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'M'’ <br />i» <br />’ • 4.5 Vr’- <br />,' K '.i . <br />h/ •:*■ " . <br />- '-r <br />‘V- - • <br />5'}’. <br />y?.; <br />).f;- <br />A <br />‘i. <br />w <br />1^. <br />fe <br />It.^v-- <br />■m\ <br />s4S'.j <br />92-47.OS <br />constituents deposited on soils were assumed to be deposited <br />within only a depth of 2 centimeters beneath the surface, <br />providing the highest possible relative concentration (this <br />assumption is only valid for the food chain model and not <br />for purposes of leaching to groundwater). since none of the <br />contaminants are significantly volatile, and soil organic <br />carbon content of 1 percent was used in the model, minimal <br />soil losses of contaminants due to leaching and <br />volatilization were assumed. Additionally, it was assumed <br />that the total contaminant concentrations in soil were <br />bioavailable. <br />Contaminant biotransfer (BTF) and bioconcentration factors <br />(BCF) were obtained from the published literature <br />(U.S. EPA, 1980, 1985; ATSDR, 1988) for specific matrices <br />and constituents, when available, or derived from related <br />chemical and matrix data. For example, predominant metal <br />species solubilities, partition coefficients, and other <br />environmental fate data were used in the derivation of BTFs <br />and BCFs (Lym? , 1982; Dragun, 1988; Verschueren, 1983; <br />Bowen, 1966). <br />Contaminant concentrations used in the assessment were <br />assumed to reflect the most toxic and environmentally <br />critical species of each constituent. For example, total <br />chrome amounts were assumed to be 100 percent hexavalent <br />chrome, the more toxic valence state of the metal <br />(Sax, 1989). <br />Generous human food consumption rates were assumed, <br />following current U.S. Department of Agriculture statistics <br />(U.S. NRC, 1977). <br />In the evaluation of contaminant bioconcentration in fish <br />tissues, a 10,000 square meter watershed was assumed as the <br />source of contaminated surface soil runoff to a 950 square <br />meter pond, in addition to contaminants contributed by air <br />concentration deposition. <br />MAJOR C0MCLU8X0NS OF STUDY <br />The results of this Health Ris)c Assessment clearly <br />demonstrate that despite the extremely conservative assumptions <br />employed in this assessment, there is no significant human health <br />ris)c due to the use of TAP as a replacement for a portion of the <br />aggregate in a section of bituminous pavement. In fact, the <br />local air quality and the health of the local residents will be <br />improved by paving the road. In addition, the beneficial effects <br />17