By Stephen Beech
Industrial pollution has been having a negative impact on human health since the height of the Roman Empire, reveals new research.
Lead pollution likely caused widespread IQ declines throughout Europe 2,000 years ago, say scientists.
Researchers used Arctic ice core records to reconstruct historic atmospheric lead pollution in Roman times and link exposure to cognitive declines.
They explained that lead exposure is responsible for several negative impacts on human health, with even relatively low levels affecting the cognitive development of children.
More than 500 kilotons of lead were released to the atmosphere during the nearly 200-year height of the Roman Empire, according to the study.
Scientists from the Desert Research Institute (DRI) in Nevada, have previously used atmospheric pollution records preserved in Arctic ice cores to identify periods of lead pollution throughout the Roman Empire.
The new study, published in the journal Proceedings of the National Academy of Sciences (PNAS), expands on those findings to identify how lead pollution may have affected the European population.
Researchers examined three ice core records to identify lead pollution levels in the Arctic between 500 BC to 600 AD.
The era spanned the rise of the Roman Republic through the fall of the Roman Empire, with the study focusing on the 200-year height of the Empire called the Pax Romana.
Lead isotopes allowed the researchers to identify mining and smelting operations throughout Europe as the likely source of pollution during that period.
Advanced computer modeling of atmospheric movement then produced maps of atmospheric lead pollution levels across Europe.
Combined with research linking lead exposure to cognitive decline, the researchers also identified likely reductions in IQ levels of at least two to three points among the European population.
Study lead author DRI Professor Joe McConnell said: “This is the first study to take a pollution record from an ice core and invert it to get atmospheric concentrations of pollution and then assess human impacts.
“The idea that we can do this for 2,000 years ago is pretty novel and exciting.”
McConnell and his team have spent decades examining ice cores from places such as Greenland and Antarctica, where sheets of ice have built up over thousands of years.
Using massive drills, they painstakingly extract columns of ice as much as 11,000 feet (3,400 meters) long, reaching more distant depths of Earth’s history with each inch.
The team creates precise timelines using records of well-dated volcanic eruptions, which stamp the ice record like postcards from the past.
Gas bubbles trapped in the ice offer insight into the atmosphere of previous eras, while pollutants like lead can be used to interpret mining and industrial activity.
McConnell began developing methods to create very detailed lead records in ice over 20 years ago, when he applied them to more recent history.
When archaeologists and historians learned of the work, they approached him hoping to apply the new techniques to the Roman period.
Study co-author Andrew Wilson, Professor of the Archaeology of the Roman Empire at Oxford University, said: “The resulting research changed our understanding of the era by finding precise linkages between the lead pollution records and historical events such as population declines associated with periodic plagues and pandemics.”
He explained that ancient lead pollution stemmed largely from silver mining, whereby the lead-rich mineral galena was melted down to extract silver.
For every ounce of silver obtained, the process produced thousands of ounces of lead – much of which was released into the atmosphere.
In the 20th Century, lead pollution predominantly came from the emissions of vehicles burning leaded petrol.
Since legislation was introduced to restrict the use of leaded fuel, researchers have tracked a “sharp decline” of lead in human blood.
McConnell said: “As lead pollution has declined during the last 30 years, it has become more and more apparent to epidemiologists and medical experts just how bad lead is for human development.”
In adults, high levels of lead exposure are linked to health issues including infertility, anaemia, memory loss, heart disease, cancer, and reduced immune response.
In children, even low levels of exposure have been connected to reduced IQ, concentration challenges, and reduced academic success.
Study co-author Dr. Nathan Chellman, of DRI, said: “Lead is known to have a wide range of human health impacts, but we chose to focus on cognitive decline because it’s something we can put a number on.
“An IQ reduction of two to three points doesn’t sound like much, but when you apply that to essentially the entire European population, it’s kind of a big deal.”
The study found that atmospheric lead pollution began during the Iron Age and reached a peak during the late 2nd Century BC at the height of the Roman Republic.
It then declined sharply during the 1st Century BC, before increasing around 15BC following the rise of the Roman Empire.
Lead pollution remained high until the Antonine Plague from 165AD to the 180s, which severely affected the Roman Empire.
It wasn’t until the High Middle Ages in the early 2nd millennium AD that lead pollution in the Arctic exceeded the sustained high levels of the Roman Empire.
McConnell added: “Humans have been impacting their health for thousands of years through industrial activity,”
