PCDDs), Dibenzofurans Research Articles

PCDD/F and PCB water column partitioning examination using natural organic matter and black carbon partition coefficient models

A 9-year water dataset from the Houston Ship Channel (HSC) was analyzed to understand partitioning in polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDD/Fs). Total PCBs had more mass as dissolved (74%) whereas total PCDD/Fs did not (11%). Generally, the limited number of PCDD/Fs (only 2378 substituted) explained these differences though differences in chemical behavior beyond log K ow also likely influence partitioning. The particular fractionation seen in the HSC also seemed related to a wide variation in particulate organic carbon (POC)/dissolved organic carbon (DOC) ratio (0.42-180%). Published and unaltered linear free energy and linear solvation energy relationships for DOC, POC, and particulate black carbon (BC) resulted in predictions that were at best 27% (PCB) and 25% root-mean-square error (RMSE) (PCDD/F) partition fraction compared to observed (using estimated BC/POC fractions of 10 and 25%, respectively). These results show, at least in light of the uncertainties in this data (e.g., precise fraction of BC), that a 25% accuracy in model prediction of operationally dissolved or suspended fraction for any one PCB or PCDD/F congener is the best prediction that may be expected. It is therefore recommended that site-specific data be used to calibrate most any water column-partitioning model if it is to be expected to describe what actually occurs in field conditions.

Endocrine-Disrupting Chemical Degradation in Hazardous Waste Using Microwave Peroxide Oxidation and Acid

Abstract Microwave peroxide oxidation (MPO) has been demonstrated as an energy-efficient and low-GHG emission technology for destroying hazardous organic compounds in solid waste. The objective of this article was to study the degradation feasibility of endocrine-disrupting chemicals (EDCs) in hazardous wastes using MPO treatment with selected acid combinations. Three EDCs, nonylphenol (NP), bisphenol A (BPA), polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/Fs), contained in different hazardous wastes (i.e., fly ash, soil, and sludge cake) were adopted in this work. Over 85% of the EDCs, including the persistent PCDDs/Fs in raw wastes could be degraded in 60 min at the temperature of 450 K using the MPO treatment. One of the most interesting findings is that nearly all NPs and BPAs, over 99%, in hazardous wastes could be degraded in 20 min at the temperature of 450 K. Degradation efficiency in order was NP, BPA, and PCDDs/Fs. It is concluded that MPO with selected acid combination provided the pote...

PBDEs, PCBs and PCDD/Fs in the sediments from seven major river basins in China: Occurrence, congener profile and spatial tendency

Polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) were extensively investigated in the sediment samples collected from seven major river basins around China. The concentrations were in the range of 0.05–6.15 × 104 ng g−1 dry weight (dw), 0.29–21.7 ng g−1 dw and 0.01–6.49 ng g−1 dw for PBDEs, PCBs and PCDD/Fs, respectively. The concentrations showed wide variations among different river basins, while the congener profiles in all the sediments were generally characterized by only a few compounds, such as BDE-209, -99 and -47, CB-11 and -28, OCDD and OCDF, etc. The spatial analysis identified a decreasing trend of these persistent organic pollutants (POPs) from south to north China, consistent with regional industrialization. However, relatively higher level of POPs was also observed in the upstream of Yellow River Basin. The present study gives insight into the spatial occurrence of the three POPs in the major river basins in China.

Assessment of polychlorinated dibenzodioxins (PCDDs)/dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) contamination in some meat products from Romania

Assessment of polychlorinated dibenzodioxins (PCDDs)/dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) contamination in some meat products from Romania

Successive self-propagating sintering process using carbonaceous materials: A novel low-cost remediation approach for dioxin-contaminated solids

The disposal of dioxin-contaminated solids was studied using a novel successive self-propagating sintering process (SSPSP) incorporating a carbonaceous material. Among the five types of carbonaceous materials investigated, Charcoal B displayed optimum adsorbent properties and was selected as the best thermal source in the current remediation approach based on economical efficiency aspects. The feasibility of this proposed approach, removal efficiencies, and congener compositions of dioxins were examined using two types of dioxin-contaminated solids (Fugan sediment and Toyo soil) that displayed different characteristics including the initial concentrations of dioxins. The removal efficiencies of DL-PCBs (“dioxin-like” polychlorinated biphenyls) were higher than those of PCDD/Fs (polychlorinated dibenzo-p-dioxins/dibenzofurans), achieving 99.9 and 92% removal in the Fugan sediment and Toyo soil, respectively. In contrast, the degradation efficiencies of DL-PCBs were lower (i.e., 89.3 and 88.8%, respectively). The initial concentrations of dioxins, available precursors, and properties of the solids strongly influenced the congener compositions and removal efficiencies of dioxins. Furthermore, the dechlorination reaction pathways of high-chlorinated PCDDs and potential regeneration pathways of PCDFs from PCBs were deduced using isotope labeling. The proposed novel low-cost remediation approach for the removal of dioxins from solids is a highly efficient and environmentally sound treatment technology.

Levels of polychlorinated dibenzo-p-dioxins, dibenzofurans (PCDD/Fs) and biphenyls (PCBs) in blood of informal e-waste recycling workers from Agbogbloshie, Ghana, and controls

The formation and environmental release of highly toxic organohalogen compounds associated with informal recycling of waste electric and electronic equipment (e-waste) is a growing problem at e-waste dumps/recycling sites (EWRSs) in many developing countries worldwide. We chose a cross-sectional study design to measure the internal exposure to polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) as well as polychlorinated biphenyls (PCBs) of individuals working on one of the largest EWRSs of Africa, located at Agbogbloshie, Accra, Ghana, and in controls from a suburb of Accra without direct exposure to EWRS activities. In whole blood samples of 21 age matched male exposed individuals (mean age: 24.7years, SD 6.0) and 21 male controls (mean age: 24.4years, SD 5.7) 17 PCDD/F congeners were determined. Moreover three indicator PCB congeners (#138, #153 and #180) were measured in blood of 39 exposed (mean age: 27.5years, SD 11.7) and 19 non-exposed (mean age: 26.8years, SD 9.7) patients. Besides a health examination, biometric and demographic data, residential and occupational history, occupational exposures and working conditions were recorded using a standardized questionnaire. In the exposed group, median PCDD/F-concentrations were 6.18pg/glipidbaseWHO2005-TEq (range: 2.1–42.7) and significantly higher compared to the control group with 4.60pg/g lipid base WHO2005-TEq (range: 1.6–11.6). Concentrations were different for 2,3,7,8-TetraCDD, three HexaCDD and all 10 PCDF congeners, indicating a combustion pattern. Using a multivariate regression analysis exposure to EWRS activities was the most important determinant for PCDD/F exposure. Median PCB levels for the indicator congeners #138, #153 and #180 were 0.011, 0.019 and 0.008μg/l whole blood (ranges: 0.002–0.18, 0.003–0.16, 0.002–0.078) in the exposed group and, surprisingly, significantly higher in the controls (0.037, 0.062 and 0.022; ranges: 0.005–0.46, 0.010–0.46, 0.004–0.21). In a multivariate regression approach e-waste related activities had no positive influence on internal PCB exposure, but rather the time living in Accra. The internal PCB exposure is in particular notable for a country where PCBs have historically never been produced or used. The impact of EWRS activities on organohalogen compound exposure of individuals working at and living in the surroundings of the Agbogbloshie EWRS, and the surprisingly high PCB exposure of people living in Accra not involved in e-waste activities require further investigation.

POLYCHLORINATED DIBENZO-P-DIOXINS, DIBENZOFURANS, AND BIPHENYLS IN FREGATA MAGNIFICENS FROM ILHA GRANDE BAY, RIO DE JANEIRO STATE, SOUTH-EASTERN BRAZIL

The purpose of this paper is to perform analyses in a fish-eating seabird species which is recognized to be at risk of accumulating toxic contaminants due to its high position in the trophic web and to its low ability to metabolize xenobiotic compounds. Fregata magnificens were collected at Ilha Grande Bay, Rio de Janeiro, Brazil (23°8'26"S, 44°14'50"W) between February, 2009 and April, 2013. Polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs), were analyzed in tissue composites, being subsequently identified and quantified using gas chromatography coupled with mass spectrometry. The concentrations were below the range of concern established by World Health Organization. The sum of PCB-congeners analyzed had the concentration of 968 pg/g lipid weight, and 13.9 pg TEQ/g lipid weight. The PCDD/F-congeners analyzed had the concentration of 331.04 pg/g lipid weight, and 13.4 pg TEQ/g lipid weight. This type of study aims to integrate information from analyses of seabirds with halogenated hydrocarbons and could also make contribution to the scientific support for political decisions on coastal zone management.

Assessment of comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry based methods for investigating 206 dioxin-like micropollutants in animal-derived food matrices

This paper evaluates different multiresidue methods based on comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC-TOF/MS) to analyze dioxin-related micropollutants in complex food matrices. In a first step, the column sets Rtx-PCB/BPX-50 and Rtx-Dioxin2/BPX-50 were compared in terms of peak shape (width and symmetry) and resolution for the separation of polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) in solvent. A satisfactory separation of 206 dioxin-related micropollutants including the 17 toxic PCDD/Fs was achieved in 75min with the column set Rtx-Dioxin2/BPX-50. In a second time, the GC×GC-TOF/MS method was spread to the analysis of dioxin-related micropollutants in complex food matrices. An extraction procedure including accelerated solvent extraction (ASE), centrifugal evaporation and gel permeation chromatography (GPC) was optimized. Starting with meat as a model matrix, a micropollutant spiking method was then set up by comparing seven methods in terms of recoveries and reproducibility. The method combining immersion of the meat in a large volume of solvent containing micropollutants followed by homogenization by blender induced recoveries in the acceptable range of 70–130% and satisfactory standard deviations (≤10%) for most of the compounds studied. Limits of detection of the GC×GC-TOF/MS method ranged between 50 and 100pg/g of spiked fresh meat for PCBs and between 65 and 227pg/g for PCDD/Fs. Potential applications of this method are discussed.

Consensus toxicity factors for polychlorinated dibenzo-p-dioxins, dibenzofurans, and biphenyls combining in silico models and extensive in vitro screening of AhR-mediated effects in human and rodent cells.

Consensus toxicity factors (CTFs) were developed as a novel approach to establish toxicity factors for risk assessment of dioxin-like compounds (DLCs). Eighteen polychlorinated dibenzo-p-dioxins, dibenzofurans (PCDD/Fs), and biphenyls (PCBs) with assigned World Health Organization toxic equivalency factors (WHO-TEFs) and two additional PCBs were screened in 17 human and rodent bioassays to assess their induction of aryl hydrocarbon receptor-related responses. For each bioassay and compound, relative effect potency values (REPs) compared to 2,3,7,8-tetrachlorodibenzo-p-dioxin were calculated and analyzed. The responses in the human and rodent cell bioassays generally differed. Most notably, the human cell models responded only weakly to PCBs, with 3,3',4,4',5-pentachlorobiphenyl (PCB126) being the only PCB that frequently evoked sufficiently strong responses in human cells to permit us to calculate REP values. Calculated REPs for PCB126 were more than 30 times lower than the WHO-TEF value for PCB126. CTFs were calculated using score and loading vectors from a principal component analysis to establish the ranking of the compounds and, by rescaling, also to provide numerical differences between the different congeners corresponding to the TEF scheme. The CTFs were based on rat and human bioassay data and indicated a significant deviation for PCBs but also for certain PCDD/Fs from the WHO-TEF values. The human CTFs for 2,3,4,7,8-pentachlorodibenzofuran, 1,2,3,4,7,8-hexachlorodibenzofuran, 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin, and 1,2,3,4,7,8,9-heptachlorodibenzofuran were up to 10 times greater than their WHO-TEF values. Quantitative structure-activity relationship models were used to predict CTFs for untested WHO-TEF compounds, suggesting that the WHO-TEF value for 1,2,3,7,8-pentachlorodibenzofuran could be underestimated by an order of magnitude for both human and rodent models. Our results indicate that the CTF approach provides a powerful tool for condensing data from batteries of screening tests using compounds with similar mechanisms of action, which can be used to improve risk assessment of DLCs.

Cerium(IV)-mediated electrochemical oxidation process for removal of polychlorinated dibenzo-p-dioxins and dibenzofurans

In this study, Ce(III)/Ce(IV) redox couple mediated electrochemical oxidation (MEO) process for degradation of liquid 2,3,7,8-TCDD (tetrachloro dibenzo-p-dioxin) and PCDD/Fs (polychlorinated dibenzo-p-dioxins/dibenzofurans) from fly ash was developed. The highest concentration of Ce(IV) was achieved under operation at 80°C, current density of 10Acm−2 with 0.9M feed concentration of Ce(III) in atmospheric pressure. Both the liquid and fly ash samples reacted with electrogenerated Ce(IV) in 10s using batch reactor and the obtained results were presented in the form of International Toxic Equivalent quantity (I-TEQ) and pgL−1. After reaction with Ce(IV), the concentration of the highly toxic liquid isomer 2,3,7,8-TCDD found 2.96pgg−1 I-TEQ from the initial value of 1200pgg−1 I-TEQ that is equal to the removal efficiency of 99.75%. HRMS data demonstrated the fly ash, the total PCDD/Fs concentrations, decreased to 33.16pgg−1 I-TEQ from the initial value of 58pgg−1 I-TEQ, which is equal to removal efficiency of 42.8%. The developed Ce(III)/Ce(IV) MEO process provides potential removal of PCDD/Fs in short time from the emissions of industrial waste incinerators.

Thyroid and growth hormone concentrations in 8-year-old children exposed in utero to dioxins and polychlorinated biphenyls.

The objective of this study was to examine the effects of in utero exposure to polychlorinated biphenyls (PCBs) and dioxins (polychlorinated dibenzo-p-dioxins, dibenzofurans (PCDD/F) on thyroid and growth hormone concentrations and growth in 8-year-old children. A total of 56 children (23 boys, 33 girls) were included in the study. All were stratified into high and low PCDD/F + PCB exposure groups based on maternal median indicator PCB and PCDD/F + PCB concentrations during pregnancy. Height, weight, body mass index, and thyroid and growth hormone concentrations were assessed and compared among the different exposure groups. There were no significant effects of indicator PCB or PCDD/F + PCB exposure levels on growth (height, weight, and bone age) among 8-year-old boys or girls. Boys exposed to high PCDD/F + PCB levels had significantly higher thyroxine-binding globulin (TBG) concentrations than boys exposed to low levels (P = 0.027). Girls exposed to high PCB levels had significantly lower IGF-binding protein-3 (IGFBP-3) concentrations than girls exposed to low levels (P = 0.038). Low levels of in utero exposure to PCDD/F+PCB and high indicator PCB levels were significantly associated with reduced serum concentrations of IGFBP-3. High levels of in utero exposure to PCDD/F+PCB plus either high or low indicator PCB levels were significantly associated with increased serum concentrations of growth hormone, T3, T4, and TBG. These findings suggest that the level of in utero exposure to PCBs and dioxins may affect serum concentrations of growth hormone, thyroid hormones, TBG, and IGFBP-3 in 8-year-old children.

Ambient air concentrations of PCDD/Fs, coplanar PCBs, PBDD/Fs, and PBDEs and their impacts on vegetation and soil

The impact of persistent organic pollutant (POP) concentration in ambient air on vegetation and soil is investigated in the present study. Ambient air, vegetation, and soil samples were collected from the vicinity of an industrial complex. For each collected sample, the polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs), coplanar polychlorinated biphenyls (coplanar PCBs), brominated dibenzo-p-dioxins/dibenzofurans (PBDD/Fs), and polybrominated diphenyl ethers (PBDEs) concentrations were analyzed. Principal component analysis (PCA) was adopted to explore the relationships between the concentration of each POP type in ambient air with those in soil and vegetation. Results show that particle-phase PCDD/Fs, PBDD/Fs, and PBDEs, respectively, account for 60.6, 98.3, and 75.7 % of the total concentration in the air, which are much higher than that of coplanar PCB (5.2 %). Results obtained by PCA suggest that PCDD/Fs in vegetation are contributed by atmospheric gas-phase PCDD/Fs, whereas in soil they are contributed by particle-phase PCDD/Fs. Coplanar PCBs concentrations in both vegetation and soil are contributed by atmospheric gas-phase coplanar PCBs. PBDD/Fs concentrations are both contributed by particle phase. PBDEs in vegetation are contributed by both gas- and particle-phase PBDEs, while soil PBDEs are contributed mainly by the particle phase. In confirmation of these results, the researchers found that the above results are consistent with those obtained from theoretical calculations and previous studies. Therefore, it is concluded that the results obtained from the present study would provide useful information for assessing the fate of ambient air POP concentration.

Spatial patterns of metals, PCDDs/Fs, PCBs, PBDEs and chemical status of sediments from a coastal lagoon (Pialassa Baiona, NW Adriatic, Italy)

The European Water Framework Directive (WFD) establishes a framework for the protection and improvement of all water bodies including transitional waters; its final objective is to achieve at least ‘good status’ by 2015. In the present work, a hierarchical sampling design was applied to analyze the influence of anthropogenic inputs on the spatial distribution of metals, polychlorinated dibenzo-p-dioxins (PCDDs) dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in sediment at four areas in Pialassa Baiona coastal lagoon. In order to assess the chemical status, levels of priority substances and other pollutants were compared with the recently developed national Environmental Quality Standards (EQS) and site specific background levels for metals. Levels of mercury and PCBs were particularly high and exceeded their national EQS values at all sampled areas, thus not contributing to the achievement of a good chemical status of this transitional water body according to the WFD classification.

A novel modeling tool with multi-stressor functionality for organic contaminant transport and fate in the Baltic Sea

The coupled physical–biogeochemical model BALTSEM, previously used to assess nutrient/carbon cycles and eutrophication in the Baltic Sea, has been expanded to include algorithms for calculations of organic contaminant environmental transport and fate. This novel model version (BALTSEM-POP) is evaluated for polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) and hexachlorobenzene (HCB) in Baltic Sea surface water and sediment. Modeled dissolved concentrations are usually within a factor of 2–4 of observed concentrations, however with larger deviations for furans. Calculated concentrations in particulate organic matter are less accurate (within factors of 1–700), likely due to errors in estimated pelagic biomass, particulate matter–water partitioning, and large natural variability in field data. Concentrations in sediments are usually predicted within a factor of 6. The good performance of the model illustrates its usefulness for exploration of contaminant fate in response to variations in nutrient input and climatic conditions in the Baltic Sea marine environment.

Dioxins contamination in the feed additive (feed grade cupric sulfate) tied to chlorine industry.

The sources of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) found in animal feed additive (feed grade cupric sulfate, CuSO4) were investigated and traced back to the formation of chlorinated organic compounds in the chlor-alkali industry. PCDD/Fs could be transported through the supply chain: hydrochloric acid (HCl) by-produced during formation of chlorinated organic compounds in chlor-alkali industry → spent acid etching solution (acid-SES) generated in printed circuit board production → industrial cupric salt → CuSO4 in animal feed, and finally enter the food chain. The concentration ranges in HCl and acid-SES were similar, of which the level in acid-SES was also consistent with that in various cupric salt products including CuSO4 based on Cu element content. PCDD/Fs also showed very similar congener profiles in all the sample types. This indicates a probable direct transport pathway of PCDD/Fs into the food chain, which may eventually be exposed to humans through consumption. To date this is the first study in China that systematically reports on the PCDD/Fs transport from industrial pollution sources to industrial processes and finally enters the human food chain.

Evidence of PCDD/Fs and PCBs contamination in trees grown in forests far from their production and contamination-free areas.

Polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) in trees grown in pathless forests were analyzed to investigate their dispersal patterns in the atmosphere. The pg/g levels of 23 PCCD, 22 PCDF, and 54 PCB congeners were identified. The total amount of PCDDs in the red pine tree sample (95.8 pg/g) was approximately 7 times that in the beech tree sample (13.2 pg/g). The total amount of PCDFs in the red pine tree sample (71.1 pg/g) was also approximately 7 times that in the beech tree sample (11.1 pg/g). The total amounts of PCBs in the red pine tree and beech tree samples were 1,380 and 1,150 pg/g, respectively. The (Cl1-Cl3)-PCBs comprised 63.1 % and 67.6 % of total PCBs in the red pine and in the beech, respectively. The results of the present study indicate that PCDD/Fs and PCBs are transferred over long distances in the atmosphere and accumulated in the contamination-free areas.

Levels of polychlorinated dibenzo-p-dioxins, dibenzofurans (PCDD/Fs) and dioxin-like PCBs in free range eggs from Vietnam, including potential health risks

Chicken and duck eggs collected from three different areas in Vietnam were examined for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). These regions included a background area, an area sprayed with Agent Orange and the Bien Hoa airbase area where Agent Orange was handled by the US Army. The latter area now is inhabited and people keep their own laying hens. Egg samples were first screened with an in vitro reporter gene bioassay and a selection was analyzed by GC/HRMS. Samples from Bien Hoa airbase showed very high PCDD/F levels, up to 249pg dioxin-equivalents (TEQ)/g fat, mainly due to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). In the sprayed areas, levels (3.2–8.2pgTEQg−1) were comparable to those observed in background areas (3.2–8.2pgTEQg−1 fat). The estimated average consumption of 22gd−1 of the highly contaminated eggs will result in a 2-fold exceedance of the current exposure limits for adults and 5-fold for children, even without considering other contaminated food sources. This indicates a potential health risk from consumption of these highly contaminated eggs, which were not yet considered as a source for exposure to PCDD/Fs of people living in the highly contaminated areas.

Relationships between dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and dioxin-like biphenyls (dl-PCBs) congener concentrations in aquatic organisms from Sydney Estuary, Australia and physiology, spatial, seasonality, trophodynamic and life history traits

Over the past few decades, there has been considerable interest in hydrophobic persistent organic pollutants (POPs) and their accumulative properties in aquatic organisms. Several factors, such as environmental concentrations (i.e. in sediment) and physiological characteristics of organisms determine species-specific accumulation patterns of POPs in marine animal tissue. The present study investigated factors that govern species-specific accumulation patterns of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and dioxin-like biphenyls (dl-PCBs) in a food web from Sydney Estuary (Australia). The results indicated that physiological characteristics, i.e. lipid %, spatial, i.e. distance from Homebush Bay (point source of POPs) and life history characteristics of the organisms, such as diet and home range, influence PCDD/F and dl-PCB tissue concentrations to a varying degree. For example, PCDD/F tissue concentrations increased with the presence of detritivorous diet, species with limited home range and close proximity to Homebush Bay. On the other hand, lipid %, piscivorous diet and close proximity to Homebush Bay were the main predictors causing increases in dl-PCB tissue levels. Distance from Homebush Bay was the only predictor affecting both PCDD/F and dl-PCB tissue levels at a similar rate, i.e. decreasing tissue concentrations as the distance increases from Homebush Bay.

Development and application of a novel method for high‐throughput determination of PCDD/Fs and PCBs in sediments

A selective pressurized liquid extraction technique was developed for the simultaneous extraction of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs) from contaminated sediments. The final method incorporated cleanup adsorbents (Florisil, alumina, and silica) into the extraction cell in a 1:1 ratio of matrix to individual adsorbent (w/w). Sulfur, a common interference found in sediments, was successfully removed by placing activated copper in the extraction bottle prior to extraction. No additional postextraction cleanup was required, and sample throughput was reduced to 2.5 h per sample. Target analytes were quantified using high-resolution gas chromatography/electron-capture negative ionization mass spectrometry and verified by high-resolution gas chromatography/high-resolution mass spectrometry. Though mean analyte recoveries (n = 3) of PCDD/Fs and dl-PCBs were 84 ± 5.8% and 70 ± 8.4%, respectively, mean surrogate recoveries for all PCDD/Fs using this novel method were greatly improved compared with US Environmental Protection Agency (USEPA) method 1613 (∼25-155%) and USEPA method 8290a (40-135%). After development, the method was used to examine surficial sediment samples from the San Jacinto River waste pits, a Superfund site in Houston, Texas, USA. In all samples, PCDD/Fs and dl-PCBs were detected, and the contaminant concentrations ranged over 5 orders of magnitude.

Prediction of binding affinities of PCDDs, PCDFs and PCBs using docking-based Comparative Molecular Similarity Indices Analysis

Polychlorinated Dibenzodioxins (PCDDs), Dibenzofurans (PCDFs) and Biphenyls (PCBs) are industrial compounds or byproducts that can cause toxic effects after binding to aryl hydrocarbon receptor (AhR). But the mechanism about PCDDs, PCDFs and PCBs binding to AhR is unclear. To study the interaction and significant amino acid residues in binding of PCDDs, PCDFs and PCBs to AhR, a docking-based Comparative Molecular Similarity Indices Analysis (CoMSIA) was performed on a set of structurally diverse PCDDs, PCDFs and PCBs with known binding affinities. The docking-based CoMSIA model (non-cross-validated regression coefficient of 0.942 and cross-validated regression coefficient of 0.768) was developed and compared with previous report, the presented docking-based CoMSIA model showed good robustness and predictive performance. The obtained docking conformations and predictive CoMSIA model could provide clues to understand key residues and interactions between receptor and compounds of interest.