Did lead poisoning cause the fall of the Roman Empire? The jury is still out

The emperors of ancient Rome did some pretty bizarre things – burst into uncontrollable laughter, name a horse a priest, dress in animal skins and attack people… the list goes on. Why did they do this? Maybe… lead poisoning.

There are a number of factors that contribute to the demise of an entire civilization, such as the collapse of the roman empire circa 476 AD. The slow decline of the empire is generally attributed barbarian invasions, failed military campaigns, economic challenges, government corruption, and over-reliance on slave labor, among other factors. But it has also been suggested that the toxic effects of lead poisoning on increasingly erratic rulers may also have contributed to its demise – a debate that has been revisited in a new one. Reactions American Chemical Society video.

Lead has a number of properties which make it attractive for practical use. It is inexpensive, widely available, resistant to corrosion when exposed to air and water, has a low melting point, and is very malleable, which means it is easy to process into a large range of products. But lead is also very toxic if it enters the human body, which is why we use it much less nowadays compared to 100 years ago. Common symptoms of lead poisoning include anemia, nervous disorders, memory loss, inability to concentrate, and even infertility. Lead exposure can also be a factor in malaria, rickets, gout and periodontal disease.

Since 1943, scientists have known that lead can adversely affect the neurological development of children, leading to behavioral problems and reduced intelligence. This is because it can easily replace calcium. Calcium is how neurons in the brain communicate, and if lead replaces it, there is either too little or too little communication between neurons. This can cause erratic mood swings or difficulty processing information, for example.

As the Reactions video points out, the ancient Romans loved their lead. They used it in pipes, to line coffins, in their pots and utensils. They also used lead acetate as a sweetener, at a time when cane sugar and honey were quite scarce. They had grapes in abundance and boiled the juice in their lead pots. The lead ions would seep into the juice and combine with the acetate from the grapes. The resulting syrup was very sweet and used in wines and a wide variety of foods. In fact, of the 450 recipes in a cookbook from this period (the Apicius cookbook), 100 requested these syrups. The Romans also loved their wine, with the aristocrats consuming between 1 and 5 liters per day. Researchers who recreated some of the syrups found lead concentrations about 60 times higher than those allowed by the EPA in public drinking water.

The current debate on the potential role of lead poisoning in the fall of the Roman Empire dates back to an article from 1983 in the New England Journal of Medicine by Jerome Nriagu, who studied the diet of Roman emperors between 30 BC and 220 AD. Nriagu noted that 19 of the 30 emperors showed a preference for “lead contaminated” food and wine, concluding that many were likely suffering from gout and lead poisoning.

Claudius, for example, is described as exhibiting “disturbed speech, weak limbs, an unsightly gait, tremors, excessive and inappropriate laughter, and inappropriate anger, and he often drooled”. Legend has it that Caligula once wanted to name his horse, Incitatus, as a consul, although historians generally believe that it was politically motivated gossip, or that Caligula conceived it as a farce. Nero is said to have mutilated people in the arena while he was dressed in animal skins.

But was lead poisoning the cause of all these symptoms, and therefore the eventual collapse of the empire? Nriagu’s hypothesis got the support of the geochemist Claire Patterson, whose work convinced governments to ban lead in gasoline in 1975. But it has been hotly contested by others, notably the the classic John Scarborough, who accused Nriagu of botched research. Nriagu in turn told the Washington Post in 2016 that Scarborough “knows nothing” about lead poisoning.

Enlarge / Ancient Roman sewer pipes stacked against a stone wall

iSidhe / iStock / Getty Images

In the decades that followed, numerous scientific articles examined various aspects of the issue of lead poisoning. For example, in 2014, French researchers studied how the lead pipes used in Roman aqueducts could have contaminated the water consumed by the ancient Romans. Specifically, they measured the concentrations of lead isotopes in the sediments of the Tiber and the port of Trajanic, and compared these levels to the amount of lead isotopes found in ancient Roman pipelines.

Although their estimates revealed that the water in these pipes could contain up to 100 times lead than the region’s spring water, the team nonetheless concluded that these concentrations were not likely to have caused serious health problems. The authors added that in their view, Nriagu’s theory that lead poisoning led to the fall of the Roman Empire has been largely debunked.

Of course, there could be other equally likely factors for the legends surrounding the strange behavior and ailments of ancient Roman rulers, such as traumatic brain injuries, strokes, or tumors. But there is evidence that lead poisoning was a problem for the ancient Romans, even though it did not directly contribute to the empire’s collapse. For example, a 2010 study tooth enamel taken from more than 200 burials at 33 sites in Britain, Ireland and Rome (around the first to the fourth century CE) revealed a marked increase in lead levels in British samples and a large range of lead levels in ancient Roman times. enamel samples.

A 2019 study found 400 times more lead in skeletal remains from the Roman Empire than in samples from the Iron Age.
Enlarge / A 2019 study found 400 times more lead in skeletal remains from the Roman Empire than in samples from the Iron Age.

YouTube / American Chemical Society

In a 2019 study, archaeologists examined several skeletons in London during Roman times for signs of exposure to toxic levels of lead. The team sampled 30 thigh bones, as well as 70 Iron Age bones as a control. They found that the Iron Age skeletons contained only 0.3 to 2.9 micrograms of lead per gram, while those of the Roman Empire contained between 8 and 123 micrograms per gram. These are levels high enough to cause widespread health effects including hypertension, fertility problems (and subsequent population decline), kidney disease, neuronal damage, gout, and more.

That said, according to the archaeologist Janet Montgomery from Durham University, bone also absorbs lead and other metals from the soil, so it can be difficult to rule out post-burial contamination as a source of these higher levels of lead. “You don’t know if the lead you are measuring [in bone] has accumulated from exposure to a fairly low level over a long period of time, or has arisen from a period of high exposure several years in the past, or something in between, ”she said. says Chemistry World.

Archaeologist Kristina Killgrove, write to Forbes, stressed that there were no lead coffins, nor many lead funeral objects, on these sites which could have contributed to this type of contamination. But she noted that it is not clear whether the skeletons of people who lived in Rome during the same period (as opposed to London) would also have high levels of lead, which requires further study. “While the question of the effects of lead poisoning on the Roman Empire is far from settled, [this] the research adds to a growing body of scientific evidence from multiple sources that shows human-made lead pollution was a serious problem two thousand years ago, ”Killgrove concluded.

List image by iSidhe / iStock / Getty Images

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