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

AX6-46
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)
Hwang et al. (2002)
South Korea
Chuang et al. (2005)
Taiwan
From the above cohort of 803 Korean Pb
workers, 212 consecutively enrolled workers,
were examined for protein kinase C (PKC)
activity and the relations between blood Pb
and neurobehavioral performance. PKC
activity assessed by measuring levels of
phosphorylation of three erythrocyte
membrane proteins. Seventy-four percent of
workers were men, mean age 36(0.8)yrs,
duration of exposure 9 (0.6) and education
93% had high school or less. For the female
workers, mean age 47 (0.9) yrs, duration of
exposure 6 (0.5), and education 95% had
high school or less.
27 workers from a glazing factory were
administered a computerized
neurobehavioral battery 3 times over 4 yrs.
At yr 1, the mean age was 40 (9.6) yrs. In
the first yr workers were compared to a
referent group matched for age and
education. Neurobehavioral performance
compared in first yr to referent group with
adjustment for age and Vocabulary.
Generalized mixed linear mixed models
analyzed relationship between blood Pb level
and neurobehavioral test performance after
adjusting for age and Vocabulary.
Male workers
Mean (SD) blood Pb 32
(13.0) µg/dL
Mean (SD) tibia Pb 38
(39.6) µg/g
Mean (SD) ZPP 69
(47.8) µg/dL
Female workers
Mean (SD) blood Pb 20
(9.2) µg/dL
Mean (SD) tibia Pb 26
(14.7) µg/g
Mean (SD) ZPP 72
(29.7) µg/dL
Pb workers
Yr 1
Mean (SD) blood Pb 26
(12)
Yr 3
Mean (SD) blood Pb 11
(6.4)
Yr 4
Mean (SD) blood Pb 8 (6.9)
Referent
Mean (SD) blood Pb 7 (4.2)
Blood Pb was associated significantly with decrements in Trails B
(∃ = !0.003 [SE 0.002], p < 0.10), SRT (∃ = !0.0005 [SE 0.0003],
p < 0.10) and Purdue Pegboard (dominant ∃ = !0.21 [SE 0.010],
p < 0.05); non-dominant (∃ = !0.021 [SE 0.010], p < 0.05); both
(∃ = !0.021 [SE 0.009], p < 0.05). PKC activity as measured by backphosphorylation
of erythrocyte membrane proteins was not associated
with neurobehavioral test scores. Addition of the interaction term of
blood Pb by back-phosphorylation dichotomized at the median found
significant effect modification with the association of higher blood Pb
and poorer neurobehavioral performance occurring only among
workers with lower back-phosphorylation levels that corresponds to
higher in vivo PKC activity. Association of blood Pb and SRT for the
52 kDa subunit with high in vivo PKC activity (adjusted ∃ = !0.001,
p < 0.01) and for low in vivo PKC (adjusted ∃ = !0.0001, p = 0.92).
The authors suggest that PKC activity may identify a subpopulation at
increase risk of neurobehavioral effects of Pb.
Referents scored significantly lower on questionnaire for chronic
symptoms in yr 1. In the mixed model analyses finger tapping
dominant (p = 0.008) and non-dominant (p = 0.025) were
significantly inversely associated with blood Pb. Pattern comparison
(p < 0.001) and Pattern memory (p = 0.06) improved significantly as
blood Pb levels improved. Chronic symptoms and neurobehavioral
performance appear to reverse when Pb exposure is decreased.
However since the referent group was not tested in yr 3 and yr 4 it
was not possible to control for practice effect known to occur with
repeat neurobehavioral testing even at two yr intervals.