Lead is one of the naturally occurring elements and has its place in the periodic table. Although it has many useful applications, it can be toxic to humans and cause numerous health risks.

But in recent decades, humans have become more exposed to lead pollution due to human activities and the use of fossil fuels, which can cause problems in various aspects of life. Sometimes, it even progresses to a decline in intelligence, just like what happened in ancient Rome, according to a study conducted by an international research group.

The researchers published their study in the journal "Proceedings of the National Academy of Sciences" on January 6, 2025.

Postcards from the past

The researchers decided to explore the corridors of the past, where the Roman Empire, whose fame spread widely, submerged thousands of pages of history today. Here, the researchers examined three records of ice core samples from the Arctic to build a model of atmospheric lead pollution in Rome between 500 BC and 600 AD.

Then, the researchers linked the elevated lead levels during that period to studies connecting lead exposure to cognitive decline. Thus, those ice samples acted as postcards from the past to tell us what happened.

Decline in intelligence?

Researchers found that lead pollution during that era caused a decrease in intelligence levels in Europe by about 2.5 to 3 points. Lead pollution levels in the atmosphere reached record highs during the late 2nd century BC due to silver mining processes that released massive amounts of lead, leading to increased lead levels in human blood.

Children in Europe experienced a significant impact on their cognition during this period. On the other hand, adults faced infertility, anemia, memory loss, cardiovascular diseases, cancer, and other health issues.

Meanwhile, the peak of the Roman Republic—which lasted for nearly 200 years—occurred, during which over 500 kilotons of lead were released into the atmosphere. After that, lead pollution decreased during the crisis of the Roman Republic, but then pollution levels rose again in 15 BC, after the start of the Roman Empire. Lead pollution levels remained high until the Antonine Plague between 165 and 180 AD.

And today, after hundreds of years, human activities that pollute the environment are causing lead levels to rise again. This is something researchers continuously warn about. It could lead to a decline in cognitive abilities for entire generations if not controlled.