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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.

Risk assessments are increasingly reliant on information from in vitro assays. The in vitro micronucleus test (MNvit) is a genotoxicity test that detects chromosomal abnormalities, including chromosome breakage (clastogenicity) and/or whole chromosome loss (aneugenicity). In this study, MNvit datasets for 292 chemicals, generated by the US EPA’s ToxCast program, were evaluated using a decision tree-based pipeline for hazard identification. Chemicals were tested with 19 concentrations ( n  = 1) up to 200 µM, in the presence and absence of Aroclor 1254-induced rat liver S9. To identify clastogenic chemicals, %MN values at each concentration were compared to a distribution of batch-specific solvent controls; this was followed by cytotoxicity assessment and benchmark concentration (BMC) analyses. The approach classified 157 substances as positives, 25 as negatives, and 110 as inconclusive. Using the approach described in Bryce et al. (Environ Mol Mutagen 52:280–286, 2011), we identified 15 (5%) aneugens. IVIVE (in vitro to in vivo extrapolation) was employed to convert BMCs into administered equivalent doses (AEDs). Where possible, AEDs were compared to points of departure (PODs) for traditional genotoxicity endpoints; AEDs were generally lower than PODs based on in vivo endpoints. To facilitate interpretation of in vitro MN assay concentration–response data for risk assessment, exposure estimates were utilized to calculate bioactivity exposure ratio (BER) values. BERs for 50 clastogens and two aneugens had AEDs that approached exposure estimates (i.e., BER < 100); these chemicals might be considered priorities for additional testing. This work provides a framework for the use of high-throughput in vitro genotoxicity testing for priority setting and chemical risk assessment.

Polychlorinated biphenyls (PCBs) are endocrine-disrupting chemicals (EDCs) with well-established effects on reproduction and behavior in developmentally-exposed (F1) individuals. Because of evidence for transgenerational effects of EDCs on the neuroendocrine control of reproductive physiology, we tested the hypothesis that prenatal PCB exposure leads to unique hypothalamic gene-expression profiles in three generations. Pregnant Sprague–Dawley rats were treated on gestational days 16 and 18 with the PCB mixture Aroclor 1221 (A1221), vehicle (3% DMSO in sesame oil), or estradiol benzoate (EB, 50 µg/kg), the latter a positive control for estrogenic effects of A1221. Maternal- and paternal-lineage F2 and F3 generations were bred using untreated partners. The anteroventral periventricular nucleus (AVPV) and arcuate nucleus (ARC), involved in the hypothalamic control of reproduction, were dissected from F1 to F3 females and males, RNA extracted, and gene expression measured in a qPCR array. We detected unique gene-expression profiles in each generation, which were sex- and lineage-specific. In the AVPV, treatment significantly changed 10, 25, and 11 transcripts in F1, F2, and F3 generations, whereas 10, 1, and 12 transcripts were changed in these generations in the ARC. In the F1 AVPV and ARC, most affected transcripts were decreased by A1221. In the F2 AVPV, most effects of A1221 were observed in females of the maternal lineage, whereas only Pomc expression changed in the F2 ARC (by EB). The F3 AVPV and ARC were mainly affected by EB. It is notable that results in one generation do not predict results in another, and that lineage was a major determinant in results. Thus, transient prenatal exposure of F1 rats to A1221 or EB can alter hypothalamic gene expression across three generations in a sex- and lineage-dependent manner, leading to the conclusion that the legacy of PCBs continues for generations. Summary sentence Prenatal exposure of rats to PCBs or estradiol alters hypothalamic gene expression across three generations in a sex- and lineage-dependent manner. Graphical Abstract

Polychlorinated biphenyls (PCBs) are worldwide chemical pollutants that have been linked to disrupted reproduction and altered sexual behaviour in many organisms. However, the effect of developmental PCB-exposure on adult passerine reproductive behaviour remains unknown. A commercial PCB mixture (Aroclor 1242) or an estrogenic congener (PCB 52) were administered in sublethal amounts to nestling zebra finches (Taeniopygia guttata) in the laboratory to identify effects of developmental PCB-exposure on adult zebra finch reproductive parameters. Results indicate that although traditional measures of reproductive success are not altered by this PCB dosage, PCBs do alter sexual behaviours such as male song and nesting behaviour. Males treated with PCB 52 in the nest sang significantly fewer syllables than control males, while females treated with Aroclor 1242 in the nest showed the strongest song preferences. PCB treatment also caused an increase in the number of nesting attempts and abandoned nests in the Aroclor 1242 treatment relative to the PCB 52 treatment, and offspring with control fathers fledged significantly earlier than those with fathers treated with Aroclor 1242. Behavioural differences between males seem to best explain these reproductive effects, most notably aggression. These findings suggest that sublethal PCB-exposure during development can significantly alter key reproductive characteristics of adult zebra finches, likely reducing fitness in the wild.

Polychlorinated biphenyls (PCBs), a class of hazardous pollutants, are difficult to dissipate in the natural environment. In this study, a cyanobacterial strain Anabaena PD-1 showed good resistance against PCB congeners. Compared to a control group, chlorophyll a content decreased 3.7% and 11.7% when Anabaena PD-1 was exposed to 2 and 5 mg/L PCBs for 7 d. This cyanobacterial strain was capable of decomposing PCB congeners which was conclusively proved by determination of chloride ion concentrations in chlorine-free medium. After 7 d, the chloride ion concentrations in PCB-treated groups (1, 2, 5 mg/L) were 3.55, 3.05, and 2.25 mg/L, respectively. The genetic information of strain PD-1 was obtained through 16S rRNA sequencing analysis. The GenBank accession number of 16S rRNA of Anabaena PD-1 was KF201693.1. Phylogenetic tree analysis clearly indicated that Anabaena PD-1 belonged to the genus Anabaena. The degradation half-life of Aroclor 1254 by Anabaena PD-1 was 11.36 d; the total degradation rate for Aroclor 1254 was 84.4% after 25 d. Less chlorinated PCB congeners were more likely to be degraded by Anabaena PD-1 in comparison with highly chlorinated congeners. Meta- and para-chlorines in trichlorodiphenyls and tetrachlorobiphenyls were more susceptible to dechlorination than ortho-chlorines during the PCB-degradation process by Anabaena PD-1. Furthermore, Anabaena PD-1 can decompose dioxin-like PCBs. The percent biodegradation of 12 dioxin-like PCBs by strain PD-1 ranged from 37.4% to 68.4% after 25 days. Results above demonstrate that Anabaena PD-1 is a PCB-degrader with great potential for the in situ bioremediation of PCB-contaminated paddy soils.

Polychlorinated biphenyls (PCBs) were added to certain marine vessel bottom paints as a plasticizer to improve the adhesion and durability of the paint. The most common PCB formulation used to amend such paints was Aroclor 1254. Fugitive Aroclor-containing paint chips generated from vessel maintenance and repair operations represent a potential source of PCB contamination to sediments. Limited published studies indicate that Aroclor-containing paint is largely inert and exhibits low PCB leaching into water; however, the rate and degree of leaching of PCBs from paint chips have not been directly studied. This laboratory-based study evaluated the rate and extent of leaching of PCBs from paint chips into freshwater. The results of this investigation demonstrate that the rate of PCB dissolution from paint chips decreased rapidly and exponentially over time. Based on this study, it is estimated that the rate of leaching of PCBs from paint chips would cease after approximately 3 years of exposure to water. When all leachable PCBs were exhausted, it is estimated that less than 1% of the mass of PCBs in the paint chips was amenable to dissolution. The results of this experiment suggest that Aroclor-containing paint chips found in sediments are likely short-term sources of dissolved-phase PCB to pore or surface waters and that the majority of the PCBs in paint chips remain in the paint matrix and unavailable for partitioning into water.Graphic Abstract

Microbial reductive dechlorination of the persistent polychlorinated biphenyls (PCBs) is attracting much attention in cleanup of the contaminated environment. Nevertheless, most PCB dechlorinating cultures require presence of sediment or sediment substitutes to maintain their dechlorination activities which hinders subsequent bacterial enrichment and isolation processes. The information on enriching sediment-free PCB dechlorinating cultures is still limited. In this study, 18 microcosms established with soils and sediments were screened for their dechlorination activities on a PCB mixture - Aroclor 1260. After one year of incubation, 10 out of 18 microcosms showed significant PCB dechlorination with distinct dechlorination patterns (e.g., Process H, N and T classified based on profiles of PCB congeners loss and new congeners formation). Through serial transfers in defined medium, six sediment-free PCB dechlorinating cultures (i.e., CW-4, CG-1, CG-3, CG-4, CG-5 and SG-1) were obtained without amending any sediment or sediment-substitutes. PCB dechlorination Process H was the most frequently observed dechlorination pattern, which was found in four sediment-free cultures (CW-4, CG-3, CG-4 and SG-1). Sediment-free culture CG-5 showed the most extensive PCB dechlorination among the six cultures, which was mediated by Process N, resulting in the accumulation of penta- (e.g., 236-24-CB) and tetra-chlorobiphenyls (tetra-CBs) (e.g., 24-24-CB, 24-25-CB, 24-26-CB and 25-26-CB) via dechlorinating 30.44% hepta-CBs and 59.12% hexa-CBs after three months of incubation. For culture CG-1, dechlorinators mainly attacked double flanked meta-chlorines and partially ortho-chlorines, which might represent a novel dechlorination pattern. Phylogenetic analysis showed distinct affiliation of PCB dechlorinators in the microcosms, including Dehalogenimonas and Dehalococcoides species. This study broadens our knowledge in microbial reductive dechlorination of PCBs, and provides essential information for culturing and stimulating PCB dechlorinators for in situ bioremediation applications.

Although most countries banned manufacturing of polychlorinated biphenyls (PCBs) over 40 years ago, PCBs remain a global concern for wildlife and human health due to high bioaccumulation and biopersistance. PCB uptake mechanisms have been well studied in many taxa; however, less is known about depuration rates and how post-exposure diet can influence PCB concentrations and immune response in fish and wildlife populations. In a controlled laboratory environment, we investigated the influence of subchronic dietary exposure to two PCB Aroclors and food deprivation on tissue-specific concentrations of total PCBs and PCB homologs and innate immune function in channel catfish (Ictalurus punctatus). Overall, we found that the concentration of total PCBs and PCB homologs measured in whole body, fillet, and liver tissues declined more slowly in food-deprived fish, with slowest depuration observed in the liver. Additionally, fish that were exposed to PCBs had lower plasma cortisol concentrations, reduced phagocytic oxidative burst activity, and lower cytotoxic activity, suggesting that PCBs can influence stress and immune responses. However, for most measures of immune function, the effects of food deprivation had a larger effect on immune response than did PCB exposure. Taken together, these results suggest that short-term dietary exposure to PCBs can increase toxicity of consumable fish tissues for several weeks, and that PCB mixtures modulate immune and stress responses via multiple pathways. These results may inform development of human consumption advisories and can help predict and understand the influence of PCBs on fish health.

The polychlorinated biphenyls (PCBs) in aquatic environment adversely affect non-target organisms, including fish. Especially, the male reproduction and next generation can be damaged through high exposure to these pollutants. Hence, the sperm cells were exposed to sublethal concentrations of Aroclor 1254 (0, 1, 5, 10, or 25 mg/l) for 4 h. The sperm quality parameters were analyzed by SCA (Sperm Class Analyzer). The fertility, eyeing, and hatching rates were determined as gamete markers. Lipid peroxidation (malondialdehyde-MDA), glutathione (GSH), and antioxidant enzymes [superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT)] were measured for determination of oxidative stress. Our results showed that Aroclor 1254 negatively affected the motility rate and duration, fertilization rate, embryogenesis, and hatching and also triggered antioxidant defense mechanisms at the highest concentration (25 mg L −1 ). Furthermore, linear speed (VSL), linearity index (LIN), and amplitude lateral head (ALH) were significantly changed after exposure to 25 mg L −1 , and the lowest concentrations (1 and 10 mg L −1 ) did not significantly affect the motility and fertilizing capacity. The embryogenesis and hatching were significantly affected by sperm exposure to 1, 10, and 25 mg L −1 of Aroclor 1254. Consequently, Aroclor 1254 causes potential hazards in male germ cells, and the exposure of sperm cells to pollutants can adversely affect next generation of wild populations.

PurposeNanoscale zero-valent iron (nZVI) could degrade chlorinated pollutants like polychlorinated biphenyls (PCBs), but may be toxic to soil beneficial microbes such as arbuscular mycorrhizal (AM) fungi. The purpose of this work was to investigate the changes in community structure and diversity of AM fungi in PCBs-contaminated soils in response to input of nZVI, focusing on the balance between PCB dissipation and AM fungal conservation.Materials and methodsBoth PCBs-amended (10 mg/kg Aroclor 1242, a PCB mixture) and control soils with three nZVI input levels (0.1, 1, and 10 g/kg) were tested in this 8-week incubation experiments. Soil pH and available P and PCB concentrations were determined, and the nested PCR amplification of the 18S rRNA gene of AM fungi was performed and sequenced on the Illumina MiSeq™ platform. Differences in soil AM fungal community structure were compared using principal component analysis (PCA). The redundancy analysis (RDA) was used to reveal the relationship between PCBs, soil properties, and AM fungal communities under different treatments.Results and discussionSoil available P concentration significantly decreased as the nZVI input level increased, but only the high input level (10 g/kg) induced significantly higher soil pH and lower richness and Shannon and Simpson’s indices of AM fungal communities compared to the low input case (0.1 g/kg). The presence of PCBs only led to differentiation in AM fungal communities in the low nZVI input case. In the PCBs-amended soils, both moderate (1 g/kg) and high input of nZVI significantly decreased the concentrations of di-, tri-, tetra-, penta-chlorinated biphenyls and total PCBs compared to the low input case, while the high input level only further significantly increased the dissipation of hexachlorinated biphenyls compared with the moderate input case.ConclusionnZVI with high adsorption effects on soil available P had greater impacts on soil AM fungi than PCBs. However, the moderate nZVI input level (1 g/kg) had no significant effects on the richness and diversity indices of AM fungal community compared to the low input case (0.1 g/kg) and seemed to be more suitable for remediating of PCBs-contaminated soils, focusing on the limited inhibition on AM fungi.