This appears to be junk science or at least exaggerated claims! Computer models still can not predict today's weather accurately beyond more than 48 hours.
What about lead smelting in other regions of the world like Asia?
This seems to be another very or extremely eurocentric study!
It is very popular and convenient to blame or associate lead exposure to all sorts of things!
"... The study examined measurements of lead pollution in 3 Arctic ice cores dating from 500 BCE to 600 CE, an era spanning the rise of the Roman Republic through to the fall of the Roman Empire.
Researchers used computer models of atmospheric movement to map atmospheric lead pollution across Europe to estimate exposure levels and human health impacts. ..."
"... The study, published ... in Proceedings of the National Academy of Sciences (PNAS), examined three ice core records to identify lead pollution levels in the Arctic between 500 BCE through 600 CE. This era spans the rise of the Roman Republic through the fall of the Roman Empire, with the study focusing on the approximately 200-year height of the Empire called the Pax Romana. Lead isotopes allowed the research team to identify mining and smelting operations throughout Europe as the likely source of pollution during this 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 research team also identified likely reductions in IQ levels of at least 2 to 3 points among the European population. ..."
"Significance
The detrimental effects of modern lead exposure on human health are widely recognized. Evidence from the Roman era indicates substantial lead exposure that potentially impacted human health more than 2,000 y ago. The most significant exposure for the rural, nonelite population may have been to background air pollution from silver mining and smelting that underpinned the Roman economy. Using detailed records of Roman-era lead pollution measured in Arctic ice cores and atmospheric modeling, we show that lead emissions from these activities elevated air concentrations throughout Europe. Based on modern epidemiological studies, this air pollution enhanced childhood blood lead levels (BLLs) by about 2.4 µg/dl leading to widespread cognitive decline including an estimated 2.5-to-3 point reduction in intelligence quotient.
Abstract
Ancient texts and archaeological evidence indicate substantial lead exposure during antiquity that potentially impacted human health. Although lead exposure routes were many and included the use of glazed tablewares, paints, cosmetics, and even intentional ingestion, the most significant for the nonelite, rural majority of the population may have been through background air pollution from mining and smelting of silver and lead ores that underpinned the Roman economy.
Here, we determined potential health effects of this air pollution using Arctic ice core measurements of Roman-era lead pollution, atmospheric modeling, and modern epidemiology-based relationships between air concentrations, blood lead levels (BLLs), and cognitive decline.
Findings suggest air lead concentrations exceeded 150 ng/m3 near metallurgical emission sources, with average enhancements of >1.0 ng/m3 over Europe during the Pax Romana apogee of the Roman Empire. The result was blood lead enhancements in young children of about 2.4 µg/dl above an estimated Neolithic background of 1.0 µg/dl, leading to widespread cognitive decline including a 2.5-to-3 point reduction in intelligence quotient throughout the Roman Empire."
Lead Pollution Likely Caused Widespread IQ Declines in Ancient Rome, New Study Finds (original news release)
Carefully preparing the longitudinal ice core samples for high-resolution lead measurements
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