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

AX6-39
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)
Lindgren et al. (2003)
New Brunswick
1992-1993
Braun and Daigneault
(1991)
Quebec
In an attempt to separate the effects of past
high Pb exposure from a lower proximate
exposure, examination of the pattern of Pb
levels of the 467 Canadian Pb smelter
workers found 40 workers who had high past
exposure followed by yrs where 90% of
blood Pb were above 40 µg/dL (High-
High = H-H) while another group of 40
workers had similar past high Pb exposure
followed by yrs where 90% of blood Pb were
below 40 µg/dL (High-Low = H-L). The
groups did not differ on age, education, yrs
of employment or CES-D. Five outcomes
examined-Purdue Pegboard assembly,
Block Design, Digit Symbol, Rey Auditory
Verbal Learning Test-total score, delayed
Logical Memory.
41 workers from a secondary Pb smelter,
mean age 35 (9.6) yrs and yrs of education
10 (2.1) were compared to a control group
mean age 37 (10.1) yrs and yrs of education
11 (1.3) on tests of cognitive and motor
function. MANCOVA and dose-effect
relationships after adjusting for potential
confounders were performed.
Mean (SD) IBL for past
exposure
H-H 633 (202.2) µg·yr/dL
H-L 557 (144.8) µg·yr/dL
Mean (SD) IBL for the
proximate exposure
H-H 647 (58.7) µg·yr/dL
H-L 409 (46.4) µg·yr/dL
Mean (SD) blood Pb
H-H 37 (5.1) µg/dL
H-L 24 (5.2) µg/dL
Mean (SD) TWA 53
(7.5) µg/dL
Mean (SD) maximum
blood Pb 87 (22.4) µg/dL
Of the five neuropsychological measures examined only RAVLT
(total score) and Logical Memory (delayed) were significantly
different after adjusting for the covariates in the two pattern groups.
Use of regression analyses found pattern group contributed
significantly (R 2 = 4%, p < 0.05) to the explanation of variance in
RAVLT after accounting for current blood Pb (R 2 = 3%, p < 0.10) and
IBL measures (R 2 = 7%, p < 0.01). For past IBL, H-H pattern
correlated more strongly with RAVLT (r = !0.21) while H-L pattern
had no relationship with past exposure (r = 0.08). For proximate IBL
the difference was maintained between H-H (r = !0.11) and H-L
pattern (r = 0.00). The authors suggested that the absence of an
association between past high Pb exposure and verbal memory in the
H-L pattern group may reflect reversibility of function when blood Pb
is maintained below 40 µg/dL.
None of the measures of cognitive executive function showed group
differences. Partial correlation adjusting for age and education with
dose related variables found no statistical significance. On motor
function the exposed workers had significantly slower simple reaction
time (p = 0.05). However partial correlations with measures of dose
found dose-effect correlation in both negative and positive directions.
Group of exposed workers was mixed for Pb exposure with 11
currently working and the remainder with no exposure up to 84 mos.
Also two of the exposed workers had been treated with chelation.