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  New Studies Indicate Heavy Metal Toxicity Still a Real Threat for Children & Adolescents

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Getting the Lead Out: Easier Said Than Done

Despite years of progress in reducing lead contamination in the environment, this pervasive heavy metal toxin stubbornly refuses to break down - remaining a hidden threat to the developing neurocognitive health of children. At the recent Joint Meeting of the Pediatric Academic Societies and American Academy of Pediatrics in Boston, several teams of investigators reported new findings linking even low dose lead exposure to problems in child and adolescent development.

Bruce P. Lanphear, M.D., M.P.H., of the Children's Hospital Medical Center of Cincinnati, and his co-researchers report that blood levels of lead even well below the level currently defined as toxic (>10 g/dL) in children are associated with poorer cognitive skills. The team evaluated data for 4,853 American children between the ages of 6 and 16 and found that as blood lead levels rise, starting at concentrations as low as 2.5 g/dL, scores for reading, math, and other basic skills significantly drop. This relationship is independent of race, region of the country, parental education, and other socioeconomic factors.

"These data suggest that 12.8 million (35%) U.S. children and adolescents who were born between 1972 and 1988 and who had a blood lead concentration in excess of 2.5 g/dL are adversely affected by environmental lead exposure," the study concluded. Dr. Lanphear argues that the current limit of 10 g is "inadequate to protect children," and should be at least half that amount.

While the possible damaging effects of lead exposure on cognitive ability in children are disturbing enough, the potential negative impact on behavior may be just as profound.

Psychiatrist Herbert L. Needleman, M.D. (recipient of the 1995 Heinz Award in the Environment for his efforts to protect children from toxic exposure), of the University of Pittsburgh and others presented strong evidence that lead exposure is an important risk factor for juvenile delinquency. Compared to agroup of controls, youths arrested and charged in a local juvenile court had bone lead levels that were, on the average, nearly seven times higher than their peers. Higher lead levels made males twice as likely, and females almost eight times more likely, to be arrested for delinquent behavior.

"Early lead exposure accounts for between 11% and 37% of arrested delinquents," the study asserts. Reducing lead exposure should be a primary prevention strategy against delinquency in adolescents, Dr. Needleman and his colleagues urge.

Parental education would undoubtedly play a strong role in such a prevention program. According to a survey by Pediatrician Hans B. Kersten, M.D., of St. Christopher's Hospital for Children in Philadelphia, this education is much needed. Based on interviews with over 240 parents of young infants, Dr. Kersten discovered that parents at an inner city pediatric clinic, like their suburban counterparts, have some basic knowledge of lead exposure and lead poisoning, yet know relatively little about specific methods of prevention and the importance of nutrition..

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Lead Stunts Sensory Mapping in the Developing Brain: Heavy Metal Toxin May Suppress Growth of Neuron Clusters

How does lead impair brain development in children? One possible explanation is that the heavy metal stunts the preliminary mapping of sensory nerve cells in the brain.

Researchers from Johns Hopkins University recently examined the experimental effect of lead toxicity on the developing structure of the neocortex region in the brain. Stacked with layers of nerve cells, the neocortex plays a critical role in processing information. Because of its plasticity during early childhood, this region is particularly vulnerable to environmental stimuli.

Soon after birth, the neocortex quickly begins forming sensory "maps" comprised of structural units called columns. In rats, these columns contain clusters of nerve cells (barrels) arranged to mirror the precise pattern of whiskers on the rat's face. This brain-whisker connection allows the rat to process tactile information it gleans from its surroundings.

For the experiment, researchers added low doses of lead to a mother rat's drinking water for 10 days after she gave birth and examined structural changes in the brains of the nursing rat pups.

Compared with a control group, the rat pups exposed to low doses of lead showed up to 12% diminished size in barrel field area - the basic information processing units. The larger the dose of lead, the more this area of brain development was stunted.

Also, the more active the barrel field, the more its growth was suppressed by heavy metal exposure, suggesting a "special vulnerability of young children to lead," the researchers observed. Metabolic activity in the brain is at its peak during early childhood.

Researchers suspect that lead may interfere with cell receptors for glutamate, an amino acid neurotransmitter that seems to spur the formation of brain's sensory mapping during early infancy. Such an impaired mechanism would stymie the ability of tree-like extensions of brain nerve cells (called dendrites) to spread and branch out, thus reducing their ability to conduct signals.

The low levels of lead used in this study were akin to current exposure levels for many poorer inner city children, investigators cautioned. At higher levels, lead exposure can actually shrink the brain itself, reducing its weight and thickness by about 13%.

According to the EPA, drinking water, the mode of exposure used in this experimental study, is estimated to comprise about 10-20% of total lead exposure in children; in infants fed with baby formulas using tap water, this proportion rises to 40-60%. Surprisingly, unless plumbers have used the new lead-free solders now available, the newer the home, the greater the risk of lead contamination in drinking water due to the greater degree of leaching from newlyjoined copper pipe.

This and other information can be found in the EPA document, "Lead in Your Drinking Water ".

For more information about the threat of lead exposure to healthy childhood development, read Developmental Disorders of Toxic Origin.

Source: Wilson MA, Johnston MV, Goldstein GW, Blue ME. Neonatal lead exposure impairs development of rodent barrel field cortex. PNAS 2000;97(10):5540-5545.

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Hyperactivity and Element Imbalances

Hyperactivity can be triggered by nutritional deficiencies and toxic accumulations of certain heavy metals in the body. Because their bodies are smaller, and because their nervous systems are still in early stages of development, children are particularly vulnerable to the effects of element imbalances.

Lead is a potent toxin very commonly associated with a host of neurobehavioral problems in children, including hyperactivity, attention deficit, and other learning disorders. A leading expert on the effects of lead toxicity in children, Dr. H.L. Needlemen of the University of Pittsburgh Medical School has conducted scores of studies over the last 20 years clearly establishing the link between lead levels in children and specific hyperactive and attention deficit behavior traits 1-4.

Follow-up studies indicate that these effects often persist into adulthood 5. A common misconception is that lead exposure is only a problem for urban children of low socioeconomic status. Actually, lead toxicity can affect children of all backgrounds, because sources of exposure include not only lead-based paint, but contaminated soil, dust, food, and water - and may begin with prenatal exposure in the womb.

According to the American Academy of Child and Adolescent Psychiatry, an estimated one out of every six children in the United States has blood lead levels in the toxic range 6. What's more, researchers have discovered that the amount of lead necessary to produce central nervous system effects is far lower than previously realized 7.

Several other element imbalances are also strongly implicated in hyperactive behavior. A pilot study on metal levels in the hair of hyperactive children, for example, found raised levels of manganese and reduced levels of zinc in comparison with controls 8. Another finding is lowered zinc and vitamin B-6 in conjunction with high lead and copper 9. And because deficiencies of calcium, selenium, zinc, and iron are thought to increase uptake of heavy metal toxins such as lead, aluminum, cadmium, and mercury, key nutrient imbalances can increase the likelihood of toxic reactions that trigger hyperactivity 10.

References:

  1. Needleman HL. The Current Status of Childhood Low-Level Lead Toxicity. Neurotoxicology 1993;14(2-3):161-6.
  2. Needleman HL. The Neurobehavioral Consequences of Low Lead Exposure in Childhood. Neurobehav Toxicol Teratol 1982;4:6, 729-32.
  3. Bellinger D, Hu H, Titlebaum L, Needleman HL. Attentional Correlates of Denin and Bone Lead Levels in Adolescents. Arch Environ Health 1994;49(2):98-105.
  4. Needleman HL, Gunnoe C, Leviton A, Reed R, Peresie H, Maher C, Barrett P. Deficits in Psychologic and Classroom Performance of Children with Elevated Dentine Lead Levels. New Eng J Med 1979:300(130):689-695).
  5. Needleman HL, Schell A, Bellinger D, Leviton A, Allred EN. The Long-term Effects of Exposure to Low Doses of Lead in Childhood: An 11-year Follow-up Report. N Eng J Med 1990;322(2):83-8.
  6. American Academy of Child and Adolescent Psychiatry. Facts for Families: Lead Exposure, 1997.
  7. Needleman HL. Childhood Lead Poisoning. Curr Opin Neurol 1994;7(2):187-90.
  8. Barlow PJ. A Pilot Study on the Metal Levels in the Hair of Hyperactive Children. Med Hypotheses 1983;11(3):309-18.
  9. Pfieffer CC, Braverman ER. Zinc, the Brain and Behavior. Biol Psychiat 1982; 17(4):513-32.
  10. Needleman HL. The Persistent Threat of Lead: Medical and Sociological Issues. Curr Probl Pediatr 1988;18(12):697-744.

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Elemental Analysis Assessment for Toxic Elements

Elemental Analysis determines levels of toxic and nutritional elements in the body using a hair, blood, or urine sample. This test examines long-term exposure to lead and other toxins, as well as nutrient adequacy, for a thorough assessment of major elements in the body affecting behavior, mood, and cognition. Each specimen type provides a unique window into element status. A hair sample will reflect chronic toxic exposure and long-term nutritional deficiencies, while blood and urine assessment will gauge the effects of more recent imbalances. Possible treatments for element imbalances include chelation therapy, nutrient supplements, vitamins, water purifying systems, dietary changes, and other natural approaches. These tests are also helpful for monitoring the effectiveness of treatment and preventive therapies. Great Smokies Diagnostic Laboratory's Elemental Analysis specialist, Bob Smith, also discusses the The Role of Four Important Metals and Minerals in Children's Health.

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Notice: Great Smokies Diagnostic Laboratory provides this information as a service to subscribers. This information is for sole use of a licensed healthcare practitioner and is for educational purposes only. It is not meant for use as diagnostic information, and reports of research findings should in no way be construed as treatment recommendations. Linking to other sites does not constitute an endorsement of products or services.


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