Tracking Rome’s Economy Through Its Lead Pipes

Wikimedia (CC BY-SA 3.0)

Rome‘s use of leaden water pipes has been blamed for everything from delinquent behavior to the “fall” of the Roman Empire, but a new study uses traces of lead found in soil deposits to track the economy and urbanization of ancient Rome.

Sarah E. Bond

A new study of the sediments at Ostia, Rome‘s harbor, reveals much about the growth and urbanization of the city of Rome from the late Republic to the mid-third century (circa 200 BCE-250 CE). Scientists and archaeologists carried out high-resolution isotopic analysis of “major and trace element concentrations and Pb [lead] isotopic compositions” on 12 meter long sediment cores taken from the harbor at Ostia.

What they found was that while anthropogenic lead was not visible in the portion of the cores dating to the early foundation of the harbor in the 4th and 3rd centuries BCE, lead contamination began to be detected in the second century BCE. As the water system of pipes and aqueducts in nearby Rome began to incorporate more leaden fistulae (water pipes), it seems that lead deposits at Ostia increased in the sandy deposits there likely due to leaching.

Many of the increases in lead levels graph nicely onto patterns of urbanization and growth within the city of Rome itself during the early imperial period. Moreover, the study found that in 250 CE, there was a decrease in lead levels that can be correlated with the diminishment of the water distribution system at Rome in the mid-third century. This is likely due to the so-called “crisis of the third century” often characterized by economic, political and social instability in the city at this time. Such upheaval appears to have had an impact on the growth of infrastructure like aqueducts.

Ancient World Mapping Center (UNC-CH)

But can we attribute the high lead levels in the cores to the water pipes alone? The authors note but then discount the other uses of lead that might have contributed to the Pb levels in the sediment at Ostia: “Lead plates, anchors, and sounding lead weights are, however, unlikely to have been significant contributors to the anthropogenic Pb signal of Ostia sediments.” Romans used lead for a variety of things in everyday life, including as a sweetener, but the sediment at Ostia was most effected by the use of lead pipes in aqueduct systems.

Metropolitan Museum of Art (CC-0).

Although sediment cores that record Pb levels have been used to pinpoint both the sixth century Gothic Wars and the Arab sack of Rome in the 846 CE, the use of Pb levels to reconstruct earlier urban events at Ostia and Rome has been more difficult. Consequently, the findings of Hugo Delilea,Duncan Keenan-Jones, and the other scientists recently studying the harbor cores is imperative to reconstructing the economy and infrastructure of the late Republic and early empire.

The study also adds to our current knowledge of lead levels in the Roman Empire more broadly. This in addition to pivotal studies done by bioarchaeologists such Kristina Killgrove. In 2012, Durham University archaeologist Janet Montgomery, as well as Kristina Killgrove and a number of other scientists published a study of lead isotope and concentration data from tooth enamel gathered from over 200 archaeological burials at sites in Britain, Ireland and Rome. Their study used lead isotope ratios found in the teeth of  Roman skeletal remains to help identify possible immigrants within the Roman Empire. The study demonstrates the variant and promising ways in which lead levels can be used to speak to us about the past.

Kristina Killgrove (Powered by Osteons)

While analyses of lead levels may provide a window into antiquity, they can also reveal the damaging effects of lead on the living today. As Prof. Killgrove has noted about lead poisoning: “The main problem with lead – the reason that it’s toxic – is that it interferes with normal enzyme reactions within the human body.  Lead can actually mimic other metals that are essential to biological functioning. But since lead doesn’t work the same way as those metals, the enzymatic reactions that depend on things like calcium, iron, and zinc are disrupted.” 

The devastating effects of lead on Roman fertility give painful insight into the news just last week that a new study of Flint, Michigan’s water supply showed that fertility rates dropped significantly in April of 2014, when the city’s water supply was modified to pull from the Flint river. The city still has not had clean drinking water in over 1200 days. If studies of Pb levels that polluted the water of the past can tell us anything about policy today, it is that a clean water supply is imperative to maintaining the health and wellbeing of any population either ancient or modern.