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.