A summary of the 209 PCB congener nomenclature.

Primary publications of congener numbering shorthand systems for PCB congener identification were reviewed, including the original Ballschmiter-Zell (BZ) system; recommended changes by Schulte and Malisch, and Guitart et al.; and listings by the Chemical Abstracts Service. Comparisons of the various congener numbering shorthands and chlorine substitution numberings in the structural name listings are presented. Several changes, to adhere more closely to IUPAC rules, have been incorporated into the BZ structural nomenclature, and these resulted in renumbering congeners. These corrected listings have been erroneously identified as "IUPAC" numbers, a misnomer, because IUPAC has not published a shorthand system. Guitart pointed out additional inconsistencies with IUPAC rules for nine congeners which would result in further order changes, but did not recommend renumbering, to avoid further confusion. We noted an additional error in the structural name for congener 97, named 2,2',3',4,5 using Ballschmiter and Zell nomenclature and 2,2',3,4',5' using strict IUPAC nomenclature. This renaming would cause the renumbering of the IUPAC number system reported by Guitart for isomers 91 through 98. No further changes are recommended, however. Tables summarizing each publication, and the discrepancies between them are provided in hopes of clarifying the current state of the nomenclature.