Table 3.
Human 5–10 μg/dL. Summary of key studies in humans outlining the neurodevelopmental, cognitive, and achievement outcomes of blood lead levels between 5–10 μg/dL reported at p< .05. Excludes studies not explicitly reporting blood lead levels. Blood lead levels are listed as averages, unless otherwise noted, and appear as reported in respective studies. The most conservative adjusted statistical outcomes available are presented. Inclusion/exclusion criteria were established to determine study selection.1
| Test | Outcome (Using adjusted scores when available) | Mean Blood Lead Level (μg/dL) | Design | Age of Testing | Reference |
|---|---|---|---|---|---|
| 5–10 μg/dL, Human | |||||
| I. Reading | |||||
| WRAT-R; Reading Subset | Deficits | 7.5–10.0 μg/dL | n=4,853 Cross-sectional, NHANES-III Multiple linear regression No reference group |
6–16 yrs | Lanphear et al., 2000 |
| WIAT; Reading Composite | Deficits | 5–10.0 μg/dL | n=389 One test point 1–2 ug/dL, reference group |
6–10 yrs | Surkan et al., 2007 |
| II. Verbal Processing/Memory | |||||
| WRAML; Verbal Memory Index | Deficits | 5–10.0 μg/dL | n=389 One test point 1–2 μg/dL, reference group |
6–10 yrs | Surkan et al., 2007 |
| Color Naming Task; Information Processing Speed | NS | <7.5 μg/dL | n=237 One test point Multiple regression using quartiles No reference group |
7.5 yrs | Chiodo et al., 2004 |
| III. Intelligence Scale/Achievement Test | |||||
| WISC-III, Full-scale & Performance | Deficits | <7.5 μg/dL | n=237 One test point Multiple regression using quartiles No reference group |
7.5 yrs | Chiodo et al., 2004 |
| WISC-III, Full-scale & Performance | Deficits | 5–10.0 μg/dL | n=389 One test point 1–2 μg/dL, reference group |
6–10 yrs | Surkan et al., 2007 |
| WISC-R, Full-scale | Deficits | 6.3–6.5 μg/dL | n=148 Longitudinal Multiple regression No reference group |
Association between 24 mos & 57 mos or 10 yrs | Bellinger et al., 1992 |
| Full-scale | NS | 6.3–7.8 μg/dL | Longitudinal | Association between 6, 12, or 18 mos & either 57 mos or 10 yrs | |
| WIAT Listening Comprehension | Deficits | 5–10.0 μg/dL | n=389 One test point 1–2 μg/dL, reference group |
6–10 yrs | Surkan et al., 2007 |
| K-TEA, Battery Composite Score | Deficits | 6.3–6.5 μg/dL | n=148 Longitudinal Multiple regression No reference group |
Association between 24 mos & 57 mos; 24 mos & 10 yrs | Bellinger et al., 1992 |
| K-TEA, Battery Composite Score | NS | 6.3–7.8 μg/dL | Longitudinal | Association between 6, 12, or 18 mos & either 57 mos or 10 yrs | |
| Stanford-Binet Intelligence Scale, Composite Score | Deficits | 7.4 μg/dL (36 mos) 7.7 μg/dL (60 mos) |
n=172 Longitudinal Nonlinear mixed model No reference group |
36 mos 60 mos |
Canfield et al., 2003 |
| WISC-III, Verbal | Deficits | 5–10.0 μg/dL | n=389 One test point 1–2 μg/dL, reference group |
6–10 yrs | Surkan et al., 2007 |
| WISC-R, Verbal | Deficits | 6.3–6.5 μg/dL | n=148 Longitudinal Multiple regression No reference group |
Association between 24 mos & 57 mos or 10 yrs | Bellinger et al., 1992 |
| WISC-R, Verbal | NS | 6.3–7.8 μg/dL | n=169 Longitudinal Multiple regression No reference group |
Association between 6, 12, or 18 mos & either 57 mos or 10 yrs | |
| WISC-R, Block Design | Deficits | 7.5–10.0 μg/dL | n=4,853 Cross-sectional, NHANES-III Multiple linear regression using quartiles No reference group |
6–16 yrs | Lanphear et al., 2000 |
| WISC-III, Block Design | Deficits | <10.0 μg/dL | |||
| WRAT, Arithmetic | Deficits | 7.5–10.0 μg/dL | |||
| WIAT, Math Composite | Deficits | 5–10.0 μg/dL | n=389 One test point 1–2 μg/dL, reference group |
6–10 yrs | Surkan et al., 2007 |
| IV. Cognition | |||||
| McCarthy Scales of Children's Abilities General Cognitive Index; Verbal Subscale | NS | 6.4–6.8 μg/dL | n=170 Longitudinal Regression analysis No reference group |
24 mos Or 57 mos |
Bellinger et al., 1991 |
| McCarthy Scale of Children's Abilities; General Cognitive Index-Quantitative Subscale | NS | 6.4–6.8 μg/dL | n=170 Longitudinal Regression analysis No reference group |
24 mos Or 57 mos |
Bellinger et al., 1991 |
| McCarthy Scale of Children's Abilities; General Cognitive Index Perceptual-Performance Subscale | Deficits | 6.4–6.8 μg/dL | n=170 Longitudinal Regression analysis No reference group |
24 mos Or 57 mos |
Bellinger et al., 1991 |
| McCarthy Scale of Children's Abilities; General Cognitive Index Motor Subscale | NS | ||||
| McCarthy Scale of Children's Abilities; General Cognitive Index Memory Subscale | NS | ||||
| V. Attention | |||||
| Child Behavior Checklist-Attention Teacher Report Form | NS | <10.0 μg/dL | n=237 One test point Multiple regression using quartiles No reference group |
7.5 yrs | Chiodo et al., 2004 |
| Child Behavior Checklist-Attention Teacher Report Form | NS | <7.5 μg/dL | |||
| Barkley Off Task | NS | <7.5 μg/dL | |||
| Barkley Off Task | Deficits | <10.0 μg/dL | |||
| Continuous Performance Test; Sustained Attention | NS | <10.0 μg/dL | |||
| Mental Rotation; Reaction Time | Deficits | <7.5 μg/dL | |||
| VI. Withdrawn | |||||
| Child Behavior Checklist-Withdrawn Teacher Report Form | Deficits | <7.5 μg/dL | n=237 One test point Multiple regression using quartiles No reference group |
7.5 yrs | Chiodo et al., 2004 |
| Child Behavior Checklist-Withdrawn Teacher Report Form | NS | <10.0 μg/dL | |||
| VII. Short-term Memory/Working Memory | |||||
| Seashore Rhythm Test; Auditory Working Memory | NS | <7.5 μg/dL | n=237 One test point Regression analysis using quartiles No reference group |
7.5 yrs | Chiodo et al., 2004 |
| Seashore Rhythm Test; Auditory Working Memory | Deficits | <10.0 μg/dL | |||
| VIII. Visual-Motor | |||||
| Bruininks-Oseretsky; Visual-Motor Control | NS | Neonatal: 8.4 μg/dL 72 mos: 10.1 μg/dL |
n=245 Longitudinal Regression analysis |
Neonatal Day 10 association at 72 mos | Dietrich et al., 1993 |
| Bruininks-Oseretsky; Visual-Motor Control | Deficits | Neonatal: 8.4 μg/dL 72 mos: 10.1 μg/dL |
n=245 Longitudinal Regression analysis |
72 mos | Dietrich et al., 1993 |
| IX. Dexterity/Balance | |||||
| Bruininks-Oseretsky; Upper Limb Speed & Dexterity | Deficits | Neonatal: 8.4 μg/dL 72 mos: 10.1 μg/dL |
n=245 Longitudinal Regression Analysis |
Neonatal Day 10 association at 72 mos | Dietrich et al., 1993 |
| Bruimnks-Oseretsky; Fine Motor Composite | Deficits | ||||
| Bruininks-Oseretsky; Bilateral Coordination | NS | ||||
| Bruininks-Oseretsky; Upper Limb Speed & Dexterity | Deficits | 72 mos: 10.1 μg/dL | n=245 Longitudinal Regression analysis |
72 mos | Dietrich et al., 1993 |
| Bruininks-Oseretsky; Fine Motor Composite | Deficits | ||||
| Bruininks-Oseretsky; Bilateral Coordination | Deficits | ||||
| X. ADHD | |||||
| DSM-IV Criteria for ADHD | Association | lst tertile: 0.2–0.8 μg/dL 2nd tertile: 0.9–1.3 μg/dL 3rd tertile: >1.3 μg/dL | n=2,588 Cross-sectional, NHANES (2001–2004) Logistic regression No reference group |
8–15 yrs | Froehlich et al., 2009s |
| XI. Conduct Disorder | |||||
| DSM-IV Criteria for Conduct Disorder | Association | 1st quartile: 0.2–0.7 μg/dL 2nd quartile: 0.8–1.0 μg/dL 3rd quartile: 1.1–1.4 μg/dL 4th quartile: 1.5–10μg/dL |
n=3,081 Cross-sectional, NHANES (2001–2004) |
8–15 yrs | Braun et al., 2008 |
Abbreviations: ADHD=Attention Deficit Hyperactivity Disorder; DSM-IV=Diagnostic and Statistical Manual of Mental Disorder IV Version; K-TEA=Kaufman Test of Educational Achievement; MOS=Months; NS=Not Significant; NHANES (2001 −2004)=National Health and Nutrition Examination Survey 2001–2004 Version; NHANES III=National Health and Nutrition Examination Survey III Version; WAIS -IV=Wechsler Adult Intelligence Scale IV Version; WIAT=Wechsler Individual Achievement Test; WISC-III=Wechsler Intelligence Scale for Children III Version; WISC-R=Wechsler Intelligence Scale for Children Revised; WRAML=Wide Range Assessment of Memory and Learning; WRAT=Wide Range Achievement Test; YRS=Years