Did the powerful Roman Empire accelerate its demise due to lead poisoning? The truth is...

The Roman Empire was once one of the most powerful empires in the world, but the Western Roman Empire collapsed in the 5th century AD, and the Eastern Roman Empire also lost its former glory and came to an end in the 15th century. Why such a huge empire came to an end has been a topic of endless debate for many years.

Recently, there have been many short videos claiming that one of the main culprits for the decline of the Roman Empire was indeed lead poisoning in water pipes.

Image source: Internet screenshot

Perhaps because it fits everyone's psychological expectation of seeing the big picture from the small, or perhaps because it caters to modern fears of chemical products, this statement is extremely widely circulated.

But is this really the case? Let’s talk about it in detail today.

What's up with the term lead water pipe poisoning?

Let me give you the answer first: It’s basically not true.

The Roman Republic and the Roman Empire had very advanced water conservancy facilities. They built huge canals to bring water into the city, to public baths, toilets, fountains and private homes, and to supply water for agriculture and mining. Pipes were inevitably used to transport water, and a considerable portion of these pipes were cast in lead. A large number of Roman lead water pipes have been unearthed, which are highly valued by archaeologists.

However, we all know today that lead is a toxic heavy metal that has a particularly great impact on children's development. Leaded gasoline and paint have basically withdrawn from the market because of this. Therefore, many people have speculated that the water was contaminated by lead when it flowed through lead pipes, which had a health impact on the residents of Roman cities and even directly contributed to the demise of the Roman Empire.

Image source: unsplash.com

Why did the Romans like lead so much?

Don't they know that lead is poisonous?

The Romans knew that lead was bad for people. Ancient Roman writings described the symptoms of acute lead poisoning, described the poisonous mist emitted by lead smelters, mentioned that substances such as white lead were poisonous to eat, and even mentioned that water near lead mines was harmful. Therefore, the ancient Roman architect Vitruvius had already proposed in his works that ceramic water pipes were better than lead water pipes.

So why do they still prefer lead? Mainly for practical reasons.

One reason is that lead is a byproduct of silver smelting, and the output is huge. Ancient Rome widely used silver as currency and decoration, but the silver ore they smelted was mainly silver-containing galena, which, as the name suggests, is mainly lead. The richest mine only has about 0.5% silver. It is estimated that the Roman Empire at its peak produced 80,000 tons of lead per year, so much lead would be wasted.

Another reason is that lead itself is really easy to use. It has a low melting point and is easy to cast. It is very suitable for making water pipes and can also be used to make various useful alloys. The chemical element symbol of lead, Pb, comes from the ancient Roman word "plumbum", which has evolved into the English word "plumber" today.

So was it really lead water pipes that ruined the Roman Empire?

Although this is an intuitive idea, it still needs to be tested by the facts. Unfortunately, new research over the past few decades has generally not supported it.

For example, a 2014 study tested the actual effects of Rome's lead water pipes and concluded that the lead content in the water in the lead pipes could be up to 100 times that of nearby groundwater. However, the base number was very low after all, and even after multiplying it by 100 times, it was still not enough to cause a widespread health threat.

Roman lead water pipe with inscriptions Source: Wikipedia

Why aren't there any serious consequences when I'm clearly following the lead flow?

There are several reasons. First, a thick layer of scale often forms in lead water pipes. For example, the Aniene River, an important river that supplies water to Rome, is famous for its hard water, with a very high calcium content. The use of Roman cement in the parts of the canal will also make the water passing through (especially rainwater containing carbon dioxide) harder. These scales are deposited on the inner surface of the pipe, interfering with the contact between water and lead.

Second, the Roman water system relied on gravity to supply water and had no faucets, so the water in the pipes flowed continuously and there was no chance of long-term contact with lead.

Third, most of the water supplied by the aqueduct to the city was used for public baths, and only a small part was used for drinking. Of course, modern water supply systems do not meet these conditions, so let's not inherit the Roman tradition and let plumbers use lead.

So lead is innocent?

We can't just say that. In fact, there are some archaeological findings that show abnormal levels of lead in the remains of ancient Romans. For example, a 2019 study found that 30 leg bones from Roman London had significantly higher levels of lead than leg bones from the Stone Age. The most extreme one had a lead content of 123 micrograms per gram, which is enough to cause health problems.

Although it is difficult to determine whether the lead was already in the body during life or was absorbed by the remains after death, such a high content and the fact that no lead coffins or lead burial objects were found nearby make it at least quite suspicious.

Image source: pixabay

Where did all that lead come from? If lead pipes were the culprit, the distribution should be more even, rather than the extreme highs seen in this sample. But there were other sources of lead in Roman life—specifically, spices.

Ancient Rome had a famous condiment, which was unfermented grape juice that was heated and concentrated into a syrup-like state, called defrutum or sapa. Some records say that defrutum was concentrated to half and sapa was concentrated to one-third, and other records have different definitions, but in short, the basic process is the same.

This condiment has many uses. It can be added directly to dishes, made into more complex sauces, or added to wine to cover up the sour taste. It is very important in Roman life.

Three silver-plated Roman pepper pots (pepper shakers) from Rome. Source: Wikipedia

Concentrated glucose syrup itself is naturally harmless, the problem lies in the production process. Ancient Roman writings repeatedly mentioned that this seasoning should be cooked slowly over low heat in copper or lead containers, and lead is better because copper will cause cross-flavoring.

Even copper vessels were not necessarily safe, as the best Roman bronze contained 10% lead alloy, and many copper vessels were plated with a silver-lead alloy to improve flavor and prevent patina from forming. The Romans did not seem to realize that their vigilance against lead and lead water pipes also applied to lead cookware.

The high temperature, long time, and acidic components of grapes mean that the lead content of the concentrated juice obtained by this operation is incomparable to the lead in water pipes. Some experiments have found that when grape juice is boiled to one-third of its volume in a lead container, the resulting syrup will contain up to one gram of lead per liter, which is outrageous. Even if the syrup is not drunk directly but mixed with wine, that one liter of wine should be enough to cause symptoms of lead poisoning.

Is the real culprit the lead in the syrup?

So is this condiment the real reason for the Romans' lead poisoning? Wait a minute. Although there is experimental support, this conjecture still has some unresolved problems.

First, the scene used in the experimental operation may not be the same as the scene in which the ancient Romans actually boiled. For example, a small pot with a capacity of 4 liters was used in a boiling experiment, but the ancient Romans often produced on a large scale and used giant pots with a capacity of more than 2,000 liters. For containers of the same shape, the larger the volume, the smaller the specific surface area, and the lower the lead pollution concentration from the wall.

For example, ancient Roman records mention that the inside of the pot should be smeared with high-quality oil and carefully rubbed, or coated with asphalt, but modern experiments do not mention whether this process was done.

Image source: pixabay

Second, it is actually difficult to know how much wine and food the ancient Romans drank and ate every day, and it is even more difficult to judge the amount of a specific seasoning. Glucose syrup is not the only wine seasoning, there are many other seasonings, and it seems that high-quality wine without seasoning is the most popular in the aristocratic circle. In addition, the Romans advocated drinking wine with a certain proportion of water, believing that wine without water was drunk by barbarians.

Third, there are not many records of lead poisoning in Roman medical literature. Descriptions of acute lead poisoning appeared in the second century BC, but if everyone was drinking poisoned wine and poisoning was extremely common, the author of the description should have mentioned it specifically.

As for the symptoms of chronic lead poisoning, it wasn’t until the seventh century that an Eastern Roman physician described it (and he didn’t realize it was lead related). If lead poisoning was severe enough to cause the empire’s destruction, there shouldn’t be so few descriptions of it.

Image source: unsplash.com

So the bottom line is that the lead pipes used by the Romans were (mostly) innocent, and the real problem was the use of lead vessels to boil syrup. However, this syrup was probably not enough to cause poisoning throughout the empire. There were almost certainly some people who got poisoned by overeating, but there were probably many other reasons that were much more important to why the Roman Empire fell.

Planning and production

Author: Fang Gang, a popular science writer

Review | Sun Yifei, Director of the Medical Education History Research Office, Hebei Medical University

Planning丨Xu Lai

Editor: Wang Mengru