This paper reflects the research and thoughts of a student at the time the paper was written for a course at Bryn Mawr College. Like other materials on Serendip, it is not intended to be "authoritative" but rather to help others further develop their own explorations. Web links were active as of the time the paper was posted but are not updated.
Biology 202, Spring 2005
First Web Papers
Lead is referred to as xenobiotic, meaning it is a foreign substance with no useful role in human physiology, toxic even in minute quantities. Rather than breaking down to be eliminated as a waste product, lead accumulates in the body's bones and tissues because the body recognizes it as if it were calcium. It may be absorbed from the gastrointestinal tract or through the respiratory system. Lead exposure can result in low sperm counts in men and can increase the risk of miscarriage or still birth among women. It damages the kidneys and gastrointestinal tract, and it can lead to a host of neurological problems including decreased cognitive abilities and increased behavior problems in children (Konopka, 2003). The trigger level for lead in children, or the level at which it is deemed harmful, has been lowered over the decades and currently stands at 10µg/dL, although recent studies suggest that adverse health effects exist in children at blood lead levels less than 10 µg/dL (Canfield et al., 2003).
The most common source of exposure to lead in the household is dust from lead paint, commonly used before 1978 when the federal government banned lead as an additive to paint used for housing (CDC). Lead may also leach into water that travels through antiquated lead pipes, particularly if the water flowing through the pipes is heated, acidic, or treated with chloramines, an alternative anti-bacterial additive to chlorine. Other common sources of exposure outside the home are remnants of used leaded fuel or other lead products in soil, older painted toys, furniture, or jewelry, food and liquids stored in lead crystal or lead-glazed pottery or porcelain, lead particles released into the air from lead smelters and cosmetics or folk remedies that contain lead, such as "greta" and "azarcon" used to treat upset stomachs (EPA).
Although lead can cause harm to children and adults alike, the most seriously deleterious effects of lead poisoning are experienced by children still developing mentally and physically. Children are more likely to be exposed to lead because are more likely to be exposed to certain toxins because they play outdoors. They are shorter than adults, which means they can breathe dust, soil, and vapors close to the ground. Children are smaller than adults, therefore childhood exposure results in higher doses of chemicals per body weight (CDC). They are more likely to be irrevocably damaged by lead poisoning because lead causes damage to the nerve cells of the brain while the brain is still developing. The dendrites of nerve cells in developing brains are cut short by lead, thereby reducing the connections between axons among adjacent neurons. Dendrites are most plentiful during the early years of childhood, especially between the ages of 1 and 5, and thin naturally with age. Thus it is crucial for healthy development to establish as many connections between neurons in the brain as possible through education and stimulation between the ages of 1 and 5. When children are exposed to lead which limits the connections being made during this important developmental period, the brain is irrevocably disadvantaged, resulting in decreased amounts of gray matter (braininjury.com). Chelation therapy, which involves reducing the lead concentrations in the bloodstream by orally administering succimer, or injecting ethylenediaminetetraacetic acid (EDTA), has been shown to be ineffective at increasing already damaged neurons and increasing diminished IQ (Rogan et al., 2001). Therefore, even when individuals undergo treatment during childhood, the damaged areas cannot be recovered.
The neurological damage resulting from exposure to lead can result in abnormal behavior, exhibited through increased irritability and violence, learning disabilities, mental retardation, and other functional difficulties. The social effects of these abnormal behaviors through teasing, peer isolation, falling behind in school, drug abuse, domestic abuse, and a lack of understanding about the basis of an individual's impairments may also compound the neurological damage, resulting in psychological trauma, which studies show can cause other types of brain damage. (Rosen, 2001) All these conditions have been known to result in an individual's inability to function in society or possess adaptive skills. Inability to function in society often results in deviancy of various kinds, and at times the deviancy that is a symptom of an individual's neurological damage is so seriously a breach of the mores of social structure that it is viewed by our legal system as criminal.
In a landmark capital trial, Atkins v. Virginia, ruled in 2002, the defendant was given life without parole rather than the death sentence because it was proved he was mentally retarded. His lawyer argued that to put to death someone who had obvious mental deficits and an inability to cope in society was against the eighth amendment guaranteeing no use of cruel and unusual punishment as well as society's standards of decency:
Clinical definitions of mental retardation require not only subaverage intellectual functioning, but also significant limitations in adaptive skills. Mentally retarded persons frequently know the difference between right and wrong and are competent to stand trial, but, by definition, they have diminished capacities to understand and process information, to communicate, to abstract from mistakes and learn from experience, to engage in logical reasoning, to control impulses, and to understand others' reactions. Their deficiencies do not warrant an exemption from criminal sanctions, but diminish their personal culpability. (536 U.S. 304, 122 S.Ct. 2242)
In light of the distinction between sanctioning criminality and administering justice fairly by acknowledging an individual's culpability, it is necessary to see that if the state of the brain determines the behavior of the individual, and if the brain is damaged by a toxin which condemned it from the earliest years of childhood, the resulting behavior can be seen as a symptom of the brain. If that behavior is criminal, and if what made the individual's actions a crime can be attributed to known symptoms of a type of brain damage, then the amount of fault of that individual cannot be as great as if the crime were committed by someone without brain damage.
http://www.epa.gov/reg3wcmd/lp-childrenrisk.htm accessed 2/21/05
http://www.epa.gov/lead/ accessed 2/21/05
Center for Disease Control:
http://www.cdc.gov/nceh/lead/spotLights/changeBLL.htm accessed 2/21/05
New England Journal of Medicine, http://content.nejm.org:
Rosen J. F., Mushak P., Primary Prevention of Childhood Lead Poisoning — The Only Solution, New England Journal of Medicine, Volume 344, 2001
Rogan W. J., Dietrich K. N., et al., The Effect of Chelation Therapy with Succimer on Neuropsychological Development in Children Exposed to Lead, New England Journal of Medicine, Volume 344, 2001
Science Direct, www.sciencedirect.com:
Canfield R. L., Henderson C. R. Jr., et al., Intellectual Impairment in Children with Blood Lead Concentrations below 10 µg per Deciliter, New England Journal of Medicine, Volume 348, 2003
Konopka, Allan, The Secret Life of Lead, Living on Earth and World Media Foundation, 2003.
http://www.braininjury.com/children.html accessed 2/21/05
Atkins V. Virginia, 536 U.S. 304, 122 S.Ct. 2242
http://www.emedicine.com/neuro/topic185.htm accessed 2/21/05
http://www.leadpoison.net/press-release3.htm accessed 2/21/05
| Course Home | Serendip Home |