A recent study suggests that the Roman Empire’s vast lead pollution from mining and metal processing may have caused widespread cognitive decline across Europe, leading to a 2- to 3-point drop in IQ. Roman physicians already knew the dangers of lead poisoning, but the metal was still widely used in everyday items. Researchers tracked lead pollution levels by analyzing ice cores from the Arctic, revealing a sharp increase in lead around 15BC and lasting until AD180. The effects of lead poisoning have been so severe that some scholars have debated whether it contributed to the fall of the empire. Lead pollution also resurged in the high middle ages and 20th century due to industrial activities.
https://www.theguardian.com/science/2025/jan/06/roman-empires-use-of-lead-lowered-iq-levels-across-europe-study-finds