Studies show that lead contamination in ancient Rome could have decreased average intelligence levels.

In ancient Rome, toxic lead was so prevalent in the air that it likely lowered the average person’s IQ by 2.5 to 3 points, a new study suggests.

The study, published Monday in the Proceedings of the National Academy of Sciences, adds to long-standing questions about what role, if any, lead pollution played in the collapse of the empire.

The authors link lead found in Greenland ice samples to ancient Roman silver smelters and determine that the incredible background pollution they produced would have affected much of Europe. .

Researchers used research on lead exposure in modern society to determine how much lead was likely in the Romans’ bloodstream and how it affected their cognition. was able to judge.

Lead, a powerful neurotoxin, remains a public health threat today. There is no safe amount to ingest into the body. Exposure is associated with an increased risk of learning disabilities, reproductive problems, mental health problems, and hearing loss, among other effects.

The researchers behind the new study said the discovery was the first clear example in history of widespread industrial pollution.

“Human and industrial activities 2,000 years ago were already having a continent-wide impact on human health,” said the study’s lead author, a researcher at the Desert Research Institute for Climate and Environment, a nonprofit research campus in Reno, Nevada. said scientist Joe McConnell. . “Lead pollution in Roman times is the earliest clear example of human impact on the environment.”

Stories of ancient pollution are buried in Greenland’s ice sheet.

The chemical composition of ice there and in other polar regions can yield important clues about what environments were like in the past. As snow falls, melts, and compacts to form a layer of ice, the chemicals trapped inside provide a kind of timeline.

“In environmental history, you’ve been building this layer cake every year,” McConnell said.

By drilling, extracting and processing long cylinders of ice, scientists can measure properties such as carbon dioxide in the atmosphere in past climates or, as in this case, lead concentrations over time.

Researchers analyzed three ice cores and found that lead levels rose and fell over roughly 1,000 years in response to important events in Rome’s economic history. For example, levels rose when Rome organized its rule over what is now Spain and increased silver production in the region.

“For every ounce of silver produced, 10,000 ounces of lead can be produced,” McConnell said. “Just as they produced silver, the Romans were smelting and mining silver for coinage and economy, and they were introducing large amounts of lead into the atmosphere.”

McConnell said lead attaches to dust particles in the atmosphere during the smelting process. A small portion of those particles were blown away and deposited in Greenland.

Once researchers determined how much lead was concentrated in Greenland’s ice, they used a climate modeling system to determine how much lead the Romans would have released to pollute Greenland to observed levels. I calculated the amount.

The research team then analyzed modern information on lead exposure to determine the health effects of atmospheric lead during the Pax Romana, a period of peace in the empire that lasted from 27 BC to 180 AD. has been identified.

The researchers found that average lead exposure is about one-third of what it was in the United States in the late 1970s, when leaded gasoline use was at its peak and before the Clean Air Act was enacted. Lead levels in Rome were about twice what American children are exposed to today, McConnell said.

Researchers believe that people who lived closest to silver mines on the Iberian Peninsula (now Spain) would have had the most lead in their blood.

“Virtually no one got away,” McConnell said.

However, these results likely do not tell the full story of the health effects of lead in ancient Rome. This is because Romans were exposed through other sources, such as wine sweetened in lead-lined vessels, lead piping, and lead goblets.

Dr. Bruce Lanphear, lead expert and professor of health sciences at Canada’s Simon Fraser University, said lead was “ubiquitous” in ancient Rome. He was not involved in this study. Therefore, the new study is limited because it only assesses lead in the atmosphere, he said, and the authors acknowledge that.

“Their estimate is likely an underestimate,” Lanphear said.

Still, the study provides evidence that lead exposure may indeed have played a role, so the findings raise questions about how lead may have contributed to the decline of ancient Rome. may stimulate the ongoing debate.

Historians and medical experts have debated for decades whether and to what extent lead contributed to the fall of the empire. Researchers in the 1980s found that the Roman elite He suffered from gout and abnormal behavior due to drinking large amounts of lead-laced wine..

“I believe that lead played a role in the decline of the Roman Empire, but it was only a contributing factor. It was never the only one,” Lanphear said.

Joe Manning, a history professor at Yale University, said most researchers believe Rome fell for a myriad of reasons, including epidemics, economic problems and climate change. Manning said it’s important to remember that ancient Rome was a tough place to survive, with an average lifespan of about 25 to 30 years.

“Under no circumstances do you want to go to a city in the ancient world. That would be the last place you want to go. ,” Manning said. “Reed has really bad hygiene.”