Polychlorinated Biphenyls In Environment Research Articles

Germ-free status but not subacute polychlorinated biphenyl (PCB) exposure altered hepatic phosphatidylcholine and ether-phosphatidylcholine levels in mice

Polychlorinated biphenyls (PCBs) are persistent organic pollutants that pose a current ecosystem and human health concern. PCB exposure impacts the gut microbiome in animal models, suggesting a mechanistic link between PCB exposure and adverse health outcomes. The presence and absence of the microbiome and exposure to PCBs independently affect the lipid composition in the liver, which in turn affects the PCB disposition in target tissues, such as the liver. Here, we investigated microbiome × subacute PCB effects on the hepatic lipid composition of conventional and germ-free female mice exposed to 0, 6, or 30 mg/kg body weight of an environmental PCB mixture in sterile corn oil once daily for 3 consecutive days. Hepatic triacylglyceride and polar lipid levels were quantified using mass spectrometric methods following the subacute PCB exposure. The lipidomic analysis revealed no PCB effect on the hepatic levels. No microbiome effect was observed on levels of triacylglyceride and most polar lipid classes. The total hepatic levels of phosphatidylcholine (PC) and ether-phosphatidylcholine (ePC) lipids were lower in germ-free mice than the conventional mice from the same exposure group. Moreover, levels of several unsaturated PCs, such as PC(36:5) and PC(42:10), and ePCs, such as ePC(36:2) and ePC(4:2), were lower in germ-free than conventional female mice. Based on a KEGG pathway meta-analysis of RNA sequencing data, the ether lipid metabolism pathway is altered in the germ-free mouse liver. In contrast to the liver, extractable lipid levels, determined gravimetrically, differed in several tissues from naïve conventional vs. germ-free mice. Overall, microbiome × subacute PCB exposure effects on hepatic lipid composition are unlikely to affect PCB distribution into the mouse liver. Further studies are needed to assess how the different extractable lipid levels in other tissues alter PCB distribution in conventional vs. germ-free mice.

Silicone wristbands as personal passive samplers of exposure to polychlorinated biphenyls in contaminated buildings.

Polychlorinated biphenyls (PCBs) were used in a number of industrial products from 1950 to 80s, including building materials. As a result, some buildings exhibit high levels of PCBs in the indoor environment. The aim of this study was to test silicone wristbands as a method for estimating personal exposure to PCBs in buildings both in controlled experiments and field settings. In the controlled study, the sampling kinetics of silicone wristbands were investigated in a 31-day uptake study. The field study focused on the application of wristbands as a personal exposure measure. It included 71 persons in a contaminated housing estate and 23 persons in a reference group. The linear uptake of PCBs ranged from 2 to 24days for PCB-8, 18, 28, 31, 40, 44, 49, 52, 66, 99, and 101 under controlled conditions. A generic sampling rate (Rk) of 2.3m3 d-1 corresponding to a mass transfer coefficient of 17mh-1 was found in the controlled kinetic study. Partitioning coefficients were also determined for the nine congeners. In the field study, an apparent generic field sampling rate (Rf) of 2.6m3 d-1 was found; when adjusted to reported hours exposed, it increased to 3.5m3 d-1. The wristbands were shown to be a good tool for predicting airborne exposure, as there was a highly significant difference between the exposed and reference group as well as a clear trend when used for ranking of exposure. In correlation analyses, highly significant correlations were observed between air and wristband levels, though adjusting by self-reported exposure time only increased the correlation marginally in the field study. The obtained kinetic data can be used for estimating the magnitude of external exposure. The advantages provided by the wristbands in the form of easy use and handling are significant, though the limitations should also be acknowledged.

Prenatal Environmental Exposure to Persistent Organic Pollutants and Reproductive Hormone Profile and Pubertal Development in Dutch Adolescents.

Persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs), may interfere with hormonal processes. Knowledge about the effects of prenatal exposure to PCBs and their hydroxylated metabolites (OH-PCBs) on pubertal development is limited. Therefore, the aim of the current study was to determine whether prenatal environmental PCB and OH-PCB exposure are associated with reproductive hormone levels and pubertal characteristics in 13- to 15-year-old children. In this Dutch observational cohort study, 194 mother–infant pairs were included (1998–2002). Maternal pregnancy serum levels of PCBs, OH-PCBs, and other POPs were measured. At follow-up (2014–2016), we measured serum or plasma levels of reproductive hormones in their children. We assessed Tanner stages and testicular volume (by clinician or standardized self-assessment), and participants completed questionnaires on pubertal onset. In total, 101 adolescents (14.4 ± 0.8 years; 53.7% of invited) participated, and 55 were boys. In boys, higher prenatal PCB levels were associated with higher testosterone levels, higher pubic hair stage, larger testicular volume, and younger age at onset of growth spurt and voice break. In girls, higher prenatal PCB levels were associated with higher stages for breast development. In conclusion, higher prenatal PCB exposure could be associated with more advanced pubertal development in 13- to 15-year-old children.

The disposition of polychlorinated biphenyls (PCBs) differs between germ-free and conventional mice

The disposition of toxicants, such as polychlorinated biphenyls (PCBs), in germ-free (GF) vs. conventional (CV) mice has received little attention to date. Here, we investigate PCB levels in three-month-old female CV and GF mice exposed orally daily for 3 days to 0, 6, or 30 mg/kg body weight of the Fox River Mixture (FRM), an environmental PCB mixture. We euthanized animals 24 h after the final dose. PCB profiles in tissues differed from the FRM profile but were similar in tissues across all 4 PCB exposure groups. PCB levels in CV but not GF mice followed the difference in PCB dose. Importantly, PCB levels were higher in CV than GF mice exposed to the same dose. Hepatic cytochrome P450 enzyme or lipid levels did not explain these trends in PCB tissue levels. Thus, toxicity studies with CV and GF animals need to assess the toxicokinetics of the toxicant investigated. CapsulePCB levels are typically higher in conventional than germ-free mice exposed to the same dose of PCBs.

Circulating MicroRNAs, Polychlorinated Biphenyls, and Environmental Liver Disease in the Anniston Community Health Survey.

Background:Polychlorinated biphenyl (PCB) exposures have been associated with liver injury in human cohorts, and steatohepatitis with liver necrosis in model systems. MicroRNAs (miRs) maintain cellular homeostasis and may regulate the response to environmental stress.Objectives:We tested the hypothesis that specific miRs are associated with liver disease and PCB exposures in a residential cohort.Methods:Sixty-eight targeted hepatotoxicity miRs were measured in archived serum from 734 PCB-exposed participants in the cross-sectional Anniston Community Health Survey. Necrotic and other liver disease categories were defined by serum keratin 18 (K18) biomarkers. Associations were determined between exposure biomarkers (35 ortho-substituted PCB congeners) and disease biomarkers (highly expressed miRs or previously measured cytokines), and Ingenuity Pathway Analysis was performed.Results:The necrotic liver disease category was associated with four up-regulated miRs (miR-99a-5p, miR-122-5p, miR-192-5p, and miR-320a) and five down-regulated miRs (let-7d-5p, miR-17-5p, miR-24-3p, miR-197-3p, and miR-221-3p). Twenty-two miRs were associated with the other liver disease category or with K18 measurements. Eleven miRs were associated with 24 PCBs, most commonly congeners with anti-estrogenic activities. Most of the exposure-associated miRs were associated with at least one serum hepatocyte death, pro-inflammatory cytokine or insulin resistance bioarker, or with both. Within each biomarker category, associations were strongest for the liver-specific miR-122-5p. Pathways of liver toxicity that were identified included inflammation/hepatitis, hyperplasia/hyperproliferation, cirrhosis, and hepatocellular carcinoma. Tumor protein p53 and tumor necrosis factor were well integrated within the top identified networks.Discussion:These results support the human hepatotoxicity of environmental PCB exposures while elucidating potential modes of PCB action. The MiR-derived liquid liver biopsy represents a promising new technique for environmental hepatology cohort studies. https://doi.org/10.1289/EHP9467

Enhanced plant-microbe remediation of PCBs in soil using enzyme modification technique combined with molecular docking and molecular dynamics.

The study on the enhanced mechanisms of the enzymes involved in plant absorption, plant degradation, and microbial mineralization in the remediation of soils contaminated with polychlorinated biphenyls (PCBs) is of great significance for the application of plant-microbe combined remediation technique in PCB-contaminated soils. The present study first used a combination of molecular docking and molecular dynamics methods to calculate the effects of the plant absorption enzyme, plant degradation enzyme, and microbial mineralization enzyme on the PCBs in the soil environment. A multifunctional plant degradation enzyme was constructed with three functional roles of absorption, degradation, and mineralization using amino acid sequence recombination and site-directed mutagenesis to modify the template of plant degradation enzyme. Finally, using the Taguchi experimental design-assisted molecular dynamics simulation method, the suitable external environmental conditions of plant-microbe combined remediation of the PCB-contaminated soil were determined. In total, six multifunctional plant degradation enzymes were designed, which exhibited a significantly improved efficiency of PCB degradation. In comparison to the complex of plant absorption enzyme, plant degradation enzyme, and microorganism mineralization enzyme (6QIM-3GZX-1B85), the six multifunctional plant degradation enzymes exhibited significantly higher efficiency (2.10-2.38 times) in degrading the PCBs, with a maximum of 2.69 times under suitable external environmental conditions.

Concentrations of polychlorinated biphenyls in ambient air and solid residues around a municipal solid waste open burning site

Open burning of municipal solid waste is a common practice in developing countries of Africa, and combustion of these wastes is an important source of polychlorinated biphenyls (PCBs) emission in the ambient air. This study determined the concentrations of polychlorinated biphenyls in ambient air and solid residues in the soil around a municipal solid waste (MSW) open burning site in Nigeria. Air samples were collected around the vicinity of the waste site using polyurethane foam (PUF) passive samplers, and solid residue samples were obtained at different locations at the burning site. Quantification of PCBs was carried out using GC–MS operated in selected ion monitoring mode. Result showed the ambient ∑ PCB concentration range of 3.12–5.04 ng/ m3. Also, ∑ PCBs in the solid residue ranged from 23.72 ng/g to 28.66 ng/g. The daily inhalation exposure dose from inhalation of PCBs in the ambient air was 0.3 pg TEQ kg−1 day−1 for children and 0.09 pg TEQ kg−1 day−1 for adult. The mean values of Hazard Quotient (HQ) calculated from accidental ingestion of PCB of the solid residue were $${4.7\times 10}^{-5}$$ and $${7.5\times 10}^{-5}$$ for adult and children, respectively, while the calculated Incremental Lifetime Cancer Risk (ILCR) are above the WHO permissible limit. In conclusion, the study may be used to evaluate the environmental contribution PCBs from MSW open burning in Nigeria

Reconstruction of temporal and spatial trends of atmospheric pollution based on polychlorinated biphenyls concentration changes in ombrotrophic bogs

To reconstruct the deposition rate of polychlorinated biphenyls (PCBs) in different historical periods and to examine the temporal and spatial trend of PCBs pollution, we analyzed the changes of PCBs concentration and deposition rate in peat cores and lake sediments, and evaluated the suitability of peat cores and lake sediments for studying PCBs deposition trend. Through the dating analysis of all samples, we found that peat bog could well record the historical sedimentation of PCBs. PCBs did not degrade in peat, and it was thus feasible to use peatland to examine the settlement of PCBs. In this study, the reconstruction time of ∑11PCBs in peat was from the beginning of 19th century to the beginning of 21st century. The mean inventory of ∑11PCBs in three peat cores of each bog changed between (37.0±5.4) and (47.2 ±27.8) μg·m-2, with the standard deviation between 14.9% and 58.9%. The highest concentration of ∑11PCBs was 6.8 ng·g-1DW, while the maximum deposition rate of reconstructed PCBs was up to 989.7 ng·m-2·a-1. The trend of deposition rate was first increasing and then decreasing. After the year 1980, the deposition rate was substantially decreasing, which was consistent with the prohibition of PCBs production in the United States in 1979. Meanwhile, the analysis of sediment samples in the lake near bog showed that concentration and maximum deposition rate of the lake sediment were comparable to those of the nearby bog. The concentrations of Di- to Hepta-PCB congeners were evenly distributed along the sediment profile. Therefore, lake sediments could not be used to analyze the historical sedimentary model of low order PCBs. This study reconstructed temporal and spatial variation of PCBs in atmospheric environment in different historical periods, which could provide basic data for the evaluation of regional environmental quality.

Developmental PCB Exposure Disrupts Synaptic Transmission and Connectivity in the Rat Auditory Cortex, Independent of Its Effects on Peripheral Hearing Threshold.

Polychlorinated biphenyls (PCBs) are enduring environmental toxicants and exposure is associated with neurodevelopmental deficits. The auditory system appears particularly sensitive, as previous work has shown that developmental PCB exposure causes both hearing loss and gross disruptions in the organization of the rat auditory cortex. However, the mechanisms underlying PCB-induced changes are not known, nor is it known whether the central effects of PCBs are a consequence of peripheral hearing loss. Here, we study changes in both peripheral and central auditory function in rats with developmental PCB exposure using a combination of optical and electrophysiological approaches. Female rats were exposed to an environmental PCB mixture in utero and until weaning. At adulthood, auditory brainstem responses (ABRs) were measured, and synaptic currents were recorded in slices from auditory cortex layer 2/3 neurons. Spontaneous IPSCs (sIPSCs) and miniature IPSCs (mIPSCs) were more frequent in PCB-exposed rats compared with controls and the normal relationship between IPSC parameters and peripheral hearing was eliminated in PCB-exposed rats. No changes in spontaneous EPSCs were found. Conversely, when synaptic currents were evoked by laser photostimulation of caged-glutamate, PCB exposure did not affect evoked inhibitory transmission, but increased the total excitatory charge, the number and distance of sites that evoke a significant response. Together, these findings indicate that early developmental exposure to PCBs causes long-lasting changes in both inhibitory and excitatory neurotransmission in the auditory cortex that are independent of peripheral hearing changes, suggesting the effects are because of the direct impact of PCBs on the developing auditory cortex.

Nontarget analysis reveals gut microbiome-dependent differences in the fecal PCB metabolite profiles of germ-free and conventional mice.

Mammalian polychlorinated biphenyl (PCB) metabolism has not been systematically explored with nontarget high-resolution mass spectrometry (Nt-HRMS). Here we investigated the importance of the gut microbiome in PCB biotransformation by Nt-HRMS analysis of feces from conventional (CV) and germ-free (GF) adult female mice exposed to a single oral dose of an environmental PCB mixture (6mg/kg or 30mg/kg in corn oil). Feces were collected for 24h after PCB administration, PCB metabolites were extracted from pooled samples, and the extracts were analyzed by Nt-HRMS. Twelve classes of PCB metabolites were detected in the feces from CV mice, including PCB sulfates, hydroxylated PCB sulfates (OH-PCB sulfates), PCB sulfonates, and hydroxylated methyl sulfone PCBs (OH-MeSO2-PCBs) reported previously. We also observed eight additional PCB metabolite classes that were tentatively identified as hydroxylated PCBs (OH-PCBs), dihydroxylated PCBs (DiOH-PCBs), monomethoxylated dihydroxylated PCBs (MeO-OH-PCBs), methoxylated PCB sulfates (MeO-PCB sulfates), mono-to tetra-hydroxylated PCB quinones ((OH)x-quinones, x=1-4), and hydroxylated polychlorinated benzofurans (OH-PCDF). Most metabolite classes were also detected in the feces from GF mice, except for MeO-OH-PCBs, OH-MeSO2-PCBs, and OH-PCDFs. Semi-quantitative analyses demonstrate that relative PCB metabolite levels increased with increasing dose and were higher in CV than GF mice, except for PCB sulfates and MeO-PCB sulfates, which were higher in GF mice. These findings demonstrate that the gut microbiome plays a direct or indirect role in the absorption, distribution, metabolism, or excretion of PCB metabolites, which in turn may affect toxic outcomes following PCB exposure.

Emerging and Historical Contaminants Detected in Desert Rodents Collected Near a Low-Level Radioactive Waste Site.

In an effort to determine contaminant presence, concentrations, and movement from a low-level radioactive waste (LLRW) burial disposal site to ecosystems in the surrounding area, a study was developed to assess concentrations of per- and polyfluoroalkyl substances (PFAS), polychlorinated biphenyls (PCBs), and tritium. To complete this assessment small mammals, vegetation, soil, and insect samples were collected from areas within and adjacent to the Beatty, Nevada, LLRW site and from a reference area located approximately 3 km south of the LLRW site. Samples underwent analysis via liquid chromatography tandem mass spectrometry, gas chromatography mass spectrometry, or scintillation spectroscopy depending on the analyte of interest. Small mammal tissues showed maximum concentrations of over 1700 ng/g for PFAS, 1600 ng/g for PCBs, and 10 000 Bq/kg for tritium. The primary contaminants found in soil samples were PCBs, with maximum concentrations exceeding 25 ng/g. Trace amounts of PFAS were also detected in soils and insects. Only qualitative data were obtained from vegetation samples because of the complex matrix of the dominant plant species (creosote bush; Larrea tridentata [Sessé & Moc. ex DC.] Coville). Overall, these data indicate the presence of various anthropogenic contaminants in the ecosystem surrounding the LLRW area, but additional analyses are necessary to confirm the sources and migration pathways of PFAS and PCBs in this hyperarid environment. Environ Toxicol Chem 2021;40:727-734. © 2020 SETAC.

Environmental PCB forensics: processes and issues.

PCB forensic science is the process of identifying the source(s) of polychlorinated biphenyls (PCBs) at a site in the context of a legal proceeding to aid in identifying the party(s) responsible for the cost of environmental remediation. The PCB forensic scientist should assemble and examine all the evidence and then develop opinions about sources, discharges, deposition, fate, transport, environmental impact, and other issues at dispute among the parties. PCBs are complex mixtures of compounds (Aroclors in USA) that can simultaneously reveal information about the source of the contamination, but also provide confounding and contradictory evidence. The issues are technically complex and the expert must systematically evaluate the facts, employ deep technical expertise, and use dispassionate judgment to provide expert opinions that assist the judge, jury, arbitrator, or allocator in rendering their decision as to the responsible party(s) or an apportionment of that responsibility. Different PCB products were used and disposed of that have characteristic congener mixture profiles. In the environment, these profiles can mix and weather over decades. Sampling and analysis can generate further uncertainties, notably the possible misidentification of Aroclors. The expert's challenge is to present their opinions clearly and authoritatively without overrepresenting the facts and data. This paper focuses on PCB contamination of sediment in aqueous sediment and uses a case study to illustrate application of forensic principles.

First polychlorinated biphenyls (PCBs) monitoring in seawater, surface sediments and marine fish communities of the Persian Gulf: Distribution, levels, congener profile and health risk assessment

Polychlorinated biphenyls (PCBs) are persistent organic pollutants that, due to their high toxicity, lipophilic property and widespread dispersal in the global environment, present a danger for human health and ecological systems. Although the inventory and use of PCBs are extensively reported worldwide, the status of PCBs in Iran is still unknown. In this study, the concentrations of PCBs were determined in the environmental matrices and in five commercially important fish species from Larak coral Island, Persian Gulf, Iran, in winter and summer 2015. A positive correlation was found among PCBs levels and congeners profiles in seawater (0.97–3.10 ng L−1), surface sediments (2.95–7.95 ng g−1dw) and fish samples (7.20–90.19 ng g−1dw), indicating fish as suitable bioindicator of environmental PCBs contamination. In all matrices, a high contribution of light and medium chlorinated congeners was detected in both seasons. In fish, the higher PCBs levels were found for both sexes in both seasons in liver and kidney than other tissues (skin, gonad, muscle) due to their high lipid content and PCBs lipophilicity. More importantly, the risks for human health associated with fish consumption were also evaluated, and it was found that all the toxicity indices measured for PCBs were within the World Health Organization (WHO) permissible limit of food consumption. However, it is highly recommended to inform the local population about potential risks attributable to dietary incorporation of locally caught fish, and establish a surveillance monitoring programme on PCBs in this region.

Historical and future polychlorinated biphenyl emission trends in Japan

Different countries produce varying amounts of polychlorinated biphenyls (PCBs), have distinct patterns of use, and regulations for treatment and disposal. Therefore, long-term countermeasures require an understanding of historical and future emission trends at the national scale. In this study, we estimate historical PCB emissions from products containing PCBs, unintentional production related thermal processes, and disposal processes for products containing PCBs from 1950 to 2030 in Japan. In addition, in order to validate the results, we estimated PCB concentrations in environmental media using an environmental fate model and a sensitivity analysis was conducted. Our results show that total PCB emissions were approximately 2.6 tons in 2017, which was a dramatic decrease from peak emissions of 68.9 tons in 1970. We suggest that PCB emissions may continue to decrease, reaching 0.707 tons in 2030. This trend might be due to a change in the emission source; it was estimated that the main emission source in past and recent years was volatilization from large products containing PCBs. However, it is predicted that the main emission sources in the future will be unintentional PCB production from thermal processes and volatilization from small untreated products containing PCBs, although the estimation of environmental PCB levels suggested that there might be unknown emission sources. Additionally, the sensitivity analysis indicated that some parameters greatly influenced the estimation of recent and future emissions. In particular, there was no detailed information concerning the applications for PCBs, which potentially had a large influence on the estimation of future emissions.

Examining multi- and transgenerational behavioral and molecular alterations resulting from parental exposure to an environmental PCB and PBDE mixture

Polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) are persistent organic pollutants extensively used during the 20th century and still present in aquatic environments despite their ban. Effects of exposure to these compounds over generations are poorly documented. Therefore, our aims were to characterize behavioral responses and underlying molecular mechanisms in zebrafish exposed to an environmentally relevant mixture of PCBs and PBDEs as well as in four unexposed offspring generations. Zebrafish (F0) were chronically exposed from the first meal onward to a diet spiked with a mixture containing 22 PCB and 7 PBDE congeners in proportions and concentrations reflecting environmental situations (ΣPCBs = 1991 and ΣPBDEs = 411 ng/g). Four offspring generations (F1 to F4) were obtained from this F0 and were not further exposed. Behavior was assessed at both larval and adult stages. Mechanisms related to behavioral defects (habenula maturation and c-fos transcription) and methylation (dnmts transcription) were monitored in larvae. Exposed adult F0 as well as F1 and F3 adults displayed no behavioral change while F2 expressed anxiety-like behavior. Larval behavior was also disrupted, i.e. hyperactive after light to dark transition in F1 or hypoactive in F2, F3 and F4. Behavioral disruptions may be related to defect in habenula maturation (observed in F1) and change in c-fos transcription (observed in F1 and F2). Transcription of the gene encoding DNA methyltransferase (dnmt3ba) was also modified in all generations. Our results lead us to hypothesize that chronic dietary exposure to an environmentally relevant mixture of PCB and PBDE triggers multigenerational and transgenerational molecular and behavioral disruptions in a vertebrate model.

PCB and PBDE contamination in Tursiops truncatus and Stenella frontalis, two data-deficient threatened dolphin species from the Brazilian coast

Polychlorinated biphenyls (PCB) and polybrominated diphenyl ethers (PBDE) levels were assessed in the liver and muscle of two data-deficient threatened dolphin species, the bottlenose dolphin (Tursiops truncatus, n = 4) and the Atlantic spotted dolphin (Stenella frontalis, n = 6), sampled off the Southeastern Brazilian coast. PCB concentrations were greater in liver compared to muscle, with males presenting higher concentrations than females. The three main detected PCB congeners were PCBs 138, 153 and 180. A predominance of hexachlorinated congeners was observed, followed by hepta- and penta-PCBs. For both species, Cl 3 and Cl 4 levels were higher in muscle compared to liver, while Cl 5 to Cl 8 and ∑PCBs were higher in liver. PBDE concentrations were significantly higher in Atlantic spotted dolphin muscle and liver compared to bottlenose dolphins. Similarly to PCBs, the highest PBDE concentrations were observed in males. The presence of PBDE congeners BDE-47, -100 and -99 in the muscle and liver of both species suggests the existence of a pollution source in Brazil by a penta-BDE mixture, as PBDEs have never been produced in Brazil. Interspecific PCB and PBDE profiles were very similar, which may be related to the similar characteristics of the analyzed species, mainly geographic distribution and life and feeding habits. This study furthers knowledge on environmental PCB and PBDE contamination, assisting in the establishment of dolphin population conservation strategies. In addition, this study calls into question the current threshold values established for PCBs and PBDEs, and demonstrates the lack of information and knowledge in this regard for cetaceans.

Occurrence, distribution and possible sources of polychlorinated biphenyls (PCBs) in the surface water from the Bay of Bengal coast of Bangladesh

Full profile of polychlorinated biphenyls (PCBs) in the coastal surface water from Bangladesh were analyzed by GC-MS/MS to explore the status of contamination, spatiotemporal distribution and to trace their potential sources. The total concentrations of dissolved PCBs (∑PCBs, sum of all congeners) varied from 32.17 to 160.7 ng/L and 46.45–199.4 ng/L in winter and summer, respectively, and the ranges were comparable to or higher than those recorded in the surface water from the coastal areas of India, China, Japan, Italy, Belgium and USA. The difference in the levels of PCBs between the two seasons was not statistically significant (p > 0.05). However, spatial distribution revealed that the areas with recent urbanization and industrialization (Chittagong, Cox's Bazar and Sundarbans) were more contaminated with PCBs than the unindustrialized area (Meghna Estuary). Lightly to moderately chlorinated (2–6 Cl) homologs dominated the PCB profiles. Our analyses (congener profile and homolog composition) elucidated that the past and on-going use of PCB-containing equipment (e.g. capacitors and transformers) as well as the anthropogenic activities such as urban developments, commercial and industrial establishments (e.g. ship breaking and port activities) might be the potential sources of PCB emission in Bangladesh. A set of congeners based on their detection frequencies and abundance were identified and categorized as potential environmental marker PCBs, which can be used for the future selective monitoring studies regarding reasonable limitations on full congener assessment. According to the existing national and international water quality guidelines/standards, PCB concentrations recorded in this study could potentially cause biological damage. Essentially, the findings of this first comprehensive report on the PCB contamination in the surface water in Bangladesh may provide a reference to future studies of these compounds in the Bay of Bengal.

Seasonal-spatial distributions, congener profile, and risk assessment of polychlorinated biphenyls (PCBS) in the surficial sediments from the coastal area of Bangladesh

ABSTRACTA comprehensive congener specific assessment of polychlorinated biphenyls (PCBs) was conducted for the first time in Bangladesh. All 209 PCB congeners in the surficial coastal sediments from the coastal areas of Bangladesh were analyzed by GC-MS/MS. The total concentrations of PCBs (∑PCBs) varied from 5.27 to 92.21 and 4.61 to 105.3 ng/g dw in winter and summer, respectively, and the ranges were comparable to or higher than those recorded in the sediments from the coastal areas of India, Korea, China, and Taiwan. The seasonal difference in the levels of PCBs was not statistically significant (p > 0.05). The spatial distribution revealed that the areas with recent urbanization and industrialization (Chittagong, Cox’s Bazar and Sundarbans) were more contaminated with PCBs than the unindustrialized area (Meghna Estuary). Moderately chlorinated (4–6 Cl) homologs dominated PCB profiles. A set of congeners based on their detection frequencies and abundance were identified and categorized as potential environmental marker PCBs, which can be used for the future selective monitoring studies where there would be limitations on whole congener assessment. Ecotoxicologically, the sedimentary PCB concentrations exceeded some of the existing environmental quality standards, suggesting a potential threat to the aquatic organisms in the Bangladeshi coastal areas.

The status and distribution of PCBs along the coast of Vietnam.

Polychlorinated biphenyls (PCBs), well-known as an important scientific achievement, are now considered as one of the most persistent organic pollutants (POPs) that need to be strictly controlled and forbidden worldwide (the Stockholm convention on POPs). Vietnam is one of the countries that encounters with serious issues from PCB contamination. This study presented a comprehensive review on the status and contamination of PCBs along the coast of Vietnam. The contaminated PCBs data in the water, sediment and biological samples from 18 provinces along Vietnam coastline were collected from various sources. A comparison in PCBs contamination between Vietnam and other Asian countries was included. The status on PCBs contamination in Vietnam since participated as a party of the Stockholm convention on POPs in 2002 was also assessed. The results showed that Vietnam is facing serious PCBs contamination problems as it evidences the spread and accumulation of PCBs in the marine environment. The implementation of the Stockholm convention on POPs (PCBs in particular) has not yet demonstrated significant effect on the reduction in PCBs contamination in the environment. This information on PCBs contamination in Vietnam urges government to strengthen the mechanism, policy and legislation, the management capacity for PCBs as well as applying advanced and modern technologies in reducing, disposing and eliminating PCBs from the environment.

Developmental exposure to PCBs alters the activation of the auditory cortex in response to GABAA antagonism

Developmental exposure of rats to polychlorinated biphenyls (PCBs) causes impairments in hearing and in the functioning of peripheral and central auditory structures. Additionally, recent work from our laboratory has demonstrated an increase in audiogenic seizures. The current study aimed to further characterize the effects of PCBs on auditory brain structures by investigating whether developmental exposure altered the magnitude of activation in the auditory cortex (AC) in response to electrical stimulation of thalamocortical afferents. Long-Evans female rats were fed cookies containing either 0 or 6mg/kg of an environmental PCB mixture daily from 4 weeks prior to breeding until postnatal day 21. Brain slices containing projections from the thalamus to the AC were collected from adult female offspring and were bathed in artificial cerebrospinal fluid (aCSF) alone, aCSF containing a gamma-aminobutyric acid (GABA) receptor antagonist (200nM SR95531), and aCSF containing an and N-methyl-d-aspartate (NMDA) receptor antagonist (50μM AP5). During each of these drug conditions, electrical stimulations ranging from 25 to 600μA were delivered to the thalamocortical afferents. Activation of the AC was measured using flavoprotein autofluorescence imaging. Although there were no differences seen between treatment groups in the aCSF condition, there were significant increases in the ratio of aCSF/SR95531 activation in slices from PCB-exposed animals compared to control animals. This effect was seen in both the upper and lower layers of the AC. No differences in activation were noted between treatment groups when slices were exposed to AP5. These data suggest that developmental PCB exposure leads to increased sensitivity to antagonism of GABAA receptors in the AC without a change in NMDA-mediated intrinsic excitability.