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

AX6-66
Table AX6-3.9. Other Neurological Outcomes Associated with Lead Exposure in Adults
Reference, Study
Location, and Period Study Description Pb Measurement Findings, Interpretation
United States
Louis et al. (2005)
New York
Louis et al. (2003)
New York
Kamel et al. (2002)
Massachusetts
63 cases of essential tremor
(ET) and 101 controls,
similar for age, 67 (16.6) and
65 (11.1) yrs, education,
gender and ethnicity were
examined for interaction of
blood Pb and ALAD gene
polymorphisms and increased
odds of ET.
100 cases of ET and 143
controls matched for age, sex,
and ethnicity.
The relationship between
blood Pb and ET was
examined.
109 cases of ALS and 256
controls matched for age, sex
and region of residence
examined the relation of Pb
and ALS.
ET
Mean (SD) blood Pb 4 (2.2) µg/dL
Controls
Mean (SD) blood Pb 3 (1.5) µg/dL
2 ET cases but no controls had blood Pb
>10 µg/dL
ET
Mean blood Pb 3 µg/dL
Controls
Mean blood Pb 2 µg/dL
Cases/controls
Mean (SD) blood Pb 5 (0.4) / 3 (0.4) µg/dL
3 cases and no controls had blood Pb >10 µg/dL
Mean (SD) patella Pb 21 (2.1) / 17 (2.0) µg/g
5 cases and 1 control had patella Pb levels
>50 µg/g
Mean (SD) tibia Pb 15 (1.6) / 11 (1.6) µg/g
2 cases and no controls had tibia Pb >50 µg/g.
Of the 63 ET cases 18 (29%) vs. 17 (17%) of 101 controls had an
ALAD2 allele (OR = 1.98 [95% CI: 0.93, 4.21]; p = 0.077). When
log blood Pb was examined by presence of ALAD2 allele in ET, log
blood Pb was highest in ET cases with and ALAD2 allele,
intermediate in ET cases without an ALAD2 allele and lowest in
controls (test for trend, ∃ = 0.10; p = 0.001). When ALAD2 allele
was present, blood Pb was significantly associated with odds of ET
(OR = 80.29 [95% CI: 3.08, 2.096]; p = 0.008). This increased
odds of ET with an ALAD2 allele was 30 times greater than in an
individual with only an ALAD1 alleles. In the highest log blood Pb
tertile, ALAD2 allele was present in 22% of ET cases and 5% of
controls. It was proposed that increased blood Pb along with the
ALAD2 allele could affect the cerebellum and thereby increase the
risk of tremor.
Ten cases and 7 controls had bone Pb levels measured that were
significantly correlated with blood Pb suggesting that higher blood
Pb may have occurred in the past. Total tremor score was
correlated with blood Pb (r = 0.14, p = 0.03). Logistic regression
adjusting for age and current cigarette smoking found the odds ratio
for ET was 1.19 (95% CI: 1.03, 1.37) per unit increase in blood Pb.
Blood Pb was higher in those 39 ET cases with no family history.
Both current and lifetime prevalence of occupational Pb exposure
was the same in ET cases and controls but those with history of
occupational exposure did have a higher blood Pb than those
without this history (median, 3.1 µg/dL vs. 2.4 µg/dL, p = 0.004).
Increased risk of ALS was found for history of occupational Pb
exposure (adjusted OR = 1.9 [95% CI: 1.1, 3.3]) increased lifetime
days of exposure (adjusted OR = 2.3 [95% CI: 1.1, 4.9]).
Association of blood Pb and ALS (adjusted OR = 1.9 [95% CI: 1.4,
2.6]). Elevation in both blood Pb and patella and tibia bone Pb was
found in ALS cases though the precision of these measurements
was questioned (Patella Pb adjusted OR = 3.6 [95% CI: 0.6, 20.6]
and tibia Pb adjusted OR = 2.3 [95% CI: 0.4, 14.5]). Therefore,
this study found Pb exposure from historical questionnaire data and
biological markers associated with ALS.