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SAFEWAY MEATPACKING G FACII.rrY, STOCKTON, CALIFORNIA <br /> TIER 11 RISK BASED CORRECTIVE ACTION <br /> FEBRUARY 26, 1996 <br /> PAGE 3 - 1 <br /> 3.0 EXPOSURE PATHWAY EVALUATION <br /> An exposure assessment describes the intensity, frequency, and duration of human contact with <br /> a chemical in the environment An exposure pathway is a route by which the chemical is <br /> contacted, they are determined by environmental conditions, the potential for the chemical to <br /> move from one medium to another, and the general lifestyles of the potentially exposed <br /> population (e g , time spent inside and outside a building) Although several potential pathways <br /> may exist, only a few may be complete If a pathway is incomplete, these is no potential for <br /> exposure to a COI For a pathway to be complete, each of the following elements must exist <br /> (USEPA, 1989a) <br /> 1 A source and mechanism for release <br /> 2 An environmental transport medium (soil, soil gas, groundwater, surface <br /> water) <br /> 3 A point of potential human contact with the medium, and <br /> 4 A human exposure route at the contact point (i e , inhalation, ingestion, or <br /> dermal contact) <br /> The occurrence of a chemical in an environmental medium does not indicated that there is a <br /> complete exposure pathway In addition,the determination that a pathway is potentially complete <br /> does not indicated that the detected compounds are harmful to health under the specific exposure <br /> scenarios or that actual exposure occurs <br /> The ASTM standard considers six possible exposure pathways (it also includes calculations of <br /> maximum allow air and groundwater concentrations, AirOut-Inh and GW-DW, respectively in <br /> Tables 9 and 10) Of these pathways, only two are potentially complete for routine site <br /> D131CDJ1 <br />