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

AX6-30
Table AX6-3.1. Neurobehavioral Effects Associated with Environmental Lead Exposure in Adults
Reference, Study
Location, and Period Study Description Pb Measurement Findings, Interpretation
United States
Krieg et al. (2005)
1988-1994
U.S.
Muldoon et al. (1996)
U.S.
4,937 adults aged 20-59 yrs from
NHANES III completed three
neurobehavioral tests. Regression analyses
of neurobehaqvioral test and log of blood
Pb concentration adjusted for sex, age
education, family income, race/ethnicity,
computer or video game familiarity,
alcohol use, test language, and survey
phase.
325 women from rural location (mean age
71) and 205 women from a city location
(mean age 69) participants in the Study for
Osteoporotic Fractures had the association
of nonoccupational Pb exposure and
cognitive function examined. Logistic
regression determined effect of blood Pb
on neuropsychological performance.
Mean blood Pb 3.3 µg/dL
Range 0.7 to 41.7 µg/dL
Rural group
Blood Pb 5 µg/dL
Urban group
Blood Pb 5 µg/dL
No statistically significant relationship between blood Pb concentration
and mean simple reaction time, symbol-digit substitution latency and
errors and serial digit learning trials to criterion and total score after
adjustments for covariates.
Groups were significantly different with the urban group more educated
and smoked and drank more. Performance in each group stratified by
exposure into three groups (low 7 µg/dL rural and >8 µg/dL) — no significant associations were
present in the urban group but the rural group had significantly poorer
performance with increasing blood Pb for Trails B (OR = 2.6 [95% CI:
1.04, 6.49]), Digit Symbol (OR = 3.73 [95% CI: 1.57, 8.84]),and
Reaction Time in the lower (OR = 2.84 [95% CI: 1.19, 6.74]) and
upper extremities (OR = 2.43 [95% CI: 1.01, 5.83]). The fact that
marked differences exist between the low Pb groups for rural and urban
(the lowest 15th percentile) suggests the differences between the two
groups are unrelated to Pb. Response time for reaction time across Pb
groups increased for the rural group and decreased or remained the
same for the urban group. As response time is sensitive to Pb effect,
this raises question whether factors not measured accounted for
difference. Namely MMSE for the whole population was 25 (15-26)
with poorer performance in the rural group. The clinical cutoff score
for MMSE is 24 suggesting the presence of clinical cognitive disorders.
Even though this is a simple neuropsychological battery up to 9 were
unable to perform some of the tests including 3 on the MMSE.