For as long as humans have been refining metals, lead has been getting into our blood—often with tragic consequences. Now, a new study published in the journal Environmental Science and Technology traces levels of lead found in remains buried at a cemetery in Rome over some 12,000 years.
As Rossella Tercatin reports for the Jerusalem Post, the team found that bones at the site started showing traces of pollution about 5,000 years ago, around the time people first began refining metals through a process known as cupellation. Levels rose gradually over time, then jumped suddenly about 2,500 years ago, as the production of coins ramped up in Rome.
“This documentation of lead pollution throughout human history indicates that, remarkably, much of the estimated dynamics in lead production is replicated in human exposure,” says lead author Yigal Erel, a geologist at the Hebrew University of Jerusalem, in a statement. “Simply put: The more lead we produce, the more people are likely to be absorbing it into their bodies. This has a highly toxic effect.”
For the study, the researchers analyzed 132 bodies buried beneath the courtyard of the Palazzo della Cancelleria, a Renaissance palace built between 1485 and 1511. Burials at the site began millennia before the palazzo’s construction and continued through the 17th century. Of the individuals studied, 127 were from Rome, while 5 were from the Mediterranean island of Sardinia.
According to Ruth Schuster of Haaretz, people probably started producing lead 8,000 years ago, in Anatolia. But this early process simply involved hammering raw ore. The invention of cupellation some 3,000 years later allowed people to separate silver and gold from impure metals, releasing elements like copper, tin and lead, which became partly vaporized.
During the Roman era, people prepared wine in lead vessels and used the toxic metal in makeup. Mining and smelting operations at the time released lead into the atmosphere, polluting the air not just in Rome, but in many parts of Europe.
After peaking at the height of the Roman Empire, lead levels in the bones fell during the early medieval period before rising once again around 1,000 years ago, reports Ellen Phiddian for Cosmos magazine. Previous research has found a historical record of rises and falls in lead pollution in glaciers and lake sediments, but this is the first study to show the same phenomenon in human bodies.
As toxicologist and writer Megan Cartwright explained for Slate in 2015, lead has been used by a variety of societies in ways now recognized as dangerous. Ancient Egyptians used it in kohl makeup. And ancient Chinese and Indian texts refer to the metal as an ingredient in medicine. Since lead interferes with brain functioning, some scientists speculate that lead may have contributed to everything from the poor health and early deaths of enslaved Roman miners to mental illness among painters like Michelangelo.
Ancient Romans were aware that lead could cause health problems in very high quantities. But modern scientists have found that even relatively low concentrations of the metal in children’s blood are associated with learning and behavioral difficulties. The World Health Organization notes that there is no known “safe” level of blood lead concentration.
In the statement, Erel says that the correlation between overall metal production and levels found in human bodies is relevant to current health issues as well as ancient ones. High demand for metals used in electronic devices represents a danger—particularly to miners and recycling facility workers, but also to anyone who encounters lead in consumer products or in the air and soil.
“Any expanded use of metals should go hand in hand with industrial hygiene, ideally safe metal recycling and increased environmental and toxicological consideration in the selection of metals for industrial use,” Erel says.