravimetric analysis; differential scanning calorimetry; thermal polarization microscopy. The main directions of the chemical interaction between polymers and sodium azide were predicted by quantum-chemical methods using the Gaussian 09 software. The reaction mechanism was confirmed by a mathematical model of kinetics. The scheme of the preferred simultaneously going reaction directions has been composed, which includes substitution of nitrate groups by the azide fragment; rupture of polymer chains by β-glycosidic bond leading to depolymerization; opening of the glucopyranose cycle with addition of the azidogroup to the formed free bonds. Use of the chlorocellulose nitrate for the azidation allows to get products with a higher degree of substitution by azidogroups, and the rate of azidation of chlorocellulose nitrate depends on halogen content directly.

SReactivation of CeO2‐based Catalysts in the HCl Oxidation Reaction: In situ Quantification of the Degree of Chlorination and Kinetic Modeling

AbstractDeactivation of CeO2‐based catalysts in the HCl oxidation reaction proceeds via selective bulk chlorination of the active CeO2 component to form CeCl3×nH2O. We study the reactivation of two bulk‐chlorinated CeO2‐based Deacon catalysts by oxygen treatment at 430 °C, namely pure CeO2 and 20 mol % of CeO2 supported on preformed ZrO2 particles (20CeO2@ZrO2), with a dedicated experiment. In the flow reactor setup we determine in‐situ the degree of chlorination of the catalyst by quantifying down‐stream with in‐situ UV‐Vis spectroscopy the total amount of chlorine in the catalyst that is exchanged by reoxidation at 430 °C. The activity of deactivated 20CeO2@ZrO2 can be fully restored by oxygen exposure at 430 °C, while that of pure CeO2 declines steadily. Since the UV‐Vis analytics is fast and sensitive, we can follow the kinetics of reoxidation. To rationalize the observed kinetics, we develop a modified Johnson‐Mehl‐Avrami‐Kolmogorov (JMAK) model based on a nucleation‐and‐growth approach for the reoxidation of the catalyst starting from the chlorinated phase. The fast reoxidation kinetics of chlorinated 20CeO2@ZrO2 is traced to a fast nucleation rate.

Trophic Magnification of Short- and Medium-Chain Chlorinated Paraffins in Terrestrial Food Webs and Their Bioamplification in Insects and Amphibians during Metamorphosis.

Studies on the biomagnification of short- and medium-chain chlorinated paraffins (SCCPs and MCCPs) in terrestrial ecosystems and their bioamplification during metamorphosis in insects and amphibians are scarce. Therefore, this study sought to characterize the occurrence and trophic dynamics of SCCPs and MCCPs in an insect-dominated terrestrial food web in an e-waste recycling site in South China. Median ∑SCCPs and ∑MCCPs concentrations in the organisms ranged from 2200 to 34 000 ng/g lipid weight and from 990 to 19 000 ng/g lipid weight, respectively. The homologue profiles of CPs in the predators were distinct from those in insects, presenting more short chain-high chlorinated congeners (C10-12Cl8-10). The trophic magnification factors (TMFs) of ∑SCCPs and ∑MCCPs were 2.08 and 2.45, respectively, indicating biomagnification in the terrestrial food web. A significant positive relationship between the TMFs and octanol-air partition coefficients was observed. TMFs were also positively correlated with chlorination degree but did not correlate with carbon chain length. Nonlinear correlations between metamorphosis-associated bioamplification and the octanol-water partition coefficients of SCCPs and MCCPs were observed for insects, whereas negative linear correlations were observed for amphibians, which suggested species-specific alterations to the chemicals during metamorphosis.

Effect of Hydrogenation and Chlorination Reactions on the β Relaxation of Poly(Vinyl Chloride)

The relaxation phenomena of polymers are very important because they play an important role in their physical properties. Dynamic mechanical analysis was used in this work in order to study the effect of tactic and compositional sequences on the relaxation processes observed in poly(vinyl chloride) (PVC). The polymers studied in this work were PVC modified by means of reductive hydrogenation and chlorination reactions at low degrees of modification. The results obtained with hydrogenated poly(vinyl chloride) indicated that the decrease in mmr tetrads at the end of the isotactic sequences in the chain by stereospecific hydrogenation led to concomitant decreases in intensity and temperature of the maximum of the β relaxation. This effect seemed to be stronger the longer the isotactic sequence associated with the said structure. On the other hand, in the case of chlorinated poly(vinyl chloride) (CPVC), the results of the evolution of the β relaxation with the degree of chlorination showed that the predominant factor was the compositional microstructure (substitution of hydrogen atoms by chlorine atoms, increasing the possibility of inter-chain interactions leading to a stiffening of the chain, with the consequent increase in the β temperature).

Adsorption and Desorption Behaviour of Polychlorinated Biphenyls onto Microplastics' Surfaces in Water/Sediment Systems.

The potential of microplastics (MPLs) in marine ecosystems to adsorb and transport other micropollutants to biota, contributing to their entry in the food chain, is a primary cause of concern. However, these interactions remain poorly understood. Here, we have evaluated the adsorption/desorption behaviour of marker polychlorinated biphenyls (PCBs), onto MPL surfaces of three widely used polymers—polystyrene (PS), polyethylene (PE), and polyethylene terephthalate (PET). The range of MPL sizes ranged from 1 to 600 μm. The adsorption/desorption was evaluated in sediment/water systems in marine microcosms emulating realistic environmental conditions for 21 days. The adsorption percentages ranged from 20 to 60%. PCBs with a lower degree of chlorination showed higher adsorption percentages because of conformational impediments of PCBs with high-degree chlorination, and also by their affinity to be adsorbed in sediments. Glassy plastic polymers as PET and PS showed a superior affinity for PCBs than rubbery polymers, such as PE. The polymers that can bond PCBs by π-π interactions, rather than van der Waals forces showed better adsorption percentages, as expected. Finally, the adsorption/desorption behaviour of selected PCBs onto MPLs was fitted to a Freundlich isotherm model, with correlations higher than 0.8 in most of the cases.

Addressing Main Challenges Regarding Short- and Medium-Chain Chlorinated Paraffin Analysis Using GC/ECNI-MS and LC/ESI-MS Methods.

The risk assessment of chlorinated paraffins (CPs), chemicals of widespread industrial use, is struggling without standardized analytical methods to obtain reliable occurrence data. Indeed, scientists face analytical challenges that hinder the comparability of analytical methods, among them uncontrolled ionization efficiency and lack of quantification standards. In this study, our goal was to investigate potential issues faced when comparing data from different mass spectrometry platforms and quantification methods. First, the injection of the same set of single-chain length standards in three different instrumental mass spectrometry set-ups (liquid chromatography-electrospray-Orbitrap (LC/ESI-HRMS), liquid chromatography-electrospray-time-of-flight (LC/ESI-MS), and gas chromatography-electron capture negative ion-Orbitrap (GC/ECNI-HRMS)) revealed a shift of homologue response patterns even in-between LC/ESI-based set-ups, which was more pronounced for CPs of low chlorination degree. This finding emphasizes the need for a comprehensive description of instrument parameters when publishing occurrence data. Second, the quantification of a data set of samples with four quantification methods showed that quantification at the sum SCCP and MCCP levels presented good comparability, while quantification at the homologue level remained unsatisfactory. In light of those results, we suggest that (i) response pattern comparison should only be performed between similar instrumental set-ups, (ii) experimental chlorination degrees should be used when quantifying according to the %Cl (instead of those provided by the suppliers), and (iii) concentration results should be expressed as the sum of SCCPs and MCCPs primarily, with an indication on the match between samples and quantification standards (for example their chlorine content).

Degradation of aliphatic halogenated contaminants in water by UVA/Cu–TiO2 and UVA/TiO2 photocatalytic processes: Structure-activity relationship and role of reactive species

This study investigated the degradation of eight aliphatic halogenated contaminants (one brominated flame retardant and seven disinfection by-products) in synthetic drinking water by the UVA/TiO2 and UVA/Cu–TiO2 processes. The degradation rate constants of 2,2-bis(bromomethyl)-1,3-propanediol and trichloromethane in the UVA/Cu–TiO2 process were 10.1 and 1.29 times, respectively, higher than those in the UVA/TiO2 process. In contrast, the degradation rate constants of dichloroacetaldehyde, monochloroacetonitrile, monobromoacetonitrile and dibromonitromethane in the UVA/Cu–TiO2 process were 8.15, 2.33, 2.84 and 1.80 times, respectively, lower than those in the UVA/TiO2 process. The degradation rate constants of monobromonitromethane and dichloronitromethane were comparable in the two processes. The relationships between the degradation rate constants and the structural characteristics of the selected contaminants were examined to explain the different degradation efficacies of the contaminants in the two processes. As suggested by a quantitative structure-activity relationship (QSAR) model, the UVA/TiO2 process favored the degradation of contaminants with more polar electron-withdrawing moieties and higher degrees of chlorination. While the UVA/Cu–TiO2 process favored the degradation of hydrophilic unsaturated contaminants with multiple bonds. The concentrations of the reactive species (e.g., HO and e−) generated in the two photocatalytic processes were quantified using competition kinetics. The UVA/Cu–TiO2 process generated >10 times higher concentrations of HO than the UVA/TiO2 process, suggesting that the former process was more suitable for the degradation of contaminants that are reactive towards HO, while e− and e−-derived superoxide radicals were non-negligible contributors to contaminant degradation in the UVA/TiO2 process.

Formation and enhanced photodegradation of chlorinated derivatives of bisphenol A in wastewater treatment plant effluent

There are many reports on the detection and removal of emerging pollutants in the wastewater effluents, while the fate of their chlorinated derivatives generated during chlorination is not well understood. Here we investigated the photodegradation of chlorinated derivatives of bisphenol A (CDBPAs), mainly including 3-chlorobisphenol A, 3,3′-dichlorobisphenol A, 3,5-dichlorobisphenol A, 3,3′,5-trichlorobisphenol A, and 3,3′,5,5′-tetrachlorobisphenol A, under simulated sunlight. Distinct from BPA, CDBPAs underwent rapid direct photodegradation due to a pronounced bathochromic shift of UV absorption. The photodegradation of CDBPAs was significantly enhanced by effluent organic matter (EfOM) from the wastewater effluent. A series of quenching experiments and laser flash photolysis analysis verified the contribution of triplet states of EfOM (3EfOM∗) for the indirect photodegradation of CDBPAs with rate constant of ∼109 M−1 s−1. Both direct and EfOM-induced indirect photodegradation of CDBPAs increased with a higher degree of chlorination. Furthermore, high-resolution mass spectrometry showed similar photoproducts for direct and indirect photodegradation of CDBPAs, mainly ascribed to the cleavage of C–Cl bond and hydroxylation with further cleavage of the benzene ring. The estrogenic activity of the photoproducts was diminished. These findings suggest that photodegradation is an important pathway for the removal and detoxication of CDBPAs from effluents and receiving natural waters under sunlight.

Impact of environmental exposure to persistent organic pollutants on lung cancer risk

BackgroundRecent studies suggest that high pre-diagnostic serum concentrations of persistent organic pollutants (POPs) might result in the development of cancers in the general population. However, the association between pre-diagnostic serum POP concentrations and lung cancer risk has not been studied. Here, we evaluated associations between low-dose environmental exposure to POPs and risk of lung cancer using pre-diagnostic serum samples in a case-cohort study based on a population-based prospective cohort. MethodsWe conducted a case-cohort study based on the Korean National Cancer Center Community Cohort, from which we included 118 lung cancer cases and 252 controls. Serum concentrations of POPs were measured by high resolution gas chromatography/high-resolution mass spectrometry, and data were analyzed using multivariable Cox proportional-hazards regression models. ResultsRisk of lung cancer increased per unit increase in the natural log-transformed concentrations of the sum of chlordane congeners, total PCBs, and all PCBs subgrouped by the number of chlorines or ortho- substituted chlorines on the molecules, except for tri/tetrachlorobiphenyls, in all models. Among individual POP analytes with a detection rate >80%, after Bonferroni adjustment, only trans-nonachlor was associated with lung cancer risk. In categorical models, risk of lung cancer was associated with serum concentration of chlordane (4th vs. 1st quartile, hazard ratio [95% confidence interval], 8.79 [2.77–27.97]). Dose-dependent relationships were also found between risk of lung cancer and serum concentrations of PCBs regardless of their degree of chlorination, substitution pattern, or binding affinity to receptors (total PCBs, P = 0.002; mid-chlorinated PCBs, P = 0.004; high-chlorinated PCBs, P < 0.001; non- and mono-ortho PCBs, P = 0.031; di-ortho PCBs, P = 0.003; PCBs with dioxin-like activity, P = 0.011; non-dioxin-like non-/mono-ortho PCBs, P = 0.060). ConclusionsSerum concentrations of chlordane and PCBs are associated with risk of lung cancer in the general population, even decades after the ban on their production and use.

NMR and GC/MS analysis of industrial chloroparaffin mixtures

Chlorinated paraffins (CPs) are high-volume chemicals used worldwide in various industries as plasticizers, lubricants, and flame retardants. CPs are produced by chlorination of alkane mixtures which leads to complex products of thousands of homologs and congeners. Classic mass spectrometric analyses of CPs allow determining carbon chain lengths and degrees of chlorination while information on the substitution patterns cannot be derived. Therefore, we performed different one- and two-dimensional nuclear magnetic resonance spectroscopy (NMR) experiments, elemental analysis (EA), and gas chromatography coupled with electron capture negative ion mass spectrometry (GC/ECNI-MS) for the analysis of ten technical CP products with 42%, 52%, and 70% chlorine content from four producers. Slight differences in chlorine content but varying chain length compositions were observed for similarly labeled products from different manufacturers. Two-dimensional heteronuclear spectral quantum coherence (HSQC) measurements helped to evaluate ten structural elements in the products and confirmed the presence of geminal chlorine atoms in primary and secondary carbons in products with 70% chlorine. The variation of signal groups increased with increasing chlorine content of the products. Two-dimensional heteronuclear multiple bond coherence (HMBC) analysis of one sample and GC/ECNI-MS measurements indicated the presence of impurities (e.g., C9-CPs, iso-alkanes) in different technical CP products. These methods could in future allow for better distinction of CP mixtures, and an improved trace-back of environmental CPs to the source, based on specific structural features. Additionally, further structural characterization could help in the development of more accurate analysis processes.Graphical

Hydrodechlorination of hexachlorobenzene in a miniaturized nano-Pd(0) reaction system combined with the simultaneous extraction of all dechlorination products

The persistent organic pollutant hexachlorobenzene (HCB) and all 11 further chlorobenzenes were hydrodechlorinated at environmentally relevant concentrations in miniaturized reaction systems, catalyzed by low concentrated Pd(0)-nanoparticles, to examine differences in dechlorination rates and pathways. Using solid-phase microextraction coupled to gas chromatography-mass spectrometry allowed the simultaneous extraction and detection of reactants, intermediate products and fully dechlorinated benzene, regardless of their different physicochemical properties. Dechlorination of HCB with formation of intermediates mainly proceeded via pentachlorobenzene, 1,2,3,4-tetrachlorobenzene, 1,2,3-trichlorobenzene, 1,2-dichlorobenzene, and monochlorobenzene to benzene. Specific catalytic activities of Pd(0)-nanoparticles (100–3400 L g−1 min−1) differed depending on chlorination degree of chlorobenzenes and position of chlorine atoms. An inductive effect is assumed to favor a removal of the vicinal chlorine atom. The presented method permits the facile determination and comparison of nanomaterials’ specific catalytic activities and allows the elucidation of dehalogenation pathways. It further enables to specifically examine formed intermediates to assess their toxicity and biodegradability.

Study on the Emission Characteristics of PCDD/Fs and Other Multiple Pollutants in Flue Gas from Sintering Plant in China

In China, sintering flue gas has become the most important source of air pollution rather than burning coal-fired flue gas.The emission characteristics and removal efficiencies of various gaseous pollutants were studiedon a 180 m2 sintering equipped with a semi-dry oxidative desulfurization and denitrification system in Tangshang, Hebei province. The emission concentrations of particulate matter, fluoride,NOX and SO2were measured in the flue gas whilepolychlorinated dibenzo-p-dioxins and dibenzofurans(PCDD/Fs) were tested in both flue gas and dust ash at 100% and 60% loadconditions. The collections and analyses ofpollutantswere used by smoke sampler, TESTO350 and dioxin sampleraccording to national standards of China. The results shown that the average emission concentration of particulate matter, fluoride, NOX and SO2 in the inlet of the flue gas purification system were 47.4 mg/m3, 0.12 mg/m3, 150 mg/m3 and 521 mg/m3 while the emission concentrations in the outlet were 1.2 mg/m3, 0.07 mg/m3, 24 mg/m3 and 20 mg/m3,respectively. Through the flue gas purification system, the PCDD/Fs concentrations were reduced from 23.12 ng/m3to 1.14 ng/m3at100% load and from 12.25 ng/m3 to 0.84 ng/m3at60% load. The PCDD/Fs concentrations in the dust ash were about 178.56~197.21 ng/kg. Thedesulfurization and denitrification system significant reduced effect on the emission of particulate matter, fluoride, NOX, SO2 and PCDD/Fs with the value 97.5%, 41.7%, 84.0%, 96.2% and 95.1% at 100% load, respectively.The removal affects increases along the chlorination degree of PCDD/Fs. Meanwhile,the different load influenced the emission concentrations and removal rates of PCDD/Fs in the flue gas, the removal effects increases as the load increases. Although the desulfurization and denitrification system has good removal effects on various pollutants, the dioxins were enriched in the dust ashso as to cause secondary pollution.

Chlorines Are Not Evenly Substituted in Chlorinated Paraffins: A Predicted NMR Pattern Matching Framework for Isomeric Discrimination in Complex Contaminant Mixtures.

Chlorinated paraffins (CPs) can be mixtures of nearly a half-million possible isomers. Despite the extensive use of CPs, their isomer composition and effects on the environment remain poorly understood. Here, we reveal the isomeric distributions of nine CP mixtures with single-chain lengths (C14/15) and varying degrees of chlorination. The molar distribution of CnH2n+2–mClm in each mixture was determined using high-resolution mass spectrometry (MS). Next, the mixtures were analyzed by applying both one-dimensional 1H, 13C and two-dimensional nuclear magnetic resonance (NMR) spectroscopy. Due to substantially overlapping signals in the experimental NMR spectra, direct assignment of individual isomers was not possible. As such, a new NMR spectral matching approach that used massive NMR databases predicted by a neural network algorithm to provide the top 100 most likely structural matches was developed. The top 100 isomers appear to be an adequate representation of the overall mixture. Their modeled physicochemical and toxicity parameters agree with previous experimental results. Chlorines are not evenly distributed in any of the CP mixtures and show a general preference at the third carbon. The approach described here can play a key role in understanding of complex isomeric mixtures such as CPs that cannot be resolved by MS alone.

Distribution and formation mechanisms of polychlorinated organic by-products upon the catalytic oxidation of 1,2-dichlorobenzene with palladium-loaded catalysts

Clarifying the oxidative products and their formation mechanisms in the catalytic oxidation of chlorinated volatile organic compounds is important to provide detailed understanding of the degradation of pollutants with the simultaneous removal of secondary pollutants. In this study, catalytic oxidation of 1,2-dichlorobenzene (1,2-DCB) using commonly commercial catalysts (Pd/γ-Al2O3, Pd/ZSM-5, and Pd/SiO2) was investigated. During the oxidation processes, substantial amounts of polychlorinated organic by-products, such as trichlorobenzene, tetrachlorobenzene and pentachlorobenzene, were detected. The reaction temperature and types of supports played a vital role in the formation of chlorinated organic by-products. With an increase of the reaction temperature, the degree of chlorination of the organic by-products increased gradually, and the concentration of polychlorinated organic by-products was increased sharply at low temperatures and then decreased when the reaction temperature was above 450 °C. Meanwhile, the amounts of polychlorinated organic by-products increased with an increasing silicate-to-aluminium ratio. Furthermore, based on the distribution of chlorinated organic by-products and characterization results of pyridine from FTIR, XPS, UV–vis-DRs, and in situ FTIR, the formation mechanisms of the polychlorinated organic compounds were proposed.

Optimized characterization of short-, medium, and long-chain chlorinated paraffins in liquid chromatography-high resolution mass spectrometry

Chlorinated paraffins (CPs), or polychlorinated n-alkanes, form a complex family of chemicals as they exist as mixtures of several thousands of isomers. To facilitate their classification, they are subdivided into short-chains (C10C13, SCCPs), medium-chains (C14C17, MCCPs), and long-chains (C≥18, LCCPs) and further subdivided according to their chlorination degree. Until recently, the most common strategy implemented for their analysis was GC-ECNI-LRMS, with the main disadvantage being the high dependence of the response to the chlorination degree and the incapability of analysing LCCPs. In this work, we developed a method based on liquid chromatography coupled with electrospray ionisation-Orbitrap mass spectrometry (LC-ESI-HRMS) to expand the analysis capabilities of CPs. Although the different physico-chemical properties of CPs have led to compromises on the choice of analytical parameters, the addition of a mixture of DCM/ACN post-column with appropriate LC-ESI(-)-HRMS parameters enabled optimal and simultaneous detection of SCCPs, MCCPs and LCCPs from 10 to 36 carbons in one single injection. The combination of both the optimised LC-ESI parameters and the high resolution of the mass spectrometer (R = 140,000 @200 m/z) allowed separation of CPs signals of interest from unwanted halogenated ones, leading to minimum interferences in the detection. The optimised method was then successfully applied to the characterization of three types of vegetable oil, which were mostly contaminated with MCCPs. Additionally, the implementation of the LCHRMS strategy enabled the identification of highly chlorinated LCCPs in edible oil for the first time at dozens of ng g-1 lw, which demonstrates the need of such comprehensive methods to expand the knowledge about CPs occurrence in food and environmental matrices.

Preparation of hollow SiC ceramic fibre from polycarbosilane fibre by diffusion-controlled cross-linking method

ABSTRACTCross-linking is favourable for increasing ceramic yield and avoiding melting or deformation of SiC ceramic precursor polycarbosilane (PCS) during pyrolysis. In order to achieve hollow SiC fibre, PCS fibre with a limited cross-linking depth was prepared by chlorinating the Si–H group in the outer layer of PCS fibre followed by hydrolysis and condensation of the formed Si–Cl group. The chlorination was implemented through a gas–solid reaction between Cl2 and PCS fibre. Based on the results of energy-dispersive spectrometer and attenuated total reflectance–Fourier transform infrared spectroscopy, the diffusion-controlled chlorination reaction was confirmed. During hydrolysis, the catalysis of ammonia gas was necessary. According to the results of dissolution and degradation experiments, cross-linked PCS outer layer formed after chlorination, hydrolysis and condensation, and the outer layer had higher ceramic yield than the core part. After pyrolysis, SiC fibre with hollow morphology was formed. By adjusting the chlorination degree, the morphology of resulting hollow SiC fibre could be modified.

Microbiome changes and oxidative capability of an anaerobic PCB dechlorinating enrichment culture after oxygen exposure

Marine sediments may represent a sink of persistent organic pollutants including polychlorinated biphenyls (PCBs), toxic compounds prone to reductive or oxidative biodegradation pathways depending on the degree of chlorination and the positions of the chlorine atoms on the biphenyl rings. Superficial marine sediments can be subjected to episodic sediment resuspension by boat traffic and wind action causing the exposure of the underlying anaerobic layer to oxygen. Under these dynamic conditions, a deeper knowledge of the adaptation capability of the autochthonous microbial communities towards severe changes of the reaction environment is required. Insights into the metabolic potential of sediment community members may contribute greatly to the definition of efficient and reliable in situ bioremediation strategies. In this study, an anaerobic PCB-dechlorinating microbial consortium, developed from the chronically polluted marine sediment of Mar Piccolo (Taranto, Italy), was used to evaluate the response of the sediment microbiome to the imposition of aerobic conditions after prolonged anaerobic incubation. Compared to the anaerobic control, a dramatic change in microbiome composition, with a marked increase of Alphaproteobacteria of up to 39.2 % of total operational taxonomic units (OTUs) was revealed by high-throughput 16S rRNA gene sequencing. Accordingly, a decrement of low chlorinated PCBs (up to 58.3 ± 7.5 % for PCB 18) and the concomitant appearance of genes coding for PCB-degrading biphenyl dioxygenase (bph) were observed at the end of the aerobic incubation, suggesting the occurrence of oxidative PCB biodegradation processes.

English

A study was conducted in Lake Victoria to assess the occurrence, levels and risks of indicator polychlorinated biphenyls (PCBs) in four processed Lates niloticus (L.) products (salted-sundried, trims, smoked and deep-fried). Samples extractions were done using QuEChERS method while detection and quantification of congeners was done using a GC- ECD and GC- MS. Six PCBs (CB 28, CB 52, CB 118, CB 138, CB 153 and CB 180) were detected at measurable quantities in fish products. The PCBs; CB 138, CB 153 and CB 180 dominated the loading due to their structures and high degree of chlorination. However, the mean concentration of &Sigma;PCBs in this study were below MRL of 75 &micro;g/kg set for fish by European Commission, implying that the fish products were safe for human consumption in regard to indicator PCBs. Similarly, indicator PCBs, CB 138, CB 153 and CB 180 were more prevalent (20 to 80%) in all fish products than other congeners. For both adults and children the cancer risks were low-to-moderate (ranging from 2.0E-04 to 3.0E-04 for adults and 2.0E-04 to 1.0E-03 for children) while the non-cancer risks were insignificant as the Hazard Indices were less than one. &nbsp; Key words: Polychlorinated biphenyls (PCBs), kayabo, trims, smoked products, deep-fried products, extracting solvent.

Assessment of persistent organochlorine compounds contamination on the Lake Victoria water and sediments: a case study in Tanzania

The current study was conducted to establish the levels of organochlorine pesticides (OCPs), its degradation products, and indicatory polychlorinated biphenyls (PCBs) in water and sediments from Lake Victoria in Tanzania. Seven indicator PCBs were identified in sediments, and five were identified in water. The PCBs loading ranged from lower than the limit of detection (LOD) to 10.28 µg kg−1 DW and 0.95 to 2.24 µg l−1 in sediments and water, respectively. PCBs, CB 138 and CB 153 dominated the load, because of their chemical stability and high degree of chlorination. In addition, ten OCPs were identified in sediments, and seven OCPs were identified in water. The levels of organochlorine compounds in sediments were higher than in water samples, implying that sediments may serve as a sink for these compounds. The presence of these compounds is probably as a result of either historical use, long-range environmental transport or environmental persistence. The levels of organochlorine compounds in the lake water and sediments are below the maximum residue limit set by EU and FAO, except for aldrin and dieldrin. Based on the Threshold Effect Concentration (TEC) for freshwater ecosystems, aldrin and dieldrin are the only OCPs that seem to be a threat to the lake environment.

Predictors of plasma polychlorinated biphenyl concentrations among reproductive-aged black women.

Polychlorinated biphenyls (PCBs) are a class of lipophilic endocrine-disrupting chemicals with wide industrial use in the U.S. from the 1930s through 1977. Due to their environmental and biological persistence, low levels of PCBs remain detected in wildlife and humans. Although U.S. studies have shown higher serum PCB concentrations among Black women compared with White women, studies of correlates of PCB exposure among Black women are scarce. We examined predictors of plasma PCB concentrations in a cross-sectional analysis of baseline data from a prospective cohort study of 1693 premenopausal Black women aged 23-35 years from Detroit, Michigan (2010-2012). We collected demographic, behavioral, dietary, and medical data via self-administered questionnaires, telephone interviews, and in-person clinic visits, as well as non-fasting blood samples. We measured concentrations of 24 PCB congeners in baseline plasma from a subset of 762 participants. We used linear regression for log-transformed lipid-adjusted PCB concentrations to calculate percentage differences across levels of selected predictors. We did this separately for individual PCBs, sum of total PCBs, and sum of PCBs by degree of chlorination and hormonal activity. PCB concentrations were positively associated with age, duration of urban residence, cigarette smoking, heavy alcohol intake, and being breastfed in infancy, and inversely associated with body mass index (BMI) and lactation duration. The strength of some associations varied by degree of chlorination. For example, a 5-kg/m2 higher BMI corresponded to a 2.9% lower summed concentration of tri- and tetra-substituted PCBs (95% CI -4.6%, -1.2%), an 8.3% lower summed concentration of penta- and hexa-substituted PCBs (95% CI -10.0%, -6.5%), and a 12.1% lower summed concentration of hepta-, octa-, nona-, and deca-substituted PCBs (95% CI -13.7%, -10.4%). Likewise, associations for age and being breastfed in infancy were stronger for higher-chlorinated PCBs. Results agree with studies on predictors of PCB body burdens, few of which include large numbers of Black women.