The available information on polychlorinated dibenzofurans is scant. For this reason, staff utilized information about polychlorinated dibenzo-p-dioxins in the assessment. The scientific theory that supports the use of the analogy is sound. Both groups of substances are thought to cause biological effects by binding with different affinities to the same intracellular receptor molecule. However, the draft document assumes the theory for one plausible effect of receptor binding, namely developmental abnormalities, and not for other effects which have been attributed to polychlorinated dibenzo-p-dioxins in previous Agency assessments, such as carcinogenicity. The Subcommittee requests that EPA either assume the same theory for all effects or provide an explanation of why carcinogenic effects do not follow from binding to the receptor.