Childhood exposure to lead dust has been associated with enduring physical and behavioral effects. Recent exploration into this public health menace has revealed that leaded gasoline, used to reduce engine knocking and to modify octane levels from the 1920’s to the 1970’s, is no less involved in the damage than the lead from paint and water supply lines (either from solder or from lead pipes). The city air that was contaminated by vehicle exhaust decades ago has been linked to increased violent crime. You might wonder how lead would stay in the air for decades. It usually doesn’t, but lead particles land on the lawn, the sidewalk, the playground, and waft into your front door, alighting on the carpet and furniture.
Recent research by Tulane toxicologist Howard W. Mielke and demographer Sammy Zahran, from Colorado State University’s Center for Disaster and Risk Analysis, compared the amount of lead released in six American cities: Atlanta, Chicago, Indianapolis, Minneapolis, New Orleans, and San Diego, covering the span from 1950 to 1985. The changes in lead values during those years were matched by parallel ups and downs of aggravated assaults, as garnered from FBI records. The analysis of data revealed that for each one percent increase in airborne lead dust exposure there was a related increase in aggravated assault by a half percent (Mielke and Zahran, 2012).
Lead has been used for thousands of years, poisoning people along the way. The complete picture of lead’s toxicity was barely realized until the second half of the 20th century, when it was finally admitted that there is no safe threshold for lead exposure—there is no known amount of lead too small to do damage.
Developing fetuses are susceptible to the lead contamination of their mothers, and are likely to be premature or of low birth weight, especially for first delivery (Torres-Sanchez, 1999) (Cleveland, 2008). Because their bodies are smaller and in a constant state of growth and development, children are more at risk for lead poisoning. They absorb it faster, suffering more physical harm than an adult, and because they spend time on the floor learning to crawl and walk, their exposure is pronounced. It’s common to see slow development of expected childhood milestones, such as talking and combining words, in cases such as this, which often eventuate to loss of appetite, abdominal distress and vomiting, weight loss, constipation, anemia, kidney failure, irritability, lethargy, failure to thrive, learning disabilities and behavioral problems (Landrigan, 2002). Early lead exposure is decidedly prophetic of later neurological abnormalities (Nie, 2011), reduced IQ among them. Blood lead concentrations that peak at age two are thought to lower IQ scores at ages 4 to 6, when IQ becomes sufficiently stable to measure (Chen, 2005).
How Did It Get There?
By this time you might think this is more an urban concern than a suburban or rural one. Depending on the age of the domicile, you’re partly right. Regardless of location, many, if not most, homes built prior to 1978 were slathered with lead paint inside and out. Because lead tastes sweet, flakes of it found their way into the mouths of toddlers, not only from walls and trim, but also from furniture and toys. The rail of a crib often served as a teething ring. Urban environs are more likely to house factories and industries that either produce lead-related goods, including batteries, wire and pipes, some medical equipment, ceramic glazes, ammunition, and circuit boards, or that recycle such commodities. That would increase the odds of lead exposure by a substantial margin. And the plumbing use of lead in solder and pipe joining was ubiquitous until the advent of plastics. On the rural side of this coin sit lead-tainted pesticides and exhaust particles from agricultural equipment and contaminated ground water from airborne lead sources miles away. Not many people eat game harvested with lead ammunition, so that source is not worth the mention. Ingesting a bullet or a piece of lead shot is a remote probability.
Lead exposure is not limited to the United States, but is problematic wherever there is cultural and industrial development. The birth-to-twenty cohort recently studied in South Africa, comprising more than a thousand adolescents, demonstrated a relationship of lead exposure to rule breaking and aggressive behavior (Naicker, 2012). To explain this behavioral anomaly, scientists looked for a neuroanatomical commonality, discovering decreases in brain volume associated with childhood lead levels. In this inquiry they found that total brain gray matter is inversely associated with blood lead concentration, particularly in the area of the brain responsible for relaying nerve signals between the right and left hemispheres, a spot that controls rational cognitive functions as well as autonomic functions such as the regulation of blood pressure, digestion and respiration (Cecil, 2008). Gray matter volume loss was more obvious in males than in females. The result is that lead affects the prefrontal cortex so dramatically that executive function and decision-making suffer, leading to persistent antisocial behavior (Tiihonen, 2008).
Society has associated underprivileged life with increased odds of criminal activity, but was heretofore unable to put a finger on causality. Acceptable lead levels for children have been 10 micrograms per deciliter. This was to have been lowered to 5 mcg/dL by 2012. Adult levels have been established at 25 mcg/dL. In children, an increase from 10 to 20 mcg is associated with almost a three point drop in IQ (Schwartz, 1994), affecting levels of GABA, which slows down the activity of nerve cells in the brain, and of NMDA, which is an amino acid derivative labeled as an excitotoxin that wires up neuronal circuits (Watkins, 2006). Lead exposure crosses socio-economic lines and thus becomes an equal opportunity toxicant that is related even to ADD/ADHD disorders (Nigg, 2010). A staggering declaration made by the National Center for Healthy Housing, after analyzing reports from The USA, Britain, Canada, Australia, France, Italy, West Germany, and New Zealand, suggests that murder could be associated with more severe cases of childhood lead poisoning, (Nevin, 2007). The urban underprivileged may have been exposed to more lead residue (Cleveland, 2008) from gasoline, paint, and food can solder than their rural counterparts, so much so that traces of lead have been found in the enamel of their teeth (Cleymaet, 1991) (Uryu, 2003), levels of which tripled from 1930’s to the mid 60’s.
As of 2002, more than a million housing units offered shelter to low-income families (earning < $30 K yearly) with children under age six. Of those, 17% of government-subsidized units had hazards. Thirty-five percent of all low-income families had hazards. For families with modestly higher earnings, it’s 19%. Understandably, the greatest risks appear in dwellings that are antiquated, often also having high lead concentrations in the soil. Housing in the Northeast had twice the danger of the rest of the country.
What To Do?
Removal of heavy metals, notably lead, mercury and cadmium, is important to body function at the cellular level. The traditional medical approach to chelation, the process whereby the chelator binds to the metal and carries it away from the body, might use succimer, which is an analogue of dimercaprol, a toxic substance with a small therapeutic range and many adverse side effects. In a succimer trial sponsored by the National Institute of Environmental Health Sciences that enrolled almost eight hundred children with blood lead levels from 20-40 mcg/dL, the lead values of the study group decreased with succimer, but also did their IQ’s by a single point, which seems insignificant. But what is significant is that their behavior worsened, as reported on a parent assessment scale, leading investigators to infer that this treatment may not be ideal for children with lead levels in the particular range, citing accompanying decline in tests of cognition and psychological function (Rogan, 2001). Later study at the University of Cincinnati that followed a like protocol also noted a decrease in blood lead levels, but, too, a lack of benefit for cognitive, learning/memory, attention, and neuromotor skills, drawing researchers to the same conclusion (Dietrich, 2004).
As a chelator, chlorella vulgaris has been found to reduce damage by lead exposure and to maintain the integrity of bone marrow (Queiroz, 2003), while reducing lead levels in blood and tissues and restoring liver function (Queiroz, 2008). Later study found chlorella to restore the activity of natural killer cells and to reverse the zinc loss caused by lead exposure (Queiroz, 2011). Ascorbic acid, vitamin C, has been known to handle lead problems since the late 1930’s, when scientists found lead-exposed factory workers to respond to daily doses of vitamin C and to excrete lead in their urine (Holmes, 1939). Sixty years later, investigators saw lead levels decline as ascorbic acid levels increased in the general population having baseline lead values of 15 mcg/dL or higher (Simon, 1999). Though both these modalities were shown to reduce lead levels, no commentary about cognitive or behavioral character is retrieved from these studies. Sadly, lead stored in bone can leach into the blood even after chelation is deemed successful.
Where lead levels are high, trace mineral levels may be low, and probably are. The earnest and judicious use of minerals that belong in the body may be able to push out those that do not belong and, by virtue of their own properties, rescue the mental and physical domains transgressed upon by lead and other heavy metals.
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