On the isolation of polychlorinated dibenzo-p-dioxins and furans from serum samples using immunoaffinity chromatography prior to high-resolution gas chromatography–mass spectrometry

Immunoaffinity chromatography (IAC) for the purification of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) from biological samples was explored as a means to simplify the cleanup procedure and thereby decrease the time and cost of dioxin analysis. A monoclonal antibody (DD3) was used to produce IAC columns and to isolate the PCDD/Fs from serum. Native and ¹³C-labeled PCDD/Fs were spiked at the ppq to ppt range into serum. Quantitation of the PCDD/Fs was performed by a standard dioxin analytical method, i.e. high-resolution gas chromatography–mass spectrometry (GC–MS), which was easily compatible with IAC. Five of the most toxic PCDD/Fs consistently showed acceptable recoveries (>25%) and were reliably quantitated. The congeners specifically recovered by this method represent almost 80% of the toxic equivalency of dioxins and furans present in the serum samples. Dioxin-like polychlorinated biphenyls (PCBs) were not recognized by this antibody column. Compared to conventional dioxin cleanup methods, IAC decreased solvent usage by 1.5 l/sample and took only 2 h to process a sample for analysis.     

Degradation of dioxin-like compounds by microorganisms

Polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF; PCDD/F, dioxins) have not been commercially produced in bulk amounts, as were polychlorinated biphenyls and other haloaromatic organics. Within the past two decades a lot␣of information has accumulated on the biodegradation of PCDD/F and other dioxin-like compounds because of their toxicity and because of significant environmental concern about many congeners of this class of chemicals. PCDD/F are subjected to reductive dehalogenations leading to less halogenated congeners, which can be attacked efficiently by fungal and bacterial oxidases and dioxygenases. In several cases these compounds can be utilized as carbon and energy sources. Pathways for their enzymatic degradation and the organisation of the corresponding degradative genes have been elucidated. Consequently, biotechnological applications will exploit the degradative potential of such microorganisms for bioremediation of contaminated sites. Received: 29 August 1997 / Received revision: 6 January 1998 / Accepted: 8 January 1998     

Recent developments in microbial biotransformation and biodegradation of dioxins

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), commonly known as dioxins (PCDD/Fs), are toxic environmental pollutants formed from various sources. Elimination of these pollutants from the environment is a difficult task due to their persistent and ubiquitous nature. Removal of dioxins by biological degradation (biodegradation) is considered a feasible method as an alternative to other expensive physicochemical approaches. Biodegradation of dioxins has been extensively studied in several microorganisms, and details concerning biodiversity, biodegradation, biochemistry and molecular biology of this process have accumulated during the last three decades. There are several microbial mechanisms responsible for biodegradation of dioxins, including oxidative degradation by dioxygenase-containing aerobic bacteria, bacterial and fungal cytochrome P-450, fungal lignolytic enzymes, reductive dechlorination by anaerobic bacteria, and direct ether ring cleavage by fungi containing etherase-like enzymes. Many attempts have been made to bioremediate PCDD/Fs using this basic knowledge of microbial dioxin degradation. This review emphasizes the present knowledge and recent advancements in the microbial biotransformation, biodegradation and bioremediation of dioxins.     

Characterization of proteins in the gonad of Limanda yokohamae from Masan Bay, Korea

The putative biological effects of the toxic organic pollutants polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and the dioxin-like polychlorinated biphenyls (DLPCBs) in the sediments of Masan Bay, Korea, on the gonad of Limanda yokohamae were investigated using proteomic and bioinformatic analyses. The results demonstrated that 11 protein spots from the bay site, Duckdong, were statistically different from the reference site Gaduck Island. We identified 20 proteins from the 11 altered protein spots and these were found to be involved in multi-cellular functions as previously demonstrated in a variety of species. The concentrations of toxic equivalents of PCDD/Fs and DLPCBs in the sediments of Masan Bay were approximately twenty six-fold higher than those from Gaduck Island. These findings indicate that the organic contaminants in the sediments of Masan Bay may have contributed to the change in the phenotypes of fish gonads.     

Phylogenetic Characterization of a Polychlorinated-Dioxin- Dechlorinating Microbial Community by Use of Microcosm Studies

Microcosms capable of reductive dechlorination of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) were constructed in glass bottles by seeding them with a polluted river sediment and incubating them anaerobically with an organic medium. All of the PCDD/F congeners detected were equally reduced without the accumulation of significant amounts of less-chlorinated congeners as the intermediate or end products. Alternatively, large amounts of catechol and salicylic acid were produced in the upper aqueous phase. Thus, the dechlorination of PCDD/Fs and the oxidative degradation of the dechlorinated products seemed to take place simultaneously in the microcosm. Denaturing gel gradient electrophoresis and clone library analyses of PCR-amplified 16S rRNA genes from the microcosm showed that members of the phyla Firmicutes, Proteobacteria, and Bacteroidetes predominated. A significant number of Chloroflexi clones were also detected. Quantitative real-time PCR with specific primer sets showed that the 16S rRNA genes of a putative dechlorinator, “Dehalococcoides,” and its relatives accounted for 0.1% of the total rRNA gene copies of the microcosm. Most of the clones thus obtained formed a cluster distinct from the typical “Dehalococcoides” group. Quinone profiling indicated that ubiquinones accounted for 18 to 25% of the total quinone content, suggesting the coexistence and activity of ubiquinone-containing aerobic bacteria. These results suggest that the apparent complete dechlorination of PCDD/Fs found in the microcosm was due to a combination of the dechlorinating activity of the “Dehalococcoides”-like organisms and the oxidative degradation of the dechlorinated products by aerobic bacteria with aromatic hydrocarbon dioxygenases.     

Cosubstrate effects in reductive dehalogenation byPseudomonas putida G786 expressing cytochrome P-450CAM

Cytochrome P-450_CAM was shown to be the primary catalyst mediating reductive dehalogenation of polychlorinated ethanes byPseudomonas putida G786. Under anaerobic conditions, the enzyme catalyzed reductive elimination reactionsin vivo with the substrates hexachloroethane, pentachloroethane, and 1,1,1,2-tetrachloroethane; the products were tetrachloroethylene, trichloroethylene, and 1,1-dichloroethylene, respectively.In vivo reaction rates were determined. No reaction was observed with 1,1,2,2-tetrachloroethane or 1,1,1-trichloroethane. Purified cytochrome P-450_CAM was used to measure dissociation constants of polychlorinated ethanes for the enzyme active site. Observed rates and dissociation constants were used to predict the course of a reaction with the three substrates simultaneously. Data obtained from experiments withP. putida G786 generally followed the simulated reaction curves. Oxygen suppressed the reductive dechlorination reactions and, in the case of 1,1,1,2-tetrachloroethane, 2,2,2-trichloroacetaldehyde was formed. Significant rates of reductive dechlorination were observed at 5% oxygen suggesting that these reactions could occur under partially aerobic conditions. These studies highlight the potential to use an aerobic bacterium,P. putida G786, under a range of oxygen tensions to reductively dehalogenate mixed wastes which are only degraded at very low rates by obligately anaerobic bacteria.Abbreviations GC/MS Gas chromatography/mass spectrometry - P-450_CAM Cytochrome m of the camphor oxidizing system ofP. putida - pca Polychlorinated ethane     

Phylogenetic characterization of a polychlorinated-dioxin- dechlorinating microbial community by use of microcosm studies

Microcosms capable of reductive dechlorination of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) were constructed in glass bottles by seeding them with a polluted river sediment and incubating them anaerobically with an organic medium. All of the PCDD/F congeners detected were equally reduced without the accumulation of significant amounts of less-chlorinated congeners as the intermediate or end products. Alternatively, large amounts of catechol and salicylic acid were produced in the upper aqueous phase. Thus, the dechlorination of PCDD/Fs and the oxidative degradation of the dechlorinated products seemed to take place simultaneously in the microcosm. Denaturing gel gradient electrophoresis and clone library analyses of PCR-amplified 16S rRNA genes from the microcosm showed that members of the phyla Firmicutes, Proteobacteria, and Bacteroidetes predominated. A significant number of Chloroflexi clones were also detected. Quantitative real-time PCR with specific primer sets showed that the 16S rRNA genes of a putative dechlorinator, "Dehalococcoides," and its relatives accounted for 0.1% of the total rRNA gene copies of the microcosm. Most of the clones thus obtained formed a cluster distinct from the typical "Dehalococcoides" group. Quinone profiling indicated that ubiquinones accounted for 18 to 25% of the total quinone content, suggesting the coexistence and activity of ubiquinone-containing aerobic bacteria. These results suggest that the apparent complete dechlorination of PCDD/Fs found in the microcosm was due to a combination of the dechlorinating activity of the "Dehalococcoides"-like organisms and the oxidative degradation of the dechlorinated products by aerobic bacteria with aromatic hydrocarbon dioxygenases.     

Dioxin/polychlorinated biphenyl body burden,diabetes and endometriosis: findings in a population-based study in Belgium

Dioxins and polychlorinated biphenyls (PCBs) are persistent organic pollutants widely distributed in the food chain, which is the main source of human exposure. Their effects on human health at background exposure levels are still poorly understood. Recent epidemiological evidence suggests a possible association between these pollutants and diabetes. We report here the results of a population-based study in Belgium on 257 (142 women and 115 men) environmentally exposed subjects, including 10 cases of endometriosis and nine cases of diabetes. Seventeen 2,3,7,8-polychlorinated dibenzodioxins/dibenzofurans (PCDD/Fs or dioxins), four coplanar PCBs (International Union of Pure and Applied Chemistry [IUPAC] nos 77, 81, 126 and 169) and 12 PCB markers (IUPAC nos 3, 8, 28, 52, 101, 118, 138, 153, 180, 194, 206 and 209) were quantified in serum fat from fasting blood samples in order to estimate the body burden of these pollutants. Whilst no difference was found between women with endometriosis and their controls, diabetic patients had significantly increased serum levels of dioxins, coplanar PCBs and the 12 PCB markers. After adjustment for age and other covariates, serum total toxic equivalent activity (sum of PCDD/Fs and coplanar PCBs) and 12 PCB marker concentrations in diabetics were 62% (p=0.0005) and 39% (p=0.0067) higher, respectively, than in controls. The risk of diabetes was significantly increased in subjects in the top decile for adjusted concentrations of dioxins (odds ratio 5.1, 95% confidence interval [CI] 1.18–21.7), coplanar PCBs (odds ratio 13.3, 95% CI 3.31–53.2) or 12 PCB markers (odds ratio 7.6, 95% CI 1.58–36.3). These findings warrant further studies to assess the significance of the associations between diabetes and environmental exposure to polychlorinated pollutants.     

Levels of Polychlorinated Dibenzo-P-Dioxins (PCDDs) and Polychlorinated Dibenzo-P-Furans (PCDFs) in the Atmosphere (PM10) of a Coastal Area of West Bengal,India

Particle-bound polychlorinated dibenzo-p-dioxins and dibenzo-p-furans (PCDDs/Fs) were analyzed in the coastal air of West Bengal, India. Total PCDD/Fs ranged from 4–2491 fg m^–3 with a mean of 355 fg m^–3 and their I-TEQ values ranged between 1 to 62.6 fg I-TEQ m^–3, with an average of 17.1 fg I-TEQ m^–3. The dominant congeners were OCDD (46%) OCDF (14%) 1,2,3,4,6,7,8-HpCDF (11%) and 1,2,3,4,6,7,8-HpCDD (10%) and accounted for >80% to the total PCDDs/Fs. TCDD (29%) > PeCDF (28%) > HxCDF (16%) > PeCDD (13%) were the dominant TEQ contributors. Rough estimates of tolerable daily intake (TDI) show a low health risk of exposure to PCDD/Fs measured in the ambient air of a rural coastal area of West Bengal, India.     

Risk Assessment of Some PCDDs,PCDFs, Dioxin-Like PCBs,and PCBs in Contaminated Dairy Products: An Egyptian Pilot Case Study

Samples of butter, cream, and white cheese were collected from the city of Ismailia, Egypt, and analyzed for polychloro dibenzo-p-dioxins, pentachloro dibenzo-p-furans, and dioxin-like polychlorinated biphenyl, PCBs. Butter samples had the highest mean content of PCDD/F and dioxin-like PCBs. Butter samples were the most contaminated samples in all dairy products analyzed in this study, whereas white cheese samples were the least contaminated. The spectrum of congeners detected in butter and cream were similar, with all congeners at detectable levels, whereas the spectrum of congeners detected in white cheese differed, with some congeners, namely 1,2,3,4,7,8-Hexa CDD, 1,2,3,4,6,7,8-Hepta CDD, and 1,2,3,7,8,9-Hexa CDD below WHO TE toxicity levels. 1,2,3,7,7-PeCDD, with its high concentration, was the principal contributor to the TEQ intake in both cream and butter samples. Similarly, the high concentration of 2,3,4,7,8-PeCDF in cream, butter, and white cheese samples was the main factor contributing to their TEQ intake. Estimated intakes of PCDDs/Fs were 129.2, 115.8, and 51.25 pg WHO-TEQ/day for butter, cream, and white cheese, respectively. Taking into account the sum of PCDDs/Fs and dioxin-like PCBs, estimated intakes were, 171.7, 155.8, and 68 pg WHO-TEQ/day, for butter, cream, and white cheese, respectively. Assuming an average bodyweight of 60 kg (WHO-TEQ/kg), these levels correspond to bodyweight-normalized intake levels of .15, 2.92 and 0.95 pg WHO-TEQ/kg/day.     

Toward the bioremediation of dioxin-polluted soil: structural and functional analyses of in situ microbial populations by quinone profiling and culture-dependent methods

In order to obtain basic information toward the bioremediation of dioxin-polluted soil, microbial communities in farmland soils polluted with high concentrations of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were studied by quinone profiling as well as conventional microbiological methods. The concentration of PCDD/Fs in the polluted soils ranged from 36 to 4,980 pg toxicity equivalent quality (TEQ) g(-1) dry weight of soil. There was an inverse relationship between the levels of PCDD/Fs and microbial biomass as measured by direct cell counting and quinone profiling. The most abundant quinone type detected was either MK-6 or Q-10. In addition, MK-8, MK-8(H2), and MK-9(H8) were detected in significant amounts. Numerical analysis of quinone profiles showed that the heavily polluted soils (> or = 1,430 pg TEQ g(-1)) contained different community structures from lightly polluted soils (< or = 56 pg TEQ g(-1)). Cultivation of the microbial populations in the heavily polluted soils with dibenzofuran or 2-chlorodibenzofuran resulted in enrichment of Q-10-containing bacteria. When the heavily polluted soil was incubated in static bottles with autoclaved compost as an organic nutrient additive, the concentrations of PCDD/Fs in the soil were decreased by 22% after 3 months of incubation. These results indicate that dioxin pollution exerted a significant effect on microbial populations in soil in terms of quantity, quality, and activity. The in situ microbial populations in the dioxin-polluted soil were suggested to have a potential for the transformation of PCDD/Fs and oxidative degradation of the lower chlorinated ones thus produced.     

Microbial reductive dehalogenation of polychlorinated biphenyls

Under anaerobic conditions, microbial reductive dechlorination of polychlorinated biphenyls (PCBs) occurs in soils and aquatic sediments. In contrast to dechlorination of supplemented single congeners for which frequently ortho dechlorination has been observed, reductive dechlorination mainly attacks meta and/or para chlorines of PCB mixtures in contaminated sediments, although in a few instances ortho dechlorination of PCBs has been observed. Different microorganisms appear to be responsible for different dechlorination activities and the occurrence of various dehalogenation routes. No axenic cultures of an anaerobic microorganism have been obtained so far. Most probable number determinations indicate that the addition of PCB congeners, as potential electron acceptors, stimulates the growth of PCB-dechlorinating microorganisms. A few PCB-dechlorinating enrichment cultures have been obtained and partially characterized. Temperature, pH, availability of naturally occurring or of supplemented carbon sources, and the presence or absence of H(2) or other electron donors and competing electron acceptors influence the dechlorination rate, extent and route of PCB dechlorination. We conclude from the sum of the experimental data that these factors influence apparently the composition of the active microbial community and thus the routes, the rates and the extent of the dehalogenation. The observed effects are due to the specificity of the dehalogenating bacteria which become active as well as changing interactions between the dehalogenating and non-dehalogenating bacteria. Important interactions include the induced changes in the formation and utilization of H(2) by non-dechlorinating and dechlorinating bacteria, competition for substrates and other electron donors and acceptors, and changes in the formation of acidic fermentation products by heterotrophic and autotrophic acidogenic bacteria leading to changes in the pH of the sediments.     

Isolation of an anaerobic bacterium which reductively dechlorinates tetrachloroethene and trichloroethene

Strain TEA, a strictly anaerobic, motile rod with one to four lateral flagella and a crystalline surface layer was isolated from a mixed culture that completely reduces chlorinated ethenes to ethene. The organism coupled reductive dehalogenation of tetrachloroethene or trichloroethene to cis-1,2-dichloroethene to growth, using molecular hydrogen as the electron donor. It was unable to grow fermentatively or in the presence of tri- or tetrachloroethene with glucose, pyruvate, lactate, acetate or formate. The 16S rDNA sequence of strain TEA was 99.7% identical to that of Dehalobacter restrictus. The two organisms thus are representatives of the same species or the same genus within the Bacillus/Clostridium subphylum of the gram-positive bacteria.     

Aerobic degradation of highly chlorinated polychlorobiphenyls by a marine bacterium, Pseudomonas CH07

Hitherto, aerobic degradation of polychlorinated biphenyls (PCBs) has been reported to be limited to the less chlorinated biphenyls. We report here a marine mercury-resistant bacterium, Pseudomonas CH07 (NRRL B-30604) which was capable of degrading a variety of highly chlorinated congeners of PCBs from the technical mixture Clophen A-50. Of the two most toxic coplanar PCBs present in Clophen A-50, one coplanar pentachloro congener CB-126 and one toxic sterically hindered heptachloro congener CB-181 were found to be degraded completely and the other coplanar tetrachloro congener CB-77 was degraded by more than 40% within 40 h by this microorganism. The apparent absence of bphC in this bacterium leads to the proposal of a different mechanism for degradation of PCBs.     

Degradation of halogenated aromatic compounds

Due to their persistence, haloaromatics are compounds of environmental concern. Aerobically, bacteria degrade these compounds by mono- or dioxygenation of the aromatic ring. The common intermediate of these reactions is (halo)catechol. Halocatechol is cleaved either intradiol (ortho-cleavage) or extradiol (meta-cleavage). In contrast to ortho-cleavage, meta-cleavage of halocatechols yields toxic metabolites. Dehalogenation may occur fortuitously during oxygenation. Specific dehalogenation of aromatic compounds is performed by hydroxylases, in which the halo-substituent is replaced by a hydroxyl group. During reductive dehalogenation, haloaromatic compounds may act as electron-acceptors. Herewith, the halosubstituent is replaced by a hydrogen atom.Abbreviations CBz chlorobenzene - DCBz dichlorobenzene - TrCBz trichlorobenzene - TCBz tetrachlorobenzene - PCBz pentachlorobenzene - HCBz hexachlorobenzene - CBA chlorobenzoic acid - BBA bromobenzoic acid - FBA fluorobenzoic acid - IBA iodobenzoic acid - CP chlorophenol - CA chloroaniline - PCBs polychlorinated biphenyls - CB chlorobiphenyl - 2,4-D 2,4-dichlorophenoxyacetic acid - 2,4,5-T 2,4,5-trichlorophenoxyacetic acid     

Contaminant sources, distribution and fate in the Athabasca, Peace and Slave River Basins, Canada

Northern river ecosystems worldwide are under increasing environmental stress from degrading developments that influence water quality and associated ecological integrity. In particular, contaminant-related threats to these systems are rising from enhanced industrial and municipal effluent discharges along with elevated non-point source inputs related to land-use activities such as forestry, agriculture, mining and long-range atmospheric transport. In this regard, the contaminants program of the Northern River Basins Study (NRBS) in western Canada identified key contaminant sources to the Athabasca, Slave and Peace river basins (particularly related to pulp-mill developments) and assessed their environmental fate and distribution in water and sediments. The study also developed and employed new analytical approaches and generated improved models to predict contaminant transport and fate in the aquatic environment and related food webs. Consequently the study focused on those contaminant families identified in characterization studies as arising from key point- and non-point sources within the basins or as being of greatest toxicological significance. These included resin acids, polychlorinated dioxins and furans, polychlorinated biphenyls, chlorinated phenolics, polyaromatic hydrocarbons and selected heavy metals such as mercury. Low or non-detectable concentrations of a number of contaminant groups were found in the ambient water phase including chlorinated phenolics, some chlorinated dioxins and furans and some resin acids. For both suspended and depositional sediments, significant declines were observed over the study period for the major chlorinated contaminant groups tested, correlating directly with the implementation of improved effluent treatment in many of the pulp mills located in the basins. In general, the environmental levels of chlorinated organic and metal contaminants in water or sediments were low and within Canadian health or environmental guidelines. It is hoped that the approaches used and lessons learned from the NRBS will be of use to others assessing contaminant and multiple stressor issues in other large river ecosystems.     

CALUX Bioassay of Dioxin-Like Compounds in Sediments from the Haihe River,China

Chemically Activated LUciferase gene eXpression (CALUX) bioassay is a rapid, effective, and cheap method to analyze dioxin-like compounds (DLCs). Using this method, total levels of DLCs, including PCDD/Fs (polychlorinated dibenzo-p-dioxin and dibenzofurans) fraction and DL-PCBs (dioxin-like polychlorinated biphenyls) fraction, in extracts of sediments from the Haihe River, China, were determined. It was found that the levels of PCDD/Fs in the sediments from the Haihe River were tens of times to hundreds of times higher than those of DL-PCBs. The DLC levels in sediments in March 2005 approximated those in November 2006. The CALUX toxic equivalents (TEQs) of DLCs were independent of the total organic carbon (TOC) of sediments. Significant correlation was observed between the PCDD/Fs TEQs and DL-PCBs TEQs. The two fractions of some samples were also analyzed by HRGC/HRMS (high-resolution gas chromatography/high-resolution mass spectrometry) method. Significant statistical correlations were observed between the CALUX TEQs and HRGC/HRMS TEQs. The difference between TEF (toxic equivalent factor) and REP (relative potency) can explain most of the discrepancy between CALUX and HRGC/HRMS analysis. A high level of DLCs was found at the sites near the influx into Bohai Bay. The dioxin pollution might be associated with industrial activities of pentachlorophenol (PCP) in the adjacent area. More attention should be paid to the increase of DLC levels and further investigation should be done for this area.     

Kinetics and organotropy of some polyfluorinated dibenzo-p-dioxins and dibenzofurans (PFDD/PFDF) in rats

While polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/PCDF) and the corresponding polybrominated congeners must be considered as animal teratogens and carcinogens, little information is available on corresponding polyfluorinated compounds (PFDD/PFDF). Kinetic studies on a few fluorinated dibenzo-p-dioxins and dibenzofurans revealed a rapid elimination, suggesting a much lower toxicity than the corresponding polychlorinated and polybrominated congeners. In order to obtain further clues on the possible toxicity, the kinetics and organ distribution (in liver, thymus and adipose tissue) of a PFDD/PFDF-mixture were studied in Wistar rats after intravenous application. The congeners investigated included four of the 2,3,7,8-substituted, and four of the not-2,3,7,8-substituted dibenzo-p-dioxins, as well as two dibenzofurans. The main result of our studies is the finding that the concentration in the thymus of several of the 2,3,7,8-substituted PFDD/PFDF greatly exceeded that in hepatic tissue. An organotropy quite different from that of the other polyhalogenated congeners must be expected, immunosuppressive effects presumably being the predominant ones. Overall, the elimination half-life of all the PFDD/PFDF studied is considerably shorter than that of the corresponding polychlorinated or polybrominated congeners, in the rat, suggesting a much lower toxicity in this species. No information is available for other species, e.g. nonhuman primates or humans.     

Dioxin/polychlorinated biphenyl body burden, diabetes and endometriosis: findings in a population-based study in Belgium

Dioxins and polychlorinated biphenyls (PCBs) are persistent organic pollutants widely distributed in the food chain, which is the main source of human exposure. Their effects on human health at background exposure levels are still poorly understood. Recent epidemiological evidence suggests a possible association between these pollutants and diabetes. We report here the results of a population-based study in Belgium on 257 (142 women and 115 men) environmentally exposed subjects, including 10 cases of endometriosis and nine cases of diabetes. Seventeen 2,3,7,8-polychlorinated dibenzodioxins/dibenzofurans (PCDD/Fs or dioxins), four coplanar PCBs (International Union of Pure and Applied Chemistry [IUPAC] nos 77, 81, 126 and 169) and 12 PCB markers (IUPAC nos 3, 8, 28, 52, 101, 118, 138, 153, 180, 194, 206 and 209) were quantified in serum fat from fasting blood samples in order to estimate the body burden of these pollutants. Whilst no difference was found between women with endometriosis and their controls, diabetic patients had significantly increased serum levels of dioxins, coplanar PCBs and the 12 PCB markers. After adjustment for age and other covariates, serum total toxic equivalent activity (sum of PCDD/Fs and coplanar PCBs) and 12 PCB marker concentrations in diabetics were 62% (p=0.0005) and 39% (p=0.0067) higher, respectively, than in controls. The risk of diabetes was significantly increased in subjects in the top decile for adjusted concentrations of dioxins (odds ratio 5.1, 95% confidence interval [CI] 1.18-21.7), coplanar PCBs (odds ratio 13.3, 95% CI 3.31-53.2) or 12 PCB markers (odds ratio 7.6, 95% CI 1.58-36.3). These findings warrant further studies to assess the significance of the associations between diabetes and environmental exposure to polychlorinated pollutants.     

Oral Bioavailability of Polychlorinated Dibenzo-p-Dioxins/Dibenzofurans in Industrial Soils

In this study, the oral bioavailabilities of numerous 2,3,7,8-PCDD/F congeners were evaluated in soil samples from an industrial site. The purpose of this study is several-fold: (1) to compare the soil bioavailability results of the different PCDD/F congeners; (2) to evaluate the consistency of the bioavailability results with those obtained in an in vitro bioaccessibility study with simulated GI tract fluids; and (3) to develop quantitative bioavailability measurements that are appropriate for use in a health risk assessment for this site. Soil samples containing PCDD/F toxic equivalent (TEQ) concentrations ranging from 0.53–45.2 ng/g were administered to female Sprague Dawley rats via oral gavage. Reference formulations of PCDD/Fs were administered intravenously or by oral gavage. The overall relative bioavailability of PCDD/Fs in the soil samples on a TEQ basis ranged from 17 to 51%, with a mean of 38%. The results of the in vitro bioaccessibility study were consistent with the bioavailability results (mean extracted TEQ of 22%). Because of the clear relationship between increasing chlorination and decreasing bioavailability and bioaccessibility observed in this study, we suggest that simply extrapolating results from one congener to another may be associated with a high degree of uncertainty.