David Pratt
MPH Candidate- Touro University California

History of Lead

Lead has the highest concentration of any heavy metal found within the composition of the earth’s crust (Tong, 2000). Environmental exposure to lead has been relatively low throughout human history before the industrial revolution and large scale mining. As a result of lead mining, it is estimated that over 300 million tons of lead have been released into the environment within the past 500 years (Tong, 2000). The first historical account of public lead exposure was recorded as early as 370 BC, and accounts of lead exposure were recorded throughout roman times due to the use of lead in water pipes and containers.

Lead Toxicity

Lead poisoning usually occurs when blood level concentrations are greater than 40 ug/dl (Cecil, 2008). Brain dysfunction due to lead exposure usually occurs when blood level concentrations are greater than 100 ug/dl, but may occur when blood level concentrations are greater than 70 ug/dl. Lead encephalopathy typically involves focal lesions in the basal ganglia, thalami, cerebellum, cortical grey matter, and subcortical white matter. Behavioral changes associated with lead poisoning may include and increased likelihood of impaired cognition and executive function, impulsiveness, aggression, and delinquent behavior.

The mechanism of action involved with lead neurotoxicity involves the alteration of neurotransmitter release which may cause excitotoxicity and apoptotic changes (Cecil, 2008). Evidence suggests that chronic lead exposure may result in developmental deficits which include a smaller cingulate gyrus, insula, frontal gray matter, total gray matter, partial white matter, and reduced total brain volume. Evidence suggests that childhood lead exposure is associated with region specific reductions in adult gray matter volume, more specifically, evidence suggests that medial regions of the prefrontal cortex are most affected by childhood lead exposure (Cecil, 2008).

Environmental Exposure to Lead

In the United States, between 1976 and 1991, the average lead blood level of persons aged 1-74 decreased by 78% (Tong, 2000). Additionally, within the same time period, average lead blood levels of children aged 1-5 decreased by 77%. This decrease can be attributed to a decline of lead for commercial use, specifically in petrol. Similar results were reported in many other developed countries including Belgium, Germany, New Zealand, Sweden, and the United Kingdom. While laws and regulations have shown a significant decline in blood lead levels within developed counties, developing countries continue to struggle with lead exposure as a contributor to public health problems (Tong, 2000).

Occupational Exposure to Lead

Persons working in the following occupations may be exposed to lead: Motor vehicle assembly, panel beating, battery manufacture and recovery, soldering, lead mining and smelting, and industries concerned with producing glass, plastics and ceramics (Tong, 2000). Occupational exposure to lead is higher in undeveloped countries due to lack of laws and regulations. More specifically, problems of occupational lead exposure in undeveloped countries become community problems through the ease of transmission of lead to community members. Such transmission includes an unsafe manufacturing processes that generates the lead fumes and dust that can spread to adults and children living nearby. This becomes problematic when lead spreads to community member housing and clothing, increasing the chance that children are exposed, and that lead may be introduced to the fetus during pregnancy (Tong, 2000).

Lead as a public health threat

Lead in our tap water comes from a variety of sources, mainly from improper disposal of the contaminant from industrial manufacturing practices, leaded gasoline, residential paints, and leaching of lead from lead-based pipe systems (Ahmedna, 2004). Tap water that contains lead in excess amounts may cause deficits in intelligence, decreased brain function, and neuro-psychiatric disorders in children. While multiple regulatory agencies within the United States insist that domestic drinking water is safe, Americans continue to spend over $5 billion annually on bottled water and home water treatment systems. Even at very low concentrations, lead poses a significant impact to public health. According to the CDC, nearly 30 million Americans consume drinking water containing levels of lead in excess of the US EPA standard. (Ahmedna, 2004).

The potential for adverse health effects resulting from lead exposure is higher in children than adults due to intake of lead per body unit, oral consumption of lead containing objects, increased physiological uptake rates, and lack of organ system development (Tong, 2000). Epidemiological evidence indicates that exposure to lead in early childhood causes a significant cognitive dysfunction during the years immediately following exposure. Data suggests that these cognitive impairments are irreversible. Human exposure and uptake of lead has consequently increased throughout history as a result of worldwide distribution. High level exposure to lead can be detrimental to human health, with damage to almost all organs and organ systems, biochemical process disruption, as well as psychological and neuro-behavioral dysfunction at low levels of exposure (Tong, 2000).

Removing Lead from Tap Water

Current commercial water filtration devices use ion exchange resin or activated carbon to remove lead and other contaminants such as zinc and copper from tap water (Ahmedna, 2004). Each of these systems have been shown to ineffectively remove all known hazardous contaminants from tap water. In order to compensate for this lack in efficiency, more expensive hybrid systems have been introduced to the commercial market that use ion exchange with the balance consisting of granular activated carbon (Ahmedna, 2004).

In order to remove lead from our tap water, a variety of water filtration methods are available (Ahmedna, 2004). The most frequently used method for most commercial systems is the ion exchange resin and activated carbon method. While these methods are effective at reducing lead and other contaminant concentrations from our tap water supply, they are more expensive than envirofilters, consisting of mixtures of carbons made from acid-activated almond or pecan shells and steam-activated pecan or walnut shells to adsorb lead, copper, and zinc (Ahmedna, 2004).

References

Ahmedna, M., Marshall, W.E., Husseiny, A., Rao, R., Goktepe, I. (2004). The Use of Nutshell Carbons in Drinking Water Filters for Removal of Trace Metals, Journal of Water Research, 38, 1062-1068.

Barn, P., Kosatsky, T. (2011). Lead in School Drinking Water: Canada Can and Should Address this Important Ongoing Exposure Source, Canadian Journal of Public Health, 102(2), 118-121.

Cecil, K., Brubaker, C., Adler, C. (2008). Decreased Brain Volume in Adults with Childhood Lead Exposure, PLOS Med, 5(5), 0741-0750.

Tong, S., Von Schirnding,Y., Prapamontol, T. (2000). Environmental Lead Exposure: A Public Health Problem of Global Dimensions, Bulletin of the World Health Organization, 78 (9), 1068-1077.