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

AX6-59
Table AX6-3.7. Postural Stability, Autonomic Testing, Electroencephalogram, Hearing Thresholds, and
Occupational Lead Exposure in Adults
Reference, Study
Location, and Period Study Description Pb Measurement Findings, Interpretation
United States
Dick et al. (1999)
U.S.
Europe
Kovala et al. (1997)
Finland
145 workers from a secondary Pb smelter, mean
age 33 (8.7) and duration of employment 5 (4.8)
yrs and 84 comparison workers mean age 30 (9.3)
and duration of employment 4 (4.3) yrs had
postural sway testing performed. The analysis of
exposure with test conditions and covariates used
mixed models.
60 workers in a Pb battery factory with a mean
age of 43 (9) yrs and mean exposure duration of
16 (8) yrs. Quantitative EEG were performed.
Relationship of Pb exposure with quantitative
EEG were examined by partial correlation and
regression analyses adjusting for age.
Pb workers
Mean (SD) blood Pb 39
(8.5) µg/dL
Mean (SD) ZPP 55 (42.2) µg/dL
Mean (SD) CBL 230
(217.9) µg·yr/dL
Mean (SD) TWA 35 9
(8.5) µg/dL
Comparison workers
Mean (SD) blood Pb 2
(1.7) µg/dL
Mean (SD) tibial Pb 26
(17) mg/kg
Mean (SD) calcaneal Pb
88 (54) mg/kg
Mean (SD) IBL 546
(399)
µg·yr/dL,
Mean (SD) TWA 34 (8.4) µg/dL,
Mean (SD) maximum blood Pb
53 (19) µg/dL
Mean (SD) blood Pb 27
(8.4) µg/dL
The postural sway test had 6 conditions that varied the
challenge to the vestibular and proprioceptive afferents and
visual system. Only blood Pb had a significant effect
primarily on the one leg condition after the effects of the
covariates age, height, mass, and race. For the left leg,
exposure slope estimate for area (b = 0.0067, t = 3.88,
p = 0.0001) and length (b = 0.0046, t = 4.11, p = 0.0001)
were significant. For the right leg only the exposure slope
estimate for length (b = 0.0033, t = 3.02, p = 0.0029) was
significant. Dose effect was only significant when Pb
workers were combined with comparison workers. If
comparison workers with blood Pb level below 12 µg/dL
removed no significant exposure effect was found.
The alpha and/or beta frequencies were more present in
workers with higher long term Pb exposure such as tibial
(p < 0.05) and calcaneal (p < 0.05), IBL (p < 0.01) and
TWA (p < 0.05). Slow alpha in workers was believed to
correlate with increased episodes of ‘microdrowsiness’.
The study had no comparison group and did not account for
the effect of smoking and alcohol use or give their usage in
this population.