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Chapter 3 Environmental Toxicants and Neurocognitive Development Overview Vulnerable periods in the neurocognitive development of children List and discuss.

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Presentation on theme: "Chapter 3 Environmental Toxicants and Neurocognitive Development Overview Vulnerable periods in the neurocognitive development of children List and discuss."— Presentation transcript:

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 1.Fetal death 2.Death at an older age related to early or recent exposure 3.Malformations related to in utero exposure 4.Growth retardation related to in utero or later exposure 5.Developmental disabilities, including intellectual disability, learning disabilities, and cerebral palsy 6.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.


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