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

AX6-63
Table AX6-3.8. Occupational Exposure to Organolead and Inorganic Lead in Adults
Reference, Study
Location, and Period Study Description Pb Measurement Findings, Interpretation
United States
Schwartz et al. (1993)
U.S.
Stewart et al. (1999)
U.S.
Two hundred and twenty-two current
employees that manufactured tetraethyl Pb
participated in a study to determine if there
was impairment on a neurobehavioral battery
associated with a measure of cumulative
exposure to organic and inorganic Pb derived
from 12 yrs of air sampling. Mean age was
44 (8.7) yrs, education 13 (1.7) yrs.
543 former organolead workers, mean yrs
since last exposure18, examined for ongoing
neurobehavioral impairment related to past
Pb exposure. Thirty-eight % were age 60 or
older, predominantly white, 93% had at least
a high school degree. Linear regression
assessed the relationship between Pb dose
and neurobehavioral function adjusting for
the covariates.
Mean (SD) cumulative Pb
exposure (inorganic and
organic) 869 (769) µg·yr/m 3
Mean (SD) yrs of exposure
13 (9.5)
Mean (SD) tibial Pb 14
(9.3) µg/g
Mean (SD) peak tibial bone
Pb (extrapolated back using a
clearance half-time of Pb in
tibia of 27 yrs) 24
(17.4) µg/g
Mean (SD) DMSA chelatable
Pb 19 (17.2) µg (urine
collected for 4 hrs)
Exposure was divided into 4 groups with the lowest for yrs of
exposure and cumulative Pb exposure serving as the reference group.
After adjustments for premorbid intellectual ability, age, race, and
alcohol consumption, cumulative Pb exposure had differential
association poorer performance in many cognitive domains but most
often in manual dexterity and verbal memory/learning. Performance
on tests associated with exposure was 5 to 22% lower in the highest
groups when compared with the low exposure reference group.
Peak tibial Pb was a significant predictor of poorer performance on
Vocabulary (∃ = !0.063, p = 0.02), serial digit learning (∃ = !0.043,
p = 0.04), RAVLT trial 1 (∃ = !0.054, p = 0.03), RAVLT recognition
(∃ = !0.019, p = 0.03), Trails B (∃ = !0.002, p = 0.03), finger tapping
nondominant (∃ = !0.042, p = 0.02), Purdue pegboard dominant
(∃ = !0.043, p = 0.00), nondominant (∃ = !0.49, p = 0.00), both
(∃ = !0.038, p = 0.00), assembly (∃ = !0.133, p = 0.00), and Stroop
(∃ = !0.014, p = 0.00).
Current tibial Pb had similar associations – Vocabulary (∃ = 0.103,
p = 0.04), Digit Symbol (∃ = !0.095, p = 0.05), finger tapping
dominant (∃ = !0.87, p = 0.02), finger tapping nondominant
(∃ = 0.102, p = 0.00), Purdue Pegboard dominant (∃ = !0.065,
p = 0.01), nondominant (∃ = !0.091, p = 0.00), both (∃ = !0.068,
p = 0.00), assembly (∃ = !0.197, p = 0.03 ), and Stroop (∃ = 0.017,
p = 0.01).
DMSA-chelatable Pb was only significantly associated with choice
reaction time (∃ = !0.001, p = 0.01).