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

AX6-60
Table AX6-3.7 (cont’d). Postural Stability, Autonomic Testing, Electroencephalogram, Hearing Thresholds, and
Occupational Lead Exposure in Adults
Reference, Study
Location, and Period Study Description Pb Measurement Findings, Interpretation
Asia
Iwata et al. (2005)
Japan
Yokoyama et al.
(1997)
Japan
Chia et al. (1994a)
Singapore
Chia et al. (1996c)
Singapore
121 workers from a battery recycling plant
and 60 age matched comparison group, mean
age 46 (11) yrs. Height, body weight, body
mass index, and alcohol use was similar in
both groups. Pb group had significantly
more smokers. ANCOVA used to evaluate
postural sway after controlling for age,
height, and smoking and drinking status.
Benchmark dose level was calculated as the
95% lower confidence limit of the
benchmark dose.
49 chemical workers exposed to Pb stearate,
mean age 48 (1.3) yrs and 23 controls, mean
age 47 (2.5) had postural sway evaluated.
ANCOVA examined group differences after
adjusting for covariates.
60 Pb storage workers, mean age 32 (7.7) yrs
and 60 controls, mean age 35 (7.4) had
postural sway parameters measured.
ANCOVA used to examine group differences
after adjusting for covariates. Linear
regression examined relationship between Pb
exposure and postural sway.
The same 60 Pb storage workers as above
and 60 control had postural sway data
examined for contribution of cumulative
blood Pb fractionated over 10 yrs of
exposure.
Mean (SD) blood Pb 40
(15) µg/dL
Referent
Not done
Mean (SD) blood Pb 18
(1.0) µg/dL
Mean (SD) maximum
blood Pb 48 (3.8) µg/dL
Mean (SD) TWA 24
(1.3) µg/dL
Mean (SD) Cumulative
blood Pb 391
(48.2) µg·yr/dL
Pb workers
Mean (SD) blood Pb 36
(11.7) µg/dL
Controls
Mean (SD) blood Pb 6
(2.4) µg/dL
Pb workers
Mean (SD) blood Pb 36
(11.7) µg/dL
Controls
Mean (SD) blood Pb 6
(2.4) µg/dL
Except for sagittal sway, all postural sway parameters with eyes open
were significantly larger in Pb workers. Blood Pb level in workers
was significantly associated with to sagittal sway at 1-2 Hz and 2-4
Hz with eyes open, and sagittal and transversal sways at 1-2 Hz and
2-4 Hz with eyes closed. The mean benchmark dose level of current
blood Pb level for postural sway was 14.3 µg/dL for the linear model
and 14.6 µg/dL for the K power model.
There were significant increases in sway in all directions at high and
low frequencies with eyes open and eyes closed (p < 0.05).
Regression analysis found blood Pb associated with sway in the
anterior-posterior direction, 0.5-1Hz (0.321, p = 0.03), 1-2Hz (0.313,
p = 0.04) and TWA associated with right to left sway (0.326,
p = 0.02) after adjustment for the covariates age, height, weight and
alcohol consumption. The authors conclude that change in the
vestibulo-cerebellum is affected by blood Pb while in the anterior
cerebellar lobe is affected by past Pb exposure.
Computerized postural sway measurements found Pb workers
have poorer postural stability that increased with eyes closed
(p < 0.01). Regression analysis adjusting for age, height, and
weight found no significant association with blood Pb.
The Pb exposed group had significantly poorer performance on all
postural sway parameters with eyes closed compared to controls after
adjusting for height, weight, age and drinking habits (p < 0.01).
All postural sway parameters with eyes closed were significantly
associated with IBL for the 2 yrs prior to testing (n = 23, p < 0.05).