METALS
Lead - An Element of
Toxicity I.
Any of a category of electropositive elements
that usually have a shiny surface, are
generally good conductors of heat and
electricity, and can be melted or fused,
hammered into thin sheets, or drawn into
wires. Typical metals form salts with
nonmetals, basic oxides with oxygen, and
alloys with one another.
Percent of Preschool Children
Exceeding Selected Blood Lead
Levels, NHANES II - III
http://www.lenntech.com/periodic-chart.htm
Pirkle JL, et al. Environ Health Perspect 1998;106:745-50.
Lead-associated Reading
Deficits
in U.S. Children
• Lead toxicity is epidemic in parts of U.S.
• Major environmental justice problem.
• Evidence of adverse effects below 10 Pg/dL.
Reading
Readin
ing Score
Lead Toxicity - Still A Major
Public Health Problem
• Systemic toxin associated with numerous
adverse conditions and diseases in humans.
Blood lead levels ((P
(Pg/dL)
Pg/dL)
Lanphear BP, et al. Public Health Reports 2000;115:521-529.
Relationship of Lead-IQ Scores among Children for
Seven Prospective Lead-Exposed Cohorts
Composite IQ Score
120
110
100
90
Cleveland
Cincinnati
Rochester
80
Yugoslavia
70
0
10
20
30
40
Concurrent Blood Lead (Pg/dl)
Canfield R, et al. NEJM 2003;348:1517-1526.
50
60
Relationship of Concurrent Blood Lead
Concentration with Children䇻s Intellectual Function
Estimated Lead-associated IQ Deficits by Concurrent
Blood Lead Concentration, 5th to 95th percentile
105
Restricted Cubic Spline
Spl
Log-linear
Range of Blood Lead
Estimated IQ
Deficit (95% CI)
2.4 to 30 Pg/dL
6.9
(4.2, 9.4)
2.4 to 10 Pg/dL
3.9
(2.4, 5.3)
10 to 20 Pg/dL
1.9
(1.2, 2.6)
20 to 30 Pg/dL
1.1
(0.7, 1.5)
IQ
100
95
90
85
0
5
10
15
20
25
30
35
40
45
50
Concurrent Blood Lead (ȝg/dL)
Lanphear BP, et al. EHP 2005;113:894-899.
Relationship of Concurrent Blood Lead Concentration
with Children䇻s Intellectual Function at Blood Lead
Levels Above and Below 7.5 Pg/dL
Relationship of Concurrent Blood Lead
Concentration with Children䇻s
Intellectual Function
105
Log-linear model
Peak blood lead •7.5 Pg/dL
Peak blood lead <7.5 Pg/dL
PPTV Score
IQ
100
95
p = 0.015
90
85
0
10
20
30
40
Concurrent Blood Lead (Pg/dL)
50
Kordas K, et al. Environmental Research 2006;100:371-386.
Body Burdens of Lead in Ancient Peoples,
Typical American and Overt Lead Poisoning
Neurite Le
Length (microns)
Effects of Lead Exposure on
Neurite Length of Dopaminergic
Neurons
Neuronal Growth in Early
Childhood
Risk for Spontaneous Abortion by
Maternal Blood Lead
Concentration
*
*
*
Pg/dL equivalent of blood lead
Blood Lead (Pg/dL)
( g/dL)
Schneider JS, et al. Neurotox & Teratol 2003:25:555-559.
Borja-Aburto VH, et al. Am J Epidemiol 1999:150:590-597.
Reading Scores by Serum Cotinine in US
Children NHANES III
Children,
III, 1998-1994
Relationship of Tobacco Use during
Pregnancy and Birthweight
92.5
90.0
87.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Cotinine (ng/ml)
Yolton K, et al. Environ Health Perspect 2005;113:98-103.
England LJ, et al . Am J Epidemiol 2001;154:694-701.
Number of Arrests by Childhood Lead Exposure:
8
The Cincinnati Lead Study
Association of Blood Lead Levels
and Delinquency in Adolescents
Delinquency Score
Number of Arrests
6
Males
4
2
Females
0
l
0
5
10
15
20
25
Six-Year Blood Lead Levels (µg/dL)
Dietrich KN, et al. Neurotox & Teratol 2001;23:511-518.
* Accounting for birthweight, age, prenatal tobacco exposure, maternal age at delivery,
maternal IQ, maternal arrest history, HOME Score.
30
Relationship of Lead Exposure
and Murder Rate (/100,000) in the
U.S.
Verb Generation Task by Lifetime Measure of
Lead Exposure
Low Lifetime Mean Blood
Lead (7.6 Pg/dL)
Nevin R. Environmental Research 2000:83;1-22
Is Lead Toxic at Blood Lead
Levels below 10 ȝg/dL?
䇾The work group concluded that, while
available evidence does not permit a
definitive causal interpretation of the
observed associations between higher BLLs
and adverse health indicators for values
<10 ȝg/dL, the weight of available evidence
favors, and does not refute, the
interpretation that these associations are, at
least in part, causal.䇿
High Lifetime Mean Blood
Lead (26 Pg/dL)
Yuan W, et al. Pediatrics (in press).
Why not change the blood lead
level of concern at this time?
• There are no effective 䇾clinical䇿 interventions to
lower blood lead for children with levels < 10 µg/dL
• Children can䇻t be classified as having blood lead
levels < or > 10 µg/dL because of the inaccuracy
inherent in laboratory testing
• There is no evidence of a threshold; thus, lowering
the 䇾level of concern䇿 would be arbitrary and
provide uncertain benefits
An Element of Prevention
Types of Prevention
Decline in Children䇻s Blood Lead Levels due to
Regulation
Lead-Based Paint
Poisoning
Prevention Act
• Education
Lead in Plumbing
Ban (1986)
Begin PhaseOut of Leaded
Gasoline
• Enforcement
Lead-Based Paint
Hazard Reduction
Act (1992)
Residential Lead
Paint ban (1978)
• Engineering
> Cost
Ban on Lead
Solder in Canned
Foods (1995)
> Efficacy
Year
Thank you for your attention!