Key Elements of a Primary Prevention Program

1
Key Elements of a Primary Prevention Program
2
Percent of Preschool Children Exceeding Selected
Blood Lead Levels, NHANES II - III
Pirkle JL, et al. Environ Health Perspect
1998106745-50.
3
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.

4
Lead-associated Reading Deficits in U.S. Children
Reading Score
Blood lead levels (?g/dl)
Lanphear BP, et al. Public Health Reports
2000115521-529.
5
Canfield R, et al. NEJM 20033481517-1526.
6
Relationship of Lead-IQ Scores among Children
for Seven Prospective Lead-Exposed Cohorts
120
Boston
110
Mexico
Port Pirie
100
IQ
90
Cleveland
Cincinnati
80
Rochester
Yugoslavia
70
0
10
20
30
40
50
60
Concurrent Blood Lead (?g/dl)
7
Relationship of Concurrent Blood Lead
Concentration with Childrens Intellectual
Function using a Restricted Cubic Spline Function
105
100
IQ
95
90
85
0
5
10
15
20
25
30
35
40
45
50
Concurrent Blood Lead (?g/dL)
8
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 2005113894-899.
9
Relationship of Concurrent Blood Lead
Concentration with Childrens Intellectual
Function at Blood Lead Levels Above and Below 7.5
?g/dL
105
Log-linear model
Peak blood lead 7.5 ?g/dL
100
Peak blood lead lt7.5 ?g/dL
IQ
95
p 0.015
90
85
0
10
20
30
40
50
Concurrent Blood Lead (?g/dL)
10
Risk for Spontaneous Abortion by Maternal Blood
Lead Concentration
Odds Ratio
Blood Lead (?g/dL)
Borja-Aburto VH, et al. Am J Epidemiol
1999150590-597.
11
Association of Blood Lead Levels and Delinquency
in Adolescents
Dietrich KN. Neurotox Teratol 200123511-518.

12
Relationship of Lead Exposure and Murder Rate
(/100,000) in the U.S.
Nevin R. Environmental Research 2000831-22
13
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 lt 10
  µg/dL
• Children cant be classified as having blood lead
  levels lt or gt 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

14
Types of Prevention

• Education
• Enforcement
• Engineering

gt Cost
gt Efficacy
15
Decline in Childrens Blood Lead Levels due to
Regulation
Lead-Based Paint Poisoning Prevention Act
Ban on Lead Solder in Canned Foods (1995)
Lead in Plumbing Ban (1986)
Begin Phase-Out of Leaded Gasoline
Lead-Based Paint Hazard Reduction Act (1992)
Residential Lead Paint ban (1978)
Year
Source CDC
16
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.

17
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.

18
Percent Increase in Blood Lead from Sources of
Lead Exposure during Early Childhood
Percent Increase
Lanphear BP, et al. Journal of Pediatrics
200214040-47.
19
Frequency of Mouthing Behaviors during Early
Childhood
Percent
Months of Age
Lanphear BP, et al. Journal of Pediatrics
200214040-47.
20
Contribution of Lead-contaminated Floor Dust to
Blood Lead Level by Age
Screening
Correlation
Age (months)
Bornschein R. (unpublished data).
21
Effect of Lead Hazard ControlsResults of
Controlled Trials

• Hazard BPb Age Change
• Control (µg/dl) (µg/dl)
• Charney Dust Control gt 30 15 - 72 - 6.9
• Farfel Abatement gt 29 9 - 72 - 1.9
• Staes Stabilization gt 25 lt 72 - 4.0
• Aschengrau Abatement 3 - 22 lt 48 6.5

Blood lead levels at baseline
22
Geometric Mean Floor Dust Lead Levels (µg/ft2) by
Abatement Status
Post- Abatement
6 Months Post-Abatement
Pre- Abatement
Farfel AJPH 1990 80 1240-1245
23
EPA Residential Standards for Lead-Contaminated
House Dust

• Floors 40 ?g/ft2
• Sills 250 ?g/ft2
• Troughs 800 ?g/ft2

24
Contribution of Lead-Contaminated Floor Dust to
Childrens Blood Lead
Floor Dust Lead (?g/ft2)
Lanphear BP, et al. Environmental Research
19987951-68.
25
Risk of blood lead levels gt 10 ?g/dl by floor
dust lead levels (?g/ft2)
Odds Ratio
Floor dust lead levels (?g/ft2)
26
Screening Characteristics for Blood Lead gt
10?g/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
2005120305-310.
27
Blood Lead Levels gt 10 µg/dL among Children in
Rochester, 1995
28
Health Outcomes and Measures of the Environment
Study
Enroll Women lt 16 weeks gestation (n 400)
Conduct prenatal surveys, collect maternal urine
and blood samples for assessing fetal exposure
to toxicants
Collection of Biomarkers and exposure assessment
in early childhood
Randomization
Meconium Collection
Injury Control Group (n 200)
Lead Hazard Group (n 200)
12 - month visit
12 - month visit
24 - month visit
24 - month visit
36 - month visit
36 - month visit
12, 24 and 36-Month Outcomes Exposures and
Biomarkers for Pesticides, Lead and
Cotinine Behavior, Cognition and Executive
Function Hearing and Growth
29
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.