proaches to dose metrics. Chapter 4 addresses exposure characterization in terms of sources, environmental fate, environmental media concentrations, food concentrations, background exposures, and potentially highly exposed populations. Chapter 5 reviews EPA’s assessment of the carcinogenicity of TCDD other TCDD, other dioxins, and DLCs, including the qualitative characterization of their carcinogenicity, the validity of the nonthreshold linear dose-response model, and the use of the animal bioassay and epidemiological data to quantify the dose response. Chapter 6 reviews EPA’s assessment of noncancer end points, including immune function, reproduction, and development. Chapter 7 focuses on risk characterization. Chapter 8 summarizes the committee’s conclusions and recommendations and succinctly addresses each component of the statement of task.