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r <br /> 4.4 ESTIMATING CHEMICAL INTAKES <br /> a. <br /> The next step in the exposure assessment was to quantify the magnitude, frequency, and <br /> t-, duration of chemical intakes by receptor populations. This step was conducted in two <br /> stages: (1) estimation of exposure point concentrations, and (2) estimation of chemical <br /> intake for each exposure pathway under consideration. Chemical intakes were calculated <br /> using guidance in Risk Assessment Guidance for Superfund (EPA 1989b) and Exposure <br /> Factors Handbook (EPA 1989x), other EPA documents and scientific journal articles, <br /> site-specific information, and professional judgement regarding exposure conditions, as <br /> appropriate. Chemical intakes were estimated using average and Reasonable Maximum <br /> Exposure (RME) estimates of chemical concentrations in each scenario, reasonable <br /> estimates of exposure parameters such as body weight, inhalation and ingestion rates, <br /> �+. and other assumptions regarding frequency and duration of exposure. The intake factors <br /> used to quantify chemical intakes are presented in Section 4.5 under Exposure <br /> Assumptions. <br /> 4.4.1 Quantifying Average and Reasonable Maximum Exposures (RME) <br /> Intake of a chemical is generally described in units of milligrams (mg) of chemical per <br /> kilogram (kg) of body weight per day (mg/kg/day). The magnitude of exposure to a <br /> chemical (or intake) is a function of exposure point concentration and values that <br /> t`" describe the exposed population (i.e., contact rate, exposure frequency and duration, <br /> body weight, etc.). <br /> Each exposure variable can be described by a range of values. For purposes of this <br /> .. assessment, two measures of exposure were defined using two types of exposure <br /> concepts: (1) an average exposure, and (2) RME. Average and RME exposures were <br /> estimated in accordance with guidance provided in EPA's Risk Assessment Guidance for <br /> Superfund (EPA 1989b). Average exposure values, applying EPA guidance and <br /> professional judgement, were estimated using average values and best conservative <br /> estimates of exposure variables to characterize the population and their normal activity <br /> patterns. Average exposure values are conservative, in that they assume that contact <br /> 4W with contaminated media occurs routinely over the course of many years. <br /> S:\LDC\YELLO.PPT May 4,1995 4-6 <br /> I <br />