For thousands of years, the Aegean Sea has been a crossroads of civilizations, from Bronze Age kingdoms to the cultural and military might of ancient Greece and Rome. But alongside their art, philosophy, and conquests, these early sea-faring societies left behind something else — traces of heavy metal pollution in the very sediment of the land and sea they occupied.

These muddy archives, pulled from the seafloor and nearby peat bogs, reveal that humans first began contaminating the environment with lead as early as 5,200 years ago — centuries earlier than previously thought. 

The Dawn of Metalworking (And Pollution)

Researchers analyzed 14 sediment cores collected from the Aegean Sea and its surrounding coastline. One core, taken from the Tenaghi Philippon peatland in northeastern Greece, contained the oldest known evidence of human-caused lead pollution. “This signal dates back to approximately 5,200 years ago,” says Dr. Andreas Koutsodendris, a geoscientist at Heidelberg University and a lead author of the study. “It’s about 1,200 years earlier than the previous record.”

Around the time the first lead pollution was deposited, early societies in the Aegean began experimenting with metallurgy and agriculture. These activities left a subtle but detectable trace in the environment.

The lead pollution, the researchers argue, is probably a byproduct of early silver production. “Because lead was released during the production of silver, among other things, proof of increasing lead concentrations in the environment is, at the same time, an important indicator of socioeconomic change,” explains Koutsodendris.

Economic Boom and a Toxic Impact

A rise in lead pollution coincides with a shift in how ancient societies used their land and resources. By analyzing pollen preserved in the same cores, the team reconstructed how vegetation in the Aegean region changed over time. By around 2,150 years ago, the Aegean region experienced accelerated deforestation and agricultural expansion.

“The changes coincide with the conquest of Hellenistic Greece by the Romans, who subsequently claimed for themselves the region’s wealth of resources,” says Heidelberg archaeologist Prof. Dr. Joseph Maran. 

The Romans intensified mining for gold, silver, and other metals, processes that required vast amounts of wood for fuel. In the north, deforestation was more pronounced in lowland areas, while high-altitude forests remained relatively untouched. In the south, the rise of agriculture was accompanied by a sharp decline in deciduous forests. This was particularly notable in areas like the Peloponnese, where olive cultivation became widespread.

Similar patterns of deforestation and pollution have been documented in other parts of the Mediterranean, including Asia Minor and the Levant.

The pollution was localized at first, confined to areas near mining centers. But it marked the beginning of a trend that would grow more pronounced over time. As societies expanded — such as during the transition from the Hellenistic to the Roman period — so did their environmental footprint. By this time, lead pollution appeared in marine sediments, indicating that the pollution was carried by rivers and atmospheric currents into the Aegean Sea.

 “This is the earliest recorded probable lead pollution in a marine environment,” notes Koutsodendris. 

Lead Pollution Across Time

The researchers also identified three distinct peaks in lead pollution over the next millennium, corresponding to periods of intense mining activity. These peaks were interrupted by brief declines, likely caused by disruptions such as plagues and political instability.

Lead pollution is dangerous now and it was dangerous in ancient times. Earlier this year, another study linked lead air pollution in the Roman Empire with a drop of up to 3 IQ points in ancient Europeans. Lead is a potent neurotoxin with no safe level of exposure. Even low concentrations are associated with cognitive decline, reproductive issues, and mental health problems.

The lead pollution recorded in the Aegean cores is a precursor to the widespread environmental changes that followed the Industrial Revolution. Yet, as this study shows, humans have been altering the planet for millennia. The sediment cores from the Aegean Sea are a reminder that every innovation, every empire, leaves a trace—sometimes buried deep beneath the waves.

The findings appeared in the journal Communications Earth & Environment.