Researchers measured lead pollution and its impact on human health through Arctic ice-core samples.
Lead pollution during the Roman Empire may have caused declines of two-and-a-half to three points in intelligence quotient (IQ) levels in the European population, according to a new study.
The research, published in the Proceedings of the National Academy of Sciences (PNAS), looked at the possible human health impacts of lead pollution during the height of the Roman Empire – a 200-year period called the Pax Romana.
The study builds on previous work by researchers at the Desert Research Institute (DRI) in the US which identified periods of significant lead pollution during the Roman Empire due to the mining and the smelting of silver and lead ores.
“What we set out to do is to try to understand how significant lead poisoning was from this background of air pollution and what its health effects might have been,” Joe McConnell, a research professor of hydrology at DRI and lead author of the study, told Euronews Health.
They found that more than 500 kilotons of lead were released into the atmosphere during the Pax Romana, resulting in pollution being deposited over the entire Roman Empire.
This period was then followed by a decline in lead pollution during the Antonine Plague outbreak from 165 to 180 CE.
How did they carry out the study?
The researchers examined records of three ice core samples collected from the Arctic to determine lead pollution levels at the height of the Roman Empire, which can be done with a high level of precision.
“We took these physical measurements of the lead pollution, used atmospheric modelling to determine what lead concentrations were like over Europe 2,000 years ago, and then use these modern epidemiological relationships to link that air pollution to blood lead levels in children,” McConnell said.
They combined this with modern research on lead levels and cognitive decline to identify IQ reductions in the population.
Today, lead exposure is known to be particularly harmful to young children and women of childbearing age.
Low levels of exposure can impact brain development including reduced IQ and behavioural or learning problems, according to the World Health Organization (WHO).
It can also cause anaemia, hypertension, kidney impairment, and reproductive problems. No level of exposure to lead is without harm, WHO says.
What does the research teach us about human history?
The researchers say they were conservative in their estimates and only looked at the direct inhalation of lead rather than exposure from soil, crops, and water.
“The two-and-a-half to three-point decline in IQ may not sound like much, but when it applies to the entire population, it’s a pretty big deal,” said McConnell.
There were also other ways besides atmospheric pollution that people were exposed to lead through utensils, paint, and cosmetics, for instance.
“One takeaway for me is that the idea that human industrial activities 2,000 years ago were having a continent-wide impact on human health is pretty surprising,” he said.
“I think it really reemphasises the need to continue to clean up the environment”.
