Production Of Polychlorinated Biphenyls Research Articles

Factors affecting the polychlorinated biphenyl signatures in serum of adults living in a highly polluted area in eastern Slovakia.

Over the years eastern Slovakia has been subject to consistent monitoring of high levels of polychlorinated biphenyls (PCBs) in both the environment and human populations attributed to the former production of PCBs at the Chemko Strážske plant. We aimed to investigate the extent to which dietary habits and residential location could affect the concentrations of PCBs in the blood serum samples of subjects. We enrolled 602 adult subjects from eastern Slovakia with an average age of 45.14 (±8.49) years. To determine the concentrations of 21 PCB congeners, we used solid phase extraction along with gas chromatography coupled with high-resolution mass spectrometry. Based on questionnaire data, the assessment of dietary habits and residential location was performed using score calculations and creating a map. Through principal component analysis, the 20 PCB congeners were classified into three groups: PC1, comprising highly chlorinated PCBs, and PC2 and PC3, consisting primarily of low chlorinated PCBs. Stepwise multivariate regression revealed positive and negative associations between PCB congeners represented by PC1-3 and scores related to the residential location and scores related to food consumption, respectively. We confirmed that levels of PCBs represented by PC1-3 increased with age. The geographical proximity to pollution sources proved to be a key contributing factor to the observed PCB levels in individuals residing in eastern Slovakia.

Modeled Pathways and Fluxes of PCB Dechlorination by Redox Potentials.

Dechlorination is one of the main processes for the natural degradation of polychlorinated biphenyls (PCBs) in an anaerobic environment. However, PCB dechlorination pathways and products vary with PCB congeners, types of functional dechlorinating bacteria, and environmental conditions. The present study develops a novel model for determining dechlorination pathways and fluxes by tracking redox potential variability, transforming the complex dechlorination process into a stepwise sequence. The redox potential is calculated via the Gibbs free energy of formation, PCB concentrations in reactants and products, and environmental conditions. Thus, the continuous change in the PCB congener composition can be tracked during dechlorination processes. The new model is assessed against four measurements from several published studies on PCB dechlorination. The simulation errors in all four measurements are calculated between 2.67 and 35.1% under minimum (n = 0) and maximum (n = 34) numbers of co-eluters, respectively. The dechlorination fluxes for para-dechlorination pathways dominate PCB dechlorination in all measurements. Furthermore, the model also considers multiple-step dechlorination pathways containing intermediate PCB congeners absent in both the reactants and the products. The present study indicates that redox potential might be an appropriate indicator for predicting PCB dechlorination pathways and fluxes even without prior knowledge of the functional dechlorinating bacteria.

Assessing Polychlorinated Biphenyls (PCBs) Contamination in Indoor Dust among University Students in Ilorin, Nigeria

Background: This study aimed to assess the contamination of Polychlorinated Biphenyls (PCBs) in indoor dust among university students in Ilorin, Nigeria. Methods: One hundred (100) indoor dust samples were collected from different locations within university hostels. Two Universities in Ilorin were sampled for the study; the Univerisity of Ilorin and Al-Hikmah University. Gas chromatography-mass spectroscopy (GC-MS) was employed to analyze and identify fourteen PCB congeners. Results: The results revealed that university students were exposed to low levels of PCB contamination in indoor dust. The concentrations of individual PCB congeners ranged from 4.993ng/g to 37.701ng/g. Notably, PCB-52 and PCB-118 were the predominant congeners, with mean concentrations of 37.701ng/g and 30.928ng/g. Conversely, PCB-44 exhibited the lowest occurrence, with a mean concentration of 4.993ng/g. The study found positive correlations among specific PCB congeners, suggesting familiar sources and environmental behaviors. However, no significant correlations were found between residential characteristics and measured PCB levels. Conclusion: The results emphasize the need for further research to minimize PCB contamination in indoor environments and protect human health. It is recommended that PCB levels be monitored in indoor environments and enforce strong regulations to control PCB production, use, and disposal.

SAT427 Effects Of Polychlorinated Biphenyls (PCBs) On Transcription Factor NFκB Activation In Neonatal Rat Microglia Primary Culture

Abstract Disclosure: C.E. Dressel: None. G.M. Valdez: None. M.R. Bell: None. Polychlorinated biphenyls (PCBs) are a class of persistent organic pollutants that are lipophilic and accumulate in the food chain. Despite bans on PCB production, human exposure continues and can cause disruptions in endocrine, nervous, and immune system functions. As such, PCBs may interfere with the actions of microglia, the innate immune cells of the central nervous system. Healthy microglia are critical for neural development, maintenance of neural functions, and responses to stress, injury, or infection. Initial studies of primary neonatal rat microglial cultures indicate that PCBs alter gene expression of proinflammatory cytokine TNF-α and IL-1β in response to a secondary inflammatory lipopolysaccharide (LPS) challenge. Production of these cytokines is, in part, regulated by transcription factor NFκB. This experiment tests the hypothesis that PCBs alter NFκB activation in neonatal microglia. The forebrains of male and female neonatal Sprague-Dawley rats were dissected to remove meninges, homogenized with collagenase and gentle trituration, and plated on coverslips in DMEM FBS+ media to establish a primary mixed glial culture. After one week, microglia were subcultured using mild trypsin treatment and maintained in conditioned media for 24 hours. The microglia were then exposed to either PCB 153 (0.1 µM) or DMSO vehicle control (0.036%) for 18 hours. After 18 hours, the cells were treated with either LPS (0.5 µg/mL) or PBS vehicle control for 4 hours and then fixed. Immunocytochemistry was used to visualize NFκB and identify microglia, with anti-p65 and Ox42 antibodies, respectively. Coverslips were mounted with DAPI-containing media and the cells were imaged via confocal microscopy. In response to immune activation, NFκB typically translocates from the cytosol to the nucleus. Therefore, we assessed NFκB activation by quantifying p65 fluorescent pixel intensity and percentage of area covered in nuclear or cytoplasmic regions according to DAPI and Ox42 channel masks using ImageJ. A two-way ANOVA was used to identify the effects of PCB vs. DMSO exposure and LPS vs. PBS challenge. Preliminary data indicated that LPS increased the ratio of nuclear to cytosolic NFκB, as expected. PCB exposed cells tended to have lower NFκB presence in the nucleus and cell as a whole, but a greater proportion of NFκB staining localized within the nucleus relative to the rest of the cell. With the current sample (n=4-6 per group, 2-3 males and females each), no interactions between PCBs and LPS were observed. Continued work will increase sample size to explore sex differences and the time course of NFκB response to PCBs, which may help broaden our understanding of the mechanisms by which PCBs affect normal brain activity and disrupt healthy endocrine, immune, and neural development. Presentation: Saturday, June 17, 2023

Congener-Specific Emissions from Floors and Walls Characterize Indoor Airborne Polychlorinated Biphenyls.

To reconcile the federal regulation of material polychlorinated biphenyl (PCB) concentrations with recently implemented state regulations of airborne PCBs, there is a need to characterize the relationship between PCB emissions from surfaces and air concentrations. We hypothesized that the magnitude and congener distribution of emissions from floors and walls fully account for the airborne PCBs measured in rooms constructed during the height of PCB production and sales. We measured emissions of PCB congeners from various wall and floor materials using polyurethane foam passive emission samplers before and after hexane wiping. Our results revealed that PCB emissions from flooring adequately predicted the magnitude and congener distribution of PCBs observed in the room air. Emissions varied by material within a single building (5 × 103 ng m-2 day-1 from wood panel walls to 3 × 104 ng m-2 day-1 from vinyl tile) and within the same room. Yet congener distributions between material emission PCB profiles and room air PCB profiles were statistically similar. Hexane wiping significantly reduced PCB emissions (>60%), indicating the importance of surface films as an ongoing source of airborne PCBs. The magnitude and congener distribution of material bulk concentrations did not explain that of material emissions or air concentrations. Passive measurements of polychlorinated biphenyl emissions from floors in a university building predict the concentrations of PCBs in room air.

Variation in natural attenuation rates of polychlorinated biphenyls (PCBs) in fish from streams and reservoirs in East Tennessee observed over a 35-year period

Environmental contamination due to human activities is a major concern, particularly for persistent chemicals. Within catchments, persistent chemicals linked to negative health outcomes such as polychlorinated biphenyls (PCBs) have great potential to be transported, through adsorption or biological uptake, with downstream locations acting as sinks for accumulation. Here we present long-term trends in PCB bioaccumulation in fish found in lower-order tributaries on the Oak Ridge Reservation, an impacted US Department of Energy property in East Tennessee, USA, and a large reservoir system adjacent to it composed of parts of the Clinch and Tennessee Rivers. Given that the reservoir system has experienced no direct PCB mitigation activities, this record offers an opportunity to explore potential natural attenuation of PCBs within a large lotic ecosystem. Attenuation rates ranged from 0% to 8% yr-1 in minnows and sunfish at stream sites and 5.4–11.3% yr-1 in catfish at reservoir sites. These rates are comparable to findings from similar studies in other regions, suggesting a consistency in responses since the banning of PCB production in 1979. Further, results suggest that PCB sources from discharge outfalls are important locally but are not primarily responsible for sustaining PCB contamination in downstream reservoirs.

PCBs in indoor air and human blood in Pittsfield, Massachusetts

Concentrations of polychlorinated biphenyls (PCBs) and three chlorinated pesticides were determined in serum from 21 residents of Pittsfield, MA and in the basement, living room and outdoor air of the 10 homes in which they lived. Median serum PCB levels were 4.2 ng/g, which are at least four times the average level in the US population, and consisted primarily of more highly chlorinated, persistent congeners. This reflects contamination with PCBs coming from the local General Electric facility. Median basement air concentration was 20.3 ng/m3, while the median living room air was 11.4 ng/m3 and median outdoor air concentration was 3.0 ng/m3. The PCB congeners detected in air were primarily low chlorinated (four and fewer) congeners, reflecting the greater volatility of PCBs with fewer chlorines. The congener pattern between basement and living room air showed a 95% correlation, while correlation with outdoor air was much less. While the congener pattern in air is very different from that of the PCB products used in Pittsfield (Aroclors 1254 and 1260), low chlorinated PCBs are detected in the vapor phase after air is blown across the commercial mixtures. The human serum samples did not show detectible levels of many of the congeners seen in the basement air samples, reflecting rapid metabolism of lower chlorinated PCBs by the human body. However, with continuous inhalation of indoor air, especially in the living room, the exposure to these non-persistent congeners may still have adverse health effects. Cellular studies of some of these non-persistent, low chlorinated congeners indicate that they are neurotoxic, mutagenic and cytotoxic. These results demonstrate the importance of consideration of inhalation of PCBs as a route of exposure, especially in indoor sites, and suggest that monitoring serum PCB concentration may not always provide a good measurement of exposure, especially to congeners that are relatively rapidly metabolized but have significant toxicity.

Temporal trend of polychlorinated biphenyls contamination in the northwestern Arabian Gulf – Evidence from sediment records

This study provides an insight into the polychlorinated biphenyls (PCBs) inventories in the sediments of the northwestern Arabian/Persian Gulf. PCBs can be used as chemical markers that correlate with historical events in the region, to estimate the sedimentation rates in the northern Gulf, and to determine the sources of pollutants in the study area. The concentrations of PCBs were generally patchy in sediments. At Station 1 the ΣPCB concentrations generally fluctuated between 0.100 and 0.400 ng g−1 dw throughout the depositional history measured in a sediment core. There were four peaks in the ΣPCB profile corresponding to 1969, 1979, 1983 and 1991. Station 2 showed a prominent peak at depth of 25 cm. The concentrations of the ΣPCBs and ΣICE congeners at this depth were 28 and 12 ng g−1 dw respectively. Concentrations then dropped dramatically thereafter by a factor of 4. The ΣPCB concentrations at Station 3 were very low compared to the concentrations measured at Stations 1 and 2. The PCB concentration in Core 4 which was taken from open waters was 2–3 orders of magnitude lower than those in the other coastal cores. However, a 1990–91 peak was omnipresent in these cores. There is no record of PCB production within the Gulf region, and PCB releases into the Kuwait marine environment are likely to originate from their use in products. These maxima in early-1990s can be correlated to inputs from war-related activities, including the reported destruction of PCB-containing transformers and military equipment during the occupation of Kuwait. None of the recent sediment core sections at the four stations had a ΣPCB concentration near the effects range-median (ERM) concentration of 180 ng g−1, or permissible exposure limits (PEL) of 189 ng g−1, or were above the effect range-low (ERL) values of 22.7 ng g−1.

Exposure to polychlorinated biphenyls and organochlorine pesticides and thyroid cancer in connecticut women

BackgroundThyroid cancer incidence has increased substantially over the past decades, and environmental risk factors have been suggested to play a role. Polychlorinated biphenyls (PCB) and organochlorine pesticides (OCP) are established thyroid hormone disruptors, but their relationship to thyroid cancer is not known. MethodsWe investigated the relationship between serum PCB and OCP concentrations and papillary thyroid cancer (PTC) in 250 incident female PTC cases and 250 female controls frequency-matched on age, all residing in Connecticut. Interviews and serum samples were collected from 2010 to 2013. Samples were analyzed for 32 different chemicals using gas chromatography with isotope dilution high resolution mass spectrometry. We calculated odds ratios (OR) and 95% confidence intervals (CI) using single pollutant logistic regression models for concentrations (per interquartile range) of individual PCB/OCP and summed groups of structurally or biologically similar PCB/OCP, adjusted for education, family history of cancer, alcohol consumption, age, and body mass index. Sub-analyses included stratification by tumor size (≤ and >1 cm) and birth before or during peak PCB production (born in 1960 or earlier and born after 1960), as exposures during early life may be important. We also applied three multi-pollutant approaches (standard multi-pollutant regression, hierarchical Bayesian modeling, principal components regression analysis) to investigate associations with co-exposures to multiple PCB/OCPs. ResultsNo PCB/OCPs were positively associated with PTC in primary analyses. Statistically significant associations were observed for 9 of the 32 chemicals and 3 summed groups of similar chemicals in the those born during peak production based on single-pollutant models. Multi-pollutant analyses suggested null associations overall. ConclusionsOur results using single and multi-pollutant modeling do not generally support an association between PCB or OCP exposure and PTC, but some associations in those born during peak production suggest that additional investigation into early-life exposures and subsequent thyroid cancer risk may be warranted.

A Critical Review of Polychlorinated Biphenyls Metabolism, Metabolites, and Their Correlation with Oxidative Stress.

Polychlorinated biphenyls (PCBs) are notorious persistent organic pollutants that were banned in the last century. However, PCBs still remain ubiquitous in the ecosystem due to their persistence and bioaccumulative potency against environmental and biological degradation. Albeit there is no longer the permission of commercial production of PCBs, they were continuously released into global biota via illegal disposal of e-waste or as byproducts of industrial supplies. The role of oxidative stress is often implicated in PCBs' toxicology. PCBs, especially coplanar ones, have a high affinity toward aryl hydrocarbon receptors and inducing CYP1A1, which is considered as a source of oxidative stress. Although commercial PCBs and coplanar individual PCBs, for example, PCB 77 and 126, induced oxidative stresses have been extensively investigated, PCB metabolite-induced oxidative stress has received less attention. PCBs can undergo phase I metabolism which metabolizes the parent PCBs into hydroquinone/semiquinone/quinone metabolites as a futile redox cycle, producing downstream reactive oxygen species (ROS) as byproducts. PCBs can also undergo phase II metabolism yielding methylsulfonyl metabolites that deplete glutathione and such. PCB metabolites induce oxidative stress generally via direct production of ROS or indirect scavenge antioxidant and inhibit antioxidant enzymes, disturbing cellular redox balance. This review aims to provide a critical summary of PCBs metabolism, PCBs parents, and daughter metabolite-induced oxidative stress. We especially focus on the connection between parent PCBs and downstream metabolites, to encourage research associated with PCB metabolite-induced oxidative stress.

Cardiovascular Effects of Polychlorinated Biphenyls and Their Major Metabolites.

Background:Xenobiotic metabolism is complex, and accounting for bioactivation and detoxification processes of chemicals remains among the most challenging aspects for decision making with in vitro new approach methods data.Objectives:Considering the physiological relevance of human organotypic culture models and their utility for high-throughput screening, we hypothesized that multidimensional chemical-biological profiling of chemicals and their major metabolites is a sensible alternative for the toxicological characterization of parent molecules vs. metabolites in vitro.Methods:In this study, we tested 25 polychlorinated biphenyls (PCBs) [PCB 3, 11, 52, 126, 136, and 153 and their relevant metabolites (hydroxylated, methoxylated, sulfated, and quinone)] in concentration–response () for effects in human induced pluripotent stem cell (iPSC)-derived cardiomyocytes (CMs) and endothelial cells (ECs) (iPSC-derived and HUVECs). Functional phenotypic end points included effects on beating parameters and intracellular flux in CMs and inhibition of tubulogenesis in ECs. High-content imaging was used to evaluate cytotoxicity, mitochondrial integrity, and oxidative stress.Results:Data integration of a total of 19 physicochemical descriptors and 36 in vitro phenotypes revealed that chlorination status and metabolite class are strong predictors of the in vitro cardiovascular effects of PCBs. Oxidation of PCBs, especially to di-hydroxylated and quinone metabolites, was associated with the most pronounced effects, whereas sulfation and methoxylation of PCBs resulted in diminished bioactivity.Discussion:Risk characterization analysis showed that although in vitro derived effective concentrations exceeded the levels measured in the general population, risks cannot be ruled out due to the potential for population variability in susceptibility and the need to fill data gaps using read-across approaches. This study demonstrated a strategy for how in vitro data can be used to characterize human health risks from PCBs and their metabolites. https://doi.org/10.1289/EHP7030

Dichlorobiphenyls and chlorinated benzoic acids – Emergent soil pollutants in model bacterial membranes. Langmuir monolayer and Grazing Incidence X-ray Diffraction studies

Abstract The multi-decade worldwide application of polychlorinated biphenyls (PCB) leads to the problem of soil pollution. The production and application of PCB was banned, so the gradual decrease of their concentration in the soils was expected. On the contrary, novel sources of dichlorobiphenyls as PCB 11 were identified and these emergent pollutants are still emitted to the environment. Dichlorobiphenyls and some chlorobenzoic acids (CBA) are known as dead-end PCB metabolites – they accumulate in the soils and being toxic to microorganisms lead to the impoverishment of soil decomposer consortia. The toxicity of PCB and CBA is connected with their membrane activity and accumulation in the bacterial membranes. The correlation between the phospholipid composition of the bacterial membrane and the toxicity of PCB and CBA is unfortunately unknown limiting the effective selection of bacterial species for bioremediation of polluted soils. To shed light on these phenomena we applied binary phospholipid Langmuir monolayers as model bacterial membranes. With these models we studied the phenomena of dichlorobiphenyls and selected CBA molecules' incorporation and the effects exerted by these molecules on the ordering of the phospholipid molecules at the molecular scale. For the studies of the organization of the model membranes we applied Grazing Incidence X-ray Diffraction. It turned out that the model membranes rich in cardiolipin can accumulate more pollutant molecules than the models containing phosphatidylglycerols. The accumulation of the pollutants did not cause any significant changes in the 2D crystalline structure of the former models whereas the latter were profoundly modified.

Evidence Implicating Non-Dioxin-Like Congeners as the Key Mediators of Polychlorinated Biphenyl (PCB) Developmental Neurotoxicity.

Despite being banned from production for decades, polychlorinated biphenyls (PCBs) continue to pose a significant risk to human health. This is due to not only the continued release of legacy PCBs from PCB-containing equipment and materials manufactured prior to the ban on PCB production, but also the inadvertent production of PCBs as byproducts of contemporary pigment and dye production. Evidence from human and animal studies clearly identifies developmental neurotoxicity as a primary endpoint of concern associated with PCB exposures. However, the relative role(s) of specific PCB congeners in mediating the adverse effects of PCBs on the developing nervous system, and the mechanism(s) by which PCBs disrupt typical neurodevelopment remain outstanding questions. New questions are also emerging regarding the potential developmental neurotoxicity of lower chlorinated PCBs that were not present in the legacy commercial PCB mixtures, but constitute a significant proportion of contemporary human PCB exposures. Here, we review behavioral and mechanistic data obtained from experimental models as well as recent epidemiological studies that suggest the non-dioxin-like (NDL) PCBs are primarily responsible for the developmental neurotoxicity associated with PCBs. We also discuss emerging data demonstrating the potential for non-legacy, lower chlorinated PCBs to cause adverse neurodevelopmental outcomes. Molecular targets, the relevance of PCB interactions with these targets to neurodevelopmental disorders, and critical data gaps are addressed as well.

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.

Polychlorinated biphenyl toxicity in the thyroid gland of wild ungulates: an in vitro model

Polychlorinated biphenyls (PCBs) are carcinogens causing endocrine disruption. While production of PCBs is now banned, wildlife exposure still occurs due to environmental contamination. We investigated thyroid toxicity in wild ungulates using three-dimensional primary thyrocyte cultures exposed to PCB 138 for 24, 48, and 72 h at concentrations ranging within 0–3000 ng/ml. Thyrocyte viability ranged within 78.71–118.34%, 98.14–104.45%, and 84.16–106.70% in fallow deer-, mouflon-, and roe deer-derived cells, respectively. Viability decreased significantly in fallow deer (P = 0.012) and roe deer (P = 0.002) thyrocytes exposed for 48 h at 30 ng/ml. While cytotoxicity ranged within 2.36–16.37%, 3.19–9.85%, and 2.76–11.21% in fallow deer, mouflon, and roe deer, respectively, only roe deer displayed significantly higher cytotoxicity at a 3 ng/ml exposure (P < 0.05) and lower cytotoxicity at 30 ng/ml (P < 0.01). Exposure to 30 ng/ml for 24 and 48 h induced reactive oxygen species in fallow deer. Iodide uptake at 30 ng/ml exposure increased after 24 h in fallow and roe deer, but showed a significant drop after 48 and 72 h in fallow deer, mouflon, and roe deer. Thyroxine T4 release at 30 ng/ml exposure decreased significantly after 48 and 72 h; 24, 48 and 72 h; and 48 h in fallow deer, mouflon, and roe deer, respectively. Our findings indicate time- and species-dependent effects of PCB on performance and thyrocyte function. Use of cell culture models reduces the number of experimental specimens, increases test species welfare and replaces whole organisms with specific target cells.

Sources of polychlorinated biphenyl blank contamination and their impact on fingerprinting

The development of high-resolution mass spectrometry methods for the measurement of polychlorinated biphenyls (PCBs) in environmental samples has dramatically reduced detection limits, leading to problems obtaining clean blanks. When PCBs are detected in samples at concentrations similar to the blanks, blank contamination must be addressed before fingerprinting and source apportionment through positive matrix factorization (PMF) can be successful. We tested a variety of blank correction methods using data from a study of water column concentrations of PCBs in the Spokane River, where concentrations of Σ209PCBs in whole water samples averaged 171 pg/L without blank correction and Σ209PCBs in the blanks averaged 88 pg/L. The results suggest that subtracting blank masses from sample masses can lead to erroneous results. Instead, censoring at one times the batch-specific blank level is a better approach. The sources of PCBs in field and method blanks were investigated by examining their congener profiles via PMF. The results suggest that commercial PCB formulations (in the US, Aroclors) continue to be the primary source of PCBs in blanks forty years after PCB production and use were banned in the United States. Other sources of PCBs to blanks include PCB 11 from pigments; PCBs 44 + 47 + 65, 45 + 51, and 68 arising from polymers cured using bis(2,4-dichlorobenzoyl) peroxide; and PCBs 1, 2, 3, 4, 8, 15 and others arising from silicone products derived from phenylsiloxanes, such as silicone-based adhesives.

Polychlorinated biphenyls in the soil–crop–atmosphere system in e-waste dismantling areas in Taizhou: Concentrations, congener profiles, uptake, and translocation

Samples of soil, air, and locally grown crops from around an old e-waste dismantling area (Fengjiang) and a new e-waste dismantling area (Binhai) in Taizhou were analyzed to investigate the behavior of polychlorinated biphenyls (PCBs) released during e-waste dismantling in the soil–crop–atmosphere system. The results indicated that PCB pollution is still widespread in the study area. The PCB concentrations were clearly higher in soil from FJ than in soil from BH, and the concentrations in the functional zones decreased strongly in the order industry park > residential area > farmland. Historical and current emissions during e-waste dismantling processes are probably the main sources of PCBs to soil because PCB production and use are banned. The long half-lives of PCBs have caused the target congener concentrations in soil not to decrease markedly over 10 years. The “halo effect” may have caused PCBs in soil in the heavily polluted FJ area to diffuse into the surrounding area. Soil–air exchange of PCBs in heavily contaminated FJ area may supply PCBs to air because the temperatures in Taizhou are often high. PCBs can accumulate in crops through various pathways. Less-chlorinated PCBs (mainly including Tri-PCBs) can enter crops by root uptake and translocated to the aerial tissues, and more-chlorinated PCBs (including Penta-PCBs and Hexa-PCBs) at high concentrations in soil can enter underground crop tissues through passive transport. More-chlorinated PCBs in underground tissues cannot be transferred to aboveground tissues of tall crops but may be transferred to aboveground tissues of short crops through the root-to-stem pathway and through soil dust being transferred to aboveground external surfaces.

The developmental neurotoxicity of legacy vs. contemporary polychlorinated biphenyls (PCBs): similarities and differences.

Although banned from production for decades, PCBs remain a significant risk to human health. A primary target of concern is the developing brain. Epidemiological studies link PCB exposures in utero or during infancy to increased risk of neuropsychiatric deficits in children. Nonclinical studies of legacy congeners found in PCB mixtures synthesized prior to the ban on PCB production suggest that non-dioxin-like (NDL) congeners are predominantly responsible for the developmental neurotoxicity associated with PCB exposures. Mechanistic studies suggest that NDL PCBs alter neurodevelopment via ryanodine receptor-dependent effects on dendritic arborization. Lightly chlorinated congeners, which were not present in the industrial mixtures synthesized prior to the ban on PCB production, have emerged as contemporary environmental contaminants, but there is a paucity of data regarding their potential developmental neurotoxicity. PCB 11, a prevalent contemporary congener, is found in the serum of children and their mothers, as well as in the serum of pregnant women at increased risk for having a child diagnosed with a neurodevelopmental disorder (NDD). Recent data demonstrates that PCB 11 modulates neuronal morphogenesis via mechanisms that are convergent with and divergent from those implicated in the developmental neurotoxicity of legacy NDL PCBs. This review summarizes these data and discusses their relevance to adverse neurodevelopmental outcomes in humans.

Identification of Sulfonated and Hydroxy-Sulfonated Polychlorinated Biphenyl (PCB) Metabolites in Soil: New Classes of Intermediate Products of PCB Degradation?

In this paper we describe the identification of two classes of contaminants: sulfonated-PCBs and hydroxy-sulfonated-PCBs. This is the first published report of the detection of these chemicals in soil. They were found, along with hydroxy-PCBs, in soil samples coming from a site historically contaminated by the industrial production of PCBs and in background soils. Sulfonated-PCB levels were approximately 0.4-0.8% of the native PCB levels in soils and about twice the levels of hydroxy-sulfonated-PCBs and hydroxy-PCBs. The identification of sulfonated-PCBs was confirmed by the chemical synthesis of reference standards, obtained through the sulfonation of an industrial mixture of PCBs. We then reviewed the literature to investigate for the potential agents responsible for the sulfonation. Furthermore, we predicted their physicochemical properties and indicate that, given the low pKa of sulfonated- and hydroxy-sulfonated-PCBs, they possess negligible volatility, supporting the case for in situ formation from PCBs. This study shows the need of understanding their origin, their role in the degradation path of PCBs, and their fate, as well as their (still unknown) toxicological and ecotoxicological properties.

Dynamics of PCB exposure in the past 50 years and recent high concentrations in human breast milk: Analysis of influencing factors using a physiologically based pharmacokinetic model

In this study we reconstruct the long-term exposure of Czech mothers to polychlorinated biphenyls (PCBs) and determine the causes of high contamination of breast milk by indicator PCBs (iPCBs). A data set containing information from more than 1000 primiparous women from the Czech Republic was used, including iPCB concentrations in breast milk, individual physiology and living characteristics. The time series of PCB intakes for the whole period from the beginning of PCB production in 1958 until 2011 were reconstructed. We estimated the individual lifetime exposure of mothers for all iPCBs, i.e. congeners 28, 52, 101, 118, 138, 153 and 180, using a physiologically based pharmacokinetic (PBPK) model. Various model scenarios were investigated to determine the influence of physiology, age at delivery, past dietary exposure, and food composition on concentrations in breast milk for all iPCBs. The highest contributions to the presence of iPCBs in breast milk were observed for food composition. The main factor determining the concentration of higher-chlorinated PCBs (138, 153 and 180) was past exposure. The most important parameter for identification of children's postnatal exposure through breast milk was the time-span from the maximum of the exposure peak to the birth of the child. The current concentrations of iPCBs in breast milk in the Czech population are still high because the maximum of the exposure peak occurred more than 10 years later than in other European countries and was very broad, e.g. covered more than 10 years.