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

AX6-36
Table AX6-3.3. Neurobehavioral Effects Associated with Occupational Lead Exposure in Adults
Reference, Study
Location, and Period Study Description Pb Measurement Findings, Interpretation
United States
Fiedler et al. (2003)
New Jersey
Canada
Lindgren et al. (1996)
Canada
40 workers with Pb exposure, mean age
48 (9.5) yrs completed a neurobehavioral
battery and was compared to 45 Pb/solvent
workers, mean age 47 (10.2), 39 solvent
exposed workers, mean age 43 (9.4), and
33 controls, mean age 44 (10.2). Group
differences and dose-effect relationships
were assessed after adjusting for potential
confounding.
467 Canadian former and current, French
and English speaking Pb smelter workers,
mean age 43 (11.0) yrs and education
10 (3.2) yrs were administered a
neuropsychological battery in English or
French. Data analyses used MANCOVA
adjusting for age, education, measure of
depressive symptoms and self reported
alcohol use.
Mean (SD) blood Pb
µg/dL; mean (SD) bone Pb
ppm (dry weight)
Pb workers
14 (11.7); 2.7 (0.7)
Pb/Solvent workers
12 (11.6); 2.8 (0.6)
Solvent workers
5 (4.1); !1.8 (1.8)
Controls
4 (1.4); !1.1 (1.6)
Mean (SD) yrs employment
18 (7.4)
Mean (SD) blood Pb 28
(8.4) µg/dL
Mean (SD) TWA 40
(4-66) µg/dL
Mean (SD) IBL 765
(1-1626) µg·yr/dL
Of nineteen outcomes, significant differences found on the California
verbal learning test (CVLT) (p = 0.05) and positive symptom distress
index on the Symptom checklist-90-R. On the CVLT the controls
performed significantly better on trials 2 and 3 demonstrating
efficiency of verbal learning. Symbol digit substitution (SDS)
approached significance (p = 0.09) with Pb and Pb/solvent group
slower on latency of response but not accuracy. Bone Pb was a
significant predictor of latency of response on SDS, total errors on
paced auditory serial addition task and simple reaction time nonpreferred
hand. Bone Pb and SRT, preferred hand approached
significance. This is a confusing study design as bone Pb is used as a
predictor in workers both with and without occupational Pb exposure.
Fourteen neuropsychological variables examined by MANCOVA
with the grouping variable exposure (high, medium and low) and the
covariates, age, education, CES-D, and alcohol use found no exposure
term significant until yrs of employment, a suppressor term, was
added as a covariate. IBL exposure groups differed significantly (df
2,417) on digit symbol (F = 3.03, p = 0.05), logical memory (F = 3.29,
P = 0.04), Purdue dominant hand (F = 4.89, p = 0.01), and trails A
(F = 3.89, p = 0.02) and B (F = 3.2, p = 0.04). This study showed a
dose-effect relationship between cumulative Pb exposure (IBL) and
neuropsychological performance at a time when there was no
association with current blood Pb.