benzofurans and 1-2-3-4-tetrachlorodibenzofuran

The potential for microbial dechlorination of the weathered polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) was determined in sediments with historical contamination by the chlorophenol wood preservative Ky-5 and its associated dimeric impurities. Sediments were collected from four sites of the Kymijoki River in South-Eastern Finland located at 0, 20, 30, and 60 km downstream from the source of contamination, and at a reference site. We examined the congener profiles of historical PCDD/Fs, including non-2,3,7,8-substituted congeners, and determined the dechlorination potential in sediments at the different sites of the river. The measured mean total concentrations for 2,3,7,8-PCDD/Fs were extremely high, 1200 mg/kg dw, at the most contaminated site, Kuusankoski. The mean concentrations for the predominant 2,3,7,8-congeners were 1,2,3,4,6,7,8-HpCDF 780 mg/kg dw, and for OCDF 380 mg/kg dw at Kuusankoski. At all other study sites of the river the mean total concentrations for 2,3,7,8-PCDD/Fs varied between 9 and 96 mg/kg dw, (6-80 mg/kg dw for 1,2,3,4,6,7,8-HpCDF, 3-13 mg/kg dw for OCDF). The sediment PCDD/F composition was similar to that of Ky-5, indicating that no or only minimal biodegradation of PCDD/F congeners has occurred in the river sediments over the last few decades since the contamination events. Microbes capable of PCDD/F dechlorination were present at all study sites based on Dehalococcoides-like Chloroflexi community determination and dechlorination of spiked 1,2,3,4-tetrachlorodibenzofuran. However, no substantial changes in the relative abundances of PCDD/Fs were observed over 2.5 years in laboratory microcosm studies, indicating that anaerobic dechlorination of weathered PCDD/Fs was limited over the course of the experiment. Therefore, concentrations of weathered PCDD/Fs in the sediments of the Kymijoki River are expected to remain at the same level for decades or centuries with further migration towards the Baltic Sea.

Topics: Benzofurans; Biodegradation, Environmental; Chloroflexi; Chlorophenols; Dibenzofurans; Finland; Geologic Sediments; Polychlorinated Biphenyls; Polychlorinated Dibenzodioxins; Rivers; Water Pollutants, Chemical; Weather

Sediments of the Kymijoki River are highly contaminated with polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). These persistent PCDD/Fs resist biotic degradation and therefore the potential for microbial reductive dechlorination was assessed to determine how microbes impact the fate of these compounds. Anaerobic sediment microcosms of five different sites in the river were spiked with 1,2,3,4-tetrachlorodibenzofuran (1,2,3,4-TeCDF) as a model compound to determine the dechlorination potential in the sediments. Dechlorinating bacteria were active in all the study sites of the river. The extent of dechlorination over 10 and 29 months corresponded to the levels of aged PCDD/Fs, with sediments of the most contaminated site at Kuusankoski being the most active for reductive dechlorination. The dechlorination activity and levels of aged PCDD/Fs were correlated within the sediment cores at the all sites. The pathway of 1,2,3,4-TeCDF dechlorination was mainly via 1,3,4-trichlorodibenzofuran (TrCDF) to 1,3-dichlorodibenzofuran (DiCDF). Dechlorination via 1,2,4-TrCDF to further dechlorination products was also detected. Lateral reductive dechlorination would decrease the toxicity of 2,3,7,8-substituted PCDD/Fs. Our data suggest that sediments of the Kymijoki River contain indigenous microorganisms that are responsible for dechlorination of PCDD/Fs, especially at the most contaminated site.

Topics: Anaerobiosis; Benzofurans; Biodegradation, Environmental; Dibenzofurans, Polychlorinated; Finland; Geologic Sediments; Humans; Polychlorinated Dibenzodioxins; Rivers

The effect of temperature on the reductive dechlorination in sediments of the PCDD/F-contaminated Kymijoki River, Finland was assessed with 1,2,3,4-tetrachlorodibenzofuran (1,2,3,4-TeCDF) at various temperatures and with co-amendment of 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP) in laboratory microcosms. The dechlorination rate of 1,2,3,4-TeCDF increased with incubation temperature, with TeCDF half-lives of 2.1 y at 21°C, 3.9 y at 15°C, and 19.0 y at 4°C. Co-amendment with 2,3,4,6-TeCP reduced the TeCDF half-life to 1.8 y at 21°C. 1,2,3,4-TeCDF was dechlorinated mainly in the lateral position to 1,3,4-TrCDF and then to 1,3-DiCDF over 29 months, but incubation temperature affected the relative molar ratios of the dechlorination products. The abundance of the Dehalococcoides-like Chloroflexi community did not substantially change in microcosms over 24 months incubation at the different temperatures. The dechlorination activity of 1,2,3,4-TeCDF was significantly limited at lower temperatures, which should be considered in predicting the environmental fate of aged PCDD/Fs in sediments of the Kymijoki River.

Topics: Anaerobiosis; Benzofurans; Biodegradation, Environmental; Chlorine; Chloroflexi; Chlorophenols; DNA, Bacterial; Geologic Sediments; Oxidation-Reduction; Polychlorinated Dibenzodioxins; RNA, Ribosomal, 16S; Temperature; Water Pollutants, Chemical

Exposure to the environmental contaminant, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), produces hydronephrosis in developing mice, the etiology of which involves hyperplasia within the ureteric luminal epithelium. Dysregulation of epidermal growth factor receptor (EGFR), EGF, and transforming growth factor-alpha expression has been implicated as playing a role in TCDD-induced hydronephrosis. In this study, changes in the expression of genes encoding the EGFR and its cognate ligands in response to TCDD were evaluated within the developing ureter. C57BL/6 dams were injected ip with 30 mug/kg TCDD on gestational day (GD) 13 or 16 and fetal tissues removed on GD 17. Aryl hydrocarbon receptor (AHR) and AHR nuclear translocator messenger RNA (mRNA) were expressed in control and treated fetal tissues at GD 14 and 17. Prototypical AHR target genes, Cyp1a1, Cyp1a2, and Cyp1b1 were upregulated in TCDD-exposed fetal tissues, demonstrating AHR transcriptional activity at these developmental stages. Amphiregulin (AREG) and epiregulin, ligands for the EGFR, were induced at the transcriptional level in ureters of fetuses exposed to TCDD for 24 h. AREG mRNA was also induced by TCDD dose- and time-dependently in the mouse hepatoma cell line Hepa-1c1c7 (Hepa-1), mimicking the induction patterns of CYP1A1 mRNA. Other AHR ligands also induced AREG mRNA in Hepa-1 cells. Furthermore, variant Hepa-1 cells (TAOBP(r)c1 cells) virtually deficient in the AHR failed to display an increase in AREG mRNA in response to TCDD. Taken together, these data suggest that the AHR cross talks with the EGFR signaling pathway by directly inducing the expression of growth factors that are important for EGFR signaling in the developing mouse ureter.

Topics: Amphiregulin; Animals; Benz(a)Anthracenes; Benzo(a)pyrene; Benzofurans; Cell Line, Tumor; Cell Proliferation; Cytochrome P-450 CYP1A1; Dose-Response Relationship, Drug; EGF Family of Proteins; Female; Gene Expression Regulation, Developmental; Gestational Age; Glycoproteins; Injections, Intraperitoneal; Intercellular Signaling Peptides and Proteins; Male; Maternal Exposure; Mice; Mice, Inbred C57BL; Polychlorinated Dibenzodioxins; Pregnancy; Receptors, Aryl Hydrocarbon; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Teratogens; Ureter

Halogenated coamendments enhanced dechlorination of 31 microM of spiked 1,2,3,4-tetrachlorodibenzo-p-dioxin (TeCDD) and 49 microM of spiked 1,2,3,4-tetrachlorodibenzofuran (TeCDF) in sediments from San Diego Bay (CA, USA) and Tuckerton (NJ, USA). Dechlorination of 1,2,3,4-TeCDD occurred to a greater extent under methanogenic than under sulfate-reducing conditions. The most effective stimulation of 1,2,3,4-TeCDD dechlorination occurred with coamendment of 25 microM of 1,2,3,4-tetrachlorobenzene (TeCB), 2,3,4,5-tetrachloroanisole (TeCA), 2,3,4,5-tetrachlorophenol, or 2',3',4'-trichloroacetophenone plus 500 microM lactate and 500 microM propionate as electron donors. The 1,2,3,4-TeCDD dechlorination was evident after three months and sequentially produced mainly 1,2,4-trichlorodibenzo-p-dioxin, 1,3-dichlorodibenzo-p-dioxin, and 2-monochlorodibenzo-p-dioxin (MCDD). Monobromophenols (2-bromo-, 3-bromo-, and 4-bromophenol), monochlorophenols (2-chloro-, 3-chloro-, and 4-chlorophenol), 2,3,5,6-tetrachlorobenzoate, or electron donors alone stimulated less 1,2,3,4-TeCDD dechlorination, with activity apparent only after six months. The 1,2,3,4-TeCDD dechlorination produced 50 mol % 2-MCDD after six months in sediments from the more contaminated Graving Dock and Paleta Creek sites in San Diego Bay. The 1,2,3,4-TeCDD dechlorination by sediments from the less contaminated Shelter Island site in San Diego Bay and in pristine Tuckerton sediments did not produce 2-MCDD. Dechlorination of 1,2,3,4-TeCDF to tri- and dichlorinated daughter products was significantly enhanced by TeCB and TeCA. These results suggest that halogenated aromatic compounds with structural similarity to 1,2,3,4-TeCDD/F stimulate bacteria with the ability to dechlorinate chlorinated dibenzo-p-dioxin and furans.

Topics: Anaerobiosis; Bacteria, Anaerobic; Benzofurans; Chlorine; Geologic Sediments; Halogens; Methane; Molecular Structure; Polychlorinated Dibenzodioxins; Rivers; Time Factors; United States