Global status of dioxin emission and China's role in reducing the emission

Dioxins and their impact: a review of toxicity, persistence, and novel remediation strategies

Dioxins rank among the most hazardous persistent organic pollutants, presenting a serious threat due to their long environmental lifespan and capacity for bioaccumulation. This comprehensive review delves into the historical, chemical, and toxicological aspects of dioxins, spotlighting significant incidents such as the Seveso disaster and the repercussions of Agent Orange. The review offers a thorough analysis of the sources of dioxin formation, encompassing natural occurrences like volcanic eruptions and wildfires, alongside man-made activities such as industrial combustion and waste incineration. It examines regional variations in dioxin contamination, revealing air concentrations that can range from less than 0.01 pg TEQ per m3 in remote regions to as high as 2 pg TEQ per m3 in urban environments. With global dioxin emissions estimated at around 97.0 kg TEQ per year, Asia and Africa emerge as the highest emitters among the continents, with the total global dioxin release approximately at 100.4 kg TEQ annually. Dioxin emissions per capita show stark contrasts across six continents, from 10.77 g TEQ per capita in Europe to a concerning 71.66 g TEQ per capita in Oceania. Furthermore, the concentration of dioxin compounds produced during combustion varies significantly, ranging from 15 to 555 ng m-2. While dioxin emission regulations are intricate and differ globally, most nations require that concentrations remain below one ng m-2. Globally, dioxin production is estimated at 17 226 kilograms annually, equating to about 287 kilograms in toxic equivalent (TEQ). This review critically examines the severe health implications of dioxins, which include carcinogenic effects, endocrine disruption, and immunotoxicity. Innovative remediation strategies, such as using nanomaterials for adsorption and advanced oxidation processes, are identified as promising pathways to tackle this pressing issue. Ultimately, this review underscores the necessity for enhanced monitoring systems and comprehensive policy frameworks to facilitate sustainable dioxin management and regulatory compliance. Taking decisive action is vital to protect public health and the environment from the ongoing threat posed by dioxins.

Dioxins and Related Compounds in Sediment and Soil from Craft Villages and Industrial Areas in Northern Vietnam

This study focuses on the determination of dioxins and related compounds (DRCs) in sediment and soil samples gathered from craft villages and industrial zones in Bac Ninh province, northern Vietnam. The PCDD/Fs and DL-PCBs levels in sediment samples ranged from 8.34 to 1302 pg/g and 34.5 to 3186 pg/g, respectively, and total equivalent toxicity (TEQ) of DRCs ranged from 0.596 to 88.1 pgTEQ/g. The total mass concentration of DRCs in the soil samples varied from 14.2 to 4857 pg/g, with corresponding total TEQ values ranging from 0.387 to 2.61 pgTEQ/g. Risk assessment based on sediment quality guideline indicators shows that DRCs at paper recycling village had moderate adverse biological effect. Some soil samples collected in industrial clusters have total carcinogenic risk (CR) values close to the threshold (1.0 × 10-6). Based on the results, it is necessary to continue monitoring and evaluating DRC compounds in craft village and industrial cluster environments and have remediation solutions to reduce these contaminated compounds.

Experimental study and mechanism analysis of high-efficiency adsorption of PCDD/Fs on N-doped hierarchical porous biochar

Adsorption removal of PCDD/Fs from flue gas is one of the important technologies for reducing environmental PCDD/Fs emissions. However, due to the lack of systematic research on the adsorption mechanism of PCDD/Fs, commercial activated carbon (AC) with a single pore size distribution and lack of surface functional groups has poor adsorption and removal efficiency for PCDD/Fs. Therefore, this study first used corncob as a raw material and prepared N-doped hierarchical porous biochar (NHPB) using a one-step activation method for efficient removal of PCDD/Fs. The removal efficiency of NHPB for 17 toxic PCDD/Fs and 136 PCDD/Fs in simulated flue gas is as high as 96.21% and 97.21%, respectively. Compared with AC, the adsorption performance of NHPB was significantly less affected by the fluctuation of temperature and concentration than AC because the adsorption performance changed little with the chlorine substitution number of PCDD/Fs, and showed excellent adsorption performance under various adsorption conditions. Subsequently, the adsorption mechanism of PCDD/Fs on NHPB was systematically studied using theoretical calculations. Molecular simulations show that the optimal adsorption pore size for PCDD/Fs is mainly micropores above 1 nm and mesopores between 2 and 5 nm. Therefore, the hierarchical pore structure of NHPB exhibits superior adsorption performance. Density functional theory (DFT) calculations show that all three N-doping forms on the surface of biochar can enhance the adsorption energy of PCDD/Fs on biochar, thereby further enhancing the adsorption performance of NHPB for PCDD/Fs.

AI-based tree modeling for multi-point dioxin concentrations in municipal solid waste incineration

Numerous investigations have shown that the municipal solid waste incineration (MSWI) has become one of the major sources of dioxin (DXN) emissions. Currently, the primary issue that needs to be addressed for DXN emission reduction control is the online measurement of DXN. Data-driven AI algorithms enable real-time DXN concentration measurement, facilitating its control. However, researchers mainly focus on building models for DXN emissions at the stack. This approach does not allow for the construction of models that online measurement of DXN generation and absorption throughout the whole process. To achieve optimal pollution control, models that encompass the whole process are necessary, not just models focused on the stack. Therefore, this article focuses on modeling the whole process of DXN concentrations, including generation, adsorption, and emission. It uses machine learning techniques based on advanced tree-based data-driven deep and broad learning algorithms. The determination of data characteristics at different phases is grounded in the understanding of the DXN mechanism, offering a novel framework for DXN modeling. State-of-the-art tree-based models, including adaptive deep forest regression algorithm based on cross layer full connection, tree broad learning system, fuzzy forest regression, and aid modeling technologies, are applied to handle diverse data characteristics. These characteristics encompass high-dimensional small samples, low-dimensional ultra-small size samples, and medium-dimensional small samples across different phases related to DXN. The most interesting is the robust validation where the proposed a whole process tree-based model for DXN is validated using nearly one year of authentic data on DXN generation, adsorption, and emission phases in an MSWI plant of Beijing. The proposed modeling framework can be used to explore the mechanism characterization and support the pollution reduction optimal control.

Multi-media environmental fate of polychlorinated dibenzo-p-dioxins and dibenzofurans in China: A systematic review of emissions, presence, transport modeling and health risks

Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) are notorious persistent organic pollutants (POPs) with proven toxicity to human and ecosystems. This review critically evaluates existing research, emphasizing knowledge gaps regarding PCDD/F emissions, environmental behavior, human exposure, and associated risks in China. The current emission inventory of PCDD/Fs in China remains highly uncertain, both in terms of total emissions and emission trends. Moreover, existing monitoring data primarily focus on areas near pollution sources, limiting comprehensive understanding of the overall spatiotemporal characteristics of PCDD/F pollution. To address this, we propose a novel approach that integrates the Multi-media Urban Mode (MUM) model with an atmospheric chemical transport model that includes a dual adsorption model to capture gas-particle partitioning of PCDD/Fs in the atmosphere. This coupled model can simulate the transport and fate of PCDD/Fs in multi-media environments with high spatiotemporal resolution, facilitating a nuanced understanding of the impacts of emissions, climate, urbanization and other factors on PCDD/F pollution. Additionally, dietary ingestion, particularly from animal-derived foods, is identified as the predominant source (up to 98%) of human exposure to PCDD/Fs. While the changes in dietary structure, population distribution, and age structure can influence human exposure to PCDD/Fs, their impacts have not yet been quantified. The proposed model lays the foundation for a systematic assessment of health risks from PCDD/F exposure through various pathways by further incorporating a food chain model. Overall, this review offers a comprehensive strategy for assessing PCDD/F pollution, encompassing the entire continuum from emissions to environmental impacts.

Linking industrial emissions and dietary exposure to human burdens of polychlorinated naphthalenes

Relationships between toxic pollutant emissions during industrial processes and toxic pollutant dietary intakes and adverse health burdens have not yet been quantitatively clarified. Polychlorinated naphthalenes (PCNs) are typical industrial pollutants that are carcinogenic and of increasing concern. In this study, we established an interpretable machine learning model for quantifying the contributions of industrial emissions and dietary intakes of PCNs to health effects. We used the SHapley Additive exPlanations model to achieve individualized interpretability, enabling us to evaluate the specific contributions of individual feature values towards PCNs concentration levels. A strong relationship between PCN dietary intake and body burden was found using a robust large-scale PCN diet survey database for China containing the results of the analyses of 17,280 dietary samples and 4480 breast milk samples. Industrial emissions and dietary intake contributed 12 % and 52 %, respectively, of the PCN burden in breast milk. The model quantified the contributions of food consumption and industrial emissions to PCN exposure, which will be useful for performing accurate health risk assessments and developing reduction strategies of PCNs.

Investigating the presence of dioxins in drinking water: implications for public health

The presence of highly toxic dioxins, specifically polychlorinated dibenzo-p-dioxins (PCDDs), in drinking water is a matter of great concern due to their long-lasting nature and harmful effects. In this study, we detected three out of the five dioxin congeners: 2, 3, 7, 8-tetrachlorodibenzodioxin (TCDD), 1, 2, 3, 7, 8-pentachlorodibenzo-p-dioxin (PeCDD), and octachlorodibenzo-p-dioxin (OCDD). The investigation revealed that three dioxins were present in water samples of winter season, while TCDD and OCDD were found in the summer season. The geometric mean concentrations of PCDDs were 229.9 ng/L (winter) and 108.4 ng/L (summer), exceeded the maximum contaminant level of 30 pg/L set by the USEPA in surface water. The estimated daily intake of PCDDs for residents through drinking water was 273.97 ng-WHO2005-TEQ/kg/days during winter and 78.875 ng-WHO2005-TEQ/kg/days during summer. Our study emphasizes the urgent need for further research on persistent organic pollutants in drinking water to safeguard public health and community well-being.

Spatial distributions, behaviors, and sources of PCDD/Fs in surface water and sediment from the Yangtze River Delta

The Yangtze River Delta (YRD), one of the most economically developed and industrialized regions in China, is confronted with challenges arising from rapid urbanization, particularly environmental pollution. The collection of surface water and sediment samples from forty-nine sites in the YRD was conducted to analyze 2378-substituted polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) congeners. The detected concentrations of PCDD/Fs were 0-5.3 pg TEQ/L in water and 0.12-1493 pg TEQ/g dw in sediment. The PCDD/Fs contamination in the sediment was widespread in the YRD. There were variations in the congener characteristics of PCDD/Fs in surface water and sediment. The proportion of OCDD was significantly lower in surface water samples compared to sediment, while the less chlorine-substituted homologs were found in larger proportions. To understand the partitioning and behavior of dioxins within the water-sediment system, we calculated the organic carbon normalized partition coefficients and fugacity fraction (ff) of PCDD/F congeners. The results revealed that the PCDD/Fs had not attained a state of distributional equilibrium, and the non-specific hydrophobic effect seemed minimally influential on their partitioning between sediment and water. The average ff values, which varied between 0.06 and 0.63, indicated differing migration directions for the PCDD/F congeners. Source identification analysis provided evidence that the dioxins in the river water were primarily attributed to industrial thermal processes. Iron and steel smelting, along with pesticide production and use, were likely responsible for the sediment contamination. This comprehensive analysis underscores the complex nature of PCDD/Fs pollution in the YRD and highlights the necessity for targeted environmental management strategies.

Unintentional persistent organic pollutants in cremation process: Emissions, characteristics, and inventory

Pollutants produced by cremation furnaces have gradually caused concern because of the increasing rate of cremation around the world. In this study, the levels, patterns, and emission factors of unintentional persistent organic pollutants (UPOPs) from cremation were investigated. The toxic equivalent (TEQ) concentrations (11 % O2 normalized) of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in flue gas ranged from 0.036 to 22 ng TEQ/Nm3, while the levels of polychlorinated biphenyls (PCBs) and polychlorinated naphthalenes (PCNs) in flue gas samples ranged from 0.0023 to 1.2 ng TEQ/Nm3 and 0.17-44 pg TEQ/Nm3, respectively. The average concentrations of UPOPs in flue gas from car-type furnaces were higher than those from flat-panel furnaces. Secondary chambers and air pollution control devices were effective for controlling UPOPs emissions. However, heat exchangers were not as effective for reducing UPOPs emissions. It was observed that the UPOPs profiles exhibited dissimilarities between fly ash and flue gas samples. HxCDF, OCDD, and PeCDF were the dominant homologs of PCDD/Fs in flue gas, while HxCDF, PeCDF, and HpCDF were the dominant homologs in fly ash. The fractions of MoCBs and MoCNs in fly ash were higher than those in flue gas. Finally, we conducted an assessment of the global emissions of UPOPs from cremation in the years of 2019 and 2021. The total emission of UPOPs in 47 countries was estimated at 239 g TEQ in 2021, which was during the peak period of the COVID-19 pandemic worldwide. The emissions in 2021 increased by approximately 24 % compared to 2019, with the impact of COVID-19 being a significant factor that cannot be disregarded.

Foraging animal origin food samples as passive indicators of dioxin-like POPs contamination in industry sites: Method development, characterisation and risk assessment

Titanium dioxide (TiO2) is an important industrial chemical, and studies suggest its major production route - the chloride process could lead to the generation of unintentional dl-POPs. However, no relevant studies assessed the occurrence of dl-POPs associated with TiO2 production in the industrial zones, which is mostly due to the ultra-trace level distribution of these compounds in environmental compartments. The present study explored the novel possibility of utilising foraging animal-origin foods as sensitive indicators for addressing this challenge and generated a globally beneficial dataset by assessing the background levels of dl-POPs in the vicinity of a TiO2 production house in Southern India. Systematic sampling of foraging cow's milk and free-ranging hen's eggs was carried out from the study site, and the dl-POPs assessments were conducted utilising an in-house developed cost-effective GC-MS/MS-based analytical methodology. The median dl-POPs levels in milk and egg samples were about 3 times higher than the control samples collected from farm-fed animals and retail markets. The contaminant loads in the foraging animal-origin food samples were further traced to their presence in environmental compartments of soil and sediment and admissible degree of correlations were observed in congener fingerprints. Elevated health risks were inferred for the population in the industrial zones with weekly intakes weighing about 0.15-17 times the European Food Safety Authority-assigned levels. The consumption of foraging cow's milk was observed to have a higher contribution towards the hazard indices and cancer risk estimates and were significantly higher (p < 0.05) for children. The study also presents a critical validation of the GC-MS/MS-based method for the purpose of regulatory monitoring of dl-POPs, which could be of practical significance in economies in transition.

Assessing the social cost of municipal solid waste management in Beijing: A systematic life cycle analysis

The increased municipal solid waste generation poses ponderous pressure on the economy, environment, and public health. The current waste treatment process has multiple limitations. To inform policymakers on the best practices and feasibility, we develop a more comprehensive social costing model to assess the impacts of municipal solid waste management throughout its life cycle. The prominent findings show that the life cycle social cost of municipal solid waste in Beijing in 2021 is 12.4 billion yuan. Incineration has the highest social cost, totaling 10.172 billion yuan. The social cost per unit of waste incineration is 2,045 yuan/t, which is higher than that of landfill (1,288 yuan/t), composting (1,132 yuan/t), anaerobic digestion (1,057 yuan/t), and recyclables resource utilization (-344 yuan/t). The life cycle assessment results show that economic costs, including collection, transportation, and treatment costs, account for about 61%, and health loss costs account for about 37%. The scenario analysis suggests a significant potential for social cost savings from food waste and recyclables utilization. Ideally, a social cost reduction of almost 38% could be achieved. Error analysis examines the influence of variation in uncertain parameters on the evaluation results. This paper provides scientific strategies for optimal investment and decision-making on the comprehensive municipal solid waste management. These findings could provide an essential reference for policymakers and stakeholders in municipal solid waste management, replicated in different cities and other emerging economies.

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.

Biodegradability analysis of Dioxins through in silico methods: Model construction and mechanism analysis

The biodegradation treatment of dioxins has long been of interest due to its good ecological and economic effects. In this study, the biodegradability of polychlorinated dibenzo-p-dioxins (PCDDs) were investigated by constructing machine learning and multiple linear regression models. The maximum chlorine atomic charge (qHirshfeldCl+), which characterizes the biodegradation ability of PCDDs, was used as the response value. The random forest model was used to rank the importance on the 1471 descriptors of PCDDs, and the BCUTp-1 h, QXZ, JGI4, ATSC8c, VE3_Dt, topoShape, and maxwHBa were screened as the important descriptors by Pearson's correlation coefficient method. A quantitative structure-activity relationship (QSAR) model was constructed to predict the biodegradability of PCDDs. In addition, the extreme gradient boosting (XGBoost) and random forest model were also constructed and proved the good predictability of QSAR model. The biodegradability of polychlorinated dibenzofurans (PCDFs) can also be predicted by the constructed three models from a certain level after adjusting some model parameters, which further proved the versatility of the models. Besides, the sensitivity analysis of the QSAR model and a 3D-QSAR model was developed to investigate the biodegradability mechanisms of PCDDs. Results showed that the descriptors BCUTp-1 h, JGI4, and maxwHBa were the key descriptors in the biodegradability effect by the sensitivity analysis of the QSAR model. Coupled with the results of PCDDs biodegradability 3D-QSAR model, BCUTp-1 h, JGI4, and maxwHBa were confirmed as the main descriptors that affect the biodegradability of dioxins. This study provides a novel theoretical perspective for the research of the biodegradation of both PCDDs and PCDFs dioxins.

Unexpected Dioxin Formation During Digestion of Soil with Oxidizing Acids

Dioxins, such as polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs), are among the most toxic unintentionally produced persistent organic pollutants, and their emission is of great concern. Herein, we discovered abundant dioxin formation in soil and various organic carbon-containing matrices after digestion with aqua regia. Σ17PCDD/Fs concentrations were in the range of 66.6-142,834 pg/g dw (5.6-17,021 pg WHO2005-TEQ/g dw) in 19 soil samples after digestion with aqua regia for 6 h. Σ17PCDD/Fs concentration was significantly and positively correlated with soil organic carbon content (R2 = 0.89; p < 0.01). Compared with cellulose and lignin, humic acid served as an important organic matter component that was converted to PCDD/Fs during soil digestion. Strong oxidation and production of reactive chlorine by aqua regia may be the key factors in the formation of PCDD/Fs. The yearly emission of PCDD/Fs due to digestion with strong acids by the inspection and testing industry was estimated to be 83.8 g TEQ in China in 2021 based on the highest level, which was ∼0.9% of the total dioxin inventory in China. Great attention should be paid to unexpected dioxin formation during digestion processes considering the potential risk of release from laboratories and enterprises.

A data-driven analysis of global research trends on dirty-dozen persistent organic pollutants

The occurrence, distribution, and fate of persistent organic pollutants (POPs) have been extensively studied worldwide; however, the patterns and dynamics of scientific publications on POPs are still unclear. In this study, the research trends on dirty dozen POPs, which are identified under the Stockholm Convention (SC) for immediate action were investigated and evaluated in a broad context to obtain up-to-date information. For this purpose, bibliometric analysis was carried out between 1945 and 2021 using the Web of Science (WoS) database. A total of 197,029 publications were analyzed. "Environmental Sciences" was the most popular research category and the USA was the leading country in dirty dozen POPs studies. The research hotspots are related to the most used keywords such as "Polychlorinated Biphenyls", "Dioxin" and "Persistent Organic Pollutants". In the evaluation of keyword clusters with highlighted research points, 7 clusters were obtained from the publications, which are related to the chemical properties, synthesis, structures, health effects, and analysis methods of dirty dozen POPs. The number of publications and, accordingly, the scientific interest in dirty dozen POPs listed under the SC has not reached equilibrium and continues regardless of the level of development of countries in the world.

Dioxin emission modeling using feature selection and simplified DFR with residual error fitting for the grate-based MSWI process

Municipal solid waste incineration (MSWI) with grate technology is a widely applied waste-to-energy process in various cities in China. Meanwhile, dioxins (DXN) are emitted at the stack and are the critical environmental indicator for operation optimization control in the MSWI process. However, constructing a high-precision and fast emission model for DXN emission operation optimization control becomes an immediate difficulty. To address the above problem, this research utilizes a novel DXN emission measurement method using simplified deep forest regression (DFR) with residual error fitting (SDFR-ref). First, the high-dimensional process variables are optimally reduced following the mutual information and significance test. Then, a simplified DFR algorithm is established to infer or predict the nonlinearity between the selected process variables and the DXN emission concentration. Moreover, a gradient enhancement strategy in terms of residual error fitting with a step factor is designed to improve the measurement performance in the layer-by-layer learning process. Finally, an actual DXN dataset from 2009 to 2020 of the MSWI plant in Beijing is utilized to verify the SDFR-ref method. Comparison experiments demonstrate the superiority of the proposed method over other methods in terms of measurement accuracy and time consumption.

Historical production and release inventory of PCDD/Fs in China and projections upon policy options by 2025

Using the source identification and classification methodology described in UNEP standardized toolkit for dioxin releases, combined with research data over the past decade, the production and release of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) from 6 major sectors in China were inventoried from 2003 to 2020, and were projected until 2025 based on current control measures and relevant industrial plans. The results showed that after ratification of the Stockholm Convention, China's production and release of PCDD/Fs began to decline after peaking in 2007, demonstrating the effectiveness of preliminary control measures. However, the continual expansion of manufacturing and energy sectors, along with the lack of compatible production control technology, reversed the declining trend of production after 2015. Meanwhile, the environmental release continued to decrease, but at a slower rate after 2015. If subject to current policies, production and release would remain elevated with an expanding gap in between. This study also established the congener inventories, revealing the significance of OCDF and OCDD in terms of both production and release, and that of PeCDF and TCDF in terms of environmental impacts. Lastly, through comparison with other developed countries and regions, it was concluded that room for further reduction exists, but can only be achieved through strengthened regulations and improved control measures.

Utility of an alternative method (to USEPA Method 1613) for analysis of priority persistent organic pollutants in soil from mixed industrial-suburban areas of Durban, South Africa

This study evaluates the adequacy of a USEPA Method 1613 alternative analytical method for analysis of persistent organic pollutants (POPs) in soil from the immediate vicinity of industrialized areas in the eThekwini municipal area in South Africa. The objective of this study is in line with the Stockholm Convention Article 11 on research, development, and monitoring. Furthermore, it became imperative to find an alternative analytical procedure to USEPA Method 1613 that could cater to studies conducted in Africa where recent reviews have indicated that most African countries lack the technical and instrumental capacity for performing analysis of dioxin-like compounds according to USEPA Method 1613, which entails the use of high-resolution chromatography and high-resolution mass spectrometry instrumentation. The study aimed to ascertain the utility of an alternative two-dimensional gas chromatography-time of flight mass spectrometry method for analysis of trace-level priority POPs in soil, along with a fast single quadrupole gas chromatography-mass spectrometry method. The analytical methods were applied to the analysis of POPs on soil samples from industrial areas with oil refineries and a pulp and paper manufacturing company, while other samples were collected near the electricity substations and a landfill site. Analytical results showed BDE 209 as the dominant contaminating polybrominated diphenyl ether (concentration ranges from 0.006 to 5.71 ng g^-1 ). Polybrominated biphenyls (PBBs) 9, 10, and 49 were the dominant PBBs detected in 78% of the sites tested, although their concentrations were below the limit of quantification (LOQ). Polychlorinated dibenzo-p-dioxins and furans and dioxin-like polychlorinated biphenyls detected could not be quantified above their respective LOQs, indicating that the Durban area has low priority pollutant contamination levels compared to other regions around the world. The methods developed are a starting point that will inform considerations for routine evaluation and management of soil contamination, which plays a vital role in environmental management. Integr Environ Assess Manag 2023;19:749-762. © 2022 SETAC.

Assessment of PCDD/Fs formation and emission characteristics at a municipal solid waste incinerator for one year

Municipal solid waste incineration (MSWI) has become a predominant emission source of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs). Research focusing on the impact of operating conditions, environmental changes, and operating time on the generation and emissions of PCDD/Fs has not been resolved. To this end, this study tracked and investigated the PCDD/Fs and 17 congener emissions of a typical grate incinerator (800 t/d) continuously for one year. Results showed that the PCDD/Fs concentration at the boiler outlet, stack inlet, and bag filter, including normal and abnormal operation conditions, ranges from 2.11E-02-41.86 ng I-TEQ/Nm³, 7.00E-04-6.76 ng I-TEQ/Nm³, and 1.12-2.90E+03 ng I-TEQ/Nm³, respectively. The 2,3,4,7,8-P₅CDF has the highest contribution in all samples, in which a proportion of TEQ ranged from 30 % to 77.73 %. Moreover, by applying the correlation analysis between PCDD/Fs and operating parameters, the emission characteristic is mainly affected by incinerators and boilers during the normal period, and it is affected by the whole MSWI process under abnormal conditions. In addition, the PCDD/Fs emission from the MSWI plant gradually increases from spring to winter. This study is beneficial for supporting the control of PCDD/Fs emission reduction and assisting the operators to optimize the relevant operating parameters of the MSWI plant to achieve a stable and up-to-substandard emissions during the operation period.

In-silico analysis of atmospheric diffusion, crop planting degrading scheme, and health risk of dioxins from a domestic waste incineration plant

Based on a domestic waste incineration power generation project, the dioxin emission from the waste incineration plant (WIP), phytoextraction and microbial degradation of dioxins, and dioxins human health risks reduction were investigated through in-silico methods. Based on the dioxins concentrations in soil (9.97 × 10^-9-7.00 × 10^-5ng/g) predicted by atmospheric dispersion model system and the Level-III fugacity model, planting schemes under different wind directions were designed considering the dioxin absorption capacity and the economic benefits for crops (i.e., barley, peanut, pea, maize and wheat). The dioxins in soils can be further degraded by five crops' rhizosphere microorganisms and fertilizers, simulated through molecular dynamic simulations. The enhanced degradation rates of dioxin by rhizosphere microorganisms of five crops reached 15.70 %-28.66 %. Finally, healthy dietary plans were developed to reduce the risk of dioxin exposure to the sensitive populations living around WIP. Results showed that the consumption of maize, fungus, mushroom and bamboo fungus could effectively reduce dioxins toxicity to humans by 58.13 %. The systematic approach developed in this study provided theoretical support for soil remediation and human health risk control of dioxins-contaminated sites.

Dioxin-like POPs emission trends as a decision support tool for developing sustainable MSW management scheme -an exploratory study

The paper reports on an innovative application of dioxin-like persistent organic pollutants (dl-POPs) emission trends as a measure of environmental performance for designing feasible municipal solid waste management (MSWM) schemes. MSWM systems are highly dependent on the income status and the population density and it is quintessential for developing countries to devise strategies suiting to its characteristics rather than simply adapting successful processes/technologies in developed nations. Hence a lower-middle-income, high-density populated state of India - Kerala, which represents the typical scenario of majority of towns in developing countries was selected as the verification study site. Annual inventorisation of dl-POPs for the current scenario of the state was developed as a spatial model at the lowest administrative block level using geographical information system for the easy and effective comparative assessment. Further, a dl-POPs emission based MSWM scheme which could reduce up to 65% of emissions from current scenario has been developed and compared it with contemporary life cycle assessment (LCA) and life cycle cost analysis (LCCA) schemes in terms of green-house gas emissions (GHG) and landfill area requirements as environmental performance validation. Daily exposure dose of dl-POPs were predicted from the per-capita annual emission associated with different MSWM schemes and hazard quotients were also calculated to provide an overview of the health risk posed by the emissions. The predicted health risk factors were observed to be 5 times higher than the threshold level in current scenario whereas 10 times reduction in dose levels could be achieved through the proposed scheme of MSWM.

New emission inventory reveals termination of global dioxin declining trend

Accurate estimates of spatiotemporally resolved Polychlorinated dibenzo-p-dioxins (PCDD/Fs, or dioxins) emissions are critical for understanding their environmental fate and associated health risks. In this study, by utilizing an empirical regression model for PCDD/Fs emissions, we developed a global emission inventory for 17 toxic PCDD/Fs congeners from 8 source sectors with a spatial resolution of 1° × 1° from 2002 to 2018. The results show that PCDD/Fs emissions decreased by 25.7 % (12.5 kg TEQ) between 2002 and 2018, mostly occurring in upper- and lower-middle income countries. Globally, open-burning processes, waste incineration, ferrous and nonferrous metal production sectors and heat and power generation were the major source sectors of PCDD/Fs. Spatially, high PCDD/Fs emissions were mainly identified in East and South Asia, Southeast Asia, and part of Sub-Saharan Africa. We find that the declining trend of dioxin emissions over the past decades terminated from the early 2010s due to increasing significance of wildfire induced emissions in the total emission. The PCDD/Fs emission inventory developed in the present study was verified by inputting the inventory as initial conditions into an atmospheric transport model, the Canadian Model for Environmental Transport of Organochlorine Pesticides (CanMETOP), to simulate PCDD/Fs concentrations in air and soil. The predicted concentrations were compared to field sampling data. The good agreement between the modeled and measured concentrations demonstrates the reliability of the inventory.

Investigation on dioxins emission characteristic during complete maintenance operating period of municipal solid waste incineration

The dioxins (DXN) are a set of pollutants encompass polychlorinated dibenzo-p-dioxin/dibenzofuran (PCDD/F), their emissions from municipal waste incineration processes (MSWI) are normally detected under steady operating conditions. However, limited studies have focused on the PCDD/F emission characteristics under a complete maintenance operating period (CMOP), which includes shut-down, cooling, maintenance, heating, startup, and normal operations. In this article, the shutdown process (SDP) starts from the normal operation, followed by shutdown, and then cooling; while the startup process (SUP) commences from heating, followed by startup, and then normal operation. The detection and analysis were conducted at the SDP and SUP stages. The PCDD/F mass and total toxic equivalent quantity (TEQ) concentrations were measured in the flue gas and bag filter fly ash (BF-FA) during a CMOP of Beijing MSWI plant. The highest PCDD/F concentrations in the flue gas were found in the "cooling" and "startup" phases; in the FA, this condition occurred in the "startup" phase. Further, the results show that the most heightened concentrations were observed for 5-6 chlorinated PCDF and 4-5 chlorinated PCDD among the 17 PCDD/F congeners in most cases. More importantly, the air pollution control devices (APCDs) which include activated carbon, lime, and BF, have high removal efficiency for PCDD/F (especially PCDD) during the "startup" phase. APCDs also easily release a considerable amount of PCDD/F because of the memory effect, which emits more PCDD/F at the "shutdown" phase than at the "startup" one. Besides, the annual PCDD/F emission in the flue gas of the MSWI plant was estimated to be 67.72 mg I-TEQ, of which the emission accounts for approx. 20% during the CMOP. Moreover, the experiment shows that the PCDD/F emissions of the MSWI plant in Beijing under unsteady conditions are more miniature than those reported earlier in other areas.

National and provincial dioxin emissions from municipal solid waste incineration in China

China presently lacks an up-to-date regional inventory of dioxin emissions from municipal solid waste incineration (MSWI), although MSWI has grown rapidly in recent decades. Based on dioxin concentrations from the official website for governments and enterprises, we created an inventory of dioxin emissions from 29 areas in mainland China. MSWI released a total of 22.56 g I-TEQ of dioxins in 2020. According to Monte Carlo simulation, the dioxin emissions with 95 %, 75 %, and 50 % certainty are 17.03-31.62, 19.24-27.71, and 20.43-25.96 g I-TEQ, respectively. Notably, Guangdong, Zhejiang, and Jiangsu provinces accounted for 38.8 %. The primary regions with considerable dioxin emission per capita and density are Zhejiang and Shanghai. Furthermore, Jilin and Heilongjiang provinces are the top two regions in terms of dioxin emissions per unit of billion gross domestic product. These indicators were affected significantly by the quantity of MSW generated and incinerated (MSWGI), capacity and operating years of incinerators, and degrees of air pollution control devices (APCDs). Dioxin emission factors (EFs) were about 100 times lower in 2020 than in 2004. Note, however, that there is a gap in dioxin EFs between China and European nations. We have proposed that MSW source classification, stable operation conditions of incinerators and APCDs, categories of incinerators selection, and technological upgrading should be China's major measures to curb dioxin emissions. Moreover, with the future increment in the quantity of MSWGI, it is essential to completely reinvent the dioxin monitoring program.

Occurrence and Source Identification of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans and Polychlorinated Biphenyls in Surface Sediments from Liangshui River in Beijing, China

Polychlorinated dibenzo-p-dioxins and dibenzofurans and polychlorinated biphenyls were measured in the surface sediments of Liangshui River, the second largest drainage river in Beijing, China. The sum concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans and polychlorinated biphenyls ranged from 3.5 to 3019 (mean value: 184) pg g^-1 dry weight and from 319 to 5949 (mean value: 1958) pg g^-1 dry weight, and the corresponding World Health Organization toxic equivalent quantity values were 0.0011-5.1 pg TEQ g^-1 dry weight and 0.0074-1.4 pg TEQ g^-1 dry weight, respectively. The spatial distributions of polychlorinated dibenzo-p-dioxins and dibenzofurans and polychlorinated biphenyls showed increasing trends from urban area and development area to suburb. Principal component analysis revealed that polychlorinated dibenzo-p-dioxins and dibenzofurans contamination in the sediments may originate from pentachlorophenol and sodium pentachlorophenate and municipal solid waste incineration. Regarding polychlorinated biphenyls, the steel industry, combustion processes and usage of some commercial polychlorinated biphenyl products were identified as the major sources. The emission from a former steel plant could be the main contributor to polychlorinated biphenyls in urban areas. The mean value of the total toxic equivalent quantities in the sediment samples exceeded the Canadian interim sediment quality guidelines. Long-term wastewater irrigation increases the load of sediment-bound pollutants in agricultural soil and may pose potential ecological risks to crops and human health.

Exposure levels of PCDD/Fs and PCBs in human blood and the transplacental transfer characteristics in cord blood of newborns near the industrialized area

Mono-to octa-chlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) in pooled blood from the general population living near a typical industrialized area were investigated. Less chlorinated PCDD/Fs (mean: 2602 pg L^-1) were 7.5 times those of highly chlorinated ones (mean: 349 pg L^-1). The average ΣPCBs and Σdl-PCBs concentrations in human (cord) blood were 2741 (117) and 18 (0.31) ng L^-1, respectively. Higher concentrations of highly chlorinated PCDD/Fs were found in females than in males across different ages. The mean concentrations (and toxic equivalents (TEQs)) of PCDD/Fs were 282 (27) pg L^-1 in males and 312 (32) pg L^-1 in females. The concentrations of the PCDD/Fs and PCBs increased with age for both males and females, which might be caused by the long half-lives of these compounds and decreases in metabolic rates with age as the metabolic of nutrients, food, and also PCDD/Fs and PCBs would trend to slow. The TEQ of total PCDD/Fs and PCBs was higher in blood from orthopedics patients (107 pg L^-1) than other patients. This result may be associated with the bone density and pollutant bioaccumulation. In addition, total concentration of PCDD/Fs and PCBs in blood of women at reproductive age were 6.6 and 37 times the cord blood of newborns, respectively. Positive correlation of PCDD/Fs and PCBs especially for the higher chlorinated compounds between female and cord blood were discovered, which might be caused by the transplacental transfer characteristics and blood barrier for macromolecules and reduce the chemical exposure risks for newborns.

Curbing dioxin emissions from municipal solid waste incineration: China's action and global share

China generates the world's second-largest amount of municipal solid waste (MSW) and incinerates the largest quantity of MSW. However, data on the latest dioxin emissions from MSW incineration (MSWI) and the related global share were lacking. In the context of MSW classification, distinguishing the long-term MSW generation and incineration quantity, and dioxin emissions was necessary for macro-control and policy-making by the Chinese Government. By considering population size and GDP per capita, China's MSW generation toward 2050 was projected based on Monte Carlo simulation. Moreover, dioxin emission factors were also assumed based on the diffusion rate of four grades of air pollution control devices (APCDs). Finally, we show that the quantity of China's MSW generation in 2050 will be 363.50 million tonnes (Mt) with 341.06-382.45 Mt of 75% certainty. China's dioxin emissions from MSWI were approximately 15.46 g I-TEQ in 2019, which accounted for 26.1% of total emissions from global MSWI. We discuss dioxin emission reduction scenarios depending on MSW diversion and APCD upgrades. China's dioxin emissions will be 70.38 g I-TEQ for the business-as-usual scenario, and the dioxin emissions will be 9.29 g I-TEQ (within the range of 8.88-9.64 g I-TEQ) for the optimal scenario in 2050. Moreover, in 2050, the APCD diffusion rate will account for 98.8% of the sensitivity of dioxin emissions from China's MSWI. According to the assumed scenarios, there is a dioxin emission reduction potential of 18.6% and 86.8% in 2050 by MSW diversion alone and maximum APCD upgrades combined with food waste diversion, respectively.

Insights into the toxicokinetic, tissue distribution and maternal transfer of polychlorinated dibenzo-p-dioxins/dibenzofurans in laying hens fed with dioxin-associated dietary

A controlled feeding experiment was conducted to investigate the toxicokinetic of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) in laying hens. The laying hens were fed with fly ash contaminated diets to replicate the typical environment-feed-chicken transfer chain in China. Levels of PCDD/Fs rapidly increased in the pectoralis, adipose tissue, liver and blood of laying hens with daily ingestion of dioxin-associated diets during the 14-days exposure period, and then a gradual decrease was observed in the 28-days depletion period. The depletion rates (k_d) of the toxic equivalent of PCDD/Fs (TEQ_PCDD/Fs) were 0.043, 0.031 and 0.030 day^-1 for pectoralis, liver and adipose tissue in the high-exposure group, respectively. The k_d of individual PCDD/Fs in liver increased with the numbers of chlorine and n-octanol/water partition coefficient (logK_OW), indicating that lower chlorinated congeners had higher half-lives in liver. Decreasing ratios of liver to adipose tissue for PCDD/Fs (L/AT) throughout the experiment suggested a tendency of equilibrium partitioning between liver and adipose tissue. Congener-specific sequestration of PCDD/Fs in liver was revealed by the positive correlation between L/AT ratios and logK_OW. Physiological bioconcentration factors of PCDD/Fs were estimated at the end of exposure, indicating the preferential accumulation of hexachlorinated congeners in most tissues. Furthermore, maternal transfer of PCDD/Fs was positively correlated with logK_OW, implying that more lipophilic congeners were transferred to egg along with the lipid circulation.