Appendix D
Procedures Used in Model Comparisons

Similar to the Agency for Toxic Substances and Disease Registry (ATSDR) Health Consultation (ATSDR 2000), data from the Field Sampling Plan Addendum (FSPA06) conducted in support of the remedial investigation (RI) (URS Greiner and CH2M Hill 2001) were used in this analysis. For the present study, however, the number of homes was slightly different for two reasons: (1) data for two houses originally tabulated in the RI were not used in the ATSDR comparison—these were added for the committee comparisons. (2) The ATSDR analysis used geometric mean house-dust values for seven houses where those data were not originally collected. In the present comparison, those houses were dropped from consideration, and the results are based solely on residences where both soil and house dust measurements were available. The data set used in these calculations (referred to below as the 75 homes’ data) is presented in Table D-1 of this appendix.

THE ONTARIO MINISTRY OF ENVIRONMENT AND ENERGY BIOKINETIC SLOPE FACTOR MODEL

The Ontario Ministry of Environment and Energy (OMOEE) has established an intake of 3.7 micrograms (μg) lead per kilograms (kg) of body weight/day as the level of intake for which more than 95% of children will have blood lead values less than 10 μg per deciliter (dL). This intake of concern (IOC) is divided by 2 to provide a safety factor; the resulting IOC is 1.85 μg of lead/kg of body weight/day. For the model comparisons, lead



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Appendix D Procedures Used in Model Comparisons Similar to the Agency for Toxic Substances and Disease Registry (ATSDR) Health Consultation (ATSDR 2000), data from the Field Sam- pling Plan Addendum (FSPA06) conducted in support of the remedial in- vestigation (RI) (URS Greiner and CH2M Hill 2001) were used in this analysis. For the present study, however, the number of homes was slightly different for two reasons: (1) data for two houses originally tabulated in the RI were not used in the ATSDR comparison—these were added for the committee comparisons. (2) The ATSDR analysis used geometric mean house-dust values for seven houses where those data were not originally collected. In the present comparison, those houses were dropped from con- sideration, and the results are based solely on residences where both soil and house dust measurements were available. The data set used in these calculations (referred to below as the 75 homes’ data) is presented in Table D-1 of this appendix. THE ONTARIO MINISTRY OF ENVIRONMENT AND ENERGY BIOKINETIC SLOPE FACTOR MODEL The Ontario Ministry of Environment and Energy (OMOEE) has es- tablished an intake of 3.7 micrograms (µg) lead per kilograms (kg) of body weight/day as the level of intake for which more than 95% of children will have blood lead values less than 10 µg per deciliter (dL). This intake of concern (IOC) is divided by 2 to provide a safety factor; the resulting IOC is 1.85 µg of lead/kg of body weight/day. For the model comparisons, lead 447

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448 TABLE D-1 FSPA06 Data Used in Calculations Arithmetic Geometric Arithmetic Geometric Mean of Mean of Mean of Mean of Yard Soil, Community Yard Soil, Community 0-1 in. Soil Vacuum 0-1 in. Soil Vacuum House (mg/kg) (mg/kg) Bag Dust House (mg/kg) (mg/kg) Bag Dust 1 663 419 606 38 278 419 427 2 804 419 480 39 1,423 568 1,020 3 174 419 764 40 364 352 341 4 448 419 173 41 766 628 682 5 4,796 110 3,140 42 769 419 23 6 1,189 419 1,000 43 688 368 1,820 7 1,610 628 1,620 44 16,026 771 6,150 8 1,080 419 978 45 718 568 2,430 9 870 419 528 46 503 419 769 10 259 419 390 47 500 568 387 11 623 257 525 48 3,054 568 2,730 12 239 257 422 49 843 568 619 13 979 419 154 50 852 771 3,300 14 290 257 389 51 56 368 626 15 665 257 765 52 319 419 504 16 342 419 332 53 256 419 492 17 760 419 1,260 54 3,026 419 621

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18 3,491 352 604 55 787 419 1,550 19 5,566 628 1,960 56 735 257 315 20 794 419 1,200 57 544 368 504 21 1,014 568 1,660 58 642 568 384 22 276 352 680 59 353 368 833 23 796 419 818 60 2,711 568 353 24 871 419 512 61 1,165 771 778 25 451 771 639 62 188 257 232 26 1,337 771 1,350 63 284 568 1,680 27 1,687 771 798 64 563 419 655 28 977 419 808 65 2,701 628 1,540 29 813 568 703 66 1,194 352 937 30 438 568 84 67 1,094 771 780 31 682 419 762 68 2,788 568 1,380 32 622 568 349 69 479 568 727 33 1,322 628 767 70 1,381 568 405 34 437 568 383 71 321 771 942 35 1,576 568 1,020 72 3,837 419 362 36 827 628 710 73 2,861 628 2,840 37 3,603 568 1,020 74 694 368 2,400 75 807 419 1,000 SOURCE: Data provided by Idaho Department of Health and Welfare, unpublished material, 2004. 449

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450 APPENDIX D intake from soils, dusts, water, air, and food is calculated from measured media concentrations and added to background default levels in non- measured media. The factor by which the estimated intake exceeds the IOC is obtained by dividing the result by 1.85 µg lead/kg body weight/day. The percentage of locations for which exposure estimates are less than a factor of 2 above the IOC is taken as the percentage of children whose blood lead values are less than 10 µg/dL. BATCH OPERATION OF THE INTEGRATED EXPOSURE UPTAKE BIOKINETIC MODEL The 75 homes’ data were used for blood lead estimates using the batch mode capability of the integrated exposure uptake biokinetic (IEUBK) model. For these comparisons, the estimated blood lead level at an age of 20 months was obtained. This age matches closely the age corresponding to maximum blood lead concentration and also corresponds approximately to the 16 kg body weight for which the OMOEE IOC computation is made. IMPLEMENTATION OF THE O’FLAHERTY MODEL The physiologically based, transport limited biokinetic model of O’Flaherty (O’Flaherty 1998) was applied to the 75 homes’ data for com- parison with the other models. Such comparisons are not exact because of differences in how the models specify input of exposure regimes and the way bioavailability is incorporated in the computations. Another impediment is the sensitivity of the O’Flaherty model to year of birth for the individual being simulated. As noted in the TRW adult lead model review (EPA 2001, Appendix K), a variety of model parameters may be adjusted in the exposure specifications to establish baseline conditions against which variations in soil and dust lead concentrations may be examined. For the O’Flaherty model implementation here (Advanced Continuous Simulation Language [ACSL] platform) the following variable values were used for model runs: year of birth, yob = 1980; frlung = 0.32 (bioavailability of inhaled lead—same as IEUBK); cair2 = 0.1 µg/m3 (same as IEUBK); concentration of lead in water, cwater = 4 µg/L (same as IEUBK); rfood2 = 20 µg of lead/day ingested by adult; rfood3 = 15 µg lead/day ingested by child; and the concentration of lead in infant formula, cfmla = 0.01 µg/L. For tabulation in Table 6-3, the midpoint between blood lead at ages 12 and 24 months was used. ADAPTATION OF MODELS FOR PREDICTIONS UNDER THE BUNKER HILL SUPERFUND SITE “BOX MODEL” CONDITIONS The study of von Lindern et al. (2003) established a set of IEUBK model conditions that best fit the observed blood lead distribution for

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APPENDIX D 451 children living within the Bunker Hill Superfund site (BHSS). Discussion of this model and an evaluation of its application to predictions of blood lead levels for children living in the Coeur d’Alene River basin outside the BHSS box is detailed in the body of the report. Important points for the present comparison of model results are as follows: (1) the soil and dust exposure regime was weighted as 40% from household dusts, 30% from the residen- tial soil, and 30% derived from the community-wide soils; and (2) bio- availability for soil and dust ingestion was set at 18%. Soil lead values for the 75 homes’ data (BHSS box conditions) were tabulated on a geographical location basis as the average between the indi- vidual residential lot surface-soil value and the geometric mean soil value for the community where the residence was located. The latter values were derived from the human health risk assessment for operable unit 3 (Terra- Graphics et al. 2001, Table 6-48). To account for the lower bioavailability of lead in soils and dusts used in the box model, concentration values for these inputs were reduced to 60% of their original values before each model’s invocation. This corresponds approximately to the change in bio- availability used in the box model version of the IEUBK model, since the default bioavailability from soil in the IEUBK is 30%. This approach was adopted because bioavailability, the fraction of lead intake that is taken up in the blood, could not be adjusted in the ATSDR model. The modification of the soil concentration achieves the same effect, because the model ex- hibits a linear response over the concentration ranges of interest. In the O’Flaherty model, the user cannot specify bioavailability, but the ACSL program constants were adjusted to reflect 40% dust and 60% soil inputs to the exposure module of the program. The O’Flaherty model uses age- specific soil/dust-ingestion rate functions that are not accessible in the ex- ecutable program structure but whose average value is about 60% of the average IEUBK default ingestion regime. REFERENCES ATSDR (Agency for Toxic Substances and Disease Registry). 2000. Health Consultation. Coeur d’Alene River Basin Panhandle Region of Idaho Including Benewah, Kootenai and Shoshone Counties. Office of Regional Operations, Region 10, Agency for Toxic Substances and Disease Registry, U.S. Public Health Service, Department of Health and Human Services [online]. Available: http://www.atsdr.cdc.gov/HAC/PHA/basinres/bas_ toc.html [accessed Jan. 4, 2005]. EPA (U.S. Environmental Protection Agency). 2001. Review of Adult Lead Models: Evalua- tion of Models for Assessing Human Health Risks Associated with Lead Exposures at Non-Residential Areas of Superfund and Other Hazardous Waste Sites. OSWER #9285.7-46. Office of Solid Waste and Emergency Response, U.S. Environmental Pro- tection Agency, Washington, DC. August 2001 [online]. Available: http://www.epa.gov/ superfund/programs/lead/products/adultreview.pdf [accessed Jan. 3, 2005]. O’Flaherty, E.J. 1998. A physiologically based kinetic model for lead in children and adults. Environ. Health Perspect. 106(Suppl. 6):1495-1503.

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452 APPENDIX D TerraGraphics/URS Greiner/CH2M Hill. 2001. Final Human Health Risk Assessment for the Coeur d’Alene Basin Extending from Harrison to Mullan on the Coeur d’Alene River and Tributaries, Remedial Investigation/Feasibility Study. Prepared for Idaho Depart- ment of Health and Welfare, Division of Health, Idaho Department of Environmental Quality, U.S. Environmental Protection Agency Region X, Seattle, WA, by TerraGraphics Environmental Engineering, Inc, URS Greiner in association with CH2M Hill [online]. Available: http://www.epa.gov/r10earth/offices/sf/BH_HHRA_final/TableOfContents.pdf [accessed Jan. 3, 2005]. URS Greiner, Inc., and CH2M Hill. 2001. Final (Revision 2) Remedial Investigation Report, Remedial Investigation Report for the Coeur d’Alene Basin Remedial Investigation/ Feasibility Study. URSG DCN 4162500.6659.05a. Prepared for U.S. Environmental Pro- tection Agency, Region 10, Seattle, WA, by URS Greiner, Inc., Seattle, WA, and CH2M Hill, Bellevue, WA. September 2001. von Lindern, I.H., S.M. Spalinger, V. Petroysan, and M. von Braun. 2003. Assessing remedial effectiveness through the blood lead: Soil/dust relationship at the Bunker Hill Superfund Site in the Silver Valley of Idaho. Sci. Total Environ. 303(1-2):139-170.