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Key Elements of a Primary Prevention Program
Percent of Preschool Children Exceeding Selected Blood Lead Levels, NHANES II - III
0
10
20
30
40
50
60
70
80
90
100
1976-80 1988-91 1991-94
10 µg/dL
15 µg/dL
20 µg/dL
25 µg/dL
Pirkle JL, et al. Environ Health Perspect 1998;106:745-50.
Lead Toxicity - Still A Major Public Health Problem
• Lead toxicity is epidemic in parts of U.S.
• Major environmental justice problem.
• Evidence of adverse effects below 10 g/dl.
• Systemic toxin associated with numerous
adverse conditions and diseases in humans.
Lead-associated Reading Deficits in U.S. Children
75
80
85
90
95
100
105
<2.5 2.5 5 7.5 10
Blood lead levels (g/dl)
Rea
ding
Sco
re
Lanphear BP, et al. Public Health Reports 2000;115:521-529.
Canfield R, et al. NEJM 2003;348:1517-1526.
Relationship of Lead-IQ Scores among Children for Seven Prospective Lead-Exposed Cohorts
70
80
90
100
110
120
0 10 20 30 40 50 60
Boston
Cincinnati
Mexico
Port Pirie
RochesterYugoslavia
Cleveland
Concurrent Blood Lead (g/dl)
IQ
Relationship of Concurrent Blood Lead Concentration with Children’s Intellectual Function using a Restricted
Cubic Spline Function
Concurrent Blood Lead (g/dL)
IQ
85
90
95
100
105
0 5 10 15 20 25 30 35 40 45 50
Estimated Lead-associated IQ Deficits by Concurrent Blood Lead Concentration, 5th to 95th percentile
Range of Blood Lead Estimated IQ Deficit (95% CI)
2.4 to 30 g/dL 6.9 (4.2, 9.4)
2.4 to 10 g/dL 3.9 (2.4, 5.3)
10 to 20 g/dL 1.9 (1.2, 2.6)
20 to 30 g/dL 1.1 (0.7, 1.5)
Lanphear BP, et al. EHP 2005;113:894-899.
Relationship of Concurrent Blood Lead Concentration with Children’s Intellectual Function at Blood Lead Levels
Above and Below 7.5 g/dL
85
90
95
100
105
0 10 20 30 40 50
Peak blood lead <7.5 g/dL
Peak blood lead ≥7.5 g/dL
Log-linear model
Concurrent Blood Lead (g/dL)
IQ
p = 0.015
Risk for Spontaneous Abortion by Maternal Blood Lead Concentration
0
2
4
6
8
10
12
< 5 5 to 9 10 to 14 > 15
Odd
s R
atio
* Borja-Aburto VH, et al. Am J Epidemiol 1999:150:590-597.
Blood Lead (g/dL)
Association of Blood Lead Levels and Delinquency in Adolescents
0
1
2
3
4
5
6
7
8
9
Lowest Low Medium High
Blood Lead Level
Total Score
Prenatal PbB
Average Childhood PbB
78 Month PbB
Dietrich KN. Neurotox & Teratol 2001;23:511-518.
Relationship of Lead Exposure and Murder Rate (/100,000) in the U.S.
Nevin R. Environmental Research 2000:83;1-22
Why not change the blood lead level of concern at this time?
• There are no effective “clinical” interventions to lower blood lead for children with levels < 10 µg/dL
• Children can’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 “level of concern” would be arbitrary and provide uncertain benefits
Types of Prevention
• Education
• Enforcement
• Engineering
> Cost > Efficacy
Decline in Children’s Blood Lead Levels due to Regulation
0
2
4
6
8
10
12
14
16
18
20
1970 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000
Blood Lead Levels (µg/dL)
YearSource: CDC
Lead-Based Paint Poisoning
Prevention Act
Begin Phase-Out of Leaded
Gasoline
Residential Lead Paint ban (1978)
Lead-Based Paint Hazard Reduction
Act (1992)
Lead in Plumbing Ban (1986)
Ban on Lead Solder in Canned
Foods (1995)
Why Primary Prevention?
• Adverse effects of lead are persistent.
• Adverse effects of lead are systemic.
• Chelation does not result in improved
neurobehavioral outcomes.
• No discernable threshold for adverse effects
of lead exposure.
• Prevention is cost-beneficial.
Steps to Prevent ChildhoodLead Exposure
• Identify sources of lead
• Identify unacceptable levels of lead in contributing sources
• Test efficacy and safety of interventions to reduce lead exposure
• Develop and implement regulations and screening programs.
Percent Increase in Blood Lead from Sources of
Lead Exposure during Early Childhood
0
10
20
30
40
50
Soil Lead Soil Ingestion Water Lead Dust Lead
Per
cen
t In
crea
se
Lanphear BP, et al. Journal of Pediatrics 2002;140:40-47.
Frequency of Mouthing Behaviors during Early Childhood
05
101520253035404550
6 12 18 24
Mouth Sill Soil Ingestion Paint Chips
Pe
rce
nt
Months of Age
Lanphear BP, et al. Journal of Pediatrics 2002;140:40-47.
Contribution of Lead-contaminated Floor Dust to Blood Lead Level by Age
00.10.20.30.40.50.60.70.80.9
1
6 9 12 18 24 30 36 42 48 60 72
Model R2
Dust Lead
Cor
rela
tion
Bornschein R. (unpublished data).
Age (months)
Screening
Effect of Lead Hazard ControlsResults of Controlled Trials
Hazard BPb * Age Change
Control (µg/dl) (µg/dl)
Charney Dust Control > 30 15 - 72 - 6.9
Farfel Abatement > 29 9 - 72 - 1.9
Staes Stabilization > 25 < 72 - 4.0
Aschengrau Abatement 3 - 22 < 48 + 6.5
* Blood lead levels at baseline
0
10
20
30
40
50
60
70
80
90
100
Geometric Mean Floor Dust Lead Levels (µg/ft2) by Abatement Status*
Pre-Abatement
Post-Abatement
6 MonthsPost-Abatement
*Farfel AJPH 1990: 80; 1240-1245
EPA Residential Standards for Lead-Contaminated House Dust
• Floors 40 g/ft2
• Sills 250 g/ft2
• Troughs 800 g/ft2
Contribution of Lead-Contaminated Floor Dust to Children’s Blood Lead
0
5
10
15
20
25
30
0 10 20 30 40 50 60 70 80 90 100
Percent Blood Lead
> 10 µg/dl
Pooled Analysis
LID Study
Floor Dust Lead (g/ft2)
Lanphear BP, et al. Environmental Research 1998;79:51-68.
Risk of blood lead levels > 10 g/dl by floor dust lead levels (g/ft2)
0123456789
2.5 to 5 5 to 10 15 to 20 20 to 25 >25
Floor dust lead levels (g/ft2)
Odd
s R
atio
Screening Characteristics for Blood Lead > 10g/dL by Lead-Contaminated Floor Dust
Floor Dust Lead (g/ft2) Sensitivity Specificity
2.5 0.95 0.16
5.0 0.87 0.38
10 0.68 0.55
15 0.54 0.72
20 0.41 0.83
25 0.33 0.88
30 0.24 0.91
35 0.19 0.93
40 0.16 0.96
Lanphear BP, et al. Public Health Reports 2005;120:305-310.
Percent > 10 µg/dL
< 10 10 - 19 20 - 29 30 - 39 40 - 49 > 50
Non-residential
Blood Lead Levels > 10 µg/dL among Children in Rochester, 1995
Health Outcomes and Measuresof the Environment Study
12, 24 and 36-Month OutcomesExposures and Biomarkers for Pesticides, Lead and Cotinine
Behavior, Cognition and Executive FunctionHearing and Growth
Randomization
Enroll Women < 16 weeks gestation (n= 400)
36 - month visit
24 - month visit
12 - month visit
Injury Control Group(n = 200)
36 - month visit
24 - month visit
12 - month visit
Lead Hazard Group(n = 200)
Meconium Collection
Collection of Biomarkers and
exposure assessment in early childhood
Conduct prenatal surveys, collect maternal urine and blood samples for assessing fetal exposure to toxicants
Implications For Prevention• Emphasis to shift from screening children to
screening houses, yards and water.
• Empirically-derived health-based standards for lead in house dust, soil and water are needed.
• Randomized trials to assess if lead hazard controls are effective in preventing exposure.
• Studies to examine adverse effects of lead exposure at lower blood lead concentrations.
• Eliminate all non-essential uses of lead and develop regulations to control lead emissions.
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