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

AX6-23
Table AX6-2.7. Effects of Lead on Sensory Acuities in Children
Reference, Study
Location, and Period Study Description Pb Measurement Findings, Interpretation
United States
Schwartz and Otto
(1991)
U.S.
Dietrich et al. (1992)
U.S.
Europe
Osman et al. (1999)
Poland
Design: Cross-sectional. 3545 subjects 6-19 yrs old
who participated in the Hispanic Health and
Nutrition Examination Survey. Pure tone
audiometric evaluations were performed at 500 Hz,
2000 Hz, and 4000 Hz. Extensive measures on
medical and sociodemographic covariates.
Design: Prospective/longitudinal. 215 subjects
drawn from the Cincinnati Pb Study at the age of 5
yrs. Children were administered the SCAN-a
standardized test of central auditory processing.
Extensive measurement of medical and
sociodemographic covariates
Design: Cross-sectional. 155 children 4-14 yr-old
living in an industrial region of Poland. Pure tone
audiometric evaluations were performed at 500 Hz,
1000 Hz, 2000 Hz, 4000 Hz, 6000Hz, and 8000 Hz.
Basic data on medical history, limited information on
sociodemographic covariates such as family
structure and income.
Blood Pb at the time of
testing
Blood Pb 50th percentile
8 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
Blood Pb at the time
of testing
Blood Pb median 7.2
(range 1.9-28) µg/dL
Following covariate adjustment, higher blood Pb
concentrations were associated with an increased risk of
hearing thresholds that were elevated above the standard
reference level at all four frequencies. Blood Pb was also
associated higher hearing threshold when treated as a
continuous outcome. These relationships extended to blood
Pb levels below 10 µg/dL. An increase in blood Pb from 6 to
18 µg/dL was associated with a 2-dB loss at all frequencies.
Authors conclude that HHANES results those reported
earlier for NHANES-II.
Higher prenatal (maternal), neonatal and postnatal blood Pb
concentrations were associated with more incorrect
identification of common monosyllabic words presented
under conditions of muffling. Following covariate
adjustment, avg childhood blood Pb level remained
significantly associated with impaired performance on the
SCAN subtest. Authors conclude that Pb-related deficits in
hearing and auditory processing may be one plausible
mechanism by which an increased Pb burden might impede a
child’s learning.
Higher blood Pb concentrations were significantly associated
with increased hearing thresholds at all frequencies studied.
This relationship remained significant when analyses were
limited to subjects with blood Pb levels below 10 µg/dL.
Authors conclude that auditory function in children is
impaired at blood Pb concentrations below 10 µg/dL.