tions described earlier in the TSD. If some other set of assumptions is being used, then it should be documented how those assumptions lead to the equations of p. A-18. In the computer code, both sets of equations are present, and indeed both are executed; but only the second has any effect.

  1. On page A-19 of the TSD, equations B-7e and B-7l contradict the statements made under MCORT(t) on page B-9, and MTRAB(t) on page B-11. In both cases, it is stated that there is an assumption that the bone (cortical or trabecular) lead concentration/blood lead concentration ratio is equal to the bone (composite) lead concentration/blood lead concentration ratio (so cortical and trabecular bone lead concentration/blood lead concentration ratios should be equal). Equations B-73 and B-7l give different concentration ratios (78.9 for cortical, 51.2 for trabecular).

  2. Equations B-4a through B-4d (p. A-9) are stated (p. B-4 and B-5) to come from an analysis of the data of Barry (1981). However, at age 0 they are contradicted by the initialization conditions given in equations B-7e through B-7l (p. A-17), which are said to be based on the same data (p. B-9, B-10, B-11). For kidney, liver, and other tissues, the tissue/blood concentration ratios implied by equations B-4a, B-4b, and B-4d at time 0 are 0.777, 1.1, and 0.931 L/kg, whereas equations B-7f, B-7g, and B-7h give 1.06, 1.30, and 1.60 L/kg, respectively. Here is another internal inconsistency, because equation B-4c gives a bone/blood concentration ratio of 6.0 L/kg at t = 0, whereas equations B-7e and B-7f give separate ratios at t = 0 of 7.89 and 5.12 L/kg for cortical and trabecular bone, respectively.

REFERENCES

Barry, P.S. 1981. Concentrations of lead in the tissues of children. Br. J. Ind. Med. 38(1): 61-71.


EPA (U.S. Environmental Protection Agency). 1994. Technical Support Document: Parameters and Equations Used in the Integrated Exposure Uptake Biokinetic (IEUBK) Model for Lead in Children (v 0.99d). EPA/540/R-94/040. OSWER 9285.7-22. PB94-963505. Office of Solid Waste and Emergency Response U.S. Environmental Protection Agency, Washington, DC [online]. Available: http://www.epa.gov/superfund/programs/lead/products/tsd.pdf [accessed Jan. 4, 2004].

EPA (U.S. Environmental Protection Agency). 2002. System Requirements and Design For The Integrated Exposure Uptake Biokinetic Model For Lead In Children (IEUBK) Windows Version – 32-Bit Version. OSWER 9285.7-43. Office of Solid Waste and Emergency Response, U.S. Environmental Protection Agency, Washington, DC. May 2002 [online]. Available: http://www.epa.gov/superfund/programs/lead/products.htm [accessed Oct. 11, 2005].



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement