What Makes Lead Poisonous?

Lead metal
James St. John/Flickr/CC BY 2.0  

People have been using lead in their daily lives for a long time. The Romans made pewter dishes and pipes for water from lead. While lead is a very useful metal, is also poisonous. The effects of poisoning from lead leaching into liquids may have contributed to the fall of the Roman empire. Lead exposure didn't end when lead-based paint and leaded gasoline were phased out. It is still found in the insulation coating electronics, leaded crystal, storage batteries, on the coating of some candles wicks, as certain plastics stabilizers, and in soldering. You are exposed to trace amounts of lead every day.

What Makes Lead Poisonous

Lead is toxic mainly because it preferentially replaces other metals (e.g., zinc, calcium and iron) in biochemical reactions. It interferes with the proteins that cause certain genes to turn on and off by displacing other metals in the molecules. This changes the shape of the protein molecule such that it can't perform its function. Research is ongoing to identify which molecules bind with lead. Some of the proteins known to be affected by lead regulate blood pressure, (which can cause developmental delays in children and high blood pressure in adults), heme production (which can lead to anemia), and sperm production (possibly implicating lead in infertility). Lead displaces calcium in the reactions that transmit electrical impulses in the brain, which is another way of saying it diminishes your ability to think or recall information.

No Amount of Lead Is Safe

Paracelsus' was a self-proclaimed alchemist in the 1600s and pioneered the use of minerals in medical practices. He believed that all things have curative and poisonous facets. Among other things, he believed lead had curative effects in low doses, but monitoring dosage doesn't apply to lead. 

Many substances are non-toxic or even essential in trace amounts, yet poisonous in larger quantities. You need iron to transport oxygen in your ​red blood cells, yet too much iron can kill you. You breathe oxygen, yet again, too much is lethal. Lead isn't like those elements. It's simply poisonous. Lead exposure of small children is a main concern because it can cause developmental issues, and kids engage in activities that increase their exposure to the metal (e.g., putting things in their mouths, or not washing their hands). There is no minimum safe exposure limit, in part because lead accumulates in the body. There are government regulations regarding acceptable limits for products and pollution because lead is useful and necessary, but the reality is, any amount lead is too much.

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Helmenstine, Anne Marie, Ph.D. "What Makes Lead Poisonous?" ThoughtCo, Sep. 9, 2021, thoughtco.com/what-makes-lead-poisonous-607898. Helmenstine, Anne Marie, Ph.D. (2021, September 9). What Makes Lead Poisonous? Retrieved from https://www.thoughtco.com/what-makes-lead-poisonous-607898 Helmenstine, Anne Marie, Ph.D. "What Makes Lead Poisonous?" ThoughtCo. https://www.thoughtco.com/what-makes-lead-poisonous-607898 (accessed May 30, 2023).