PCB 77 dechlorination products modulate pro-inflammatory events in vascular endothelial cells

Persistent organic pollutants such as polychlorinated biphenyls (PCBs) are associated with detrimental health outcomes including cardiovascular diseases. Remediation of these compounds is a critical component of environmental policy. Although remediation efforts aim to completely remove toxicants, little is known about the effects of potential remediation byproducts. We previously published that Fe/Pd nanoparticles effectively dechlorinate PCB 77 to biphenyl, thus eliminating PCB-induced endothelial dysfunction using primary vascular endothelial cells. Herein, we analyzed the toxic effects of PCB congener mixtures (representative mixtures of commercial PCBs based on previous dechlorination data) produced at multiple time points during the dechlorination of PCB 77 to biphenyl. Compared with pure PCB 77, exposing endothelial cells to lower chlorinated PCB byproducts led to improved cellular viability, decreased superoxide production, and decreased nuclear factor kappa B activation based on duration of remediation. Presence of the parent compound, PCB 77, led to significant increases in mRNA and protein inflammatory marker expression. These data implicate that PCB dechlorination reduces biological toxicity to vascular endothelial cells.     

Extensive biodegradation of polychlorinated biphenyls in Aroclor 1242 and electrical transformer fluid (Askarel) by natural strains of microorganisms indigenous to contaminated African systems

Evidence for substantial aerobic degradation of Aroclor 1242 and Askarel fluid by newly characterized bacterial strains belonging to the Enterobacter, Ralstonia and Pseudomonas genera is presented. The organisms exhibited degradative activity in terms of total PCB/Askarel degradation, degradation of individual congeners and diversity of congeners attacked. Maximal degradation by the various isolates of Askarel ranged from 69% to 86% whereas, Aroclor 1242, with the exception of Ralstonia sp. SA-4 (9.7%), was degraded by 37% to 91%. PCB analysis showed that at least 45 of the representative congeners in Aroclor 1242 were extensively transformed by benzoate-grown cells without the need for biphenyl as an inducer of the upper degradation pathway. In incubations with Aroclor 1242, no clear correlation was observed between percentage of congener transformed and the degree of chlorination, regardless of the presence or absence of biphenyl. Recovery of significant but nonstoichiometric amounts of chloride from the culture media showed partial dechlorination of congeners and suggested production of partial degradation products. Addition of biphenyl evidently enhanced dechlorination of the mixture by some isolates. With the exception of Ralstonia sp. SA-5, chloride released ranged from 24% to 60% in the presence of biphenyl versus 0.35% to 15% without biphenyl.     

Coating effects on the glass adsorption of polychlorinated biphenyl (PCB) congeners

The effects of coating materials on polychlorinated biphenyl (PCB) adsorption in aqueous solution were assessed in an attempt to minimize PCB sorption loss during sampling processes. A coating material, which enhances PCB adsorption and allows adsorbed PCBs to be readily extracted by solvents, can act as a sampling concentrator to reduce PCB losses from both adsorption and evaporation. Several coating materials were evaluated, including paraffin oil, silicone oil, dimethyldichlorosilane (Sylon-CT), Prosil 28^® and polydimethylsiloxane (PDS) with viscosity 0.65, 50 (PDS 50), and 500 (PDS 500) cSt. PDS and silicone oil enhanced adsorption for all five congeners examined (IUPAC No. 28, 52, 101, 138, and 180). Sylon-CT, paraffin oil and Prosil 28^® had inconsistent effects on adsorption of different congeners. Desorption of adsorbed PCBs onto all coating types was assessed. The recovery efficiency of extracting PCBs with solvents was enhanced greatly with all coatings as opposed to non-coated surfaces, with the exception of paraffin oil. Coating with silicon oil, PDS 50, and 500 resulted in virtually 100% recovery of adsorbed PCBs. It was also found that Teflon containers were poor substitutes for glass containers and failed to minimize PCB losses. Among the materials studied, the best coating that could be used as a sampling concentrator was PDS 500.     

Reductive dechlorination of polychlorinated biphenyls as affected by sediment characteristics

The effect of sediment sources on the selection of polychlorinated biphenyl (PCB) dechlorinating competence was investigated using sediments from two different locations, the Grasse River and Owasco Lake. These two sediments had a similar organic carbon content but different particle size distribution. The two PCB-free sediments were spiked with Aroclor 1248 and inoculated with microorganisms from the Reynolds and General Motors sites in the St. Lawrence River, which exhibited different dechlorination patterns. When each inoculum was serially transferred into fresh sediments four times (every 8-10 weeks), they still maintained the initial dechlorination patterns regardless, the source of sediments and the number of transfers, and dechlorination patterns of the two inocula in the same sediments did not converge. In a parallel approach, when the acclimated microorganisms from the Reynolds site were inoculated into fresh sediments from both sources as well as sediments enriched with organic carbon (2%, w/v), the dechlorination pattern remained unchanged after a 40-week incubation. These results suggest that the sediment characteristics or organic carbon content did not play a role in the selection of dechlorinating populations.     

Development of a new polyclonal antibody for the determination of polychlorinated biphenyls in indoor air by ic-ELISA

A new polyclonal antibody (pAb) was prepared and used for the determination of polychlorinated biphenyls (PCBs) in air samples to promote the application of immunoassay technology in the determination of PCBs. Three PCB congeners immunogen mixture was used to stimulate immune responses in rabbits. The specific pAb to PCBs was obtained and used to develop an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA). A standard curve for Aroclor 1248 was prepared using concentrations ranging from 0.1 to 100 μg L^?1. The average IC₅₀ value was 16.21 μg L^?1 and the limit of detection at 10 % inhibition (IC₉₀) was 0.069 μg L^?1. The entire procedure was then evaluated using spiked air samples. The recoveries of Aroclor 1248 at various spiking levels in the air samples ranged from 84 to 113 %, with relative standard deviations of 3 to 6 %. Under optimum conditions, the cross-reactivity profiles of the assays were obtained using three selected congeners, four Aroclor products, and other structurally related compounds of PCBs. The assays were found to be highly specific for PCB congeners and Aroclors 1248 and 1242. The air samples were then analyzed using gas chromatography coupled with high-resolution mass spectrometry to confirm the ic-ELISA results. The attained results demonstrated that the proposed method was an effective and inexpensive technique for the PCBs determination in air samples.     

PCB accumulation in osprey exposed to local sources in lake sediment

We examined the accumulation of PCBs in ospreys (Pandion haleaetus) that were exposed to local sediment sources. Eggs, chick plasma, and sediment samples were collected over a range of 14 km (0.2-14.2 km) from a PCB source in Sturgeon Lake, ON. Sum PCB concentrations declined in chick plasma (range 422.5-58.3 ng/g) as distance from the PCB source increased, but there was a poor relationship with sum PCBs in eggs. Both tissues indicated an Aroclor 1248/1254 source. Aroclor 1254 comprised an average of 66.9% of sum PCBs in chick plasma from Sturgeon Lake, but comprised only from 27.0 to 44.4% in plasma from other Great Lake colonies. Dietary differences among osprey colonies were not sufficient to explain the PCB patterns observed. There was weak evidence that the ability to metabolize PCBs may differ between juveniles and adults, based upon the PCB profile in eggs and chick plasma.     

Dechlorination of PCBs by electrochemical reduction with aromatic radical anion as mediator

Mediated electrochemical reduction was applied to the dechlorination of polychlorinated biphenyls (PCBs) in tetra-n-butylammonium perchlorate/dimethylformamide solution. Rapid and complete dechlorination was possible with biphenyl or naphthalene as the mediator, whereas the reaction was much slower with anthracene or 9,10-diphenylanthracene. The reaction rate was so high with naphthalene or biphenyl radical anion that differences in reactivity could not be observed between congeners. Side reactions, other than biphenyl formation, could occur depending upon the mediators and the substrates, but contributed less than 10% of the total products in the case of naphthalene-mediated dechlorination. Almost all chloride ion formed in the dechlorination remained in the cathode solution. The order of the reaction was determined to be 0.5 for the substrate and 1 for the mediator (naphthalene) in the dechlorination of 2-chlorobiphenyl; identical to results for the mediated dechlorination of 1-chloronaphthalene. The reaction rate in practical PCB dechlorination could be estimated with the use of the initial concentration of the mediator and chlorine content of the solution provided that the problem of the deactivation of the electrode surface could be solved.     

Aroclor misidentification in environmental samples: how do we communicate more effectively between the laboratory and the data user?

Disposal of carbonless copy paper (CCP) paper sludge during the 1960s contaminated a site in the USA with PCBs. Despite historic records of CCP sludge disposal and absence of evidence of any other disposal, a dispute arose among the parties over the source of the PCBs. Aroclor 1242 is well documented as the PCB mixture used in CCP, yet Aroclors 1242, 1248, 1254, and 1260 were reported by the analytical laboratory. How could the PCBs at a single, small site be reported as four different Aroclors? Some claimed that there had to be at least four Aroclors source inputs to the site. Disposal of four different Aroclors at this site would simply defy logic and the historic record. Weathering of the mixtures is part of the story. A larger issue is the conflict between the intent of the USEPA 8082 method to determine the total PCB content in environmental samples to facilitate environmental cleanup and disposal decisions within a regulatory context versus the data users’ intent to identify the PCB sources. This inappropriate extension of the data leads to erroneous conclusions. To mitigate problems like this, laboratory analysis requests need to be matched to the intended data usage; conversely, the data must not be over-interpreted beyond the limits of the method. The PCB analysis community needs to develop a better articulation of the limits of Aroclor identification for the broader community that may naïvely assume that if the laboratory reports “Aroclor 1248,” then someone must have placed Aroclor 1248 at the site. After all, when a laboratory reports “lead” or “chloroform,” those identifications are never in question.     

Biodegradation of polychlorinated biphenyls using biofilm grown with biphenyl as carbon source in fluidized bed reactor

This study investigated the use of biofilms in the biodegradation of polychlorinated biphenyls. The biofilm used was developed on modified cement particles using mixed microbial culture isolated from PCB-contaminated soil. The biofilm formed was first acclimatized to PCBs by feeding the reactor alternately with biphenyl and PCBs. The acclimatized biofilm was tested on simulated PCB-contaminated water containing Aroclor 1260 by using a three-phase fluidized-bed reactor operated in batch mode. The initial batch run yielded 80+/-2.38% PCB removal from medium in one day and 91+/-1.34% in 5 days. The percent PCB removal gradually increased in the succeeding runs reaching 92+/-2.48% in one day and a steady state value of 95+/-2.01% in 5 days from batch eight onwards. PCB removal from the medium was highest during the first day reaching 80-92%. The sudden decrease in PCB concentration was attributed to an initial adsorption of the PCB on the biofilm and then the compound was degraded gradually. Yellow intermediates were observed as the pH of the medium decreased. These intermediate products were further metabolized as indicated by the disappearance of the yellow substance.     

Record of PCB congeners, sorbents and potential toxicity in core samples in Indiana Harbor and Ship Canal

Indiana Harbor and Ship Canal (IHSC) is an active navigational system that serves a heavily industrial area of southern Lake Michigan. We have determined the amount of polychlorinated biphenyls (PCBs), congener distributions, sorbent types and potential for dioxin-like PCB toxicity from two IHSC sediment cores. Vertical distributions of ΣPCBs (sum of 161 individual or coeluting congeners) ranged from 410 to 91000 and 1800 to 41000 ng g(-1) dry weight (d.w.) for cores 1 and 2, respectively. Core 1 showed its highest accumulation rate for the year ～1979 and exhibits a strong Aroclor 1248 signal in sediments accumulating over the last 60 years. It appears that from the late 1930s until the beginning of the 1980s there was a large and constant input of PCBs into this system. This pattern differs from lake cores from the Great Lakes region which commonly exhibit a rapid increase, a peak, followed by a sharp decrease in the PCB accumulation rates. Core 2 also has a strong Aroclor 1248 signal in the top layers, but deeper layers show evidence of mixtures of Aroclors and/or weathering processes. High levels of black carbon as a fraction of total organic carbon were found in both cores (median ～30%), which reflect the long history of local combustion sources. No strong relationship was found between ΣPCB concentration and sorbents. Both cores contain dioxin-like PCBs that are highest in concentration below the surface. The high levels of PCBs in the deep sediments are of concern because of plans to dredge this system.     

Spatial distribution and source apportionment of PCBs in sediments around İzmit industrial complexes, Turkey

The spatial distribution, degree of pollution and major sources of PCBs were evaluated in surficial sediments within the heavily urbanized and industrialized ?zmit Bay and its main freshwater inputs. ΣPCB concentrations range from 2.90 to 85.4ngg(-1) in marine sediments and from ND to 47.7ngg(-1) in freshwater sediments. Results suggest that high concentrations of ΣPCBs were localized around a chlor-alkali plant and an industry that handles bulk liquid, dry and drummed chemicals, and petroleum products in the Bay. Using a chemical mass balance receptor model (CMB), major sources of PCBs in the region were investigated. The CMB model identified Aroclor 1254 and 1260 to be the major PCB sources in marine sediments and the less chlorinated Aroclor 1248 and 1242 as the major PCB sources in freshwater sediments. The potential sources for the PCBs were briefly discussed in terms of their use in various industrial applications.     

Microbial dechlorination of polychlorinated biphenyls in anaerobic sewage sludge.

The potential of a chlorophenol (CP)-adapted consortium to dechlorinate polychlorinated biphenyls (PCBs) in sewage sludge was investigated. Results show that dechlorination rates differed significantly depending on sludge source and PCB congener. Higher total solid concentrations in sewage sludge and higher concentrations of chlorine in PCB resulted in slower dechlorination rates. No significant difference was found for 2,3,4,5-CB dechlorination from pH 6.0 to pH 8.0; however, dechlorination did not occur at pH 9.0 during a 41-day incubation period. Results show that at concentrations of 1 to 10 mg/L, the higher the PCB concentration, the faster the dechlorination rate. In addition, dechlorination rates were in the following order: methanogenic conditions > sulfate-reducing conditions > denitrifying conditions. The addition of acetate, lactate, pyruvate, and ferric chloride decreased lag times and enhanced dechlorination; however, the addition of manganese dioxide had an inhibitory effect. Dechlorination rates were also enhanced by the addition of PCB congeners, including 2,3,4-CB, 2,3,4,5-CB and 2,3,4,5,6-CB in mixture. Overall results show that the CP-adapted consortium has the potential to enhance PCB dechlorination. The optimal dechlorination conditions presented in this paper may be used as a reference for feasibility studies of PCB removal from sludge.     

PCB dechlorination hotspots and reductive dehalogenase genes in sediments from a contaminated wastewater lagoon

Polychlorinated biphenyls (PCBs) are a class of persistent organic pollutants that are distributed worldwide. Although industrial PCB production has stopped, legacy contamination can be traced to several different commercial mixtures (e.g., Aroclors in the USA). Despite their persistence, PCBs are subject to naturally occurring biodegradation processes, although the microbes and enzymes involved are poorly understood. The biodegradation potential of PCB-contaminated sediments in a wastewater lagoon located in Virginia (USA) was studied. Total PCB concentrations in sediments ranged from 6.34 to 12,700 mg/kg. PCB congener profiles in sediment sample were similar to Aroclor 1248; however, PCB congener profiles at several locations showed evidence of dechlorination. The sediment microbial community structure varied among samples but was dominated by Proteobacteria and Firmicutes. The relative abundance of putative dechlorinating Chloroflexi (including Dehalococcoides sp.) was 0.01–0.19% among the sediment samples, with Dehalococcoides sp. representing 0.6–14.8% of this group. Other possible PCB dechlorinators present included the Clostridia and the Geobacteraceae. A PCR survey for potential PCB reductive dehalogenase genes (RDases) yielded 11 sequences related to RDase genes in PCB-respiring Dehalococcoides mccartyi strain CG5 and PCB-dechlorinating D. mccartyi strain CBDB1. This is the first study to retrieve potential PCB RDase genes from unenriched PCB-contaminated sediments.     

Dechlorination of trichloroethylene by a steel converter slag amended with Fe(II)

This study aims to assess the feasibility of using slag, byproduct from iron and steel making industries, as a new reactive material for dechlorination reactions and to investigate dechlorination chemistries of the systems containing the slag and Fe(II). Initially, screening experiments were conducted to evaluate various systems containing slags with or without Fe(II). A combination of the steel converter slag and Fe(II) showed a potential to be developed as a reactive material to treat chlorinated organics. Further kinetic studies with the steel converter slag/Fe(II) systems revealed that the dechlorination capacity of the slag/Fe(II) system is comparable to that of zero-valent iron and generally higher than the cement/Fe(II) system. The slag/Fe(II) system can substantially dechlorinate trichloroethylene (TCE) in the neutral pH region, although the dechlorination rate was greatest in the pH region between 12 and 13. TCE reductions in the slag/Fe(II) system were observed to occur through reductive beta-elimination pathways that produce primarily acetylene and no chlorinated intermediates such as vinyl chloride. These results demonstrate that the steel converter slag with Fe(II) has sound characteristics for an alternative reactive medium for subsurface remediation.     

Comparisons of PCBs dechlorination occurrences in various contaminated sediments

A comparison was made of reductive dechlorination occurrences of polychlorinated biphenyls (PCBs) by microorganisms collected from contaminated sediments including Er-Jen River (Tainan, Taiwan), Hudson River (Ft. Edward, NY), Silver Lake (Pittsfield, MA) and Puget Sound (Washington State). Comparisons was made in terms of chromatographic data (referring to the biological activity, including microbial availability) and thermodynamic data (demonstrating the selectivity of anaerobic microorganisms in the dechlorination of chlorinated compounds). Chromatographic data was established in terms of difference in relative retention time (delta ln RRT) and thermodynamic data was estimated as heat of reaction (delta H(r)0). Both were calculated and correlated to occurrences of dechlorination reactions. Observed dechlorination reactions for individually introducing PCB congener had delta ln RRT levels measured as >0.47 (Er-Jen River), >0.29 (Hudson River), >0.36 (Silver Lake) and >0.45 (Puget Sound, for Aroclor 1254 dechlorination). Critical of delta H(r)0 and delta ln RRT values showed that Hudson River and Silver Lake microorganisms were capable of dechlorinating PCBs through reactions with larger H(r)0 value (lower levels of released energy) and smaller delta ln RRT value compared with those found in Er-Jen River and Puget Sound sediments. Differences in the critical delta ln RRT values of these sediments may be due to differences in their levels of PCB contamination.     

Microbial reductive dechlorination of polychlorinated biphenyls in heat treated and bromoethanesulfonate treated anaerobic sediment slurries

Anaerobic reductive dechlorination of polychlorinated biphenyls (PCBs) in heat treated, bromoethanesulfonate (BES) treated, and untreated slurries of PCB-contaminated upper Hudson River sediment was investigated to better understand the microorganisms that mediate this process. Extensive meta-and para-dechlorination of Aroclor 1242 and 2,3,4-trichlorobiphenyl (2,3,4-CB) occurred in both the untreated and heat treated slurries. Heat treatment of the slurries eliminated methanogenesis, enhanced 2,3,4-CB dechlorination, and caused extensive meta- and para-dechlorination of Aroclor 1242 earlier than in untreated slurries. BES treatment (1 mM) of the slurries caused a 90% reduction in methanogenesis and inhibited metadechlorination of PCB congeners containing 2,3- and 2,5-dichlorophenyl groups. The results suggest that there are at least two distinct microbial PCB reductive dechlorination activities in PCB-contaminated upper Hudson River sediment, a meta-dechlorination activity and a para-dechlorination activity on Aroclor 1242. Both of these microbial activities are apparently not methanogenic and are resistant to or activated by heat treatment. In addition, the meta- but not the para-dechlorinating activity is inhibited by BES treatment.     

Correlation of gas chromatographic properties of chlorobenzenes and polychlorinated biphenyls with the occurrence of reductive dechlorination by untamed microorganisms

To understand the dechlorination ability of chlorobenzenes (CBs) and polychlorinated biphenyls (PCBs) by untamed microorganisms under anaerobic condition and to correlate gas chromatographic properties with the occurrence of reductive dechlorination, introduction of CBs and PCBs in the culture medium inoculated with microorganisms from sludge and sediment, respectively, were performed. Three kinds of culture media preparing from sludge, river water and a synthetic medium were used in the experiments. HCB was degraded to 1,3,5-trichlorobenzene (1,3,5-TCB) and 1,3-dichlorobenzene (1,3-DCB) in both sludge medium and synthetic medium with inoculated microorganisms. Three PCB congeners including 2,3,4-, 3,4,5- and 2,3,4,5-CBp (chlorinated biphenyl) were not found to be dechlorinated in the river water medium with inoculation culture but to be dechlorinated in the synthetic medium. MNDO methodology was used to compute theoretical dechlorination reaction heats and GC-ECD techniques were used to estimate chromatographic data of CB and PCB congeners. Both CB and PCB congeners showed that dechlorination by untamed microorganisms under anaerobic mixed cultures were more likely to occur when larger amounts of energy were released and greater deltaln RRT value between the parent congener and the daughter product was observed. Deltaln RRT provided a more precise information on the singularity of PCBs ortho-dechlorination in an aspect of thermodynamic favorable rule.     

Using solar and ultraviolet light to degrade PCBs in sand and transformer oils

The present study describes the effect of the operating variables in the sensitized solar photolysis of sandy sediments contaminated by polychlorinated biphenyls (PCBs) in alkaline isopropanol. PCBs were almost completely removed in two weeks with stoichiometric release of chloride and biphenyl (BP) by a mechanism of reductive dechlorination. The concentration of the sensitizer (acetone) was the variable found to have most influence on the process. Under the same conditions, only partial dechlorination of the PCBs (34%) was observed in dielectric fluids without generating biphenyl to any appreciable extent. Direct photolysis (ultraviolet light at 254nm) of dielectric oils dissolved in alkaline isopropanol lead to 92% removal of PCBs in 60min. The observed mechanism was again that of reductive dechlorination, with stoichiometric release of chloride, and the accumulation of biphenyl, quaterphenyl and condensation products of biphenyl with isopropanol.     

Enhancing polychlorinated biphenyl dechlorination in fresh water sediment with biostimulation and bioaugmentation

Polychlorinated biphenyls (PCBs) are toxic compounds ubiquitously distributed in ecosystems. Microbial attenuation of these contaminants is a potential means of remediation. Two promising microbial PCB remediation technologies, biostimulation and bioaugmentation, were investigated in different sediments. Biostimulation experiments in which electron donor was supplied (H2 via elemental iron, Fe(0)) resulted in only a marginal improvement in the dechlorination of amended 2,3,4,5-tetrachlorobiphenyl (2,3,4,5-CB), likely because of an inadequate population of indigenous H2-utilizing dechlorinators. Extensive dechlorination was observed, however, after bioaugmenting microcosms with a PCB-dechlorinating enrichment culture. Dechlorination of 2,3,4,5-CB began prior to the 20th day of incubation and proceeded to 2-chlorobiphenyl. This extensive dechlorination activity was maintained in both sediments over 70d at 10 and 25 degrees C. This research demonstrates that although past studies of biostimulation were promising, a great deal must be known about the PCB-dechlorinating organisms present before successful biostimulation is expected. Bioaugmentation, however, appears to be a promising PCB remediation strategy and should be further pursued.     

Evaluation of cumulative PCB exposure estimated by a job exposure matrix versus PCB serum concentrations

Although polychlorinated biphenyls (PCBs) have been banned in many countries for more than three decades, exposures to PCBs continue to be of concern due to their long half-lives and carcinogenic effects. In National Institute for Occupational Safety and Health studies, we are using semiquantitative plant-specific job exposure matrices (JEMs) to estimate historical PCB exposures for workers (n?=?24,865) exposed to PCBs from 1938 to 1978 at three capacitor manufacturing plants. A subcohort of these workers (n?=?410) employed in two of these plants had serum PCB concentrations measured at up to four times between 1976 and 1989. Our objectives were to evaluate the strength of association between an individual worker’s measured serum PCB levels and the same worker’s cumulative exposure estimated through 1977 with the (1) JEM and (2) duration of employment, and to calculate the explained variance the JEM provides for serum PCB levels using (3) simple linear regression. Consistent strong and statistically significant associations were observed between the cumulative exposures estimated with the JEM and serum PCB concentrations for all years. The strength of association between duration of employment and serum PCBs was good for highly chlorinated (Aroclor 1254/HPCB) but not less chlorinated (Aroclor 1242/LPCB) PCBs. In the simple regression models, cumulative occupational exposure estimated using the JEMs explained 14–24 % of the variance of the Aroclor 1242/LPCB and 22–39 % for Aroclor 1254/HPCB serum concentrations. We regard the cumulative exposure estimated with the JEM as a better estimate of PCB body burdens than serum concentrations quantified as Aroclor 1242/LPCB and Aroclor 1254/HPCB.