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

AX6-15
Table AX6-2.4 (cont’d). Effects of Lead on Academic Achievement in Children
Reference, Study
Location, and Period Study Description Pb Measurement Findings, Interpretation
United States (cont’d)
Bellinger et al. (1992)
U.S.
Leviton et al. (1993)
U.S.
Australia
Fergusson et al. (1993,
1997); Fergusson and
Horwood (1993)
New Zealand
Design: Prospective longitudinal. 148 children in
the Boston Pb Study cohort were examined at 10 yrs
of age. The short-form of the Kaufman Test of
Educational Achievement (KTEA) was used to assess
academic achievement. Primary outcome was the
Battery Composite Score. Extensive assessment of
medical and sociodemographic covariates.
Design: Prospective cohort. Teachers of ~2000 eight
yr-old children born in 1 hospital in Boston between
1979 and 1980 filled out the Boston Teachers
Questionnaire (BTQ) to assess academic
performance and behavior. Limited information is
provided on the assessment of covariate factors but a
number were considered and controlled for in
multivariable analyses.
Design: Prospective cohort. Academic performance
was examined in a birth cohort of 1200 New Zealand
children enrolled in the Christchurch Health and
Development Study. Measures of academic
performance at 12-13 yrs included the Brut Reading
Test, Progressive Achievement Test, Test of
Scholastic Abilities, and teacher ratings of classroom
performance in the areas of reading, writing, and
mathematics. The growth of word recognition skills
from 8 to 12 yrs was also examined using growth
curve modeling methods. Academic achievement in
relationship to Pb was re-examined in this cohort at
18 yrs. Measures of academic achievement included
the Burt Reading Test, number of yrs of secondary
education, number of certificates passed (based on
national examinations), and leaving school without
formal qualifications (failing to graduate). Extensive
assessment of medical and social 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
Cord blood Pb
Cord blood Pb 6.8 µg/dL
Tooth (dentin) Pb
Tooth Pb 2.8 µg/g
Tooth (dentin) Pb
Tooth Pb 6.2 (SD 6.2) µg/g
After covariate-adjustment, blood Pb levels at 24 mos were
significantly predictive of lower academic achievement
(∃ = !0.51, SE 0.20). Battery Composite Scores declined by
8.9 points for each 10 µg/dL increase in blood Pb. This
association was significant after adjustment for IQ. Authors
conclude that Pb-sensitive neuropsychological processing and
learning factors not reflected in measures of global intelligence
may contribute to deficits in academic achievement.
Following adjustment for potential confounding variables,
elevated dentin Pb concentrations were associated with
statistically significant reading and spelling difficulties as
assessed by the BTQ among girls in the sample. Authors
conclude that their findings support the case for Pb-associated
learning problems at levels that were prevalent at that time in
the general population. However, authors add that the inability
to assess child-rearing quality in this study conducted by mail
limits the inferences that can be drawn.
Following covariate adjustment, dentin Pb levels were
significantly associated with virtually every formal index of
academic skills and teacher ratings of classroom performance
in 12-13 yr-olds. After adjustment for covariates, tooth Pb
levels greater than 8 µg/g were associated with significantly
slow growth in word recognition abilities with no evidence of
catch up. At 18 yrs, tooth Pb levels were significantly
associated with lower reading test scores, having a reading
level of less than 12 yrs, failing to complete three yrs of high
school, leaving school without qualifications, and mean
number of School Certificates passed. Authors conclude that
early exposure to Pb is independently associated with
detectable and enduring deficits in children’s academic
abilities. They further conclude that their findings are
particularly significant in that they confirm the findings of
Needleman (1990), albeit in a cohort with lower levels of
exposure to environmental Pb.