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

AX6-56
Table AX6-3.6. Evoked Potentials and Occupational Lead Exposure in Adults
Reference, Study
Location, and Period Study Description Pb Measurement Findings, Interpretation
Canada
Bleecker et al. (2003)
New Brunswick
1992-1993
Europe
Abbate et al. (1995)
Italy
Discalzi et al. (1992)
Italy
359 currently employed smelter workers, mean age 41
yrs, had brainstem auditory evoked potentials (BAEP)
measured. Relationship between absolute latencies
and interpeak latencies assessed using linear regression
after adjusting for potential confounders. Exposure
was assessed in cases with clinical abnormalities in
Wave I and I-V interpeak latency compared to those
workers with normal BAEP using post-hoc analysis.
300 Pb exposed men ages 30 to 40 yrs in good health
with no other neurotoxic exposure had P100 latency
measured for visual evoked potentials (VEP) for 15
and 30 minute of arc. Groups created based upon
blood Pb had VEPS examined followed by linear
regression for each group.
49 Pb exposed workers and 49 age and sex matched
controls had BAEPs measured. Relationship of 6
BAEP outcome variables and Pb exposure examined
with analysis of variance and linear regression.
Mean blood Pb 28 µg/dL
Mean TWA 39 µg/dL
Mean IBL 719 µg·yr/dL
Blood Pb 17 to 60 µg/dL
range
Mean blood Pb for 4 groups
n = 39 23 µg/dL
n = 113 30 µg/dL
n = 89 47 µg/dL
n = 59 56 µg/dL
Mean blood Pb 55 µg/dL
Mean TWA for previous
3 yrs 54 µg/dL
Linear regression after the contribution of age found blood
Pb and TWA were significantly associated with Wave I
while IBL was significantly associated with Wave III and I-
III interpeak interval. Four groups created with increasing
abnormalities based upon clinical cut-off scores for Wave I
and I-V interpeak interval had similar age. blood Pb, TWA
and IBL were all significantly higher in the group with
prolonged Wave I and I-V interpeak interval compared
to the group with normal BAEP = s. These findings
support involvement of the brainstem and auditory nerve
with Pb exposure.
ANOVA of the blood Pb and P100 latencies were
significantly prolonged for 15 and 30 minutes of arc.
Linear regression found the association of blood Pb and
P100 were significant in each group but the relationship
was not proportional (angular coefficient). Effect of blood
Pb on VEP began at 17-20 µg/dL. With age limited to one
decade, contribution from age was not a concern. Even
though no comparison group, careful screening ruled out
other medical and eye conditions and other potential
exposures.
Latencies for waves I, III, V and interpeak latencies, I-V, I-
III, and III-V were all significantly prolonged in the Pbexposed
workers (p < 0.04). No significant association
found with linear regression between BAEP outcomes and
exposure variables. In those workers with TWA
>50 µg/dL, I-V latency was significantly prolonged
compared to workers with TWA