Chapter 23. Lead in our Lives

Lead in our Lives

Uses of lead range from deadly bullets to stained glass windows in churches.

Read the article below. Then complete the comprehension questions that follow.

Lead is both useful and toxic to humans

Lead is an inexpensive metallic element that is durable, resistant to corrosion, and malleable. Unfortunately, it’s also a toxin that can enter our bodies in tiny quantities, accumulate in our tissues, and cause great harm—particularly to our nervous system. Through this combination of usefulness and toxicity, lead has both helped and poisoned humans for thousands of years. Let’s see how lead has been useful, as well as how it can adversely affect our bodies.

Bullets, pipes, paints, and gas

Humans have found countless uses for lead throughout history. Ancient Egyptians mixed lead into pottery glazes, and Romans used it to make water pipes. Lead is in the stained glass windows that have graced churches since medieval times, as well as in the moveable type of printing presses that promoted literacy and free expression.

Considering all the people killed by them, lead bullets have also had an enormous impact on history—though generally the result of damage done to the body, and not because of lead’s toxicity. The toxicity of lead bullets can be a serious problem for other animals, however. (See the section on “Lead & Condors” below.)

Most of the toxicity of lead to the systems of the human body has come from three sources: pipes, paints, and gasoline. Lead was a common component of all three a little more than a generation ago.

The practice of making water pipes from lead far outlasted the Roman Empire. Lead was still being used for pipes well into the 20th century, and lead-based solder to join copper pipes was still used in the 1980s. For hundreds of years humans were ingesting toxic lead particles along with the water they drank from these pipes.

Lead was in paint for a long time, too. As recently as the 1970s, house paints contained lead, and undercoats of paint in many homes, schools, and workplaces still do. This puts children and pets—who spend much of their time on the floor where paint dust and chips land—at particular risk. Lead was even breathed in from the air. Tetraethyl lead was added to gasoline from the 1920s until the 1970s. The dangers of toxic emission created by leaded gas caused its gradual reduction and eventual banning.

How lead acts in the body

Lead was once added to gasoline to improve performance, but it also put lead into the air.

The dangers of lead have long been in evidence. The Greek physician Nikander described lead poisoning 2300 years ago, and historians tell us that Roman aristocrats suffered from psychosis and infertility—both symptoms of lead poisoning. But how does lead wreak havoc when it enters our bodies?

Lead is carried by the blood to soft tissue and bone where it can be stored for many years. Exposure can be harmful to several organs— including kidneys—as well as the nervous system. Long-term exposure to lead can cause memory loss and learning impairment. Recent studies have linked early childhood exposure to behavioral problems and juvenile delinquency. Death can result from sustained exposure.

Many of lead’s toxic properties stem from its ability to mimic calcium, altering cellular processes. Even at low concentrations, lead interferes with the release of neurotransmitters (chemicals used by the nervous system to communicate with nearby cells), especially in the brain. Star-shaped cells, called astrocytes, can be impacted by lead as well. Astrocytes help repair scarring in the brain and spinal cord and provide nutrients to nervous tissue. This is why lead poisoning in high doses can result in brain hemorrhaging.

Lead also interferes with the protective sheath that insulates nerve cells in the central nervous system, and alters the integrity of the blood-brain barrier. This damage can lead to severe impairment, especially in children. Tots with lead poisoning might complain of stomachaches and exhibit hyperactivity, sleeping problems, or irritability. Because these symptoms mimic other conditions, lead poisoning is sometimes mistaken for a cold or the flu.

Getting the lead out of your life

Conservation groups and public health department campaigns continue to warn the public about lead pollution. Even though the metal is now banned in pipes, paint, and most gasoline, many of us who live, work, and go to school in older buildings can come into contact with lead, and lead-contaminated soil lines many streets and roadways.

What can you do to reduce your exposure to lead? If you have doubts about the safety of your home or workplace, have tests done on the water and paint. Most importantly, watch for the warning signs of lead poisoning, especially in children. The only way to diagnose lead poisoning is by having a blood test, but treatment shortly after exposure can sometimes help prevent severe damage.

© 2015 WH Freeman and Company.

23.1 Comprehension & Application Questions

Answer the following questions to demonstrate your understanding of the article.

Question 23.10

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2

Yes. As the graph indicates, the child’s blood lead levels were hovering near 50 micrograms/deciliter in late July, warranting chelation treatment.

Try again. Take another look at the graph. You have one attempt remaining.

Incorrect. The graph indicates that the child’s blood lead levels were hovering near 50 micrograms/deciliter in late July, warranting chelation treatment.