PCBQ: Computerized quantification of total PCB and congeners in environmental samples

Computerized methodologies for the quantification of total PCBs, PCB in Aroclor mixtures and individual PCB congeners in environmental samples are presented. The method for total PCBs is based on a multiple-linear regression analysis using data from capillary gas chromatography of Arocolor standards. PCB congeners were identified and their weight percentages determined in Aroclor mixtures by GC/MS. PCB congeners and total PCBs were accurately quantified in predetermined test data and environmental samples.     

Congener-specific egg contribution of polychlorinated biphenyls to nestlings in two passerine species

Quantifying polychlorinated biphenyl (PCB) residues in nestlings of avian species is a common method for assessing trophic transfer and risk at PCB-contaminated sites. The proportion of nestling PCB mass due to maternal transfer is often accounted for by subtracting total PCB mass in eggs from nestlings. However, variation in physicochemical properties and metabolism among congeners may lead to differences between egg contribution based on total PCBs and dioxin-like congeners. We examined congener-specific variation in contribution of PCBs from eggs to nestlings in tree swallows and European starlings. Egg contribution of total PCB mass was 14.3 and 16.2%, respectively, whereas contribution based on dioxin-like congeners was 14.8 and 13.6%, respectively. These data suggest that using total PCB mass in eggs to adjust estimates of PCB accumulation in nestlings may not reflect patterns for dioxin-like congeners, potentially over or under-estimating the risk of toxicity of PCBs.     

Pure non-dioxin-like PCB congeners suppress induction of AhR-dependent endpoints in rat liver cells

The relative potencies of non-ortho-substituted coplanar polychlorinated biphenyl (PCB) congeners to activate the aryl hydrocarbon receptor (AhR) and to cause the AhR-dependent toxic events are essential for their risk assessment. Since some studies suggested that abundant non-dioxin-like PCB congeners (NDL-PCBs) may alter the AhR activation by PCB mixtures and possibly cause non-additive effects, we evaluated potential suppressive effects of NDL-PCBs on AhR activation, using a series of 24 highly purified NDL-PCBs. We investigated their impact on the model AhR agonist-induced luciferase reporter gene expression in rat hepatoma cells and on induction of CYP1A1/1B1 mRNAs and deregulation of AhR-dependent cell proliferation in rat liver epithelial cells. PCBs 128, 138, and 170 significantly suppressed AhR activation (with IC₅₀ values from 1.4 to 5.6 μM), followed by PCBs 28, 47, 52, and 180; additionally, PCBs 122, 153, and 168 showed low but still significant potency to reduce luciferase activity. Detection of CYP1A1 mRNA levels in liver epithelial cells largely confirmed these results for the most abundant NDL-PCBs, whereas the other AhR-dependent events (CYP1B1 mRNA expression, induction of cell proliferation in confluent cells) were less sensitive to NDL-PCBs, thus indicating a more complex regulation of these endpoints. The present data suggest that some NDL-PCBs could modulate overall dioxin-like effects in complex mixtures.     

Multivariate toxicity profiles and QSAR modeling of non-dioxin-like PCBs--an investigation of in vitro screening data from ultra-pure congeners

The non-dioxin-like PCBs (NDL-PCBs) found in food and human samples have a complex spectrum of adverse effects, but lack a detailed risk assessment. The toxicity profiles of 21 carefully selected PCBs (19 NDL-PCBs) were identified by in vitro screening in 17 different assays on specific endpoints related to neurotoxicity, endocrine disruption and tumor promotion. To ensure that the test results were not affected by polychlorinated dioxins, dibenzofurans or DL-PCB contaminants, the NDL-PCB congeners were thoroughly purified before testing. Principal component analysis (PCA) was used to derive general toxicity profiles from the in vitro screening data. The toxicity profiles indicated different structure-activity relationships (SAR) and distinct mechanisms of action. The analysis also indicated that the NDL-PCBs could be divided into two groups. The first group included generally smaller, ortho-substituted congeners, comprising PCB 28, 47, 51, 52, 53, 95, 100, 101, 104 and 136, with PCB 95, 101 and 136 as generally being most active. The second group comprising PCB 19, 74, 118, 122, 128, 138, 153, 170, 180 and 190 had lower biological activity in many of the assays, except for three endocrine-related assays. The most abundant congeners, PCB 138, 153, 170, 180 and 190, cluster in the second group, and thereby show similar SAR. Two quantitative structure-activity relationship (QSAR) models could be developed that added information to the SAR and could aid in risk assessments of NDL-PCBs. The QSAR models predicted a number of congeners as active and among these e.g., PCB 18, 25, 45 and 49 have been found in food or human samples.     

Accumulation and tissue distribution of selected polychlorinated biphenyl congeners in chickens

During one to three consecutive periods of 2 weeks, broiler chickens (n = 108) received test dies to which different amount of PCBs (7 congeners) were added. The relationship between exposure time and accumulation of individual congeners in different chicken tissues, such as breast, thigh and abdominal fat tissue, was observed. In all tissues, the vast majority of the PCB accumulation occurred during the first 2 weeks of exposures. After that, PCB concentrations only increased in the abdominal fat tissue of the animals. The individual PCBs were distributed differently in the various tissues. While CBs 28, 118, 138, 153 and 180 accumulated in the chickens, CBs 52 and 101 were metabolized, but no methyl sulphone metabolites of these congeners could be detected. Our results provide information on the absorption, tissue distribution and biotransformation of the individual PCB congeners and confirm the structure-activity relationships for metabolism of PCBs in birds, which are different from those in fish or mammalian species.     

PCBs and PCDD/Fs in lake sediments of Grosser Arbersee, Bavarian Forest, South Germany

Despite their environmental importance, there are still relatively few historical studies of the environmental occurrence of polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), especially in middle Europe. Trends in PCBs and PCDD/Fs were, therefore, assessed in lake sediments of the Grosser Arbersee over the past 130 years (1860-1990). Ballschmiter-PCB concentrations (congeners # 28, 52, 101, 138, 153, 180) increased between 1946 and 1972 from 4.2 to 32.0 microg kg(-1) dry wt, but have since decreased to 25.6 microg kg(-1) dry wt. High chlorinated PCB congeners reached their maxima earlier (1968-1972) than low chlorinated congeners (1985-1991). These trends were consistent with patterns expected from the production and use of PCBs and their precursors. PCDD/F concentrations increased between 1950 from 0.6 microg kg(-1) dry wt to 2.3 microg kg(-1) dry wt in 1977, falling to 1.7 microg kg(-1) dry wt by 1993. PCDF concentrations exceeded those of PCDD until 1968, but afterwards PCDDs (especially OCDD) were predominant. These patterns suggest that domestic heating and waste combustion were the most likely sources, but pollution from local industries, such as metal smelting and glass production, might also have been involved. The data provide a valuable case study from central Europe which confirms the overall declining trends of PCB and PCDD/F contamination shown elsewhere.     

Serum polychlorinated biphenyl and organochlorine insecticide concentrations in a Faroese birth cohort

A prospective birth cohort of 1022 participants was established in the Faroe Islands over a 21-month period during 1986-1987. We collected questionnaire data on potential persistent organic pollutant (POP) concentration predictors, such as duration of breastfeeding and blubber consumption. To assess the participants' exposure from in utero to 14 years of age to polychlorinated biphenyls (PCBs) and the insecticide p,p'-DDT and its primary degradate p,p'-DDE, we measured 37 PCB congeners and pesticides in 316 umbilical cord samples taken from participants at birth, in 124 serum samples collected from participants at approximately 7 years of age, and in 795 serum samples collected from participants at 14 years of age. Measurements of higher chlorination PCB congeners made on individuals' serum samples collected at 7 years and 14 years were highly correlated (typically r > 0.5, p > 0.01), although their concentrations at 7 years were generally two to three times higher than at 14 years. Similarly, umbilical cord PCB concentrations were correlated with PCB concentrations in both 7- and 14-year serum samples. Sex-specific differences in higher chlorination PCB and p,p'-DDE concentrations were found at 14 years but not at 7 years, although a sex interaction with blubber consumption and nursing duration was observed at both ages. Both duration of breastfeeding and consumption of blubber were significant predictors of serum summationPCB concentrations at 7 and 14 years. Multivariate analyses showed that breastfeeding duration was the primary contributor to serum summationPCB concentrations at 7 years, and blubber consumption was the primary contributor at 14 years. These data suggest that infant exposures from breastfeeding were sufficiently large so that continued exposures to PCBs, p,p'-DDT, and p,p'-DDE through the diet have not fully diluted their contribution to the summationPCB and p,p'-DDE body burden of the children.     

Background levels of non-ortho-substituted (coplanar) polychlorinated biphenyls in human serum of Missouri residents

This study characterizes the levels of polychlorinated biphenyls (PCB) congeners PCB 77, PCB 81, PCB 126, and PCB 169, in a group of 150 men and women with no documented exposure to PCBs. Its purpose is to provide current referent levels of coplanar PCBs in Missouri residents and to compare those levels to levels reported in the literature from the United States and other countries. Although this study used an extensive questionnaire assessing potential sources of exposure, no positive relations were found between these exposure sources and participants' PCB levels. The PCB levels for the four congeners measured were lower than any reported in the literature. PCBs 126 and 169 are only two of the dioxin-like congeners; however, their contribution makes up 11% of the total TEQ. Age was significantly related to PCB 126 and PCB 169. For every one-year increase in age, both PCB congeners increased by approximately 0.4 parts per trillion (ppt). There was no gender difference for PCB 126; however, PCB 169 levels were 3 ppt higher in males than females.     

Polychlorinated biphenyls (PCBs) in the British environment: sinks, sources and temporal trends

This paper estimates the present UK environmental loading of polychlorinated biphenyls (PCBs). Of the estimated approximately 40,000 t SigmaPCB sold in the UK since 1954, only an estimated 1% (400 t) are now present in the UK environment. Comparisons of estimated production and current environmental loadings of congeners 28, 52, 101, 138, 153 and 180 suggest that PCB persistence broadly increases with increasing chlorination. Those PCBs that are not now present in the UK environment are considered to have been destroyed--by natural or anthropogenic mechanisms, to be still in use, to reside in landfills or to have undergone atmospheric and/or pelagic transport from the UK. The dramatic fall in PCB levels in archived UK soils and vegetation between the mid-1960s and the present is evidence that the latter mechanism is the most important and that a significant proportion of PCBs released into the UK environment in the 1960s have subsequently undergone environmental transport away from the UK. The bulk (93.1%) of the estimated contemporary UK environmental burden of SigmaPCBs is associated with soils, with the rest found in seawater (3.5%) and marine sediments (2.1%). Freshwater sediments, vegetation, humans and sewage sludge combined account for 1.4% of the present burden, whilst PCB loadings in air and freshwater are insignificant. Although consideration of individual congeners does not reveal any major deviations from the relative partitioning of Sigma PCBs, the importance of sinks other than soils is enhanced for individual congeners, particularly 138 and 180. In particular, around 2% of the total UK burden of congener 180 is present in humans, implying that biodata as a whole may constitute an important sink for the higher chlorinated congeners. The contemporary flux of SigmaPCBs to the UK surface is estimated at 19 t yr(-1), compared with an estimated annual flux to the atmosphere of 44-46 t. This implies that the major sources of PCBs to the UK atmosphere have been identified and that there is currently a net loss of these compounds from the UK. These sources are: volatilisation from soils (88.1%), leaks from large capacitors (8.5%), the production of refuse-derived fuel (RDF) (2.2%), leaks from transformers (0.6%), the recovery of contaminated scrap metal (0.5%) and volatilisation from sewage sludge-amended land (0.2%). Interestingly, whilst large excesses of estimated annual fluxes to the atmosphere over deposition fluxes for individual congeners exist for congeners 28, 52 and 101, estimates of fluxes in both directions across the soil-atmosphere interface agree closely for congeners 138, 153 and 180. This suggests that lower chlorinated congeners are more susceptible to both long-range environmental transport beyond the UK and to atmospheric degradation. Retrospective analysis of dated sediment cores, vegetation and soils indicates that environmental transport from North America and continental Europe introduced PCBs into the British environment well before the onset of their commercial production in the UK in 1954. Since that time, the input of PCBs to the UK environment has essentially reflected temporal trends in UK use. After peaking in the 1960s they declined rapidly through the 1970s following restrictions on PCB use. Recent evidence, however, is that the rate of decrease has diminished and that further significant reductions in fresh environmental input will take some time to occur. Such reductions will be especially slow for humans and other biota with long life-spans. This stems partly from cross-generational transfer from parents to offspring and also because the persistence of PCBs in biota means that present body burdens will reflect past as well as current exposure.     

Concentration levels and congener profiles of polychlorinated biphenyls, pentachlorobenzene, and hexachlorobenzene in commercial pigments

The concentration levels and congener profiles of polychlorinated biphenyls (PCBs), pentachlorobenzene (PeCBz), and hexachlorobenzene (HxCBz) were assessed in commercially available organic pigments. Among the azo-type pigments tested, PCB-11, which is synthesized from 3,3′-dichlorobendizine, and PCB-52, which is synthesized from 2,2′,5,5′-tetrachlorobendizine, were the major congeners detected. It is speculated that these were byproducts of chlorobendizine, which has a very similar structure. The total PCB concentrations in this type of pigment ranged from 0.0070 to 740 mg/kg. Among the phthalocyanine-type pigments, highly chlorinated PCBs, mainly composed of PCB-209, PeCBz, and HxCBz were detected. Their concentration levels ranged from 0.011 to 2.5 mg/kg, 0.0035 to 8.4 mg/kg, and 0.027 to 75 mg/kg, respectively. It is suggested that PeCBz and HxCBz were formed as byproducts and converted into PCBs at the time of synthesizing the phthalocyanine green. For the polycyclic-type pigments that were assessed, a distinctive PCB congener profile was detected that suggested an impact of their raw materials and the organic solvent used in the pigment synthesis. PCB pollution from PCB-11, PCB-52, and PCB-209 pigments is of particular concern; therefore, the monthly variations in atmospheric concentrations of these pollutants were measured in an urban area (Sapporo city) and an industrial area (Muroran city). The study detected a certain level of PCB-11, which is not included in PCB technical mixtures, and revealed continuing PCB pollution originating from pigments in the ambient air.     

Quantifying the global fractionation of polychlorinated biphenyls

Due to the wide range of their physical-chemical properties, polychlorinated biphenyls (PCBs) have played an important role in the derivation of the global fractionation hypothesis, which predicts changes in the composition of persistent organic pollutant mixtures with latitude. Recent historical emission estimates, the derivation of an internally consistent property data set, in combination with a zonally averaged global fate and transport model, allow a quantitative investigation of the compositional shifts PCBs experience as a function of environmental compartment, latitude and time. Model simulations reproduce the higher relative abundance of lighter PCB congeners with increasing latitude, observed in air and soil, and quantify the relative importance of partitioning, persistence and emissions in establishing PCB patterns. Compositional variations consistent with global fractionation, as well as inverted concentration profiles with higher levels in the Arctic than at lower latitudes, are consistent with only minor fractions of the global PCB inventory being transferred northward.     

Congener-specific analysis of non-dioxin-like polychlorinated biphenyls in blood collected from 195 pregnant women in Sapporo City, Japan

We conducted a congener-specific analysis of non-dioxin-like polychlorinated biphenyls (non-dioxin-like PCBs) in blood collected between July 2002 and July 2004 from 195 pregnant women living in Sapporo City of Hokkaido Prefecture, Japan. The present study is one of the few studies in which full congener concentrations of non-dioxin-like PCBs have been measured in the blood of pregnant women. Of the 195 pregnant women, 101 were primipara (mean: 28.8 years, median: 28.0 years) and 94 were multipara (mean: 32.3 years, median: 33.0 years). Among the 197 non-dioxin-like PCB congeners, 58 congeners were identified in the blood of pregnant women. The arithmetic mean total concentrations of 58 non-dioxin-like PCB congeners in the blood of primiparous and multiparous mothers in Sapporo City were 42.2-329.3 (mean: 114.5, median: 98.6) and 31.5-258.0 (mean: 100.3, median: 91.4)ngg(-1)lipid, respectively. The results show that the contamination of non-dioxin-like PCBs in the blood of women has decreased compared to past levels in other domestic areas, in which the subject age was similar to that in this study. The results of the present study indicate that current levels of non-dioxin-like PCBs in the blood of Japanese women and can be used as baseline data for future temporal trends. The sums of the ratios of the concentrations of hexaCBs and heptaCBs to the total concentrations of 58 non-dioxin-like PCB congeners in the blood of primiparous and multiparous mothers were 78.5% and 77.7%, respectively. The hexaCBs ratios in the blood of primiparous and multiparous mothers were 45.4% and 44.7%, respectively. HexaCB-153 among hexaCBs congeners, the most abundant congener in the blood of primiparous and multiparous mothers, contributed approximately 22.0% and 21.8% to the total concentrations of 58 non-dioxin-like PCBs congeners that were measured in the blood, respectively. Among the non-dioxin-like PCB congeners measured in the present study, hexaCB-138, heptaCB-170, heptaCB-180, and heptaCB-182/heptaCB-187 also showed high ratios to total concentrations of 58 non-dioxin-like PCB congeners detected in the blood of primiparous and multiparous mothers. With regard to the relationship between the total concentrations of 58 non-dioxin-like PCB congeners in maternal blood and the number of deliveries or the age of primiparous and multifarious mothers, the total levels of these PCB congeners tended to decreases with increases in the number of deliveries and significantly increased with increasing maternal age in both groups. Furthermore, significant correlations were observed between the total concentrations of these PCB congeners in blood and the age of primiparae and multiparae. The concentrations of hexaCB-153 in the blood of primiparous and multiparous mothers showed a close correlation to the total concentrations of these PCBs, suggesting that hexaCB-153 could be an indicator of total concentrations of non-dioxin-like PCB congeners in the blood of pregnant women.     

Human biomonitoring of polychlorinated biphenyls and polychlorinated dibenzodioxins and dibenzofuranes in teachers working in a PCB-contaminated school

Eighteen teachers from a highly contaminated school and 11 teachers from a control school participated in this study. Total polychlorinated biphenyl (PCB) indoor air concentration (six indicator congeners x 5) was beyond 12000 ng/m3 in some rooms of the contaminated school. PCB 28 and PCB 52 were the prevailing congeners. Whole blood was taken from each participant by the local health authority, pooled in two groups and analysed for the six PCB indicator congeners, non-ortho PCBs and polychlorinated dibenzodioxins (PCDD)/polychlorinated dibenzofurans (PCDF). Blood analysis showed elevated mean PCB 28 and PCB 52 levels for the exposed group, however the two groups were almost identical with regard to PCB 101, 138, 153 and 180. Moreover no difference can be observed for the concentration of non-ortho PCBs and PCDD/PCDF. The data support the finding, that heavy indoor air contamination with low chlorinated PCBs causes an increase of PCB 28 and PCB 52 blood levels. However, this increment was small compared to their total PCB load.     

Process-diagnostic patterns of chlorobiphenyl congeners in two radiochronologically characterized sediment cores from the northern Baffin Bay.

Polychlorinated biphenyl (PCB) patterns were interpreted in two radioisotopically constrained sediment cores from the Arctic ocean in order to seek clues about their large-scale environmental fates. Low but clearly measurable fluxes of individual PCB congeners were observed in deeper layer sediments, corresponding to the past 170 years, in a single dated core from the Baffin Bay shelf. Fluxes of the dominant individual congeners in the surface sediments were 20-100 pg m(-2) d(-1). Combining these data with the sediment data from the Arctic Monitoring and Assessment Program, it appears that the PCB distribution in Arctic surface sediments is governed by the organic carbon (OC) content of the sediments. The historical development of the PCB congener fingerprint suggests that the modern sediments are enriched in medium-chlorinated congeners, implying that there are at least two significant, but distinctly different, sink processes acting on the PCB pool. The relative abundance of light-to-heavy congeners, in mid-shelf marine sediments of similar ages, between 40 degrees N and 76 degrees N latitude suggests a northward dilution of PCBs which is stronger attenuated for heavier congeners, consistent with a temperature-driven global fractionation process. The significant presence of PCB in historical archives pre-dating the organochlorine society, as observed in this and several previous studies, awaits a fuller explanation.     

Polychlorinated biphenyls (PCBs) in sediments in Hong Kong: a congener-specific approach to the study of coplanar PCBs in aquatic ecosystems

Patterns of contamination by polychlorinated biphenyls (PCBs) were investigated in fourteen samples of coastal sediments from Hong Kong. Congener-specific analyses revealed nine sediment samples from Junk Bay to contain PCBs at concentrations ranging from 31 to 2200 ng g(-1) dry weight, concentrations generally increasing with distance north in the Bay. By contrast, five sediments from the Tolo area to the north-east of Hong Kong exhibited total PCB levels of only 6.6 to 45 ng g(-) dry weight. The patterns of relative abundance of PCB congeners in the northern Junk Bay sediments suggested the existence of ongoing source(s) of PCBs in this area; biphenyls of lower chlorination were present at high concentration in these samples. Three coplanar PCBs (3', 4, 4'-tetrachlorobiphenyl; 3,3',4,4',5-pentachlorobiphenyl; and 3,3',4,4',5,5'-hexachlorobiphenyl) were found to be present in Junk Bay sediments; these are highly toxic and are cause for concern in aquatic environments. The abundance of the three coplanar PCBs in the sediments studied was similar to that in commercial PCB mixtures, suggesting that these congeners are not enriched over other PCBs by the sediments of coastal ecosystems. It is concluded that the preferential enrichment of coplanar PCBs occurs in the biosphere, rather than in sediments.     

Persistency of highly toxic coplanar PCBs in aquatic ecosystems: uptake and release kinetics of coplanar PCBs in green-lipped mussels (Perna viridis Linnaeus)

The bioaccumulation potential of three highly toxic coplanar PCB isomers [3,3',4,4'-tetrachlorobiphenyl (T(4)CB); 3,3',4,4',5-pentachlorobiphenyl (P(5)CB); and 3,3',4,4',5,5'-hexachlorobiphenyl (H(6)CB)] was investigated using green-lipped mussels (Perna viridis Linnaeus) as a bioindicator, through a transplantation experiment at two locations in Hong Kong waters. By contrast to the relatively rapid uptake and release of many other PCB isomers, the non-ortho chlorine substituted coplanar PCB congeners exhibited slow uptake and clearance. The kinetic parameters of coplanar PCBs based on lipid weight-related data, and the degree of bioaccumulation based on the proportion of coplanar PCBs in total PCBs in mussels, clearly indicate that coplanar PCBs are highly bioaccumulative in lower organisms. On the assumption that mussels are unlikely to be particularly unusual with respect to their bioaccumulation of coplanar PCBs, it appears most likely that these highly toxic and persistent PCB congeners are concentrated by all aquatic organisms, and may reach higher consumers (including humans) in quantities of toxicological concern.     

Detailed PCB congener patterns in incinerator flue gas and commercial PCB formulations (Kanechlor)

In this study, we determined the detailed PCB congener patterns in flue gases from eight incinerators and four commercial PCB formulations (Kanechlors). About 160 PCB peaks were identified in samples using a DB-5 column and HRGC/HRMS. The concentration of incinerator stack emission gas ranged from 0.02 to 44 ngWHO-TEQ/Nm3. The ratios of dioxin-like PCBs in the total PCB concentration were from 3.4% to 25.7% and from 0.63% to 9.1% in stack emission gases and Kanechlor samples, respectively. The PCB congener profiles of Kanechlor samples were similar to those of previous studies. To determine characteristic congeners in flue gas and Kanechlor samples, principal component analysis (PCA) of the data was conducted using STATISTICA for Windows 5.0J (StatSoft, Inc.). As a result, we obtained four principal components (PCs) and accounted for 74% of the total variance. PC 1 was interpreted combustion, PC 2 and PC 3 were interpreted the difference in the number of substituted chlorines and, PC 4 could not be determined. Moreover, we obtained three groups according to the PCB congeners pattern among samples by PCA. These specific congeners that represent characteristics of each class were identified. These data will be useful for the source analysis of PCBs in the environment.     

PCB levels and congener patterns from Korean municipal waste incinerator stack emissions

Congener specific polychlorinated biphenyl (PCB) data from the stack gas of nine Korean municipal waste incinerators was used to determine characteristic congener patterns of emitted PCBs. Principal component analysis revealed three classes of incinerators according to their pattern of PCB congener emissions: those resembling the background sampling material; those producing large quantities of a few tetra-chlorinated congeners; those producing large proportions of mono (MO-) and non-ortho (NO-) congeners relative to di-ortho (DO-) levels. Also, correlations between individual PCB congeners and polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) were discovered for several NO-PCBs and tetra and penta chlorinated PCDFs. Full PCB congener data is presented along with operating conditions for each incinerator.     

Digestibility, retention and incorporation of low-level dietary PCB contents in laying hens

Polychlorinated biphenyls (PCBs) are persistent and hazardous environmental contaminants, which tend to bioaccumulate in the food chain. In the present report the long-term effect of low-level dietary PCB concentrations was studied on performance, egg quality, apparent PCB digestibility, apparent PCB retention and PCB accumulation in laying hens that were fed experimental diets for 41 weeks. The tested dietary concentrations of supplemented PCBs, based on the sum of seven reference congeners, were 0, 1.5 and 6 ng/g. PCB ingestion did not significantly affect performance or egg quality parameters. The PCB concentration in egg yolk reached a nearly constant level after approximately 40 and 70 days of consumption of the diets containing 1.5 and 6 ng PCBs/g, respectively. Apparent faecal PCB digestibility and apparent retention were not influenced by dietary levels of added fat varying between 1.5% and 4.5%, but were significantly higher in hens fed diets containing added PCBs. Moreover, apparent PCB digestibility and retention increased significantly with age. Among the seven individual PCB congeners, no systematically significant differences with regard to apparent faecal digestibility were observed throughout the experiment. Accumulation of PCBs in the fat fraction of egg yolk, abdominal adipose tissue and thigh and breast muscle greatly depended upon PCB intake, but never exceeded the maximally allowed concentration of 200 ng/g. As PCBs 52 and 101 were hardly found in egg yolks and hen tissues, it was concluded that both congeners were greatly metabolised. Comparison of relative contents of individual PCB congeners revealed that PCBs 118, 138 and 153 were preferentially incorporated in yolk and body tissues.