Chronic Aroclor 1260 exposure alters the mouse liver proteome, selenoproteins, and metals in steatotic liver disease

The prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD) continues to increase due in part to the obesity epidemic and to environmental exposures to metabolism disrupting chemicals. A single gavage exposure of male mice to Aroclor 1260 (Ar1260), an environmentally relevant mixture of non-dioxin-like polychlorinated biphenyls (PCBs), resulted in steatohepatitis and altered RNA modifications in selenocysteine tRNA 34 weeks post-exposure. Unbiased approaches identified the liver proteome, selenoproteins, and levels of 25 metals. Ar1260 altered the abundance of 128 proteins. Enrichment analysis of the liver Ar1260 proteome included glutathione metabolism and translation of selenoproteins. Hepatic glutathione peroxidase 4 (GPX4) and Selenoprotein O (SELENOO) were increased and Selenoprotein F (SELENOF), Selenoprotein S (SELENOS), Selenium binding protein 2 (SELENBP2) were decreased with Ar1260 exposure. Increased copper, selenium (Se), and zinc and reduced iron levels were detected. These data demonstrate that Ar1260 exposure alters the (seleno)proteome, Se, and metals in MASLD-associated pathways.

Experimental study of catalytic hydro-dechlorination (HDC) of Aroclor 1232

Polychlorinated biphenyls (PCBs) is a group of persistent organic pollutants that still requires remediation and reduction long after the production is discontinued. Aroclor 1232 is a commercial PCB mixture that has been much less studied. To address this void, this paper presented catalytic hydro-dechlorination (HDC) of Aroclor 1232 using palladium on activated carbon (Pd/AC) at atmospheric pressure. Experimental variables studied including three mild temperatures, 22.5 °C, 50 °C, and 80 °C, and four different co-catalyst loadings. This batch of Aroclor 1232 constituted of more than 83% of mono-, di-, and tri-, chlorinated biphenyls (CB), in addition to biphenyl, tetra- and penta CBs. HDC efficiency increased with temperature, and reached 99.9% within 4 h of reaction at 80 °C. HDC efficiency also increased with co-catalyst loading. HDC efficiencies followed the trend of para > meta > ortho positions among isomers. The increase of temperature and Et3N dosage are especially effective in dechlorination at ortho and meta positions. The apparent activation energy of Aroclor 1232 HDC was estimated as 25.57 kJ/mol based on pseudo-first order assumption, indicating that the reaction may be diffusion limited. Given the modest reaction conditions used, the HDC of Aroclor 1232 can potentially be a low-cost process.

Polyurethane Foam Emission Samplers to Identify Sources of Airborne Polychlorinated Biphenyls from Glass-Block Windows and Other Room Surfaces in a Vermont School

We hypothesized that emissions of polychlorinated biphenyls (PCBs) from Aroclor mixtures present in building materials explain their concentrations in school air. Here, we report a study of airborne concentrations and gas-phase emissions in three elementary school rooms constructed in 1958. We collected airborne PCBs using polyurethane foam passive air samplers (PUF-PAS, n = 6) and PCB emissions from building materials using polyurethane foam passive emission samplers (PUF-PES, n = 17) placed over flat surfaces in school rooms, including vinyl tile floors, carpets, painted bricks, painted drywall, and glass-block windows. We analyzed all 209 congeners represented in 173 chromatographic separations and found that the congener distribution in PUF-PES strongly resembled the predicted diffusive release of gas-phase PCBs from a solid material containing Aroclor 1254. Concentrations of airborne total PCBs ranged from 38 to 180 ng m-3, a range confirmed by an independent laboratory in the same school. These levels exceed action levels for all aged children set by the State of Vermont and exceed guidance levels set by the U.S. EPA for children under age 3. Emissions of PCBs from the glass-block windows (30,000 ng m-2 d-1) greatly exceeded those of all other surfaces, which ranged from 35 to 2700 ng m-2 d-1. This study illustrates the benefit of the direct measurement of PCB emissions to identify the most important building remediation needed to reduce airborne PCB concentrations in schools.

A review of the mechanisms of by-product PCB formation in pigments, dyes and paints

There has been an increased awareness of paints and pigments as a source of by-product PCBs in the environment. The majority of existing work has focused only on reporting the presence of the main PCBs in different products with a specific focus on the most PCB congeners, PCB11 and PCB209. This gives the impression that only a handful of PCBs are found in paints. However, this is not the case. PCB profiles in paints and pigments can be just as complex as commercial technical mixtures. This review identified the presence of 149 different PCBs in paint samples. For reference, only 141 different PCBs have been reported in all of the 5 main commercial Aroclor formulations (A1016, A1242, A1248, A1254 (early & late) and A1260). The total PCB concentrations in some paint samples can be substantial, with concentrations as high as 919 mg kg^-1 reported in azo pigments. When trying to identify sources of PCBs in the environment, pigments, dyes and paints are often overlooked. In this manuscript, we have compiled congener profiles from 140 different samples from the available scientific literature and presented this in the supplementary information as valuable resource for others to use in source identification applications. We have also proposed detailed mechanisms for the formation of PCBs in pigments, dyes and paints. In many cases, the PCB congeners predicted by these mechanisms provide an excellent match for what has been observed in the scientific literature. We have also identified several additional classes of pigments that are expected to contain PCBs but have yet to be verified by experimental data.

Effect of microplastics on microbial dechlorination of a polychlorinated biphenyl mixture (Aroclor 1260)

Microplastics (MPs) and polychlorinated biphenyls (PCBs) generally coexist in the environment, posing risks to public health and the environment. This study investigated the effect of different MPs on the microbial anaerobic reductive dechlorination of Aroclor 1260, a commercial PCB mixture. MP exposure inhibited microbial reductive dechlorination of PCBs, with inhibition rates of 39.43%, 23.97%, and 17.53% by polyethylene (PE), polypropylene (PP), and polystyrene (PS), respectively. The dechlorination rate decreased from 1.63 μM Cl^- d^-1 to 0.99-1.34 μM Cl^- d^-1 after MP amendment. Chlorine removal in the meta-position of PCBs was primarily inhibited by MPs, with no changes in the final PCB dechlorination metabolites. The microbial community compositions in MP biofilms were not significantly different (P > 0.05) from those in suspension culture, although possessing greater Dehalococcoides abundance (0.52-0.81% in MP biofilms; 0.03-0.12% in suspension culture). The co-occurrence network analysis revealed that the presence of MPs attenuated microbial synergistic interactions in the dechlorinating culture systems, which may contribute to the inhibitory effect on microbial PCB dechlorination. These findings are important for comprehensively understanding microbial dechlorination behavior and the environmental fate of PCBs in environments with co-existing PCBs and MPs and for guiding the application of in situ PCB bioremediation.

Distinguishing Aroclor and non-Aroclor sources to Chicago Air

Many polychlorinated biphenyl (PCB) congeners are found in both legacy Aroclor mixtures and modern materials, and both contribute to PCBs levels in ambient air. The various sources of PCBs make it difficult to quantify the relative importance of emissions from remaining legacy materials and emissions of PCBs released from production and use of modern products. To address this challenge, we utilized active and passive sampling, analytical methods optimized for PCBs, and Positive Matrix Factorization (PMF) and cos theta to examine the chemical signature of PCBs in Chicago air. Here we report our findings for over 640 samples collected over 7 years and analyzed for all 209 congeners. We conclude that Aroclor sources (1254, 1016/1242, and 1260) are consistent and dominant contributors to Chicago air. However, non-Aroclors sources accounted for 13%-16% of the total PCBs measured. Our analysis indicates non-Aroclor sources explain 99% of PCB11, 90% of PCB 68, and 58-69% of congeners with 8 to 10 chlorines in Chicago air. All of these are known to be emitted from paints or silicone polymers. Additionally, we identified over 20 congeners that have non-Aroclor contributions of more than 50% including PCB 3 (4-monochlorobiphenyl, 83% non-Aroclor) as well as 7 congeners of unknown sources: PCBs 43, 46, 55, 89, 96, 137, and 139 + 140. Non-Aroclor emission sources contribute to the entire range of congeners from mono- to deca-chlorobiphenyls. We found evidence of highly localized non-Aroclor sources including a signature similar to that of green paint. We also found source signals similar to the PCB congeners volatilizing from and absorbing to neighboring Lake Michigan. The measured profiles vary from season to season: lower chlorinated congeners dominate in winter months while higher chlorinated congeners contribute more in summer.

Intracity occurrence and distribution of airborne PCB congeners in Chicago

To evaluate the magnitude and extent of airborne PCBs in an urban area, we measured and investigated the temporal and spatial behavior of atmospheric concentrations of individual polychlorinated biphenyl (PCB) congeners as well as the sum of all congeners (ΣPCB) in both gas and particle phases at 27 locations across the City of Chicago in a single year (2009). In total, 141 gas-phase air samples were collected, including 22 pairs (44 samples) deployed at the same time but at two different locations, and 46 particle-phase samples. ΣPCB in the gas-phase ranged from 80 to 3000 pg/m³, with a geometric mean (GM) of 530 pg/m³, whereas particle-phase ranged from 8 to 160 pg/m³, with a GM of 28 pg/m³. We found the temporal variability to be about three times larger than the variability over space for all gas-phase congeners and ΣPCB. Around 50% of the sample PCB profiles resembled a mixture of a 1:1 vapor Aroclor mixture of 1016 + 1254, with most of the rest (30%) showing enrichment of PCB 3 (>0.1), which did not match any Aroclor profiles. PCB 11 contributed to ~5% in all samples. The fractions of PCB congeners bound to particles ranged from 0.001 to 0.97. Our analysis shows that airborne PCBs are widely distributed across Chicago and confirms that most locations have a similar PCB distribution, but differ in the concentration levels. Volatilization continues to be the main release process of PCBs into the atmosphere, including both Aroclor and non-Aroclor congeners.

Passive-Sampler-Based Bioavailability Assessment of PCB Congeners Associated with Aroclor-Containing Paint Chips in the Presence of Sediment

This is the first investigation of the bioavailability of PCBs associated with paint chips (PC) dispersed in sediment. Bioavailability of PCB-containing PC in sediment was measured using ex situ polyethylene passive samplers (PS) and compared to that of PCBs from field-collected sediments. PC were mixed in freshwater sediment from a relatively uncontaminated site with no known PCB contamination sources and from a contaminated site with non-paint PCB sources. PC < 0.045 mm generated concentrations in the PS over one order of magnitude higher than coarser chips. The bioavailable fraction was represented by the polymer-sediment accumulation factor (PSAF), defined as the ratio of the PCB concentrations in the PS and organic carbon normalized sediment. The PSAF was similar for both field sediments. The PSAFs for the field sediments were ~ 50-60 and ~ 5 times higher than for the relatively uncontaminated sediment amended with PC for the size fractions 0.25-0.3 mm and < 0.045 mm, respectively. These results indicate much lower bioavailability for PCBs associated with PC compared to PCBs associated with field-collected sediment. Such information is essential for risk assessment and remediation decision-making for sites where contamination from non-paint PCBs sources is co-located with PCB PC.

Electrostimulated bio-dechlorination of a PCB mixture (Aroclor 1260) in a marine-originated dechlorinating culture

Aroclor 1260, a commercial polychlorinated biphenyl (PCB) mixture, is highly recalcitrant to biotransformation. A negatively polarized cathode (-0.35 V vs. standard hydrogen electrode) was applied for the first time to a marine-origin PCB dechlorinating culture that substantially increased the microbial dechlorination rate of Aroclor 1260 (from 8.6 to 11.6 μM Cl^- d^-1); meta-chlorine removal was stimulated and higher proportions of tetra-CBs (43.2-46.6%), the predominant dechlorination products, were observed compared to the open circuit conditions (23.7-25.1%). The dechlorination rate was further enhanced (14.1 μM Cl^- d^-1) by amendment with humin as a solid-phase redox mediator. After the suspension culture was renewed using an anaerobic medium, dechlorination activity was effectively maintained solely by cathodic biofilms, where cyclic voltammetry results indicated their redox activity. Electric potential had a significant effect on microbial community structure in the cathodic biofilm, where a greater abundance of Dehalococcoides (2.59-3.02%), as potential dechlorinators, was observed compared to that in the suspension culture (0.41-0.55%). Moreover, Dehalococcoides adhering to the cathode showed a higher chlorine removal rate than in the suspension culture. These findings provide insights into the dechlorination mechanism of cathodic biofilms involving Dehalococcoides for PCB mixtures and extend the application prospects of bioremediation to PCB contamination in the natural environment.

Leaching Rate of Polychlorinated Biphenyls (PCBs) from Marine Paint Chips

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.

Detection and Quantification of Polychlorinated Biphenyl Sulfates in Human Serum

Polychlorinated biphenyls (PCBs) are persistent toxic chemicals with both legacy sources (e.g., Aroclors) and new sources (e.g., unintentional contaminants in some pigments and varnishes). PCB sulfates are derived from further metabolism of hydroxylated PCBs (OH-PCBs), which are oxidative metabolites of PCBs. While OH-PCBs and PCB sulfates are implicated in multiple toxicological effects, studies of PCB sulfates in human serum have been limited by available analytical procedures. We have now developed a method for extraction of PCB sulfates from serum followed by differential analysis with, and without, sulfatase-catalyzed hydrolysis to OH-PCBs. A sulfatase from Helix pomatia was purified by affinity chromatography, and it displayed broad specificity for PCB sulfates without contaminant glucuronidase activity. Following sulfatase-catalyzed hydrolysis of the PCB sulfates extracted from serum, the corresponding OH-PCBs were derivatized to methoxy-PCBs and quantitated by GC-MS/MS. In a pooled sample of human serum, we identified 10 PCB sulfates, with three PCB sulfate congeners exhibiting the highest concentrations from 1200 to 3970 pg/g of serum. In conclusion, we have developed a sensitive and specific method for the determination of PCB sulfates in human serum.

Sources of polychlorinated biphenyls to Upper Hudson River sediment post-dredging

The Upper Hudson River (UHR) has been contaminated with polychlorinated biphenyls (PCBs) since the 1940s due to the manufacture of capacitors at two plants near Hudson Falls and Fort Edward, NY by General Electric (GE). Dredging of portions of the UHR was conducted from 2009 to 2015 as a partial remedy for this contamination. In 2017, the New York State Department of Environmental Conservation undertook a comprehensive post-dredging survey of sediment contamination in the UHR. Thousands of samples were collected, and 130 of these were analyzed for PCBs using EPA method 1668A. This data set was analyzed using Positive Matrix Factorization. Six factors were observed. One factor resembled the dominant Aroclors used by GE with little alteration. Three factors represented different pathways and/or extents of microbial dechlorination. One factor resembled a mixture of microbial dechlorination products and a higher molecular weight Aroclor used by GE. The congener patterns of the dechlorination factors suggest that removal of chlorines at the ortho position does occur in the UHR sediment, in agreement with several laboratory studies showing that such ortho dechlorination is possible. This ortho dechlorination could theoretically lead to complete dechlorination of PCBs to biphenyl in UHR sediment. Only one factor was not attributable to GE. It represents inputs of PCBs from tributaries and urban areas and explains 1.7% of the PCB mass in the sediments. The small contribution from the non-GE PCB source suggests that recontamination of the sediment after dredging was minor.

Polychlorinated Biphenyls in Food

We measured the concentrations of 205 polychlorinated biphenyl (PCB) congeners in 26 food items: beef steak, butter, canned tuna, catfish, cheese, eggs, french fries, fried chicken, ground beef, ground pork, hamburger, hot dog, ice cream, liver, luncheon meat, margarine, meat-free dinner, milk, pizza, poultry, salmon, sausage, shrimp, sliced ham, tilapia, and vegetable oil. Using Diet History Questionnaire II, we calculated the PCB dietary exposure in mothers and children participating in the AESOP Study in East Chicago, Indiana, and Columbus Junction, Iowa. Salmon had the highest concentration followed by canned tuna, but fish is a minor contributor to exposure. Other animal proteins are more important sources of PCB dietary exposure in this study population. Despite the inclusion of few congeners and food types in previous studies, we found evidence of a decline in PCB concentrations over the last 20 years. We also found strong associations of PCB congener distributions with Aroclors in most foods and found manufacturing byproduct PCBs, including PCB11, in tilapia and catfish. The reduction in PCB levels in food indicates that dietary exposure is comparable to PCB inhalation exposures reported for the same study population.

A semi-target analytical method for quantification of OH-PCBs in environmental samples

Hydroxylated polychlorinated biphenyls (OH-PCBs) are oxidative metabolites of PCBs and residuals found in original Aroclors. OH-PCBs are known to play a role as genotoxicants, carcinogens, and hormone disruptors, and therefore it is important to quantify their presence in human tissues, organisms, and environmental matrices. Of 837 possible mono-OH-PCBs congeners, there are only ~ 70 methoxylated PCB (MeO-PCB) standards commercially available. Hence, a semi-target analytical method is needed for unknown OH-PCBs. The mass concentrations of these unknowns are sometimes determined by assuming the peak responses of other available compounds. This can bias the results due to the choices and availabilities of standards. To overcome this issue, we investigated the peak responses of all commercially available MeO-PCB standards with gas chromatography (GC) coupling with triple quadrupole (QqQ) mass spectrometry (MS) system, with positive electron impact (EI) ionization at 20-70 eV in selected ion monitoring (SIM) mode. We found correlations between the relative peak responses (RRFs) and the number of chlorine (#Cl) in the molecules of MeO-PCBs. Among the studied models, the quadratic regression of #Cl is the most suitable model in the RRF prediction (RRF = β₁ × #Cl^² + β₀) when the peak responses are captured at 30 eV. We evaluated the performance of the model by analyzing 12 synthesized MeO-PCB standards and a PCB-contaminated sediment collected from a wastewater lagoon. We further demonstrate the utility of the model using a different chromatography column and GC-EI-MS system. We found the method and associated model to be sufficiently simple, accurate, and versatile for use in quantifying OH-PCBs in complex environmental samples.

A semi-target analytical method for quantification of OH-PCBs in environmental samples

Hydroxylated polychlorinated biphenyls (OH-PCBs) are oxidative metabolites of PCBs and residuals found in original Aroclors. OH-PCBs are known to play a role as genotoxicants, carcinogens, and hormone disruptors, and therefore it is important to quantify their presence in human tissues, organisms, and environmental matrices. Of 837 possible mono-OH-PCBs congeners, there are only ~ 70 methoxylated PCB (MeO-PCB) standards commercially available. Hence, a semi-target analytical method is needed for unknown OH-PCBs. The mass concentrations of these unknowns are sometimes determined by assuming the peak responses of other available compounds. This can bias the results due to the choices and availabilities of standards. To overcome this issue, we investigated the peak responses of all commercially available MeO-PCB standards with gas chromatography (GC) coupling with triple quadrupole (QqQ) mass spectrometry (MS) system, with positive electron impact (EI) ionization at 20-70 eV in selected ion monitoring (SIM) mode. We found correlations between the relative peak responses (RRFs) and the number of chlorine (#Cl) in the molecules of MeO-PCBs. Among the studied models, the quadratic regression of #Cl is the most suitable model in the RRF prediction (RRF = β1 × #Cl^2 + β0) when the peak responses are captured at 30 eV. We evaluated the performance of the model by analyzing 12 synthesized MeO-PCB standards and a PCB-contaminated sediment collected from a wastewater lagoon. We further demonstrate the utility of the model using a different chromatography column and GC-EI-MS system. We found the method and associated model to be sufficiently simple, accurate, and versatile for use in quantifying OH-PCBs in complex environmental samples.

Evidence for Major Contributions of Unintentionally Produced PCBs in the Air of China: Implications for the National Source Inventory

Polychlorinated biphenyls (PCBs) were not widely manufactured or used in China before they became the subject of international bans on production. Recent work has shown that they have reached China associated with imported wastes and that there are considerable unintentional sources of PCBs that have only recently been identified. As such, it was hypothesized that the source inventory and profile of PCBs may be different or unique in China, compared to countries where they were widely used and which have been widely studied. For the first time in this study, we undertook a complete analysis of 209 PCB congeners and assessed the contribution of unintentionally produced PCBs (UP-PCBs) in the atmosphere of China, using polyurethane foam passive air samplers (PUF-PAS) deployed across a wide range of Chinese locations. ∑₂₀₉ PCBs ranged from 9 to 6856 pg/m³ (median: 95 pg/m³) during three deployments in 2016-2017. PCB 11 was one of the most detected congeners, contributing 33 ± 19% to ∑₂₀₉ PCBs. The main sources to airborne PCBs in China were estimated and ranked as pigment/painting (34%), metallurgical industry/combustion (31%), e-waste (23%), and petrochemical/plastic industry (6%). For typical Aroclor-PCBs, e-waste sources were dominated (>50%). Results from our study indicate that UP-PCBs have become the controlling source in the atmosphere of China, and an effective control strategy is urgently needed to mitigate emissions from multiple industrial sources.

Emissions of Tetrachlorobiphenyls (PCBs 47, 51, and 68) from Polymer Resin on Kitchen Cabinets as a Non-Aroclor Source to Residential Air

Both Aroclor and non-Aroclor sources of airborne polychlorinated biphenyls (PCBs) were found in residential homes. We deployed passive air samplers at 16 residences and found PCB-47, PCB-51, and PCB-68 to account for up to 50% of measured indoor ΣPCBs (2700 pg m-3). Although PCB-47 and PCB-51 are neurotoxins present in Aroclor mixtures (<2.5 and <0.3 wt %, respectively), we found them at much higher levels than expected for any Aroclor source. PCB-68 is not present in Aroclor mixtures. Another non-Aroclor congener, PCB-11, a byproduct of pigment manufacturing, was found inside and outside of every household and was frequently the predominate congener. We conducted direct measurements of surface emissions and identified finished cabinetry to be a major source of PCB-47, PCB-51, and PCB-68. We hypothesize that these congeners are inadvertent byproducts of polymer sealant manufacturing and produced from the decomposition of 2,4-dichlorobenzoyl peroxide used as an initiator in free-radical polymerization of polyester resins. The presence of these three compounds in polymer products, such as silicone, has been widely noted, but to our knowledge they have never been shown to be a significant environmental source of PCBs.

Airborne PCBs and OH-PCBs Inside and Outside Urban and Rural U.S. Schools

PCBs appear in school air because many school buildings were built when PCBs were still intentionally added to building materials and because PCBs are also present through inadvertent production in modern pigment. This is of concern because children are especially vulnerable to the toxic effects of PCBs. Here we report indoor and outdoor air concentrations of PCBs and OH-PCBs from two rural schools and four urban schools, the latter near a PCB-contaminated waterway of Lake Michigan in the United States. Samples (n = 108) were collected as in/out pairs using polyurethane foam passive air samplers (PUF-PAS) from January 2012 to November 2015. Samples were analyzed using GC/MS-MS for all 209 PCBs and 72 OH-PCBs. Concentrations inside schools were 1-2 orders of magnitude higher than outdoors and ranged from 0.5 to 194 ng/m³ (PCBs) and from 4 to 665 pg/m³ (OH-PCBs). Congener profiles were similar within each sampling location across season but different between schools and indicated the sources as Aroclors from building materials and individual PCBs associated with modern pigment. This study is the first cohort-specific analysis to show that some children's PCB inhalation exposure may be equal to or higher than their exposure through diet.

Terrestrial ecosystem recovery following removal of a PCB point source at a former pole vault line radar station in Northern Labrador

Saglek Bay (LAB-2), located on the northeast coast of Labrador is a former Polevault station that was operated by the U.S. Air Force from 1953 to 1971 when it was abandoned. An environmental assessment carried out in 1996 determined that the site was contaminated with polychlorinated biphenyls (PCBs) with concentrations in soils far exceeding the Canadian Environmental Protection Agency (CEPA) regulation of 50 μg/g in three areas of the site (Beach, Site Summit, Antenna Hill). This led to remediation work carried out between 1999 and 2004 to remove and/or isolate all PCB-contaminated soil exceeding 50 μg/g and to further remediate parts of the site to <5 μg/g PCBs. In this study, spatial and temporal trends of PCB concentrations in soil, vegetation (Betula glandulosa and Salix spp.), and deer mice (Peromyscus maniculatus) were investigated over a period of fourteen (1997-2011) years in an effort to track ecosystem recovery following the removal of the PCB point sources. The data collected shows that PCB levels in vegetation samples are approximately four times lower in 2011 than pre-remediation in 1997. Similarly, PCB concentrations in deer mice in 2011 are approximately three times lower than those measured in 1997/98. Spatial trends in vegetation and deer mice continue to demonstrate that areas close to the former point sources of PCBs have higher PCB concentrations than those further away (and higher than background levels) and these residual PCB levels are not likely to decrease in the foreseeable future given the persistent nature of PCBs in general in the environment, and in particular in cold climates.

Levels and sources of polychlorinated biphenyls in Ankara creek sediments, Turkey

The spatial distribution, degree of pollution and major sources of polychlorinated biphenyls (PCBs) were evaluated in surficial sediments of Ankara Creek, located in the capital of Turkey and serving as one of the tributaries in the third largest watershed in Turkey. Sediment ΣPCB concentrations analyzed on Aroclor and congener basis (seven indicator congeners) range from 5.5 to 777.6 ng g(-1) and 3.7 to 743.3 ng g(-1) dw as Aroclor and congener based concentrations, respectively. High concentrations of ΣPCBs were observed in the samples located at the downstream sections of the Creek, after discharge from Ankara municipal wastewater treatment plant. Using a chemical mass balance receptor model (CMB), major sources of PCBs affecting the sediments were investigated. The CMB model identified Aroclor 1254 and 1260 to be the major PCB sources affecting sediments. The potential sources for the PCBs were briefly discussed in terms of their use in various industrial applications.

In vitro biotransformation of flavonoids by rat liver microsomes

1. Sixteen naturally occurring flavonoids were investigated as substrates for cytochrome P450 in uninduced and Aroclor 1254-induced rat liver microsomes. Naringenin, hesperetin, chrysin, apigenin, tangeretin, kaempferol, galangin and tamarixetin were all metabolized extensively by induced rat liver microsomes but only to a minor extent by uninduced microsomes. No metabolites were detected from eriodictyol, taxifolin, luteolin, quercetin, myricetin, fisetin, morin or isorhamnetin. 2. The identity of the metabolites was elucidated using lc-ms and 1H-nmr, and was consistent with a general metabolic pathway leading to the corresponding 3',4'-dihydroxylated flavonoids either by hydroxylation or demethylation. Structural requirements for microsomal hydroxylation appeared to be a single or no hydroxy group on the B-ring of the flavan nucleus. The presence of two or more hydroxy groups on the B-ring seemed to prevent further hydroxylation. The results indicate that demethylation only occurs in the B-ring when the methoxy group is positioned at C4', and not at the C3'-position. 3. The CYP1A isozymes were found to be the main enzymes involved in flavonoid hydroxylation, whereas other cytochrome P450 isozymes seem to be involved in flavonoid demethylation.

Cytochrome P450-dependent desaturation of lauric acid: isoform selectivity and mechanism of formation of 11-dodecenoic acid

Cytochrome P450-catalyzed desaturation reactions have been reported infrequently in the literature. Previously, we documented the formation of the terminal olefinic metabolite of valproic acid by various members of the CYP2B and CYP4B sub-families. However, despite the extensive use of fatty acid substrates in drug metabolism studies, other examples of terminal desaturation at non-activated carbon centers are lacking. The goals of the present studies were to determine whether the archetypal P450 substrate, lauric acid (dodecanoic acid; DDA), also undergoes desaturation reactions, identify specific rabbit P450 isoforms which catalyze this reaction and examine its mechanism. A highly sensitive, capillary GC/MS assay was developed to separate and quantitate the trimethylsilyl derivatives of 11-ene-DDA, cis- and trans-10-ene-DDA and cis- and trans-9-ene-DDA. Among all of these potential olefinic metabolites, only 11-ene-DDA was formed at a significant rate by rabbit liver microsomes. The formation of 11-ene-DDA was NADPH-dependent, and was induced markedly by acetone pre-treatment, but not by phenobarbital, rifampin or Arochlor 1254. Studies with seven purified, reconstituted rabbit P450 isoforms showed that the most rapid rates of desaturation were obtained with CYP2E1, CYP4A5/7 and CYP4B1. Non-competitive, intermolecular isotope effect experiments, conducted with [12,12,12-2H3]DDA and [11,11-2H2]DDA, demonstrated further that CYP4B1-mediated terminal desaturation of DDA is initiated by removal of a hydrogen atom from the omega-1 rather than the omega position.

Impairment of human neutrophil oxidative burst by polychlorinated biphenyls: inhibition of superoxide dismutase activity

We report evidence of a novel mechanism by which polychlorinated biphenyls might act as potent inducers of inflammation. Aroclor 1242 (A1242), a polychlorinated biphenyl mixture, and 2,2',4,4'-tetrachlorobiphenyl (PCB47), a constituent of A1242 that produces the same patterns of effects, impaired the oxidative burst of human neutrophils by inhibiting the antioxidant enzyme superoxide dismutase, which converts O2- to H2O2. Pre-incubation of neutrophils with A1242 or PCB47 before stimulation with phorbol 12-myristate 13-acetate heightened the respiratory burst, producing a significant increase in intracellular O2- production along with a significant decrease in H2O2 production compared with unexposed agonist-stimulated neutrophils. This was also evident in a physiologically relevant situation in which neutrophils pre-incubated with A1242 were subsequently stimulated with a combination of N-formyl-L-methionyl-L-leucyl-L-phenylalanine and tumor necrosis factor-alpha. Incubation of bovine copper-zinc superoxide dismutase (EC 1.15.1.1) with A1242 or PCB47 in a cell-free system reversed the enzyme-mediated inhibition of 6-hydroxydopamine autoxidation, indicating that polychlorinated biphenyls inhibited superoxide dismutase activity. Low superoxide dismutase activity in neutrophils leads to imbalances between production of free radicals and antioxidant defense mechanisms, which can in turn induce tissue damage and hasten the onset of neutrophil apoptosis.

Cometabolic oxidation of polychlorinated biphenyls in soil with a surfactant-based field application vector

Polychlorinated biphenyl (PCB)-degradative genes, under the control of a constitutive promoter, were cloned into a broad-host-range plasmid and a transposon. These constructs were inserted into a surfactant-utilizing strain, Pseudomonas putida IPL5, to create a field application vector (FAV) in which a surfactant-degrading organism cometabolizes PCB. By utilizing a surfactant not readily available to indigenous populations and a constitutive promoter, selective growth and PCB-degradative gene expression are decoupled from biphenyl. Since PCB degradation via the biphenyl degradation pathway is nonadaptive in the absence of biphenyl, there is no selective pressure for PCB gene maintenance. The recombinant strains exhibited degradative activity against 25 of 33 PCB congeners in Aroclor 1248 in the absence of biphenyl. Whole-cell enzyme assays indicated that PCB-degradative activity of a recombinant strain carrying the PCB genes on a plasmid was approximately twice that of the same strain carrying the PCB genes on a transposon. Plasmid loss rates in the absence of antibiotic selection averaged 7.4% per cell division and were highly variable between experiments. Surfactant-amended slurries of PCB-contaminated electric power plant substation soil were inoculated with approximately 10(5) recombinant cells per ml. The populations of the added strains increased to greater than 10(9) cells per ml in 2 days, and cell growth coincided with PCB degradation. By 15 days, 50 to 60% of the indicator congener 2,3,2',5'-tetrachlorobiphenyl was degraded. The effectiveness of PCB degradation by the plasmid-containing strain depended on plasmid stability. The transposon-encoded PCB genes were much more stable, and in surfactant-amended soil slurries, PCB degradation was more consistent between experiments.

Mutagenic activity of newly synthesized sulfa drugs to Salmonella typhimurium

The mutagenic activity of seven newly synthesized sulfa drugs was studied in Salmonella typhimurium, using forward mutation to 8-azaguanine (8-AG) resistance and reversion mutation assays (Ames test) both in the absence and presence of Aroclor induced rat liver S9. In forward mutation assays, N1-methylsulfanilamide, N4-acetyl-N1-methylsulfanilamide and N4-acetyl-N1-diethylsulfanilamide were mutagenic to S. typhimurium TM677 both in the presence and absence of metabolic activation while N4-acetylsulfanilamide, N1-diethylsulfanilamide and 4-nitro-N-2-pyridinylbenzenesulfonamide [2-(p-nitrobenzenesulfonamido)pyridine] were mutagenic only in the presence of metabolic activation. But 2-(N4-acetylsulfanilamido)pyridine was mutagenic in neither the presence nor the absence of metabolic activation. However, none of the seven compounds had any mutagenic effect on S. typhimurium TA98 or TA100 in the absence or presence of metabolic activation, by the Ames test preincubation method. The relationship between the structure of the compounds and their mutagenic activity is also discussed.

Cytochrome P450-dependent metabolism and mutagenicity of 15,16-dihydro-11-methylcyclopenta[a]phenanthren-17-one and their implications in its carcinogenicity

Methylation of the non-carcinogen 15,16-dihydrocyclopenta[a]phenanthren-17-one (CPP-17-one) at the bay region to form 11-CH3-CPP-17-one confers carcinogenic potential. In the present study we have investigated the in vitro metabolism and mutagenicity of the methylated compound by hepatic microsomal preparations from rats pretreated with various prototype inducers of cytochrome P450 proteins in order to provide a rationale for this marked difference in carcinogenic activity. The most effective metabolism of 11-CH3-CPP-17-one occurred in the presence of Aroclor 1254-induced microsomes, the principal metabolites being oxidative products of the A- and D-rings and of the methyl substituent. When benzo[a]pyrene-induced microsomes served as the metabolising system, the major A-ring metabolite was the 3,4-diol. A similar metabolic pattern was seen with microsomes from rats treated with 11-CH3-CPP-one itself, but the overall effect of metabolism was lower than that observed with benzo[a]pyrene-treated microsomes but higher than that of control animals. In contrast, microsomes from rats treated with clofibrate, dexamethasone, isoniazid and phenobarbitone failed to enhance the metabolism of 11-CH3-CPP-17-one when compared with control microsomes and the metabolites reflected primarily oxidation of the D-ring. When 11-CH3-CPP-17-one was employed as a promutagen in the Ames test, a mutagenic response was evident only in the presence of microsomes from benzo[a]pyrene-induced rats, but induction with phenobarbitone, isoniazid, dexamethasone, clofibrate and the compound itself, failed to elicit a positive mutagenic response. When 3,4-dihydroxy-11-CH3-CPP-17-one served as the promutagen, a mutagenic response was observed in the presence of benzo[a]pyrene-induced and, to a lesser extent, 11-CH3-CPP-17-one-induced microsomes. Treatment of rats with 11-CH3-CPP-17-one caused a marked increase in the O-deethylation of ethoxyresorufin and, to a much lesser extent in epoxide hydrolase activity. It is concluded that (i) 11-CH3CPP-17-one is an inducer of the CYP1 family; (ii) under the present experimental conditions only the CYP1 family can oxidise the A-ring to form the 3,4-dihydroxy-11-CH3-CPP-17-one, the precursor of the ultimate carcinogen and (iii) only the CYP1 family oxidizes the diol to generate the ultimate carcinogen.(ABSTRACT TRUNCATED AT 400 WORDS)

A scientific basis for proposed quality assurance of a new screening method for tumor-like growths in the planarian, Dugesia dorotocephala

Various abnormal growths appear on planarians, Dugesia dorotocephala, during and after exposure to polychlorinated biphenyls (PCBs) 28, 110, and 126; Aroclor 1254; cadmium sulfate; and L-buthionine-(R,S)-sulfoximine (BSO). Daily observations under magnification were used to describe the location, development, and morphology of three different types of tumor-like growths ("tumors"). "Post-head tumors" were found to be highly invasive, progressive, and lethal to the animal depending on concentrations and combinations of the compounds used. Survivors from post-head tumors exhibited aberrant morphogenesis, but developmental abnormalities were eventually shed. Post-head tumors occurred within 2 weeks of initial exposure, while "round tail tip tumors" appeared after 2-3 weeks. The rate of progression and invasiveness was greater for the round tail tip tumors. "Pigmented rose thorn tail tumors" occurred in low incidence (4-20%) and appeared to be harmless and noninvasive, requiring months to develop from the first appearance of pigmentation. The aggressive, proliferative, and invasive characteristics of post-head and round tail tip tumors are analogous to those of malignant tumors, while pigmented rose thorn tumors were benign. High dose of cadmium alone were sufficient to initiate the post-head and round tail tip tumors. PCBs potentiated the tumorigenicity of low cadmium doses and enhanced the very low spontaneous incidence of pigmented rose thorn tumors. PCBs also impaired motor activity, causing the graceful gliding locomotion to be replaced by a twisting serpentine movement accompanied by muscular dystrophy. In addition, high (50 micrograms) doses of PCB 110 depressed activity, while lower (5 micrograms) doses and 50 micrograms Aroclor 1254 induced restlessness and enhanced locomotion. These data provide the basis for quality assurance.

Alternatives to Aroclor 1254-induced S9 in in vitro genotoxicity assays

A working party was set up by the UK Environmental Mutagen Society to consider alternatives to Aroclor 1254 (Aroclor)-induced S9 in in vitro genotoxicity assays, with the aims of considering whether a replacement for Aroclor in its role in general screening assays could be readily identified. The working party concluded that there was sufficient support in the literature to justify the use of an appropriate phenobarbital/beta-naphthoflavone regime as an acceptable alternative to Aroclor.

1-C-glucuronidation of N-nitrosodiethylamine and N-nitrosomethyl-n-pentylamine in vivo and in primary hepatocytes from rats pretreated with inducers

The organ specificity of the carcinogenic action of nitrosamines is partly explained by organ specific activation. The specificity might also be determined by conjugation of reactive intermediates in e.g. the liver. 14C-Labeled N-nitrosodiethylamine (NDEA) a liver carcinogen and N-nitrosomethyl-n-pentylamine (NMPentA) which induces esophageal and nasal tumors were administered to rats or incubated with primary cells. Urine and cell extracts were separated by HPLC after addition of synthetic marker glucuronides and these were quantified by liquid scintillation counting. In urine of rats treated with NDEA 0.03% of administered nitrosamine was recovered as the O-glucuronide derived from N-nitroso-1-hydroxyethylethylamine. In rats treated with NMPentA 2.86% was metabolized to the glucuronide at the methyl group. In hepatocytes of untreated rats 0.03% of the added NDEA was conjugated to the glucuronide, phenobarbital pretreatment induced this conjugation reaction 5-fold. Hepatocytes from untreated rats metabolized 1.2% of NMPentA to the primary glucuronide; after phenobarbital pretreatment this value increased to 1.6%. In hepatocytes from 3-methylcholanthrene-pretreated rats, 0.04% of NMPentA was metabolized to the glucuronide derived from N-nitroso-1-hydroxy-n-pentyl-methylamine, while 0.85% was derived from N-nitroso-hydroxymethyl-n-pentylamine. In hepatocytes from Aroclor-pretreated rats, 0.09% were pentyl conjugates and 1.1% methyl conjugates. The induction pattern and organ specificity of glucuronidation indicate that all three 1-hydroxy nitrosamines are conjugated by group II phenobarbital inducible UDP-glucuronosyltransferase activity. The lipophilicity of a nitrosamine seems to determine the extent of glucuronidation in hepatocytes and in vivo. No glucuronides derived from either NDEA or NMPentA were detectable in incubations with kidney cells, nor was the glucuronide of NDEA found in incubations with whole bladders.

[Content of cytochrome P-450 and its induction capacity in primary liver tumors in rats]

The content of cytochrome P-450 has been measured in primary hepatomas induced by diethylnitrosamine. As a rule, the enzyme content in hepatomas was decreased, as compared to normal liver and tumor-affected liver, but some hepatomas contained cytochrome P-450 in greater amount than normal tissue. Aroclor 1254 induced an increase in cytochrome P-450 content, which was identical in hepatomas, normal liver and tumor-affected liver. The dependence of hepatoma morphology on cytochrome P-450 content was not detected.

Microsomal activation of constituents of white snakeroot (Eupatorium rugosum Houtt) to form toxic products

Components of white snakeroot, a plant toxic to livestock and human beings, were activated by Aroclor 1254-induced rat liver microsomes. The toxic products of microsomal activation were evaluated in murine melanoma (B16F1) cell cultures. Toxic products in white snakeroot were inactive in cell culture systems without microsomal activation. This activation system revealed that at least 2 fractions of white snakeroot were metabolically activated to cytotoxic agents. The autocatalytic inactivator of cytochrome P-450, 1-aminobenzotriazole, inhibited activation of white snakeroot constituents by rat liver microsomes.

Temporal effects on antipyrine metabolite kinetics in Aroclor 1254-treated rats

The in vivo consequences of a single dose of Aroclor 1254 (50 mg/kg) on the drug metabolizing capacity of rats were investigated. A noninvasive method, employing [N-methyl-14C]-antipyrine where both 14CO2 exhalation and urinary excretion of 4-hydroxy-, 3-hydroxymethyl-, and norantipyrine were monitored, was used. A group of rats were sequentially tested over a 3-week period to characterize temporal patterns. The antipyrine metabolite kinetic approach demonstrated that induction of hepatic cytochrome P-450 is maximal 3-6 days after Aroclor 1254 administration and the effects were apparent for at least a further 14-17 days. Evidence is presented to suggest selective effects of Aroclor 1254 on different cytochromes P-450 are apparent in vivo.

Permeation of polychlorinated biphenyls and solutions of these substances through selected protective clothing materials

Polychlorinated biphenyls (PCBs) have been used in a number of applications, particularly in the electric power industry. While these materials are no longer manufactured in the United States, they still exist in the field. Because of the hazardous nature of these compounds, effective chemical protective clothing is required. The permeation of neat PCBs, and solutions with trichlorobenzene and paraffin oil, through 11 different protective garment materials was determined. These experiments were done both with a permeation cell with water collection medium, and by periodically swiping thumb cots which contained the challenge liquids. Contamination was a continuing problem because of the resinous, nonvolatile properties of PCBs. While the results from the two methods were not identical, they did agree qualitatively. The best protection against PCBs was provided by nitrile, Viton, Viton SF and Vitrile. While the results with PVA and Teflon were also very good, these materials have other characteristics which may make their use suspect. For most of the other materials, the performance depended on the challenge liquid. The weight and volume changes which occurred when the materials were soaked in the challenge liquids were determined. The volume changes of 80 percent of those challenge/material combinations which exhibited breakthrough correlated with the breakthrough times normalized to the square of the material thickness.

[Cytochrome P-450 and aryl hydroxylase activity in cells of a long-term transplantable tumor]

A functionally active system of microsomal monooxygenases has been found in a long-term transplanted tumor MC-II of C57B1/6j mice. In microsomal fraction of the tumor, one could detect cytochrome P-450 and benzo(a)pyrene hydroxylase (BP hydroxylase) activity. The latter one increased more than 2 times after the animals received 3-MC and aroclor 1254. In in-vitro experiments, the microsomal monooxygenase inhibitors, SKF 525-A and metyrapone, did not affect BP hydroxylation, whereas alpha-naphthoflavone inhibited the enzyme. It is assumed that tumor MC-II contains hemoprotein that is similar to cytochrome P1-450.

Aroclor 1254-induced intestinal metaplasia and adenocarcinoma in the glandular stomach of F344 rats

Ingestion of diets containing Aroclor 1254, a mixture of polychlorinated biphenyls, for 2 years led to a dose-related increase in the incidence of focal lesions in the glandular stomachs of male and female F344 rats. The incidence of stomach lesions was 6% in control specimens and in specimens from rats fed a diet containing 25, 50, or 100 ppm Aroclor 1254, the incidences of stomach lesions were 10, 17, and 35%, respectively. The majority of gastric lesions in treated rats were histologically identified as intestinal metaplasia characterized by an architecture resembling that of intestinal crypts and particularly by goblet cells, which stained with Alcian blue and periodic acid-Schiff reagent. Adenocarcinomas were found in six specimens. Most (88%) of the lesions were located in the pyloric region of the glandular stomach. No multiple lesions were observed among 47 control specimens examined; however, nine cases of multiple lesions were observed in 30 lesion-containing specimens from Aroclor 1254-treated rats. Although the exact relationship between gastric intestinal metaplasia and adenocarcinoma remains to be established, they commonly coexist and may share initiating mechanisms.

Influence of microsomal and cytosolic fractions from rat, mouse, and hamster liver on the mutagenicity of dimethylnitrosamine in the Salmonella plate incorporation assay

Dimethylnitrosamine (DMN) was mutagenic in the Salmonella plate incorporation assay (Ames test) at a level of 10 mumol/plate (3.7 mM) in the presence of hamster liver S-9. Mutagenicity of DMN at this level was not observed when the S-9 was derived from mouse or rat liver, although the mouse liver and hamster liver S-9 had similar DMN demethylase activities. Both mouse and rat liver S-9 inhibited the mutagenicity of DMN mediated by hamster liver S-9; the inhibitory factor was contained in the microsomal fraction. Mouse or rat liver microsomes did not inhibit the DMN demethylase activity of hamster liver S-9. The microsomal inhibitor from rat or mouse liver was stable at 60 but was inactivated at 70 degrees. DMN demethylase from both rat and mouse liver was inactivated at 60 degrees. Although the DMN demethylase activity of hamster liver S-9 was contained in the microsomal fraction, DMN mutagenesis under conditions of the assay required the presence of both microsomal and cytosolic (S-105) fractions; the cytosols from hamsters, mice, and rats were all effective. The cytosolic factor required for DMN mutagenesis was sensitive to trypsin and was not dialyzable. The presence of an inhibitor of DMN activation in rat and mouse microsomes may account for, or contribute to, the failure of liver S-9 preparations from these species to activate DMN to a mutagen under standard conditions of the Ames test. The requirement for the cytosolic fraction may indicate that DMN demethylase is not sufficient for the activation of DMN to a mutagen under the conditions used in these studies.

Detection of mutagenicity of procarbazine by the host-mediated assay with polychlorinated biphenyl (aroclor 1254) as enzyme inducer

Procarbazine [N-isoppropyl-alpha-(2-methylhydrazino)-p-toluamide] was tested for mutagenicity with Salmonella typhimurium G46 in the host-mediated assay by using male BALB/c mice pretreated orally with polychlorinated biphenyl (PCB, Aroclor 1254). Procarbazine was weakly mutagenic without PCB pretreatment, but the pretreatment greatly enhanced the mutagenicity of this compound. The administration of 500 mg PCB/kg 1 day before procarbazine dosage was suitable for the detection of the mutagenicity. Among PCB, 3-methylcholanthrene (3-MC) and phenobarbital sodium (PB), the former 2 inducers showed much stronger enhancing effects than PB. The pretreatment with 3-MC in combination with PB did not cause further enhancement compared with 3-MC alone.

Evaluation of feasibility of mutagenic testing of shale oil products and effluents

In an effort to gather preliminary information on the potential genetic hazards of proposed or existing oil shale technologies, we have begun a correlated analytical and genetic analysis of a number of test materials. The work is divided into two phases: one deals with known compounds expected to occur in the environment through shale oil production or use; the other deals with actual samples from existing or experimental processes. A fractionation procedure has been applied to crude product and aqueous product material from an oil shale process. Mutagenicity of the various fractions was assayed by using reversion of histidine-requiring auxotrophs of Salmonella typhimurium (strain TA100, base-substitution mutant; TA98 and TA1537, frameshift mutants). In order to incorporate metabolic activation of these fractions and compounds, we used liver homogenates (S-9) from rats induced with Aroclor 1254 in the standard plate assay. Preliminary results implicate chemical constituents of these fractions (identified or predicted) were tested individually for their mutagenic activity and correlated with the genetic monitoring.

Comparison of the compositions of Aroclor 1242 and Aroclor 1016

The complete polychlorinated biphenyl compositions of two American products, Aroclor 1242 and its more modern replacement, Aroclor 1016, have been determined by gas-liquid chromatography (GLC) on twelve liquid phases of differing selectivities. Attempts were made to determine the degree of contamination of these Aroclors with chlorinated naphthalenes, using GLC with multiple ion-monitoring mass spectrometry. Chlorinated dibenzofurans, indetectable in Aroclor 1016, were tentatively identified by negative chemical-ionization mass spectrometry and their retention times relative to dieldrin on two GLC liquid phases. Quantitation of the dibenzofurans was initially accomplished using an electron-capture detector, and confirmed by negative chemical-ionization mass spectrometry. Aroclor 1242 contained less than 0.05 mol.% chloronaphthalenes, while Aroclor 1016 contained less than 0.06 mol.% of these compounds. Aroclor 1242 had approximately 150 ppb of chlorinated dibenzofurans, of which 43% was the toxic 2,3,7,8-tetrachloro isomer.

An animal model of hepatotoxicity associated with halothane anesthesia

Hepatic necrosis was induced in rats by a single exposure to 1 per cent halothane in oxygen following pretreatment with a single dose of Aroclor 1254, a polychlorinated biphenyl. The hepatic lesion was centrilobular and multifocal, and morphologically similar to that reported to occur in man. In-vitro incubation with 14C-halothane indicated an enhanced covalent binding of halothane metabolites to hepatic microsomal macromolecules, particularly lipids, following Aroclor 1254 pretreatment. Lipoperoxidation of microsomal unsaturated fatty acids was not observed with these animals.