Ancient Roman emperors were known for some bizarre behaviors. Caligula apparently appointed his horse
as a priest and Nero would cover himself in wild animal skins, run into an arena and
brutally mutilate people. Claudius was known for his clumsy walk, sudden fits of rage and
bursting into uncontrollable laughter. Most historians think these stories are exaggerated
gossip spread by political rivals, but even if they're just 10% true, something was going on.
Could have been a bunch of things, stroke, tumor, maybe a traumatic brain injury, but it also could
have been caused by eating a lot of lead. So did lead lead to the fall of the Roman empire?
Ancient Rome was really into lead. Lead is super malleable and corrosion resistant
so it was used in tons of stuff. Dishes and utensils contained lead. Pipe,
transporting water were made of lead. Even coffins had lead in them.
Because it was in so much stuff, lead also made its way into food and drink. And Roman rulers and
aristocrats were notorious gluttons. A cookbook from back then called The Roman Apicius Cookbook,
has about 450 recipes and lead is in almost a hundred of them in the form of lead acetate, often
called sugar of lead. When I read that, my first question was “You guys ever heard a sugarcane?”
Turns out sugar cane wasn't big back then. So the options to sweeten something were honey,
which there also wasn't a lot of or grapes, which they had plenty of. They boiled down
grape juice to concentrate the sugars, but then they found that if they boiled it in lead pots,
the syrup would become even sweeter. What was happening was that the acetate from the grapes
was combining with lead ions that were leaching out of the pot to form lead acetate and lead
acetate is sweet. So it was used in a bunch of different foods and wine. And apparently Roman
aristocrats were drinking somewhere between one and five liters of wine per day. That's
a lot of inadvertent lead consumption. One story goes that the politician Lucullus served around
4 million liters of wine for just one of his banquets. I apologize for nothing.
Why were they so okay with drinking and eating that much lead? Well, they had no idea it was
toxic. Lead serves zero purpose in our bodies. Lead's bad for all of our organs, but what we
often hear about is how much it damages our brains. Lead is able to substitute for calcium.
And that's usually why it's so toxic. Your brain needs calcium to send messages between neurons and
lead competing with calcium can cause two major things. One-- the calcium that should be getting
into your neurons and triggering that message isn't or two--neurons that aren't supposed to
active start randomly sending messages. Too much or too little signaling in your brain can cause a
bunch of behavioral changes. Think Claudia’s erratic mood swings, or it can cause issues
processing information, which might make you think appointing a horse to be a priest is a good idea.
Today we still use lead in some stuff like car batteries. But compared to the amount of lead that
the Roman empire used 2000 years ago, or even the amount of lead that we used a hundred years ago,
we're using very little. But it is still in our environment and the stuff that was
made before people realized how toxic it was, like water pipes in Flint, Michigan.
Corroded pipes leached lead into the water, making a lot of people very sick.
Okay. Back to ancient Rome. Was all the led that they were eating and drinking enough
to take down an empire? People have been trying to figure that out for a while. Throughout the 1900s,
researchers recreated some of those syrups that were commonly used in foods and wine,
and they found lead concentrations of 240 milligrams to one gram
per liter. That's around 60 times more than what the EPA allows in public drinking water. And that
was enough to convince a lot of people that lead played a big role in ancient Rome's downfall.
But the research didn't stop there. In 2014, a team dredged for sediment in the waters around
Rome and compared the amount of lead in that sediment to the amount preserved in ancient
Rome's pipes. They figured out that the water in ancient Rome probably had way more lead in it
than today's tap water, but not enough to be that harmful or be a major culprit in Rome's demise.
So we know there was at least a good amount of lead in ancient Rome's water and the syrup
they use to sweeten stuff. But how much of that lead was getting into people?
You need to study skeletons to answer that. Most Roman empire rulers like Claudius were cremated
so their skeletons aren't around anymore. But since the 1970s archeologists have been
studying the skeletons of Roman commoners to find some answers. In 2019, a team compared skeletons
from the Roman empire to skeletons from the Iron Age, before lead was popular. Skeletons from the
iron age contained 0.3 to 2.9 micrograms of lead per gram. Whereas the ones from the Roman empire
had from 8 to 123 micrograms per gram. That's up to 400 times more lead, absolutely enough
to be messing with brain chemistry. But does it mean that it caused the Roman empire to implode?
Can't say for sure. What we do know is that human created lead pollution
was a serious problem 2000 years ago. And unfortunately it's still causing problems today.