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Superfund and Mining Megasites: Lessons from the Coeur d'Alene River Basin (2005)

Chapter: Appendix D Procedures Used in Model Comparisons

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Suggested Citation:"Appendix D Procedures Used in Model Comparisons." National Research Council. 2005. Superfund and Mining Megasites: Lessons from the Coeur d'Alene River Basin. Washington, DC: The National Academies Press. doi: 10.17226/11359.
×

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

Suggested Citation:"Appendix D Procedures Used in Model Comparisons." National Research Council. 2005. Superfund and Mining Megasites: Lessons from the Coeur d'Alene River Basin. Washington, DC: The National Academies Press. doi: 10.17226/11359.
×

TABLE D-1 FSPA06 Data Used in Calculations

House

Arithmetic Mean of Yard Soil, 0-1 in. (mg/kg)

Geometric Mean of Community Soil (mg/kg)

Vacuum Bag Dust

House

Arithmetic Mean of Yard Soil, 0-1 in. (mg/kg)

Geometric Mean of Community Soil (mg/kg)

Vacuum 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

Suggested Citation:"Appendix D Procedures Used in Model Comparisons." National Research Council. 2005. Superfund and Mining Megasites: Lessons from the Coeur d'Alene River Basin. Washington, DC: The National Academies Press. doi: 10.17226/11359.
×

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.

Suggested Citation:"Appendix D Procedures Used in Model Comparisons." National Research Council. 2005. Superfund and Mining Megasites: Lessons from the Coeur d'Alene River Basin. Washington, DC: The National Academies Press. doi: 10.17226/11359.
×

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 comparison 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

Suggested Citation:"Appendix D Procedures Used in Model Comparisons." National Research Council. 2005. Superfund and Mining Megasites: Lessons from the Coeur d'Alene River Basin. Washington, DC: The National Academies Press. doi: 10.17226/11359.
×

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 residential soil, and 30% derived from the community-wide soils; and (2) bioavailability 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 individual 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 (TerraGraphics 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 bioavailability 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 exhibits 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 executable 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: Evaluation 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 Protection 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.

Suggested Citation:"Appendix D Procedures Used in Model Comparisons." National Research Council. 2005. Superfund and Mining Megasites: Lessons from the Coeur d'Alene River Basin. Washington, DC: The National Academies Press. doi: 10.17226/11359.
×

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 Department 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 Protection 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.

Suggested Citation:"Appendix D Procedures Used in Model Comparisons." National Research Council. 2005. Superfund and Mining Megasites: Lessons from the Coeur d'Alene River Basin. Washington, DC: The National Academies Press. doi: 10.17226/11359.
×
Page 447
Suggested Citation:"Appendix D Procedures Used in Model Comparisons." National Research Council. 2005. Superfund and Mining Megasites: Lessons from the Coeur d'Alene River Basin. Washington, DC: The National Academies Press. doi: 10.17226/11359.
×
Page 448
Suggested Citation:"Appendix D Procedures Used in Model Comparisons." National Research Council. 2005. Superfund and Mining Megasites: Lessons from the Coeur d'Alene River Basin. Washington, DC: The National Academies Press. doi: 10.17226/11359.
×
Page 449
Suggested Citation:"Appendix D Procedures Used in Model Comparisons." National Research Council. 2005. Superfund and Mining Megasites: Lessons from the Coeur d'Alene River Basin. Washington, DC: The National Academies Press. doi: 10.17226/11359.
×
Page 450
Suggested Citation:"Appendix D Procedures Used in Model Comparisons." National Research Council. 2005. Superfund and Mining Megasites: Lessons from the Coeur d'Alene River Basin. Washington, DC: The National Academies Press. doi: 10.17226/11359.
×
Page 451
Suggested Citation:"Appendix D Procedures Used in Model Comparisons." National Research Council. 2005. Superfund and Mining Megasites: Lessons from the Coeur d'Alene River Basin. Washington, DC: The National Academies Press. doi: 10.17226/11359.
×
Page 452
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For more than 100 years, the Coeur d’ Alene River Basin has been known as "The Silver Valley" for being one of the most productive silver, lead, and zinc mining areas in the United States. Over time, high levels of metals (including lead, arsenic, cadmium, and zinc) were discovered in the local environment and elevated blood lead levels were found in children in communities near the metal-refining and smelter complex. In 1983, the U.S. Environmental Protection Agency (EPA) listed a 21-square mile mining area in northern Idaho as a Superfund site. EPA extended those boundaries in 1998 to include areas throughout the 1500-square mile area Coeur d'Alene River Basin project area. Under Superfund, EPA has developed a plan to clean up the contaminated area that will cost an estimated $359 million over 3 decades--and this effort is only the first step in the cleanup process. Superfund and Mining Megasites: Lessons from Coeur d'Alene River Basin evaluates the issues and concerns that have been raised regarding EPA’s decisions about cleaning up the area. The scientific and technical practices used by EPA to make decisions about human health risks at the Coeur d'Alene River Basin Superfund site are generally sound; however, there are substantial concerns regarding environmental protection decisions, particularly dealing with the effectiveness of long-term plans.

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