Higher Chlorinated Polychlorinated Biphenyls Research Articles

Polychlorinated biphenyls in glaciers. 2. Model results of deposition and incorporation processes.

In previous work, Alpine glaciers have been identified as a secondary source of persistent organic pollutants (POPs). However, detailed understanding of the processes organic chemicals undergo in a glacial system was missing. Here, we present results from a chemical fate model describing deposition and incorporation of polychlorinated biphenyls (PCBs) into an Alpine glacier (Fiescherhorn, Switzerland) and an Arctic glacier (Lomonosovfonna, Norway). To understand PCB fate and dynamics, we investigate the interaction of deposition, sorption to ice and particles in the atmosphere and within the glacier, revolatilization, diffusion and degradation, and discuss the effects of these processes on the fate of individual PCB congeners. The model is able to reproduce measured absolute concentrations in the two glaciers for most PCB congeners. While the model generally predicts concentration profiles peaking in the 1970s, in the measurements, this behavior can only be seen for higher-chlorinated PCB congeners on Fiescherhorn glacier. We suspect seasonal melt processes are disturbing the concentration profiles of the lower-chlorinated PCB congeners. While a lower-chlorinated PCB congener is mainly deposited by dry deposition and almost completely revolatilized after deposition, a higher-chlorinated PCB congener is predominantly transferred to the glacier surface by wet deposition and then is incorporated into the glacier ice. The incorporated amounts of PCBs are higher on the Alpine glacier than on the Arctic glacier due to the higher precipitation rate and aerosol particle concentration on the former. Future studies should include the effects of seasonal melt processes, calculate the quantities of PCBs incorporated into the entire glacier surface, and estimate the quantity of chemicals released from glaciers to determine the importance of glaciers as a secondary source of organic chemicals to remote aquatic ecosystems.

Effectiveness of recombinant protein AlnA in enhancing the extractability of polychlorinated biphenyls from contaminated soils

One of the major limitations in bioremediation of polychlorinated biphenyls (PCBs) in contaminated soils is their low water solubility and high adsorbability. In the present study, effectiveness of recombinant protein AlnA as a biosurfactant in increasing extractability of PCBs was first investigated. The AlnA surface tension measurements allowed for determination of the minimum value of 37.89mN/m with critical micelle concentration of 1.07g/L. The solubilization of PCBs and desorption experiments were performed. It was observed that AlnA at 20μg/mL could enhance solubility of selected crystal PCBs varying from 1.87 to 6.12 folds and it is easier to recover PCBs from contaminated soils compared with Tween-80 and cyclodextrin. Pot experiments indicated AlnA elevated 1.4–2.1-fold PCBs accumulation in roots by Alfalfa. The homology modeling and docking revealed PCBs congeners had different interactions with AlnA and higher-chlorinated PCBs possessed higher binding affinity. Results showed AlnA had considerable application potential in remediation of PCBs pollution.

Distribution and risk assessment of polychlorinated biphenyls (PCBs) in the remote air and soil of Manipur, India

∑25PCB congeners including dioxin-like compounds were analyzed at three sites of Manipur India to assess the level of polychlorinated biphenyls (PCBs) in air and soil. The ∑25PCBs were higher in urban air (average 2,454 pg/m3), followed by the mountain air (average 2,109 pg/m3) and rural air (average 1,756 pg/m3). PCB levels observed in urban air were higher compared to PCB levels reported in major Indian metropolitan cities especially along the coastal region and were comparable with the pristine sites of India and also with some pockets of China and Europe. The heavier congeners (tetra, penta, tri and hexa) were dominant in both air and soil samples and show significant correlation with the ambient temperature. Emission of PCB congeners was investigated from soil surface. The total organic carbon present in soil shows the significant correlation (r 2 = 0.8; p < 0.05) with the PCBs could indicate that the PCBs originated from the similar sources. Principal component analysis revealed that the sources of higher chlorinated PCB congeners are local emissions while long-range atmospheric transport process is responsible behind elevated levels of lower chlorinated PCBs. Total calculated toxic equivalent (TEQ) levels in soil (37.17–160.5 pg/g) were superior to reported TEQ level of agricultural soil in Delhi, India (0.01–105.40 pg/g). Back trajectory analysis showed that the observed high levels of PCB at Manipur may due to movement of air masses, mostly from the Northern and Southern India and to some extent from Myanmar.

Degradation of Di- Through Hepta-Chlorobiphenyls in Clophen Oil Using Microorganisms Isolated from Long Term PCBs Contaminated Soil.

Present work describes microbial degradation of selected polychlorinated biphenyls (PCBs) congeners in Clophen oil which is used as transformer oil and contains high concentration of PCBs. Indigenous PCBs degrading bacteria were isolated from Clophen oil contaminated soil using enrichment culture technique. A 15days study was carried out to assess the biodegradation potential of two bacterial cultures and their consortium for Clophen oil with a final PCBs concentration of 100mgkg(-1). The degradation capability of the individual bacterium and the consortium towards the varying range of PCBs congeners (di- through hepta-chlorobiphenyls) was determined using GCMS. Also, dehydrogenase enzyme was estimated to assess the microbial activity. Maximum degradation was observed in treatment containing consortium that resulted in up to 97% degradation of PCB-44 which is a tetra chlorinated biphenyl whereas, hexa chlorinated biphenyl congener (PCB-153) was degraded up to 90% by the consortium. This indicates that the degradation capability of microbial consortium was significantly higher than that of individual cultures. Furthermore, the results suggest that for degradation of lower as well as higher chlorinated PCB congeners; a microbial consortium is required rather than individual cultures.

An interdisciplinary approach to the problem of neutralization of man-made polychlorinated biphenyls

19 Currently, biological methods of degradation of manmade polychlorinated biphenyls (PCBs) are becoming increasingly important in connection with the selection of new efficient PCB degrading strains. The most successful studies in the field of biodegrada tion of PCBs are associated with the use of low chlo rinated PCB congeners [1, 2]. It has been found that the biodegradability of PCB congeners increases with decreasing number of chlorine atoms in the initial sub strates. At the same time, interest persists in the search for surfactants capable of transferring more hydropho bic medium and high chlorinated PCB congeners into an aqueous medium in order to create stable emulsions available for efficient operation of bacterial strains [3, 4].

Dynamics of Organohalogenated Contaminants in Human Serum from Obese Individuals during One Year of Weight Loss Treatment

We investigated the dynamics of several organohalogenated contaminants (OHCs) and their metabolites in an obese population during weight loss. Serum samples from obese individuals were taken before patients lost weight and after three, six, and twelve months. Samples were also collected from a matched lean control population. Analyzed OHCs were polychlorinated biphenyls (PCBs) and their hydroxylated metabolites (HO-PCBs), pentachlorophenol (PCP), polybrominated diphenyl ethers, and organochlorine pesticides (OCPs). Significantly lower concentrations of major PCBs, their metabolites, and PCP were measured in obese individuals at the initial moment of their enrolling in the project. While dilution differences might be responsible for the lower concentrations in the neutral OHCs, we suggest that a lower CYP-mediated metabolic activity can partially explain the data for the HO-PCBs. Additionally, lower chlorinated substituted PCBs had a higher percentage contribution to the sum PCBs in obese individuals, while higher chlorinated PCBs had a higher contribution for the controls. Increasing serum levels for all OHCs were observed during weight loss. The release from adipose tissue seemed dependent on the octanol-water partition coefficient, since OHCs with higher log Kow values displayed a higher release in serum. This also influenced the HO-PCBs profile after weight loss with lower chlorinated HO-PCBs increasingly gaining importance. Although weight loss is beneficial, it also influences the release of OHCs from adipose tissue and their metabolism. Therefore, the increase in the levels of compounds with endocrine effects might be of concern.

Nonlegacy PCBs: Pigment Manufacturing By-Products Get a Second Look

Polychlorinated biphenyls (PCBs) were commercially manufactured in the United States from about 1930 until 1979, when their production was banned under the Toxic Substances Control Act (TSCA) because of concerns about their extreme environmental persistence, ability to bioaccumulate, and adverse human health effects. PCBs were used in numerous industrial and consumer applications, most notably as insulation fluids in electrical transformers and generators but also in products including fluorescent lamp ballasts, caulk, and carbonless copy paper. These now-discontinued manufactured chemicals have received a great deal of attention in terms of research and environmental remediation. But other, lesser-known PCBs continue to be generated and released into the environment, not from intentionally created commercial products but as unintentional by-products of manufacturing processes including, according to recent studies, those used to make certain pigments used in dyes, inks, and paints. PCBs do not occur naturally, and once in the environment they can last for decades. Until recently, PCBs that were being detected in the environment were thought to come entirely from “legacy” sources. Yet developments in analytical technology have given researchers a better understanding of PCB sources, of the patterns of individual PCBs (or congeners) that are being detected environmentally, and the fate of PCBs in the environment—how they move between soil, sediment, water, and air. These advances have also enabled the detection of individual congeners at very low levels and the identification of many new and ongoing sources of PCBs beyond those resulting from historical commercial mixtures. Unintentionally produced PCBs were known to be present in inks and dyes when the U.S. Environmental Protection Agency (EPA) announced the final rule barring commercial PCB production in 1979. A rule allowing exemptions for PCBs in controlled manufacturing processes and as unintentional contaminants was promulgated under TSCA a few years later. This rule allowed for PCB concentrations of up to 50 ppm in certain products as a result of manufacturing processes.1 Recently, manufacturing by-product PCBs have been identified in wastewater, sediments, and air in numerous locations. They have also been positively identified in testing of new products colored with such pigments, so it is clear these PCBs are not occurring as a result of legacy commercial mixtures. What is emerging is an increasingly complex picture of the prevalence of nonlegacy PCBs alongside the persisting environmental presence of legacy PCBs, and a concurrent and likewise complex picture of how PCBs can affect human health at very low levels of exposure.

Biostimulation of the autochthonous microbial community for the depletion of polychlorinated biphenyls (PCBs) in contaminated sediments

In this study, the effect of the biostimulation of the autochthonous microbial community on the depletion of polychlorinated biphenyls (PCBs) in historically contaminated sediments (6.260 ± 9.3 10(-3) μg PCB/ g dry weight) has been observed. Biostimulation consisted of (1) the amendment of an electron donor to favor the dehalogenation of the high-chlorinated PCBs and (2) the vegetation of sediments with Sparganium sp. plants to promote the oxidation of the low-chlorinated PCBs by rhizodegradation. The effects of the treatments have been analyzed in terms of both PCB depletion and changes of the autochthonous bacterial community structure. The relative abundance of selected bacterial groups with reference to untreated sediments has been evaluated by quantitative real-time PCR. The amendment of acetate determined the enrichment of anaerobic dechlorinators like Dehalococcoides sp. Vegetation with Sparganium sp. plants determined the enrichment of either (3) the dechlorinators, Dehalococcoides and the Chloroflexi o-17/DF-1 strains or (4) the Acidobacteria, β-Proteobacteria, Actinobacteria, α-Proteobacteria, Bacteroidetes, and Firmicutes. The combination of the two biostimulation strategy determined the 91.5 % of abatement of the initial PCB content.

Fifteen years of monitoring of POPs in the breast milk, Czech Republic, 1994–2009: trends and factors

The breast milk has been recommended to carry out as a monitoring tool for effectiveness evaluation of the Stockholm Convention on Persistent Organic Pollutants (POPs). Polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloro-ethane (DDT) and its metabolites (DDX), hexachlorbenzene (HCB) and isomers of hexachlocyklohexane (HCHs) have been monitored in the breast milk of nursing mothers in the Czech Republic since 1994 as a part of The Environmental Health Monitoring System. Knowledge about long-term POPs distribution and accumulation in the human body is crucial to understanding uptake, degradation and subsequent effects as well as to conduct risk assessments. The main aim of this study is to evaluate 15-years long-term trends of selected POPs in human milk in the Czech Republic and to elucidate the questionnaire information about the age, parity and social habits, to the final concentrations. This effectiveness evaluation of POPs restriction is quite precisely after 15-years monitoring campaigns. The human milk samples (4,753 samples) were analysed for a number of chlorinated organic chemicals including PCBs and selected chlorinated pesticides (OCPs, HCB, HCHs, DDX). The relative change of concentration per year for all chemicals was analysed. The remaining percentages of POPs in breast milk in comparison to 1994 are also expressed. Czech population half-lives of POPs in breast milk, derived from either linear or exponential models were computed. The long-term data indicates a continuation of a decreasing trend of POPs concentrations on breast milk. Our study did not confirm lactation and parity as an important outflux resulting in the decrease in concentrations in mothers, which is in the antagonism with most of the studies. The higher BMI was associated with higher amounts of HCB and lower amounts of higher chlorinated PCBs. The results confirm the effectiveness of restrictions of POPs usage in the Czech Republic. This ongoing long-term study is very useful tool for parametric effectiveness evaluation of Stockholm Convention.

PCBs and OCPs on a East-to-West Transect: The Importance of Major Currents and Net Volatilization for PCBs in the Atlantic Ocean

Air-water exchange gradients of selected polychlorinated biphenyl (PCB) congeners across a large section of the tropical Atlantic suggested net volatilization of PCBs to the atmosphere. Only for the higher chlorinated PCB 153 and hexachlorobenzene (HCB) were gradients near equilibrium detected. The use of passive samplers also enabled the detection of dichlorodiphenyltrichloroethane (DDT) and its transformation products across the tropical Atlantic, indicating net deposition. There were clear differences between the southern and northern hemisphere apparent in terms of atmospheric concentrations: Once the ship moved from the southern into the northern hemisphere air, concentrations of HCB and other organochlorine pesticides increased several-fold. For large swaths of the tropical Atlantic Ocean, neither PCB nor organochlorine pesticide dissolved concentrations varied much longitudinally, probably due to efficient mixing by ocean currents. In selected samples, dissolved concentrations reflected the influence of river plumes and major ocean currents far away from the continents. Dissolved concentrations of PCBs 28, 52, 101, 118, and HCB increased in the Amazon plume and the Gulf Stream. While the Amazon plume flushed only a few kg of PCBs and HCB, the Gulf Stream is potentially delivering tons of PCBs into the North Atlantic annually.

Using SPMDs to Assess Natural Recovery of PCB-contaminated Sediments in Lake Hartwell, SC: I. A Field Test of New In-Situ Deployment Methods

Results from the field testing of some innovative sampling methods developed to evaluate risk management strategies for polychlorinated biphenyl (PCB) contaminated sediments are presented. Semipermeable membrane devices (SPMDs) were combined with novel deployment methods to quantify the availability of PCBs at the Sangamo-Weston Lake Hartwell Superfund Site in SC. Three locations in Lake Hartwell were examined: a background site (BKG) with little detectable contamination and two contaminated sites (T-M/N and T-O). PCB availability was quantified using sediment surface samplers designed to hold SPMDs in contact with surface sediments, benthic dome samplers designed to enclose and suspend SPMDs at the sediment-water interface, and commercially obtained SPMD cages suspended in the water column. A two-way analysis of variance showed significant effects by sampler type (P < 0.0001) and site (P < 0.0001) for mean time-weighted average (TWA) total PCBs (t-PCBs). Regardless of the SPMD sampler used, mean TWA t-PCBs were directly proportional to the level of contamination present (BKG < T-M/N < T-O). Water column and surface sediment sampler t-PCB uptake patterns were described by a significant linear fit of the data (r2 = 0.9625, p < 0.0001, and r2 = 0.8188, p < 0.0001, respectively). Dome and sediment surface SPMD samples had a higher percentage of higher chlorinated PCBs compared to water column samples.

Biological monitoring of indoor-exposure to dioxin-like and non-dioxin-like polychlorinated biphenyls (PCB) in a public building

The release of PCBs from sealant material in public buildings and the resulting indoor air levels have raised growing concerns about possible human health effects connected with this exposure. Ambient monitoring of PCBs in a public building has revealed a contamination with the more volatile lower chlorinated PCB 28, PCB 52 and PCB 101. This gave reason for a large biological monitoring study in order to examine the internal exposure to PCBs in persons working in that building. Blood samples from 209 persons employed in the PCB-contaminated building were drawn. 98 persons matched for age and gender working in non-contaminated buildings served as control group.Plasma samples were analysed for the six indicator PCBs (PCB 28, 52, 101, 138, 153, 180) and 12 dioxin-like PCBs using GC/MS (LOD: 0.01μg/L). Significant differences between both collectives were only found for the plasma levels of the lower chlorinated PCB 28, PCB 52 and PCB 101 and for the dioxin-like congeners PCB 105 and PCB 118, which are due to inhalative exposure to these congeners via indoor air. Median plasma levels of PCB 28, PCB 52 and PCB 101 in the employees of the contaminated building were 0.087μg/L, 0.024μg/L and 0.012μg/L, respectively. The concentrations of the higher chlorinated PCBs and all other dioxin-like congeners investigated were within the normal range of the general population.There was no relationship between indoor air measurements and internal exposure of the employees in the corresponding office, but estimated lifetime exposure of the employees turned out to be a significant factor for plasma levels of PCB 28. Our biomonitoring results served as a basis for individual risk communication and successful risk management.

Pilot study on the exposure of the German general population to non-dioxin-like and dioxin-like PCBs

In the past, polychlorinated biphenyls (PCBs) have been widely used and were distributed in the environment. Due to their high persistence and bioaccumulative potential, they can still be detected in the blood of the general population, despite their ban more than 20 years ago. Among the various congeners, the presence of dioxin-like PCBs in blood raises the highest environmental concerns due to their critical toxicological properties. We determined the plasma concentrations of 6 non-dioxin-like and 12 dioxin-like PCBs as well as the organochlorine pesticides HCB and p,p'-DDE (p,p'-dichlorodiphenyldichloroethylene) in a group of 105 non-smokers out of the German general population by GC/MS as an estimate of the background burden to these compounds. The organochlorine compounds were extracted from plasma with n-hexane, cleaned up on a silica gel column and finally quantified using GC/MS and (13)C(12)-labelled internal standards. The limit of detection for all congeners was determined to be 0.01 μg/Lplasma. Age had a strong influence on the plasma levels of HCB (hexachlorobenzene), p,p'-DDE and all higher chlorinated PCB congeners, while no gender difference was observed. Among the dioxin-like PCBs, PCB 118, PCB 156 and PCB 167 were detectable in 74-98% of all samples. Highly significant correlations between several PCB-congeners were observed. Our results provide for the first time volume-based data on the extent of the age-related background burden to dioxin-like PCBs in Germany.

Levels and Distribution of PCBs and Organochlorine Pesticides in the Air, Pine Needles, and Human Milk

This review presents the findings on the distribution and levels of 20 congeners of polychlorinated biphenyls (PCBs) and 7 organochlorine pesticides (OCPs) all over the world, based on measurements in samples of air, human milk and pine needles. The Institute for Medical Research and Occupational Health has been conducting research in all three matrices for many years, and this review summarises its results too. Significant decrease in concentrations of organochlorine compounds has been seen after the legal ban of their use, but that decresing trend has been slowed down and they are still found in all samples. In general, higher PCB levels are found in samples from urban locations, pesticides levels are higher in samples from locations where has been their probable usage in agriculture, while HCB levels are usually indicator of industrial activity.γ-HCH has been found in the highest concentration in air and pine needles samples, while in humans DDE and β-HCH are the most abundant compounds. Indicator PCB congeners are also differently present in environment and humans: in air and pine needles lower-chlorinated, more volatile PCB congeners have higher concentrations while in humans that goes for more persistent higher-chlorinated PCB congeners. Among toxic ortho-substituted PCB congeners in human and environmental samples the most abundant is PCB-118 while three non-ortho substituted congeners (PCB-77, PCB-126 and PCB-169) that are the most toxic ones are rarely detected. From organochlorine pesticides, DDD is found in lowest concentrations in all samples.

Organochlorine Contaminants in Fishes from Coastal Waters West of Amukta Pass, Aleutian Islands, Alaska, USA

Organochlorines were examined in liver and stable isotopes in muscle of fishes from the western Aleutian Islands, Alaska, in relation to islands or locations affected by military occupation. Pacific cod (Gadus macrocephalus), Pacific halibut (Hippoglossus stenolepis), and rock greenling (Hexagrammos lagocephalus) were collected from nearshore waters at contemporary (decommissioned) and historical (World War II) military locations, as well as at reference locations. Total (Sigma) polychlorinated biphenyls (PCBs) dominated the suite of organochlorine groups (SigmaDDTs, Sigmachlordane cyclodienes, Sigmaother cyclodienes, and Sigmachlorinated benzenes and cyclohexanes) detected in fishes at all locations, followed by SigmaDDTs and Sigmachlordanes; dichlorodiphenyldichloroethylene (p,p'DDE) composed 52 to 66% of SigmaDDTs by species. Organochlorine concentrations were higher or similar in cod compared to halibut and lowest in greenling; they were among the highest for fishes in Arctic or near Arctic waters. Organochlorine group concentrations varied among species and locations, but SigmaPCB concentrations in all species were consistently higher at military locations than at reference locations. Moreover, all organochlorine group concentrations were higher in halibut from military locations than those from reference locations. A wide range of molecular weight organochlorines was detected at all locations, which implied regional or long-range transport and deposition, as well as local point-source contamination. Furthermore, a preponderance of higher-chlorinated PCB congeners in fishes from contemporary military islands implied recent exposure. Concentrations in all organochlorine groups increased with delta15N enrichment in fishes, and analyses of residual variation provided further evidence of different sources of SigmaPCBs and p,p'DDE among species and locations.

NADPH oxidase is involved in polychlorinated biphenyl‐mediated alterations of tight junction proteins in cells of the gastrointestinal tract

Exposure to polychlorinated biphenyls (PCBs) can contribute to numerous disease states. The main route of exposure to PCBs is through the gastrointestinal tract; however, little is known about the effects of PCBs on intestinal epithelial barrier functions. In the present study, we evaluated the effects of several highly‐chlorinated PCBs using human intestinal Caco‐2 cell line as an in vitro epithelial model system. Epithelial cells are comprised of tight junction (TJ) proteins that form an intricate assembly of membrane, cytoplasmic and accessory proteins linked to an actin cytoskeleton and which contribute to limited paracellular diffusion between adjacent epithelium. We demonstrated that exposure to PCBs increased permeability of FITC‐labeled dextran (4 kDa) across Caco‐2 monolayers. Consistent with permeability results, PCB disrupted expression of TJ proteins occludin and ZO‐1. These effects were associated with upregulation of the expressions of NADPH oxidase subunits as detected by immunoblotting. In addition, inhibition of NAPDH oxidase by apocynin significantly blocked PCB‐mediated increase in epithelial permeability and alterations of TJ protein expression. Similar effects were exerted by pretreatment with Rho kinase and Ras inhibitors suggesting that PCBs can disrupt epithelial barrier integrity through induction of redox‐regulated mechanisms. Supported by NIH/NIEHS (P42 ES 07380).

Comparing Polychaete and Polyethylene Uptake to Assess Sediment Resuspension Effects on PCB Bioavailability

Polyethylene sampler uptake was compared to polychaete uptake to assess bioavailability of polychlorinated biphenyls (PCBs) from resuspended sediments. New Bedford Harbor (MA, U.S.) sediment contaminated with PCBs, was resuspended under four different water column oxidation conditions: resuspension alone, resuspension under aeration, resuspension under helium, and no resuspension (control). Residuals were tested for differences in PCB availability to the marine polychaete Nereis virens and to polyethylene (PE) passive samplers. Few significant differences between the four resuspension treatments were observed: under aeration, three of 23 PCBs analyzed showed significant increases in polychaete accumulation, while resuspension alone showed increased concentrations in PE samplers for nine of 23 PCBs. Otherwise, no differences were observed and overall we concluded that resuspension had no effect on residual PCB availability. The relationship between disequilibrium-corrected PE and lipid-normalized polychaete PCB concentrations was nearly 1:1 with a strong linear correlation (r2 = 0.877), demonstrating PCBs are taken up similarly into PE and lipid. On average, PE samplers suggested dissolved PCB concentrations 3.6 times greater than those calculated with lipid-water partitioning, though on a congener-specific basis this was only observed for lower chlorinated PCBs; for higher chlorinated PCBs, PE-water partitioning suggested lower dissolved concentrations than those based on lipid. Organic carbon (OC)-water and OC and black carbon combined (OC+BC)-water partitioning suggested average dissolved concentrations 29 and 10 times greater, respectively, than those estimated with lipid-water partitioning. This demonstrates that PE-measured porewater concentrations can provide a more reliable estimate of bioavailability than sediment geochemistry.

Protective role of estrogen receptor-alpha on lower chlorinated PCB congener-induced DNA damage and repair in human tumoral breast cells

Polychlorinated biphenyls (PCBs) are ubiquitous environmental contaminants. Much of the research has focused on the carcinogenic potential of higher chlorinated PCBs, but accumulative evidence has shown that lower chlorinated PCB congeners have initiating and promoting activities. The goal of this study was to examine the potential of lower chlorinated PCBs, including 2,2',5,5'-tetrachlorobiphenyl (PCB52) and 3,3',4,4'-tetrachlorobiphenyl (PCB77), to induce DNA damage and apoptosis in human MDA-MB-231 (MDA) and MCF-7 breast cancer cells. Results confirmed that treatment of cells with PCB52 and PCB77 resulted in oxidative stress and caspase-dependent apoptosis in both MDA and MCF-7 cells. We noticed that at non-cytotoxic concentrations PCB52 and PCB77-induced decreases in intracellular NAD(P)H in MDA cells but not in MCF-7 cells. Further investigation confirmed that decreases in intracellular NAD(P)H in PCB-treated MDA cells are primarily due to reduction in intracellular NAD(+) pool mediated by poly(ADP-ribose)polymerase-1 activation through formation of DNA strand breaks. Antagonism was observed between PCB52 and PCB77 for the effect on induction of DNA strand breaks in MDA cells. Overall, this evidence demonstrates that at non-cytotoxic concentrations, lower chlorinated PCB congeners are capable of inducing oxidative DNA lesions in ERalpha(-)/MDA cells but not in ERalpha(+)/MCF-7 cells and that functional ERalpha plays a protective role in modulating the PCB-induced DNA damage in human breast cancer cells.

Inter-species differences for polychlorinated biphenyls and polybrominated diphenyl ethers in marine top predators from the Southern North Sea: Part 2. Biomagnification in harbour seals and harbour porpoises

Harbour porpoises ( Phocoena phocoena) and harbour seals ( Phoca vitulina) were found to differ in the ability to metabolize polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs). Biomagnification factors (BMFs), calculated between both predators and their prey (sole – Solea solea and whiting – Merlangius merlangus), had a large range of variation (between 0.5 and 91 for PCBs and between 0.6 and 53 for PBDEs). For the higher chlorinated PCBs and the highest brominated PBDEs, the BMF values in adult males were significantly higher than in the juvenile individuals of both species. BMF values of hexa- to octa-PCBs were the highest, suggesting reduced ability to degrade these congeners. Harbour porpoises had higher BMFs for lower chlorinated PCBs and for all PBDEs compared to harbour seals. Other factors, which may influence biomagnification, such as the octanol–water partition coefficients and the trophic level position measured through stable isotope ( δ 15N) analysis, were found to be of lesser importance to predict biomagnification in the studied food chain.

Biomarker Responses and Decreasing Contaminant Levels in Ringed Seals (Pusa hispida) from Svalbard, Norway

Blubber was analyzed for a wide range of contaminants from five subadult and eight adult male ringed seals sampled in 2004, namely, for polychlorinated biphenyls (PCBs), hexachlorobenzene (HCB), toxaphenes, chlordanes, dichlorodiphenyldichloroethylene (DDE), and polybrominated diphenylethers (PBDEs). Contaminant levels were compared to previously sampled animals from the same area, as well as data from literature for other arctic wildlife species from a wide variety of locations. Ringed seals sampled in 2004 showed 50–90% lower levels of legacy contaminants such as PCBs and chlorinated pesticides compared to animals sampled in 1996 of similar age (14 subadults and 7 adult males), indicating that the decline of chlorinated contaminants observed during the 1990s in a variety of arctic wildlife species is continuing into the 21st century. The results also indicated that PBDE declined in ringed seals; levels in 2004 were about 70–80% lower than in animals sampled in 1998. This is one of the first observations of reduced exposure to these compounds and might be a first indication that restrictions of production and use of these contaminants have resulted in lower exposures in the Arctic. The PCB pattern shifted toward the less chlorinated (i.e., less persistent) PCBs, especially in adult ringed seals, possibly as a result of reduced overall contaminant exposures and a consequently lower cytochrome P-450 (CYP) induction, which results in a slower metabolism of less persistent PCBs. The overall effect would be relative increases in the lower chlorinated PCBs and a relative decreases in the higher chlorinated PCB. Possibly due to low exposure and consequent low induction levels, ethoxyresorufin O-deethylation (EROD) activity proved to be a poor biomarker for contaminant exposure in ringed seals in the present study. The close negative correlation (r 2 = 70.9%)between EROD activity and percent blubber indicates that CYP might respond to increased bioavailability of the contaminant mixtures when they are mobilized from blubber during periods of reduced food intake.