Polychlorinated Dibenzo-p-dioxins And Dibenzofurans Research Articles

Toxicokinetic modeling of the transfer of polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) into milk of high-yielding cows during negative and positive energy balance

A toxicokinetic modeling approach was used to study the transfer of 7 polychlorinated dibenzo-p-dioxins (PCDDs), 10 dibenzofurans (PCDFs), 12 dioxin-like polychlorinated biphenyls (dl-PCB) and 3 non-dioxin like (ndl) PCBs in dairy cows. The model describes the concentration–time profile of each congener in milk and blood of high-yielding dairy cows. It was parametrized using an in-house transfer study with 3 cows exposed to a defined synthetic congener mixture for two dosing periods, as well as 3 control cows to account for background exposure. The first dosing was administered during negative energy balance (NEB) after calving, and the second during positive energy balance (PEB) in late lactation. Results include extrapolated steady-state transfer rates and elimination half-lives, many of which have never been reported before. Transfer rates (TRs) were significantly higher during the NEB by a median of 27%, likely due to an increase in non-milk elimination during PEB. The difference draws attention to the influence of the metabolic state of food-producing animals in risk assessment. Comparison of the TRs derived here with those reported in the literature showed that they were, in median, 43% higher in the NEB phase and 16% higher in the PEB phase probably because we report TRs in steady-state unlike most literature sources.

Occurrence and Formation Mechanism of PCDD/Fs and SCCPs in Chlorinated Paraffin Products.

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and short-chain chlorinated paraffins (SCCPs) can be formed during the production of chlorinated paraffins (CPs). Detection and accurate quantification of PCDD/Fs in CPs are challenging because of their matrix complexity. Therefore, the occurrence and formation mechanisms of PCDD/Fs from CPs have not been studied extensively in the past. In this study, 15 commercial samples including solid and liquid CPs were collected in 2022 from China. The average ΣSCCP concentrations detected in the solid and liquid CPs were 158 and 137 mg/g, respectively. The average International Toxic Equivalent (I-TEQ) values of 2,3,7,8-PCDD/F in solid and liquid CPs were 15.8 pg I-TEQ/g and 15.0 pg I-TEQ/g, respectively. The solid and liquid CPs had different predominant congener groups for SCCPs and PCDD/Fs. Possible formation routes for the generation of PCDD/Fs were analyzed by screening precursors in paraffin and laboratory-scale thermochemical experiments of CPs. The transformation between 2,3,7,8-PCDD/Fs and non-2,3,7,8-PCDD/Fs was recognized by calculating the successive chlorination preference. The first reported occurrence of PCDD/Fs in CP commercial products indicated that exposure to CPs and downstream products might be an assignable source of PCDD/F emission, which is of great significance to further explore the control factors of PCDD/Fs in the whole life cycle of CPs.

Estimation of dietary intake of polychlorinated dibenzo-p-dioxins and dibenzofurans and dioxin-like polychlorinated biphenyls from the Thai total diet study in 2019

Dietary intakes of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (DL-PCBs) were assessed in the Thai Total Diet Study (TDS) in 2019. Food samples including portable water (n = 1048) were collected from four regions of Thailand to represent a whole diet of Thai population, prepared as consumed and analyzed. To estimate the dietary intakes of PCDD/Fs and DL-PCBs, the concentrations in 18 food groups were combined with the respective food consumption from the national consumption data of Thailand and with a mean body weight of 57.57 kg for Thai population aged ≥ 3 years. The dietary intakes of PCDD/Fs, DL-PCBs and ∑PCDD/Fs/DL-PCBs were estimated to be 8.09, 4.93 and 13.02 pg WHO2005-TEQ kg−1 body weight month−1, respectively (upper bound). The major contributors to the total dietary intake were marine animals, followed by milk and milk products, freshwater animals, pork and pork products, and eggs, corresponding to 26, 22, 21, 10 and 9%, respectively. In comparison to health-based guidance value (HBGV), the intake of ∑PCDD/Fs/DL-PCBs (upper bound) was equal to 19% of the provisional tolerable monthly intake set by JECFA in 2001. Moreover, a comparison with other HBGVs was additionally presented and discussed.

Electrochemical degradation of key drugs to treat COVID-19: Experimental analysis of the toxic by-products formation (PCDD/Fs)

Drug consumption has grown exponentially in recent decades, particularly during the COVID-19 pandemic, leading to their presence in various water sources. In this way, degradation technologies for pollutants, such as electrochemical oxidation (ELOX), have become crucial to safeguard the quality of natural resources. This study has as its starting point a previous research, which demonstrated the efficacy of ELOX in the removal of COVID-19 related-drugs, such as dexamethasone (DEX), paracetamol (PAR), amoxicillin (AMX), and sertraline (STR), using the electrolytes NaCl and Na2SO4. The present research aims to study the potential risks associated with the generation of toxic by-products, during the ELOX of cited drugs, specifically focusing on the highly chlorinated persistent organic pollutants (POPs), such as polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Dioxins and furans can be formed potentially in electrochemical systems from precursor molecules or non-precursor molecules in chloride medium. First, the degradation of the parent compounds was found to be complete. At this point, a comprehensive investigation was conducted to identify and analyse the by-products formed during the degradation process; precursors of PCDD/Fs, such as chlorophenols or hydroquinones were identified. Additionally, in continuation of the previous study, PCDD/Fs congeners were investigated, revealing elevated concentrations; the highest concentration obtained was for the congener 1,2,3,4,6,7,8-HpCDF (234.6 pg L−1 in NaCl) during degradation of the AMX. Finally, an assessment of the toxicity based on TEQ values was conducted, with DEX exhibiting the highest concentration among all compounds: 30.1 pg L−1 for NaCl medium. Therefore, the formation of minor by-products should not be underestimated, as they can significantly enhance the toxicity of the final sample, so the selection of the appropriate remediation technology, as well as the optimization of experimental operating variables, is determining in the treatment of pharmaceutical-contaminated waters.

Enabling efficient and economical degradation of PCDD/Fs in MSWIFA via catalysis and dechlorination effect of EMR in synergistic thermal treatment

Catalytic thermal treatment is an efficient and low-energy consumption method for degrading polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in municipal solid waste incineration fly ash (MSWIFA). However, catalysts with high activity are expensive, difficult to separate and reuse from the treated MSWIFA, and they usually pose a risk of heavy metal pollution. Herein, a synergistic thermal treatment method of MSWIFA and electrolytic manganese residue (EMR) at relatively low temperatures was proposed after an in-depth analysis of their mineralogy composition to achieve detoxification of PCDD/Fs in MSWIFA. The mass and WHO-TEQ degradation efficiencies of PCDD/Fs significantly increased from −92.79% and −51.46%–98.57% and 96.10%, respectively, by the addition of electrolytic manganese residue (EMR) with an MSWIFA/EMR ratio of 3:7 in the thermal treatment of MSWIFA at 250 °C for 60 min. The WHO-TEQ concentration of PCDD/Fs in the treated sample decreased to 3.7 ng WHO-TEQ/kg, meeting the European end-of-waste criteria (20 ng WHO-TEQ/kg). The excellent degradation effect of EMR on PCDD/Fs in MSWIFA could be attributed to two aspects: 1) the manganese oxides in EMR has a catalytic effect on the degradation of PCDD/Fs; 2) the NH3 generated by the decomposition of (NH4)2SO4 in EMR is conducive to the degradation and resynthesis inhibition of PCDD/Fs. Besides, the thermodynamic calculations indicated that CaClOH in MSWIFA played a crucial role in the decomposition of (NH4)2SO4 in EMR. In addition, the degradation pathways and mechanisms of PCDD/Fs-homologues under the synergistic effect of manganese oxides, ammonia, and thermal field were investigated through comparative analysis of concentration and fingerprint of PCDD/Fs.

Heterogeneous photochemical conversion of chlorobenzene on γ-Al2O3: A chamber experiment study

Atmospheric photochemical conversion of chlorinated volatile organic compounds (CVOCs) is crucial for secondary aerosol formation and tropospheric chlorine chemistry. However, their corresponding conversion pathways and the reaction products are lack of sufficient exploration. Herein, the photochemical conversion of chlorobenzene (CB) on the mineral γ-Al2O3 particulates was chosen as a model reaction to unveil the atmospheric chemistry of CVOCs. Chamber experiments were performed to determine the decay rates of CB with/without SO2 or NH3 under light irradiation. Reaction products were evaluated, along with the in situ diffuse reflectance infrared Fourier transform spectroscopy measurements, to explore the CB conversion pathways under different conditions. We showed that the CB could be greatly degraded by γ-Al2O3 under light irradiation, and the added SO2 significantly inhibited this conversion owing to surface acidification. However, the presence of NH3 was shown to facilitate the CB conversion by immobilizing Cl− as NH4Cl, and recovering surface oxygen vacancies for oxygen activation. In particular, we found that polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) could be generated from the photochemical CB conversion over γ-Al2O3, regardless of SO2 or NH3 coexistence, indicating a potential origin of PCDD/Fs on the atmospheric particulates from the heterogeneous photochemical CVOC conversion.

Experimental Study on the Transfer of Polychlorinated Biphenyls (PCBs) and Polychlorinated Dibenzo-p-dioxins and Dibenzofurans (PCDD/Fs) into Milk of High-Yielding Cows during Negative and Positive Energy Balance.

Dioxin-like polychlorinated biphenyls (dl-PCBs) as well as polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) are a major concern for food safety, especially in fat-containing foods of animal origin, such as milk. Due to the lipophilic character of PCDD/Fs and PCBs, it is of special interest to explore whether the metabolic state of high-yielding cows influences the transfer rates into milk. Five German Holstein cows were orally exposed to a mixture of 17 PCDD/Fs, 12 dl-PCBs, and 6 non-dioxin-like PCBs (ndl-PCBs) for two dosing periods of 28 days each. The first period covered the negative energy balance (NEB) after calving, while the second period addressed the positive energy balance (PEB) in late lactation. Each dosing period was followed by a depuration period of around 100 days. During the NEB phase, the transfer rates of 14 PCDD/Fs and 7 dl-PCBs quantified were significantly (p ≤ 0.1) higher compared to the PEB phase, indicating an influence of the metabolic state on the transfer. Furthermore, the congener-specific transfer rates (0.3-39%) were in the range of the results from former studies. This indicates that the milk yield of the exposed cows is not the only determining factor for the transfer of these congeners into milk.

Pollution profile, source identification, and risk assessments of persistent organic pollutants (POPs) and toxic elements in the sediments of one of the water supply areas (Sultanbahçedere lake) to Istanbul, Türkiye

This study was done to comprehensively exhibit the pollution level of surface sediments taken from Sultanbahçedere dam lake in terms of some persistent organic pollutants (POPs) and toxic elements, to decide the possible sources of polycyclic aromatic hydrocarbons (PAHs), to perform the ecological and human health risk assessments, and to evaluate the pollution profile with the hierarchically clustered heatmap (HCHM) analysis and principal component analysis (PCA). Naphthalene, Benzo(b)fluoranthene, Fluoranthene, Pyrene for PAHs; p,p-DDE, p,p-DDD, alpha-HCH, p,p-DDT, Endrin for OCPs; hexa and hepta chlorinated congeners accounting for 50.63% and 28.44% for polychlorinated biphenyls (PCBs); 1234678-HpCDD, OCDD for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs); PCB 118, PCB 105, PCB 167 for dioxin like-PCBs (DL-PCBs) and Al, Fe, Ca for elements were predominant in almost all of the sediments with a few exceptions. S4 site, which is one of the mid-sites of reservoir, has high concentrations in most of these pollutants. According to PAH diagnostic analysis, PAHs in the surface sediments are mostly affected by pyrogenic sources. The concentrations of POPs do not pose any toxic risk to aquatic organisms according to sediment quality guideline (SQG) and the limit values of other countries accepted in the world. Also, since none of the elements exceeded the effect range median (ERM) values, they do not pose a significant toxic risk to aquatic organisms. There is no risk for non-carcinogenic and carcinogenic hazards both for children and for adults considering hazard quotient (HQ), hazard index (HI), and lifetime cancer risk (LCR) values of all pollutants.

Legacy persistent organic pollutants (POPs) in eggs of night herons and poultries from the upper Yangtze Basin, Southwest China.

Black-crowned night heron (Nycticorax nycticorax) eggs have been identified as useful indicators for biomonitoring the environmental pollution in China. In this study, we investigated thirty eggs of black-crowned night heron collected from the upper Yangtze River (Changjiang) Basin, Southwest China, for the occurrence of legacy persistent organic pollutants (POPs), including polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs). Our results showed a general presence of POPs in night heron eggs with OCPs being the dominant contaminants, having a geometric mean concentration of 22.2 ng g-1 wet weight (ww), followed by PCBs (1.36 ng g-1 ww), PBDEs (0.215 ng g-1 ww), and PCDD/Fs (23.0 pg g-1 ww). The concentration levels were found to be significantly higher in night heron eggs than in poultry eggs by one or two magnitude orders. Among OCP congeners, p,p'-DDE was found to be predominant in night heron eggs, with a geometric mean concentration of 15.1 ng g-1 ww. Furthermore, species-specific congener patterns in eggs suggested similar or different sources for different POPs, possibly associated with contaminated soil and parental dietary sources. Additionally, estimated daily intakes (EDIs) were used to evaluate non-carcinogenic and carcinogenic risk associated with consumption of bird eggs. Our results revealed non-negligible non-cancer and cancer risk for humans who consume wild bird eggs as a regular diet instead of poultry eggs.

Insight into the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans in hazardous waste incineration and incinerators: Formation process and reduction strategy

Incineration technology has been widely adopted to safely dispose of hazardous waste (HW). While the incineration process causes the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Due to its extreme toxicity, many scholars have been committed to determining the PCDD/F formation process and reducing emissions in incinerators. Previous studies ignored the impact of incineration and fluctuation of feeding materials on PCDD/F formation in hazardous waste incinerators (HWIs). In this study, differences in PCDD/F formation between HWIs and municipal solid waste incinerators (MSWIs) were pointed out. The incineration section in HWIs should be carefully considered. Laboratory experiments, conventional analysis and thermogravimetry experiments were conducted. An obvious disparity of PCDD/F formation between 12 kinds of HWs was found. Distillation residue was found with remarkably higher PCDD/F concentrations (11.57 ng/g). Except for the Cl content, aromatic rings and C–O bond organics were also found with high correlation coefficients with PCDD/F concentrations (>0.92). And PCDD/Fs were formed through a chlorination process and structure formation process. All of these are helpful to further understand the PCDD/F formation process during HW incineration, optimize the operation conditions in HWIs and reduce the emission pressure of PCDD/Fs in the future.

Biological wastewater treatment plants as sources of environmental pollution by persistent organic pollutants (on the example of Odesa industrial-and-urban agglomeration)

Formulation of the problem. Effective mechanism of wastewater treatment (WT) are important components of reducing anthropogenic load on the environment. One of the most widespread mechanisms of urban wastewater treatment is the biological treatment on a Biological Wastewater Treatment Plant (BWTP). However, increasing the nomenclature of pollutants concentrated in urban wastewater seriously affects the effectiveness of WT on BWTPs, which are not intended for such a wide spectrum of specific pollutants such as, in particular, Persistent Organic Pollutants (POPs). The control of their intake into the environment must be regulated according to the Stockholm convention. The goal of the research is the evaluation of the intake of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) into the environment from the wastewater of Odesa Industrial-and-Urban Agglomeration (IUA) and determining the volumes of their accumulation in the sea environment. Purpose. The assessment of the amount of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) entering the environment with the wastewater from Odesa IUA and determining the amount of their accumulation in the sea environment. Methods. In our research, all available official methods of calculation of the unintentional formation of POPs were reviewed, as a result – the main and most complete methods were selected: «UNEP (2013). Toolkit for Identification and Quantification of Releases of Dioxins, Furans and Other Unintentional POPs» and «EMEP/EEA air pollutant emission inventory guidebook. Technical guidance to prepare national emission inventories, 2019». For evaluation of PCDD/F accumulation in the sea environment an improved by authors methodology for calculation of PCDD/F accumulation with their cumulative effect and half life taken into account was used. Results. The work provides justification for the necessity of use of calculation methodologies for determing the intake of PCDD/F to the sea environment adjacent to Odesa IUA; annual massed of PCDD/F entering the sea environment as part of treated, insufficiently treated and untreated wastewater are calculated; massed of PCDD/F that accumulate in waste activated sludge (WAS) on BWTP are calculated; volumes and specifics of PCDD/F accumulation in the sea basin, where the wastewater of Odesa IUA is being discharged to are determined using the improved methodology that enables taking into account the cumulative effect and half life period of these substances; mass and concentration of PCDD/F, immobilized in WAS, are determined, the excess level of concentration of PCDD/F in WAS compared to the maximum permissible concentration is determined. The total accumulation of PCDD/F in the sea environment over 2007-2017 period is determined. Conclusions. It was established that the use of calculation methodologies for evaluating PCDD/F volumes in the water environment is the only and necessary condition for satisfying the requirements of the Stockholm convention due to the impossibility of performing a regular instrumental monitoring of PCDD/F intake into the water environment. The use of suggested by us improved methodology for calculation of PCDD/F accumulation with their cumulative effect and half-life period taken into account allows for calculation of PCDD/F masses that were formed throughout the year under consideration, taking into account the PCDD/F masses that were formed during previous years as well.

Buffering effect of the economizer against PCDD/Fs in flue gas from solid waste incineration plants

The emission of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from solid waste incineration is always a crucial concern for the society. Less attention has been paid to differentiate its formation and migration in the low temperature range of economizer, leading to a fuzzy understanding on the control of PCDD/Fs before flue gas cleaning. This study first reveals the buffering effect against PCDD/Fs in the economizer, which is contrary to the well-known memory effect, and first recognizes the intrinsic mechanism by 36 sets of full-scale experimental data under three typical operating conditions. Results indicated that the buffering effect, which includes interception and releasing, could remove averagely 82.9 % of PCDD/Fs in flue gas and reconcile PCDD/Fs profiles. The interception effect is dominant and in compliance with the condensation law. The low temperature range of economizer is exactly suitable for the condensation of lowly chlorinated congeners, which condense behind highly chlorinated ones. The releasing effect was non-staple but stimulated by the sudden change of operating condition, proving that PCDD/Fs formation rarely exists in the economizer. The buffering effect is mainly controlled by the physical migration of PCDD/Fs among different phases. The condensation of PCDD/Fs leads to their migration from vapor phase to aerosol and solid phases during flue gas cooling in the economizer. There is no need for excessive anxiety about PCDD/Fs formation in the economizer because it rarely exists. Intensifying the condensation process of PCDD/Fs in the economizer can help relieve the pressure of end-of-pipe measures for PCDD/Fs control.

Full replacement of fish oil with algae oil in farmed Atlantic salmon (Salmo salar) – Debottlenecking omega 3

The global goal of developing sustainable aquafeed has faced increased complexity in sourcing raw materials. The limited availability of fish oil (FO) is a well-known bottleneck for the aquaculture industry and pairing it with EFSA (EFSA CONTAM, 2018) reduced tolerable weekly intake of marine contaminants [polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) and dioxin-like polychlorinated biphenyls (DLPCB)] creates another challenge for wild caught FO and its use in fish feed. In recent years, commercial algal alternatives have increasingly become available. Not only would omega-3 sources from algae reduce the reliance on FO; it would allow for restoration of the long chain omega-3 levels in farmed salmon. To this end, a study was conducted to establish knowledge on full replacement of FO by algae oil (Schizochytrium sp.) in Atlantic salmon with the aim of reducing contaminants levels in the fillet and maintaining the level of omega-3 fatty acid (FA), growth performance, health, and final product quality. Atlantic salmon (531 g) were distributed into twelve 5 × 5 × 5 m sea cages and fed one of four diets for 369 days: a control diet (Control) containing FO + rapeseed oil (VO1); a diet where AlgaPrime (AP) replaced 50% of the sum of EPA + DHA from FO (50AP + VO1); a diet where AP replaced 100% of the sum of EPA + DHA from FO (100AP + VO1), and a diet the same as the previous but using linseed instead of rapeseed oil (VO2; 100AP + VO2). All diets were balanced for key micronutrients. At the end of the trial, zootechnical parameters were obtained, health and welfare assessed, and final fillet quality analysed for contaminants and fillet quality post slaughter. Full replacement of FO significantly reduced the levels of PCDD/F and DLPCB in the fillet of 4 kg salmon by 70% and 79% respectively for 100AP + VO1 and 40% and 43% respectively for 100AP + VO2 fed fish. Fish gained an average of 3.7 kg across treatments (average final weight 4235.8 g ± 191.8); almost an 8-fold increase for all treatments. No significant differences were found among diets for performance, feed intake, gut health, histology, welfare, pigmentation, or fillet quality. This study demonstrates that AlgaPrime can be used to fully replace FO in Atlantic salmon grower feed without negative effects, achieving an important impact on food safety and sustainability for aquafeed producers and salmon consumers.

Inventory of PCDD/Fs and Fly Ash Characteristics during the e-Waste and Municipal Solid Waste Co-Incineration Process

In the face of a challenging situation for yearly e-waste (EW) increment and disposition, EW co-incineration (EWC) with municipal solid waste (MSW) is a promising solution whose emission characteristics remain unclear. This study is conducted in a 400 tons/day MSW incineration (MSWI) plant to characterize polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and fly ash (FA) properties. Analytical methods include high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS) for PCDD/F determination, as well as X-ray diffraction (XRD), X-ray fluorescence (XRF), ion chromatography (IC), and leaching toxicity test for FA. The results indicate that toxic PCDD/F amounts are doubled by EWC in both primary exhaust gas (EG) and FA with international toxic equivalent quantity (I-TEQ) concentrations of 19.00 ± 6.32 ng I-TEQ/Nm3 and 1.33 ± 0.56 ng I-TEQ/g. After the clean-up of the air pollution control system (APCS), emitted PCDD/Fs in solid and gas phases, as well as major air pollutants (CO, NOx, SO2, HCl, and particulate matter), are permissive within the limit values of national standards GB 18485-2014 and GB 16889-2008. Distribution patterns for 136 PCDD/F isomers are analogous in both MSWI and EWC conditions. De novo synthesis is always the major formation route for both EWC and MSWI conditions, while dibenzodioxin/dibenzofuran (DD/DF) chlorination also contributes. The generation of 136 PCDD/Fs is enhanced by EWC, and the correlation coefficients of Cl and Cu in the fuel with the generation of 136 PCDD/F isomers are found to be R = 0.92 and 0.88, respectively. The main components in FA from MSWI and EWC differ less, both containing CaO, SiO2, and Al2O3. However, Cl and Cu contents, as well as leaching toxicity in FA are elevated by EW. Heavy metals, except for Cd, Ni, and Pb, meet the requirement of the standard.

N-P-based inhibitors for PCDD/Fs suppression with model fly ash: Inhibition mechanism during de novo synthesis

Chemical inhibitors are essential for controlling polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) formation during municipal solid waste incineration, while conventional N-S-based inhibitors emit secondary pollutants such as NOx and SO2. Developing novel inhibitors is crucial to reduce secondary pollution. Here, the N-P-based inhibitors diammonium hydrogen phosphate (DAP) and ammonium polyphosphate (APP) were proposed to explore the inhibition effects and mechanisms of PCDD/Fs. The findings demonstrated that using DAP at a 1% mass ratio in the model fly ash (MFA) significantly increased I-TEQ inhibition efficiency to 98.8%, a 27.4% improvement compared to the standard inhibitor, thiourea (TUA). The inhibition mechanisms were investigated through experiments and density functional theory (DFT) calculations. We observed that the phase transition (from CuCl2 to CuHPO4, Cu2P2O7) weakened the catalytic action of CuCl2, while the chlorination action of CuCl2 was also blocked during PCDD/F formation. TGA-MS results showed DAP and APP released NH3, which consumed Cl2 and impeded the chlorination process. Furthermore, they were more eco-friendly than TUA, as they did not emit NOx or SO2. Additionally, DFT calculations revealed that inhibitors impaired the catalysis process, ranked by binding energy to the catalyst: Ebenzene-b (−0.59 eV) > EHPO4-b (−3.15 eV) > ENH4-b (−3.24 eV) > EP2O7-b (−4.67 eV) > ECH4N2S-b (−11.38 eV). Moreover, economic feasibility analysis indicated that the DAP and APP had large cost advantages over the TUA, reducing costs by 67.7% and 19.8%, respectively. The proposed strategy, which achieved superior inhibition effects for PCDD/Fs and reduction of inhibitor costs, appears promising for industrial application.

A new insight into the CaO-induced inhibition pathways on PCDD/F formation: Metal passivation, dechlorination and hydroxide substitution

Ca-based inhibitors (especially CaO) for PCDD/F (polychlorinated dibenzo-p-dioxin and dibenzofuran) formation are considered as economic inhibitors with low toxicity and strong adsorption of acidic gases (e.g., HCl, Cl2, and SOx), whereas the insight understanding of its inhibition mechanisms is scarcely explored. Herein, CaO was used to inhibit the de novo reaction for PCDD/F formation (250–450 °C). The evolution of key elements (C, Cl, Cu, and Ca) combined with theoretical calculations was systematically investigated. The concentrations and distribution of PCDD/Fs demonstrated the significant inhibition effect of CaO on I-TEQ (international toxic equivalency) concentrations of PCDD/Fs (inhibition efficiencies: > 90 %) and hepta~octa chlorinated congeners (inhibition efficiencies: 51.5–99.8 %). And the conditions (5–10 % CaO, 350 °C) were supposed to be the preferred conditions applied in real MSWIs (municipal solid waste incinerators). CaO significantly suppressed the chlorination of carbon matrix (superficial organic Cl (CCl) reduced from 16.5 % to 6.5–11.3 %) and the formation of unsaturated hydrocarbons or aromatic carbon (superficial CC decreased from 6.7 % to 1.3–2.1 %). Also, CaO promoted the dechlorination of Cu-based catalysts and Cl solidification (e.g., conversion of CuCl2 to CuO, and formation of CaCl2). The dechlorination phenomenon was validated by the dechlorination of highly chlorinated PCDD/F-congeners (via DD/DF chlorination pathways). Density functional theory calculations revealed that CaO facilitated the substitution of Cl by -OH on the benzene ring to inhibit the polycondensation of the chlorobenzene and chlorophenol (Gibbs free energy reduced from +74.83 to −36.62 and − 148.88 kJ/mol), which also indicates the dechlorination effect of CaO on de novo synthesis.

Emission reduction of PCDD/Fs by flue gas recirculation and activated carbon in the iron ore sintering

One of the main sources of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the environment is the sintering of iron ore. Both flue gas recirculation (FGR) and activated carbon (AC), which have the impact of decreasing both PCDD/Fs and conventional pollutants (NOx, SO2, etc.), are significant technologies for the abatement of PCDD/Fs from the sintering exhaust gas. This work involved the first measurement of PCDD/Fs emissions during FGR and a thorough analysis of the impact of PCDD/Fs reduction following the coupling of FGR and AC technologies. According to the measured data, the ratio of PCDFs to PCDDs in the sintered flue gas was 6.8, indicating that during the sintering process, the PCDD/Fs were primarily produced by de novo synthesis. Further investigation revealed that FGR initially removed 60.7% of PCDD/Fs by returning it to the high temperature bed, and AC further removed 95.2% of the remaining PCDD/Fs through physical adsorption. While AC is better at removing PCDFs and can efficiently remove tetra-to octa-chlorinated homologs, FGR is more effective at removing PCDDs and has higher removal efficiency for hexa-to octa-chlorinated PCDD/Fs. Together, they complement each other with a removal rate of 98.1%. The study's findings are instructional for the process design of combining FGR and AC technologies to reduce PCDD/Fs in the sintered flue gas.

PCDD/Fs in indoor environments of residential communities around a municipal solid waste incineration plant in East China: Occurrence, sources, and cancer risks

Prolonged exposure to polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) can pose several adverse outcomes on human health. However, there is limited information on public health associated with indoor PCDD/F exposure in residential environments. Here, we examined PCDD/F concentrations in indoor air and indoor dust samples obtained from households near a municipal solid waste incineration (MSWI) plant. Our measurements revealed that the toxic equivalent (TEQ) concentrations of PCDD/Fs in indoor air ranged from 0.01 to 0.05 pg TEQ/m3, which were below intervention thresholds (0.6 pg TEQ/m3). Additionally, the TEQ concentrations of PCDD/Fs in indoor dust ranged from 0.30 to 11.56 ng TEQ/kg. Higher PCDD/F levels were found in household dust in the town of Taopu compared to those in the town of Changzheng. Principal component analysis (PCA) of PCDD/Fs suggested that waste incineration was the primary source of PCDD/Fs in indoor air, whereas PCDD/Fs in indoor dust came from multiple sources. The results of the health risk assessment showed the carcinogenic risk due to indoor PCDD/F exposure was higher for adults than for nursery children and primary school children. The carcinogenic risks of PCDD/Fs for age groups residing near the MSWI plant were all less than the risk threshold (10−5). Our findings will help to better understand the levels of PCDD/F exposure among urban populations living in residential communities around the MSWI plant and to formulate corresponding control measures to reduce probabilistic risk implications.

PCBs, PCNs, and PCDD/Fs in Soil around an Industrial Park in Northwest China: Levels, Source Apportionment, and Human Health Risk.

The concentrations of polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were determined in soil samples collected around an industrial park in Northwest China, to investigate the potential impacts of park emissions on the surrounding environment. The total concentration ranges of PCBs, PCNs, and PCDD/Fs in the soil samples were in 13.2-1240, 141-832, and 3.60-156 pg/g, respectively. The spatial distribution and congener patterns of PCBs, PCNs, and PCCD/Fs indicated that there might be multiple contamination sources in the study area, so source apportionments of PCBs, PCNs, and PCCD/Fs were performed by a positive matrix factorization model based on the concentrations of all target congeners together. The results revealed that these highly chlorinated congeners (CB-209, CN-75, and OCDF) might be derived from phthalocyanine pigments, the legacy of Halowax 1051 and 2,4-D products, which together contributed nearly half of the total concentration of target compounds (44.5%). In addition to highly chlorinated congeners, the local industrial thermal processes were mainly responsible for the contamination of PCBs, PCNs, and PCDD/Fs in the surrounding soil. The total carcinogenic risk of PCBs, PCNs, and PCDD/Fs in a few soil samples (0.22 × 10-6, 0.32 × 10-6, and 0.40 × 10-6) approached the threshold of potential carcinogenic risk (1.0 × 10-6). Since these pollutants can continuously accumulate in the soil, the contamination of PCBs, PCNs, and PCDD/Fs in surrounding soil deserves continuous attention.

Formation and Inventory of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans and Other Byproducts along Manufacturing Processes of Chlorobenzene and Chloroethylene

Chlorinated organic chemicals are produced and used extensively worldwide, and their risks to the biology and environment are of increasing concern. However, chlorinated byproducts [e.g., polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs)] formed during the commercial manufacturing processes and present in organochlorine products are rarely reported. The knowledge on the occurrences and fate of unintentional persistent organic chemicals in the manufacturing of organochlorine chemical is necessary for accurate assessment of the risks of commercial chemicals and their production. Here, PCDD/Fs were tracked throughout chlorobenzene and chloroethylene production processes (from raw materials to final products) by target analysis. Other byproducts that can further transform into PCDD/Fs were also identified by performing non-target screening. As a result, the PCDD/F concentrations were mostly the highest in bottom residues, and the octachlorinated congeners were dominant. Alkali/water washing stages may cause the formation of oxygen-containing byproducts including PCDD/Fs and acyl-containing compounds, so more attention should be paid to these stages. PCDD/Fs were of 0.17 and 0.21-1.2 ng/mL in monochlorobenzene and chloroethylene products, respectively. Annual PCDD/F emissions (17 g toxic equivalent in 2018) during chlorobenzene and chloroethylene production were estimated using PCDD/F emission factors. The results can contribute to the improvement of PCDD/F inventories for the analyzed commercial chemicals.