Dietary intakes of polychlorinated dibenzo-p-dioxins, dibenzofurans and dioxin-like polychlorinated biphenyls in Spain.

Congener-specific analyses of seventeen 2,3,7,8-substituted PCDD/Fs, three non-ortho and 8 mono-ortho dioxin-like polychlorinated biphenyls (PCBs) were performed on 258 Spanish foodstuff samples, mainly of animal origin, for 2000--03. Daily dietary intakes of PCDD/Fs and PCBs, expressed as toxic equivalents (WHO-TEQs), were estimated by combining food consumption data from the Spanish National Institute Statistics survey and concentration levels measured in individual samples, using upper bound determination values (not detectable = limit of detection). The calculated dietary intake of PCDD/Fs for a person weighing 70 kg was 1.35+/-0.11pg WHO-TEQs kg(-1) bw day(-1), and 3.22+/-0.75 pg WHO-TEQs kg(-1) bw day(-1) if dioxin-like PCBs (non- and mono-ortho PCBs) were included, showing the importance of their inclusion in monitoring studies. Both values were within the range of tolerable daily intake (TDI) proposed by the WHO (1-4pg WHO-TEQs kg(-1) bw day(-1)). The current levels are lower than earlier intakes estimates conducted in Spain. Meat and meat products accounted for more than 35% of the intake, followed by milk and milk products (29%), vegetables oils (19%), fish and seafood (11%) and eggs (4%). Dioxin-like PCBs are an important component in the total WHO-TEQs in foodstuffs. This is particularly true for the fish food group, where the total WHO-TEQs is dominated by dioxin-like PCBs (up to 80% of WHO-TEQs in some cases).     

婴儿配方乳粉中二噁英及其类似物污染分析

目的 了解婴儿配方乳粉中二噁英及其类似物污染水平,为相关研究提供基础数据.方法 采集601份市售婴儿配方乳粉,按照GB 5009.205-2013《食品安全国家标准食品中二噁英及其类似物毒性当量的测定》对17种多氯代苯并二噁英和多氯代苯并呋喃(PCDD/Fs)和12种二噁英样多氯联苯(dl-PCBs)进行测定.结果 P...     

Polychlorinated dibenzo-p-dioxins,dibenzofurans and dioxin-like polychlorinated biphenyls in food and feed in Latvia in 2009–2011

During 2009–2011 a monitoring programme for 17 polychlorinated dibenzo-p-dioxins (PCDDs)/polychlorinated dibenzofurans (PCDFs) and 12 dioxin-like polychlorinated biphenyls (DL-PCBs) was conducted in the Latvian food and feed market. Using ISO 17025-accredited analytical methodology, investigation of 121 food (milk, dairy products, meat, eggs, fish, fish products) and 66 feed samples (fish meal and oil, compound and mineral feed, vegetable and animal fats) was performed. Most samples showed contamination below the European Commission (EC) Regulation No. 1881/2006 and Commission Directive 2006/13/EC limits. Average total toxicological equivalent (total-TEQ₍₁₉₉₈₎) concentrations within the food sample groups, except fish and fish products, ranged between 0.41 and 15.1 pg total-TEQ₍₁₉₉₈₎ g^?1 fat. Fish and fish products showed contamination levels from 0.18 to 46.0 pg total-TEQ₍₁₉₉₈₎ g^?1 fresh weight (f.w.). Fifty-seven per cent of cod liver samples were non-compliant. The most contaminated feed samples were fish meal and fish oil. A comparison with WHO-TEF₍₂₀₀₅₎ data is given.     

Congener-specific composition of polychlorinated naphthalenes, coplanar PCBs, dibenzo-p-dioxins, and dibenzofurans in the Halowax series

Concentrations and congener compositions of polychlorinated naphthalenes (PCNs), coplanar polychlorinated biphenyls (Co-PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and dibenzofurans (PCDFs) were determined in seven Halowax (HW) preparations. In HW 1000 and 1031, low-chlorinated naphthalenes (CNs) and in HW 1051, highly chlorinated naphthalenes were dominant, whereas tri- through penta-CNs were major homologues in other Halowaxes. Concentrations of Co-PCBs were in the range of 2.0-2600 ng/g. CB 105 and 118 were dominant in all Halowaxes. Concentrations of PCDDs/DFs were in the range of 92-5900 ng/g. The 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQs) in Halowaxes calculated from the amounts of PCNs, Co-PCBs, and PCDDs/DFs were in the range of 2800-220,000 ng-TEQ/g. PCNs accounted for most of the total TEQs in Halowaxes, and the contribution of PCDDs/DFs and Co-PCBs to total TEQs was less than 1/1000 that of PCNs. Congeners that most significantly contributed to TEQs were CN 69, 73, 70, and 63. Total TEQs roughly estimated from the Japanese production of technical PCNs, 210 kg-TEQ, was about half from technical PCBs, 440 kg-TEQ on average.     

Spatial distibution and temporal accumulation of polychlorinated dibenzo-p-dioxins,dibenzofurans, and biphenyls in the Gulf of Finland

Dated sediment cores and surface sediments were analyzed from the Gulf of Finland, a part of the Baltic Sea, to study the sources, levels, distribution, and total amounts of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs). The gulf was found to be severely polluted, with PCDD/F sum concentrations as high as 101000 ng/kg and 479 ng/kg WHO-TEQ in dry weight. The source of pollution was the former manufacturing and use of a chlorophenol based wood preservative along the Kymijoki River. It was estimated thatthe impacted sedimentary area stretched a distance of 75 km away out from the coast and that the PCDD/F sum load attributed to the wood preservative source was 1770 kg of PCDD/Fs or 12.4 (+/-2.8) kg WHO-TEQ. The surface sediments contained 24-66% of the maximum concentrations present in the 1960-1970s, showing that the river still acts as a significant PCDD/F source and may contribute to the high levels in fish. Moreover, the reduced PCDD/F and PCB concentrations were partly due to the dilution by increased dry matter deposition. PCBs were uniformly distributed over the gulf, and the PCB load in the polluted area was 2020 kg or 0.14 kg WHO-TEG.     

Statistically designed survey of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and co-planar polychlorinated biphenyls in U. S. meat and poultry, 2002-2003: results, trends, and implications

To obtain information on dioxin levels in the human diet, the Food Safety and Inspection Service of the United States Department of Agriculture recently determined levels of dioxin-like compounds (dioxins/dibenzofurans/PCBs) in four major slaughter classes (steers and heifers, market hogs, young chickens, and young turkeys) that comprise over 90% of the meat and poultry production in the United States. The data were analyzed and compared to data from smaller surveys carried out from 1994 to 1996. These surveys were conducted by different laboratories nearly 10 years apart, so a direct comparison of the data was not straightforward. Three approaches were taken: (1) comparison with nondetects set to zero, (2) comparison with nondetects set to half the limit of detection, and (3) comparison applying the earlier surveys' limits of detection to the newer data. The data analyses indicated that dioxin levels appear to have declined in three of the four slaughter classes, with young chickens, market hogs, and young turkeys declining 20-80%, while any declines in cattle dioxin levels, if real, are less than those observed in the other slaughter classes. Further study is needed to examine factors that might explain the differences in dioxin levels and distribution profiles in the four slaughter classes. A small number of market hog and steers/ heifers samples had dioxin toxic equivalency levels (TEQs) greater than 2 pg/g lipid weight. Follow-up investigations for those samples indicated a common source for the market hog samples (a dioxin-contaminated mineral supplement), but no commonality was found for the steers/ heifers samples.     

Polychlorinated dibenzo-p-dioxins, dibenzofurans, and polychlorinated biphenyls in human tissues, meat, fish, and wildlife samples from India

Concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and non- and mono-ortho-substituted polychlorinated biphenyls (dioxin-like PCBs) were measured in tissues of humans, fishes, chicken, lamb, goat, predatory birds, and Ganges River dolphins collected from various locations in India. PCDDs/DFs were found in most of the samples analyzed with the liver of spotted owlet containing the highest concentration of 3,300 pg/g, fat wt. 2,3,7,8-Substituted PCDDs and PCDFs were found in human fattissues at concentrations ranging from 170 to 1,300 pg/g, fat wt. Concentrations of PCDDs were generally greaterthan those of PCDFs in human tissues, fishes, animal fat, and dolphin. Among fishes, meat, and wildlife samples analyzed, concentrations of PCDDs/DFs were found in the following order: country chicken < goat/lamb fat < fishes < river dolphins < predatory birds. Hepta-CDDs and OCDD were the major PCDD homologues found in humans, fishes, meat products, and dolphins. 2,3,7,8-Tetrachlorodibenzo-p-dioxin equivalents of PCDDs/DFs were greater than those of PCBs in selected fish, dolphin, and human samples. To our knowledge, this is the first report of PCDDs and PCDFs in human tissues, fishes, meat, and wildlife collected from India.     

Dietary exposure and risk assessment of polychlorinated dibenzo-p-dioxins,polychlorinated dibenzofurans and dioxin-like polychlorinated biphenyls of the population in the Region of Valencia (Spain)

Dietary exposure of the Valencia Region population to polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and PCBs was assessed in the Region of Valencia in 2010–2011. A total of 7700 food samples were collected. Occurrence data were combined with consumption data to estimate dietary exposure in adults (>15 years of age) and young people (6–15 years of age). The estimated intake was calculated by a probabilistic approach. Average intake levels (upper-bound scenario) were 1.58 and 2.76 pg toxic equivalent (TEQ) kg^?1 body weight (bw) day^?1 for adults and young people, respectively. These average intakes are within range of the tolerable daily intake of 1–4 pg WHO-TEQ kg^?1 bw day^?1 recommended by WHO, and slightly above the tolerable weekly intake (TWI) of 14 pg TEQ kg^?1 bw week^?1 and the Provisional tolerable monthly intake of 70 pg TEQ kg^?1 bw month^?1 set by the Scientific Committee on Food and the Joint FAO/WHO Expert Committee on Food, respectively. These results show that the contamination levels in food and therefore the exposure of the general population to PCDD/Fs and PCBs have declined in this region and therefore show the efficiency of the European risk-management measures. In terms of risk characterisation, the results showed that, under the upper-bound scenario, 22% of the adult and 58% of the young people population could exceed the TWI.     

Risk assessments of polychlorinated dibenzo- p-dioxins, polychlorinated dibenzofurans, and dioxin-like polychlorinated biphenyls in food

The polychlorinated dibenzo-p-dioxins (PCDD), polychlorinated dibenzofurans (PCDF), and dioxin-like polychlorinated biphenyls (dioxin-like PCB) are ubiquitous in food of animal origin and accumulate in fatty tissues of animals and humans. The most toxic congener is 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The toxic responses include dermal toxicity, immunotoxicity, carcinogenicity, and reproductive and developmental toxicity. Toxic equivalency factors have been established for the other PCDD, PCDF and dioxin-like PCB relative to TCDD, and the combined toxicity of a sample can be expressed as toxic equivalent (WHO-TEQ). The EC Scientific Committee for Food evaluated these compounds in 2001. The assessment used the most sensitive adverse toxicological end-points of TCDD in experimental animals. These were developmental and reproductive effects in the male offspring of rats administered TCDD during pregnancy. Because of the large difference between rats and humans in the biological half-life of TCDD, the assessment used a body burden approach to compare across species and derived a tolerable weekly intake of 14 pg TCDD/kg of body weight (bw), which was extended to include all the 2,3,7,8-substituted PCDD and PCDF, and the dioxin-like PCB, and expressed as a group tolerable weekly intake of 14 pg WHO-TEQ/kg bw. The FAO/WHO Joint Expert Committee on Food Additives (JECFA) performed a similar assessment whereas the US Environmental Protection Agency (US EPA) has paid more attention to human data on carcinogenicity.     

Characterization of trophic transfer for polychlorinated dibenzo-p-dioxins, dibenzofurans, non- and mono-ortho polychlorinated biphenyls in the marine food web of Bohai Bay, North China

Many investigations have highlighted the bioaccumulation of dioxins in animals, but little is known about the trophodynamics of dioxins in the food web. In this study, the trophic transfer of nine dibenzo-p-dioxin (PCDD) congeners, eleven dibenzofuran (PCDF) congeners, and twelve non-, mono-ortho polychlorinated biphenyl (non- and mono-ortho PCBs) congeners in a marine food web were determined. The concentrations of PCDDs, PCDFs, non- and mono-ortho PCBs were analyzed in phytoplankton/ seston, zooplankton, three invertebrate species, six fish species, and one seabirds species collected from Bohai Bay, representing approximately 4 trophic levels based on stable nitrogen isotope values. Positive relationships were found between trophic levels and lipid equivalent concentrations of non- and mono-ortho PCBs except for PCB-77, PCB-81, PCB-126, PCB-156, and PCB-167, indicating bioaccumulation of these compounds in this food web. But lipid equivalent concentrations of low chlorinated 2,3,7,8-substituted-PCDD/Fs did not exhibit statistically significant trends with trophic levels. And lipid equivalent concentrations of high chlorinated 2,3,7,8-substituted-PCDD/Fs and three non-2,3,7,8-substituted-PCDD/Fs declined significantly with increasing trophic levels providing that these isomers undergo trophic dilution. The similarity in log Kow values for non-, mono-ortho PCBs, non-2,3,7,8-substituted-PCDD/Fs, and some 2,3,7,8-substituted-PCDD/Fs suggests that the difference of trophic transfer is mainly due to their different metabolic transformation rates.     

Dietary intakes of polychlorinated dibenzo- p -dioxins, dibenzofurans and polychlorinated biphenyls in Finland

Samples of cow milk, pork, beef, eggs, rainbow trout, flours and vegetables were analysed for 17 polychlorinated dibenzo- p -dioxins and dibenzofurans (PCDD/F) and 36 polychlorinated biphenyls (PCB). Daily dietary intake of PCDD/Fs as toxic equivalent (I-TEq) and PCBs (PCB-TEq) was assessed using food consumption data from a 24-h dietary recall study for 2862 Finnish adults. The calculated intake of PCDD/F was 46pg I-TEq day -1 . The current level was about half of the earlier estimation of intake in Finland made in 1992. The assessed PCB intake was 53pg PCBTEqday -1 . Thus, the total intake of PCDD/Fs and PCBs was 100pg TEqday -1 (1.3pg TEqkg -1 b.w.day -1 ), which is within the range of tolerable daily intake (TDI) proposed by the WHO (1-4pg TEqkg -1 b.w.day -1 ).     

Biota--sediment accumulation factors for polychlorinated biphenyls, dibenzo-p-dioxins, and dibenzofurans in southern Lake Michigan lake trout (Salvelinus namaycush)

A set of high-quality, age-specific biota-sediment accumulation factors (BSAFs) for polychlorinated biphenyls (PCBs), dibenzo-p-dioxins (PCDDs), and dibenzofurans (PCDFs) have been determined from concentrations measured with high-resolution gas chromatography/high-resolution mass spectrometry, by use of the 13C isotopic dilution technique, in lake trout and surficial (0-2 cm) sediment samples from southern Lake Michigan. BSAFs ranged from <0.1 to 18 for PCBs and from <0.001 to 0.32 for PCDDs and PCDFs detected in the fish. PCBs with zero or one chlorine in an ortho position had smaller BSAFs than other PCBs. PCDDs and PCDFs with chlorines at the 2,3,7,8-positions had larger BSAFs than most other PCDDs and PCDFs. The fidelity of the relative bioaccumulation potential data between independent lake trout samples, within and among age classes, suggests that differences in slight rates of net metabolism in the food chain are important and contribute to the apparent differences in BSAFs, not only for PCDDs and PCDFs but also possibly for some PCBs. A complicating factor for non-ortho- and mono-ortho-PCBs is the uncertain contribution of enhanced affinity for black carbon (and possibly volatility) acting in concert with metabolism to reduce measured BSAFs for lake trout. On the basis of the association between chemicals with apparent slight rates of metabolism and measured dioxin-like toxicity, several PCDFs with similar measured BSAFs but unknown toxicity may be candidates for toxicity testing.     

Intake estimation of polychlorinated dibenzo-p-dioxins, dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) in salmon: the inclusion of uncertainty

Dioxins and dioxin-like PCBs are given toxic equivalency factors (TEFs) in order to calculate the combined toxic equivalence (TEQ) of these contaminants in a sample of food. This study calculates the probability of an average consumer exceeding the recommended tolerable daily intake of 1-4 pg WHO-TEQ kg^-1 bw day^-1 as the amount of salmon in the diet is increased. Probabilistic risk analysis is used to account for the known uncertainties in this calculation. When the TEF uncertainty was excluded with no salmon consumption, the background dietary intake ranged from 1.36 to 1.78 pg TEQ kg^-1 bw day^-1. A weekly consumption of three standard salmon portions resulted in a 36% chance of exceeding the upper limit of the TDI. Inclusion of the TEF uncertainty increased the background dietary intake range from 2.1 to 4.4 pg TEQ kg^-1 bw day^-1, and the weekly consumption of one salmon portion resulted in a 79% chance of the average consumer exceeding the upper TDI. The most important factors contributing to the uncertainty in these results were, in order of magnitude, the TEF for PCB 126 and the sampling uncertainty (sample size) followed by the measurement uncertainty of PCB 126. We recommend that it is more important to increase sample size and produce more precise estimates in the TEF than to improve analytical accuracy.     

Survey of polychlorinated dibenzo-p-dioxins,polychlorinated dibenzofurans and non-ortho-polychlorinated biphenyls in US meat and poultry, 2012–13: toxic equivalency levels,patterns, temporal trends and implications

ABSTRACT

The US Department of Agriculture (USDA) conducts a statistically based survey of the domestic meat supply (beef, pork, chicken and turkey) to determine current levels of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and non-ortho-polychlorinated biphenyls (no-PCBs) every 5 years. Fat samples for each slaughter class were collected from US federally licensed slaughter facilities. The samples were processed and analysed for 17 PCDD/Fs and three no-PCBs. The sum of PCDD, PCDF and no-PCB toxic equivalencies (sum-TEQ) calculated using 2005 toxic-equivalency factors for all slaughter classes ranged from non-detect (n.d.) to 6.47 pg TEQ g^–1 lipid. The median sum-TEQs, when n.d. = 0.5 LOD, for beef, pork, chicken and turkey were 0.66, 0.12, 0.13 and 0.34 pg TEQ g^–1 lipid respectively. A comparison of the current survey with the previous three surveys shows a declining trend, with decreasing differences between medians; differences between the median sum-TEQs from 2007–08 and 2012–13 were –10%, –29%, –33% and –25% for beef, pork, chicken and turkey respectively. Several beef samples underwent further characterisation and congener patterns from these beef samples suggested pentachlorophenol treated wood as the likely exposure source. US consumer exposure to these compounds is relatively low and no slaughter class contributed more than 26% to the US Environmental Protection Agency (USEPA) chronic oral reference dose of 0.7 pg TEQ kg^–1 bw day^–1.     

Concentrations and profiles of polychlorinated dibenzo-p-dioxins and dibenzofurans in soils from Korea

Soil samples were collected from Changwon and Masan Cities, Korea, and analyzed for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/DFs). Nearly all tetra- through octachlorinated PCDDs/DFs including the 17 2,3,7,8-substituted PCDDs/DFs were detected in all samples. Total concentrations of PCDDs/DFs and of 2,3,7,8-tetrachlorinated dibenzo-p-dioxin (TeCDD) equivalents (TEGs) in soils ranged from 35 to 121,400 pg/g, dry weight, and from 0.2 to 3720 pg of I-TEQ/g, respectively. On the basis of guidelines for TEQ concentrations established in Germany and the United States, 9 of 23 soil samples (39% of the total samples analyzed) could not be expected to pose human health hazards. The rest of 61% of soils need measures such as investigations of source identification, soil decontamination, and/or soil removal. Total concentrations of PCDDs/DFs were greater at or near four industrial sites, which are concerned with the steel industry, petrochemical-related industry, and industrial waste incineration, than other areas. This indicates the presence of potential source areas. Soil collected from a site 50 m from an open-burning industrial waste incinerator in an industrial complex was heavily contaminated, containing a total concentration of PCDDs/DFs of 121,400 pg/g, dry weight. PCDDs/DFs were also detected in soils from the top of a 200 m mountain indicating a wide dispersal of PCDDs/DFs by atmospheric transport from point source areas. The congener pattern and relative proportions of PCDFs in soils suggest that commercial PCB preparations such as Kanechlors may be one of the sources. The wide range of PCDD/DF isomers detected in soils from many locations also suggests a multitude of sources, in addition to commercial PCBs, such as incineration of industrial wastes such as car tires, scrap wires, plastics, papers, and emission of automobile exhaust.     

Importance of chlorine speciation on de novo formation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans

The role of chlorine speciation on de novo formation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDDs/Fs) has been studied thoroughly in an entrained flow reactor during simulated waste combustion. The effects of gas-phase chlorine species such as chlorine (Cl2), hydrogen chloride (HCl), and chlorine radicals (Cl*), as well as ash-bound chlorine, on PCDD/F de novo formation were isolated for investigation. The ash-bound chlorine alone was observed to be a sufficient chlorine source for PCDD/F formation. The addition of HCl to the system did not influence the yields of the PCDDs/Fs nor the degree of chlorination due to its poor chlorinating ability. Addition of 200 ppm of Cl2 to the ash-feed system resulted in increased PCDD/F yields, especially for the octa- and hepta-chlorinated congeners. Altering the reaction temperature to enable the presence of only Cl2 to the system did not change the yields of PCDD/F compared to those when both Cl2/Cl* were present. However, comparison between ash-bound and gas-phase chlorine, the latter at a concentration typical of a realistic combustion process, revealed ash-bound chlorine to be the more important chlorine source for de novo formation of PCDD/F in a full-scale incinerator.     

Distribution and elimination of polychlorinated dibenzo-p-dioxins,dibenzofurans, biphenyls,and p,p'-DDE in tissues of bald eagles from the Upper Peninsula of Michigan

Liver, muscle, fat, kidney, and gall bladder of eight bald eagles (Haliaeetus leucocephalus) found dead in the Upper Peninsula of Michigan during 2000 were analyzed for the presence of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and biphenyls (including coplanar PCBs), p,p'-DDE, and hexachlorobenzene (HCB). Necropsy results showed that the birds suffered from peritonitis, bacterial infection, or trauma. Concentrations of PCDD/DFs in livers ranged from 23 to 4500 pg/g on a wet weight basis (wet wt), whereas the least concentrations were found in blood plasma of bald eagle nestlings (2.3-49 pg/g, wet wt). A maximum total PCB concentration of 280,000 ng/g, wet wt, was found in the liver of a dead bald eagle affected by peritonitis. The greatest concentrations of p,p'-DDE and HCB in eagle livers were 17,000 and 120 ng/g, wet wt, respectively. Eagles with elevated 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or total PCB concentrations tended to have great TCDD/TCDF or PCB126/PCB77 ratios, hypothesized to be due to induction of cytochrome P450 enzymes and subsequent metabolism of TCDF and PCB77. Concentrations of TCDD toxic equivalents (TEQs) in the tissues of bald eagles exceeded the thresholds for toxicity in a few avian species. Non-ortho coplanar PCBs accounted for 68-88% of the total TEQs in bald eagle tissues. PCDDs and PCDFs collectively accounted for, on average, 17% of the total TEQs. On the basis of the analysis of a single gall bladder with bile, biliary excretion rates of PCDDs, PCDFs, and PCBs were estimated as 0.015-0.02% per day.     

Evidence for a specific pattern of polychlorinated dibenzo-p-dioxins and dibenzofurans in bivalves

The occurrence of the polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDDs/PCDFs) was studied in four different bivalve species (mussels, oysters, carpetshells, and cupped oysters) collected in three different sampling stations at the Spanish Coast from 1994 onward. The analysis revealed an unexpected isomer distribution of chlorosubstituted dioxins and furans characterized by a complex mixture of TCDF and TCDD, including both toxic and nontoxic isomers and highly chlorinated congeners, mainly OCDD. Principal component analysis revealed similarities between identical species collected from the different sites. A dioxin fingerprint could be easily distinguished between bivalve species collected in the same sampling point. The dioxin fingerprint found in filter-feeders was also compared to other marine species showing remarkable differences. Due to the habits of the bivalve species, sediment samples were also analyzed within this study. No similarities in the pattern were found for both matrices, the sediments and the bivalves. In the absence of a potential source of these toxicants affecting these species the hypothesis of a specific metabolism of the bivalves is suggested. No values higher than 4 pg WHO-TEQ/g whole weight were determined, and all samples met the current limit proposed by European Regulations. Independently of the bivalve species considered, the major contribution to the total WHO-TEQ comes from 2,3,7,8-TCDF and 2,3,4,7,8-PeCDF, at about the same levels of the 2,3,7,8-TCDD and 1,2,3,7,8-PCDD.     

Key parameters for de novo formation of polychlorinated dibenzo-p-dioxins and dibenzofurans

De novo formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs and PCDFs) was investigated in an Entrained Flow Reactor (EFR) to simulate combustion conditions. The parameters investigated were carbon content and nature in fly ash; type of gas-phase environment (oxidative versus reducing conditions) influence of combustion gases such as water, carbon monoxide, and carbon dioxide; amount of gas-phase chlorine; reaction temperature (250-600 degrees C); and reaction time (minutes vs hours). The comprehensive data set was further evaluated with principal component analysis (PCA) to statistically determine the role and importance of each parameter for de novo formation of PCDDs and PCDFs. Results revealed that an initial fast de novo formation occurs within the first minutes with a formation rate in the orders of hundreds of pmol per minutes; however, the reactivity of the ash was found to decline with time. An average formation rate as low as 3 pmol/min was measured after 6 h. The slower de novo formation of PCDDs and PCDFs was found to be through different reaction mechanisms and, thus, controlled by different parameters. The amount of Cl2 in the gas phase was observed to be an important parameter for PCDFs formation; meanwhile the levels of O2 were not found to be a PCDF rate controlling parameter. The formation rate of PCDDs was significantly lower than the PCDFs, and two mechanisms appear to be controlling the formation, one depending on the amount of O2 and one on the amount of Cl2 present in the gas phase. Overall the most significant parameter for the rate of formation for both PCDDs and PCDFs was revealed to be the reaction temperature. A maximum rate of formation was observed between 300-400 degrees C for the PCDDs and 400-500 degrees C for the PCDFs.     

Formation of polychlorinated dibenzo-p-dioxins/dibenzofurans from soot of benzene and o-dichlorobenzene combustion

Soots were prepared from flame combustion of benzene and o-dichlorobenzene (ODCB), creating one soot without carbon-chlorine bonds (benzene soot) and one with such bonds (ODCB soot). ODCB soot was tested for PCDD/F formation between 277 and 600 degrees C without additional chlorine, but levels were very low. Copper and Cu2O were added as potential catalysts for ODCB soot oxidation, but levels of PCDD/F observed were even lower than without these additives. Both benzene soot and ODCB soot produced PCDD/F after adding CuCl2 to the reaction mixtures, suggesting that a (volatile) metal chloride was needed in order for PCDD/F formation to take place. Under the various conditions of [Cu2+], time, and temperature tested, ODCB soot was always more reactive than benzene soot in forming PCDD/F. It seemed plausible that, despite the fact that CuCl2 was very effective in creating C-Cl bonds in benzene soot, the C-Cl bonds created in ODCB soot during preparation were of a reactivity so as to make this soot especially prone to PCDD/F formation. High temperature (gas phase) chlorination of soots by HCI or other chlorinating agents, followed by deposition of these soots and condensed metal chlorides on the ducts and walls of the postcombustion zone, could create an effective mechanism for de novo formation of PCDD/F.