Long-term persistence of polychlorinated dibenzo-p-dioxins and dibenzofurans in air, soil and sediment around an abandoned pentachlorophenol factory in China

Serum PCDD/F levels in metropolitan populations living near a municipal solid waste incinerator in Eastern China

Ambient exposure to polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) is suspected to cause adverse human health outcomes. Herein, serum samples from 40 residents in the neighborhood of a municipal solid waste incinerator (MSWI) in the metropolitan area were measured for PCDD/Fs. The mean toxic equivalent (TEQ) concentration of total PCDD/Fs in human serum samples was 16.8 pg TEQ/g lipid. Serum PCDD/F levels were significantly higher in residents adjacent to the MSWI than in those from areas far from the emission source (p < 0.01). In addition, there were no significant associations between serum PCDD/Fs levels and factors, such as gender, age, and BMI in donors. For non-occupationally exposed populations, OCDD and 1,2,3,7,8-PeCDD in serum are available as indicators of total PCDD/Fs and total TEQ, respectively. The atmospheric PCDD/Fs levels were within a relatively low range in areas upwind and downwind of the MSWI. The results of the principal component analysis showed a distinct difference in PCDD/F congener patterns between air and serum samples, suggesting inhalation exposure could have a limited influence on the human body burden. Our findings will deepen the current knowledge of endogenous PCDD/F exposure in urban populations, and also facilitate public health protection strategies near MSWIs.

Source apportionment of polychlorinated dibenzo-p-dioxins and dibenzofurans in the sediments of an urban estuary

Polychlorinated dibenzo-p-dioxins and dibenzofurans in the sediments of aquatic systems are a persistent global problem that poses serious health risks. Identifying the sources of dioxins in natural water systems and the extent of their contributions to observed sediment concentrations is important from a health advisory and mitigation perspective. This paper proposes novel distribution-based qualitative and quantitative methods as source apportionment techniques and alternatives to conventional source attribution methods. Using sampled data, air, runoff, industrial effluent, and industrial paper and pulp wastes were identified as four distinct dioxin contributors to concentrations found in the sediments of the test bed region: the Houston Ship Channel-San Jacinto River-Galveston Bay (HSC-SJR-GB) estuarine system that also includes 2 Superfund sites with dioxin contamination. Two qualitative methods, the Kullback-Leibler divergence (K-L divergence) and the Bhattacharya measure (BM), and a quantitative method, the L₂ norm, were used to investigate the spatial and temporal sourcing patterns of dioxins in the system sediments. The results indicated a global contribution from air and runoff sources across the estuarine system and over time with more localized impacts of the Superfund sites and the industrial sources. The results using the developed methodologies were compared with the output from the more conventional positive matrix factorization (PMF) method. Statistically significant correlations were observed among source contributions from the proposed methods and the PMF method, with Spearman's ρ ranging between - 0.596 to - 0.963 and 0.652 to 0.719, demonstrating the utility of the sourcing approaches used in the study. Additionally, the proposed methods were found to be rigorous in terms of elucidating spatial and temporal changes in the sourcing of dioxin to the estuary, indicating their suitability for use for other contaminants and other estuarine systems.

Fingerprinting and source apportionment of dioxin contamination of soils and chicken eggs in Southeast and Central Vietnam

Free-range chicken eggs and topsoil samples from private households in Southeast and South Central Coast of Vietnam were investigated to identify potential PCDD/F sources using Positive Matrix Factorization (PMF) approach. The PMF-extracted egg congener patterns were transformed to soil patterns using bioaccumulation factors and then compared to extracted soil and known dioxin sources patterns described in the literature. Free-range chicken egg PCDD/F profiles allowed to more precisely identify and distinguish potential PCDD/F sources. Five main PCDD/F sources were identified: open burning, vehicle emissions, background atmospheric deposition, Agent Orange, and so-called OCDD dechlorination pattern. The latter is characteristic for natural formation or ultimate weathering under tropical conditions of any primary source with predominant OCDD. Agent Orange source contribution ranged from 48 to 96% in soils, from 9 to 94% in eggs in hotspots, and from 10 to 31% in soil and from 4 to 45% in eggs in sprayed areas, respectively. Contributions of other sources varied significantly between sites.

Mechanism and kinetic properties for the complete series reactions of chloro(thio)phenols with O(3P) under high temperature conditions

Polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) and polychlorinated dibenzothiophenes/thianthrenes (PCDT/TAs) are two groups of dioxin-like compounds with oxygen and sulfur substitution, respectively. Chlorophenols (CPs) and chlorothiophenols (CTPs) are direct precursors in PCDD/F and PCDT/TA formation. The formation of chlorophenoxy radicals (CPRs) and chlorothiophenoxy radicals (CTPRs) from chlorophenols (CPs) and chlorothiophenols (CTPs) with O(3P) is an important initial step for the formation of PCDD/Fs and PCDT/TAs, respectively. In this paper, the formation of CPRs/CTPRs from the complete series reactions of 19 CP/CTP congeners with O(3P) was studied using the density functional theory (DFT) method. The rate constants of each reaction were calculated using canonical variational transition state (CVT) theory along with a small-curvature tunneling (SCT) contribution over a wide temperature range of 600-1200 K. The effect of the chlorine substitution pattern on the structural parameters, thermochemical properties and rate constants in both CPs and CTPs was discussed. This study shows that the reactions between CPs and O(3P) can be affected by the chlorine substitution at the para-position, and the reactions between CTPs and O(3P) are mostly influenced by both ortho-substitutions. The thiophenoxyl-hydrogen abstraction from CTPs by O(3P) is more likely to occur than the phenoxyl-hydrogen abstraction from CPs by O(3P). Comparison of the reactivity of CP/CTPs with O(3P) with our previous work on CP/CTPs with H and OH shows that the order for phenoxyl-hydrogen abstraction potential is CP + OH > CP + O(3P) > CP + H, and the order for thiophenoxyl-hydrogen abstraction potential is CTP + O(3P) > CTP + H > CTP + OH.

Occurrence and dietary exposure assessment of pentachlorophenol in livestock, poultry, and aquatic foods marketed in Guangdong Province, China: Based on food monitoring data from 2015 to 2018

As a persistent organic pollutant, pentachlorophenol (PCP) has serious impacts on human health. However, its presence in animal source food products sold in the Guangdong Province (GD) of China, and the resultant dietary exposure have not been elucidated. To address this gap, 3,100 samples from seven food categories, including beef, pork, mutton, offals, broilers, hen eggs, and farmed freshwater fish, marketed throughout four geographical regions of GD, were collected from 2015 to 2018. Gas chromatography coupled with mass spectrometry was employed to detect PCP levels in these food matrices. PCP was found in all food categories, but the average contamination levels were low, ranging from 0.40 µg/kg wet weight (ww) (hen eggs) to 5.85 µg/kg ww (offals). However, higher concentrations of PCP were detected (P < 0.05) in animal source food from the North region. Additionally, a temporal declining trend was observed in this four-year consecutive survey. The estimated human dietary exposure of PCP to population groups, including the general population and subgroups (male and female, children, and adults), was found to be far below the permissible daily intake (3 µg/kg body weight). Therefore, the health impacts of PCP should be correspondingly low for local residents, based on current toxicological knowledge. Regional exposure patterns varied due to different extents of contamination in the four areas, and pork, broilers, and freshwater fish were the major sources of dietary PCP exposure. PRACTICAL APPLICATION: As a persistent organic pollutant, pentachlorophenol (PCP) has serious impacts on human health. However, its presence in animal source food products sold in Guangdong Province of China, and the resultant dietary exposure have not been elucidated. In this study, we conducted an in-depth investigation on the occurrence of PCP in major foodstuff categories, including beef, pork, mutton, broilers, offals, hen eggs, and farmed freshwater fish, marketed in all 21 prefecture-level divisions of Guangdong Province, in order to provide integral insights for regulatory authorities.

Natural organic matter does not diminish the mammalian bioavailability of 2,3,7,8-tetrachlorodibenzo-p-dioxin

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a toxic and persistent organic pollutant found in soils and sediments. It has been linked to several adverse health outcomes in humans and wildlife, including suppression of the immune system. TCDD is strongly sorbed to soils/sediments due to its extremely low water solubility. Presently, the bioavailability of soil/sediment-sorbed TCDD to mammals is not completely understood. Our previous studies demonstrated that TCDD adsorbed to representative inorganic geosorbents (i.e. porous silica and smectite clay) exhibited the same bioavailability to mice as TCDD dissolved in corn oil, whereas sequestration by activated carbons eliminated TCDD bioavailability. In this study, we evaluated the effects of amorphous natural organic matter (NOM), primarily in the form of aquatic humic and fulvic acids, on the mouse bioavailability of TCDD. An aqueous suspension of TCDD mixed with NOM was administered to mice via oral gavage. The relative bioavailability of TCDD was assessed by two sensitive aryl hydrocarbon receptor-mediated responses in mice: 1) hepatic induction of cyp1A1 mRNA; and 2) suppression of immunoglobulin M (IgM) antibody-forming cell (AFC) response which is an indicator of immunotoxicity. Hepatic induction of cyp1A1 mRNA and suppression of IgM AFC induced by TCDD were similar in the NOM-sorbed form and dissolved in corn oil, revealing no loss of bioavailability when associated with NOM. Hence, NOM-associated TCDD is as capable of suppressing humoral immunity in mice as TCDD dissolved in corn oil, indicating that NOM-sorbed TCDD is likely to fully retain its bioavailability to mammals and, by inference, humans.

A review of levels and profiles of polychlorinated dibenzo-p-dioxins and dibenzofurans in different environmental media from China

This review provides a summary of the levels and profiles of PCDD/Fs throughout China, as reported in peer reviewed literatures since 1997. The literature shows that PCDD/Fs are widespread in various environmental media including air, water, sediment, and soil. PCDD/Fs concentrations in air were relatively low in most regions, with only a few areas considered polluted. Many studies reported seasonal trends, with higher and lower concentrations in winter and summer, respectively. We analyzed the factors affecting the concentrations of dioxins in air and summarized the causes of seasonal changes. As hydrophobic organic compounds, PCDD/Fs readily accumulate in sediments. The distribution of dioxins in sediment in Bohai Sea area was mainly introduced and the factors affecting concentrations of dioxins were studied. The levels of dioxins in soil in different regions varied greatly, with higher levels in areas close to pollution sources. We examined the dioxins concentrations in soil in places where the levels were very low (including the Tibet Plateau and other remote areas), contaminated areas, and other areas. Apart from the contaminated areas, the dioxins concentrations in soil were low. The results of the relatively low number of studies that have investigated PCDD/Fs in water have reported no obvious pollution in some waters, apart from Dongting Lake. PCDD/Fs levels across China are similar to those worldwide. Point sources, mainly related to local geographic, economic, and historical factors, were the most common source of contamination. E-waste dismantling and chemical production has the greatest impact on PCDD/Fs in different media.

Redox fluctuations shape the soil microbiome in the hypoxic bioremediation of octachlorinated dibenzodioxin- and dibenzofuran-contaminated soil

The biodegradation of polychlorinated-p-dioxins and dibenzofurans (PCDD/Fs) has been recently demonstrated in a single reactor under hypoxic conditions. Maintaining hypoxic conditions through periodic aerations results in a marked fluctuation of reduction-oxidation (redox) potential. To further assess the effects of redox fluctuations, we operated two fed-batch continuously stirred tank reactors (CSTRs) with sophisticated redox controls at different anoxic/oxic fluctuations to reduce PCDD/Fs in contaminated soil. The results of long-term reactor operation showed that the CSTR with redox fluctuations at a narrow range (-63 ± 68 mV) (CSTR_A) revealed a higher substrate hydrolysis level and PCDD/F degradation rate than did the CSTR with a redox potential that fluctuated at a broad range (-13 ± 118 mV) (CSTR_B). In accordance with analyses of bacterial 16S rRNA genes, the designated hypoxic conditions with added compost supported survival of bacterial populations at a density of approximately 10⁹ copies/g slurry. The evolved core microbiome was dominated by anoxic/oxic fluctuation-adapted Bacteroidetes, Alphaproteobacteria, and Actinobacteria, with higher species diversity and functionality, including hydrolysis and degradation of dioxin-like compounds in CSTR_A than in CSTR_B. Taken together, the overall results of this study expand the understanding of redox fluctuations in association with the degradation of recalcitrant substrates in soil and the corresponding microbiome.

Sources of polychlorinated dibenzo-p-dioxins and dibenzofurans to Baltic Sea herring

Levels of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in herring (Clupea harengus) remain high in several parts of the Baltic Sea, despite declines in PCDD/F emissions since the 1980s. The reasons behind this are not well understood. This study applied a statistical modeling approach where sources of PCDD/Fs that contaminate Baltic biota were quantitatively assessed by analyzing existing datasets. PCDD/F patterns were extracted from a herring dataset using positive matrix factorization (PMF). The extracted biota patterns were transformed into sediment patterns using fish-to-sediment transformation factors, and the resulting patterns were compared with known source PCDD/F patterns. The model distinguished three model patterns, which explained 85% of the data. These patterns were matched to tetra-chlorophenol (TCP), penta-chlorophenol/atmospheric background (PCP/AB), and thermal source patterns, respectively. The thermal source was the largest contributor to toxic equivalents (TEQ) in herring, but the level decreased from 42 ± 9.0 pg TEQ g^-1 lipid weight (lw) before year 2000 (pre-2000) to 15 ± 2.4 pg TEQ g^-1 lw post-2000, i.e., a decline of around one-third in the original TEQ concentration. The contribution of TCP more than doubled, from 2.1 ± 0.62 pg TEQ g^-1 lw to 5.6 ± 1.1 pg TEQ g^-1 lw, and the relative contribution of PCP/AB also increased. These increasing trends suggest that, as primary air emissions of PCDD/Fs are managed and levels decline, the impact of TCP and PCP/AB sources on Baltic Sea biota will become more important over time and that PCDD/F-contaminated sites in coastal areas and marine environments require more attention.

Fatty acids, polychlorinated dibenzo-p-dioxins and dibenzofurans, and dioxin-like polychlorinated biphenyls in paired muscle and skin from fish from the Bohai coast, China: Benefits and risks associated with fish consumption

Fish consumption benefits early cognitive development and cardiovascular health because of the n-3 long-chain polyunsaturated fatty acids in the fish, but toxic pollutants in fish, like dioxin-like polychlorinated biphenyls (dl-PCBs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), may decrease or counteract these benefits. In this study, the fatty acids, dl-PCBs, and PCDD/Fs were analyzed in paired muscle and skin from 13 fish and one squid species from the Bohai coast, which have been influenced by serious dioxin pollution from the Bohai Rim Region. The total fatty acid concentrations in the muscle and skin were 2.6-87 and 3.6-156 mg/g wet weight (ww), respectively. The total polyunsaturated fatty acid concentrations were higher in skin than muscle for almost half of the species. The total PCDD/F and dl-PCB toxic equivalents in the muscle and skin were 0.055-0.68 and 0.0099-0.43 pg/g ww, respectively, and were up to five times higher in the muscle than in the skin for eight species. Few benefit-risk studies for fish consumption with and without skin have been performed, so benefit-risk quotients (BRQs) for eating only muscle, only skin, and eating both were calculated. To achieve the recommended 250 mg of EPA + DHA intake, eating only muscle, only skin, and eating both from seven species with BRQs < 1 would cause no significant risk. Removing skin before eating is not necessary for these species. Three fish species had BRQs < 1 for muscle only but BRQs > 1 for skin only. Removing skin before eating would be better for these species. The other four fish species had BRQs > 1 for eating only muscle, only skin, and eating both, indicating the potential risk caused by PCDD/F and dl-PCB. Amounts of the four fish species consumed should be decreased, and other sources of EPA and DHA should be selected.

Photocatalytic reductive dechlorination of 2-chlorodibenzo-p-dioxin by Pd modified g-C3N4 photocatalysts under UV-vis irradiation: Efficacy, kinetics and mechanism

Polychlorinated dibenzo-p-dioxins (PCDDs), as a group of notorious anthropogenic environmental toxicants, are arguably ubiquitous in nature. In this study, we investigated the photocatalytic reductive dechlorination of 2-chlorodibenzo-p-dioxin (2-CDD) over Pd/g-C₃N₄ catalysts under UV-vis irradiation. The g-C₃N₄ and a series of Pd/g-C₃N₄ catalysts were prepared by thermal polymerization and mechanical mixing-illumination method and characterized by XRD, TEM, BET, SEM and UV-vis DRS analyses. Among all the samples, the Pd/g-C₃N₄ (5 wt%) yielded the optimal dechlorination activity with a total 2-CDD conversion of 54% within 4 h, and 76% of those converted 2-CDD were evolved to dibenzo-p-dioxin (DD). The kinetics of dechlorination could be described as pseudo-first-order decay model (R² > 0.84). Corresponding rate constants (k) increased from 0.052 to 0.17 h^-1 with Pd contents up to 5 wt% and decreased to 0.13 h^-1 with a 10 wt% of Pd. The enhanced activities originated from the surface plasmonic resonance (SPR) effect of Pd nanoparticles and the formation of Schottky barrier between Pd and g-C₃N₄, which extend the spectrum responsive range and suppress the charge recombination of g-C₃N₄. This is the first report on the photocatalytic reductive removal of PCDDs and may provide a new approach for PCDDs pollution control.

Occurrence and characteristics of PCDD/Fs formed from Chlorobenzenes production in China

China had a large production capacity of chlorobenzenes. An extensive investigation was conducted to understand the occurrence and characteristics of PCDD/Fs from four chlorobenzene production plants. The concentrations of PCDD/Fs in mono-CB production and in a new di-CB production routine were revealed. Concentrations of PCDD/Fs in residues, byproducts, products and wastewater varied between 8.4*10³-4.0*10⁶ ng TEQ/kg, 1.5-5.0*10⁴ ng TEQ/kg, ND∼0.12 ng TEQ/kg and 6.0*10⁴-9.1*10⁴ pg TEQ/L, respectively. OCDF, 2,3,4,7,8-PeCDF, 1,2,3,4,7,8-HxCDF, and 2,3,7,8-TeCDF were the most abundant congeners of the 17 2,3,7,8-substituted PCDD/Fs. In most samples, PCDFs contributed more than 99% of the total TEQs of PCDD/Fs, in which 2,3,4,7,8-PeCDF was the dominating contributor. It is inferred PCDFs were mainly formed in the chlorination reactions. The emission factors were suggested and the amount of PCDD/Fs formed in CB production was estimated to be 450 g TEQ in 2012. Residue, byproduct and wastewater were potentially the main pathways of PCDD/Fs to the environmental releases.

Depositional time trends of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in a dated sediment core from the Northern Arabian Gulf

The historical record of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) deposition was reconstructed from the analysis of a dated sediment core collected from a remote area in the northwestern Arabian Gulf not influenced by any point sources of contamination. The sedimentary record showed that PCDD/F concentrations started to increase above pre-industrial background levels in the mid-1960s. This was followed by an exponential increase in concentrations attaining a maximum of 7.5pg/g (dry wt) in the early 1980s and stayed fairly constant thereafter. The homolog profiles in sediments remained fairly consistent throughout the core with PCDD contributing 75% of the ΣPCDD/F concentrations. The homolog profile was dominated by OCDD which contributed approximately 55% of the total dioxins throughout the core. The consistency in the homolog patterns throughout the core suggests that the source of dioxins have remained fairly unchanged throughout the sedimentary record represented by the core.

Concentrations of and health risks posed by polychlorinated dibenzo-p-dioxins and dibenzofurans around industrial sites in Hebei Province, China

Sintering and steel production as the main emission sources of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) may affect environment and human health. The concentrations, profiles, and distributions of PCDD/Fs in soil samples from around four typical sintering and steel production plants in Hebei Province, China, were determined. Forty-six soil samples were collected at distances from 500 to 9000 m from industrial plant chimneys. The concentrations of total 17 2,3,7,8-substituted PCDD/F congeners in the soil samples from sites A, B, C, and D were in the range 11-130, 13-284, 2.6-378, and 21-231 pg/g, respectively, and the internationally accepted toxic equivalent (I-TEQ) concentrations were 0.37-13.2, 0.31-12.1, 0.13-13.7, and 1.60-22.7 pg I-TEQ/g, respectively. Soil ingestion was estimated the major exposure pathway to PCDD/Fs. At current PCDD/F concentrations, the local population will be exposed to low amounts of PCDD/Fs in soil from around the industrial sites, and this exposure will pose potential health risks for the local population living at distances of less than 1000 m from nearest stack but will have no high health risks for people living further away. These results will be helpful when planning measures to control PCDD/F sources. The data will also benefit local environmental monitoring studies and be useful when assessing the risks posed by PCDD/Fs around the industrial sites to the environment and humans.

State of the art and advances in the impact assessment of dioxins and dioxin-like compounds

Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs) are toxic and persistent organic pollutants that are able to enter the food chain, accumulate in the fat tissues of animals, and consequently pose a serious risk for human health. Consolidated tools for exposure assessment have been implemented during the last decades and widely used, both in the environmental monitoring and in modeling activities. Although the emissive trend and the concentrations in the environment have gradually decreased during the last 20 years, some situations are still underrated and not adequately controlled by the environmental legislation. On the other hand, a complete monitoring of all the pathways of exposure to PCDD/Fs and PCBs is technically and economically unfeasible. Therefore, this paper aims at providing an overview of the traditional approaches used to assess the impacts of PCDD/Fs and PCBs and presenting the novelties introduced during the last years. After an initial characterization of their toxicity and their effects on health, this paper focuses on activities and situations that can result in critical releases of PCDD/Fs and PCBs into the atmosphere and that can represent a hidden threat for the population. In the final part, this study presents the current methodologies for exposure assessment, summarizes the food chain models in a unified way, and puts the light on new methods that can help environmental scientists, risk assessors, and decision makers to estimate the risk related to exposure to PCDD/Fs in different contexts.

Declining Dioxin Concentrations in the Rhone River Basin, France, Attest to the Effectiveness of Emissions Controls

Emission-control policies have been implemented in Europe and North America since the 1990s for polychlorodibenzodioxins (PCDDs) and furans (PCDFs). To assess the effect of these policies on temporal trends and spatial patterns for these compounds in a large European river system, sediment cores were collected in seven depositional areas along the Rhone River in France, dated, and analyzed for PCDDs and PCDFs. Results show concentrations increase in the downstream direction and have decreased temporally at all sites during the last two decades, with an average decrease of 83% from 1992 to 2010. The time for a 50% decrease in concentrations (t1/2) averaged 6.9±2.6 and 9.1±2.9 years for the sum of measured PCDDs and PCDFs, respectively. Congener patterns are similar among cores and indicate dominance of regional atmospheric deposition and possibly weathered local sources. Local sources are clearly indicated at the most downstream site, where concentrations of the most toxic dioxin, TCDD, are about 2 orders of magnitude higher than at the other six sites. The relatively steep downward trends attest to the effects of the dioxin emissions reduction policy in Europe and suggest that risks posed to aquatic life in the Rhone River basin from dioxins and furans have been greatly reduced.

Long-time monitoring of polychlorinated dibenzo-p-dioxins and dibenzofurans over a decade in the ambient air of Porto, Portugal

As part of a monitoring program initiated in 1998 and conducted by IDAD - Institute for Environment and Development and supported by regional municipal solid waste (MSW) management authorities, an extensive database of dioxins' and furans' (PCDD/PCDF) concentrations in ambient air was collected in Porto, in two sites classified as suburban. The present paper summarizes the analytical results of PCDD/PCDF in ambient air obtained from 2001 to 2014 through this intensive monitoring work. The toxic equivalent (WHO-TEQ 1998) concentrations of the PCDD/PCDF in the air ranged from 8.2 to 904.4 fg TEQ m(-3), with an average and median values of 104.5 fg TEQ m(-3) and 49.8 fg TEQ m(-3), respectively. The PCDD/PCDF concentration trend in Porto's ambient air shows a clear drop of the annual average values occurred during the study period. The presence of seasonal variations is very clear in the present study. Winter levels (average: 154.3 fg TEQ m(-3)) are significantly higher than summer levels (average: 42.9 fg TEQ m(-3)). The PCDD/PCDF profiles' details show that several differences occurred over time. The homologue profiles presented changes and the PCDD congeners have decreased in terms of mass. The analysis of concentrations in combination with specific homologue and congener patterns of PCDD/PCDF allowed identification of potential emission sources.

Formation Pathways of Mono- to Octa-Chlorinated Dibenzo-p-dioxins and Dibenzofurans in Main Organochemical Industries

The concentrations and formation pathways of mono- to octa-chlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) were investigated in main organochemical industries. High levels of PCDDs and PCDFs were detected. The total concentrations of 27 PCDD/F congeners in chloranil, 2,4-D, and 1,4-dichlorobenzene were 5302397 ± 8944449, 20963 ± 15908, and 242 ± 67 pg g(-1), respectively, and the less-chlorinated PCDD/F levels were 12006 ± 20155, 9536 ± 5594, and 195 ± 94 pg g(-1), respectively. The distribution trends of less and more chlorinated PCDD/Fs were similar in different chemical plants because of their similar formation pathways, which may also be related to the degree of chlorination of chemical products and purification processes. 1,2,3,4-TeCDF and 2,4,8-TrCDF were selected as model molecules to calculate the bond dissociation energy, showing that 2-MCDF, 3-MCDF, and 2,8-DCDF are more easily formatted as shown by the analytical results. The formation pathways of less to more chlorinated PCDFs are proposed to explain why 2-MoCDF, 2,8-DiCDF, 2,4,8-TrCDF, and 2,3,4,7,8-PeCDF are the dominant congeners and to explain why 2,3,4,7,8-PeCDF is the largest contributor of I-TEQs in most studies.

Passive air sampling for determining the levels of ambient PCDD/Fs and their seasonal and spatial variations and inhalation risk in Shanghai, China

The seasonal and spatial variations, compositional profiles, and possible sources of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in ambient air samples in Shanghai of China were investigated by passive air samplers, and the potential inhalation risks posed by these chemicals were evaluated. The following results were obtained: (1) The World Health Organization (WHO) toxic equivalency (TEQ) values for PCDD/Fs were in the range of 10.8-259 fg m(-3) (mean 63.4 fg m(-3)) in summer and 24.1-154 fg m(-3) (mean 83.4 fg m(-3)) in winter. Atmospheric PCDD/F levels were in the following order: industrial areas > commercial and residential areas > rural areas. (2) 2,3,4,7,8-PeCDF (24 %), 2,3,7,8-TeCDD (16 %), 1,2,3,7,8-PeCDD (13 %), and 2,3,7,8-TeCDF (12 %) were the predominant contributors to the TEQ of PCDD/Fs. (3) There was a slight seasonal trend with higher TEQ values in winter than in summer, which could be related to seasonal variations in the dispersion of PCDD/Fs in ambient air. (4) The children's daily intake was at the lower end of the range for the tolerable daily intake of PCDD/Fs recommended by WHO, which indicates that the inhalation risk of PCDD/Fs for local residents in Shanghai is relatively low.

Assessment of PCDD/F source contributions in Baltic Sea sediment core records

Spatial and temporal trends of sources of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the Baltic Sea were evaluated by positive matrix factorization (PMF) and principal component analysis (PCA). Sediment cores were sampled at eight coastal, one coastal reference, and six offshore sites covering the northern to the southern Baltic Sea. The cores, which covered the period 1919-2010, were sliced into 2-3 cm disks among which 8-11 disks per core (in total 141 disks) were analyzed for all tetra- through octa-CDD/Fs. Identification and apportionment of PCDD/F sources was carried out using PMF. Five stable model PCDD/F congener patterns were identified, which could be associated with six historically important source types: (i) atmospheric background deposition (ABD), (ii) use and production of penta-chlorophenol (PCP), (iii) use and production of tetra-chlorophenol (TeCP), (iv) high temperature processes (Thermal), (v) hexa-CDD-related sources (HxCDD), and (vi) chlorine-related sources (Chl), all of which were still represented in the surface layers. Overall, the last four decades of the period 1920-2010 have had a substantial influence on the Baltic Sea PCDD/F pollution, with 88 ± 7% of the total amount accumulated during this time. The 1990s was the peak decade for all source types except TeCP, which peaked in the 1980s in the northern Baltic Sea and has still not peaked in the southern part. The combined impact of atmospheric-related emissions (ABD and Thermal) was dominant in the open sea system throughout the study period (1919-2010) and showed a decreasing south to north trend (always >80% in the south and >50% in the north). Accordingly, to further reduce levels of PCDD/Fs in the open Baltic Sea ecosystem, future actions should focus on reducing atmospheric emissions.

Combination of a fast cleanup procedure and a DR-CALUX® bioassay for dioxin surveillance in Taiwanese soils

Our goal was to determine dioxin levels in 800 soil samples collected from Taiwan. An in vitro DR-CALUX^® assay was carried out with the help of an automated Soxhlet system and fast cleanup column. The mean dioxin level of 800 soil samples was 36.0 pg-bioanalytical equivalents (BEQs)/g dry weight (d.w.). Soil dioxin-BEQs were higher in northern Taiwan (61.8 pg-BEQ/g d.w.) than in central, southern, and eastern Taiwan (22.2, 24.9, and 7.80 pg-BEQ/g d.w., respectively). Analysis of multiple linear regression models identified four major predictors of dioxin-BEQs including soil sampling location (β = 0.097, p < 0.001), land use (β = 0.065, p < 0.001), soil brightness (β = 0.170, p < 0.001), and soil moisture (β = 0.051, p = 0.020), with adjusted R² = 0.947 (p < 0.001) (n = 662). An univariate logistic regression analysis with the cut-off point of 33.4 pg-BEQ/g d.w. showed significant odds ratios (ORs) for soil sampling location (OR = 2.43, p < 0.001), land use (OR = 1.47, p < 0.001), and soil brightness (OR = 2.83, p = 0.009). In conclusion, four variables, including soil sampling location, land use, soil brightness, and soil moisture, may be related to soil-dioxin contamination. Soil samples collected in northern Taiwan, and especially in Bade City, soils near industrial areas, and soils with darker color may contain higher dioxin-BEQ levels.

Concentrations, atmospheric partitioning, and air-water/soil surface exchange of polychlorinated dibenzo-p-dioxin and dibenzofuran along the upper reaches of the Haihe River basin, North China

Polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/PCDF) were overall measured and compared in ambient air, water, soils, and sediments along the upper reaches of the Haihe River of North China, so as to evaluate their concentrations, profiles, and to understand the processes of gas-particle partitioning and air-water/soil exchange. The following results were obtained: (1) The average concentrations (toxic equivalents, TEQs) of 2,3,7,8-PCDD/PCDF in air, water, sediment, and soil samples were 4,855 fg/m(3), 9.5 pg/L, 99.2 pg/g dry weight (dw), and 56.4 pg/g (203 fg TEQ/m(3), 0.46 pg TEQ/L, 2.2 pg TEQ/g dw, and 1.3 pg TEQ/g, respectively), respectively. (2) Although OCDF, 1,2,3,4,6,7,8-HpCDF, OCDD, and 1,2,3,4,6,7,8-HpCDD were the dominant congeners among four environmental sinks, obvious discrepancies of these congener and homologue patterns of PCDD/PCDF were observed still. (3) Significant linear correlations for PCDD/PCDF were observed between the gas-particle partition coefficient (K p) and the subcooled liquid vapor pressure (P L (0)) and octanol-air partition coefficient (K oa). (4) Fugacity fraction values of air-water exchange indicated that most of PCDD/PCDF homologues were dominated by net volatilization from water into air. The low-chlorinated PCDD/PCDF (tetra- to hexa-) presented a strong net volatilization from the soil into air, while high-chlorinated PCDD/PCDF (hepta- to octa-) were mainly close to equilibrium for air-soil exchange.

Occurrence, possible sources, and temporal trends of polychlorinated dibenzo-p-dioxins and dibenzofurans in water and sediment from the lower Yangtze River basin, Jiangsu and Shanghai areas of Eastern China

The concentrations, compositional profiles, and possible sources of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/PCDF) in water column and surface sediment samples from the lower reaches of the Yangtze River were investigated, and the potential risks posed by these chemicals were evaluated. Concentrations of the 17 2,3,7,8-substituted PCDD/PCDF in the water and sediment samples ranged from 0.45 to 10.0 pg TEQ/L (mean 2.34 pg TEQ/L) and from 0.31 to 51 pg TEQ/g dw (mean 5.25 pg TEQ/g dw), respectively. Water and sediments from the Nanjing-Nantong sections of the Yangtze River were found to have elevated PCDD/PCDF levels, and the PCDD/PCDF TEQ concentrations in 13 sediment samples exceeded the probable effect levels (PEL), above which adverse biological effects are likely. Multivariate statistical analysis indicated that the principal PCDD/PCDF contamination source for the water and sediment was the production and use of pentachlorophenol (PCP) or sodium pentachlorophenate (PCP-Na). PCDD/PCDF concentrations were stable over time near the Yangtze River Estuary but had increased sharply in recent decades in the Nanjing-Nantong section, which will have been related to the growth in industrial activities and other anthropogenic PCDD/PCDF sources. Total organic carbon (TOC) and PCDD/PCDF concentrations correlated significantly (R=0.474, P<0.01), suggesting that TOC plays an important role in the transport and re-distribution of PCDD/PCDF in the Yangtze River basin.

Portuguese inventory of dioxins and furans atmospheric emissions

This article presents the results of the most recent estimation of polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) atmospheric emissions in Portugal, which has covered the period 2004-2009 and includes 27 emission sources types. The results are compared with previous emissions inventories published for Portugal. The main objective of this work is to provide relevant information about the amounts of the compounds that are released into the atmosphere in Portugal, and identify their major sources and trends. The methodology involved the identification of relevant sources, the collection of information to characterize these sources, the selection of appropriate emission factors and their application to estimate the emissions. Furthermore, several studies conducted in Portugal were considered, namely reports from PCDD/PCDF measurements performed in some industrial facilities. The inventory covered 27 emission sources types. However the results show that only 8 were relevant, i.e. with emission amounts greater than 1 g I-TEQ year(-1). The total emissions of PCDD/PCDF in Portugal reached between 40 and 105 g I-TEQ year(-1), for the period of 2004-2009. The largest emission source and at same time with greater variation is forest fires, with emissions between 3 g I-TEQ year(-1) and 67 g I-TEQ year(-1) in 2008 and 2005, respectively. Excluding the emissions from forest fires, the total emission is more or less constant over the years and around 37 g I-TEQ year(-1).

A review of environmental fate, body burdens, and human health risk assessment of PCDD/Fs at two typical electronic waste recycling sites in China

This paper reviews the levels of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in different environmental media, human body burdens and health risk assessment results at e-waste recycling sites in China. To provide an indication of the seriousness of the pollution levels in the e-waste recycling sites in China, the data are compared with guidelines and available existing data for other areas. The comparison clearly shows that PCDD/Fs derived from the recycling processes lead to serious pollution in different environmental compartments (such as air, soil, sediment, dust and biota) and heavy body burdens. Of all kinds of e-waste recycling operations, open burning of e-waste and acid leaching activities are identified as the major sources of PCDD/Fs. Deriving from the published data, the estimated total exposure doses via dietary intake, inhalation, soil/dust ingestion and dermal contact are calculated for adults, children and breast-fed infants living in two major e-waste processing locations in China. The values ranged from 5.59 to 105.16 pg WHO-TEQ/kg bw/day, exceeding the tolerable daily intakes recommended by the WHO (1-4 pg WHO-TEQ/kg bw/day). Dietary intake is the most important exposure route for infants, children and adults living in these sites, contributing 60-99% of the total intakes. Inhalation is the second major exposure route, accounted for 12-30% of the total exposure doses of children and adults. In order to protect the environment and human health, there is an urgent need to control and monitor the informal e-waste recycling operations. Knowledge gaps, such as comprehensive dietary exposure data, epidemiological and clinical studies, body burdens of infants and children, and kinetics about PCDD/Fs partitions among different human tissues should be addressed.

The immunotoxic effects of dual exposure to PCP and TCDD

Pentachlorophenol (PCP) was a commonly used fungicide, herbicide, insecticide, and bactericide in industrial, agricultural, and domestic settings; however, it was also contaminated with polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). It has been reported that technical grade PCP had immunosuppressive effects and that the immune system was the major target of PCDD/PCDFs toxicity. Although the immune response after exposure to PCP or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has been studied, the toxic effects of exposure to both PCP and TCDD have not yet been reported. The aim of this study was to evaluate the effects on immune cells from mice intraperitoneally immunized with OVA and subsequently treated with PCP or TCDD alone or in combination by gavage. The animals were terminated on day 7 and 14, and the spleen and plasma samples were collected for immunotoxicity evaluation. The numbers and populations of splenocytes, T cell-derived cytokines produced by splenocytes, splenocyte-generated cytotoxicity and OVA-specific antibodies in plasma were investigated. Our results indicate that the spleen/body weight ratio and splenocyte number was reduced by TCDD alone; in addition, this reduction was enhanced when TCDD was combined with PCP. Exposure to TCDD alone or in conjunction with PCP suppressed many ovalbumin (OVA)-stimulated cytokines, including IL-2, IFN-γ, IL-4, IL-5, and IL-10. Furthermore, the immunoglobulins IgG and IgM were suppressed in mice administered by PCP alone, but the suppressive effects were greater in mice treated with TCDD alone or in combination with PCP. Co-exposure to PCP and TCDD resulted in an antagonistic effect on TCDD-induced suppression of IFN-γ and IL-10. Our results demonstrate that PCP alone is immunotoxic, regardless of the presence of TCDD. PCP led to mild changes in cytokine secretion, and it compromised splenocyte-generated cytotoxicity and IgM and IgG antibody production on day 7. The finding that PCP antagonizes TCDD-induced IFN-γ suppression could be due to the competitive binding of PCP to AhR (aryl hydrocarbon receptor).

Evaluation of PCDD/F pollution in surface sediments of Izmit Bay

This study evaluates PCDD/F pollution in the surface sediments of Izmit Bay (Turkey) and assesses the possible sources of PCDD/F inputs to the bay. The results showed that concentrations of toxic PCDD/F congeners in the sediments varied between 0.45 and 255 ng WHO2005-TEQ/kg dry weight. Pollution mapping shows that PCDD/F levels in the central section of Izmit Bay are much higher than those in the eastern and the western sections. Sediments collected from the northern part of the central section showed very high PCDD/F concentrations. The samples reveal three different congener profiles dominated by OCDF, 1,2,3,4,6,7,8-HpCDF, and OCDD respectively. The dominance of OCDF in the sediment samples taken from the central section was attributed to the former production of vinyl chloride monomer in the area, while that of 1,2,3,4,6,7,8-HpCDF was attributed to the (previously unknown) use of a chlorophenol-based fungicide in the region. The OCDD dominated group was explained by the use of pentachlorophenol. The results indicate that historic industrial discharges are the main contributor to the PCDD/F pollution in the sediments.

Severe pollution of PCDD/Fs and dioxin-like PCBs in sediments from Lake Shihwa, Korea: tracking the source

Concentrations of polychlorinated dibenzo-p-dioxins, dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (DL-PCBs) were determined in surface sediments from Lake Shihwa and from creeks that discharge into this artificial lake. The toxic equivalents (TEQs) in sediments ranged from 1.0 to 1770 pg/g dry weight, which were some of the highest values ever reported so far for coastal sediments on a global basis. The concentrations of PCDD/Fs and DL-PCBs decreased with increasing distance from the creeks to offshore regions of the lake. Based on a multivariate statistical analysis and congener profiles, it was found that high contamination by PCDD/Fs in creek sediments collected around Lake Shihwa was associated with releases from chlor-alkali processes. Significant correlations were found for total organic carbon content and the concentrations of highly chlorinated PCDD/F congeners. This is the first report to document chlor-alkali processes as a significant source of PCDD/F contamination in Korean coastal waters.

Environmental and human exposure to soil chlorinated and brominated polycyclic aromatic hydrocarbons in an urbanized region

Nine chlorinated and brominated polycyclic aromatic hydrocarbons (Cl/BrPAHs) and five parent polycyclic aromatic hydrocarbons (PAHs) were measured in urban surface soil and fly ash samples collected from Shenzhen, south China in winter 2010. The concentrations of total Cl/BrPAHs and PAHs in soil ranged from below the reporting limit to 142 ng/g and from 4.34 to 158 µg/g, respectively, and in fly ash they ranged from 17.7 to 19.5 ng/g and 26.1 to 28.3 µg/g, respectively. Concentrations of Cl/BrPAHs and parent PAHs were not significantly correlated with each other in soil or in fly ash, suggesting that Cl/BrPAHs were formed mainly by mechanisms other than direct halogenation of parent PAHs. Estimated mass inventories of 2-BrFlu varied from 68.1 kg in commercial land to 669 kg in countryside land, the highest among all Cl/BrPAHs. Loss fluxes via soil erosion accounted for only small proportions of total soil mass inventories of Cl/BrPAHs. Average daily human intake via soil ingestion decreased with increasing age, with 2-BrFlu as the main contributor. Children of 0 to 8 years old were the most sensitive subgroup (13.7 pg/kg body wt/d for total Cl/BrPAHs), and females were more sensitive than males in the same age group. The mean dioxin-like toxic equivalency quotient (TEQ) concentration of total Cl/BrPAHs (0.008 ng-TEQ/g) was lower in soil than in fly ash (0.06 ng-TEQ/g). Conversely, the mean TEQ concentration of total parent PAHs (2.23 ng-TEQ/g) was higher in soil than in fly ash.