In April 2019 the world watched in horror as flames engulfed one of Europe’s most iconic buildings, leaving little more than a charred and broken ruin. But fast forward one year, and experts are hard at work renovating the gothic beams and arches of Notre-Dame de Paris. In amidst the piles of ash and debris in the cathedral, however, a scientist made a somewhat disturbing discovery.
In order to understand the gravity of the situation, though, let’s recap the horrifying events. The first sign that something was amiss came in the early evening of April 15, 2019, when an alarm notified staff of a fire somewhere in the famous cathedral. After evacuating the building, they rushed to put out the blaze – only to find that they weren’t in the right place. And when they finally reached the correct spot, the flames had, unfortunately, already taken hold.
For those in charge of looking after the cathedral, it was a disaster that they’d long feared. With parts of this vast structure dating back to the 12th century, the precarious state of its stonework was already extremely vulnerable. And in the attic and spire, oak beams from the 1200s had dried out, posing a worrisome fire risk.
In fact, by April 2019 Notre-Dame was being monitored by fire wardens on several occasions each day. Sadly, however, that didn’t stop a blaze from breaking out, probably as a result of an electrical issue. And for more than three hours, Parisians looked on in shock as flames tore through the roof of the historic cathedral.
During the blaze, hundreds of firefighters worked tirelessly to extinguish the flames. And in the meantime, the emergency services formed a human chain to remove priceless artifacts from the terrifying inferno. By the time that the fire was put out, however, the iconic building was a mere shadow of its former self.
When the sun rose the next morning, then, it illuminated a damaged and broken Notre-Dame. In the fire, some two-thirds of the cathedral’s roof had been destroyed, and its 19th-century spire had fallen. Moreover, as it tumbled down, it pierced the ceiling of the vault below, which catastrophically exposed the building’s interior to the burning wreckage.
As the citizens of Paris grieved, news outlets across the globe broke the story of the staggering loss. Reporters also clamored to find out the fate of the priceless artifacts that the cathedral had held in its walls. Which among them had been saved from the fire – and which had been destroyed by the relentless flames?
At the time, you see, Notre-Dame had housed many important religious artifacts, such as a crown of thorns purported to have been worn by Jesus Christ. Additionally, the cathedral also held a piece of ancient wood that was said to have come from the cross used at the Crucifixion. But it wasn’t only objects associated with Christianity that were in peril as the building burned.
That’s right: onlookers also feared for the fate of Notre-Dame’s 18th-century organ, which is so revered that musicians have to register with the cathedral years in advance just for a chance to play it. And what of the countless statues, some of which dated back to the 1300s? Or the famous Mays paintings, gifted to the cathedral annually between 1630 and 1707?
Thankfully, the worst-case scenario didn’t materialize. In fact, some of Notre-Dame’s most famous pieces of art weren’t even in the building at the time that the fire broke out. Towards the end of 2018 repair work had commenced at the cathedral, and as a result, a number of items had been taken from the vault for safekeeping.
Yes, many of Notre-Dame’s religious treasures were stored within the sacristy – a nearby building that wasn’t damaged in the blaze. And as for the artifacts that were within the burning cathedral, many were saved by rescue workers. Not all of the masterpieces of this beloved landmark could be saved, however.
“We have avoided a complete disaster,” the Observatory for Religious Heritage’s Maxime Cumunel told Reuters in 2019. “But some five to 10 percent of the artwork has probably been destroyed, [and] we have to face up to that.” And as smoke-damaged paintings were removed from the cathedral’s blackened ruins, the grave reality of the situation began to hit home.
In the days and weeks following the fire, a number of companies and individuals came forwards with generous donations to help pay for the restoration of Notre-Dame. The French businessman Bernard Arnault, for example, gave the equivalent of $200 million to the cause. However, experts believed that renovation work could cost several billion dollars.
In the meantime, then, restoration experts began to pick their way through the shell of Notre-Dame, clad in helmets to protect against falling debris. While the ruins still smoldered, the French president had promised the world that the icon church would be reconstructed. And now, it was the task of these experts to work out how.
At first, these specialists were comforted by how many of the cathedral’s relics had been spared. In a 2020 interview with Science magazine, Aline Magnien from the Historical Monuments Research Laboratory, or LRMH, explained. “What matters isn’t the roof and vault so much as the sanctuary they protect,” she said. “The heart of Notre-Dame has been saved.”
Nevertheless, the restoration looks set to be a mammoth undertaking. For Magnien’s team at LRMH, the first task has been to try to stop any additional destruction from taking place. Then, the 23-strong group hopes to use its research to instruct constructors on how best to rebuild the church.
There have been many hurdles for the team to conquer along the way, however – and it looks as though there will be more to come. For example, one of the first problems that researchers encountered was reaching the cathedral’s damaged stonework. Climbing onto the top of the vault, they reasoned, could cause the entire structure to collapse. But at the same time, observing it from underneath would put them at risk from tumbling detritus.
So researchers have been unable to determine just how unstable the ruins of Notre-Dame really are. Nonetheless, they’ve found that analyzing the color of the stonework has delivered some surprisingly useful results. According to the experts, you see, limestone blocks take on a different hue depending on the temperatures that they have been exposed to.
At between 570°F and 750°F, for example, the iron inside the limestone decomposes, leaving behind a layer of red. And as temperatures rise even further, the color shifts to black. Ultimately, at around 1,500°F, the blocks are little more than powder. Armed with this knowledge, then, researchers have been able to determine the sturdiness of individual stones simply by evaluating their color.
Another issue for researchers has been the amount of water that has made its way into the ruins of Notre-Dame. During the blaze, it seems, firefighters were instructed to aim their water jets away from the fragile stained-glass windows. However, they couldn’t do the same for the stone vault, as the flames threatened to engulf it.
As the firefighters turned their hoses on the limestone walls of the cathedral, the porous material absorbed the water – drastically increasing its weight in some instances. And almost a year later, researchers have noted that it still hasn’t completely dried out. What’s more, the water in the stones expands and contracts depending on the temperature, further wreaking havoc with the unstable structure.
Today, work to protect the fragile shell of Notre-Dame and to restore it to its former glory continues. Macron, you see, has promised that the cathedral will be ready for the public to enter as early as 2024. In the meantime, though, researchers have been enjoying a unique insight into the now-blackened landmark that’s defined Paris for hundreds of years.
Philippe Dillmann, a metal specialist working with LRMH, told Science magazine, “We’re sorting these thousands of fragments – some from our world, some from another and more ancient world. And it’s like we’re communicating with the Middle Ages,” Elsewhere, experts have been seizing the opportunity to deduce the techniques of the 13th-century stonemasons who built the cathedral.
In fact, even the loss of Notre-Dame’s great attic hasn’t been completely without a silver lining. According to experts, an analysis of the remaining beams suggests that they were grown-to-order in a dedicated forest. And given the age of the wood, this implies that the construction of the cathedral was intended for at least a century prior to building work commencing.
But while it might seem that Notre-Dame itself had a somewhat lucky escape, the citizens of Paris have perhaps not been quite so fortunate. Apparently, while the roof of the cathedral burned, great quantities of poisonous lead melted and were released into the atmosphere. Shockingly, though, it has yet to be traced.
Even today, lead is present in roofs across the planet. However, it can also be toxic, with exposure to it sometimes resulting in a number of physical and neurological problems. As well as behavioral difficulties, for instance, it’s believed that the substance can also lead to conditions such as infertility, seizures and even death.
In the aftermath of the Notre-Dame fire, many Parisians grew concerned that lead from the roof may have contaminated the areas surrounding the cathedral. At first, though, the science seemed reassuring. According to metallurgist Aurélia Azéma, a section chief at LRMH, the blaze didn’t reach the temperatures necessary for reducing the material to gas.
Moreover, much of the melted lead from the roof clearly remained in the cathedral, where it solidified to form stalactites. And as officials declined to issue public warnings about the issue, many residents might have assumed that they were safe. However, a far more sinister story was playing out behind the scenes.
Some witnesses, you see, had spotted a yellow haze forming over Notre-Dame as the fire raged below. And according to some of the experts, the inferno did, in fact, exceed the temperatures at which lead combines with oxygen, essentially creating an aerosol effect. So, it seems clear that a portion of the toxic material did find its way into the atmosphere around Paris.
But where did it go? Worryingly, authorities didn’t test the neighborhoods close to the cathedral for several weeks. And when they did, they discovered that a number of local schools contained significant levels of lead. Some recreational areas returned readings of more than 60 times the recommended limit, too.
Because of lead’s toxic nature, French law states that only trace amounts of the substance are allowed on buildings. There have been rumors, however, that officials have attempted to cover up the dangerous levels released by the Notre-Dame fire. Indeed, a 2019 report by The New York Times claims that the risk was known within a couple of days of the disaster – but authorities failed to act.
In September 2019, representatives from Robin Hood, an environmental organization based in France, announced some worrying news. The residents of an apartment one mile from Notre-Dame had asked for some lead tests to be conducted at their property. And on the balcony, experts had found levels of around 20 times the recommended limit.
In addition, lead content eight times the legal limit was detected at a Paris police station. And in a 2019 interview with The Daily Telegraph, union representative Frédéric Guillo explained his concerns. He said, “It proves once again that the lead contamination caused by Notre-Dame fire is a serious, long-term problem that authorities need to protect their citizens from.”
But while the people of Paris are rightly concerned about the lead drifting around in their atmosphere, Notre-Dame itself remains ground zero for this toxic leak. In fact, Azéma detected traces of the material throughout the cathedral – even inside the pipes of an organ. And elsewhere in the building, another scientist made an alarming discovery.
In the ruins of Notre-Dame, wood specialist Emmanuel Maurin, who also leads a team at LRMH, ran tests on surfaces made from oak and other materials. And when he looked at the results, he discovered levels of lead at around 70 times the recommended limit. Despite this, however, those working in the cathedral in the months after the fire weren’t even equipped with proper precautionary clothing.
Thankfully, by March 2020, all that had changed. Researchers working at Notre-Dame were now obliged to submit to rigorous decontamination procedures. According to reports, they’re limited to two and a half hours inside the ruins, after which they must throw away their disposable garments. The scientists are then required to take a thorough shower, a task that they sometimes complete up to five times a day.
Although researchers must follow these strict guidelines, there are some who believe that Notre-Dame might have been releasing toxic lead into the environment for years. Even before the fire, for example, it’s thought that rainwater may have washed the material from the roof into the nearby River Seine. And as a result, it could have already been contaminating the region for hundreds of years.
What’s more, there are other factors that could be affecting lead levels across Paris, including the use of gasoline and toxic paints. So, exactly how much of it can be traced back to the fire at Notre-Dame? In an attempt to solve the mystery, then, scientist Sophie Ayrault plans to compare samples taken at the cathedral to those gathered elsewhere in Paris. This vital work has yet to take place, however.
In the meantime, the team at LRMH have been busy trying to find ways of removing lead traces from the ruins of Notre-Dame. So far, ideas have included using a special putty to extract the toxic material and deploying lasers to cleanse the porous stones. But according to geologist Véronique Vergès-Belmin, who heads up the LRMH’s stone department, the process will likely involve a series of different approaches.
Still, as The Guardian reported back in April 2019, Macron promised that Notre-Dame would be rebuilt “more beautiful than before.” And now, researchers at LRHM are echoing this sentiment. Speaking to Science magazine, Magnien claimed, “Notre-Dame will come out of this experience enriched. And so will we.” But if it can be proven that toxic lead has leaked from the cathedral into Paris’ parks and schools, it seems likely that the fire will leave behind a far darker legacy.