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IQ and blood lead from 2 to 7 years of age: Are the effects in older children the residual of high blood lead concentrations in 2-year-olds?

Date Added to Library: 
Tuesday, November 13, 2018 - 10:15
Digital Object Identifier (DOI): 
10.1289/ehp.7625
Priority: 
normal
Individual Author: 
Chen, Aimin
Dietrich, Kim N.
Ware, James H.
Radcliffe, Jerilynn
Rogan, Walter J.
Reference Type: 
Published Date: 
May 2005
Published Date (Text): 
May 2005
Publication: 
Environmental Health Perspectives
Volume: 
113
Number of Volumes: 
5
Page Range: 
597-601
Year: 
2005
Language(s): 
Abstract: 

Increases in peak blood lead concentrations, which occur at 18-30 months of age in the United States, are thought to result in lower IQ scores at 4-6 years of age, which IQ becomes stable and measurable. Data from a prospective study conducted in Boston suggested that blood lead concentrations at 2 years of age were more predictive of cognitive deficits in older children than were later blood lead concentrations or blood lead concentrations measured concurrently with IQ. Therefore, cross-sectional associations between blood lead and IQ in school-age children have been widely interpreted as the residual effects of higher blood lead concentrations at an earlier age or the tendency of less intelligent children to ingest more leaded dust or paint chips, rather than as a causal relationship in older children. Here we analyze data from a clinical in which children were treated for elevated blood lead concentrations (20-44 ug/dL) at about 2 years of age and followed until 7 years of age with serial IQ tests and measurements of blood lead. We found that cross-sectional associations increased in strength as the children became older, whereas the relation between baseline blood lead and IQ attenuated. Peak blood lead levels thus does not fully account for the observed association in older children between their lower blood lead concentrations and IQ. The effect of concurrent blood level on IQ may therefore be greater than currently believed. (Author abstract)

Target Populations: 
Geographic Focus: 
Page Count: 
5
Topical Area: 
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