Identification of bioaccumulating polychlorinated naphthalenes and their toxicological significance

Assessment of polychlorinated naphthalenes in Korean foods: Levels, profiles, and dietary intake

Concerns about dioxin-like compounds have increased; however, the monitoring of polychlorinated naphthalenes (PCNs) in food and the assessment of dietary intake remain limited. In this study, various foods were collected from Korean markets and analyzed for PCNs. Fishery products exhibited the highest mean concentration (48.0 pg/g ww) and toxic equivalent (TEQ) (0.0185 pg-TEQ/g ww). Agricultural products were the largest contributors (35.7%) to the total dietary intake of PCNTEQ, followed by livestock products (33.6%), fishery products (20.2%), and processed foods (10.5%). The mean intake of PCNTEQ for the Korean population was 0.901 pg-TEQ/day for males and 0.601 pg-TEQ/day for females. Generally, males and younger groups had higher daily intakes of PCNTEQ, but they did not exceed the tolerable weekly intakes. Nonetheless, it is important to manage potential health risks associated with PCNs and other dioxin-like compounds by identifying major food items contributing to PCN exposure and considering age and gender differences.

Polychlorinated Naphthalenes in Foods from the French Market: Occurrence, Dietary Exposure, and Evaluation of Relative Contributions to Dioxin-like Contaminants

Despite the growing interest in PCNs and the dioxin-like toxicity exhibited by a number of congeners, a comprehensive assessment of their contribution to the cocktail of dioxin-like contaminants is still lacking. To address such a shortcoming, this study investigated the PCN contamination in foodstuffs recently acquired in France, together with that of the regulatory polychlorinated dibenzodioxins/furans (PCDD/Fs) and polychlorinated biphenyls (PCBs). PCNs were ubiquitous at levels (∑70 PCNs = 2.5-150 pg g-1 wet weight) similar to those reported in other countries, with maximum concentrations observed in fish and fishery products from the North-East Atlantic Ocean. Their congener patterns further suggested unintentional releases of PCNs, while those of the other foodstuffs were correlated to the historical PCN profiles. Low risk from dietary exposure was estimated (∑70 PCNs-EDIs of 60-360 pg kg-1 bw d-1, ∑24 PCNs-TEQ-EDIs of 8 × 10-3-2.2 × 10-2 pg TEQ kg-1 bw d-1), with milk and dairy products being the highest contributors, followed by meat and meat products. Finally, the rather high contributions of PCNs to the total PCNs+PCDD/Fs+PCBs concentrations (0.9-50%, average of 9%) and the toxic equivalents (0.2-24%, average of 5%) show that these substances are not minor components of the PCNs+PCDD/Fs+PCBs cocktail.

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.

Novel biomonitoring method for determining five classes of legacy and alternative flame retardants in human serum samples

Flame retardants (FRs) are ubiquitous in environment and biota and may pose harm to human health. In recent years, concern regarding legacy and alternative FRs has been intensified due to their widespread production and increasing contamination in environmental and human matrices. In this study, we developed and validated a novel analytical method for simultaneous determination of legacy and alternative FRs, including polychlorinated naphthalenes (PCNs), short- and middle-chain chlorinated paraffins (SCCPs and MCCPs), novel brominated flame retardants (NBFRs), and organophosphate esters (OPEs) in human serum. Serum samples were prepared by liquid-liquid extraction using ethyl acetate, and purified with Oasis® HLB cartridge and Florisil-silica gel columns. Instrumental analyses were carried out using gas chromatography-triple quadrupole mass spectrometry, high-resolution gas chromatography coupled with high-resolution mass spectrometry, and gas chromatography coupled with quadrupole time-of-flight mass spectrometry, respectively. The proposed method was validated for linearity, sensitivity, precision, accuracy, and matrix effects. Method detection limits for NBFRs, OPEs, PCNs, SCCPs, and MCCPs were 4.6 × 10^-4-8.6 × 10^-2, 4.3 × 10^-3-1.3, 1.1 × 10^-5-1.0 × 10^-4, 1.5, and 9.0 × 10^-1 ng/mL, respectively. Matrix spike recoveries ranged from 73%-122%, 71%-124%, 75%-129%, 92%-126%, and 94%-126% for NBFRs, OPEs, PCNs, SCCPs, and MCCPs, respectively. The analytical method was applied for detection of real human serum. CPs were the dominant FRs in serum, indicating CPs were widely presented in human serum and should be pay more attention for their health risk.

Spatial and temporal trends of polychlorinated naphthalenes in the Arctic atmosphere at Ny-Ålesund and London Island, Svalbard

Polychlorinated naphthalenes (PCNs) are ubiquitous atmospheric pollutants that can even be found in the most remote region of the Arctic. However, temporal trend analysis and reports on mono- to octa-CN in the Arctic air are still scarce. In the present study, 8 years of atmospheric monitoring data of PCNs on Svalbard was investigated using XAD-2 resin passive air samplers (PASs) from 2011-2019. The concentrations of ∑₇₅ PCNs in the Arctic air ranged from 4.56 to 85.2 pg/m³, with a mean of 23.5 pg/m³. The mono-CNs and di-CNs were the dominant homologue groups accounting for 80 % of the total concentrations. The most abundant congeners were PCN-1, PCN-2, PCN-24/14, PCN-5/7, and PCN-3, respectively. A declining time trend of PCN concentration was observed from 2013 to 2019. The reduction in PCN concentrations is likely due to declining global emissions and banned production. However, no significant spatial difference was observed among the sampling sites. The total PCN toxic equivalency (TEQ) concentrations in the Arctic atmosphere ranged from 0.043 to 1.93 fg TEQ/m³ (mean 0.41 fg TEQ/m³). The fraction of combustion-related congeners to ∑PCNs (tri- to octa-CN) analysis results indicated that the sources of PCNs in the Arctic air were contributed mainly from reemissions of historical Halowax mixtures and combustion-related sources. To the best of our knowledge, this is the first research to report all 75 PCN congeners and homologue groups in Arctic air. Therefore, this study provides data on recent temporal trend analysis as well as all the 75 PCN congeners in the Arctic atmosphere.

Health risk assessment to polychlorinated naphthalenes dioxin-like compounds in French sea food consumers

There has been a recent revival of interest in some historical contaminants such as polychlorinated naphthalenes (PCNs). However, occurrence data are still lacking in some countries although industrial production of PCNs has been reported. This observation led to the first ever assessment of their presence in fish and seafood products in France in the present work. Their analysis was integrated in an already validated method applied for polychlorinated dibenzodioxins/furans (PCDD/Fs) and polychlorinated biphenyls (PCBs), based on the structural similarity existing between these POPs. Performances of the method (LODs in the range 0.10-0.28 pg g^-1 wet weight (ww), LOQs in the range 0.33-0.93 pg g^-1 ww), enabled monitoring 69 di-to octachlorinated congeners in a large representative set of fish and seafood samples collected in 2005 in four coastal areas of the French mainland (n > 30). Their systematic presence was demonstrated in all the investigated seafood products, with levels (ΣPCNs in the range 2-440 pg g^-1 wet weight) close to those already reported in other European fish and seafood sampled at a similar period. In addition, the robust measurement of almost all possible PCNs (69/75) allowed a fine interpretation of the observed profiles, highlighting in particular the specificities between species and fishing areas. Compared to the PCDD/Fs, PCBs, and polybrominated diphenylethers levels also measured for this set of samples, PCNs were observed as minor contributors to total concentrations (0.05-3.2%). The specific PCN related dietary dioxin-like exposure could be evaluated at 0.028-0.051 pg of toxic equivalent (TEQ) per kg of body weight per week for an adult, based on fish and seafood consumption only. Overall, this study provides the first baseline data on the occurrence of a large number of PCNs in France, which will allow future evaluation of temporal trends and associated risks.

The toxicological profile of polychlorinated naphthalenes (PCNs)

The legacy of polychlorinated naphthalenes (PCNs) manufactured during the last century continues to persist in the environment, food and humans. Metrological advances have improved characterisation of these occurrences, enabling studies on the effects of exposure to focus on congener groups and individual PCNs. Liver and adipose tissue show the highest retention but significant levels of PCNs are also retained by the brain and nervous system. Molecular configuration appears to influence tissue disposition as well as retention, favouring the higher chlorinated (≥ four chlorines) PCNs while most lower chlorinated molecules readily undergo hydroxylation and excretion through the renal system. Exposure to PCNs reportedly provokes a wide spectrum of adverse effects that range from hepatotoxicity, neurotoxicity and immune response suppression along with endocrine disruption leading to reproductive disorders and embryotoxicity. A number of PCNs, particularly hexachloronaphthalene congeners, elicit AhR mediated responses that are similar to, and occur within similar potency ranges as most dioxin-like polychlorinated biphenyls (PCBs) and some chlorinated dibenzo-p-dioxins and furans (PCDD/Fs), suggesting a relationship based on molecular size and configuration between these contaminants. Most toxicological responses generally appear to be associated with higher chlorinated PCNs. The most profound effects such as serious and sometimes fatal liver disease, chloracne, and wasting syndrome resulted either from earlier episodes of occupational exposure in humans or from acute experimental dosing of animals at levels that reflected these exposures. However, since the restriction of manufacture and controls on inadvertent production (during combustion processes), the principal route of human and animal exposure is likely to be dietary intake. Therefore, further investigations should include the effects of chronic lower level intake of higher chlorinated PCN congeners that persist in the human diet and subsequently in human and animal tissues. PCNs in the diet should be evaluated cumulatively with other similarly occurring dioxin-like contaminants.

Comprehensive Evaluation of Dietary Exposure and Health Risk of Polychlorinated Naphthalenes

Intake from food is considered an important route of human exposure to polychlorinated naphthalenes. To our knowledge, several studies have quantified dietary exposure but only in European countries and measuring only a few of the 75 congeners. In addition, the influence of source diversity on human exposure has seldom been assessed. We analyzed 192 composite food samples composed of 17,280 subsamples from 24 provinces in China to measure the concentrations of polychlorinated naphthalenes and estimate their daily intake and potential health risks on a national scale. The estimated cancer risk was in the range of 6.8 × 10^-8 to 4.6 × 10^-7. We compared our findings for 75 congeners with reports in the literature that quantified only 12 congeners. We estimate that these 12 congeners contribute only approximately 4% to the total mass daily intake of polychlorinated naphthalenes and 70% to the total toxic equivalent quantity, indicating underestimation of dietary exposure. The contributions of combustion-associated congeners to the total concentrations of polychlorinated naphthalenes were in the range of 31-52%, suggesting that the ongoing unintentional release of these compounds from industrial thermal processes is an important factor in polychlorinated naphthalene contamination and human exposure in China.

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.

Insights into the Formation and Profile of Chlorinated Polycyclic Aromatic Hydrocarbons during Chlorobenzene and Chloroethylene Manufacturing Processes

Chlorinated polycyclic aromatic hydrocarbons including chlorinated naphthalenes and congeners with three to five rings are ubiquitous atmospheric pollutants. Congener profiles and formation mechanisms from typical chemical manufacturing have not been researched extensively. We measured the concentrations of 75 chlorinated naphthalenes and 18 chlorinated polycyclic aromatic hydrocarbons in raw materials, intermediates, products, and bottom residues from chemical plants producing monochlorobenzene and chloroethylene by different techniques. The findings confirmed that these chemical manufacturing processes are newly identified sources of atmospheric emissions of these compounds. More-chlorinated naphthalenes were formed from chloroethylene production than from monochlorobenzene production, which could be explained by the higher temperatures in the former process. Successive chlorination appeared to be an important formation pathway of polychlorinated naphthalenes according to their congener profiles and was supported by quantum chemical calculations of electrophilic chlorination on various positions of naphthalene. Chlorinated polycyclic aromatic hydrocarbons were more likely to be formed during the production of monochlorobenzene than chloroethylene. Moreover, we suggested that ring rearrangement and ring coupling are important transformation reactions between polychlorinated naphthalenes and chlorinated polycyclic aromatic hydrocarbons.

Distributions of Polychlorinated Naphthalenes in Sediments of the Yangtze River, China

The pollution status of polychlorinated naphthalenes (PCNs) in the sediment of the Yangtze River Basin, Asia's largest river basin, was estimated. The total concentrations of PCNs (mono- to octa-CNs) ranged from 0.103 to 1.631 ng/g. Mono-, di-, and tri-PCNs-consisting of CN-1, CN-5/7, and CN-24/14, respectively, as the main congeners-were the dominant homolog groups. Combustion indicators and principal component analysis showed that the emissions from halowax mixtures were the main contributor to PCNs in sediment, among most of the sampling sites. The mean total toxic equivalent (TEQ) was calculated to be 0.045 ± 0.077 pg TEQ/g, which indicates that the PCNs in sediments were of low toxicity to aquatic organisms. This work will expand the database on the distribution and characteristics of PCNs in the river sediment of China.

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.

Polychlorinated Naphthalenes across the Great Lakes: Lake Trout and Walleye Concentrations, Trends, and TEQ Assessment-2004-2018

Polychlorinated naphthalenes (PCNs) were measured in lake trout and walleye over the period 2004-2018, utilizing isotope dilution techniques with high-resolution gas chromatography/high-resolution mass spectrometry to assess concentrations and toxic equivalence (TEQ). An age-trend model was applied to mitigate the effect of a changing lake trout age structure. Most Great Lakes Fish Monitoring and Surveillance Program sampling sites demonstrated significant half-life and percent decreases for lake trout total PCNs and total TEQ over the 2004-2018 period, the exceptions being Lake Erie lake trout and walleye which illustrated increasing concentrations. Great Lakes total PCN concentrations ranged between 5701 and 100 pg/g ww, whereas total PCN TEQ concentrations ranged between 8.89 and 0.13 pg-TEQ/g ww. Based on the average number of chlorines per naphthalene, we determined that the overall lake trout and walleye PCN congener distribution has significantly shifted to a lower-chlorinated composition in the Great Lakes (5.33 to 4.48 Cl/CN) and has resulted in a substantial 59.1% reduction of the overall total PCN TEQ burden. A prominent PCN concentration trend breakpoint was observed in Lake Ontario lake trout over the 2012-2016 period likely associated with hazardous waste cleanups, channel dredging, and spoils disposal in the Detroit River and western-basin of Lake Erie.

Bridging the Energy Benefit and POPs Emission Risk from Waste Incineration

Incineration has been the globally controversial and concerned method of solid waste disposal. Energy recovery and volume reduction are the benefits from waste incineration, but risk due to release of persistent organic pollutants is the major public concern in the world. In this study, the emission of organic pollutants including dioxins and polychlorinated naphthalenes from solid waste incineration in China was comprehensively evaluated, and a relationship between energy benefit and pollutant emission was firstly established. The results show that production of medical and industrial waste was smaller than that of municipal waste but yielded comparable or even higher emission of dioxins. The energy benefit-to-emission index for organic pollutants (EBEI_OP) for evaluation of solid waste management on a local or regional scale was proposed. Significant correlations between net energy benefit and pollutant emission for provinces with higher EBEI_OP values were found. Furthermore, higher EBEI_OP values were associated with economic factors while lower values were influenced by emission from incineration of medical and industrial waste. We suggest that an EBEI_OP value of ≥60 can serve as a reference for “profitable” solid waste management, assisting decision making during energy benefit and environmental risk assessment.

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Emission of trace organic pollutants from solid waste incineration in China was comprehensively evaluated.

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The energy benefit-to-emission index for organic pollutants (EBEI_OP) for evaluation of solid waste management on a local or regional scale was proposed.

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Production of medical and industrial waste was smaller than that of municipal waste but yielded comparable or even higher emission of dioxins.

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Higher EBEI_OP values were associated with economic factors, while lower values were influenced by emissions from incineration of medical and industrial waste.

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An EBEI_OP value of ≥60 can serve as a reference for “profitable” solid waste management, assisting decision making during energy benefit and environmental risk assessment.

Hexachloronaphthalene Induces Mitochondrial-Dependent Neurotoxicity via a Mechanism of Enhanced Production of Reactive Oxygen Species

Hexachloronaphthalene (PCN67) is one of the most toxic among polychlorinated naphthalenes. Despite the known high bioaccumulation and persistence of PCN67 in the environment, it is still unclear to what extent exposure to these substances may interfere with normal neuronal physiology and lead to neurotoxicity. Therefore, the primary goal of this study was to assess the effect of PCN67 in neuronal in vitro models. Neuronal death was assessed upon PCN67 treatment using differentiated PC12 cells and primary hippocampal neurons. At 72 h postexposure, cell viability assays showed an IC₅₀ value of 0.35 μg/ml and dose-dependent damage of neurites and concomitant downregulation of neurofilaments L and M. Moreover, we found that younger primary neurons (DIV4) were much more sensitive to PCN67 toxicity than mature cultures (DIV14). Our comprehensive analysis indicated that the application of PCN67 at the IC₅₀ concentration caused necrosis, which was reflected by an increase in LDH release, HMGB1 protein export to the cytosol, nuclear swelling, and loss of homeostatic control of energy balance. The blockage of mitochondrial calcium uniporter partially rescued the cell viability, loss of mitochondrial membrane potential (ΔΨ_m), and the overproduction of reactive oxygen species, suggesting that the underlying mechanism of neurotoxicity involved mitochondrial calcium accumulation. Increased lipid peroxidation as a consequence of oxidative stress was additionally seen for 0.1 μg/ml of PCN67, while this concentration did not affect ΔΨ_m and plasma membrane permeability. Our results show for the first time that neuronal mitochondria act as a target for PCN67 and indicate that exposure to this drug may result in neuron loss via mitochondrial-dependent mechanisms.

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.

Law and mechanism analysis of biodegradability of polychlorinated naphthalenes based on principal component analysis, QSAR models, molecular docking and molecular dynamics simulation

The quantization parameters, infrared and Raman spectra of 75 polychlorinated naphthalenes (PCNs) and 42 environmentally friendly CN-56 (CN-56: No. 56 PCN molecule; 1, 2, 3, 7, 8-PentaCN) molecules that are easier to degrade were first calculated via the density functional theory (DFT) method, and the structural characteristics of the molecules were analysed to obtain the substituent characteristics. The principal component analysis method was used to systematically analyse and summarize the effects of macroscopic substituent characteristics, microscopic quantitative parameters and spectral information on the biodegradability of PCNs and 42 environmentally friendly CN-56 molecules, and then the quantitative structure-activity relationship (QSAR), molecular docking and molecular dynamics simulation methods were used to further investigate the biodegradation mechanism from the perspective of molecules and protein receptors. The results showed that PCNs and new PCNs extracted 5 and 6 principal components from 21 kinds of original parameter indicators, respectively, which can effectively explain the original variable information. Besides that, electrostatic activity is the primary factor affecting the degradation of PCNs; reducing the para-substitution logarithm or increasing the total number of substituents and introducing electrostatic groups in the ortho or meta position of PCN molecules can design new PCN derivatives with higher degradability; enhancing the irradiation of Raman light or reducing the irradiation of infrared light properly can increase the biodegradation rate of PCN molecules.

Inventory of Polychlorinated Naphthalene Emissions from Waste Incineration and Metallurgical Sources in China

Polychlorinated naphthalenes (PCNs) are highly toxic persistent organic pollutants (POPs) that are a relatively new addition to the Stockholm Convention as of 2015. The levels of unintentional emissions of PCNs from important industrial thermal sources on national scales are unclear but are important for understanding potential human exposure. In this study, an inventory was compiled of PCN emissions from priority industrial sources of unintentional POPs in China. Estimated emissions from four typical POP sources in the reference year (2014) in China were 511.6 kg by mass and 7650.8 mg of toxic equivalent. Waste incineration, secondary nonferrous smelting, electric arc furnace steelmaking, and iron ore sintering plants contributed 38.8, 15.4, 29.2, and 16.6%, respectively, to the total emissions. The Eastern Seaboard of China and the Hebei region in North China, which have intensive industrial activity and high population densities, were dominant contributors of PCNs. Only 18.6% of the counties where waste incineration plants were located emitted PCNs at a level higher than 1.00 × 10^-1 mg of toxic equivalent, whereas 80% of the counties where metallurgical plants were located emitted PCNs at this level. These results indicate effective implementation of POP control in the waste incineration industry in China. This study clarifies the unintentionally emission levels of PCNs in China and provides important information for strategy development to control source emissions.

Fuzzy risk assessment of modified polychlorinated naphthalenes for enhanced degradation

The three-dimensional quantitative structure-activity relationship (3D-QSAR) model is established for polychlorinated naphthalenes (PCNs) using the biological degradability (total score) results to modify CN-56 to design 37 new derivatives with higher degradability (increased by 14.55-38.79%). Furthermore, five new CN-56 derivatives are selected through evaluation of their persistent organic pollutant properties (toxicity, bioconcentration, long-range transport) and practicability (stability, insulativity, flame retardancy) using 3D-QSAR, density functional theory (DFT) and molecular docking methods. Environmental and health-based risk assessments are conducted using the multimedia fugacity model and fuzzy theory for complete screening of the new CN-56 derivatives. Whereas CN-56 is classed as high risk, three new derivatives can be classed as medium risk. The biodegradability mechanism analysis of the PCNs indicates that the electrostatic property is the main factor that affects the degradability, which provides a favorable theoretical reference to obtain environmentally friendly fire retardant and insulating materials.

The occurrence and distribution of polychlorinated naphthalenes (PCNs), focusing on tissue-specific bioaccumulation in crucian carp in South Korea

The occurrence and distribution of 41 congeners of polychlorinated naphthalenes (PCNs) were investigated in major tissues of crucian carp (muscle, gonad, liver, and blood) and in river sediment to assess the bioaccumulation potential of PCNs. The total PCN concentrations in sediment ranged from 4.37 to 19.5 pg/g dry weight (dw), mainly comprising CN-13, CN-33/34/37, and CN-38/40. Among fish tissues, higher PCN concentrations were observed in the gonads (29.6 ± 10.3 pg/g wet weight, ww) and liver (25.7 ± 4.35 pg/g ww) of crucian carp than in the muscle (2.17 ± 0.68 pg/g ww). CN-28/43, CN-33/34/37, CN-42, CN-52/60, CN-53/55, and CN-66/67 congeners were detected most frequently and had the highest concentration among all crucian carp tissues. We investigated the association between the PCN concentration in each tissue (muscle, liver, and gonad) and the size of the fish (total length and weight) and found positive correlations between the PCN concentration in the gonads and the total length and weight (p < 0.05, Spearman correlation).

Concentrations of POPs based wood preservatives in waste timber from demolished buildings and its recycled products in Japan

One of the major proportions of recycled persistent organic pollutants (POPs)-containing waste is timber originating from old buildings, utility poles, and cross-arms because POPs-based treatments were once a common means of preserving wood. In 2016 and 2017, we conducted the first survey in Japan on the residue concentrations of chlordanes (CHLs), pentachlorophenol (PCP), pentachloroanisole (PCA), and polychloronaphthalenes (PCNs) in waste timber (n = 55) and its recycled products (woodchip, n = 42; particle board, n = 3). In the recycled products, the highest concentrations detected were 0.86 mg kg^-1 CHLs, 3.0 mg kg^-1 PCP, 1.1 mg kg^-1 PCA, and 2.6 mg kg^-1 PCNs, which were one to two orders lower than the low POP content (LPC) limits for the environmentally sound management of wastes defined under the Basel Convention (50, 100, and 10 mg kg^-1, respectively). In the waste timber, which included bearers and columns from demolished buildings, the highest concentrations were 15 mg kg^-1 CHLs, 0.20 mg kg^-1 PCP, and 0.036 mg kg^-1 PCNs, no higher than about 30% of the LPC limit. The concentration of CHLs in timber bearer was significantly higher than those in timber column (p < 0.05). Although none of the waste timber or recycled products had concentrations exceeding the LPC limits, one means of ensuring low POP concentrations in recycled products is separating timber bearer from timber column when demolishing wooden buildings, according to the results in Japan. The timber column can be used to produce recycled products and the remaining timber can be used for heat utilization and power generation.

Environmentally friendly polychlorinated naphthalenes (PCNs) derivatives designed using 3D-QSAR and screened using molecular docking, density functional theory and health-based risk assessment

A complete design and screening system for environmental-friendly polychlorinated naphthalene (PCN) derivatives was established through three-dimensional quantitative structure-activity relationship (3D-QSAR), molecular docking, density functional theory (DFT) methods and health-based risk assessment based on dynamic multimedia fugacity model. Two types of 3D-QSAR models were established for PCNs using the experimental biological toxicity (logEC₅₀) of 14 PCNs to carry out a modification to lower the logEC₅₀ of CN-70. Consequently, 67 new monosubstituted and disubstituted derivatives with a lower biological toxicity than CN-70 were designed. Furthermore, 21 new CN-70 derivatives were selected through the evaluation of their persistent organic pollutant properties (biological toxicity, bio-concentration, long-range transport potential, biodegradability) and practicability (stability, insulativity, flame retardancy) using 3D-QSAR, molecular docking and DFT methods. Finally, the non-carcinogenic and carcinogenic risks of 19 new CN-70 derivatives in different exposure pathways were reduced, and 5 derivatives with a significant decrease both in biological toxicity (amplitude reduction: 12.73%-32.51%) and risk (amplitude reduction: 32.18%-59.19%) were selected as environmental-friendly PCN derivatives, which had been screened using the health-based risk assessment system associated with dynamic multimedia fugacity model. This study provides a theoretical basis for the design of environmental-friendly flame retardants and insulating materials.

Thermal destruction of wastes containing polychlorinated naphthalenes in an industrial waste incinerator

A series of verification tests were carried out in order to confirm that polychlorinated naphthalenes (PCNs) contained in synthetic rubber products (Neoprene FB products) and aerosol adhesives, which were accidentally imported into Japan, could be thermally destroyed using an industrial waste incinerator. In the verification tests, Neoprene FB products containing PCNs at a concentration of 2800 mg/kg were added to industrial wastes at a ratio of 600 mg Neoprene FB product/kg-waste, and then incinerated at an average temperature of 985 °C. Total PCN concentrations were 14 ng/m³N in stack gas, 5.7 ng/g in bottom ash, 0.98 ng/g in boiler dust, and 1.2 ng/g in fly ash. Destruction efficiency (DE) and destruction removal efficiency (DRE) of congener No. 38/40, which is considered an input marker congener, were 99.9974 and 99.9995 %, respectively. The following dioxin concentrations were found: 0.11 ng-TEQ/m³N for the stack gas, 0.096 ng-TEQ/g for the bottom ash, 0.010 ng-TEQ/g for the boiler dust, and 0.072 ng-TEQ/g for the fly ash. Since the PCN levels in the PCN destruction test were even at slightly lower concentrations than in the baseline test without PCN addition, the detected PCNs are to a large degree unintentionally produced PCNs and does not mainly stem from input material. Also, the dioxin levels did not change. From these results, we confirmed that PCNs contained in Neoprene FB products and aerosol adhesives could be destroyed to a high degree by high-temperature incineration. Therefore, all recalled Neoprene FB products and aerosol adhesives containing PCNs were successfully treated under the same conditions as the verification tests.

Legacy of legacies: Chlorinated naphthalenes in Lake Trout, Walleye, Herring Gull eggs and sediments from the Laurentian Great Lakes indicate possible resuspension during contaminated sediment remediation

Polychlorinated naphthalenes (PCNs) are legacy contaminants, produced primarily as flame retardants and dielectrics until phased-out in Europe and North America in the 1970s. Spatial and temporal trends (1979-2013) of PCN concentrations were studied in whole fish and herring gull eggs throughout the Great Lakes and St. Lawrence River, whereas sediments were analyzed for 2011-2013 only. For both fish and gull eggs, concentrations of PCNs were highest in western Lake Erie (7660 & 3020pg/gww respectively), and declined downstream to St. Lawrence River (range: 34-2370pg/gww). For sediments, concentrations were highest in suspended sediments from the Detroit River (264,000pg/g), and were lower in surficial sediments downstream to the St. Lawrence River (range=440-19,300pg/g). PCNs declined at all sites from ~1980 to 1995, but in Lake Erie concentrations of PCNs increased in gulls fish from 1995 until 2005. The resurgence in PCNs in biota corresponded to the timing of remedial dredging of sediment highly contaminated with PCNs in the Detroit River, whose effects appear to manifest themselves downstream to Lake Ontario. Congener profiles of PCNs differed between Lake Erie and Lake Ontario until post-dredging, where PCN profiles of fish in both lakes became increasingly more similar. PCNs in gull eggs were mostly hepta-PCNs, whereas fish had higher concentrations of lower chlorinated PCNs. Patterns of PCNs in gulls and fish appear to be influenced by differences in not only routes of exposure and differential metabolic ability, but also resuspension of PCN contaminated sediments.

First report of bioaccumulation and bioconcentration of aliphatic hydrocarbons (AHs) and persistent organic pollutants (PAHs, PCBs and PCNs) and their effects on alcyonacea and scleractinian corals and their endosymbiotic algae from the Persian Gulf, Iran: Inter and intra-species differences

The coral reefs of the Persian Gulf are the most diverse systems of life in the marine environment of the Middle East. Unfortunately, they are highly threatened by local and global stressors, particularly oil pollutants. This is the first quantitative and qualitative study aimed at assessing the concentration and sources of n-alkanes and POPs (PAHs, PCBs and PCNs) in coral tissues, symbiotic algae (zooxanthellae), reef sediments and seawaters in coral reefs of Lark and Kharg in the Persian Gulf, Iran. This work was conducted on eight species of six genera and three families of hard corals and one family of soft coral. A significant variation in the concentration of ∑30n-alkanes and POPs (∑40PAHs, ∑22PCBs and 20PCNs) was found in the decreasing order: zooxanthellae > coral tissue > skeleton > reef sediment > seawater. The bioaccumulation of these compounds was 2-times higher in ahermatypic than in hermatypic corals, among which significant variations were observed in both sites. In Kharg, Porites lutea had the highest mean concentration of ∑30n-alkanes and ∑40PAHs in soft tissue, whereas the lowest values were in Platygyra daedalea. A contrasting trend was documented for ∑22PCBs and 20PCNs, with the highest level reported in soft tissue of P. daedalea and the lowest in P. lutea at Kharg. Compositional pattern of AHs and PAHs demonstrated the predominance of LMW-PAHs and n-alkanes. In skeleton and reef sediments, tetra, penta and tri-CBs were the most abundant PCBs congeners followed by di-CB > hexa-CB > hepta-CB > octa-CB,whiletri-CB > di-CB > tetra-CB > penta-CB > hexa-CB > hepta-CB > octa-CB was observed for soft tissue, zooxanthellae and seawater. The results of RAD test indicated significantly negative correlation between total concentration of these compounds with zooxanthellae density, the chlorophyll-a and C₂ in corals at both reefs. This is the first report on levels, health assessment and source apportionments of POPs in zooxanthellae and a first step in the implementation of specific coral reef management measures.

Levels, patterns, trends and significance of polychlorinated naphthalenes (PCNs) in Great Lakes fish

Polychlorinated naphthalenes (PCNs) were introduced to market about a century ago and their production is thought to have ceased by the early 1980s. However, relatively limited knowledge exists on their abundance in the edible portion of a variety of Great Lakes fish to aid in understanding their potential risk to human consumers. We studied levels, patterns, trends and significance of PCNs in a total 470 fillet samples of 18 fish species collected from the Canadian waters of the Great Lakes between 2006 and 2013. A limited comparison of fillet and wholebody concentrations in Carp and Bullhead was also conducted. The ∑PCN ranged from 0.006-6.7ng/g wet weight (ww) and 0.15-190ng/g lipid weight (lw) with the dominant congeners being PCN-52/60 (34%), -42 (21%) and -66/67 (15%). The concentrations spatially varied in the order of the Detroit River>Lakes Erie>Ontario>Huron>Superior. PCN-66/67 was the dominating congener contributing on average 76-80% of toxic equivalent concentration (TEQ_PCN). Contribution of TEQ_PCN to TEQ_Total (TEQ_{Dioxins+Furans+dioxin-likePCBs+PCNs}) was mostly <15%, especially at higher TEQ_Total, and PCB-126 remains the major congener contributing to TEQ_Total. The congener pattern suggests that impurities in PCB formulations and thereby historical PCB contamination, instead of unintentional releases from industrial thermal processes, could be an important source of PCNs in Great Lakes fish. A limited temporal change analysis indicated declines in the levels of PCN-66/67 between 2006 and 2012, complemented by previously reported decrease in PCNs in Lake Ontario Lake Trout between 1979 and 2004. The whole body concentrations were 1.4-3.2 fold higher than the corresponding fillets of Carp and Bullhead. Overall, the study results suggest that only targeted monitoring of PCNs in Great Lakes fish, especially at the Detroit River, Lake Erie and Lake Ontario, is necessary to assess continued future improvements of this group of contaminants of concern.

Polychlorinated naphthalenes (PCNs) in seafood: Estimation of dietary intake in Korean population

Polychlorinated naphthalenes (PCNs) were measured in 33 seafood species including fish, mollusks and crustaceans purchased from local markets in five Korean cities between 2012 and 2013. Five samples were collected from each species for the measurements. Thirty-seven PCN congeners from tetra-CN to octa-CN were measured. Octa-CN (octachloronaphthalene) was not detected in any of the samples. Tetra-CN and penta-CN were the predominant homologues of PCNs in seafood samples with PCN 51 and PCN 52/60 being the most abundant congeners in the samples. Total PCNs concentrations and their corresponding dioxin-like toxic equivalent (TEQ) values ranged from non-detection (ND) to 110pg/g on a wet weight (ww) basis and from ND to 0.14pg-TEQ/g ww, respectively. The estimated daily intake of total PCNs based on an absolute content and TEQ potency were estimated for the Koreans to be 570pg/day and 0.44pg-TEQ/day, respectively. However, the estimated TEQ value of PCNs intake from seafood, represented only a small fraction (3.0%) of the total TEQ intake from consumption of seafood in Korean population. This is the first report to exhibit the presence of PCNs in seafood samples collected from local markets in Korea and their intake by general population.

Concentrations and trophic magnification of polychlorinated naphthalenes (PCNs) in marine fish from the Bohai coastal area, China

Polychlorinated naphthalenes (PCNs) have been found widely in the aquatic environment and can be transferred through food chains, which can magnify or dilute their toxic effects on humans. In this study, PCNs were analyzed in samples of 17 species of fish with different dietary habits collected in the Bohai coastal area in China. Dichloronaphthalenes, which have rarely been quantified in previous studies, were determined. The total PCN concentrations were from 7.3 to 214 pg/g wet weight, and the highest concentration was found in ditrema. The trichloronaphthalenes were the most abundant PCNs, followed by the dichloronaphthalenes and pentachloronaphthalenes. The relatively high contributions of the less-chlorinated homologs to the total PCN concentrations indicated that the main PCN sources around the Bohai were industrial thermal process emissions rather than technical PCN formulations. The trophic magnification factors of the PCN homologs were from 3.1 to 9.9, indicating that PCNs were biomagnified by fish. The trophic magnification factor of dichloronaphthalene and trichloronaphthalenes was 5.8 and 6.4, respectively, indicating for the first time that dichloronaphthalene and trichloronaphthalenes can undergo trophic magnification by fish. The two highest trophic magnification factors were for the pentachloronaphthalenes and hexachloronaphthalenes, probably because these PCNs having fewer vicinal carbon atoms without chlorine atoms attached are less easily biotransformed than the other homologs. The dioxin-like toxicities of the PCNs in the samples, expressed as potential toxic equivalences (TEQs), were assessed. The highest total TEQ was 0.0090 pg/g ww, in Pacific herring, and the hexachloronaphthalenes were the dominant contributors to the total TEQs in the fish samples. The PCN TEQs were much lower than the polychlorinated dibenzo-p-dioxin and dibenzofuran and dioxin-like polychlorinated biphenyl TEQs found in fish from the Bohai in previous studies, and made marginal contributions to overall human exposure to dioxin-like TEQs, suggesting that PCNs pose no toxicological concerns.

Acute toxicity of polychlorinated naphthalenes and their effect on cytochrome P450

Polychlorinated naphthalenes (PCNs) are able to induce cytochrome P-450-dependent microsomal monooxygenase activities in vivo and in vitro. The aim of this study was to investigate the toxicity of a PCN mixture, and its effect on the levels of cytochrome P-450 in rats.

The animals were intragastrically administered a mixture of PCNs in single doses of 250, 500 and 1000 mg/kg b.w. Dissection of animals was performed 24, 72 and 240 hours after administration.

After PCN administration (all doses) the body weight loss (up to 30% in comparison with the control group, 240 hours after administration) and an increase of relative liver mass (about 126 - 153% of controls, 72 hours after administration) were observed.

The exposure to PCN evoked an increase in the level of total cytochrome P-450 as well as the activity of CYP 1A (mediated 7-ethoxyresorufin O-deethylation) at all time points. The maximum activity of CYP 1A (about 12-to 15-fold increase in comparison with the control group) was observed 72 hours after dosing.

Malondialdehyde (MDA), determined in the liver, showed a high increase and 240 hours after administration, the level of MDA was about one order of magnitude greater in comparison with control.

Developmental toxicity of hexachloronaphthalene in Wistar rats. A role of CYP1A1 expression

Hexachloronaphthalene (HxCN) is one of the most toxic congeners of polychlorinated naphthalenes (PCNs). This study assesses the prenatal toxicity of HxCN after daily administration at doses of 0.1-1.0mg/kg b.w. to pregnant Wistar rats during organogenesis. We evaluated also the expression of CYP1A1 mRNA and protein in the livers of dams and fetuses, as well as the placenta. The results indicate that 0.3mg/kg b.w. was the lowest HxCN toxic dose for dams (LOAEL) while a dose of 0.1mg/kg b.w. was sufficient to impair the intrauterine development of embryos/fetuses without maternal toxicity. Regardless of the applied dose, HxCN generated embryotoxic effects. Dose-dependent fetotoxic effects were associated with HxCN exposure. HxCN was found to be a strong inducer of maternal and fetal CYP1A1. Expression of CYP1A1 mRNA in the placenta appears to be the most sensitive marker of HxCN exposure.

Role of hydrogen abstraction acetylene addition mechanisms in the formation of chlorinated naphthalenes. 1. A quantum chemical investigation

The addition of chloroacetylene or tetrachlorovinylacetylene to 2,4,5-trichlorophenyl radicals, leading to the formation of tetra-, penta-, and hexachloronaphthalene congeners, has been explored at the M06-2X/6-311+G(3df,3p)//B3LYP/6-31G(d) level of theory. The accuracy of this method was justified by comparing the barriers of several pertinent reactions against energies from single point calculations at the B3LYP/cc-pVDZ, CCSD(T)/6-31G(d), and G2MS levels. Bittner-Howard and Frenklach hydrogen abstraction acetylene addition mechanisms were developed, as was a channel based on acetylene additions to chlorinated [4.2.0]octa-1,3,5-trien-7-yl congeners. While the latter channel exhibits relatively high C2HCl addition barriers and may be a minor growth channel at best, both the Bittner-Howard and Frenklach sequences appear facile. In all mechanisms, the additions of C2HCl leading to a β-chlorinated adduct is favored by ∼15 kJ mol(-1) relative to the α-chlorinated analogue, and the addition products typically access a variety of facile cyclization channels. The α-chlorinated product of C2HCl addition to 2,4,5-trichlorophenyl, however, undergoes a particularly rapid Cl-loss leading to 1-ethynyl-2,4,5-trichlorobenzene, effectively shutting down further growth. Generalization implies that α-chlorinated C6H5-CH═CH congeners do not participate in growth reactions. Addition of 2,4,5-trichlorophenyl to the C≡C bond of tetrachlorovinylacetylene and subsequent cyclization is found to be a facile route to hexachloronaphthalene formation and may be operative in fully chlorinated systems where the C6Cl5-CCl═CCl congeners cannot participate in the major growth processes.

Role of hydrogen abstraction acetylene addition mechanisms in the formation of chlorinated naphthalenes. 2. Kinetic modeling and the detailed mechanism of ring closure

The dominant formation mechanisms of chlorinated phenylacetylenes, naphthalenes, and phenylvinylacetylenes in relatively low pressure and temperature (∼40 Torr and 1000 K) pyrolysis systems are explored. Mechanism elucidation is achieved through a combination of theoretical and experimental techniques, the former employing a novel simplification of kinetic modeling which utilizes rate constants in a probabilistic framework. Contemporary formation schemes of the compounds of interest generally require successive additions of acetylene to phenyl radicals. As such, infrared laser powered homogeneous pyrolyses of dichloro- or trichloroethylene were perturbed with 1,2,4- or 1,2,3-trichlorobenzene. The resulting changes in product identities were compared with the major products expected from conventional pathways, aided by the results of our previous computational work. This analysis suggests that a Bittner-Howard growth mechanism, with a novel amendment to the conventional scheme made just prior to ring closure, describes the major products well. Expected products from a number of other potentially operative channels are shown to be incongruent with experiment, further supporting the role of Bittner-Howard channels as the unique pathway to naphthalene growth. A simple quantitative analysis which performs very well is achieved by considering the reaction scheme as a probability tree, with relative rate constants being cast as branching probabilities. This analysis describes all chlorinated phenylacetylene, naphthalene, and phenylvinylacetylene congeners. The scheme is then tested in a more general system, i.e., not enforcing a hydrogen abstraction/acetylene addition mechanism, by pyrolyzing mixtures of di- and trichloroethylene without the addition of an aromatic precursor. The model indicates that these mechanisms are still likely to be operative.

Experimental and theoretical studies into the formation of C4-C6 products in partially chlorinated hydrocarbon pyrolysis systems: a probabilistic approach to congener-specific yield predictions

This work presents a study of the pyrolytic formation of vinylacetylene and benzene congeners formed from chlorinated hydrocarbon precursors, a complex, multipath polymerization system formed in a monomer-rich environment. (Co-)pyrolyses of dichloro- and trichloroethylene yield a rich array of products, and assuming a single dominant underlying growth mechanism, this (on comparing expected and observed products) allows a number of potentially competing channels to C4 and C6 products to be ruled out. Poor congener/isomer descriptions rule out even-carbon radical routes, and the absence of C3 and C5 products rule out odd-carbon processes. Vinylidenes appear unable to describe the increased reactivity of acetylenes with chlorination noted in our experiments, leaving molecular acetylene dimerization processes and, in C6 systems, the closely related Diels-Alder cyclization as the likely reaction mechanism. The feasibility of these routes is further supported by ab initio calculations. However, some of the most persuasive evidence is provided by congener-specific yield predictions enabled by the construction of a probability tree analogue of kinetic modeling. This approach is relatively quick to construct, provides surprisingly accurate predictions, and may be a very useful tool in screening for important reaction channels in poorly understood congener- or isomer-rich reaction systems.

Gas chromatography-triple quadrupole mass spectrometry for the determination of atmospheric polychlorinated naphthalenes

Atmospheric polychlorinated naphthalenes (PCNs) ranging from mono-CNs to octa-CNs were detected using isotope-dilution gas chromatography coupled with triple quadrupole mass spectrometry (GC-MS/MS). The developed instrumental method was successfully applied to the determination of PCNs in technical products. It was observed that there were significant differences in concentrations, homologue profiles, chlorinated contents and total toxic equivalents (∑TEQs) of PCNs for four Halowax products. Subsequently, the validation of the analytical method was evaluated for the determination of PCNs in air samples in terms of method detection limit (MDL), recovery and matrix effect. The results demonstrated that this method could provide satisfactory sensitivity and adequate selectivity with lower cost. It was conducted to comprehensively evaluate the levels, composition patterns, ∑TEQs, and daily intake exposure of PCNs in indoor and outdoor air samples. Concentrations and ∑TEQs of PCNs in air samples ranged 47.7-832.7 pg m(-3) and 1.31-5.99 fg m(-3), respectively, and the predominant homologues were di- and tri-CNs in the gas phase. The results indicated that this analytical method was useful for the accurate and specific evaluation of dioxin-like toxicity and human exposure levels of PCNs in the atmosphere.

Concentration and distribution of PCNs in ambient soil of a municipal solid waste incinerator

The impact of a typical municipal solid waste incinerator (MSWI) on polychlorinated naphthalene (PCN) concentrations in surrounding soil was studied. We collected 6 stack gas samples from the MSWI and 21 soil samples from sampling sites at distances of between 300 and 1,700 m from the MSWI stack. Total dl-PCN (dioxin-like PCN) concentrations in the stack gas samples ranged from 6898 and 89,032 pg m(-3), with a mean value of 36,241 pg m(-3). The total dl-PCN concentrations in the soil samples ranged from 30.35 to 280.9 pg g(-1), with a mean value of 87.03 and a median value of 70.32 pg g(-1), while the TEQ values were between 7.7 and 130.2 fg TEQ g(-1), with a mean value of 41.12 fg TEQ g(-1) and a median value of 31.52fg TEQ g(-1). The PCN homologue patterns and the results of Principal Component Analysis suggested that the MSWI may be a source of PCNs in the soils. A contour map, created using an ordinary Kriging interpolation technique, showed that a limited area (≤ 1,000 m radius) surrounding the MSWI was influenced by the emissions from the MSWI. Furthermore, an exponential function equation was proposed to quantify the relationship between TEQs of PCNs and the distance from the stack.

Congener specific analysis, spatial distribution and screening-level risk assessment of polychlorinated naphthalenes in water and sediments from two tributaries of the River Chenab, Pakistan

The number of reports regarding PCN screening-levels and ecological risk assessment in environmental compartments is limited. This study presents information on congener specific analysis, distribution pattern of PCN and ecological risk assessment via PCN exposure/contamination through water and sediment from two tributaries of the River Chenab, Pakistan. A total twenty eight samples of water and sediment were collected during Jan, 2013 to June, 2013 to analyze the ∑39PCN congeners. ∑39PCN concentrations ranged between 8.94 and 414 ng g(-1) dw and 178-489 ng l(-1) in sediment and water, respectively. Water exhibited higher TEQ values while in case of sediments TEQ values were at higher than the previously reported data from other parts of the world. This is the first report of PCNs' distribution pattern and screening-level risk assessment from Pakistan. The results of toxicity exposure of PCN warrant auxiliary devotion in future, to this group of contaminant.

Destruction of polychlorinated naphthalenes by a high-temperature melting treatment (GeoMelt process)

A series of treatment experiments were carried out to evaluate the applicability of a high-temperature melting treatment (GeoMelt process) to the destruction of polychlorinated naphthalene (PCN) formulation. We started with 10-kg-scale experiments in which a small melting furnace was used and then scaled up to a 1-t-scale experiment in which a melting furnace that resembled an actual treatment system was used. These runs were evaluated whether destruction efficiency (DE) of total PCNs was more than 99.999% and whether concentrations of PCNs and polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/DFs) in vitrified materials, emission gas, and scrubber water were below the target levels. Because DE values and the target levels of PCNs and PCDDs/DFs in these runs were satisfactory, then we carried out a demonstrative experiment using the actual treatment system and confirmed destruction of PCNs. Based on good results of the demonstrative experiment, stock of PCN formulation was successfully treated continuously.

The toxicological effects of halogenated naphthalenes: a review of aryl hydrocarbon receptor-mediated (dioxin-like) relative potency factors

There is no doubt that chloronaphthalenes (PCNs) and their brominated counterparts (PBNs) are dioxin-like compounds, but there is less evidence for mixed bromo/chloronaphthalenes (PXNs). In this article we review information relating to the dioxin-like potency of PCNs and PBNs obtained in vivo, in vitro, and in silico. The aim was to help and improve the quality of data when assessing the contribution of these compounds in the risk analysis of dioxin-like contaminants in foods and other sample types. In vivo and in vitro studies have demonstrated that PCN/PBN congeners are inducers of aryl hydrocarbon hydroxylase, ethoxyresorufin O-deethylase, and luciferase enzymes that are features specifically indicative of planar diaromatic halogenated hydrocarbons such as dioxin and dioxin-like compounds. PCNs in the environment are of multisource origin. The limited data on PBNs in the environment suggest that these also appear to originate from different sources. The toxicological data on these compounds is even scarcer, most of it directed toward explaining the exposure risk from accidental contamination of feed with the commercial PBN containing product, Firemaster BP-6. The occurrence of PBNs and PXNs is possible as ultra-trace environmental and food-chain contaminants produced at least from combustion processes at unknown concentrations. Available toxicological and environmental data enable a focus on PCNs as dioxin analogues to an extent that specific local or regional environmental influences could result in a risk to human health. There is the possibility that they may act synergistically with the better-known classic dioxin and other dioxin-like compounds. PBNs and PXNs are much less studied than the dioxins, but are known to be products of anthropogenic processes that contaminate the environment. A continuously increasing use of bromine for manufacture of brominated flame retardants over the past three decades is anticipated as a stream of "brominated" wastes, that when degraded (combusted), will release PBNs and PXNs. This calls for advanced analytical methods and greater interest toxicologically to understand and control pollution and exposure by PBNs and PXNs. Particular congeners of bromonaphthalene in single studies were found to be much more toxic than their chlorinated counterparts. In addition, brominated/chlorinated naphthalenes also seem to be more potent toxicants than PCNs. About 20% of PCN congeners exhibit a dioxin-like toxicity with relative potencies varying between around 0.003 and 0.000001, but additional and more rigorous data are needed to confirm these figures. Recent food surveys have estimated a small but relevant human exposure to these compounds in foods, giving an additional source of dioxin-like toxicity to those compounds already covered by the World Health Organization-Toxic Equivalency Factors (TEFs) scheme. Given the additivity of response postulated for other dioxin-like compounds, it would seem unwise to ignore this additional contribution. Few data available showed that PBN congeners also exhibit a dioxin-like toxicity and are even more potent than PCN congeners, but the relative potency values were not derived for them until now. There are no toxicological data available for PXNs.

Spatial distribution of polychlorinated naphthalenes in the atmosphere across North China based on gridded field observations

Polychlorinated naphthalenes (PCNs) belong to a group of dioxin-like pollutants; however little information is available on PCNs in North China. In this study, gridded field observations by passive air sampling at 90 sites were undertaken to determine the levels, spatial distributions, and sources of PCNs in the atmosphere of North China. A median concentration of 48 pg m(-3) (range: 10-2460 pg m(-3)) for ∑29PCNs indicated heavy PCN pollution. The compositional profile indicated that nearly 90% of PCNs observed were from thermal processes rather than from commercial mixtures. Regarding the source type, a quantitative apportionment suggested that local non-point emissions contributed two-thirds of the total PCNs observed in the study, whereas a point source of electronic-waste recycling site contributed a quarter of total PCNs. The estimated toxic equivalent quantity for dioxin-like PCNs ranged from 0.97 to 687 fg TEQ m(-3), with the electronic-waste recycling site with the highest risk.

Action of Halowax 1051 on Enzymes of Phase I (CYP1A1) and Phase II (SULT1A and COMT) Metabolism in the Pig Ovary

Polychlorinated naphthalenes (PCNs) are a group of organochlorinated compounds exhibiting dioxin-like properties. Previously published data showed the direct action of PCN-rich Halowax 1051 on ovarian follicular steroidogenesis. Taking into consideration that the observed biological effects of PCNs may be frequently side effects of metabolites generated by their detoxification, the aim of this study was to determine the activity and expression of enzymes involved in phase I (cytochrome P450, family 1 (CYP1A1)) and phase II (sulfotransferase (SULT1A) and catechol-O-methyltransferase (COMT)) detoxification metabolism. Cocultures of granulosa and theca interna cells collected from sexually mature pigs were exposed to 1 pg/mL to 10 ng/mL of Halowax 1051 for 1 to 48 hours, after which levels and activities of CYP1A1, SULT1A, and COMT were measured. Dose-dependent increases of CYP1A1 activity and expression were observed. High doses of Halowax 1051 were inhibitory to COMT and SULT1A activity and reduced their protein levels. In conclusion, fast activation of phase I enzymes with simultaneous inhibition of phase II enzymes indicates that the previously observed effect of Halowax 1051 on follicular steroidogenesis may partially result from metabolite action occurring locally in ovarian follicles.

Repeated dose toxicity and relative potency of 1,2,3,4,6,7-hexachloronaphthalene (PCN 66) 1,2,3,5,6,7-hexachloronaphthalene (PCN 67) compared to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) for induction of CYP1A1, CYP1A2 and thymic atrophy in female Harlan Sprague-Dawley rats

In this study we assessed the relative toxicity and potency of the chlorinated naphthalenes 1,2,3,4,6,7-hexachloronaphthalene (PCN 66) and 1,2,3,5,6,7-hexachloronaphthalene (PCN 67) relative to that of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Chemicals were administered in corn oil:acetone (99:1) by gavage to female Harlan Sprague-Dawley rats at dosages of 0 (vehicle), 500, 1500, 5000, 50,000 and 500,000 ng/kg (PCN 66 and PCN 67) and 1, 3, 10, 100, and 300 ng/kg (TCDD) for 2 weeks. Histopathologic changes were observed in the thymus, liver and lung of TCDD treated animals and in the liver and thymus of PCN treated animals. Significant increases in CYP1A1 and CYP1A2 associated enzyme activity were observed in all animals exposed to TCDD, PCN 66 and PCN 67. Dose response modeling of CYP1A1, CYP1A2 and thymic atrophy gave ranges of estimated relative potencies, as compared to TCDD, of 0.0015-0.0072, for PCN 66 and 0.00029-0.00067 for PCN 67. Given that PCN 66 and PCN 67 exposure resulted in biochemical and histopathologic changes similar to that seen with TCDD, this suggests that they should be included in the WHO toxic equivalency factor (TEF) scheme, although the estimated relative potencies indicate that these hexachlorinated naphthalenes should not contribute greatly to the overall human body burden of dioxin-like activity.

Behavioral effects following repeated exposure to hexachloronaphthalene in rats

Polychlorinated naphthalenes (PCNs), including hexachloronaphthalene (HxCN), are widespread global environmental contaminants. Our experiments were aimed at assessing HxCN effects on motor behavior, long-term memory, pain sensitivity, magnitude of stress-induced analgesia, auditory function and sensorimotor gating, following repeated intragastric administration (28 days) of HxCN at 0.3 and 1.0 mg/kg body weight. Three weeks after the exposure termination, male Wistar rats were subjected to the neurobehavioral tests battery performed in the following order: open-field test, passive avoidance test, hot-plate test and acoustic startle response test. Repeated administration of HxCN induced disorders of motivational processes manifested by: anorectic effect caused by aphagia and adipsia; significantly reduced motor activity (hypokinesia); impaired long-term memory and acquired passive avoidance reaction; reduced pain threshold and shortened duration of anxiety reaction after pain stimulus (sensory neglect). Some of these neurobehavioral effects (impaired long-term memory, reduced pain threshold and stress-induced analgesia) were observed at 0.3 mgHxCN/kg body weight without any signs of overt toxicity. The outcome of our study shows that HxCN, like other compounds of the persistent organic pollutants (POPs) group, creates a potential risk of behavioral changes in the central nervous system in the general population as a result of environmental exposure.