Air Quality Criteria for Lead Volume II of II - (NEPIS)(EPA) - US ...

AX6-3
Table AX6-2.1. Prospective Longitudinal Cohort Studies of Neurocognitive Ability in Children
Reference, Study
Location, and Period Study Description Pb Measurement Findings, Interpretation
United States
Bellinger et al. (1992)
U.S.
Dietrich et al.
(1991, 1992, 1993a);
Ris et al. (2004)
U.S.
Canfield et al. (2003a)
U.S.
148 subjects from the Boston Prospective Study
were re-evaluated at 10 yrs of age. The WISCR
was used to index intellectual status. Extensive
assessment of medical and sociodemographic
covariates.
253-260 children followed since birth in the
Cincinnati Pb Study were re-evaluated at 4, 5, and
6.5 yrs of age. At 4 and 5 yrs, the KABC was used
to index intellectual status. At 6.5 yrs, the WISCR
was administered. At 15-17 yrs of age, 195
Cincinnati Pb Study subjects were re-evaluated by
use of a comprehensive neuropsychological battery
that yielded a “Learning/IQ” factor in a principal
components analysis. Extensive assessment of
medical and sociodemographic covariates.
172 predominantly African-American, lower
socioeconomic status children in Rochester, NY
followed since they were 5 to 7 mos were evaluated
at 3 and 5 yrs. An abbreviated form of the
Stanford-Binet Intelligence Scale-4 (SBIS-4) was
used to index intellectual status. Extensive
assessment of medical and sociodemographic
covariates.
Cord and serial postnatal
blood Pb assessments
Cord blood Pb grouping 10 µg/dL
Blood Pb at 2 yrs 6.5
(SD 4.9) µg/dL
Prenatal (maternal) and serial
postnatal blood Pb
assessments
Prenatal blood Pb 8.3
(SD 3.7) µg/dL
Blood Pb at 2 yrs 17.4
(SD 8.8) µg/dL
Serial postnatal blood Pb
Blood Pb at 2 yrs
9.7 µg/dL
Increase of 10 µg/dL in blood Pb level at age two was
associated with a decrement of ~6 IQ points. Relationship
was stronger for verbal compared to performance IQ.
Prenatal exposure to Pb as indexed by cord blood Pb levels
was unrelated to psychometric intelligence.
Few statistically significant relationships between blood Pb
indices and covariate-adjusted KABC scales at 4 and 5 yrs
of age. One KABC subscale that assesses visual-spatial
skills was associated with late postnatal blood Pb levels
following covariate adjustment. After covariate
adjustment, avg postnatal blood Pb level was significantly
associated with WISCR performance IQ at 6.5 yrs. Blood
Pb concentrations >20 µg/dL were associated with deficits
in performance IQ on the order of 7 points compared with
children with mean blood Pb concentrations