An international team of scientists, including Andreas Stohl, ECH member, meteorologist and Vice Dean at the Faculty of Earth Sciences, Geography and Astronomy at the University of Vienna, used information stored in ice cores to model lead air pollution in the Roman Empire – and its likely consequences for human cognitive function.
The study, published in the Proceedings of the National Academy of Sciences (PNAS), takes a closer look at the heyday of the Roman Empire (around 200 years, known as the Pax Romana), a period known for its peace, territorial expansion and iconic structures such as the Colosseum. This period was also marked by widespread silver mining – the melting of minerals to extract silver, a process that releases lead into the air. Lead has been shown to have significant effects on human health, including memory loss, infertility, cancer risk and – crucially – lower IQ.
“Postcards From the Past”
Ice cores preserve atmospheric records, including lead concentrations over the centuries. Using cores from the Russian Arctic and Greenland, as well as historical climate data, the researchers were able to model lead levels in Europe during the Pax Romana.
Ice core probes analysed for lead and other chemicals. | © Jessi LeMay
The results suggest that the Roman Empire produced between 3 and 4 kilotons of atmospheric lead per year, totalling more than 500 kilotons over the course of the Pax Romana. As much of the rural Roman population was exposed to significant air pollution from silver mining and smelting, the health effects were likely to have been severe. The study estimates that cognitive function declined by an average of 2.5 to 3 IQ points across the Roman Empire, with the most pronounced effects in areas close to mining regions, such as present-day France, Spain, the UK and the eastern Adriatic.
The benefits of interdisciplinary collaboration
Commenting on his work in the scientifically diverse team, Stohl said: “There are not many groups in the world that collaborate with ice core experts on transport modelling like we do. As a result, we have already published many interesting results. But calculating air quality for the Pax Romana period was a completely new idea. As a meteorologist, I find it very exciting to contribute to a better understanding of history and human health. Our study shows very well how rewarding interdisciplinary collaboration across many disciplines can be”.
This research provides a unique insight into early, large-scale human pollution and its potential impact on human health.
