US EPA

The Integrated Exposure Uptake Biokinetic (IEUBK) Model for Lead in Children was developed by the U.S. EPA to support assessments of health risks from exposures of children to Pb (lead). This report documents the performance evaluation of the IEUBK v2.0 model as it would be typically applied at Superfund sites to predict blood lead levels (BLLs) in populations of children. The IEUBK v2.0 model was evaluated by comparing model predictions of BLLs to approximately 1200 observed BLLs in a population of children at the Bunker Hill Mining and Metallurgical Complex Superfund Site (BHSS) for which there were paired estimates of environmental Pb concentrations. Predicted site-wide population geometric mean (GM) BLLs (GM: 3.4 μg/dL, 95% confidence interval [CI]: 3.3, 3.5) were within 0.26 μg/dL of the observed GM (3.6 μg/dL, 95% CI: 3.5, 3.8).

The model predicted the observed age trend in GM BLLs and explained approximately 90% of the variance in the observed age-stratified GM BLLs. Differences (predicted minus observed) between area-stratified GM BLLs ranged from -0.44 to +0.36 μg/dL (mean difference: -0.1 μg/dL). The predicted site-wide probability of exceeding 5 μg/dL (P5) was 26.7% (95% CI: 24.0, 29.1) and within 5.5% of observed P5 (32.1%, CI: 29.4, 34.8). Differences between area-stratified P5 values ranged from -10.8 to +13.8%.

Although the more general applicability of these findings remains to be determined in future studies of other populations, these results support applications of the IEUBK v2.0 model for informing risk-based discussions regarding remediation of soils and mitigation of exposures at Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) sites where the majority of the exposure unit GM BLLs are expected to be ≤5 μg/dL.

The IEUBK Model for Lead in Children was developed by the U.S. EPA to support assessments of health risks from exposures of children to Pb. The IEUBK v2.0 model required a performance evaluation due to changes in influential default intake parameters, namely daily soil/dust ingestion rates. This report documents the performance evaluation of the IEUBK v2.0 model as it would be typically applied at Superfund sites to predict BLLs in populations of children.

U.S. EPA. Advancing Pb Exposure and Biokinetic Modeling for U.S. EPA Regulatory Decisions and Site Assessments Using Bunker Hill Mining and Metallurgical Complex Superfund Site Data. U.S. EPA Office of Research and Development, Washington, DC, EPA/600/R-21/017F, 2021.