Lead is a metal that occurs naturally in the earth’s crust, but human activity, such as mining, burning fossil fuels and manufacturing, has caused it to become more widespread. This element, however, has no known purpose that can be beneficial for humanity. Rather, it is an extremely harmful chemical that can cause serious damage and even potentially death when at high concentrations. Events, like the one in Flint, Michigan, where shortcuts by the government caused serious lead poisoning in the town via tap water, should be avoided at all costs when the shortcomings of lead toxicity are understood.
The cause of lead poisoning, or its etiology, is quite simply the build up of lead in the body. Sometimes, even small amounts of lead can be toxic and lead to serious health conditions. These smaller amounts are especially problematic for children under the age of 6, as the exposure to lead can severely affect mental and physical development. HIgher levels of lead poisoning can be ultimately fatal. There are many common ways in which lead can infiltrate the body.
The first is lead in paint, as those lead-based paints used to be used for homes, children’s toys, and household furniture, although lead in those specific items has been banned in the United States since 1978. These lead-based paints, however, still persist in older homes and apartments, and because of that most lead poisoning in children results from eating lead-based paint chips. In Flint, Michigan, the medium for the lead poisoning was through water pipes.
These lead pipes, brass plumbing fixtures, and copper pipes soldered with lead can release lead particles into tap water, as the water slowly deteriorates the lining and subsequently the lead mixes with the water. Some lead poisoning has even been traced to some older medicines, such as greta,litarigio, ba-baw-san, ghasard, and daw tway. Finally, lead particles have also settled in the soil from leaded gasoline or paint cans, and this pollution lasts for many years. Lead-contaminated soil is still a major problem around highways and in some urban settings.
All of the following methods allow for lead to accumulate in one’s body and therefore, via ingestion or breathing, lead poisoning can occur. Lead enters the intravascular space and binds quickly to red blood cells. It has a half-life of approximately 30 days in the blood, from where it diffuses into the soft tissues, including the kidneys, brain, liver, and bone marrow. Lead in the bones and teeth is bound tightly and is generally not thought to be harmful, although the estimated half-life of lead in bone is from 20 to 30 years.
The problem with this is that the bone can introduce lead into the bloodstream after the initial exposure is gone. Subsequently, the pathophysiology of lead occurs because it creates reactive radicals which damage cells structures including DNA and cell membranes, which results in a variety of different effects on the body. Lead also interferes with DNA transcription, the enzymes that aid in the synthesis of vitamin D, and enzymes that maintain the cell membrane. Anemia may occur when the cell membranes of the red blood cells become more fragile due to that damage to the membranes.
The of lead toxicity is due to increased generation of reactive oxygen species (ROS), such as hydrogen peroxide, and interference with generation of antioxidants. In adults, about 35-40% of inhaled lead dust is deposited in the lungs, and about 95% of that goes into the bloodstream. It also interferes with the activity of other antioxidant enzymes including superoxide dismutase and catalase. The increase in oxidative stress leads to cell membrane damage due to lipid peroxidation.
Lead may also alter the permeability of blood vessels and collagen synthesis, or even be harmful to the development of the immune system by causing the production of excessive inflammatory proteins, a possible risk factor for asthma in children. Finally, lead toxicity has also been known to decrease the activity of immune cells and interfere with the normal metabolism of calcium with cells, causing it to build up within them. Overall, lead poisoning presents a lot of complications to the body that can hinder proper function.
The high levels of lead in the bloodstream also have a major affect on the neurological system. The brain requires a specific balances of ions on both sides of their membranes, and the increase of lead near the brain alters this balance. The lead can potentially penetrate the brain through the Calcium pumps and wreck havoc with cellular function. The release neurotransmitters within the synapses to signal neighboring neurons are hindered by the presence of lead in the neuron due to this change in ion balance.
The lead disturbs the chemical balance because it is very similar chemically to the calcium ion, a key ion that allows action potentials to work within the synapses. The calmodulin protein kinase II (CPK II) system signals vesicles to bind to the cell membrane and release their neurotransmitters into the synapse, however, the lead corrupts its processes because it has a greater ability to form a complex than the calcium ion. Subsequently, lead activates the CPK II at lower concentrations and for longer periods of time than the calcium ions, which causes an increase in neurological activity.
This is very harmful for children because the synapses that are not supposed to be activated can be activated with the presence of lead, leading to major developmental issues. A receptor that is especially affected is the NDMA receptor, a key receptor involved in the development of neural plasticity. Neural plasticity is especially important in children because they are constantly forming new synapses and reconfiguring neural pathways, so lead poisoning is an even bigger problem for children under the age of 6.
Moreover, a recent Johns Hopkins study has found that the presence of lead also directly prevents the formation of these NDMA receptors, even more problematic for children and even adults. There is one major treatment for lead poisoning, however, the first step one should take if they have lead poisoning is to remove the source of the lead to prevent further harm. After doing so, the procedure to removing the lead is called “chelation therapy”.
Chelation therapy is when a doctor prescribes a medicine to the patient to bind with heavy metals, like lead, in the body and neutralize their reactive potential, so they can be excreted through the urine. A common chelating agent is dimercaprol, which is effective because of its sulfhydryl group. Lead tends to react with enzymes that have sulfhydryl groups, so the dimercaprol binds with the lead rather than the lead binding to important receptors in the body. Unfortunately, dimercaprol is toxic and can cause kidney damage, so it must be prescribed at very small doses.
Another type of chelation therapy, called EDTA therapy, treats adults with lead levels greater than 45 mcg/dL of blood with a chemical called ethylenediaminetetraacetic acid (EDTA). In severe cases, however, lead can enter the bones of the inflicted person at a rapid rate, since lead is so similar to calcium yet stronger. Once lead is in the bones, the chelating agents cannot neutralize it, and there is a potential danger of it being re-released later on, causing long term issues. Ultimately, lead is a very dangerous substance that can be extremely detrimental at high concentrations.
The world should take special care to understand all of the problems that can arise through lead poisoning. Subsequently, with that knowledge, decisions can be made and steps can be taken to ensure that no one can be at major risk of lead poisoning. Events like the one in Flint, Michigan, should never happen and would never happen had everyone had the prior knowledge of the extreme drawbacks of lead poisoning. By obtaining a greater knowledge of such diseases, humanity can take a step forward in the right direction and address issues that would not even exist with basic understanding.
