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

AX6-53
Table AX6-3.5 (cont’d). Neurophysiological Function and Occupational Lead Exposure in Adults
Reference, Study
Location, and Period Study Description Pb Measurement Findings, Interpretation
Asia (cont’d)
Chuang et al. (2000)
Taiwan
Chia et al. (1996a)
Singapore
206 Pb battery workers, mean age 41 yrs,
with annual blood Pb for the previous five
yrs had vibration perception measured in
hand and foot. Relationship of Pb exposure
term and vibration perception threshold
assessed with multiple regressions, hockey
stick regression analysis after adjusting for
potential confounders.
72 workers in a Pb battery manufacturing
factory with a mean age of 30 yrs and
reference group of 82 workers had nerve
conduction studies and blood Pb performed
every 6 mos over the course of three yrs.
Only 28 Pb battery workers completed the
program. At the end of the first yr of the 82
workers in the comparison group only 26
remained and by yr 3 this had decreased to 4.
Mean nerve conduction values examined by
ANCOVA between the exposed and
reference after adjustment for age, ethnic
group, smoking and drinking habits.
Analysis of serial nerve conduction values
and blood Pb treated as a clustered sample
had the within-cluster regression coefficient
examined. The 28 exposed workers were
stratified by blood Pb level and the
relationship between nerve conduction values
and blood tested within the cluster.
Mean blood Pb 28 µg/dL
Mean blood Pb over past
5 yrs 32 µg/dL
Mean maximum blood Pb
39 µg/dL
Mean index of cumulative
exposure 425 µg·yr/dL
Mean TWA 32 µg/dL
Mean working duration
13 yrs and life span in
work 31%
Geometric mean blood Pb
concentrations for the 6
testing periods: 37, 41, 42,
40, 41, and 37 µg/dL
Overall range for blood Pb
16-73 µg/dL
After adjustment for age, sex, body height, smoking, alcohol
consumption, and use of vibrating hand tools, significant association
between mean blood Pb and mean TWA and vibration perception in
the foot were found. After adjustment for the covariates, a hockey
stick regression analysis of foot vibration threshold vs. mean blood
Pb concentration for 5 yrs found an inflection point around 30 µg/dL
with a positive linear relation above this point suggesting a potential
threshold.
The relationship between blood Pb levels and nerve conduction
values for the 28 exposed workers was significant for all outcomes
except median motor conduction velocity and ulnar sensory nerve
conduction velocity and ulnar sensory amplitude. The regression
correlation coefficients for blood Pb >40 µg/dL was significant for
all parameters except the median sensory conduction velocity and
for blood Pb