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Low level lead exposure and intelligence in the preschool years
C B Ernhart1, M Morrow-Tlucak, A W Wolf
1Department of Psychiatry, Case Western Reserve University, Cleveland, OH 44109.
The Science of the Total Environment
|June 1, 1988
Summary
Low-level lead exposure in children does not significantly impact cognitive development. The study found that the caretaking environment, not lead levels, influences preschool intelligence outcomes.
Area of Science:
- Environmental Health
- Developmental Psychology
- Neurotoxicology
Background:
- Prospective studies are crucial for understanding the neuropsychological effects of low-level lead (Pb) exposure in child development.
- The critical developmental window from mid-infancy to three years is when behavioral and physiological characteristics correlate with environmental lead intake and retention.
Purpose of the Study:
- To investigate the relationship between blood lead levels (PbB) and developmental assessments in children from infancy to three years.
- To determine if early childhood lead exposure has a lasting impact on cognitive development, controlling for environmental factors.
Main Methods:
- The Cleveland study measured blood lead levels (PbB) at six months, two, and three years.
- Developmental assessments included the Mental Development Index (MDI) of the Bayley Scales of Infant Development (at six months, one, and two years) and Stanford Binet Intelligence Scale IQ (at three years).
- Multiple regression analyses were used to examine the association between PbB and developmental outcomes, with demographic data and caretaking environment measures as covariates.
Main Results:
- Blood lead levels at six months showed no significant association with any of the five developmental assessments.
- Initial significant correlations between later PbB measures and developmental assessments were completely attenuated after statistically controlling for confounding variables.
- The caretaking environment emerged as a significant factor influencing the observed relationship between lead exposure and cognitive outcomes.
Conclusions:
- Early childhood lead exposure, as measured by blood lead levels, did not demonstrate a direct, independent effect on cognitive development up to age three.
- The findings suggest that the apparent correlation between lead exposure and preschool intelligence is confounded by the quality of the caretaking environment.
- Further research should focus on the interplay between environmental factors and neurodevelopmental outcomes in children exposed to low levels of lead.
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