Present and Long Term Effect of Environmental Lead Exposure Over Intellectual Impairment in Children

Abstract

ISEE-632 Objective: To determine if there is an association between early blood lead concentration and present intellectual ability in exposed schoolchildren, despite lead abatement in the area. Materials and Methods: 442 exposed children had blood lead evaluation in 1998. Of those, 47.5% had lead levels >10 μg/dL. After 7 years a cross-sectional study was conducted in 188 children between 7 and 16 years old, representing 43% of the group studied originally. We used past (1998) and current (2005) blood lead concentration as explanatory variables for intellectual ability (IQ) measured by the WISC-r test. Multiple regression models were used to evaluate the relationship between IQ and blood lead concentration, adjusting by maternal intelligence (WAIS scale), home stimulus (HOME questionnaire), sex, and SES. Results: Blood lead concentration was 3.6±2.3 μg/dL (range 0.5–14) in 2005 and 10.6 + 6.9 μg/dL (range 1–33) in 1998 with a correlation of 0.44 (P = 0.0001). Adjusting for the covariates, we found a significant inverse association between IQ and blood lead in 2005; however, we could not demonstrate a similar association with blood lead in 1998. An increase in the current blood lead concentration of 1 μg/dL was associated with a decrease of 1.03 IQ points (P = 0.012). The deleterious effect is greater the higher the blood lead level as shown through 4 categories of exposure: reference (1.4±0.41 μg/dL); low (2.6±0.37); medium (3.6±0.29) and high (6.5±2.5). Respectively the IQ deficits were: 1.9, 4.3, and 5.1 compared to the reference. Conclusions: Our findings provide additional evidence for deleterious effect of environmental lead on intellectual impairment at blood lead concentrations below 10 μg/dL. Recent blood lead seems more important than past blood lead. Policy efforts should target to prevent lead exposure to optimize children's intellectual potential.