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

AX6-37
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
Canada (cont’d)
Bleecker et al. (2002)
Canada
Bleecker et al. (2005a)
Canada
256 smelter workers from the above
population were currently employed and
took the test battery in English. Their mean
age was 41 (7.9) yrs, and education 10 (2.8)
yrs. The goal was to determine if
educational achievement as measured by
WRAT-R Reading modified performance on
MMSE. Linear regression assessed the
contribution of age, WRAT-R, education,
alcohol intake, cigarette use, IBL and
IBLΗWRAT-R on MMSE performance.
256 smelter workers currently employed and
took the test battery in English. Their mean
age was 41 (7.9) yrs, and education 10 (2.8)
yrs. The purpose was to determine whether
components of verbal memory as measured
on the Rey Auditory Verbal Learning Test
(RAVLT) were differentially affected by Pb
exposure. Linear regression and ANCOVA
assessed the relationship of Pb and
components of verbal learning and memory.
Mean (SD) blood Pb 28
(8.8) µg/dL
Mean (SD) IBL 725 (434)
µg·yr/dL
Mean (SD) blood Pb 28
(8.8) µg/dL
Mean (SD) TWA 39 (12.3)
µg/dL
Mean (SD) IBL 725 (434)
µg·yr/dL
MMSE had a median (range) score of 29 (19-30). The most common
errors were recall of 3 items (38%), spell world backwards (31%),
repetition of “no ifs ands or buts” (21%) and copy a design to two
intersecting pentagons (16%). WRAT-R reading used as an additional
measure of educational achievement because it was a stronger predictor
of MMSE performance than yrs of education. The significant
interaction (♠R 2 = 2%, p = 0.01) explained by a dose-effect between
IBL and MMSE only in the 78 workers with a WRAT-R reading grade
level less than 6. The workers with higher reading grade levels and the
same cumulative Pb exposure were able to compensate for the effects
of Pb on the MMSE because of increased cognitive reserve.
Outcome variables RAVLT a word list test included measures of
immediate memory span and attention (Trial 1), best learning (Trial V),
incremental learning across the five trials (Total Score), and storage
(Recognition) and retrieval (Delayed Recall) of verbal material. TWA
significantly contributed to the explanation of variance for Trial V
(♠R 2 = 1.4%, p < 0.03) and Delayed Recall (♠R 2 = 1.4%, p = 0.03)
after adjusting for age and WRAT-R while IBL did the same with
Recognition (♠R 2 = 2.0%, p =