Polychlorinated Biphenyls Formulations Research Articles

Effect of membrane filtration on the fate of polychlorinated biphenyls in wastewater treatment

The Spokane River is impacted by levels of polychlorinated biphenyls (PCBs) that have triggered fish consumption advisories and exceed water quality standards. Select wastewater treatment plants (WWTPs) on the river have been upgraded from secondary (biological) treatment to tertiary treatment in the form of membrane filtration to address phosphorus contamination. Because membrane filtration is effective at removing particles, it is likely to reduce PCB concentrations in the effluent as well. In this work, PCBs measured in the influents and effluent of several WWTPs discharging to the river were examined. Implementation of membrane filtration reduced PCB concentrations in the effluent (and therefore PCB loads to the river) by 33% at a facility that produces recycled and virgin paper and by ∼55% at municipal WWTPs, compared to secondary (activated sludge) treatment. Largest reductions in concentrations in effluent and loads were achieved for higher molecular weight (MW) PCB congeners (i.e. those with six or more chlorines), homologs, and formulations. The more modest reductions in effluent concentrations achieved at the paper WWTP may be due to the mix of PCBs in the wastewater there: it contained primarily the low MW Aroclor 1242 (presumably from carbonless copy paper) and PCB 11 (3,3′-dichlorobiphenyl) possibly from pigments. PCBs that appear to be associated with silicone products such as caulk, tubing, and o-rings are relatively more abundant in the effluent of some plants compared to the influent, suggesting that these congeners arise from contamination during sampling or from within the plant itself. At some WWTPs, this contamination accounts for nearly a third of PCBs measured in the effluent.

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.Graphic

Sources of polychlorinated biphenyl blank contamination and their impact on fingerprinting

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

Alterations in fingerprints of polychlorinated biphenyls in benthic biota at the Portland Harbor Superfund Site (Oregon, USA) suggest metabolism

In order to understand the sources and fate of polychlorinated biphenyls (PCBs) in several species of benthic biota, including clams (Corbicula fluminea), oligochaetes (Lumbriculus variegatus), and mussels (Margaritifera falcata and Anodonta nuttalliana) at the Portland Harbor Superfund Site (PHSS), their congener fingerprints were examined. First, diagnostic ratios of congeners known to be metabolizable vs. recalcitrant in the cytochrome P450 (CYP) pathway were significantly lower in biota than in its co-located sediment, indicating metabolism may have occurred. Next, the congener patterns were analyzed using Positive Matrix Factorization (PMF). The dominant fingerprint (by mass) in benthic biota is related to Aroclor 1260 but displays differences in the fingerprint that are consistent with weathering via absorption, distribution, metabolism, and excretion (ADME). This fingerprint is similar to one isolated from PCBs in fish from Washington State, indicative of common metabolic pathways and consistent with CYP metabolism. When metabolism is taken into account, the spatial distribution of the PMF-isolated PCB fingerprints in biota matches well with those from co-located sediment samples, suggesting that the same mix of sources at one location partitions into biota and sediment. In accordance to their higher hydrophobicity, higher molecular weight (MW) PCB formulations were proportionately more abundant in biota than in sediment, although low MW PCBs (e.g., PCBs 4 and 11) do bioaccumulate in benthic organisms and should not be ignored in risk assessment efforts. Finally, fingerprinting suggests potential reasons why lab-based and field-based biota-sediment accumulation factors (BSAFs) differ substantially for bivalves.

Polychlorinated biphenyls (PCBs) in commonly consumed seafood from the coastal area of Bangladesh: occurrence, distribution, and human health implications.

Dietary intake is the most important route of polychlorinated biphenyls (PCBs) exposure and seafood is the major dietary component for the coastal populations. It is, therefore, an urgent need to assess the levels of PCBs in seafood. A comprehensive congener-specific evaluation of PCBs was carried out for the first time in Bangladesh. All 209 congeners of PCBs in 48 seafood samples (5 finfish and 2 shellfish species) collected in winter and summer of 2015 were measured by GC-MS/MS. Regardless of season and site, the ∑PCBs (ng/g wet weight) in finfish and shellfish were in the range of 6.4-86.2 and 3.8-37.7, respectively. The results were comparable to or higher than those observed in other studies worldwide, particularly from Spain, China, Korea, Thailand, and Hong Kong. No significant seasonal variation was observed in the levels of ∑PCBs in the examined seafood (p > 0.05); however, interspecies differences were significant (p < 0.05). Nonetheless, spatial distribution revealed seafood collected from the areas with recent urbanization and industrialization (Chittagong, Cox's Bazar, and Sundarbans) were more contaminated with PCBs than the area unaffected by industries (Meghna Estuary). Moderately chlorinated (4-6 Cl) homologs dominated the PCB profiles. The congener profile and homolog composition revealed that the source origin of PCBs in the Bangladeshi seafood was related to mixtures of technical PCBs formulations. The dietary exposure assessment revealed that the coastal residents are sufficiently exposed to the dietary PCBs through seafood consumption which may cause severe health risk including dioxin-like toxic effects.

Congener-specific analysis of polychlorinated naphthalenes (PCNs) in the major Chinese technical PCB formulation from a stored Chinese electrical capacitor.

Impurity of polychlorinated naphthalenes (PCNs) in commercial polychlorinated biphenyl (PCB) formulations has been recognized as a relevant source of PCNs in the environment. Congener-specific analysis of most main PCB formulations has been accomplished previously, excluding the Chinese product. The insulating oil in a stored Chinese electric capacitor containing the major Chinese technical formulation "PCB3" was sampled and tested by isotope dilution technology using high-resolution gas chromatography coupled to high-resolution mass spectrometry (HRGC/HRMS). The detected concentration of PCNs in the Chinese PCB oil sample was 1,307.5 μg/g and therefore significantly higher than that reported in PCB formulations from other countries, as well as that in the transformer oil (ASKAREL Nr 1740) additionally tested in the present study for comparison. Based on the measurement, the total amount of PCNs in Chinese PCB3 oil is estimated to be 7.8 t, which would mean only 0.005 % of global production of PCNs of 150,000 t. The homolog profile is similar to those of PCN in Aroclor 1262 and Clophen A40, where the contributions from hexa-CNs and hepta-CNs are predominant and accounted for similar proportions. The Toxic Equivalent Quantity (TEQ) concentration of dioxin-like PCN congeners is 0.47 μg TEQ/g, with the dominant contributors of CN-73 and CN-66/67. This TEQ content from PCN is higher than that in most other PCB formulations with the exemption of the Russian Sovol formulation. The total TEQ in the historic 6,000 t of the Chinese PCB3 formulation is estimated to be 2.8 kg TEQ.

China action of “Cleanup Plan for Polychlorinated Biphenyls Burial Sites”: Emissions during excavation and thermal desorption of a capacitor-burial site

Scarce data are available so far on emissions in a given scenario for excavation and thermal desorption, a common practice, of soils contaminated with polychlorinated biphenyls (PCBs). As part of China action of “Cleanup Plan for PCBs Burial Sites”, this study roughly estimated PCBs emissions in the scenario for a capacitor-burial site. The concentrations of total PCBs (22 congeners) in soils were in the range of 2.1–16,000μg/g with a mean of 2300μg/g, among the same order of magnitude as the highest values obtained in various PCBs-contaminated sites. Only six congeners belonging to Di-, Tri-, and Tetra-CBs were observed above limits of detection in air samples in the scenario, partially which can be estimated by the USEPA air emission model. Comparing concentrations and composition profiles of PCBs in the soil and air samples further indicated a leaked source of commercial PCBs formulations of trichlorobiphenyl (China PCB no. 1). The measures taken if any to mitigate the volatilization and movement of PCBs and to minimize worker exposure were discussed for improvements of the excavation practice.

Detailed analysis of PCBs and PCDD/Fs impurities in a dielectric oil sample (ASKAREL Nr 1740) from an imported transformer in China

Homolog and congener profiles of polychlori- nated biphenyls (PCBs), polychlorinated dibenzo-p- dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in commercial PCBs formulations are useful information for the source appointment of PCBs contam- ination as well as the risk assessment caused by potential exposure. Dielectric oil (ASKAREL Nr 1740) in an imported transformer found in China was sampled and analyzed by isotope dilution technology using high resolution gas chromatography-high resolution mass spectrometry (HRGC/HRMS). The detailed homolog and congener profiles of PCBs obtained were compared with those of known Aroclor formulations. High similarity in the homolog profile between the oil sample and Aroclor 1260 was found, with the hexachlorinated and hepta- chlorinated biphenyls accounting for more than 80.2% of the total PCBs concentration. Severn indicator PCBs contribute about 30%, while 12 PCB congeners (i.e., #153, #143, #168, #180, #149, #165, #138, #170, #190, #187, #174, #181) account for more than 50% of the total PCB concentrations. Total concentration of PCDDs, PCDFs and dioxin-like PCBs (DL-PCBs) was found to be 740 ng TEQ/g, of which 620 ng TEQ/g came from DL-PCBs. The contribution of PCDDs to the total TEQ was neglectable. The concentration of PCDFs homologs follows the order of OCDF>HxCDFs>HpCDFs>PeCDFs>TeCDFs, which is in consistence with the previous study on Aroclor 1260. Three DL-PCBs congeners (i.e., #118, #156, #157) accounted for 77% of the total concentration of DL-PCBs, also they contribute 72% in the TEQ caused by DL-PCBs.

Levels and sources of planar and non-planar PCBs in pine needles across Poland

Under a small project, one-year-old Scots Pine needles collected from 25 spatially distant sites were examined in monitoring the extent of environmental diffusion and possible sources of polychlorinated biphenyls (PCBs) in ambient air, their depositions and uptake by plants in Poland. The congener-specific determination of planar and non-planar chlorobiphenyls was achieved by isotope dilution HRGC-HRMS method after a highly refined extraction on multi-layer column of silica gel and alumina layer and clean-up, and fractionations, followed by Hypercarb-HPLC and PYE-HPLC sub-fractionation steps. Contents of 117 chlorobiphenyls determined in pine needles varied for the 25 sites studied and is between 2.7 and 49 ng/g wet weight. The PCBs pollution and congener-specific composition of pine needles to some degree varied according to the site or region surveyed depending on population density and industrialization. Many of the country-side areas showed lower concentrations between 2.7 and 8.9 ng/g ww. Pine needles in areas close to well populated and industrial regions of Opole, Kutno, Włocławek and Dębica showed the highest PCB pollution with concentrations varying between 30 and 49 ng/g ww. The Kutno site showed the highest pollution and this fact probably can be explained by possible emission from transformer manufactures located at some distance west of the Kutno area. Factor analysis (FA) and depending on the site revealed on relationship of PCBs composition of pine needles both with highly chlorinated PCB constituents of the mixtures such as Chlorofen, Aroclor 1254, Aroclor 1268 and Sovol but also of lower chlorinated PCB constituents of Aroclor 1242, Aroclor 1248, Clophen A40 or Delor 103. Thermal processes were considered a less significant source of PCBs in ambient air over Poland compared to evaporative sources related to technical PCB formulations. Supplemental materials are available for this article. Go to the publisher's online edition of Journal of Environmental Science and Health: Part A to view the free supplemental file.

Passive air monitoring of PCBs and PCNs across East Asia: A comprehensive congener evaluation for source characterization

A comprehensive congener specific evaluation of polychlorinated biphenyls (PCBs) and polychlorinated naphthalenes (PCNs) in the atmosphere was conducted across East Asia in spring 2008, applying polyurethane foam (PUF) disk passive air sampler (PAS) as monitoring device. Mean concentrations derived for Japan, China and Korea were 184±24, 1100±118, and 156±20pgm−3 for ∑202 PCBs, and 9.5±1.5, 61±6, and 16±2.4pgm−3 for ∑63 PCNs, respectively. Relative to reported data from 2004, the present results suggest that air PCBs concentrations have not changed much in Japan and Korea, while it has increased by one order of magnitude in China. From principal component analysis, combustion emerged highly culpable in contemporary emissions of both PCBs and PCNs across the East Asian sub-region. Another factor derived as important to air PCBs was re-emissions/volatilization. Signals from PCBs formulations were also picked, but their general importance was virtually consigned to the re-emissions/volatilization tendencies. On the contrary, counterpart PCNs formulations did not appear to contribute much to air PCNs.

Determination of PCBs, PCDDs and PCDFs in insulating oil samples from stored Chinese electrical capacitors by HRGC/HRMS

Homologue and congener profiles of polychlorinated biphenyls (PCBs), polychlorinated dibenzo- p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in commercial PCBs formulations are key information for the source identification of PCBs contamination as well as for the risk assessment caused by potential exposure. The isotope dilution technology in combination with high resolution gas chromatography–high resolution mass spectrometry (HRGC/HRMS) has made the accurate determination of such profiles possible. So far, various commercial PCB formulations except Chinese products have been successfully determined. Two PCBs containing insulating oil samples from stored Chinese electrical capacitors have been determined with the same methodology for comparability. The total concentration PCBs in two oil samples were 790 000 μg g −1 and 720 000 μg g −1, respectively. TriCBs, TetraCBs, and DiCBs were found to be most abundant. Concentration of dioxins contamination in two samples is 650–670 ngTEQ g −1, of which 69–71 ngTEQ g −1 from PCDD/Fs with the predominant congeners of 1,2,7,8-TeCDF; 2,3,7,8-TeCDF; 2,3,4,7,8-PeCDF and 1,2,3,7,8-PeCDF. The contributions of DL-PCBs in total TEQ in both samples were more than 85%. The dioxin-like toxicity in insulating oils contained in electrical capacitors could be considered receive attention as an important dioxins source if such wastes are not managed in an environmentally sound manner.

Persistent organic pollutants in two Finnish watercourses: Levels, congener profiles and source estimation by mussel incubation

Mussel incubation was used to compare two Finnish watercourses, which have been contaminated by effluents from pulp mills and are known to be polluted with polychlorinated biphenyls (PCBs). Lake mussels ( Anodonta Piscinalis) incubated in 1998 and 2004 in the rivers Kymijoki and Vuoksi were analysed for PCBs and polychlorinated dibenzo- p-dioxins (PCDDs), dibenzofurans (PCDFs), naphthalenes (PCNs), diphenyl ethers (PCDEs), hydroxy diphenyl ethers (HO-PCDEs), methoxy diphenyl ethers (MeO-PCDEs), and polybrominated diphenyl ethers (PBDEs). The contamination of the River Kymijoki, which descends to the Baltic Sea, proved significantly greater than that of the River Vuoksi, with no decreasing apparent trend, except for the PBDEs. The River Vuoksi represented more a background area compared to the River Kymijoki, excluding the PCBs. The concentration of the PCDD/PCDFs in the Kymijoki mussels exceeded the EU’s maximum permissible level for PCDD/PCDFs in foodstuffs (4 pg g −1 fresh weight). Analyses of perfluorooctanesulphonate and perfluorooctanoate in the mussels incubated in 2005 and 2006 in the River Kymijoki revealed no significant contamination of the river with these compounds. Comparison of the data of the mussels with that of sediments and commercial formulations showed that the past manufacture of a chlorophenol-based wood preservative has remained a significant source of the PCDD/PCDFs, HO-PCDEs and PCDEs in the River Kymijoki. PCB formulations are believed to represent the major sources of the PCBs and PCNs in both watercourses, though situation in the River Kymijoki had been influenced by a chlor-alkali plant. Municipal wastewaters are believed to represent the major source of the PBDEs.

Growth of the genetically engineered strain Cupriavidus necator RW112 with chlorobenzoates and technical chlorobiphenyls

Cupriavidus necator (formerly Ralstonia eutropha) strain H850 is known to grow on biphenyl, and to co-oxidize congeners of polychlorinated biphenyls (PCBs). Using a Tn5-based minitransposon shuttle system and the TOL plasmid, the rational construction of hybrids of H850 was achieved by subsequent introduction of three distinct elements carrying 11 catabolic loci from three other biodegrading bacteria into the parent strain, finally yielding C. necator RW112. The new genetic elements introduced into H850 and its derivatives were tcbRCDEF, which encode the catabolic enzymes needed for chlorocatechol biodegradation under the control of a transcriptional regulator, followed by cbdABC, encoding a 2-halobenzoate dioxygenase, and xylXYZ, encoding a broad-spectrum toluate dioxygenase. The expression of the introduced genes was demonstrated by measuring the corresponding enzymic activities. The engineered strain RW112 gained the ability to grow on all isomeric monochlorobenzoates and 3,5-dichlorobenzoate, all monochlorobiphenyls, and 3,5-dichloro-, 2,3'-dichloro- and 2,4'-dichlorobiphenyl, without accumulation of chlorobenzoates. It also grew and utilized two commercial PCB formulations, Aroclor 1221 and Aroclor 1232, as sole carbon and energy sources for growth. This is the first report on the aerobic growth of a genetically improved bacterial strain at the expense of technical Aroclor mixtures.

Chemical Characterization of Polychlorinated Biphenyls, -Dibenzo-p-Dioxins, and -Dibenzofurans in Technical Kanechlor PCB Formulations in Japan

Technical polychlorinated biphenyl (PCB) formulations-Kanechlor KC-200, KC-300, KC-400, KC-500, KC-600 and KC-1000-produced in Japan were analyzed for the chemical characterization of PCBs, -dibenzo-p-dioxins (PCDDs), and -dibenzofurans (PCDFs) using high-resolution gas chromatography-high-resolution mass spectrometry (HRGC-HRMS) by isotope dilution technique. The homologue/congener profiles of Kanechlor formulations resembled those of Clophen, Aroclor, and Delor, respectively, from Germany, the United States, and Czechoslovakia. Twenty-seven major PCB congeners contributed 50% (in KC-200) to 69-71% (in KC-600, 1000, and 500) to total PCBs. Average total PCB concentrations were 510,000, 800,000, 830,000, 840,000, 870,000, and 880,000 mug/g in KC-1000 (51%), KC-200 (80%), KC-500 (83%), KC-400 (84%), KC-300 (87%), and KC-600 (88%), respectively. Kanechlors also contained PCDDs and PCDFs (4.3 to 0.35 microg/g) as impurities which were approximately 1/10,000 to the PCB concentrations. Congener characterization and concentrations of PCBs and PCDFs were considerably varied in between Kanechlor formulations. The potential for the emissions of PCDDs and PCDFs from Kanechlor was estimated to be 1.94 kg and 464.4 kg, respectively. The average WHO-toxic equivalent (TEQ) was 16 (KC-500) >12 (KC-400) >10 (KC-1000) >4.1 (KC-600) >3.5 (KC-300) >1.9 (KC-200) on microgTEQ/g. Non- and mono-ortho PCBs were the major contributors to the total TEQ in Kanechlor formulations, whereas the PCDD/DF contribution was <2.0%. The environmental input of TEQs from Kanechlors can be estimated to be between 112 and 941 kg.

Isotope dilution analysis of polychlorinated biphenyls (PCBs) in transformer oil and global commercial PCB formulations by high resolution gas chromatography–high resolution mass spectrometry

Special polychlorinated biphenyls (PCBs) standards (native and isotope labeled) were analyzed by isotope dilution method using HRGC–HRMS. Multiple analysis of special PCBs standards by three different laboratories produced the relative response factors (RRFs) and relative standard deviations (RSDs %) was in the average of 0.979 and 3.86, respectively. Additionally, inter-laboratory analysis of various forms of transformer oil revealed the PCBs concentrations were in the following order; PCBs fortified transformer oil (940–1300 ng/g) > PCB polluted transformer oil (490–680 ng/g) > chemically degraded-transformer oil (480–490 ng/g) and PCBs free oil (ND-17 ng/g). Chemical degradation resulted in an order of magnitude decrease in the PCB concentrations. Specifically, higher chlorinated PCBs degraded into lower chlorinated PCBs. Also, composition of PCBs have been determined in PCB formulations from Japan (Kanechlor), Germany (Clophen), USA (Aroclor), Russia (Sovol) and Poland (Chlorofen). Major PCBs (24-PCB congeners) contributed 54–67%, 55–68%, 16–69%, 71% and 72% in Kanechlor, Clophen, Aroclor, Sovol and Chlorofen, respectively to total PCBs. The homologue pattern of Kanechlor, Aroclor and Clophen in technical fromulation was similar (e.g., Kanechlor-300 resembled to those of Clophen A-30 and Aroclor-1242). Furthermore, congener-specific distributions of major PCBs/dioxin-like PCBs and toxic equivalency quantities (TEQ) were calculated. Based on our tentative assumption calculations, cumulative production of five different technical PCB formulations, WHO–TEQ emission was estimated to be approximately 16.05 tons.

Contamination of PCBs in Nakdong river estuary, Korea

Polychlorinated biphenyls (PCBs) were determined in the sediments, soils, fishes and birds from Nakdong River estuarine environment in Korea which included both industrial and non‐industrial areas. PCB levels (30–8500 ng/g, dry wt.) in sediments from industrial areas, were significantly higher than those from non‐industrial areas (0.3–32 ng/g, dry wt.). Lower chlorinated PCBs (KC‐300, 400) were the major components in the polluted sediments, based on the comparison with technical PCB formulations. The residual patterns of PCBs in fish samples from the industrial area were similar to those of sediments collected at the same area. In bird samples, elevated concentrations in muscle tissues in migratory birds indicated exposure to the aquatic food web in this area.

A kinetic distribution model of evaporation, biosorption and biodegradation of polychlorinated biphenyls (PCBs) in the suspension of Pseudomonas stutzeri

Kinetics of distribution of PCBs in an active bacterial suspension of Pseudomonas stutzeri was studied by monitoring the evaporated amounts and the concentration remaining in the liquid medium with the biomass. To determine the biodegradation rate constants of the individual congeners of the PCB formulation Delor 103, a model considering biosorption, evaporation, and primary biodegradation constructed previously was used. Rate constants of biodegradation imply that biodegradation of individual congeners is structure-dependent process. Biodegradability decreases with increasing number of chlorine substituents in the molecule, especially if they are in the ortho and para positions. On the other hand, the increasing number of free ortho and meta positions in the biphenyl molecule leads to better biodegradability. For a simple empirical determination of the influence of the chlorine substitution pattern on biodegradability, the di- and trichlorobiphenyl rate constants of biodegradation were analysed.

Distribution of Polychlorinated Naphthalene Congeners inEnvironmental and Source-Related Samples

Polychlorinated naphthalene (CN) congener profiles inenvironmental and source related samples were compared graphically and byprincipal component analysis. Samples investigated included biological,sediment, water, and air samples, technical polychlorinated biphenyl (PCB)and polychlorinated naphthalene (PCN) formulations, as well as municipalwaste incineration (MWI) fly ash and graphite electrode sludge. Biologicalsamples showed a preferential enrichment of planar, 1,3,5,7-substitutedtetra-, penta-, and hexachlorinated congeners and most of these samplesshowed profiles that displayed some similarity to those found in thetechnical PCB formulations. Sediment samples representing diffuse pollution,i.e., sediment samples from remote sites, showed an elevatedabundance of the planar hexa- and heptaCN congeners(1,2,3,4,6,7-/1,2,3,5,6,7- and 1,2,3,4,5,6,7-). The CN congener profile foundin these sediment samples and the two air samples were more similar to thetechnical PCB formulations than to the investigated MWI and graphite sludgesamples. Samples from three PCB contaminated lakes displayed similar congenerprofiles as Aroclor 1242, 1254 and Clophen A40. Two sediment samples and apike sample collected from the vicinity of a chloroalkali plant showedprofiles that were closely related to the investigated graphite electrodesludge sample. None of the environmental samples displayed profiles similarto low or medium chlorinated technical PCN (Halowax 1099, 1013, and 1014).

Distribution and Characterization of Polychlorinated Biphenyl Congeners in Soil and Sediments from a Superfund Site Contaminated with Aroclor 1268

The use of Aroclor 1268 at a former chlor-alkali plant in coastal Georgia (United States) has resulted in extensive contamination of soils on-site and also of sediments in the adjacent brackish marsh. The concentrations of total polychlorinated biphenyls (PCBs) in soil and marsh sedi ments ranged between 9.6 and 567 μg/g dry wt. A nearly 100-fold decline in total PCBs with distance away from the site suggests a high attenuation of PCBs by the marsh environment. Isomer-specific analysis of PCBs in Aroclor 1268 and in soils and sediments from the site revealed that a comparable proportion of octa- and nonachlorobiphenyl congeners, characteristic of the source, were present. The distribution of PCBs in marsh sediments was similar to that in Aroclor 1268, which suggests a high degree of stability of this PCB formulation in this environment. The estimated 2,3,7,8-TCDD equivalents of coplanar PCBs in soil and sediments were between 1.6 and 28.6 ng/g dry wt and also declined by 2 orders of magnitude along the contamination gradient; the non-ortho congener, IUPAC No. 126, contributed greater than 50% of the toxic equivalents in these samples.

Reassessment of the carcinogenicity of polychlorinated biphenyls (PCBS)

The current policy for regulating polychlorinated biphenyls (PCBs) is based on one chronic bioassay that examined the carcinogenicity of a 60% chlorinated PCB (Norback & Weltman, 1985). All studies originally considered by the U.S. Environmental Protection Agency (EPA) for use in calculating a cancer slope factor (CSF) for PCBs were reevaluated and new CSFs calculated based on the results of a pathology reassessment (Moore et ah, 1994). When studies of 60% chlorine PCBs from 3 different laboratories were compared, there was no scientific basis for selecting only 1 data set for deriving CSF estimates. Using a geometric mean to calculate a CSF based on all studies of PCBs with 60% chlorine replaces the current value of 7.7 (mg/kg/d)−1 with a value of 1.9 (mg/kg/d)−1. CSFs for PCBs containing less than 60% chlorine (54% and 42%) were less than 1.0 (mglkgld)−1. Using a toxic equivalency factor (TEF) approach similar to that of 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin shows no correlation between toxic equivalent dose and CSFs, indicating that use of TEFs is not predictive of cancer potency for PCBs. Based on these findings, PCB cancer risk assessment policy would more closely reflect scientific data if (1) separate risk assessments were developed for each major PCB formulation and (2) all appropriate data were used when calculating cancer potency for PCB mixtures of 60% chlorine.