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1^:, <br />/■' <br />e®;. <br />;:•*i: <br />5^: <br />'-^- V- <br />92 4 -T <br />“• 4 / . J D <br />They are designed for prevention of human health effects <br />associated with lifetime exposure (70-year lifetime) of an <br />average adult (70 kg) consuming 2 liters of water per day. <br />ivmhi ant Water Quality Criteria (Awoc) - AWQC are <br />nonenforceable regulatory guidelines that are used to <br />identify a contaminant's potential effects on aquatic <br />species. AWQCs are research based minimum surface water <br />concentrations which reflect acute and chronic effects in <br />aquatic species. <br />Rsfarence Dose (RfD) - RfDs were developed by the U.5. EPA <br />for chronic and/or subchronic human exposure to hazardous <br />chemicals and are based solely on the nonca:;cinogenic <br />effects of chemical substances. It is expressed in <br />mg/kg/day and is calculated by dividing the no observable <br />adverse effect level (NOAEL) or the lowest observed adverse <br />effect level (LOAEL) of a chemical by a series of <br />uncertainty factors a’"d modifying factors. The reference <br />dose can be multiplied by the weight of an adult (70 kg) to <br />obtain an acceptable daily intake (ADI) for an adult. <br />Although the RfD is an acceptable luideline for the <br />evaluation of noncarcinogenic risk, t.ie associated <br />uncertainties in the modification of a particular NOAEL <br />preclude its use in precise risk quantitation. <br />Carcinogenic Slope Factor (C8F) - csFs are applicable for <br />estimating the lifetime probability (assumed 70-year life <br />span) of human receptors contracting cancer as a result of <br />exposure to known or suspected carcinogens. This factor is <br />generally reported in units of kg/day/mg, and is derived <br />through an assumed low-dosage linear relationship and the <br />extrapolation from high to low dose-responses determined <br />from animal studies. The CSF is the upper bound slope of <br />the dose-response curve as determined by the U.S. EPA <br />multistage dose-response model (U.S. EPA, 1987). <br />Exposure Assessment <br />This component of the risk assessment evaluates the <br />potential for human and environmental confact (exposure) with the <br />contaminants identified in the three roadway materials. A <br />complete exposure pathway has four components: (1) a source of <br />chemicals released to the environment; (2) a route of contaminant <br />transport through an environmental media; (3) an exposure or <br />contact point; and (4) the presence of a human or environmental <br />receptor at the exposure point. Exposure pathways, =. r means of <br />contact, with contaminants considered in this assessment include: <br />]