D. Tillitt L. Eriksson K. Lundgren C. Rappe M. Tysklind 1994 <div id="abstract-1" class="section abstract"><p id="p-1">The ethoxyresorufin <i>O</i>-deethylase (EROD) induction of 20 polychiorinated dibenzofurans (PCDFs) was examined in the H4IIE rat hepatoma cell bioassay. The selection of the compounds tested was based on a multivariate chemical characterization laying the groundwork for covering the whole chemical series of PCDFs. The EROD induction potency was found to vary in ED50 values from 25 to 100,000,000 pg/mg, i.e., nearly seven orders of magnitude. The response of the bioassay was calibrated against the 2,3,7,8-tetrachlorodibenzo-<i>p</i>-dioxin, enabling the corresponding toxic equivalency factors (TEFs) to be calculated. In order to establish a quantitative structure-activity relationship (QSAR) for the TEF values, 37 physicochemical descriptor variables were used to chemically characterize the 87 tetra- to octachlorinated PCDFs. Using partial least-squares modeling on a training set of 10 congeners, a QSAR model with sound predictive power was obtained. The QSAR model was validated with a validation set of additional 10 congeners. The predicted TEFs indicate that a large number of congeners are potent EROD inducers.</p></div><div id="fn-group-1" class="section fn-group"><br data-mce-bogus="1"></div> application/pdf 10.1093/toxsci/22.2.277 en Oxford Journals A toxic equivalency factor scale for polychlorinated dibenzofurans article