Haws, L. Roundtable: Is it time to reevaluate the toxic equivalency factors for PCDDs, PCDFs, and dioxin-like PCBs? The use of toxicity equivalence factors (TEFs) for PCDDs, PCDFs, and dioxin-like PCBs in risk assessment: Improving the process. Dioxin 2004. September Berlin, Germany, September 2004.