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

AX6-47
Table AX6-3.3 (cont’d). Neurobehavioral Effects Associated with Occupational Lead Exposure in Adults
Reference, Study
Location, and Period Study Description Pb Measurement Findings, Interpretation
Asia (cont’d)
Tsai et al. (2000)
Taiwan
Chia et al. (2004)
Singapore
Chia et al. (1997)
Singapore
19 Pb workers and 19 referents included in
the above publication, mean age 39 yrs in
both groups and mean education 10 (2.9) and
9 (3.2) yrs, respectively, were tested with a
computerized neurobehavioral battery.
Alcohol use was similar. Mean duration of
Pb exposure 6 (2.5) yrs. Student’s t
compared neurobehavioral performance
between the two groups.
120 workers from Pb stabilizer factories,
mean age 40 (10.7) yrs, duration of exposure
10.2 (7.9) were given a neurobehavioral
battery. Genotyping of ALAD
polymorphisms was performed. ANCOVA
used to test for differences in
neurobehavioral performance among ALAD
polymorphism types adjusting for age,
exposure duration and blood Pb.
50 Pb battery manufacturing workers, mean
age 36 (10.6) yrs, education 8.6 (2.1) yrs
duration of employment 9 (7.4) yrs and
97 controls, mean age 34 (3.7) yrs, and
education 12 (1.8) yrs were administered a
neurobehavioral battery. ANCOVA and
linear regression used to assess relationship
of Pb dose and performance.
Mean (SD) blood Pb 32
(12.2) µg/dL
Referent
Mean (SD) blood Pb 7
(2.7) µg/dL
Mean (SD) blood Pb 22
(9.4) µg/dL
Mean (SD) ALAD0.6
(0.25) µm of
porphobilinogen/h/ml of
RBC
Mean (SD) ALAU0.9
(0.56) mg/g creatinine
Pb workers
Median (range) blood Pb of
38 (13.2-64.6) µg/dL
Median (range) IBL 264
(10.0-1146.2) µg·yr/dL
Controls
Median (range) blood Pb 6
(2.4-12.4) µg/dL
Poorer performance in Pb workers for finger tapping, dominant and
non-dominant, and continuous performance task but only finger
tapping was significant. Pb workers performed better than referents
on Associate Learning, Pattern Comparison Test, Pattern Memory
Test, Visual Delay and Associate Learning Delayed that was
attributed to higher mean education.
Frequency of ALAD11, 87%, ALAD12, 12%, and ALAD22, 1%.
Mean blood Pb adjusting for age and exposure duration was 20 µg/dL
for ALAD11 (n = 107) and 20.4 µg/dL for ALAD12 and 22 (n = 13).
However ALAU was significantly higher in ALAD11 (p = 0.023).
After adjusting for the covariates significant differences for grooved
pegboard dominant hand (p = 0.01), non-dominant hand (p = 0.04),
and grooved pegboard mean time (p = 0.006) were found between
ALAD11 and ALAD12 and 22. Considering cognitive tests were part
of battery it is surprising education was ignored. As noted by the
authors the study only had 13 in the group with better performance
and the ALAD12 or 22 genotypes limiting the power.
Significant group differences for Santa Ana, grooved pegboard, digit
symbol, pursuit aiming and Trails A and B after adjusting for age,
education, smoking, ethnic group and alcohol use. When the exposed
group was stratified by age, in the group >35 yrs the poorer
performance on digit symbol and Trails A was significantly
associated with cumulative Pb and not blood Pb after adjusting
for age and education.