title: Persistence and dioxin-like toxicity of carbazole and chlorocarbazoles in soil.
abstract: Halogenated carbazoles have recently been detected in soil and water samples, but their environmental effects and fate are unknown. Eighty-four soil samples obtained from a site with no recorded history of pollution were used to assess the persistence and dioxin-like toxicity of carbazole and chlorocarbazoles in soil under controlled conditions for 15 months. Soil samples were divided into two temperature conditions, 15 and 20 °C, both under fluctuating soil moisture conditions comprising 19 and 44 drying-rewetting cycles, respectively. This was characterized by natural water loss by evaporation and rewetting to -15 kPa. Accelerated solvent extraction (ASE) and cleanup were performed after incubation. Identification and quantification were done using high-resolution gas chromatogram/mass spectrometer (HRGC/MS), while dioxin-like toxicity was determined by ethoxyresorufin-O-deethylase (EROD) induction in H4IIA rat hepatoma cells assay and multidimensional quantitative structure-activity relationships (mQSAR) modelling. Carbazole, 3-chlorocarbazole and 3,6-dichlorocarbazole were detected including trichlorocarbazole not previously reported in soils. Carbazole and 3-chlorocarbazole showed significant dissipation at 15 °C but not at 20 °C incubating conditions indicating that low temperature could be suitable for dissipation of carbazole and chlorocarbazoles. 3,6-Dichlorocarbazole was resistant at both conditions. Trichlorocarbazole however exhibited a tendency to increase in concentration with time. 3-Chlorocarbazole, 3,6-dibromocarbazole and selected soil extracts exhibited EROD activity. Dioxin-like toxicity did not decrease significantly with time, whereas the sum chlorocarbazole toxic equivalence concentrations (∑TEQ) did not contribute significantly to the soil assay dioxin-like toxicity equivalent concentrations (TCDD-EQ). Carbazole and chlorocarbazoles are persistent with the latter also toxic in natural conditions.
authors.affiliation: German Research Center for Environmental Health, Molecular EXposomics (MEX), Helmholtz Zentrum München, Ingolstädter Landstraße 1, 85764, Neuherberg, Germany.
authors.forename: John
authors.initials: J
authors.lastname: Mumbo
authors.forename: Bernhard
authors.initials: B
authors.lastname: Henkelmann
authors.forename: Ahmed
authors.initials: A
authors.lastname: Abdelaziz
authors.forename: Gerd
authors.initials: G
authors.lastname: Pfister
authors.forename: Nghia
authors.initials: N
authors.lastname: Nguyen
authors.forename: Reiner
authors.initials: R
authors.lastname: Schroll
authors.forename: Jean Charles
authors.initials: JC
authors.lastname: Munch
authors.forename: Karl-Werner
authors.initials: KW
authors.lastname: Schramm
mesh_terms: D000818:Animals; D001419:Bacteria / Q000187:drug effects / Q000254:growth & development / Q000302:isolation & purification; D002227:Carbazoles / Q000737:chemistry / Q000633:toxicity*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004147:Dioxins / Q000032:analysis / Q000633:toxicity; D064006:Dodecenoyl-CoA Isomerase; D008401:Gas Chromatography-Mass Spectrometry; D051381:Rats; D012987:Soil / Q000737:chemistry; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000737:chemistry / Q000633:toxicity*
chemical_list: D002227:Carbazoles; D004147:Dioxins; D012987:Soil; D012989:Soil Pollutants; C041514:carbazole; D064006:Dodecenoyl-CoA Isomerase