OCDD Research Articles

The human body burden of polychlorinated dibenzo-p-dioxins and dibenzofurans and dioxin-like polychlorinated biphenyls in residents' human breast milk from Beijing in 2007

To investigate contamination levels of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs) in human breast milk from Beijing residents, and evaluate the human body burden of PCDD/Fs and dl-PCBs of general population. A total of 110 human milk samples were collected from 11 regions in Beijing in 2007. After 11 pooled samples were made, concentrations of PCDD/Fs and dl-PCBs in breast milk pooled samples were measured by a high resolution gas chromatography - high resolution mass spectrometry (HRCG-HRMS) with isotope dilution. For congeners of PCDD/Fs and dl-PCBs in human breast milk from Beijing, the highest content of congeners was octachlorodibenzo-p-dioxin (OCDD), polychlorinated biphenyl (PCB)-118, and PCB-105 with the median of 20.6 pg/g fat, 4.07 ng/g fat and 1.63 ng/g fat, respectively. The concentration median of total dioxins in 11 pooled human milk samples from Beijing was 7.4 pg TEQ/g fat. The highest was 13.5 pg TEQ/g fat from Tongzhou, and the lowest was 4.3 pg TEQ/g fat from Pinggu. The contamination level of PCDD/Fs and dl-PCBs in human milk from Beijing is relatively low. However, with the rapid industrialization in China, the human body burden of PCDD/Fs and dl-PCBs will be likely to rise. Thus, further studies should be conducted to continuously monitor the trend of contamination level.

Circulating levels of persistent organic pollutants (POPs) are associated with left ventricular systolic and diastolic dysfunction in the elderly

Background and objectiveMajor risk factors for congestive heart failure (CHF) are myocardial infarction, hypertension, diabetes, atrial fibrillation, smoking, left ventricular hypertrophy (LVH) and obesity. However, since these risk factors only explain part of the risk of CHF, we investigated whether persistent organic pollutants (POPs) might also play a role. MethodsIn the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study, left ventricular ejection fraction, (EF), E/A-ratio and isovolumic relaxation time (IVRT), were determined by echocardiography and serum samples of 21 POPs were analyzed in serum measured by high-resolution chromatography coupled to high-resolution mass spectrometry (HRGC/HRMS) in 998 subjects all aged 70 years. ResultsIn this cross-sectional analysis, high levels of several of the polychlorinated biphenyls (PCB congeners 99, 118, 105, 138, 153, and 180) and octachlorodibenzo-p-dioxin (OCDD) were significantly related to a decreased EF. Some POPs were also related to a decreased E/A-ratio (PCBs 206 and 209). All the results were adjusted for gender, hypertension, diabetes, smoking, LVH and BMI, and subjects with myocardial infarction or atrial fibrillation were excluded from the analysis. ConclusionsCirculating levels of POPs were related to impairments in both left ventricular systolic and diastolic function independently of major congestive heart failure risk factors, suggesting a possible role of POPs in heart failure.

Levels, profiles and source identification of PCDD/Fs in farmland soils of Guiyu, China

The present study finished the first comprehensive survey of polychlorinated dibenzo-p-dioxin and dibenzofurans (PCDD/Fs) in farmland soils of Guiyu, China. Guiyu was a major electronic wastes (EWs) dismantling area, but primitive and crude EWs disposal manner had led to severe PCDD/Fs pollution there. Twenty-three farmland soil samples covering the entire Guiyu region were analyzed. Toxic equivalent quantities (I-TEQs) of soils in EWs disposal areas were 5.7–57pg TEQ g−1, and the total concentrations of tetra- to octa-homologues were 2816–17738pgg−1. The SL district was a heavily contaminated area, and the neighboring SMP town was influenced by Guiyu. EWs disposal might be the source of PCDD/Fs. The homologue profiles were of three types, representing different disposal manner of EWs. Tetrachlorodibenzo-p-dioxins (TCDDs) and octachlorodibenzo-p-dioxin (OCDD) could be used as indicators for source identification, open thermal disposal of EWs was inclined to lead to formation of TCDDs, OCDD was a product of non-thermal processes.

Reductive dechlorination of octachlorodibenzo-p-dioxin by nanosized zero-valent zinc: Modeling of rate kinetics and congener profile

Polychlorinated dibenzo-p-dioxins (PCDDs), a group of recalcitrant toxic compounds, are ubiquitous in nature. Amongst them, octachlorodibenzo-p-dioxin (OCDD) is not only prevalent in soil and sediment due to its high lipophilicity and hydrophobicity, but also detected in ground water and surface water. The present study examined the degradation of OCDD in aqueous solutions using four different zero-valent metal nanoparticles; zero-valent aluminum (nZVAL), zero-valent zinc (nZVZ), zero-valent iron (nZVI) and zero-valent nickel (nZVN). Only nZVZ was found to efficiently degrade OCDD into lower chlorinated congeners [OCDD→1,2,3,4,6,7,9-HxCDD (63%)→1,2,3,6,8,9-HpCDD (21%)→1,2,4,7,8-PeCDD (46%)→1,2,4,7-TeCDD (19%)] under ambient conditions. Simulations were also performed to predict the OCDD dechlorination pathway using a linear free energy relationship (LFER) model. Additionally, toxic equivalent quantity (TEQ) and homologue patterns were calculated by LFER modeling. The experimentally observed congener profiles were in excellent agreement with the model-predicted results, especially considering the complexity of the OCDD dechlorination pathway (256 theoretically possible reactions). This study proposes nZVZ as a suitable candidate for OCDD dechlorination and constitutes the first report on OCDD degradation using zero-valent metal nanoparticles under ambient conditions.

Mass Balance of Dioxins Derived from Pesticides in Sendai Bay, Japan

We calculated the mass balance of major congeners of dioxins derived from chloronitrophen (CNP) and pentachlorophenol (PCP) found in Sendai Bay, in order to characterize the present status of marine pollution caused by dioxins and enable the establishment of appropriate countermeasures against dioxin contamination. According to published statistics, about 58 000 t of CNP and about 22 000 t of PCP were shipped to Miyagi Prefecture over a 40-year period, and based on the these amounts of CNP and PCP, we estimated that 30.7 t of 1,3,6,8-tetrachlorinated dibenzo-p-dioxin (1,3,6,8-TeCDD), 1,3,7,9-TeCDD, and octa-chlorodibenzo-p-dioxin (OCDD) were introduced into the terrestrial environment as impurities contained in both pesticides. Mass balance analysis results show that most of these dioxins remained in the terrestrial environment and were not transported by runoff into Sendai Bay. Moreover, degradation mainly reduced the amount of dioxins in the terrestrial environment, instead of runoff or volatilization. Although large amounts of CNP and PCP were shipped to Miyagi Prefecture, only 0.8% of the total quantity of 1,3,6,8-TeCDD, 1,3,7,9-TeCDD, and OCDD contained in pesticides that were applied to paddy fields reached Sendai Bay via the discharge of major rivers. Moreover, most dioxins transported to the bay either flowed offshore or settled at the bottom of the bay. And there was very little bioaccumulation in marine organisms, particularly commercially valuable species.

The role played by some factors of intramolecular interaction in nonradiative deactivation of the lowest triplet state of octachlorodibenzo-p-dioxin

We have studied how intramolecular interactions, such as vibronically induced spin-orbit (VISO) and nonadiabatic interactions, which are governed by different structural elements of the octachlorodibenzo-p-dioxin (OCDD) molecule, affect the deactivation of its lowest triplet state. In the nonadiabatic approximation, taking into account out-of-plane vibrational modes as promoting ones, we have estimated the values of rate constant Kdgs of the nonradiative energy deactivation of in-plane triplet sublevels (s = z, y) of the triplet state of the OCDD molecule.

Distribution patterns and major sources of dioxins in soils of the Changsha-Zhuzhou-Xiangtan urban agglomeration, China

Surface soils from an industrial base, the Changsha-Zhuzhou-Xiangtan urban agglomeration in central China were analyzed for 2378-substituted polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). The PCDD/F concentrations ranged from 268 to 7510pgg−1 dry weight (dw), 72% of which were above the U.S. guideline value (1000pgg−1). It was found that octachlorodibenzo-p-dioxin (OCDD) was the most dominant congener accounting for 78.4–99.3% of the total PCDD/Fs, which was consistent with the PCDD/F profiles reported in other Asian countries. It is recommended that the four major sources of PCDD/Fs in the region can be diesel-fuel vehicles, open straw burning, mass burn-water wall (MB-WW), pentachlorophenate (PCP)/PCP-Na and boilers-hazardous waste incineration. This study is one of the few studies with a focus on the PCDD/F pollution in central China, providing evidences for establishing priorities in reduction of ecological risks posed by PCDD/Fs in central China and elsewhere.

Evidence for Dechlorination of Polychlorinated Biphenyls and Polychlorinated Dibenzo-p-Dioxins and -Furans in Wastewater Collection Systems in the New York Metropolitan Area

Polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) are persistent organic pollutants targeted by the Stockholm Convention. Both contain aromatic chlorines and are subject to microbial dechlorination. Dechlorination of PCBs in sewers in the Delaware River basin was recently reported. In this work, two data sets on concentrations of PCBs and PCBs+PCDD/Fs in wastewater treatment plant influents and effluents were analyzed to look for evidence that these compounds undergo dechlorination in the sewers of the New York/New Jersey Harbor area. The two data sets come from the Contamination Assessment and Reduction Project (CARP) and were analyzed via Positive Matrix Factorization (PMF). Analysis of the data set containing only PCB concentrations suggests that PCBs are dechlorinated in the sewers of the NY/NJ Harbor via the same pathways observed in the sewers of the Delaware River basin and that advanced dechlorination of PCB mixtures is more likely to occur in combined sewers vs separate sanitary sewers. When the combined data set of PCBs+PCDD/Fs was analyzed, the factor containing PCB dechlorination products also contained high proportions of 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin (HpCDD), a known product of the dechlorination of octachlorodibenzo-p-dioxin (OCDD), and other known dechlorination products of PCDD/Fs. Despite being the most abundant PCDD/F congener in all of the samples in the database, OCDD was a minor component in the dechlorination factor. This provides the first evidence that PCDD/Fs may be dechlorinated in sewers.

POPs are associated with left ventricular systolic and diastolic dysfunction

Purpose: Major risk factors for congestive heart failure (CHF) are myocardial infarction, hypertension, diabetes, atrial fibrillation, smoking, left ventricular hypertrophy (LVH) and obesity. However, since these risk factors only explain a part of the risk of CHF, we investigated if persistent organic pollutants (POPs) might also play a role.Materials and methods: In the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS), left ventricular ejection fraction, (EF), E/A-ratio and isovolumic relaxation time (IVRT), were determined by echocardiography and 21 POPs were measured by high-resolution chromatography coupled to high resolution mass spectrometry (HRGC/HRMS) in 998 subjects all aged 70 years.Results: In this cross-sectional analysis, high levels of several of the polychlorinated biphenyls (PCB congeners 99, 118, 105, 138, 153, and 180) and octachlorodibenzo-p-dioxin (OCDD) were significantly related to a decreased EF. Some POPs were also related to a decreased E/A-ratio (PCBs 206 and 209). All the results were adjusted for gender, hypertension, diabetes, smoking, LVH and BMI, and subjects with myocardial infarction or atrial fibrillation were excluded from the analysis.Conclusion: Circulating levels of POPs were related to impairments in both left ventricular systolic and diastolic function independently of major congestive heart failure risk factors, suggesting a possible role of POPs in heart failure.

Characterization and Inventory of PCDD/F Emissions from the Ceramic Industry in China

The ceramic industry is considered to be a potential source of dioxins (polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), considering the widespread distribution of dioxins in kaolinitic clays. Nevertheless, studies on the emission of dioxins from the ceramic industry are still very scarce. In this study, raw clays and stack gases from six typical ceramic plants in China were collected and analyzed to estimate the emission of dioxins from the ceramic industry. Dioxin profiles in raw clays were characterized by the domination of the congener octachlorodibenzo-p-dioxin (OCDD), and the contents of other congeners declined with the decreasing degree of chlorination. During the ceramic firing process, a considerable amount (16.5-25.1 wt % of the initial quantity in raw clays) of the dioxins was not destroyed and was released to the atmosphere. Dechlorination of OCDD generated a broad distribution within the PCDD congeners including a variety of non-2,3,7,8-substituted ones with the mass abundance of 0.4-3.6%. Based on the mean concentrations measured in this study, the inventory of PCDD/Fs from the manufacturing of ceramics on the Chinese scale was estimated to be 7.94 kg/year; the corresponding value on the I-TEQ basis is 133.6 g I-TEQ/year. This accounts for about 1.34% (I-TEQ basis) of the total emission of dioxins to the environment in China. The results suggest that the ceramic industry is a significant source of dioxins in the environment.

Methoxy-substituted octachlorodibenzo-p-dioxins in the Vietnamese soil

A lot of data have been accumulated to date on the sources of formation of polychlorinated dibenzodiox� ins (PCDD) and dibenzofurans (PCDF), their envi� ronmental levels, and effects on living organisms, but there relatively few data about the properties of these compounds (1). Indeed, the octachlorodibenzop� dioxin (OCDD) phenomenon, in particular, the fact that it is detected in very high concentrations in soils that have not been affected by any human interven� tion, while the concentrations of other PCDD in these soils exponentially decrease and the PCDF level is negligibly low, has not been explained as yet. Often, this abnormal profile is detected in hot climate areas such as Australia, Thailand (2, 8), and Vietnam (4). Moreover, this compound is not characteristic of any industrial process. The source of OCDD in these areas is unknown but probably detection of some precursors or metabolites would help to estimate the theory of natural formation of OCDD from pentachlorophenol (PeCP), which was indirectly supported by our earlier study (5). Here, we present the results of detailed analysis of a soil sample with abnormally high OCDD concentra� tion collected at the Sa Pa mountain range in the North of Vietnam. Due to the low absolute concentra� tions of PCDD/PCDF, these compounds are deter� mined most efficiently by gas chromatography/high� resolution mass spectrometry (GC/HRMS) with recording of selected characteristic ions. Since the compounds to be determined were unknown before� hand, we applied GC/HRMS in the full scan mode, i.e., recorded the full highresolution mass spectrum. EXPERIMENTAL The soil and bottom sediment samples were taken in 2010 by expeditions organized by the Russian- Vietnam Tropical Center. The samples were analyzed at the Laboratory for Analytical Ecotoxicology of the Institute of Ecology. In all samples, PCDD, PCDF, and PeCP were determined by gas chromatogra� phy/highresolution mass spectrometry (GC/HRMS) with isotope dilution (4). The possible OCDD metab� olites were determined by recording GC/MS patterns in the full scan mode and the selected ion detection (SID) mode. The samples were extracted with a toluene-ace� tone mixture and with an aqueous solution of sodium hydroxide; this was followed by acidification of the aqueous phase and reextraction into dichloromethane. The extracts were analyzed without purification and after passing through a silica gel layer impregnated with sulfuric acid.

Distribution patterns of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in sediments of the Xiangjiang River, China

We investigated the occurrence and distribution patterns of 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in six sediment samples from the Xiangjiang River, Hunan Province, People's Republic of China. Total concentrations of PCDD/Fs ranged from 876 to 497,759 (mean 160,766) ng/kg dw, the highest of which exceeded that have ever been reported for sediment samples. World Health Organization total toxicity equivalent (WHO-TEQ) concentrations in three out of six samples were significantly higher than the guidance level (21.5 ng WHO-TEQ/kg dw) suggested by Canadian Sediment Quality Guideline. A predominance of octachlorodibenzo-p-dioxin (OCDD) was observed with an average contribution of 90.8% to the total PCDD/F concentrations, while 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin (HpCDD) was the major contributor to the PCDD/F WHO-TEQ concentrations in most of the sites. Such high levels of OCDD and HpCDD may be attributed to the presence of PCP/PCP-Na pollution, although MB-WW, agricultural straw open burning, and boilers-hazardous wastes were also the potential sources of PCDD/Fs. This is the first report for the concentrations and congener profiles of PCDD/Fs in sediment samples from the Xiangtan, Zhuzhou, and Changsha sections of the Xiangjiang River, providing scientific evidence for establishing priorities to reduce ecological risks posed by PCDD/Fs in the rapidly developing areas of Hunan Province and elsewhere.

Comparison of Emission of Dioxins and Furans from Gasohol- and Ethanol-Powered Vehicles

ABSTRACT The exhaust emissions of 17 polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) were investigated in two spark-ignition light-duty vehicles, one gasohol-fueled and a flexible-fuel one fueled with hydrated ethanol. Gasohol is a mixture of gasoline and 22% ethanol. The influence of fuel type and quality, lubricant oil type, and use of fuel additives on the formation of these compounds was tested using standardized U.S. Federal Test Procedure (FTP)-75 cycle tests. The sampling of the PCDD/Fs followed the recommendations of a modified U.S. Environmental Protection Agency (EPA) Method 23 (http://www.epa.gov/ttn/emc/promgate/m-23.pdf) and the analysis basically followed the U.S. EPA Method 8290 (http://www.epa.gov/osw/hazard/testmethods/sw846/pdfs/8290a.pdf). Results showed that emission factors of PCDD/Fs for the gasohol vehicle varied from undetected to 0.068 pg international toxic equivalency (I-TEQ) km−1 (average of 0.0294 pg I-TEQ km−1), whereas in the ethanol vehicle they varied from 0.004 to 0.157 pg (I-TEQ) km−1 (average of 0.031 pg I-TEQ km−1). In the gasohol-powered vehicle, the use of fuel additive diminished the emission of Octachlorodibenzo-p-dioxin (OCDD) significantly, whereas in the ethanol vehicle no significant associations were observed between the investigated variables and the emissions. IMPLICATIONS The objective of this work was to analyze differences in emissions from a traditional fossil fuel (gasoline) and an alternative renewable fuel (ethanol from sugarcane), and the influence of fuel additives and lubricant oils on the formation of chlorinated dioxins and furans in spark-ignition light-duty gasohol and ethanol vehicles. Renewable fuels are very important in terms of climate change but the risk to the population's health must not increase. Thus the results of this work could help in the development of environmental impact studies as well as orienting policy-makers in formulating strategies for air pollution control.

Distribution, Characteristics, and Worldwide Inventory of Dioxins in Kaolin Ball Clays

Distribution, characteristics, and global inventory of dioxins (polychlorinated dibenzo-p-dioxins [PCDDs] and dibenzofurans [PCDFs] and dioxin like polychlorinated biphenyls) in kaolin clays collected from 10 countries were investigated. Dioxins were found in all kaolin clay samples analyzed, at total concentrations ranging from 1.2 pg/g (Brazil) to 520,000 pg/g (USA). Dioxin concentrations in kaolin clays from a few countries (e.g., Brazil and UK) were lower than those reported for background soils in Japan. Dioxin profiles in kaolin clays were characterized by the domination of the congener octachlorodibenzo-p-dioxin (OCDD), and the concentrations of other congeners decreased in the order of reduction in the levels of chlorination. Furthermore, specific distribution of congeners, with predominant proportions of 1,4,6,9-substituted PCDDs within each homologue group, was found in most clay samples. The ratios of concentrations of PCDD to PCDF and 1,2,3,7,8,9-HxCDD to 1,2,3,6,7,8-HxCDD indicated differences in the profiles found for anthropogenic sources (including pentachlorophenol) and kaolin clays. Concentrations of PCDD/Fs in kaolin clays, except for American ball clays, did not exceed the environmental criteria set by the Law Concerning Special Measures against Dioxins in Japan. Based on the average concentrations measured in our study, inventories of PCDD/Fs from the production/usage of ball clays on a global scale were estimated to be 650 kg/yr; the corresponding value on a TEQ basis is 2400 g-TEQ/yr. More than 480 kg of OCDD is estimated to be released annually from the production of kaolin clays worldwide, suggesting that kaolin clays can be a major contributor for additional source of dioxins, especially OCDD, in the environment.

Circulating levels of persistent organic pollutants associate in divergent ways to fat mass measured by DXA in humans

BackgroundEnvironmental contaminants have recently been implicated in the pathogenesis of obesity. ObjectiveTo explore relations between persistent organic pollutants (POPs) and fat mass independently of body stature, using a cross-sectional design. MethodsIn the Prospective Study of the Vasculature in Uppsala Seniors (PIVUS), fat mass was determined in 70-year-old subjects (n=890) by dual-energy X-ray absorptiometry (DXA). The plasma levels of 21 POPs (including 16 PCB congeners, 3 OC pesticides, 1 BDE47, and 1 dioxin) were measured by high resolution chromatography coupled with high resolution mass spectrometry (HRGC/HRMS). ResultsLipid-standardized plasma concentrations of octachlorodibenzo-p-dioxin (OCDD), the PCBs 74, 99, 105 and 118, and the pesticides HCB, TNK, and DDE were all positively related to fat mass (p=0.03–0.0001). Subjects in the fifth quintile for PCB 105 showed a mean fat mass that was 4.8kg more than subjects in the first quintile. On the other hand, the PCBs 156, 157, 169, 170, 180, 189, 194, 206, and 209 were negatively related to fat mass (p=0.0001). For PCB 194, subjects in the fifth quintile showed a mean fat mass that was 10.8kg less than subjects in the first quintile. Following adjustment for smoking, physical activity, education level, height, lean mass, and gender, these results remained significant (p=0.01–0.0001) except for the PCBs 74 and 99. For some PCBs, the associations vs. fat mass were more pronounced in women than in men. ConclusionPlasma concentrations of some pesticides are positively related to fat mass, while divergent associations are seen for the PCBs. These results implicate a complex role of POPs in obesity.

Clay Mediated Route to Natural Formation of Polychlorodibenzo-p-dioxins

Recent studies have documented the ubiquitous occurrence of polychlorodibenzo-p-dioxins and dibenzofurans (PCDD/Fs) of unknown origin in soils and clay deposits. Interestingly, the PCDD/F congener profiles do not match any known natural or anthropogenic source, and global PCDD/F budgets fail to account for the observed levels in soils. To reconcile these observations, clay minerals had been hypothesized to play a central role in the natural in situ synthesis of PCDD/Fs. We recently demonstrated the clay-mediated formation of the most prevalent PCDD congener in soils, octachlorodibenzo-p-dioxin (OCDD), supporting this hypothesis. Here we report the formation of the direct precursors ("predioxins") of the most toxic PCDD congener, 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD), and of 1,2,4,7,8-pentachlorodizenzodioxin (1,2,4,7,8-PeCDD), and two additional dimers, from the reaction of 2,4,5-trichlorophenol (2,4,5-TCP) with Fe(III)-montmorillonite clay. We propose plausible reaction pathways, each initiated by single electron transfer from 2,4,5-TCP to Fe(III)-montmorillonite forming the 2,4,5-TCP radical cation. The operative reaction mechanisms, inferred from experimental results, are supported by quantum mechanical calculations. The key role of montmorillonite is apparently to stabilize the reactive radical cation intermediate. Fortuitously, PCDD formation reactions on clay surfaces are more facile for less toxic higher chlorinated congeners like OCDD, as predicted by the proposed reaction mechanism and consistent with the observed PCDD congener distributions in soils. Importantly, increasing the toxicity equivalency factor of OCDD would immediately cause many soils to exceed PCDD regulatory levels due to the predominance of this congener.

PCDD/Fs in sediments of Central Vietnam coastal lagoons: In search of TCDD

Samples from nine Central Vietnam coastal lagoons, together with three soils and sediments collected in two freshwater reservoirs of the Thua Thien-Hué province, were analysed for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Total concentrations are low, from 192 to 2912pgg−1 and depth profiles in Tam Giang-Cau Hai (TG-CH) sediment cores show only minor changes over time in PCDD/F input and composition. Octachloro dibenzo-p-dioxin (OCDD) is the prevailing congener (approximately 90%), indicating combustion as the main PCDD/F source to these coastal systems, whereas natural formation might be partly responsible for the presence at depth. 2,3,7,8-Tetrachloro dibenzo-p-dioxin (TCDD), largely sprayed together with Agent Orange over the study areas during the war (1961–1971), is absent or very low. This result supports the hypothesis of strong degradation soon after spraying. Multivariate statistical analyses account for the presence of local, short-range sources as observed in the northern part of the TG-CH lagoon.

Destruction of Polychlorinated Aromatic Compounds by Spinel-Type Complex Oxides

Destruction of polychlorinated aromatic compounds was carried out over spinel-type catalysts XY2O4 (where X = Mg, Ca, Cu, Ni, Zn, and Y = Al, Fe). The catalysts were characterized by XRD, nitrogen adsorption-desorption isotherms and FTIR. The performance of these catalysts toward the decomposition of hexachlorobenzene (HCB) and octachlorodibenzo-p-dioxin (OCDD) was evaluated in a closed system. The spinel-type catalyst with mesoporous structure demonstrated high catalytic activity for the hydrodechlorination of polychlorinated aromatic compounds. Among them, the copper-aluminum spinel (CuAl2O4), specifically calcined at 600 degrees C, exhibited the best activity. More than 85% dechlorination efficiency of HCB and 99% decomposition of polychlorinated dibenzodioxin (PCDD) were achieved at 250 degrees C for 30 min over the above catalyst which was more effective than the corresponding metallic copper and copper oxide catalysts during the thermal degradation of polychlorinated aromatic compounds. The correlation of catalytic performance to structural characteristics is discussed based on the detailed characterization. The simple preparation procedure and reasonable cost of the spinel-type catalysts present a good potential for the thermal treatment of polychlorinated aromatic pollutants at lower temperatures.

Characterization of persistent-bioaccumulative-toxic (PBTs) substances in hazardous waste: Integration of chemical analysis and in vitro fish cells response

High-resolution gas chromatography mass spectrometry (HRGC/MS) is the standard method for analyzing dioxin, furan, and polybrominated retardants in hazardous waste. Methods based on biological interactions (ligand–receptor recognition) have begun only recently to be investigated in the context of environmental applications. We have compared dioxin, furan, and polybrominated diphenyl ethers toxicity levels by two analytical approaches: HRGC/MS analysis and a battery of in vitro bioassays with the fish cell line rainbow trout gonad cell line-2 (RTG-2), in nine (liquid and solid) hazardous waste samples. The battery assays included a cytotoxicity neutral red bioassay, a Kenacid blue protein content bioassay, an ethoxyresorufin O-deethylase bioassay, and a β-galactosidase bioassay. A dose-dependent stimulation of enzymatic activities was observed in four of the nine samples, associated to high levels of octachlorodibenzo-p-dioxin (OCDD) and/or polychlorinated biphenyls (PCB) 77 congener. The enzymatic values of the whole samples were higher than the extracts’ values, which indicated that there had to be other effective compounds in the waste samples that could be lost in the extraction-purification process. The outcome of both approaches makes the bioassay useful as a rough estimate for the synergistic or antagonistic effects of polychlorinated dibenzo-p-dioxins (PCDDs)/Fs and dl-PCBs in extracts from the samples, and it can provide preliminary information regarding the characterization procedure in ecological risk.

Reduced graphene oxide films used as matrix of MALDI-TOF-MS for detection of octachlorodibenzo-p-dioxin

A reduced graphene oxide (rGO) film was used as the matrix in the matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF-MS) for the detection of octachlorodibenzo-p-dioxin (OCDD) with a detection weight as low as 500 pg.