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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/m³near metallurgical emission sources, with average enhancements of >1.0 ng/m³over 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 found in ice cores extracted from polar ice sheets and glaciers reflects human activities, including mining and smelting related to early silver production, as well as coal, oil, and gasoline burning. Isotopic analyses of lead in glacier ice can be used to identify past changes in emission sources. Between October 2021 and September 2024, lead isotopic records were developed from four Greenland Ice Cores (GrIP) (Tunu2022a, Tunu2022b, North Greenland Ice Core Project 2 [NGRIP2], and REnland ice CAP project [RECAP]) at the Desert Research Institute's Trace Chemistry/Ice Core Laboratory. Lead isotopic analyses were performed on discrete meltwater samples using a High Resolution Inductively Coupled Plasma Mass Spectrometer (HR-ICP-MS). The original overarching goals of the project, were to (1) exploit recently refined methods developed for urban geochemistry to develop high-resolution records of lead (Pb) isotopes (206Pb, 207Pb, 208Pb) in Greenland ice cores, (2) use these records to identify and quantify changes in anthropogenic emission sources during the past 2,500 years, and (3) evaluate linkages between these changes and historical events extending from Antiquity through the Middle Ages to the present. These records have implications for understanding of how events such as plague, social upheaval, warfare, and technological advancements in mining and smelting influenced human history.