Dioxin-like activity of brominated dioxins as individual compounds or mixtures in in vitro reporter gene assays with rat and mouse hepatoma cell lines

Emission of Dioxin-like Compounds and Flame Retardants from Commercial Facilities Handling Deca-BDE and Their Downstream Sewage Treatment Plants

“…As shown in Table , the concentration of TCDD-EQ PBDD/DFs was much higher than that of TCDD-EQ PCDD/DFs in DHF effluents. As possible major contributors, PBDD/DFs with dioxin-like activity ,,,− were analyzed to evaluate their contribution to the TCDD-EQ PBDD/DFs for the effluents of DHF-3, -4, -8, -9, and -10. The contribution ratio of theoretical TCDD-EQ PBDD/DFs to TCDD-EQ PBDD/DFs ranged from 0.23 to 63% (median: 3.9%) (Tables and S9), indicating that the ratios were very different among the facilities.…”

“…The concentrations of PBDD/DFs in the extracts were determined by GC–HRMS; the measurement conditions are described in the Supporting Information, and the target compounds and their abbreviations are shown in Table S5. WHO-TEQ or theoretical TCDD-EQ values (WHO-TEQ PBDD/DFs ; theoretical TCDD-EQ PBDD/DFs ) were calculated by multiplying the concentration of each detected PBDD/DF by the WHO-toxicity equivalency factor of their chlorinated analogue or their respective CALUX-REP and then summing the individual WHO-TEQs or theoretical TCDD-EQs to obtain the total WHO-TEQ or theoretical TCDD-EQ.…”

“…Impurities in commercial BFR preparations may also pose risks to human health and the environment. For example, brominated dioxins have been reported as unintentional low-level (0.1 to 100 ppm) impurities in commercial preparations of the polybrominated diphenyl ethers (PBDEs) penta-BDE, octa-BDE, and deca-BDE. , This is an issue because brominated dioxins such as polybrominated dibenzo- p -dioxins and dibenzofurans (PBDD/DFs) have been shown to have similar toxicity profiles as their chlorinated analogues, many of which have dioxin-like activities. − In addition to the presence of brominated dioxins as impurities in commercial preparations of BFRs, their formation is also reported to be induced by exposure of PBDEs to sunlight and by the thermal treatment and combustion of various BFRs. − Also, these compounds are gradually released over time from products that were treated with BFRs during manufacture. − Consequently, it is likely that brominated dioxins make a marked contribution to the daily human exposure to dioxins and dioxin-like compounds (DLCs). − The amounts of these compounds emitted to the environment were expected to decrease after the addition of penta-BDE (May 2009), octa-BDE (May 2009), and deca-BDE (May 2017) to the list of persistent organic pollutants (POPs) in the Stockholm Convention.…”

Elucidating the aryl hydrocarbon receptor antagonism from a chemical-structural perspective

“…Certainly, informative experimental bioassays will be necessary to obtain greater insight on the AhR-ligand interaction modes, and particularly to discriminate between agonistic and antagonistic modulations. One of the most popularized assays is the in vitro AhR Chemically Activated LUciferase eXpression (CALUX) bioassay, which has been reported to be useful in the detection of the AhR antagonistic and agonistic effects of dioxin and dioxin-like chemical compounds [26,27]. This assay is based on the analysis of the induced luciferase response in a recombinant cell line driven by several CYP1A1 dioxin response elements (DREs) as a direct reflection of AhR-mediated transcriptional activity.…”