Polychlorinated Biphenyl Residues Research Articles

Baseline contamination assessment for a new resource recovery facility in Germany Part IV: Atmospheric concentrations of polychlorinated biphenyls and hexachlorobenzene

The atmospheric levels of hexachlorobenzene (HCB) and polychlorinated biphenyls (PCBs) were measured continuously over almost 1 year at 8 sites near the southern German city of Augsburg. The PCB profiles were similar at all locations, but the levels were about two times higher at sampling points on the edge of the city than at a more remote location. Whereas the PCB profile in the total air varied with time, the profile in the gas phase was very constant over the whole year at all stations. A pronounced annual cycle in the gaseous levels of the PCBs was observed, with levels in summer that were up to 5 times higher than levels in winter. The data were fully consistent with the hypothesis that the concentrations of PCBs in the atmosphere are determined by volatilization of PCB residues stored in soils and other sorbents on the earth's surface. The same behaviour as for the PCBs was also observed for HCB. Equations for the gaseous concentrations of these compounds as a function of temperature were derived and found to explain 90% of the variability in the monitoring data. However, the enthalpies of phase change estimated from the data were about two times less than the enthalpies of vaporization of the compounds. Although there are a number of possible explanations for this observation, more research into the exchange of semivolatile organic contaminants between the atmosphere and the earth's surface is needed to establish why the enthalpies of phase change are so much lower than expected.

Immunoquantitation and Microsomal Monooxygenase Activities of Hepatic Cytochromes P4501A and P4502B and Chlorinated Hydrocarbon Contaminant Levels in Polar Bear (Ursus maritimus)

Contamination of the Arctic ecosystem by anthropogenic compounds has resulted in exposure of polar bear (Ursus maritimus) to lipophilic chlorinated hydrocarbon contaminants (CHCs) accumulated through the marine food web. Liver samples were collected from 16 adult male polar bears in the Canadian arctic and subjected to chemical analysis for CHCs and metabolites, determination of alkoxyresorufinO-dealkylase activities, and immunoquantitation of cytochrome P450 (CYP) protein levels. We report on the relationships between the hepatic microsomal levels of immunoreactive CYP1A and CYP2B isozymes, catalytic activities, and hepatic CHC and metabolite concentrations in polar bear. We specifically explored the influence of several CHCs on the induction of hepatic CYP in polar bear and the potential use of immunoassay quantitation as a bioindicator of CHC exposure. Polychlorinated biphenyls (PCBs) classed as CYP1A and mixed CYP1A/CYP2B inducers accounted for about 25% of the total PCB residues present (18,680 ± 5053 ng/g lipid). CYP1A protein content correlated strongly with hepatic levels of PCBs, PCDDs (0.032 ± 0.018 ng/g lipid), and PCDFs (0.011 ± 0.007 ng/g lipid) and their corresponding toxic equivalents (TEQ, 0.377 ± 0.182 ng/g lipid). Mono-ortho-CB-156, CB-157, and CB-105 were the predominant TEQ contributors. Correlations between CYP2B protein content and CHC residue levels in polar bear liver suggested thatortho-chlorine-substituted PCBs and chlordanes were the major contributors to CYP2B induction. CYP1A and CYP2B contents were therefore good indicators of CHC exposure in polar bear liver. Ethoxyresorufin, pentoxyresorufin, and benzyloxyresorufinO-dealkylase activities increased with increasing CYP1A protein content up to protein levels of approximately 5 pmol/mg, suggesting that all three activities were primarily CYP1A-mediated. These results were substantiated by antibody inhibition experiments. In summary, immunoquantitated CYP1A and CYP2B isozymes are a more reliable measure of exposure to CHC inducers than alkoxyresorufinO-dealkylase activities in polar bear.

Capillary gas chromatography combined with atomic emission detection for the analysis of polychlorinated biphenyls

Capillary gas chromatography with atomic emission detection (GC-AED) was evaluated for the analysis of polychlorinated biphenyls (PCBs). Since Cl-responses were almost independent of the PCB structure, individual PCBs were quantitated with an accuracy better than 10% utilizing a Cl-calibration plot based on a single randomly selected congener (universal calibration). In addition, within a 5–10% accuracy, GC-AED enabled estimation of total PCB residue levels and calculation of the percentage by weight of chlorine in contaminating PCB mixtures. Thus, although PCB detection limits were higher with GC-AED than with GC-ECD, the former technique was very attractive for PCB investigations and enabled significant simplification of PCB quantitation.

Persistence and fate of polychlorinated biphenyls (PCBs) in sewage sludge-amended agricultural soils

Four metal enriched sewage sludges containing different concentrations of polychlorinated biphenyls (PCBs) were applied to two field soils in the UK in 1968. Samples of the sludges, sludge-amended soils and soils from untreated control plots were stored and analysed retrospectively. Sludge concentrations ranged from 1 to 7 mg ∑PCB kg −1. The pattern of PCBs was similar in three of the four sludges, with congeners 14, 18, 28 and 52 present at the highest concentrations. The fourth sludge contained higher amounts of congeners 149, 153, 138 and 180. ∑PCB concentrations in control plot soil have declined over the last 20 years, indicating a reduction in atmospheric deposition inputs of PCBs to the soil. ∑PCB concentrations also declined on the sludge-amended plots, reaching control plot concentrations (30–60 μg ∑PCB kg −1) in the late-1980s. Half-lives ranged from < 1 to 8.5 years for congeners 18, 28 and ∑PCB. Biodegradation and/or the formation of reversibly sorbed soil PCB residues could not account for the losses observed. Volatilisation is implicated as the most important loss process on both the control and sludge-amended plots. Using the fugacity approach, congener concentrations in soils at Luddington were predicted still to have not reached equilibrium with the air. Further losses to the atmosphere are likely.

Postmortem tissue levels of polychlorinated biphenyls in female rhesus monkeys after more than six years of daily dosing with Aroclor� 1254 and in their non-dosed offspring

Polychlorinated biphenyl (PCBs) analyses were made on prenecropsy blood samples and postmortem adipose, liver, kidney, and brain tissues from female rhesus monkeys fed a daily dose of 0, 5, 20, 40, or 80 micrograms Aroclor 1254/kg body weight for approximately 6 years. During this time, the females were bred with non-dosed males. All resulting offspring were nursed for 22 weeks and fed no additional PCBs until they were necropsied at approximately 120 weeks after birth. PCBs were also measured in necropsied infant tissues to determine PCB levels due to intake of PCB-contaminated milk from the dosed dams, in addition to in utero exposure. Polychlorinated biphenyl levels in all tissues of the adult monkeys increased with their dosage. The highest PCB levels were found in adipose tissue and the lowest levels were found in the brain. Polychlorinated biphenyl residues in the cortex of the kidney were lower than in the medulla, while in the brain no appreciable differences were observed between the occipital and frontal lobes. Necropsy tissues of infants from dosed dams contained more PCBs than those nursed by controls, but less than tissues from stillborn infants. Although no differences were observed between PCB tissue levels from monkeys having offspring and those having no offspring, those having a stillborn infant had higher PCB levels in their tissues than those with a viable infant. Similarly, monkeys that were euthanized because of poor health had higher PCB levels in their tissues than those necropsied at the conclusion of the study and showed a dramatic shift from tetra- and hexachlorobiphenyls to penta- and heptachlorobiphenyls in their tissues. The PCB distribution pattern in tissues from a dosed mother/infant pair differed considerably. A larger percentage of heptachlorobiphenyls was found in the infant than in its dam. The adipose/blood PCB ratio in the adult monkeys remained remarkably constant.

Uterotropic and enzyme induction effects of 2,2?,5-trichlorobiphenyl

Polychlorinated biphenyls (PCBs) are among the ubiquitously persistent chemicals possessing endocrine-disrupting effects. Most of the environmentally abundant CB congeners have one or more ortho chlorines in the biphenyl ring. Because ortho-chlorinated CB congeners do not avidly bind to the aryl hydrocarbon (Ah) receptor, this clearly suggests that the estrogenicity of PCBs is not related to potency as Ah receptor agonists. It is important to investigate the estrogenicity of those ortho-chlorinated CB congeners in order to more accurately predict the hazards from PCB residues in the environment. The hydroxylated metabolites are presumably more reactive with the estrogen receptor, but induction of phase 2 enzymes at the higher doses could sequester the metabolites resulting in the lower serum residues of parent compound and attenuated estrogenic activity observed at higher doses. It was of interest to determine if a di-ortho CB congener which is more readily metabolized and an ineffective PROD inducer exhibited similar nonlinear dose:response relationships for estrogenicity and serum residues as observed for CB 153. CB 18 (2,2{prime}, 5-trichlorobiphenyl) is very rapidly metabolized to more polar products by sheep liver microsomes, rats and house flies. The detection of greater amounts of mono-hydroxylated metabolites from slower metabolized congeners than from CB 18more » reflects further secondary metabolism in these extended (up to 1 hour) microsomal incubations. Such secondary metabolism should be relatively constant up to very high doses in vivo, since CB 18 should be a very poor P450 2B1 inducer. Even though CB 18 commonly occurs in environmental samples, there is little information regarding its biological effects. In this study, we used immature Sprague-Dawley female rats as an animal model to examine the uterotropic response, thyrotoxic effect and enzyme induction potency of CB 18. 17 refs., 3 tab.« less

Pesticides and total polychlorinated biphenyls residues in raw and cooked walleye and white bass harvested from the Great Lakes.

To provide data for public health and other government officials to quantitate the degree of exposure a human might receive from consumption of commonly sought open water fish species prepared and cooked by commonly used methods, five species of Great Lakes fish were chosen. Data is presented for walleye harvested from Lakes Erie, Huron and Michigan which were baked and char-broiled as skin-on fillets with additional walleye from Lake Michigan being deep fat fried. Skin-on white bass fillets from Lakes Erie and Huron also were pan fried. Packed column PCB and pesticide analyses were conducted for all fish species by the Michigan Department of Public Health. The DDT complex (p,p{prime}DDT, p,p{prime}DDE and p,p{prime}DDD), dieldrin, hexa-chlorobenzene (HCB), chlorodane complex (alpha and gamma chlordane, oxychlordane, cis- and trans-nonachlor), toxaphene, heptachlor epoxide, and total PCBs (expressed as Arochlor{sup R} 1254) were found at above the minimum level of detection for many of the species studied. Residues were expressed as ppm wet tissue and then converted to micrograms per fillet to calculate the percentage loss due to cooking. 9 refs., 3 tabs.

Dietary exposure of mink to carp from Saginaw Bay, Michigan. 1. Effects on reproduction and survival, and the potential risks to wild mink populations.

Carp (Cyprinus carpio) collected from Saginaw Bay, Michigan, containing 8.4 mg total polychlorinated biphenyls (PCBs)/kg and 194 ng of 2,3,7,8-tetrachloro-dibenzo-p-dioxin equivalents (TEQs)/kg, were substituted for marine fish at levels of 0, 10, 20, or 40% in the diets of adult ranch mink (Mustela vison). The diets, containing 0.015, 0.72, 1.53, and 2.56 mg PCBs/kg diet, or 1.03, 19.41, 40.02, and 80.76 ng TEQs/kg diet, respectively, were fed to mink prior to and throughout the reproductive period to evaluate the effects of a naturally-contaminated prey species on their survival and reproductive performance. The total quantities of PCBs ingested by the mink fed 0, 10, 20, or 40% carp over the 85-day treatment period were 0.34, 13.2, 25.3, and 32.3 mg PCBs/mink. respectively. The corresponding quantities of TEQs ingested by the mink over the same treatment period were 23, 356, 661, and 1,019 ng TEQs/mink, respectively. Consumption of feed by mink was inversely proportional to the PCB and TEQ content of the diet. The diet containing Saginaw Bay carp caused impaired reproduction and/or reduced survival of the kits. Compared to controls, body weights of kits at birth were significantly reduced in the 20 and 40% carp groups, and kit body weights and survival in the 10 and 20% carp groups were significantly reduced at three and six weeks of age. The females fed 40% carp whelped the fewest number of kits, all of which were stillborn or died within 24 hours. Lowest observable adverse effect levels (LOAEL) of 0.134 mg PCBs/kg body weight/day or 3.6 ng TEQs/kg body weight/day for adult female mink were determined. The potential effects of exposure of wild mink to contaminated Great Lakes fish were assessed by calculating "maximum allowable daily intakes" and "hazard indices" based on total concentrations of PCB residues in several species of Great Lakes fish and mink toxicity data derived from the study.

Molecular diagnostics for polychlorinated biphenyl degradation in contaminated soils.

Molecular diagnostic methods using DNA hybridization with specific gene probes are being developed for the monitoring of microbial populations capable of polychlorinated biphenyl (PCB) degradation in contaminated soils. Evaluation of composite samples from contaminated electrical substation soil by gas chromatography (GC) indicated that the PCBs present in the soil (approximately 200 ppm) resulted from contamination with Aroclor 1248. The PCBs have been weathered or degraded so that the lower molecular weight PCB congeners are no longer present. Microbiological and molecular site characterizations are in progress to determine the abundance of PCB degradative organisms and catabolic genes present. Cloned DNA fragments for the bphC gene (2,3-dihydroxybiphenyl dioxygenase) from the biphenyl/chlorobiphenyl degradative pathways of different organisms were used as gene probes to identify indigenous microorganisms with bphC gene sequences. In colony hybridization experiments, positive signals with the pDA251 gene probe were detected in cultures from both contaminated and uncontaminated soils. The degradative abilities of indigenous microorganisms and an added PCB-degradative bacterial strain were also monitored with [14C]4-chlorobiphenyl mineralization assays and gas chromatography of PCB residues extracted from the soils. Enrichment of the contaminated soil with biphenyl and chlorobiphenyls did not stimulate the indigenous microorganisms to degrade the soil PCB. Nevertheless, enrichment of the contaminated soil with biphenyl and chlorobiphenyl and addition of the PCB-degrading strain Alcaligenes eutrophus GG4202 did result in additional degradation of the soil PCB. The results obtained from these experiments should assist in developing and monitoring a remediation plan for these PCB-contaminated soils.

Congener-specific data of polychlorinated biphenyl residues in human adipose tissue in Poland

Adipose tissue of inhabitants of the Gdańsk city located at the southern coast of the Baltic Sea and the province of Skierniewice of inland Poland have been investigated for congeners of polychlorinated biphenyls (PCBs) by the capillary GC-MS technique. PCB IUPAC No. 153 was a high contributor of the congener occupying 23% of the total PCB content, and together with No. 138 of 18% and No. 180 of 13% were the most prevalent members. Samples taken from Gdańsk citizens in 1990 contained 1.5 ± 1.3 μg/g of total PCBs on a fat weight basis while the citizens from the province of Skierniewice, sampled in 1979, contained 1.2 ± 0.4 μg/g, which seemed to indicate a persistent PCB exposure in Poland. Among Gdańsk citizens, randomly selected autopsy samples of liver cancer from dead persons contained 4.7 μg/g of PCBs, while in all other samples the level was between 0.75 and 1.9 μg/g of PCBs. TCDD TEQ of 13 detectable coplanar members of PCBs in adipose tissue of Gdańsk, and Skierniewice inhabitants, was 210 and 190 pg/g on a lipid weight basis, respectively, including 45 and 59 pg/g of non- ortho, 142 and 110 pgg/g of mono- ortho and 24 and 16 pg/g of di- ortho chlorobiphenyls. A fingerprint of chlorobiphenyl composition in the samples examined was virtually the same for human adipose tissue taken in 1990 from the coastal city of Gdańsk and in 1979 from the inland province of Skierniewice, in spite of geographic variations and sampling intervals.

Polychlorinated biphenyl residues in various fatty foods consumed in Guipúzcoa, the Basque Country (Spain).

Three congeners of polychlorinated biphenyls (PCBs)--the 2, 2', 3, 4, 4', 5'-, 2, 2', 4, 4', 5, 5'-hexachloro, and 2, 2', 3, 4, 4', 5, 5'-heptachlorobiphenyls--were determined in 18 samples of butter, 44 of fish (hake and anchovy) and 24 of egg, all of which came from markets in Guipúzcoa. The total content as Araclor 1260 was also determined. Quantitation was carried out by gas chromatography in a capillary column and electron capture detector. The total content in butter ranged from 20 to 60 ng/g (fat basis), in fish from 10 to 250 ng/g (edible part), and in eggs from 1 to 10 ng/g (edible part). None of these exceeded the tolerance limits established by the Canadian Government Guideline and USFDA.

Screening of Organochlorine Pesticide and Polychlorinated Biphenyl Residues in Nonfatty Seafood Products by Tandem Solid-Phase Extraction Cleanup

Abstract A rapid multiresidue solid-phase extraction (SPE) technique for the isolation and subsequent gas chromatographic (GC) determination of organo-chlorine pesticide and polychlorinated biphenyl (PCB) residues in nonfatty fish, crabmeat, shrimp, and scallops is described. Samples are extracted with acetonitrile, and the extract is subjected to a cleanup using both C18 and Florisil SPE columns. The residues are determined by GC with electron capture detection. Because the injected extracts are free from matrix interferences, the amount of residue present is easily calculated. The average recoveries of 9 spiked (0.01–0.40 ppm) organo-chlorine pesticide residues from 6 different seafood products ranged from 93.8 to 98.4%. The average recoveries of spiked (0.50 ppm) PCB mixtures from 4 different seafood products ranged from 88.5 to 107.2%. This SPE method and the AOAC multiresidue method for organochlorine residues in fish produced comparable results for nonfatty seafood samples containing incurred organochlorine pesticide and PCB residues. The SPE method reduces organic solvent consumption by 95% and hazardous waste by 85% compared with the AOAC method. We were able to carry 10 seafood samples through the extraction and cleanup in less than 2 h by using the SPE method.

Congener-specific analysis of polychlorinated biphenyls in white-tailed sea eagles Haliaeetus albicilla collected in Poland

The concentrations of polychlorinated biphenyl (PCBs) congeners including highly toxic non-, mono-, and di-ortho coplanar members as well as their pattern were determined in breast muscles of white-tailed sea eagles collected dead between 1982 and 1990 in Poland. There was a wide variation in total PCB residue concentrations among eagles from various breeding sites, with the Baltic Sea coast registering the highest concentrations. The pattern of PCB residues differed between the eagles examined. Hexa-, hepta-, and pentachlorobiphenyls contributed between 45 and 56%, 18-and 37%, and 9 and 22% in total PCBs, respectively. Toxic equivalents (TEQs) of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) for non-, mono-, and di-ortho coplanar PCBs were very high (8.0–72 μg/g wet wt) in white-tailed sea eagles from breeding sites of the coastal area of the southwestern Baltic Sea, and were relatively lower (0.69–4.0 μg/g wet wt) in other birds, including two specimens from breeding sites of inland Poland, which died because of acute lead poisoning. PCB IUPAC Nos. 118, 105, 126, and 156 were the highest contributors to the TCDD TEQ of coplanar members, occupying between 39.1 and 57.0%, 9.8 and 17.5%, 7.4 and 22.3%, and 7.0 and 14.2%, respectively. The concentrations of coplanar PCBs in adult white-tailed sea eagles were the highest ever reported in wildlife, but that of total PCBs were similar to those reported in dead eagles from the breeding sites of the coastal area of the northern Baltic in Sweden and Finland in the 1960s and 1970s.

Assessment of chlorinated pesticides and polychlorinated biphenyls in adipose breast tissue using a supercritical fluid extraction method.

A precise and highly reproducible analytical method was developed for the assessment of organochlorinated pesticide and polychlorinated biphenyl residues in adipose tissue (> or = 50 mg). The method can be utilized for epidemiological studies on the significance of these environmental pollutants in the etiology of breast cancer. Supercritical fluid extraction (SFE) with CO2 and modified CO2 (addition of 5% dichloromethane) is employed to remove incurred pesticide residues from adipose tissues that have been surgically removed from breast cancer patients and controls. An alumina sorbent, placed in the extracting vessel together with a specimen, removes the bulk of co-extracted lipids; a subsequent purification of the SFE extracts by column chromatography on alumina removes the remaining traces of lipids that would interfere with the gas chromatographic analysis with electron capture detection. The method was tested by analyzing a Certified Reference Material 430 pork fat with known amounts of pesticide residues that are commonly found in fat or in foods with a high fat content. The recoveries of analytes ranged from 73.4% for endrin to 115% for alpha-, beta- and gamma-hexachlorocyclohexane, hexachlorobenzene and dieldrin, with standard deviations of 4-12% for individual analytes. The analysis of adipose tissue for organochlorinated compounds on the basis of this new method suggested that the pesticide levels were higher in breast cancer patients than in controls. However, the small number of samples analyzed in this study (n = 5, both groups) precludes definitive conclusions. The most abundant compounds in both cases and controls were p, p-DDE (379 +/- 286 and 160 +/- 149 p.p.b.) and PCB (223 +/- 145 and 124 +/- 65.7 p.p.b.), followed by the termiticide chlordane residues oxychlordane and transnonachlor.

Effect of sublethal chlorinated discharges on PCB accumulation in transplanted Asiatic clams (Corbicula fluminea)

From 1987–1990, uncontaminated Asiatic clams (Corbicula fluminea) were placed in cages and transplanted into two streams receiving industrial discharges to help identify and quantify polychlorinated biphenyl (PCB) contamination to the streams. Clams accumulated substantial PCB residues at most sites monitored, with the exception of the sites closest to chlorinated discharges. Clams placed nearest to the chlorinated stream reaches consistently underestimated PCB contamination, based on the amount of PCBs found in fish and sediment at those sites. In a separate experiment, clams exposed in stream-side tanks to untreated (total residual chlorine ranged from 0.02–0.07 mg−1 L daily) and dechlorinated stream water exhibited differing degrees of valve movement, growth, and PCB accumulation after a four-week exposure to the two treatments. Clams exposed to untreated (chlorinated) stream water closed their shells more often, exhibited less growth, and accumulated substantially lower PCB concentrations than clams exposed to dechlorinated stream water. Clams apparently close their shells to avoid chlorine exposure, thus isolating clam tissues from PCBs found in the stream water and in the clams' food. Because chlorine and PCBs occur together in many industrial discharges, this finding is a significant consideration for monitoring programs that utilize clams to assess PCB bioavailability.

Incidence of organochlorine pesticide and PCB residues in an aquatic ecosystem of river duero in castile and Leon (Spain)

The occurrence of organochlorine pesticides and polychlorinated biphenyls (PCBs) in an aquatic ecosystem of River Duero was checked by means of a bioindicator organism: the grey heron (Ardea cinerea). Analyses of water, sediments, fish fat tissues and heron viscera revealed a marked bioaccumulation of organochlorine compounds, particularly hexa‐ and heptachlorinated biphenyls of industrial origin, which may account for the gradual decline in the number of individuals that make up the heron colonies studied.

Application of semipermeable membrane devices (SPMDs) as passive air samplers

The semipermeable membrane device (SPMD), consisting of a neutral lipid (triolein) enclosed in polyethylene layflat tubing, is demonstrated to be a highly efficient passive air sampler. These devices readily sequester lipophilic organic contaminants from the vapor phase. Specifically, the SPMDs are shown to concentrate polychlorinated biphenyl (PCB) residues from a laboratory atmosphere in a linear manner through 28 days. Under the conditions of this study, a three device composite (1.4 g triolein) extracted PCB residues from ≈ 7 m 3 of air per day.

Measures of reproductive success and polychlorinated biphenyl residues in eggs and chicks of Forster's terns on Green Bay, Lake Michigan, Wisconsin—1988

Data on reproductive success of Forster's tern (Sterna forsteri) from Green Bay, Lake Michigan in 1983 are compared with data collected in 1988. In 1988 measures of reproductive performance (hatching success, number of young fledged, and length of incubation) were improved. Concentrations of total polychlorinated biphenyls (PCBs) and planar PCB congeners in the eggs were compared between years. Median total PCB residue was 67% lower in 1988 (\(\bar X\)=7.3 μg/g). This corresponds to a 42% reduction in tetrachlorodibenzo-p-dioxin equivalents (TCDD-EQ) from 1983 to 1988. We suggest that contaminant reduction and improved reproductive performance were due to low river flows in 1988 and associated reduced PBC loading into Green Bay. Forty-two percent of the matured chicks died before fledgling, and their body weight growth curves were much lower than normal. Young accumulate total PCBs at a rate of 17.6 μg/day. A no-observable-adverse-effects level (NOAEL) of 40–84 μg/kg/day was estimated from the two year results using the least observable adverse effects level (LOAEL)/NOAEL rating values.

Toxic potential of non-ortho and mono-ortho coplanar polychlorinated biphenyls in Aroclors, seals, and humans.

Mono-ortho and non-ortho coplanar polychlorinated biphenyls (PCBs) were analyzed in Aroclors, seals, and humans by graphitized carbon, a recently developed HPLC method (Hong et al. 1992b) and high-resolution gas chromatography with electron capture detection (HRGC/ECD). The concentration data were multiplied by potency factors derived from aryl hydrocarbon hydroxylase (AHH) induction to give 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) equivalents. The ability to separate coplanar PCBs from the majority of PCBs has allowed the use of TCDD toxicity equivalence to compare the relative dioxin-like potency of PCB residues in the complex mixtures. The most active mixtures, Aroclors 1254, 1248, and 1242, contained 42-54% by weight of chlorine. The results demonstrate that the apparent dioxin-like potency of PCB residues in Aroclors, seals, and humans is dominated by three congeners, 3,3',4,4'-tetra-, 2,3,3'-4,4'-, and 3,3',4,4',5-pentachlorobiphenyl (IUPAC nos. 77, 105, 126).

Polychlorinated biphenyl residues in food and human milk: determination of co-planar and mono-ortho substituted congeners

An analytical method is described for determining the residues of coplanar as well as mono-ortho substituted PCB congeners both exhibiting toxicological relevance, in foods of animal origin and in human milk. The unsophisticated procedure, convenient for routine analyses, includes the extraction of lipids, clean-up steps using liquid/liquid partition and column chromatography, fractionation of the congeners using HPLC on a special carbon column with an optimal gradient elution, and capillary column gas chromatography with electron capture or mass spectrometric detection. As preliminary results indicate, the low-chlorinated PCB technical products contribute more to the actual contamination of environment and foods than has been estimated so far. Obviously the co-planar congeners are accumulated during the food chain in a portion different from that found for the other congeners.