Human Health Risk Assessment - Raytheon

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24 Human Health Risk Assessment DRAFT of the subsurface excavation. Estimated outdoor air concentrations in the vicinity of subsurface excavation activities are provided in Table 5. Note that worker protection evaluations administered under OSHA typically require air monitoring as opposed to this type of EPC estimation and that estimation of worker exposure in this scenario is not represented to be an alternative to complying with OSHA requirements. 4.2.5 Subsurface Soil For the purpose of estimating potential exposures to construction or utility workers from incidental ingestion of soil, subsurface soil concentrations in contact with shallow groundwater were estimated assuming equilibrium partitioning with shallow groundwater according to equation (4-12). where: C s C ( θ + ρ K f ) w w b oc oc = (4-12) ρb Cs = Concentration in soil (mg/kg) Cw = Concentration in groundwater (mg/L) θw = Volumetric water content (0.39; unitless) ρb = Dry soil bulk density (1.62 kg/L) Koc = Organic carbon-water partition coefficient (L/kg) foc = Fraction of organic carbon in soil (0.01; unitless) Soil parameters were chosen to be consistent with a loamy sand. Subsurface soil EPCs are provided in Table 5. 4.2.6 Irrigation Water A recent well survey conducted in 2008 identified a number of irrigation wells located within a ½ mile radius of the Site. If these irrigation wells are screened within the area of impacted groundwater, residents may be exposed to COPCs via dermal contact with irrigation water, inhalation of COPCs volatilized during irrigation and incidental ingestion. In addition, if residents are involved in gardening activities and irrigate their crops with well water, residents could be exposed to COPCs from incidental ingestion of surface soils during gardening and ingestion of homegrown produce. Recreational use of irrigation water to fill a child’s wading pool or operate a sprinkler for children to play in has also been evaluated. Potential outdoor air concentrations generated by volatilization of constituents during lawn irrigation were estimated by assuming an upper bound estimate of the fraction of COPCs volatilized to outdoor air. The fraction volatilized from groundwater during irrigation was estimated using the procedure described by McKone (1987) where the transfer efficiency from
25 Human Health Risk Assessment DRAFT water to air is estimated relative to the transfer efficiency for radon. This procedure assumes that the transfer efficiency is proportional to the overall mass transfer coefficient at the air/water boundary layer. The volatilized COPCs are released into a “box” and resulting outdoor air concentrations are estimated using equation (4-3). The emission rate of volatile COPCs into the box is calculated based on an assumed irrigation rate of one inch per hour applied over a 2500 square foot area. This rate is consistent with recommended values provided by the University of Florida Institute of Food and Agricultural Sciences for Florida lawns. 8 The corresponding volume rate of water applied to the lawn is approximately 1.64 liters per second or 26 gallons per minute and the emission rate of volatile COPCs into the atmosphere is calculated according to equation (4-13). where: Eirr = Emission rate during irrigation (mg/m 2 -s) E irr Cirr ⋅ ARirr ⋅ f = (4-13) A Cirr = Concentration of constituent in irrigation water (mg/L) ARirr = Irrigation water application rate (L/s) f = Fraction volatilized to outdoor air (unitless) A = Area of lawn irrigated (m 2 ) and the fraction volatilized to outdoor air is chemical specific and calculated according to the equation below (McKone, 1987) where: f COPC = f Radon ⎛ 2. 5 ⎜ ⎝ D ⎛ 2. 5 ⎜ ⎝ D 2 / 3 w 2 / 3 w R T ⎞ + Da H ⎟ 2 / 3 ⎠ R T ⎞ + Da H ⎟ 2 / 3 ⎠ Radon COPC fCOPC = Fraction of COPC volatilized to outdoor air fRadon = Fraction of radon volatilized to outdoor air (assumed to be 100%) Da = Diffusivity in air (cm 2 /s) Dw = Diffusivity in water (cm 2 /s) 8 http://polkfyn.ifas.ufl.edu/lawn_irrigation_guide.shtml (4-14)
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Page 5 and 6: Executive Summary 1 Human Health Ri
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Page 21 and 22: • Inhalation of Outdoor Air On-Si
Page 27: u = Wind speed (m/s) 23 Human Healt
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Page 35 and 36: where: DAD = Dermal absorbed dose (
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Page 41 and 42: non-carcinogenic effects (µg/L) Ri
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Page 59 and 60: 7 Uncertainty Analysis 55 Human Hea
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Page 75 and 76: DRAFT Table 6. Summary of Exposure
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Human Health Risk Assessment DRAFT
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DRAFT Primary Primary Secondary Sec
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DRAFT Table A-1. Dose and Risk Calc
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DRAFT CSFd RfDd DA event C w DAD LA
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DRAFT CSFd RfDd DA event C w DAD LA
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DRAFT Table A-13. Dose and Risk Cal
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