Ancient Greece, renowned for its contributions to democracy and philosophy, also holds the unfortunate distinction of producing the world's earliest recorded lead pollution.
Researchers analyzing sediment cores from mainland Greece and the Aegean Sea have discovered evidence of lead contamination dating back approximately 5,200 years.
This finding predates the previous record of lead pollution, found in a Serbian peat bog, by 1,200 years.
In ancient times, lead was released into the atmosphere during the smelting of ore for copper and silver.
The toxic metal then settled as dust onto the soil.
"Silver was used for jewelry, for special objects – but it wasn’t found in a pure state," but mined in ore combined with lead, explained Heidelberg University archaeologist Joseph Maran, a co-author of the study published in Communications Earth and Environment.
The site with the oldest lead contamination, Tenaghi Philippon (Philippi Swamp), is located in northeastern Greece, near the island of Thasos. Archaeological evidence suggests Thasos was a major center for silver mining and metalwork in the region, Maran said.
"Lead released from smelting is the world’s first form of toxic or industrial pollution," noted Yale historian Joseph Manning, who was not involved in the study.
Lead contamination levels in ancient Greece remained relatively low and localized throughout the Bronze Age, the Classical period, and the Hellenistic period. The Classical period is known for Athenian democracy, Socrates, and Plato, while the Hellenistic period saw Greek cultural influence spread across the Mediterranean.
However, around 2,150 years ago, researchers detected a "very strong and abrupt increase" in lead emissions due to human activity across Greece, said co-author Andreas Koutsodendris of Heidelberg University.
This spike coincided with the Roman conquest of the Greek peninsula in 146 BC.
The Roman era saw increased demand for silver coins, driven by expanding trade and colonization, which led to more lead-releasing smelting, Koutsodendris explained. The Romans also used lead for tableware and construction, including pipes.
While previous research, including ice core analysis from Greenland, had revealed high lead levels across the Northern Hemisphere during Roman times, this new study provides a more "specific and local picture to how lead levels changed," said Nathan Chellman, an environmental scientist at the University of Nevada, Reno, who was not involved in the research.