1. Lead and Children’s IQ Clark D. Carrington, Ph.D., D.A.B.T.
Chemical Hazards Assessment Team
Center for Food Safety and Applied Nutrition
US Food and Drug Administration

2. Lead (Pb) - Hazards
There is little to no margin of exposure/safety - there is some level of risk, all be it small, associated with low levels of exposure. Bioavailability of ingested lead are age specific.
In humans the incidence of lead induced effects (adverse below a blood Pb level of 10 µg/dL ?) is observable and verifiable.
Placenta presents a minimal barrier to movement of lead from maternal to fetal circulation.
Food consumption per body mass is greater in infants & younger children (up to approx. 7 years of age and younger) as compared to adults.
Infants & younger children absorb lead from the GI tract more readily than adults by about a factor of four.
Immature status of developing organs - brain, kidneys & liver - more sensitive to toxic insult. The magnitude of response is dose and organ system dependent.
Key effect of low blood lead levels is on neurocognitive development.

3. Prospective studies: estimated change in full scale IQ (and 95% confidence interval) for increase in blood lead from 10 to 20 µg/dl, using three measures of blood lead in each study. Pocock et al., BMJ 309: , 1994.

4. Carrington & Bolger, Food. Ad. Contamin. 13:61-76, 1996.

5. Pb and IQ: Model Uncertainty JECFA, 2000 http://www. inchem

6. Lanphear (2005) Meta-analysis Hill Model

7. Lanphear (2005) Meta-analysis Bilinear Model

8. Lead Issues Quantitative Dimensions
Individual Response Magnitude
No Threshold (but that doesn’t mean you have to care)
Uncertainty (Sampling, Model)
No Variability
Epidemiological Studies as the Basis for Dose-Response
No Raw Data (usually)
Association means Causation?
Multivariate Analysis (One Wrong, all Wrong)
Systematic Error