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

Scientometric trends and knowledge maps of global polychlorinated naphthalenes research over the past four decades

Polychlorinated naphthalenes (PCNs) were included in the banned list of the Stockholm Convention due to their potential to provoke a wide range of adverse effects on living organisms and the environment. Many reviews have been written to clarify the state of knowledge and identify the research needs of this pollutant class. However, studies have yet to analyse the scientometric complexities of PCN literature. In this study, we used bibliometric R and vosviewer programs as a scientometric tool to fill this gap by focusing on articles indexed on Web of Science and Scopus databases and those published between 1973 and 2022. A total of 707 articles were published within this period with a publication/author, author/publication, and co-authors/publication ratios of 0.45, 2.19, and 4.86, respectively. Developed countries dominated most scientometric indices (number of publications, citations, and collaboration networks) in the survey period. Lotka's inverse square rule of author productivity showed that Lotka's laws do not fit PCN literature. An annual percentage growth rate of 7.46% and a Kolmogorov-Smirnoff goodness-of-fit of 0.88 suggests that more output on PCNs is likely in years to come. More research is needed from scholars from developing countries to measure the supremacy of the developed nations and to effectively comply with the Stockholm Convention agreement.

Nanoplasmonic biosensors for environmental sustainability and human health

Monitoring the health conditions of the environment and humans is essential for ensuring human well-being, promoting global health, and achieving sustainability. Innovative biosensors are crucial in accurately monitoring health conditions, uncovering the hidden connections between the environment and human well-being, and understanding how environmental factors trigger autoimmune diseases, neurodegenerative diseases, and infectious diseases. This review evaluates the use of nanoplasmonic biosensors that can monitor environmental health and human diseases according to target analytes of different sizes and scales, providing valuable insights for preventive medicine. We begin by explaining the fundamental principles and mechanisms of nanoplasmonic biosensors. We investigate the potential of nanoplasmonic techniques for detecting various biological molecules, extracellular vesicles (EVs), pathogens, and cells. We also explore the possibility of wearable nanoplasmonic biosensors to monitor the physiological network and healthy connectivity of humans, animals, plants, and organisms. This review will guide the design of next-generation nanoplasmonic biosensors to advance sustainable global healthcare for humans, the environment, and the planet.

Organic matter sources and distribution along land-use gradient in a Himalayan foothills River: Insights from molecular markers

The analysis of hydrocarbon biomarkers in surface sediments along the Markanda River in the foothills of the Indian Himalayas was conducted to gain insights into the distribution and composition of organic matter (OM) within the sediments. This investigation is essential for comprehending how anthropogenic changes are influencing the OM dynamics in river systems. The study involved identification and quantification of various compound groups such as n-alkanes, hopanes, steranes, polycyclic aromatic hydrocarbons (PAHs), linear alkyl benzenes (LABs) and phthalate esters along with their respective parametric ratios. The variation in distribution of n-alkanes and associated indices (odd-even carbon number predominance (OEP), average chain length (ACL), terrigenous to aquatic ratio (TAR), carbon preference index (CPI), and natural n-alkanes ratio (NAR)) were used to distinguish the natural source of organic content from those influenced by anthropogenic contamination. The detection of petroleum contamination was indicated by the presence of prominent unresolved complex mixtures (UCM) as well as specific petroleum biomarkers such as hopanes, diasteranes, and steranes. The study revealed varying concentrations of the analyzed organic pollutants, with the average of PAHs at 24.6 ng/g dw, LABs at 18.1 ng/g dw, and phthalates at 8.3 μg/g dw. The variability in concentration of the investigated compound groups across different locations indicated spatial heterogeneity, and the land use patterns appears to modulate the sources of OM in surface sediments. The source contribution of PAHs and phthalates determined by positive matrix factorization (PMF) shows the predominant sources of the anthropogenic hydrocarbons were linked primarily to petroleum/petroleum-derived products emissions, industrial discharges, cultural practices and common household waste/sewage disposal. This analysis provides insights for developing mitigation strategies and informing relevant policy changes globally, thereby contributing to the broader understanding of anthropogenic impacts on water ecosystems.

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.

Quantitative characterization of resident' exposure to typical semi-volatile organic compounds (SVOCs) around a non-ferrous metal smelting plant

To comprehensively characterize residents' exposure to major semi-volatile organic compounds (SVOCs), samples of indoor floor wipes, size-segregated airborne particles, gaseous air, food, and paired skin wipes were simultaneously collected from residential areas around a large non-ferrous metal smelting plant as compared with the control areas, and three typical SVOCs (including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and halogenated PAHs (HPAHs)) were determined. Comparison and correlation analysis among matrices indicated PAHs were the major contaminants emitted from metal smelting activities compared to HPAHs and PCBs, with naphthalene verified as the most important characteristic compound, and their accumulation on skin may be a comprehensive consequence of contact with floor dust and air. While patterns of human exposure pathways for the SVOCs were found to be clearly correlated to their vapor pressure, dermal absorption was the major contributor (51.1-76.3%) to total carcinogenic risk (TCR) of PAHs and HPAHs for surrounding residents, especially for low molecular weight PAHs, but dietary ingestion (98.6%) was the dominant exposure pathway to PCBs. The TCR of PAHs exceeded the acceptable level (1 × 10-4), implying smelting activities obviously elevated the health risk. This study will serve developing pertinent exposure and health risk prevention measures.

Polychlorinated naphthalenes in milk-based infant and toddler formula sold on the Chinese market

Polychlorinated naphthalenes (PCNs) are dioxin-like compounds that have been reported to be present in a wide variety of foodstuffs. Milk-based infant and toddler formula sometimes plays an important role in the diet of young children and could potentially cause adverse effects if contaminated with PCNs. This study investigated the concentrations of PCNs in commercial milk-based formula produced in different countries and sold on the Chinese market for three age groups: 0-6, 6-12 and 12-36 months. The total concentrations of PCNs in 72 samples from different countries of formula based on cow milk ranged from 7.8 to 30.3 pg/g whole weight (ww). Although the PCN concentrations in formula produced in Asia, Europe and South Pacific varied, all had comparable toxic equivalent (TEQ) values. Tri-CNs were the predominant PCN homologue in all samples. No significant differences in the concentrations of PCNs were found between samples of formula for each of the three age groups. The mean TEQ for PCNs in goat milk formula samples (0.0031 pg TEQ/g ww) was higher than the value for cow milk formula (0.0009 pg TEQ/g ww) produced in China, and the proportion of higher chlorinated PCNs in goat milk formula was also higher. Based on dry weight, the mean concentration of PCNs in the raw cow milk (119 pg/g dry weight (dw)) used to produce infant and toddler formula was higher than that in the actual formula (24.2 pg/g dw), and the PCN profiles also varied between the raw milk and formula. A risk assessment indicated that, in China, consuming formula poses a lower risk to infants and toddlers from based on exposure to PCNs compared with consuming breast milk.

Distributions of polychlorinated naphthalenes in beef from China and associated health risks

Polychlorinated naphthalenes (PCNs) are toxic and can accumulate through the food chain. PCNs have been detected in different categories of foods. Intake of animal-derived foods is an important pathway for human exposure to PCNs. However, information on PCNs in meat from farmed animals is scarce. In this study, PCNs were assessed in beef sourced from local markets in Beijing and six provinces in China. The mean PCN concentrations in beef samples from the seven regions varied from 41.2 to 88.7 pg/g wet weight (ww). The homologue profiles of PCNs in the specimens were similar, with tri- and di-CNs being dominant. The mean concentration of PCNs in the flank (74.7 pg/g ww) was higher than that in the round (58.2 pg/g ww) or shank (53.6 pg/g ww), likely because the former contained a higher proportion of lipids than the latter. Significantly different PCN distributions in beef and dairy cow milk were identified using machine learning. The toxic equivalencies (TEQs) of PCNs in all beef samples ranged from 0.0003 to 0.022 pg TEQ/g ww. PCNs contributed to approximately 4.6% of the total TEQ values of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, polychlorinated biphenyls, and PCNs in the beef. Health risks related to the intake of PCNs through beef consumption by the average person living in China were minimal.

Modification of Ti/Sb-SnO2/PbO2 Electrode by Active Granules and Its Application in Wastewater Containing Copper Ions

Active granule (WC/Co3O4) doping Ti/Sb-SnO2/PbO2 electrodes were successfully synthesized by composite electrodeposition. The as-prepared electrodes were systematically characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electrochemical performance, zeta potential, and accelerated lifetime. It was found that the doping of active granules (WC/Co3O4) can reduce the average grain size and increase the number of active sites on the electrode surface. Moreover, it can improve the proportion of surface oxygen vacancies and non-stoichiometric PbO2, resulting in an outstanding conductivity, which can improve the electron transfer and catalytic activity of the electrode. Electrochemical measurements imply that Ti/Sb-SnO2/Co3O4-PbO2 and Ti/Sb-SnO2/WC-Co3O4-PbO2 electrodes have superior oxygen evolution reactions (OERs) relative to those of Ti/Sb-SnO2/PbO2 and Ti/Sb-SnO2/WC-PbO2 electrodes. A Ti/Sb-SnO2/Co3O4-PbO2 electrode is considered as the optimal modified electrode due to its long lifetime (684 h) and the remarkable stability of plating solutions. The treatment of copper wastewater suggests that composite electrodes exhibit low cell voltage and excellent extraction efficiency. Furthermore, pilot simulation tests verified that a composite electrode consumes less energy than other electrodes. Therefore, it is inferred that composite electrodes may be promising for the treatment of wastewater containing high concentrations of copper ions.

Pilot study on the effect of secondary copper smelters on polychlorinated naphthalene contamination in surrounding agricultural areas

Polychlorinated naphthalenes (PCNs) are dioxin-like persistent organic pollutants that are primarily produced unintentionally during industrial thermal processes. These compounds are harmful to the environment and human health. This study investigated the occurrences of all 75 PCN congeners in agricultural areas near secondary copper smelters in China. The PCN concentrations in aquatic foods, eggs, crops, sediments and soils within 10 km of these smelters were higher than those in samples collected 20-30 km away from such facilities. In contrast, the PCN concentrations in compound animal feed samples collected at different distances from the secondary copper smelters were comparable to one another. Similar PCN homologue patterns were found in crop, egg, feed and soil samples collected at different distances from the smelters but the homologue profiles of PCNs in aquatic food and sediment samples collected from different distances varied. Lower chlorinated naphthalenes were the predominant homologues in most samples. The contamination of farm animals and crops with PCNs might result from the emission of these compounds from such sources into the surrounding environment. However, the health risks associated with human exposure to PCNs through food consumption are low for both distances (<10 km and 20-30 km) from secondary copper smelters.

Distribution and source identification of polychlorinated naphthalenes in bees, bee pollen, and wax from China

Polychlorinated naphthalenes (PCNs) are highly toxic and persistent organic pollutants that can cause adverse effects in the environment and on human health. PCNs have been detected in remote areas because of their long-range transportation. Bees and bee products are commonly used as biomonitors for various pollutants in the environment. However, information on PCNs in apiaries is scarce. The aim of this study was to evaluate the occurrences of PCNs in bees and bee products from apiaries located in different geographical regions of China, and to identify potential pollution sources and assess exposure risks to humans. Our results showed that the average Σ₇₅PCNs concentrations in bees, pollen, and wax were 74.1, 96.3, and 141 pg/g dry weight, respectively. The homologue and congener profiles of PCNs in bees, pollen, and wax were similar, and di- and tri-chlorinated naphthalenes (>60%) were the predominant homologues. The concentrations and distributions of PCNs in bees, pollen, and wax varied among different geographical regions, but their occurrences were correlated with PCN metallurgical sources in China. The health risks of PCNs in pollen were evaluated, and both carcinogenic and non-carcinogenic risks of PCNs exposure to humans through the diet were low.

Concentration and risk assessment of PCNs in green tea in different locations in China

Polychlorinated naphthalenes (PCNs) were added to the Stockholm Convention list of persistent organic pollutants in 2015. PCNs are mainly unintentionally produced during industrial processes nowadays, and can be widely found in environmental media and foodstuffs. Dietary intake is the primary pathway for human exposure to PCNs. PCNs in different categories of foodstuffs have been reported. However, little information on PCN concentrations in green tea, a popular beverage worldwide is available. In this study, all 75 PCN congener concentrations and distributions in green tea samples (n = 102) from 11 regions in China were determined, and risk assessment of human exposure to PCNs through tea consumption was conducted. The PCN concentrations in all the green tea samples were 3.62-175 pg/g dry weight (mean 36.1 pg/g dry weight). Similar PCN homolog and congener profiles were found in green tea samples from different areas. The dominant PCN homologs in all of the green tea samples were di-CNs, tetra-CNs, and tri-CNs. No direct relationships were found between PCN emission sources and PCN concentrations in the green tea samples. The brewing technique could affect the PCN concentrations and homolog profiles in tea leaves. PCNs in green tea from China were found to pose little risk to humans.

Metal-Catalyzed Formation of Organic Pollutants Intermediated by Organic Free Radicals

Metal compounds play important roles in the formation of organic pollutants during thermal-related processes. However, the metal-catalyzed predominant organic pollutants have not previously been characterized nor have any detailed catalytic mechanisms been clarified. Here, we preciously distinguished the multiple organic free radical intermediates on metal catalyst surfaces during the organic pollutant formation through laboratory and theoretical studies. Differences between the organic free radical intermediate species, concentrations, and formation mechanisms under the catalysis of different metal compounds were investigated. The results were verified mutually with the differed characteristics of organic pollutant products. CuO predominantly catalyzed the formation of highly chlorinated phenoxy radical intermediates and dioxins. High proportions of semiquinone radicals and oxygen-containing derivatives were found on ZnO surfaces. Differently, methyl-substituted phenoxy radicals and long-chain products formed on Al₂O₃ surfaces. The results will be instructive for the target emission control of priority organic pollutants during thermal-related processes rich in different metal compounds.

Variation in the formation characteristics of PBDD/F, brominated PAH, and PBDE congeners along the secondary copper smelting processes

Simultaneous determination of 58 congeners of polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs), brominated polycyclic aromatic hydrocarbons (Br-PAHs), and polybrominated diphenyl ethers (PBDEs) from multiple stages of industrial-scale secondary copper smelting plants was conducted with the aim of understanding their variations and control. In addition to the historical manufacture of PBDEs as brominated flame retardants, this study confirmed that PBDEs can be unintentionally produced and released from the secondary copper industry. The average mass emission factors of PBDD/Fs, PBDEs, and Br-PAHs from different sources were 10.0, 5.21 × 10³, and 7.24 × 10³ μg t^-1, respectively. Therefore, the emission of brominated persistent organic pollutants (POPs) in the secondary copper industry should be of concern. The concentration of brominated POPs increased from the gas cooling stage to stack outlet due to the possible "memory effect" and the regenerated POPs were mainly low-brominated homologs. A comparison of brominated POPs with corresponding chlorinated analogs in the same process indicated that the formation pathway of Br-PAHs was consistent with that of chlorinated PAHs. However, unlike chlorinated dioxins and furans, PBDD/Fs can also be formed from PBDEs as precursors, leading to obvious increases in highly brominated furans. Therefore, inhibiting the unintentional formation of PBDEs is important for controlling brominated POPs emissions.

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.

Hexachloronaphthalene (HxCN) impairs the dopamine pathway in an in vitro model of PC12 cells

Among polychlorinated naphthalenes (PCNs), listed by the Stockholm convention as Persistent Organic Pollutants (POPs), hexachloronaphthalenes are considered the most toxic and raise the highest concern. Of these, 1,2,3,5,6,7-hexachloronaphthalanene (PCN67) is considered the main congener affecting human health due to its hepatotoxicity and its ability to disturb the reproductive, endocrine, and hematological systems. It is also prevalent in human serum/plasma, milk, and adipose tissue. However, little is known about its neurotoxicity, despite the fact that anorectic effects have been observed in workers occupationally exposed to PCNs and in animal research on PCN67. Since dopamine is involved in many aspects of food intake, the aim of this study was to confirm whether PCN67 affects dopamine synthesis in differentiated PC12 cells, a widely used model of neurosecretion. Our results show that exposure to PCN67 resulted in diminished dopamine content and release. Moreover, PCN67 also affected the expression of tyrosine hydroxylase and lowered the expression of vesicular monoamine transporter 1 (VMAT1). In addition, significantly lower expression of antioxidant enzymes, including catalase, glutathione peroxidase and copper/zinc superoxide dismutase, was observed in comparison to the vehicle. In conclusion, PCN67 appears to disturb dopaminergic transmission by altering tyrosine hydroxylation, reducing VMAT1 expression and impairing antioxidant protection. Our study provides a potential mechanism for how PCN67 may cause dopamine deficiency and contribute to neuronal death by affecting cellular antioxidant potency; however, this conclusion requires further research.

Profiles, spatial distributions and inventory of brominated dioxin and furan emissions from secondary nonferrous smelting industries in China

Nonferrous metallurgical processes are important sources of carcinogenic polybrominated dibenzo-p-dioxin and dibenzofuran (PBDD/Fs) that transport globally. Studies on the profiles, spatial distributions and inventory of PBDD/F emissions into the atmosphere from nonferrous metallurgical plants are needed for better source control. In this study, field investigations on PBDD/F emissions from typical nonferrous metallurgical plants were conducted to characterize the PBDD/F profiles and derive their emission factors. Based on the PBDD/F profiles, diagnostic ratios of PBDD/Fs for secondary copper, zinc and lead smelting were proposed for identifying the potential sources of PBDD/Fs in environment. The PBDD/F emission factors for the secondary copper, lead, and zinc smelting plants were 0.71, 1.65, and 1.54 μg toxic equivalents/t, respectively. The estimated annual input of PBDD/Fs into atmosphere by secondary nonferrous metallurgical plants in China was 212.4 g by mass and 3511.3 mg by toxic equivalents, which is of significance for further evolving a global inventory. The spatial distribution of PBDD/F emissions from nonferrous metallurgical plants in China was mapped. Larger amounts of PBDD/Fs were emitted in the southeastern coastal region and northern China than elsewhere in China.

Occurrence, profiles, and control of unintentional POPs in the steelmaking industry: A review

The steelmaking industry is an important source of unintentionally produced persistent organic pollutants (UP-POPs). This review summarizes the emission levels, characteristics, and formation mechanisms of UP-POPs, including halogenated dioxins, polychlorinated biphenyls, polychlorinated naphthalenes, and penta- and hexa- chlorobenzenes in the steelmaking industry to improve our understanding of the emissions of UP-POPs from the steelmaking industry. The factors influencing UP-POP formation during the iron ore sintering (IOS) process are also reviewed. The raw materials and temperature during the steelmaking process are important factors influencing UP-POP generation. Raw materials containing plastics, paints, cutting oil, rubber, and iron from electronic waste recycling can contribute to high emissions of UP-POPs during steelmaking processes. Electrostatic precipitator dust contains chlorine, carbon, and metals, which are usually recycled as a component of the raw material, and could also promote dioxin formation and emissions from IOS. Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) are easily formed in high concentrations at temperatures in the range of 200 °C-650 °C. This review also provides a comprehensive summary of the UP-POP emission limits in the steel industry worldwide and the best available techniques and environmental practices for UP-POP emission reduction. The information in this review will be useful for the reduction of UP-POPs in the steelmaking process.

Polychlorinated naphthalenes (PCNs) in food products in Latvia: Congener-specific analysis, occurrence, and dietary exposure of the general population

A study was performed to evaluate the dietary exposure of the Latvian population to polychlorinated naphthalenes (PCNs). Based on the toxicological characteristics, provisional levels of occurrence, congener patterns, and the availability of analytical standards, twenty-six congeners were included in the analysis. Considering the planar structure of PCNs, an analytical protocol on the basis of destructive clean-up and isolation of analytes on carbon was applied, while GC-HRMS and isotope dilution were used for the detection and quantification of analytes. Commonly consumed foods were analyzed for the content of PCNs, followed by per capita intake calculations. By applying the available in vitro relative potency (REP) factors, putative toxic equivalents (TEQ) were determined, in order to assess the "dioxin-like" effect arising from the presence of PCNs in food. The daily intake (EDI) for total PCNs (∑_PCN) and PCN-TEQ for the general population were calculated to be 116 pg kg^-1 body weight (b.w.) and 0.036 pg TEQ kg^-1 b.w., respectively. Fish and fish products were found to provide the main contribution to the dietary "dioxin-like" burden of PCNs, constituting ∼60% of the total PCN-TEQ intake. For some fish samples, PCN-TEQ could additionally contribute up to ∼3% to the regulated PCDD/F-PCB-TEQ, while for other matrices this contribution could be lower by an order of magnitude. The obtained data indicated that the estimated dietary exposure to PCNs is likely to be of low concern, although PCN-TEQ could be recognized as a contributor to the overall "dioxin-like" TEQ loading that results from the exposure to halogenated aromatics.