Appendix D: Human Health Risk Assessment - Garfield County ...

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Appendix D Screening Level Human Health Risk Assessment February 2011 Battlement Mesa, Colorado Health Impact Assessment Colorado School of Public Health • Some residents live within ½ mile of more than one well pad and are exposed to emissions from well completion activities for at least 20 months. • A resident, including elderly adult, lives, works, and otherwise stays at the home for 24 hours per day for 20 months. • The air the resident adult breathes, both while indoors and outdoors, contains the same concentration of contaminants measured during odor events in the 2005- 2007 ambient air study. • The concentration of contaminants in ambient air will stay constant over the 20month period. Table 3-2 summarizes intake rates for ambient air. The intake equation for the intermediate exposure scenario follows. AI = (EPCs x EFs x EDs x ET x 1 day/24 hours)/AT AI = Air Intake (µg/m 3 ) EPCs = Subchronic exposure point concentration (µg/m 3 ) EFs = Subchronic exposure frequency = 350 days/year EDs = Subchronic exposure duration = 20 months (1.66 years) ET = Exposure time = 24 hours/day Non-cancer AT = averaging time = 583 days 3.5.4 Child Resident Living Near Well Pad Acute Exposure Assumptions and Intake Equations Only ambient air and surface water pathways were quantitatively evaluated for the child acute exposure scenario because data on which to estimate surface soil EPCs is not available. The acute exposure area for contaminants in ambient air is homes and yards located near a well pad. The acute exposure areas for contaminants in surface water are puddles in the yards of homes adjacent to well pads resulting from well pad run-off during precipitation events. A child resident was evaluated as the receptor for this exposure scenario because a child is more likely to play in a puddle and is a more sensitive receptor than an adult. The acute EPCs for ambient air were the 95% UCL and the maximum detected concentration observed in grab samples collected during odor events in CPDHE’s 2005- 2007 ambient air study and grab samples collected by Antero during well completion activities in August 2010. The EPC for a puddle of surface water run-off was estimated from contaminants observed in snow-melt run-off collected from a well pad within the three-mile radius of the former Project Rulison near Rulison, Colorado (URS 2008), as presented in Table 3-3. The following assumptions for acute exposure of a child resident to contaminants in surface water puddles are used in this HHRA based on EPA methodology. Appendix D page 27
Appendix D Screening Level Human Health Risk Assessment February 2011 Battlement Mesa, Colorado Health Impact Assessment Colorado School of Public Health • A child lives, plays, and otherwise stays at the home for 24 hours per day for 7 days. • The child is 3-6 years old. • The air the child breathes, both while indoors and outdoors, contains the same concentration of contaminants measured during odor events in the 2005-2007 ambient air study. • The concentration of contaminants in ambient air will stay constant over the 7-day period. • The surface water puddle will exist for 7 days before it evaporates or is absorbed into the ground • A child will play for 2 hours per day in the puddle (EPA 2009 and professional judgment). • The child has a body mass of 18.6 kg (EPA 2009) • The child will have an exposed skin surface area (arms, hands, legs, and feet) of 5190 cm 2 (EPA 2009). • The child does not ingest the water. Table 3-3 summarizes intake rates for surface water. The following equations were used to calculate the intake rates for surface water. SWI = [(EPC x ET x EF x ED x CF)/(BW x AT)] x [(PC x SA)] SWI = Surface Water Intake (mg/kg-day) EPC = Exposure Point Concentration (mg/L for surface water, µg/m 3 for air) ET = Exposure Time = 2 hours/day EF = Exposure Frequency = 7 days per year ED = Exposure Duration = 1 year BW = Body Weight = 18.6 kg AT = Averaging time = 7 days PC = chemical-specific dermal permeability constant (cm/hour) SA = exposed skin surface area = 5190 cm 2 CF = conversion factor = 1 L/1000 cm 3 3.5.5 Adult Residents Living Near Well Pad Acute Exposure Assumptions and Intake Equations Only the ambient air pathway was quantitatively evaluated for the adult acute exposure scenario because data on which to estimate surface soil EPCs is not available. The acute exposure area for contaminants in ambient air is homes and yards located near a well pad. The acute EPCs for ambient air for the acute exposure scenarios are described in the preceding section. The following assumptions for acute exposure of an adult resident, including elderly adults, to contaminants ambient air are used in this HHRA based on EPA methodology. Appendix D page 28
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Table 2-3 Comparison of MRLs for 20
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Chemical Number of samples Table 2-
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Table 2-4 Summary Statistics and Se
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Number of Samples Table 2-7 Summary
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Table 2-8 Ambient Air Summary Stati
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Table 2-8 Ambient Air Summary Stati
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Chemical Table 2-9 95% UCLs and Sel
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2010) 4 of 4 Table 2-9 95% UCLs and
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Chemical Table 2-10 95% UCLs and Se
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Chemical Table 2-11 95% UCLs and Se
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Statistic Table 2-12 Comparison of
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Table 3-1 Cancer and Non-Cancer Air
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Table 3-2 Cancer and Non-Cancer Air
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Table 3-3 EPCs and Surface Water In
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Table 4-1 Cancer and Non-Cancer Inh
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4 of 4 Table 4-1 Cancer and Non-Can
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Chemical Available Toxicity Values
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Table 5-1 Baseline Risk Characteriz
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Table 5-2 Comparison of EPCs to BTV
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1 of 2 Table 5-4 Chronic Risk Chara
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1 of 1 Table 5-5 Subchronic Risk Ch
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Table 5-7 Acute Risk Characterizati
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Table 6-1 Chemicals Identified from
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Benzene, Ethylbenzene, and d m&p-Xy
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Sources Potential Releases Exposure
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Excess Canc cer Risk per one Millio
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Appendix D: Human Health Risk Assessment - Garfield County ...

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