Established and deduced aromatic hydrocarbon (Ah) receptor (AhR) agonists and their relative potency

This list is dedicated to provide an explanation for the gap between TCDD toxic equivalent (TEQ) levels apparently observed in environmental samples by bioanalytical methods and TEQ levels calculated from chemical analysis using toxic equivalency (TEF) factors. More specifically, the compounds in this list which are shown with one or more relative potency values of any kind have been preselected by the RIKZ research institution (Groningen, The Netherlands) because of their possible relevance to sediment samples form the Zeehavenkanaal (Delfzijl, The Netherlands) from a more elaborate list including less relevant AhR agonists, such as AhR agonists originating from living organisms (these have been added as an appendix of compound names). The purpose if this list is to provide a value for the relative potency as an AhR agonist for as many of these relevant compounds as possible, and, when available, a value suitable for the calculation of reliable TEQ levels from chemically determined compound levels. In this way, the TEQ contribution for as many compounds found in the Zeehavenkanaal samples as possible will be assessed in order to diminish the gap between TEQ levels measured by the DR-CALUX reporter gene assay and those calculated on the basis of chemical levels. Therefore, if several different relative potency (REP) parameters are available for a compound, priority has been given to a REP/TEF value based on CALUX analysis, followed by other categories of relative potency values in the rank order as indicated below: 1. CALUX-based REP values 2. TEF values based on expert judgement and resulting from carefully weighted AhR-mediated toxic and biochemical endpoints 3. Other experimentally determined relative potency values (CYP1A/EROD/AHH induction potencies; AhR binding affinities, etc.) 4. REP values calculated on the basis of quantitative structure-activity relationship (QSAR) analysis If several sources give inconsistent information on a certain compound, more then one value may be listed in order to allow further evaluation of the most appropriate value and re-evaluation on the basis of obtained preliminary results