Pollution In Ancient Rome Caused The IQ Of People To Decline Across Europe
Lead exposure has left its toxic fingerprints all over history. We’ve come a long way in reducing its presence, but even low levels of lead can wreak havoc, especially on the cognitive development of children.
Previously, scientists have analyzed atmospheric pollution preserved in ice cores to uncover periods of lead contamination during the Roman Empire. Now, new research has dug deeper into how this pollution might have impacted the European population.
In the study, the research team examined three ice core records to determine what the lead pollution levels in the Arctic were between 500 B.C.E. and 600 C.E., an era that spanned the rise of the Roman Republic to the collapse of the Roman Empire.
By looking at lead isotopes, the team was able to pinpoint mining and smelting operations throughout Europe as the primary source of pollution during this period. They also used advanced computer modeling to produce maps of atmospheric lead pollution levels across Europe.
Then, they combined this information with research linking lead exposure to cognitive decline and identified widespread declines in IQ levels of at least two to three points among the European population.
“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,” said Joe McConnell, the lead author of the study and a research professor of hydrology at the Desert Research Institute (DRI). “The idea that we can do this for 2,000 years ago is pretty novel and exciting.”
Ancient lead pollution resulted mostly from silver mining, which involved melting the lead-rich mineral galena to extract silver.
For every ounce of silver extracted, the process generated thousands of ounces of lead that were released into the atmosphere.
In the 20th century, the majority of lead pollution came from vehicle emissions burning leaded gasoline. After the Clean Air Act was passed in the U.S. in 1970, which restricted the use of leaded gasoline, there was a dramatic decrease of lead in human blood.
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The nationwide exposure, especially among children born between 1950 and 1985, enabled scientists to study the effects of lead on health and brain development.
High levels of lead exposure are associated with infertility, anemia, cancer, cardiovascular disease, memory loss, and more in adults.
Even low levels of exposure have been linked to reduced IQ, problems with concentration, and less academic success in children.
“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,” said Nathan Chellman, a co-author of the study and an assistant research professor of snow and ice hydrology at DRI.
“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.”
According to the study, atmospheric lead pollution started during the Iron Age and reached its height during the late 2nd century B.C.E., the strongest point of the Roman Republic.
Then, it dropped sharply during the 1st century B.C.E. and increased again around 15 B.C.E., which was when the Roman Empire rose to power.
Lead pollution remained high until the Antonine Plague from 165 to the 180s C.E. Overall, more than 500 kilotons of lead were unleashed into the atmosphere during the Roman Empire’s reign, which lasted nearly 200 years.
The study was published in the Proceedings of the National Academy of Sciences.
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