How lead exposure became the Notre-Dame fire's toxic legacy

Notre-Dame de Paris is preparing to open its doors to the public on December 8 after five years of rebuilding. From its iconic spire to its impressive roof, the cathedral is once again visible on the Paris skyline. But behind the scenes of this grand reopening lies a darker truth.

“It was the perfect opportunity to raise awareness of the dangers of lead,” said Mathé Toullier, who spearheads Notre-Dame Lead (collectif “plomb Notre-Dame” in French), a group of associations. “But we missed our chance.” Founded just after the fire that ravaged the cathedral in 2019, the group was created to sound the alarm on the dangers associated with the metal.

Touiller is also president of an organisation that supports victims of lead poisoning and their families. When she saw the huge yellow cloud rising from Notre-Dame five years ago, she quickly became concerned. “I immediately knew what was happening. Lead dust was spreading all across the capital,” she recalled.

As the flames engulfed the cathedral, a whopping 400 tonnes of lead from the roof and spire went up in smoke, according to French authorities. The cloud then continued its journey well beyond the city of light and travelled 16 kilometres east of Paris, according to the National Centre for Scientific Research (CNRS).

Dangers of lead

It has been widely documented that lead can be toxic, even in small doses. “However much a person is exposed, lead poisoning can cause neurological, renal or cardiovascular problems – especially in children but also in adults. It can also impact fertility, increase the risk of cancer or cause foetal abnormalities in pregnant women,” explained Annie Thébaud-Mony, a public health researcher at France’s national institute of health and medical research (INSERM) and president of the Henri Pézérat association.

“There is no level of exposure to lead that is known to be without harmful effects,” the World Health Organization reports in its lead poisoning fact-sheet. And according to a study published in 2023 by the Lancet Planetary Health journal, 5.5 million people worldwide died from lead-related cardiovascular illnesses in 2019.

The day after Notre-Dame caught fire, Toullier and Thébaud-Mony launched their collective, immediately sounding the alarm on the dangers of lead. For weeks the two women, flanked by volunteers, handed out leaflets around the site of the cathedral – in bars, shops and near apartment buildings. They informed local residents of best practices like regular hand-washing, cleaning clothes at high temperatures and taking shoes off before walking into their homes, imploring them to avoid anything that could spread toxic lead dust.

In the meantime, the collective also called on authorities to take urgent action to confine the cathedral and decontaminate it immediately – but also inform those working or living near the site about the risks. “Nothing was done,” Toullier lamented.

A pause in construction

Lead pollution only became a topic of concern three months after the fire, in the summer of 2019. Faced with very high levels of the metal and no measures implemented to curb its presence, the French Labour Inspectorate warned of a “dangerous situation for workers” inside the stricken cathedral. The city of Paris was eventually forced to suspend the reconstruction of Notre-Dame and cordon off the square in front of it, a move widely covered by media at the time.

In the weeks that followed, drastic protection measures were put into practice. Workers were required to wear overalls and high-protection masks, and a mandatory shower and foot bath system was implemented. “Measures to prevent lead exposure are stricter than anywhere else,” French MP Sophie Mette stated in a 2022 parliamentary report on the site.

“But Notre-Dame was not the only location to be affected,” Toullier pointed out. “Lead levels were very high all around the cathedral, on metro platforms, in bookshops on the Place Saint-Michel and even in surrounding schools.”

At the end of summer 2019, Notre-Dame Lead reported levels of up to 123,000 μg/m², which represented 25 times the “standard” threshold of 5,000 µg/m² set by the regional health authority ARS, at the Place Saint-Michel, a 10-minute walk from the cathedral. “Yet no significant clean-up operation was carried out. It was as if the problem didn’t exist,” Toullier lamented.

Widely shared by the collective, the alarming figures pushed some artisans to action. “Some unionised workers demanded to exercise their right of withdrawal [from the works] or asked for lead tests to be carried out so they could measure the level of lead in their blood,” explained Benoît Martin, secretary of the Paris branch of the CGT trade union and member of the Notre-Dame Lead group. Some surrounding schools even decided to postpone the start of the new academic year in order to carry out a thorough clean-up.

In June 2021, the French Public Health agency concluded that the Notre-Dame fire had not caused a “significant” increase in blood lead levels for children living nearby. The public was reassured, but the collective remained sceptical. “We don’t know who had their blood tested or when,” Thébaud-Mony said. “But more importantly, the authorities waited far too long to carry out the tests. Once three weeks have passed it is no longer possible to detect lead in the bloodstream. It has either been evacuated or stored in the bones.”

Tired of not being heard, the collective eventually filed a complaint for endangering others in July 2021. The investigation is still ongoing.

For Judith Rainhorn, a historian specialised in lead pollution, the silence from authorities came as no surprise. For her, it is “yet another episode in the long history of denying the toxicity of lead”.

“We have been using lead on a massive scale since the 19^th century. It is a familiar product and that is why we tend to play down the risks,” Rainhorn explained. “Unlike asbestos, it still has a fairly positive reputation. That is starting to change, but it is taking time.”

Rebuilding an identical structure – lead roof and all

The decision to rebuild the spire and roof of Notre-Dame exactly as they had been in the 19^th century by covering them in lead deepened the anger already felt by the members of Notre-Dame Lead and raised the eyebrows of politicians, non-profits and local residents.

To justify the decision, the institution in charge of restoring the cathedral, Rebuilding Notre-Dame de Paris, ruled out any danger of direct exposure to the substance. “Covering the roof structures of the nave, the choir and two arms of the transept with lead does not expose any member of the public to lead, as they are located some forty metres from the ground and are inaccessible,” the institution told French daily newspaper La Croix in a December 2023 article, assuring it was taking the matter “very seriously”.

“But what about run-off water from the roof, which will be laden with lead?” asked Thébaud-Mony. In a notice published in January 2021, the French High Council for Public Health estimated that “the roof of Notre-Dame alone … would emit around 21kg of lead per year (about two tonnes per century) in run-off water”.

“And what will happen if there is another fire?” Thébaud-Mony insisted.

“We are obviously complying with the law and regulations in all areas concerned. No one’s health is being put at risk. In addition to new fire protection of the highest standard, including a misting system in the attic … we are going to innovate by installing a system that collects and filters rainwater running off the cathedral roof,” the institution told French daily Le Figaro in December 2023.

“Lead could have been replaced by another substance like zinc or copper,” said Thébaud-Mony. “When alternatives exist, why choose lead and risk human health?” This was the case for the Chartres cathedral, destroyed by a fire in 1836. The original structure had lead roofing, which was replaced by copper when it was rebuilt. Though perceived as less stable, copper is significantly less toxic.

Long-term monitoring

With just a few days to go before the grand reopening, the collective has decided not to give up. “I am worried because lead pollution, regardless of whether it is inside or outside, is still there – especially with the new spire and roof. We cannot give up,” Thébaud-Mony concluded.

“Sensors should be installed to measure lead levels inside the cathedral on a regular basis,” union representative Martin insisted. “We need to ensure there are no risks to visitors.”

For now, the collective is calling on authorities to ensure workers who helped rebuild Notre-Dame and local residents are monitored in the long-run. “What we fear is that people will fall ill without necessarily making the connection to lead,” Martin said. “Illness can creep in long after exposure and the link to lead can quickly be forgotten.”

(This article was originally published in French and translated into English by Lara Bullens)