This work describes a single and fast approach using a filtering script as a means of prioritizing sample processing of data acquired by GC×GC-TOF MS for the identification of potentially novel persistent and bioaccumulative halogenated chemicals. The proposed script is based on the recognition of a generic halogenated isotope cluster pattern that allows for the simultaneous detection of chlorinated, brominated, or mixed halogen-substituted compounds in a single classification. Once developed, the script was applied to the identification of organohalogens in stream sediments collected across the southern region of Ontario (Canada). Classified peaks were first compared with available analytical standards and reference libraries to confirm the known chemicals. Unknown potential persistent organic pollutants (POPs) were evaluated for occurrence within the samples and high resolution mass spectrometry was used in order to identify some of the most prevalent compounds in the samples and resulting in the identification of three decachlorinated dechlorane analogs (C18H14Cl10), two undecachlorinated dechlorane species (C18H13Cl11), and a novel mixed chloro/bromo-carbazole (C12H5NCl2Br2) in a number of sediments analyzed. Relative peak abundances of these unknown halogenated compounds were in the same order of magnitude or slightly higher than levels observed for conventional POPs detected in the samples.

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This paper deals with the characterization and aryl hydrocarbon receptor (AhR) agonist activities of a series of chlorinated, brominated, and mixed bromo/chlorocarbazoles, some of which have been identified in various environmental samples. Attention is directed here to the possibility that halogenated carbazoles may currently be emitted into the environment as a result of the production of carbazole-containing polymers present in a wide variety of electronic devices. We have found that any carbazole that is not substituted in the 1,3,6,8 positions may be lost during cleanup of environmental extracts if a multilayer column is utilized, as is common practice for polychlorinated dibenzo-p-dioxin (dioxin) and related compounds. In the present study, (1)H NMR spectral shift data for 11 relevant halogenated carbazoles are reported, along with their gas chromatographic separation and analysis by mass spectrometry. These characterization data allow for confident structural assignments and the derivation of possible correlations between structure and toxicity based on the halogenation patterns of the isomers investigated. Some halogenated carbazoles exhibit characteristics of persistent organic pollutants and their potential dioxin-like activity was further investigated. The structure-dependent induction of CYP1A1 and CYP1B1 gene expression in Ah-responsive MDA-MB-468 breast cancer cells by these carbazoles was similar to that observed for other dioxin-like compounds, and the magnitude of the fold induction responses for the most active halogenated carbazoles was similar to that observed for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). 2,3,6,7-Tetrachlorocarbazole was one of the most active halogenated carbazoles and, like TCDD, contains 4 lateral substituents; however, the estimated relative effect potency for this compound (compared to TCDD) was 0.0001 and 0.0032, based on induction of CYP1A1 and CYP1B1 mRNA, respectively.