The Romans, at the height of their empire, left an indelible mark on many facets of the ancient world, from architecture to infrastructure. However, a recent study, published in PNASsuggests that their intensive exploitation of natural resources also had consequences on the health of European populations, particularly in terms of cognitive development. Indeed, the increase in lead pollution during this period could have had a lasting impact on the intelligence quotient (IQ) of Europeans.
Lead exposure
From 100 BC, driven by imperial expansion, the Roman Empire intensified mining, particularly for lead and silver. This industrial activity has generated unprecedented levels of air pollution. Analyzes of ice cores extracted in the Arctic have revealed that concentrations of lead in the air reached peaks between the 1st century BCE and the 2nd century CE. These levels were even higher that the Romans developed metallurgical techniques on a large scale.
According to researchers, a child born during this time in the Roman Empire would have had on average three times more lead in their blood than an American child today.
To understand the extent of exposure to this toxic metal, it is useful to compare the blood lead levels of Roman children with those of modern children. In Roman times, children had an estimated blood lead level of 3.4 µg/dl, a much higher level than that of children today, whose average level is 0.6 to 0.8 µg/dl thanks to the efforts to reduce lead pollution worldwide.
Neurological consequences
Based on current knowledge of the effects of lead pollution, researchers estimate that such exposure could have caused a drop in intelligence quotient (IQ) of approximately 2.5 to 3 points for populations in the Roman Empire, including areas like Gaul, North Africa, Spain and Brittany. Nathan Chellman, hydrologist, points out that a drop of 2 to 3 points may seem minor on an individual scale, but on the scale of the European population, the consequences would be considerable.
Even low levels of lead in the blood can have negative effects, and the higher the concentration, the more serious the consequences. Today, studies show that blood lead levels as low as 3.5 µg/dl in children can lead to lower IQ and learning disabilities.
-In the United States, lead pollution is often referred to as the nation’s “oldest epidemic,” and studies estimate that lead exposure since the 1940s has reduced the average IQ of the population.
Widespread pollution
We must not forget that lead was not only present in the air. Lead pipes and containers used for water storage in Roman cities were another vector of contamination. Urban populations, and in particular the Roman elites, were directly exposed to this toxic metal through the water they consumed daily.
According to the researchers, lead pollution has affected not only urban populations but also rural areas, where this “background” pollution has persisted for centuries, due to the large-scale exploitation of lead and lead ores. money. This type of chronic exposure could have been one of the main sources of contamination for rural populations.
The results of this study are consistent with other research based on ice cores, which also found a peak in lead pollution during the Roman Empire. Archaeological digs have also revealed high levels of lead in the teeth of many Roman children.
Joe McConnell, hydrologist and lead author of the study, says this is the first study to analyze ice core data to obtain atmospheric concentrations of lead and assess its impacts on humanity. This innovative approach makes it possible to understand the extent of air pollution in such distant times. In addition, here are 10 absolutely fascinating facts about the Roman Empire.
