Identifying iron foundries as a new source of unintentional polychlorinated naphthalenes and characterizing their emission profiles

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.

Polychlorinated naphthalenes in freshwater fish from Beijing markets: Species-specific differences, effects of cooking, and health risk assessment

Fish are an important source of human dietary exposure to polychlorinated naphthalenes (PCNs). The occurrence and sources of PCNs in different species of freshwater fish are unknown, and few studies have assessed human exposure risks to PCNs through freshwater fish. In this study, 140 freshwater fish samples from 10 species were collected from Beijing markets, China. The Σ75CNs concentration range in the fish was 20.7-1310 pg/g wet weight (ww). The highest median Σ75PCNs concentration (80.4 pg/g ww) was found in mandarin fish (Siniperca chuatsi), and the lowest (29.6 pg/g ww) in snakehead (Channa argus). Di- and tri-CNs were the dominant PCN homologues with contributions of 35.3 % and 30.8 %, respectively. Unintentionally produced PCNs from metal smelting might be the source of PCN contamination in freshwater fish. The cooking temperature and time did not significantly affect the PCN concentrations in fish or the PCN homologue profiles. The highest toxic equivalent (TEQ) value was observed in sturgeon (Acipenser sinensis), followed by mandarin fish. Hexa-CNs were the most abundant homologue for the PCN TEQs. A risk assessment indicated that the dietary exposure risks for local residents to PCNs through freshwater fish were low. However, the relatively high concentrations of PCNs in the samples deserve attention to avoid PCNs exposure risks for groups with high fish consumption rates. Furthermore, freshwater fish likely contain a mixture of contaminants including dioxin and furans which also display a similar mode of toxicity as the PCNs and could enhance the risk to fish consumers.

An updated global overview of the manufacture and unintentional formation of polychlorinated naphthalenes (PCNs)

This review updates information on the historical manufacture and unintentional production of polychlorinated naphthalenes (PCNs). The direct toxicity of PCNs as a result of occupational human exposure and through contaminated feed in livestock was recognised decades ago, making PCNs a precursor chemical for consideration in occupational medicine and occupational safety. This was confirmed by the listing of PCNs by the Stockholm Convention as a persistent organic pollutant in the environment, food, animals and humans. PCNs were manufactured globally between 1910 ∼ 1980, but reliable data on the volumes produced or national outputs are scarce. A total figure for global production would be useful for the purposes of inventory and control and it is clear that combustion related sources such as waste incineration, industrial metallurgy and use of chlorine are current major sources of PCNs to the environment. The upper bound estimate of total global production has been put at 400,000 metric tons but the amounts (at least, many 10 s of tonnes) that are currently emitted unintentionally every year through industrial combustion processes should also be inventoried along with estimates for emissions from bush and forest fires. This would however require considerable national effort, financing and co-operation from source operators. The historical (1910-1970 s) production and resulting emissions through diffusive/evaporative releases through usage, are still reflected in documented occurrence and patterns of PCNs in human milk in Europe and other locations worldwide. More recently, PCN occurrence in human milk from Chinese provinces has been linked to local unintentional emissions from thermal processes.

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.

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.

Occurrence of polychlorinated naphthalenes in dairy cow farms in proximity to an iron smelting plant in China: A preliminary study

Animal derived foods are the primary pathway for human exposure to polychlorinated naphthalenes (PCNs), and various foodstuffs have been reported to contain PCNs. However, information on how PCN emission sources affect surrounding animal farms is scarce. The present study determined PCN levels in cow's milk, excrement, feed, plant and soil samples collected from four dairy farms situated within 10 km of an iron smelting plant in China. PCN concentrations in the milk samples from all four farms were in the range from 470 to 797 pg/g lipid weight while the PCN concentrations in the other specimens decreased in the order: plant > soil > excrement > feed. Higher PCN concentrations appeared in silage than in other feedstuffs, and the relationships between PCNs in milk, excrement and feed were closer than those in plant and soil. Human exposure risk to PCNs by consuming milk from this region was relatively higher than in less polluted areas.

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.

The Homogeneous Gas-Phase Formation Mechanism of PCNs from Cross-Condensation of Phenoxy Radical with 2-CPR and 3-CPR: A Theoretical Mechanistic and Kinetic Study

Chlorophenols (CPs) and phenol are abundant in thermal and combustion procedures, such as stack gas production, industrial incinerators, metal reclamation, etc., which are key precursors for the formation of polychlorinated naphthalenes (PCNs). CPs and phenol can react with H or OH radicals to form chlorophenoxy radicals (CPRs) and phenoxy radical (PhR). The self-condensation of CPRs or cross-condensation of PhR with CPRs is the initial and most important step for PCN formation. In this work, detailed thermodynamic and kinetic calculations were carried out to investigate the PCN formation mechanisms from PhR with 2-CPR/3-CPR. Several energetically advantageous formation pathways were obtained. The rate constants of key elementary steps were calculated over 600~1200 K using the canonical variational transition-state theory (CVT) with the small curvature tunneling (SCT) contribution method. The mechanisms were compared with the experimental observations and our previous works on the PCN formation from the self-condensation of 2-CPRs/3-CPRs. This study shows that naphthalene and 1-monochlorinated naphthalene (1-MCN) are the main PCN products from the cross-condensation of PhR with 2-CPR, and naphthalene and 2-monochlorinated naphthalene (2-MCN) are the main PCN products from the cross-condensation of PhR with 3-CPR. Pathways terminated with Cl elimination are preferred over those terminated with H elimination. PCN formation from the cross-condensation of PhR with 3-CPR can occur much easier than that from the cross-condensation of PhR with 2-CPR. This study, along with the study of PCN formation from the self-condensation 2-CPRs/3-CPRs, can provide reasonable explanations for the experimental observations that the formation potential of naphthalene is larger than that of 1-MCN using 2-CP as a precursor, and an almost equal yield of 1-MCN and 2-MCN can be produced with 3-CP as a precursor.

Occurrence and source analysis of polychlorinated naphthalenes in raw cow milk

The potential contamination of food items with polychlorinated naphthalenes (PCNs) has attracted increasing attention because of their toxicity, persistence and bioaccumulative characteristics. Humans are exposed to PCNs primarily through consuming animal-derived foodstuffs. However, the pathways by which PCNs can enter the food supplying chain are poorly understood. In this study, Σ₇₅PCNs were determined in raw cow milk (n = 82) collected from three different regions that varied in the intensity of PCNs emission sources in North China, using high-resolution gas chromatography/high-resolution mass spectrometry method. Higher PCN concentrations (214-2050 pg/g lw) were found in raw cow milk from dairy cow farms located in the region with relatively higher intensity of emission sources. Less chlorinated congeners were dominant in all raw cow milk samples. PCNs in cow milk might result from industrial fly ash emissions that contaminate animal feed through atmospheric deposition. Risks posed to humans through consuming PCNs in cow milk were low.

Partitioning and potential sources of polychlorinated naphthalenes in water-sediment system from the Yangtze River Delta, China

Spatial trends, partitioning behavior, and potential sources of polychlorinated naphthalenes (PCNs) in water-sediment system from the Yangtze River Delta (YRD) were investigated in this study. The total concentrations of 75 PCNs in water and sediment samples were 0.022-0.310 ng/L and 0.01-1.59 ng/g dry weight, respectively. The homolog patterns in the sediment and water samples were somewhat different. Di-to tetra-CNs made larger contributions in the sediment, while the mono-to tri-CNs were dominant homologs in the water. Overall, the low-chlorinated naphthalenes (mono-to tetra-CNs) were found to be the dominant homologs in the YRD water and sediment samples, and the homolog group contributions to the total PCNs concentrations decreased as the number of chlorine atoms increased. CN-5/7 and CN-24/14 were found at high concentrations in both the water and sediment. Partitioning and transfer of PCNs between water and sediment were assessed by calculating the partition coefficients and fugacity fractions. The partition coefficients showed that PCNs were not in equilibrium status in the water-sediment system, and hydrophobicity played an important role in PCNs partitioning. The fugacity fractions indicated that mono- to tri-CNs had stronger tendencies to escape from the sediment into the water, while the high-chlorinated naphthalenes close to equilibrium. Principal component analysis and correlation analysis indicated that industrial thermal processes and the use and disposal of products containing PCNs industrial products are sources of PCNs in the YRD water-sediment system.

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.

Burden and Risk of Polychlorinated Naphthalenes in Chinese Human Milk and a Global Comparison of Human Exposure

Polychlorinated naphthalenes (PCNs) are carcinogenic contaminants. Residues from historical production and ongoing unintentional releases from industrial thermal sources have led to the ubiquitous presence of PCNs in the environment. Our previous study has revealed that unintentional releases may be the main sources of PCNs in human milk from China. However, an assessment of PCN burden in human milk and exposure differences between historical residues and unintentional release exposure has not been conducted. In this study, we performed the first comparison of human exposure to PCNs and evaluated the differences between the estimated health risks from historical residues and unintentional releases. Three characteristic PCN congener patterns found in Chinese human milk specimens collected from 100 cities/counties can be considered characteristic of PCN exposures in regions with unintentional industrial releases as the main PCN sources. The health risk assessment suggested potential noncarcinogenic health effects in infants aged 0-6 months. The hazard index calculated for infants in Sweden indicates a strong impact of historical residues that nonetheless decreases over time, and a comparison of the hazard indices calculated for China and Ireland suggests that ongoing unintentional formation and release of PCNs from industrial processes should be a matter of public health concern.

Occurrence of dioxin-like POPs in soils from urban green space in a metropolis, North China: implication to human exposure

Urban green space is a special space for urban life and natural contact and has an important impact on human health. However, little information is available on dioxin-like persistent organic pollutants (POPs) in the soils from the specific areas. We measured the concentrations of polychlorinated naphthalenes (PCNs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and polychlorinated biphenyls (PCBs) in the soils from urban green space in a metropolis, North China, and found total concentrations of PCDD/Fs, PCBs, and PCNs in the range of 11.5-91.4, 14.7-444, and 82.5-848 pg/g, respectively. It was worth to notice that the concentrations of PCDD/Fs in public park soil from urban center were significantly higher than those in the road greenbelts and resident lawns (Kruskal-Wallis test, p = 0.004). The source analysis indicated that sewage sludge from wastewater treatment plants were important sources of PCNs and PCDD/Fs in urban green land soils, and atmospheric deposition from municipal solid waste incinerator (MSWI) also play an important role in PCDD/F sources. The rough exposure risk evaluation showed that the residents were at a safe level with the daily doses being 0.172-3.144 fg/kg BW/day for children and 0.022-0.406 fg/kg BW/day for adult. Due to the complex and variable sources of PCDD/Fs in urban areas, dioxin-like POPs in urban green land should be given more attention to weaken human exposure.

Validity of using a relative potency factor approach for the risk management of dioxin-like polychlorinated naphthalenes

Here, we characterized the dioxin-like activities of 42 polychlorinated naphthalenes (PCNs) and 6 technical Halowax formulations by using the DR-CALUX (dioxin-responsive chemically activated luciferase expression) assay with rat hepatoma luciferase-expressing H4IIE cells. Of the 42 PCNs examined, 31 showed dioxin-like activities, for which the mass-based REP-EC_5TCDD (potency relative to that of 2,3,7,8-tetrachlorodibenzo-p-dioxin based on the 5% effective concentration determined from the dose-response curve for 2,3,7,8-TCDD) ranged from 0.00000012 to 0.0051, indicating that some of the PCNs (e.g., 1,2,3,6,7,8-HxCN and 1,2,3,4,6,7-HxCN) had dioxin-like activities that were equal to or higher than the WHO-TEFs and the mass-based REP-EC_5TCDD reported for dioxins such as octachlorodibenzo-p-dioxin, octachlorodibenzofuran, 3,3',4,4'-tetrachlorobiphenyl (PCB-77), 3,4,4',5-tetrachlorobiphenyl (PCB-81), and 3,3',4,4',5,5'-hexachlorobiphenyl (PCB-169). For PeCNs to OCN with high dioxin-like activities, REPs determined in previous studies were comparable to the REP values obtained in the present study. The TCDD-EQs (2,3,7,8-TCDD equivalents) obtained experimentally for the Halowax formulations decreased in the order HW1051 (37 mg/kg) > HW1014 (30 mg/kg) > HW1013 (5.6 mg/kg) > HW1099 (2.9 mg/kg) > HW1001 (0.60 mg/kg) > HW1031 (<0.10 mg/kg) and were comparable to the theoretical TCDD-EQs calculated by multiplying the concentration and REP of each PCN. In addition, the theoretical TCDD-EQs for PCNs in emission gases produced by thermal processes were below the Japanese emission standard of 0.1-10 ng WHO-toxicity equivalent (TEQ)/m³N, and 3 to 4 orders of magnitude lower than the corresponding WHO-TEQ. Based on a comparison of theoretical and experimental TCDD-EQs, we found that our REP-based approach was suitable for the risk management of industrially produced and unintentionally generated dioxin-like PCNs. This approach will be particularly useful for the risk management of unintentionally generated PCNs in emission gases because the contribution of dioxin-like PCNs to the whole dioxin-like toxicity of emission gases can be elucidated.

Exposure of polychlorinated naphthalenes (PCNs) to Pakistani populations via non-dietary sources from neglected e-waste hubs: A problem of high health concern

To date limited information's are available concerning unintentional productions, screening, profiling, and health risks of polychlorinated naphthalenes (PCNs) in ambient environment and occupational environment. Literature reveals that dust is a neglected environmental matrix never measured for PCNs. To our knowledge, this is the first study to investigate the concentrations and health risks of PCNs in indoor dust, air, and blood of major e-waste recycling hubs in Pakistan. Indoor air (n = 125), dust (n = 250), and serum (n = 250) samples were collected from five major e-waste hubs and their vicinity to measure 39 PCN congeners using GC-ECNI-MS. ∑₃₉PCN concentrations in indoor air, dust, and serum (worker > resident > children) samples ranged from 7.0 to 9583 pg/m³, from 0.25 to 697 ng/g, and from 0.15 to 401 pg/g lipid weight, respectively. Predominant PCN congeners in indoor air and dust were tri- and tetra-CNs, while tetra- and penta-CNs were dominant in human serum samples. The higher PCNs contribution was recorded at the recycling units, while the lower was observed at the shops of the major e-waste hubs. Higher contribution of combustion origin CNs in air, dust and human samples showed combustion sources at the major e-waste hubs, while Halowax and Aroclor based technical mixture showed minor contribution in these samples. Mean toxic equivalent (TEQ) concentrations of PCNs were 2.79E⁺⁰⁰ pg-TEQ/m³, 1.60E^-02 ng-TEQ/g, 8.11E^-01 pg-TEQ/g, 7.14E^-01 pg-TEQ/g, and 6.37E^-01 pg-TEQ/g for indoor air, dust, and serum samples from workers, residents, and children, respectively. In our study, CNs- 66/67 and -73 in indoor air, dust, and human serum were the great contributors to total TEQ concentrations of PCNs. This first base line data directs government and agencies to implement rules, regulation to avoid negative health outcomes and suggests further awareness in regard of provision of proper knowledge to the target population.

Polychlorinated naphthalenes in human milk: Health risk assessment to nursing infants and source analysis

Polychlorinated naphthalenes are teratogenic environmental contaminants. Mother milk is the most important food for nursing infants. The World Health Organization actively promotes breastfeeding for its immunological, psychological, and economic advantages. We firstly measured concentrations of polychlorinated naphthalenes in human milk from 19 provinces in China and estimated their potential health risks to nursing infants and their possible sources. Concentrations ranged from 211.07 to 2497.43 pg/g lipid. The high prevalence of highly toxic hexachlorinated naphthalenes (Hexa-CN66/67) in human milk samples indicated a higher health risk in the sampling areas. Cancer risk posed to nursing infants was not significant, but potential non-carcinogenic adverse health effects were suggested and should be emphasized in some sampling areas. Unintentional emission of polychlorinated naphthalenes from industries that employ thermal processes appears to be the main source for PCNs in human milk in most sampling areas. Correlation analysis also suggested PCNs as impurities in polychlorinated biphenyl mixtures as a previously unrecognized source of polychlorinated naphthalenes in human milk.

Temporal trends in polychlorinated naphthalene emissions from sintering plants in China between 2005 and 2015

The Chinese Government has established stringent policies since 2005 to control SO₂, particulate matter, and NO_x emissions from sintering plants with the aim of tackling severe air pollution in China. Notably, sintering is also important sources of polychlorinated naphthalenes (PCNs), but it is not clear whether the air pollution control policies have led to decreased PCN emissions. In this study, the PCN concentrations in 144 stack gas, 87 discarded fly ash, and 24 desulfurization by-product samples from 24 Chinese sintering plants were determined. This study revealed that desulfurization processes decreased PCN emissions by 47.2%-72.2%. However, these PCNs were not completely eliminated, and transformed to desulfurization by-product. PCN emission in such previously ignored solid residues, including of desulfurization by-product and fine particles, produced in the process of cutting down air pollutants emissions from Chinese sintering plants between 2005 and 2015 was found contained 324 kg, and these residues therefore need to be managed better than currently. Furthermore, PCN concentrations were higher from produced in old plants than produced in new plants, so it is necessary to increase the rate at which out-of-date sintering plants are eliminated. Phasing out old sintering processes decreased total PCN emissions in China by 1549 kg between 2005 and 2015.

Polychlorinated naphthalene (PCN) emissions and characteristics during different secondary copper smelting stages

The amounts and characteristics of polychlorinated naphthalenes (PCNs) emitted by a secondary copper smelter were investigated. Differences in the amounts and characteristics of PCNs emitted during different smelting stages were investigated, and the main stage during which PCNs were emitted was identified. PCN concentrations in stack gases emitted during secondary copper smelting were 477.0-762.5 ng/m³ (4.4-8.3 pg toxic equivalents/m³). The contributions of the different stages to total PCN emissions decreased in the order feeding-fusion stage (65% of total PCN emissions) > oxidation stage (27%) > deoxidation stage (8%). The main contributor to PCN emissions during secondary copper smelting was the feeding-fusion stage. PCN concentrations and profiles in stack gas, fly ash, and deposit ash collected during different smelting stages were determined. PCNs in stack gases were mainly less-chlorinated homologs, and fly ash and deposit ash were dominated by highly-chlorinated homologs. These results will help improve strategies for decreasing and eliminating PCN emissions during secondary copper production.

Unintentional persistent organic pollutants in cement kilns co-processing solid wastes

Co-processing solid waste in cement kilns has become increasingly widespread in recent years. Persistent organic pollutants (POPs) can be unintentionally produced and emitted from cement kilns, especially kilns in which solid waste is co-processed. Unintentionally produced POP formation and emission by cement kilns co-processing solid waste therefore need to be studied in detail to allow the potential risks posed by cement kiln co-processing techniques to be assessed. Many field studies and laboratory simulation experiments have been performed to investigate the formation and release of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). However, the formations, characteristics and emission factors of various emerging unintentionally produced POPs have not been comprehensively reviewed. Here, emissions of well-known unintentionally produced POPs (PCDD/Fs and polychlorinated biphenyls) and emerging unintentionally produced dioxin-like POPs (polybrominated dibenzo-p-dioxins and dibenzofurans, polychlorinated naphthalenes, and chlorinated and brominated polycyclic aromatic hydrocarbons) in cement kilns co-processing solid waste are reviewed, focusing on formations and influencing factors of those unintentional POPs. Data from field studies indicated that the main stages in which POPs are unintentionally produced in cement kilns co-processing solid waste are the cyclone preheater outlet, suspension preheater boiler, humidifier tower, and back-end bag filter. The raw material composition, chlorine and bromine contents, and temperature are the most important factors affecting POP formation. The homolog distributions and congener profiles of POPs formed unintentionally in cement kilns were compared, and it was found that larger amounts of less-chlorinated homologs than more-chlorinated homologs are emitted. Emission factors for various unintentionally produced POPs for cement kilns co-processing solid waste were summarized, and could be useful for compiling global emission inventories for pollutants covered by the Stockholm Convention. This comprehensive review improves our understanding of unintentional production and emissions of POPs by cement kilns co-processing solid waste.

Measurement of PCNs in sediments collected from reservoir and river in northern Taiwan

Sediment samples were collected from a large reservoir and a river in northern Taiwan to investigate the occurrence and characteristics of Σ73PCNs analyzed. Results indicate that total concentrations of PCNs (Di- to Octa-CNs) measured in sediments collected in reservoir (29.2 ± 7.11 pg/g-dw) are significantly lower than that of samples collected in river (987 ± 440 pg/g-dw). The increasing trend of PCN concentration from upstream to downstream is found for the sediments collected in reservoir. PCN concentrations measured in surface sediments are relatively higher than that measured in sub-surface sediments collected in reservoir. Tetra-CNs consistently dominate in reservoir sediments, however, Penta-, Tetra- and Mono-CNs dominate in sediments collected at different sampling sites of the river investigated, suggesting that various sources contribute to PCNs collected from river. Indeed, diagnostic ratios indicate that mix-source contribute to PCNs measured in sediments collected from the reservoir and river in northern Taiwan.

Gas chromatography-Orbitrap mass spectrometry screening of organic chemicals in fly ash samples from industrial sources and implications for understanding the formation mechanisms of unintentional persistent organic pollutants

Clarifying the occurrences of organic chemicals in fly ash produced during industrial thermal processes is important for improving our understanding of the formation mechanisms of toxic pollutants such as polycyclic aromatic hydrocarbons (PAHs), halogenated PAHs, dioxins, and other unintentional persistent organic pollutants. We developed a highly sensitive gas chromatography-Orbitrap mass spectrometry (GC-Orbitrap/MS) method and applied it to screening of organic pollutants in fly ash samples from multiple industrial thermal processes. The GC-Orbitrap/MS method could detect and quantify organic pollutants at part per billion (ppb) levels. In total, 96 organic chemicals, including alkanes, benzene derivatives, phenols, polycyclic aromatic hydrocarbons, and biphenyl derivatives were identified in the fly ash samples. Several organic chemicals with chlorine or bromine substituents were abundant in secondary copper smelter fly ash, and these might act as precursors for formation of dioxins, brominated dioxins, and other dioxin-like compounds. Several chlorinated and brominated PAH compounds were also found in the secondary copper smelter fly ash. PAHs were dominant chemicals in the secondary aluminum smelter fly ash samples, and were present in much higher concentrations than in the samples from other industries. This indicates that there are different chemical formation pathways in different industries. Possible formation pathways of PAHs and dioxins were investigated and deduced in this study. These results improve our understanding of the formation mechanisms of toxic unintentional persistent organic pollutants and could be useful for reducing their source emissions.

Probabilistic risk-based pollution prevention model for a foundry: a case study of casting

Hazardous air pollutants from industrial activities have long been associated with serious health effects. Traditional health risk assessment uses point estimates of inhalation concentrations based on standard Gaussian diffusion models with steady-state emission rate assumptions. This traditional approach was criticized because it does not account for variability and thus leading to a potential overestimate of the health risk from the batch processes. To overcome this deficiency, a probabilistic risk assessment model is proposed. The foundry industry with processes typically associated with several hazardous air pollutants is identified and iron casting is chosen as a case study to compare risk estimates. Existing data, representing historical proprietary information of the case study, were used to deliver representative risk values and help identify potential replacements or interventions in the manufacturing process. A probability distribution function of emitted concentrations was simulated to model the batch process emissions from mold and core resin binders, a major source of pollution. The same method was applied to exposure factors to feed into the risk model resulting in a probabilistic risk evaluation. Several alternative resin binders in commercial use were examined to offer a risk-based substitute to the resin binder in use. The risk results provided an opportunity to consider newer and environmentally friendlier options. A comparison of the results from this approach and those from the point estimate analysis reveals a gross over estimation of risks. The point estimate risk values were about eight time larger than the mean value and about twice the 95th percentile values of the probabilistic risk approach. The wide range of variability among resin binders associated risk results, close to two orders of magnitude in some cases, presented opportunities to select from a variety of binders with lesser emissions and lower risk. Optimal selection will depend on several pollutants emitted from this process to help address cumulative impacts of multiple pollutants. Investigations are underway for a multi-pollutant strategy including trade-offs, and other quality controls vital to the decision-making.

Chlorine levels and species in fine and size resolved atmospheric particles by X-ray absorption near-edge structure spectroscopy analysis in Beijing, China

An understanding of the species of chlorine is crucial in the metropolis-Beijing, which is suffering serious haze pollution with high frequency. Particulate Matters (PMs) with five different sizes were collected in Beijing from July 2009 to March 2016, and characterized non-destructively by X-ray absorption near edge structure spectroscopy. PM_<0.2, PM_0.2-0.5 and PM_>2.5 contributed for the major PMs mass in spring and summer, PM_0.5-1.0 and PM_1.0-2.5 contributed for the major PMs mass in autumn and winter. The concentrations of the three chlorine species were in the order of inorganic chlorine (Cl_inorg) > aliphatic chlorine (Cl_ali) > aromatic chlorine (Cl_aro), indicating that Cl_inorg constituted the primary chlorine fraction and less toxic Cl_ali constituted the primary total organic chlorine (Cl_ali + Cl_aro, abbreviated as Cl_org) in the PMs in Beijing. In addition, these three chlorine species exhibited identical seasonal variation in PM_2.5: winter > autumn > spring > summer. Wet precipitation is an important factor to result in the lower mass concentrations of these three chlorine species in summer. The temporal variations of both size resolved PM mass concentrations and chlorine species concentrations suggested that the air pollution prevention and control in Beijing has just won initial success.

Pivotal Roles of Metal Oxides in the Formation of Environmentally Persistent Free Radicals

Environmentally persistent free radicals (EPFRs) are emerging pollutants that can adversely affect human health. Although the pivotal roles of metal oxides in EPFR formation have been identified, few studies have investigated the influence of the metal oxide species, size, or concentration on the formation of EPFRs. In this study, EPFR formation from a polyaromatic hydrocarbon with chlorine and hydroxyl substituents (2,4-dichloro-1-naphthol) was investigated using electron paramagnetic resonance spectroscopy. The effect of the metal oxide on the EPFR species and its lifetime and yield were evaluated. The spectra obtained with catalysis by CuO, Al₂O₃, ZnO, and NiO were obviously different, indicating that different EPFRs formed. The abilities of the metal oxides to promote EPFR formation were in the order Al₂O₃ > ZnO > CuO > NiO, which were in accordance with the oxidizing strengths of the metal cations. A decay study showed that the generated radicals were persistent, with a maximum 1/e lifetime of 108 days on the surface of Al₂O₃. The radical yields were dependent on the concentration and particle size of the metal oxide. Metal oxide nanoparticles increased the EPFR concentrations more than micrometer-sized particles.

Polychlorinated naphthalene (PCN) emissions from scrap processing steel plants with electric-arc furnaces

Polychlorinated naphthalene (PCN) emissions of scrap iron processing steel plants were explored by measuring concentrations in stack gases of five plants, in the atmosphere (n=11) at a site close to those plants, and in soil at several sites in the region (n=40) in Aliaga, Izmir, Turkey. Observed stack-gas Σ₃₂PCN levels from the plants without scrap preheating (189±157ngNm^-3, average±SD, n=4) showed that they are substantial PCN emitting sources. Stack-gas Σ₃₂PCN level for the plant with scrap preheating was considerably higher (1262ngNm^-3). Similarly, Σ₃₂PCN emission factor for this plant was substantially higher (11.9mgton^-1) compared to those without scrap preheating (1.30±0.98mgton^-1). Results have also suggested that the investigated steel plants emit large quantities of fugitive particle-phase PCNs. Measured soil Σ₃₂PCN concentrations that are considered to be representative of the atmospheric levels were greatly variable in the region, ranging between 0.003 and 10.02μgkg^-1 (dry wt). Their spatial distribution showed that main PCN sources in the region were the iron-steel plants. Ambient air levels (1620±800pgm^-3) were substantially higher than ones observed around the world and in the study area verifying that the steel plants with electric arc furnaces (EAFs) are important PCN sources. Investigation of possible mechanisms suggested that the combustion processes also contribute to emissions from EAFs in addition to evaporation of PCNs present in the scrap iron.

Concentrations and patterns of polychlorinated naphthalenes in urban air in Beijing, China

Air samples were collected, using a high-volume air sampler, at an urban site in Beijing from April 2014 to March 2015. The polychlorinated naphthalene (PCN) concentration in the atmosphere in each season was determined. The total PCN (total target tri- to octachloronaphthalene congeners) concentrations were 1.99-19.0 pg/m(3), and the mean was 7.20 pg/m(3). The PCN concentrations were higher in fall than summer, indicating that the concentrations varied significantly over time. The trichloronaphthalene homolog was the predominant PCN homolog in all four seasons. The PCN toxic equivalent (TEQ) concentrations were 0.42-6.89 fg/m(3), and the mean was 1.74 fg/m(3). The CN-66/67 and CN-73 congeners were the predominant contributors to the TEQ concentrations. The mean seasonal TEQ concentration decreased in the order fall (3.18 fg/m(3)) > winter (1.41 fg/m(3)) > summer (1.11 fg/m(3)) > spring (1.03 fg/m(3)). The TEQ concentrations and the PCN concentrations did not follow the same seasonal trends, but the highest TEQ and PCN concentrations were both found in fall. Correlation analysis, ratio analysis, and principal component analysis were used to investigate the sources of PCNs to the Beijing atmosphere. The results suggested that combustion processes may be the main sources of PCNs to the Beijing atmosphere.

Polychlorinated naphthalenes in the air over the equatorial Indian Ocean: Occurrence, potential sources, and toxicity

Monitoring of marine polychlorinated naphthalenes (PCNs) is crucial, as they are considered persistent organic pollutants (POPs) by the Stockholm Convention. Data on PCNs in marine environment are scarce. In this study, 19 air samples were collected during a cruise in the equatorial Indian Ocean on board the Chinese research vessel Shiyan I from 4/2011 to 5/2011. PCN concentration of these air samples ranged from 0.033 to 2.56pgm(-3), with an average of 0.518pgm(-3), equal to or lower than the values reported for other oceans, seas, and lakes worldwide. Tri- and tetra-CNs were the main homologues in most samples. Reemission of Halowax mixtures and incineration processes were the major sources of atmospheric PCNs in the study area. The PCN-corresponding toxic equivalency values ranged from 0 to 0.190fgm(-3) (average: 0.038fgm(-3)), falling in the low end of global range.

Removal of polychlorinated naphthalenes by desulfurization and emissions of polychlorinated naphthalenes from sintering plant

The sintering flue gas samples were collected at the inlets and outlets of the desulfurization systems to evaluate the influence of the systems on PCNs emission concentrations, profiles, and emission factors. The PCNs concentrations at the inlets and outlets were 27888-153672 pg m(-3) and 11988-42245 pg m(-3),respectively. Desulfurization systems showed excellent removal for PCNs, and the removal efficiencies of PCNs increase with increasing chlorination level. Lower chlorinated homologs are more sensitive to the desulfurization process than higher ones. High levels of PCNs were also detected in the gypsum (11600-29720 pg g(-1)) and fly ash samples (4946-64172 pg g(-1)). The annual total emissions of PCNs released to flue gas and gypsum from the sintering plants were about 394 kg, 48.5% of which was in gypsum. The surface area of the fly ash samples increased significantly from the first to the fourth stage of the series-connected electrostatic precipitator, accompanying obvious rising of concentration of PCNs in the fly ash samples.

Removal of polychlorinated biphenyls by desulfurization and emissions of polychlorinated biphenyls from sintering plants

The influence of desulfurization on polychlorinated biphenyls (PCBs) from sintering plants was investigated. The concentrations of dioxin-like (dl) PCBs, toxic equivalents (TEQs), indicator PCBs, and total tri- to deca-chlorinated PCB homolog groups (∑PCBs) in the flue gases at the desulfurization system inlets were 290-1906 pg m(-3) (2.4-18.8 pg World Health Organization (WHO) TEQ m(-3)), 420-2885 pg m(-3), and 6496-22,648 pg m(-3), respectively. Desulfurization reduced the values to 43.3-500 pg m(-3) (0.46-9.5 pg WHO-TEQ m(-3)), 183-587 pg m(-3), and 2383-11,639 pg m(-3), respectively. The removed PCBs were adsorbed by gypsum from the flue gas; the PCB concentration distributions at the inlets and outlets and in the gypsum samples were similar. The emission factors were 9.86 ng WHO-TEQ t(-1) for the flue gas and 8.37 ng WHO-TEQ t(-1) for gypsum. Desulfurization decreased the annual atmospheric PCB emissions from 48.6 to 30.7 g WHO-TEQ, and the estimated annual emissions in gypsum were 8.06 g WHO-TEQ. PCBs in the gypsum have not been effectively eliminated and will probably reenter the environment and in turn become a new source of PCB emission. The PCB concentrations in fly ashes from series-connected electrostatic precipitators clearly increased.

Tracking the fingerprints and combined TOC-black carbon mediated soil-air partitioning of polychlorinated naphthalenes (PCNs) in the Indus River Basin of Pakistan

This study reports the first investigation of polychlorinated naphthalenes (PCNs) in air and soil samples from ecologically important sites of the Indus River Basin, Pakistan. The concentrations of ∑39-PCNs in air and soil were found in a range between 1-1588 pg m(-3) and 0.02-23 ng g(-1) while the mean TEQ values were calculated to be 5.4E(-04) pg TEQ m(-3) and 1.6E(+01) pg TEQ g(-1), respectively. Spatially, air and soil PCN concentrations were found to be high at Rahim Yar Khan (agricultural region). Lower-medium chlorinated PCNs (sum of tri-, tetra- and penta-CNs) predominated in both air and soil, altogether constituting 87 and 86% of total PCNs in the two environmental matrices, respectively. According to the data, soil-air partitioning of PCNs was interpreted to be similarly controlled by the combined effect of black carbon and organic matter in the Indus River Basin, with no preferential implication of the recalcitrant organic form.