Temporal and spatial trends of atmospheric polychlorinated biphenyl concentrations near the Great Lakes

Polychlorinated biphenyl (PCB) concentrations were measured in the atmosphere at six regionally representative sites near the five Great Lakes from 1990 to 2003 as part of the Integrated Atmospheric Deposition Network (IADN). Concentration data for several individual PCB congeners and for total PCBs were analyzed for temporal and spatial trends after correcting for the temperature dependency of the partial pressures. Atmospheric PCB concentrations are decreasing relatively slowly for tetra- and pentachlorinated congeners, an observation that is in agreement with primary emissions modeling. Relatively rapid decreases in PCB concentrations at the sites near Lakes Michigan and Ontario may reflect successful reduction efforts in Chicago and Toronto, respectively. Atmospheric PCB concentrations near Lakes Superior and Huron are now so low that the air and water concentrations may be close to equilibrium. Atmospheric PCB concentrations at sites near Lakes Michigan, Erie, and Ontario are relatively higher than those measured at sites near Lakes Superior and Huron. The highest PCB level was observed at the site near Lake Erie, most likely due to nearby urban activity. However, this relatively higher concentration is still 6-10 times lower than that previously reported at the Chicago site. A correlation between average gas-phase PCB concentration with local population indicates a strong urban source of PCBs. The temperature dependence of gas-phase PCB concentrations is similar at most sites except at Burnt Island on Lake Huron, where very low concentrations, approaching virtual elimination, prevent reliable temperature correlation calculations.     

Elimination half-lives of polychlorinated biphenyl congeners in children

The elimination kinetics of polychlorinated biphenyls (PCBs) in humans is difficult to assess in observational studies, because PCB exposure is never completely abolished. In a community with high dietary PCB exposures from whale blubber, we examined two groups of children with increased body burdens from breast-feeding. Follow-up was from ages 4.5 to 7.5 years (99 subjects) and 7 to 14 years (101 subjects). The calculations were performed by the use of structural equation models, with adjustment for body weight and dietary blubber intake as the main source of postnatal exposure. As a likely result of background exposures, apparent elimination half-lives were unexpectedly long when based on results from all cohort members. Subjects with exposures above the median and in the highest quartile showed half-lives of about 3-4 years for CB-138 and 4.5-5.5 years for CB-105 and CB-118; 6.5-7.5 years for CB-156, CB-170, and CB-187; and 7-9 years for CB-153 and CB-180. The longest half-lives correspond to elimination of the parent PCB solely with a daily fat excretion rate of 1-2 g, whereas shorter half-lives assume metabolic break-down.     

Modeling of polychlorinated biphenyl removal from contaminated soil using steam

Microwave-generated steam technology shows promise as an effective remediation alternative for removal of polychlorinated biphenyls (PCBs) from contaminated soils, based on our laboratory-scale experiments. The overall process can be described by a nonisothermal, unsteady, coupled heat and multicomponent PCB mass-transport model in a multiphase, variably saturated, porous soil medium. In this paper, a multicomponent PCB mass-transport model is presented that assumes evaporation is an important removal mechanism and that is based on first-order mass transfer between the interface of PCB films and the bulk steam. The model was calibrated using the experimental data, and the calibrated model was verified by computational mass-balance checks and comparisons with laboratory-scale column experimental results. From a qualitative point of view, the calibrated model successfully simulated the transport of PCBs in variably saturated soil media. The calculated increase/decrease factors of physicochemical properties of PCBs as a function of temperature in the soil, water, and free phases were consistent with the model hypothesis of an evaporation process. The effects of mass-transfer coefficients and initial PCB concentrations in the soils on PCB removal rates were investigated using the numerical code. It was determined that the PCB removal rates were sensitive to mass-transfer coefficients and initial PCB concentrations. Although the steam:soil mass ratios required to achieve a given percentage removal were lower for lower initial PCB soil concentrations, steam: soil mass ratios required to achieve a given unit mass removal were higherfor lower initial PCB soil concentrations.     

Enantiomeric composition of chiral polychlorinated biphenyl atropisomers in aquatic bed sediment

Enantiomeric ratios (ERs) for eight polychlorinated biphenyl (PCB) atropisomers were measured in aquatic sediment from selected sites throughout the United States by using chiral gas chromatography/mass spectrometry. Nonracemic ERs for PCBs 91, 95, 132, 136, 149, 174, and 176 were found in sediment cores from Lake Hartwell, SC, which confirmed previous inconclusive reports of reductive dechlorination of PCBs at these sites on the basis of achiral measurements. Nonracemic ERs for many of the atropisomers were also found in bed-sediment samples from the Hudson and Housatonic Rivers, thus indicating that some of the PCB biotransformation processes identified at these sites are enantioselective. Patterns in ERs among congeners were consistent with known reductive dechlorination patterns at both river sediment basins. The enantioselectivity of PCB 91 is reversed between the Hudson and Housatonic River sites, which implies that the two sites have different PCB biotransformation processes with different enantiomer preferences.     

Reevaluation of polychlorinated biphenyl concentrations in milk and body fat of lactating cows

Polychlorinated biphenyls occur as mixtures of congeners, each of which may be absorbed, excreted, or metabolized differently. Quantification of polychlorinated biphenyls by packed-column GLC has been difficult. Many quantification techniques, generally based on quantification of a selected group of the congeners present, have been used by researchers. Results of these studies have not provided a consistent basis to determine the relationship between the amounts of polychlorinated biphenyls consumed and residual polychlorinated biphenyls in milk and animal tissues. In the present study, we hypothesized that if a standardized quantification procedure was applied, consistent dose:residue predictions could be made. Weighted percentage of each peak in the polychlorinated biphenyl mixture procedures was used as a standard method to quantify polychlorinated biphenyls in milk fat from published and unpublished studies where lactating cows were fed between 3.5 and 1000 mg/d (Aroclor 1254) for greater than or equal to 15 d. When steady state occurred by 60 d of dosing, the relationship between concentration in milk fat (microgram/g) and daily dose as mg and as mg/kg BW were described by the equations: [polychlorinated biphenyls, microgram/g]milk fat = .28 (daily dose, mg).82, and [polychlorinated biphenyls, microgram/g]milk fat = 50.2 (daily dose, mg/kg BW).81. Similar equations described the relationships between daily dose and concentrations in adipose tissue and blood plasma. Concentrations of polychlorinated biphenyls residues in milk fat of 79 animals that were dosed with known quantities of polychlorinated biphenyls for 15 to 107 d confirmed that the equations could be valuable in predicting exposure over a wide range of exposure durations and concentrations.     

Modeling polychlorinated biphenyl mass transfer after amendment of contaminated sediment with activated carbon

The sorption kinetics and concentration of polychlorinated biphenyls (PCBs) in historically polluted sediment is modeled to assess a remediation strategy based on in situ PCB sequestration by mixing with activated carbon (AC). We extend our evaluation of a model based on intraparticle diffusion by including a biomimetic semipermeable membrane device (SPMD) and a first-order degradation rate for the aqueous phase. The model predictions are compared with the previously reported experimental PCB concentrations in the bulk water phase and in SPMDs. The simulated scenarios comprise a marine and a freshwater sediment, four PCB congeners, two AC grain sizes, four doses of AC, and comparison with laboratory experiments for up to 540 days of AC amendment slowly mixed with sediment. The model qualitatively reproduces the observed shifts in the PCB distribution during repartitioning after AC amendment but systematically overestimates the overall effect of the treatment in reducing aqueous and SPMD concentrations of PCBs by a factor of 2-6. For our AC application in sediment, competitive sorption of the various solutes apparently requires a reduction by a factor of 16 of the literature values for the AC-water partitioning coefficient measured in pure aqueous systems. With this correction, model results and measurements agree within a factor of 3. We also discuss the impact of the nonlinearity of the AC sorption isotherm and first-order degradation in the aqueous phase. Regular mixing of the sediment accelerates the benefit of the proposed amendment substantially. But according to our scenario, after AC amendment is homogeneously mixed into the sediment and then left undisturbed, aqueous PCB concentrations tend toward the same reduction after approximately 5 or more years.     

Predictors of polychlorinated biphenyl concentrations in adipose tissue in a general Danish population

Polychlorinated biphenyls (PCBs) are ubiquitously present in the environment and suspected of carcinogenic, neurological, and immunological effects. Our purpose was to identify predictors of adipose tissue levels of mono-, di-, and tri-ortho-substituted PCBs experienced by a general population and to establish whether predictors vary according to substitution group. In this study of 245 randomly selected persons from a prospective Danish cohort of 57,053 persons, we examined geographical area, age, lactation, BMI, and intake of eight major dietary groups as potential determinants of adipose concentrations of mono-, di-, and tri-ortho-substituted PCBs by linear regression analyses. Lactation, BMI, and intake of fruit, vegetables, and dairy products showed negative associations with PCB concentrations in adipose tissue in all models, and living in Copenhagen city, age, and consumption of fish (particularly fatty fish) were positively associated. The associations between several of the predictors and mono-ortho-substituted PCBs tended to differ from the associations found for di- and tri-ortho-substituted PCBs. In conclusion, geography, age, lactation, BMI, and consumption of fatty fish consistently predicted the concentration of PCBs in adipose tissue. Our results indicate that predictors of PCBs varied according to substitution group, suggesting that ortho-substituted groups should be analyzed separately.     

The absorption and translocation of polychlorinated biphenyl congeners by Cucurbita pepo ssp pepo

The mobility of polychlorinated biphenyl (PCB) congeners within Cucurbita pepo ssp pepo cv. Howden (pumpkin), a PCB phytoextracting plant, was investigated through a comparison of field-weathered soil, root, shoot, and xylem sap congener profiles. This is the first study to show the presence of PCBs in xylem sap (range: 0.03-0.18 μg·mL(-1)), confirming that PCB translocation throughout the plant occurs via this medium. A comparison of soil (5.2 ± 2.5 μg·g(-1)), root (27.1 ± 2.1 μg·g(-1)), shoot (range: 1.9 ± 0.5 μg·g(-1) - 8.2 ± 1.4 μg·g(-1)), and xylem sap (0.09 ± 0.04 μg·g(-1)) samples showed significant differences in congener profiles, with lower chlorinated congeners (predominately trichlorinated ones) found within xylem sap in higher amounts than higher chlorinated congeners. The total PCB concentrations of xylem sap samples collected at various lengths along the primary plant shoot were not significantly different from each other, while those of primary shoot tissue samples significantly decreased (two-sample t test, p = 0.01) as the distance from the plant base increased. PCA analysis of individual congeners in the roots, shoots and xylem sap indicated that movement of the PCB congeners in the plant was affected by the number of chlorines in the molecule, and hence possibly log K(ow) and molecular weight, but not by planarity.     

Enhanced airborne polychlorinated biphenyl (PCB) concentrations and chlorination downwind of Lake Ontario

Air samples were collected simultaneously at three sites downwind of Lake Ontario and at a control site near Lake Erie from March to July of 1999. The Lake Erie site (Stockton, NY) had PCB concentrations similar to rural Integrated Atmospheric Deposition Network (IADN) sampling sites across the Great Lakes, exhibited limited seasonal variation, and approximates regional background. Samples taken along Lake Ontario's southeastern shore (Rice Creek and Sterling, NY) had elevated PCB concentrations averaging approximately 1 ng/m3 and were more chlorinated than air collected at IADN sites and at Stockton. Air samples from Potsdam (approximately 75 km inland) had similar concentrations but were less chlorinated. Clausius-Clapeyron plots revealed a strong correlation between PCB fugacity and temperature near Lake Ontario; however, the extent of chlorination of the air samples rules out volatilization from the lake as a major source. It is hypothesized that volatilization from local surfaces, enriched in higher chlorinated congeners by meteorological or geographic factors, drives both the concentration and composition of airborne PCBs along Lake Ontario's southeastern shore.     

Enhanced reductive dechlorination of polychlorinated biphenyl impacted sediment by bioaugmentation with a dehalorespiring bacterium

Anaerobic reductive dehalogenation of commercial PCBs such as Aroclor 1260 has a critical role of transforming highly chlorinated congeners to less chlorinated congeners that are then susceptible to aerobic degradation. The efficacy of bioaugmentation with the dehalorespiring bacterium Dehalobium chlorocoercia DF1 was tested in 2-L laboratory mesocosms containing sediment contaminated with weathered Aroclor 1260 (1.3 ppm) from Baltimore Harbor, MD. Total penta- and higher chlorinated PCBs decreased by approximately 56% (by mass) in bioaugmented mesocosms after 120 days compared with no activity observed in unamended controls. Bioaugmentation with DF-1 enhanced the dechlorination of doubly flanked chlorines and stimulated the dechlorination of single flanked chlorines as a result of an apparent synergistic effect on the indigenous population. Addition of granulated activated carbon had a slight stimulatory effect indicating that anaerobic reductive dechlorination of PCBs at low concentrations was not inhibited by a high background of inorganic carbon that could affect bioavailability. The total number of dehalorespiring bacteria was reduced by approximately half after 60 days. However, a steady state level was maintained that was greater than the indigenous population of putative dehalorespiring bacteria in untreated sediments and DF1 was maintained within the indigenous population after 120 days. The results of this study demonstrate that bioaugmentation with dehalorespiring bacteria has a stimulatory effect on the dechlorination of weathered PCBs and supports the feasibility of using in situ bioaugmentation as an environmentally less invasive and lower cost alternate to dredging for treatment of PCB impacted sediments.     

Peroxidase-mediated removal of a polychlorinated biphenyl using natural organic matter as the sole cosubstrate

Natural organic matter (NOM) of hydroxylated aromatic character can undergo catalyst-mediated self-coupling reactions to form larger molecular aggregates. Indeed, such reactions are central to natural humification processes. Nonhydroxylated persistent aromatic contaminants such as polychlorinated biphenyls (PCBs) are, conversely, inert with respect to such reactions. It is here demonstrated however that significant coincidental coupling and removal of a representative aqueous-phase PCB occurs during horseradish peroxidase (HRP)-catalyzed oxidative coupling reactions of a representative aquatic NOM. Experiments with Suwannee River fulvic acid as a reactive cosubstrate indicate that 2,2'-dichlorobiphenyl (PCB-4) is covalently incorporated into aggregating NOM, likely through fortuitous cross-coupling reactions. To develop a better understanding of potential mechanisms by which the observed phenomenon occurs, two hydroxylated monomeric cosubstrates of known molecular structure, phenol and 4-methoxyphenol, were investigated as alternative cosubstrates. PCB-4 removal appears from these experiments to relate to certain molecular characteristics of the native cosubstrate molecule (reactivity with HRP, favorability for radical attack, and hydrophobicity) and its associated phenoxy radical (stability). The findings reveal potential pathways by which PCBs, and perhaps other polyaromatic contaminants, may be naturally transformed and detoxified in nature. The results further provide a foundation for development of enhanced-humification strategies for remediation of PCB-contaminated environmental systems.     

Health risk of coplanar polychlorinated biphenyl congeners in edible fish from the Mediterranean Sea

The muscle tissue of different species of fish was analyzed for polychlorinated biphenyls (PCBs) in order to estimate the daily intake of these contaminants. Contamination levels among the different species varied between 108 and 678 ng/g lipid weight. Isomer-specific analysis in the muscle tissue of the various fish revealed a profile dominated by hexa- and pentachlorobiphenyls, followed by hepta- and tetrachlorobiphenyls. Other congeners, including those with fewer than four or more than nine chlorine atoms, were below the instrumental limit of detection in all samples. PCB dietary intake was below the range of 1 to 4 pg 2,3,7,8-tetrachloro-p-dioxin equivalents per kg body weight per day set by the World Health Organization. From a public health point of view, there is no indication of important risks associated with the consumption of these seafoods.     

Current combustion-related sources contribute to polychlorinated naphthalene and dioxin-like polychlorinated biphenyl levels and profiles in air in Toronto,Canada

Polychlorinated naphthalenes (PCNs) and mono- and non-ortho substituted PCBs were analyzed in air from two sites in Toronto, Ontario, Canada to determine whether current combustion-related sources contribute to the levels and profiles of PCNs found in urban air. High-volume air samples were collected periodically at the University of Toronto (UT, a downtown site) and in north Toronto at the Meteorological Service of Canada (MSC). SigmaPCN concentrations ranged from 31 to 78 pg m(-3) at UT and from 7 to 84 pg m(-3) at MSC with concentrations lower at MSC than UT for paired samples. Ambient air congener profiles contrasted between the two sites with MSC profiles indicating inputs from combustion-related sources when compared to combustion fly ash and technical PCN and PCB mixture profiles. Combustion markers, including CN-44, -29, and -54, the more toxic CN-66 and -67 congeners, and non-ortho PCBs, were enriched in air at MSC on a mass percent basis in several samples. As a result, CN-66/67 contributed proportionally more to dioxin toxic equivalents at MSC than at UT. Downtown air PCN profiles resembled those of technical PCN and PCB mixtures, reflecting evaporative emissions from past uses, while PCN levels and profiles at MSC, a more industrialized location, are also influenced by current combustion sources, contributing as much as an estimated 54% of sigmaPCN in samples collected.     

The determination of polychlorinated biphenyl residues: a review with special reference to foods

The determination of polychlorinated biphenyls presents several unique analytical problems, not least of which is the need to identify and quantify 209 possible analytes. Moreover, congener-specific analysis is essential because of structure-activity effects on toxicity and environmental stability. Although significant advances have been achieved in identification/quantification procedures with the aid of highly efficient, inert open tubular chromatography columns and coupled GC-MS, sampling and extraction procedures have not developed to the same extent. The primary focus of this review is the determination of polychlorinated biphenyls in foods. However, the problems of separation and identification overshadow the importance of the sample matrix, and relevant data from other areas of analysis are quoted.