Table 16: Final Human Health State of the Science Report on Lead

Table 16. Summary of dose-response assessments by international agencies and regulatory authorities of BLLs versus IQ deficits based on Lanphear et al. (2005)
Organization Endpoint assessed Assessment results Reference
BMD: Benchmark Dose. BMDL: Benchmark Dose (lower confidence limit).
IQ deficits in children (based on Lanphear et al. 2005) Calculated the average change in IQ over a range of 1 to 10 μg/dL based on the best-fit log-linear model presented in Lanphear et al. (2005)from 2.4 to 30 μg/dL (the 5th and 95th percentiles, respectively, for the pooled data set) to develop a child-specific health guidance value: benchmark incremental change in blood lead concentration (ΔPbB) of 1 μg/dL of blood in children's blood that would reduce IQ by up to 1 point (de minimus) OEHHA 2007
EFSA IQ deficits in children (based on Lanphear et al. 2005) BLL Logarithmic model Piecewise linear model Budtz-Jørgensen 2010; EFSA 2010;
BMD01 (μg/dL) BMDL01 (μg/dL) BMD01 (μg/dL) BMDL01 (μg/dL)
Concurrent 0.35 0.26 1.8 1.20
Peak 0.39 0.27 1.03 0.69
Life-time 0.36 0.25 1.48 0.97
Early childhood 0.56 0.34 3.77 1.61
Concluded the piecewise linear model, using the segment fit to the lower BLLs, provided less uncertain estimates of the BMDL01. Determined the 95th percentile lower confidence limit of the benchmark dose (BMD) of 1% extra risk (BMDL01) of 1.2 μg/dL as a reference point for the risk characterization of lead when assessing the risk of intellectual deficits in children measured by the Full Scale IQ score
JECFA IQ deficits in children Based on a dose-response analyses (not provided), estimated that the previously established PTWI of 25 μg/kg-body weight is associated with a decrease of at least 3 IQ points in children. The Committee concluded that the PTWI could no longer be considered health protective and withdrew it. JECFA 2010
U.S. EPA IQ deficits in children (based on Lanphear et al. 2005) BLL (μg/dL) Incremental IQ loss (IQ points per μg/dL) U.S. EPA 2007
Log-linear with cut point Log-linear with low-exposure linearization Two-piece linear
<2 0.94 2.29 0.45
<5 0.87 1.41 0.45
<7.5 0.73 1.09 0.45
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