What happens in lead poisoning, exactly?

What is it?

Poisoning usually means ingesting or inhaling substances that harm the body, and in lead poisoning, this substance is lead. Lead harms all tissues, but it is particularly dangerous to the nervous system. The symptoms of lead poisoning are often subtle and non-specific, including headache, stomach pain, and memory problems.

Everyone is exposed to lead to some extent. Globally, lead poisoning is thought to account for 0.2% of all deaths. People in the developing world, as well as people in the developed world who have low levels of education and who live in poor areas, are at a higher risk.

What causes it?

Shockingly, lead poisoning is caused by high levels of lead in the body.  In adults, the leading cause for lead poisoning is having a job where one is exposed to the metal. This includes working in a factory that produces lead-containing products, but a range of other jobs from plumbing to auto mechanics can also lead to heightened exposure. Living in a house that’s painted with lead-based paint, pollution in its many forms, and being in contact with bullets are all risk factors.

What happens during it?

Enzymes are big molecules that are used to make the chemical reactions that are essential to life more efficient. Without enzymes, we would die of starvation, because it would take us years to break down a meal. The biggest problem with lead is that it binds to enzymes and hence interferes with many vital chemical reactions.

Our cells need oxygen to function, and it is transported from our lungs to the cells via the bloodstream. In the blood, oxygen binds to a molecule called hemoglobin. Lead has the ability to bind to an enzyme essential to the formation of hemoglobin. This, in turn, leads to a reduced ability to transport oxygen, which can cause all sorts  of problems including anemia.

The brain is generally well protected against any harmful substances circulating in the blood, but lead is able to pass through this defense. It is particularly harmful to children, because it intervenes with many developmental processes, like the formation of connections between neurons. The brain uses molecules called neurotransmitters to transmit signals between neurons. They work by binding to a receptor on one neuron’s surface after being released by another. Much of lead’s toxic effect is thought to be attributable to it’s ability to bind to the receptors for the neurotransmitter glutamate, through this making the communication between neurons hard.

How can it be treated?

Obviously, the most important thing to do is to identify the source of lead that has lead to the poisoning, and to remove it. People with very high lead levels and/or symptoms of poisoning can be given chelation therapy. In it, the patient is given a substance with negatively charged groups that allow it to bind to the positively charged lead. The product is a non-poisonous complex, that can then be excreted with urine. Chelation is not risk-free and might not be useful for people with lower lead levels, which is why it’s usually only used in more severe cases. Iron, calcium and zinc deficiencies are associated with higher levels of lead absorption, which is why they are also targeted in treatment.

 

 

Sources: https://en.wikipedia.org/wiki/Lead_poisoning, https://en.wikipedia.org/wiki/Chelation_therapy

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