The hundreds of tons of lead that burned in the April 2019 fire that nearly destroyed Notre Dame Cathedral in Paris created a dangerous dust that landed in parks, buildings and playgrounds, raising health alarms. Now, scientists say, some of that lead has found its way to a surprising place: honey produced by urban beehives.
A study outlined this week in Environmental Science & Technology Letters found that honey collected northwest of the cathedral, downwind from the fire, contained nearly three times as much lead on average than did those from before the fire.
As investigators continue to seek the origins of the fire that ravaged the 850-year-old cathedral, and scientists, architects and historians study the building’s fragile structure and the debris, other research has focused on the pollution caused by the 460 tons of lead that burned that night.
The honey study, conducted by Kate Smith and Dominique Weis of the University of British Columbia, is one of the first to explore the relationship between pollution from the fire and its effect on residents through a product they can ingest directly.
The honey’s lead concentration — an average of 2.3 nanograms per gram — fell within consumable standards, said Smith, a doctoral candidate in geological sciences and the lead author of the study.
She said the higher lead levels matched the geographical distribution of the dust cloud that was carried across Paris from the fire.
“The evidence is pretty strong that the fire caused the lead elevation observed in the honey,” Smith said.
Urban beekeeping has increased sharply in cities like Paris over the past decade, and the city estimated recently that it has more than 1,000 hives. Bees have taken up residence on the roofs of the gilded Opera Garnier and prestigious restaurants, in the flower-rich Luxembourg Gardens, and at Notre Dame, too, where 200,000 bees that lived on the roof survived the fire.
The study on the Parisian hives drew from 36 honey samples that were collected in July 2019, several months after the fire. Samples from before the fire were used as a reference point.
It found that honey collected downwind of Notre Dame had lead levels three times those in samples collected elsewhere in central Paris not only before the fire, but also after. In one hive, the levels were nearly nine times normal.
Smith said that while the levels measured in the honey were safe, Parisians were right to have been worried about alarming lead concentrations in the aftermath of the fire. “Lead is recognized for its toxicity,” Smith said. “The health risk doesn’t diminish simply because the lead was not deposited recently.”
Smith’s research focuses on how bees can act as sensitive pollution detectors. When bees forage for pollen or nectar, they pick up tiny particles of lead and other metals, and the honey they produce provides a snapshot of their hive’s immediate surroundings.
Researchers continue to be concerned about the effects of pollution from the Notre Dame fire.
In a study of lead levels in Parisian soils published earlier this month, scientists at Columbia University found that people living within 1,100 yards and downwind of the fire were likely to have been exposed to more lead fallout than previously announced.
Previous investigations by French news website Mediapart and later by The New York Times found unsafe lead levels in dozens of places across Paris, including schools, parks and day care centers.
City and state authorities did not order lead testing until a month after the fire, and it took four months to complete a full decontamination of the cathedral’s neighborhood.
If ingested, lead can produce cognitive damage, especially in children. City officials have acknowledged that Paris needs a more comprehensive lead-abatement plan, and scientists are investigating whether rainwater dropping from the roof of Notre Dame may have polluted the Seine river for centuries.
Weis, the other lead author of the study, was in Paris the day after the fire and said she has stayed far from the cathedral out of fear of lead exposure. Although the lead levels measured in the honey accounted for “80 drops of water in an Olympic swimming pool,” she said, they should still act as a warning.
“For Paris, it’s not dramatically high, and it doesn’t mean that the honey cannot be eaten,” Weis added about the lead levels. “But honey here is the canary in the coal mine.”