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

AX6-44
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
Latin America
Maizlish et al. (1995)
Venezuela
Asia
Schwartz et al.
(2001a)
South Korea
43 workers from a Pb smelter, mean age 34
(9) yrs and 47 nonexposed workers, mean
age 35 (11) yrs completed the WHO
neurobehavioral core test battery. ANCOVA
and linear regression adjusting for potential
confounders examined relationship of Pb
exposure and NCTB.
803 Korean Pb-exposed workers, 80% men
and 20% women, mean age 40 (10.1) yrs
from a variety of industries, and 135
controls, 92% men and 8% women, mean
age 35 (9.1) yrs. Educational levels Pbexposed
workers/controls
#6 yrs = 23% / 7%, 7-9 yrs 23% / 11%, 10-
12 yrs = 46% / 70%, and >12 yrs 8% / 12%.
Group differences on neurobehavioral testing
after controlling for covariates and linear
regression controlling for covariates
examined the presence of a dose-effect
relationship.
Pb workers
Mean (SD) blood Pb 43
(12.1) µg/dL
Mean (SD) peak blood Pb
60 (20.3) µg/dL
Mean (SD) TWA 48
(12.1) µg/dL
Controls
Mean (SD) blood Pb 15
(6) µg/dL
Mean (SD) peak blood Pb
15 (6) µg/dL
Mean TWA 15 (6) µg/dL
Pb workers
Mean (SD) blood Pb 32
(15) µg/dL
Mean (SD) tibia bone Pb
37 (40.3) µg/g
Mean (SD) DMSAchelatable
Pb level 186
(208.1) µg
Controls
Mean (SD) blood Pb 5
(1.8) µg/dL
Mean (SD) Tibia bone Pb 6
(7) µg/g
Group comparison was significant for SRT (p = 0.06) but the Pb
exposed workers performed faster. Linear regression found SRT
poorer performance with blood Pb and TWA but not significant.
With peak blood Pb SRT improved with increasing Pb exposure.
In this study only symptoms were significantly different between
the groups.
Nineteen outcomes examined. Compared to controls Pb exposed
workers performed significantly worse on SRT, Digit Span, Benton
Visual Retention, Colored Progressive Matrices, Digit Symbol, and
Purdue Pegboard after controlling for age, gender and education. The
association of DMSA with test performance was lost by the addition
of blood Pb. Bone Pb was not associated with neurobehavioral
performance. Blood Pb was the best predictor for significant
decrements in neurobehavioral performance on trails B (∃ = !0.0025
[SE 0.0009], p < 0.01), Purdue Pegboard (dominant ∃ = !0.0159 [SE
0.0042], p < 0.01; non-dominant ∃ = 0.0169 [SE 0.0042], p < 0.01;
both ∃ = !0.0142 [SE 0.0038], p < 0.01; assembly ∃ = !0.0493 [SE
0.0151], p < 0.01), and Pursuit Aiming (# correct ∃ = !0.1629 [SE
0.0473], p < 0.01; # incorrect ∃ = !0.0046 [SE 0.0023], p < 0.05). The
magnitude of the effect for these eight tests significantly associated
with blood Pb was an increase in blood Pb of 5 µg/dL was equivalent
to an increase of 1.05 yrs in age. Use of Lowess lines for Purdue
Pegboard (assembly) and Trails B suggested a threshold at blood Pb
18 µg/dL after which there is a decline of performance.