1. Chapter 3 Environmental Toxicants and Neurocognitive Development
Overview
Vulnerable periods in the neurocognitive development of children
List and discuss several known neurotoxicants
Possible mechanisms of action of neurotoxicants
Current limitations on protecting children from neurotoxins and other hazardous chemicals
Chapter 3 slides in Children with Disabilities, Seventh Edition, Online Companion Materials.
Copyright © 2013 Paul H. Brookes Publishing Co., Inc. All rights reserved.

2. Sample Case Study: Thalidomide
Morning-sickness drug marketed over the counter in Europe, Canada, and Japan in the 1950s and early 1960s
Caused ~10,000 infants to be born with birth defects due to first-trimester exposure
Chapter 3 slides in Children with Disabilities, Seventh Edition, Online Companion Materials.
Copyright © 2013 Paul H. Brookes Publishing Co., Inc. All rights reserved.

3. Effects of Neurotoxicants
Fetal death
Death at an older age related to early or recent exposure
Malformations related to in utero exposure
Growth retardation related to in utero or later exposure
Developmental disabilities, including intellectual disability, learning disabilities, and cerebral palsy
Subclinical outcomes, such as statistically significant decrements in IQ, executive functioning, and/or adaptive skills
Chapter 3 slides in Children with Disabilities, Seventh Edition, Online Companion Materials.
Copyright © 2013 Paul H. Brookes Publishing Co., Inc. All rights reserved.

4. Scope of the Issue
3% of all neurobehavioral disorders in children directly caused by exposure to environmental contaminants
25% of all neurobehavioral disorders in children caused by interactions among environmental factors
13% of all neuropsychiatric diseases caused by environmental factors
Chapter 3 slides in Children with Disabilities, Seventh Edition, Online Companion Materials.
Copyright © 2013 Paul H. Brookes Publishing Co., Inc. All rights reserved.

5. Susceptible Periods of Development
Before conception, by influencing the sperm or ova
During pregnancy
After birth
For the first two decades of life
Chapter 3 slides in Children with Disabilities, Seventh Edition, Online Companion Materials.
Copyright © 2013 Paul H. Brookes Publishing Co., Inc. All rights reserved.

6. Toxicants Lead: Found in lead-based paint
Peripheral neuropathy in adults, CNS damage in children
Attention deficit, decreased adult gray matter, decreased brain volume, and impaired language function
Mercury:
Found in thermometers, barometers, and fluorescent lighting and as MeHg in contaminated fish or shellfish
Severe brain damage with microcephaly, seizures, severe cognitive delay, and motor deficits with prenatal exposure to high doses
Cognitive and motor deficits with childhood exposure to acute doses
Minimal effects in exposed adults
Chapter 3 slides in Children with Disabilities, Seventh Edition, Online Companion Materials.
Copyright © 2013 Paul H. Brookes Publishing Co., Inc. All rights reserved.

7. Toxicants (continued)
Arsenic:
Found in contaminated drinking water or industrial sites
Problems with learning, short-term memory, decreased IQ, and concentration
Alcohol:
Fetal alcohol spectrum disorder (FASD) from maternal ingestion during pregnancy
Range of physical, behavioral, and cognitive problems
More severe cases: fetal alcohol syndrome (FAS)
Milder cases: partial fetal alcohol syndrome (pFAS)
FAS: microcephaly, behavior problems, attention-deficit/hyperactivity disorder (ADHD), executive function deficits, learning problems, decreased brain volume, and brain abnormalities
Chapter 3 slides in Children with Disabilities, Seventh Edition, Online Companion Materials.
Copyright © 2013 Paul H. Brookes Publishing Co., Inc. All rights reserved.

8. Toxicants (continued)
Polychlorinated biphenyls (PCBs):
In electronics, plastics, paint, and pesticides, fish, and farm-raised salmon
Cross the placenta and are found in breast milk
High-dose contamination: cognitive delays, behavior disorders, and growth retardation
Low-dose contamination: deficits in neuromotor develop-ment and IQ; problems with attention and impulse control
Pesticides:
Over 1,300 registered chemicals
Dichlorodiphenyltrichloroethane (DDT): crosses the placenta; found in breast milk; has variable effects
Chlorpyrifos: increased risk of developmental delay, ADHD, and autism at age 3
Chapter 3 slides in Children with Disabilities, Seventh Edition, Online Companion Materials.
Copyright © 2013 Paul H. Brookes Publishing Co., Inc. All rights reserved.

9. Toxicants (continued)
Endocrine disrupting chemicals:
Phthalates, PCBs, brominated flame retardants, DDT, bisphenol A, and others
Interferes with homeostatic, reproductive, and developmental hormones
Estrogenic, antiestrogenic, antiandrogenic, antithyroid, or antiprogestin effects
Decreased IQ and other neurodevelopmental abnormalities
Mixed toxicants:
Difficult to replicate in lab settings or determine outcome
Chapter 3 slides in Children with Disabilities, Seventh Edition, Online Companion Materials.
Copyright © 2013 Paul H. Brookes Publishing Co., Inc. All rights reserved.

10. Toxicants (continued)
Environmental tobacco smoke:
Over 4,000 chemicals
Occurs prenatally through maternal smoking or exposure
Reductions in cortical gray matter, alteration in white matter development, and deficits in speech and language skills, visual/spatial abilities, behavior, and IQ
Dietary exposures and ADHD:
Not conclusively linked by the U.S. Food and Drug Administration
Small subset of children with ADHD have worsening behavior due to certain foods
Chapter 3 slides in Children with Disabilities, Seventh Edition, Online Companion Materials.
Copyright © 2013 Paul H. Brookes Publishing Co., Inc. All rights reserved.

11. Public Policy Implications
Certain infant bottles, toys, and cookware a concern
No U.S.-required testing for nonpharmaceutical and nonpesticide chemicals
No commercial incentives to conduct safety studies
Pending legislation to remediate this
Chapter 3 slides in Children with Disabilities, Seventh Edition, Online Companion Materials.
Copyright © 2013 Paul H. Brookes Publishing Co., Inc. All rights reserved.

12. Summary Over 1,000 chemicals are neurotoxicants
Similar effects in humans as in animals with same exposure time
Exposure to same toxicant at different times = different effects
Most damage caused by toxicants is irreversible; focus is on prevention
Chapter 3 slides in Children with Disabilities, Seventh Edition, Online Companion Materials.
Copyright © 2013 Paul H. Brookes Publishing Co., Inc. All rights reserved.