Humans have polluted the sea with lead for far longer than we realised, study shows

Archaeologists have traced the earliest case of lead pollution by humans to the Aegean Sea region around 5,200 years ago.

The findings, published in the journal Communications Earth & Environment, suggest humans began polluting the environment with lead more than 1,200 years earlier than previously thought.

A further spike in levels of human-caused lead pollution was observed about 2,150 years ago.

This period saw the expansion of the Roman Empire across the Aegean region, which hosted some of the earliest cultural centres in ancient Europe.

In the study, scientists analysed the lead content of marine sediment cores taken from across the Aegean Sea and a sediment core taken from the Tenaghi Philippon peatland, located in northeastern Greece.

Map of the sediment cores analysed in the study (Andreas Koutsodendris et al.)

Scientists then analysed the pollen and spore content of several of the cores, combining this with similar existing data for the region and lead content data.

This enabled them to investigate how the region’s ecosystems were affected by the social and cultural changes at the time.

The study documents the earliest recorded signal of probable human-caused lead pollution, occurring around 5,200 years ago in the Tenaghi Philippon core.

Researchers say this is about 1,200 years earlier than the previous earliest suspected lead pollution, recorded in samples from peatlands in the Balkan Peninsula.

The findings also point to a change in the vegetation record and an increase in lead pollution around 2,150 years ago.

Grass covered mounds mark the site of the Roman-era lead mine at Charterhouse on Mendip in the UK (Andrew Wilson)

These are likely linked to the expansion of the Roman Empire into Ancient Greece at that time, scientists say.

“The onset of ubiquitous lead pollution in both terrestrial and marine environments 2,150 years ago is linked to a fundamental political change,” researchers write.

“We argue that this change was brought about by the subordination of Greece to the Roman Empire after 146 BCE,” they say.

This period of Roman expansion was marked by a significant increase in the mining of gold, silver, and other metals for use in currency and other items.

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“The incorporation of Greek regions into the Roman political sphere provided the new rulers with the opportunity to benefit from the natural resources, which led to an unprecedented increase in the exploitation of Greek mining districts to extract gold, silver, and other metal resources,” the scientists said.

“High lead contents persist throughout the times of the Roman Empire and the first half of the Byzantine Empire,” they wrote.

Scientists also found lead in marine sediment cores, which they say could be the earliest recorded probable lead pollution in a marine environment.

“This first manifestation of marine pollution coincides with maximum deforestation and agricultural expansion, signalling pervasive human impact on ecosystems connected to the advanced monetised societies during the Hellenistic and Roman periods in Ancient Greece,” the researchers wrote.

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