Polychlorinated carbazoles usually occur as a mixture of various isomers. This mixture can have a certain frequency pattern (congener pattern) from which conclusions can be drawn about the causes of formation.
PCCZs are not manufactured purposefully. They are formed under certain conditions as by-products of thermal processes. In environmental samples, mixed halogenated carbazoles are also found.[1][2]
Juliane Kirst: Synthesis of polyhalogenated carbazoles and total synthesis of amaryllidaceae alkaloids pratosine and hippadine. Dissertation, Dresden, 2009. (in German) DNB-IDN100727316X/34
^M. Pena-Abaurrea, K. J. Jobst, R. Ruffolo, L. Shen, R. McCrindle, P. A. Helm, E. J. Reiner: Identification of Potential Novel Bioaccumulative and Persistent Chemicals in Sediments from Ontario (Canada) Using Scripting Approaches with GC×GC-TOF MS Analysis. Environ. Sci. Technol., 2014, 48(16), 9591–9599, doi:10.1021/es5018152.
^J. Guo, D. Chen, D. Potter, K. J. Rockne, N. C. Sturchio, J. P. Giesy, A. Li: Polyhalogenated Carbazoles in Sediments of Lake Michigan: A New Discovery. Environ. Sci. Technol., 2014, 48(21), 12807–12815, doi:10.1021/es503936u.