https://stacks.cdc.gov/view/cdc/37676/cdc_37676_DS1.pdf

Toxicological Profile for Lead

The development of the cerebral hemispheres was assessed by using measures of electroencephalographic coherence and phase in 577 children ranging in age from 2 months to early adulthood. Two categories of age-dependent change in electroencephalographic coherence and phase were noted: continuous growth processes that were described best by an exponential growth function, and discrete growth spurts that appeared in specific anatomical locations at specific postnatal periods. The left and right hemispheres developed at different rates and with different postnatal onset times with the timing of growth spurts overlapping the timing of the major developmental stages described by Piaget.

https://science.sciencemag.org/content/sci/236/4805/1110.full.pdf

Human cerebral hemispheres develop at different rates and ages.

Heavy metals: Implications associated to fish consumption.

This review summarizes the level of epidemiologic evidence for relationships between prenatal and/or early life exposure to environmental chemical contaminants and fetal, child, and adult health. Discussion focuses on fetal loss, intrauterine growth restriction, preterm birth, birth defects, respiratory and other childhood diseases, neuropsychological deficits, premature or delayed sexual maturation, and certain adult cancers linked to fetal or childhood exposures. Environmental exposures considered here include chemical toxicants in air, water, soil/house dust and foods (including human breast milk), and consumer products. Reports reviewed here included original epidemiologic studies (with at least basic descriptions of methods and results), literature reviews, expert group reports, meta-analyses, and pooled analyses. Levels of evidence for causal relationships were categorized as sufficient, limited, or inadequate according to predefined criteria. There was sufficient epidemiological evidence for causal...

Epidemiologic evidence of relationships between reproductive and child health outcomes and environmental chemical contaminants

Cadmium (Cd) is a heavy metal that has received considerable concern environmentally and occupationally. Cd has a long biological half-life mainly due to its low rate of excretion from the body. Thus, prolonged exposure to Cd will cause toxic effect due to its accumulation over time in a variety of tissues, including kidneys, liver, central nervous system (CNS), and peripheral neuronal systems. Cd can be uptaken from the nasal mucosa or olfactory pathways into the peripheral and central neurons; for the latter, Cd can increase the blood brain barrier (BBB) permeability. However, mechanisms underlying Cd neurotoxicity remain not completely understood. Effect of Cd neurotransmitter, oxidative damage, interaction with other metals such as cobalt and zinc, estrogen-like, effect and epigenetic modification may all be the underlying mechanisms. Here, we review the in vitro and in vivo evidence of neurotoxic effects of Cd. The available finding indicates the neurotoxic effects of Cd that was associated with both biochemical changes of the cell and functional changes of central nervous system, suggesting that neurotoxic effects may play a role in the systemic toxic effects of the exposure to Cd, particularly the long-term exposure.

https://downloads.hindawi.com/journals/omcl/2013/898034.pdf

Cadmium and Its Neurotoxic Effects

Hair cadmium and lead content were related to intelligence tests, motor impairment assessments, and school achievement scores from 149 children aged 5 to 16 yr enrolled in rural Maryland public school systems. Hair cadmium and lead were significantly correlated with both intelligence scores and school achievement scores, but not motor impairment scores. Significant relations with I.Q. were obtained after regressing out demographic factors and were observed, even in children within a normal I.Q. range. Evidence of different effects of cadmium and lead on cognitive development was obtained. Hierarchical regression analyses suggest that cadmium has a significantly stronger effect on verbal I.Q. than does lead and that lead has a stronger effect on performance I.Q. than does cadmium.

Effects of low levels of cadmium and lead on cognitive functioning in children.

Hair lead content, intelligence tests, school achievement, and motor impairment assessments were obtained from 149 public school children aged 5 to 16. Hair lead concentration significantly discriminated between groups and significantly predicted IQ scores, independent of group classifications. Regression analyses showed a significant negative correlation between lead and intellectual functioning, even in the normal to gifted IQ range. These results demonstrate a continuous inverse relationship between intelligence and relatively low levels of body lead in which the higher levels of cognitive function are affected before any signs of gross motor impairment are seen.

Intelligence and Lead Toxins in Rural Children

Although many different types of information are important to a complete science of learning disabilities, information about “alterable variables” is of particular value as we attempt to apply our science to helping children. This month's Topical Review addresses a set of environmental and diet variables that are clearly alterable and that may have an important impact on the way children think and learn. The studies reviewed here have employed advanced technology to assess the effects of these “alterable variables” on both brain functioning and cognitive performance. Although the subjects employed in the studies are not formally diagnosed as learning disabled, the implications of the findings for children who experience special learning problems are nevertheless quite clear.—JKT

R. W. Thatcher

Papers

Effects of low levels of cadmium and lead on cognitive functioning in children.

Intelligence and Lead Toxins in Rural Children

Nutrition, Environmental Toxins and Computerized EEG: A Mini-Max Approach to Learning Disabilities