Unintentionally Produced Persistent Organic Pollutants Research Articles

Congener profiles and process distributions of polychlorinated biphenyls, polychlorinated naphthalenes and chlorinated polycyclic aromatic hydrocarbons from secondary copper smelting

Secondary copper smelting is an important industrial source of unintentionally produced persistent organic pollutants (UPOPs) emissions. Herein, field study on industrial-scale plants was conducted to clarify the levels and profiles of polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs) and chlorinated polycyclic aromatic hydrocarbons (> 3 rings, Cl-PAHs) from secondary copper smelting plants. The three UPOPs emission levels from the oxygen-enriched smelting furnace were higher than that from the anode furnace, which was attributed to the low-grade raw materials used. The toxic equivalent quantity concentrations of Cl-PAHs were 1.3–4.4 and 4.6–18.9 times higher than that of PCBs and PCNs, respectively. Thus, the emission control of Cl-PAHs in the secondary copper industry should be of concern. The chlorination degree of PCBs and PCNs was ~4 after the gas-cooling stage but was reduced to 1–2 in the stack outlet. This result indicated that the PCBs and PCNs congeners that were generated during the cooling stage were mainly higher-chlorinated. After purification by air pollution control devices (APCDs), the high-chlorinated congeners were removed simultaneously with the fly ash, whereas the low-chlorinated congeners may be regenerated and transferred into the stack gas due to possible memory effect within the APCDs.

Rapid detoxification of dioxin and simultaneous stabilization of targeted heavy metals: New insight into a microwave-induced pyrolysis of fly ash

Presently, it is a great challenging issue to inhibit the regeneration for dioxin and simultaneously detoxify Municipal solid waste incinerators (MSWI) fly ash with conventional Hagenmaier pyrolysis process (250–400 °C). The addition of inorganic S- and/or N-containing dioxin inhibitors could effectively inhibit the catalytic roles of residual heavy metals (HMs; e.g. Cu, Pb) for formation pathway of dioxin. In this study, we conducted a newly-proposed single-mode Microwave (MW)-based Hagenmaier process to investigate the impact of N, S-containing inhibitors of Thiourea (TU) on inhibiting the catalytic roles of targeted HMs and simultaneously detoxifying fly ash as well as to elucidate the corresponding mechanism. Synchrotron radiation analysis verified the sulfidation of targeted HMs including Cu and Pb, indicating the inhibition routes for dioxin regeneration. Moreover, the pyrolysis products of TU could apparently increase the MW-absorption properties of fly ash layer, and shorten by ~81.5% of processing time compared with that in the absence of TU. Under the optimized conditions (pyrolysis temperature of 480 °C, a mass ratio of fly ash to SiC as 1:9 and the addition of 23.1 wt% TU), ~99.2% of dioxin and ~94.1% of the bioassay-derived 2,3,7,8-tetrachlorodibenzo-p-dioxin toxic equivalent values (Bio-TEQs) were eliminated. Furthermore, the fundamental mechanism of a single-mode MW-induced Hagenmaier process was also proposed in detail. Additionally, a series of Unintentionally-Produced Persistent Organic Pollutants (UP-POPs) including chlorobenzenes were also detoxified by a single-mode MW-based Hagenmaier pyrolysis process, simultaneously. To the best of our knowledge, this is the first report adopting TU to inhibit the regeneration of dioxin and simultaneously detoxify fly ash by a single-mode MW-based pyrolysis process.

Formation of Environmentally Persistent Free Radicals during Thermochemical Processes and their Correlations with Unintentional Persistent Organic Pollutants.

Attention is increasingly being paid to environmentally persistent free radicals (EPFRs), which are organic pollutants with the activities of free radicals and stabilities of organic pollutants. EPFRs readily form during thermal processes through the decomposition of organic precursors such as phenols, halogenated phenols, and quinone-type molecules, which are also important precursors of toxic unintentionally produced persistent organic pollutants (UPOPs). We have found that EPFRs are important intermediates for UPOP formation during thermal-related processes. However, interest in EPFRs is currently mostly focused on the toxicities and formation mechanisms of EPFRs themselves. Little information is available on the important roles EPFRs play in toxic UPOP formation during thermal processes. Here, we review the mechanisms involved in EPFR formation and transformation into UPOPs during thermal processes. The review is focused on typical EPFRs, including cyclopentadiene, phenoxy, and semiquinone radicals. The reaction temperature, metal species present, and oxygen concentration strongly affect EPFR and UPOP formation during thermal-related processes. Gaps in current knowledge and future directions for research into EPFR and UPOP formation, transformation, and control are presented. Understanding the relationships between EPFRs and UPOPs will allow synergistic control strategies to be developed for thermal-related industrial sources of EPFRs and UPOPs.

Concentrations and profiles of persistent organic pollutants unintentionally produced by secondary nonferrous metal smelters: Updated emission factors and diagnostic ratios for identifying sources

Secondary nonferrous metal smelters are important sources of unintentionally produced persistent organic pollutants (UPOPs) including polychlorinated biphenyls (PCBs), polychlorinated naphthalenes, pentachlorobenzene, and hexachlorobenzene. Quantifying UPOP emissions by the main sources is an important step when evaluating UPOP emissions and establishing an inventory. In this study, field investigations were performed to allow UPOP emissions and distributions in stack gases emitted by secondary nonferrous metal smelters to be compared. A total of 25 stack gas samples were collected from secondary copper smelters (SCus), secondary zinc smelters, and secondary lead smelters in China. The mean toxic equivalent concentrations (TEQs) and mass concentrations of most of the UPOPs were highest in the secondary zinc smelter stack gas samples, next highest in the SCu stack gas samples, and lowest in the secondary lead smelter stack gas samples. The mean dioxin-like PCB and polychlorinated naphthalene TEQs were ∼8.9 and ∼6.6 times higher in stack gases from a SCu equipped with an oxygen-enriched smelting furnace than in stack gases from a SCu with a converter furnace. The mean PCB-118 to PCB-123 ratios and CN-10 to CN-35 ratios varied strongly and could be used as diagnostic ratios for apportioning the sources of UPOPs in the environment. Emission factors for dioxin-like PCBs, polychlorinated naphthalenes, pentachlorobenzene, and hexachlorobenzene in stack gases from secondary nonferrous metal smelters were derived and updated. The results improve our understanding of UPOP emission and provide data for establishing UPOP emission inventories for secondary nonferrous metal smelters.

Characterization of PCDD/Fs and dioxin-like PCBs in flue gas from thermal industrial processes in Vietnam: A comprehensive investigation on emission profiles and levels

The emission profiles and levels of unintentionally produced persistent organic pollutants (U-POPs) comprising polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs) were comprehensively investigated in flue gas released from 20 facilities belonging to 11 thermal industrial processes in Vietnam. Levels and patterns of PCDD/Fs and dl-PCBs in flue gas samples varied widely between sectors and different facilities in the same sector, suggesting different formation mechanisms involved. Flue gas concentrations of PCDD/Fs and dl-PCBs generally decreased in the order: industrial waste incinerator > secondary zinc production > coal fired craft boiler > coal fired power plant ≈ medical waste incinerator > steel production ≈ cement production > secondary copper production > coal fired industrial boiler > secondary tin production ≈ municipal waste incinerator. Results obtained from diagnostic ratio and fingerprint analysis have revealed that the stack emissions of PCDD/Fs and dl-PCBs were probably attributed to the de novo formation and incomplete destruction of input materials containing technical PCB oils or paints. The average emission factors of PCDD/Fs and dl-PCBs ranged from 0.011 to 374 μg WHO-TEQ tonne−1 for the studied facilities. A total emission amount of 4.89–11.4 g WHO-TEQ year−1 was estimated for the 20 facilities investigated in our study. This is the first comprehensive investigation on the unintentional emissions of PCDD/Fs and dl-PCBs from a wide range of industrial sectors in Vietnam.

Simultaneous Removal of Polychlorinated Dibenzo-p-dioxins/dibenzofurans, Polychlorinated Biphenyls, and Polychlorinated Naphthalenes From Flues Gases From Coke Gas Burning Using Selective Catalytic Reduction Equipment

The removal efficiencies of typical unintentionally produced persistent organic pollutants (UP-POPs) from flues gases from coke gas burning were obtained using selective catalytic reduction (SCR) equipment installed in a large coking plant. The total congeners of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), and polychlorinated naphthalenes (PCNs) in the flue gases at the inlet and outlet of the SCR equipment and the dustfall were analyzed. The results show that the removal efficiency of the total PCDD/Fs was the highest (94.6%). The removal efficiencies of total PCBs and total PCNs were 74.7% and 78.4%, respectively. The homologue profile of UP-POPs in the flue gases at the inlet of the SCR equipment notably differed from that at the outlet. Highly chlorinated UP-POPs predominated over the homologue profile of UP-POPs in the inlet flue gas, while low-chlorinated UP-POPs were predominant in the outlet flue gas. The SCR equipment achieved a better removal efficiency with respect to highly chlorinated UP-POPs. Catalytic reduction and catalytic oxidation degradation are both important mechanisms for the removal of UP-POPs from flue gas using SCR equipment.

Mechanical Treatment of MSWI Fly Ash: A Way Forward to Inhibit PCB Reformation

ABSTRACT Fly ash from municipal solid waste incinerators has been classified as hazardous waste due to the presence of unintentionally-produced Persistent Organic Pollutants (POPs), with Polychlorinated biphenyls (PCB) being a major group among such POPs. Fly ash can be mechanically (MC) treated to destroy organic pollutants before final disposal or reuse. In this study, model fly ash (MFA) doped with 0.2% CuCl2 was artificially prepared and subjected to high intensity ball milling for 0 (original sample), 1, 2, 4, and 8 h of treatment. Furthermore, to explore PCB reformation in the MC treated fly ash, de novo tests were conducted at single reaction time, temperature, and air flow rate. It was found that the sum of PCB, dioxin like PCB, and corresponding International Toxic Equivalent concentrations (∑PCB, ∑dl-PCB and ∑I-TEQ, respectively) were greatly reduced both in gas and in solid phase of MFA after 8 h of treatment. Though chlorination degree successively decreased with prolonged milling, the homologue and isomer signatures of PCB were varied in concentration. Reformation of few isomers was also observed. Results from present study suggest that MC treatment is an effective method to control reformation of pollutants in the long term. However, few suggestions are made for further ongoing research work on MC treatment of fly ash, which are based on surprising results and experimental limitations obtained in this study.

Spatial variation of PCDD/F and PCB emissions and their composition profiles in stack flue gas from the typical cement plants in China

Cement production processes are important sources of unintentionally produced persistent organic pollutants (UP-POPs), such as polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and polychlorinated biphenyls (PCBs). The emissions of PCDD/Fs and PCBs in the stack flue gases from eight typical cement plants in China were investigated in this study, including one wet process rotary kiln, three dry process rotary kilns and four vertical shaft kilns. PCBs exhibited relatively higher mass concentrations with the dioxin-like (dl) and indicator PCBs of 0.14–17.36 and 0.42–12.90 ng/Nm3, respectively. However, PCDD/Fs contributed most to the total toxic equivalent concentrations, with the proportions exceeding 90%. The international toxicity equivalency (I-TEQ) concentrations of PCDD/Fs varied greatly from 0.01 to 0.46 ng I-TEQ/Nm3 in stack gases, two of which exceeded the exhaust gas concentration limit of 0.1 ng I-TEQ/Nm3 established by the European Union Directive. In weight units, 1,2,3,4,6,7,8-HpCDF was the most abundant congener in the stack gases from various types of cement kilns, with the factions of 17.0–27.8%. TCDFs and PeCDFs were the first two most abundant homologue groups. 2,3,4,7,8-PeCDF was the largest contributor to the total I-TEQ. The emission factors of PCDD/Fs and PCBs in the eight cement kilns were estimated to be 0.01–1.35 μg I-TEQ/t clinker and 8.20 × 10−4∼8.23 × 10−2 μg World Health Organization TEQ (W-TEQ)/t clinker, respectively. No obvious differences of the PCDD/F and PCB emission factors were found among the varied cement production technologies.

Emission of unintentionally produced persistent organic pollutants (UPOPs) from municipal waste incinerators in China

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), pentachlorobenzene (PeCBz) and hexachlorobenzene (HxCBz), which are listed in the Stockholm Convention, are commonly known as unintentionally produced persistent organic pollutants (UPOPs). As municipal waste incinerators (MWIs) have burgeoned in China, the emission of UPOPs is of great concerns. Compared to the extensive studies of PCDD/Fs emission, not much information of non-dioxin UPOPs (i.e., PCBs, HxCBz, and PeCBz) is available. In the present study, samples from raw gas (RG) after boiler, stack gas (SG) after air pollution control devices (APCDs) and fly ash (FA) samples were collected from typical MWIs in China. The analyses of SG samples indicate that PCDD/Fs are the major contributor to TEQ value, but non-dioxin UPOPs are the dominant compounds in terms of mass concentration. The mean emission factors of dl-PCBs, PeCBz, and HxCBz in SG are 0.372, 144, and 84.7 μg/t, respectively. In contrast with gaseous samples, FA contains higher mass concentration of PCDD/Fs and PCBs than that of PeCBz and HxCBz. In terms of homologues distribution of PCBs, di- to tetra-CBs were the predominant species in both SG and FA samples. PCB-126 is the major contributor to the TEQ concentration. The comparison of UPOPs composition in SG and RG samples shows that activated carbon adsorption process is capable of removing most PCDD/Fs, but less efficient for the removal of non-dioxin UPOPs.

Catalytic decomposition of dioxins and other unintentional POPs in flue gas from a municipal waste incinerator (MWI) in China: a pilot testing.

Unintentionally produced persistent organic pollutants (UPOPs) include polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), dioxin-like polychlorinated biphenyls (dl-PCBs), pentachlorobenzene (PeCBz), and hexachlorobenzene (HxCBz). With the booming of municipal waste incinerators (MWIs) in China, the emission of UPOPs has generated great concern. As an alternative technology of dioxin control, catalytic decomposition has not been used in China, mainly due to the absence of national demonstration projects. Also, the simultaneous removal of various UPOPs has not been well investigated.In this study, a pilot-scale selective catalytic oxidative (SCO) system using a self-developed honeycomb catalyst was built and tested in a typical municipal waste incinerator (MWI) of China. The original concentration of PCDD/Fs in flue gas after the treatment of activated carbon injection (ACI) still exceeded the national emission standard (0.1ng I-TEQ/Nm3), while the concentrations of PeCBz and HxCBz were one order of magnitude higher than that of PCDD/Fs. For the testing temperature varying from 300 to 200°C, the removal efficiency of PCDD/Fs range from 39 to 95%, followed by dl-PCBs with the range of 56-89%. PeCBz and HxCBz were also removed, though their removal efficiencies were lower than those of PCDD/Fs and dl-PCBs. Both temperature and degree of chlorination influence the removal efficiencies.

Regenerable magnetic octahedral layer catalyst for gaseous UPOPs removal

Hexachlorobenzene (HCBz), pentachlorobenzene (PeCBz), and polychlorinated biphenyls (PCBs) are a group of unintentionally produced persistent organic pollutants (UPOPs) emitted from waste combustion and industrial processes. In this study, Fe3O4 fabricated manganese oxide octahedral layer (Fe/OL) and Cu-doped OL (Fe/Cu-OL) catalysts were synthesized and they exhibited high activity for catalytic destruction of UPOPs, but also suffered from deactivation. The deactivation of Fe/Cu-OL can be assigned to the formation of surface MnClx species. As for Fe/OL, Mn sites are protected from chlorination by tunnel K+, and the deactivation is ascribed to the blocking of active sites by KCl crystal. Simple water washing can completely regenerate the spent catalysts due to the dissolution of surface MnClx or KCl. With the advantage of magnetism, catalysts can be easily separated from water. Although Fe/Cu-OL has higher catalytic activity than Fe/OL, it is less stable in water washing due to the collapse of Mn framework structure. Considering the protection role of K+, the spent Fe/Cu-OL was regenerated by KNO3 solution to induce additional K+ onto the structure. In this way, the activity can be recovered while the unwanted dissolution of Mn is avoided.

Characterization of polychlorinated dibenzo-p-dioxins and dibenzofurans, dioxin-like polychlorinated biphenyls, and polychlorinated naphthalenes in the environment surrounding secondary copper and aluminum metallurgical facilities in China

Unintentionally produced persistent organic pollutants (UP-POPs) were determined in ambient air from around five secondary non-ferrous metal processing plants in China, to investigate the potential impacts of the emissions of these plants on their surrounding environments. The target compounds were polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), dioxin-like polychlorinated biphenyls (dl-PCBs), and polychlorinated naphthalenes (PCNs). The PCDD/F, dl-PCB, and PCN concentrations in the ambient air downwind of the plants were 4.70–178, 8.23–7520 and 152–4190 pg/m3, respectively, and the concentrations upwind of the plants were lower. Clear correlations were found between ambient air and stack gas concentrations of the PCDD/Fs, dl-PCBs, and PCNs among the five plants, respectively. Furthermore, the UP-POPs homolog and congener patterns in the ambient air were similar to the patterns in the stack gas samples. These results indicate that UP-POPs emissions from the plants investigated have obvious impacts on the environments surrounding the plants.

Estimation and characterization of unintentionally produced persistent organic pollutant emission from converter steelmaking processes

Unintentionally produced persistent organic pollutants (UP-POPs) including polychlorinated dibenzo-p-dioxins, and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), and polychlorinated naphthalenes (PCNs) were characterized and quantified in stack gas and fly ash from the second ventilation systems in five typical converters in five differentsteelmaking plants. The 2378-substituted PCDD/Fs (2378-PCDD/Fs) and dioxin-like PCB (dl-PCBs) toxic equivalents (TEQs) were 1.84-10.3pg WHO-TEQ Nm(-3) in the stack gas and 5.59-87.6pg WHO-TEQ g(-1) in the fly ash, and the PCN TEQs were 0.06-0.56pg TEQ Nm(-3) in the stack gas and 0.03-0.08pg TEQ g(-1) in the fly ash. The concentrations of UP-POPs in the present study were generally lower than those in other metallurgical processes, such as electric arc furnaces, iron ore sintering, and secondary metallurgical processes. Adding scrap metal might increaseUP-POP emissions, indicating that raw material composition was a key influence on emissions. HxCDF, HpCDF, OCDF, HpCDD, and OCDD were the dominant PCDD/Fs in the stack gas and fly ash. TeCB and PeCB were dominant in the stack gas, but HxCB provided more to the total PCB concentrations in the fly ash. The lower chlorinated PCNs were dominant in all of the samples. The 2378-PCDD/F, dl-PCB, and PCN emission factors in stack gases from the steelmaking converter processes (per ton of steel produced) were 1.88-2.89, 0.14-0.76, and 229-759μgt(-1), respectively.

Concentrations, profiles, and emission factors of unintentionally produced persistent organic pollutants in fly ash from coking processes

The coking process has been found to be an important source of unintentionally produced persistent organic pollutants (UP-POPs). However, the concentrations, profiles, and emission factors of UP-POPs in fly ash from coke plants have not been studied. In this study, six UP-POPs (polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), hexachlorobenzene (HxCBz), and pentachlorobenzene (PeCBz)) were identified and quantified in fly ash from eight coke plants. The average concentrations of the PCDDs, PCDFs, and “dioxin-like” PCBs were 1.5, 2.26, and 0.26pgTEQg−1, respectively, and the average concentrations of the PCNs, HxCBz, and PeCBz were 256, 290, and 146pgg−1, respectively. The proportion each homolog contributed to the total concentration of the PCDFs, PCBs, and PCNs decreased with increasing chlorination level. The PCDFs contributed the biggest proportion of the total UP-POPs toxic equivalents (TEQs), and the average emission factors in fly ash were 10.5, 17.3, and 1.82ngTEQt−1 for the PCDDs, PCDFs, and “dioxin-like” PCBs, respectively, and 1792, 2028, and 1025ngt−1 for the PCNs, HxCBz, and PeCBz, respectively. These data are essential for establishing an integrated UP-POP release inventory.

Progress in the studies associated with formation and emission of unintentionally produced persistent organic pollutants

Polychlorinated dibenzo-p-dioxins and dibenzofurans, polychlorinated biphenyls, polychlorinated naphthalenes, pentachlorobenzene and hexachlorobenzene could be unintentionally produced and released during many industrial processes, and often termed as unintentionally produced persistent organic pollutants (UP-POPs). There are close correlations among these types of pollutants for their formation during industrial processes. This review focuses on the basic properties, emission characteristics, and formation mechanisms of UP-POPs during industrial processes. The sources and emission levels of UP-POPs on global or regional scales are also summarized. Finally, the progress in the studies associated with the emission characteristics and emission factors of UP-POPs from Chinese industries are reviewed.

Catalytic oxidation of hexachlorobenzene in simulated gas on V2O5–WO3/TiO2 catalyst

Hexachlorobenzene (HCB) is one of priority unintentionally produced persistent organic pollutants (UPOPs) listed in Stockholm Convention. In this study, V2O5–WO3/TiO2 catalyst was used to oxidize vapor phase hexachlorobenzene (HCB). It is found that the HCB oxidation efficiency is positively correlated with temperature and oxygen concentration while negatively correlated with gas hourly space velocity (GHSV) and water vapor content. The catalytic oxidation kinetics of HCB could be well fitted by the power rate law model, and the partial reaction orders and activation energy were obtained. The role of lattice oxygen was investigated with the aid of oxygen on–off experiment and XPS analysis. The intermediates from oxidation of HCB were detected by the stationary experiment conducted in glass ampule and conformed by off gas analysis. Desorption of chlorinated intermediates from catalyst surface to gas phase was observed at high GHSV (60,000h−1) but could be minimized at high temperature and low GHSV. The electrophilic attack of oxygen on benzene structure followed by ring-cracking and oxygen insertion is the possible oxidation mechanism.

Estimation and Congener-Specific Characterization of Polychlorinated Naphthalene Emissions from Secondary Nonferrous Metallurgical Facilities in China

Secondary nonferrous production is addressed as one of the potential sources of the unintentionally produced persistent organic pollutants (UP-POPs) due to the impurity of raw material. Although there are inventories of dioxin emissions from secondary nonferrous metallurgical facilities, release inventories of polychlorinated naphthalenes (PCNs) are scarce. This study selected typical secondary copper, aluminum, zinc, and lead plants to investigate the emissions of PCNs in secondary nonferrous production in China. The toxic equivalency (TEQ) emission factor for PCNs released to the environment is highest for secondary copper production, at 428.4 ng TEQ t(-1), followed by secondary aluminum, zinc, and lead production, at 142.8, 125.7, and 20.1 ng TEQ t(-1), respectively. PCNs released in secondary copper, aluminum, lead, and zinc production in China are estimated to be 0.86, 0.39, 0.009, and 0.01 g TEQ a(-1), respectively. Analysis of stack gas emission from secondary nonferrous production revealed that less-chlorinated PCNs are the dominant homologues, with mono- to tri-CNs making the most important contributions to the concentration. However, for fly ash, the more highly chlorinated PCNs such as octa-CN are the dominant homologues.

Atmospheric Emission of PCDD/Fs, PCBs, Hexachlorobenzene, and Pentachlorobenzene from the Coking Industry

The coking process is considered to be a potential source of unintentionally produced persistent organic pollutants (UP-POPs). However, intensive studies on the emission of UP-POPs from the coking industry are still very scarce. Emission of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs), dioxin-like polychlorinated biphenyls (dl-PCBs), hexachlorobenzene (HxCBz), and pentachlorobenzene (PeCBz) covered under the Stockholm Convention were investigated for the coking process in this study. Stack gases from some typical coke plants in China were collected and analyzed to estimate the emission of UP-POPs from the coking industry. Emission factors of 28.9 ng WHO-TEQ tonne(-1) for PCDD/Fs, 1.7 ng WHO-TEQ tonne(-1) for dl-PCBs, 596 ng tonne(-1) for HxCBz, and 680 ng tonne(-1) for PeCBz were derived based on the investigated data. The annual emissions from the global coking industry were estimated to be 15.8 g WHO-TEQ for PCDD/Fs, 0.93 g WHO-TEQ for dl-PCBs, 333 g for HxCBz, and 379 g for PeCBz, respectively (reference year 2007). According to the distribution of PCDD/Fs, we argued for the de novo synthesis to be the major pathway of PCDD/F formation. With regard to the characteristics of dl-PCBs, the most abundant congener was CB-118, and the most dominant contributor to the total WHO-TEQ of dl-PCBs was CB-126.