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.     

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.     

De novo synthesis of polychlorinated dibenzo-p-dioxins and dibenzofurans on fly ash from a sintering process

Fly ash, collected in the electrostatic precipitator of a sinter plant in Belgium, has been examined and characterized in terms of its behavior with respect to thermal polychlorodibenzo-p-dioxins (PCDD) and polychlorodibenzofurans (PCDF) formation. Thermal experiments of the fly ash were conducted in a flow of air. The temperature was varied from 250 to 450 degrees C, and the reaction time varied from 30 min to 6 h. For comparison, the oxidative degradation of carbon in the fly ash was studied by differential scanning calorimetry (DSC) in the temperature range from 50 to 500 degrees C. Besides the known maximum of formation of PCDD/Fs around 325 degrees C generally found on experiments with incinerator fly ash, a second maximum of formation around 400 degrees C is observed on the sinter fly ash used in this study. DSC measurements on the fly ash show that the oxidative degradation of carbon appears at these two different temperatures confirming that the de novo synthesis on this kind of fly ash take place at two different optimum temperatures. About the reaction time, already after 30 min, an important quantity of PCDD/Fs is formed; the fast increase in PCDD/Fs amount is followed by a slower formation rate between 2 and 4 h. At longer reaction time, the formation slows down, and decomposition reactions become important. Analysis of homologue distribution indicates that the profile of PCDD/Fs is independent of the reaction time but that an increase of the temperature leads to a rise of lower chlorinated species. In all experiments, PCDF are formed preferentially (total PCDF/PCDD ratios larger than 5). The PCDF/PCDD ratio is clearly independent of the reaction time. Concerning the temperature, the apparently better stability of PCDF at high temperature (PCDF/PCDD ratio higher at high temperature) results in the fact of different PCDF/PCDD ratios for the different family and modifications of homologue distribution with the temperature. The isomer distribution shows little reaction time or temperature dependency, which is an argument in favor of a thermodynamic control of the isomer distribution during de novo formation of PCDD/Fs. Differences within the isomer distribution patterns of PCDD/Fs obtained from the laboratory de novo synthesis experiments and the original fly ash, reflecting the formation under the industrial process, suggest a different mechanism of formation in the sinter plant for the PCDD and PCDF. The de novo synthesis is sufficient to explain the PCDF formation in the real process, but synthesis from precursors must play a role for the PCDD formation.     

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.     

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...     

Formation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F) in fires of arsenic-free treated wood: role of organic preservatives

This article demonstrates that biocidal organochlorines such as tebuconazole and permethrin, employed in formulations of wood preservatives, produce significant quantities of polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran (PCDD/F) when subjected to thermal decomposition under oxidative conditions. Both tebuconazole and permethrin form PCDD/F during gas-phase oxidation, but much greater yields occurred in the presence of surrogate ash corresponding to wood treated with copper-based fungicides. The significant yields have implications for the increased toxicity of PCDD/F emissions during fires of wood impregnated by combination of organic and copper-based preservatives. The oxidative pyrolysis of tebuconazole and permethrin over simulated wood ash generated amounts of PCDD/F exceeding those of untreated wood by 3 orders of magnitude. We obtained yields of 1000 ng WHO97-TEQ/g tebuconazole and 5500 ng WHO97-TEQ/g permethrin when reacting the organochlorines in an oxidizing atmosphere over surrogate wood ash. Gas-phase oxidation also produce measurable quantities of PCDD/F, corresponding to 1 ng WH097-TEQ/g tebuconazole and 36 ng WHO97-TEQ/g permethrin. In the case of tebuconazole, the present measurements correlate well with those obtained from oxidative pyrolysis of CBA-treated wood in the cone calorimeter. It appears that permethrin and tebuconazole provide phenyl and diphenyl precursors to formation of PCDD/F and both constitute a source of chlorine upon fragmentation.     

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).     

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.     

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.     

Effectiveness of activated carbon and biochar in reducing the availability of polychlorinated dibenzo-p-dioxins/dibenzofurans in soils

Five activated carbons (ACs) and two biochars were tested as amendments to reduce the availability of aged polychlorinated dibenzo-p-dioxin/dibenzofurans (PCDD/Fs) in two soils. All sorbents (ACs and biochars) tested substantially reduced the availability of PCDD/Fs measured by polyoxymethylene (POM) passive uptake and earthworm (E. fetida) biouptake. Seven sorbents amended at a level of 0.2 × soil total organic carbon (0.2X) reduced the passive uptake (physicochemical availability) of total PCDD/Fs in POM by 40% to 92% (or toxic equivalent by 48% to 99%). Sorbents with finer particle sizes or more macropores showed higher reduction efficiencies. The powdered regenerated AC and powdered coconut AC demonstrated to be the most effective and the two biochars also performed reasonably well especially in the powdered form. The passive uptake of PCDD/F in POM increased approximately 4 to 5 fold as the contact time between POM and soil slurry increased from 24 to 120 d while the efficacy of ACs in reducing the physicochemical availability remained unchanged. The reduction efficiencies measured by POM passive uptake for the regenerated AC were comparable to those measured by earthworm biouptake (bioavailability) at both dose levels of 0.2X and 0.5X. The biota-soil accumulation factor (BSAF) values for unamended soil ranged from 0.1 for tetra-CDD/F to 0.02 for octa-CDD/F. At both dose levels, the regenerated AC reduced the BSAFs to below 0.03 with the exception of two hexa-CDD/Fs. The reduction efficiencies measured by earthworm for coconut AC and corn stover biochar were generally less than those measured by POM probably due to larger particle sizes of these sorbents that could not be ingested by the worms.     

Congener-specific distribution of polychlorinated dibenzo-p-dioxins, dibenzofurans and biphenyls in animal feed.

Polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) were extracted by accelerated solvent extraction from animal feed samples and analysed by high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS). In all of the feed samples analysed, the concentrations of PCDD/Fs and PCBs were below the existing tolerance limit of 5 pg I-TEQ g(-1) and 200 ng g(-1) fat, respectively. The mean concentrations of the total PCDDs, total PCDFs and total PCBs were 1.73-11.50 pg g(-1), 0.23-11.91 pg g(-1) and 60.00-234.40 pg g(-1) feed, respectively. Investigation of the correlations among the concentrations of PCDDs, PCDFs and PCBs showed that samples containing increased amounts of PCDFs also contained higher concentrations of PCDDs, with an average ratio of PCDF:PCDD of about 1.23:1 (r(2)=0.72, p<0.05). The correlation between the concentrations of PCDD/Fs and PCBs was positive but not significant.     

Effect of nitrogen-containing compounds on polychlorinated dibenzo-p-dioxin/dibenzofuran formation through de novo synthesis

An experimental study was conducted to clarify the suppression effect of nitrogen-containing compounds, that is, ammonia and urea, on the formation of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) through the de novo synthesis reaction. In the experiment, graphite and copper chloride contained in a mixture were used as sources of carbon and chlorine, respectively. The granulated sample mixture was charged as a packed-bed in the glass tube and heated at 300 degrees C in the flow of Ar-O2 gas mixture. In some cases, urea was added as aqueous solution to the sample, while ammonia was added to the gas flowed through the sample bed. The amount of PCDD/Fs formed decreases significantly by the addition of both ammonia and urea. Particularly, the addition of urea reduces the amount of PCDD/Fs discharged in the outlet gas by approximately 90%. The oxidation rate of carbon in the early stage of the experiment, that is, the heating period, is promoted bythe addition of nitrogen-containing compounds. However, soon afterthe temperature reaches 300 degrees C, the formation rate becomes lower than that of the case without the addition of nitrogen-containing compounds. On the other hand, organic compounds containing amino (-NH2) or cyanide (-CN) groups and those containing nitrogen within the carbon ring frame were detected in the outlet gas in the case of urea addition. Typically observed aromatic compounds are chlorobenzonitriles, chlorobenzeneamines, and chloropyridines. This suggests a possibility that hydrogen and/or chlorine combined with PCDD/Fs are also substituted by such nitrogen-containing groups, and this decreases the formation rate of their frame of carbon rings. This phenomenon was also consistent with the fact that a significant reduction was observed in the amount of PCDD/Fs released to the outlet gas when urea was added.     

Reduction of atmospheric polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) during the 2008 Beijing Olympic games

A total of 120 air samples were collected at three urban and one rural location in Beijing, China in the summers of 2007-2010, and before, during, and after the Beijing 2008 Olympic Games (BOG), in order to assess the effectiveness of long-term and short-term emission-control measures in reducing polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the atmosphere. During the BOG (August, 2008), the PCDD/Fs concentrations decreased to an average value of 1150 fg m(-3) (63 fg I-TEQ m(-3)), which was reduced by approximately 70% from the average in 2007 and by 29% from that in July 2008, before the Olympic event began. Although 2009-2010 levels of PCDD/Fs were significantly higher than 2008, the overall temporal trend was decreasing for summer months during the sampling campaign period. The apparent half-lives of atmospheric PCDD/Fs were estimated to be 3.2-5.8 years by statistically regressing the logarithm PCDD/Fs concentrations versus the number of years passed since 2006. The air concentrations of total suspended particulates (TSP) during the BOG ranged between 135 and 183 μg m(-3), showing a 52% reduction from 2007 and 26% decrease from those prior to the Olympic event. No significant relationships were found between meteorological parameters (temperature, humidity, and wind speed) and PCDD/Fs or TSP during the BOG, whereas the PCDD/Fs concentrations were significantly dependent on the air quality (p < 0.05, positive against TSP and negative against visibility). This work is one of few temporal trend studies of atmospheric PCDD/Fs in mainland China, and provides unique insight into the effects of large-scale control measures in improving air quality and reducing one of the most ubiquitous and toxic organic pollutants in the environment.     

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.     

Influence of an industrial waste incinerator as assessed by the levels and congener patterns of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans

To assess the spatial change in the influence of an industrial waste incinerator, a total of 47 soil samples (in continuous manner with distance) and 65 human blood samples (40 within 5 km and 20 at 7 and 12 km) were analyzed for polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDD/Fs). The influence was not clearly observed both on the soil and blood levels of PCDD/Fs as the levels in the near zone (within 5 km) were not statistically different from those in the far zones at 7 and 12 km. Assessment was conducted on the congener patterns by using principal component analysis and by characterizing the congener fractions as a function of distance. In soil, the congener fractions of 2,3,4,7,8-PeCDF, 1,2,3,4,7,8-HxCDF, 1,2,3,6,7,8-HxCDF, 1,2,3,4,6,7,8-HpCDF, and OCDF decreased progressively with the distance. Blood was consistent with soil in that each congener fraction of these PCDFs (except OCDF) was statistically greater in the near zone than the far zones. The decreases in these PCDFs were balanced by OCDD in both soil and blood. It was concluded that although not obviously observed in the contamination levels, the influence of the incinerator was clearly shown by the congener patterns of PCDD/Fs in both soil and blood that changed with distance.     

Role of chlorine in combustion field in formation of polychlorinated dibenzo-p-dioxins and dibenzofurans during waste incineration

Combustion experiments performed in the presence of hydrogen chloride (HCl) in a laboratory-scale fluidized-bed reactor were carried out to elucidate the role of chlorine in the formation of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs; together: PCDD/Fs) in various sections of a municipal waste incinerator. We first demonstrated that the homologue profile and the pattern of the congener proportions of PCDD/Fs for a model waste containing poly(vinyl chloride) (PVC) combusted in the absence of HCl were similar to those for a PVC-free waste combusted in the presence of HCl. This showed no difference between PVC in the waste and injected HCl in the role as a chlorine source in PCDD/F formation during incineration. Next, to investigate PCDD/F formation in each section of the incinerator, we carried out combustion experiments with the PVC-free waste, injecting HCl at different locations of the incinerator. The amounts of PCDDs and PCDFs formed were significantly reduced when HCI was not supplied to the main combustion section. The presence of HCI in the main combustion section was essential for the formation of PCDD/Fs, even in the downstream sections. This finding indicates that compounds that were able to form PCDD/Fs in the downstream sections were mainly formed in the main combustion section in the presence of HCl.     

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.     

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.     

Characterizing the emissions of polychlorinated dibenzo-p-dioxins and dibenzofurans from crematories and their impacts to the surrounding environment

This study was set out to characterize PCDD/F emissions from crematories and assess their impacts on the surrounding environment. Two crematories located in southern Taiwan were investigated, including the one (C1) with no air pollution control device installed and the other (C2) installed with a bag filter. Results show the mean PCDD/F emissions (11% oxygen) from the stacks of Cl and C2 were 2.36 and 0.322 ng I-TEQ Nm(-3), respectively. The mean emission factors for C1 and C2 were 13.6 and 6.11 microg I-TEQ body(-1), respectively. The removal efficiency of the bag filter on PCDD/Fs was 55.1%. The estimated PCDD/F emission rate for all crematories in Taiwan was 0.838 g I-TEG yr(-1) accounting for 227% and 112% of the annual emissions from all medical waste incinerators and municipal waste incinerators, respectively. The above results indicate that PCDD/F emissions from crematories were quite significant. To assess the impact of PCDD/F emissions from a crematory to the surrounding environment, ambient air samples were collected from the downwind site of C1 with the maximum ground concentration. We found the estimated maximum ground concentration at the downwind site of C1 (= 0.521 pg I-TEQ Nm(-3)) was much higherthan thatfound atthe background, rural area, residential area, urban area, and industrial area (= 0.006, 0.023, 0.052, 0.093, and 0.190 pg I-TEG Nm(-3), respectively). The above results suggestthat PCDD/F emissions from a crematory did significantly affect its surrounding environment. In conclusion, a proper control strategy should be taken immediately in order to eliminate PCDD/F emissions from crematories.