How Romans accidentally lowered their IQs

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The Romans created concrete, aqueducts, and the foundation of the modern calendar. However, their accomplishments might have been even more impressive if their brains had not been affected by lead poisoning, a research study indicates.

Researchers at the University of Oxford discovered that lead pollution resulted in a significant decrease of two to three points among the European population's IQ levels.

“An IQ reduction of two to three points doesn’t seem like a lot, but when you apply that to the whole European population, it actually adds up to a pretty significant thing,” study co-author Nathan Chellman said.

“Lead exposure is known to have a wide range of negative effects on human health, but we decided to focus on cognitive decline because we could quantify it.”

Exposure to lead can cause a variety of health problems, including negative effects on cognitive development, even at relatively low levels.

Researchers studied three ice core records to determine pollution levels in the Arctic between 500 BC and 600 AD.

From the time of the founding of the Empire in the West, up to the point where it fell, the research concentrated on the two hundred year "golden age" known as the Pax Romana, a period of great prosperity that lasted from 27 BC to 180 AD.

The team focused specifically on lead isotopes, which help reveal the metal's origin, in this instance indicating its connection to mining and smelting activities.

The contamination of the environment with lead was primarily caused by the process of extracting silver from the lead ore galena through smelting.

For every ounce of silver produced, this process generated thousands of ounces of lead – much of which was released into the air. The analysis discovered that the resulting air pollution began during the Iron Age and reached its peak during the late 2nd century BCE, the height of the Roman Republic.

The population of the city increased around 15 BCE, as the Roman Empire rose to power.

High levels of lead pollution persisted until the Antonine Plague, which occurred approximately from 165 to the 180s CE and severely affected the Roman Empire. According to research, over 500 kilotons of lead were released into the atmosphere during the nearly 200-year peak of the Roman Empire.

In fact, ice core records indicate that Arctic lead pollution was approximately 40 times higher during the peak levels reached in the early 1970s. Nonetheless, the findings of this study reveal that humans have been influencing their health negatively through industrial activities over thousands of years, according to the researchers.

“Over the past 30 years, as lead exposure has decreased, it has become increasingly clear to experts in epidemiology and medicine just how detrimental lead is for human development.”

"This is the first study to take a pollution record from an ice core and flip it to determine atmospheric pollution levels, and then evaluate the impact of pollution on humans," said Dr. Joe McConnell, a research professor of hydrology and the lead author of the study.

“Doing this for 2,000 years in the past is quite an innovative and thrilling idea.”

The research was published in the Proceedings of the National Academy of Sciences of the US.